JP3797759B2 - Optical measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a measuring apparatus for optically measuring a specific substance in a scattering substance such as a liquid, food, or human body, for example, measuring glucose, hemoglobin, sugar in a fruit, etc. in blood or urine. Suitable for.
[0002]
[Prior art]
2. Description of the Related Art In recent years, various optical measurements have been performed by irradiating a measurement object with light and using transmitted and scattered light of the light from the measurement object. In this specification, the term “transmitted scattered light” is used to include all the light that has entered a light scattering measurement object and then exited from the measurement object. The so-called transmitted light that exits is also used to include all the so-called reflected light that exits in the direction opposite to the incident direction.
[0003]
In these measurements, the intensity of the transmitted scattered light obtained by irradiating the measurement object is measured for each wavelength to obtain information in the measurement object. For this reason, it is necessary to spectrally divide the light irradiated on the measurement object (pre-spectral) or to spectrally disperse the transmitted scattered light (post-spectral). Various types of spectroscopic means are used. Currently used in general, FTIR (Fourier Transform Infrared Spectrometer) or a method of spectroscopically separating light of continuous wavelength by moving parts such as an optical grating increases the measurement time, and the amount of light drifts during that time. There are problems that are likely to occur and affect accuracy. Spectroscopy at a separate wavelength using a filter as a spectroscopic element or using an LD (laser diode) or LED (light emitting diode) as a light source not only increases the cost, but also increases the time required for spectroscopy. In order to convert the wavelength, it is necessary to replace hardware components such as a filter and a light source, and there is a problem that the number of components increases.
[0004]
On the other hand, as a combination of a continuous light source and a spectroscopic device, there is a spectroscopic device using an acousto-optic element (AOTF). The acoustooptic device is obtained by attaching an acoustic wave transducer to an acoustooptic crystal, and a wavelength that passes through the crystal is selected according to an acoustic wave (RF) frequency applied from the transducer to the acoustooptic crystal. The acoustooptic device does not have a mechanically movable part and can perform wavelength scanning at high speed. Spectrophotometers using acousto-optic elements are commercially available.
As a measuring method using an acousto-optic element as a spectroscopic element, for example, a method of measuring differential absorption of two wavelengths (EP401453A1) or a method of measuring a difference spectrum in a state where the blood volume of the tissue of the measurement object is different (USP5 372,135).
[0005]
[Problems to be solved by the invention]
However, a relative measurement method such as two-wavelength measurement can measure a component with high accuracy if it is a simple system such as an aqueous solution system containing only a single component, but it can be used in many cases such as food and human bodies. For a complex system having components, it is very difficult to measure each component with high accuracy. Because if the measurement object is different, even if the change of one component is the same, the rate of change of the other component is different. It is difficult to extract. Furthermore, since it is necessary to extract a very weak signal, errors due to changes in conditions such as blood volume at the measurement site (for example, pressure, surface reflectance, path length, etc.) occur. It is also difficult to extract only the signal of the component of interest from among the signals including the.
[0006]
When measuring transmitted scattered light from a measurement sample, if the measurement light is very weak and the detection signal and the noise intensity are equal, an ordinary amplifier can obtain an output signal with a high S / N ratio. Can not. For example, FIG. 1 shows an absorption spectrum of water. As shown in the spectrum, the absorbance varies greatly depending on the spectral wavelength. In general, the detected intensity of the transmitted scattered light of a sample also varies greatly depending on the wavelength. As described above, when the measurement signal from the detector changes in a large range, in an amplifier whose amplification is kept constant, the measurement signal is taken into a computer through an A / D converter in a weak wavelength region. This may cause the measurement resolution to be lowered.
[0007]
In order to improve the purity of the spectral wavelength in the acoustooptic device, the light incident on the acoustooptic device needs to satisfy certain optical conditions. However, in the conventional spectrophotometer, the adjustment of the light beam incident on the acoustooptic device from the light source is not sufficient, the ratio of the 0th order light included in the + 1st order diffracted light or the −1st order diffracted light is large, and the purity of the spectral wavelength is sufficient. It is not very big.
In addition, the + 1st order diffracted light and the −1st order diffracted light emitted from the acoustooptic device are different in direction from the 0th order light, but are close to each other, so that the 0th order light is included in the extracted + 1st order diffracted light or −1st order diffracted light. It is easy to mix.
[0008]
In order to measure a measurement signal whose intensity changes in a large range while maintaining the resolution, the amplification degree must be switched. For example, when measuring a spectrum with a large dynamic range as shown in FIG. 1, a semiconductor relay circuit such as a multiplexer is used to increase the amplification degree of a signal having a low intensity, and the measurement value of a signal having a high intensity is not saturated. Thus, it is necessary to switch the amplification degree so as to lower the amplification degree. When performing measurement, pulse noise is generated by such a switching operation and affects the measured value, causing a measurement error.
[0009]
When amplifying a very weak signal, for example, a measurement signal voltage having a noise level slightly larger than the thermal noise of a circuit element, a feedback amplifier circuit using a transistor circuit or a differential amplifier circuit using an operational amplifier (operational amplifier) In the amplification method according to, noise is also amplified at the same time, so that it is impossible to distinguish between the measurement signal and noise. Therefore, it is necessary to have a circuit configuration that suppresses the noise generated from the circuit itself below the level of the measurement signal, and suppresses the influence from disturbance outside the device below the measurement signal level.
[0010]
The S / N ratio requires 100,000 or more. In conventional equipment, the S / N ratio in FTIR is not more than 10,000.
In order to eliminate the influence of noise (random noise) in which the frequency band is uniformly distributed, it is necessary to perform measurement value averaging processing by repeatedly performing measurement in the measurement wavelength band and performing integration processing.
Even if the measurement wavelength spans multiple wavelengths, if measurement is not performed in a short time, the measurement signal is affected by long-period fluctuation (drift).
[0011]
Accordingly, the present invention enables high-speed wavelength scanning using an acoustooptic element as a spectroscopic element in order to enable noninvasive measurement of a specific substance in a scattering substance with high accuracy. It is an object of the present invention to provide an optical measuring device that can increase the purity of a spectral wavelength and improve the measurement accuracy when measuring a weak signal.
[0012]
[Means for Solving the Problems]
The optical measurement device of the present invention includes a light source device that irradiates light to a measurement object, a light detection device that receives and detects transmitted scattered light from the measurement object as measurement light, and operations of the light source device and the light detection device. And a control unit for controlling.
The light source device includes a light source, an acoustooptic element as a spectroscopic element having an acoustooptic crystal in an acoustooptic crystal, and performs spectroscopic analysis by changing an acoustic wave frequency applied to the acoustooptic crystal from the acoustooptic transducer. Acoustooptic device driving device that modulates output light of acoustooptic device by intensity modulation of drive signal, and propagation of light from light source with light flux smaller than window size of acoustooptic device and smaller than allowable angle of acoustooptic device A light source optical system that enters the acoustooptic device as a light beam having an angle, a condensing optical system that condenses the + 1st order diffracted light and the −1st order diffracted light emitted from the acoustooptic device, respectively, at spatially different positions, An irradiation optical system for irradiating the measurement object with at least one of the + 1st order diffracted light and the −1st order diffracted light collected by the optical optical system; To have.
[0013]
The photodetection device includes a detection element that outputs a signal corresponding to a change in the modulated measurement light, an amplifier that receives the output of the detection element, and outputs a plurality of signals having different amplification levels at the same time, and an amplification level of the amplifier. A / D converter that converts each of a plurality of different output signals into a digital signal and a plurality of output signals of A / D converter are input, and the value of amplifier or A / D converter is saturated among these signals Channel selection means for selecting the one having the highest amplification degree, synchronization signal processing means for superimposing the selected signal on an oscillation signal synchronized with the modulation frequency obtained by modulating the measurement light, and processing the synchronization signal And a data processing unit including an integration unit for obtaining a measurement value by signal integration.
[0014]
“Propagation angle” is the angle between the optical axis of the light beam and the direction in which the light beam in the light beam propagates through space. When the optical axis of the light beam is perpendicularly incident on the acousto-optic device, the propagation angle is acoustic. Only light rays smaller than the allowable angle of the optical element contribute to the first-order diffracted light. Therefore, the intensity of the first-order diffracted light increases as the number of light beams having a propagation angle smaller than the allowable angle of the acoustooptic element in the light beam perpendicularly incident on the acoustooptic element. Preferably, the propagation angle of all light rays incident on the acoustooptic device is smaller than the allowable angle of the acoustooptic device.
[0015]
The optical axis of the light beam incident on the acoustooptic element is preferably perpendicular to the incident surface of the acoustooptic element, but the angle formed by the light beam included in the light beam and the direction perpendicular to the incident surface of the acoustooptic element is If the condition of being smaller than the allowable angle is satisfied, the direction of the optical axis of the light beam incident on the acoustooptic element is not required to be strictly perpendicular to the incident surface of the acoustooptic element.
[0016]
The light source optical system is adjusted so that the light from the light source is incident on the acoustooptic element as a light beam having a light beam smaller than the size of the window of the acoustooptic element and having a propagation angle smaller than the allowable angle of the acoustooptic element. This increases the purity of the first-order diffracted light and increases the intensity. Further, the 0th-order light, the + 1st-order diffracted light, and the −1st-order diffracted light emitted from the acoustooptic device are condensed at spatially different positions, so that the mixing of the 0th-order light into the first-order diffracted light can be suppressed. . As a result, light having a desired wavelength can be accurately extracted from the light source.
[0017]
Wavelength scanning can be performed at high speed by performing spectroscopy by changing the acoustic wave frequency applied from the acoustic wave transducer to the acousto-optic crystal. As a result, the measurement time can be shortened, and a light amount drift within the measurement time can be suppressed.
[0018]
The output light from the acoustooptic device can be modulated by intensity modulation of the drive signal of the acoustic wave transducer. By modulating the intensity, modulation synchronization detection (detection) is possible for the detection of the optical signal. Therefore, in order to remove random noise, the output light from the acoustooptic device is modulated to modulate the measurement signal, and only the modulation frequency component is obtained by applying a synchronization signal process corresponding to the lock-in process at the modulation frequency. Extract accurately.
[0019]
The measurement accuracy is improved by manipulating the amplification degree according to the signal intensity. At that time, the signal value from the detection element is simultaneously amplified at a plurality of different amplification levels by an amplifier, the output is A / D converted, and the signal amplified to the maximum is selected without being saturated among the signals. This suppresses the generation of pulse noise that would have occurred when a switching device such as a relay circuit or a multiplexer was used.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
An example of an optical system that adjusts the light from the light source to be incident on the acoustooptic device as a light beam having a smaller beam size than the window size of the acoustooptic device and a propagation angle smaller than the allowable angle of the acoustooptic device. A front mirror disposed in front of the optical axis of the light source and reflecting light from the light source in the direction of the acoustooptic device, and an optical system in which the mirror surface of the front mirror is in a conjugate relationship with the incident surface of the acoustooptic device. When the window size of the acousto-optic device is small, a mask is provided to reduce the luminous flux.
[0021]
A rear mirror disposed behind the light source on the optical axis and reflecting light from the light source toward the front mirror can be further provided. Thereby, the utilization efficiency of the light source energy from the light source to the acoustooptic device is increased.
A preferred example of the irradiation optical system is an optical system that synthesizes the + 1st order diffracted light and the −1st order diffracted light collected by the condensing optical system on the same optical axis and irradiates the measurement object. Thus, by using both the + 1st order diffracted light and the −1st order diffracted light, the utilization efficiency of the light source energy is increased.
[0022]
A preferable example of the irradiation optical system that combines the + 1st order diffracted light and the −1st order diffracted light on the same optical axis is a branched optical fiber having one end branched into at least two and the other end joined into one. The + 1st order diffracted light and the −1st order diffracted light collected by the optical optical system are incident on the branched ends of the branched optical fiber, and the measurement object is irradiated with the light emitted from the joined other end. . At this time, it is preferable that the end portion where the + 1st order diffracted light or the −1st order diffracted light is incident on the focal plane of the condensing optical system.
[0023]
A more preferable example of the irradiation optical system that combines the + 1st order diffracted light and the −1st order diffracted light on the same optical axis is a branched optical fiber having one end branched into three and the other end joined into one. Measurement of emitted light from the joined other end by making + 1st order diffracted light and −1st order diffracted light collected by the optical optical system incident on two of the branched ends of the branched optical fiber, respectively. The transmitted scattered light from the object is incident again on the end from which the emitted light is emitted, and is guided to the photodetector by the remaining one of the three branched ends.
Use of such a branched optical fiber simplifies the configuration.
[0024]
A plurality of acoustooptic elements having different spectral wavelength regions may be arranged in series on the optical path of the light source optical system, and one of the acoustooptic elements may be selected and driven. Thereby, the wavelength range which can be utilized spreads.
In order to obtain a more stable output result, it is preferable to receive the 0th-order light out of the output light from the acoustooptic device or the light source light from the lamp light source and correct the fluctuation of the light source intensity.
[0025]
A preferred example of an amplifier that simultaneously outputs a plurality of signals having different amplification degrees includes an input buffer circuit that inputs a modulation output of a detection element, and a voltage-current that converts an output voltage variation of the input buffer circuit into a current variation by a resistance element. A conversion circuit, a current-voltage conversion circuit that converts a current fluctuation caused by the voltage-current conversion circuit to a voltage fluctuation amplified by a predetermined factor using a resistance element, and an output buffer circuit that outputs the voltage fluctuation output of the current-voltage conversion circuit And an amplifying circuit for inputting a plurality of signals with different magnifications. The voltage-current conversion circuit and the current-voltage conversion circuit constitute a preamplifier, and the amplification circuit that outputs a plurality of signals having different magnifications constitutes a subamplifier. Amplification is determined by a combination of amplifying a signal at the time of voltage-current conversion by the preamplifier and further amplifying the signal at the time of current-voltage conversion. Then, the sub-amplifier simultaneously outputs the preamplifier signals with different amplification degrees.
[0026]
The data processing unit includes a low-pass filter unit that removes a high-frequency component unnecessary for the synchronization signal processing from the signal selected by the channel selection unit, and a signal that has passed through the low-pass filter unit, between the channel selection unit and the synchronization signal processing unit. It is preferable to further include data thinning means that uses a value extracted from the column for each unit number at regular intervals as a signal value. Since the data measured at a high sample frequency has a large Nyquist bandwidth, the characteristics of the low-pass filter for preventing aliasing noise can be moderated. When the thinning process is performed so that the data can be processed with a small amount of data, the apparent sampling frequency is reduced by the thinning process, and thus the frequency spectrum of the measurement value is overlapped. Before performing the thinning process, a low-pass filter is used to remove the influence of noise.
[0027]
It is preferable to perform band-pass filter processing having a pass band near the modulation frequency before performing synchronization signal processing.
In addition, since the frequency of the signal may deviate from the modulation frequency before the synchronization signal processing is performed, the accuracy of the synchronization signal processing can be improved by correcting the deviation. Therefore, the frequency deviation is measured by measuring the deviation between the frequency of the signal input to the synchronization signal processing means and the modulation frequency generated using the computer clock signal as a reference signal, and correcting the synchronization frequency of the synchronization signal processing means based on the result. It is preferable that correction means is further provided.
[0028]
Since the signal modulated by the synchronization signal processing has a constant value (DC component), it is preferable to remove the high frequency component by a low-pass filter. For this reason, it is preferable that a low-pass filter means for removing high-frequency components unnecessary for the synchronization signal processing is further provided between the synchronization signal processing means and the integration means.
The digital integration process is more accurate as the integration time constant is larger, but takes more time. Therefore, the calculation speed can be improved by converging the calculation with a value close to the true value with a small time constant in advance, and then converging with the large time constant as the initial value.
[0029]
When an amplifier outputs a plurality of different amplification degrees, an error occurs in the magnification between the sub-amplifiers having the respective amplification degrees. For example, an output with 100 times amplification is not necessarily exactly five times that with 20 times amplification. In order to correct the error, a fixed signal is input and a signal of each amplification degree is output. A certain output signal is used as a reference to obtain a correction data, and the correction data is used when digital processing is performed. Thus, by correcting the error between the amplification degrees, it is possible to eliminate the machine difference between the signals having different amplification degrees. Therefore, when a signal having a constant amplitude is input to the amplifier, a plurality of outputs having different amplification degrees of the amplifier are compared, and the difference storage means for storing the result as a difference between outputs having different amplification degrees, It is preferable to further include an amplifier output correcting means for correcting the output of the amplifier based on the machine difference stored in the difference storing means.
[0030]
If the power supply voltage of the amplifier is measured with a measuring instrument and corrected by taking a ratio with a preset reference voltage, the deviation of the absolute value of the measured value can be corrected. Therefore, it is preferable to further include a measurement result correction unit that measures the power supply voltage of the amplifier and corrects the measurement result based on a ratio to a preset reference voltage.
[0031]
In the present invention, when measuring light and reference light (zero-order light or light source light from an acousto-optic device) are measured simultaneously, a detecting element and an amplifier are provided for measuring light detection and reference light detection, respectively. The D converter converts both the measurement light detection signal and the reference light detection signal into digital signals, and the data processing unit performs similar data processing on the reference light detection signal, and the data processing result of the measurement light detection signal is obtained. It is preferable to divide and correct by the data processing result of the reference light detection signal.
[0032]
【Example】
FIG. 2 schematically shows an optical measuring apparatus according to an embodiment, and a light source device 202 that irradiates light to the measuring object 200 and transmitted scattered light from the measuring object 200 are received as measuring light. A light detection device 204 that detects the light source device 202 and a control unit 206 that controls operations of the light detection device 204 are provided.
[0033]
The light source device 202 is a spectral light source device, and changes the acoustic wave frequency applied from the acoustic wave transducer to the acoustooptic crystal by changing the light source 6, the acoustooptic device 4 as a spectroscopic element provided with the acoustooptic crystal in the acoustooptic crystal. The acoustooptic device driving device 214 that performs spectroscopy and modulates the output light of the acoustooptic device by intensity modulation of the drive signal of the acoustic wave transducer, and the light from the light source 6 with a light flux smaller than the window size of the acoustooptic device 4, And a light source optical system 216 that vertically enters the acoustooptic device 4 as a light beam having a propagation angle smaller than the allowable angle of the acoustooptic device 4, and zero-order light, + 1st-order diffracted light emitted from the acoustooptic device 4, and The condensing optical system 20 that condenses the first-order diffracted light at spatially different positions, and +1 next time the light is condensed by the condensing optical system 20 At least one of light and -1-order diffracted light and an irradiation optical system 220 for irradiating the measuring object 200.
[0034]
The light detection device 204 includes a light receiving unit 230 and a data processing unit 107. The light receiving unit 230 outputs a detection element that outputs a signal corresponding to the fluctuation of the modulated measurement light, an amplifier that receives the output of the detection element, and outputs a plurality of signals with different amplification degrees simultaneously, and an amplification degree of the amplifier. An A / D converter that converts a plurality of different output signals into digital signals is provided. The data processing unit 107 inputs a plurality of output signals of the A / D converter, and selects a signal having the highest amplification degree from which the value of the amplifier or the A / D converter is not saturated. At least a channel selection unit, a synchronization signal processing unit that superimposes the selected signal with an oscillation signal synchronized with a modulation frequency obtained by modulating the measurement light, and an integration unit that obtains a measurement value by integrating the signal subjected to the synchronization signal processing ing.
[0035]
The irradiation optical system 220 is a branched optical fiber having one end branched into two and the other end joined into one, and the + 1st order diffracted light and the −1st order diffracted light collected by the condensing optical system 20 are branched light. Light incident on each branched end of the fiber and emitted from the joined other end is irradiated onto the measuring object 200. Transmitted scattered light from the measuring object 200 is guided to the light receiving unit 230 by the optical fiber 222.
[0036]
The optical fiber of the irradiation optical system 220 and the optical fiber 222 for receiving transmitted scattered light are three-branched light in which the end facing the measurement object 200 is combined into one optical fiber bundle and the other end is branched into three. A fiber is preferred. In that case, since the + 1st order diffracted light and the −1st order diffracted light can be incident on two of the end portions branched into three and the other end portions can be guided to the light receiving portion, the configuration is simplified.
[0037]
In addition, in order to receive 0th-order light out of the output light from the acoustooptic device 4, correct fluctuations in the light source intensity, and obtain a more stable output result, 0 collected by the condensing optical system 20. The next light is guided to the light receiving unit 230 by the optical fiber 224.
Reference numeral 240 denotes a calculation unit that calculates the concentration of the target substance in the measurement object 200 from the measurement value obtained by the data processing unit 107, and reference numeral 242 denotes an output device such as a printer, a recorder, or a CRT that outputs the measurement result.
[0038]
The acoustooptic device 4 is tellurium dioxide (TeO). ₂ ) A crystal is used as an acousto-optic crystal, and an acoustic wave transducer is attached to one side thereof. Depending on the frequency applied to the crystal from the acoustic wave transducer, the wavelength is selected in the range of 800 to 2400 nm and scanned. Further, the output light of the acoustooptic device 4 is modulated by intensity modulation of the drive signal of the acoustic wave transducer. This wavelength scanning and modulation is performed by controlling the acoustooptic device driving device 214 from the control unit 206.
[0039]
When a predetermined acoustic wave frequency is given from the transducer of the acoustooptic device 4, diffracted light corresponding to the frequency is divided and emitted as + 1st order diffracted light and −1st order diffracted light, and other wavelength light is converted into 0th order light. To Penetrate. The + 1st order diffracted light and the −1st order diffracted light are combined on the same optical axis by the irradiation optical system and irradiated onto the measurement object. The zero-order light is not irradiated symmetrically, but is used for correcting the measurement light intensity as a light source intensity.
[0040]
3 to 8 show specific examples of the light source device 202 in one embodiment. FIG. 3 shows the light source chamber 2 and the acousto-optic device 4 that splits the continuous wavelength light from the light source chamber 2. The light source chamber 2 is provided with a halogen lamp as the light source 6, and is provided with a light source optical system that collects light from the light source 6 and makes it incident on the acoustooptic device 4 as substantially parallel light. A front mirror 10 is disposed in front of the optical axis 8 of the light source 6 and a rear mirror 12 is disposed behind. In order to make the light from the light source 6 collected by the mirrors 10 and 12 into parallel light, a lens 14 and mirrors 16 and 18 are disposed on the optical path between the mirror 10 and the acoustooptic device 4, and these optical systems. Then, the light source light is incident on the acoustooptic device 4.
[0041]
FIG. 4 shows the optical system in the light source chamber 2 in detail. The front mirror 10 and the rear mirror 12 are spherical mirrors having the same focal length, and are set so that the distance from the filament of the light source 6 to the rear mirror 12 is approximately twice the focal length. Further, the optical axis direction of the rear mirror 12 is set so that the filament image of the light source formed by the rear mirror 12 is slightly shifted from the filament itself. Such a design is intended to increase the utilization efficiency of the light source energy.
[0042]
The light from the light source 6 is primarily imaged behind the convex lens 14 by the front mirror 10 and the convex lens 14. At that position, a mask 15 for limiting the luminous flux is arranged as necessary. The primary imaged light image is secondarily formed on the incident surface of the acoustooptic device 4 by the spherical mirror 18. The mirror 16 is a plane mirror that only bends the optical path. By the optical system including the mirrors 10 and 12, the lens 14, and the mirrors 16 and 18, the light source light enters the incident surface of the acoustooptic device 4 as parallel light and enters perpendicularly. The propagation angle of the light beam incident after secondary imaging on the acoustooptic device 4 and the allowable value of the spot diameter are determined by the acoustooptic crystal of the acoustooptic device 4. For example, the tolerance of the propagation angle is about 6 °, and the spot diameter is 10 mm or less. The curvature of each mirror 10, 12, 18, the focal length of the lens 14, and their length are set so that the propagation angle of the light beam incident on the acoustooptic element 4 and its spot diameter fall within the tolerance range determined by the acoustooptic element 4. Size, position and angle are set.
[0043]
For example, if the tolerance of the propagation angle is 6 °, the propagation angle of all the rays in the light beam whose optical axis is perpendicularly incident on the incident surface of the acoustooptic device 4 is in the range of 0 ± 6 °. The optical system is adjusted.
Further, when the spot diameter of incident light on the acoustooptic element 4 is larger than the allowable value, a mask 15 is provided to limit the spot diameter.
The front mirror 10 and the rear mirror 12 are not limited to spherical mirrors, and may be parabolic mirrors, for example. The mirrors 10 and 12 can be designed according to the parallelism of the incident light to the acoustooptic device 4 and the allowable width of the spot diameter.
[0044]
FIG. 5 shows an example of the irradiation optical system. The light source chamber 2 and the acoustooptic device 4 are those shown in FIG. The 0th order light 26, the + 1st order diffracted light 22 and the −1st order diffracted light 24 from the acoustooptic device 4 are condensed by the lens 20 as a condensing optical system. The optical axes of the + 1st order diffracted light 22, the −1st order diffracted light 24, and the 0th order diffracted light 26 are different, and prisms 28 and 30 are arranged on the optical paths of the + 1st order diffracted light 22 and the −1st order diffracted light 24, respectively. The branched ends 32 and 34 of the branched optical fiber are arranged as incident ends on the respective optical paths. Since the 0th-order light 26, the + 1st-order diffracted light 22 and the -1st-order diffracted light 24 generated from the acoustooptic device 4 are substantially parallel lights, they are condensed on the focal plane of the lens 20. The branched ends 32 and 34 of the branched optical fiber are respectively disposed on the focal plane of the lens 20. The optical paths of the + 1st order diffracted light 22 and the −1st order diffracted light 24 are bent by the prisms 28 and 30 to separate the spatial positions from each other, and the branched ends 32 and 34 of the branched optical fiber of the irradiation optical system 220 are respectively bent. Are arranged on each bent optical path. The + 1st order diffracted light 22 and the −1st order diffracted light 24 incident on the end portions 32 and 34 of the branch optical fiber are combined on the same optical axis at the other end of the branch optical fiber and then irradiated onto the measurement object.
[0045]
Although the optical axes of the + 1st order diffracted light 22, the −1st order diffracted light 24, and the 0th order diffracted light 26 are spatially close to each other, the optical paths of the + 1st order diffracted light 22 and the −1st order diffracted light 24 The prisms 28 and 30 are used to change the light intensity, and the 0th-order light is prevented from entering each optical path. In order to change the optical paths of the + 1st order diffracted light 22 and the −1st order diffracted light 24, a mirror may be used instead of the prism.
[0046]
FIG. 6A shows an example of a branched optical fiber used in the irradiation optical system 220. (B) is an end view of the branched end of the branched optical fiber, and (C) is an end view of the joined end. This example is a three-branch optical fiber in which one end is branched into three ends 32, 34, and 36, and the other end 38 is merged into one. The optical fiber used here has a core material of GeO. ₂ Containing SiO ₂ The core diameter is 127 ± 7μm, and the cladding material is fluorine-containing SiO ₂ The clad diameter is 140 ± 5 μm. The primary coating material of each single-core optical fiber is silicone resin, the diameter of the primary coating is 165 ± 5 μm, and the numerical aperture NA value is 0.35. At the branched end portions 32, 34, and 36, the optical fibers are bundled to form a bundle fiber. The diameter of each bundle fiber is 5 mm, and the outer diameter of the coating material of these bundle fibers is 12 mm. The filling rate of the optical fiber in the bundle fiber is about 90%.
The bundle fiber diameter at the joined other end portion 38 is 8.7 mm, and the outer diameter of the coating material is 19 mm.
[0047]
FIG. 6D is a schematic diagram thereof, and at the collecting end 38, three branched optical fibers are randomly gathered. The + 1st order diffracted light 22 and the −1st order diffracted light 24 respectively incident from the branched ends 32 and 34 gather at the gathering end 38. The other one end 36 of the three branches is used to transmit the transmitted scattered light from the measurement object to the detector.
[0048]
FIG. 7 shows another example of an acoustooptic device.
Two acoustooptic elements 4a and 4b in the spectral wavelength region are arranged in series on the optical path of the light source optical system, and one of the acoustooptic elements is selected and driven. In the acoustooptic elements 4a and 4b, an acoustooptic crystal having a characteristic of diffracting into different wavelength regions is selected and used. For example, if the acoustooptic element 4a emits diffracted light in the near infrared region and the acoustooptic element 4b emits diffracted light in the visible region, one of the acoustooptic elements 4a and 4b is operated. In this way, the infrared region and the visible region can be selected. Then, by selecting the acoustic wave frequency from the transducer in each wavelength region, it becomes possible to select a wavelength in a wide wavelength region ranging from infrared to visible.
[0049]
Since the 0th-order light, the + 1st-order diffracted light, and the -1st-order diffracted light of the diffracted light generated from the acoustooptic elements 4a and 4b are substantially parallel lights, a common light is collected on the diffracted light from the acoustooptic elements 4a and 4b. By disposing the lens, the diffracted light from the acousto-optic element 4a and the diffracted light from the acousto-optic element 4b can be condensed on the focal plane of the common condenser lens. By arranging the branched end portion of the branched optical fiber as shown in FIG. 5 on the condensing surface, both the diffracted light from the acoustooptic element 4a and the diffracted light from the acoustooptic element 4b are made into the same branched optical fiber. It becomes possible to make it enter.
[0050]
FIG. 8 shows a measuring apparatus for comparing characteristics as light sources between the embodiment and a conventional spectrophotometer.
FIG. 8A shows the arrangement of one embodiment. The + 1st order and −1st order diffracted light from the acoustooptic device 4 is incident on the incident ends 32 and 34 of the three-branch optical fiber, respectively. The light is incident on the FTIR 40 from the end 38 and separated. The light dispersed by the FTIR 40 is detected by a detector (indium antimony: InSb) built into the FTIR 40 (existing). The zero-order light is incident on one end 42 of another optical fiber, is incident on another PbS element 48 from the other end 44 of the optical fiber, and is detected as monitor light that monitors fluctuations in light source intensity.
Only one of the + 1st order and −1st order diffracted light from the acoustooptic device 4 may be used, and the other may be shielded.
[0051]
On the other hand, the conventional spectrophotometer shown in FIG. 8B has a photodetector inside thereof. The light emitted from the spectroscopic unit (main body) 50 enters the branched one end 52 of the bifurcated optical fiber, enters the FTIR 40 from the collective end 56, and is split. The light dispersed by the FTIR 40 is detected by a detector built in the FTIR 40, and the light intensity is detected.
[0052]
FIG. 9 shows a first spectrum according to one embodiment. Using the measurement system of FIG. 8A, of the + 1st order diffracted light and the −1st order diffracted light, the −1st order diffracted light is incident on the incident end 34, and the other This is a spectrum obtained by performing wavelength scanning by changing the acoustic frequency of the acoustooptic device 4 in a state where light is shielded so that diffracted light does not enter the incident end 32. The vertical axis of the spectrum diagram represents energy, and E-01, E + 00, and E + 01 are 10 respectively. ^-1 , 10 ⁰ , 10 ¹ Represents.
[0053]
FIG. 10 shows the sensitivity of the vertical axis of the spectrum of FIG. 9 increased, and it is the zero-order light component that appears as a continuous spectrum at the bottom.
[0054]
FIG. 11 shows a second spectrum according to one embodiment, which is a spectrum obtained when both the + 1st order diffracted light and the −1st order diffracted light are incident and synthesized in the measurement system of FIG. 8A. Compared with the spectrum of FIG. 9, it can be seen that the energy intensity is increased. In principle, the spectral intensity of FIG. 11 is about twice the spectral intensity of FIG.
[0055]
FIG. 12 is a spectrum according to a comparative example, and represents the first-order diffracted light spectrum of the commercially available spectrophotometer shown in FIG. 8B. As apparent from comparing the scale of the vertical axis with that of the examples of FIGS. 9 and 11, the energy intensity is small.
[0056]
FIG. 13 shows the sensitivity measured on the vertical axis of the spectrum of FIG. 12 with the same magnitude as that of the embodiment of FIG. It can also be seen that the 0th-order light is more mixed than in the example.
[0057]
FIG. 14 compares the peak energy (peak height) of the + 1st order diffracted light and the ± 1st order diffracted light in the example. The peak energy of the ± 1st order diffracted light synthesized from the + 1st order diffracted light and the −1st order diffracted light is + 1st order. It can be seen that it is about twice the peak energy of the origami.
[0058]
FIG. 15 compares the peak energy of the + 1st order diffracted light in the example and the first order diffracted light of the conventional device of the comparative example. It can be seen that the peak energy is much higher in the example than in the comparative example.
[0059]
FIG. 16 is a comparison of the ± 1st order diffracted light in the example and the peak energy of the 1st order diffracted light of the conventional device of the comparative example. It can be seen that the peak energy is higher in the example than in the comparative example.
[0060]
FIG. 17 shows the peak area ratio of the first-order diffracted light to the output light of the + 1st-order diffracted light and ± 1st-order diffracted light at each wavelength in the example. The peak area ratio of the first-order diffracted light means that the energy of the + 1st-order diffracted light and ± 1st-order diffracted light is the output light energy (all light energy output from the acoustooptic device, including ± 1st-order diffracted light and mixed 0th-order light )), The ratio of each area is shown using the area ratio. The meaning of “peak area ratio of first-order diffracted light” is the same in FIGS. 18 and 19. The purity of the first-order diffracted light is higher when both of the + 1st-order diffracted light and the −1st-order diffracted light are combined and used.
[0061]
FIG. 18 shows a comparison of the peak area ratio (purity) of the first-order diffracted light with respect to the output light, with the + 1st-order diffracted light at each wavelength in the example and the first-order diffracted light of the conventional device of the comparative example. It can be seen that the purity of the first-order diffracted light is higher in the example.
[0062]
FIG. 19 shows the peak area ratio of the first-order diffracted light to the output light of the ± first-order diffracted light at each wavelength in the example and the first-order diffracted light of the conventional device of the comparative example. It can be seen that the purity of the first-order diffracted light is higher in the example than in the comparative example.
[0063]
FIG. 20 schematically shows an example of the light detection device 204. The first-order diffracted light measurement light A modulated by the acousto-optic device 4 and the 0-order light reference light B similarly modulated are received by the respective detection elements 101 and 102. The detection elements 101 and 102 are, for example, PbS elements. The detection outputs of the detection elements 101 and 102 are respectively input to and amplified by amplifiers 103 and 104 that output signals having a plurality of different amplification degrees. A plurality of output signals having different amplification levels from the amplifiers 103 and 104 are taken into the data processing unit 107 through the A / D converter 106. Reference numeral 105 denotes a power supply device for the amplifiers 103 and 104.
[0064]
The data processing unit 107 receives a plurality of output signals from the A / D converter 106, and among these signals, the values of the amplifiers 103 and 104 or the A / D converter 106 do not saturate, and the amplification degree is the highest. It comprises at least a channel selection means for selecting a signal, a synchronization signal processing means for processing the selected signal with a modulation frequency obtained by modulating the measurement light, and an integration means for integrating the signal subjected to the synchronization signal processing.
[0065]
FIG. 21 is a diagram showing in detail the flow of signal processing until the signal detected by the detection element 101 or 102 in FIG. 20 is processed by the data processing unit 107. The circuit configuration of the detection element 101, the amplifier 103, and the power source 105 is the same as the circuit configuration of the detection element 102, the amplifier 104, and the power source 105. The PbS element 111 in FIG. 21 corresponds to the detection element 101 or 102 in FIG. The components from the PbS element bias circuit 110 and the input buffer circuit 112 in FIG. 21 to the operational amplifier 122 correspond to the amplifier 3 or 4 in FIG. The PbS element bias circuit 110 is provided to supply a constant current to the PbS element 111. The output voltage fluctuation of the PbS element 111 that receives the modulated light is input to the input buffer circuit 112. The voltage-current conversion circuit 114 converts the output voltage fluctuation of the input buffer circuit 112 into current fluctuation by a resistance element. The current-voltage conversion circuit 118 receives the current fluctuation generated by the voltage-current conversion circuit 114 via the current mirror circuit 116 and converts it into voltage fluctuation amplified by a predetermined magnification by a resistance element. The operational amplifier 122 inputs the voltage fluctuation output of the current-voltage conversion circuit 118 via the output buffer circuit 120, outputs a plurality of signals with different magnifications to the A / D converter 106, and the measured value is obtained by the data processing unit 107. Calculated.
[0066]
Each part of the amplifier will be described in more detail. The bias circuit 110 operates as a constant current source and supplies a maximum bias voltage of 14 V to the PbS element 111. An example of the bias circuit 110 is a current mirror constant current circuit 132 in which a current is set by a current setting resistor 130 as shown in FIG. 22 and supplies a constant bias current to the PbS element 111. The bias current flowing through the PbS element 111 is set by the current setting resistor Rs as in the following equation, for example.
Bias current = 14.0 / Rs [A]
However, Rs> PbS element dark resistance.
[0067]
Returning to FIG. When light enters the PbS element 111, its resistance value changes, and a voltage drop proportional to the resistance value of the element occurs at both ends of the PbS element 111.
The input buffer circuit 112 uses the voltage drop of the PbS element 111 as an input signal. The input part of the input buffer circuit 112 is a source follower circuit using an N-channel FET, and the output part is an emitter follower circuit using a bipolar transistor. The amplification factor is 1 time, a high input impedance, and a low output impedance circuit.
[0068]
The voltage-current conversion circuit 114 is composed of only a fixed resistor. When the output voltage of the input buffer circuit 112 is Vo, the output resistance of the input buffer circuit 112 is Rio, the input resistance of the current mirror circuit 116 is Rci, and the resistance of the voltage-current conversion circuit 114 is Rvi, the input to the current mirror circuit 116 The current is as follows.
Current mirror circuit input current = Vo / (Rio + Rvi + Rci)
The current mirror circuit 116 operates as a current buffer having a low input impedance, a high output impedance, and a current amplification factor = 1.
[0069]
The current-voltage conversion circuit 118 is composed of only a fixed resistor. When the output current of the current mirror circuit 116 is Io, the input resistance of the output buffer circuit 120 is Roi, and the resistance of the current-voltage conversion circuit 118 is Riv, the output buffer circuit The input voltage of 120 is as follows.
Output buffer input voltage = Io, Riv, Roi / (Riv + Roi)
The output buffer circuit 120 is an emitter follower circuit using bipolar transistors, and has an amplification factor of 1 ×, a high input impedance, and a low output impedance circuit.
[0070]
The output from the output buffer is branched and input to the four operational amplifiers 122. The operational amplifier 122 is used as a non-inverting amplifier and constitutes an amplifier circuit that outputs at four amplification factors (1, 5, 25, 100 times).
The DC servo circuit 124 applies negative feedback in the DC region in order to prevent damage to elements constituting the circuit when an excessive DC offset and drift occur in the output buffer circuit 120.
[0071]
In the amplifier shown in FIG. 21, the output voltage (amplifier output voltage) from the operational amplifier 122 is expressed by the following equation with respect to the resistance Rd of the PbS element 111.
Amplifier output voltage
= (Vb ・ Rd / Rs) × [{Riv ・ Roi / (Riv + Roi)} / (Rio + Rvi + Rci)] × (op amp amplification)
Vb: bias circuit voltage (voltage across the bias current setting resistor)
Rd: PbS element resistance (Ω)
Rs: Bias current setting resistance (Ω)
Rio: Input buffer output resistance (Ω)
Rvi: Voltage-current conversion resistance (Ω)
Rci: Current mirror circuit input resistance (Ω)
Riv: Current-voltage conversion resistance (Ω)
Roi: Output buffer input resistance (Ω)
[0072]
Usually, since Rvi >> (Rio + Rci) and Riv << Roi, the amplifier output voltage is as follows.
Amplifier output voltage
≒ (Vb ・ Rd / Rs) x (Riv / Rvi) x (amplification of operational amplifier)
[0073]
FIG. 23 shows a function of the data processing unit 107 as a block diagram. The data processing unit 107 performs synchronization signal processing on the PbS element output data stored in the data file, and stores the result in the data file. In FIG. 20, the same data processing is performed by the two systems of the detection elements 101 and 102.
[0074]
The channel selection unit 140 is configured to obtain the maximum analog input channel data from the amplifier 103 or 104 shown in FIG. Select, convert to real and store in specified buffer. The channel selection determines that the A / D data is saturated when the 16-bit resolution A / D data is “8000H” or “7FFFH”. Conversion of the A / D data from the integer type to the real number type is performed by the following equation.
Real number data
= (Integer data) x (10.0 / 32768) x (correction gain) x (calibration data)
[0075]
There are four analog input channels from the operational amplifier 122 to the A / D converter 106 shown in FIG. 21 in each system of the measurement signal and the reference signal, and the amplifier amplification degree in each system is 100000 times in channel 0, channel 1 25000 times, channel 2 5000 times, and channel 3 1000 times, the correction gains are 0.01, 0.04, 0.2, and 1.0, respectively.
[0076]
The calibration data corrects an error in amplification between each input. Comparing multiple outputs with different amplifier amplification levels when a signal with a constant amplitude is input to the amplifier, equipped with machine difference storage means for storing the difference between the outputs with different amplification degrees as calibration data Yes. Amplifier output correcting means for correcting the output of the amplifier based on the machine difference stored in the machine difference storing means is further provided.
[0077]
Since data measured at a high sampling frequency has a high sampling frequency, the amount of data per unit time increases. Therefore, a low-pass filter unit 142 that removes high-frequency components from the signal selected by the channel selection unit 140, and a data thinning unit 144 that uses a value extracted for each unit number from the signal sequence that has passed through the low-pass filter unit 142 as a signal value. I have. The thinning process enables processing with a small amount of data.
[0078]
Since the apparent sampling frequency is reduced by the thinning process, the spectrum of aliasing noise corresponding to the sampling frequency overlaps the frequency spectrum of the measurement value. The frequency spectrum immediately after the A / D conversion is periodically distributed around the frequency that is an integer multiple of Fs in the period of the sampling frequency Fs. For example, when 1/2 decimation is performed on this signal, the spectrum centered on the sampling frequency Fs changes to a spectrum centered on Fs / 2. As a result, aliasing noise centered at Fs / 2 appears in the signal band as a noise component, and the S / N ratio is lowered. The reason why low-pass filter processing is performed before thinning-out processing is to prevent this.
[0079]
In order to extract only the modulation frequency component of the signal from the thinned data, the synchronization signal processing by the synchronization signal processing means 148 is performed to extract only the modulation frequency component with high accuracy. Before the synchronization signal processing is performed, the S / N ratio of the synchronization signal processing is improved by using a bandpass filter having a pass band in the modulation frequency.
[0080]
In addition, since the frequency of the signal may deviate from the modulation frequency before the synchronization signal processing is performed, the accuracy of the synchronization signal processing can be improved by correcting the deviation. The frequency deviation correction means 150 measures the deviation between the frequency of the signal input to the synchronization signal processing means 148 and the modulation frequency, and corrects the synchronization frequency of the synchronization signal processing means 148 based on the result. In this correction, a point (zero cross point) at which the input signal changes from positive to negative or from negative to positive is obtained, and the frequency of the input signal is obtained from the interval between the zero cross points. By determining the frequency as the local transmission frequency, synchronization signal processing with high synchronization accuracy is realized.
Since a constant value (DC component) is required from the signal modulated by the synchronization signal processing, the high-frequency component is removed by the low-pass filter unit 152.
[0081]
Data that has passed through the low-pass filter unit 152 is integrated by the digital integration unit 154. The amplitude value of the measurement signal is obtained by integration. The integration is more accurate as its time constant is larger, but takes more time. Therefore, the calculation speed is improved by converging the calculation with a value close to the true value in advance with a small time constant and then converging with the large time constant as the initial value. The integrated data is stored in the storage device 156.
[0082]
If the power supply voltage of the amplifier is measured with a measuring instrument and corrected by taking a ratio with a preset reference voltage, the deviation of the absolute value of the measured value can be corrected. Therefore, it further includes measurement result correction means for measuring the power supply voltage of the amplifier and correcting the measurement result by a ratio with a preset reference voltage.
This data processing is performed independently for the measurement light and the reference light. The drift component of the measurement value is removed by dividing and correcting the data processing result of the measurement light detection signal by the data processing result of the reference light detection signal.
[0083]
The flowchart in FIG. 24 collectively shows the operations in the data processing unit. A / D conversion is performed on a plurality of outputs having different amplification levels from the amplifier, and a signal that does not saturate and has the maximum amplification level is selected. The low-pass filter process is performed on the selected signal, and then a data thinning process is performed using the value extracted for each unit as the signal value. In order to remove random noise from the thinned data, a synchronization signal process is performed through a band pass filter process. In the synchronization signal processing, the difference between the signal frequency and the modulation frequency is measured to correct the synchronization frequency. After the high frequency component is removed from the signal subjected to the synchronization signal processing by the low-pass filter processing, the integration processing is performed and the data is stored.
[0084]
【The invention's effect】
The present invention increases the purity of the + 1st order diffracted light and the −1st order diffracted light emitted from the acoustooptic element by adjusting the light source optical system on the light source side that irradiates the measurement object with light, and the acoustic wave transducer changes to the acoustooptic crystal. Spectroscopy is performed by changing the applied acoustic wave frequency, and the output light from the acoustooptic device is modulated by intensity modulation of the drive signal of the acoustic wave transducer. On the detection side, which receives and detects transmitted scattered light from the measurement object as measurement light, it performs synchronous signal processing equivalent to lock-in processing at the modulation frequency of the measurement light to accurately extract only the modulation frequency component, and also detects the detection signal. Are simultaneously amplified at a plurality of different degrees of amplification, and generation of pulse noise is suppressed by selecting a signal amplified to the maximum without saturation. Thereby, the specific substance in the scattering substance can be measured non-invasively with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram showing an absorption spectrum of water by FTIR.
FIG. 2 is a block diagram schematically illustrating an embodiment.
FIG. 3 is a schematic plan view showing a light source chamber and an acoustooptic device in one embodiment.
4A and 4B are diagrams showing an optical system in a light source chamber, where FIG. 4A is a plan view and FIG. 4B is a front view.
FIG. 5 is a schematic plan view showing a light source chamber, an acoustooptic device, and an irradiation optical system in one embodiment.
6A is a schematic front view showing an example of a branched optical fiber used in the irradiation optical system, FIG. 6B is an end view of the branched end, and FIG. 6C is an end view of the joined end; (D) is an approximate line figure showing the operation.
FIG. 7 is a schematic plan view showing an acoustooptic device according to another embodiment.
8A is a layout diagram showing an optical system for measuring characteristics in one embodiment, and FIG. 8B is a layout chart showing an optical system for measuring characteristics of a spectrophotometer which is a conventional AOTF device.
FIG. 9 is a diagram showing a spectrum measured using the measuring apparatus of the example of FIG. 8 (A) and entering only −1st order diffracted light.
10 shows the sensitivity of the vertical axis of the spectrum in FIG. 9 increased.
FIG. 11 is a diagram showing a spectrum measured using the measuring apparatus of the example of FIG. 8A and making both −1st order diffracted light and + 1st order diffracted light incident.
FIG. 12 is a diagram showing a first-order diffracted light spectrum of the conventional spectrophotometer shown in FIG. 8 (B).
13 shows the sensitivity of the vertical axis of the spectrum of FIG. 12 increased.
FIG. 14 is a diagram comparing peak energy of + first order diffracted light and ± first order diffracted light in an example.
FIG. 15 is a diagram showing a comparison of the peak energies of the + 1st order diffracted light in the example and the 1st order diffracted light in the comparative example.
FIG. 16 is a graph showing comparison of peak energies of ± first-order diffracted light in an example and first-order diffracted light in a comparative example.
FIG. 17 is a diagram showing a peak area ratio of first-order diffracted light to output light of + 1st-order diffracted light and ± first-order diffracted light in Examples.
FIG. 18 is a diagram showing a peak area ratio of the first-order diffracted light to the output light of the + 1st-order diffracted light in the example and the first-order diffracted light in the comparative example.
FIG. 19 is a diagram showing a peak area ratio of the first-order diffracted light to the output light of the ± first-order diffracted light in the example and the first-order diffracted light in the comparative example.
FIG. 20 is a block diagram schematically showing a light detection device portion in one embodiment.
FIG. 21 is a block diagram illustrating an amplifier.
FIG. 22 is a block diagram illustrating an example of a bias circuit of a PbS element.
FIG. 23 is a block diagram illustrating functions of a data processing unit.
FIG. 24 is a flowchart showing the operation of the data processing unit.
[Explanation of symbols]
4 Acousto-optic elements
6 Light source
8 Optical axis of light source
10 Front mirror
12 Post mirror
14 Lens
16, 18 mirror
20 lenses
22, 24 1st order diffracted light
26 0th order light
28, 30 prism
32, 34, 36 Branched end of branch optical fiber
38 Collective end of branch optical fiber
101, 102 detection element
103,104 Amplifier
105 power supply
106 A / D converter
107 Data processing unit (computer)
110 Bias circuit
111 PbS element
112 Input buffer circuit
114 Voltage-current conversion circuit
116 Current mirror circuit
118 Current-voltage conversion circuit
120 output buffer circuit
122 operational amplifier
124 DC servo circuit
130 Current setting resistor
132 Current mirror constant current circuit
140 Channel selection means
142 Low-pass filter means
144 Data thinning means
146 Band pass filter means
148 Synchronization signal processing means
150 Frequency deviation correction means
152 Low-pass filter means
154 Digital integration means
156 storage device
200 Measurement object
202 Light source device
204 Photodetector
206 Control unit
214 Acousto-optic device driver
220 Irradiation optical system
222,224 optical fiber
230 Light receiver
242 output device

Claims (17)

A light source device that irradiates light to a measurement object, a light detection device that receives and detects transmitted scattered light from the measurement object as measurement light, and a control unit that controls operations of the light source device and the light detection device In an optical measuring device,
The light source device includes a light source, an acoustooptic element as a spectroscopic element including an acoustooptic crystal in an acoustooptic crystal, and performs spectroscopy by changing an acoustic wave frequency applied to the acoustooptic crystal from the acoustic wave transducer. An acoustooptic device driving apparatus that modulates the output light of the acoustooptic device by intensity modulation of the drive signal of the wave transducer, and the light from the light source is a light flux smaller than the window size of the acoustooptic device, and the acoustooptic device A light source optical system that is incident on the acoustooptic device as a light beam having a propagation angle smaller than an allowable angle, and the + 1st order diffracted light and the −1st order diffracted light emitted from the acoustooptic device are condensed at spatially different positions. And at least one of + 1st order diffracted light and −1st order diffracted light collected by the light collecting optical system. And an irradiation optical system for irradiating a constant object,
The light detection device includes a detection element that outputs a signal corresponding to a modulated measurement light, an amplifier that receives the output of the detection element, and outputs a plurality of signals having different amplification degrees at the same time, and the amplification degree of the amplifier A / D converter that converts a plurality of different output signals into digital signals respectively, and a plurality of output signals of the A / D converter are input, and among these signals, the amplifier or the A / D converter Channel selecting means for selecting the one having the highest amplification degree without saturation, the synchronizing signal processing means for superimposing the selected signal on the oscillation signal synchronized with the modulation frequency obtained by modulating the measuring light, and the synchronization thereof An optical measurement apparatus comprising: a data processing unit including an integration unit that obtains a measurement value by integrating a signal-processed signal. The light source optical system is disposed in front of the optical axis of the light source and reflects a light from the light source in the direction of the acoustooptic element, and a mirror surface of the front mirror is conjugated with an incident surface of the acoustooptic element. The optical measuring device according to claim 1, further comprising: The optical measurement apparatus according to claim 2, wherein the light source optical system further includes a rear mirror disposed behind the optical axis of the light source and configured to reflect light from the light source toward the front mirror. 4. The optical system according to claim 1, wherein the irradiation optical system is an optical system that irradiates a measurement target by combining the + 1st order diffracted light and the −1st order diffracted light collected on the same optical axis. The optical measuring device described. As the irradiation optical system, a branched optical fiber having one end branched into at least two and the other end joined into one is used.
The + 1st order diffracted light and the −1st order diffracted light collected by the condensing optical system enter the respective branched ends of the branched optical fiber, and light emitted from the joined other end is irradiated onto the measurement object. The optical measuring device according to claim 4. As the irradiation optical system, a branched optical fiber having one end branched into three and the other end joined into one is used.
The + 1st order diffracted light and the −1st order diffracted light collected by the condensing optical system are respectively incident on two of the branched three ends of the branched optical fiber, and output from the joined other end. 6. The spectral light source according to claim 5, wherein the transmitted scattered light from the object to be measured is incident on the other end portion where the light is merged and is guided to the photodetector by the remaining one of the three branched ends. apparatus. The optical measuring device according to any one of claims 1 to 6, wherein an end portion on which the + 1st order diffracted light or -1st order diffracted light is incident on the irradiation optical system is disposed on a focal plane of the condensing optical system. 8. The optical device according to claim 1, wherein a plurality of acoustooptic elements having different spectral wavelength regions are arranged in series on an optical path of the light source optical system, and any one of the acoustooptic elements is selectively driven. measuring device. The amplifier includes an input buffer circuit that inputs a modulation output of the detection element;
A voltage-current conversion circuit that converts the output voltage fluctuation of the input buffer circuit into a current fluctuation by a resistance element;
A current-voltage conversion circuit that converts a current fluctuation caused by the voltage-current conversion circuit into a voltage fluctuation amplified by a predetermined factor using a resistance element;
The optical measurement apparatus according to claim 1, further comprising: an amplification circuit that inputs a voltage fluctuation output of the current-voltage conversion circuit via an output buffer circuit and outputs a plurality of signals having different magnifications. The data processing unit includes, between the channel selection unit and the synchronization signal processing unit, a low-pass filter unit that removes a high-frequency component unnecessary for the synchronization signal processing from the signal selected by the channel selection unit, and the low-pass filter 10. The optical measurement device according to claim 1 or 9, further comprising data thinning means using a value extracted from the signal train that has passed through the means at regular intervals for each unit number as a signal value. The optical measurement apparatus according to claim 1, 9 or 10, wherein the synchronization signal processing unit further includes a band-pass filter unit that allows the modulation frequency to pass therethrough. 2. A frequency shift correction unit that measures a shift between a frequency of a signal input to the synchronization signal processing unit and the modulation frequency, and corrects the synchronization frequency of the synchronization signal processing unit based on the result. , 9, 10 or 11. 13. The optical measurement apparatus according to claim 1, further comprising a low-pass filter unit that removes a high-frequency component unnecessary for an integration process between the synchronization signal processing unit and the integration unit. The integration means performs an integration process for an appropriate time with an appropriate integration time constant, sets the result as an initial value, and performs the integration process again with an integration time constant larger than the integration time constant. The optical measuring device according to 10, 11, 12, or 13. A difference storage means for comparing a plurality of outputs having different amplification levels when a signal having a constant amplitude is input to the amplifier, and storing the result as a difference between outputs having different amplification degrees; 15. The optical measuring device according to claim 1, further comprising amplifier output correcting means for correcting the output of the amplifier based on the machine difference stored in the storing means. The measurement result correction means for measuring the power supply voltage of the amplifier and correcting the measurement result by a ratio with a preset reference voltage is further provided according to claim 1, 9, 10, 11, 12, 13, 14, or 15. The optical measuring device described. The detection element and the amplifier are provided for measurement light detection and reference light detection, respectively, and the A / D converter converts both the measurement light detection signal and the reference light detection signal into digital signals, and the data processing The unit performs similar data processing on the reference light detection signal, and divides and corrects the data processing result of the measurement light detection signal by the data processing result of the reference light detection signal. The optical measuring device according to any one of 11, 12, 13, 14, 15 and 16.

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