EP2245441A1

EP2245441A1 - Microspectrometer

Info

Publication number: EP2245441A1
Application number: EP09714805A
Authority: EP
Inventors: Dominik Rabus; Michael Winkler; Christian Oberndorfer
Original assignee: Buerkert Werke GmbH and Co KG
Current assignee: Buerkert Werke GmbH and Co KG
Priority date: 2008-02-26
Filing date: 2009-02-25
Publication date: 2010-11-03
Also published as: US20110080583A1; JP2011513717A; US8885160B2; DE202008003977U1; WO2009106313A1

Abstract

The compact microspectrometer for fluid media has, in a fixed spatial assignment in a housing (20b), a light source, a fluid passage (28b), a reflective optical grating (38b) and a detector (40b). The optical measurement path starting from the light source passes through the fluid passage and strikes the optical grating. The spectral light components which are reflected by the optical grating strike the detector.

Description

microspectrometer

The invention relates to a microspectrometer.

Microspectrometers are known. Typically, components such as optical grating, mirrors, evaluation electronics and optical fibers are arranged in a housing or on a base plate, which couple the light to be analyzed into the spectrometer. Outside the microspectrometer is a light source and the sample to be analyzed, which is irradiated by the light of the external light source. The light, which is separated from the optical grating into its spectral components, passes via optical fibers to a plurality of photodetectors.

The invention provides a microspectrometer which can be made extremely compact and without external components and has only a fluidic interface and electrical connections to the outside. Amongst other things, the advantage of the invention set out in the appended claims is that it permits the continuous spectroscopy of an analyte, e.g. in the monitoring of drinking water quality is of great importance.

In addition, possible sources of error are excluded because the source of light ^'does not have to be realigned for each measurement to the containing the analyte to be measured container.

Additional lenses, which are required in known microspectrometer to couple light into the optical fiber, as the optical fiber itself are superfluous. The light separated into its spectral components by the optical grating can be picked up directly from a photodetector line via optical fibers without detours. In an alternative embodiment, the optical grating is rotatably arranged, so that instead of a detector line, a single photodetector can be used.

It is particularly favorable, the housing of the microspectrometer as a rigid molded body by injection molding from at least partially transparent To manufacture plastic. The fluid channel is then passed across a solid portion of the molded article from one side surface to the opposite surface. In an advantageous embodiment, the required optical grating is molded during injection molding in a surface of the molding. But it is also possible to use a grid after injection into a recess of the housing.

For reflective surfaces that are to act as a mirror, metal layers can subsequently be vapor-deposited, or suitable film is back-sprayed. The light source may e.g. be an LED and integrated as Einlegteil in the molding. The light source could also be inserted into a recess of the plastic part and then attached, for example, by gluing.

It is also possible to use OLED or use other known methods such as laser technology to generate the light source.

If several different light sources are integrated into a microspectrometer, it is advantageously possible to carry out a plurality of spectral measurements of different wavelengths with one instrument.

Thus, a further light source could be arranged below / above the fluid channel. The scattered light would then be radiated at an angle of 90 ° on the same path as the test section described. The scattered light falls on the grid, is spectrally decomposed and reaches the evaluation electronics.

According to a variant or additionally, the fluid channel is transversely irradiated by a separate light source, and the scattered light occurring in this case is collected directly (without spectral decomposition) by means of another photodiode. The scattered light intensity is measured and evaluated separately.

Advantageous embodiments will now be described in detail with reference to the drawings. In the attached figures show:

1 is a schematic plan view of an embodiment of the microspectrometer with the housing open; 2 shows a plan view of a second exemplary embodiment of the microspectrometer with the housing open in a schematic illustration;

Fig. 3 section of Fig. 2;

Fig. 4 sectional view of another embodiment;

5 shows a rigid molded body, which is suitable as a housing. Fig. 6 shows an embodiment using the housing of Fig. 5;

Fig. 7 shows a further embodiment using the housing according to Fig. 5; and FIG. 8 shows a further embodiment using a rigid shaped body as the housing.

In the embodiment of a microspectrometer according to the invention according to FIG. 1, a light source 2 and an optical grating 6 are arranged in a housing 1 on opposite sides. The housing 1 is penetrated by a fluid channel 3. The channel 3 can either be filled and sealed with medium to be analyzed, or this medium can flow continuously through the channel. For this purpose, the fluid channel 3 can be connected to lines (not shown in FIG. 1) in which the medium is transported to and from the spectrometer. The fluid channel 3 is arranged in the housing such that it is located on the optical measuring path between the light source 2 and the grating 6.

The fluid channel 3 must be made of translucent material. Of the

Fluid channel 3 can be either completely or partially provided in the injection mold for the housing 1 of the microspectrometer, or this or window-like parts thereof are subsequently made of transparent material such

Glass or PMMA inserted into the housing.

In order to filter unwanted scattered light, located between the fluid channel 3 and grid 6, a diaphragm 4, wherein the opening is placed so that light from the light source 2 on the grid 6 falls. The diameter of the aperture 4 is ideally adjustable.

Between aperture 4 and grating 6, a mirror 5 is arranged so that light reflected by the grating 6 is incident on it. The mirror 5 may for example be part of Aperture 4, arranged so that it faces the grating 6 and not the light source 2.

The mirror 5 directs incident light on to an evaluation unit (not shown in FIG. 1). This evaluation unit can e.g. a photodetector like an organic photodiode array.

In Fig. 1, except for the individual components required for the spectrometer, the beam path 7 of the optical measuring path is shown. Light from the light source 2 ideally passes through the fluid channel 3 at an angle of incidence of 90 °, passes through the diaphragm 4 to the grating 6, which spectrally splits the light and reflects it onto the mirror 5, which redirects the light to the evaluation unit.

The evaluation unit can be arranged inside the microspectrometer or can also be located outside.

As shown in Fig. 2 and Fig. 3, in a second embodiment, below the fluid channel, a second light source 2a, e.g. LED arranged, which also sends light across the fluid channel. From the main beam at an angle of 90 ° sloping stray light (dashed line) passes according to beam path 8, for. for the purpose of turbidity measurement by the diaphragm 4 on the optical grating 6 and the evaluation unit. In this case, the light source 2 is not activated simultaneously with the light source 2a. When the two light sources 2 and 2a are activated alternately, the turbidity and the concentration of constituents in liquids can thus be determined in succession with the same device.

In this embodiment, the evaluation of the scattered light with spectral decomposition takes place through the optical grating 6.

4 shows the sectional view of a further exemplary embodiment in which the evaluation of the scattered light takes place without spectral decomposition.

The arrangement of the individual components is identical to that of the first embodiment, except that in addition below the fluid channel 3 is a photodiode 2b.

The photodiode 2b detects scattered light radiated at an angle of 90 ° from the main beam emitted from the light source 2 and which transmits the light Transmitted fluid channel 3 transversely. The beam path of the scattered light is shown in dashed lines according to arrow 9.

In this embodiment, at the same time the main beam of the light source 2 can be optically decomposed and evaluated by means of grids and the scattered light occurring thereby can be collected directly by means of the photodiode 2b and the scattered light intensity can be measured.

The rigid shaped body 20, which is suitable as a housing of the microspectrometer and is shown in FIG. 5, is a flat cuboid with a solid block 20a, which merges with a step 22 into a flat region 20b in which a rectangular recess 24 is formed. This recess 24 can be closed by a cover 26, which is flush with the block 20a. The molded body 20 is produced by injection molding of a particularly transparent plastic, such as polymethyl acrylate. In the block 20a, a channel 28 is recessed, which is guided from one side surface up to the opposite side surface. Furthermore, a cylindrical recess 30 is introduced perpendicular to the channel 28 in the block 20 a.

As shown in FIG. 6, a light source such as an LED 32 is inserted in the recess 30. The channel 28 is provided at its ends with fluidic fittings 34. The recess 24 accommodates all further components of the microspectrometer: the diaphragm 36, the optical grating 38 and the photodetector row 40 with evaluation electronics 42. Of course, further optical and / or electronic components can be arranged in the recess 24. Likewise, a plurality of light sources for different spectral ranges can be arranged in the block 20a. To the outside, the micro-spectrometer has only a fluidic interface in the form of the connecting pieces 34 and electrical connections that can be realized by connectors. Since all optical components are in a rigid spatial relationship, no adjustments are required to make measurements.

The embodiment in Fig. 7 differs from that of Fig. 6 by the use of a rotatably mounted optical grating 38a with rotary drive 44 and the use of a single photodiode 40a as a detector. The rotary drive 44 is activated by the evaluation electronics 42a in such a way. Experts that the photodiode 40a successively detects all the spectral components of the light reflected from the grid.

In the embodiment according to FIG. 8, the shaped body 20b forms a uniform flat cuboid made of transparent plastic. A recess 46, which is introduced into the molded body 20b parallel to the channel 28b, accommodates the photodetector row 40b and the evaluation electronics 42b. The optical grating 38b is formed in the outer surface of the molded body 20b opposite to the light source 32b and provided with a reflective coating, e.g. is applied by vapor deposition. Suitably, the grid 38b is covered with a protective layer.

Claims

claims

1. A micro-spectrometer for fluid media, comprising a housing, which contains a solid spatial allocation of a light source, a fluid channel, a reflective optical grating and a detector, wherein the emanating from the light source optical measuring path passes through the fluid channel and hits the optical grating and wherein the spectral light components reflected from the optical grating strike the detector.

2. Microspectrometer according to claim 1, wherein a preferably adjustable optical aperture is arranged on the optical measuring path between the fluid channel and the optical grating.

3. microspectrometer according to claim 1 or 2, comprising a mirror which is fixedly disposed in the housing and the optical grating, which is designed as a reflection grating, facing.

4. A microspectrometer according to claim 2 and 3, wherein the mirror is attached to the diaphragm.

5. Microspectrometer according to one of the preceding claims, wherein the housing is made by injection molding.

6. microspectrometer according to claim 5, wherein the fluid channel is limited at least in the region of the optical measuring path by a transparent wall.

7. A microspectrometer according to claim 5, wherein the fluid channel is formed at least in the region of the optical measuring path by an inserted into the housing pipe section of transparent material.

8. A microspectrometer according to any one of the preceding claims, wherein the fluid channel has ports for insertion into a pipeline.

9. microspectrometer according to one of the preceding claims, in which an opto-electrical evaluation unit is fixedly arranged in the housing.

10. Microspectrometer according to one of the preceding claims, in which a plurality of light sources with different light spectra are fixedly arranged in the housing.

11. A microspectrometer according to one of the preceding claims, wherein a separate light source for scattered light measurement transversely to the optical measuring path radiates into the fluid channel and the transversely to the fluid channel escaping scattered light falls on the optical grating.

12. A microspectrometer according to one of the preceding claims, wherein the scattered light emerging transversely to the optical measurement path from the fluid channel for scattered light measurement is received by a separate light receiver without spectral decomposition.

13. A microspectrometer according to one of the preceding claims, wherein the housing is designed as a rigid molded body made of at least partially transparent material with recesses for receiving optical components and the fluid channel from one side of the molded body starting from this traversing is guided to the opposite side.

14. A microspectrometer according to claim 13, wherein the optical grating is formed in an outer surface of the rigid molded body.

15. A microspectrometer according to claim 13, wherein the rigid molded body has a recess in which the optical grating is rotatably mounted and coupled to a rotary drive.