WO2025172370A1

WO2025172370A1 - Method for calibrating a spectrometer device

Info

Publication number: WO2025172370A1
Application number: PCT/EP2025/053742
Authority: WO
Inventors: Szu-Yu Huang; Felix Schmidt; Celal Mohan OEGUEN; Henning ZIMMERMANN
Original assignee: TrinamiX GmbH
Current assignee: TrinamiX GmbH
Priority date: 2024-02-13
Filing date: 2025-02-12
Publication date: 2025-08-21
Anticipated expiration: 2026-08-13

Abstract

A method for calibrating a spectrometer device (110) is disclosed. The spectrometer device (110) comprises at least one detector element (112) configured for generating at least one detector signal in response to an illumination of the detector element (112) by incident light. The spectrometer device (110) further comprises at least one light source (118) configured for emitting illumination light (120) in at least one optical spectral range. The spectrometer device (110) further comprises at least one sample interface (126) configured for allowing the illumination light (120) from the light source (118) to illuminate at least one object (128) and configured for allowing detection light (130) from the object (128) to propagate to the detector element (112). The spectrometer device (110) further comprises at least one temperature sensor (134) configured for determining at least one temperature of the detector element (112). The method comprises: i. providing at least one predetermined calibration model (146), wherein the predetermined calibration model (146) comprises a plurality of items of calibration information for at least one temperature range; ii. illuminating the detector element (112) via the sample interface (126) having no object (128) applied to the sample interface (126) to obtain at least one open port detector signal (156); iii. determining at least one temperature (154) of the detector element (112); and iv. determining at least one temperature-corrected calibration model (148) using the predetermined calibration model (146) and taking into account the open port detector signal (156) and the temperature (154) of the detector element (112).

Description

Method for calibrating a spectrometer device

Technical Field

The invention relates to a method for calibrating a spectrometer device, to a method of determining at least one calibrated optical property of at least one object and to a spectrometer device. The invention further relates to computer programs and computer-readable storage media. Such devices and methods can, in general, be used for investigating or monitoring purposes, in particular, in the infrared (IR) spectral region, especially in the near-infrared (NIR) spectral region, and in the visible (VIS) spectral region, e.g. in a spectral region allowing to mimic a human's ability of color sight. However, further applications are feasible.

Background art

Spectrometer devices are known to be efficient tools for obtaining information on the spectral properties of an object, when emitting, irradiating, reflecting and/or absorbing light. Spectrometer devices, thus, may assist in analyzing objects or other tasks in which information on the spectral properties of the object is of interest.

Usually, in spectrometer devices, spectral information is obtained via one or more detectors and one or more wavelength-selective optical elements, such as one or more dispersive optical elements, filters such as bandpass filters, prisms, gratings, interferometers, or the like. The detectors may comprise any type of light-sensitive element, such as one or more single or multiple pixel detectors, line detectors or array detectors having one- or two-dimensional arrays of pixels.

WO 2023/052608 A1 describes a spectral measurement device for measuring optical radiation provided by at least one measurement object in at least one classification based spectral measurement. The spectral measurement device comprises: at least one radiation source configured for emitting optical radiation at least partially towards the measurement object, wherein the optical radiation is at least partially in the spectral range of interest for the classification based spectral measurement; at least two photodetectors, wherein each photodetector comprises at least one pixel, wherein each pixel is an active pixel or a darkened pixel, wherein the spectral measurement device comprises at least two active pixels, wherein the spectral measurement device comprises at least one darkened pixel, wherein each active pixel is configured for generating at least one photodetector signal dependent on an illumination of the active pixel, wherein at least two of the active pixels are configured for detecting optical radiation in at least partially different spectral ranges, wherein each darkened pixel is configured for generating at least one photodetector signal independent on an illumination of the darkened pixel; at least one readout device configured for measuring the photodetector signals and generating at least one item of spectral data; and at least one evaluation device comprising at least one processor and at least one memory storage, wherein the memory storage is configured for storing at least one classification model comprising a set of different classes, wherein each class refers to at least one spectral characteristic, wherein the classification model is configured for classifying at least one item of input data into the classes, and at least one transfer function configured for transferring the item of spectral data into the item of input data applicable to the classification model. The evaluation device is configured for generating at least one item of measurement information by applying the classification model and the transfer function to the item of spectral data.

WO 2023/091709 A1 describes on-line compensation of instrumental drifts in miniaturized spectrometers due to variations in environmental conditions and due to other sources of instrumental drift. The spectrometer may include a light modulator, a detector, and a processor. The spectrometer may further include a sensor configured to obtain a value of a condition contributing to instrumental drifts in the spectrometer. The processor may be configured to extract a set of correction parameters from a correction matrix associating a plurality of sets of correction parameters with sensor values based on the value and to apply the set of correction parameters to an output of the detector to produce a corrected spectrum of a sample under test. The correction matrix may be generated for the spectrometer or may be based on a global correction matrix fitted to the spectrometer.

In general, analyzing objects with spectrometer devices may require performing multiple measurements, e.g. performing calibration measurements to account for background light present during object measurement. However, detectors are known to be temperature-sensitive elements and temperature may change in between two measurements. Thus, the signal from the spectrometer device may drift with temperature changes. The temperature drift of the spectrometer device may cause difficulties to perform calibration measurements under the same temperature as the sample measurement. Some spectrometer devices may use thermoelectric coolers to stabilize the temperature of the spectrometer device. However, the additional hardware requirements may render the spectrometer device complex and bulky. Alternatively or additionally, some spectrometer device may use calibrated models to predict temperature variation in the signal. The calibrated models may comprise performing one or more calibration measurements. However, the calibrated models may become inaccurate when the status of the spectrometer device changes, e.g. due to temperature changes and/or contamination of a sample interface of the spectrometer device. For example, the calibration measurement may not be reliable in case temperature between the calibration measurement and the object measurement changes. Additionally, aging, hysteresis, contamination on sample interfaces, such as smear or scratches, may interfere the calibration measurement. These effects may impede global temperature compensation of the spectrometer device. Thus, there is a need for compensating both detrimental effects due to temperature drift and due to aging, hysteresis and/or contamination at the spectrometer device.

Problem to be solved It is therefore desirable to provide methods and devices which at least partially address the above-mentioned technical challenges and at least substantially avoid the disadvantages of known methods and devices. In particular, it is an object of the present invention to provide a spectrometer device and methods which provide a compensation of detrimental effects due to temperature drift and due to aging, hysteresis and/or contamination at the spectrometer device.

Summary

This problem is addressed by a method for calibrating a spectrometer device, a method of determining at least one calibrated optical property of at least one object, a spectrometer device and by computer programs and computer-readable storage media with the features of the independent claims. Advantageous embodiments which might be realized in an isolated fashion or in any arbitrary combinations are listed in the dependent claims as well as throughout the specification.

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

The term “calibrating” or “calibration” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of at least one of determining, correcting, adjusting and compensating measurement inaccuracies at the spectrometer device. The calibration may comprise determining at least one item of calibration information. Consequently, the term “item of calibration information”, as used herein, may refer, without limitation, to at least one item of information on a result of the calibration, such as a calibration function, a calibration factor, a calibration matrix or the like. The item of calibration information may be used for transforming one or more measured values into one or more calibrated or “true” values. Measurement inaccuracies may, as an example, arise from uncertainties in temperature variation and/or from intrinsic and/or extrinsic interferences on measurement signals of the spectrometer device. The calibration of the sensing device may comprise a temperature calibration. The calibration may comprise at least one two-step process, wherein, in a first step, information on a deviation of a measurement signal of the spectrometer device from a known standard is determined, wherein, in a second step, this information is used for correcting and/or adjusting the measurement signal of the spectrometer device in order to reduce, minimize and/or eliminate the deviation. The calibration may comprise applying the at least one item of calibration information, for example to a measurement signal and/or to a measurement spectrum of the spectrometer device. The calibration may improve and/or maintain accuracy of measurements performed with the calibrated spectrometer device.

The term “spectrometer device” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an optical device configured for acquiring at least one item of spectral information on at least one object. Specifically, the at least one item of spectral information may refer to at least one optical property or optically measurable property which is determined as a function of a wavelength, for one or more different wavelengths. More specifically, the optical property or optically measurable property, as well as the at least one item of spectral information, may relate to at least one property characterizing at least one of a transmission, an absorption, a reflection and an emission of the at least one object, either by itself or after illumination with external light. The at least one optical property may be determined for one or more wavelengths. The spectrometer device specifically may form an apparatus which is capable of recording a signal intensity with respect to the corresponding wavelength of a spectrum or a partition thereof, such as a wavelength interval, wherein the signal intensity may, specifically, be provided as an electrical signal which may be used for further evaluation.

The spectrometer device, as an example, may be or may comprise a device which allows for a measurement of at least one spectrum, e.g. for the measurement of a spectral flux, specifically as a function of a wavelength or detection wavelength. The spectrum may be acquired, as an example, in absolute units or in relative units, e.g. in relation to at least one reference measurement. Thus, as an example, the acquisition of the at least one spectrum specifically may be performed either for a measurement of the spectral flux (unit W/nm) or for a measurement of a spectrum relative to at least one reference material (unit 1 ), which may describe the property of a material, e.g., reflectance over wavelength. Additionally or alternatively, the reference measurement may be based on a reference light source, an optical reference path, a calculated reference signal, e.g. a calculated reference signal from literature, and/or on a reference device.

Specifically, the at least one spectrometer device may be a diffusive reflective spectrometer device configured for acquiring spectral information from the light which is diffusively reflected by the at least one object, e.g. at least one sample. Additionally or alternatively, the at least one spectrometer device may be or may comprise an absorption- and/or transmission spectrometer. In particular, measuring a spectrum with the spectrometer device may comprise measuring absorption in a transmission configuration. Specifically, the spectrometer device may be configured for measuring absorption in a transmission configuration. As outlined above, however, other types of spectrometer devices are also feasible.

The at least one spectrometer device, specifically and as will be outlined in further detail below, may comprise at least one light source which, as an example, may be at least one of a tunable light source, a light source having at least one fixed emission wavelength and a broadband light source. The spectrometer device, as will be outlined in further detail below, further comprises at least one detector element which may be configured for detecting light, such as light which is at least one of transmitted, reflected or emitted from the at least one object. The spectrometer device further may comprise, as will be outlined in further detail below, at least one wavelength- selective element, such as at least one of a grating, a prism and a filter, e.g. a length variable filter having varying transmission properties over its lateral extension. The wavelength-selective element may be used for separating incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector such as a detector having a detector array as described below in more detail.

The spectrometer device specifically may be configured for acquiring at least one spectrum or at least a part of a spectrum of detection light propagating from the object to the spectrometer. The spectrum may describe the radiometric unit of spectral flux, e.g. given in units of watt per nanometer (W/nm), or other units, e.g. as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, e.g. in the NIR spectral range, in a specific wavelength band. The spectrum may contain one or more optical variables as a function of the wavelength, e.g. the power spectral density, electric signals derived by optical measurements and the like. The spectrum may indicate, as an example, the power spectral density and/or the spectral flux of the object, e.g. of a sample, e.g. relative to a reference sample, such as a transmittance and/or a reflectance of the object, specifically of the sample.

The spectrum, as an example, may comprise at least one measurable optical variable or property of the detection light and/or of the object, specifically as a function of the illumination light and/or the detection light. As an example, the at least one measurable optical variable or property may comprise at least one radiometric quantity, such as a spectral density, a power spectral density, a spectral flux, a radiant flux, a radiant intensity, a spectral radiant intensity, an irradiance and/or a spectral irradiance. Specifically, as an example, the spectrometer device, specifically the detector, may measure the irradiance in Watt per square meter (W/m²), more specifically the spectral irradiance in Watt per square meter per nanometer (W/m²/nm). Based on the measured quantity the spectral flux in Watt per nanometer (W/nm) and/or the radiant flux in Watt (W) may be determined, e.g. calculated, by taking into account an area of the detector.

The spectrometer device, specifically, may be a portable spectrometer device. The term “portable” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the property of at least one object of being moved by human force, such as by a single user. Specifically, the object characterized by the term “portable” may have a weight not exceeding 10 kg, specifically not exceeding 5 kg, more specifically not exceeding 1 kg or even not exceeding 500 g. Additionally or alternatively, the dimensions of the object characterized by the term “portable” may be such that the object extends by no more than 0.3 m into any dimension, specifically by no more than 0.2 m into any dimension. The object, specifically, may have a volume of no more than 0.03 m³, specifically of no more than 0.01 m³, more specifically no more than 0.001 m³ or even no more than 500 mm³. In particular, as an example, the portable spectrometer device may have dimensions of e.g.

10 mm by 10 mm by 5 mm. Specifically, the portable spectrometer device may be part of a mobile device or may be attachable to a mobile device, such as a notebook computer, a tablet, a cell phone, such as a smart phone, a smartwatch and/or a wearable computer, also referred to as “wearable”, e.g. a body borne computer such as a wrist band or a watch. In particular, the a weight of the spectrometer device, specifically the portable spectrometer device, may be in the range from 1 g to 100 g, more specifically in the range from 1 g to 10 g.

The spectrometer device comprises at least one detector element configured for generating at least one detector signal in response to an illumination of the detector element by incident light. The spectrometer device further comprises at least one light source configured for emitting illumination light in at least one optical spectral range. The spectrometer device further comprises at least one sample interface configured for allowing the illumination light from the light source to illuminate at least one object and configured for allowing detection light from the object to propagate to the detector element. The spectrometer device further comprises at least one temperature sensor configured for determining at least one temperature of the detector element.

The term “detector element” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device configured for qualitatively and/or quantitatively detecting, i.e. for at least one of determining, measuring and monitoring, at least one optical parameter. The detector element is configured for generating at least one detector signal, specifically at least one electrical detector signal, such as an analogue and/or a digital detector signal. Consequently, the term “detector signal”, as used herein, may refer, without limitation, to the signal, specifically the at least one electrical signal, such as an analogue and/or a digital signal, generated by the detector element indicative of the detected parameter. The detector signal may provide information on the at least one parameter measured by the detector element. The detector signal may directly or indirectly be provided by the detector element to an evaluation unit, as will be outlined in further detail below, such that the detector element and the evaluation unit may be directly or indirectly connected. The detector signal may be used as a “raw” detector signal and/or may be processed or preprocessed before further used, e.g. by filtering and the like. Thus, the detector element may comprise at least one processing device and/or at least one preprocessing device, such as at least one of an amplifier, an analogue/digital converter, an electrical filter and a Fourier transformation.

The detector element may be configured for detecting light propagating from the object to the spectrometer device or more specifically to the detector element of the spectrometer device, which is referred to as “detection light”, as will be outlined in further detail below. Thus, specifically, the detector element may be or may comprise at least one optical detector element. The optical detector element may be configured for determining at least one optical parameter, such as an intensity and/or a power of light by which at least one sensitive area of the detector element is irradiated. More specifically, the optical detector element may comprise at least one photosensitive element and/or at least one optical sensor, such as at least one of a photodiode, a photocell, a photosensitive resistor, a phototransistor, a thermophile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier and a bolometer. The detector element, thus, may be configured for generating at least one detector signal, more specifically at least one electrical detector signal, in the above-mentioned sense, providing information on at least one optical parameter, such as the power and/or intensity of light by which the detector element or a light-sensitive area of the detector element is illuminated.

The detector element may comprise one single optically sensitive element or area or a plurality of optically sensitive elements or areas. Specifically, the detector element may be or may comprise at least one detector array, more specifically an array of optically sensitive elements, as will be outlined in further detail below. Each of the optically sensitive elements may comprise at least a photosensitive area which may be adapted for generating an electrical signal depending on the intensity of the incident light, wherein the electrical signal may, in particular, be provided to an evaluation unit, as will be outlined in further detail below.

The photosensitive area as comprised by each of the optically sensitive elements may, especially, be a single, uniform photosensitive area which is configured for receiving the incident light which impinges on the individual optically sensitive elements. However, other arrangements of the optically sensitive elements may also be conceivable.

The array of optically sensitive elements may be designed to generate detector signals, preferably electronic signals, associated with the intensity of the incident light which impinges on the individual optically sensitive elements. The detector signal may be an analogue and/or a digital signal. The electronic signals for adjacent pixelated sensors can, accordingly, be generated simultaneously or else in a temporally successive manner. By way of example, during a row scan or line scan, it is possible to generate a sequence of electronic signals which correspond to the series of the individual optically sensitive elements which are arranged in a line. In addition, the individual optically sensitive elements may, preferably, be active pixel sensors which may be adapted to amplify the electronic signals prior to providing it to an evaluation unit. For this purpose, the detector element may comprise one or more signal processing devices, such as one or more filters and/or analogue-digital-converters for processing and/or preprocessing the electronic signals.

In case the detector element comprises an array of optically sensitive elements, the detector element, as an example, may be selected from any known pixel sensor, in particular, from a pixelated organic camera element, preferably, a pixelated organic camera chip, or from a pixelated inorganic camera element, preferably, a pixelated inorganic camera chip, more preferably from a CCD chip or a CMOS chip, which are, commonly, used in various cameras nowadays. As an alternative, the detector element generally may be or comprise a photoconductor, in particular an inorganic photoconductor, especially PbS, PbSe, Ge, InGaAs, ext. InGaAs, InSb, or HgCdTe. As a further alternative, it may comprise at least one of pyroelectric, bolometer or thermophile detector elements. Thus, a camera chip having a matrix of 1 x N pixels or of M x N pixels may be used here, wherein, as an example, M may be < 10 and N may be in the range from 1 to 50, preferably from 2 to 20, more preferred from 5 to 10. Further, a monochrome camera element, preferably a monochrome camera chip, may be used, wherein the monochrome camera element may be differently selected for each optically sensitive element, especially, in accordance with the varying wavelength along the series of the optical sensors. Thus, the array may be adapted to provide a plurality of the electrical signals which may be generated by the photosensitive areas of the optically sensitive elements comprised by the array. The electrical signals as provided by the array of the spectrometer device may be forwarded to an evaluation unit.

The optically sensitive elements may be sensitive to differing spectral ranges of the light from the object. The differing spectral sensitivity may be implemented by using optically sensitive elements having inherently differing spectral sensitivities, such as by using differing integrated filters and/or differing sensitive materials, such as semiconductor materials. Additionally or alternatively, the differing spectral sensitivity may be achieved by using one or more wavelength-selective elements in one or more beam paths of the detection light, such as one or more of a filter, a grating, a prism or the like, configured to allow forward differing spectral portions of the detection light from the object to reach the individual optically sensitive elements, sequentially or simultaneously.

The spectrometer device may further comprise at least one wavelength-selective element. As used herein, the term “wavelength-selective element” is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary optical element which interacts with differing spectral portions of incident light in a different manner, e.g. by having at least one wavelength-dependent optical property, such as at least one wavelength-dependent optical property selected from the list consisting of a degree of reflection, a direction of reflection, a degree of refraction, a direction of refraction, an absorption, a transmission, an index of refraction.

Therein, the wavelength selection by the at least one wavelength-selective element may take place in the at least one beam path of the illumination light, thereby selecting and/or modifying a wavelength of the illumination of the object, and/or in the detection beam path of the detection light, thereby selecting and/or modifying a wavelength of detection, e.g. for the detector element in general and/or for each of the optically sensitive elements. Thus, as an example, the at least one wavelength-selective element may comprise at least one of a wavelength-selective element disposed in a beam path of the illumination light and a wavelength-selective element disposed in a beam path of the detection light.

The wavelength-selective element, specifically may be selected from the group of a tunable wavelength-selective element and a wavelength-selective element having a fixed transmission spectrum. By using a tunable wavelength selective element, as an example, differing wavelength ranges may be selected sequentially, whereas, by using a wavelength-selective element having a fixed transmission spectrum, the selection of the wavelength ranges may be fixed and may, however, be dependent e.g. on a detection position, thereby allowing, as an example, in the detection light beam path, for simultaneously exposing different detector elements and/or different optically sensitive elements of the detector element to differing spectral ranges of light. Thus, as an example, the at least one wavelength-selective element may comprise at least one of a filter, a grating, a prism, a plasmonic filter, a diffractive optical element and a metamaterial. More specifically, the spectrometer device may comprise at least one filter element disposed in a beam path of the light from the object, i.e. in the beam path of the detection light, wherein the filter element, specifically may be configured such that each of the optically sensitive elements is exposed to an individual spectral range of the light from the object. As an example, a variable filter element may be used, the transmission of which depends on a position on the filter element, such that, when the variable filter element is placed on top of the array of optically sensitive elements, the individual optically sensitive elements are exposed to differing spectral ranges of the incident light, specifically the detection light from the object. Additionally or alternatively the at least one wavelength-selective element may comprise at least one of the following elements: an array of individual bandpass filters, an array of patterned filters, an MEMS-ln- terferometer, an MEMS-Fabry Perot interferometer. Further elements are feasible.

The term “illumination” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an amount of incident light. Specifically, the illumination of the detector element by incident light may comprise an amount of light impinging onto the detector element, specifically onto the light-sensitive area of the detector element. The illumination may specifically comprise a power and/or an intensity of light by which the detector element or a light-sensitive area of the detector element is illuminated.

The term “light” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to electromagnetic radiation in one or more of the infrared, the visible and the ultraviolet spectral range. Herein, the term “ultraviolet spectral range”, generally, refers to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably of 100 nm to 380 nm. Further, in partial accordance with standard ISO- 21348 in a valid version at the date of this document, the term “visible spectral range”, generally, refers to a spectral range of 380 nm to 760 nm. The term “infrared spectral range” (IR) generally refers to electromagnetic radiation of 760 nm to 1000 pm, wherein the range of 760 nm to 1.5 pm is usually denominated as “near infrared spectral range” (NIR) while the range from 1 .5 p to 15 pm is denoted as “mid infrared spectral range” (MidlR) and the range from 15 pm to 1000 pm as “far infrared spectral range” (FIR). Preferably, light used for the typical purposes of the present invention is light in the infrared (IR) spectral range, more preferred, in the near infrared (NIR) and/or the mid infrared spectral range (MidlR), especially the light having a wavelength of 1 pm to 5 pm, preferably of 1 pm to 3 pm. This is due to the fact that many material properties or properties on the chemical constitution of many objects may be derived from the near infrared spectral range. It shall be noted, however, that spectroscopy in other spectral ranges is also feasible and within the scope of the present invention. The term “optical spectral range” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a spectral range at least partially located in one or more of the infrared, the visible and the ultraviolet spectral range. The optical spectral range may comprise a single spectral range located in one or more of the infrared, the visible and the ultraviolet spectral range or, alternatively, a plurality of spectral ranges located in one or more of the infrared, the visible and the ultraviolet spectral range, wherein, in particular, the plurality of spectral ranges do not necessarily overlap with each other.

The term “light source” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device configured for generating or providing light in the sense of the above-mentioned definition. The light source specifically may be or may comprise at least one electrical light source, such as an electrically driven light source.

As will be outlined in further detail below, the light source generally can be embodied in various ways. Thus, the light source can be for example part of the spectrometer device in a housing of the spectrometer device. Alternatively or additionally, however, the at least one light source can also be arranged outside a housing, for example as a separate light source. The light source can be arranged separately from the object and illuminate the object from a distance.

In spectroscopy, various sources and paths of light are to be distinguished. In the context of the present invention, a nomenclature is used which, firstly, denotes light propagating from the light source to the object as “illuminating light” or “illumination light”. Secondly, light propagating from the object to the detector element and/or from the sample interface to the detector element is denoted as “detection light”. The detection light may comprise at least one of illumination light reflected by the object and/or the sample interface, illumination light scattered by the object and/or the sample interface, illumination light transmitted by the object and/or the sample interface, luminescence light generated by the object and/or the sample interface, e.g. phosphorescence or fluorescence light generated by the object and/or the sample interface after optical, electrical or acoustic excitation of the object and/or the sample interface by the illumination light or the like. Thus, the detection light may directly or indirectly be generated through the illumination of the object and/or the sample interface by the illumination light.

Further, as will be outlined in detail below, within the light source itself, a distinction may be made between various light sources, such as primary light sources and secondary light sources. Thus, as will be outlined in further detail below, “primary light”, also referred to as “pump light”, may be generated by a primary light source such as at least one light-emitting diode and may subsequently be transformed into “secondary light”, such as by using light conversion, e.g. through one or more phosphor materials. The illumination light may be or may comprise at least one of the primary light or a part thereof, the secondary light or a part thereof, or a mixture of both.

The light source may comprise at least one light-emitting diode and at least one luminescent material for light-conversion of primary light generated by the light-emitting diode, wherein, specifically, the illumination light may be a combination of the primary light and light generated by the light-conversion by the luminescent material or light generated by the light conversion of the luminescent material, also referred to as secondary light.

The term “light-emitting diode” or briefly “LED”, as used herein, is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an optoelectronic semiconductor device capable of emitting light when an electrical current flows through the device. The optoelectronic semiconductor device may be configured for generating the light due to various physical processes, including one or more of spontaneous emission, induced emission, decay of metastable excited states and the like. Thus, as an example, the light-emitting diode, may comprise one or more of: a light-emitting diode based on spontaneous emission of light, in particular an organic light emitting diode, a light-emitting diode based on superluminescence (sLED), or a laser diode (LD) In the following, without narrowing the possible embodiments of the light-emitting diode to any of the before-mentioned physical principles or setups, the abbreviation “LED” will be used for any type of light-emitting diode. Specifically, the LED may comprise at least two layers of semiconductor material, wherein light may be generated at at least one interface between the at least two layers of semiconductor material, specifically due to a recombination of positive and negative electrical charges, e.g. due to electronhole recombination. The at least two layers of semiconductor material may have differing electrical properties, such as at least one of the layers being an n-doped semiconductor material and at least one of the layers being a p-doped semiconductor material. Thus, as an example, the LED may comprise at least one pn-junction and/or at least one pin-set up. It shall be noted, however, that other device structures are feasible, too. The at least one semiconductor material may specifically be or may comprise at least one inorganic semiconducting material. It shall be noted, however, that organic semiconducting materials may be used additionally or alternatively.

Generally, the LED may convert electrical current into light, specifically into the primary light, more specifically into blue primary light, as will be outlined in further detail below. The LED, thus, specifically may be a blue LED. The LED may be configured for generating the primary light, also referred to as the “pump light”. Thus, the LED may also be referred to as the “pump LED”. The LED specifically may comprise at least one LED chip and/or at least one LED die. Thus, the semiconductor element of the LED may comprise an LED bare chip.

Various types of LEDs suitable for generating the primary light are known to the skilled person and may also be applied in the present invention. Specifically, p-n-diodes may be used. As an example, one or more LEDs selected from the group of an LED on the basis of indium gallium nitride (InGaN), an LED on the basis of GaN, an LED on the basis of InGaN/GaN alloys or combinations thereof and/or other LEDs may be used. Additionally or alternatively, quantum well LEDs may also be used, such as one or more quantum well LEDs on the basis of InGaN. Additionally or alternatively, superluminescence LEDs (sLED) and/or Quantum cascade lasers may be used.

The term “luminescence” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of spontaneous emission of light by a substance not resulting from heat. Specifically, luminescence may refer to a cold-body radiation. More specifically, the luminescence may be initiated or excited by irradiation of light, in which case the luminescence is also referred to as “photoluminescence”. The property of a material being capable of performing luminescence, in the context of the present invention, is referred to by the adjective “luminescent”. The at least one luminescent material specifically may be a photo-luminescent material, i.e. a material which is capable of emitting light after absorption of photons or excitation light. Specifically, the luminescent material may have a positive Stokes shift, which generally may refer to the fact that the secondary light is red-shifted with respect to the primary light.

The at least one luminescent material, thus, may form at least one converter, also referred to as a light converter, transforming primary light into secondary light having different spectral properties as compared to the primary light. Specifically, a spectral width of the secondary light may be larger than a spectral width of the primary light, and/or a center of emission of the secondary light may be shifted, specifically red-shifted, compared to the primary light. Specifically, the at least one luminescent material may have an absorption in the ultraviolet and/or blue spectral range and an emission in the near-infrared and/or infrared spectral range. Thus, generally, the luminescent material or converter may form at least one component of the phosphor LED converging primary light or pump light, specifically in the blue spectral range, into light having a longer wavelength, e.g. in the near-infrared or infrared spectral range.

Various types of conversion and/or luminescence are known and may be used in the context of the present invention. Thus, specifically, the conversion can occur via a dipole-allowed transition in the luminescent material, also referred to as fluorescence, and/or via a dipole-forbidden, thus long-lived, transition in the luminescent material, often also referred to as phosphorescence.

The luminescent material, specifically, may, thus, form at least one converter or light converter. The luminescent material may form at least one of a converter platelet, a luminescent and specifically a fluorescent coating on the LED and phosphor coating on the LED. The luminescent material may, as an example, comprise one or more of the following materials: Cerium-doped YAG (YAG:Ce³⁺, or Y₃AI₅0i2:Ce³⁺); rare-earth-doped Sialons; copper- and aluminum-doped zinc sulfide (ZnS:Cu,AI). The LED and the luminescent material, together, may form a so-called “phosphor LED”. Consequently, the term “phosphor light-emitting diode” or briefly “phosphor LED”, as used herein, is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a combination of at least one light-emitting diode configured for generating primary light or pump light, and at least one luminescent material, also referred to as a “phosphor”, configured for light-conversion of the primary light generated by the light-emitting diode. The phosphor LED may form a packaged LED light source, including the LED die, e.g. a blue LED emitting blue pump light, as well as the phosphor, which, as an example, fully or partially coats the LED, which is, as an example, configured for converting the primary light or blue light into light having differing spectral properties, specifically into near-infrared light. Generally, the phosphor LED may be packaged in one housing or may be unpackaged. Thus, the LED and the at least one luminescent material for light-conversion of the primary light generated by the light-emitting diode may specifically be housed in a common housing. Alternatively, however, the LED may also be an unhoused or bare LED which may fully or partially be covered with the luminescent material, such as by disposing one or more layers of the luminescent material on the LED die. The phosphor LED, generally, may form an emitter or light source by itself.

The at least one luminescent material specifically may form at least one layer. Generally, various alternatives of positioning the luminescent material with respect to the light-emitting diode are feasible, alone or in combination. Firstly, the luminescent material, e.g., at least one layer of the luminescent material, such as the phosphor, may be positioned directly on the light-emitting diode, which is also referred to as a “direct attach”, e.g. with no material in between the LED and the luminescent material or with one or more transparent materials in between, such as with one or more transparent materials, specifically transparent for the primary light, in between the LED and the luminescent material. Thus, as an example, a coating of the luminescent material may be placed directly or indirectly on the LED. Additionally or alternatively, the luminescent material, as an example, may form at least one converter body, such as at least one converter disk, which may be placed on top of the LED, e.g. by adhesive attachment of the converter body to the LED. Additionally or alternatively, the luminescent material may also be placed in a remote fashion, such that the primary light from the LED has to pass an intermediate optical path before reaching the luminescent material. This placement may also be referred to as a “remote placement” or as a “remote phosphor”. Again, as an example, the luminescent material in the remote placement may form a solid body or converter body, such as a disk or converter disk.

Further, in case of the remote placement, the luminescent material may also be a coating. In particular, an object which is transmitting light, e.g. a thin glass substrate comprising and/or being made of glass or plastics, may be coated with the phosphor. Alternatively, a reflective surface may be coated with the phosphor. This could be a flat or rough mirror, which may comprise and/or be made of a high-reflective index material substrate, e.g. silicon, or a gold, silver, aluminum or chromium coated flat or rough surface, e.g. glass, or a plastic. In the intermediate optical path, one or more optical elements may be placed, such as one or more of a lens, a prism, a grating, a mirror, an aperture or a combination thereof. Thus, specifically, an optical system having imaging properties may be placed in between the LED and the luminescent material, in the intermediate optical path. Thereby, as an example, the primary light may be focused, or bundled onto the converter body.

The term “sample interface” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a port of the spectrometer device through which light in the optical spectral range, such as in at least one partition of the optical spectral range or in the full optical spectral range, may enter the spectrometer device, specifically for the purpose of the spectral sensing, and/or may leave the spectrometer device, e.g. for the purpose of illuminating the at least one object. The sample interface, as an example, may define an optical plane, e.g. a plane either material or imaginary, of the spectrometer device, through which the illumination light illuminates the object and/or through which the detection light from the object travels to reach the detector element, e.g. to generate the detector signal. The sample interface may be a fictional plane The sample interface may or may not be constituted by a physical element and/or barrier, such as a transparent element, e.g. a glass or quartz window. The sample interface may also be the sample surface itself or a plane where the sample can be placed or aligned. As an example, the sample interface may be or may comprise at least one element comprising at least one transparent material being at least partially transparent in the optical spectral range, such as in at least one partition of the optical spectral range or in the full optical spectral range. The sample interface may be configured for transmitting light in the optical spectral range. The sample interface may be arranged in an optical path of the spectrometer device to allow the illumination light emitted from the light source to illuminate the object placed in front of the spectrometer device, specifically in front of the sample interface. The transparent material may, as an example, comprise one or more of a glass material, such as silica, soda lime, borosilicate or the like, and/or a polymeric material, such as polymethylmethacrylate or polystyrene.

The term “temperature sensor” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device configured for qualitatively and/or quantitatively detecting, i.e. for at least one of determining, measuring and monitoring, at least one temperature parameter, such as at least one parameter which is directly the temperature and/or at least one parameter which can be used to derive the temperature. The temperature sensor may be or may comprise at least one of an integrated circuit (IC) sensor, a thermistor, a resistive temperature detector (RTD) and a thermocouple. The spectrometer device may specifically comprise at least one temperature sensor for each optically sensitive element. For example, as outlined above, the detector element may comprise one single optically sensitive element or a plurality of optically sensitive elements. The spectrometer device may comprise at least one temperature sensor associated with each optically sensitive element to determine the temperature of each optically sensitive element. The method comprises the following steps which, as an example, may be performed in the given order. It shall be noted, however, that a different order is also possible. Further, it is also possible to perform one, more than one or even all of the method steps once or repeatedly. Further, it is possible to perform two or more of the method steps simultaneously or in a timely overlapping fashion. The method may comprise further method steps which are not listed.

The method comprises: i. providing at least one predetermined calibration model, wherein the predetermined calibration model comprises a plurality of items of calibration information for at least one temperature range;

II. illuminating the detector element via the sample interface having no object applied to the sample interface to obtain at least one open port detector signal; ill. determining at least one temperature of the detector element; and iv. determining at least one temperature-corrected calibration model using the predetermined calibration model and taking into account the open port detector signal and the temperature of the detector element.

The term “providing” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of making available. The providing of the predetermined calibration model may specifically comprise making available the predetermined calibration model for further processing. The providing may comprise retrieving the predetermined calibration model from at least one of an external storage device and an internal storage device, such as a storage device of an evaluation unit, and/or supplying the predetermined calibration model to one or more processing units, such as processing units of an evaluation unit, as will be outlined in further detail below.

The term “calibration model” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a model configured for at least partially calibrating a device or element. Specifically, the calibration model may be configured for at least partially calibrating the spectrometer device. The calibration model comprises the plurality of items of calibration information which, specifically, may be used individually and/or in combination with each other to calibrate the spectrometer device. The items of calibration information of the calibration model may be used directly and/or indirectly, such as via one or more further evaluation and/or calibration steps, for calibrating the spectrometer device. The calibration model may comprise a function, specifically a continuous or discontinuous function, a curve, a lookup table, an operator or any other means describing a relation of the item of calibration information and the temperature. The calibration model may specifically comprise a course of the plurality of items of calibration information as a function of temperature, in particular, either in relative terms, such as relative to a given temperature set point, or, alternatively, in absolute terms. As an example, the items of calibration information may comprise open port detector signals, specifically predetermined open port detector signals, such as open port detector signals obtained by using the spectrometer device in a controlled environment and/or under known conditions.

The term “predetermined” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a situation in which an item of information is obtained or determined previously to the method. Specifically, the predetermined calibration model may be determined previously to the performing of the method and, thus, may be referred to as “predetermined”. For example, the predetermined calibration model may be determined in a factory calibration, such as in a factory calibration process of the spectrometer device.

The term “plurality of items of calibration information” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a set of three or more items of calibration information.

The term “temperature range” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a coherent interval of temperatures. Specifically, the temperature range may comprise a coherent interval of temperatures for which the calibration model comprises one or more items of calibration information. The calibration model may specifically comprise items of calibration information for more than one temperature range, e.g. for two or more distinct temperature ranges. The one or more temperature ranges may represent a temperature interval in which the spectrometer device is expected to operate. For example, the temperature range may comprise temperatures in the range of -50°C to 100°C, specifically in the range of 20°C to 50°C.

The term “illuminating” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of exposing at least one element to light. Specifically, the illuminating of the detector element may comprise exposing the detector element to detection light. The illuminating of the detector element in step II. may specifically comprise exposing the detector element to detection light originating from light interaction with the sample interface, as outlined above.

The term “open port detector signal” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a detector signal obtained by illuminating the detector element without having an object applied to the sample interface. The predetermined calibration model may comprise the plurality of items of calibration information as a function of temperature in the temperature range. For example, the plurality of items of calibration information may comprise predetermined open port signals. The predetermined calibration model may comprise at least one relation relating open port detector signals and temperatures in the temperature range. The relation may be given by one or more of a function, specifically a continuous or discontinuous function, a curve, a lookup table, an operator or any other means describing the relation between the open port detector signals and the temperature.

The term “determining” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of generating at least one representative result, in particular, by evaluating at least one measurement signal as acquired by at least one sensing element. Specifically, the determining of the temperature of the detector element may comprise evaluating at least one measurement signal as acquired by the temperature sensor to generate the temperature of the detector element. The determining of the temperature-corrected calibration model may comprise evaluating the predefined calibration model, the open port detector signal as acquired by the detector element and the temperature of the detector element to generate the temperature-corrected calibration model.

The term “temperature-corrected” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to at least one modified item of information. Specifically, the temperature-corrected calibration model may comprise at least one modified calibration model, such as a calibration model obtained by performing one or more modification steps on the predefined calibration model taking into account the temperature of the detector element and, optionally, further parameters having an impact on the calibration model. The temperature-corrected calibration model may specifically comprise the predefined calibration model being adapted to a specific temperature, e.g. to the temperature of the detector element. The temperature-corrected calibration model may be configured for at least partially compensating temperature drifts of the spectrometer device, specifically of the detector element of the spectrometer device, at the specific temperature, e.g. at the temperature of the detector element. The temperature-corrected calibration model may comprise at least one temperature-corrected item of calibration information which can be used for temperature compensation of temperature drifts at the spectrometer device, specifically for at least partially compensating temperature drifts of the detector element of the spectrometer device. The temperature-corrected calibration model may specifically comprise a plurality of temperature-corrected items of calibration information, each temperature-corrected item of calibration information being configured for at least partially compensating a temperature drift at the spectrometer device at a certain temperature or for a certain temperature change. The temperature-corrected items of calibration information may be obtained by using the plurality of items of calibration information of the predetermined calibration model, the open port detector signal and the temperature of the detector element.

The term “taking into account” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process of considering at least one first item of information during determination of a second item of information. For example, the determining of the temperature-corrected calibration model taking using the predetermined calibration model and taking into account the open port detector signal and the temperature of the detector element may comprise considering the open port detector signal and the temperature of the detector element during determination of the temperature-corrected calibration model.

The process of determining the temperature of the detector element and/or determining the temperature-corrected calibration model may be performed by using at least one evaluation unit. Specifically, the spectrometer device may comprise at least one evaluation unit. The term “evaluation unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device or a combination of devices configured to evaluate or process at least one first item of information, in order to determine at least one second item of information thereof. Thus, specifically, the evaluation unit may be configured for processing at least one input signal and to generate at least one output signal thereof. The at least one input signal, as an example, may comprise the at least one detector signal, specifically the open port detector signal, provided directly or indirectly by the at least one detector element and, additionally, at least one signal directly or indirectly provided by the temperature sensor.

As an example, the evaluation unit may be or may comprise one or more integrated circuits, such as one or more application-specific integrated circuits (ASICs), and/or one or more data processing devices, such as one or more of computers, digital signal processors (DSP), field programmable gate arrays (FPGA) preferably one or more microcomputers and/or microcontrollers. Additional components may be comprised, such as one or more preprocessing devices and/or data acquisition devices, such as one or more devices for receiving and/or preprocessing of the detector signals, such as one or more AD-converters and/or one or more filters. Further, the evaluation unit may comprise one or more data storage devices. Further, the evaluation unit may comprise one or more interfaces, such as one or more wireless interfaces and/or one or more wire-bound interfaces.

The at least one evaluation unit may be adapted to execute at least one computer program, such as at least one computer program performing or supporting the step of determining the items of information. As an example, one or more algorithms may be implemented which, by using the predefined calibration model, the open port detector signal and the temperature of the detector element, as input variables, may perform a predetermined transformation for deriving the temperature-corrected calibration model. For this purpose, the evaluation unit may, particularly, comprise at least one data processing device, also referred to as a processor, in particular an electronic data processing device, which can be designed to generate the desired information by evaluating the detector signal and further items of information. The evaluation unit may use an arbitrary process for generating the required information, such as by calculation and/or using at least one stored and/or known relationship. The evaluation unit specifically may be configured for performing at least one digital signal processing (DSP) technique on the primary detector signal or any secondary detector signal derived thereof.

The temperature-corrected calibration model may be configured for compensating variations in the detector signal due to temperature changes. The term “variation” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to temperature-induced changes of the detector signal. Specifically, as outlined above, the detector element may be a temperature-sensitive element. The detector signal may vary with varying temperatures even if the illumination of the detector element is constant. The variation in the detector signal may thus also be referred to as “temperature drift”.

The term “temperature change” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an increase and/or a decrease in temperature. The temperature change may specifically comprise an increase and/or a decrease in the temperature of the detector element starting at an initial temperature and, optionally, a return of the temperature of the detector element to the initial temperature. Specifically, in the latter case, a hysteresis effect may occur at the detector element comprising the variation in the detector signal of the detector element after return to the initial temperature.

The determining of the at least one temperature-corrected calibration model may comprise adapting the predetermined calibration model to match the open port detector signal at the temperature of the detector element.

The predetermined calibration model may comprises at least one mathematical function S_o assigning predetermined open port detector signals to each temperature within the temperature range. For example, the mathematical function S_o may be given by a polynomial S_o = * T^l, wherein Et denotes temperature parameter of the predetermined calibration model, wherein T denotes the temperature of the detector element. However, other functions, such as power functions, rational functions and/or combinations thereof, are also feasible. As an example, the mathematical function S_o may be given by a second order polynomial S_o = E_o + E_± * T + E₂ * T². The determining of the temperature-corrected calibration model may comprise determining at least one offset such that the mathematical function S_o matches the open port detector signal at the temperature of the detector element. In case the mathematical function is given by a second order polynomial S_o = E₀ + E₁ * T + E₂ * T², the temperature-corrected calibration model may be given by S_o* = (E_o + A) + E_± * T + E₂ * T² , wherein A denotes the offset. Alternatively or additionally, the determining of the at least one temperature-corrected calibration model may comprise determining at least one linear approximation of the mathematical function S_o at the open port detector signal at the temperature of the detector element. The linear approximation may specifically be determined in case a temperature variation may be less than 2 K, preferably less than 1 K, more preferably less than 500 mK, most preferably less than 250 mK. The temperature variation may refer to a temperature difference between the temperature of the detector element during the determination of the open port detector signal and the temperature of the detector element during a determination of an object detector signal. For example, as outlined above, the mathematical function S_o may be given by a second order polynomial S_o = E₀ + E₁ * T + E₂ * T². The linear approximation may then be given by S_o ^! = E_± + E₂ * T. The temperature-corrected calibration model may be evaluated at the temperature of the detector element during a determination of an object detector signal to obtain a temperature-corrected open port detector signal.

The method may be at least partially computer-implemented, specifically at least step iv.. The term “computer-implemented” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a process which is fully or partially implemented by using a data processing means, such as data processing means comprising at least one processing unit. The method, specifically step iv., may be computer-implemented, e.g. by using the evaluation unit of the spectrometer device. Further, method steps i. to ill. may be at least computer-controlled or computer-assisted, e.g. by using the evaluation unit of the spectrometer device.

In a further aspect of the present invention, a method of determining at least one calibrated optical property of at least one object is disclosed.

The term “optical property” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an item of information, e.g. on at least one object and/or radiation emitted by at least one object, characterizing at least one optical property of the object, more specifically at least one item of information characterizing, e.g. qualifying and/or quantifying, at least one of a transmission, an absorption, a reflection and an emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one intensity information, e.g. information on an intensity of light being at least one of transmitted, absorbed, reflected or emitted by the object, e.g. as a function of a wavelength or wavelength sub-range over one or more wavelengths, e.g. over a range of wavelengths. Specifically, the intensity information may correspond to or be derived from the signal intensity, specifically the electrical signal, recorded by the spectrometer device with respect to a wavelength or a range of wavelengths of the spectrum. The term “calibrated” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an item of information obtained by using at least one calibration or at least one calibrated device. Thus, specifically, the calibrated optical property may be obtained by using a calibrated spectrometer device, more specifically the spectrometer device being calibrated by using the method for calibrating a spectrometer device according to the present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below.

The term “object” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary body, chosen from a living object and a non-living object. Thus, as an example, the at least one object may comprise one or more articles and/or one or more parts of an article, wherein the at least one article or the at least one part thereof may comprise at least one component which may provide a spectrum suitable for investigations. Additionally or alternatively, the object may be or may comprise one or more living beings and/or one or more parts thereof, such as one or more body parts of a human being, e.g. a user, and/or an animal. The object specifically may comprise at least one sample which may fully or partially be analyzed by spectroscopic methods. As an example, the object may be or may comprise at least one of: human or animal skin; edibles, such as fruits; plastics and textile.

The method comprises the following steps which, as an example, may be performed in the given order. It shall be noted, however, that a different order is also possible. Further, it is also possible to perform one, more than one or even all of the method steps once or repeatedly. Further, it is possible to perform two or more of the method steps simultaneously or in a timely overlapping fashion. The method may comprise further method steps which are not listed.

The method comprises: a. determining at least one temperature-corrected calibration model by performing the method for calibrating a spectrometer device according to the present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below; b. illuminating the detector element via the sample interface having the at least one object applied to the sample interface to obtain at least one object detector signal; and c. determining the at least one calibrated optical property of the at least one object by using the object detector signal and the temperature-corrected calibration model.

In the method, step c. may comprise evaluating the temperature-corrected calibration model to obtain at least one actual item of calibration information, specifically at least one open port detector signal, at a temperature of the object measurement in step b.. Specifically, the temperature of the object measurement may be determined by using the temperature sensor of the spectrometer device. For example, in case the spectrometer device comprises two or more temperature sensors, the temperature of the object measurement in step b. may be determined by averaging the temperature readings from the two or more temperature sensors. Further, the item of calibration information may be used for determining the at least one calibrated optical property of the at least one object.

For possible embodiments of the spectrometer device and definitions of terms, reference is made to the description of the method for calibrating a spectrometer device above.

In a further aspect of the present invention, a spectrometer device is disclosed, comprising at least one detector element configured for generating at least one detector signal in response to an illumination of the detector element by incident light. The spectrometer device further comprises at least one light source configured for emitting illumination light in at least one optical spectral range. The spectrometer device further comprises at least one sample interface configured for allowing the illumination light from the light source to illuminate at least one object and configured for allowing detection light from the object to propagate to the detector element. The spectrometer device further comprises at least one temperature sensor configured for determining at least one temperature of the detector element. The spectrometer device further comprise at least one evaluation unit configured for evaluating the detector signal. The spectrometer device is configured for performing a method of determining at least one calibrated optical property of at least one object according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below.

In a further aspect of the present invention, a computer program is disclosed, comprising instructions which, when the program is executed by the spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method for calibrating a spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below.

Similarly, a computer-readable storage medium, specifically a non-transient computer-readable storage medium, is disclosed, comprising instructions which, when the instructions are executed by the spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method for calibrating a spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below. In a further aspect of the present invention, a computer program is disclosed, comprising instructions which, when the program is executed by the spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method of determining at least one calibrated optical property of at least one object according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below.

Similarly, a computer-readable storage medium, specifically a non-transient computer-readable storage medium, is disclosed, comprising instructions which, when the instructions are executed by the spectrometer device according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method of determining at least one calibrated optical property of at least one object according to present invention, such as according to any one of the embodiments disclosed above and/or according to any one of the embodiments disclosed in further detail below.

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

The spectrometer device and the methods according to the present invention, in one or more of the above-mentioned embodiments and/or in one or more of the embodiments described in further detail below, provide a large number of advantages over known devices and methods of similar kind. Specifically, the spectrometer device and the methods according to the present invention may provide a compensation of detrimental effects due to temperature drift and due to aging, hysteresis and/or contamination at the spectrometer device. The method for calibrating a spectrometer device may correct for both effects of temperature and aging on the detector signal variation. The method allows for accounting for aging, hysteresis, and/or contamination of the spectrometer device, such as smear and scratches on the sample interference, by using a measurement without sample to obtain the open port detector signal. Additionally, the temperature determination may allow for accounting for temperature effects using the predetermined calibration model. Both effects may be combined by correcting the calibration model based on the open port detector signal measurement and the temperature measurement. Further, the method for calibrating a spectrometer device may allow correction of a calibration process of the spectrometer device to enhance the performance of the produced signal. Additionally, it may be possible to test the aging problem of the spectrometer device. As an example, the method for calibration a spectrometer device may comprise calibrating the temperature behavior of the open port detector signal from the spectrometer device under a defined temperature range. The method may further comprise taking one open port measurement only with the background light in the spectrometer device. The method may further comprise using the measured open port detector signal to correct the predetermined calibration model and using the corrected calibration model to predict the open port detector signal at the temperature of the sample measurement.

As used herein, the terms “have”, “comprise” or “include” or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions “A has B”, “A comprises B” and “A includes B” may both refer to a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

Further, it shall be noted that the terms “at least one”, “one or more” or similar expressions indicating that a feature or element may be present once or more than once typically are used only once when introducing the respective feature or element. In most cases, when referring to the respective feature or element, the expressions “at least one” or “one or more” are not repeated, nonwithstanding the fact that the respective feature or element may be present once or more than once.

Further, as used herein, the terms "preferably", "more preferably", "particularly", "more particularly", "specifically", "more specifically" or similar terms are used in conjunction with optional features, without restricting alternative possibilities. Thus, features introduced by these terms are optional features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such way with other optional or non-optional features of the invention.

Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

Embodiment 1 : A method for calibrating a spectrometer device, the spectrometer device comprising at least one detector element configured for generating at least one detector signal in response to an illumination of the detector element by incident light, the spectrometer device further comprising at least one light source configured for emitting illumination light in at least one optical spectral range, the spectrometer device further comprising at least one sample interface configured for allowing the illumination light from the light source to illuminate at least one object and configured for allowing detection light from the object to propagate to the detector element, the spectrometer device further comprising at least one temperature sensor configured for determining at least one temperature of the detector element, wherein the method comprises: i. providing at least one predetermined calibration model, wherein the predetermined calibration model comprises a plurality of items of calibration information for at least one temperature range;

Embodiment 2: The method according to the preceding embodiment, wherein the temperature-corrected calibration model is configured for compensating variations in the detector signal due to temperature changes.

Embodiment 3: The method according to any one of the preceding embodiments, wherein the predetermined calibration model comprises the plurality of items of calibration information as a function of temperature in the temperature range.

Embodiment 4: The method according to the preceding embodiment, wherein the plurality of items of calibration information comprise predetermined open port signals.

Embodiment 5: The method according to any one of the preceding embodiments, wherein the predetermined calibration model comprises at least one relation relating open port detector signals and temperatures in the temperature range.

Embodiment 6: The method according to any one of the preceding embodiments, wherein the predetermined calibration model is determined in a factory calibration.

Embodiment 7: The method according to any one of the preceding embodiments, wherein the determining of the at least one temperature-corrected calibration model comprises adapting the predetermined calibration model to match the open port detector signal at the temperature of the detector element.

Embodiment 8: The method according to any one of the preceding embodiments, wherein the predetermined calibration model comprises at least one mathematical function S_o assigning predetermined open port detector signals to each temperature within the temperature range. Embodiment 9: The method according to the preceding embodiment, wherein the mathematical function S_o is given by a polynomial S_o = i oE; * T^l, wherein Et denotes temperature parameter of the predetermined calibration model, wherein T denotes the temperature of the detector element.

Embodiment 10: The method according to any one of the two preceding embodiments, wherein the mathematical function S_o is given by a second order polynomial S_o = E_o + E_± * T + E₂ * T².

Embodiment 11 : The method according to any one of the three preceding embodiments, wherein the determining of the temperature-corrected calibration model comprises determining at least one offset such that the mathematical function S_o matches the open port detector signal at the temperature of the detector element.

Embodiment 12: The method according to the preceding embodiment, wherein the mathematical function is given by a second order polynomial S_o = E₀ + E₁ * T + E₂ * T², wherein the temperature-corrected calibration model is given by S_o* = (E_o + A) + E_± * T + E₂ * T² , wherein A denotes the offset.

Embodiment 13: The method according to any one of the five preceding embodiments, wherein the determining of the at least one temperature-corrected calibration model comprises determining at least one linear approximation of the mathematical function S_o at the open port detector signal at the temperature of the detector element.

Embodiment 14: The method according to the preceding embodiment, wherein the linear approximation is determined in case a temperature variation is less than 2 K, preferably less than 1 K, more preferably less than 500 mK, most preferably less than 250 mK.

Embodiment 15: The method according to any one the two preceding embodiments, wherein the mathematical function S_o is given by a second order polynomial S_o = E_o + E_± * T + E₂ * T², wherein the linear approximation is given by S_o' = E₁ + E₂ * T.

Embodiment 16: The method according to anyone of the preceding embodiments, wherein the method is at least partially computer-implemented.

Embodiment 17: A method of determining at least one calibrated optical property of at least one object, the method comprising: a. determining at least one temperature-corrected calibration model by performing the method for calibrating a spectrometer device according to any one of the preceding embodiments; b. illuminating the detector element via the sample interface having the at least one object applied to the sample interface to obtain at least one object detector signal; and c. determining the at least one calibrated optical property of the at least one object by using the object detector signal and the temperature-corrected calibration model.

Embodiment 18: The method according to the preceding embodiment, wherein step c. comprises evaluating the temperature-corrected calibration model to obtain at least one actual item of calibration information, specifically at least one open port detector signal, at a temperature of the object measurement in step b..

Embodiment 19: The method according to the preceding embodiment, wherein the item of calibration information is used for determining the at least one calibrated optical property of the at least one object.

Embodiment 20: A spectrometer device comprising at least one detector element configured for generating at least one detector signal in response to an illumination of the detector element by incident light, the spectrometer device further comprising at least one light source configured for emitting illumination light in at least one optical spectral range, the spectrometer device further comprising at least one sample interface configured for allowing the illumination light from the light source to illuminate at least one object and configured for allowing detection light from the object to propagate to the detector element, the spectrometer device further comprising at least one temperature sensor configured for determining at least one temperature of the detector element, the spectrometer device further comprising at least one evaluation unit configured for evaluating the detector signal, wherein the spectrometer device is configured for performing a method of determining at least one calibrated optical property of at least one object according to any one of the preceding embodiments referring to a method of determining at least one calibrated optical property of at least one object.

Embodiment 21 : A computer program comprising instructions which, when the program is executed by the spectrometer device according to any one of the preceding embodiments referring to a spectrometer device, cause the spectrometer device to perform the method for calibrating a spectrometer device according to any one of the preceding embodiments referring to a method for calibrating a spectrometer device.

Embodiment 22: A computer-readable storage medium, specifically a non-transient computer- readable storage medium, comprising instructions which, when the instructions are executed by the spectrometer device according to any one of the preceding embodiments referring to a spectrometer device, cause the spectrometer device to perform the method for calibrating a spectrometer device according to any one of the preceding embodiments referring to a method for calibrating a spectrometer device.

Embodiment 23: A computer program comprising instructions which, when the program is executed by the spectrometer device according to any one of the preceding embodiments referring to a spectrometer device, cause the spectrometer device to perform the method of determining at least one calibrated optical property of at least one object according to any one of the preceding embodiments referring to a method of determining at least one calibrated optical property of at least one object.

Embodiment 24: A computer-readable storage medium, specifically a non-transient computer- readable storage medium, comprising instructions which, when the instructions are executed by the spectrometer device according to any one of the preceding embodiments referring to a spectrometer device, cause the spectrometer device to perform the method of determining at least one calibrated optical property of at least one object according to any one of the preceding embodiments referring to a method of determining at least one calibrated optical property of at least one object.

Short description of the Figures

Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

In the Figures:

Figure 1 shows an embodiment of a spectrometer device in a schematic view;

Figure 2 shows a flow chart of an embodiment of a method for calibrating a spectrometer device;

Figures 3A and 3B show different examples of temperature-corrected calibration models;

Figure 4 shows a flow chart of an embodiment of a method of determining at least one calibrated optical property of at least one object; and

Figures 5A and 5B shows exemplary results of the method of determining at least one calibrated optical property of at least one object.

Detailed description of the embodiments

Figure 1 shows an exemplary embodiment of a spectrometer device 110 in a schematic view. The spectrometer device 110 may, as an example, be a portable spectrometer device. Specifically, the portable spectrometer device may be part of a mobile device (not shown in the Figure) or may be attachable to a mobile device, such as a notebook computer, a tablet, a cell phone, such as a smart phone, a smartwatch and/or a wearable computer, e.g. a body borne computer such as a wrist band or a watch.

The spectrometer device 110 comprises at least one detector element 112 configured for generating at least one detector signal in response to an illumination of the detector element 112 by incident light. In the exemplary embodiment of Figure 1 , the detector element 112 may comprise a plurality of optically sensitive elements (not shown in Figure 1 ). Specifically, the detector element 112 may be or may comprise at least one detector array 114, more specifically an array of optically sensitive elements. For example, the detector element 112 may comprise a number of nine optically sensitive elements arranged in a two-dimensional detector array. Each of the optically sensitive elements may comprise at least a photosensitive area which may be adapted for generating an electrical signal depending on the intensity of the incident light, wherein the electrical signal may, in particular, be provided to an evaluation unit 116, as will be outlined in further detail below.

The spectrometer device 110 further comprises at least one light source 118 configured for emitting illumination light 120 in at least one optical spectral range. For example, the light source 118 may comprise at least one light-emitting diode 122 and at least one luminescent material 124 for light-conversion of primary light generated by the light-emitting diode 122, wherein, specifically, the illumination light 120 may be a combination of the primary light and light generated by the light-conversion by the luminescent material 124 or light generated by the light conversion of the luminescent material 124, also referred to as secondary light. As an example, the LED 122 and the luminescent material 122 may form a so-called phosphor LED. However, other light sources 118 are also feasible.

The spectrometer device 110 further comprises at least one sample interface 126 configured for allowing the illumination light 120 from the light source 118 to illuminate at least one object 128 and configured for allowing detection light 130 from the object 128 to propagate to the detector element 112.

As can be seen in Figure 1 , the spectrometer device 110 may further comprise at least one wavelength-selective element 132. In the exemplary embodiment of Figure 1 , the wavelength selection by the at least one wavelength-selective element 132 may take place in the detection beam path of the detection light 130, thereby selecting and/or modifying a wavelength of detection, e.g. for the detector element 112 in general and/or for each of the optically sensitive elements. However, additionally or alternatively, a wavelength selection in the beam part of the illumination light 120 may also be possible. Thus, the at least one wavelength-selective element 132 may comprise a wavelength-selective element disposed in a beam path of the detection light 130. The wavelength-selective element 132 may comprise at least one of a filter, a grating, a prism, a plasmonic filter, a diffractive optical element and a metamaterial. More specifically, the spectrometer device 110 may comprise at least one filter element disposed in a beam path of the light from the object 128, i.e. in the beam path of the detection light 130, wherein the filter element, specifically may be configured such that each of the optically sensitive elements is exposed to an individual spectral range of the light from the object 128. As an example, a variable filter element may be used, the transmission of which depends on a position on the filter element, such that, when the variable filter element is placed on top of the array of optically sensitive elements, the individual optically sensitive elements are exposed to differing spectral ranges of the incident light, specifically the detection light 130 from the object 128.

The spectrometer device 110 further comprises at least one temperature sensor 134 configured for determining at least one temperature of the detector element 112. As outlined above, in this example, the detector element 112 may comprise the detector array 114 with a plurality of optically sensitive elements. The spectrometer device 100 may specifically comprise at least one temperature sensor 134 for each optically sensitive element. The spectrometer device 110 may comprise at least one temperature sensor 134 associated with each optically sensitive element to determine the temperature of each optically sensitive element. For example, the temperature sensor 134 may be or may comprise at least one of an integrated circuit (IC) sensor, a thermistor, a resistive temperature detector (RTD) and a thermocouple.

The spectrometer device 110 further comprise the at least one evaluation unit 116 configured for evaluating the detector signal. As indicated in Figure 1 , the evaluation unit 116 may be connected to the detector element 112 and/or to the temperature sensor 134 to receive at least one of the detector signal and the temperature therefrom, respectively. The spectrometer device 110 is configured for performing a method of determining at least one calibrated optical property of at least one object 128 according to present invention, such as according to the exemplary embodiment shown in Figure 4 and/or according to any other embodiment disclosed herein. Thus, for a description of the method of determining at least one calibrated optical property, reference is made to the description of Figure 4.

Figure 2 shows a flow chart of an embodiment of a method for calibrating a spectrometer device 110 (denoted by reference number 136). The spectrometer device 110 comprises the at least one detector element 112 configured for generating at least one detector signal in response to an illumination of the detector element 112 by incident light. The spectrometer device 110 further comprises the at least one light source 118 configured for emitting illumination light 120 in at least one optical spectral range. The spectrometer device 110 further comprises the at least one sample interface 126 configured for allowing the illumination light 120 from the light source 118 to illuminate the at least one object 128 and configured for allowing detection light 130 from the object 128 to propagate to the detector element 112. The spectrometer device 110 further comprises the at least one temperature sensor 134 configured for determining at least one temperature of the detector element 112. The spectrometer device 110 may specifically be embodied as shown in the exemplary embodiment of Figure 1 . Thus, for a detailed description of the spectrometer device 110, reference is made to the description of Figure 1 .

The method comprises: i. (denoted by reference number 138) providing at least one predetermined calibration model, wherein the predetermined calibration model comprises a plurality of items of calibration information for at least one temperature range;

II. (denoted by reference number 140) illuminating the detector element 112 via the sample interface 126 having no object 128 applied to the sample interface 126 to obtain at least one open port detector signal; ill. (denoted by reference number 142) determining at least one temperature of the detector element 112; and iv. (denoted by reference number 144) determining at least one temperature-corrected calibration model using the predetermined calibration model and taking into account the open port detector signal and the temperature of the detector element 112.

The predetermined calibration model may comprise the plurality of items of calibration information as a function of temperature in the temperature range. For example, the plurality of items of calibration information may comprise predetermined open port signals. The predetermined calibration model may comprise at least one relation relating open port detector signals and temperatures in the temperature range.

The determining of the at least one temperature-corrected calibration model may comprise adapting the predetermined calibration model to match the open port detector signal at the temperature of the detector element 112.

Exemplary embodiments of predetermined calibration models 146 and temperature-corrected calibration models 148 are shown in Figures 3A and 3B. Specifically, Figures 3A and 3B show diagrams with a signal intensity 150 of open port detector signals as a function of temperature 152. In the Figures, the temperature of the detector element 112 determined in step ill. of the method may be denoted by reference number 154 and the open port detector signal determined in step II. of the method may be denoted by reference number 156.

In the exemplary embodiments of Figures 3A and 3B, the predetermined calibration model 146 may comprises at least one mathematical function S_o assigning predetermined open port detector signals to each temperature within the temperature range. For example, the mathematical function S_o may be given by a polynomial S_o = i o E; * T^l, wherein Et denotes temperature parameter of the predetermined calibration model 146, wherein T denotes the temperature of the detector element 112. However, other functions, such as power functions, rational functions and/or combinations thereof, are also feasible. As an example, the mathematical function S_o may be given by a second order polynomial S_o = E_o + E_± * T + E₂ * T². As shown in Figure 3A, the determining of the temperature-corrected calibration model 148 may comprise determining at least one offset 158 such that the mathematical function S_o matches the open port detector signal 156 at the temperature 154 of the detector element 112. In case the mathematical function is given by a second order polynomial S_o = E_o + E₁ * T + E₂ * T², the temperature-corrected calibration model 148 may be given by S_o* = (E_o + A) + E_± * T + E₂ * T² , wherein A denotes the offset 158.

Alternatively or additionally, as shown in Figure 3B, the determining of the at least one temperature-corrected calibration model 148 may comprise determining at least one linear approximation 160 of the mathematical function S_o at the open port detector signal 156 at the temperature 154 of the detector element 112. The linear approximation 158 may specifically be determined in case a temperature variation 162 may be less than 2 K, preferably less than 1 K, more preferably less than 500 mK, most preferably less than 250 mK. The temperature variation 162 may refer to a temperature difference between the temperature 154 of the detector element 112 during the determination of the open port detector signal 156 and the temperature 164 of the detector element 112 during a determination of an object detector signal. For example, as outlined above, the mathematical function S_o may be given by a second order polynomial S_o = E_o + E_± * T + E₂ * T². The linear approximation 158 may then be given by S_o' = E_± + E₂ * T. The temperature-corrected calibration model 148 may be evaluated at the temperature 164 of the detector element 112 during a determination of an object detector signal to obtain a temperature-corrected open port detector signal 166.

Figure 4 shows a flow chart of an embodiment of a method of determining at least one calibrated optical property of at least one object 128. In the method, a spectrometer device 110 according to the present invention, such as according to the exemplary embodiment of Figure 1 and/or according to any other embodiment disclosed herein, may be used. Thus, for a detailed description of the spectrometer device 110, reference is made to the description of Figure 1 .

The method comprises: a. (denoted by reference number 136) determining at least one temperature-corrected calibration model 148 by performing the method for calibrating a spectrometer device according to the present invention, such as according to the exemplary embodiment shown in Figure 2 and/or according to any other embodiment disclosed herein; b. (denoted by reference number 168) illuminating the detector element 112 via the sample interface 126 having the at least one object 128 applied to the sample interface 126 to obtain at least one object detector signal; and c. (denoted by reference number 170) determining the at least one calibrated optical property of the at least one object 128 by using the object detector signal and the temperature- corrected calibration model 148.

In the method, step c. may comprise evaluating the temperature-corrected calibration model 148 to obtain at least one actual item of calibration information, specifically at least one open port detector signal, at a temperature of the object measurement in step b.. Specifically, the temperature of the object measurement may be determined by using the temperature sensor 134 of the spectrometer device 110. For example, in case the spectrometer device 110 comprises two or more temperature sensors 134, the temperature of the object measurement in step b. may be determined by averaging the temperature readings from the two or more temperature sensors 134. Further, the item of calibration information may be used for determining the at least one calibrated optical property of the at least one object 128.

Figures 5A and 5B shows exemplary results of the method of determining at least one calibrated optical property of at least one object 128. Specifically, Figure 5A shows a temperature behavior of an optical property 172 of the object 128 as a function of temperature 152 which was obtained without performing the method for calibrating a spectrometer device 110, wherein Figure 5B shows a temperature behavior of an optical property 172 of the object 128 as a function of temperature 152 which was obtained by performing the method of determining at least one calibrated optical property of at least one object 128, i.e. with performing the method for calibrating a spectrometer device 110. In Figure 5A, the non-calibrated optical property is denoted by reference number 174. In Figure 5B, the calibrated optical property is denoted by reference number 176. In this example, the optical property 172 is an indirect optical property of the object 128. The optical property 172 may be a moisture score of the object 128 obtained by evaluating an absorption of the object 128 at different wavelengths. However, alternatively of additionally, the optical property 172 may also be directly the absorption and/or reflection coefficient of the object 128 at a specific wavelength. As indicated in Figures 5A and 5B by the arrow in the diagrams, the calibrated optical property 176 of Figure 5B shows less temperature dependency than the non-calibrated optical property 174 of Figure 5A. Thus, the method for calibrating a spectrometer device 110 may improve performance of the calibrated spectrometer device 110 due to a corrected calibration.

List of reference numbers spectrometer device detector element detector array evaluation unit light source illumination light light-emitting diode luminescent material sample interface object detection light wavelength-selective element temperature sensor method for calibrating a spectrometer device providing a predetermined calibration model illuminating the detector element determining a temperature determining a temperature-corrected calibration model predetermined calibration model temperature-corrected calibration model signal intensity temperature temperature of the detector element at open port detector signal determination open port detector signal offset linear approximation temperature variation temperature of the detector element at object detector signal determination temperature-corrected open port detector signal illuminate the detector element determining a calibrated optical property optical property non-calibrated optical property calibrated optical property

Claims

1 . A method for calibrating a spectrometer device (110), the spectrometer device (110) comprising at least one detector element (112) configured for generating at least one detector signal in response to an illumination of the detector element (112) by incident light, the spectrometer device (110) further comprising at least one light source (118) configured for emitting illumination light (120) in at least one optical spectral range, the spectrometer device (110) further comprising at least one sample interface (126) configured for allowing the illumination light (120) from the light source (118) to illuminate at least one object (128) and configured for allowing detection light (130) from the object (128) to propagate to the detector element (112), the spectrometer device (110) further comprising at least one temperature sensor (134) configured for determining at least one temperature of the detector element (112), wherein the method comprises: i. providing at least one predetermined calibration model (146), wherein the predetermined calibration model (146) comprises a plurality of items of calibration information for at least one temperature range; ii. illuminating the detector element (112) via the sample interface (126) having no object (128) applied to the sample interface (126) to obtain at least one open port detector signal (156); iii. determining at least one temperature (154) of the detector element (112); and iv. determining at least one temperature-corrected calibration model (148) using the predetermined calibration model (146) and taking into account the open port detector signal (156) and the temperature (154) of the detector element (112).

2. The method according to the preceding claim, wherein the temperature-corrected calibration model (148) is configured for compensating variations in the detector signal due to temperature changes.

3. The method according to any one of the preceding claims, wherein the predetermined calibration model (146) comprises the plurality of items of calibration information as a function of temperature in the temperature range, wherein the plurality of items of calibration information comprise predetermined open port signals.

4. The method according to any one of the preceding claims, wherein the determining of the at least one temperature-corrected calibration model (148) comprises adapting the predetermined calibration model (146) to match the open port detector signal (156) at the temperature (154) of the detector element (112).

5. The method according to any one of the preceding claims, wherein the predetermined calibration model (146) comprises at least one mathematical function S_o assigning predetermined open port detector signals to each temperature within the temperature range.

6. The method according to the preceding claim, wherein the mathematical function S_o is given by a polynomial S_o = i oE; * T^l, wherein Et denotes temperature parameter of the predetermined calibration model (146), wherein T denotes the temperature of the detector element (112).

7. The method according to any one of the two preceding claims, wherein the determining of the temperature-corrected calibration model (148) comprises determining at least one offset (158) such that the mathematical function S_o matches the open port detector signal

(156) at the temperature (154) of the detector element (112).

8. The method according to the preceding claim, wherein the mathematical function is given by a second order polynomial S_o = E_o + E₁ * T + E₂ * T² , wherein the temperature-corrected calibration model (148) is given by S_o* = (E_o + A) + E_± * T + E₂ * T² , wherein A denotes the offset (158).

9. The method according to any one of the four preceding claims, wherein the determining of the at least one temperature-corrected calibration model (148) comprises determining at least one linear approximation (160) of the mathematical function S_o at the open port detector signal (156) at the temperature (154) of the detector element (112).

10. The method according to the preceding claim, wherein the linear approximation (160) is determined in case a temperature variation (162) is less than 2 K.

11 . The method according to any one the two preceding claims, wherein the mathematical function S_o is given by a second order polynomial S_o = E₀ + E₁ * T + E₂ * T², wherein the linear approximation (148) is given by S_o' = E_± + E₂ * T.

12. A method of determining at least one calibrated optical property (176) of at least one object (128), the method comprising: a. determining at least one temperature-corrected calibration model (148) by performing the method for calibrating a spectrometer device (110) according to any one of the preceding claims; b. illuminating the detector element (112) via the sample interface (126) having the at least one object (128) applied to the sample interface (126) to obtain at least one object detector signal; and c. determining the at least one calibrated optical property (176) of the at least one object (128) by using the object detector signal and the temperature-corrected calibration model (148).

13. A spectrometer device (110) comprising at least one detector element (112) configured for generating at least one detector signal in response to an illumination of the detector element (112) by incident light, the spectrometer device (110) further comprising at least one light source (118) configured for emitting illumination light (120) in at least one optical spectral range, the spectrometer device (110) further comprising at least one sample interface (126) configured for allowing the illumination light (120) from the light source (118) to illuminate at least one object (128) and configured for allowing detection light (130) from the object (128) to propagate to the detector element (112), the spectrometer device (110) further comprising at least one temperature sensor (134) configured for determining at least one temperature (154) of the detector element (112), the spectrometer device (110) further comprising at least one evaluation unit (116) configured for evaluating the detector signal, wherein the spectrometer device (110) is configured for performing a method of determining at least one calibrated optical property (176) of at least one object (128) according to the preceding claim.

14. A computer program comprising instructions which, when the program is executed by the spectrometer device (110) according to any one of the preceding claims referring to a spectrometer device (110), cause the spectrometer device (110) to perform the method for calibrating a spectrometer device (110) according to any one of the preceding claims referring to a method for calibrating a spectrometer device (110).

15. A computer program comprising instructions which, when the program is executed by the spectrometer device (110) according to any one of the preceding claims referring to a spectrometer device (110), cause the spectrometer device (110) to perform the method of determining at least one calibrated optical property (176) of at least one object (128) according to any one of the preceding claims referring to a method of determining at least one calibrated optical property (176) of at least one object (128).