Spectroscopy calibration based on LED signal relationship

Abstract

The present invention relates to a method for calibrating a spectrometer device (126) for obtaining items of calibration information, wherein the method comprises the following steps: 1) emitting first light (136) along a first beam path (134) onto a detector (132) of the spectrometer device (126) by using at least one first light emitting element (154) of the spectrometer device (126) in order to generate at least one first detector signal by at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the first beam path (134) is configured for first light (136) propagating along the first beam path (134) passing at least one sample interface (130) of the spectrometer device (126); wherein at least one calibration target is arranged on the sample interface (130) in a manner that the first light (136) interacts with the at least one calibration target having at least one known optical characteristic; 2) emitting second light (146) along a second beam path (144) onto the detector (132) by using at least one second light emitting element (156) of the spectrometer device (126) in order to generate at least one second detector signal by the at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the second beam path (144) is configured for second light (146) propagating along the second beam path (144) without passing the at least one sample interface (130) of the spectrometer device (126), 3) obtaining the items of calibration information xi, wherein items of calibration information xi are used to derive at least one item of spectral information R = Formula (l) with n ≥ 2 of an object (128), wherein the at least one item of spectral information depends on the at least one first detector signal S1 and the at least one second detector signal S2, wherein the items of calibration information xi are obtained by evaluating one or more data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal S1 and the generated at least one second detector signal S2.

Description

[0001] Spectroscopy Calibration Based on LED Signal Relationship

[0002] Technical Field

[0003] The invention relates to a method for calibrating a spectrometer device for obtaining items of calibration information, a method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object, a spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, a mobile device, a computer program and a non-transitory computer-readable storage medium.

[0004] The methods and devices according to the present invention specifically may be employed for example in various areas of daily life, security technology, gaming, traffic technology, production technology, photography such as digital photography or video photography for arts, documentation or technical purposes, safety technology, information technology, agriculture, crop protection, maintenance, cosmetics, medical technology or in the sciences. However, other applications are also possible.

[0005] Background art

[0006] Spectrometer devices are, typically, used for obtaining at least one item of spectral information on an object, such as a measurement object. For obtaining the item of spectral information, the object may be illuminated with illumination light in a manner that the object generates detection light. The received detection light may then be analyzed for obtaining the spectral information.

[0007] In this process an item of information derived in a calibration process, typically, is evaluated.

[0008] Usually, spectrometers are calibrated by using reference standards, such as by using a calibration target. This approach requires user interaction. For the consumer market, calibration should be done without user interaction.

[0009] In order to minimize user interactions, typical solutions use internal calibration targets. In this approach, a calibration target may be arranged inside of the spectrometer in a manner that reflection of emitted light may be detected in absence of an object at the sample interface. In a factory calibration, a relation between the reflection of the internal calibration target and a known reference standard may be obtained. Under the assumption that the relation between the internal target and the reference standard is constant and long term stable, the internal measurement using the internal target may be performed instead of using a reference standard.

[0010] The correction with the second light emitting element may not sufficiently deal with responsivity changes between an open port measurement and a sample measurement. Particularly, a hysteresis behavior of the detector cannot be corrected this way. Further, such a correction may have to utilize additional compensation schemes and non-ideal conditions due to the factory calibration of factors between the first light emitting element and the second light emitting element behavior. Further crosstalk between the light emitting elements may not be accounted for. In addition, non-linearity of the detector may not be accounted for and differences in detector response due to different modulation frequencies may not be accounted for.

[0011] Problem to be solved

[0012] It is therefore desirable to provide a method for calibrating a spectrometer device for obtaining items of calibration information, a method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object, a spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, a mobile device, a computer program and a non-transitory computer-readable storage medium, which at least partially address the above-mentioned technical challenges and at least substantially avoid the disadvantages of known methods and devices.

[0013] In particular, it is an object of the present invention to provide methods and devices that require minimum user interactions and account for effects related to the detector, which have not been considered for in a factory calibration procedure. In particular, it is an object of the present invention to provide methods and devices that account for effects related to the detector, which cannot be corrected in a factory calibration procedure, particularly since these effects change with time due to degradation and / or aging and / or drifting of at least one component of the spectrometer device, such as light emitting elements and / or detectors.

[0014] Summary

[0015] This problem is addressed by the method for calibrating a spectrometer device for obtaining items of calibration information, the method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object, the spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, the mobile device, the computer program and the non-transitory computer-readable storage medium 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.

[0016] In a first aspect, a method for calibrating a spectrometer device for obtaining items of calibration information is disclosed. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect.

[0017] The steps of the method for calibrating a spectrometer device for obtaining items of calibration information may be performed in the given order. A different order, however, may also be feasible. Further, two or more of the method steps may be performed simultaneously. Thereby, the method steps may at least partly overlap in time. Further, the method steps may be performed once or repeatedly. Thus, one or more or even all of the method steps may be performed once or repeatedly. The method may comprise additional method steps, which are not listed herein.

[0018] The method for calibrating a spectrometer device for obtaining items of calibration information may be a computer-implemented method. Alternatively or in addition, at least one of the method steps, preferably any one of the method steps, which involve the use of an evaluation unit, may be performed by using a device comprising at least one processor and / or a memory. The term "computer implemented method" 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 method, which involves at least one apparatus, specifically a computer, or a plurality of apparatus, particularly connected via a computer network. The plurality of apparatus may be connected, particularly for transmitting data, via a network by using at least one connection interface at any one of the apparatuses of the plurality of apparatus. The computer-implemented method may be implemented as at least one computer program that may be provided on a storage medium carrying the computer program, whereby at least one of the steps of the computer-implemented method are performed by using the at least one computer program. Preferably any one of the steps may be performed using the at least one computer program. Alternatively, the at least one computer program may be accessible by an apparatus which may be adapted for performing the method via a network, such as via an in-house network, via internet, or via a cloud. With particular regard to the present invention, the present method can, thus, be performed on a programmable apparatus, which is configured for this purpose, such as by providing a computer program, which is configured for such a purpose.

[0019] 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.

[0020] The method comprises the following steps:

[0021] 1 ) emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein at least one calibration target is arranged on the sample interface in a manner that the first light interacts with the at least one calibration target having at least one known optical characteristic;

[0022] 2) emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device,

[0023] 3) obtaining the items of calibration information xt, wherein the items of calibration information xtare used to derive at least one item of spectral information of an object, wherein the at least one item of spectral information depends the at least one first detector signal Si and the at least one second detector signal S2, wherein the items of calibration information xtare obtained by evaluating one or more data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal Si and the generated at least one second detector signal S2. The at least one item of spectral information may depend on a relationship between the at least one first detector signal Si and the at least one second detector signal S2. n may be a natural number larger than 2. n may be the order of the polynomial function.

[0024] As already disclosed, the method comprises emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein at least one calibration target is arranged on the sample interface in a manner that the first light interacts with the at least one calibration target having at least one known optical characteristic.

[0025] As further used herein, 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.

[0026] Consequently, the term “light emitting element”, also referred to as an “illumination 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, specifically “first light” and / or “second light” in the sense of the above-mentioned definition for the term “light”. The light emitting element specifically may be or may comprise at least one electrical light source. The “first light” and / or “second light” that is emitted by the respective light emitting element may be referred to as “illumination light”.

[0027] As further used herein, the term “detection 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 light that is generated by the object, particularly generated in an interaction of the illumination light with the object. The light may interact with the object by scattering, reflecting and / or transmitting. The detection light may be first light and / or second light that is reflected and / or scattered back through the sample interface to the at least one detector. At least a portion of the illumination light may be transmitted and / or absorbed by the object in a manner that it is not detected by the at least one detector. The “first light” and / or “second light” that is generated by the object and related to the respective light emitting element may be referred to as “detection light”.

[0028] The light emitting element may be a thermal radiator. The thermal radiator may be selected from an incandescent lamp or a thermal infrared emitter. The term “incandescent lamp” 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 electric light having a heatable element, such as a wire filament, which is capable of being heated to a temperature at which it emits light, especially infrared light. Since the incandescent lamp can, therefore, be considered as a thermal emitter within the infrared spectral range, an emission power of the incandescent lamp decreases with increasing wavelength. The thermal radiator may be selected from an incandescent lamp or a thermal infrared emitter. The term “thermal infrared emitter” 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 micro-machined thermally emitting device, which comprises a radiation emitting surface as the light emitting element that emits the optical radiation to be monitored.

[0029] Alternatively or in addition, the light emitting element may be a microelectromechanical system (MEMS)-based emitter. The term “microelectromechanical system (MEMS)-based emitter” 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 apparatus configured for generating and / or emitting light comprising at least one element, wherein the element is associated with MEMS technology. MEMS technology, typically, involves the manufacture of mechanical and / or electrical elements on a microscale, typically below 1 pm or 100 pm or 1 mm or 5 mm or 50 mm. Alternatively or in addition, the light emitting element may be a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region.

[0030] The term “vertical-cavity surface-emitting laser” 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 semiconductor laser diode configured for laser beam emission perpendicular with respect to a top surface. VCSELs are generally known to the skilled person such as from WO 2017 / 222618 A.

[0031] Alternatively or in addition, the radiation emitting element may be a light-emitting diode (LED), specifically a LED emitting light that is at least partially located in the infrared spectral range. Alternatively or in addition, the radiation emitting element may be a LED emitting light that is illuminating a luminescent material, specifically a phosphor, for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0032] 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 electron-hole 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.

[0033] Generally, the LED may convert electrical current into light, specifically light that is at least partially located in the infrared spectral range. Alternatively or in addition, LED may convert electrical current into primary light, more specifically into blue primary light. The LED, thus, specifically may be a blue LED. The LED may be configured for generating the primary light, particularly for the light-conversion in the phosphor, 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.

[0034] 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 with 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 photoluminescent 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.

[0035] 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 con- verging 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.

[0036] 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 Y3AI5O12:Ce3+); rare-earth-doped Sialons; copper- and aluminum-doped zinc sulfide (ZnS:Cu,AI).

[0037] 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.

[0038] The illumination light may have a spectral range at least partially located in the near-infrared spectral range, specifically in the spectral range from 1 to 3 pm, preferably from 1.3 to 2.5 pm, more preferably from 1 .5 to 2.2 pm.

[0039] The term “beam path” 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 trajectory or a route taken by a beam of light. The trajectory or the route taken by the beam of light may be through space and / or at least one optical component. The first beam path may be different from the second beam path, particularly in a manner that at least a portion of their trajectory or route differ.

[0040] The “first beam path” is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device. By passing the sample interface, the first light may leave the spectrometer device. The first beam path may be configured for directing the first light, specifically first illumination light, onto the object. Thereby, the first light may interact with the object in a manner that first detection light may be generated. When the first light interacted with the object, the first light might propagate to the detector and generate at least one detector signal.

[0041] The verb “to detect” 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 at least one of determining, measuring and monitoring at least one parameter, qualitatively and / or quantitatively, such as at least one of a physical parameter, a chemical parameter and a biological parameter. Specifically, the physical parameter may be or may comprise an electrical parameter. Consequently, the term “photosensitive detector”, or “detector” 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 detecting, i.e. for at least one of determining, measuring and monitoring at least one parameter, qualitatively and / or quantitatively, such as at least one of a physical parameter, a chemical parameter and a biological parameter. The at least one detector may be configured for generating at least one detector signal, more specifically at least one electrical detector signal, such as an analogue and / or a digital detector signal, the detector signal providing information on the at least one parameter measured by the detector. The detector signal may directly or indirectly be provided by the at least one detector to the evaluation unit, such that the at least one detector and the evaluation unit may be directly or indirectly connected. The detector signals 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 at least one detector 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 first detector signal may also be referred to as the “first detector signal S±“. The second detector signal may also be referred to as the “second detector signal S2“. A detector signal may be generated by the at least one detector of the spectrometer device.

[0042] The at least one detector may be configured for detecting light propagating from the object to the spectrometer device or more specifically to the at least one detector of the spectrometer device. The at least one detector 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 is irradiated. More specifically, the at least one detector 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 at least one detector, 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 or a sensitive area of the detector is illuminated. The at least one detector may be a Lead Sulfide (PbS) detector. The detector may comprise a plurality of photosensitive elements, wherein each of the photosensitive elements may be configured for generating at least one detector signal for deriving the spectral information. The plurality of photosensitive elements may be arranged in an array. The term “array” 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 series of optical sensors which may, preferably, be arranged in a single line as a one-dimensional matrix along the length of the length variable filter or in more than one line, especially in two, three, or four parallel lines, in form of a two-dimensional matrix, in particular, in order to receive most of the intensity of the incident light as possible. Thus, a number N of photosensitive elements in one direction may be higher compared to a number M of photosensitive elements in a further direction such that the one-dimensional 1 x N matrix or a rectangular two-dimensional M x N matrix may be obtained, wherein M < 10 and N > 10, preferably N > 20, more preferred N > 50. In addition, the matrixes may also be placed in a staggered arrangement.

[0043] The plurality of photosensitive elements may be sensitive to differing, particularly not overlapping, wavelength intervals. Particularly consequently, a first photosensitive element may detect light within a first wavelength range and a second photosensitive element may detect light within a second wavelength range, wherein the first and the second wavelength range are different from each other, particularly in a manner that the wavelength ranges do not overlap. There may be a third photosensitive element having a further different, particularly not overlapping, wavelength range, and so on.

[0044] The detector may comprise at least one of: at least one of photosensitive element; at least one readout circuitry; at least one bias voltage.

[0045] 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 an arbitrary surface, such as measurement surface, at which an object is intended to interact with an optical measurement system, such as the spectrometer device. The measurement surface may be a measurement plane. For interacting with the object, the spectrometer device may emit the illumination light, particularly in a manner that the object generates the detection light. In addition, the spectrometer may receive the detection light. Particularly to allow the interaction with the object as intended, the sample interface may define a measurement pose of the object. When the object assumes the measurement pose, particularly as defined by the sample interface, at least one of: receiving the illumination light by the object and, thereby, generating the detection light is performed in a manner as intended, such as that when the object assumes the measurement pose, the signal-to-noise ratio of the spectrometer device is minimized.

[0046] The term “measurement pose” 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 spe- cial or customized meaning. The term specifically may refer, without limitation, to a relative position and / or orientation of the object relative to the sample interface, which is intended to be assumed during the spectral measurement, particularly to allow an interaction between the spectrometer device and the object as intended, such as intended by the setup and / or arrangement of the components of the spectrometer device.

[0047] The term “calibration target” 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 reference object having known characteristics, such as a predetermined and / or a predefined characteristic, describing the interaction with light. The calibration target may be used to calibrate the spectrometer device. The at least one known optical characteristic may be at least one of: a reflectance; transmittance; a scattering behavior; a spectral characteristic; a surface roughness of the object, a spectral absorbance of the object. The at least one known optical characteristic may also be referred to as “known optical characteristic K". The calibration target may be an external calibration target.

[0048] The calibration target may be or may comprise a material selected from at least one of:

[0049] - at least one layer of Polytetrafluoroethylene (PTFE),

[0050] - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0051] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0052] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter;

[0053] - at least one optical grating.

[0054] PTFE may be solid and / or rough and / or porous, such as attained from sintering. The Metal coating may be or may comprise a flat surface or, preferably, a surface with known or defined roughness.

[0055] As already disclosed, the method comprises emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device.

[0056] The “second beam path” is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device. By not passing the sample interface, the second light may remain in the spectrometer device. An internal calibration target having at least one known optical characteristic may be arranged in the second beam path in a manner that the second light interacts with the at least one reference target. The second light may interact with at least one internal calibration target inside the spectrometer device in a manner that second detection light may be generated. When the second light interacted with the internal calibration target, the second light may propagate to the detector and generate at least one detector signal.

[0057] The term “internal calibration target” 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 calibration target integrated in the spectrometer device, in particular in the second beam path of the spectrometer device. Specifically, the internal calibration target may be configured for interacting with the second light, such as the second illumination light, in the second optical path in a predetermined or pre-defined manner. The internal calibration target may be configured for receiving the second light emitted from the light source and transferring the second light via the second beam path onto the wavelength selective element. In particular, the internal calibration target may be configured for ensuring that the illumination light emitted from the second light emitting element propagates via the second beam path to the wavelength selective element without passing the sample interface, e.g. by interacting with the second light, such as by reflecting and / or scattering and / or filtering and / or directing, the second light onto the optical filter.

[0058] The internal calibration target may comprise at least one diffusive reflective surface. The term “diffuse reflective surface” 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 surface configured for scattering incident light at a plurality of different angles, e.g. in ideal case Lambertian reflection. The internal calibration target may have diffusive scattering properties and a reflectance not equal to zero. Specifically, the internal calibration target may function as a diffuse mirror. The internal calibration target may comprise a surface roughness configured for generating a Lambertian reflection profile. The surface roughness may be selected such that a specular reflection on the surface has a Lambertian profile due to a ratio of the wavelength of the incident radiation and the surface roughness, thereby creating a “diffuse mirror”. The surface roughness may be selected depending on the wavelength of the impinging light, e.g. such that the reflection (e.g. Fresnel reflection generated by a metal or partial Fresnel and partial diffuse reflection generated by a dielectric material) has a Lambertian profile.

[0059] For example, the internal calibration target comprises one or more of: at least one layer of Polytetrafluoroethylene (PTFE), at least one optical coating, such as a white surface coating, e.g. available from Nextel® Suede coating 3101 , a dielectric coating, at least one partially reflective dielectric mirror, at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter. For example, the internal calibration target may be applied to the substrate by one or more of spray coating, stamping, printing, gluing, at least one squeegee process. The substrate may be at least partially covered by the internal calibration target. The internal calibration target may cover 0.1 to 99.9 % of the substrate, specifically 0.5 to 25 % of the substrate, more specifically 1 to 10% of the substrate. For example, 1 to 10 % of the substrate may be covered by the internal calibration target and a rest, e.g. of 99 to 90% may be used for the first optical path for measuring the object.

[0060] The internal calibration target may comprise at least one white reflection element such as a coating, film or foil. The term “white” 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 characterize, without limitation, the reflection of the element, i.e. that the reflection is essentially wavelength independent in the wavelength range of interest, in particular that there are no dominant absorption peaks in the reflection spectrum of the element in the given wavelength range. The term “white reflection 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 a material layer having an at least partially diffusive reflective surface. The white reflection element may provide a diffusive reflective surface. The white reflection element may be semi-transparent at at least one given wavelength range. The wavelength range for which the white reflection element is semi-transparent may be selected such that it matches at least partially the wavelength range of the light source. However, the wavelength range for which the white reflection element may be different from the wavelength range of the light source, e.g. narrower. The white reflection element may be configured for at least partially reflecting and / or partially transmitting incident light. The white reflection element may comprise one or more of at least one layer of Polytetrafluoroethylene (PTFE), at least one optical coating, such as a white surface coating, e.g. a white varnish available from Nextel® Suede coating 3101.

[0061] The white reflection element may be arranged directly on the substrate. The term “arranged directly” 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 application without any further element between the substrate and the white reflection element. For example, white reflection element may be coated, e.g. spray coated, on the substrate. However, other processes may be possible such as stamping, printing, gluing, at least one squeegee process and the like.

[0062] The internal calibration target may comprise at least one carrier element via which the white reflection element is arranged onto the substrate. The term “carrier 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 at least one element and / or layer arranged between two other elements, e.g. the substrate and the white reflection element. The carrier element may be configured for providing at least one supporting function for mounting at least one further element of the internal calibration target onto the substrate. For example, the white reflection element and the carrier element may function together as internal calibration target and / or the carrier element may support the white reflection element. The carrier element may be diffuse reflective in at least one wavelength range. The carrier element may comprise at least one reflection material. The white reflection element may be semi-transparent. The carrier element may be configured for scattering light upon transmission of the white reflection element. Thus, the reflective carrier can increase overall reflectivity. The mounting of the white reflection element onto the carrier element may be performed e.g. using a transparent adhesive, e.g., epoxy glue, or in at least one spray coating (varnish) process. However, other processes are possible.

[0063] In one embodiment, the module cover window may comprise a stack. The stack may comprise at least the white reflection element, the carrier element and the substrate. In one embodiment, the stack may comprise the carrier element, with the white reflection element coated thereon, wherein the carrier element is coated directly onto the substrate. For example, the carrier element comprises at least one metal layer comprising one or more of gold, silver, aluminum, chromium, wherein the metal layer is coated onto the substrate, e.g. in at least one thin-film process. In an embodiment, the stack may comprise the carrier element, with the white reflection element coated thereon, which is mounted to the substrate by using at least one adhesive. For example, the carrier element comprises a metal film fixed to the substrate by means of an adhesive. In one embodiment, the stack may comprise the carrier element mounted to the substrate by using at least one adhesive and the white reflection element is mounted to the carrier element by using at least one transparent adhesive. For example, the carrier element comprises a metal film which is fixed by an adhesive on the substrate, wherein the white reflective element is a reflective coating which is fixed by a transparent adhesive on the carrier element.

[0064] For example, the white reflective element comprises at least one layer of PTFE and the carrier element further may comprise at least one aluminum foil functioning as a reflector. The layer of PTFE may be mounted on the aluminum foil using a transparent adhesive. The PTFE may function as diffusor and can in combination with the reflector function as internal calibration target.

[0065] The module cover window is at least partially structured. The term “structured” 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 non-uniform distribution of one element.

[0066] For example, the internal calibration target may be non-uniformly distributed on the substrate. For example, the internal calibration target may comprise at least one pattern. The term “pattern” 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 structured element. The pattern may be at least one pattern selected from the group consisting of a dot pattern, a checkerboard pattern or a random pattern, or any other pattern, which feature a macroscopic 2D homogeneity over the surface area of the calibration target. The pattern may be embodied such that the pattern only partially covers the substrate. For example, the white reflection element may be structured in such a way that it itself is scattering the light for a given wavelength range.

[0067] As already disclosed, the method comprises obtaining the items of calibration information xt, wherein the items of calibration information xtare used to derive at least one item of spectral information of an object, wherein the at least one item of spectral information depends on the at least one first detector signal Si and the at least one second detector signal S2, wherein the items of calibration information xtare obtained by evaluating data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal and the generated at least one second detector signal. The items of calibration information may describe a dependency of the item of spectral information between the at least one first detector signal and the at least one second detector signal. The items of calibration information may be obtained or determined by evaluating the data pairs.

[0068] WO 2023 / 161416 A1 describes that the item of spectral information may be derived from with the detector signal Sl objgenerated by the object illuminated via the first beam path and the detector signal S2generated by the internal calibration target illuminated via the second beam path. The factors may be derived from an detector signal Sl opengenerated by an open port measurement via the first beam path, the detector signal SliWOO / oTargetgenerated by an external reference target having 100% reflectivity and the detector signal S2generated by the internal calibration target.

[0069] This formula, typically, does not account for any influence of the object on S2when it is arranged at the sample interface. Additionally this formula assumes a linear relationship between the signal S10bjand the spectral information of the object. Specifically these disadvantages are overcome by the invention. The items of calibration information xtare obtained by evaluating data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal Si and the generated at least one second detector signal S2

[0070] The items of calibration information xtmay be derived solving m equations for the items of calibration information x with m being larger than n, such as m = n+1. K, is the known optical characteristic of the at least one calibration target, S1 CaiTis the at least one first detector signal generated by the calibration target placed at or arranged on the sample interface illuminated via the first beam path and S2is the at least one second detector signal generated by the internal calibration target illuminated via the second beam path. Each equation may be related to a differing known optical characteristic Kj. Each equation may be associated with a data pair. The number of data pairs m may be equal to n+1 or larger than n+1. m may be a natural number larger than n.

[0071] Alternatively or in addition, the items of calibration information xtmay be derived solving for the items of calibration information xtwith m being larger than n, such as m = n+1. K, is the known optical characteristic of the at least one calibration target, S1 CaiTis the at least one first detector signal generated by the calibration target placed at or arranged on the sample interface illuminated via the first beam path and S2is the at least one second detector signal generated by the internal calibration target illuminated via the second beam path. Each known optical characteristic Kj may be different from each other. Each m may be associated with a data pair. The number of data pairs m may be equal to n+ 1 or larger than n+ 1.

[0072] In order to improve the accuracy S1 CaiTmay be an average of several generated signals and / or S2may be an average of several generated signals. Alternatively or in addition, further at least one data pair may be considered that is related to a further known optical characteristic Km. The further known optical characteristic Kmmay equal a known optical characteristic Kj already considered in either (1) or (2).

[0073] Each data pair may comprise

[0074] - the known optical characteristic of the at least one calibration target Kj - the generated at least one first detector signal that is generated for the at least one calibration target Kj and

[0075] - the generated at least one second detector signal that is generated for the at least one calibration target Kj.

[0076] The method comprises obtaining the items of calibration information. The term “item of calibration information”, also referred to as “item of calibration information x “, 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 details obtained by evaluating data obtained in a calibration procedure. The items of calibration information may be evaluated in a method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object to bring the data obtained in the measurement procedure in alignment with at least one standard and / or at least one specification established in the calibration procedure.

[0077] The items of calibration information may provide the dependency of the item of spectral information on a relationship between the at least one first detector signal and the at least one second detector signal.

[0078] The term “relationship” 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 connection and / or association between at least two factors that may be expressed by a mathematical operation or a mathematical formula. When the relationship is known, it enables the derivation or calculation of a third factor.

[0079] The relationship between the at least one first detector signal and the at least one second detector signal may be a ratio between the at least one first detector signal and the at least one second detector signal; or vice versa. The relationship between the at least one first detector signal and the at least one second detector signal may be a quotient between the at least one first detector signal and the at least one second detector signal; or vice versa.

[0080] The term “dependency” 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 relationship between at least two factors where one factor determines or influences a further factor. The dependency may be described by a function describing how one factor, such as the dependent variable, changes in response to a further factor, such as the independent variable. The item of spectral information R may depend on the items of calibration information*; and the at least one first detector signal and the at least one second detector signal. By performing the method for calibrating a spectrometer device for obtaining items of calibration information, the items of calibration information are obtained. The items of calibration information may be evaluated in the method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object in order to obtaining at least one item of spectral information on at least one object.

[0081] Therefore, the at least one first detector signal is measured with the at least one object being arranged on the sample interface in a manner that first light interacts with the at least one object and the at least one second detector signal is measured.

[0082] The items of calibration information are obtained by evaluating data pairs comprising the at least one known optical characteristic, the at least one first detector signal and the at least one second detector signal. The one or more data pairs may further comprise information on the emittance spectra of the first light emitting element and / or the second light emitting element, specifically information on the intensity of the first light emitting element and / or the second light emitting element.

[0083] The term “data pair” 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 at least two related factors and / or items of information. The factors and / or items of information comprised by a specific data pair may be used to determine or obtain a relationship and / or a dependency between these factors.

[0084] A data pair may comprise the at least one known optical characteristic of the at least one calibration target, , the generated at least one first detector signal and the generated at least one second detector signal. A data pair may comprise a specific known optical characteristic, such as a reflectance and or a transmission characteristic. The specific known optical characteristic may be, preferably, given for a specific wavelength range. The specific wavelength range may be assigned to a specific photosensitive element. A data pair may comprise a specific generated at least one first detector signal and a specific generated at least one second detector signal, preferably, given for the specific wavelength range.

[0085] For performing the method for calibrating a spectrometer device for obtaining items of calibration information, it may be required to perform a plurality of measurements. The plurality of measurements may differentiate in that a differing setting of the spectrometer device and / or a differing calibration target is used. A data pair may comprise exclusively items of information related to a single measurement of the plurality of measurements. The items of information within the data pair may be correlated to a data point. The data point may be evaluated in order to determine the items of calibration information. For obtaining the items of calibration information, a plurality of data points may be evaluated.

[0086] Obtaining the items of calibration information may comprise deriving a function describing the dependency of the item of spectral information on the relationship between the at least one first detector signal and the at least one second detector signal.

[0087] The term “function” 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 mathematical description of a relationship or a dependency between at least two factors and / or values and / or sets. The function may be

[0088] Deriving the function describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal may comprise performing a regression analysis by evaluating a plurality of different data pairs, specifically at least 3; at least 5; at least 9; at least 14; at least 20 data pairs.

[0089] For obtaining the different data pairs, step 1) and 2) may be performed repeatedly with differing spectrometer setting and / or differing calibration targets. Each data pair may comprise information derived from a plurality of measurements with the same spectrometer setting and the same calibration target.

[0090] The term “regression analysis” 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 statistical technique used to model a relationship and / or a dependency between differing factors, such as one or more dependent variables and one or more independent variables. A regression analysis may involve identifying a best-fitting mathematical function that describes the relationship and / or the dependency between the factors, particularly by adjusting parameters of the function.

[0091] The function may be

[0092] - an / 7-th order polynomial function, specifically where n is between 2 and 5.

[0093] The different data pairs may be obtained by

[0094] - using a plurality of different calibration targets;

[0095] - varying a distance between a single calibration target and the at least one sample interface and, thereby, varying the known optical characteristic of the calibration target;

[0096] - emitting first light with a plurality of different emittance spectra, specifically by emitting first light with a plurality of different intensities, particularly by applying different driving currents to the first light emitting element in order to emit first light with a plurality of different intensities; - emitting second light with a plurality of different emittance spectra, specifically by emitting second light with a plurality of different intensities, particularly by applying different driving currents to the second light emitting element in order to emit second light with a plurality of different intensities.

[0097] At least one item of calibration information of the items of calibration information may be resolved for a plurality of different wavelength ranges. Each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector.

[0098] The term “resolved” 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 accounting and / or quantifying for an influence of a factor. The wavelength range may influence the at least one item of calibration information, particularly in a manner that for differing wavelengths ranges differing items of spectral information obtained from the item of calibration information apply although the relationship between the at least one first detector signal and the at least one second detector signal is the same.

[0099] For the at least one item of calibration information to be resolved for a plurality of different wavelength ranges, the at least one item of calibration information may account for different wavelength ranges. Consequently, the at least one item of calibration information may comprise differing dependencies of the item of spectral information of the object on the relationship between the at least one first detector signal and the at least one second detector signal, wherein each specific dependency of the differing dependencies is assigned to a specific wavelength range.

[0100] Obtaining the items of calibration information may further comprise evaluating the emittance spectrum of the first light emitting element and / or the emittance spectrum of the second light emitting element.

[0101] The term “emittance spectrum” 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 distribution of emitted light at different wavelengths, preferably emitted by a material and / or an object. The emittance spectrum may particularly describe the intensity and / or the amount of light emitted by the material and / or the object dependent on a wavelength and / or a wavelength range.

[0102] The emittance spectrum may comprise information on at least one of:

[0103] - at least one item of information on a wavelength range of the light emitted by the respective light emitting element;

[0104] - at least one item of information on an intensity of the light emitted by the respective light emitting element.

[0105] The information may be described by the distribution of emitted light. Obtaining the emittance spectrum of the first light emitting element and / or the emittance spectrum of the second light emitting element further may comprise evaluating at least one item of information on a dependency of the emittance spectrum of the respective light emitting element on a driving current applied to the respective light emitting element and / or a forward voltage applied to the respective light emitting element.

[0106] An emittance spectrum of the first light emitted by the first light emitting element may equal an emittance spectrum of the second light emitted by the second light emitting element. Alternatively, the second light emitted by the second light emitting element may have a smaller bandwidth than the first light emitted by the first light emitting element.

[0107] The first light emitting element may be driven in a polarization multiplexing mode at at least one first polarization. The second light emitting element may be driven in a polarization multiplexing mode at one or more second polarizations, particularly wherein the at least one first polarization is different than the one or more second polarizations. The respective light element may be driven by using a driving unit.

[0108] The term “to drive” 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. For driving the at least one light emitting element, the spectrometer device may comprise a driving unit. The term specifically may refer, without limitation, to the process of providing one or both of at least one control parameter and / or electrical power to another device. Consequently, the term “driving 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 for providing one or both of at least one control parameter and / or electrical power to another device, such as, in the present case, to the first light emitting element and the second light emitting element. For example, the driving unit specifically may be further configured for at least one of measuring and controlling one or more electrical parameters of an electrical power provided to the respective light emitting element. The light generated by the respective light emitting element may be dependent on the control parameter and / or the electrical power.

[0109] As an example, the driving unit may be configured for providing an electrical current, such as the driving current, to the respective light emitting element, specifically for controlling an electrical current through the respective light emitting element. Therein, as an example, the driving unit may be configured for adapting and measuring a voltage provided to the respective light emitting element, the voltage being required for achieving a specific electrical current through the respective light emitting element. The driving unit, specifically, may comprise one or more of: a current source, a voltage source, a current measurement device, such as an Ampere-me- ter, a voltage measurement device, such as a Volt-meter, a power measurement device. Specifically, the driving unit may comprise at least one current source for providing at least one predetermined current to the respective light emitting element, wherein the current source specifically may be configured for adjusting or controlling a voltage applied to the respective light emitting element in order to generate the predetermined current. The driving unit, as an example, may comprise one or more electrical components, such as integrated circuits, for driving the light source. The driving unit may fully or partially be integrated into the light source or may be separated from the light source.

[0110] The term “polarization multiplexing mode” 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 procedure for multiplexing a plurality of signals carried by light waves, allowing a plurality of channels of information to be transmitted on the same carrier by using waves of different polarization states. The evaluation unit may be configured for assigning at least one detector signal to the first beam path, e.g. the first light emitting element, or the second beam path, e.g. the first light emitting element, by evaluating the polarization of the detected first light and the polarization of the detected second light.

[0111] The first light emitting element may be driven in a frequency multiplexing mode at at least one first frequency. The second light emitting element may be driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies.

[0112] The term “frequency multiplexing mode” 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 procedure for multiplexing a plurality of signals carried by light waves, allowing a plurality of channels of information to be transmitted on the same carrier by using waves of different frequency states. The evaluation unit may be configured for assigning at least one detector signal to the first beam path, e.g. the first light emitting element, or the second beam path, e.g. the second light emitting element, by evaluating the frequency of the detected first light and the frequency of the detected second light.

[0113] The one or more second frequencies may comprise a first second frequency that is smaller than the first frequency, and the one or more second frequencies comprise a second second frequency that is larger than the first frequency.

[0114] In a further aspect, a method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object is disclosed. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect. The steps of the method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object may be performed in the given order. A different order, however, may also be feasible. Further, two or more of the method steps may be performed simultaneously. Thereby, the method steps may at least partly overlap in time. Further, the method steps may be performed once or repeatedly. Thus, one or more or even all of the method steps may be performed once or repeatedly. The method may comprise additional method steps, which are not listed herein.

[0115] The method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object may be a computer-implemented method. Alternatively or in addition, at least one of the method steps, preferably any one of the method steps, which involve the use of an evaluation unit, may be performed by using a device comprising at least one processor for executing the steps. The term "computer implemented method" 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 method, which involves at least one apparatus, specifically a computer, or a plurality of apparatus, particularly connected via a computer network. The plurality of apparatus may be connected, particularly for transmitting data, via a network by using at least one connection interface at any one of the apparatuses of the plurality of apparatus. The computer-implemented method may be implemented as at least one computer program that may be provided on a storage medium carrying the computer program, whereby at least one of the steps of the computer-implemented method are performed by using the at least one computer program. Preferably any one of the steps may be performed using the at least one computer program. Alternatively, the at least one computer program may be accessible by an apparatus which may be adapted for performing the method via a network, such as via an in-house network, via internet, or via a cloud. With particular regard to the present invention, the present method can, thus, be performed on a programmable apparatus, which is configured for this purpose, such as by providing a computer program, which is configured for such a purpose.

[0116] The term “spectral information”, also referred to as “spectroscopic information”, as “an item of spectral information” or as “an item of spectral information R ”, 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, a reflection 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 reflected 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 “object” may, generally, be 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.

[0117] The method comprises the following steps:

[0118] 1 . emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein the at least one object is arranged on the sample interface in a manner that first light interacts with the at least one object;

[0119] 2. emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device;

[0120] 3. obtaining the item of spectral information on the object by evaluating the at least one first detector signal Si and the at least one second detector signal S2by using an evaluation unit, wherein evaluating the at least one first detector signal Si and the at least one second detector signal S2comprises evaluating items of calibration information x particularly wherein obtaining the item of spectral information R on the object is performed by using an evaluation unit.

[0121] The detector may comprise at least one of: at least one of photosensitive element; at least one readout circuitry; at least one bias voltage.

[0122] At least one item of calibration information of the items of calibration information may be resolved for a plurality of different wavelength ranges. Consequently, the at least one item of calibration information may comprise differing dependencies of the item of spectral information of the object on the relationship between the at least one first detector signal and the at least one second detector signal, wherein each specific dependency of the differing dependencies is assigned to a specific wavelength range. The specific dependency of the differing dependencies that is evaluated to obtain a specific item of spectral information on the object may be selected in accordance with the wavelength range assigned to the item of spectral information. Alternatively or in addition, the specific function of the differing functions that is evaluated to obtain a specific item of spectral information on the object may be selected in accordance with the wavelength range assigned to the item of spectral information.

[0123] Each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector.

[0124] The relationship between the at least one first detector signal and the at least one second detector signal may be a ratio or a quotient between the at least one first detector signal and the at least one second detector signal; or vice versa. The items of calibration information may be used in a function describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal.

[0125] The function may be

[0126] - an / 7-th order polynomial function, specifically where n is between 2 and 5.

[0127] The items of calibration information may be obtained in a factory calibration process. The term “factory calibration process” 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 procedure performed during manufacturing of a device in order to tune the accuracy, the precision and the functionality of the device, particularly before the device is dispatched from the production facility. In contrast to a factory calibration process, a field calibration process may be performed post-manufacturing or during routine maintenance, particularly by a user of the device.

[0128] A internal calibration target having at least one known optical characteristic may be arranged in the second beam path in a manner that the second light interacts with the at least one reference target.

[0129] The reference target may be or may comprise a material selected from at least one of:

[0130] - at least one layer of Polytetrafluoroethylene (PTFE),

[0131] - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0132] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0133] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter;

[0134] - at least one optical grating. An emittance spectrum of the first light emitted by the first light emitting element may equal an emittance spectrum of the second light emitted by the second light emitting element. The second light emitted by the second light emitting element may have a smaller bandwidth than the first light emitted by the first light emitting element.

[0135] The first light emitting element may be driven in a polarization multiplexing mode at at least one first polarization. The second light emitting element may be driven in a polarization multiplexing mode at one or more second polarizations. The at least one first polarization may be different than the one or more second polarizations.

[0136] The first light emitting element may be driven in a frequency multiplexing mode at at least one first frequency. The second light emitting element may be driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies. The one or more second frequencies may comprise a first second frequency that is smaller than the first frequency, and the one or more second frequencies may comprise a second second frequency that is larger than the first frequency.

[0137] The items of calibration information may be obtained by performing the method for calibrating the spectrometer device for obtaining the items of calibration information as elsewhere disclosed herein.

[0138] In a further aspect, a spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement is disclosed. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect.

[0139] The spectrometer device comprises: a) at least one sample interface, wherein the sample interface is configured for defining a measurement pose of the at least one object outside of the spectrometer device; b) at least one detector, wherein the detector is configured for generating at least one detector signal when detecting light; c) at least one first beam path, wherein the first beam path is configured in a manner that first light propagating along the first beam path passes the sample interface of the spectrometer device and interacts with the at least one object, d) at least one second beam path, wherein the second beam path is configured in a manner that second light propagating along the second beam path does not pass the sample interface of the spectrometer device, e) at least one first light emitting element, wherein the first light emitting element is configured for emitting first light along the first beam path onto the detector; f) at least one second light emitting element, wherein the second light emitting element is configured for emitting second light along the second beam path onto the detector; g) at least one evaluation unit, wherein the evaluation unit is configured for obtaining the item of spectral information by using the method for operating the spectrometer device as elsewhere disclosed herein.

[0140] The at least one detector may comprise a plurality of photosensitive elements sensitive to differing wavelength intervals.

[0141] The spectrometer device further may comprises at least one wavelength-selective element, wherein the wavelength-selective element is disposed in at least one of:

[0142] - the at least one first beam path;

[0143] - the at least one second beam path.

[0144] The at least one the wavelength-selective element may be configured and / or may be arranged in a manner that any photosensitive element of the plurality of photosensitive elements is exposed to an individual spectral range of light.

[0145] 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.

[0146] The wavelength-selective element may be configured such that each of the photosensitive detectors may be exposed to the same spectral range of the detection light. The wavelength-selective element 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 detectors and / or different photosensitive detectors of the detector to differing spectral ranges of light.

[0147] Thus 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 wavelength-selective element disposed in a beam path of the light from the object, i.e. in the beam path of the detection light, wherein the wavelength-selective element, specifically may be configured such that each of the photosensitive detectors is exposed to an individual spectral range of the light from the object. As an example, a variable wavelength-selective element may be used, the transmission of which depends on a position on the wavelength-selective element, such that, when the variable wavelength-selective element is placed on top of the array of photosensitive detectors, the individual photosensitive detectors are exposed to differing spectral ranges of the incident light, specifically the detection light from the object.

[0148] The wavelength-selective element may be selected from the group of a tunable wavelength-selective element and a wavelength-selective element having a fixed transmission spectrum. The wavelength-selective element may be or may comprise at least one of: a length variable filter; a static filter; a tunable filter, particularly a MEMS Fabry-Perot cavity; an optical lens; a diffractive element.

[0149] The term “length variable filter” 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 filter which comprises a plurality of individual filter elements, preferably a plurality of interference filter elements, which may, in particular, be provided in a continuous arrangement of the individual filter elements. Herein, each of the filter elements may form a bandpass with a variable center wavelength for each spatial position on the filter, preferably continuously, along a single dimension, which is, usually, denoted by the term “length”, on a receiving surface of the length variable filter. The variable center wavelength may be a linear function of the spatial position of each filter element, in which case the length variable filter is usually referred to as a “linearly variable filter” or by its abbreviation “LVF”. However, other kinds of functions may be applicable to the relationship between the variable center wavelength and the spatial position on the individual filter elements. Herein, the individual filter elements may be located on a transparent substrate which may, in particular, comprise at least one material that may show a high degree of optical transparency within in the infrared (IR) spectral range, especially, within the near-infrared (NIR) spectral range as described below in more detail, whereby varying spectral properties, especially continuously varying spectral properties, of the filter along length of the filter may be achieved. In particular, the length variable filter may be a wedge filter that may be adapted to carry at least one response coating on a transparent substrate, wherein the response coating may exhibit a spatially variable property, in particular, a spatially variable thickness. However, other kinds of length variable filters which may comprise other materials or which may exhibit a further spatially variable property may also be feasible. At a normal angle of incidence of an incident light ray or light beam, each of the filter elements as comprised by the length variable filter may have a bandpass width that may amount to a fraction of the center wavelength, typically to a few percent, of the particular filter.

[0150] The term “static filter” 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 filter, particularly a bandpass filter, which blocks and / or selects light of a predetermined wavelength range, specifically by reflecting and / or absorbing. The wavelength range may be fixed. A fixed wavelength length may be unchangeable and / or static. The optical properties of the static filter may not be time-varying.

[0151] The term “tunable filter” 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 filter which blocks and / or selects light of an adjustable wavelength range. The optical properties of the tunable filter may be time-varying. An interferometer may be used as a tunable filter, specifically a Fabry-Perot interferometer, Mach-Zehnder interferometer and / or a Michelson interferometer. Alternatively, angle-dependent wavelength shifts of a static filter may be utilized. This may be realized by using at least one micro electro mechanical system, MEMS, where moving parts of the interferometer are realized be using micro actuators.

[0152] The term “diffractive 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 item for shaping the incident radiation by diffraction of the incident radiation at an optical grating.

[0153] The length variable filter may comprise at least two bandpass filters, wherein each bandpass filter may be assigned to a respective pixelated sensor by being arranged within the field of view of the respective pixelated sensor, wherein each bandpass filter may be configured for selecting at least one wavelength of the accepted incident radiation. The term “bandpass filter” 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 filter that allows only incident radiation having a wavelength that is within a predefined range to pass. Incident radiation having a wavelength below and / or above the predefined range may be blocked or may be significantly attenuated. The selected at least one wavelength may be within the predefined range. The selected at least one wavelength may be transferred onto the respective pixelated sensor. The term “assigned to a respective pixelated 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 transmitting the accepted incident radiation onto the respective pixelated sensor. Thereby, the at least two bandpass filters may be arranged in a manner that each bandpass filter of the at least two bandpass filters is placed within a field of view of a different pixelated sensor.

[0154] The length variable filter may comprise at least two bandpass filters, wherein each bandpass filter may be arranged in the field of view of a specific photosensitive element, wherein each bandpass filter may be configured for selecting at least one wavelength range of the detection light.

[0155] The first light emitting element may be at least one of: - a thermal radiator;

[0156] - a microelectromechanical system (MEMS)-based emitter;

[0157] - a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region;

[0158] - a light-emitting diode (LED), particularly o a LED emitting light that is at least partially located in the infrared spectral range and / or o a LED illuminating a phosphor for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0159] The second light emitting element may be at least one of:

[0160] - a thermal radiator;

[0161] - a microelectromechanical system (MEMS)-based emitter;

[0162] - a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region;

[0163] - a light-emitting diode (LED), particularly o a LED emitting light that is at least partially located in the infrared spectral range and / or o a LED illuminating a phosphor for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0164] In a further aspect, a mobile device is disclosed, wherein the mobile device comprises a spectrometer device as elsewhere disclosed herein. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect.

[0165] The term “mobile 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 a mobile electronics device more specifically to a mobile communication device, configured for providing access to at least one telecommunication network, such as a cell phone, smart phone or a wearable. The mobile device may be a portable device.

[0166] 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 m3or 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.

[0167] In a further aspect, a computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method as elsewhere disclosed herein. The computer may be an evaluation unit of the spectrometer device as elsewhere disclosed herein. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect.

[0168] In a further aspect, a non-transitory computer-readable storage medium is disclosed, the computer-readable storage medium including instructions that when executed by a computer, cause the computer to perform the method as elsewhere disclosed herein. The computer may be an evaluation unit of the spectrometer device as elsewhere disclosed herein. For this aspect, reference may be made to any further aspect, particularly any definition, Embodiment or claim given in the context of any further aspect.

[0169] As used herein, the “computer-readable storage medium” specifically may refer to non-transi- tory data storage means, such as a hardware storage medium having stored thereon computerexecutable instructions. The stored computer-executable instruction may be associate with the computer program. The computer-readable data carrier or storage medium specifically may be or may comprise a storage medium such as a random-access memory (RAM) and / or a readonly memory (ROM).

[0170] 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.

[0171] 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.

[0172] 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.

[0173] The method for calibrating a spectrometer device for obtaining items of calibration information, the method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object, the spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, the mobile device, the computer program and the non-transitory computer-readable storage medium according to the present invention discussed elsewhere herein provide a large number of advantages over known devices and methods of similar kind.

[0174] Particularly, the present invention may require a minimum of user interactions and accounts for effects related to the detector, which have not been explicitly considered for in a factory calibration procedure. Particularly the present invention may account for effects related to the detector, which cannot be corrected directly in a factory calibration procedure, particularly since these effects change with time due to degradation and / or aging and / or drifting of at least one component of the spectrometer device, such as light emitting elements and / or detectors.

[0175] This presented disclosure may replace a common way of calculating and determining a reflectivity and / or an absorbance of an object by obtaining the reflectivity directly from the relation of detector signal values obtained from a light emitting element interacting with the object and a further light emitting element interacting with an internal reference target.

[0176] Only a calibrated dependency, such as a function, which may provide the dependency between the signal relationship and a reflectivity may be required. This calibrated function may be obtained by different ways.

[0177] A second light emitting element or a second light emitting diode (LED) may be used. A second internal optical beam path to the detector may be used to provide a defined optical signal. This measurement may be performed simultaneously with the object measurement via a first light emitting element and a first optical channel, i.e. via frequency division multiplexing and / or polarization division multiplexing. The second detector signal may be independent from the object, i.e. it may change only slightly when the reflectivity of the object changes.

[0178] In this case, the quotient between a detector signal related to the first light emitting element or a first light emitting diode (LED) and a detector signal related to the second light emitting element or the second light emitting diode (LED) may depend on the reflectivity of the object and a well defined internal calibration target in the second internal optical beam path. Therefore, a factory calibration may be performed to determine the dependency between the object reflectivity and the detector signal quotient. The factory calibration may also account for any parasitic effects such as signal interaction with the object and / or crosstalk between the light emitting elements or the beam paths. In contrast to an open-port-reference-sample approach, this approach may be better in dealing with non-linearity, as these may actually be accounted for by using multiple different reflectivity targets in the factory calibration.

[0179] In a first factory calibration, reflectivity spectroscopy may be based on an detector signal quotient. At least 2, preferably 3 or more reference target having a different reflectivity may be measured with a spectrometer device with at least one light source interacting with an internal target and at least one further light source interacting with the reference target applied at the sample interface. Then the signal quotient of the detector signals of the two light emitting element may be calculated for each reference target and a fit function may be calculated between the signal quotient and the reflectivity of the calibration targets. Then each measurement of an object yields a quotient of the two detector signal related to the two light emitting element, which may be used to directly calculate the reflectivity via the fit function.

[0180] Reflectivity spectroscopy may be based on detector signal quotient with reduced calibration targets. Therefore, the calculation of the objects reflectivity from the detector quotient via the fit function may works exactly as in the previous embodiment. In a second factory calibration, fewer calibration targets may used, such as only a single standard reflection target may be used, and, optionally, a measurement with no reference target applied to the sample interface may be performed. In order to get sufficient data points for determining the fit function, multiple measurements with different currents applied to the light emitting element that is interacting with the target may be performed, particularly while keeping the current to the light emitting element interacting with the internal target constant.

[0181] It may be an advantage that a factory calibration method is provided, that may account for light source channel crosstalk and / or is robust against degradation and / or aging effects.

[0182] Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0183] Embodiment 1 : A method for calibrating a spectrometer device for obtaining items of calibration information, wherein the method comprises the following steps: 1 ) emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein at least one calibration target is arranged on the sample interface in a manner that the first light interacts with the at least one calibration target having at least one known optical characteristic;

[0184] 2) emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device,

[0185] 3) obtaining the items of calibration information xt, wherein the items of calibration information xtare used to derive at least one item of spectral information of an object (128), wherein the at least one item of spectral information depends on the at least one first detector signal Si and the at least one second detector signal S2, wherein the items of calibration information xtare obtained by evaluating one or more data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal Si and the generated at least one second detector signal S2.

[0186] Embodiment 2: The method according to the preceding Embodiment, wherein the detector comprises at least one of:

[0187] - at least one of photosensitive element;

[0188] - at least one readout circuitry;

[0189] - at least one bias voltage.

[0190] Embodiment 3: The method according to any one of the preceding Embodiments, wherein at least one item of calibration information of the items of calibration information are resolved for a plurality of different wavelength ranges.

[0191] Embodiment 4: The method according to any one of the preceding Embodiments, wherein each wavelength range of the plurality of different wavelength ranges is assigned to a specific photosensitive element of the detector.

[0192] Embodiment 5: The method according to any one of the preceding Embodiments, wherein obtaining the items of calibration information further comprises evaluating the emittance spectrum of the first light emitting element and / or the emittance spectrum of the second light emitting element.

[0193] Embodiment 6: The method according to the preceding Embodiment, wherein obtaining the emittance spectrum of the first light emitting element and / or of the second light emitting element further comprises evaluating at least one item of information on a dependency of the emittance spectrum of the respective light emitting element on a driving current applied to the respective light emitting element and / or a forward voltage applied to the respective light emitting element.

[0194] Embodiment 7: The method according to any one of the two preceding Embodiments, wherein the emittance spectrum comprises information on at least one of:

[0195] - at least one item of information on a wavelength range of the light emitted by the respective light emitting element;

[0196] - at least one item of information on an intensity of the light emitted by the respective light emitting element.

[0197] Embodiment 8: The method according to any one of the preceding Embodiments, wherein the relationship between the at least one first detector signal and the at least one second detector signal is a ratio, specifically a quotient, between the at least one first detector signal and the at least one second detector signal; or vice versa.

[0198] Embodiment 9: The method according to any one of the preceding Embodiments, wherein obtaining the items of calibration information comprises deriving a function describing the dependency of the item of spectral information on the relationship between the at least one first detector signal and the at least one second detector signal.

[0199] Embodiment 10: The method according to any one of the preceding Embodiments, wherein deriving the function describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal comprises performing a regression analysis by evaluating a plurality of different data pairs, specifically at least 3; at least 5; at least 9; at least 14; at least 20 data pairs.

[0200] Embodiment 11 : The method according to the preceding Embodiment, wherein the function is

[0201] - an / 7-th order polynomial function, specifically where n is between 2 and 5.

[0202] Embodiment 12: The method according to any one of the preceding Embodiments, wherein the different data pairs are obtained by

[0203] - using a plurality of different calibration targets; - varying a distance between a single calibration target and the at least one sample interface and, thereby, varying the known optical characteristic of the calibration target;

[0204] - emitting first light with a plurality of different emittance spectra, specifically by emitting first light with a plurality of different intensities, particularly by applying different driving currents to the first light emitting element in order to emit first light with a plurality of different intensities;

[0205] - emitting second light with a plurality of different emittance spectra, specifically by emitting second light with a plurality of different intensities, particularly by applying different driving currents to the second light emitting element in order to emit second light with a plurality of different intensities.

[0206] Embodiment 13: The method according to any one of the preceding Embodiments, wherein an emittance spectrum of the first light emitted by the first light emitting element equals an emittance spectrum of the second light emitted by the second light emitting element.

[0207] Embodiment 14: The method according to any one of the preceding Embodiments 1 to 12, wherein the second light emitted by the second light emitting element has a smaller bandwidth than the first light emitted by the first light emitting element.

[0208] Embodiment 15: The method according to any one of the preceding Embodiments, wherein the first light emitting element is driven in a polarization multiplexing mode at at least one first polarization.

[0209] Embodiment 16: The method according to the preceding Embodiment, wherein the second light emitting element is driven in a polarization multiplexing mode at one or more second polarizations, particularly wherein the at least one first polarization is different than the one or more second polarizations.

[0210] Embodiment 17: The method according to any one of the preceding Embodiments, wherein the first light emitting element is driven in a frequency multiplexing mode at at least one first frequency.

[0211] Embodiment 18: The method according to the preceding Embodiment, wherein the second light emitting element is driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies.

[0212] Embodiment 19: The method according to the preceding Embodiment, wherein

[0213] - the one or more second frequencies comprise a first second frequency that is smaller than the first frequency, and

[0214] - the one or more second frequencies comprise a second second frequency that is larger than the first frequency. Embodiment 20: The method according to any one of the preceding Embodiments, wherein the calibration target is or comprises a material selected from at least one of:

[0215] - at least one layer of Polytetrafluoroethylene (PTFE),

[0216] - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0217] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0218] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter;

[0219] - at least one optical grating.

[0220] Embodiment 21 : A method for operating a spectrometer device for obtaining at least one item of spectral information on at least one object, wherein the method comprises the following steps:

[0221] 1 . emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein the at least one object is arranged on the at least one sample interface in a manner that first light interacts with the at least one object;

[0222] 2. emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector of the spectrometer device; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device;

[0223] 3. obtaining the item of spectral information on the object by evaluating the at least one first detector signal Si and the at least one second detector signal S2by using an evaluation unit, wherein evaluating the at least one first detector signal Si and the at least one second detector signal S2comprises evaluating items of calibration information xt.

[0224] Embodiment 22: The method according to the preceding Embodiment referring to a method for operating a spectrometer device, wherein the detector comprises at least one of:

[0225] - at least one of photosensitive element;

[0226] - at least one readout circuitry;

[0227] - at least one bias voltage. Embodiment 23: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein at least one item of calibration information of the items of calibration information is resolved for a plurality of different wavelength ranges.

[0228] Embodiment 24: The method according to the preceding Embodiment, wherein each wavelength range of the plurality of different wavelength ranges is assigned to a specific photosensitive element of the detector.

[0229] Embodiment 25: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the relationship between the at least one first detector signal and the at least one second detector signal is a ratio, specifically a quotient, between the at least one first detector signal and the at least one second detector signal; or vice versa.

[0230] Embodiment 26: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the items of calibration information are used in a function describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal.

[0231] Embodiment 27: The method according to the preceding Embodiment referring to a method for operating a spectrometer device, wherein the function is

[0232] - an / 7-th order polynomial function, specifically where n is between 2 and 5.

[0233] Embodiment 28: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the items of calibration information are obtained in a factory calibration process.

[0234] Embodiment 29: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein an internal calibration target having at least one known optical characteristic is arranged in the second beam path in a manner that the second light interacts with the at least one reference target.

[0235] Embodiment 30: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the reference target is or comprises a material selected from at least one of:

[0236] - at least one layer of Polytetrafluoroethylene (PTFE),

[0237] - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0238] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0239] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter; at least one optical grating.

[0240] Embodiment 31 : The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein an emittance spectrum of the first light emitted by the first light emitting element equals an emittance spectrum of the second light emitted by the second light emitting element.

[0241] Embodiment 32: The method according to any one of the preceding Embodiments 20 to 28 referring to a method for operating a spectrometer device, wherein the second light emitted by the second light emitting element has a smaller bandwidth than the first light emitted by the first light emitting element.

[0242] Embodiment 33: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the first light emitting element is driven in a polarization multiplexing mode at at least one first polarization.

[0243] Embodiment 34: The method according to the preceding Embodiment referring to a method for operating a spectrometer device, wherein the second light emitting element is driven in a polarization multiplexing mode at one or more second polarizations, particularly wherein the at least one first polarization is different than the one or more second polarizations.

[0244] Embodiment 35: The method according to any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein the first light emitting element is driven in a frequency multiplexing mode at at least one first frequency.

[0245] Embodiment 36: The method according to the preceding Embodiment referring to a method for operating a spectrometer device, wherein the second light emitting element is driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies.

[0246] Embodiment 37: The method according to the preceding Embodiment referring to a method for operating a spectrometer device, wherein

[0247] - the one or more second frequencies comprise a first second frequency that is smaller than the first frequency, and

[0248] - the one or more second frequencies comprise a second second frequency that is larger than the first frequency.

[0249] Embodiment 38: The method according to the any one of the preceding Embodiments referring to a method for operating a spectrometer device, wherein items of calibration information are obtained by performing the method for calibrating the spectrometer device for obtaining the items of calibration information according to any one of the preceding Embodiments referring to the method for calibrating the spectrometer device. Embodiment 39: A spectrometer device for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, wherein the spectrometer device comprises: a) at least one sample interface, wherein the sample interface is configured for defining a measurement pose of the at least one object outside of the spectrometer device; b) at least one detector, wherein the detector is configured for generating at least one detector signal when detecting light; c) at least one first beam path, wherein the first beam path is configured in a manner that first light propagating along the first beam path passes the sample interface of the spectrometer device and interacts with the at least one object, d) at least one second beam path, wherein the second beam path is configured in a manner that second light propagating along the second beam path does not pass the sample interface of the spectrometer device, e) at least one first light emitting element, wherein the first light emitting element is configured for emitting first light along the first beam path onto the detector; f) at least one second light emitting element, wherein the second light emitting element is configured for emitting second light along the second beam path onto the detector; g) at least one evaluation unit, wherein the evaluation unit is configured for obtaining the item of spectral information by using the method for operating the spectrometer device according to any one of the preceding Embodiments referring to a method for operating a spectrometer device.

[0250] Embodiment 40: The spectrometer device according to the preceding Embodiment referring to a spectrometer device, wherein the at least one detector comprises a plurality of photosensitive elements sensitive to differing wavelength intervals.

[0251] Embodiment 41 : The spectrometer device according to any one of the preceding Embodiments referring to a spectrometer device, wherein the spectrometer device further comprises at least one wavelength-selective element, wherein the wavelength-selective element is disposed in at least one of:

[0252] - the at least one first beam path;

[0253] - the at least one second beam path.

[0254] Embodiment 42: The spectrometer device according to the preceding Embodiments referring to a spectrometer device, wherein the at least one the wavelength-selective element is configured and / or arranged in a manner that any photosensitive element of the plurality of photosensitive elements is exposed to an individual spectral range of light.

[0255] Embodiment 43: The spectrometer device according to any one of the preceding Embodiments referring to a spectrometer device, wherein at least one of

[0256] - the first light emitting element; - the second light emitting element; is at least one of:

[0257] - a thermal radiator;

[0258] - a microelectromechanical system (MEMS)-based emitter;

[0259] - a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region;

[0260] - a light-emitting diode (LED), particularly o a LED emitting light that is at least partially located in the infrared spectral range and / or o a LED illuminating a phosphor for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0261] Embodiment 44: A mobile device, wherein the mobile device comprises a spectrometer device according to any one of the preceding Embodiments referring to a spectrometer device.

[0262] Embodiment 45: A computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to any one of the method Embodiments.

[0263] Embodiment 46: The computer program according to the preceding Embodiment, wherein the computer is an evaluation unit of the spectrometer device according to any one of the preceding Embodiments referring to the spectrometer device.

[0264] Embodiment 47: A non-transitory computer-readable storage medium, the computer-readable storage medium including instructions that when executed by a computer, cause the computer to perform the method according to any one of the method Embodiments.

[0265] Embodiment 48: The non-transitory computer-readable storage medium according to the preceding Embodiment, wherein the computer is an evaluation unit of the spectrometer device according to any one of the preceding Embodiments referring to a spectrometer device.

[0266] Short description of the Figures

[0267] 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:

[0268] Figure 1 shows an exemplary method for calibrating a spectrometer device;

[0269] Figure 2 shows an exemplary method for operating a spectrometer device;

[0270] Figure 3 shows an exemplary spectrometer device for obtaining at least one item of spectral information; and

[0271] Figure 4 shows a function between at least one first detector signal and at least one second detector signal in dependency of a reflectivity of a calibration target

[0272] Detailed description of the embodiments

[0273] Figure 1 shows an exemplary method for calibrating a spectrometer device 110 for obtaining items of calibration information is disclosed. The method 110 comprises the following steps:

[0274] 1 ) in a step 112, emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector 132 of the spectrometer device 126; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein at least one calibration target is arranged on the sample interface in a manner that the first light interacts with the at least one calibration target having at least one known optical characteristic;

[0275] 2) in a step 114, emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector 132 of the spectrometer device 126; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device,

[0276] 3) in a step 116, obtaining the items of calibration information xt, wherein items of calibration information xtare used to derive at least one item of spectral information of an object (128), wherein the at least one item of spectral information depends on the at least one first detector signal Si and the at least one second detector signal S2, wherein the items of calibration information xtare obtained by evaluating one or more data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal Si and the generated at least one second detector signal S2.

[0277] Steps 112 and 114 may, preferably be performed simultaneously. Differentiating between differing two detector signals may be possible be multiplexing, such as frequency division multiplexing.

[0278] The detector may comprise at least one of at least one of photosensitive element; at least one readout circuitry; at least one bias voltage.

[0279] In a step 116, obtaining the items of calibration information may further comprise evaluating the emittance spectrum of the first light emitting element and / or the emittance spectrum of the second light emitting element. Obtaining the emittance spectrum of the first light emitting element and / or the emittance spectrum of the second light emitting element further may comprise evaluating at least one item of information on a dependency of the emittance spectrum of the respective light emitting element 154, 156 on a driving current applied to the respective light emitting element 154, 156 and / or a forward voltage applied to the respective light emitting element 154, 156.

[0280] The emittance spectrum may comprise information on at least one of:

[0281] - at least one item of information on a wavelength range of the light (136, 146) emitted by the respective light emitting element 154, 156;

[0282] - at least one item of information on an intensity of the light 136, 146 emitted by the respective light emitting element 154, 156.

[0283] The relationship between the at least one first detector signal and the at least one second detector signal may be a ratio or a quotient between the at least one first detector signal and the at least one second detector signal; or vice versa.

[0284] In the following Figure 4 is discussed. On the horizontal axis 176 depicted in Figure 4, a reflectivity of the calibration target is indicated. On the vertical axis 178 depicted in Figure 4, the relationship, specifically the quotient, between the at least one first detector signal and the at least one second detector signal, particularly the respective quotient, is indicated. Each detector signal may be quantized as detector current in mA, FFT weight, counts or arbitrary units. As the quotient gives the relation of the detector signals the quotient is unitless.

[0285] Obtaining the items of calibration information may comprise deriving a function 174 describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal.

[0286] For the sake of clarity not all functions are indicated with reference sign 174.

[0287] The function may be

[0288] Deriving the function describing the dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal may comprise performing a regression analysis by evaluating a plurality of different data pairs, specifically at least 3; at least 5; at least 9; at least 14; at least 20 data pairs.

[0289] The data pairs are depicted as data points 180 in Figure 4. A data point 180 is obtained by evaluating a data pair.

[0290] The function may be

[0291] - an / 7-th order polynomial function 182 (indicated by the solid lines in Fig. 4), specifically where n is between 2 and 5.

[0292] As shown in Figure 4, the / 7-th order polynomial function 182 (indicated by the solid lines in Fig.

[0293] 4) represents the data points 180 more accurate than a linear function 184 (indicated by the dashed lines in Fig. 4).

[0294] The different data pairs may be obtained by

[0295] - using a plurality of different calibration targets;

[0296] - varying a distance between a single calibration target and the at least one sample interface and, thereby, varying the known optical characteristic of the calibration target;

[0297] - emitting first light with a plurality of different emittance spectra, specifically by emitting first light with a plurality of different intensities, particularly by applying different driving currents to the first light emitting element in order to emit first light with a plurality of different intensities;

[0298] - emitting second light with a plurality of different emittance spectra, specifically by emitting second light with a plurality of different intensities, particularly by applying different driving currents to the second light emitting element in order to emit second light with a plurality of different intensities.

[0299] At least one item of calibration information of the items of calibration information may be resolved for a plurality of different wavelength ranges. Each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector.

[0300] As may be derived from Figure 4, for the at least one item of calibration information of the items of calibration information to be resolved for a plurality of different wavelength ranges, the at least one item of calibration information may account for different wavelength ranges. Consequently, the at least one item of calibration information may comprise differing dependencies of the item of spectral information of the object on the relationship between the at least one first detector signal and the at least one second detector signal.

[0301] Particularly since each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector, a specific dependency of the item of spectral information on the object on the relationship between the at least one first detector signal and the at least one second detector signal of the differing dependencies may be assigned to a specific photosensitive element. Particularly since each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector, a specific function of the differing functions may be assigned to a specific photosensitive element.

[0302] In Figure 4, the differing dependency and / or the differing functions are indicated by the differing gray scales. Exclusively, specific data pairs and / or specific data points assigned to a specific wavelength range may be evaluated to obtain a specific dependency of the differing dependencies and / or a specific function of the differing functions assigned to the specific wavelength range.

[0303] An emittance spectrum of the first light emitted by the first light emitting element may equal an emittance spectrum of the second light emitted by the second light emitting element.

[0304] The second light emitted by the second light emitting element may have a smaller bandwidth than the first light emitted by the first light emitting element. The first light emitting element may be driven in a polarization multiplexing mode at at least one first polarization.

[0305] The second light emitting element may be driven in a polarization multiplexing mode at one or more second polarizations, particularly wherein the at least one first polarization is different than the one or more second polarizations. The first light emitting element may driven in a frequency multiplexing mode at at least one first frequency.

[0306] The second light emitting element may be driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies.

[0307] The one or more second frequencies may comprise a first second frequency that is smaller than the first frequency, and the one or more second frequencies may further comprise a second second frequency that is larger than the first frequency.

[0308] The calibration target may be or may comprise a material selected from at least one of:

[0309] - at least one layer of Polytetrafluoroethylene (PTFE), - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0310] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0311] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter;

[0312] - at least one optical grating.

[0313] In Figure 2 an exemplary method for operating a spectrometer device 118 for obtaining at least one item of spectral information on at least one object is disclosed. The method 118 comprises the following steps:

[0314] 1 . in a step 120, emitting first light along a first beam path onto a detector of the spectrometer device by using at least one first light emitting element of the spectrometer device in order to generate at least one first detector signal by at least one detector 132 of the spectrometer device 126; wherein the spectrometer device is configured in a manner that the first beam path is configured for first light propagating along the first beam path passing at least one sample interface of the spectrometer device; wherein the at least one object is arranged on the sample interface in a manner that first light interacts with the at least one object;

[0315] 2. in a step 122, emitting second light along a second beam path onto the detector by using at least one second light emitting element of the spectrometer device in order to generate at least one second detector signal by the at least one detector 132 of the spectrometer device 126; wherein the spectrometer device is configured in a manner that the second beam path is configured for second light propagating along the second beam path without passing the at least one sample interface of the spectrometer device;

[0316] 3. in a step 124, obtaining the item of spectral information on the object (128) by evaluating the at least one first detector signal Si and the at least one second detector signal S2by using an evaluation unit, wherein evaluating the at least one first detector signal Si and the at least one second detector signal S2comprises evaluating items of calibration information xt.

[0317] Steps 120 and 122 may, preferably be performed simultaneously. Differentiating between differing two detector signals may be possible be multiplexing, such as frequency division multiplexing.

[0318] The detector may comprise at least one of: at least one photosensitive element; at least one readout circuitry; at least one bias voltage.

[0319] At least one item of calibration information of the items of calibration information may be resolved for a plurality of different wavelength ranges. Each wavelength range of the plurality of different wavelength ranges may be assigned to a specific photosensitive element of the detector. The specific dependency of the differing dependencies that is evaluated to obtain a specific item of spectral information on the object may be selected in accordance with the wavelength range assigned to the item of spectral information. The specific function of the differing functions that is evaluated to obtain a specific item of spectral information on the object may be selected in accordance with the wavelength range assigned to the item of spectral information.

[0320] The relationship between the at least one first detector signal and the at least one second detector signal may be a ratio, specifically a quotient, between the at least one first detector signal and the at least one second detector signal; or vice versa.

[0321] The function may be

[0322] - an / 7-th order polynomial function, specifically where n is between 2 and 5.

[0323] The items of calibration information may be obtained in a factory calibration process.

[0324] An internal calibration target having at least one known optical characteristic may be arranged in the second beam path in a manner that the second light interacts with the at least one reference target.

[0325] The reference target may be or may comprise a material selected from at least one of:

[0326] - at least one layer of Polytetrafluoroethylene (PTFE),

[0327] - at least one optical coating, such as a white surface coating or at least one color coating, e.g. a near infra-red reflecting color coating,

[0328] - at least one dielectric coating, at least one partially reflective dielectric mirror,

[0329] - at least one metal coating or metal foil comprising one or more of gold, silver, aluminum, chromium, and at least one beam splitter;

[0330] - at least one optical grating.

[0331] An emittance spectrum of the first light emitted by the first light emitting element may equal an emittance spectrum of the second light emitted by the second light emitting element.

[0332] The second light emitted by the second light emitting element may have a smaller bandwidth than the first light emitted by the first light emitting element.

[0333] The first light emitting element may be driven in a polarization multiplexing mode at at least one first polarization.

[0334] The second light emitting element may be driven in a polarization multiplexing mode at one or more second polarizations. The at least one first polarization may be different than the one or more second polarizations. The first light emitting element may be driven in a frequency multiplexing mode at at least one first frequency.

[0335] The second light emitting element may be driven in a frequency multiplexing mode at one or more second frequencies, particularly wherein the at least one first frequency is different than the one or more second frequencies.

[0336] The one or more second frequencies may comprise a first second frequency that is smaller than the first frequency, and the one or more second frequencies may comprise a second second frequency that is larger than the first frequency.

[0337] The items of calibration information may be obtained by performing the method for calibrating the spectrometer device 110 for obtaining the items of calibration information as elsewhere disclosed herein.

[0338] In Figure 3, an exemplary spectrometer device 126 for obtaining at least one item of spectral information on at least one object 128 by spectroscopic measurement is shown. A mobile device 170 may comprise the spectrometer device 126. The spectrometer device 126 comprises: a) at least one sample interface 130, wherein the sample interface 130 is configured for defining a measurement pose of the at least one object 128 outside of the spectrometer device 126; b) at least one detector 132, wherein the detector 132 is configured for generating at least one detector signal when detecting light; c) at least one first beam path 134, wherein the first beam path 134 is configured in a manner that first light 136 propagating along the first beam path 134 passes the sample interface 130 of the spectrometer device 126 and interacts with the at least one object 128, particularly the first illumination light 140 may interact with the object 128 and, thereby, generate first detection light 142; d) at least one second beam path 144, wherein the second beam path 144 is configured in a manner that second light 146 propagating along the second beam path 144 does not pass the sample interface 130 of the spectrometer device 126, particularly an internal calibration target 152 may be arranged in the second beam path 144, such that second illumination light 148 may interact with the internal calibration target 152 and, thereby, generate second detection light 150; e) at least one first light emitting element 154, wherein the first light emitting element 154 is configured for emitting first light 136 along the first beam path 134 onto the detector 132; f) at least one second light emitting element 156, wherein the second light emitting element 156 is configured for emitting second light 146 along the second beam path 144 onto the detector 132; g) at least one evaluation unit 158 , wherein the evaluation unit 158 is configured for obtaining the item of spectral information by using the method for operating the spectrometer device 126 as elsewhere disclosed herein. The at least one detector 132 may comprise one or more photosensitive elements 160 sensitive to differing wavelength intervals. Alternatively or in addition, the at least one detector 132 may comprise one or more read-out electronics 162. The spectrometer device 126 may further comprise at least one wavelength-selective element 164, wherein the wavelength-selective element 164 is disposed in at least one of:

[0339] - the at least one first beam path 134;

[0340] - the at least one second beam path 144.

[0341] The at least one wavelength-selective element 164 may be configured and / or arranged in a manner that any photosensitive element of the plurality of photosensitive elements 160 is exposed to an individual spectral range of light.

[0342] The first light emitting element 154 may be at least one of:

[0343] - a thermal radiator;

[0344] - a microelectromechanical system (MEMS)-based emitter;

[0345] - a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region;

[0346] - a light-emitting diode (LED), particularly o a LED emitting light that is at least partially located in the infrared spectral range and / or o a LED illuminating a phosphor for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0347] The second light emitting element 156 may be at least one of:

[0348] - a thermal radiator;

[0349] - a microelectromechanical system (MEMS)-based emitter;

[0350] - a laser, specifically a vertical cavity surface emitting laser (VCSEL), particularly emitting at least one wavelength in the infrared region;

[0351] - a light-emitting diode (LED), particularly o a LED emitting light that is at least partially located in the infrared spectral range and / or o a LED illuminating a phosphor for light-conversion of light generated by the LED, wherein the luminescent material generates converted light that is at least partly located in the near-infrared spectral range.

[0352] The first light emitting element 154 may be driven by a first driving unit 166 of the spectrometer device 126. The second light emitting element 156 may be driven by a second driving unit 168 of the spectrometer device 126.

[0353] The invention further relates to a computer program comprising instructions (not shown) which, when the program is executed by a computer, cause the computer to perform the method 110 or the method 118 as disclosed elsewhere herein. The computer may be an evaluation unit 158 of the spectrometer device 126. The invention further relates to a non-transitory computer-read- able storage medium (not shown), the computer-readable storage medium including instructions that when executed by a computer, cause the computer to perform the method 110 or the method 118 as disclosed elsewhere herein. The computer may be an evaluation unit 158 of the spectrometer device 126.

[0354] List of reference numbers

[0355] 110 method for calibrating a spectrometer device

[0356] 112 emitting first light along a first beam path onto a detector

[0357] 114 emitting second light along a second beam path onto a detector

[0358] 116 obtaining the items of calibration information

[0359] 118 method for operating a spectrometer device

[0360] 120 emitting first light along a first beam path

[0361] 122 emitting second light along a second beam path

[0362] 124 obtaining the item of spectral information

[0363] 126 spectrometer device

[0364] 128 object

[0365] 130 sample interface

[0366] 132 detector

[0367] 134 first beam path

[0368] 136 first light

[0369] 140 first illumination light

[0370] 142 first detection light

[0371] 144 second beam path

[0372] 146 second light

[0373] 148 second illumination light

[0374] 150 second detection light

[0375] 152 internal calibration target

[0376] 154 first light emitting element

[0377] 156 second light emitting element

[0378] 158 evaluation unit

[0379] 160 photosensitive elements

[0380] 162 read-out electronics

[0381] 164 wavelength-selective element

[0382] 166 first driving unit

[0383] 168 second driving unit mobile device reference target function horizontal axis vertical axis data points polynomial function linear function

Claims

Claims1 . A method for calibrating a spectrometer device (126) for obtaining items of calibration information xt, wherein the method comprises the following steps:1 ) emitting first light (136) along a first beam path (134) onto a detector (132) of the spectrometer device (126) by using at least one first light emitting element (154) of the spectrometer device (126) in order to generate at least one first detector signal by at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the first beam path (134) is configured for first light (136) propagating along the first beam path (134) passing at least one sample interface (130) of the spectrometer device (126); wherein at least one calibration target is arranged on the sample interface (130) in a manner that the first light (136) interacts with the at least one calibration target having at least one known optical characteristic;2) emitting second light (146) along a second beam path (144) onto the detector (132) by using at least one second light emitting element (156) of the spectrometer device (126) in order to generate at least one second detector signal by the at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the second beam path (144) is configured for second light (146) propagating along the second beam path (144) without passing the at least one sample interface (130) of the spectrometer device (126),3) obtaining the items of calibration information xt, wherein the items of calibration information xtare used to derive at least one item of spectral informationof an object (128), wherein the at least one item of spectral information xtdepends on the at least one first detector signal Si and the at least one second detector signal S2, wherein the items of calibration information xtare obtained by evaluating one or more data pairs comprising the at least one known optical characteristic of the at least one calibration target, the generated at least one first detector signal Si and the generated at least one second detector signal S2.

2. The method according to the preceding claim, wherein the items of calibration information Xi are derived from the equationwith the known optical characteristic Kt of the at least one calibration target, the at least one first detector signal S1 CaiTgenerated by the calibration target arranged on the sample interface (130) illuminated via the first beam path (134) and the at least one second detector signal S2generated via the second beam path (144) for / 77 differing data pairs, wherein each data pair m is related to a differing known optical characteristic Kt.

3. The method according to any one of the preceding claims, wherein at least one item of calibration information of the items of calibration information is resolved for a plurality of different wavelength ranges.

4. The method according to the preceding claim, wherein each wavelength range of the plurality of different wavelength ranges is assigned to a specific photosensitive element of the detector (132).

5. The method according to any one of the preceding claims, wherein obtaining the items of calibration information further comprises evaluating the emittance spectrum of the first light emitting element (154) and / or the emittance spectrum of the second light emitting element (156).

6. The method according to the preceding claim, wherein obtaining the emittance spectrum of the first light emitting element (154) and / or the emittance spectrum of the second light emitting element (156) further comprises evaluating at least one item of information on a dependency of the emittance spectrum of the respective light emitting element (154, 156) on a driving current applied to the respective light emitting element (154, 156) and / or a forward voltage applied to the respective light emitting element (154, 156).

7. The method according to any one of the two preceding claims, wherein the emittance spectrum comprises information on at least one of:- at least one item of information on a wavelength range of the light (136, 146) emitted by the respective light emitting element (154, 156);- at least one item of information on an intensity of the light (136, 146) emitted by the respective light emitting element (154, 156).

8. The method according to any one of the preceding claims, wherein the different data pairs are obtained by- using a plurality of different calibration targets;- varying a distance between a single calibration target and the at least one sample interface (130) and, thereby, varying the known optical characteristic of the calibration target;- emitting first light (136) with a plurality of different emittance spectra;- emitting second light (146) with a plurality of different emittance spectra.

9. A method for operating a spectrometer device (126) for obtaining at least one item of spectral information on at least one object (128), wherein the method comprises the following steps:1 . emitting first light (136) along a first beam path (134) onto a detector (132) of the spectrometer device (126) by using at least one first light emitting element (154) of the spectrometer device (126) in order to generate at least one first detector signal by at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the first beam path (134) is configured for first light (136) propagating along the first beam path (134) passing at least one sample interface (130) of the spectrometer device (126); wherein the at least one object is arranged on the at least one sample interface (130) in a manner that first light (136) interacts with the at least one object;2. emitting second light (146) along a second beam path (144) onto the detector (132) by using at least one second light emitting element (156) of the spectrometer device (126) in order to generate at least one second detector signal by the at least one detector (132) of the spectrometer device (126); wherein the spectrometer device (126) is configured in a manner that the second beam path (144) is configured for second light (146) propagating along the second beam path (144) without passing the at least one sample interface (130) of the spectrometer device (126);3. obtaining the item of spectral informationon the object (128) by evaluating the at least one first detector signal Si and the at least one second detector signal S2by using an evaluation unit, wherein evaluating the at least one first detector signal Si and the at least one second detector signal S2comprises evaluating items of calibration information x wherein the items of calibration information are obtained by performing the method for calibrating the spectrometer device (126) for obtaining the items of calibration information according to any one of the preceding claims referring to the method for calibrating the spectrometer device (126).

10. A spectrometer device (126) for obtaining at least one item of spectral information on at least one object by spectroscopic measurement, wherein the spectrometer device (126) comprises: a) at least one sample interface (130), wherein the sample interface (130) is configured for defining a measurement pose of the at least one object outside of the spectrometer device (126); b) at least one detector (132), wherein the detector (132) is configured for generating at least one detector signal when detecting light; c) at least one first beam path (134), wherein the first beam path (134) is configured in a manner that first light (136) propagating along the first beam path (134)passes the sample interface (130) of the spectrometer device (126) and interacts with the at least one object, d) at least one second beam path (144), wherein the second beam path (144) is configured in a manner that second light (146) propagating along the second beam path (144) does not pass the sample interface (130) of the spectrometer device (126), e) at least one first light emitting element (154), wherein the first light emitting element (154) is configured for emitting first light (136) along the first beam path (134) onto the detector (132); f) at least one second light emitting element (156), wherein the second light emitting element (156) is configured for emitting second light (146) along the second beam path (144) onto the detector (132); g) at least one evaluation unit (158), wherein the evaluation unit (158) is configured for obtaining the item of spectral information by using the method for operating the spectrometer device (126) according to any one of the preceding claims referring to a method for operating a spectrometer device (126).

11. A mobile device (170), wherein the mobile device (170) comprises a spectrometer device (126) according to any one of the preceding claims referring to a spectrometer device (126).

12. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to any one of the method claims, wherein the computer is an evaluation unit (158) of the spectrometer device (126) according to the preceding claim referring to the spectrometer device (126).

13. A non-transitory computer-readable storage medium, the computer-readable storage medium including instructions that when executed by a computer, cause the computer to perform the method according to any one of the method claims, wherein the computer is an evaluation unit (158) of the spectrometer device (126) according to the preceding claim referring to a spectrometer device (126).

Images