DE102016216842B4 - Method and device for operating a spectrometer - Google Patents

Abstract

Device (102) for operating a spectrometer (100), the device (102) having the following features: a determining device (122) for determining a compensation value (126) for compensating an offset (120) of one detected by the spectrometer (100) Spectrum (104) using an angular value (128), the angular value (128) representing an angle of incidence (116) of light (106) which was incident on the spectrometer (100) during acquisition of the spectrum (104); and compensation means (124) for compensating the spectrum (104) using the compensation value (126) to obtain an angle-compensated spectrum (130), characterized by an angle detection means (132) adapted to measure the angle of incidence (116) from during a Detection of the spectrum (104), light (106) incident on the spectrometer and imaging in the angle value (128), the angle detection device (132) having a photodetector (110) which has a pixel field (134) with a plurality of one each Pixels (136) providing intensity value (112), wherein the angle detection device (132) is designed to determine the angle value (128) using the intensity values (112) and wherein the device (102) has an illumination device (200) which is laterally offset from the photodetector (110), the pixels (136) being located on an axis between the lighting device (200) and the photodetector (110) are aligned.

Description

State of the art

The invention is based on a device or a method according to the type of the independent claims. The present invention also relates to a computer program.

The post-published publication DE 10 2016 212 088 A1 discloses a device for limiting an angle of incidence for a spectrometer and a method for operating such a device.

The publication EP 1 213 568 A2 discloses a device for image-wise measurement of a flat measurement object.

Disclosure of the invention

In the case of a spectrometer, a recorded spectrum can have an offset if the light falls on the spectrometer at an angle.

Against this background, the approach presented here presents a method for operating a spectrometer, a device using this method, a spectrometer, and finally a corresponding computer program in accordance with the main claims. The measures listed in the dependent claims allow advantageous developments and improvements of the device specified in the independent claim.

The wavelength error caused by obliquely incident light when acquiring a spectrum depends on an angle of incidence of the light.

In the approach presented here, the angle of incidence is therefore determined and used to determine a compensation value for the spectrum. The compensation value is applied to the offset spectrum and the spectrum is shifted.

• Ermitteln eines Kompensationswerts zum Kompensieren eines Offsets eines von dem Spektrometer erfassten Spektrums unter Verwendung eines Winkelwerts, wobei der Winkelwert einen Einfallswinkel von Licht repräsentiert, welches während eines Erfassens des Spektrums auf das Spektrometer eingefallen ist; und

A method for operating a spectrometer is presented, the method comprising the following steps:

• Determining a compensation value for compensating an offset of a spectrum captured by the spectrometer using an angle value, the angle value representing an angle of incidence of light which was incident on the spectrometer while the spectrum was being acquired; and

Compensate for the spectrum using the compensation value to obtain an angle compensated spectrum.

This method can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

• eine Ermittlungseinrichtung zum Ermitteln eines Kompensationswerts zum Kompensieren eines Offsets eines von dem Spektrometer erfassten Spektrums unter Verwendung eines Winkelwerts, wobei der Winkelwert einen Einfallswinkel von Licht repräsentiert, welches während eines Erfassens des Spektrums auf das Spektrometer eingefallen ist; und
• eine Kompensationseinrichtung zum Kompensieren des Spektrums unter Verwendung des Kompensationswerts, um ein winkelkompensiertes Spektrum zu erhalten.

Furthermore, a device for operating a spectrometer is presented, the device having the following features:

• determining means for determining a compensation value for compensating an offset of a spectrum acquired by the spectrometer using an angle value, the angle value representing an angle of incidence of light which was incident on the spectrometer during acquisition of the spectrum; and
• compensation means for compensating the spectrum using the compensation value to obtain an angle compensated spectrum.

A spectrometer can be understood to mean a component which has a spectral element in an optical path in front of a detector. A spectrum is an intensity curve over a wavelength range. The spectrum can be recorded in parallel or in series. In the case of parallel recording, the entire spectrum is spatially resolved by the spectral element and a plurality of intensity values with several pixels are recorded in a single time slot via a line-shaped detector. In the case of serial recording, the spectral element only lets through a limited wavelength range of the incident light and an intensity value of the wavelength range is recorded. Different wavelength ranges are transmitted in several time slots in succession and the resulting intensity values are recorded. The spectrum is composed of the intensity values recorded one after the other. The angle value can be detected using an angle sensor. Compensation values can be stored in a table.

The device has an angle detection device which is designed to detect an angle of incidence of light incident on the spectrometer during detection of the spectrum and to depict it in the angle value. The angle detection device can be integrated in the spectrometer. This enables the actual angle of incidence to be recorded while the spectrum is being acquired.

The angle detection device has a photodetector which has a pixel field with a plurality of pixels each providing an intensity value, the angle detection device being designed to determine the angle value using the intensity values. The angle can be determined using a center of gravity of light incident on the detector. The photodetector can use the light used to acquire the spectrum. A systematic error can thus be avoided. A total of the intensity values can be used to acquire the spectrum.

The device has an illuminating device which is arranged laterally offset from the photodetector, the pixels being aligned on an axis between the illuminating device and the photodetector. A lighting device can have an LED, for example. The lighting device can be aligned obliquely to an optical axis of the optical element. By means of the lighting device, the angle of incidence of the incident light can represent a relationship to a distance between an illuminated object and the spectrometer. The spectrometer can be used to measure distance.

The photodetector can be designed to detect the spectrum. The photodetector can use the light used to acquire the spectrum. A systematic error can thus be avoided.

The pixels can be arranged in a two-dimensional area. Pixels aligned in a first direction can capture the spectrum. Pixels aligned at right angles can provide the intensity values. Due to the flat arrangement of the pixels, the spectrum and the angle of incidence can be recorded in parallel.

Furthermore, a spectrometer with a device according to the approach presented here is presented.

A spectral element of the spectrometer can be designed as a linearly variable filter. The spectrum can be recorded in parallel using the linearly variable filter.

The spectral element of the spectrometer can be designed as a micromechanical interferometer. A simple photo detector can be used with the interferometer.

Also advantageous is a computer program product or computer program with program code, which can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and for carrying out, implementing and / or controlling the steps of the method according to one of the embodiments described above is used, in particular if the program product or program is executed on a computer or a device.

• 1 ein Blockschaltbild eines Spektrometers mit einer Vorrichtung zum Betreiben gemäß einem Ausführungsbeispiel;
• 2 eine Darstellung einer Winkelerfassung unter Verwendung eines Pixelfelds gemäß einem Ausführungsbeispiel;
• 3 eine Darstellung eines mittig auf einen Fotodetektor gemäß einem Ausführungsbeispiel auftreffenden Beleuchtungsspots;
• 4 eine Darstellung eines erfassten Spektrums;
• 5 Darstellungen von außermittig auf einen Fotodetektor gemäß einem Ausführungsbeispiel auftreffenden Beleuchtungsspots;
• 6 eine Darstellung eines Spektrums mit Offset;
• 7 eine Darstellung eines Spektrometers mit einem linear variablen Filter gemäß einem Ausführungsbeispiel;
• 8 eine Darstellung eines Spektrometers mit einem Interferometer gemäß einem Ausführungsbeispiel; und
• 9 ein Ablaufdiagramm eines Verfahrens zum Betreiben eines Spektrometers gemäß einem Ausführungsbeispiel.

Embodiments of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

• 1 a block diagram of a spectrometer with a device for operation according to an embodiment;
• 2 an illustration of an angle detection using a pixel field according to an embodiment;
• 3 an illustration of an illumination spot hitting the center of a photodetector according to an exemplary embodiment;
• 4 a representation of a recorded spectrum;
• 5 Representations of off-center lighting spots hitting a photodetector according to an embodiment;
• 6 a representation of a spectrum with offset;
• 7 a representation of a spectrometer with a linearly variable filter according to an embodiment;
• 8th a representation of a spectrometer with an interferometer according to an embodiment; and
• 9 a flowchart of a method for operating a spectrometer according to an embodiment.

In the following description of favorable exemplary embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the different figures and acting in a similar manner, and a repeated description of these elements is omitted.

1 shows a block diagram of a spectrometer 100 with one device 102 to operate according to an embodiment. The spectrometer 100 is trained to be a spectrum 104 of incident light 106 capture. The spectrometer points to this 100 a spectral element 108 on. The spectral element 108 is trained to incident light 106 to separate into its contained wavelengths. A photo detector 110 forms radiation intensities of the wavelengths in intensity values 112 from. A detection device 114 captures the intensity values and forms them in the spectrum 104 from.

The spectral element is sensitive to angles. When the incident light is at an angle of incidence 116 at an angle to a working axis 118 of the spectrometer 100 occurs, the separated wavelengths are offset by an angle 120 postponed. This offset 120 is also in the spectrum 104 displayed. The spectrum 104 shows the offset 120 on.

The device 102 has an investigating device 122 and a compensation device 124 on. The investigative facility 122 is designed to provide a compensation value 126 to compensate for the offset 120 using an angle value 128 to investigate. The angle value 128 represents the angle of incidence 116 while capturing the spectrum 104 , The compensation device 124 is trained to use the spectrum 104 using the compensation value 126 to compensate for an angle compensated spectrum 130 to obtain.

The device 102 has an angle detection device 132 on. The angle detection device 132 is designed to measure the angle of incidence 116 to capture and in the angular value 128 map. For example, the angle detection device 132 next to the spectral element 108 be arranged. Here is the angle detection device 132 Part of the spectrometer 100 ,

The angle detection device 132 includes the photo detector 110 , The photo detector 110 has a pixel field 134 with a plurality of pixels 136 on. The pixels 136 form those in the area of the pixel 136 incident radiation intensity of light 106 in an intensity value 112 from. Because the position of each pixel 136 relative to the working axis 118 is known can be in a determination device 138 the angle detection device 132 from the simultaneously recorded intensity values 112 of the individual pixels 136 on the angle of incidence 116 getting closed. The destination facility 138 forms the angle of incidence 116 in the angle signal 128 and captures the intensity values recorded at the same time 112 to an intensity value 112 together.

In one embodiment, the spectral element is 108 as an interferometer 108 educated. The interferometer 108 has two mirrors spaced apart by a gap. A gap width 140 of the gap is determined by the interferometer 108 transmitted wavelength. A drive device 142 is designed to the gap width 140 in response to a control signal 144 adjust the gap width.

The control signal 144 can from the detection device 114 be provided to the gap width 140 set to a new wavelength when a wavelength is detected.

In one embodiment shows 1 a component 100 or a miniature spectrometer 100 , consisting of a light source, not shown, a spectral element 108 with limited aperture and a photo detector 110 that as an at least two-part photodiode, quadrant photodiode or detector array 134 is executed. In the angle determination device 132 becomes a difference signal 112 the photodiode 110 to determine the main angle of incidence 116 used.

The spectral element 108 can be a micromechanical Fabry-Perot interferometer device 108 his. The interferometer then consists of at least two mirror elements which are spaced apart from one another by a gap and are arranged one above the other. Knowing the main angle of incidence is used to correct the spectral offset 120 used.

The spectral element 108 can also be a linear variable filter 108 with a change in wavelength in X his. Then the detector can 110 a two-dimensional detector array 134 with pixels 136 in X for the wavelength and pixels 136 in Y for the angle correction. The difference between detector lines becomes the detection of the main angle of incidence 116 used. Knowing the main angle of incidence 116 is used to correct the spectral offset 120 used.

The approach presented here compensates for angle-dependent and thus distance-dependent wavelength offset errors in the case of an eccentric lighting approach 120 for spectrometers 100 reached. By compensating for the wavelength offset 120 can have higher accuracy of the wavelength spectrum 130 at different distances, making the system more robust 100 in handling by the end user.

2 shows an illustration of an angle detection using a pixel field 134 according to an embodiment. The angle of incidence 116 is using a spectrometer 100 recorded, such as in 1 is shown. The spectrometer 100 here comprises a lighting device 200 that laterally offset to the photo detector 110 is arranged. The lighting device 200 is oblique to the working axis 118 aligned. A lighting axis 202 the lighting device 200 intersects the working axis 118 , An illuminating beam of the lighting device 200 is divergent. If a distance 204 between the spectrometer 100 and an illuminated object becomes smaller, an illuminated area moves 206 on the object along the lighting axis 202 towards the lighting device 200 , The illuminated area 206 smaller. If the distance 204 the illuminated area moves 206 along the lighting axis 202 from the lighting device 200 path. The illuminated area 206 greater. In other words, changes due to the oblique lighting axis 202 the angle of incidence 116 between the spectrometer 100 and the illuminated area 206 when the distance 204 changes. The illuminated area 206 can be called a target.

If that's in the illuminated area 206 reflected light 106 through a pinhole 208 or lens optics 208 on the photo detector 110 falls, changes with the angle of incidence 116 also a position of one reflected by the light 106 caused lighting spots on the photodetector 110 , The pixel field 134 has two neighboring pixels here 136 on. The pixels are along a connecting line between the lighting device 200 and the photo detector 110 aligned. Depending on the position of the lighting spot, a light intensity of the light changes 106 on the pixels 136 , The light intensity is in turn reflected in the intensity values of the pixels 136 displayed.

A typical eccentric light arrangement is in 2 shown. If at different intervals 204 is measured, there are different entry angles 116 , Between the pinhole 208 and the detector 110 For example, a Fabry Perot filter is integrated as a spectral element (not shown), which reacts sensitively to changes in input angle. Input angle deviations from the detector axis 118 are always shifted to shorter wavelengths.

3 shows a representation of a center on a photo detector 110 according to one embodiment, lighting spots 300 , The photo detector 110 corresponds essentially to the representations in the 1 and 2 , Here is the pixel field 134 circular and has four equally sized pixels 136 on. The pixels 136 are circular sector shaped. The lighting spot 300 essentially meets the center of the pixel field 134 , This is one illuminated area per pixel 136 essentially identical. The pixels 136 convert the proportion of light from the lighting spot that falls on them 300 in essentially the same electrical intensity values.

When using a pinhole or a lens system, the lighting spot shifts 300 depending on the distance on the detector 110 lateral. A pixel array 134 or a detector divided into at least two parts 110 can the different focus of the reflected lighting spot 300 on the detector 110 measure up. Here are the focal points using the four sectors 136 measured. This difference is a measure of the angle of incidence and thus of the distance of the target. Based on this data, the respective spectrum offset can be processed using signal processing as in 1 Getting corrected.

Four-part detectors 110 can give an indication of sample homogeneity because the lateral sectors 136 should have the same signal. Large differences can indicate a target inhomogeneity. Furthermore, it can be checked whether the illumination path or the mechanical positioning of the pinhole to the detector 110 was changed.

With large angles of incidence, it is advantageous that the focus analysis of the lighting spot 300 is carried out over the entire spectrum because different wavelengths and different angles of incidence are measured at the same time. Depending on the setting of the spectral element, strongly varying spectra could lead to different measurement results. A plausibility check of the measurement result can be achieved by measuring the entire spectrum and comparing the focus positions.

4 shows a representation of a recorded spectrum 104 , The spectrum 104 is plotted in a diagram which shows the wavelength λ on the abscissa and an intensity on the ordinate. The measured spectrum 104 has been detected by light incident essentially perpendicular to a spectral element. For example, the spectrum 104 on the in 3 shown lighting spot has been recorded. The spectrum 104 corresponds to an actual spectrum due to the vertically incident light 400 or target spectrum.

5 shows representations of off-center on a photo detector 110 according to one embodiment, lighting spots 300 , The photo detector 110 is shown twice and essentially corresponds to the photodetector in FIG 3 , The light here is oblique through one in front of the detector 110 arranged optics or aperture. The lighting spot 300 is on the side of the pixel field 134 postponed. Here are the proportions of the lighting spots 300 each uneven on the pixels 136 of the pixel field 134 distributed. With that put the pixels 136 different intensity values ready.

6 shows a representation of a spectrum 104 with offset 120 , The spectrum 104 is like in 4 plotted in a diagram which has the wavelength λ on the abscissa and an intensity on the ordinate. The spectrum 104 has been detected by light incident obliquely on a spectral element. For example, the spectrum 104 at one of the in 5 shown lighting spots were recorded. The intensity values of the spectrum 104 are about offset 120 versus the actual spectrum 400 postponed.

Since using the different intensity values of the pixels in 5 The angle value of the angle of incidence can be determined, a correction value can be used to compensate for the offset 120 can be read from a stored table, for example. The correction value can also be calculated using a calculation rule. The captured spectrum 104 can be shifted by the correction value to the compensated spectrum 130 to get that essentially the actual spectrum 400 equivalent.

7 shows a representation of a spectrometer 100 with a linear variable filter 108 according to an embodiment. The spectrometer essentially corresponds to the spectrometer in 1 , The pixel field 134 is here as a matrix with pixels 136 trained in rows and columns. The lines are at a filter direction of the linearly variable filter 108 or an x-direction, while the columns are oriented transversely to the filter direction or in a y-direction. The linear variable filter 108 has two dielectric mirrors 700 which have a decreasing distance from one another over the filter direction. The distance determines a transmitted wavelength. Due to the decreasing distance, the filter leaves 108 in the filter direction through a wavelength curve, whereby the lines of the pixel field 134 the spectrum 104 to capture. The columns of the pixel field 134 capture the angle of incidence.

8th shows a representation of a spectrometer 100 with an interferometer 108 according to an embodiment. The spectrometer essentially corresponds to the spectrometer in 2 , The pixel field 134 is here as a matrix with pixels 136 trained in rows and columns. The interferometer 108 acts as the pinhole 208 , The interferometer 108 transmits a resonance wavelength and its harmonics at a time. The harmonics can be filtered out. The spectrum is recorded by many individual measurements that follow one another at different wavelengths. In contrast to 7 here both the rows and the columns record the angle of incidence 116 , The angle of incidence 116 is recorded in two spatial directions.

In other words, is in 8th a spectrometer 100 represented with a Fabry-Pérot interferometer 108 for distance measurement and for angle of incidence measurement.

Micromechanical Fabry-Perot Interferometer (FPI) 108 consist of two mirror elements, which are arranged on a substrate above a through hole. interferometer 108 can also be constructed from two substrates with through holes. The beam of light 106 should be guided vertically through the sandwich design with two highly reflecting mirrors, whereby narrow-band areas are transmitted around a resonance wavelength and their overtones depending on the distance between the two mirrors. The desired resonance wavelength can be set by varying the distance in a subsequent detector 110 be measured and thus a spectrum can be recorded serially. An additional bandpass filter in front of it can filter out the desired order so that errors caused by other orders are minimized.

For Fabry-Pérot interferometers (FPI) 108 as a linear variable filter 108 or mechanically tunable interferometer 108 causes a variation in the angle of incidence 116 of the light beam 106 a shift in the wavelength to be measured. Beams of light come at the same time 106 with different angles of incidence 116 on the spectral element 108 , the possible wavelength resolution is reduced. As a result, spectra with strong transmission variations or absorption variations in a narrow wavelength range can no longer be resolved easily. This distribution is the angle of incidence 116 but at a certain angle 116 away from the normal 118 centered, this leads to a shift of the entire spectrum, i.e. a wavelength offset error.

The triangulation method uses the illumination axis and the optical axis 118 of the detector 110 differently. With vertical displacements of the target 206 there is a lateral displacement of the lighting spot, which is caused by the detector 110 is measured.

In the approach presented here, a triangulation method is combined with the spectrum measurement technology.

For spectrometers 100 the larger the offset of the wavelength shift, the denser the target 206 or object on the spectrometer 100 is positioned. With the same lateral displacement to the optical axis 118 of the spectrometer 100 this results in an increase in the angle of incidence 116 to the surface normal 118 ,

The closer the object is to the spectrometer 100 can be positioned, the more reflected power is collected and the signal to noise ratio can be improved. The photons of an illuminating body are collected with a certain angle of incidence and reflection, absorption or destructive interference of the photons not required, so that no false signals are generated. The target is illuminated eccentrically by a lateral displacement of the illumination area 206 in relation to the optical axis 118 of the spectrometer 100 to create. This shift produces a photon change in the angle of incidence on the spectrometer 100 , which leads to an offset shift of the shaft detection. The lighting spot position is measured, for example, via the light center at the location of the detector 110 , The device according to the approach presented here carries out a correction of the wavelength spectrum offset as a function of the lighting spot position on the detector 110 out.

In one embodiment, the spectral element is 108 as in 7 a linear variable filter 108 , The lighting 200 is arranged eccentrically. A variation in the sample distance results in a varying angle of incidence 116 the diffusely reflected radiation. The linear variable filter ensures each line 108 for a mapping of the spectrum. The variation of the angle 11 ensures a shift of the difference signal between the lines, from which the angle 116 can be determined.

9 shows a flow chart of a method 900 for operating a spectrometer according to an embodiment. The procedure 900 has a step 902 of identifying and taking a step 904 of compensation. In step 902 of the determination, a compensation value for compensating an offset of a spectrum recorded by the spectrometer is determined using an angle value. The angle value represents an angle of incidence of light which has been incident on the spectrometer while the spectrum is being acquired. In step 904 of compensation, the spectrum is compensated using the compensation value to obtain an angle compensated spectrum. In the step of determining ( 902 ) the angle of incidence ( 116 ) from during a spectrum acquisition ( 104 ) light falling on the spectrometer ( 106 ) from the angle detection device ( 132 ) recorded and in the angular value ( 128 ) mapped. The angle detection device ( 132 ) has a photo detector ( 110 ) on a pixel field ( 134 ) with a plurality of intensity values each ( 112 ) providing pixels ( 136 ) having. The angle detection device ( 132 ) is designed to use the intensity values ( 112 ) the angular value ( 128 ) to determine. A lighting device ( 200 ) is provided which is laterally offset to the photodetector ( 110 ) is arranged. The pixels ( 136 ) are on an axis between the lighting device ( 200 ) and the photo detector ( 110 ) aligned.

If an exemplary embodiment comprises a “and / or” link between a first feature and a second feature, this is to be read in such a way that the embodiment according to one embodiment has both the first feature and the second feature and according to a further embodiment either only that has the first feature or only the second feature.

Claims (12)

Device (102) for operating a spectrometer (100), the device (102) having the following features: a determining device (122) for determining a compensation value (126) for compensating an offset (120) of one detected by the spectrometer (100) Spectrum (104) using an angular value (128), the angular value (128) representing an angle of incidence (116) of light (106) which was incident on the spectrometer (100) during acquisition of the spectrum (104); and compensation means (124) for compensating the spectrum (104) using the compensation value (126) to obtain an angle-compensated spectrum (130), characterized by an angle detection means (132) which is designed to determine the angle of incidence (116) of during a detection of the spectrum (104) to detect light (106) incident on the spectrometer and to image it in the angle value (128), the angle detection device (132) having a photodetector (110) which has a pixel array (134) with a plurality of Each has an intensity value (112) providing pixels (136), the angle detection device (132) being designed to determine the angle value (128) using the intensity values (112), and the device (102) has an illumination device (200) , which is arranged laterally offset to the photodetector (110), the pixels (136) on an axis between the lighting device (20 0) and the photodetector (110) are aligned. Device (102) according to Claim 1 , in which the photodetector (110) is designed to determine an angle using a center of gravity of light incident on the photodetector (110). Device (102) according to any one of the preceding claims, in which the photodetector (110) is designed as an at least two-part photodiode, quadrant photodiode or detector array (134). Device (102) according to one of the preceding claims, wherein that of the angle detection device (132) is designed to infer the angle of incidence (116) from the simultaneously acquired intensity values (112) of the individual pixels (136). Device (102) according to one of the preceding claims, in which the pixels (136) are arranged two-dimensionally flat, with pixels (136) aligned in a first direction being designed to capture the spectrum (104) and pixels (106) aligned transversely thereto ) are designed to provide the intensity values (112). Device (102) according to one of the preceding claims, in which the photodetector (110) is designed to detect the spectrum (104). Spectrometer (100) with a device (102) according to one of the Claims 1 to 6 , Spectrometer (100) according to Claim 7 , in which a spectral element (108) of the spectrometer (100) is designed as a linearly variable filter (108). Spectrometer (100) according to Claim 7 , in which a spectral element (108) of the spectrometer (100) is designed as a micromechanical interferometer (108). Method (900) for operating a spectrometer (100) according to one of the Claims 7 to 9 The method (900) comprises the following steps: determining (902) a compensation value (126) for compensating an offset (120) of a spectrum (104) acquired by the spectrometer (100) using an angle value (128), the Angle value (128) represents an angle of incidence (116) of light (106), which was incident on the spectrometer (100) while the spectrum (104) was being acquired; and compensating (902) the spectrum (104) using the compensation value (126) to obtain an angle compensated spectrum (130), characterized in that in the step of determining (902) the angle of incidence (116) from during an acquisition of the spectrum (104) light incident on the spectrometer (106) is detected by the angle detection device (132) and is imaged in the angle value (128), the angle detection device (132) having a photodetector (110) which has a pixel field (134) with a A plurality of pixels (136) each providing an intensity value (112), the angle detection device (132) being designed to use the intensity values (112) to determine the angle value (128) and an illumination device (200) is provided which is laterally offset from the photodetector (110), the pixels (136) being located on an axis between the lighting device (200) and the photodetector (11 0) are aligned. Computer program, which is set up according to the method (900) Claim 10 perform. Machine-readable storage medium on which the computer program is based Claim 11 is saved.

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