WO2021058260A1 - Spectrometer device and method for calibrating a spectrometer device - Google Patents

Abstract

The present invention relates to a spectrometer device and to a calibration method for a spectrometer device. A calibrating element having one or more known extinction curves is disposed in the beam path between light emitter and photodetector of the spectrometer device. A precise correlation between control of the spectral element and corresponding wavelength can be generated by determining the setting of a spectral element that corresponds to an extinction curve of the calibrating element.

Description

description

title

Spectrometer device and method for calibrating a spectrometer device

The present invention relates to a spectrometer device and a method for calibrating a spectrometer device.

State of the art

Spectral sensors are currently gaining in importance. For example, spectral sensors can be used to examine substances or objects for their material composition. The increasing miniaturization of sensors in particular results in increasingly interesting areas of application. For the implementation of a spectral filter element in a spectrometer, for example, a tunable microelectromechanical system with a Fabry-Perot interferometer represents a promising approach to miniaturizing the overall system.

The publication DE 102018200378 A1 describes an interferometer, for example an ME MS-Fabry-Perot interferometer with two mirrors which are applied to two substrates which are connected to one another.

Disclosure of the invention

The present invention provides a spectrometer device and a method for calibrating a spectrometer device having the features of the independent patent claims. Further advantageous embodiments are the subject of the dependent claims.

Accordingly, it is provided:

A spectrometer device having a light emitter, a spectral element, a photodetector and a calibration element. The light emitter is also included designed to emit light in a predetermined spectrum. In particular, the light emitter can emit the light in the direction of a sample. The photodetector is designed to detect light. Furthermore, the photodetector can provide an output signal corresponding to the detected light.

The spectral element is arranged in an optical path between the sample and the photodetector. The calibration element is arranged in a beam path from the light emitter and the photodetector. The calibration element can have one or more extinction lines. In other words, light components with one or more wavelengths or wavelength ranges which correspond to the corresponding extinction lines are at least partially absorbed by the calibration element. The remaining light components that do not correspond to the wavelength or the wavelength ranges of the extinction lines, on the other hand, can transmit largely unhindered through the calibration element.

It is also provided:

A method of calibrating a spectrometer device. The spectrometer device includes a light emitter and a photodetector. Furthermore, the spectrometer device comprises a calibration element which is arranged in a beam path between the light emitter and the photodetector and which has one or more extinction lines. The method comprises a step of controlling a spectral element which is located in the beam path between the light emitter and the photodetector. By controlling the spectral element, the filter properties of the spectral element can be adapted. In particular, the wavelength or the wavelength range through which the spectral element can pass can be adapted in accordance with the control. The method further comprises a step of identifying a setting of the spectral element which corresponds to an extinction line of the calibration element. In other words, it is determined at which control of the spectral element the spectral element is set to a wavelength or a wavelength range which corresponds to an extinction line of the calibration element.

Advantages of the invention The present invention is based on the knowledge that spectrometer devices must be calibrated very precisely in order to be able to precisely identify the wavelength or wavelength ranges of the light to be analyzed. In addition, the present invention is based on the knowledge that the settings of the spectrometer device can change over the operating time or the lifetime of a spectrometer device due to numerous effects, such as the effects of temperature, aging, etc. Therefore, such spectrometer devices may need to be recalibrated.

It is therefore an idea of the present invention to take this knowledge into account and to create a possibility for a calibration of a spectrometer device that is as simple, inexpensive and efficient as possible.

For this purpose, it is provided according to the invention to provide an additional element in the light path between the emitter and detector of a spectrometer which has known and as stable as possible absorption properties for light of a known wavelength or a known wavelength range. Thus, by appropriately controlling the spectral element in the spectrometer device, a setting can be identified in which the spectral element is set as precisely as possible to an extinction line, i.e. an absorption range of the calibration element in the beam path between the light source and the photodetector. This results in one or more precisely known calibration points. Using these calibration points, the setting or the evaluation of the measuring process of the spectrometer device can then be adapted in a simple manner. Since the calibration element can already be built into the spectrometer device during manufacture of the spectrometer device, a simple and quick calibration can take place in this way at any later point in time. Since no additional external components are required for the calibration, the calibration can also be carried out on site.

According to one embodiment, the calibration element has at least one extinction line in the spectral filter range of the spectral element. Accordingly, the spectrometer device can identify a setting for the spectral element in which the spectral element is set to the extinction line of the calibration element. According to one embodiment, the calibration element has at least one extinction line in the lower and / or upper spectral edge region of the filter region of the spectral element. By choosing extinction lines in the edge area of the spectral filter element, calibration points can be determined which are very well suited as support points for a calibration characteristic. In addition, calibration points in the edge area of the filter area of the spectral element are generally only slightly disruptive for the operational operation of the spectrometer device. In addition to one or more individual extinction lines, the calibration element can also include any known extinction line shapes, in particular complex spectra or the like.

According to one embodiment, the calibration element is arranged in the beam path between the sample and the spectral element. For example, the calibration element can be attached to a cover glass or the like, which covers the spectral element. Such a cover glass can be provided over the spectral element, for example, as protection against contamination or damage.

According to one embodiment, the calibration element is arranged in the beam path between the light emitter and the sample. For example, the calibration element can be arranged on a cover glass which covers the light emitter. Alternatively, the calibration element can also be arranged on any optical element which deflects or focuses the light from the light emitter.

According to one embodiment, the calibration element can be arranged in a luminous layer of the light emitter. In this way, for example, light can already be emitted by the light emitter in which one or more predetermined wavelengths or wavelength ranges are not included.

According to one embodiment, the calibration element can be arranged on the photodetector. For example, a surface of the photodetector can be coated with a suitable substance which has one or more extinction lines.

According to one embodiment, the spectrometer device comprises a further photodetector. In this case, the calibration element can be in a beam path between the light emitter and the further photodetector be arranged. In this way, the beam path for analyzing a sample is not influenced by the absorption of one or more wavelengths by the calibration element.

According to one embodiment, the spectrometer device comprises a control device. The control device can be designed to determine a setting of the spectral element that corresponds to the extinction line. The setting can include, for example, a control voltage or the like. By determining the setting corresponding to the extinction line, a calibration value can be determined which can be used as a basis for evaluating the measurement data during the analysis of a sample. In particular, if the calibration element has several extinction lines, a suitable function can be determined which can be used as a basis for the calibration. The function can include a linear function, but also a function of a higher degree.

According to one embodiment, the control device is designed to carry out a measuring process for analyzing a sample using the settings corresponding to the extinction lines of the calibration element. In this way, a measurement of a sample can be carried out with constant quality and quality. In particular, aging effects and fluctuations due to temperature effects or the like can be compensated for by regular calibration.

According to one embodiment, the spectral element comprises a Fabry-Perot interferometer, a grating spectrometer, a static or movable Fourier transform spectrometer and / or a wavelength-selective filter. In principle, any elements or assemblies that are capable of filtering or separating the light coming from the object to be examined in a spectral manner are possible as a spectral element.

According to one embodiment, at least one of the extinction lines of the calibration element shifts with the temperature by less than 0.5 nm / K (nanometers per Kelvin). At least one of the extinction lines of the calibration element is preferably shifted by less than 0.05 nm / K. In particular, the calibration element can have at least one extinction line which shifts with the temperature by less than 0.01 nm / K. By using of the temperature-stable extinction lines, a reliable calibration can be achieved which does not depend, or at least only to a very small extent, on the temperature.

The above configurations and developments can be combined with one another as required, as far as this makes sense. Further refinements, developments and implementations of the invention also include combinations, which are not explicitly mentioned, of features of the invention described above or below with regard to the exemplary embodiments. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic forms of the invention.

Brief description of the drawings

Further features and advantages of the invention are explained below with reference to the figures. Show:

Figure 1: a schematic representation of a cross section through a

Spectrometer device according to an embodiment;

Figure 2 is a schematic representation of a course that detects the

Intensity as a function of an activated signal for the spectral element of a spectrometer device according to one embodiment; and

Figure 3: a flow chart of how a method for calibrating a

This is based on the spectrometer device according to one embodiment.

Description of embodiments

FIG. 1 shows a schematic representation of a cross section through a spectrometer device 1 according to an embodiment. The spectrometer device 1 comprises a light emitter 10, a spectral element 20 and a photodetector 30. The light emitter 10 can emit light in a predetermined spectrum. The predetermined spectrum can be light in the visible or invisible wavelength range. In particular, the light emitter 10 can also be infrared in addition to visible light or emit ultraviolet light. Furthermore, the light emitter 10 can comprise optics in order to emit or focus the emitted light in the direction of a sample 100.

The light from the light emitter 10 can interact with the sample. For example, the light can be reflected or scattered on the sample. Part of the light scattered by the sample 100 is reflected / scattered in the direction of the spectral element 20. The spectral element 20 can be a Fabry-Perot interferometer, for example. In particular, it can be a tunable Fabry-Perot interferometer with a microelectromechanical system (MEMS). In addition, however, any other spectral elements are also possible in principle. For example, the spectral element 20 can comprise a grating spectrometer, a static or moving Fourier transform spectrometer and / or another wavelength-selective filter.

The spectral element 20 can filter the incident light in such a way that only light of a narrow-band spectrum can pass the spectral element 20. The filtered light strikes the photodetector 30. The photodetector 30 can provide an output signal corresponding to the light intensity. Analogously, a signature can also be impressed on the passing light by the spectral element 20, which makes it possible, for example by means of a suitable computing unit and an evaluation algorithm, to determine the spectrum of the light reflected or scattered by the sample 100.

To adapt the filter characteristic of the spectral element 20, the spectral element 20 can be controlled with a corresponding control signal. For example, this can be an electrical voltage, the value of which corresponds to the filter frequency of the spectral element. As a rule, there can be a fixed relationship between the control signal and the filter frequency of the spectral element 20. However, this relationship can change due to aging effects or environmental influences, such as temperature or the like. It is therefore necessary to carry out a calibration in order to obtain as precise a knowledge as possible about the relationship between the control signal and spectral properties, such as, for example, the filter frequency, of the spectral element 20. For this purpose, a calibration element 40a-d can be provided in the beam path between light emitter 10 and photodetector 30. The calibration element 40a-d can be permanently installed in the spectrometer device 10. In particular, the calibration element 40a-d also remains in the spectrometer device 1 during the normal measuring process.

For example, the calibration element 40c can be arranged in the beam path between the sample 100 and the spectral element 20. For example, the calibration element 40c can be applied to a cover glass or the like, which covers the spectrometer device 1, in particular the area with the spectral element 20.

Alternatively, the calibration element 40b can also be arranged in the beam path between the light emitter 10 and the sample 100. In this case, for example, the calibration element 40b can be arranged on a cover glass which covers the light exit, in particular the area above the light emitter 10.

Furthermore, it is also possible that the calibration element 40d is located between the spectral element 20 and the photodetector 30, in particular it can be located directly above the photodetector 30. For example, the calibration element 40d can be applied to a surface of the photodetector 30.

In addition, it is also possible for the calibration element 40a to be introduced directly into the light emitter 10. For example, the calibration element 40a can be introduced into the phosphor or a luminescent layer of the light emitter 10.

Alternatively, it is also possible to provide an additional further photodetector after the spectral element 20 in the spectrometer device 1. In this case, the calibration element 40a-d can be arranged in the beam path between the light emitter 10 and the further photodetector. In this way, the calibration element 40a-d does not influence the measuring process by means of the actual photodetector 30.

The spectrometer device 1 can have a control device for controlling the calibration process and for evaluating a measurement process exhibit. The control device can, for example, provide the necessary control signals for controlling the spectral element 20. Furthermore, the control device can receive and evaluate the signals provided by the photodetector 30. In this way, the control device can determine a relationship between the control of the spectral element 20 and the corresponding wavelength.

The calibration element 40a-d is a substance which has one or more extinction lines or a more complex extinction spectrum. The calibration element 40a-d thus absorbs / scatters the light of the wavelength corresponding to the extinction lines. This property can therefore be used for a calibration process of the spectrometer device 1. For example, the spectral element 20 can be tuned through the filter area, and the light intensity detected by the photodetector 30 can be related to the corresponding control of the spectral element 20. This then results in a significant drop in the detected light intensity precisely at the extinction lines of the calibration element 40a-d.

Additionally or alternatively, the calibration element 40a-d can have one or more fluorescence lines, in which the calibration element 40a-d emits light with one or more wavelengths corresponding to the fluorescence lines after a corresponding excitation. In this case there is a significant increase in the detected light intensity at the wavelengths of the fluorescence lines.

FIG. 2 shows a schematic representation of the course of the detected light intensity I over a control signal V for the spectral element 20. As can be seen here, a narrow-band significant drop in the detected intensity I can be seen both at the lower and upper edge area. If the exact wavelength of the extinction lines of the calibration element 40a-d is known, then these notches in the detected intensity I can be assigned to the corresponding wavelengths. In this way, the relationship between the wavelengths of the extinction lines and the corresponding control signal for the spectral element 20 is also known. This information can be used for a calibration, for example a linear interpolation of the relationship between wavelength and control signal. But also any other calibration method, For example, the determination of complex functions of a higher degree or the like are also possible.

The embodiment shown here with two extinction lines is only used for better understanding. In addition, the calibration can in principle also be carried out with only one extinction line or more than two extinction lines in the calibration element 40a-d.

The extinction lines of the calibration element 40a-d are preferably located in the edge area of the filter area of the spectral element 20. In this way, the extinction lines influence the actual measuring process of the spectrometer device 1 only to a small extent.

For example, plasmonic filter elements can be used as substances for the calibration element 40a-d. In particular, such filter elements can be based on so-called Fano resonances, for example. Furthermore, nanostructures or structures with nanoparticles are also possible, which have special materials, in particular dielectric particles or special molecules, which lead to the desired extinction lines. In addition, special materials with a sharp extinction spectrum, such as erbium or the like, can also be used. Of course, any other materials, structures, particles or the like that have the desired properties with characteristic extinction lines are also possible. The half-width of the extinction lines should preferably be significantly narrower than the resolution of the spectral element.

For the selection of the materials for the calibration element 40a-d, substances with the best possible temperature stability are preferably suitable. In this way, fluctuations due to a variation in the temperature can be avoided or at least greatly restricted. For example, calibration elements 40a-d are possible in which the extinction lines fluctuate by less than 0.5 nm / K (nanometers per Kelvin). The extinction lines preferably fluctuate less than 0.05 nm / K. Calibration elements 40a-d in which the extinction lines vary by less than 0.01 nm / K are particularly suitable. FIG. 3 shows a schematic representation of a flowchart on the basis of a method for calibrating a spectrometer device 1 according to an embodiment. In this case, the method can in particular also include any steps, as already described above in connection with FIGS. 1 and 2. Analogously, the spectrometer device 1 described above can also have any components, as will be described below in connection with the calibration process.

The calibration method can be carried out with any spectrometer device 1 in which a calibration element 40a-d with at least one extinction line is arranged between the light emitter 10 and the photodetector 30. In a step S1, light is emitted by the light emitter 10 and, in the process, a spectral element 20 is activated, which is located in the beam path between the light emitter 10 and the photodetector 20. In step S2, a setting of the spectral element 20 is identified which corresponds to an extinction line of the calibration element 40a-d.

Based on the identified setting of the spectral element 20, which corresponds to the extinction line of the calibration element 40a-d, a subsequent measuring process of the spectrometer device 1 can be evaluated on the basis of this setting.

In summary, the present invention relates to a spectrometer device and a calibration method for a spectrometer device. A calibration element with one or more known extinction lines is arranged in the beam path between the light emitter and the photodetector of the spectrometer device. By determining the setting of a spectral element that corresponds to an extinction line of the calibration element, a precise association between the control of the spectral element and the corresponding wavelength can be made.

Claims

Expectations 1. Spectrometer device (1), with a light emitter (10) which is designed to emit light in a predetermined spectrum in the direction of a sample (100); a photodetector (30) which is designed to detect light and to provide an output signal corresponding to the detected light; a spectral element (20) disposed in an optical path between the sample (100) and the photodetector (30); and a calibration element (40a-40d) which is arranged in a beam path between the light emitter (10) and the photodetector (30) and which has one or more extinction lines. 2. Spectrometer device (1) according to claim 1, wherein the calibration element (40a-40d) has at least one extinction line in the spectral filter range of the spectral element (20). 3. Spectrometer device (1) according to claim 1 or 2, wherein the calibration element (40a-40d) has at least one extinction line in the spectral edge region of the filter region of the spectral element (20). 4. Spectrometer device (1) according to one of claims 1 to 3, wherein the calibration element (40a-40d) comprises a plasmonic filter structure, a nanoparticle structure and / or an element with a sharp extinction spectrum. 5. Spectrometer device (1) according to one of claims 1 to 4, wherein the calibration element (40c) is arranged in the beam path between the sample (100) and the spectral element (20). 6. spectrometer device (1) according to any one of claims 1 to 4, wherein the calibration element (40b) is arranged in the beam path between the light emitter (10) and the sample (100). 7. spectrometer device (1) according to any one of claims 1 to 4, wherein the calibration element (40d) is arranged in the beam path between the spectral element (20) and photodetector or on the photodetector (30). 8. spectrometer device (1) according to one of claims 1 to 4, wherein the calibration element (40a) is arranged in a luminous layer of the light emitter (10). 9. spectrometer device (1) according to one of claims 1 to 8, with a further photodetector, wherein the calibration element (40a-40d) is arranged in a beam path between the light emitter (10) and the further photodetector 10. Spectrometer device (1) according to one of claims 1 to 9, with a control device which is designed to determine a setting of the spectral element (20) corresponding to the extinction line. 11. The spectrometer device (1) according to claim 10, wherein the control device is designed to carry out a measuring process using the setting corresponding to the extinction line of the calibration element (40a-40d). 12. Spectrometer device (1) according to one of claims 1 to 11, wherein the spectral element (20) comprises a Fabry-Perot interferometer, a grating spectrometer, a static or moving Fourier transform spectrometer and / or a wavelength-selective filter. 13. Spectrometer device (1) according to one of claims 1 to 12, wherein one or more extinction lines of the calibration element (40a-40d) shift with the temperature by less than 0.5 nm / K. 14. A method for calibrating a spectrometer device (1), wherein the spectrometer device (1) between a light emitter (10) and a Photodetector (30) comprises a calibration element (40a-40d) with at least one extinction line, and wherein the method comprises the following steps: controlling (Sl) a spectral element (20) which is in an optical path between the light emitter (10) and the photodetector (30) is located; and Identifying (S2) a setting of the spectral element (20) which corresponds to an extinction line of the calibration element (40a-40d).