How to calibrate a spectrometer device

Abstract

A method for calibrating a spectrometer device (112) is disclosed, the method comprising the steps of: a) illuminating at least one detector arrangement (118) of said spectrometer arrangement (112) with at least one broadband light source (114) through at least one narrow bandpass filter (116), in particular through a plurality of narrow bandpass filters (116) having a plurality of predetermined transmission bands; b) generating a plurality of detector signals (170) in response to the illumination of step a) by using said detector arrangement (118), said detector arrangement (118) comprising at least one optical element (120) configured to separate the incident light into a spectrum of constituent wavelength components and further comprising a plurality of photosensitive elements (122), each photosensitive element configured to receive at least one portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least one portion of the respective constituent wavelength components; c) determining at least one item of wavelength calibration information, said item of wavelength calibration information including at least one assignment of wavelengths, in particular wavelength bands, of incident light to corresponding photosensitive elements responsive to these wavelengths, in particular assigning at least one of said photosensitive elements to each of the predefined transmission bands, and more in particular assigning one or more of pixel positions (174) and / or identification numbers of said photosensitive elements to each of the predefined transmission bands, in particular to each of the predefined transmission bands; d) determining at least one item of stray light calibration information based on the plurality of detector signals (170), said item of stray light calibration information comprising at least one signal distribution function, in particular at least one signal distribution matrix, said signal distribution function describing the distribution of the response of said photosensitive element to incident light having a particular wavelength; Includes. Additionally, a system (110) for calibrating a spectrometer device (112), a computer program, and a computer readable storage medium are disclosed.

Description

[Technical field]

[0001] The present invention relates to a method for calibrating a spectrometer device and a system for calibrating a spectrometer device. Furthermore, the present invention relates to a computer program and a computer readable storage medium for carrying out the method for calibrating a spectrometer device. The method and device of the present invention can be used in particular for calibrating spectrometer devices used for investigations in the infrared spectral range, in particular in the near infrared and mid infrared spectral range. However, other spectrometer devices are also possible. [Background technology]

[0002] Spectroscopy is widely used in research, industrial and consumer applications, enabling multiple applications such as optical analysis and / or quality control. It finds use in food, agriculture, pharmaceutical, medical, life sciences and many other fields. A variety of methods are available, such as photometry, absorption, fluorescence and Raman spectroscopy, allowing qualitative and / or quantitative sample analysis. These methods typically involve mapping spectral information, such as the irradiance of a sample at a particular wavelength, to a particular physical section of the spectroscopic device, e.g. a detector pixel, a time interval, etc.

[0003] In general, spectroscopy requires reliable performance of the application of spectroscopic instruments with negligible variability, especially when measurements from different spectroscopic instruments are compared with each other. In particular, the spectral data of a particular sample should be at least similar or identical on different spectroscopic instruments of the same type.

[0004] For spectroscopic devices, two system characteristics are generally important for reliable performance: First, wavelength calibration is very important, meaning that the displayed or measured wavelength is correct, at least within a given tolerance. In pixelated spectroscopic devices, which use light-sensitive pixels assigned to specific wavelengths, wavelength calibration may involve mapping individual pixels or time domains of a Fourier transform-based spectroscopy to their respective wavelengths. Second, crosstalk calibration, also known as stray light calibration, may be very important. In ideal operation, a spectroscopic device maps the spectral information of the sample being investigated to multiple signal channels. Ideally, one single channel may contain information from the sample in a very narrow spectral range and no spectral information outside this spectral range, i.e., the spectral information can be mapped one-to-one to the output channels. However, undesirable effects in a spectroscopic device, such as diffuse scattering and / or diffraction on surfaces, can cause crosstalk between multiple channels of the spectroscopy. Thus, spectral information in a narrow spectral range can affect multiple output channels. Stray light calibration may include information about how a detector signal at one wavelength is affected by another signal at another wavelength.

[0005] Further calibration of the spectroscopic device, such as a sensitivity calibration of the spectroscopic device, is often not necessary, especially if relative measurements, ie the absorption and / or reflectance of the sample, need to be determined.

[0006] Various methods for wavelength calibration and / or stray light calibration are known in the art. For example, ME Schaepman and S. Dangel describe a laboratory calibration of a nonimaging spectroradiometer based on a measurement plan in "Solid laboratory calibration of a nonimaging spectroradiometer", Applied Optics, Vol. 39, No. 21, 2000. The individual calibration steps include characterization of signal-to-noise ratio, noise equivalent signal, dark current, wavelength calibration, spectral sampling interval, nonlinearity, directional and position effects, spectral scattering, field of view, polarization, source size effects, and temperature dependence of the specific device.

[0007] C. Tseng, JF Ford, CK Mann and TJ Vickers: "Wavelength Calibration of a Multichannel Spectrometer", Applied Spectroscopy, Vol. 47, No. 11, 1993, discloses an automated procedure for the wavelength calibration of a multichannel spectrometer, using a neon atomic beam as the wavelength standard.

[0008] A.K. Gaigalas, L. Wang, H.-J. He and P. DeRose: “Procedures for Wavelength Calibration and Spectral Response Correction of CCD Array Spectrometers,” Journal of Research of the National Institute of Standards and Technology, Volume 114, Number 4, 2009, describes procedures for acquiring spectra of interest over a wide wavelength range and verifying wavelength and intensity assignments.

[0009] US 2020 / 0056939 A1 describes a method of calibrating a spectrometer module. The method includes performing measurements using the spectrometer module to generate wavelength vs. operating parameter calibration data for the spectrometer module, performing measurements using the spectrometer module to generate optical crosstalk and dark noise calibration data for the spectrometer module, and performing measurements using the spectrometer module to generate total system response calibration data for the spectrometer module relative to a known reflectance standard. The method further includes storing a calibration record incorporating the wavelength vs. operating parameter calibration data, the optical crosstalk and dark noise calibration data, and the total system response calibration data in a memory coupled to the spectrometer module, and applying the calibration record to measurements by the spectrometer module.

[0010] CN 103226095 B discloses a method for real-time online wavelength calibration of a spectrometer using sulfur dioxide standard gas in a DOAS flue gas analyzer.

[0011] US 7,839,502 B2 describes a method for wavelength calibration of a spectrometer. The method is based on the principle of stepwise relative shifting of corresponding measurement value blocks of model and calibration spectra, and for each shift step a correlation value is calculated. A shift value is determined for each measurement value block at which the correlation value reaches an optimum. A value pair consisting of a position marker of the measurement value block and an associated shift value is determined for each measurement value block. These value pairs represent design points for fitting a suitable allocation function. The coefficients thus obtained can be used directly as coefficients of the wavelength allocation or can be combined with the coefficients of an existing first wavelength allocation, for example replacing or offsetting the coefficients of the existing first wavelength allocation.

[0012] C. Pope and A. Baumgartner: "Light source for stray light characterisation of EnMAP spectrometers", Proceeding of SPIE 11151, Sensors, Systems, and Next-Generation Satellites XXIII, 1115123, 2019, discloses a light source developed for stray light characterisation of satellite spectrometers and its use to characterise in-band, in-field stray light.

[0013] Y. Zong, SW Brown, BC Johnson, KR Lykke and Y. Ohno: "Simple spectral stray light correction method for array spectroradiometers", Applied Optics, Vol. 45, No. 6, 2006, describes a method to correct the response of a spectroradiometer for measurement errors arising from the instrument's spectral stray light. By characterizing the instrument's response to a set of monochromatic laser sources covering the instrument's spectral range, a spectral stray light signal distribution matrix is ​​obtained that quantifies the magnitude of the spectral stray light signal in the instrument. Using these data, a spectral stray light correction matrix is ​​derived, allowing the instrument's response to be corrected with a simple matrix multiplication.

[0014] A. Kreuter and M. Blumthaler: "Stray light correction for solar measurements using array spectrometers", Review of Scientific Instruments, 80, 096108, 2009, discloses a stray light matrix correction method for array spectrometers, specifically tailored to solar spectrum measurements. The stray light distribution function based on a single laser line measurement is approximated with an analytical function using only three parameters. This function is the basis of the stray light correction matrix. A cutoff filter is then used to adjust the offset parameters so that the stray light corrected data is spectrally flat and near zero below the cutoff wavelength.

[0015] ME Feinholz, SJ Flora, SW Brown, Y. Zong, KR Lykke, MA Yarbrough, BC Johnson and DK Clark: "Stray light correction algorithm for multichannel hyperspectral spectrographs", Applied Optics, Vol. 51, No. 16, 2012, describes an algorithm to correct a multichannel fiber-coupled spectrometer for stray or scattered light within the system. The algorithm is based on characterization measurements using a tunable laser system and can be extended to correct for finite point spread response in imaging systems.

[0016] Y. Zong, SW Brown, BC Johnson, KR Lykke and Y. Ohno: "Correction of stray light in spectrographs: implications for remote sensing", Proceeding of SPIE 5882, Earth Observing Systems X, 588201, 2005, discloses a method to correct stray light errors in spectrographs. By measuring a series of monochromatic laser sources covering the spectral range of the instrument, the stray light properties of the instrument are characterized and a stray light correction matrix is ​​derived.

[0017] WO 2018 / 085841 A1 discloses the calibration of hyperspectral sensors and camera systems, more specifically, apparatus and methods are disclosed for measuring the characteristics of camera systems based on active pixel sensors having Fabry-Perot filters deposited directly on the active pixel array, and for use in such systems in a variety of applications, including agriculture, medicine, and other fields of use that would benefit from better calibrated hyperspectral systems.

[0018] US 2018 / 224334 A1 discloses a spectrophotometer and spectroscopic process that can provide for in-line calibration with every spectrum acquisition, which can also provide for continuous response correction during sample processing. The spectrophotometer includes a plurality of polychromatic light sources with characteristic emission spectra for use as an internal wavelength drift calibration system independent of environmental factors. The correction function provided by the internal calibration process can be applied continuously and across the entire sample spectrum. The intensity response of each spectrometer of the spectrophotometer can also be monitored and continuously corrected for stray light, dark current, read noise, etc.

[0019] Despite the advantages achieved by known methods and devices, some technical challenges remain. In particular, known wavelength calibration and stray light calibration are usually performed independently in a laboratory or during factoring, using delicate and expensive equipment such as Penley lamps, standard lamps using argon, and monochromator systems. Each calibration is performed by an independent process and an independent measurement configuration. Wavelength calibration is usually performed based on atomic gauges, i.e. the radiation of various atomic species can be used as a universal standard for wavelength calibration. Typical light sources are helium-neon lasers, argon lamps, and mercury lamps. Alternatively, rare earth calibration standards are also available. The emission spectrum of the atoms is recorded and its position is compared with reference data, for example from a central standardization and metrology institute. Stray light correction can generally be identified and / or quantified using a narrowband light source, such as light from a monochromator or a tunable laser. In most cases, separate light sources for each output channel of the spectroscopic device need to be used. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] US 2020 / 0056939 A1 [Patent Document 2] CN 103226095 B [Patent Document 3] US 7,839,502 B2 [Patent Document 4] WO 2018 / 085841 A1 [Patent Document 5] US 2018 / 224334 A1 [Non-patent literature]

[0021] [Non-Patent Document 1] ME Schaepman, S. Dangel, "Solid laboratory calibration of a nonimaging spectroradiometer," Applied Optics, Vol. 39, No. 21, 2000. [Non-Patent Document 2] C. Tseng, JF Ford, CK Mann and TJ Vickers, "Wavelength Calibration of a Multichannel Spectrometer", Applied Spectroscopy, Vol. 47, No. 11, 1993. [Non-Patent Document 3] A.K. Gaigalas, L. Wang, H.-J. He and P. DeRose, "Procedures for Wavelength Calibration and Spectral Response Correction of CCD Array Spectrometers," Journal of Research of the National Institute of Standards and Technology, Vol. 114, No. 4, 2009. [Non-Patent Document 4] C. Pope and A. Baumgartner, "Light source for stray light characterisation of EnMAP spectrometers", Proceeding of SPIE 11151, Sensors, Systems, and Next-Generation Satellites XXIII, 1115123, 2019. [Non-Patent Document 5] Y. Zong, SW Brown, BC Johnson, KR Lykke and Y. Ohno, "Simple spectral stray light correction method for array spectroradiometers," Applied Optics, Vol. 45, No. 6, 2006. [Non-Patent Document 6] A. Kreuter and M. Blumthaler, "Stray light correction for solar measurements using array spectrometers," Review of Scientific Instruments, 80, 096108, 2009 [Non-Patent Document 7] ME Feinholz, SJ Flora, SW Brown, Y. Zong, KR Lykke, MA Yarbrough, BC Johnson and DK Clark, "Stray light correction algorithm for multichannel hyperspectral spectrographs", Applied Optics, Vol. 51, No. 16, 2012. [Non-Patent Document 8] Y. Zong, SW Brown, BC Johnson, KR Lykke, and Y. Ohno, "Correction of stray light in spectrographs: implications for remote sensing," Proceeding of SPIE 5882, Earth Observing Systems X, 588201, 2005. Summary of the Invention [Problem to be solved by the invention]

[0022] It is therefore desirable to provide a method and apparatus that at least partially addresses the above-mentioned technical challenges related to the calibration of a spectrometer device. In particular, a method and system for calibrating a spectrometer device is proposed that provides high flexibility for accurately calibrating the spectrometer device by using simple components at low cost and with low effort. [Means for solving the problem]

[0023] This problem is solved by a method for calibrating a spectrometer device, a system for calibrating a spectrometer device, a computer program and a computer readable storage medium having the features of the independent claims. Advantageous embodiments, which can be realized independently or in any combination, are set out in the dependent claims and in the specification as a whole.

[0024] As used herein, the terms "having", "comprises" or "including", or any grammatical variants thereof, are used in a non-exclusive manner. Thus, these terms may refer both to the situation where, apart from the features introduced by these terms, no further features are present in the entity described in this context, and to the situation where one or more further features are present. As an example, the expressions "A has B", "A comprises B" and "A includes B" may refer both to the situation where no other elements are present in A apart from B (i.e., A is solely and exclusively composed of B), and to the situation where, in addition to B, one or more further elements are present in the entity A, such as element C, elements C and D, or further elements.

[0025] Furthermore, it should be noted that the terms "at least one," "one or more," or similar language indicating that a feature or element may be present one or more times, are typically used only once when introducing each feature or element. In most cases, the language "at least one" or "one or more" will not be repeated when referring to each feature or element, regardless of the fact that each feature or element may be present one or more times.

[0026] Furthermore, as used herein, the terms "preferably", "more preferably", "particularly", "more particularly", "particularly", "more particularly" or similar terms are used in connection with any feature without limiting the possibility of substitution. Thus, features introduced by these terms are optional features and are not intended to limit the scope of the claims in any way. The invention can be implemented by using alternative features, as the skilled person will recognize. Similarly, features introduced by "in one embodiment of the invention" or similar expressions are intended to be optional features, without any limitation on alternative embodiments of the invention, without any limitation on the scope of the invention, and without any limitation on the possibility of combining the feature introduced in such a way with other optional or non-optional features of the invention.

[0027] In a first aspect of the present invention, a method for calibrating a spectrometer device is disclosed.

[0028] The term "spectrometer device" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, without limitation, a device capable of optically analyzing at least one sample and thereby generating at least one item of information regarding at least one spectral characteristic of the sample. In particular, the term may refer to a device capable of recording signal intensity with respect to a corresponding wavelength of the spectrum or a division thereof, e.g., a wavelength interval, and the signal intensity may preferably be provided as an electrical signal that can be used for further evaluation. Optical elements, in particular optical elements comprising at least one wavelength-selective element such as an optical filter and / or a dispersive element, can be used to separate the incident light into a spectrum of constituent wavelength components whose respective intensities are determined by using a detector. Furthermore, optical elements designed to receive the incident light and transmit the incident light to the optical element can be used. The spectrometer device may generally be operable in a reflection mode and / or in a transmission mode. For possible embodiments of the spectrometer device, please refer to the description of the spectrometer device outlined in more detail below.

[0029] The term "calibration" as used herein (the process or the result of the process is also referred to as "calibration") is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, without limitation, at least one process of determining, correcting, and adjusting the measurement inaccuracies in a spectrometer device. Thus, the result of the calibration process, often also referred to as an "item of calibration information", may be or include at least one item of information regarding the result of the calibration process, such as, for example, a calibration function, a calibration coefficient, a calibration matrix, etc., for converting one or more measured values ​​into one or more calibration values ​​or "true" values. The measurement inaccuracies may result, by way of example, from uncertainties in the wavelength determination and / or from inherent and / or extraneous interferences with the measurement signal of the spectrometer device. Thus, as outlined in more detail below, the calibration of the spectrometer device may include at least one of a wavelength calibration, a stray light calibration, a dark current calibration, a spectral bandwidth calibration, an intensity distribution calibration, and a signal linearity calibration. Calibration, in particular each calibration, may comprise at least one two-step process, where in a first step information about deviations of a measurement signal of the spectrometer device from a known standard is determined and in a second step this information is used to correct and / or adjust the measurement signal of the spectrometer device in order to reduce, minimize and / or eliminate the deviation. Thus, a calibration may comprise, for example, applying an item of calibration information to the measurement signal and / or the measurement spectrum of the spectrometer device. Calibration of a spectrometer device may improve and / or maintain the accuracy of measurements performed with the calibrated spectrometer device.

[0030] The method includes, by way of example, the following steps, which may be performed in a given order. However, it should be noted that different orders are possible. Furthermore, it is also possible to perform one or more of the method steps once or repeatedly. Furthermore, it is also possible to perform two or more method steps simultaneously or with overlapping times. The method may include further method steps not listed.

[0031] The method comprises the steps of: a) illuminating at least one detector device of a spectrometer device with at least one broadband light source through at least one narrow band pass filter, in particular through a plurality of narrow band pass filters having a plurality of predetermined transmission bands; b) generating a plurality of detector signals in response to the illumination of step a) by using a detector arrangement comprising at least one optical element configured to separate the incident light into a spectrum of constituent wavelength components and further comprising a plurality of photosensitive elements, each photosensitive element configured to receive at least one portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least one portion of the respective constituent wavelength components; c) determining at least one item of wavelength calibration information, the item of wavelength calibration information including at least one assignment of wavelengths of incident light, in particular wavelength bands, to corresponding photosensitive elements responsive to these wavelengths, in particular assigning at least one of the photosensitive elements to each of the predefined transmission bands, and more in particular assigning one or more pixel positions and / or identification numbers of the photosensitive elements to each predefined transmission band, in particular to each of the predefined transmission bands; d) determining at least one item of stray light calibration information based on the plurality of detector signals, said item of stray light calibration information comprising at least one signal distribution function, in particular at least one signal distribution matrix, said signal distribution function describing the distribution of responses of said photosensitive elements to incident light having a particular wavelength; Includes.

[0032] The term "broadband light source" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. The term may specifically refer to a device that emits light in a broad spectral range, such as light having a spectral width of at least 5 nm, specifically at least 10 nm, for example 10 nm to 2000 nm, without being limited thereto. For example, the broadband light source may comprise at least one incandescent lamp having a spectral radiance corresponding to blackbody radiation at a temperature in the range of 2000 K to 3000 K, specifically at a temperature of 2700 K. However, other examples of broadband light sources are possible, as outlined in more detail below. The broad spectral range of the broadband light source may at least partially cover the spectral range of the spectrometer device, specifically the complete spectral range of the spectrometer device. For example, the broadband light source may emit light in a broad spectral range of 400 nm to 3000 nm. As used herein, the term "light" generally refers to a section of electromagnetic radiation, usually referred to as the "optical spectrum range", including one or more of the visible spectrum range, the ultraviolet spectrum range, and the infrared spectrum range. The term "ultraviolet spectrum" or "UV" generally refers to electromagnetic radiation having wavelengths between 1 nm and 380 nm, preferably between 100 nm and 380 nm. The term "visible" generally refers to wavelengths between 380 nm and 760 nm. The term "infrared" or "IR" generally refers to wavelengths between 760 nm and 1000 μm, with wavelengths between 760 nm and 3 μm usually referred to as "near infrared" or "NIR", wavelengths between 3 μm and 15 μm usually referred to as "mid infrared" or "MidIR", and wavelengths between 15 μm and 1000 μm usually referred to as "far infrared" or "FIR". The broad spectral range of the broadband light source may include at least one of the visible spectrum range, the ultraviolet spectrum range, and the infrared spectrum range. Light used for typical purposes of the present invention can include, inter alia, light having a wavelength in at least one of the IR spectral range, specifically the NIR or MidIR spectral range, more specifically between 1 μm and 5 μm, and even more specifically between 1 μm and 3 μm.

[0033] The term "bandpass filter" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. The term may specifically refer to, but is not limited to, an optical element configured to transmit incident light having wavelengths within at least one particular spectral range, also referred to as a "transmission band", and to reflect, absorb and / or attenuate incident light having wavelengths outside at least one particular spectral range, such as wavelengths above an upper threshold of the particular spectral range and / or wavelengths below a lower threshold of the particular spectral range. The term "predetermined" as used in the context of "predetermined transmission band" may refer to a situation in which the spectral range of the transmission band is known when a narrow bandpass filter is used to perform step a). In particular, the spectral range of the transmission band of the narrow bandpass filter may be known, for example, by using a standard with known transmission characteristics from a data sheet of the narrow bandpass filter and / or by prior determination of the spectral range, for example, by using a calibrated spectrometer device.

[0034] The width of the spectral range of the bandpass filter, i.e. the spectral bandwidth of the transmission band, may be lower than the spectral resolution of the spectrometer device, and thus the bandpass filter is a "narrow bandpass filter". The method according to the invention can use one narrow bandpass filter with multiple transmission bands, or alternatively multiple narrow bandpass filters, each with a transmission band, specifically different from the transmission bands of the other narrow bandpass filters.

[0035] As outlined above, the method includes illuminating a detector device with a broadband light source through a narrow band pass filter, specifically through a plurality of narrow band pass filters. The term "illuminating" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, but is not limited to, the act of actively or passively directing light emitted from a broadband light source to a detector device. In particular, illuminating a detector device through a narrow band pass filter, specifically through a plurality of narrow band pass filters, may refer to a situation in which light emitted from a broadband light source is at least partially transmitted through a narrow band pass filter, specifically through a plurality of narrow band pass filters, before the detector device is illuminated.

[0036] The term "detector device" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, without limitation, any device or combination of devices capable of recording and / or monitoring incident light. The detector device may be configured to respond to incident illumination and generate an electrical signal indicative of the intensity of the illumination. The detector device may have sensitivity in one or more of the visible, ultraviolet, or infrared spectral ranges, specifically the near-infrared spectral range (NIR). The detector device may specifically be or comprise at least one optical sensor, such as an optical semiconductor sensor. As an example, specifically when the detector device has sensitivity in the infrared spectral range, such as the near-infrared spectral range, the semiconductor sensor may be or comprise at least one semiconductor sensor comprising at least one material selected from the group consisting of PbS, PbSe, InGaAs, and extended InGaAs. As an example, the detector device may comprise at least one optical detector, such as at least one CCD or CMOS device. The detector device may specifically comprise at least one detector array comprising a plurality of pixelated sensors, each of which is configured to detect at least a portion of at least one of the constituent wavelength components. The detector device comprises at least one optical element and a plurality of photosensitive elements.

[0037] The term "optical element" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to any element or combination of elements suitable for one or more of transmitting, reflecting, deflecting, or scattering light in a wavelength-dependent manner, without limitation. The optical element may further be specifically configured to separate incident light into a spectrum of constituent wavelength components and then transmit the spectrum to a plurality of photosensitive wavelength elements. Specifically, the wavelength-dependent transmission, reflection, deflection, or scattering of incident light in the optical element results in a spatial separation of the constituent wavelength components of the spectrum, which may then be transmitted directly or indirectly onto a plurality of photosensitive elements.

[0038] As mentioned above, the optical element is configured to separate the incident light into a spectrum of constituent wavelength components. The term "spectrum" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to at least one partition of an optical spectrum range, particularly an IR spectrum range, particularly an NIR spectrum range or a MidIR spectrum range, interrogated by a spectrometer device, without being limited thereto. Each part of the spectrum may be constituted by an optical signal defined by a signal wavelength and a corresponding signal intensity. Thus, the term "constituent wavelength components" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to an optical signal forming a part of a spectrum, without being limited thereto. In particular, the optical signal may include a signal intensity corresponding to each wavelength or wavelength interval.

[0039] The term "photosensitive element" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically, but without limitation, refer to individual light sensors included by the detection device, each light sensor having at least one light-sensitive area configured to record the optical response of the light-sensitive element by generating at least one output signal that depends on the intensity of a portion of the constituent wavelength components incident on the particular light-sensitive area. The at least one light-sensitive area addressed by each individual light sensor may be a single homogeneous area specifically designated to receive the incident light incident on the light-sensitive area. The at least one output signal may specifically be used as a detector signal and preferably be provided to an external evaluation unit for further evaluation.

[0040] Therefore, the term "detector signal" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer, without limitation, to a signal generated by at least one detector, specifically at least one output signal of a photosensitive element. The at least one output signal may be selected from at least one of an electronic signal and an optical signal. The at least one output signal may be an analog signal and / or a digital signal. The output signals of adjacent photosensitive elements may be generated simultaneously or successively in time. As an example, during a row or line scan, it may be possible to generate a series of output signals corresponding to a series of photosensitive elements that may be arranged in a row. Furthermore, each individual photosensitive element may be an active pixel sensor, preferably adapted to amplify the output signal before supplying it as a detection signal to an external evaluation unit. For this purpose, the photosensitive element may be equipped with one or more signal processing devices, such as one or more filters and / or analog-to-digital converters for processing and / or pre-processing the electronic signal.

[0041] As outlined above, the method includes determining at least one item of wavelength calibration information. The term "item of wavelength calibration information" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. The term may specifically refer to at least one item of information generated by at least one process of determining, correcting and adjusting wavelength inaccuracies in a spectrometer device, without being limited thereto. The at least one item of information may specifically be or include at least one of a calibration function, a calibration coefficient and a calibration matrix. The item of wavelength calibration information includes at least one assignment of wavelengths of incident light, specifically wavelength bands, to corresponding photosensitive elements responsive to these wavelengths. The term "wavelength band" as used herein may refer to a wavelength interval assigned to a photosensitive element. In particular, by determining an item of wavelength calibration information, it may be possible to assign a wavelength and / or a wavelength interval to at least one of the photosensitive elements, in particular to each of the photosensitive elements, illuminated by the constituent wavelength components of the spectrum separated by the optical element and transmitted to the respective photosensitive element. The item of wavelength calibration information, in particular the assignment, can be determined by mapping at least one of the photosensitive elements to a predetermined transmission band of a narrow band pass filter, in particular a plurality of narrow band pass filters.

[0042] An item of wavelength calibration information may specifically include at least one assignment that assigns at least one of the photosensitive elements to each of the predefined transmission bands, specifically at least one assignment that assigns one or more pixel positions and / or identification numbers of the photosensitive elements to each predefined transmission band, specifically for each of the predefined transmission bands. The term "pixel position" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, without limitation, any item of position information of a photosensitive element in a detection device. The pixel information may specifically describe the position of a photosensitive element in a detection device in one, two, or even three dimensions by using one or more of absolute position information and relative position information. The term "identification number" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may in particular, but without being limited to, refer to a numerical or alphanumeric item of information that uniquely identifies each light-sensitive element contained by the detector device. For example, the light-sensitive elements of a detector device may be numbered with respect to their order of occurrence in the detector device. However, other options for identifying the light-sensitive elements of a detector device are possible.

[0043] The term "assignment" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to, but is not limited to, an item of information that associates a first item of information with a second item of information, for example, by using a mathematical relationship such as a continuous function and / or a discrete function. As a result, the process of "assigning" may refer to a process of associating a first item of information with a second item of information. In particular, the assignment may associate a photosensitive element, in particular one or more pixel locations and / or identification numbers of the photosensitive element, with wavelengths and / or wavelength bands that illuminate the photosensitive element.

[0044] As further outlined above, the method includes determining at least one item of stray light calibration information. The term "item of stray light calibration information" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. The term may specifically refer to at least one item of information generated by at least one process of determining, correcting and adjusting stray light inaccuracies in a spectrometer device, without being limited thereto. The at least one item of information may specifically be or include at least one of a calibration function, a calibration coefficient and a calibration matrix. Stray light may arise in the spectrometer device due to diffuse scattering at surfaces, diffraction, e.g., at optical elements, and / or other undesirable effects. The item of stray light calibration information may include a signal distribution of stray light on the detector device, specifically on a plurality of light sensitive elements. Furthermore, the item of stray light calibration information may include the determined signal distribution in a format such that the measurement signal, in particular the measurement signal of the sample being analyzed, may be corrected and / or adjusted to minimize and / or eliminate the adverse effects of stray light on the measurement signal.

[0045] At least one item of stray light calibration information includes at least one signal distribution function, specifically at least one signal distribution matrix, which describes the distribution of the response of the photosensitive elements to incident light having a particular wavelength. The term "signal distribution function" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term may specifically refer to a mathematical function, such as a continuous function and / or a discrete function, which describes the distribution of stray light on the detector device, specifically the signal distribution of the stray light, specifically without limitation. Specifically, the signal distribution function may include a signal distribution on a plurality of photosensitive elements for one of the constituent wavelength components of the spectrum. An item of stray light calibration information may include at least one signal distribution function for each of the constituent wavelength components of the spectrum. The signal distribution functions, including multiple signal distribution functions, specifically one signal distribution function for each of the constituent wavelength components, may be recorded in a signal distribution matrix.

[0046] Thus, the term "signal distribution matrix" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. This term specifically includes, but is not limited to, the matrix elements a i,j (i=1,...,n,representing the ith photosensitive element and j=1,...,n,representing the jth constituent wavelength component of the spectrum), where matrix element a i,j describes the signal intensity of the jth constituent wavelength component at the ith photosensitive element. As an example, the calculation and / or application of the signal distribution matrix is ​​described in more detail in Y. Zong, SW Brown, BC Johnson, KR Lykke and Y. Ohno: "Simple spectral stray light correction method for array spectroradiometers", Applied Optics, Vol. 45, No. 6, 2006.

[0047] The broadband light source may comprise at least one of the following: an incandescent lamp; a black body radiator; an electric filament; a light emitting diode (LED); a superluminescent diode (SLD); a microelectromechanical system (MEMS) black body radiator. Alternatively or additionally, the broadband light source may comprise a combination of two or more of the aforementioned light emitting devices, and / or a combination of at least one of the aforementioned light emitting devices with at least one other light emitting device, for example, a combination of two or more LEDs each having a different wavelength, and / or a combination of at least one incandescent lamp and at least one LED. The broadband light source may be an internal light source provided by the spectrometer device, or it may be an external light source.

[0048] The spectral bandwidth of the transmission band of the narrow bandpass filter may be lower than the spectral resolution of the spectrometer device, in particular the detector device. For example, the spectral bandwidth of the transmission band of the narrow bandpass filter may not exceed 10 nm, in particular 5 nm, more particularly 1 nm. The spectral resolution of the spectrometer device, in particular the detector device, may be lower than 100 nm, in particular lower than 10 nm, more particularly lower than 5 nm.

[0049] In the method, the multiple detector signals can correspond to the spectrum of the narrow band pass filter, specifically the multiple narrow band pass filters, the spectrum including the wavelength position of the predetermined transmission band. The term "corresponding" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to a special or customized meaning. The term can specifically refer to partial and / or complete equivalence of two or more objects, information items, properties, etc., without being limited thereto. Specifically, the multiple detector signals can be at least partially equivalent to the spectrum of the at least one narrow band pass filter in at least a portion of a particular spectral range, such as, for example, one or more of the visible spectral range, the ultraviolet spectral range, and / or the infrared spectral range. Alternatively or additionally, the multiple detector signals can be completely equivalent to the spectrum of the at least one narrow band pass filter, for example, the multiple detector signals can cover the entire spectral range of the at least one narrow band pass filter in one or more of the visible spectral range, the ultraviolet spectral range, and the infrared spectral range.

[0050] The method, specifically step c), further comprises: c.1) determining at least one of pixel locations and identification numbers of the plurality of photosensitive elements producing intensity peaks in a plurality of detector signals; c.2) allocating at least one of the predetermined transmission bands of the narrow bandpass filter to a plurality of intensity peaks; c.3) determining a wavelength calibration function, the wavelength calibration function assigning at least one of pixel locations and identification numbers of the photosensitive elements to wavelength locations; It may include at least one of the following:

[0051] In particular, the wavelength calibration function may include a polynomial function of order N, where a plurality of at least N+1 intensity peaks may be used. The polynomial function may be

number

[0052] Furthermore, the method, specifically step d), may further comprise: d.1) processing the plurality of detector signals by applying at least one of offset correction and digital filtering, specifically noise filtering techniques, to the plurality of detector signals; d.2) interpolating the plurality of processed detector signals to obtain, for a plurality of constituent wavelength components, and in particular for each constituent wavelength component, an illumination intensity at each photosensitive element comprised by the detector arrangement; d.3) generating a plurality of signal distribution functions by using the interpolated detection signals, specifically the plurality of signal distribution functions recorded in a signal distribution matrix; It may include at least one of the following:

[0053] The method may further include applying at least one of the items of wavelength calibration information and the items of stray light calibration information to a measured spectrum determined by using the spectrometer device. The measured spectrum may refer to a spectrum of the analyte sample determined by using the spectrometer device. In particular, applying the items of stray light calibration information may include applying an inverse of a signal distribution matrix to the measured spectrum.

[0054] The method may further comprise, in particular prior to step a), determining a transmission band of the narrow band pass filter, in particular of a plurality of narrow band pass filters, by using a calibrated spectrometer device.

[0055] The method may further include determining a blueshift correction. The term "blueshift correction" as used herein is a broad term and should be given its ordinary and customary meaning to those skilled in the art and should not be limited to any special or customized meaning. The term may specifically refer, without limitation, to qualifying and / or quantifying an additional item of wavelength calibration information, specifically a blueshift in a spectrometer device. The blueshift may occur due to an effect in an optical element that, as an example, separates the incident light into a spectrum of constituent wavelength components differently depending on the angle of incidence of the incident light at the optical element. In particular, when a detector device separate from the spectrometer device is used in the method of calibrating the spectrometer device, the incident light used to calibrate the spectrometer device may have a different angle of incidence at the optical element compared to the incident light of the detector device incorporated in the spectrometer device. Thus, a blueshift may occur with the calibrated detector device incorporated in the spectrometer device. For the blueshift correction, multiple additional detector signals may be generated with the detector device incorporated in the spectrometer device. The blueshift correction may include at least one further item of wavelength calibration information determined by repeating step c) using a plurality of additional detector signals. The blueshift correction may include at least one item of correction information that compensates for the blueshift of the assembled detector arrangement, in particular by compensating for angular-dependent effects in the optical elements.

[0056] Additionally or alternatively, the method may include determining at least one temperature of the detector arrangement. The method may include determining at least one of the items of wavelength calibration information and the items of stray light calibration information for a number of different temperatures. Environmental operating conditions may require different temperatures of the detector arrangement. However, the items of wavelength calibration information and / or the items of stray light calibration information may be temperature dependent. Thus, by determining the items of wavelength calibration information and / or the items of stray light calibration information at a number of different temperatures, it may be possible to take into account these temperature effects.

[0057] In the method, the item of wavelength calibration information and the item of stray light calibration information can be determined using the same multiple detector signals. Thus, the method may include generating multiple detector signals once to determine two items of calibration information, in particular an item of wavelength calibration information and an item of stray light calibration information. In principle, no further measurements may be necessary to calibrate the spectrometer device.

[0058] The method can be performed at a user site and / or a manufacturer site. In particular, the method can be performed in-field, i.e. directly at a user site, and / or in-lab, i.e. at a manufacturer site.

[0059] The method can be performed using at least one of a detached detector device and an integrated detector device. For example, if the spectrometer device is operated in a transmission mode, the method can be performed with the detector device integrated into the spectrometer device. If the spectrometer device is operated in a reflection mode, the method can be performed with the detector device detached from the spectrometer device. However, alternatively or additionally, the detector device of a spectrometer device operated in a reflection mode can also be used integrated into the spectrometer device. Furthermore, the method can further include determining at least one correction factor by determining a plurality of detector signals of the reference sample using at least one detector device integrated into the spectrometer device. In particular, when performing the method using a detector device detached from the spectrometer device, the method can further include determining at least one correction factor using a detector device integrated into the spectrometer device. As an example, the correction factor can be determined by comparing a plurality of detector signals of the reference sample with a known detector signal of the reference sample.

[0060] The method can be specifically computer-implemented, specifically computer-assisted or computer-controlled. With reference to computer-implemented aspects of the invention, one or more of the method steps of the method according to one or more embodiments disclosed herein, or even all of the method steps, can be specifically performed or at least supported or controlled by using an evaluation unit of a system comprising at least one processor. Thus, in general, any method step involving the provision and / or manipulation of data can be performed by using an evaluation unit. In general, these method steps can include any method step, except for those that typically require manual work, such as certain aspects of providing a sample and / or performing the actual measurement. Thus, in particular, at least method steps c) and d) can be computer-implemented, and optionally steps a) and b) can be at least partially computer-controlled. Further aspects related to computer-implemented aspects of the invention are outlined in more detail below.

[0061] In a further aspect of the invention, a system for calibrating a spectrometer device is disclosed. The system comprises at least one broadband light source and at least one narrow bandpass filter, in particular a plurality of narrow bandpass filters having a plurality of predetermined transmission bands. The system further comprises at least one detector device of the spectrometer device, the detector device configured to determine a plurality of detector signals in response to illumination of the detector device, the detector device comprising at least one optical element configured to separate the incident light into a spectrum of constituent wavelength components, and further comprising a plurality of photosensitive elements. Each photosensitive element is configured to receive at least a portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least a portion of the respective constituent wavelength components. The system is configured for carrying out a method for calibrating a spectrometer device according to the invention, for example according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in more detail below.

[0062] For definitions and embodiments of the system, please refer to the definitions and embodiments mentioned in the method for calibrating a spectrometer device.

[0063] The optical element may comprise at least one wavelength-selective element, which may be selected from the group consisting of: a prism; a diffraction grating; a linear variable filter; an optical filter, in particular a narrow bandpass filter; and an interferometer.

[0064] The detection device may in particular comprise a plurality of photosensitive elements arranged in a linear array, the array of photosensitive elements may comprise a number of photosensitive elements between 10 and 1000, in particular a number of 100 and 500, in particular a number of 200 and 300, more particularly a number of 256. Each photosensitive element may in particular be selected, independently of one another, from the group consisting of: a pixelated inorganic camera element, in particular a pixelated inorganic camera chip, more particularly a CCD chip or a CMOS chip; a monochrome camera element, in particular a monochrome camera chip; at least one photoconductor, in particular an inorganic photoconductor, more particularly PbS, PbSe, Ge, InGaAs, extended InGaAs, InSb or HgCdTe.

[0065] Each photosensitive element may be sensitive to electromagnetic radiation in a wavelength range of 760 nm to 1000 μm, specifically in a wavelength range of 760 nm to 15 μm, more specifically in a wavelength range of 1 μm to 5 μm, and more specifically in a wavelength range of 1 μm to 3 μm.

[0066] The system may comprise at least one evaluation unit. The evaluation unit may in particular comprise one or more processors. The evaluation unit may be configured to execute the method for calibrating a spectrometer device according to the invention, such as according to any one of the embodiments disclosed above and / or any one of the embodiments disclosed in more detail below. The evaluation unit, in particular the processor, may refer to any logic circuit configured to perform the basic operations of a computer or system, and / or generally to a device configured to perform calculations or logical operations. In particular, the evaluation unit may be configured to process basic instructions that drive a computer or system. As an example, the evaluation unit may comprise at least one arithmetic logic unit (ALU), at least one floating point unit (FPU), such as a mathematical coprocessor or numeric coprocessor, a number of registers, in particular registers configured to supply operands to the ALU and to store the results of the operations, and memories, such as an L1 cache memory and an L2 cache memory. In particular, the evaluation unit may be a multi-core processor. In particular, the evaluation unit may be or comprise a central processing unit (CPU). Additionally or alternatively, the evaluation unit may be or comprise a microprocessor, and thus, in particular, the elements of the evaluation unit may be included in one single integrated circuit (IC) chip. Additionally or alternatively, the evaluation unit may be or comprise one or more chips, such as one or more application specific integrated circuits (ASICs) and / or one or more field programmable gate arrays (FPGAs) and / or one or more tensor processing units (TPUs) and / or dedicated machine learning optimization chips. The evaluation unit may be specifically configured, such as by software programming, to perform, control and / or support one or more, in particular all, of the method steps.

[0067] The system may comprise at least one spectrometer device, in particular a handheld spectrometer device, comprising at least one detector device. Thus, by way of example, the system may comprise a spectrometer device including a detector device integrated therein, and the method may be performed with the integrated spectrometer device. However, alternatively, the system may comprise only the detector device of the spectrometer device, and the method may be performed with the detector device removed.

[0068] The spectrometer device may specifically be a handheld spectrometer device. The term "handheld" used in the context of a spectrometer device may specifically refer, without limitation, to the property of a spectrometer device being mobile and / or movable by a human user, specifically the property of being portable by a human user, specifically the property of being portable by a human user in one hand. Specifically, a handheld spectrometer device may be dimensioned to be carried by a human user, for example by having an extension of any dimension not exceeding 500 mm, specifically any dimension not exceeding 300 mm. Additionally or alternatively, the handheld spectrometer device may have a mass not exceeding 5 kg, specifically a mass not exceeding 3 kg, or even a mass not exceeding 0.5 kg, in order to be carried by a human user.

[0069] As an example, the spectrometer device may specifically comprise at least one broadband light source. Alternatively or additionally, the broadband light source of the system may be an external broadband light source. As outlined above, the broadband light source may emit light in a broad spectral range, such as light having a spectral width of at least 5 nm, specifically at least 10 nm, for example a spectral width of 10 nm to 2000 nm. For example, the broadband light source may emit light in a broad spectral range of 400 nm to 3000 nm. For example, the broadband light source may comprise at least one of an incandescent lamp; a black body radiator; an electric filament; an LED; an SLD; a MEMS black body radiator.

[0070] The spectrometer device may comprise at least one housing having at least one optically transparent entrance window. The housing of the spectrometer device may refer to an element or combination of elements configured to fully or partially surround and / or provide a mechanical cover for one or more other elements of the spectrometer device. Thus, by way of example, the housing may be or include at least one rigid housing, such as at least one rigid housing made of at least one of a plastic material or a metal material. The entrance window may refer to an element, such as an optically transparent element made of one or more of glass, quartz, sapphire, or a plastic material, or an opening of the spectrometer device that allows light to enter the housing.

[0071] Furthermore, the spectrometer device may comprise at least one further optical element arranged between the entrance window and the detector device, in particular at least one optical element selected from the group consisting of: an optical lens; a mirror; a reflector; an aperture; a diffractive optical element; a dispersive element; a light modulator; a polarizing filter; a bandpass filter; and a liquid crystal display (LCD). The further optical element may in particular be configured to collect and / or transmit the light incident from the entrance window to the optical element.

[0072] In a further aspect of the present invention, a computer program is disclosed comprising instructions which, when the program is executed by an evaluation unit of the system, cause the system described herein, and in particular the evaluation unit of the system, to perform a method for calibrating a spectrometer device according to the present invention, such as according to any one of the embodiments disclosed above and / or any one of the embodiments disclosed in more detail below.

[0073] In a further aspect of the present invention, a computer readable storage medium is disclosed which comprises instructions which, when executed by an evaluation unit of a system as described herein, cause the system, and in particular the evaluation unit of the system, to perform a method for calibrating a spectrometer device according to the present invention, such as according to any one of the embodiments disclosed above and / or any one of the embodiments disclosed in more detail below.

[0074] As used herein, the term "computer-readable storage medium" may specifically refer to a non-transitory data storage means, such as a hardware storage medium having computer-executable instructions stored thereon. The computer-readable storage medium may specifically be or may comprise a storage medium, such as a random access memory (RAM) and / or a read-only memory (ROM).

[0075] The method and apparatus according to the invention may provide a number of advantages over known methods and apparatus. In particular, the method and apparatus according to the invention may include using a broadband light source, such as an incandescent light source, a light bulb, a black body radiator and / or a thin electric filament, for the purpose of calibrating the spectrometer device. These broadband light sources are generally readily available at low cost. The broadband light source may be part of the spectrometer device itself. Furthermore, the method and apparatus according to the invention may include using a set of narrow bandpass filters, which may be specifically configured to transmit light from the broadband light source only in a specific narrow spectral range, for the purpose of calibrating the spectrometer device. Each of the narrow bandpass filters may cover a different spectral range. The spectral range of each narrow bandpass filter may be predetermined, for example, based on spectral high-resolution data obtained using a calibrated standard spectrometer device. The multiple narrow bandpass filters may be combined with one or more neutral density filters to generate narrow wavelength bands of light from a broadband light source with known spectral irradiance. The detector device may then determine signals resulting from the multiple narrow bandpass filters. Subsequently, based on the predetermined transmission band of the narrow bandpass filter, the items of wavelength calibration information and the items of stray light calibration information of the spectrometer arrangement may be determined, in particular based on the same data, by means of a computer program.

[0076] Furthermore, the method for calibrating the spectrometer device may specifically include the use of a narrow bandpass filter for determining the item of wavelength calibration information and a calculation method for determining the item of stray light calibration information based on the same data. The calibration may be performed either in-lab at the manufacturer's site and / or in-field at the user's site. The system may specifically refer to a setup where both wavelength and stray light calibration measurements can be performed on the final spectrometer device, or alternatively a setup that allows calibration measurements on a detector device that is subsequently integrated into the spectrometer device. An additional method step may include determining and / or correcting a blue-shift correction that depends on the pixel position. In some cases, all calibrations can be performed at different temperatures of the detector device, since it may be necessary to change the temperature of the detector device depending on the environmental operating conditions of the spectrometer device. In this way, the items of wavelength calibration information and the items of stray light calibration information may depend on the temperature of the detector and can be taken into account when performing multiple calibrations at different temperatures.

[0077] In contrast to known methods and devices, the method and device according to the invention may allow to determine both items of calibration information, namely the item of wavelength calibration information and the item of stray light calibration information, from a single measurement cycle and by using robust and reliable components. The calibration of the spectrometer device may require only two components: a broadband light source and a narrow bandpass filter, in particular a number of narrow bandpass filters having a number of predefined transmission bands. The method of calibrating the spectrometer device may allow a simple and reliable factory calibration as well as a simple and reliable field calibration. Thus, the user of the spectrometer device may calibrate or recalibrate the spectrometer device without going through the manufacturer.

[0078] In particular, in contrast to known methods, the method according to the invention does not require atomic gauge standards, such as an argon pen light lamp, nor narrow band light sources, such as monochromators or lasers. Thus, the method for calibrating a spectrometer device can be applied using easily accessible components, allowing calibration to be performed at low cost and with low effort. Furthermore, the spectrometer device can be calibrated or recalibrated in situ, which is particularly important for mass applications of spectroscopy. Furthermore, the stray light calibration step can improve known methods of calibrating stray light effects by using noise filtering techniques.

[0079] The spectrometer device may be operated in a transmission mode, specifically using a light source to illuminate the sample interface and at least one further optical element to obtain a relative transmission signal from the sample. In this configuration, the system including the spectrometer may be operated in a transmission mode and at least one narrow bandpass filter may displace the sample to obtain multiple detector signals for performing the calibration. Multiple detector signals for determining the wavelength calibration information item and the stray light calibration information item may be collected at one time. In this simple configuration, the method for calibrating the spectrometer device may be used without further post-processing or additional information.

[0080] Alternatively, the spectrometer device may be operated in reflection mode. To perform the method for calibrating the spectrometer device, the spectrometer device does not have to be finally assembled. The system for calibrating the spectrometer device may only comprise a detector device of the spectrometer device. The method may include a reference measurement of a reference sample of the spectrometer device operating in reflection mode to determine the raw signal distribution on the detector device. To perform the method, the system may include modified further optical elements. The configuration of the system does not change compared to the optical path of the spectrometer device, but at least one narrow band pass filter may be inserted in the optical path. The at least one narrow band pass filter may be automatically changed in the system of interchangeable slots. Alternatively or additionally, another transmission reference sample may be inserted in the interchangeable slot. By not inserting a sample or a filter in the interchangeable slot, measurements using the original spectrometer device configuration are also possible.

[0081] Alternatively or additionally, the system may operate the spectrometer device in reflection mode and include an assembled detector device. In this example, the broadband light source of the spectrometer device may not be used. The broadband light source may be switched off at all times and a method of calibrating the spectrometer device using an external broadband light source may be performed. The light from this broadband light source may be filtered with at least one narrow bandpass filter necessary to determine the items of wavelength calibration information and the items of stray light calibration information. It may be configured to measure other reference samples, etc.

[0082] In summary, without excluding further possible embodiments, the following embodiments can be envisaged: Embodiment 1: A method for calibrating a spectrometer device, the method comprising the steps of: a) illuminating at least one detector device of said spectrometer device with at least one broadband light source through at least one narrow band pass filter, in particular through a plurality of narrow band pass filters having a plurality of predetermined transmission bands; b) generating a plurality of detector signals in response to the illumination of step a) by using said detector arrangement, said detector arrangement comprising at least one optical element configured to separate incident light into a spectrum of constituent wavelength components and further comprising a plurality of photosensitive elements, each photosensitive element configured to receive at least one portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least one portion of the respective constituent wavelength components; c) determining at least one item of wavelength calibration information, said item of wavelength calibration information including at least one assignment of wavelengths, in particular wavelength bands, of incident light to corresponding photosensitive elements responsive to these wavelengths, in particular assigning at least one of said photosensitive elements to each of the predefined transmission bands, and more in particular assigning one or more pixel positions and / or identification numbers of said photosensitive elements to each of the predefined transmission bands, in particular to each of the predefined transmission bands; d) determining at least one item of stray light calibration information based on the plurality of detector signals, said item of stray light calibration information comprising at least one signal distribution function, in particular at least one signal distribution matrix, said signal distribution function describing the distribution of responses of said photosensitive elements to incident light having a particular wavelength; A method comprising:

[0083] Embodiment 2: The method of the preceding embodiment, wherein the broadband light source comprises at least one of an incandescent lamp; a blackbody radiator; an electric filament; an LED; an SLD; a MEMS blackbody radiator.

[0084]

[0023] Embodiment 3: The method of any one of the preceding embodiments, wherein the spectral bandwidth of the transmission band of the narrow bandpass filter is lower than the spectral resolution of the spectrometer device.

[0085] Embodiment 4: The method of any one of the preceding embodiments, wherein the plurality of detector signals correspond to the narrow bandpass filters, in particular to the spectra of the plurality of narrow bandpass filters, the spectra including the wavelength positions of the predetermined transmission bands.

[0086] Embodiment 5: Step c) comprises: c.1) determining at least one of pixel locations and identification numbers of the plurality of photosensitive elements producing intensity peaks in the plurality of detector signals; c.2) allocating at least one of the predetermined transmission bands of the narrow bandpass filter to a plurality of intensity peaks; c.3) determining a wavelength calibration function, the wavelength calibration function assigning at least one of the pixel locations and the identification numbers of the photosensitive elements to wavelength locations; 13. The method of any one of the preceding embodiments, comprising at least one of:

[0087] Embodiment 6: The method of the preceding embodiment, wherein the wavelength calibration function comprises a polynomial function of degree N and a plurality of at least N+1 intensity peaks are used.

[0088] Embodiment 7: Step d) comprises: d.1) processing the plurality of detector signals by applying at least one of offset correction and digital filtering, in particular noise filtering techniques, to the plurality of detector signals; d.2) interpolating the plurality of processed detector signals to obtain, for a plurality of constituent wavelength components, and in particular for each constituent wavelength component, an illumination intensity at each photosensitive element comprised by said detector arrangement; d.3) generating a plurality of signal distribution functions by using the interpolated detection signals, specifically recorded in a signal distribution matrix; 13. The method of any one of the preceding embodiments, comprising at least one of:

[0089] Embodiment 8: A method as described in any one of the preceding embodiments, wherein the method further comprises applying at least one of the items of wavelength calibration information and the items of stray light calibration information to a measured spectrum determined by using the spectrometer device.

[0090] Embodiment 9: The method of any preceding embodiment, wherein applying the item of stray light calibration information comprises applying an inverse of the signal distribution matrix to the measured spectrum.

[0091] Embodiment 10: The method according to any one of the preceding embodiments, wherein the method further comprises, in particular prior to step a), determining the transmission bands of the narrow bandpass filter, in particular the plurality of narrow bandpass filters, by using a calibrated spectrometer device.

[0092] Embodiment 11: The method of any one of the preceding embodiments, wherein the method further comprises determining a blueshift correction, for which a plurality of additional detector signals are generated with the detector device incorporated in the spectrometer device.

[0093] Embodiment 12: The method of the preceding embodiment, wherein the blue-shift correction includes at least one further item of wavelength calibration information determined by repeating step c) using the plurality of additional detector signals.

[0094] Embodiment 13: The method of any one of the preceding embodiments, wherein the method includes determining a temperature of at least one of the detection devices.

[0095] Embodiment 14: The method of any preceding embodiment, wherein the method includes determining at least one of the items of wavelength calibration information and the items of stray light calibration information for a plurality of different temperatures.

[0096] Embodiment 15: A method according to any one of the preceding embodiments, wherein the item of wavelength calibration information and the item of stray light calibration information are determined using the same plurality of detector signals.

[0097]

[0023] Embodiment 16: The method of any one of the preceding embodiments, wherein the method is performed at least one of a user site and a manufacturer site.

[0098] Embodiment 17: The method of any one of the preceding embodiments, wherein the method is performed using at least one of a detached detector device and an installed detector device.

[0099] Embodiment 18: The method of any one of the preceding embodiments, wherein the method further comprises determining at least one correction factor by determining a plurality of detector signals of a reference sample using the at least one detector device incorporated in the spectrometer device.

[0100] Embodiment 19: The system of any one of the preceding embodiments, wherein the method is computer-implemented.

[0101] Embodiment 20: A system for calibrating a spectrometer device, comprising at least one broadband light source and at least one narrow bandpass filter, in particular a plurality of narrow bandpass filters having a plurality of predetermined transmission bands, the system further comprising at least one detector device of the spectrometer device, the detector device configured to determine a plurality of detector signals in response to illumination of the detector device, the detector device comprising at least one optical element configured to separate incident light into a spectrum of constituent wavelength components, and further comprising a plurality of photosensitive elements, each photosensitive element configured to receive at least a portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least a portion of the respective constituent wavelength components, the system being configured for performing a method for calibrating a spectrometer device according to any one of the preceding embodiments referring to a method for calibrating a spectrometer device.

[0102] Embodiment 21: The system of the preceding embodiment, wherein the optical element comprises at least one wavelength-selective element.

[0103] Embodiment 22: The system according to the preceding embodiment, wherein the wavelength-selective element is selected from the group consisting of: a prism; a diffraction grating; a linear variable filter; an optical filter, in particular a narrow bandpass filter; and an interferometer.

[0104] Embodiment 23: A system according to any one of the preceding three embodiments, wherein the detection device comprises the plurality of photosensitive elements arranged in a linear array, the array of photosensitive elements comprising a number of 10-1000, in particular a number of 100-500, in particular a number of 200-300, more particularly a number of 256 photosensitive elements.

[0105] Embodiment 24: A system described in any one of the preceding four embodiments, wherein each photosensitive element is selected from the group consisting of: a pixelated inorganic camera element, in particular a pixelated inorganic camera chip, more in particular a CCD chip or a CMOS chip; a monochrome camera element, in particular a monochrome camera chip; at least one photoconductor, in particular an inorganic photoconductor, more in particular PbS, PbSe, Ge, InGaAs, extended InGaAs, InSb or HgCdTe.

[0106] Embodiment 25: A system according to any one of the preceding five embodiments, wherein each photosensitive element is sensitive to electromagnetic radiation in the wavelength range of 760 nm to 1000 μm, specifically in the wavelength range of 760 nm to 15 μm, more specifically in the wavelength range of 1 μm to 5 μm, and even more specifically in the wavelength range of 1 μm to 3 μm.

[0107] Embodiment 26: A system described in any one of the preceding six embodiments, wherein the system comprises at least one evaluation unit, the evaluation unit comprising one or more processors, and the evaluation unit is configured to perform a method for calibrating a spectrometer device according to any one of the preceding embodiments referring to a method for calibrating a spectrometer device.

[0108] Embodiment 27: A system according to any one of the preceding seven embodiments, wherein the system comprises at least one spectrometer device, in particular a handheld spectrometer device, comprising at least one detector device.

[0109] Embodiment 28: The system of the preceding embodiment, wherein the spectrometer device comprises at least one broadband light source.

[0110] Embodiment 29: A system according to any one of the preceding two embodiments, wherein the spectrometer device comprises at least one housing having at least one optically transparent entrance window.

[0111] Embodiment 30: The system described in the preceding embodiment, wherein the spectrometer device comprises at least one further optical element arranged between the entrance window and the detector device, in particular at least one optical element selected from the group consisting of an optical lens; a mirror; a reflector; an aperture; a diffractive optical element; a dispersive element; an optical modulator; a polarizing filter; a bandpass filter; and a liquid crystal display (LCD).

[0112] Embodiment 31: A computer program comprising instructions which, when executed by an evaluation unit of a system according to any one of the preceding embodiments referring to the system, cause the system, and in particular the evaluation unit of the system, to perform a method for calibrating a spectrometer device according to any one of the preceding embodiments referring to the method for calibrating a spectrometer device.

[0113] Embodiment 32: A computer-readable storage medium comprising instructions that, when executed by an evaluation unit of a system described in any one of the preceding embodiments referring to the system, cause the system, and in particular the evaluation unit of the system, to perform a method for calibrating a spectrometer device according to any one of the preceding embodiments referring to a method for calibrating a spectrometer device. [Brief description of the drawings]

[0114] Further optional features and embodiments are disclosed in more detail in the following description of the embodiments, preferably in conjunction with the dependent claims. Here, as a person skilled in the art will understand, each optional feature can be realized in an independent manner or in any feasible combination. The scope of the present invention is not limited by the preferred embodiments. The embodiments are illustrated diagrammatically in the figures, in which identical reference numbers refer to identical or functionally equivalent elements. [Figure 1] FIG. 1 shows in a schematic diagram an embodiment of a system for calibrating a spectrometer device. [Diagram 2] FIG. 1 shows in a schematic diagram an embodiment of a system for calibrating a spectrometer device. [Diagram 3] FIG. 1 shows in a schematic diagram an embodiment of a system for calibrating a spectrometer device. [Figure 4] FIG. 1 shows a flow chart of an embodiment of a method for calibrating a spectrometer device. [Diagram 5] FIG. 1 shows a flow chart of an embodiment of a method for calibrating a spectrometer device. [Figure 6] 6A to 6D are diagrams for stray light calibration. [Figure 7] FIG. 3 shows a flow chart of an embodiment of a method for calibrating a spectrometer device by using the system according to FIG. 2. [Figure 8] FIG. 4 shows a flow chart of an embodiment of a method for calibrating a spectrometer device by using the system according to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0115] Detailed Description of the Embodiments 1 to 3 show in schematic form an exemplary embodiment of a system 110 for calibrating a spectrometer device 112. In the following, the system 110 is described in combination with the broadband light source 114, at least one narrow bandpass filter 116, in particular a number of narrow bandpass filters 116 having a number of predetermined transmission bands, and at least one detector device 118 of the spectrometer device 112.

[0116] The system 110 may, by way of example, comprise a spectrometer device 112. The exemplary embodiment of the system 110 shown in Figure 1 may comprise a spectrometer device 112 that comprises a detector device 118 and operates in a transmission mode. The exemplary embodiment of the system 110 shown in Figure 3 may comprise a spectrometer device 112 that comprises a detector device 118 and operates in a reflection mode. However, alternatively, the exemplary embodiment of the system 110 shown in Figure 2 may comprise only the detector device 118 detached from the spectrometer device 112.

[0117] The detector arrangement 118 is configured to determine a plurality of detector signals in response to illumination of the detector arrangement 118. The detector arrangement 118 comprises at least one optical element 120 configured to separate the incident light into a spectrum of constituent wavelength components, and further comprises a plurality of photosensitive elements 122. Each photosensitive element (not shown) is configured to receive at least a portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least a portion of the respective constituent wavelength components.

[0118] The optical element 120 may comprise at least one wavelength-selective element 124. The wavelength-selective element 124 may be selected from the group consisting of: a prism; a diffraction grating; a linear variable filter; an optical filter, in particular a narrow bandpass filter; and an interferometer.

[0119] As shown in Figures 1 and 3, the spectrometer device 112 can include at least one housing 126 having at least one optically transparent entrance window 128. The housing 126 of the spectrometer device 112 can refer to an element or combination of elements configured to fully or partially surround and / or provide a mechanical cover for one or more other elements of the spectrometer device 112. Thus, by way of example, the housing 126 can be or include at least one rigid housing, such as at least one rigid housing made of at least one of a plastic material or a metal material. The entrance window 128 can refer to an element, such as an optically transparent element made of one or more of a glass, quartz, sapphire, or plastic material, or an opening in the spectrometer device 112 that allows light to enter the housing 126.

[0120] Furthermore, the spectrometer arrangement 112 may comprise at least one further optical element 130 arranged between the entrance window 128 and the detector arrangement 118, in particular at least one optical element selected from the group consisting of: an optical lens; a mirror; a reflector; an aperture; a diffractive optical element; a dispersive element; a light modulator; a polarizing filter; a bandpass filter; and a liquid crystal display (LCD). The further optical element 130 may be configured in particular to focus and / or transmit the incident light from the entrance window 128 to the optical element 120.

[0121] The broadband light source 114 may be included in the spectrometer arrangement 112 or, alternatively or additionally, may be an external broadband light source. The broadband light source 114 may comprise at least one of an incandescent lamp; a black body radiator; an electric filament; an LED; an SLD; a MEMS black body radiator. As shown in Figures 1-3, the broadband light source 114 may be disposed in the system 110 to illuminate the detector arrangement 118 through a narrow band pass filter 116, in particular through a plurality of narrow band pass filters 116.

[0122] As can be seen from the exemplary embodiments of Figures 2 and 3, the spectrometer device 112 and / or system 110 including the broadband light source 114 may further include at least one electronic driving device 132 for driving the broadband light source 114 and at least one further optical element 130 for collecting and / or transmitting light from the broadband light source 114 to a sample interface 134 of the reference sample 136.

[0123] If the system 110 comprises a spectrometer device 112 as shown in Figures 1 and 3, the at least one narrow band pass filter 116, in particular the plurality of narrow band pass filters 116, may be arranged between the broadband light source 114 and the spectrometer device 112, in particular the entrance window 128. In this example, the at least one narrow band pass filter 116, in particular the plurality of narrow band pass filters 116, may be replaced by an analyzed sample 138. Alternatively, however, if the system 110 comprises only a removed detector device 118 as shown in Figure 2, the at least one narrow band pass filter 116, in particular the plurality of narrow band pass filters 116, may be replaced by a further optical element 130, in particular in a slot 140 for inserting an exchangeable sample such as a reference sample, no sample, and / or the at least one narrow band pass filter 116.

[0124] The system 110 is configured to perform a method for calibrating the spectrometer device 112 according to the present invention, such as according to any one of the embodiments described in Figures 4, 5, 7 and 8, and / or according to other embodiments disclosed herein. In particular, the system 110 may comprise at least one evaluation unit 142. The evaluation unit 142 may in particular comprise one or more processors 144. The evaluation unit 142 is configured to perform a method for calibrating the spectrometer device 112 according to the present invention, such as according to any one of the embodiments described in Figures 4, 5, 7 and 8, and / or according to other embodiments disclosed herein. The evaluation unit 142 may further be configured to transmit data, such as optical data, e.g. measured optical data, to the computing device 146 via a wired interface and / or a wireless interface.

[0125] 4 shows a flow chart of a first exemplary embodiment of a method for calibrating a spectrometer device 112. The method includes the following steps, which may be performed in a given order, by way of example. It should be noted, however, that a different order is also possible. Furthermore, it is also possible to perform one or more method steps once or repeatedly. Furthermore, it is also possible to perform two or more method steps simultaneously or with suitable overlap. The method may include further method steps not listed.

[0126] The method comprises the steps of: a) illuminating at least one detector device 118 of a spectrometer device 112 (denoted by reference numeral 148) with at least one broadband light source 114 through at least one narrow bandpass filter 116, in particular through a plurality of narrow bandpass filters 116 having a plurality of predetermined transmission bands; b) generating a plurality of detector signals in response to the illumination of step a) by using a detector arrangement 118 (denoted by reference numeral 150), the detector arrangement 118 comprising at least one optical element 120 configured to separate the incident light into a spectrum of constituent wavelength components and further comprising a plurality of photosensitive elements 122, each photosensitive element configured to receive at least one portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least one portion of the respective constituent wavelength components; c) determining at least one item of wavelength calibration information (indicated by reference numeral 152), the item of wavelength calibration information including at least one assignment of wavelengths of incident light, in particular wavelength bands, to corresponding photosensitive elements responsive to these wavelengths, in particular assigning at least one of the photosensitive elements to each of the predefined transmission bands, and more in particular assigning one or more pixel positions and / or identification numbers of the photosensitive elements to each predefined transmission band, in particular to each of the predefined transmission bands; d) determining at least one item of stray light calibration information based on the plurality of detector signals (indicated by reference numeral 154), said item of stray light calibration information comprising at least one signal distribution function, in particular at least one signal distribution matrix, said signal distribution function describing the distribution of the response of said photosensitive element to incident light having a particular wavelength; Includes.

[0127] For further possible embodiments of the method, see Figures 5, 7 and 8.

[0128] In Fig. 5, a flow chart of a second exemplary embodiment of a method for calibrating a spectrometer device 112 is shown. As shown in Fig. 5, the method may further include, specifically before step a), determining a transmission band of a narrow band pass filter 116, specifically a plurality of narrow band pass filters 116 (indicated by reference number 156) by using the calibrated spectrometer device 112. For example, determining a transmission band of a narrow band pass filter 116 may include determining a spectrum of the narrow band pass filter 116 (indicated by reference number 158) using the calibrated spectrometer device 112 and determining at least one spectral range of the narrow band pass filter 116 (indicated by reference number 160).

[0129] The method further includes step a) (indicated by reference numeral 148), i.e., illuminating at least one detector device 118 of the spectrometer device 112 with at least one broadband light source 114 via at least one narrow bandpass filter 116, and step b) (indicated by reference numeral 150), i.e., generating a plurality of detector signals in response to the illumination of step a) by using the detector device 118.

[0130] As shown in FIG. 5 , the method, and in particular step c), (indicated by reference numeral 152), further comprises: c.1) determining at least one of pixel locations and identification numbers of the plurality of photosensitive elements producing intensity peaks in a plurality of detector signals; c.2) allocating at least one of the predetermined transmission bands of the narrow bandpass filter to a plurality of intensity peaks; c.3) determining a wavelength calibration function, the wavelength calibration function assigning at least one of pixel locations and identification numbers of the photosensitive elements to wavelength locations; It may include at least one of the following:

[0131] In particular, the wavelength calibration function may include a polynomial function of order N, where a plurality of at least N+1 intensity peaks may be used. The polynomial function may be

number

[0132] As outlined above, the method further includes step d) (indicated by reference number 154), i.e. determining at least one item of stray light calibration information based on the plurality of detector signals. As can be seen from Fig. 5, the method may further include a step (indicated by reference number 168) of applying at least one of the items of wavelength calibration information and the items of stray light calibration information to a measured spectrum determined by using the spectrometer device 112. The measured spectrum may refer to the spectrum of the analyzed sample 138 determined by using the spectrometer device 112. In particular, applying the items of stray light calibration information may include applying an inverse of a signal distribution matrix to the measured spectrum.

[0133] In Fig. 6A-6D, diagrams of the stray light calibration are shown that correspond specifically to the various sub-steps of determining the items of stray light calibration information carried out in step d). In Fig. 6A, a plurality of detector signals 170 can be seen that are generated by using the detector arrangement 118 in response to illumination of the detector arrangement 118 with a broadband light source 114 through at least one narrow band pass filter 116. In particular, in the diagram of Fig. 6A, the signal intensity 172 of the plurality of detector signals 170 is shown as a function of pixel position 174. In this example, the plurality of narrow band pass filters 116 may comprise six narrow band pass filters 116. However, other numbers of narrow band pass filters 116 are also possible. The plurality of detector signals 170 for one of the narrow band pass filters 116 may also be referred to as the line spread function (LSF) of the narrow band pass filter 116. In the example of Fig. 6, a plurality of detector signals 170 are shown for a narrow band pass filter 116 having a transmission band of 1456 nm (indicated by reference number 176), for a narrow band pass filter 116 having a transmission band of 1664 nm (indicated by reference number 178), for a narrow band pass filter 116 having a transmission band of 1840 nm (indicated by reference number 180), for a narrow band pass filter 116 having a transmission band of 2057 nm (indicated by reference number 182), for a narrow band pass filter 116 having a transmission band of 2241 nm (indicated by reference number 184), and for a narrow band pass filter 116 having a transmission band of 2446 nm (indicated by reference number 186). The spectral bandwidth of the transmission band of the narrow band pass filter 116 may preferably be lower than the spectral resolution of the spectrometer device 112. The plurality of detector signals 170 as shown in Fig. 6A may be used as input data for determining an item of wavelength calibration information and / or an item of stray light calibration information.

[0134] The method, specifically step d), may further comprise step d.1), i.e. processing the detector signals 170 by applying at least one of an offset correction and a digital filter, specifically a noise filtering technique, to the detector signals 170. In Fig. 6B, the diagram shows the processed detector signals 188, specifically after applying an offset correction and a digital filter, e.g. a Savitzky-Golay filter, to the detector signals 170, as shown in Fig. 6A. Specifically, in the diagram of Fig. 6B, the signal intensity 172 of the processed detector signals 188 is shown as a function of pixel position 174. Thus, method step d.1) may comprise processing the line spread function of at least one narrow bandpass filter 116.

[0135] The method, specifically step d), may further comprise step d.2), i.e., interpolating the plurality of processed detector signals 188 to obtain, for a plurality of constituent wavelength components, specifically for each of the constituent wavelength components, the illumination intensity at each photosensitive element comprised by the detector arrangement 118. FIG. 6C shows an interpolated detector signal 190, specifically the intensity 172 of the interpolated detector signal 190 as a function of pixel position 174. Thus, method step d.2) may comprise determining the spectral response at any pixel position 174 using an interpolation of the spectral shape and an interpolation of the peak amplitude using linear interpolation of adjacent transmission peaks. The values ​​of the interpolated detector signal 190 may be stored in a so-called signal distribution function (SDF) matrix.

[0136] Therefore, the method, specifically step d), may further comprise step d.3), i.e., generating a plurality of signal distribution functions, specifically recorded in a signal distribution matrix, by using the interpolated detector signal 190. The plurality of signal distribution functions, specifically the signal distribution matrix, may be used to correct the measured spectrum of the spectrometer device 112 for stray light by applying the inverse of the signal distribution function, specifically the signal distribution matrix, to the measured spectrum, as described in more detail in Y. Zong, SW Brown, BC Johnson, KR Lykke and Y. Ohno: "Simple spectral stray light correction method for array spectroradiometers", Applied Optics, Vol. 45, No. 6, 2006. The effect of applying an item of stray light calibration information to the measured spectrum is shown in FIG. 6D. In FIG. 6D, an uncorrected measured spectrum 192 of a PET sample and a corresponding corrected measured spectrum 194 obtained by applying an item of stray light calibration information to the uncorrected measured spectrum 192 are shown. As can be seen from FIG. 6D, by applying the stray light calibration information, the spectral resolution can be improved and the effects of stray light can be reduced.

[0137] In Fig. 7 a flow chart of an embodiment of a method for calibrating the spectrometer device 112 by using the system 110 according to Fig. 2 is shown. In the exemplary embodiment shown in Fig. 7 the method may comprise performing the method steps a) to d) with the detector device 118 removed from the spectrometer device 112 and placed in the system 110 according to Fig. 2. Thus, the method may comprise as a first step (indicated with reference number 196) a step of inserting the detector device 118 into the system 110. This first method step may be followed by a) (indicated with reference number 148), i.e. illuminating at least one detector device 118 of the spectrometer device 112 with at least one broadband light source 114 via at least one narrow bandpass filter 116, and b) (indicated with reference number 150), i.e. generating a plurality of detector signals 170 in response to the illumination of step a) by using the detector device 118. Further in this exemplary embodiment, method steps c) (indicated by reference numeral 152), i.e. determining at least one item of wavelength calibration information, and d) (indicated by reference numeral 154), i.e. determining at least one item of stray light calibration information, may be subsequently performed.

[0138] As shown in FIG. 7, the method may further include assembling the detector device 118 to the spectrometer device 112 (indicated by reference number 198). Furthermore, the method may include applying at least one of the items of wavelength calibration and stray light calibration information to the measured spectrum determined by using the spectrometer device 112 (indicated by reference number 168). Subsequently, the method may include determining a plurality of detector signals of at least one reference sample 136 using the calibrated detector device 118 (indicated by reference number 200). The same reference sample 136 can be used for subsequent method steps. The method may further include determining at least one correction factor (indicated by reference number 202) by determining a plurality of detector signals of the reference sample 136 using the detector device 118 integrated in the spectrometer device 112 (indicated by reference number 204). As an example, the correction factor may be determined by comparing a plurality of detector signals of the reference sample 136 with a known detector signal of the reference sample 136. The correction factor may be applied to subsequent calibration measurements, as indicated by reference numeral 206. The correction factor may improve the accuracy of an item of stray light calibration information.

[0139] Fig. 8 shows a flow chart of an embodiment of a method for calibrating a spectrometer device 112 by using the system 110 according to Fig. 3. The exemplary embodiment of Fig. 8 may broadly correspond to the exemplary embodiment shown in Fig. 7. Therefore, for the description of Fig. 8, please refer to the description of Fig. 7.

[0140] 8 may further include determining a blue-shift correction (indicated by reference numeral 208), where for the blue-shift correction a plurality of additional detector signals may be generated having a detector device 118 incorporated in the spectrometer device 112. The blue-shift correction may include at least one further item of wavelength calibration information determined by repeating step c) using the plurality of additional detector signals (indicated by reference numeral 210). The blue-shift correction may improve the wavelength calibration of the spectrometer device 112, particularly those operating in reflectance mode, by taking into account the angular effect of illumination of the detector device 118 by the external broadband light source 114. [Explanation of symbols]

[0141] 110 System 112 Spectrometer equipment 114 Broadband Light Source 116 Narrow Bandpass Filter 118 Detector Equipment 120 Optical Elements 122 Multiple photosensitive elements 124 Wavelength Selection Element 126 Housing 128 Entrance Window 130 Further Optical Elements 132 Electronic Drive Unit 134 Sample Interface 136 Reference Sample 138 Samples to be analyzed 140 Slots 142 evaluation units 144 processors 146 Computer Equipment 148 Irradiating at least one detector device 150 Generating multiple detector signals 152 Determine at least one item of wavelength calibration information 154 Determining at least one stray light calibration 156 Determining the transmission band of a narrow bandpass filter 158 Determining the Spectrum of a Narrow Bandpass Filter 160 Determining at least one spectral range of a narrow bandpass filter 162 Determining at least one of pixel locations and identification numbers of the plurality of photosensitive elements. 164 Assigning at least one of the predetermined transmission bands of the narrow bandpass filter to a plurality of intensity peaks 166 Determining the wavelength calibration function 168 At least one of the wavelength calibration information items and stray light calibration information items must be applied to the measured spectrum. 170 Multiple Detector Signals 172 Signal Strength 174 pixel position 176 1456nm transmission band 178 1664nm transmission band 180-1840nm transmission band 182 2057nm transmission band 184 2241nm transmission band 186 2446nm transmission band 188 Multiple Processed Detector Signals 190 Interpolated detector signal 192 Uncorrected measured spectrum 194 Interpolated Measured Spectrum 196 Inserting detector devices 198 Incorporating detector devices into spectrometer devices 200. Using a calibrated detector device, determining a plurality of detector signals of a reference sample. 202 Determining at least one correction factor 204 Determining a plurality of detector signals of a reference sample using a detector device incorporated in the spectrometer device. 206 Applying correction factors 208 Determining the blueshift correction 210 Determine further items of wavelength calibration information

Claims

1. 1. A method for calibrating a spectrometer device (112), said method comprising the steps of: a) illuminating at least one detector device (118) of said spectrometer device (112) with at least one broadband light source (114) through at least one narrow bandpass filter (116) having a plurality of predetermined transmission bands; b) generating a plurality of detector signals (170) in response to the illumination of step a) by using said detector device (118), said detector device (118) comprising at least one optical element (120) configured to separate incident light into a spectrum of constituent wavelength components, and further comprising a plurality of photosensitive elements (122), each photosensitive element configured to receive at least one portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least one portion of the respective constituent wavelength components; c) determining at least one item of wavelength calibration information, said item of wavelength calibration information including at least one assignment assigning wavelengths of incident light to corresponding photosensitive elements responsive to those wavelengths; d) determining at least one item of stray light calibration information based on a plurality of detector signals (170), said item of stray light calibration information including at least one signal distribution function, said signal distribution function describing a distribution of responses of said photosensitive elements to incident light having a particular wavelength; Including, A method wherein the item of wavelength calibration information and the item of stray light calibration information are determined using the same plurality of detector signals (170).

2. The method of claim 1 , wherein the broadband light source (114) comprises at least one of an incandescent lamp; a blackbody radiator; an electric filament; an LED; an SLD; or a MEMS blackbody radiator.

3. Step c) comprises: c. 1) determining at least one of pixel locations (174) and identification numbers of the plurality of photosensitive elements (122) that produce intensity peaks in the plurality of detector signals (170); c.2) assigning at least one of the predetermined transmission bands of the narrow bandpass filter (116) to a plurality of intensity peaks; c. 3) determining a wavelength calibration function, the wavelength calibration function assigning at least one of the pixel locations (174) of the photosensitive elements and the identification numbers to wavelength locations; The method of claim 1 , comprising at least one of:

4. Step d) comprises: d. 1) processing the plurality of detector signals (170) by applying at least one of an offset correction and a digital filter to the plurality of detector signals (170); d. 2) interpolating the plurality of processed detector signals (188) to obtain illumination intensities at each photosensitive element comprised by said detector arrangement (118) for a plurality of constituent wavelength components; d. 3) generating a plurality of signal distribution functions by using the interpolated detection signal (190), specifically the plurality of signal distribution functions recorded in a signal distribution matrix; The method of claim 1 , comprising at least one of:

5. 2. The method of claim 1, further comprising applying at least one of the items of wavelength calibration information and the items of stray light calibration information to a measured spectrum determined by using the spectrometer device (112).

6. The method of claim 1 , further comprising determining a transmission band of the narrow bandpass filter by using a calibrated spectrometer device.

7. 2. The method of claim 1, further comprising determining a blueshift correction, for which a plurality of additional detector signals are generated with the detector device (118) incorporated into the spectrometer device (112), and wherein the blueshift correction includes at least one further item of wavelength calibration information determined by repeating step c) using the plurality of additional detector signals.

8. 2. The method of claim 1, wherein the method includes determining at least one temperature of the detection device (118), and determining at least one of the items of wavelength calibration information and the items of stray light calibration information for a plurality of different temperatures.

9. 2. The method of claim 1, further comprising determining at least one correction factor by determining a plurality of detector signals of a reference sample using the at least one detector device incorporated in the spectrometer device.

10. A system (110) for calibrating a spectrometer device (112), said system (110) comprising at least one broadband light source (114) and at least one narrow band-pass filter (116), in particular a plurality of narrow band-pass filters (116) having a plurality of predetermined transmission bands, said system (110) further comprising at least one detector device (118) of the spectrometer device (112), said detector device (118) configured to determine a plurality of detector signals (170) in response to illumination of said detector device (118), said detector device (118) dividing incident light into constituent wavelength components.

10. A system (110) for calibrating a spectrometer device (112), comprising at least one optical element (120) configured to separate a spectrum of constituent wavelength components, and further comprising a plurality of photosensitive elements (122), each photosensitive element configured to receive at least a portion of the constituent wavelength components and to generate a respective detector signal in response to illumination of the respective photosensitive element by at least a portion of the respective constituent wavelength component, the system (110) being configured to perform a method for calibrating a spectrometer device (112) according to claim 1, which refers to a method for calibrating a spectrometer device (112).

11. 11. The system of claim 10, wherein the optical element comprises at least one wavelength-selective element selected from the group consisting of a prism; a diffraction grating; a linear variable filter; an optical filter, in particular a narrow bandpass filter; and an interferometer.

12. The system (110) according to claim 10 or 11, wherein the system (110) comprises at least one evaluation unit (142), the evaluation unit (142) comprising one or more processors (144), the evaluation unit (142) being configured to perform a method for calibrating a spectrometer device (112) according to claim 1, which refers to a method for calibrating a spectrometer device (112).

13. 12. The system (110) of claim 10 or 11, wherein the system (110) comprises at least one spectrometer device (112) comprising at least one detector device (118).

14. 12. A computer program comprising instructions that, when executed by an evaluation unit (142) of a system (110) according to claim 10 or 11, referencing the system (110), cause the system (110) to perform the method for calibrating a spectrometer device (112) according to claim 1, referencing the method for calibrating a spectrometer device (112).

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