Arrangement for multispectral light emission and multispectral sensor equipped therewith

Description

Technical application area

[0001] The present invention relates to an arrangement for multispectral light emission comprising at least one broadband light source emitting light of a spectral range, a filter array consisting of several spectral filters with a spectral width that lies within the spectral range of the light source, and an optical switching device for controlling the passage of the light emitted by the light source through the filter array. The invention also relates to a multispectral sensor equipped with this arrangement.

[0002] Numerous applications for the selective analysis of, for example, liquid or gaseous media require the use of optical radiation with variable wavelengths or wavelength ranges. Examples include absorption spectroscopy and photoacoustic spectroscopy. Every gas has a characteristic absorption spectrum with one or more absorption peaks (fingerprint). In photoacoustic spectroscopy, the specific light absorption at an absorption peak generates a pressure change or acoustic wave in the medium, which is detected and converted into an electrical signal. A microphone, for example, can be used as a detector. The detected pressure change is a measure of the concentration of the corresponding gas. A photoacoustic gas sensor (PGS) can measure a large number of substances in various states of matter at very low concentrations. However, these measurements require adjustment of the wavelength or wavelength range.The wavelength range of the incident light is directed at the gas being measured. The excitation wavelength can be adjusted, for example, using a spectral filter or a tunable laser. The number of gases that can be measured simultaneously with a photoacoustic gas sensor correlates with the number of optical spectral channels of this gas sensor. State of the art

[0003] For example, EP 3 508 836 B1 discloses a photoacoustic gas sensor in which light from a broadband IR light source is directed through a bandpass filter into a measuring chamber containing the gas to be measured. The optical bandpass filter only allows a specific portion of the light spectrum to pass through. The central wavelength of the filter is matched to the absorption maximum of the gas being detected. By temporally modulating the IR light source at up to 100 Hz, a sound wave is generated within the measuring chamber due to the absorption of the light by the gas. This sound wave is measured by a highly sensitive pressure sensor on the measuring chamber. The measured amplitude is proportional to the concentration of the absorbing gas. For many applications, such a gas sensor with a small volume, i.e., in a miniaturized form, is required, and due to its simple design, it can also be realized with the sensor described in EP 3 508 836 B1.However, the gas sensor in this publication is only equipped with a spectral filter, and can therefore only detect a gas with an absorption maximum at the corresponding filter wavelength.

[0004] In principle, a filter wheel can be used between the excitation light source and the measurement chamber to change the excitation wavelength. The number of gases that can be measured simultaneously correlates with the number of available optical spectral channels, i.e., the number of spectral filters. However, the number of different filters is limited in filter wheels. Due to their mechanical size, miniaturization is very complex, and the measurement time increases with the number of filters used. Another disadvantage of the filter wheel is that only one filter can be used at a time.

[0005] When using a tunable laser as a light source, especially a quantum cascade laser (QCL), no spectral filters are required. The wavelength can be freely adjusted within the laser's tuning range. For example, by combining several quantum cascade lasers, a broad spectral range can be covered seamlessly, enabling the measurement of a wide variety of gases. However, quantum cascade lasers are relatively expensive. The need for multiple quantum cascade lasers to cover a broad spectral range further increases the cost. Furthermore, further miniaturization is not possible with such lasers.

[0006] Therefore, currently, only cost-effective photoacoustic sensors with a single bandpass filter, as in the EP 3 508 836 B1 mentioned above, are known, and these typically only allow the measurement of one gas. For the selective analysis of complex samples, even in the sub-ppb range, as enabled by photoacoustic sensors, no cost-effective solution with a small form factor is available.

[0007] Patent specification US 8 991 261 B2 discloses an arrangement for multispectral light emission according to the preamble of claim 1.

[0008] US patent 2012 / 059232 A1 discloses an arrangement for multispectral light emission with an array of monochromatic LEDs that can be individually controlled.

[0009] The object of the present invention is to provide an arrangement for multispectral light emission and a multispectral sensor based thereon, which can be implemented cost-effectively in a miniaturized design. In particular, the arrangement should allow for simple and rapid adjustment or modification of the emitted wavelengths. Description of the invention

[0010] The problem is solved by the arrangements of claims 1 and 2 and the multispectral sensor according to claim 8. Advantageous embodiments of the arrangements and the multispectral sensor are the subject of the dependent claims or can be found in the following description and the exemplary embodiments.

[0011] The proposed arrangement for multispectral light emission comprises at least one broadband light source, a filter array, and a switching device for controlling the passage of at least a portion of the light emitted by the light source through the filter array. The broadband light source emits light within a specific spectral range. The spectral filters of the filter array have a correspondingly narrower spectral width, which lies at least partially within the spectral range of the light source. Preferably, the spectral width of the spectral filters is less than 1 µm.

[0012] In a first alternative of the proposed arrangement, the switching device is designed as an optical switching device, and the light source, filter array, and optical switching device are arranged such that light emitted by the light source is guided via the optical switching device, optionally also via further optical elements such as deflectors or lenses, and the filter array to the output of the arrangement, where the appropriately filtered light exits the arrangement. The optical switching device comprises an array of micromirrors or microapertures and is designed and arranged such that it can selectively guide light emitted by the light source to the output of the arrangement only through one or more arbitrarily definable spectral filters of the filter array. The optical switching device can be controlled accordingly.

[0013] In the second alternative, the light source either comprises an array of light emitters that can be controlled separately via the switching device and is designed and arranged such that, by controlling the light emitters via the switching device, the light emitted by the light source can be selectively directed only through one or more arbitrarily definable spectral filters of the filter array. In another embodiment of this second alternative, the light source is formed by a single light emitter, and the switching device has a mechanical XY adjustment device for this single emitter or the filter array, with which the single emitter can be positioned under different filters of the filter array, so that the light emitted by the light source can be selectively directed only through an arbitrarily definable spectral filter of the filter array.In this second alternative arrangement, the light-emitting surface of the light emitters is preferably not larger than the lateral dimensions of the individual spectral filters of the filter array.

[0014] In a preferred embodiment, the individual spectral filters of the filter array have small lateral dimensions of ≤ 10 x 10 mm. The filter array is preferably configured such that the spectral filters are arranged row-wise and column-wise within the array. However, other arrangements are also possible in principle, for example, a concentric arrangement, a purely row-wise arrangement, or even a completely arbitrary arrangement of the individual filters within the filter array. Preferably, the arrangement of the individual spectral filters of the filter array correlates with the arrangement of the micromirrors or microapertures of the first alternative or with the arrangement of the individual light emitters of the array of light emitters of the second alternative, such that they are arranged in the same way, i.e., correspondingly row-wise and column-wise.The number of units (micromirrors, microapertures, light emitters) on the optical switching device or the light source preferably corresponds to the number of spectral filters in the filter array, so that each unit is assigned a spectral filter through which only the light emitted by that unit is passed. It is also possible to choose a greater number of filters than the number of these units, in which case each unit is assigned a group of adjacent spectral filters, for example, two or four filters. Furthermore, it is possible to choose a smaller number of filters than the number of these units, in which case each filter is assigned several adjacent units.

[0015] The proposed arrangement allows for the adjustment or variation of the wavelength or spectral distribution of the emitted optical radiation according to the number and characteristics of the different filters in the filter array. This makes it possible to tailor the spectral distribution of the emitted light to the specific application. The chosen design allows for the miniaturization of the filter array, the light source, and the optical switching device. The arrangement does not require expensive light sources.

[0016] Preferably, filters based on subwavelength structures or plasmonic filters are used in the filter array. This allows a large number of filters to be implemented cost-effectively in a very small space. For example, this enables the simulation of an absorption spectrum for almost any substance by appropriately combining the individual optical channels or filters, i.e., by simultaneously passing light through several of the spectral filters. The filters can also be designed as interference filters and can be combined with polarizing filters. A combination of these filter types within the filter array is also possible in principle.

[0017] In the first alternative, the optical switching device can be implemented as a single module together with the light source or separately. In the second alternative, the array-shaped light source can again be implemented as a single module together with the filter array or separately. Additionally, in both alternatives, a device to prevent optical crosstalk between the individual optical channels is arranged along the beam path between the light source and the filter array, for example, in the form of a suitably designed aperture and / or lens array.

[0018] The proposed arrangement enables the realization of a multispectral sensor with a measuring chamber into which light emitted from the arrangement is coupled, and one or more detectors. These detectors allow the detection of the result of the interaction between the light coupled into the measuring chamber and a medium introduced into the chamber. For example, the multispectral sensor can be designed as a photoacoustic gas sensor, in which at least one of the detectors is a pressure sensor, such as a microphone. In this case, the light source of the proposed arrangement is modulated in time during a measurement to generate sound waves through the absorption of the light coupled into the measuring chamber by the gas being measured. Depending on the number of filters in the filter array, this gas sensor can then measure a larger number of gases or gas components.Other applications, such as absorption spectroscopy, also in combination with photoacoustic spectroscopy, can be realized with such a multispectral sensor.

[0019] The proposed configuration and the multispectral sensor equipped with it can be used in many fields, such as medicine, environmental protection, process engineering, and civil security. This includes, for example, the analysis of industrial processes and parameters (process monitoring), quality assurance, early fire detection, aroma analysis, the detection of off-odors, breath gas analysis, security applications, environmental analyses, non-destructive surface testing via reflectance measurement, and use as an electronic nose or tongue. This is, of course, not an exhaustive list. Brief description of the drawings

[0020] The proposed arrangement and the multispectral sensor equipped with it are explained in more detail below using exemplary embodiments in conjunction with the drawings. These show: Fig. 1 a schematic representation of a multispectral sensor with an optical switching device; Fig. 2 an example of flexible adaptation of the light spectrum with the proposed arrangement to the absorption spectrum of a gas to be measured; Fig. 3 a schematic representation of a multispectral sensor with an array-shaped light source; Fig. 4 an example of an embodiment of the proposed arrangement based on an array-shaped light source; Fig. 5 an example according to the invention of an embodiment of the proposed arrangement based on an array-shaped light source; Fig. 6 an example of an embodiment according to the invention of the proposed arrangement with a micro-aperture array as an optical switching device; Fig. 7 an example of an embodiment of the proposed arrangement based on a single emitter with a mechanical XY adjustment device; Fig. 8 a first example of a setup of the proposed multispectral sensor; Fig.Fig. 9 An example of an embodiment of the proposed arrangement with a micromirror array as an optical switching device; Fig. 10 An example of a micromirror array in which the spectral filters of the filter array are applied to the micromirrors; Fig. 11 A second example of a setup of the proposed multispectral sensor; Fig. 12 An example of an embodiment of the proposed multispectral sensor with multiple measuring chambers; Fig. 13 An example of a filter array that can be used in the proposed arrangement; and Fig. 14 An example of an embodiment of a spectral filter of the filter array that can be used in the proposed arrangement with polarization filters. Ways to implement the invention

[0021] Not all arrangements shown in the figures incorporate all features of the invention. The invention is defined by the accompanying claims.

[0022] In Figure 1The diagram shows a highly schematic representation of the structure of a multispectral sensor, which consists of the proposed arrangement for multispectral light emission 14 and a measuring device 15. Light with the desired spectral distribution, generated by the arrangement 14, exits the arrangement and enters the measuring device 15, as indicated in the figure. The arrangement for multispectral light emission 14 comprises a broadband light source 1, a device referred to below as an optical switching array 2, and a filter array 4. The measuring device 15 comprises a measuring chamber 5, one or more receivers 6, and an electronic device 7 for signal processing and evaluation. Light from the light source 1 is directed via the optical switching array 2 (optical switching device) onto the filter array 4. The optical switching array 2 is configured to direct the light onto one or more selected filters 4(A), 4(B), 4(C).

[0023] In a transmission configuration, the optical switch array 2 is implemented by a micro-aperture array, in which each element 3(A), 3(B), 3(C), hereinafter also referred to as an optical switch, represents a micro-aperture that can be controlled independently of the others to open and close. Control to change the aperture diameter (with the aperture open) is also preferably possible. The light is then directed via the selected micro-apertures onto one or more of the filters of the filter array 4. The remaining apertures are closed.

[0024] In a reflective configuration, the optical switch array 2 is designed as a micromirror array. Each element of the switch array is a micromirror. The mirrors can, in turn, be individually controlled so that the incident light is directed onto one or more filters 4(A), 4(B), 4(C) of the filter array 4. The other mirrors are adjusted so that they do not direct the incident light onto the filter array 4. The areas between the micromirrors (or microapertures in the above case) are opaque to light.

[0025] Filter array 4 consists of several spectral filters. In the Figure 1In the illustrated example, only filters or filter elements 4(A), 4(B), and 4(C) are exposed, thus allowing only specific wavelengths, corresponding to the filter characteristics of these filters, to pass through and enter the measuring chamber 5. The optical switch array 2 allows any filters of the filter array 4 to be illuminated sequentially or simultaneously to generate an optimal spectrum for the respective measurement task. For example, as with a measurement using a monochromator, the required filters can be controlled or exposed sequentially. Thus, by controlling only element 3(A) to expose filter 4(A), light of a single wavelength can be generated if filter 4(A) is sufficiently narrowband.

[0026] In a further embodiment, the light source 1 can be designed as an array of light emitters, as described below in conjunction with Figure 3This will be described in more detail later. The individual light emitters can be controlled as desired to direct light specifically onto one or more filters of the filter array 4. Preferably, the light source and the filter array form a single unit. In this embodiment, no optical switch array 2 is required.

[0027] The sample to be measured is located in the measuring chamber 5. It can be in various states of matter, for example, as a liquid or a gas. The measurement can be performed by reflection or transmission. Different sensors or detectors with different physical measurement principles can be used as receivers 6. Examples include IR detectors for absorption spectroscopy or a pressure sensor, for example, in the form of one or more MEMS microphones, in photoacoustic spectroscopy. A combination of several detectors or sensors is also possible, for example, the use of a pressure sensor in a transparent measuring chamber in conjunction with an absorption detector outside the measuring chamber.

[0028] During a measurement, by appropriately controlling the switch array 2 or, in the case of an array of light emitters, the light emitters, one or more filters of the filter array 4 can be used to generate a desired spectral distribution, for example, a single wavelength or a superposition of specific wavelengths, and utilize it for the application. This spectral distribution can be changed at any time by using a different control method. The control, the output of the acquired data, the signal processing, and the evaluation are implemented via electronics and software.

[0029] This allows the light spectrum generated by the proposed arrangement to be flexibly adapted to the absorption spectrum of a sample in the measuring chamber. Figure 2 This is an example of such flexible adaptation. Figure 2aFigure 1 shows an abstract absorption spectrum of a substance to be measured. This substance has three characteristic absorption peaks (A1, A2, A3). This absorption spectrum can be replicated using a combination of suitable elements from the optical switch array 2 and the filter array 4. In this example, the optical switches 3(A), 3(B), and 3(C) are open, thus exposing the filters 4(A), 4(B), and 4(C) from the filter array 4. In certain configurations, not only can the positions of the individual absorption peaks be replicated, but also the amplitude ratios between the peaks can be adjusted. Figure 2b The graph shows the three individual spectra of filters 4(A), 4(B), and 4(C). The simultaneously exposed filters of filter array 4 are shown in Figure 2d The areas shown in white are black. Figure 2c shows the complete spectrum 4(A) + 4(B) + 4(C) of the light after filter array 4. This light spectrum is optimally adapted to the in Fig. 2aThe absorption spectrum of the substance being measured is adjusted as shown. Intensity adjustment can be achieved by modifying parameters such as the current for the individual light emitters when using a light emitter array without an optical switch array, or by adjusting the transmittance of the optical switch array. The latter applies particularly to the use of a micro-aperture array with an adjustable aperture or a liquid crystal-based micro-aperture array with adjustable transmittance.

[0030] Figure 3Figure 1 shows an example of an embodiment of the proposed multispectral sensor and the multispectral light emission arrangement used therein, in which the light source 1 is formed by an array of a plurality of individual light emitters 1(N). The left-hand figure schematically depicts the structure of the multispectral sensor, and the right-hand figure shows the structure of the associated arrangement. In this embodiment, no optical switching device is used, as in [reference to previous figure]. Figure 1 required. The individual light emitters of the array-shaped light source 1 can be individually controlled or switched on and off as needed. This allows for flexible adaptation of the light spectrum emitted by the arrangement to the absorption spectrum of the sample to be measured, in the same way as is already possible in conjunction with the Figure 1 and 2 was explained. In the example of the Figure 3The two light emitters 1(A) and 1(B) are switched on, while the other light emitters of the light source 1 are switched off. As a result, only filters 4(A) and 4(B) on the filter array 4 arranged above them are exposed, as schematically indicated in the figure. In this example, the light-emitting surfaces of the light emitters 1 have an area smaller than the dimensions of the filters 4(N) of the filter array 4, as shown in the right-hand part of the figure. Figure 3 As indicated, by maintaining a sufficiently small distance between the filter array 4 and the light source 1, only those filters of the filter array 4 that are located directly above the respective light emitter 1(N) can be exposed by appropriately controlling the individual light emitters 1(N).

[0031] Preferably, an array of IR light sources emitting light with a spectral range of 1 µm to 15 µm is used as the light source 7. This allows, for example, the measurement of a gaseous sample in the measuring chamber 5 by photoacoustic spectroscopy. One or more pressure sensors, for example in the form of one or more microphones, are then used as the receiver 6. Thus, in the configuration according to Figure 3 An array of so-called microheaters, as described, for example, in LD Williams et al., "Design and characterization of a microheater array device fabricated with SwIFT-Lite™", J. Micro / Nanolith. MEMS MOEMS 7(4), 043035 (2008), can be used as an array-shaped light source. Such an array can be fabricated using MEMS technology.

[0032] Figure 4This shows another example of a multispectral light emission setup with an array-shaped light source. Such a setup could therefore also be used in a multispectral sensor according to... Figure 3 can be used. In this example, the filter array and the array-shaped light source form a single unit. Figure 4 Figure 1 shows an array of monolithically constructed spectral channels. A spectral channel is a combination of light source or light emitter 9(1), 9(2) ... 9(n) and filter 4(1), 4(2), ... 4(n) of the filter array. The in Figure 4The array shown can be fabricated using semiconductor technology or by post-processing. The desired number of spectral channels can thus be arranged as an array on a substrate 20. Both the individual filters, which can be designed, for example, as plasmonic filters or filters based on subwavelength structures, and the light source, for example in the form of MEMS microheaters, can be implemented using semiconductor technology. The filters can consist of one or more structured metal or dielectric layers. Figure 4Figure 1 shows a cross-section of such a unit. The layered structure of several layers 21-25 on the substrate 20 with the vias 26, as is frequently used in semiconductor processes, is clearly visible in the figure. In this example, layer 22 represents the IR light source array with light emitters 9(1), 9(2) ... 9(n). The IR light sources can be implemented, for example, as microspirals or microheaters. The filter array with filters 4(1), 4(2) ... 4(n) is implemented in the uppermost layer 25. Each filter can be constructed from one or more individual layers. The filter layers can consist of at least one array-shaped metal layer structured in sub-wavelength dimensions or a dielectric layer. The filter properties can be freely defined for each spectral channel. The optical properties of the filters depend on the feature size and the feature shape (e.g.,The filter arrays (holes or islands) depend on the periodicity and can be defined via the filter design. Filter arrays in configurations with an optical switching device can also be implemented in this way. Layer 21 represents one of the layers of a typical layer structure in a semiconductor process and can, for example, also serve as a reflector for the light source in layer 22. Suitable openings for the transmission of light are formed in layers 23 and 24. These layers generally consist of a metallic material and are separated from each other by dielectric layers. The vias 26 prevent light from passing between the individual spectral channels in this array.

[0033] Examples of suitable infrared optical filters can be found in IJH McCrindle et al., "Infrared plasmonic filters integrated with an optical and terahertz multi-spectral material", Phys. Status Solidi A 212, No. 8, 1625 to 1633 (2015) and in A. Wang et al., "Mid-infrared plasmonic multispectral filters", Scientific Reports (2018) 8: 11257. The filters presented in these publications are based on structured metal layers and can be modeled using finite-difference time-domain (FDTD) simulation. The simulation allows the design of the filters to be determined for the desired spectral transmission, bandwidth, and central wavelength position.

[0034] Figure 5 shows a modification of the arrangement according to the invention for multispectral light emission of the Figure 3Since light source 1 and filter array 4 are manufactured separately and stacked on top of each other in this arrangement, a gap is created between light source 1 and filter array 4. To prevent optical crosstalk between the individual optical channels, the following is used in the example of the Figure 5A suitably designed aperture or lens array 8 is arranged in this free space, preventing optical crosstalk between the individual channels. Without this aperture or lens array 8, the light from a light emitter could potentially strike not only the filter directly above it, but also neighboring filters. For example, with the use of this aperture or lens array 8, the light from light emitter 1(B) strikes only the filter 4(B) above it. Without the aperture or lens array 8, due to the large beam angle of light emitter 1(B), its light would also strike neighboring filters, such as filter 4(C).

[0035] In Figure 6Figure 1 shows an example of an arrangement according to the invention for multispectral light emission, in which a microshutter array is used as the optical switch array 2 above the light source 1. Such a microshutter array can be manufactured, for example, using MEMS technology, as is known, for example, from MJ Li et al., "Fabrication of Microshutter Arrays for Space Application", Proceedings of SPIE vol. 4407 (2001), 295 to 303. In the example of the Figure 6Shutters 2(A) and 2(B) or micro-apertures are open, and filters 4(A) and 4(B) are exposed. The remaining micro-apertures are closed, and their corresponding filters are not exposed. The elements of the aperture array can be controlled individually or as a group to open and close. This allows the light spectrum emitted by the arrangement to be flexibly adapted to the absorption spectrum of a sample, as in the previous examples. The micro-aperture or optical switch array 2 and the light source 1 located below it can be implemented as a single unit. To prevent crosstalk between individual channels, an additional aperture or lens array 8 is arranged both between light source 1 and optical switch array 2, and between optical switch array 2 and filter array 4, as shown in the left part of the figure. Figure 6 as indicated.

[0036] Figure 7This shows another example of a possible design for the proposed arrangement for multispectral light emission. In the example of the Figure 7A single light emitter is used as the light source 1, which can be moved under the filter array 4 via a mechanical XY adjuster 12. Here, too, an aperture or lens array 8 can be integrated, as in some of the preceding embodiments, to prevent optical crosstalk. This limits the beam angle and prevents adjacent filters from being unintentionally exposed. In the present example, the filter array 4 is located on a substrate transparent to the light from the light source, for example, silicon in the case of an IR light source. The light source 1 is located on the XY adjuster 12. The filter array 4 is scanned with the light source 1 according to the desired filter or the resulting spectral characteristic. In this way, different spectral characteristics can be generated successively, as shown in the left part of the figure. Figure 7The top view of the filter array 4 schematically illustrates this. The small travel distance of the XY adjuster, given the correspondingly small lateral dimensions of the individual filters in the filter array 4, can be achieved, for example, using a piezoelectric drive. Alternatively, the light source 1 can be fixed in place and the filter array 4 moved above the light source. In the example of the Figure 7 The filters F1 to Fx of filter array 4 are scanned one after the other.

[0037] Figure 8 Figure 1 shows an example of a photoacoustic gas sensor (PGS) as it can be implemented according to the present invention. The arrangement for multispectral light emission, in Figure 8The module 13, which can be implemented in principle as in one of the previously described embodiments, features a micro-aperture array 11 as the optical switching device. A lens array 8 is arranged between the light source 1 and the micro-aperture array 11 in this example, preventing crosstalk between the individual spectral channels. The lenses of this lens array 8 collimate or focus the light emitted by the light source 1 towards the respective micro-aperture. In this example, the electronics of the gas sensor are separated from the measuring chamber 5. The measuring chamber has an optical window 10 for coupling in the excitation radiation. In this example, the filter substrate of the optical filter array 4 is used as the optical window 10. The filters of the filter array can be arranged above or below this optical window.In the present example, the filters are arranged above the optical window 10, i.e., within the measuring chamber 5. A pressure sensor, for example in the form of a MEMS microphone, is located in the measuring chamber 5 and serves as receiver 6. The output signal of this microphone is evaluated in the signal processing and evaluation unit 7 (electronics, software). The left part of the diagram shows... Figure 8A top view of the filter array 4 is shown. Filter 4(A) on the filter array is exposed (spot 42). The other filters of the filter array 4 are not exposed. As explained in the preceding embodiments, several filters can, of course, be exposed simultaneously. In a PGS sensor, an IR light source is usually used as the light source 1, emitting light in the wavelength range of 1 to 15 µm. The measuring chamber 5 has at least one inlet for feeding the sample. Additional sensors, for example for temperature and humidity, can also be located in the measuring chamber 5.

[0038] Figure 9Figure 1 shows another example of an arrangement for multispectral light emission. In this example, a micromirror array 16 is used as an optical switch array. This mirror array 16 can, for example, be a DLP module (MEMS). In this module, individual mirrors or mirror regions, i.e., regions with multiple mirrors, can be switched on and off or tilted accordingly. The individual mirrors of the module can be very small, for example, with dimensions of 10 x 10 µm. In the example of the Figure 9 The individual mirrors of the mirror array 16 direct the light either in direction 1 or in direction 2. The light from a light source 1 illuminates the mirror array 16. When deflected in direction 2, the respective light beam is directed via an optical system 18, for example a concave mirror, onto the optical filter array 4 and illuminates, for example, as shown in Figure 9The optical system 18 is based on either lens or mirror optics. Mirror optics are preferred because the mirror coating enables very low absorption across a very broad spectral range. The selection of the individual filters of the filter array 4 is achieved via the activated areas of the optical mirror array. In this example, mirror or mirror area 16(A) is activated, thus deflecting the incident light in direction 2. Mirror or mirror area 16(B) is deactivated, so the associated mirror(s) deflect the light in direction 1 onto an absorber 17, where the deflected light is absorbed. By appropriately controlling the individual mirrors of the mirror array, the desired filters of the filter array 4 can therefore be exposed.

[0039] Alternatively, the filter array 4 with the individual filters, preferably plasmonic filters, can also be applied directly to the mirrors of the mirror array 16, as shown in Figure 10 This is shown schematically. A separate filter array 4 as in the left part of the Figure 9 It will then not be needed.

[0040] The filter array and the MEMS mirror array can be implemented together using semiconductor technology. The respective filter can consist of one or more structured metal or dielectric layers. Figure 10 Figure 1 shows a top view of an example of such a micromirror array 16 with applied filters. In this example, four of the mirrors are grouped together to form a group or mirror region 16(A), 16(B) ... 16(n), each coated with the same filter. This is shown in the Figure 10as indicated by the respective pattern. Filters based on subwavelength structures or plasmonic filters are preferably used here. This allows a reflection spectrum for almost any material to be measured to be recreated by a combination of different mirror regions 16(A), 16(B) ... 16(n). The corresponding mirrors are simply switched on, i.e., they reflect the incident radiation into the measuring chamber. A specific filter, optimized for a particular wavelength, can be applied to each mirror region. A mirror region can consist of ≥ 1 mirror, in the example of the Figure 10 made of four mirrors.

[0041] Figure 11 shows an example of a design for a photoacoustic gas sensor using the following Figure 9 or 10The illustrated arrangement is for multispectral light emission. In this example, the electronics and optics are separated from the measuring chamber 5. The measuring chamber has an optical window 10, which, in this example as well, is formed by the filter substrate of the optical filter array 4. The filters of the filter array can, in turn, be arranged above or below the optical window 10. In the present example, the filters are arranged below the optical window 10, i.e., they are located outside the measuring chamber. The measuring chamber 5 contains at least one pressure sensor as a receiver 6, which can, for example, be designed as a MEMS microphone. The output signal of this pressure sensor is evaluated in the signal processing and evaluation unit 7 (electronics, software). In the left part of the illustration, Figure 11A top view of the filter array 4 is shown. Filter 4(A) on the filter array is exposed (spot 42). The other filters in the array are not exposed. As shown in previous embodiments, several filters can, of course, be exposed simultaneously. In a PGS sensor, the light source 1 is typically an IR light source that emits in a broad range between 1 and 15 µm. The measuring chamber 5 has at least one inlet 19 for feeding the sample. Additional sensors, for example for measuring temperature and humidity, can also be located in the measuring chamber.

[0042] Figure 12Figure 1 shows an example of a multispectral sensor setup according to the present invention, in which more than one measuring chamber is used. In this example, three measuring chambers 5(A), 5(B), 5(C) are arranged in series. This is possible because, when measuring gases, the weak gas absorption results in only a slight attenuation of the excitation light emitted into the measuring chambers as it passes through them. Each measuring chamber has optical windows 35(A), 35(B), 35(C), 35(D). The beam 37, emitted from the multispectral light emission arrangement, propagates through the individual chambers 5(A), 5(B), 5(C). A radiation receiver 27 can be installed after the last chamber. This allows fluctuations in light intensity to be measured. Various samples can be introduced into the measuring chambers. These can be unknown gases or calibration gases. A calibration gas has a defined concentration and a known spectrum.A multiport sampler can be implemented by using multiple measurement chambers. For example, an IR detector or a photodiode can be used as the radiation receiver 27.

[0043] Figure 13 Figure 1 shows an example of a filter array that can also be used in the proposed arrangement and the proposed multispectral sensor. Such a filter array, in this example in the form of an "infrared linear variable filter" such as those commercially available from Vortex Optical Coatings Ltd., can be fabricated using thin-film technology. This type of filter has multiple spectral channels (bandpass filters) and can be optimized for a specific spectral range. The filter array 4 from the preceding embodiments can be replaced by such a filter. The filters F1, F2, and Fn can be exposed individually or as a group via an optical switch.

[0044] In the proposed arrangement for multispectral light emission and the associated multispectral sensor, the spectral filters can also be combined with polarization filters. Figure 14This shows a combination of a spectral filter with several polarizing filters. The absorption and scattering spectra of substances can depend on the polarization state of the light. For this reason, additional information about a substance can be obtained through polarized spectral illumination. In the preceding embodiments, unpolarized light was used. In the present example, a spectral channel or filter 4(A) is combined with several polarizing filters 40(A), 40(B), and 40(C). There is no polarizing filter at position 41. This position represents a reference channel with unpolarized light. The filters 40(A), 40(B), and 40(C) can be exposed sequentially via the optical switch array. In this example, the spot 42 is located on polarizing filter 40(A).The light after passing through spectral filter 4(A) always has the same spectrum, but can be polarized differently depending on the local illumination. The right-hand figure shows an example of such a filter built using semiconductor technology. The basic structure was already described in connection with [reference missing]. Figure 4 As explained, in this example, grid-like structures are implemented in metal layer 23. These grid-like metal struts polarize the light depending on the angle. In this example, angles of +90°, +45°, and -45° are used. Above this, a spectral filter 4(A) is built in layer 25. This can, for example, be based on subwavelength structures. Reference symbol list

[0045] 1 Light source 1(N) Light emitter 2 Optical switch array 2(N) Micro apertures 3(N) Elements of the switch array 4 Filter array 4(N) Selected filters 5 Measuring chamber 6 Receiver 7 Signal processing and evaluation unit 8 Lens or aperture array 9(N) Light emitter 10 Optical window 11 Micro aperture array 12 XY adjuster 13 Module 14 Arrangement for multispectral light emission 15 Measuring device 16 Micromirror array 16(N) Micromirror, micromirror area 17 Absorber 18 Optical system 19 Inlet 20 Substrate 21-25 Layers 26 Via 27 Radiation receiver 35 Optical window 37 Beam array 40 Polarizing filter 41 Position on spectral filter 42 Exposure spot

Claims

1. Assembly for multispectral light emission comprising at least - a wide-band light source (1) that emits light in a spectral range, - a filter array (4) made up of a plurality of spectral filters having a spectral width which lies at least in part within the spectral range of the light source (1), and - an optical switch device (2) for controlling a passage of the light emitted by the light source through the filter array (4), wherein the light source (1), the filter array (4) and the optical switch device (2) are arranged such that the light emitted by the light source (1) is guided via the optical switch device (2) and the filter array (4) to an outlet of the assembly, - wherein the optical switch device (2) comprises an array of micromirrors (16) or micro-diaphragms and is designed and arranged in such a way that it can selectively guide the light emitted by the light source (1) only through one or more arbitrarily specifiable spectral filters of the filter array (4) to the outlet of the assembly, wherein each combination of one or more elements (3) of the optical switch device (2) and an associated spectral filter of the filter array (4) represents an optical channel, characterized in that a device (8) for preventing optical crosstalk between the optical channels is arranged between the light source (1) and the filter array (4).

2. Assembly for multispectral light emission comprising at least - a wide-band light source (1) that emits light in a spectral range, - a filter array (4) of multiple spectral filters having a spectral width that is at least partially within the spectral range of the light source (1), and - a switch device for controlling passage of the light emitted by the light source (1) through the filter array (4), - wherein the light source (1) comprises an array of light emitters controllable separately via the switch device and is designed and arranged in such a way that by activating the light emitters via the switch device, the light emitted by the light source (1) can be guided in a targeted manner only through one or more arbitrarily specifiable spectral filters of the filter array (4), - wherein the filter array (4) is arranged directly above the array of light emitters that can be activated separately via the switch device, and - wherein each combination of one or more light emitters with a spectral filter of the filter array (4) arranged directly above represents an optical channel and a device for avoiding optical crosstalk between the optical channels is arranged between the array of light emitters which can be controlled separately via the switch device and the filter array (4).

3. Assembly according to Claim 1 or 2, characterized in that the individual spectral filters of the filter array (4) have small lateral dimensions of ≤10 x 10 mm.

4. Assembly according to one of Claims 1 to 3, characterized in that the filter array (4) is a filter array based on sub-wavelength structures or a plasmonic filter array.

5. Assembly according to one of Claims 1 to 4, characterized in that the spectral filters are arranged in rows and columns in the filter array (4).

6. Assembly according to one of Claims 1 and 3 to 5 in conjunction with Claim 1, characterized in that when the optical switch device (2) is designed as an array of micromirrors (16), the filters of the filter array (4) are applied directly to the micromirrors.

7. Assembly according to one of Claims 1 to 6, characterized in that the spectral filters in the filter array (4) are combined with polarization filters (40).

8. Multispectral sensor comprising - an assembly according to one or more of the preceding claims, - a measuring chamber (5) into which light emerging from the assembly is coupled, and - one or more detectors (6) by means of which a result of an interaction of the light coupled into the measuring chamber (5) and a medium introduced into the measuring chamber (5) can be detected.

9. Multispectral sensor according to Claim 8, characterized in that an inlet window (10) of the measuring chamber (5) is formed by a carrier substrate of the filter array (4) of the assembly.

10. Multispectral sensor according to Claim 8 or 9, which is designed as a photo-acoustic sensor, in particular as a photo-acoustic gas sensor.

11. Multispectral sensor according to Claim 8 or 9, which is designed as an absorption sensor or as a combined absorption and photo acoustic sensor.