CN120752501A - Factory or on-site calibration of thermoelectric and thermo-optical properties - Google Patents

Abstract

The invention relates to a method of operating a spectrometer device (110) for obtaining spectroscopic information about at least one object (112), the method comprising in particular evaluating a detector (128) signal by using at least one evaluation unit (136) of the spectrometer device (110) to obtain spectroscopic information about the object (112) therefrom, the evaluation unit (136) being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of at least one operating parameter and for taking into account the selected correction information item to obtain spectroscopic information. The invention further relates to a calibration method of compiling a set of correction information items, a spectrometer device (110) for obtaining spectroscopic information about at least one object (112), a computer program, a computer readable storage medium and a non-transitory computer readable medium. The invention has the advantage that the operating parameters can provide reliable correction parameters, especially in cases where ambient temperature is considered. Thereby, fluctuations in the spectral flux of the at least one light source (114) and/or fluctuations (in particular, offsets) in the spectral characteristics of the at least one light source (114) may be compensated.

Description

Factory or field calibration of thermoelectric and thermo-optic properties

Technical Field

The invention relates to a method of operating a spectrometer device for obtaining spectroscopic information about at least one object, a calibration method of compiling a set of correction information items, and a spectrometer device for obtaining spectroscopic information about at least one object. The invention further relates to a computer program, a computer readable storage medium, and a non-transitory computer readable medium.

In general, such methods and apparatus may be used for research or monitoring purposes, particularly in the Infrared (IR) spectral region, particularly in the Near Infrared (NIR) spectral region, and in the Visible (VIS) spectral region, for example in spectral regions that allow simulating human color vision capabilities. However, additional applications are also possible.

Background

Spectrometer devices are known to be efficient tools for obtaining information about the spectral characteristics of an object when emitting, irradiating, reflecting and/or absorbing light. Thus, the spectrometer device may help analyze the sample or other tasks interested in information about the spectral characteristics of the object.

Typically, in a spectrometer device, the spectral information is obtained via one or more detectors and one or more wavelength selective optical elements, such as one or more dispersive optical elements, filters (e.g., bandpass filters), prisms, gratings, interferometers, etc. The detector may comprise any type of photosensitive element, such as one or more single-or multi-pixel detectors, a line detector, or an array detector having a one-or two-dimensional array of pixels. Further, the spectrometer device may comprise one or more light sources. Thus, in spectroscopy, tunable light sources (e.g., lasers) and/or broadband emission light sources (e.g., halogen gas filled bulbs and/or hot filaments) are typically used. However, in addition or alternatively, other light sources, such as light emitting diodes, are also proposed for the visible spectral region.

As an example, US 2010/208261 A1 describes a device for determining at least one optical property of a sample. The apparatus comprises a tunable excitation light source for applying excitation light to the sample. The apparatus further comprises a detector for detecting detection light emitted from the sample. The excitation light source includes an array of light emitting diodes configured at least in part as a monolithic array of light emitting diodes. The monolithic light emitting diode array comprises at least three light emitting diodes, each light emitting diode having a different emission spectrum.

US 8,164,050 B2 describes a multi-channel light source assembly for downhole spectroscopy having individual light sources that generate optical signals spanning wavelengths of a spectral range. The combining component optically combines the generated signals into a combined signal, and the routing component separates the combined signal into a reference channel and a measurement channel. Control circuitry electrically coupled to the light sources modulates each of the light sources at a unique or independent frequency during operation.

Further, US 7,061,618 B2 describes an integrated spectroscopy system in which, in some examples, an integrated tunable detector using one or more fabry-perot tunable filters is provided. Other examples use integrated tunable light sources that combine one or more diodes, such as superluminescent diodes (SLEDs), with a fabry-perot tunable filter or gauge.

Furthermore, US 5,475,221A describes an optical device that uses an array of light emitting diodes controlled by a multiplexing scheme to replace conventional broadband light sources in devices such as spectrometers.

Typically, spectrometer devices are subject to various internal and external influences (such as environmental influences), which may have an impact on the results of the spectroscopic measurements. To correct and/or compensate for these effects, various calibration and/or correction methods are known. These calibration methods may be performed, for example, once or several times by the manufacturer, such as under laboratory conditions. However, a variety of online calibration techniques are also known, which may be performed by performing one or more correction and/or calibration steps between two spectral measurements or even during the measurements.

US 09360366 B1 discloses a self-referencing spectrometer that uses a shared aperture as an optical input to simultaneously automatically calibrate and measure the spectrum of a physical object. The simultaneous measurement and self-calibration capability enables it to be an accessory spectrometer on a mobile computing device without requiring off-line calibration using an external reference light source. The obtained spectral information and the captured image may be distributed over a wireless communication network by a mobile computing device.

DE 1020100113848 B4 discloses a micro-spectrometer, in particular a NIR micro-spectrometer for mobile applications in battery powered terminals, to overcome the limitations of the above-described system configuration in terms of non-miniaturization and handedness, as well as a micro-spectrometer system and a calibration method. The design of such miniaturized NIR spectrometers does not require active temperature stability. In contrast, according to the present invention, as part of the factory temperature calibration step, the spectral sensitivity function (qeλ=f (T); measured using an integrated temperature sensor) is recorded at several levels within the expected operating temperature range.

WO 2019/191698 A2 relates to a self-referencing spectrometer for simultaneously measuring background or reference spectral density and sample or other spectral density. The self-referencing spectrometer includes an interferometer optically coupled to receive an input beam and to direct the input beam along a first optical path to produce a first interference beam and to direct the input beam along a second optical path to produce a second interference beam, wherein each interference beam is produced before an output of the interferometer. The spectrometer further includes a detector optically coupled to detect the first interference signal generated from the first interference beam and the second interference signal generated from the second interference beam simultaneously, and a processor configured to process the first interference signal and the second interference signal and to utilize the second interference signal as a reference signal when processing the first interference signal.

US 20210293620 A1 discloses a spectrometer comprising an illumination device for illuminating a spectral measurement region, a detection unit for detecting electromagnetic radiation from the spectral measurement region, and a spectral element arranged in a beam path between the illumination device and the detection unit. The lighting device comprises a light emitting diode having a first center wavelength, the light emitting diode being designed to emit first electromagnetic radiation having a first spectrum, and a light emitting element for converting a first component of the first electromagnetic radiation having the first spectrum into second electromagnetic radiation having a second spectrum. The first center wavelength is 550 nm or 3000 nm, or has a value between 550 nm and 3000 nm. The first spectrum and the second spectrum have an overlap.

US 06667802 B2 discloses a method of calibrating a spectroscopic detection system. The method includes providing a plurality of packages, each of the plurality of packages containing a set of articles, wherein each set of articles has a known composition, measuring reflectance values of each set of articles and obtaining a set of reference reflectance values therefrom, normalizing the set of reference reflectance values and producing a set of normalized reference reflectance values therefrom, and storing the set of normalized reference reflectance values.

US 06717669 B2 discloses auto-calibration spectrometers and methods that measure the transmission or reflection of a sample as a function of wavelength without long-term calibration. Reflectance and transmittance spectrometers and automated calibration methods for use therewith are disclosed. The light is focused onto the sample using a lens or similar optical element that transmits light to the sample, reflects light impinging thereon, and transmits light reflected from the sample. If the light reflected from the first lens and the sample is monitored, very useful information about the response of the system over time can be obtained. Reflected light from the first lens and the sample is monitored and used to correct for system variations over time.

US 09448114 B2 discloses a spectrometer comprising a plurality of isolated optical channels comprising a plurality of isolated optical paths. The isolated optical paths reduce crosstalk between the optical paths and reduce the length of the spectrometer and improve resolution. In many embodiments, the isolated optical paths include isolated parallel optical paths that provide a significant reduction in the length of the device. In many embodiments, each isolated optical path extends from a filter in the filter array, through a lens in the lens array, through a channel in the support array, to a region of the sensor array. Each region of the sensor array includes a plurality of sensor elements, wherein a location of a sensor element corresponds to a wavelength of the received light, the wavelength being based on an angle of the light received at the location, a focal length of the lens, and a center wavelength of the filter.

US 2013/0093936 A1 discloses an energy dispersive device, spectrometer and method that can be used to evaluate the composition of a substance in the field without the need for specialized training or expensive equipment. The energy dispersive device or spectrograph may be used with a digital camera or a cell phone. The device of the invention comprises a stack of mono-or bi-dispersive diffraction gratings which are rotated about their normal, thereby generating a plurality of diffraction orders on the basis of which meaningful measurements and determinations of the qualitative or quantitative properties of a substance can be made.

EP2,818,837 A1 discloses a non-contact dental apparatus for determining the color of a tooth, which non-contact dental apparatus comprises an illumination device for illuminating the tooth to be inspected with ambient illumination light. At least one color sensor for capturing light reflected by the tooth and for performing a spectral examination thereof is creatively provided, wherein a filtering means is associated with the color sensor for at least partially separating a signal component originating from the illumination light from a signal component originating from the ambient light. An evaluation device for determining the tooth color based on a signal component originating from the illumination light is arranged downstream of the filtering device.

US 2002/0109839 A1 discloses a method of calibrating a spectroscopic detection system comprising providing a plurality of packages, each of the plurality of packages comprising a group of articles, wherein each group of articles has a known composition, measuring reflectance values of each group of articles and obtaining therefrom a set of reference reflectance values, normalizing the set of reference reflectance values and thereby producing a set of normalized reference reflectance values, and storing the set of normalized reference reflectance values.

DE 10 2014 013 848 B4 discloses a miniature spectrometer designed as a miniaturized near infrared spectrophotometer with an InGaAs detector array and an integrated temperature sensor for measuring a temperature calibration step to store information about the detector temperature, which is designed to operate with mathematical temperature compensation based on converting the current QE (T) function into a function valid for the set temperature at the time of measurement, whereby the measured spectrum can be corrected with the obtained QE (T) function and corresponds to a virtual spectrum at the measured set temperature.

US 2011/024159 A1 discloses a light generating system comprising Solid State Emitters (SSEs) and a stability control system for controlling the spectral stability of the SSEs. In a particular case, a stability control system may include a power regulator to regulate power supplied to a subset of the plurality of SSEs, a constant current circuit connected to the power regulator to provide a constant current to the subset of SSEs, a current regulation set point connected to the constant current circuit, and a controller configured to set the regulation set point based on metering data related to the status of the SSEs.

Thomas Tetzlaff et al, in 2018, 4, 15, international conference on microelectronics and microsystems, thermal, mechanical and multiple physical field simulations and experiments (EUROSIME), IEEE published Hardware implementation of LED forward voltage measurement for junction temperature estimation [ LED forward voltage measurement hardware implementation for junction temperature estimation ], describe that LED junction overheating can significantly reduce LED lifetime. The color and light intensity typically vary with temperature, resulting in a decrease in the quality of the light. Therefore, thermal management is necessary to prevent overheating. Even very short temperature peaks can affect the lifetime and light quality of the LED.

Despite the advantages of the known methods and devices, there are still technical challenges in the fields of spectroscopy and spectroscopic devices, in particular in the near infrared range. Thus, in particular, calibration techniques to correct for various effects are needed, especially techniques to correct for these effects online in the field (i.e., where spectroscopic measurements are taken). In particular, the temperature is known to have a significant impact on the result and accuracy of the spectroscopic measurements. Temperature changes may occur due to external influences, such as changes in ambient temperature. Additionally or alternatively, temperature variations may occur due to internal influences such as currents and resistances within the spectroscopic device, e.g. due to electrical power dissipation. These temperature changes may occur in a short period of time and/or may occur in the form of long term drift. Further, it must be considered that temperature changes do not necessarily occur in a global range and/or do not necessarily occur when the entire spectrometer device is in thermal equilibrium. As a result, local temperature variations may occur, particularly at locations that are difficult to monitor, such as locations within the spectrometer device and/or interfaces within components of the spectrometer device (e.g., at semiconductor interfaces). Furthermore, the temperature dependence of the system may change. For example, even if the temperature is kept constant, the system may exhibit different properties over time (e.g., due to degradation, aging, or changes in the optical or electrical interface due to frequent use).

Problems to be solved

It is therefore desirable to provide a method and an apparatus that at least partly solve the above technical challenges and at least substantially avoid the drawbacks of the known methods and apparatus. In particular, it is an object of the present invention to provide a spectrometer device and a method of obtaining spectroscopic information about at least one object, which spectrometer device and method are capable of correcting external and/or internal influences, such as temperature variations.

Disclosure of Invention

This problem is solved by a method of operating a spectrometer device for obtaining spectroscopic information about at least one object, a calibration method of compiling a set of correction information items, a spectrometer device for obtaining spectroscopic information about at least one object, a computer program, a computer readable storage medium and a non-transitory computer readable medium. Advantageous embodiments that can be realized in a separate manner or in any arbitrary combination are listed in the dependent claims and throughout the description.

In a first aspect, a method of operating a spectrometer device for obtaining spectroscopic information about at least one object is disclosed. The method comprises the following steps that may be performed in a given order. However, different sequences are also possible. In particular, one, more than one or even all method steps may be performed once or repeatedly. Further, the method steps may be performed sequentially or, alternatively, one or more method steps may be performed in a timely overlapping manner or even in parallel and/or in a combined manner. The method may further comprise additional method steps not listed.

As used herein, the term "spectrometer device" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, an optical device configured for acquiring at least one item of spectral information about at least one object. In particular, the at least one item of spectral information may be at least one optical property or an optically measurable property that is determined as a function of wavelength for one or more different wavelengths. More particularly, the optical or optically measurable property and the at least one item of spectral information may relate to at least one property characterizing at least one of transmission, absorption, reflection and emission of the at least one object itself or after external light irradiation. At least one optical characteristic may be determined for one or more wavelengths. The spectrometer device may in particular form a device capable of recording signal intensities with respect to corresponding wavelengths of the spectrum or a partition thereof, such as a wavelength interval, wherein the signal intensities may in particular be provided as electrical signals which may be used for further evaluation.

As an example, the spectrometer device may be or may comprise a device allowing measuring at least one spectrum (e.g. for measuring spectral flux, in particular as a function of wavelength or detection wavelength). As an example, the spectrum may be acquired in absolute units or relative units (e.g., relative to at least one reference measurement). Thus, as an example, the acquisition of the at least one spectrum may be performed in particular for a measurement of the spectral flux (in W/nm) or a measurement of the spectrum (in 1) with respect to at least one reference material, which may describe a property of the material (e.g. the change of reflectivity with wavelength). Additionally or alternatively, the reference measurement may be based on a reference light source, an optical reference path, a calculated reference signal (e.g., a calculated reference signal from the literature), and/or a reference device.

In particular, the at least one spectrometer device may be a diffuse reflectance spectrometer device configured to obtain spectral information from light diffusely reflected by the at least one object (e.g., the at least one sample). Additionally or alternatively, the at least one spectrometer device may be or may comprise an absorption spectrometer and/or a transmission spectrometer. In particular, measuring the spectrum with the spectrometer device may comprise measuring the absorption in a transmissive configuration. In particular, the spectrometer device may be configured for measuring absorption in a transmissive configuration. However, as outlined above, other types of spectrometer devices are also possible.

In particular and as will be outlined in further detail below, the at least one spectrometer device may comprise at least one light source, which may be, as an example, at least one of a tunable light source, a light source having at least one fixed emission wavelength, and a broadband light source. As will be outlined in further detail below, the spectrometer device further comprises at least one detector device configured for detecting light, such as at least one of light transmitted, reflected or emitted from the at least one object. As will be outlined in further detail below, the spectrometer device may further comprise at least one wavelength selective element, such as at least one of a grating, a prism and a filter (e.g. a variable length filter with varying transmission characteristics over its lateral extension). The wavelength selective element may be used to separate the incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector, such as a detector having a detector array as described in more detail below.

The spectrometer device may in particular be a portable spectrometer device. As used herein, the term "portable" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, the property that at least one object is moved by human force, such as by a single user. In particular, the weight of the object characterized by the term "portable" may not exceed 10 kg, in particular not exceed 5kg, more in particular not exceed 1kg or even not exceed 500 g. Additionally or alternatively, the size of the object characterized by the term "portable" may be such that the object extends no more than 0.3 m to any dimension, in particular no more than 0.2 m to any dimension. In particular, the volume of the object may not exceed 0.03 m3, in particular not exceed 0.01 m3, more in particular not exceed 0.001 m3 or even not exceed 500 mm ³. In particular, as an example, the portable spectrometer device may have dimensions of, for example, 10mm ×10mm ×5mm. In particular, the portable spectrometer device may be part of, or may be attachable to, a mobile device, such as a notebook computer, a tablet computer, a cell phone (such as a smartphone), a smart watch, and/or a wearable computer (also referred to as a "wearable device", e.g., a body worn computer (such as a wristband or watch)). In particular, the weight of the spectrometer device, in particular the portable spectrometer device, may be in the range of 1g to 100 g, more particularly in the range of 1g to 10 g.

As used herein, the term "spectroscopic information" (also referred to as "spectroscopic information" or "item of spectroscopic information") is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, for example, an information item about at least one object and/or radiation emitted by at least one object, which characterizes at least one optical property of the object, more particularly characterizes at least one information item, for example, at least one of a transmission, an absorption, a reflection and an emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one item of intensity information, e.g. information about the intensity of light transmitted, absorbed, reflected or emitted by the object, e.g. as a function of wavelength or wavelength sub-ranges within one or more wavelengths (e.g. within a wavelength range). In particular, the intensity information may correspond to or be derived from a signal intensity (in particular an electrical signal) recorded by the spectrometer device in relation to the wavelength or wavelength range of the spectrum.

The spectrometer device may in particular be configured for acquiring at least one spectrum or at least a part of a spectrum of detection light propagating from the object to the spectrometer. The spectrum may describe the units of radiation measurement of the spectral flux, for example given in watts per nanometer (W/nm), or in other units, for example as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, for example, in the NIR spectral range, in a particular band. The spectrum may contain one or more optical variables that vary with wavelength, such as power spectral density, electrical signals obtained by optical measurements, and the like. As an example, a spectrum may indicate a power spectral density and/or a spectral flux of an object (e.g., a sample), such as a transmittance and/or a reflectance of the object (particularly a sample), e.g., relative to a reference sample.

As an example, the spectrum may comprise at least one measurable optical variable or property of the detection light and/or the object, which optical variable or property is in particular a function of the illumination light and/or the detection light. As an example, the at least one measurable optical variable or property may include at least one radiation metric, such as at least one of spectral density, power spectral density, spectral flux, radiant intensity, spectral radiant intensity, irradiance, spectral irradiance. Specifically, as an example, a spectrometer device (specifically a detector) may measure irradiance in watts per square meter (W/m ²), more specifically spectral irradiance in watts per square meter per nanometer (W/m ²/nm). Based on the measured quantities, the spectral flux in watts per nanometer (W/nm) and/or the radiant flux in watts (W) may be determined (e.g., calculated) by taking into account the area of the detector.

As used herein, the term "object" is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any body selected from the group consisting of living and inanimate objects. Thus, as an example, at least one object may comprise one or more items and/or one or more portions of items, wherein at least one item or at least one portion thereof may comprise at least one component that may provide a spectrum suitable for investigation. Additionally or alternatively, the subject may be or may include one or more living beings and/or one or more portions thereof, such as one or more body parts of a human (e.g., user) and/or animal. In particular, the object may comprise at least one sample, which may be wholly or partly analyzed by spectroscopic methods. By way of example, the object may be or may include at least one of human or animal skin, edibles such as fruit, plastics and textiles.

The method comprises the following steps:

i. illuminating the object with illumination light generated by at least one light source of the spectrometer device, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode;

Determining at least one actual value of at least one operating parameter of the spectrometer device by using at least one drive unit of the spectrometer device, the drive unit being configured for electrically driving the light source;

Detecting detected light from the object by using at least one detector of the spectrometer device and generating at least one detector signal, and

Evaluating the detector signal by using at least one evaluation unit of the spectrometer device, thereby obtaining therefrom spectroscopic information about the object, the evaluation unit being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of the at least one operating parameter, and for taking into account the selected correction information item for obtaining the spectroscopic information.

In step i. the object is illuminated with illumination light generated by at least one light source of the spectrometer device, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode.

As further used herein, the term "light" as used herein is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, electromagnetic radiation in one or more of the infrared, visible and ultraviolet spectral ranges. In this context, the term "ultraviolet spectral range" generally refers to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably 100 nm to 380 nm. Further, the term "visible spectral range" generally refers to the spectral range of 380 nm to 760 nm, in part according to standard ISO-21348, an active version of the date of this document. The term "infrared spectral range" (IR) generally refers to electromagnetic radiation of 760 nm to 1000 μm, with the range 760 nm to 1.5 μm generally referred to as the "near infrared spectral range" (NIR), while the range 1.5 μm to 15 μm is referred to as the "mid-infrared spectral range" (MidIR), and the range 15 μm to 1000 μm is referred to as the "far infrared spectral range" (FIR). Preferably, the light used for the typical purposes of the present invention is light in the Infrared (IR) spectral range, more preferably in the Near Infrared (NIR) and/or mid infrared spectral range (MidIR), especially light having a wavelength of 1 μm to 5 μm, preferably 1 μm to 3 μm. This is because the material properties of many objects or properties concerning chemical composition can be derived from the near infrared spectrum. However, it should be noted that spectral analysis of other spectral ranges is also applicable and within the scope of the present invention.

Thus, as used herein, the term "light source" (also referred to as an "illumination source") is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device configured to generate or provide light in the sense of the definition above. The light source may in particular be or may comprise at least one electric light source, such as an electrically driven light source.

As will be outlined in further detail below, the light source may generally be implemented in various ways. Thus, the light source may be, for example, a part of the spectrometer device in a housing of the spectrometer device. Alternatively or additionally, however, the at least one light source may also be arranged outside the housing, for example as a separate light source. The light source may be arranged separately from the object and illuminate the object from a distance.

In spectroscopy, various light sources and light paths are distinguished. In the context of the present invention, the nomenclature used first refers to the light propagating from the light source to the object as "illumination light" (illuminating light or illumination light). Second, light propagating from the object to the detector is referred to as "detection light". The detection light may comprise at least one of illumination light reflected by the object, illumination light scattered by the object, illumination light transmitted by the object, luminescence light generated by the object (e.g. phosphorescence or fluorescence generated by the object after optical, electrical or acoustic excitation of the object by the illumination light, etc.). Thus, the detection light may be generated directly or indirectly by illumination of the object by the illumination light.

Further, as will be outlined in detail below, within the light source itself, a distinction can be made between various light sources (such as primary and secondary light sources). Thus, as will be outlined in further detail below, the "primary light" (also referred to as "pump light") may be generated by a primary light source, such as at least one light emitting diode, and may then be converted into "secondary light", such as by using light conversion (e.g. by one or more phosphor materials). The illumination light may be or may comprise at least one of primary light or a part thereof, secondary light or a part thereof, or a mixture of primary light and secondary light.

Thus, as used herein, the term "illumination" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of exposing at least one element to light.

As outlined above, the light source comprises at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, wherein in particular the illumination light may be a combination of the primary light and light generated by light converting of the luminescent material or light generated by light converting of the luminescent material (also referred to as secondary light).

As used herein, the term "light emitting diode" or simply "LED" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, an optoelectronic semiconductor device which is capable of emitting light when a current flows through the device. The optoelectronic semiconductor device may be configured to generate light as a result of various physical processes including one or more of spontaneous radiation, induced radiation, decay of metastable excited states, and the like. Thus, by way of example, the light emitting diode may comprise one or more of a light emitting diode based on spontaneous emission of light (in particular an organic light emitting diode), a super-emission based light emitting diode (sLED), or a Laser Diode (LD). In the following, the abbreviation "LED" will be used for any type of light emitting diode without shrinking the possible embodiments of the light emitting diode to any of the aforementioned physical principles or arrangements. In particular, the LED may comprise at least two layers of semiconductor material, wherein light may be generated at least one interface between the at least two layers of semiconductor material, in particular due to recombination of positive and negative charges (e.g. electron-hole recombination). The at least two layers of semiconductor material may have different electrical properties, such as at least one of the layers being an n-doped semiconductor material and at least one of the layers being a p-doped semiconductor material. Thus, as an example, the LED may comprise at least one pn junction and/or at least one pin structure. However, it should be noted that other device configurations are possible. The at least one semiconductor material may in particular be or may comprise at least one inorganic semiconductor material. However, it should be noted that organic semiconductor materials may additionally or alternatively be used.

Generally, as will be outlined in further detail below, the LEDs may convert a current into light, in particular into primary light, more in particular into blue primary light. Thus, the LED may in particular be a blue LED. The LEDs may be configured to generate primary light, also referred to as "pump light". Thus, the LED may also be referred to as a "pump LED". The LEDs may in particular comprise at least one LED chip and/or at least one LED die. Accordingly, the semiconductor element of the LED may include an LED bare chip.

Various types of LEDs suitable for generating primary light are known to the skilled person and can also be applied in the present invention. In particular, a p-n junction diode may be used. As an example, one or more LEDs selected from the group of indium gallium nitride (InGaN) based LEDs, gaN based LEDs, inGaN/GaN alloy based LEDs, or combinations thereof, and/or other LEDs may be used. Additionally or alternatively, quantum well LEDs, such as one or more InGaN-based quantum well LEDs, may also be used. Additionally or alternatively, super-radiating LEDs (slds) and/or quantum cascade lasers may be used.

As used herein, the term "light emitting" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process in which a substance spontaneously radiates light that is not caused by heat. In particular, luminescence may refer to cold body radiation. More specifically, luminescence may be initiated or excited by irradiation of light, in which case luminescence is also referred to as "photoluminescence". In the context of the present invention, the properties of a material capable of emitting light are referred to by the adjective "luminescent". The at least one luminescent material may in particular be a photoluminescent material, i.e. a material that is capable of emitting light after absorption of photons or excitation light. In particular, the luminescent material may have a positive stokes shift, which may generally refer to the fact that the secondary light is red shifted with respect to the primary light.

Thus, the at least one luminescent material may form at least one converter (also referred to as a light converter) that converts the primary light into secondary light having different spectral properties than the primary light. In particular, the spectral width of the secondary light may be larger than the spectral width of the primary light and/or the emission center of the secondary light may be shifted (in particular red shifted) compared to the primary light. In particular, the at least one luminescent material may have an absorption in the ultraviolet and/or blue spectral range and an emission in the near infrared and/or infrared spectral range. Thus, in general, the luminescent material or the converter may form at least one component of the phosphor LED that concentrates primary light or pump light, in particular in the blue spectral range, into light with a longer wavelength, for example in the near infrared or infrared spectral range.

Various types of conversion and/or luminescence are known and may be used in the context of the present invention. Thus, in particular, the conversion may occur via a dipole-allowed transition in the luminescent material (also referred to as fluorescence) and/or via a dipole-forbidden, thus longer-lived transition in the luminescent material (also commonly referred to as phosphorescence).

The luminescent material may thus particularly form at least one converter or light converter. The luminescent material may form at least one of a conversion plate, a luminescent coating (in particular a fluorescent coating) on the LED, and a phosphor coating on the LED. By way of example, the luminescent material may comprise one or more of cerium doped YAG (YAG: ce ³⁺ or Y ₃Al₅O₁₂:Ce³⁺), rare earth doped Sialon, copper aluminum co-doped zinc sulfide (ZnS: cu, al).

The LED and the luminescent material together may form a so-called "phosphor LED". Thus, as used herein, the term "phosphor light emitting diode" or simply "phosphor LED" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a combination of at least one light emitting diode configured for generating primary light or pump light and at least one luminescent material (also referred to as "phosphor") configured for light conversion of the primary light generated by the light emitting diode. Phosphor LEDs may form a packaged LED light source comprising an LED die (e.g. a blue LED emitting blue pump light) and a phosphor, for example, fully or partially coating the LED, and being configured for converting primary light or blue light into light having different spectral characteristics (in particular into near infrared light), as an example. In general, phosphor LEDs may be packaged in a housing or may be unpackaged. The LED and the at least one luminescent material for light conversion of the primary light generated by the light emitting diode may thus be accommodated in particular in a common housing. Alternatively, however, the LEDs may also be unpackaged or bare LEDs, which may be fully or partially covered with luminescent material, such as by providing one or more layers of luminescent material on the LED die. Phosphor LEDs may generally themselves form the emitter or light source.

In a light source, in particular a phosphor LED, at least one luminescent material may in particular be positioned relative to the light emitting diode such that heat transfer from the light emitting diode to the luminescent material is possible. More specifically, the luminescent material may be positioned such that heat transfer may be by one or both of heat radiation and heat conduction (more preferably by heat conduction). Thus, as an example, the luminescent material may be in thermal and/or physical contact with the light emitting diode. As an example, the luminescent material may form one or more coatings or layers in contact with or in close proximity to the light emitting diode, such as in contact with one or more of the semiconductor materials of the light emitting diode. Thus, in general, the temperature of the luminescent material and the temperature of the light emitting diode may be coupled.

The at least one luminescent material may in particular form at least one layer. In general, various alternatives for positioning the luminescent material relative to the light emitting diode are possible, which may be used alone or in combination. First, the luminescent material (e.g., at least one layer of luminescent material, such as a phosphor) may be positioned directly on the light emitting diode, also referred to as "direct attachment", e.g., with no material between the LED and the luminescent material, or with one or more transparent materials between the two, such as with one or more transparent materials (especially transparent to primary light) between the LED and the luminescent material. Thus, as an example, a coating of luminescent material may be placed directly or indirectly on the LED. Additionally or alternatively, as an example, the luminescent material may form at least one conversion body, such as at least one conversion disc, which conversion body may be placed on top of the LED, for example by attaching the conversion body to the LED with an adhesive. Additionally or alternatively, the luminescent material may also be placed in a remote manner, such that the primary light from the LED has to pass through an intermediate light path before reaching the luminescent material. Such placement may also be referred to as "remote placement" or "remote phosphor. Also, as an example, the remotely located luminescent material may form a solid or conversion body, such as a disk or conversion disk. Further, in case of remote placement, the luminescent material may also be a coating. In particular, light-transmitting objects (e.g. thin glass substrates, module windows) may be coated with phosphors, which objects comprise and/or are made of glass or plastic. Alternatively, the reflective surface may be coated with a phosphor. This may be a flat or rough mirror, which may comprise and/or be made of a high reflectivity material substrate (e.g. silicon), or a flat or rough surface (e.g. glass or plastic) coated with gold, silver, aluminium or chromium. In the intermediate optical path, one or more optical elements, such as one or more of lenses, prisms, gratings, mirrors, apertures, or combinations thereof, may be placed. Thus, in particular, an optical system with imaging properties may be placed in the intermediate light path, between the LED and the luminescent material. Thus, as an example, the primary light may be focused or concentrated onto the conversion body.

In step ii, at least one actual value of at least one operating parameter of the spectrometer device is determined by using at least one drive unit of the spectrometer device, the drive unit being configured for electrically driving the light source.

As used herein, the term "drive" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of providing one or both of at least one control parameter and/or electrical power to another device. Thus, as used herein, the term "drive unit" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device or combination of devices configured to provide one or both of at least one control parameter and/or electrical power to another device (e.g., to at least one light source in this example).

For example, the drive unit may in particular be configured for at least one of measuring and controlling one or more electrical parameters of the electrical power provided to the light source (in particular to the at least one light emitting diode). As an example, the driving unit may be configured for providing a current to the LED, in particular for controlling the current through the LED. Wherein, as an example, the driving unit may be configured to adapt and measure the voltage provided to the LED, which is required to achieve a specific current through the LED. The drive unit may comprise a measurement unit, which may in particular comprise one or more of a current source, a voltage source, a current measurement device (such as an ammeter), a voltage measurement device (such as a voltmeter), a power measurement device, a thermometer. In particular, the driving unit may comprise at least one current source for providing at least one predetermined current to the LED, wherein the current source may in particular be configured for adjusting or controlling the voltage applied to the LED in order to generate the predetermined current. As an example, the drive unit may comprise one or more electrical components (such as an integrated circuit) for driving the light source. The drive unit may be fully or partially integrated into the light source or may be separate from the light source.

The drive unit may further determine at least one operating parameter of the spectrometer device, in particular by providing and/or measuring. As used herein, the term "operating parameter" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, factors and/or conditions that directly and/or indirectly affect the operation process and/or the function of the device (in particular the spectrometer device), in particular the function of the spectrometer device in determining at least one item of spectroscopic information about the object. The at least one control parameter and/or the electrical power provided by the drive unit may be an operating parameter. Alternatively or additionally, at least one external factor of the environment in which the spectrometer device operates (such as an environmental condition, in particular an environmental temperature) may be an operating parameter. Additional operating parameters may be present, particularly as described elsewhere herein.

In step iii, the detection light from the object is detected by using at least one detector of the spectrometer device and at least one detector signal is generated.

As further outlined above, the spectrometer device comprises at least one detector configured for detecting detection light, such as diffuse reflected light, from the object. As used herein, the verb "detect" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of at least one operation of qualitatively and/or quantitatively determining, measuring and monitoring at least one parameter, such as at least one of a physical parameter, a chemical parameter and a biological parameter. In particular, the physical parameter may be or may comprise an electrical parameter. Thus, the term "detector" as used herein is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device configured for detecting, i.e. qualitatively and/or quantitatively determining, measuring and monitoring at least one of the at least one parameter, such as at least one of the physical parameter, the chemical parameter and the biological parameter. The detector may be configured for generating at least one detector signal, more particularly at least one electrical detector signal, such as an analog and/or digital detector signal, the detector signal providing information about at least one parameter measured by the detector. The detector signal may be provided directly or indirectly by the detector to the evaluation unit, so that the detector and the evaluation unit may be connected directly or indirectly. The detector signal may be used as a "raw" detector signal and/or may be processed or pre-processed (e.g., by filtering, etc.) prior to further use. Thus, the detector may comprise at least one processing device and/or at least one preprocessing device, such as at least one of an amplifier, an analog/digital converter, an electrical filter and a fourier transform.

In this example, the detector is configured to detect light propagating from the object to the spectrometer device or more specifically to the detector of the spectrometer device, which light is referred to as "detected light" according to the above nomenclature. Thus, in particular, the detector may be or may comprise at least one optical detector. The optical detector may be configured for determining at least one optical parameter, such as the intensity and/or power of light irradiating at least one sensitive area of the detector. More specifically, the optical detector may comprise at least one photosensitive element and/or at least one optical sensor, such as at least one of a photodiode, a photocell, a photoresistor, a phototransistor, a thermopile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier, and a bolometer. Thus, the detector may be configured for generating at least one detector signal, more particularly at least one electrical detector signal in the above sense, which provides information about at least one optical parameter, such as the power and/or intensity of the light illuminating the detector or a sensitive area of the detector.

The detector may comprise a single optical sensor or area or a plurality of optical sensors or areas. In particular, the detector may be or may comprise at least one detector array (more particularly an array of light sensitive elements), as will be outlined in further detail below. Each light sensitive element may comprise at least a light sensitive area, which may be adapted to generate an electrical signal depending on the intensity of the incident light, wherein the electrical signal may in particular be provided to an evaluation unit, as will be outlined in further detail below.

The photosensitive area comprised by each optical sensor may in particular be a single, uniform photosensitive area configured to receive incident light impinging on the respective optical sensor. However, other arrangements of the optically sensitive elements are also conceivable.

The array of optical sensing elements may be designed to generate detector signals, preferably electronic signals, associated with the intensity of incident light impinging on the respective optical sensing elements. The detector signal may be an analog signal and/or a digital signal. Accordingly, the electronic signals of adjacent pixelated sensors may be generated simultaneously or in a temporally continuous manner. For example, during a row scan or line scan, a series of electrical signals corresponding to a series of individual optical sensing elements arranged in a row may be generated. In addition, these individual optical sensitive elements may preferably be active pixel sensors, which may be adapted to amplify the electronic signals before they are provided to the evaluation unit. For this purpose, the detector may comprise one or more signal processing devices, such as one or more filters and/or analog-to-digital converters, for processing and/or preprocessing the electronic signals.

Where the detector comprises an array of optically sensitive elements, the detector may be selected from any known pixel sensor, in particular from a pixelated organic camera element, preferably a pixelated organic camera chip, or from a pixelated inorganic camera element, preferably a pixelated inorganic camera chip, more preferably from a CCD chip or CMOS chip, as examples, of the type commonly used in the types of cameras currently available. Alternatively, the detector may generally be or include a photoconductor, particularly an inorganic photoconductor, particularly PbS, pbSe, ge, inGaAs, extended InGaAs, inSb, or HgCdTe. As a further alternative, the detector may comprise at least one of a pyroelectric element, a bolometer element or a thermopile detector element. Thus, a camera chip having a matrix of 1×n pixels or m×n pixels may be used herein, where, as an example, M may be <10, and N may be in the range from 1 to 50, preferably from 2 to 20, more preferably from 5 to 10. Further, a monochrome camera element, preferably a monochrome camera chip, may be used, wherein the monochrome camera element may be selected differently for each optically sensitive element, in particular according to a wavelength that varies over a range of optical sensors.

Thus, the array may be adapted to provide a plurality of electrical signals, which may be generated by the photosensitive areas of the optically sensitive elements comprised by the array. The electrical signals provided by the array of spectrometer devices may be forwarded to an evaluation unit.

In step iv, the detector signal is evaluated by using at least one evaluation unit of the spectrometer device, from which spectroscopic information about the object is derived, the evaluation unit being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of the at least one operating parameter, and for taking into account the selected correction information item for deriving the spectroscopic information.

As further described above, the spectrometer device comprises at least one evaluation unit for evaluating at least one detector signal generated by the detector and for deriving spectroscopic information about the object from the detector signal. As used herein, the term "evaluate" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of processing at least one first information item in order to thereby generate at least one second information item. Thus, as used herein, the term "evaluation unit" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device or combination of devices configured to evaluate or process at least one first information item in order to generate at least one second information item thereof. Thus, in particular, the evaluation unit may be configured for processing the at least one input signal and generating at least one output signal thereof. As an example, the at least one input signal may comprise at least one detector signal provided directly or indirectly by at least one detector, and additionally at least one signal provided directly or indirectly by a drive unit.

By way of example, the evaluation unit may be or may comprise one or more integrated circuits, such as one or more Application Specific Integrated Circuits (ASICs), and/or one or more data processing devices, such as one or more of a computer, a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), preferably one or more microcomputers and/or microcontrollers. Additional components may be included, such as one or more preprocessing devices and/or data acquisition devices, such as one or more devices for receiving and/or preprocessing detector signals, such as one or more AD converters and/or one or more filters. Further, the evaluation unit may comprise one or more data storage devices. Further, the evaluation unit may comprise one or more interfaces, such as one or more wireless interfaces and/or one or more wired interfaces.

The at least one evaluation unit may be adapted to execute at least one computer program, such as at least one computer program that performs or supports the information item generating step. As an example, one or more algorithms may be implemented that, by using the at least one detector signal and the at least one operating parameter as input variables, may perform a predetermined transformation for deriving spectroscopic information about the object, such as for deriving a corrected spectrum and/or for deriving at least one item of spectroscopic information describing at least one characteristic of the object. The at least one further parameter may be considered as an input variable and/or included by an input variable. The evaluation unit may be configured to take into account at least one further parameter and/or variable.

For this purpose, the evaluation unit may particularly comprise at least one data processing device (also referred to as a processor, in particular an electronic data processing device) which may be designed to generate the desired information by evaluating the detector signal and/or the at least one operating parameter. The evaluation unit may be configured to take into account at least one further parameter and/or variable. The evaluation unit may use any procedure to generate the desired information, such as by calculating and/or using at least one stored and/or known relationship.

The evaluation unit may in particular be configured for performing at least one Digital Signal Processing (DSP) technique, in particular at least one fourier transformation, on the primary detector signal or any secondary detector signal derived therefrom. Additionally or alternatively, the evaluation unit may be configured to perform one or more further digital signal processing techniques, such as windowing, filtering, goertzel algorithms, cross-correlation and auto-correlation, on the primary detector signal or any secondary detector signal derived therefrom. The relation may be influenced in addition to the detector signal and the at least one operating parameter. The relationship may be determined or determinable by empirical, analytical or semi-empirical methods. As an example, the relationship may comprise at least one of a model or a calibration curve, at least one set of calibration curves, at least one function, or a combination of the mentioned possibilities. The one or more calibration curves may be stored, for example, in the form of a set of values and their associated function values, for example, in a data storage device and/or table. Alternatively or additionally, however, the at least one calibration curve may also be stored, for example, in parameterized form and/or as a function equation. A separate relationship for processing the detector signals into information items may be used. Alternatively, at least one combination for processing the detector signals is possible. Various possibilities are conceivable and these may also be combined.

As outlined above, the evaluation unit may in particular be configured for selecting at least one correction information item from a predetermined set of correction information items, for example by software programming. Thus, as an example, the evaluation unit may be configured for determining a spectrum, such as a spectrum indicative of a photometric parameter or a radiation parameter as a function of wavelength, from at least one detector signal provided by the detector. Alternatively or additionally, the evaluation may be configured for selecting the at least one correction information item by taking into account at least one operating parameter. The at least one correction information item selected may depend on at least one operating parameter, in particular at least two different correction information items are selected for at least two different operating parameters. The spectrum may be corrected by applying at least one correction function (e.g., a correction factor, such as a wavelength dependent correction factor of the correction function) to the spectrum, thereby generating a corrected spectrum. The correction information item may be and/or may comprise and/or may refer to at least one correction function, e.g. a correction factor, e.g. a wavelength dependent correction factor of the correction function. Thus, as an example, the correction factor may in particular be or may comprise at least one correction factor that is a function of at least the wavelength of the detection light and at least one operating parameter. As an example, the detector signal may provide a signal as a function of the wavelength of the detected light, wherein each function value of the detector signal may be multiplied by a corresponding correction factor determined by the at least one operating parameter by using the correction factor.

As an example, the detector signal may comprise a plurality of detector signals that are at least a function of the wavelength of the detected light, and optionally also a function of time, in particular for time-dependent detector signals. The plurality of detector signals may form a spectrum including an option of digital or analog spectrum. Thus, as an example, each detector signal may summarize information from a predetermined spectral range defined by the spectral resolution of the detector. As will be outlined in further detail below, the detector may comprise a plurality of photosensitive elements, each photosensitive element being sensitive in a different spectral range and/or being exposed to a different part of the spectrum of the detection light. All detector signals of the photosensitive element may form the detector signal or, as an example, define the spectral information, a part thereof or a precursor thereof as a whole. Since the spectral range of the sensitivity of each light sensitive element may be known, the intensity of the detection light as a function of the detection wavelength may be derived from this detector signal by combining the data pairs of the light sensitive elements, each data pair comprising the respective signal and the sensitivity wavelength of the light sensitive element. Each of the respective signals of the photosensitive elements may be corrected by using a corresponding correction factor of the respective wavelength, wherein the correction factor as a function of the at least one operating parameter is provided by the evaluation unit. However, it should be noted that other ways of generating spectral information are possible, such as by sequentially exposing the same detector to different spectral portions of the detection light, for example by using a scannable wavelength selective element. Correction of these sequentially determined spectra may be performed in a similar manner by using correction factors as a function of wavelength and by correcting the spectra accordingly.

Thus, as generally used herein, the term "correction" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a modification or a process of modifying at least one item of interest in accordance with one or more information items indicative of parameters known to have an effect on the item of interest. Thus, the measured spectrum may be corrected in such a way that the corrected spectrum corresponds to a spectrum under precisely known conditions or standardized conditions (e.g. at a specific temperature and/or under predetermined operating parameters). Thus, the corrected spectrum may be compared to a reference spectrum determined under precisely known or standardized conditions (e.g., at a particular temperature and/or under predetermined operating parameters). As an example, the correction may comprise modifying the measured spectrum comprised by the detector signal to correspond to standardized conditions, such as under predetermined operating parameters required for driving the light emitting diode, in particular under predetermined operating parameters. Thus, step iv. May comprise a correction in which the measured spectrum derived from the detector signal may be modified to correspond to the corrected spectrum, in particular a spectrum which may have been obtained under predetermined standard conditions (e.g. under predetermined operating parameters). The normalization conditions may be defined by using appropriate conditions, for example by using room temperature as the predetermined temperature and/or using a specific measurable quantity, in particular a specific forward voltage, required to drive the light emitting diode measured at room temperature at a predetermined forward current. However, other standard conditions are also possible.

To determine the correction factor, in particular the correction function, one or more calibration measurements may be performed, in particular by performing a calibration method that compiles a set of correction information items for the method as described elsewhere herein. Thus, the correction may be based on one or more calibration measurements. As an example, these calibration measurements may determine at least one detector signal as a function of an operating parameter (and further, optionally, also as a function of a detection wavelength). As outlined above, at least one condition may be determined as a standard condition, e.g. at least one specific operating parameter required for driving the light emitting diode. As an example, specific operating parameters may be predetermined to define standard conditions for each wavelength, for example. By determining the ratio between the detector signal measured for any operating parameter and the detector signal measured for a particular operating parameter, the correction factor exemplarily provided by the correction information item can be determined for each wavelength. Any operating parameter may be known, in particular from at least one measurement via at least one sensor. Thus, in particular, in case any operating parameter provided by the drive unit indicates that any operating parameter deviates from the standard, the correction factor may be selected such that the corrected detector signal corresponds to a detector signal that would have been measured if the conditions were the same as the predetermined standard conditions (e.g. room temperature). Additionally or alternatively, the temperature may be varied in a targeted manner, such as to set or adjust the temperature to two or more target temperatures. In particular, the standard conditions may comprise a set of two or more predefined target temperatures and/or a set of corresponding operating parameters. For each of these temperatures, the at least one operating parameter may be measured. The correction factor may then be determined as described above. As used herein, the term "predetermined set of correction information items" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a collection of a plurality of correction information items given for at least two different predetermined operating parameter values of the same operating parameter.

In particular, the correction may be based on a model describing a functional relationship between the spectral characteristics of the light source and at least one operating parameter, in particular the forward voltage and/or the temperature. The model may be an empirical model, a semi-empirical model, or a theoretical model. Thus, as an example, and as will be described in further detail below, the effect of a change in an operating parameter on a measured spectrum (particularly compared to a reference spectrum) may be measured in one or more calibration measurements, for example by using a standardized or reference object and measuring a spectrum that varies with the operating parameter. The correction may then be determined, for example, by using the particular operating parameter as a standard, and correcting the spectrum determined for the other operating parameter to correspond to the normalized spectrum. At least one model describing the functional relationship between the modification of the spectroscopic and/or spectroscopic information about the object and the operating parameter and/or describing the functional relationship between the correction and the operating parameter required to correct the spectroscopic and/or spectroscopic information about the object may be predetermined and may be stored in at least one data storage device of the spectrometer device, as an example.

The detector may provide at least one raw detector signal in step iii, wherein in step iv the evaluation unit corrects the raw detector signal to at least one corrected detector signal by using the at least one selected correction information item.

As further outlined above, the evaluation unit may be configured for correcting the at least one detector signal by using a correction. Thus, as an example, the evaluation unit may be configured, for example by software programming, for directly or indirectly transforming the detector signal, in particular the raw detector signal (e.g. the spectrum resulting therefrom), into a corrected detector signal, for example into a corrected spectrum. As an example and as further outlined above, the correction may in particular comprise multiplying at least one detector signal (i.e. the "original" detector signal or a secondary detector signal derived therefrom, e.g. a spectrum generated by using the detector signal) with at least one correction factor. Thereby, a correction of the spectrum can be performed, which takes the operating parameter into account as correction parameter. The evaluation unit may in particular be configured for deriving the spectroscopic information using the corrected detector signal.

As an example, the detector may be configured for generating the detector signal for at least one spectral range (in particular for at least two different spectral ranges) of the light from the object, in particular at least one of sequential generation and simultaneous generation. For example, as outlined above, the detector may comprise an array of photosensitive elements, wherein each photosensitive element may be sensitive in a different spectral range and/or may be exposed to light in a different spectral range. The evaluation unit may be configured for individually correcting the detector signals in different spectral ranges and for combining the individually corrected detector signals to obtain the spectroscopic information. Thus, the individually corrected detector signals may be combined, for example, to generate a corrected spectrum.

Thus, in general, the detector may comprise an array of photosensitive elements, wherein each photosensitive element may be configured for generating at least one detector signal. The evaluation unit may generally be configured for individually correcting each detector signal and for combining the detector signals to obtain the spectroscopic information. Thus, in particular, in case each light sensitive element is sensitive in different spectral ranges and/or is exposed to light in different spectral ranges, e.g. by detecting one or more suitable filters in the beam path of the light, the influence of the operating parameter as correction parameter may be corrected for each light sensitive element individually.

As outlined above, the light sensitive element may be sensitive to different spectral ranges of the light from the object. The different spectral sensitivities may be implemented by using photosensitive elements with inherently different spectral sensitivities, such as by using different integrated filters and/or different sensitive materials, such as semiconductor materials. Additionally or alternatively, the different spectral sensitivities may be achieved by using one or more wavelength selective elements (such as one or more of filters, gratings, prisms, etc.) in one or more beam paths of the detection light, the one or more wavelength selective elements being configured to allow forward different spectral portions of the detection light from the object to reach the respective photosensitive elements sequentially or simultaneously.

The set of correction information items may be specific to at least one of:

separate spectrometer devices, or

A plurality of the spectrometer devices are arranged in a plurality of the spectrometer devices,

In particular, wherein the set of correction information items is assigned to each spectrometer device in accordance with its serial number. The set of correction information items may further be specific to individual detectors, in particular individual detectors in an array of individual detectors. Thus, a single spectrometer device comprising a single detector array with N detectors may comprise a single N sets of correction information. Thus, the same type of spectrometer device may use a separate set of correction information items. The first set of individual correction information items may be assigned to exactly one or more first spectrometer devices and the second set of individual correction information items may be assigned to exactly one or more second spectrometer devices, wherein the first spectrometer devices and the second spectrometer devices may be of the same type and in particular may be identical in terms of their components, in particular in terms of the function and/or arrangement and/or type of components. As used herein, the term "type" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, the same series of components and/or spectrometers which have deviations in their function and/or structure only due to inaccuracies in the manufacturing process. Thus, for a particular type of spectrometer device, multiple sets of individual correction information items may be used.

The evaluation unit may comprise a database having stored therein a plurality of correction information items, such as the set of correction information, as a function of the value of the at least one different operating parameter. The database may comprise at least one look-up table, which is in particular configured for providing the set of correction information items considered by the evaluation unit for deriving the spectroscopic information. As used herein, the term "database" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, an organized data set. The evaluation unit may comprise a data storage device on which the database may be stored. Alternatively or additionally, at least a portion of the database may be provided by a remote data storage device and/or an external data storage device, in particular as comprised by a remote server. The database may be implemented as and/or may include a lookup table. As used herein, the term "look-up table" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, replacing the run-time computed array with a simpler array indexing operation. The look-up table may provide the required correction information items for the evaluation unit as correction information.

The at least one operating parameter comprises a set of at least two operating parameters.

The at least two operating parameters may be independently selected from the group consisting of an input current applied to the light emitting diode, a voltage applied to the light emitting diode, an electrical power applied to the light emitting diode, a forward voltage of the light emitting diode, a forward current of the light emitting diode, an ambient temperature, a temperature within the spectrometer device, in particular within at least one of the light source, the drive unit, the detector or the evaluation unit, an operating scheme parameter, in particular the number and/or sequence of measurements, a measurement duration, a duty cycle, a parameter related to an operating scheme of the light source, a parameter related to an operating parameter of the detector. The at least two operating parameters include at least one temperature (in particular at least one of an ambient temperature and a temperature within the spectrometer device), and at least one of an electrical operating parameter of the spectrometer device and an optical operating parameter of the spectrometer device. The at least two operating parameters may further include at least one operating recipe parameter. Additional and/or different operating recipe parameters may be considered as defined elsewhere herein.

As used herein, the term "forward voltage" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a voltage to be applied to the LED in a forward direction, i.e. a positive contact of a voltage or current source is applied to the p-layer of the LED and a negative contact is applied to the n-layer of the LED in order to generate a predetermined current through the LED. As an example, the predetermined current defining the forward voltage may be a current known to generate a predetermined light output of the light source and/or the light emitting diode. The predetermined current may specifically be in the range of 10 mA to 500 mA, more specifically in the range of 50 mA to 300 mA. Additionally or alternatively, the term "forward voltage" may refer to a minimum voltage to be applied to the LED in the forward direction in order to generate a significant current through the LED, in particular a predetermined current defined as a minimum current, e.g. a current reaching a minimum threshold and/or above a minimum threshold. As an example, the forward voltage may be a voltage that may be derived from the diode characteristics of the LED (i.e., from a graph indicating current as a function of voltage applied to the LED). As an example, the forward voltage may be derived from a logarithmic graph of the diode characteristics of the LED, for example, by determining an inflection point in the forward branch of the characteristics, and/or by determining a voltage at the intersection of a straight line characterizing the steep portion of the forward branch and a transverse axis or voltage axis. Thus, the forward voltage may generally represent the voltage to be applied to the LED in the forward direction (p to n) in order to drive a current (specifically, forward current) through the diode. The forward voltage may depend on the bandgap of the LED. Thus, in general, LEDs having a primary emission wavelength or primary emission wavelength range in a short wavelength range (e.g., in the blue spectral range) may generally require a higher forward voltage than LEDs emitting light in a longer wavelength range (e.g., red light). The forward voltage is sometimes referred to as a "forward bias" or "junction voltage". For forward voltage, a sign may be usedOr (b)。

Thus, in general, the direction of current through the LED (where current flows from the p-doped layer to the n-doped layer of the LED), and/or where the p-side or p-doped layer of the LED is connected to the positive connector of the power supply and where the n-side or n-doped layer of the LED is connected to the negative connector of the power supply may be determined as the "forward direction".

The measuring unit comprised by the driving unit may be configured for determining at least one actual value of the at least one operating parameter. As used herein, the term "measurement unit" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device or combination of devices configured for measuring one or more operating parameters. The measuring unit may comprise one or more measuring devices or measuring elements, such as one or more voltage measuring devices. As an example, the at least one actual value of the at least one operating parameter may be provided by the measurement unit in the form of at least one electrical signal and/or electrical information, e.g. comprising one or both of an analog signal and a digital signal. The electrical signal comprising at least one actual value of the at least one operating parameter may be provided directly or indirectly to the evaluation unit. The electrical signal may be time dependent or static. The measuring unit may be considered as a functional part of the drive unit. However, the measurement unit may be comprised as a physical entity by the evaluation unit and/or the drive unit.

As used herein, the term "operating recipe parameters" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a parameter related to at least one step included in a sequence of steps of a process. The operating recipe parameters may be considered to correct the spectroscopy information when determining the actual operating recipe parameters. Alternatively or additionally, the operating regime parameters may be considered to correct the spectroscopy information at a later time than the actual operating regime parameters are determined. Thus, operating recipe parameters influencing at least one subsequent measurement can be taken into account, in particular as correction information in at least one subsequent measurement. The operating recipe parameters of the previous measurement may be considered as correction information in the subsequent measurement. Thus, operating recipe parameters having an influence and/or possibly a previous measurement of a subsequent measurement can be considered, in particular as correction information in the subsequent measurement.

The operating scheme parameters may be selected from at least one of the number and/or sequence of measurements, the duration of the measurements, parameters related to the operating scheme of the light source, in particular parameters describing the mode of the light source, such as continuous wave mode, modulation mode and/or duty cycle mode, parameters related to the operating parameters of the detector, in particular parameters describing the mode of the detector, such as gain mode, dark current mode and/or correction mode, the voltage level of the internal and/or external power supply of the spectrometer device, the operating load of the evaluation unit, the power dissipation of the internal and/or external power supply of the spectrometer device to the spectrometer device and at least one peripheral module (such as a camera) further connected to the internal and/or external power supply of the spectrometer device, or the wear and/or storage conditions of the spectrometer device.

The method may in particular be performed on-line in the field. As used herein, the term "online" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, the property that a certain process is performed during the course of another process, such as during the course of the other process, and preferably does not have to be initiated or initiated separately by a user. Thus, in particular, by taking into account at least one operating parameter, the correction of the detector signal may be performed as an on-line correction during the acquisition of the spectroscopic information about the at least one object.

The method may be at least partially implemented by a computer. The method described above and/or according to any of the embodiments described in further detail below may be wholly or partially at least one of computer-controlled, computer-implemented and computer-aided, for example by using one or more computer programs running on at least one processor (e.g., at least one processor of a spectrometer device (e.g., at least one processor integrated within a detector and/or within an evaluation unit)). In particular, as outlined above, at least step iv of the method may be at least one of computer controlled, computer implemented and computer assisted. It should be noted, however, that other steps of the method may also be wholly or partially at least one of computer-controlled, computer-implemented and computer-aided, such as one or more of steps i., ii, and iii.

In another aspect, a calibration method of compiling a set of correction information items for use in a method of operating a spectrometer device for obtaining spectroscopic information about at least one object is disclosed. The calibration method includes the following steps that may be performed in a given order. However, different sequences are also possible. In particular, one, more than one or even all method steps may be performed once or repeatedly. Further, the method steps may be performed sequentially or, alternatively, one or more method steps may be performed in a timely overlapping manner or even in parallel and/or in a combined manner. The method may further comprise additional method steps not listed.

The calibration method comprises the following steps:

I. performing a plurality of calibration measurements under different operating conditions of the spectrometer device, each calibration measurement comprising measuring a system response of the spectrometer device in a controlled environment, the system response comprising spectral information;

Recording at least one value of the at least one operating parameter for each of the calibration measurements;

a set of correction information is compiled by comparing the spectral information with the recorded at least one value of the at least one operating parameter for each of the calibration measurements.

As used herein, the term "controlled environment" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a surrounding and/or area of the spectrometer device in which at least one parameter, such as at least one operating parameter, is at a known and/or predetermined (particularly standard) value, in particular by being controlled to take on the known and/or predetermined value. In a controlled environment, predetermined standard conditions, particularly those defined elsewhere herein, may apply.

The calibration method may comprise performing calibration measurements under in particular these predetermined and controlled environmental conditions. Thus, in particular, the ambient temperature, i.e. the temperature within the spectrometer device, in particular the temperature within at least one of the lamp, the drive unit, the detector and/or the evaluation unit, may be controlled to assume a predetermined value.

Step iii may comprise storing at least one of the emission spectrum, a correction function of the emission spectrum or a correction factor of the emission spectrum in a look-up table. The calibration measurements may be performed at different ambient temperatures. Step i. may comprise using an external detector, in particular at least one of an external spectrometer and an external power meter. As used herein, the term "power meter" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a calibrated device capable of measuring spectral flux. For measuring the spectral flux, the power meter may comprise at least one detector. The external power meter is a power meter not comprised by the spectrometer device. The calibration method may comprise using an external power meter having at least one wavelength selective element, in particular at least one of an optical filter, a dispersive element and a diffractive element. As used herein, the term "wavelength selective element" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any optical element that interacts with different spectral portions of incident light in different ways, for example by having at least one wavelength dependent optical property, such as at least one wavelength dependent optical property selected from the list consisting of reflectance, reflectance direction, refraction direction, absorption, transmission, refraction index.

Step i. may comprise using a light source of the spectrometer device and using at least one calibration target, in particular using at least one diffuse reflectance calibration target having known reflectance spectral characteristics, wherein step i. further comprises performing a plurality of spectral measurements with light emitting diodes of the light source at a predetermined repetition rate, in particular at least a repetition rate of 0.1 Hz, 0.5 Hz, 1 Hz,2 Hz, 5 Hz or 10 Hz. Thereby, the spectrometer device may be heated, in particular by heating the light source, more in particular by heating the light emitting diode. The use of an external detector may ensure that calibration may be independent of heating effects on the external detector, which would not be heated by performing the above steps. In this way, it can be ensured that the external detector signal for calibration is stable. Alternatively or additionally, the spectrometer device may be heated by performing a continuous spectral measurement having a predetermined length. Typically, the continuous spectrum measurement may have a predetermined length of at least 0.1 s, 0.5 s, or 1 s.

The spectral measurement, in particular of the at least one calibration target, may further be performed within a predetermined time span before the measurement for obtaining the spectroscopic information about the object under analysis. The predetermined time span may be at least 1 s, 5 s, or 10 s, 20 s, or 30 s long. Alternatively or additionally, the predetermined time span may be at least 5min, or 10min long. Alternatively or additionally, the spectrometer device may be heated when the spectrometer device and/or software related to the use of the spectrometer device may be activated. The at least one diffusely reflective calibration target for determining the at least one performance parameter related to the detector may be comprised by an integrating sphere, wherein the integrating sphere is configured for connecting the spectrometer device to an external detector and/or an external light source, e.g. by using at least one optical port.

The step ii. May comprise recording at least two, in particular at least three, and more particularly all operating parameters of a list of operating parameters consisting of an input current applied to the light emitting diode, a voltage applied to the light emitting diode, a forward voltage of the light emitting diode and a forward current of the light emitting diode, operating recipe parameters, in particular as number and/or sequence of measurements, measurement duration, parameters related to an operating recipe of the light source, parameters related to an operating parameter of the detector, and wherein the calibration method further comprises recording at least one light signal, wherein the at least one light signal comprises at least one of a detector signal of the detector of the spectrometer device and a signal provided by an external detector, in particular an external power meter, and wherein the step iii. Comprises deriving the correction information by taking the light signal into account. Additional and/or different operating recipe parameters may be considered as defined elsewhere herein.

Another correction information item for correcting the at least one determined actual value of the at least one operating parameter determined by the drive unit may be determined by using an external measurement setting, and wherein step iii. May comprise taking the another correction information item into account when compiling the set of correction information. In particular, thereby, the drive unit and/or the measurement unit can be calibrated. The external measurement setting may be at least one optical sensor configured to detect time-resolved spectroscopic data. For example, an external optical sensor and/or a light flux meter and/or an external spectrometer, in particular in combination with at least one static and/or at least one dynamic optical filter.

The light source may be driven in a predefined scheme by setting the temperature of the light source to a predefined value, in particular by taking into account the further correction information item and/or the thermal mass of the light source. As used herein, the term "driven in a predefined scheme" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, introducing a specific amount of energy into the light source to heat the light source.

Performing a plurality of calibration measurements in step i. at different operating conditions of the spectrometer device may be performed by determining at least one performance parameter using an external light source, in particular an external light source having a known emission spectrum, or using an external detector, in particular an external detector having a known spectral efficiency, wherein a set of correction information may be compiled taking into account the at least one performance parameter. As used herein, the term "performance parameter" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, quantized values representing, in particular, the relationship between input and output. The input may relate to at least one temperature and the output may relate to the sensitivity, responsivity, and/or dark resistance of at least one detector. Alternatively or additionally, the input may relate to temperature, forward voltage, forward current, and/or electrical power, and the output may relate to spectral flux, shift of at least one peak wavelength, shift of at least one peak amplitude, shift of total flux of the external light source. Thus, the performance parameter may be specifically related to the electronic value.

The calibration method may be repeated for another light source of the same type, wherein another set of correction information is compiled. Thus, the same type of spectrometer device may use a separate set of correction information items.

In another aspect, a spectrometer apparatus for obtaining spectroscopic information about at least one object is disclosed. The spectrometer apparatus includes:

A. At least one light source for generating illumination light for illuminating the object, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode;

B. At least one driving unit for driving the light source, the driving unit being configured for determining at least one actual value of at least one operating parameter of the spectrometer device;

C. at least one detector for detecting light from the object and for generating at least one detector signal, and

D. At least one evaluation unit for evaluating the detector signal and for deriving therefrom spectroscopic information about the object, the evaluation unit being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of at least one operating parameter and for taking into account the selected correction information item for deriving the spectroscopic information.

The light source may comprise a phosphor light emitting diode. The light emitting diode may in particular have a primary emission range at least partly within the spectral range 250 nm to 940 nm. The light emitting diode may particularly have a primary emission range at least partially within the spectral range 420 nm to 460 nm, more particularly within the range 440 nm to 445 nm, more particularly at 440 nm.

The illumination light may have a spectral range at least partly within the near infrared spectral range, in particular within a spectral range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.

In another aspect, a computer program is disclosed that includes instructions that, when executed by the spectrometer device, cause the spectrometer device to perform a method of operating a spectrometer device. In another aspect, a computer readable storage medium is disclosed, comprising instructions for performing a method of operating a spectrometer device when the program is executed by the spectrometer device. In another aspect, a non-transitory computer-readable medium is disclosed that includes instructions that, when executed by one or more processors of an evaluation unit of the spectrometer device, cause the one or more processors to perform a method of operating a spectrometer device.

As used herein, the terms "computer-readable data carrier," "computer-readable storage medium," and "non-transitory computer-readable medium" are broad terms and are to be given their ordinary and customary meaning to those of ordinary skill in the art and are not limited to a special or custom meaning. These terms may particularly refer to, but are not limited to, data storage devices, particularly non-transitory data storage devices such as hardware storage media having computer-executable instructions stored thereon. The computer-readable data carrier or storage medium or computer-readable medium may in particular be or may comprise a storage medium such as a Random Access Memory (RAM) and/or a Read Only Memory (ROM).

As used herein, the terms "having," "including," or "containing," or any grammatical variation thereof, are used in a non-exclusive manner. Thus, these terms may refer to both the absence of an additional feature in the entity described in this context and the presence of one or more additional features in addition to the features introduced by these terms. As an example, the expressions "a has B", "a includes B" and "a includes B" may refer to both a case where no other element is present in a except B (i.e., a case where a is composed of B only and alone) and a case where one or more additional elements (such as elements C, C and D, or even additional elements) are present in an entity a in addition to B.

Further, it should be noted that the terms "at least one," "one or more," or the like, indicating that a feature or element may appear one or more times, typically are used only once when introducing the corresponding feature or element. In most cases, the expression "at least one" or "one or more" is not repeated when referring to the corresponding feature or element, but in fact the corresponding feature or element may appear one or more times.

Further, as used herein, the terms "preferably," "more preferably," "particularly," "more particularly," "specifically," "more specifically," or similar terms are used in combination with optional features without limiting the alternatives. Thus, the features introduced by these terms are optional features and are not intended to limit the scope of the claims in any way. As the skilled person will appreciate, the invention may be implemented using alternative features. Similarly, features introduced by "in embodiments of the invention" or similar expressions are intended to be optional features, without any limitation to alternative embodiments of the invention, without any limitation to the scope of the invention, and without any limitation to the possibility of combining features introduced in this way with other optional or non-optional features of the invention.

The spectrometer device and method according to the invention provide a number of advantages over known devices and methods of similar type in one or more of the above-described embodiments and/or in one or more of the embodiments described in further detail below. In particular, an on-line correction or calibration for temperature variations (even for local temperature variations inside the light source) may be performed, which may have an influence on the emission characteristics of the light source. More specifically, the operating parameters may provide reliable correction parameters, especially if ambient temperature is considered. Thereby, fluctuations in the spectral flux of the at least one light source and/or fluctuations (in particular, shifts) in the spectral characteristics of the at least one light source may be compensated. By generating specific and/or individual, in particular serial number specific, sets of correction information items, the accuracy and/or repeatability of the spectrometer measurement can be improved, in particular because the correction is optimized.

Further, the use of phosphor LEDs may provide several advantages in lieu of or in addition to conventional heat emitters, such as incandescent lamps having tungsten filaments as the light source. Thus, in general, thermal emitters are generally less suitable for mass spectrometer production, even though they can provide flat spectra, low temperature dependence, and high power spectral density even at long wavelengths (such as in the NIR range). Thus, in general, disadvantages of the thermal emitter include high complexity of the manufacturing process, low efficiency of conversion of electric power to optical power, and physical limitation of miniaturization. These drawbacks can be overcome by using LEDs, in particular phosphor LEDs. LEDs have proven to be reliable light sources, such as standardized light sources in the visible light regime.

In the context of the present invention, a broadband light source may be provided by using one or more phosphor LEDs in a spectrometer device, the one or more phosphor LEDs comprising at least one light emitting diode and at least one luminescent material or phosphor. Thus, as an example, a white light source and/or a broadband light source in the infrared range, in particular in the NIR range, may be produced. The phosphor may convert photons having a shorter wavelength and thus a higher energy into photons having a longer wavelength or lower energy, for example by transferring a portion of the primary photon energy to a phosphor material, such as to a phosphor lattice. The remaining lower energy may result in the emission of long wavelength photons.

Thus, the luminescent material may be configured to absorb one or more primary photons generated by the light emitting diode and may emit one or more secondary photons in response to such absorption. The emission of the secondary photons may occur instantaneously or after a delay or decay time. Thus, as outlined above, the luminescent material may be or may comprise at least one of a phosphorescent material and a fluorescent material. Phosphorescence may result in the effect that after switching off the primary light, such as short wavelength or high energy pump light, the luminescent material may be at a characteristic lifetime(Tau) internally emits secondary light (such as long wavelength light) due to, for example, forbidden quantum optical transitions or forbidden dipole transitions. Thus, in particular, in luminescent materials, the emission of secondary light may occur through forbidden transitions (such as forbidden dipole transitions), which have a longer lifetime than allowed by spontaneous dipoles, as may be the case for many fluorescent materials.

In particular, as outlined above, luminescent materials, in particular phosphorescent materials, may be used, which have an absorption in the blue spectral range and an emission in the infrared spectral range. As an example, luminescent materials may be used that have the ability to convert blue primary light or pump light having a wavelength of, for example, 440 nm into near infrared secondary light (e.g. secondary light having a wavelength in the range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm). Additionally or alternatively, the primary light or pump light may be generated by an infrared LED having a wavelength in the range of 850 nm to 940 nm, and then the primary light or pump light may be converted by the luminescent material into near infrared secondary light having a wavelength in the range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.

A phosphor LED comprising at least one light emitting diode and at least one luminescent material may be implemented as a single element. Thus, in the state of the art, a phosphor LED may comprise a plurality of sub-components.

First, the phosphor LED may comprise one or more functional components, such as an LED die comprising at least one junction, such as at least one p-n junction, between at least two semiconductor regions. In an LED die, primary light, such as short wavelength pump light, for example, in the blue spectral range may be generated.

Further, the phosphor LED may comprise at least one luminescent material, in particular at least one phosphorescent material, which may in particular be placed directly on top of the LED die and which may convert primary light (in particular pump light) into secondary light (in particular into long wavelength near infrared light).

Further, the phosphor LED may comprise one or more substrates, in particular one or more electrically insulating substrates. Thus, as an example, a phosphor LED may comprise one or more ceramic substrates. The at least one substrate may be configured to hold at least one LED die and at least one luminescent material. Further, at least one substrate may hold or include one or more electrical connection components, such as one or more contact pads and/or one or more electrical leads, such as one or more metal contacts and/or one or more metal leads. In addition, the substrate (e.g., ceramic substrate) may be configured to act as a heat sink. For example, during the conversion process, heat may be generated in both the LED die and the luminescent material (e.g., due to limited conversion of electrical energy to photon energy), as well as in the luminescent material. The heat may be dissipated in a substrate, such as a ceramic substrate.

A spectrometer device using at least one LED may be configured to apply a Continuous Wave (CW) mode and/or preferably at least one modulation driving scheme to improve the accuracy and reliability of the measurement. Thus, for example, the at least one driving unit may be configured for applying a modulation driving scheme to the LEDs, and the evaluation device may be configured for taking into account the modulation driving scheme to derive the at least one item of spectroscopic information from the at least one detector signal. As an example, phase lock techniques, filtering techniques, etc. may be applied, as known to those skilled in the art.

Thus, the spectrometer device may be configured to apply a modulation drive scheme to the LEDs to compensate for the DC background of the detector and/or reduce detector noise. Thus, as an example, a band pass filter may be applied to the detector signal in order to eliminate the DC component.

Illumination light generated by a light source, in particular a phosphor LED, may be directed to illuminate the sample. To direct the illumination light, as an example, one or more mirrors may optionally be used. Detection light (e.g., reflected light) from the object may be directed to the detector, wherein optionally one or more optical components may be used. As an example, one or more wavelength selective elements, such as one or more dispersive elements, may be used, for example, for separating the detection light into its spectral components.

By means of the detector, one or more detector signals may be recorded, for example by using readout electronics comprised by the spectrometer device, which readout electronics may in particular be comprised by one or both of the detector and the evaluation device. As an example, the readout electronics may comprise one or more signal processing devices. Thus, as outlined above, for evaluation by the evaluation device, the "raw" detector signal and/or one or more secondary detector signals derived therefrom (such as one or more filtered detector signals) may be used. Further, at least one detector signal (primary or secondary) may also be combined with further information, such as information about the wavelength, e.g. derived from the number of the photosensitive element of the array of photosensitive elements from which the detector signal was derived, which photosensitive element is known to be exposed to a specific wavelength within a certain wavelength range. In the context of the present invention, in particular in the context of the evaluation unit evaluating the detector signals, it is possible to evaluate the option of the original detector signals and/or the option of the secondary detector signals, such as the preprocessed detector signals, the processed detector signals or the combined detector signals. However, the invention is still significant, in particular, for correcting "raw" detector signals, in particular detector signals that indicate a change in signal strength with detection wavelength. However, other options are also possible.

As an example, the detector signal may be processed or preprocessed (e.g. by the detector itself and/or by the evaluation unit) into a secondary detector signal by applying one or more fourier transforms. As an example, a fast fourier transform may be applied. From the processed secondary detector signal, at least one item of spectroscopic information may be obtained, for example by software executed by the evaluation unit. Thus, as an example, the fourier transform of the detector signal may be read out by the software of the spectroscopic device (in particular the evaluation device) and post-processed into spectroscopic information about the object.

Thus, as outlined above, LEDs and phosphor LEDs may provide an efficient light source that may be modulated in order to perform a specific evaluation scheme and to reduce noise and artifacts. By using at least one information item about an operating parameter as correction or calibration parameter, in particular, temperature variations within the light source, in particular within the LED, may be fully or partially compensated. Thus, for a typical LED as used herein, the temperature of the various components of the light source (in particular, the temperature of the LED) may vary over a large temperature range when operating at the maximum voltage and current that the LED may withstand. As an example, the standard operating current may range from 2 mA to 1000 mA, typically from 10 mA to 300 mA. As an example, the forward voltage may be in the range of 1.5V to 3.5V, typically in the range of 2.25V to 3V. Thus, as an example, under maximum operating conditions, the junction temperature of the emitter may be 135 ℃. The operating envelope temperature may vary from-40 ℃ to 135 ℃ and the storage temperature of the emitter may vary from-40 ℃ to 125 ℃. The ESD sensitivity of the led may be 250V according to the standard ANSI/ESDA/JEDEC JS-001-2012. These typical parameters show a large range of temperature variations, which may have an effect on the spectroscopic information about the object obtained by the spectrometer device. It should be noted that other parameters and other parameter ranges are also possible.

It is generally known that phosphor LEDs generate different spectra in the case of different compositions of the luminescent material, such as different compositions of the phosphor. Typically, each phosphor LED has multiple peaks in the spectrum, where the spectrum is typically distributed over a broad wavelength range. However, even if the same current is supplied to the phosphor LED, the spectral characteristics or spectrum may vary with temperature. These changes may include shifts in emission peaks, broadening or narrowing of the spectrum, increases or decreases in emission, and the like. However, in many cases, the emissions at some wavelengths are affected to a greater extent than the emissions at other wavelengths. Thus, typically, there is a specific center wavelength within the spectrum, where the power (specifically the power spectral density) is typically not a function of temperature. Thus, with respect to the increment/decrement of power, each wavelength typically has its own temperature coefficient. Thus, the shape of the spectrum varies with temperature. By using the operating parameters as correction parameters, individual temperature corrections can be performed for the spectra at different wavelengths. Thus, as outlined above, the evaluation unit may be configured for individually correcting detector signals in different spectral ranges and for combining the individually corrected detector signals to obtain the spectroscopic information. More specifically, as also outlined above, such an individual correction may be performed by using an array of photosensitive elements, wherein each photosensitive element may be configured to generate at least one detector signal, and wherein each detector signal may be individually corrected by using the operating parameter as correction parameter. Finally, the corrected detector signals may be combined to obtain the spectroscopy information.

By using the operation as a correction parameter, the temperature variation of the phosphor LED and the respective characteristics can be corrected. Thus, as an example, when the same current is applied to an LED, the forward voltage of the LED generally decreases with increasing temperature. Each type of LED has its own forward voltage-temperature characteristic. Typically, the forward voltage of an LED decreases linearly with increasing temperature, e.g., withTo the point ofSlope in the range of V/K.

Further, the spectrometer apparatus and method may consider the characteristics of the luminescent material used in the light source. Thus, as outlined above, typically, there is a delay between the luminescent material absorbing at least one primary photon and the luminescent material emitting at least one secondary photon. This delay may be defined by a so-called "characteristic time constant"(Also referred to as a "time constant", "decay time", or "saturation time"). As is well known to the skilled person, the term "time constant" is a broad term and will be given its ordinary and customary meaning to a person skilled in the art and is not limited to a special or custom meaning. When used in the context of a process in which the rate or probability of a process (such as photon emission) is proportional to the population of one or more states or process states, the population typically varies exponentially. In these processes, time constantThe 1/e time of the process can be determined. Two different time constants may occur for the luminescent material or the converter, in particular for the phosphor. First, the first time constant may describe a typical time for reaching emission saturation of the converted light. Second, the second time constant may describe a typical time of afterglow of the luminescent material or the converter.

Typical time constants for phosphor converters are in the range of 0.1 ms to <10 ms. These time constants are typically different between different phosphor LEDs and/or between different types of luminescent materials or phosphors. In general, phosphors that emit short wavelengths exhibit smaller time constants. In addition, the damping constantConstant of growthMay depend on the wavelength. The time constant is typically extracted from the step response of the optical signal by applying/switching off a forward current.

After switching off the forward current, the signal or emission generally decays according to equation (1):

(1)

After switching on the forward current, the signal or emission generally increases according to equation (2):

(2)

For equations (1) and (2), Is when the forward current is applied/switched off,Optical signal level at that time.Is thatThe optical signal level reached at that time.

Another characteristic of LEDs is that the light output power varies with forward current. Thus, in general, by increasing the input current, the allowable power of the LED increases. The shape (e.g., slope) of the curve of light output as a function of forward current is a characteristic of each LED.

As outlined above, using the operating parameters as control or correction parameters for spectroscopic analysis purposes, efficient and reliable online correction or online calibration can be achieved. Thus, various challenges of a typical spectrometer and its corresponding calibration can be overcome. In particular, during a typical spectroscopic analysis, the reference measurement of the spectrometer allows the calibration instrument to respond, so the measurement only provides information about the sample. However, if the optical components of the spectrometer device change between the reference measurement and the sample measurement, the sample information may be affected by the system change, and thus the information about the sample may be distorted. In particular, when the spectrum of the light sourceDuring reference measurement (during which the light source has a spectrum) And actual sample measurement (during which the light source has a spectrum) When the spectrum is changed, the spectrum information about the image or sample is distorted, because the spectrum is generally based on two spectra、Is biased by the ratio of (c). In phosphor LEDs, the situation is often even more complicated, as the spectrum of a phosphor LED is a combination of the spectra of the LED and the luminescent material. Both components of the phosphor LED may be affected by temperature variations in different ways. Thus, for phosphor LEDs, the spectrum can be generally described by equation (3):

(3)

Wherein, the Representing the spectrum of the light source LS as wavelengthP-n junction temperature of LEDAnd the temperature of the phosphorIs a function of (2).Representing the spectrum of an LED (e.g., blue LED), andRepresenting the spectrum of the luminescent material, e.g. phosphor.

Both the LED and the luminescent material sub-components show separate temperature responses. Thus, a system temperature change or shift or an ambient temperature change or shift (particularly between a reference measurement and a sample measurement) will typically affect the spectrum by affecting both the LED junction and the luminescent material.

In summary, and without excluding further possible embodiments, the following embodiments are conceivable:

embodiment 1 a method of operating a spectrometer device for obtaining spectroscopic information about at least one object, the method comprising:

i. illuminating the object with illumination light generated by at least one light source of the spectrometer device, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode;

Determining at least one actual value of at least one operating parameter of the spectrometer device by using at least one drive unit of the spectrometer device, the drive unit being configured for electrically driving the light source;

Detecting detected light from the object by using at least one detector of the spectrometer device and generating at least one detector signal, and

Evaluating the detector signal by using at least one evaluation unit of the spectrometer device, thereby obtaining therefrom spectroscopic information about the object, the evaluation unit being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of the at least one operating parameter, and for taking into account the selected correction information item for obtaining the spectroscopic information.

Embodiment 2 the method according to the previous embodiment, wherein the set of correction information items is specific to at least one of:

separate spectrometer devices, or

A plurality of the spectrometer devices are arranged in a plurality of the spectrometer devices,

In particular, wherein the set of correction information items is assigned to each spectrometer device in accordance with the serial number of each spectrometer device.

Embodiment 3. The method according to any of the preceding embodiments, wherein the detector provides at least one raw detector signal in step iii. Wherein in step iv. The evaluation unit corrects the raw detector signal to at least one corrected detector signal by using the at least one selected correction information item.

Embodiment 4. The method according to any of the preceding embodiments, the evaluation unit comprising a database having a plurality of correction information items stored therein as a function of the value of the at least one different operating parameter.

Embodiment 5 the method according to the previous embodiment, wherein the database comprises at least one look-up table, which is in particular configured for providing the plurality of correction information items considered by the evaluation unit for deriving the spectroscopy information.

Embodiment 6 the method of any of the preceding embodiments, wherein the at least one operating parameter comprises a set of at least two operating parameters.

Embodiment 7 the method according to the previous embodiment wherein the at least two operating parameters are independently selected from the group consisting of input current applied to the light emitting diode, voltage applied to the light emitting diode, electric power applied to the light emitting diode, forward voltage of the light emitting diode, forward current of the light emitting diode, ambient temperature, temperature within the spectrometer device, in particular within at least one of the light source, the drive unit, the detector or the evaluation unit, operating scheme parameters, in particular the number and/or sequence of measurements, measurement duration, duty cycle, parameters related to the operating scheme of the light source, parameters related to the operating parameters of the detector.

Embodiment 8 the method according to any one of the two previous embodiments, wherein the at least two operating parameters comprise at least one temperature, in particular at least one of an ambient temperature and a temperature within the spectrometer device, and at least one of an electrical operating parameter of the spectrometer device and an optical operating parameter of the spectrometer device.

Embodiment 9 the method of the previous embodiment, wherein the at least two operating parameters further comprise at least one operating recipe parameter.

Embodiment 10 the method according to any of the preceding method embodiments, wherein the method is at least partially implemented by a computer.

Embodiment 11a calibration method of compiling a set of correction information items for use in a method according to any one of the preceding embodiments, the calibration method comprising:

I. performing a plurality of calibration measurements under different operating conditions of the spectrometer device, each calibration measurement comprising measuring a system response of the spectrometer device in a controlled environment, the system response comprising spectral information;

Recording at least one value of the at least one operating parameter for each of the calibration measurements;

A set of correction information is compiled by comparing the spectral information with the recorded at least one value of the at least one operating parameter for each of the calibration measurements.

Embodiment 12 the calibration method according to the previous embodiment, comprising performing the calibration measurements under predetermined and controlled environmental conditions.

Embodiment 13. The calibration method according to any one of the two previous embodiments, wherein step III. Comprises storing at least one of the emission spectrum, a correction function of the emission spectrum, or a correction factor of the emission spectrum in a look-up table.

Embodiment 14. The calibration method according to any of the three previous embodiments, wherein the calibration measurements are performed at different ambient temperatures.

Embodiment 15 the calibration method according to any of the preceding embodiments related to calibration methods, wherein step i. comprises using an external detector, in particular at least one of an external spectrometer and an external power meter.

Embodiment 16 the calibration method according to the previous embodiment, wherein the calibration method comprises using an external power meter having at least one wavelength selective element, in particular at least one of an optical filter, a dispersive element and a diffractive element.

Embodiment 17 the calibration method according to any of the preceding embodiments related to calibration methods, wherein step i. Comprises using a light source of the spectrometer device and using at least one calibration target, in particular using at least one diffuse reflection calibration target having known reflection spectral characteristics, wherein step i. Further comprises performing a plurality of spectral measurements with a light emitting diode of the light source at a predetermined repetition rate, in particular at least 0.1 Hz, 0.5Hz, 1 Hz, 2Hz, 5Hz or 10 Hz.

Embodiment 18. The calibration method according to any of the preceding embodiments relating to calibration methods, wherein step ii. Comprises recording at least two, in particular at least three, and more particularly all operating parameters of a list of operating parameters consisting of an input current applied to the light emitting diode, a voltage applied to the light emitting diode, a forward voltage of the light emitting diode and a forward current of the light emitting diode, an operating scheme parameter (in particular as number and/or order of measurements), a measurement duration, a parameter related to an operating scheme of the light source, a parameter related to an operating parameter of the detector, and wherein the calibration method further comprises recording at least one light signal, wherein the at least one light signal comprises at least one of a detector signal of the detector of the spectrometer device and a signal provided by an external detector, in particular an external power meter, and wherein step iii. Comprises deriving the correction information by taking the light signal into account.

Embodiment 19. The calibration method according to any of the preceding embodiments related to a calibration method, wherein a further correction information item for correcting the at least one determined actual value of the at least one operating parameter determined by the drive unit is determined by using an external measurement setting, and wherein step iii. Comprises taking the further correction information item into account when compiling the set of correction information.

Embodiment 20. The calibration method according to any of the preceding embodiments involving calibration methods, wherein the light source is driven in a predefined scheme by setting the temperature of the light source to a predefined value, in particular by taking into account the further correction information item and/or the thermal mass of the light source.

Embodiment 21 the calibration method according to any of the preceding embodiments related to a calibration method, wherein performing a plurality of calibration measurements in step i. at different operating conditions of the spectrometer device is performed by determining at least one performance parameter by at least one of:

Use of an external light source, in particular having a known emission spectrum, for determining in particular the at least one performance parameter associated with the detector, or

Using an external detector, in particular having a known spectral efficiency, to determine in particular the at least one performance parameter associated with the detector;

Wherein in step iii, a set of correction information is compiled taking into account the at least one performance parameter.

Embodiment 22. The calibration method according to any of the preceding embodiments involving a calibration method, wherein the calibration method is repeated for another light source of the same type, wherein another set of correction information specific to the other light source is compiled.

Embodiment 23 a spectrometer apparatus for obtaining spectroscopic information about at least one object, the spectrometer apparatus comprising:

A. At least one light source for generating illumination light for illuminating the object, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode;

B. At least one driving unit for driving the light source, the driving unit being configured for determining at least one actual value of at least one operating parameter of the spectrometer device;

C. at least one detector for detecting light from the object and for generating at least one detector signal, and

D. at least one evaluation unit for evaluating the detector signal and for deriving therefrom spectroscopic information about the object, the evaluation unit being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of the at least one operating parameter and for taking into account the selected correction information item for deriving the spectroscopic information.

Embodiment 24 the spectrometer device according to the previous embodiment, wherein the light source comprises a phosphor light emitting diode.

Embodiment 25 the spectrometer device according to any of the preceding embodiments involving a spectrometer device, wherein the light emitting diode has a primary emission range at least partially within the spectral range of 420nm to 460 nm, more particularly within the range of 440 nm to 455 nm, more particularly at 440 nm.

Embodiment 26 the spectrometer device according to any of the preceding embodiments related to a spectrometer device, the illumination light having a spectral range at least partly within the near infrared spectral range, in particular within a spectral range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.

Embodiment 27 is a computer program comprising instructions which, when the program is executed by a spectrometer device according to any of the previous embodiments relating to spectrometer devices, cause the spectrometer device to perform a method of operating a spectrometer device according to any of the previous embodiments relating to a method of operating a spectrometer device.

Embodiment 28 is a computer readable storage medium comprising instructions which, when the program is executed by a spectrometer device according to any of the previous embodiments relating to spectrometer devices, cause the spectrometer device to perform a method of operating a spectrometer device according to any of the previous embodiments relating to a method of operating a spectrometer device.

Embodiment 29 a non-transitory computer-readable medium comprising instructions that, when executed by one or more processors of an evaluation unit of a spectrometer device according to any of the preceding embodiments relating to a spectrometer device, cause the one or more processors to perform a method of operating a spectrometer device according to any of the preceding embodiments relating to a method of operating a spectrometer device.

Drawings

Further optional features and embodiments will be disclosed in more detail in the subsequent embodiments, preferably in connection with the dependent claims. Wherein the respective optional features may be implemented in a stand-alone manner as well as in any arbitrary feasible combination, as will be appreciated by the skilled person. The scope of the invention is not limited by the preferred embodiments. Embodiments are schematically depicted in the drawings. Wherein like reference numerals designate identical or functionally equivalent elements throughout the several views.

In the drawings:

fig. 1 shows a schematic overview of a spectrometer device;

fig. 2 shows a schematic cross-sectional view of a light source;

FIG. 3 shows a schematic flow chart illustrating the generation and processing of detector signals;

FIG. 4 shows a graph representing the superposition of infrared radiation spectra of phosphor LEDs at various temperatures;

FIG. 5 shows a graph representing the variation of transmit power with temperature for a selected number of wavelengths;

FIG. 6 shows a graph of forward voltage as a function of temperature for a selected current;

FIGS. 7A and 7B show spectra of two different types of phosphor LEDs;

FIGS. 8A and 8B show graphs representing the decay constant (FIG. 8A) and the growth constant (FIG. 8B) as a function of wavelength for phosphor LEDs emitting between 1.3 μm and 2 μm;

FIGS. 9A and 9B show graphs representing the decay constant (FIG. 9A) and the growth constant (FIG. 9B) as a function of wavelength for phosphor LEDs emitting between 1.6 μm and 2.1 μm;

FIG. 10 shows a graph representing normalized light output as a function of forward current;

FIG. 11 illustrates a method of operating a spectrometer device for obtaining spectroscopic information about at least one object;

FIG. 12 shows a calibration method for compiling a set of correction information items, and

Fig. 13 illustrates an exemplary calibration setup.

Detailed Description

In fig. 1, a schematic overview of a spectrometer device 110 for obtaining spectroscopic information about at least one object 112 is shown. The spectrometer device 110 may include a number of components as illustrated in fig. 1. Possible components of the spectrometer device 110 and their interactions will be described below with specific reference to fig. 1. The spectrometer device 110 comprises at least one light source 114 for generating illumination light 116 for illuminating the object 112. The light source 114 may be at least one of a tunable light source, a light source having at least one fixed emission wavelength, and a broadband light source. The light source 114 may specifically be or may comprise at least one electric light source. The light source 114 comprises at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118. By way of example, the light emitting diode 118 may include one or more of a Light Emitting Diode (LED) based on light spontaneous emission, a light emitting diode (sLED) based on superemission, a laser diode (LLED).

The LED 118 may in particular comprise at least two layers of semiconductor material 121, wherein light may be generated at least one interface between the at least two layers of semiconductor material 121, in particular due to recombination of positive and negative charges. The at least two layers of semiconductor material 121 may have different electrical properties, such as at least one of the layers being an n-doped semiconductor material 121 and at least one of the layers being a p-doped semiconductor material 121. Thus, as an example, the LED 118 may comprise at least one pn junction and/or at least one pin structure. However, it should be noted that other device configurations are possible.

The light emitting diode 118 may generate primary light, which may also be referred to as "pump light". The primary light may then be converted into "secondary light", such as by using light conversion (e.g., by one or more luminescent materials 120, such as phosphor materials). Thus, the at least one luminescent material 120 may form at least one converter (also referred to as a light converter) that converts the primary light into secondary light having different spectral properties than the primary light. In particular, the spectral width of the secondary light may be larger than the spectral width of the primary light and/or the emission center of the secondary light may be shifted (in particular red shifted) compared to the primary light. In particular, the at least one luminescent material 120 may be absorbing in the ultraviolet and/or blue spectral range and emissive in the near infrared and/or infrared spectral range. The illumination light 116 may be or may include at least one of primary light or a portion thereof, secondary light or a portion thereof, or a mixture of primary and secondary light.

As indicated in fig. 1, the light source 114 may specifically comprise a phosphor light emitting diode 122, also referred to as a phosphor LED 122. The phosphor LED 122 may be a combination of at least one light emitting diode 118 configured to generate primary light or pump light and at least one luminescent material 120 (also referred to as "phosphor") configured to light convert the primary light generated by the light emitting diode 118. The phosphor LED 122 may form a packaged LED light source comprising an LED die 124 (e.g., a blue LED that emits blue pump light) and a phosphor, for example, that completely or partially coats the LED 118 and is configured to convert primary or blue light into light having different spectral characteristics (specifically into near infrared light), as examples. Fig. 2 shows a more detailed view of the light source 114 implemented as a phosphor LED 122.

In general, the light source 114 may be implemented in various ways. Thus, the light source 114 may be, for example, a portion of the spectrometer device 110 in a housing 126 of the spectrometer device 110, as illustrated in fig. 1. Alternatively or additionally, however, the at least one light source 114 may also be arranged outside the housing 126, for example as a separate light source 114 (not shown). The light source 114 may be arranged separately from the object 110 and illuminate the object 110 from a distance, as indicated in fig. 1.

Illumination light 116 as generated by light source 114 may propagate from light source 114 to object 112. In fig. 1, illumination light 116 generated by light source 114 and propagating to object 112 is shown by arrows. In particular, the object 112 may comprise at least one sample, which may be wholly or partially analyzed by spectroscopic methods.

As is apparent from fig. 1, the spectrometer device 110 further comprises at least one detector 128 configured for detecting detection light 130 from the object 112. Light propagating from the light source 114 to the object 112 may be referred to as illumination light 116, while light propagating from the object 112 to the detector 128 may be referred to as "detection light" 130. In fig. 1, detection light 130 is shown by an arrow. The detection light 130 may include at least one of illumination light 116 reflected by the object 112, illumination light 116 scattered by the object 112, illumination light 116 transmitted by the object 112, luminescence light generated by the object 112 (e.g., phosphorescence or fluorescence generated by the object 112 after optical, electrical, or acoustic excitation of the object 112 by the illumination light 116, etc.). Thus, the detection light 130 may be generated directly or indirectly by illumination of the object 112 by the illumination light 116.

The detector 128 may be or may include at least one optical detector 132. The optical detector 132 may be configured to determine at least one optical parameter, such as the intensity and/or power of light irradiating at least one sensitive area of the detector 132. More specifically, the optical detector 132 may include at least one photosensitive element and/or at least one optical sensor, such as at least one of a photodiode, a photocell, a photoresistor, a phototransistor, a thermopile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier, and a bolometer. Thus, the detector 128 may be configured for generating at least one detector signal, more particularly at least one electrical detector signal in the above sense, providing information about at least one optical parameter, such as power and/or intensity of light illuminating the detector 128 or a sensitive area of the detector 128.

The detector 128 may include a single optical sensor or region or multiple optical sensors or regions. As indicated in fig. 1, the detector 130 may comprise at least one detector array, more particularly an array of photosensitive elements 134. Each photosensor 134 can be configured to generate at least one detector signal. In particular, each light sensitive element 134 may comprise at least a light sensitive region, which may be adapted to generate an electrical signal depending on the intensity of the incident light, wherein the electrical signal may in particular be provided to an evaluation unit 136 of the spectrometer device, as will be outlined in further detail below.

Where the detector 128 comprises an array of optically sensitive elements 134, the detector 128 may for example be selected from any known pixel sensor, in particular from a CCD chip or a CMOS chip. Alternatively, the detector 128 may generally be or include a photoconductor, particularly an inorganic photoconductor, particularly PbS, pbSe, ge, inGaAs, extended InGaAs, inSb, or HgCdTe. As a further alternative, the detector may comprise at least one of a pyroelectric element, a bolometer element or a thermopile detector element.

The spectrometer apparatus 110 comprises at least one evaluation unit 136 for evaluating at least one detector signal generated by the detector 128 and for deriving spectroscopic information about the object 112 from the detector signal. The detector 128 may directly or indirectly provide the detector signal to the evaluation unit 136. Thus, the detector 128 and the evaluation unit 136 may be directly or indirectly connected, as indicated by the arrow in fig. 1. The detector signal may be used as a "raw" detector signal and/or may be processed or pre-processed (e.g., by filtering, etc.) prior to further use. Thus, the detector 128 may include at least one processing device and/or at least one preprocessing device, such as at least one of an amplifier, an analog/digital converter, an electrical filter, and a fourier transform.

The at least one evaluation unit 136 is configured for evaluating the detector signals and for deriving therefrom spectroscopic information about the object. The evaluation unit 136 is further configured for selecting at least one correction information item from a predetermined set of correction information items in dependence of an actual value of the at least one operating parameter, and for taking the selected correction information item into account for obtaining the spectroscopic information.

As shown in fig. 1, the spectrometer device 110 further comprises at least one drive unit 138 for electrically driving the light source 114. The spectrometer device 110 comprises at least one measurement unit 139. The measurement unit 139 is configured for generating at least one item of information about at least one operating parameter (in particular the forward voltage) required for driving the light emitting diode 118. The measurement unit 139 may be an element of the drive unit 138, as indicated in fig. 1. In particular, the drive unit 138 may be configured for providing a current to the LED 118, in particular for controlling the current through the LED 118. Therein, as an example, the drive unit 138 may be configured to adapt and measure the voltage provided to the LED 118, which is required to achieve a specific current through the LED 118. The drive unit 138 may specifically include one or more of a current source 140, a voltage source, a current measurement device (such as an ammeter), a voltage measurement device 142 (such as a voltmeter), a power measurement device. In particular, the drive unit 138 may comprise at least one current source 140 for providing at least one predetermined current to the LED 118, wherein the current source 140 may in particular be configured for adjusting or controlling the voltage applied to the LED 118 in order to generate the predetermined current. As an example, the drive unit 138 may include one or more electrical components (such as an integrated circuit) for driving the light source 114. The drive unit 138 may be fully or partially integrated into the light source 114 or may be separate from the light source 114, the latter configuration being illustrated in fig. 1.

As outlined above, the drive unit 138 is configured for generating at least one item of information about at least one operating parameter (in particular the forward voltage) required for driving the light emitting diode 118. The forward voltage may be applied to the LED in the forward direction, i.e., a positive contact of a voltage or current source 140 is applied to the p-layer of the LED 118 and a negative contact is applied to the n-layer of the LED 118, so as to generate a predetermined current through the LED 118. As an example, the predetermined current defining the forward voltage may be a current known to generate a predetermined light output of the light source 114 and/or the light emitting diode 118.

In order to generate at least one item of information about at least one operating parameter (in particular the forward voltage) required for driving the light emitting diode 118 (e.g. driving the LED 118 with a predetermined current in the forward direction), the measurement unit 139 may comprise one or more measurement devices or measurement elements, such as one or more voltage measurement devices 142. As an example, the at least one information item about the at least one operating parameter may be provided by the measurement unit 139 in the form of at least one electrical signal and/or electrical information, for example comprising one or both of an analog signal and a digital signal. The electrical signal comprising at least one information item about at least one operating parameter may be provided directly or indirectly to the evaluation unit 136. The electrical signal may be time dependent or static.

As outlined above, and as shown in fig. 1, the spectrometer apparatus 110 comprises at least one evaluation unit 136 for evaluating at least one detector signal generated by the detector 128 and for deriving spectroscopic information about the object 112 from the detector signal. The evaluation unit 136 is configured for taking into account information items about at least one operating parameter when deriving the spectroscopic information from the detector signal. In particular, the evaluation unit 136 may be configured for processing at least one input signal and generating at least one output signal thereof. As an example, the at least one input signal may comprise at least one detector signal provided directly or indirectly by the at least one detector 128, and additionally at least one signal provided directly or indirectly by the measurement unit 139, the signal comprising at least one information item about the at least one operating parameter. The arrow between the drive unit 138 (which comprises the measuring unit 139 in the embodiment illustrated in fig. 1) and the evaluation unit 136 in fig. 1 illustrates the process of providing a signal to the evaluation unit 136 and/or retrieving a signal by the evaluation unit 136, which signal comprises at least one information item about at least one operating parameter.

The evaluation unit 136 may be or include one or more integrated circuits, such as one or more Application Specific Integrated Circuits (ASICs), and/or one or more data processing devices 144, such as one or more of a computer, a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), preferably one or more microcomputers and/or microcontrollers. Additional components may be included, such as one or more preprocessing devices 146 and/or data acquisition devices, such as one or more devices for receiving and/or preprocessing detector signals, such as one or more AD converters and/or one or more filters. Further, the evaluation unit may comprise one or more data storage devices 148, as shown in fig. 1. Further, the evaluation unit 136 may comprise one or more interfaces, such as one or more wireless interfaces and/or one or more wired interfaces.

In particular, the evaluation unit 136 may be configured, for example by software programming, for determining at least one correction from the information item about the at least one operating parameter, in particular a correction based on a model describing a functional relationship between the spectral characteristics of the light source 114 and the at least one operating parameter. The evaluation unit 136 may be further configured for correcting the at least one detector signal by using the correction. As described in detail above and as will be described further in an exemplary manner below, correcting may in particular comprise multiplying the at least one detector signal with at least one correction factor. The evaluation unit 136 may in particular be configured for using the corrected detector signal to derive the spectroscopic information.

As described in more detail above, the detector 128 may specifically include an array of photosensitive elements 134. Each photosensitive element may be configured to generate at least one detector signal. The evaluation unit 136 may be configured for individually correcting each detector signal and for combining the detector signals to obtain the spectroscopic information. The spectrometer device 110 may be configured such that the photosensitive elements of the detector 128 are sensitive to different spectral ranges of light from the object 112. In particular, the detector 128 may be configured for generating detector signals for at least two different spectral ranges of light from the object, in particular at least one of sequentially and simultaneously. The spectrometer 110 may in particular comprise at least one filter element 150 arranged in the beam path of the light from the object. The filter element 150 may in particular be configured such that each photosensitive element is exposed to a separate spectral range of light from the object 112.

The spectrometer device 110 can further include one or more optical components 151, such as one or more of at least one mirror, at least one lens, at least one aperture, and at least one wavelength selective element 152. Specifically, one or more optical components 151 may be disposed in at least one of the beam path of the illumination light 116 and the beam path of the detection light 130. The spectrometer device 110 may in particular comprise at least one wavelength selective element 152. The wavelength selective element 152 may in particular be selected from the group comprising a tunable wavelength selective element 152 and a wavelength selective element 152 having a fixed transmission spectrum. By way of example, by using a tunable wavelength selective element 152, different wavelength ranges may be sequentially selected, while by using a wavelength selective element 152 with a fixed transmission spectrum, the selection of wavelength ranges may be fixed, but may also depend on the detector position, for example. The wavelength selective element 152 may be used to separate the incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector, such as the detector 128 of the spectrometer device 110, which may include an array of photosensitive elements 134. The at least one wavelength selective element 152 may, for example, comprise at least one of a filter, a grating, and a prism. The wavelength selective element 152 may specifically include at least one of a wavelength selective element 152 disposed in a beam path of the illumination light 116 and a wavelength selective element 152 disposed in a beam path of the detection light 130. Fig. 1 illustrates an embodiment of a spectrometer device 110 having one wavelength selective element 152 arranged in the beam path of illumination light 116 and one wavelength selective element 152 arranged in the beam path of detection light 130.

The spectrometer device 110 as schematically represented in fig. 1 is configured for obtaining spectroscopic information about at least one object 112. In particular, the spectrometer device may be configured for obtaining an information item, for example, about at least one object and/or radiation emitted by at least one object, the information item characterizing at least one optical property of the object, more particularly at least one information item, for example, characterizing and/or quantifying at least one of transmission, absorption, reflection and emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one item of intensity information, e.g. information about the intensity of light transmitted, absorbed, reflected or emitted by the object, e.g. as a function of wavelength or wavelength sub-ranges within one or more wavelengths (e.g. within a wavelength range). Accordingly, the spectrometer device 110 may be configured to acquire at least one spectrum or at least a portion of a spectrum of the detection light 130 propagating from the object 112 to the detector 128. The spectrum may describe the units of radiation measurement of the spectral flux, for example given in watts per nanometer (W/nm), or in other units, for example as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, for example, in the NIR spectral range, in a particular band. The spectrum may contain one or more optical variables that vary with wavelength, such as power spectral density, electrical signals obtained by optical measurements, and the like. Examples of spectra are shown, for example, in fig. 4, 7A and 7B. The spectrometer device 110 may in particular be a portable spectrometer device 110, which may in particular be used in the field.

A schematic cross-sectional view of the light source 114 is shown in fig. 2. The at least one light source 114 of the spectrometer device 110 may be configured to generate or provide electromagnetic radiation in one or more of the infrared, visible, and ultraviolet spectral ranges. Because many material properties or chemical composition properties of many objects 112 are available from the near infrared spectrum, light used for typical purposes of the present invention is light in the Infrared (IR) spectrum, more preferably in the Near Infrared (NIR) and/or mid-infrared (MidIR) spectrum, especially light having a wavelength of 1 to 5 μm, preferably 1 to 3 μm. The light source 114 comprises at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118. As described above, the LED 118 and the luminescent material 120 together may form a phosphor LED 122.

As illustrated in fig. 2, the phosphor LED 122 may include one or more functional components. In particular, the phosphor LED 122 may comprise one or more substrates 154, in particular one or more electrically insulating substrates 154. In particular, the phosphor LED 122 may include one or more ceramic substrates 156, as shown in fig. 2. The substrate 154 may be configured to hold the at least one LED die 124 and the at least one luminescent material 120. Further, the at least one substrate 154 may hold or include one or more electrical connection components, such as one or more contact pads 158 and/or one or more electrical leads, such as one or more metal contacts and/or one or more metal leads, as shown in fig. 2. The substrate 154 may be configured to act as a heat sink. For example, during the conversion process, heat may be generated in the LED die 124 (e.g., due to limited conversion of electrical energy to photon energy) and in the luminescent material 120. The heat may be dissipated in the substrate 154, such as in a ceramic substrate.

As shown in fig. 2, the phosphor LED 122 may include a light emitting diode 118. The light emitting diode 118 may be configured to convert current into primary light, such as blue primary light, using at least one LED chip and/or at least one LED die 124 as illustrated in fig. 2. In particular, a p-n junction diode may be used. As an example, one or more LEDs 118 selected from the group of indium gallium nitride (InGaN) based LEDs 118, gaN based LEDs 118, inGaN/GaN alloy based LEDs 118, or combinations thereof, and/or other LEDs 118 may be used. Additionally or alternatively, quantum well LEDs 118 may also be used, such as one or more InGaN-based quantum well LEDs 118. Additionally or alternatively, super-radiating LEDs (slds) and/or quantum cascade lasers may be used. As is further apparent from fig. 2, the phosphor LED may comprise at least one luminescent material 120 configured for light conversion of primary light generated by the light emitting diode 118. Various types of conversion and/or luminescence are known and may be used in the context of the present invention. Specifically, the luminescent material 120 may include at least one of cerium doped YAG (YAG: ce ³⁺ or Y ₃Al₅O₁₂:Ce³⁺), rare earth doped Sialon, copper aluminum co-doped zinc sulfide (ZnS: cu, al).

The luminescent material 120 may in particular form at least one layer. In general, various alternatives for positioning the luminescent material 120 relative to the light emitting diode 118 are possible, which may be used alone or in combination. First, the luminescent material 120 (e.g., at least one layer of luminescent material 120, such as a phosphor) may be positioned directly on the light emitting diode 118, e.g., with no material between the LED 118 and the luminescent material 120, or with one or more transparent materials therebetween, such as with one or more transparent materials (particularly transparent to primary light) between the LED and the luminescent material 120. Thus, as an example, a coating of luminescent material 120 may be placed directly or indirectly on the LEDs 118 (not shown). Additionally or alternatively, as an example, the luminescent material 120 may form at least one conversion body 160, such as at least one conversion plate, which may also be referred to as conversion plate. The conversion body 160 may be placed on top of the LED 118, for example, as illustrated in fig. 2, by adhesively attaching the conversion body 160 to the LED 118. Additionally or alternatively, the luminescent material 120 may also be placed in a remote manner such that the primary light from the LED 118 has to pass through an intermediate light path before reaching the luminescent material 120 (not shown). Also, as an example, the remotely located luminescent material may form a solid or conversion body 160, such as a disk or conversion disk. In the intermediate optical path, one or more optical elements, such as one or more of lenses, prisms, gratings, mirrors, apertures, or combinations thereof, may be placed. Thus, in particular, an optical system with imaging properties may be placed in the intermediate light path between the LED 118 and the luminescent material 120. Thus, as an example, the primary light may be focused or focused onto the conversion body 160.

In the light source 114, in particular the phosphor LED 122, at least one luminescent material 120 may be positioned relative to the light emitting diode 118 such that heat transfer from the light emitting diode 118 to the luminescent material 120 is possible. More specifically, the luminescent material 120 may be positioned such that heat transfer may be by one or both of thermal radiation and thermal conduction (more preferably by thermal conduction). Thus, as an example, the luminescent material 120 may be in thermal and/or physical contact with the light emitting diode 118, as shown in fig. 2. Thus, in general, the temperature of the luminescent material 120 and the temperature of the light emitting diode 118 may be coupled.

As shown in fig. 2, the light source 114 (and in particular the phosphor LED 122) may include further components such as at least one side coating 162 covering at least one side (such as a top surface, a bottom surface, and/or one or more lateral sides) of at least one of the substrate 154, the contact pads 158, the light emitting diode 118, and the luminescent material 120. In particular, the side coating 162 may cover voids and/or gaps that may be present in a layered arrangement of the light sources 114, as shown in fig. 2. Other components of the light source 114, in particular components not shown in fig. 2, are possible. In general, the light sources 114 (and in particular the phosphor LEDs 122) may be packaged in a housing (not shown in fig. 2) or may be unpackaged. Thus, the LED 118 and the at least one luminescent material 120 for light conversion of the primary light generated by the light emitting diode 118 may in particular be accommodated in a common housing. Alternatively, however, the LEDs 118 may also be shell-less or bare LEDs 118, as illustrated in fig. 2.

The schematic flow chart of fig. 3 illustrates a process of generating a detector signal and processing the detector signal to, for example, generate a corrected signal. In particular, a hardware component 164 that may be involved in the process or in the generation and/or preprocessing of the detector signals and a software component 166 that may be involved in the processing and/or correction of the detector signals are illustrated in fig. 3. The hardware component 164 (also referred to simply as "hardware" 164) may specifically include at least one light emitting diode 118 (particularly a blue LED 118) of the spectrometer device 110 configured to emit blue primary light. The hardware component 164 may further include a luminescent material 120 (also referred to as an LED phosphor), an object 112, and one or more optical components 151 (e.g., at least one wavelength-selective element 152) and a detector 128.

As part of the correction that the evaluation unit 136 may perform, a correction of temperature variations (even of local temperature variations inside the light source 114) may be performed, which temperature variations may have an influence on the emission characteristics of the light source 114. In addition to the hardware component 164, the temperature of the selected hardware component 164 is indicated in FIG. 3. For example, depending on the arrangement of hardware components 164 (such as the relative position and distance of the hardware components in spectrometer device 110), hardware components 164 may have different or the same temperatures. Specifically, as described above, the temperature of the light emitting material 120 and the temperature of the light emitting diode 118 may be coupled, for example, due to heat transfer caused by one or both of heat radiation and heat conduction between the light emitting diode 118 and the light emitting material 120. Thus, in particular, the temperature of the LED 118 (which may also be referred to as "T _pn") and the temperature of the luminescent material 120 (which may also be referred to as "T _Ph") may be similar or even identical. In fig. 3, the temperature of the LED 118 is indicated by reference numeral 168, the temperature of the luminescent material 120 is indicated by reference numeral 170, and the temperature of the detector 128 (also referred to as "T _D") is indicated by reference numeral 172.

When a current flows through the LED 118 (e.g., due to the drive unit 138 applying an appropriate voltage to the LED), the LED 118 may emit primary light to generate a particular current (e.g., a predetermined current). The target signal S _t, as indicated by reference numeral 174 in fig. 3, may be provided to, for example, the drive unit 138 to drive the LED 118 to emit blue primary light. In particular, the target signal S _t 174 may be a predetermined current value through the LED 118 to be generated, for example, by applying an appropriate voltage. In particular, the predetermined current value may be in the range of 10 mA to 500 mA, more particularly in the range of 100 mA to 300 mA, for example a current value of 50 mA. Thus, the known predetermined current may generate a predetermined light output of the LED 118, such as blue primary light. LED 118 may be at a temperature "T _pn" indicated by reference numeral 168. The blue primary light may be converted by the luminescent material 120 into secondary light, such as into light in the infrared spectral range. The luminescent material 120 may be at a temperature "T _ph" indicated by reference numeral 170. The illumination light 116 generated by the light source 114 may illuminate the object 112, which may include at least one of primary light or a portion thereof, secondary light or a portion thereof, or a mixture of primary light and secondary light. To direct the illumination light 116, one or more optical components 151 (such as one or more mirrors, lenses, wavelength-selective elements 152, or other optical components 151) may be used, for example, by placing the optical components 151 in the beam path of the illumination light 116. Detection light (e.g., reflected light) from the object 112 may be directed to the detector 128. In the beam path of the detection light 130, also optionally, one or more optical components 151 may be used. As an example, one or more wavelength selective elements 152, such as one or more dispersive elements, may be used, for example, to separate the detection light 130 into its spectral components.

As described in more detail above, the detector 128 may, for example, include an array of photosensitive elements 134. In particular, the detector 128 may be or may include a pixel sensor, such as a CCD chip or a CMOS chip, including a plurality of pixels arranged on the chip. As an example, each pixel may correspond to a predetermined spectral range, for example by being sensitive to the predetermined spectral range. Thus, the detector 128 may generate a detector signal S _px,i, 176, as indicated by reference numeral 176 in fig. 3, comprising a plurality of detector signals. Thus, each of the plurality of detector signals may correspond to an electronic signal generated by one of the plurality of pixels of the detector 128. Each of the plurality of detector signals may be given, for example, as a value corresponding to a count number of the respective pixels measured, for example, during a predetermined time span. Thus, the detector signal S _px,i 176,176 may specifically be a function of the wavelength of the detection light 130, as indicated by the index "px". Signal S _px,i 176,176 may further be a function of time (e.g., in the case of a time-dependent detector signal), as indicated by index "i".

The plurality of signals comprised by the detector signal S _px,i 176,176 may be generated simultaneously or in a time-sequential manner. The detector signal S _px、i 176,176 may be determined using readout electronics 178 as shown in fig. 3. The detector signal S _px、i 176,176 may be processed, for example as part of a pre-processing and/or as part of a further processing step. As an example, the pixels comprised by the detector 128 may in particular be active pixel sensors, which may be adapted to amplify the electronic detector signal S _px,i 176,176, e.g. as part of a pre-processing procedure before further processing, which may be performed, e.g., by one or more of the software components 166.

The signal S _px,i 176 generated by the detector 128 may also be referred to as "frame signal S _px,i 176". Fig. 3 illustrates with an arrow the process of providing a signal S _px,i 176,176 to one of the software components 166. In particular, the software component 166 configured to process and/or correct the detector signal S _px,i 176,176 may include at least one first software 180 (which may also be referred to as "software 1") and at least one second software 182 (which may also be referred to as "software 2"). The first software 180 may be configured to perform at least one first processing step 184 (also referred to as "process 1") on the detector signal S _px,i 176, such as by applying at least one algorithm to the detector signal S _px,i 176. Specifically, the first processing step 184 may include at least one correction for transient effects or time-dependent effects. Thus, as an example, the first processing step 184 may include one or more of correcting for dark signals, correcting for dark signal drift, correcting for effects of fluctuations, correcting for individual detector elements or individual time step photo-detector responses, correcting for environmentally induced (e.g., temperature induced) photo-detector response variations, extracting information for subsequent processing, adding or multiplying with parameters generated from information about at least one operating parameter or about device temperature. The first software 180 may be configured to perform at least one further step comprising performing at least one fast fourier transform 186 on the detector signal. Thus, as a result of the application of the first processing step 184 and/or the fast fourier transform 186 to the detector signal S _px,i, a signal S _px 188 (also referred to as "pixel signal S _px 188") may be generated, which may no longer be a function of time. In particular, the time dependence of the frame signal S _px,i 176,176 may be eliminated by one or more of the steps forming part of the first software component 1, while the wavelength dependence may still be present in the turn-on signal S _px 188, as indicated by the index "pn". Fig. 3 further illustrates the process of providing the signal S _px 188,188 to the second software 182 with an arrow. The second software 182 may be configured to perform at least one second processing step 190 (also referred to as "process 2") on the signal S _px 188,188, such as by applying at least one algorithm to the signal S _px 188,188, thereby generating at least one corrected signal S _px,corr 191. In particular, the second processing step 190 may include one or more of correction of dark signals, correction of dark signal drift, correction of wave effects, correction of photo-detector response of individual detector elements or individual time steps, correction of photo-detector response variations caused by the environment (e.g. caused by temperature), extraction of information for subsequent processing, manipulation of at least one parameter, e.g. addition or multiplication with a parameter, generated from information about at least one electrically measurable quantity (in particular forward voltage) or about the device temperature. In particular, corrected signal S _px,corr 191 may include a plurality of corrected signals, such as a plurality of corrected electronic signals. Each of the plurality of corrected signals may specifically correspond to a correction count number of the respective pixel.

The spectrometer apparatus 110 comprises at least one evaluation unit 136 for evaluating at least one detector signal generated by the detector 128 and for deriving spectroscopic information about the object 112 from the detector signal. The evaluation unit 136 is configured for taking into account information items about at least one operating parameter when deriving the spectroscopic information from the detector signal. The evaluation unit 136 may be configured, in particular by software programming, for evaluating and/or processing the detector signals as part of the first processing step 184 of the at least one first software 180. The evaluation unit 136 may in particular be configured for determining at least one correction from the item of information about the at least one operating parameter and may further be configured for correcting the at least one detector signal by using the correction. Thus, the evaluation unit 136 may process and correct the signal S _px 188,188 to generate a signal S _px,i,corr, which may then be further processed, for example by applying a fast fourier transform 186.

For example, as described in more detail above, both the light emitting diode 118 and the light emitting material 120 may be based on different materials and/or different material compositions, which typically affect the spectrum 192 of the phosphor LED 122. However, the spectrum 192 or spectral characteristics of a particular phosphor LED 122 may vary with temperature even when operated at a particular predetermined current. These changes may include shifts in emission peaks 193, broadening or narrowing of spectrum 192, increases or decreases in emission, and the like. However, in many cases, the emissions at some wavelengths are affected to a greater extent than the emissions at other wavelengths. This effect is illustrated by the graph shown in fig. 4, which represents the superposition of the infrared radiation spectra 192 of the phosphor LED 122 at various temperatures. Specifically, the graph in FIG. 4 shows the power spectral density (PDS) 194 in microwatts per nanometer (μW/nm) on the y-axis 196 as a function of wavelength 198 in nanometers on the x-axis 200. For the spectrum 192 represented, the temperature range at which the phosphor LED 122 generates the illumination light 116 is from 25 ℃ to 50 ℃. Typically, there is a specific center wavelength within the spectrum 192, where the power spectral density is typically invariant with temperature. Thus, with respect to the increment/decrement of power, each wavelength typically has its own temperature coefficient. Thus, as is apparent from fig. 4, the shape of the spectrum 192 varies with temperature. To more clearly visualize this effect, a number of four specific wavelength intervals are indicated in fig. 4, each centered on one of the four specific wavelengths within the spectrum 192 range. The wavelength interval is delimited by a dashed line. Specifically, the following four wavelengths and their corresponding intervals are labeled with reference numeral 1643 nm as indicated by reference numeral 202, 1750 nm as indicated by reference numeral 204, 1802 nm as indicated by reference numeral 206, and 1950 nm as indicated by reference numeral 208. For each of these wavelengths, the variation of the transmit power with temperature normalized to the variation of the transmit power at 25 ℃ over the temperature range from 25 ℃ to 50 ℃ is shown in the graph of fig. 5. In the graph of fig. 5, the transmit power variation (given in percent) normalized to the transmit power variation at 25 ℃ is shown on the y-axis 196 and indicated by reference numeral 219, while the temperature in units of ℃ is indicated on the x-axis 200 (indicated by reference numeral 220). The line in the graph in fig. 5 indicates a fitted curve 236. As is apparent from fig. 5, the transmit power at the center wavelength of 1802 nm may have very little variation (i.e., transmit power variation to zero or near zero) over the observed temperature range, while for other wavelengths (e.g., for 1643 nm or 1953 nm) the transmit power variation may have significant variation.

When a particular current (such as a particular predefined value of current) through the light emitting diode 118 is generated by applying a forward voltage to the light emitting diode 118, the appropriate forward voltage may be a function of the temperature of the light emitting diode 118. Thus, when the same current is applied to the light emitting diode 118, the forward voltage of the LED 118 generally decreases with increasing temperature. Each type of LED 118 has its own forward voltage-temperature characteristic. Typically, the forward voltage of the LED 118 decreases linearly with increasing temperature, such as withTo the point ofSlope in the range of V/K. Fig. 6 illustrates this relationship for a particular LED 118. In particular, the graph of fig. 6 shows a forward voltage applied to the LED 118 for generating a direct current through 150 mA of the LED 118 that varies with the temperature of the LED 118. The forward voltage in volts is represented by reference numeral 224 on the y-axis 196. The temperature in degrees Celsius is indicated by reference numeral 220 on the x-axis 200. As is apparent from fig. 6, in this case, the forward voltage linearly decreases with an increase in temperature. The curve in fig. 5 can be described by the following equation:

Wherein, the Representing forward voltageIndicating temperature. In the graph of fig. 6, the measurement points 221 represented by gray solid circles and the dashed lines corresponding to the given fitting curve 236 described above are shown. Instead of the relation and/or curve between forward voltage and temperature as described above in an exemplary manner, another relation between an electrically measurable quantity required to drive the light source and temperature may be used, such as feeding in electrical power, current, resistance, inductance, capacitance, etc.

Thus, by using at least one operating parameter as a correction parameter, separate temperature corrections can be performed for the spectrum 192 at different wavelengths. In particular, the evaluation unit 136 may be configured for individually correcting the plurality of detector signals of the detector signal S _px,i and for combining the individually corrected detector signals to obtain the spectroscopy information. As outlined above, the individual correction may be performed by using an array of photosensitive elements 134, wherein each photosensitive element may be configured for generating at least one detector signal, and wherein each detector signal may be individually corrected by using at least one operating parameter as correction parameter. Finally, the corrected detector signals may be combined to obtain the spectroscopy information.

In order to obtain spectroscopic information (in particular a spectrum) about the object 112, the spectrometer device 110 (in particular the evaluation unit 136) may in particular take into account the characteristics of the luminescent material 120 used in the light source 114. As outlined in more detail above, the luminescent material 120 may be configured to absorb primary photons generated by the light emitting diode 118 and, in response, may emit secondary photons instantaneously or after a delay or decay time. The signal or emission of the phosphor LED 122 after turning off the forward current may be described using equations (1) and (2) as described above.

Thus, the characteristics of the luminescent material 120 may be in particular the decay constant228 And growth constantThe decay constant may describe a typical time for afterglow of luminescent material 120 and the increase constant may describe a typical time to reach emission saturation of the converted light. Time constantAndTypically different between different phosphor LEDs 122 and/or between different types of luminescent materials 120. In addition, the damping constantConstant of growthMay depend on the wavelength. The time constant is typically extracted from the step response of the optical signal by applying/switching off a forward current. Fig. 7A and 7B show spectra 192 of two different types of phosphor LEDs 122 that emit light in the near infrared range. In particular, the power spectral density is shown as a function of wavelength, given in nm. As is apparent from fig. 7A and 7B, the spectra 192 of the two different phosphor LEDs 122 are different. Thus, by way of example, the spectrum 192 shown in fig. 7A reflects a high emission in the range from 1400 nm to 1600 nm, while the emission in this region is negligible for the phosphor LED 122, whose spectrum 192 is shown in fig. 7B. Decay constant of phosphor LED 122 (the spectrum of which is shown in fig. 7A)Constant of growthAre given as a function of wavelength in fig. 8A and 8B, respectively. Decay constant of phosphor LED 122 (the spectrum of which is shown in fig. 7B)Constant of growthAre given as a function of wavelength in fig. 9A and 9B, respectively. In particular, FIGS. 8A and 9A show the corresponding decay constant in ms on the y-axis 196(Indicated by reference numeral 228) with wavelength 198 in nm on x-axis 200, and FIGS. 8B and 9B show the corresponding growth constant in ms on y-axis 196Relationship (indicated by reference numeral 230) to wavelength 198 in nm on the x-axis 200. Data points from different repeated measurements are marked with different shades of gray.

Another characteristic of the LED 118 is that the light output power varies with forward current. Thus, in general, by increasing the forward current (specifically the input current), the power emitted by the LED 118 will increase. The shape (e.g., slope) of the curve of light output as a function of forward current is a characteristic of each LED 118. An example of such a curve is shown in fig. 10. Specifically, in the graph of fig. 10, the normalized light output 232 of the phosphor LED is shown as a function of forward current 234, which is given in amperes.

In fig. 11, a method 236 of operating a spectrometer device 110 for obtaining spectroscopic information about at least one object 112 is illustrated. The method 236 comprises the following method steps:

i. A step 238 of illuminating the object with illumination light 116 generated by at least one light source 114 of the spectrometer device 110, the light source 114 comprising at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118;

Step 240 of determining at least one actual value of at least one operating parameter of the spectrometer device 110 by using at least one drive unit 138 of the spectrometer device 110, the drive unit 138 being configured for electrically driving the light source 114;

step 242 of detecting the detected light from the object 112 by using the at least one detector 128 of the spectrometer device 110 and generating at least one detector 128 signal, and

Step 244 of evaluating the detector signal by using at least one evaluation unit 136 of the spectrometer device 110 to obtain therefrom spectroscopic information about the object 112, the evaluation unit 136 being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence of an actual value of the at least one operating parameter and for taking into account the selected correction information item to obtain the spectroscopic information.

The set of correction information items may be specific to an individual spectrometer device 110 and/or specific to a plurality of spectrometer devices 110, in particular wherein the set of correction information items is assigned to each spectrometer device 110 in accordance with the serial number of that spectrometer device 110.

The detector 128 may provide at least one raw detector 128 signal in step iii. Wherein in step iv the evaluation unit 136 may correct the raw detector 128 signal to at least one corrected detector 128 signal by using the at least one selected correction information item. The evaluation unit 136 may comprise a database having a plurality of correction information items stored therein as a function of the values of at least one different operating parameter. The database may comprise at least one look-up table which is in particular configured for providing a plurality of correction information items considered by the evaluation unit 136 for deriving the spectroscopic information.

The at least one operating parameter comprises a set of at least two operating parameters. The at least two operating parameters may be independently selected from the group consisting of an input current applied to the light emitting diode 118, a voltage applied to the light emitting diode 118, an electrical power applied to the light emitting diode, a forward voltage of the light emitting diode 118, a forward current of the light emitting diode 118, an ambient temperature, a temperature within the spectrometer device 110, in particular a temperature within at least one of the light source 114, the drive unit 138, the detector 128 or the evaluation unit 136, an operating scheme parameter, in particular a number and/or sequence of measurements, a measurement duration, a duty cycle, a parameter related to an operating scheme of the light source 114, a parameter related to an operating parameter of the detector 128.

The at least two operating parameters include at least one temperature (specifically at least one of an ambient temperature and a temperature within the spectrometer device 110), and at least one of an electrical operating parameter of the spectrometer device 110 and an optical operating parameter of the spectrometer device 110. The at least two operating parameters may further include at least one operating recipe parameter. The method may be at least partially computer-implemented, in particular step iv.

In fig. 12, a calibration method 246 is shown that compiles a set of correction information items for use in a method 236 of operating a spectrometer device 110. The calibration method 246 includes the following method steps:

I. A step 248 of performing a plurality of calibration measurements under different operating conditions of the spectrometer device 110, each calibration measurement comprising measuring a system response of the spectrometer device 110 in a controlled environment, the system response comprising spectral information;

Step 250 of recording at least one value of at least one operating parameter for each of the calibration measurements;

Step 252 of compiling a set of correction information by comparing the spectral information with the recorded at least one value of the at least one operating parameter for each of the calibration measurements.

The method 246 may include performing calibration measurements under predetermined and controlled environmental conditions. Step iii may comprise storing at least one of the emission spectrum, a correction function of the emission spectrum or a correction factor of the emission spectrum in a look-up table. The calibration measurements may be performed at different ambient temperatures.

As further illustrated in fig. 13, which shows an exemplary calibration setup 266, step i. may include using an external detector 254, specifically at least one of an external spectrometer 268 and an external power meter 270. The calibration method may include using an external power meter 270 having at least one wavelength selective element, in particular at least one of an optical filter, a dispersive element and a diffractive element.

Step i. may comprise using the light source 114 of the spectrometer device 110 and using at least one calibration target 260, in particular using at least one diffusely reflective calibration target 260 having known reflectance spectral characteristics, wherein step i. may further comprise performing a plurality of spectral measurements with the light emitting diode 118 of the light source 114 at a predetermined repetition rate, in particular at least a repetition rate of 0.1 Hz, 0.5 Hz, 1 Hz, 2 Hz, 5 Hz or 10 Hz. The at least one diffusely reflective calibration target 260 for determining at least one performance parameter associated with the detector 128 may be comprised by an integrating sphere 272, wherein the integrating sphere 272 is configured for connecting the spectrometer device 110 to an external detector and/or an external light source, e.g. by using at least one optical port.

Step ii. May comprise recording at least two, in particular at least three, and more particularly all, of the operating parameters in the list of operating parameters consisting of the input current applied to the light emitting diode 118, the voltage applied to the light emitting diode 118, the forward voltage of the light emitting diode 118 and the forward current of the light emitting diode 118, the operating recipe parameters (in particular as number and/or order of measurements), the measurement duration, the parameters related to the operating recipe of the light source 114, the parameters related to the operating parameters of the detector 128, and wherein the calibration method may further comprise recording at least one light signal, wherein the at least one light signal comprises at least one of the detector 128 signal of the detector 128 of the spectrometer device 110 and the signal provided by the external detector 254, in particular an external power meter, and wherein step iii. May comprise deriving the correction information by taking into account the light signal.

Another correction information item for correcting the at least one determined actual value of the at least one operating parameter determined by the drive unit 138 may be determined by using the external measurement settings 262 and wherein step iii. May comprise taking the another correction information item into account when compiling the set of correction information. As further illustrated in fig. 13, the external measurement setup 262 may be electronically coupled to the spectrometer device 110 through the use of an electronic coupling 264.

The light source 114 may be driven in a predefined scheme in such a way that the temperature of the light source 114 may be set to a predefined value, in particular by taking into account the further correction information item and/or the thermal mass of the light source 114.

Performing calibration measurements in step i. at different operating conditions of the spectrometer device 110 may be performed by determining at least one performance parameter using an external light source 256, in particular an external light source having a known emission spectrum, in particular determining at least one performance parameter related to the detector 128, or using an external detector 254, in particular an external detector having a known spectral efficiency, in particular determining at least one performance parameter related to the detector 128, wherein the at least one performance parameter is taken into account in step iii. Thus, in particular, the external light source 256 and/or the external detector 254 may be optically connected to the spectrometer device 110, for example by using at least one optical fiber and/or a plurality of optical fibers (e.g. comprised by a bundle of optical fibers). The optical coupling 258 may be via a diffusely reflective calibration target 260, in particular comprised by an integrating sphere 272. The optical connection may be configured to propagate light in a first direction and/or in a second direction opposite to the first direction. In particular, light generated by the spectrometer device 110 may thereby propagate from the diffusely reflective target to at least one of the spectrometer device 110, the external light source 256, or the external detector 254.

The determination of the performance parameter of the light source 114 may be performed after the performance parameter of the detector 128 is determined, in particular in order to ensure that the detector 128 is not affected by the heat generated by the light source 114.

The calibration method may be repeated for another light source 114 of the same type, wherein another set of correction information specific to the other light source 114 may be compiled.

List of reference numerals

110 Spectrometer apparatus

112 Object

114 Light source

116 Illumination light

118 Light emitting diode

120 Luminescent material

121 Semiconductor material

122 Phosphor light emitting diode

124LED die

126 Shell

128 Detector

130 Detection light

132 Optical detector

134 Array of photosensitive elements

136 Evaluation unit

138 Drive unit

139 Measuring unit

140 Current source

142 Voltage measuring device

144 Data processing apparatus

146 Pretreatment equipment

148 Data storage device

150 Filter element

151 Optical component

152 Wavelength selective element

154 Substrate

156 Ceramic substrate

158 Contact pad

160 Switch body

162 Side coating

164 Hardware component

166 Software component

Temperature of 168LED

170 Temperature of luminescent material

172 Temperature of detector

174 Target signal S _t

176 Electronic detector signal S _px,i

178 Readout electronic device

180 Software 1

182 Software 2

184 First processing step

186 Fast fourier transform

188 Pixel signal S _px

190 Second process step

191 Signal S _px,corr

192 Spectrum

193 Peak value

194 Power spectral density in microwatts per nanometer

196Y axis

198 Wavelength, unit: nm

200X axis

2021643 nm

2041750 nm

2061802 nm

2081950 nm

219 Normalized to 25 ℃ transmit power variation (given in percent)

220 Temperature in degrees C

221 Measuring point

224 Forward voltage in volts

226 Signals, expressed in count number

228 Decay constantUnit of ms

230 Growth constantUnit of ms

232 Normalized light output

234 Forward current in amperes

236 Method of operating a spectrometer device

238 Method step i. irradiating an object

240 Method step ii.) determining a value of the operating parameter

242 Method step iii. detecting detection light from the subject

244 Method step iv., evaluating detector signals

246 Assembly of a set of correction information items

248 Method step i. performing multiple calibration measurements

Method step II.A value of an operating parameter is recorded

252 Method step iii. compiling a set of correction information

254 External detector

256 External light source

258 Optical coupling element, optical fiber

260 Calibration targets

262 External measurement setup

264 Electronic coupling

266 Calibration setup

268 External spectrometer

270 External power meter

272 Integrating sphere

Claims (14)

1. A method (236) of operating a spectrometer device for obtaining spectroscopic information about at least one object (112), the method comprising:

i. Illuminating the object (238) with illumination light (116) generated by at least one light source (114) of the spectrometer device (110), the light source (114) comprising at least one light emitting diode (118) and at least one luminescent material (120) for light converting primary light generated by the light emitting diode (118);

Determining at least one actual value (240) of at least one operating parameter of the spectrometer device (110) by using at least one drive unit of the spectrometer device (110), the drive unit being configured for electrically driving the light source (114);

Detecting detected light (242) from the object (112) by using at least one detector (128) of the spectrometer device (110) and generating at least one detector (128) signal, and

-Evaluating the detector signal (244) by using at least one evaluation unit (136) of the spectrometer device (110) to obtain therefrom the spectroscopic information about the object (112), the evaluation unit (136) being configured for selecting at least one correction information item from a predetermined set of correction information items depending on an actual value of the at least one operation parameter, wherein the at least one operation parameter comprises a set of at least two operation parameters, wherein the at least two operation parameters comprise at least one temperature, and at least one of an electrical operation parameter of the spectrometer device (110) and an optical operation parameter of the spectrometer device (110), and for taking into account the selected correction information item to obtain the spectroscopic information.

2. Method according to the preceding claim, the evaluation unit (136) comprising a database having stored therein a plurality of correction information items as a function of the value of the at least one different operating parameter.

3. Method according to the preceding claim, wherein the database comprises at least one look-up table.

4. The method according to any one of the preceding claims, wherein the at least two operating parameters further comprise at least one operating recipe parameter.

5. A calibration method (246) of compiling a set of correction information items for use in a method according to any preceding claim, the calibration method comprising:

I. Performing a plurality of calibration measurements (248) under different operating conditions of the spectrometer device (110), each calibration measurement comprising measuring a system response of the spectrometer device (110) in a controlled environment, the system response comprising spectral information;

recording at least one value (250) of the at least one operating parameter for each of the calibration measurements;

compiling a set of correction information (252) by comparing the spectral information with the recorded at least one value of the at least one operating parameter for each of the calibration measurements, wherein the at least one operating parameter comprises a set of at least two operating parameters, wherein the at least two operating parameters comprise at least one temperature, and at least one of an electrical operating parameter of the spectrometer device (110) and an optical operating parameter of the spectrometer device (110).

6. The calibration method (246) according to any of the preceding claims related to a calibration method, wherein step i. comprises using a light source (114) of the spectrometer device (110) and using at least one calibration target, wherein step i. further comprises performing a plurality of spectral measurements with a light emitting diode (118) of the light source (114) at a predetermined repetition rate.

7. The calibration method (246) according to any one of the preceding claims directed to a calibration method, wherein step ii. Comprises recording at least two of an input current applied to the light emitting diode (118), a voltage applied to the light emitting diode (118), a forward voltage of the light emitting diode (118) and a forward current of the light emitting diode (118), an operating scheme parameter, a measurement duration, a parameter related to an operating scheme of the light source (114), a parameter related to an operating parameter of the detector (128), and wherein the calibration method further comprises recording at least one light signal, wherein the at least one light signal comprises at least one of a detector (128) signal of the detector (128) of the spectrometer device (110) and a signal provided by an external detector (254), and wherein step iii. Comprises deriving the correction information by taking the light signal into account.

8. Calibration method (246) according to any of the preceding claims related to a calibration method, wherein a further correction information item for correcting the at least one determined actual value of the at least one operating parameter determined by the drive unit is determined by using an external measurement setting (262), and wherein step iii. Comprises taking the further correction information item into account when compiling the set of correction information.

9. The calibration method (246) according to any of the preceding claims related to a calibration method, wherein the light source (114) is driven in a predefined scheme by setting the temperature of the light source (114) to a predefined value.

10. Calibration method (246) according to any of the preceding claims related to a calibration method, wherein performing a plurality of calibration measurements in step i. with different operating conditions of the spectrometer device (110) is performed by determining at least one performance parameter by at least one of the following operations:

Using an external light source (256) to determine the at least one performance parameter associated with the detector (128), or

Determining the at least one performance parameter associated with the detector (128) using an external detector (254);

Wherein in step iii, a set of correction information is compiled taking into account the at least one performance parameter.

11. A spectrometer device (110) for obtaining spectroscopic information about at least one object (112), the spectrometer device (110) comprising:

A. At least one light source (114) for generating illumination light (116) for illuminating the object (112), the light source (114) comprising at least one light emitting diode (118) and at least one luminescent material (120) for light converting primary light generated by the light emitting diode (118);

B. at least one driving unit for driving the light source (114), the driving unit being configured for determining at least one actual value of at least one operating parameter of the spectrometer device (110);

C. At least one detector (128) for detecting light from the object (112) and for generating at least one detector (128) signal, and

D. At least one evaluation unit (136) for evaluating the detector (128) signal and for deriving therefrom the spectroscopic information about the object (112), the evaluation unit (136) being configured for selecting at least one correction information item from a predetermined set of correction information items in dependence on an actual value of the at least one operation parameter and for taking the selected correction information item into account for deriving the spectroscopic information, wherein the at least one operation parameter comprises a set of at least two operation parameters, wherein the at least two operation parameters comprise at least one temperature, and at least one of an electrical operation parameter of the spectrometer device (110) and an optical operation parameter of the spectrometer device (110).

12. A computer program comprising instructions which, when the program is executed by a spectrometer device (110) according to any of the preceding claims directed to a spectrometer device (110), cause the spectrometer device (110) to perform a method of operating a spectrometer device (110) according to any of the preceding claims directed to a method of operating a spectrometer device (110).

13. A computer readable storage medium comprising instructions which, when the program is executed by a spectrometer device (110) according to any of the preceding claims directed to a spectrometer device (110), cause the spectrometer device (110) to perform a method of operating a spectrometer device (110) according to any of the preceding claims directed to a method of operating a spectrometer device (110).

14. A non-transitory computer readable medium comprising instructions that, when executed by one or more processors of an evaluation unit (136) of a spectrometer device (110) according to any one of the preceding claims directed to a spectrometer device (110), cause the one or more processors to perform a method of operating a spectrometer device (110) according to any one of the preceding claims directed to a method of operating a spectrometer device (110).