Combination of two LEDs and open port calibration

Abstract

A method of calibrating a sensing device (110) is disclosed. The method comprises: I. illuminating the at least one detector element (112) via at least one first light path (128) to obtain at least one first detector signal, where the first light path (128) is configured to allow light emitted from the at least one light source (124) to propagate to the detector element (112) without passing through the at least one sample interface (126); iI. Illuminating the detector element (112) via at least one second optical path (130) without applying the sample onto the sample interface (126) to obtain at least one open port detector signal, where the second optical path (130) is configured to allow light emitted from the light source (124) to propagate to the detector element (112) by at least one pass through the sample interface (126); and III. Determining at least one piece of operational calibration information by using the first detector signal, the open port detector signal and at least one piece of factory calibration information, where the factory calibration information comprises a predefined relationship between the open port detector signal and a reference signal of the second optical path (130).

Description

Technical Field

[0001] The present invention relates to a method for calibrating a sensing device, a method for determining at least one calibrated optical property of at least one sample, and a sensing device. The present invention further relates to a computer program and a computer-readable storage medium for implementing these methods. Such methods and devices can generally be used for investigation and / or monitoring purposes in the infrared spectral region, particularly in the near-infrared and mid-infrared spectral regions. However, other applications (e.g., in the visible spectral region) are also possible. Background Art

[0002] Generally, sensing devices are known that collect optical information from a sample. For example, spectral sensing devices are known that collect information about the spectral composition of light from a sample when it is illuminated, reflected, and / or absorbed. To allow comparison of spectra from multiple spectral sensing devices, these spectral sensing devices must be calibrated, for example, using known calibration standards.

[0003] During operation of such sensing devices, particularly spectral sensing devices (such as diffuse reflectance, transmission, and / or hyperspectral sensing devices), it may be necessary to periodically recalibrate the sensing device to account for any drift in optical and / or optoelectronic components. Sensing devices may include, among other things, detectors, electronics (such as analog front ends for digitizing analog detector signals), and / or power management, which are often unstable with varying operating conditions (such as varying temperature and / or humidity). Similarly, radiation sources (such as infrared radiation sources) may degrade over time and / or use, and may also depend on environmental and / or operating conditions. This drift may be caused by various internal and / or external physical changes, including but not limited to: degradation of the light source and / or detector; temperature drift of the light source and / or detector; changes in ambient temperature; changes in device temperature, such as changes in the temperature of the detector and / or electronics (such as readout circuitry); mechanical expansion and / or contraction of mechanical components (such as mechanical housings and / or brackets); and mechanical expansion and / or contraction of optical components (such as bandpass filters and dispersive elements (e.g., prisms, gratings, etc.)). If these drifts are not corrected from time to time via calibration, the drifts may distort the measurement data, rendering the results obtained with uncalibrated sensing devices uncertain.

[0004] Furthermore, the detectors of sensing devices may exhibit hysteresis. This can be compensated for by using a temperature stabilization unit. For example, the detectors of sensing devices can be cooled using a thermoelectric cooler to reduce drift in the detector signal due to variations in operating temperature or changes in the detector's inherent characteristics, thereby reducing hysteresis. However, sensing devices with such temperature stabilization units are typically bulky, complex, and costly.

[0005] Therefore, known sensing devices are typically frequently recalibrated using known reference standards to eliminate drift and / or hysteresis effects. Known calibration procedures for spectral sensing devices may involve periodically calibrating the spectral sensing device for the wavelength-dependent sensitivity of the detector using known external calibration standards before measuring a sample. However, in handheld devices, using known external calibration standards may not be practical and may reduce the user experience because the user should be involved in the complex calibration process.

[0006] Furthermore, even individual detectors of the same type may have variations in characteristics (e.g., temperature coefficient of resistance, responsivity, and / or detectivity) due to manufacturing tolerances. Consequently, it may not be practical to use designated "reference" detectors, and in particular, to use the signals from these reference detectors to calibrate and / or correct the remaining detectors that measure light from the sample. A reference detector may be a detector that does not receive any radiation from the sample, and therefore, its signal may not depend on the presence or absence of any sample.

[0007] Known calibration procedures may require light calibration and dark calibration. Different types of calibration measurements may be performed that require an external calibration standard (such as a predefined reflection target) and / or an empty radiation path in front of the detector to ensure that no reflected radiation reaches the detector. Dark calibration may recalibrate the "dark current", "dark noise" and / or "dark resistance". In order to perform a dark calibration, a calibration target may not be required. Dark calibration may include preventing the detector from being illuminated by turning off the light source and / or by blocking the light path between the light source and the detector. Light calibration may include calibrating the wavelength-dependent sensitivity of a photosensitive detector. In particular, for reflectance spectroscopy, calibration may be performed by employing an external calibration standard with a predefined reflection spectrum to ensure a known and reproducible calibration signal. The external calibration standard can be positioned in the radiation path of the detector, similar to spectral measurements of a sample. However, for these calibrations, the user may be responsible for positioning the external calibration standard and / or removing any objects within the sensing range of the sensing device.

[0008] Some methods and devices are known to overcome the need for external calibration standards during the calibration process. For example, the calibration process can include compensating for responsivity drift of a single component, such as a detector of a sensing device. This can be achieved in a self-referencing scheme: an environmentally sensitive characteristic of the detector is measured and then used to compensate for the detector responsivity. However, using this approach, compensating for drift of the sensing device (such as the systematic effects of combining all components into a single sensing device and its dependence on the environment) can be technically challenging.

[0009] As another example, the calibration process can include using a built-in reference and measuring the light reflection from it in the absence of a sample, also known as an "open-port measurement." This measurement can be used to calculate a fixed factor during factory calibration by comparing the open-port measurement results with measurements using an external calibration standard. Calibration is typically based on the assumption that the calibration factor is constant and stable over time throughout the lifecycle of the sensing device. Under this assumption, the open-port measurement results can be used to analytically determine the reference value. This calibration scheme may typically require performing open-port measurements before and / or after the sample measurement. Each measurement may generate heat from active components (such as the lamp driver, light source, analog-to-digital converter, etc.). After each measurement, this heat may dissipate into the sensing device, potentially changing the temperature of other components (such as the detector). Therefore, ensuring that all components of the sensing device are under the same operating conditions when performing open-port and sample measurements can often be technically challenging. This technical challenge can be overcome by performing open-port measurements before and after the sample measurement and approximating the reference signal by linearly fitting the results before and after the measurements. However, this approach can introduce further uncertainty due to the nonlinear thermal response of the sensing device. Additionally, this calibration scheme can suffer from drawbacks due to the fact that during field use, open-port measurements can be perturbed by misoperation of the sensing device. For example, partial coverage of the measurement port by an undefined sample can cause a perturbation. This perturbation further increases the measurement uncertainty of the calibration factor.

[0010] As another example, the calibration process can include using at least two optical paths, where the first optical path is unaffected by the presence or absence of a sample, and the detector signal in the second optical path is dependent on the presence or absence of a sample. The signals in the first and second optical paths can be distinguished through time multiplexing or frequency multiplexing. In the case of frequency multiplexing, the two optical paths illuminate the detector simultaneously but at different modulation frequencies. Therefore, in this case, thermal changes affecting components of the sensing system (such as the detector, light source, and readout electronics) are likely to be the same. Thermal drift can be compensated for by normalizing the detector signal of the second optical path relative to the first optical path. In this approach, the open port signal and reference signal of the second optical path can depend on the signal in the first optical path. Calibration often assumes that the calibration factor is independent of environmental and operating conditions. However, this assumption is generally valid only if the illumination via the two optical paths is likely to be constant and / or the drift of the two optical paths is likely to be the same. A possible implementation of this calibration scheme can include using two light sources operating at different frequencies for the first and second optical paths, respectively. However, manufacturing tolerances of the light sources can affect calibration. Similarly, producing other components of the sensing device (such as semiconductor chips, phosphor coatings of LEDs, filaments of incandescent lamps, and / or other light sources) with low manufacturing tolerances may require significant efforts in production accuracy. Manufacturing tolerances may typically result in deviations in the temperature coefficients of the electrical and / or optical properties of the light source. Deviations can be minimized by using light sources with similar temperature coefficients, so that deviations are typically not observed at small temperature changes of a few Kelvin. However, at large temperature differences between factory calibration and sample measurements, for example at temperature differences of more than 10 K, manufacturing tolerances may become significant. In general, the assumption of a constant calibration factor may become inaccurate. Additionally, the assumption of a constant calibration factor may become inaccurate due to aging effects that affect the two light sources differently.

[0011] Problem to be solved

[0012] It is therefore desirable to provide methods and devices that at least partially address the above technical challenges and at least substantially avoid the disadvantages of known methods and devices.In particular, it is an object of the present invention to provide methods and devices for user-friendly and accurate calibration of a sensing device. Summary of the Invention

[0013] This problem is solved by a method for calibrating a sensing device, a method for determining at least one calibrated optical property of at least one sample, and a sensing device having the features of the independent claims. The problem is further solved by a computer program and a computer-readable storage medium for executing the method. Advantageous embodiments, which can be implemented independently or in any arbitrary combination, are listed in the dependent claims and throughout the description.

[0014] In a first aspect of the present invention, a method of calibrating a sensing device is disclosed.

[0015] As used herein, the term "sensing device" is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, an optical device configured to acquire at least one piece of optical information about at least one sample. For example, a sensing device may be an optical device configured to determine and / or detect and / or sense a sample, such as a 3D detector. For example, a sensing device may be an optical device configured to acquire at least one piece of spectral information about a sample. Specifically, the at least one piece of spectral information may refer to at least one optical or optically measurable property determined as a function of wavelength, for one or more different wavelengths. More specifically, the optical or optically measurable property and the at least one piece of spectral information may relate to at least one property of the sample itself or after exposure to external light, including at least one of transmission, absorption, reflection, and emission. The at least one optical property may be determined for one or more wavelengths. The sensing device may specifically be a device capable of recording signal intensity for a corresponding wavelength or a subregion (e.g., a wavelength interval) of a spectrum, wherein the signal intensity may be provided as an electrical signal that can be used for further evaluation.

[0016] Sensing equipment includes:

[0017] a. at least one detector element configured to generate at least one detector signal in response to incident light irradiating the detector element;

[0018] b. at least one light source configured to emit light within at least one optical spectral range;

[0019] c. at least one sample interface configured to allow light from a light source to illuminate at least one sample and to allow light from the sample to propagate to a detector element, in particular via at least one wavelength selective element;

[0020] d. at least one first optical path, wherein the first optical path is configured to allow light emitted from the light source to propagate to the detector element, specifically via the wavelength selective element, without passing through the sample interface;

[0021] e. At least one second optical path, wherein the second optical path is configured to allow light emitted from the light source to propagate to the detector element by passing through the sample interface at least once, in particular via the wavelength selective element.

[0022] As used herein, the term "detector element" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, any device or combination of devices capable of recording and / or monitoring incident light. A detector element may be responsive to incident light and may be configured to generate an electrical signal indicative of the intensity of the incident light. For example, a detector element may include at least one photosensor having at least one photosensitive region configured to record a light response by generating at least one output signal that is dependent on the intensity of the incident light incident on the photosensitive region. The detector element may be sensitive in one or more of the visible spectral range, the ultraviolet spectral range, or the infrared spectral range, specifically the near-infrared spectral range (NIR). The detector element may specifically be or may include at least one optical sensor, such as an optical semiconductor sensor. As an example, in particular, in the case where the detector element is sensitive in the infrared spectral range (such as in the near infrared spectral range), the semiconductor sensor may be or may include at least one semiconductor sensor, at least one material of which is selected from the group consisting of: Si, PbS, PbSe, InGaAs and extended InGaAs. As an example, the detector element may include at least one photodetector, such as at least one CCD or CMOS device. The detector element may specifically include at least one detector array, which includes a plurality of pixelated sensors, wherein each pixelated sensor is configured to detect at least a portion of the incident light. Alternatively or additionally, the detector element may include a single photosensitive element that responds in a wide spectral range (such as in one or more of the visible spectral range, the ultraviolet spectral range and the infrared spectral range).

[0023] As used herein, the term "detector signal" is a broad term and is to be given its ordinary and customary meaning for a person of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically, but not limited to, refer to a signal generated by at least one detector, specifically an electrical signal of a detector element, and more specifically at least one output signal of a photosensitive element. The at least one detector signal may be an analog signal and / or a digital signal. The detector element (specifically, each photosensitive element) may include an active pixel sensor, which may be adapted to amplify the output signal before providing it as the detector signal to an internal or external evaluation unit. For this purpose, the detector element (specifically, the photosensitive element) may include one or more signal processing devices, such as one or more filters and / or analog-to-digital converters, for processing and / or pre-processing the electronic signal.

[0024] As used herein, the term "irradiation" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, the amount or intensity of light incident on a certain area (specifically, the photosensitive area of ​​a detector element). As used herein, the term "light" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, a subregion of electromagnetic radiation commonly referred to as the "optical spectral range" and including one or more of the visible, ultraviolet, and infrared spectral ranges. The term "ultraviolet spectral range" or "UV" may generally refer to electromagnetic radiation having wavelengths between 1 nm and 380 nm, preferably between 100 nm and 380 nm. The term "visible spectral range" may generally refer to wavelengths between 380 nm and 760 nm. The term “infrared spectral range” or “IR” may generally refer to wavelengths of 760 nm to 1000 µm, wherein wavelengths of 760 nm to 3 µm may generally be referred to as the “near infrared spectral range” or “NIR”, while wavelengths of 3 µm to 15 µm may generally be referred to as the “mid-infrared spectral range” or “MidIR”, and wavelengths of 15 µm to 1000 µm are referred to as the “far infrared spectral range” or “FIR”.

[0025] The sensing device may further include at least one wavelength-selective element configured to pass incident light within at least one selected wavelength range to the detector element. As used herein, the term "wavelength-selective element" is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a specific or customary meaning. The term may specifically refer to, but is not limited to, any element or combination of elements adapted to transmit, reflect, deflect, or scatter light in a wavelength-dependent manner. The wavelength-selective element may be specifically configured to perform wavelength-dependent transmission by spatially separating incident light having different wavelengths. For example, the wavelength-selective element may be configured to separate the incident light into a spectrum having component wavelengths and transmit the wavelength components within a selected wavelength range to the detector element. The wavelength-dependent transmission, reflection, deflection, or scattering of the incident light at the wavelength-selective element may result in spatial separation of the incident light. Alternatively or additionally, the wavelength-selective element may be configured to perform wavelength-dependent transmission by reducing the intensity of light having wavelengths outside the selected wavelength range, such as by using a filter element (specifically, a narrow bandpass filter). The wavelength selective element may be selected from the group consisting of: a prism; a grating; a linear gradient filter; an optical filter, in particular a narrow bandpass filter; a patterned filter; a multichannel filter (butchers block filter); a hyperspectral filter; a Fabry-Perot filter; a tunable microelectromechanical system (MEMS) filter, in particular a MEMS Fabry-Perot filter; an interferometer, in particular a Michelson interferometer; a tunable MEMS Michelson interferometer; a metamaterial-based grating; a metamaterial-based filter; an absorption filter; and a filter foil. Alternatively or additionally, the wavelength selective element may be incorporated into a detector element, such as a detector element sensitive to a specific wavelength range. For example, the detector element sensitive to a specific wavelength range may provide a combination of a detector element and a wavelength selective element. As an example, the detector element may include at least one quantum dot sensor and / or at least one organic photodiode.

[0026] As used herein, the term "selected wavelength range" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or customized meaning. The term specifically refers to, but is not limited to, a wavelength range of light that is transmitted, reflected, deflected, or scattered by a wavelength selective element onto a detector element.

[0027] As used herein, the term "light source" is a broad term and is to be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to any special or custom meaning. The term specifically refers to, but is not limited to, any device configured to emit light within the optical spectral range (i.e., within one or more of the visible, infrared, and ultraviolet spectral ranges). Specifically, a light source can be configured to emit light within the infrared spectral range, such as light with a wavelength of 760 nm to 100 µm, or more specifically, light within the near-infrared spectral range, such as light with a wavelength of 760 nm to 3 µm. A light source can be configured to simultaneously emit light having different wavelengths, such that the light source can be configured to emit white light. By way of example, the light source can be or include at least one light-emitting diode (LED). However, other options are also possible, such as a thermal emitter, such as an incandescent lamp or a thermal infrared emitter, or a blackbody radiator. Alternatively or additionally, the light source can include one or more monochromatic light sources, each configured to emit monochromatic light within one or more of the visible, infrared, and ultraviolet spectral ranges.

[0028] As used herein, the term "sample interface" is a broad term and is to be given its ordinary and customary meaning for persons of ordinary skill in the art and is not limited to a special or customary meaning. The term may specifically, but is not limited to, refer to a port of a sensing device (particularly a spectrometer device) through which light within an optical spectral range (such as at least one subregion of the optical spectral range or the full optical spectral range) can enter the sensing device, particularly for the purpose of spectral sensing, and / or can exit the sensing device, for example, for the purpose of illuminating at least one sample. By way of example, the sample interface may define an optical plane of the sensing device, such as a material plane or an imaginary plane, through which light from a second optical path can travel to a sample, and / or through which reflected light from the sample can travel to a detector, for example, to generate a second detector signal, as will be explained in further detail below. The sample interface may or may not be comprised of physical elements and / or barriers, such as transparent elements, such as glass or quartz windows. The sample interface may also be the sample surface itself, or a plane upon which a sample can be placed or aligned. As an example, the sample interface may be or may include at least one element comprising at least one transparent material that is at least partially transparent within an optical spectral range (e.g., within at least one subregion of the optical spectral range or the entire optical spectral range). The sample interface may be configured to transmit light within the optical spectral range. The sample interface may be arranged in an optical path of the sensing device, specifically in a second optical path, to allow light emitted from a light source to illuminate a sample placed in front of the sensing device, specifically in front of the sample interface. As an example, the transparent material may include one or more of a glass material (e.g., silicon dioxide, soda lime, borosilicate, etc.) and / or a polymer material (e.g., polymethyl methacrylate or polystyrene).

[0029] As used herein, the term "sample" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, any object or element selected from living or non-living objects and having at least one optical property, the determination of which is preferably of interest to a user when using a sensing device. The sample may be suitable for interfacing with the sensing device, specifically, with a sample interface.

[0030] As outlined above, the sensing device includes at least one first optical path and at least one second optical path. As used herein, the term "optical path" is a broad term and is to be given its ordinary and conventional meaning to a person of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, the trajectory of light in the sensing device. The optical path of light in the sensing device may be affected by reflection, refraction, dispersion and / or absorption at one or more optical elements (such as lenses, prisms, mirrors, gratings, etc.) included in the sensing device. As generally used herein, the terms "first" and "second" are used for naming purposes only and do not imply any ordering or numbering.

[0031] As used herein, the term "first optical path" is a broad term and is to be given its ordinary and conventional meaning to a person of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, an optical path that does not interact with the sample. In particular, the detector signal obtained via the first optical path may not be affected by the presence and / or absence of the sample at the sensing device. For example, the detector signal obtained via the first optical path when the sample is applied to the sensing device may be equal to the detector signal obtained via the first optical path when the sample is not applied to the sensing device, in particular assuming constant environmental conditions. In particular, as outlined above, the first optical path is configured to allow light emitted from the light source to propagate to the detector element, in particular via the wavelength selective element, without passing through the sample interface, in particular without being reflected at the sample. For example, via the first optical path, light emitted from the light source may be transferred to the wavelength selective element and subsequently to the detector element without interacting with the sample. The first optical path may be arranged entirely within the sensing device, such as within a housing of the sensing device. Light following a first optical path can be emitted by a light source and directed directly or indirectly (e.g., via reflection, refraction, and / or dispersion) to a detector element, specifically a wavelength-selective element, and subsequently to the detector element. As an example, the first optical path can include a fiber-coupled optical path that transfers light from the light source to the detector element. The detector element can be configured to generate at least one detector signal in response to illumination by incident light via the first optical path.

[0032] As used herein, the term "second optical path" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a specific or customary meaning. The term may specifically refer to, but is not limited to, an optical path that interacts with a sample. Specifically, the detector signal obtained via the second optical path can be affected by the presence and / or absence of the sample at the sensing device. For example, the detector signal obtained via the second optical path when a sample is applied to the sensing device can differ from the detector signal obtained via the second optical path when the sample is not applied to the sensing device, specifically regardless of constant ambient conditions. Specifically, the second optical path is configured to allow light emitted from the light source to propagate to the detector element by passing through the sample interface at least once, specifically via a wavelength-selective element. For example, the second optical path may allow light emitted from the light source to propagate to the sample interface and then to the detector element via the wavelength-selective element. Light emitted from the light source may be guided to the sample interface directly or indirectly (e.g., by reflection, refraction, and / or dispersion) via the second optical path. The second optical path may be partially disposed outside the sensing device, such as outside the sensing device housing. Specifically, the light in the second optical path can leave the sensing device, in particular the housing of the sensing device, at the sample interface to illuminate a sample arranged outside the sensing device. The second optical path can be configured to couple light reflected at the sample back into the sensing device. The light reflected at the sample interface can be guided directly or indirectly (such as by reflection, refraction and / or dispersion) to the detector element, in particular to the wavelength selection element and subsequently to the detector element. The reflection at the sample interface can include diffuse reflection. In particular, the light in the second optical path that illuminates the wavelength selection element and subsequently illuminates the detector element can be diffusely reflected light. The detector element can be configured to generate at least one detector signal in response to illumination by incident light via the second optical path.

[0033] One or more of the first optical path and the second optical path may include at least one built-in reference target. The built-in reference target may completely cover the first optical path used to determine the first detector signal, such as by having a first light source on the first optical path, wherein the second optical path may be only partially covered by the built-in reference target. Thus, a portion of light from the light source on the second optical path may pass through the sample interface, wherein another portion of the light may be reflected back to the detector element to determine the open port detector signal. Alternatively or additionally, the built-in reference target may be split into two built-in reference targets, one on the first optical path and the other on the second optical path.

[0034] This method is a method for calibrating a sensing device. As used herein, the term "performing a calibration" (also referred to as "calibration") is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or customary meaning. The term may specifically refer to, but is not limited to, the process of determining, correcting, adjusting, and compensating for at least one of measurement inaccuracies at a sensing device. Calibration may include determining at least one piece of calibration information. Calibration information may include at least one piece of information regarding the calibration results, such as a calibration function, calibration factor, calibration matrix, etc. Calibration information may be used to convert one or more measured values ​​into one or more calibrated or "true" values. For example, measurement inaccuracies may arise from uncertainty in wavelength determination and / or from intrinsic and / or extrinsic interference with the sensing device's measurement signal. Calibrating the sensing device may include at least one of wavelength calibration, stray light calibration, and dark current calibration. Calibration may include at least one two-step process, wherein, in a first step, information regarding the deviation of the sensing device's measurement signal from a known standard is determined, and, in a second step, this information is used to correct and / or adjust the sensing device's measurement signal to reduce, minimize, and / or eliminate the deviation. Calibration may include applying at least one piece of calibration information to, for example, a measurement signal and / or a measurement spectrum of the sensing device.Calibration of the sensing device may improve and / or maintain the accuracy of measurements performed using the calibrated sensing device.

[0035] The method includes the following steps, which may be performed in the order given by way of example. However, it should be noted that different orders are also possible. Furthermore, one, more than one, or even all of the method steps may be performed once or repeatedly. Furthermore, two or more method steps may be performed simultaneously or in a timely overlapping manner. The method may include additional method steps not listed.

[0036] The method includes:

[0037] I. Illuminating a detector element via at least one first light path to obtain at least one first detector signal ;

[0038] II. Illuminating the detector element via at least one second optical path without a sample applied to the sample interface to obtain at least one open port detector signal ;as well as

[0039] III. By using the first detector signal , open port detector signal and at least one piece of factory calibration information to determine at least one piece of operational calibration information, wherein the factory calibration information includes an open port detector signal and a predefined relationship with a reference signal of the second optical path.

[0040] As used herein, the term "irradiating" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, the process of providing, delivering, and / or directing light to at least one of a device or element to be illuminated. Specifically, a detector element may be illuminated with light via at least one of a first optical path and a second optical path, wherein light emitted from a light source of a sensing device may be directed onto the detector element. Irradiation may include direct irradiation of the detector element, such as directing light emitted from a light source to the detector element directly without interacting with a sample, and / or indirect irradiation of the detector element, such as directing light emitted from a light source to the detector element with an intermediate interaction with the sample. Irradiating the detector element may include light reaching a photosensitive area of ​​the detector element, thereby causing the detector element to generate a detector signal, such as an electronic signal indicative of irradiation of the detector element. Irradiating the detector element may specifically include directing light emitted from a light source to the detector element via at least one of a first optical path and a second optical path.

[0041] As used herein, the term "first detector signal" is a broad term and is to be given its ordinary and conventional meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, a detector signal obtained by illuminating a detector element via a first optical path. A first detector signal may be a detector signal that does not interact with one or more of the sample interface and the sample. As outlined above, the term "first" (also used in the context of a detector signal) is used for naming purposes and not for providing ranking purposes. Further, since the term is used only for naming purposes, the term does not necessarily imply the presence of other similar elements (such as the presence of additional detector signals in this example). As used herein, the term "open port detector signal" is a broad term and is to be given its ordinary and conventional meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, a detector signal obtained by illuminating a detector element via a second optical path when a sample is not applied to the sample interface.

[0042] As used herein, the term "operational calibration information" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, calibration information based at least in part on a first detector signal and a second detector signal of a sensing device. The operational calibration information may be determined during operation of the sensing device, such as during a calibration procedure and / or during a measurement procedure. For example, the operational calibration information may be determined in a calibration procedure during operation of the sensing device and / or during a measurement procedure at a client. The operational calibration information may be the first detector signal , open port detector signal and factory calibration information. The operational calibration information may depend on varying operating conditions (such as varying temperature and / or humidity) and / or degradation of the sensing device (such as degradation of the light source and / or detector elements). The operational calibration information may be configured to account for drift effects due to varying operating conditions and / or degradation of the sensing device, and specifically to compensate the detector signal for such drift effects.

[0043] As used herein, the term "factory calibration information" is a broad term and is to be given its ordinary and customary meaning to one of ordinary skill in the art and is not limited to a special or customized meaning. The term may specifically refer to, but is not limited to, predefined and / or predetermined calibration information determined during at least one factory calibration process. As an example, the factory calibration process may include determining the factory calibration information using at least one reference sample, such as at least one sample having known optical properties (e.g., known reflectivity and / or absorbance). The factory calibration process may be performed at the manufacturing site of the sensing device. The factory calibration process may include determining the calibration information using multiple sensing devices, such as determining calibration information for a batch of sensing devices. The factory calibration may be predetermined calibration information. For example, the factory calibration information may be determined prior to step I of the method for calibrating the sensing device. The factory calibration information may be assumed to be constant over the lifetime of the sensing device.

[0044] As outlined above, the factory calibration information includes the open port detector signal The predefined relationship between the reference signal of the second optical path and the reference signal of the second optical path. For example, the predefined relationship can be represented by the following mathematical function gives:

[0045]

[0046] in, Indicates the reference signal of the second optical path.

[0047] Mathematical functions It may include at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher-order polynomial function; power function; exponential function; power-law function; or the sum of two or more of the above functions. For example, the predefined relationship may be given by the following formula:

[0048]

[0049] in, is a constant, .

[0050] The predefined relationship may be determined before step I., in particular in a factory calibration of the sensing device performed before step I.

[0051] The first relation can be expressed by the following mathematical function gives:

[0052]

[0053] in, Indicates the reference signal of the second optical path.

[0054] Mathematical functions It may include at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher-order polynomial function; power function; exponential function; power-law function; or the sum of two or more of the above functions. For example, the first relationship can be given by the following formula:

[0055]

[0056] in, is a constant, .

[0057] The method of calibrating a sensing device may comprise determining a first relationship, specifically determining a factor Determining the first relationship may include using factory calibration information, specifically the open port detector signal For example, by using factory calibration information, specifically a predefined relationship (such as that exemplified by Equation 2), the open port detector signal To determine the first relationship, specifically the factor .

[0058] The operational calibration information may further include information about the first detector signal With open port detector signal For example, the second relationship can be represented by the following mathematical function gives:

[0059]

[0060] Mathematical functions It may include at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher-order polynomial function; power function; exponential function; power-law function; or the sum of two or more of the above functions. For example, the second relationship can be given by the following formula:

[0061]

[0062] in, is a constant, .

[0063] The method of calibrating a sensing device may comprise determining a second relationship, specifically determining a factor .

[0064] In the method for calibrating a sensing device, steps I and II may be performed using at least one multiplexing method selected from the group consisting of: a time multiplexing method; a frequency multiplexing method. For example, steps I and II may be performed using a frequency multiplexing method. The sensing device may include two light sources, wherein the first light source arranged on the first optical path may be arranged at a frequency of operation, while the second light source arranged on the second optical path can operate at a frequency Operation, where For example, steps I and II may be performed using a time multiplexing method. The light source of the sensing device may be operated sequentially to illuminate the first light path and the second light path in sequence.

[0065] In another aspect of the invention, a method of determining at least one calibrated optical property of at least one sample is disclosed.For definitions of terms and possible embodiments, reference is made to the description of the method of calibrating a sensing device as outlined above.

[0066] As used herein, the term "optical property" is a broad term and is to be given its ordinary and conventional meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, at least one piece of information of a sample that describes the interaction of the sample with light. The optical property can be detected by determining the interaction of the sample with light. As used herein, the term "calibrated optical property" is a broad term and is to be given its ordinary and conventional meaning to one of ordinary skill in the art and is not limited to a special or custom meaning. The term may specifically refer to, but is not limited to, an optical property converted by using at least one piece of operational calibration information. In particular, the calibrated optical property can correct, adjust and / or compensate for one or more measurement inaccuracies at the sensing device, such as measurement inaccuracies caused by uncertainties in wavelength determination and / or intrinsic and / or extrinsic interference with the measurement signal of the sensing device. As an example, a calibrated optical property may be an optical property of a sample that has been corrected, adjusted and / or compensated for drift effects of optical components of the sensing device, such as drift effects caused by temperature and / or humidity variations at the detector elements, degradation effects of the light source and / or other optical components of the sensing device. The calibrated optical property may be the result of a method for determining at least one calibrated optical property of at least one sample, wherein in particular, the calibration may be performed at least partially simultaneously with the presence of the sample at the sensing device (e.g., in a partially temporally overlapping manner) and / or sequentially with the presence of the sample at the sensing device. The calibrated optical property of the sample may include one or more of the light absorbance and light reflectance of the sample.

[0067] The method includes the following steps, which may be performed in the order given by way of example. However, it should be noted that different orders are also possible. Furthermore, one, more than one, or even all of the method steps may be performed once or repeatedly. Furthermore, two or more method steps may be performed simultaneously or in a timely overlapping manner. The method may include additional method steps not listed.

[0068] The method includes:

[0069] i. providing a sensing device according to the present invention, such as a sensing device according to the embodiments of the sensing device defined with respect to the method of calibrating a sensing device outlined above and / or a sensing device according to any other embodiment disclosed in further detail below;

[0070] ii. Providing at least one sample, specifically providing at least one sample to the sample interface;

[0071] iii. Illuminating the detector element via at least one first light path to obtain at least one first detector signal ;

[0072] iv. Illuminating the detector element via at least one second light path to obtain at least one second detector signal ;as well as

[0073] v. By using the first detector signal , the second detector signal and at least one operational calibration information for determining at least one calibrated optical property of the sample, the at least one operational calibration information being determined by using a method for calibrating a sensing device according to the present invention, such as according to any of the above-described embodiments and / or according to any other embodiments disclosed in further detail below.

[0074] The sensing device used in the method for determining at least one calibrated optical property of at least one sample can be implemented identically or similarly to the sensing device used in the method for calibrating a sensing device according to the present invention (e.g., according to any of the above-described embodiments). In fact, the same sensing device can be used for both methods. However, other embodiments of the sensing device provided in step i. are also possible, such as any of the embodiments of the sensing device disclosed in further detail below.

[0075] As outlined above, operational calibration information may include information about the first detector signal The reference signal of the second optical path For example, the first relationship can be given by the following formula:

[0076]

[0077] in, is a constant, .

[0078] The operational calibration information may further include information about the first detector signal With open port detector signal For example, the second relationship can be given by the following formula:

[0079]

[0080] in, is a constant, .

[0081] For example, the calibrated optical property of the sample can be the light reflectivity of the sample Generally, the reflectivity of a sample can be determined according to the following formula:

[0082]

[0083] Using Equations 7 and 8, the light reflectance of the sample can be:

[0084]

[0085] Furthermore, the method of determining at least one calibrated optical property of at least one sample may comprise redetermining the operational calibration information, in particular redetermining one or more items of information about the first relationship and the second relationship, respectively, more particularly redetermining the factor and One or more of .

[0086] The sensing device may further include at least one monitoring device for monitoring at least one operating condition of the sensing device, specifically one or more of the following: ambient temperature, temperature of one or more components of the sensing device (e.g., a light source and / or a detector element), ambient humidity, etc. If the monitored operating condition deviates from a nominal value by more than a predefined threshold, operational calibration information may be re-determined. For example, the monitored operating condition may be the temperature of the sensing device. If the temperature deviates from a previously determined temperature value in operational calibration information by more than a predefined threshold (e.g., by more than 10 K), operational calibration information may be re-determined. In this case, the nominal value may be the previously determined temperature value. Re-determining the operational calibration information may include executing a method for calibrating the sensing device according to the present invention (e.g., according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below). Alternatively or additionally, the monitored operating condition may be the ambient temperature of the sensing device.

[0087] In the method for determining at least one calibrated optical characteristic of at least one sample, steps iii. and iv. may be performed using at least one multiplexing method selected from the group consisting of: a time multiplexing method; and a frequency multiplexing method. An exemplary embodiment of such a multiplexing method is described with reference to the method for calibrating a sensing device. Therefore, for the description of the multiplexing method, reference is made to the description of the method for calibrating a sensing device.

[0088] In another aspect of the invention, a sensing device is disclosed.For definitions of terms and possible embodiments, reference is made to the description of the method of calibrating a sensing device as outlined above.

[0089] Sensing equipment includes:

[0090] a. at least one detector element configured to generate at least one detector signal in response to incident light irradiating the detector element;

[0091] b. at least one light source configured to emit light within at least one optical spectral range;

[0092] c. at least one sample interface configured to allow light from a light source to illuminate at least one sample and to allow light from the sample to propagate to a detector element, in particular via at least one wavelength selective element;

[0093] d. at least one first optical path, wherein the first optical path is configured to allow light emitted from the light source to propagate to the detector element, specifically via the wavelength selective element, without passing through the sample interface;

[0094] e. at least one second optical path, wherein the second optical path is configured to allow light emitted from the light source to propagate to the detector element by passing through the sample interface at least once, in particular via the wavelength selective element; and

[0095] f. At least one evaluation unit configured to determine at least one calibrated optical property of a sample by using the method for determining at least one calibrated optical property of at least one sample according to the present invention, such as according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below.

[0096] As used herein, the term "evaluation unit" is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or customary meaning. The term may specifically, but not limited to, refer to any logic circuitry configured to perform the basic operations of a computer or system, and / or generally refers to a device configured to perform computational or logical operations. An evaluation unit may include one or more processors. In particular, the evaluation unit may be configured to process the basic instructions that drive the computer or system. By way of example, the evaluation unit may include at least one arithmetic logic unit (ALU), at least one floating point unit (FPU) (such as a math coprocessor or digital coprocessor), multiple registers (specifically, registers configured to provide operands to the ALU and store operation results), and memory (such as L1 and L2 cache memory). In particular, the evaluation unit may be a multi-core processor. In particular, the evaluation unit may be or include a central processing unit (CPU). Additionally or alternatively, the evaluation unit may be or include a microprocessor, and thus, in particular, the elements of the evaluation unit may be contained within a single integrated circuit (IC) chip. Additionally or alternatively, the evaluation unit may be or may include one or more application-specific integrated circuits (ASICs) and / or one or more field-programmable gate arrays (FPGAs) and / or one or more tensor processing units (TPUs) and / or one or more chips (such as dedicated machine learning optimization chips, etc.).

[0097] The evaluation unit can be configured, for example, through software programming, to determine the calibrated optical property of the sample by performing step v. of the method for determining at least one calibrated optical property of at least one sample according to the present invention. Furthermore, the evaluation unit can be configured, for example, through software programming, to determine at least one piece of operational calibration information by using the method for calibrating a sensing device according to the present invention (e.g., according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below). Specifically, the evaluation unit can be configured to determine the calibration information by performing step III. of the method for calibrating a sensing device according to the present invention.

[0098] The sensing device may further comprise at least one wavelength selective element configured to pass incident light within at least one selected wavelength range onto the detector element.For possible embodiments of the wavelength selective element, reference is made to the above description of the method.

[0099] The sensing device may further include at least one monitoring device for monitoring at least one operating condition of the sensing device. As used herein, the term "sensing device" is a broad term and will be given its ordinary and conventional meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term specifically may refer to, but is not limited to, any element configured to perform one or more of the following: detect, measure or monitor at least one measurement variable or measurement characteristic. Specifically, the monitoring device may be capable of generating at least one signal, such as a measurement signal, such as an electrical signal, which is a qualitative or quantitative indicator of the measurement variable and / or measurement characteristic. For example, the monitoring device may be configured to monitor the ambient temperature of the sensing device. For example, the monitoring device may be configured to monitor the ambient humidity of the sensing device. For example, the monitoring device may be configured to monitor both the ambient temperature and the ambient humidity of the sensing device.

[0100] In another aspect of the present invention, a computer program for calibrating a sensing device is disclosed, the computer program comprising instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of the sensed device), cause the computer or computer network to perform at least step III. of the method for calibrating a sensing device according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0101] The computer program may further comprise instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to control the execution of steps I. and II. of the method for calibrating a sensing device according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0102] Similarly, a computer-readable storage medium, in particular a non-transitory computer-readable storage medium, is disclosed, which comprises instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or the computer network to perform at least step III. of the method for calibrating a sensing device according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0103] As used herein, the term "computer-readable storage medium" may specifically refer to a non-transitory data storage device, such as a hardware storage medium, on which computer-executable instructions are stored. A computer-readable data carrier or storage medium may specifically be or include a storage medium such as a random access memory (RAM) and / or a read-only memory (ROM).

[0104] The computer-readable storage medium may further comprise instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to control the execution of steps I. and II. of the method for calibrating a sensing device according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0105] In another aspect of the present invention, a computer program for determining at least one calibrated optical property of at least one sample is disclosed, the computer program comprising instructions which, when the program is executed by a computer or a computer network (e.g. an evaluation unit of a sensing device), cause the computer or computer network to perform at least step v. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0106] The computer program may further comprise instructions which, when the program is executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to control the execution of steps iii. and iv. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0107] The computer program may further comprise instructions which, when the program is executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to prompt a user to perform steps i. and ii. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0108] Similarly, a computer-readable storage medium, in particular a non-transitory computer-readable storage medium, is disclosed, which comprises instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or the computer network to perform at least step v. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0109] The computer-readable storage medium may further comprise instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to control the execution of steps iii. and iv. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0110] The computer-readable storage medium may further comprise instructions which, when executed by a computer or a computer network (e.g. an evaluation unit of a sensed device), cause the computer or computer network to prompt a user to perform steps i. and ii. of the method for determining at least one calibrated optical property of at least one sample according to the present invention (e.g. according to any of the embodiments disclosed above and / or according to any of the embodiments disclosed in further detail below).

[0111] This document further discloses and proposes a computer program comprising computer-executable instructions for executing the method according to the present invention in one or more of the embodiments contained herein when the program is executed on a computer or computer network. Specifically, the computer program can be stored on a computer-readable data carrier and / or a computer-readable storage medium.

[0112] Thus, in particular, one, more than one or even all of the method steps I. to III. described above and / or one, more than one or even all of the method steps i. to v. can be performed, controlled and / or assisted by using a computer or a computer network, preferably by using a computer program.

[0113] This document further discloses and proposes a computer program product having program code means for performing the method according to the present invention in accordance with one or more of the embodiments contained herein when the program is executed on a computer or computer network. Specifically, the program code means can be stored on a computer-readable data carrier and / or a computer-readable storage medium.

[0114] The present invention further discloses and proposes a data carrier having a data structure stored thereon, which, after being loaded into a computer or a computer network (for example, loaded into a working memory or main memory of the computer or the computer network), can execute a method according to one or more of the embodiments disclosed herein.

[0115] This document further discloses and proposes a computer program product having program code means stored on a machine-readable carrier for performing, when executed on a computer or computer network, a method according to one or more of the embodiments disclosed herein. As used herein, a computer program product refers to a program that is a tradable product. The product can generally be in any format, such as paper, or on a computer-readable data carrier and / or computer-readable storage medium. Specifically, the computer program product can be distributed via a data network.

[0116] Finally, a modulated data signal containing instructions readable by a computer system or computer network for executing a method according to one or more of the embodiments disclosed herein is disclosed and proposed herein.

[0117] With reference to the computer-implemented aspects of the present invention, one or more, or even all, of method steps I. to III. and / or method steps i. to v. of the methods according to one or more of the embodiments disclosed herein can be performed using a computer or computer network. Thus, generally, any of the method steps involving the provision and / or manipulation of data can be performed using a computer or computer network. Generally, these method steps can include any method steps, with the exception of those that typically require manual work, such as providing samples and / or performing certain aspects of the actual measurements.

[0118] Specifically, this article further discloses:

[0119] - a computer or a computer network comprising at least one processor, wherein the processor is adapted to perform one or more methods according to one of the embodiments described in this specification,

[0120] - a computer-loadable data structure adapted to perform one or more methods according to one of the embodiments described in this specification when the data structure is executed on a computer,

[0121] - a computer program, wherein the computer program is adapted to perform one or more methods according to one of the embodiments described in this description when the program is executed on a computer,

[0122] - a computer program comprising program means for carrying out one or more methods according to one of the embodiments described in this description when the computer program is executed on a computer or on a computer network,

[0123] - a computer program comprising the program means according to the preceding embodiment, wherein the program means is stored on a computer-readable storage medium,

[0124] a storage medium on which a data structure is stored and wherein the data structure is suitable for carrying out one or more methods according to one of the embodiments described in this description after being loaded into a main storage device and / or a working storage device of a computer or a computer network, and

[0125] A computer program product having program code means, wherein the program code means can be stored or stored on a storage medium for performing one or more methods according to one of the embodiments described in this description when the program code means are executed on a computer or a computer network.

[0126] The method, the sensing device, and the computer program and computer-readable storage medium according to the present invention may provide a number of advantages over known methods and devices. The method according to the present invention, in particular the method for calibrating a sensing device, may comprise a combination of the calibration schemes discussed above, i.e., a combination of a built-in reference target and at least two separate optical paths, for example by using two light sources modulated at different frequencies. This solution may assume only one piece of factory calibration information (e.g., a constant calibration factor ), depends only on the mechanical features of the sensing device (such as the sensing device housing and / or built-in reference target), wherein the sensing device housing and / or built-in reference target may not degrade significantly over its lifetime since they are only passive optical components. Therefore, depending on the environmental and operating conditions, the user may be able to perform an open port calibration, thereby allowing recalculation of operational calibration information, such as the factor and .

[0127] The sensing device can be configured (e.g., by including a monitoring device) to monitor environmental and / or operating conditions (e.g., temperature and / or humidity), and optionally save the monitored environmental and / or operating conditions during user calibration. For example, if the temperature change is less than a predefined threshold (e.g., less than 3 K, specifically less than 2 K), recalculated operational calibration information can be used for further measurements of the sample. The monitoring device can be configured to notify the user if the temperature deviation exceeds a predefined threshold limit, such as if the temperature deviation exceeds 10 K, and to notify and / or cause recalibration.

[0128] The method according to the present invention, in particular the method for calibrating a sensing device, can combine the advantages of two previously used calibration methods and mitigate their disadvantages. Based on open-port calibration, the method for calibrating a sensing device can use an open-port calibration based on only one light source. Thus, aging and / or environmental influences, such as temperature dependence, can be calibrated, since the operational calibration information depends only on the corresponding light path. Additionally, a long-term reliable calibration of the light source can be achieved by means of a built-in reference target. Furthermore, calibration via the first light path and the second light path can calibrate the response of the sensing device while performing a sample measurement. This can mitigate the disadvantages of open-port calibration.

[0129] The proposed solution may further eliminate the need for a temperature stabilization unit and the need for user-involved external calibration standards, thereby allowing the sensing device to be miniaturized to fit into, for example, a mobile device (such as a smartphone or any handheld device) for easy operation.

[0130] Furthermore, the built-in reference target may avoid the disadvantages of external calibration targets defined by the prior art, specifically, external calibration targets that degrade over time due to environmental influences, such as external calibration standards used in muddy environments, etc. The built-in reference target may be shielded from such environmental influences.

[0131] As used herein, the terms "having," "including," or "comprising," or any grammatical variations thereof, are used in a non-exclusive manner. Thus, these terms can refer to the absence of additional features in the entity described in that context, in addition to the features introduced by these terms, or the presence of one or more additional features. By way of example, the expressions "A has B," "A includes B," and "A contains B" can refer to the absence of any other elements in A besides B (i.e., A consists solely and solely of B), or the presence of one or more additional elements in entity A, such as element C, elements C and D, or even additional elements, in addition to B.

[0132] Furthermore, it should be noted that the terms "at least one", "one or more", or similar expressions indicating that a feature or element may occur once or more than once are typically used only once when introducing the corresponding feature or element. In most cases, when referring to the corresponding feature or element, the expression "at least one" or "one or more" is not repeated, but in fact, the corresponding feature or element may occur once or more than once.

[0133] 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 limiting the possibilities of alternatives. Therefore, the features introduced by these terms are optional features and are not intended to limit the scope of the claims in any way. As the skilled person will recognize, the present invention can be carried out through the use of alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any limitation on alternative embodiments of the invention, without any limitation on the scope of the invention, and without any limitation on the possibility of combining features introduced in this manner with other optional or non-optional features of the invention.

[0134] In summary, and without excluding further possible embodiments, the following embodiments may be envisaged:

[0135] Embodiment 1: A method for calibrating a sensing device, the sensing device comprising:

[0136] a. at least one detector element configured to generate at least one detector signal in response to incident light irradiating the detector element;

[0137] b. at least one light source configured to emit light within at least one optical spectral range;

[0138] c. at least one sample interface configured to allow light from the light source to illuminate at least one sample and to allow light from the sample to propagate to the detector element, in particular via at least one wavelength selective element;

[0139] d. at least one first optical path, wherein the first optical path is configured to allow light emitted from the light source to propagate to the detector element specifically via the wavelength selective element without passing through the sample interface;

[0140] e. at least one second optical path, wherein the second optical path is configured to allow light emitted from the light source to propagate to the detector element by passing through the sample interface at least once, specifically via the wavelength selective element;

[0141] The method includes:

[0142] I. Illuminating the detector element via the at least one first light path to obtain at least one first detector signal ;

[0143] II. Illuminating the detector element via the at least one second optical path without a sample applied to the sample interface to obtain at least one open port detector signal ;as well as

[0144] III. By using the first detector signal , the open port detector signal and at least one piece of factory calibration information to determine at least one piece of operational calibration information, wherein the factory calibration information includes the open port detector signal and a predefined relationship between the reference signal of the second optical path and the reference signal of the second optical path.

[0145] Embodiment 2: The method of the preceding embodiment, wherein the sensing device further comprises at least one wavelength selective element configured to pass incident light within at least one selected wavelength range onto the detector element.

[0146] Embodiment 3: The method according to any one of the preceding embodiments, wherein the predefined relationship is represented by the following mathematical function gives:

[0147]

[0148] in, Represents the reference signal of the second optical path.

[0149] Embodiment 4: The method according to the previous embodiment, wherein the mathematical function including at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher degree polynomial function; power function; exponential function; power-law function; the sum of two or more of the above functions.

[0150] Embodiment 5: The method according to any one of the two aforementioned embodiments, wherein the predefined relationship is given by the following formula:

[0151]

[0152] in, is a constant, .

[0153] Embodiment 6: The method according to any one of the preceding embodiments, wherein the predefined relationship is determined before step I., specifically determined in a factory calibration of the sensing device performed before step I.

[0154] Embodiment 7: The method according to any one of the preceding embodiments, wherein the operational calibration information includes information about the first detector signal and information of a first relationship between the signal and the reference signal of the second optical path.

[0155] Embodiment 8: The method according to the previous embodiment, wherein the first relationship is represented by the following mathematical function gives:

[0156]

[0157] in, Represents the reference signal of the second optical path.

[0158] Embodiment 9: The method according to the previous embodiment, wherein the mathematical function including at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher degree polynomial function; power function; exponential function; power-law function; the sum of two or more of the above functions.

[0159] Embodiment 10: The method according to any one of the three aforementioned embodiments, wherein the first relationship is given by the following formula:

[0160]

[0161] in, is a constant, .

[0162] Embodiment 11: The method according to any one of the four embodiments above, wherein the method comprises determining the first relationship in step III, specifically determining the factor , wherein determining the first relationship comprises using the factory calibration information, specifically the open port detector signal and a predefined relationship between the reference signal of the second optical path and the reference signal of the second optical path.

[0163] Embodiment 12: The method according to any one of the preceding embodiments, wherein the operational calibration information includes information about the first detector signal With the open port detector signal The information of the second relationship between them.

[0164] Embodiment 13: The method according to the previous embodiment, wherein the second relationship is represented by the following mathematical function gives:

[0165]

[0166] Embodiment 14: The method according to the previous embodiment, wherein the mathematical function including at least one function selected from the group consisting of: a linear function; a polynomial function, in particular a quadratic function ( ) or higher degree polynomial function; power function; exponential function; power-law function; the sum of two or more of the above functions.

[0167] Embodiment 15: The method according to any one of the three aforementioned embodiments, wherein the second relationship is given by the following formula:

[0168]

[0169] in, is a constant, .

[0170] Embodiment 16: The method according to any one of the four preceding embodiments, wherein the method comprises determining the second relationship in step III, specifically determining the factor .

[0171] Embodiment 17: The method according to any one of the preceding embodiments, wherein steps I. and II. are performed using at least one multiplexing method selected from the group consisting of: a time multiplexing method; a frequency multiplexing method.

[0172] Embodiment 18: A method of determining at least one calibrated optical property of at least one sample, the method comprising:

[0173] i. Providing a sensing device as defined in Example 1;

[0174] ii. providing the at least one sample, specifically providing the at least one sample to the sample interface;

[0175] iii. Illuminating the detector element via the at least one first light path to obtain at least one first detector signal ;

[0176] iv. illuminating the detector element via the at least one second light path to obtain at least one second detector signal ;as well as

[0177] v. By using the first detector signal , the second detector signal and determining at least one calibrated optical property of the sample using the at least one piece of operational calibration information, the at least one piece of calibration information being determined by using the method of calibrating a sensing device according to any one of the preceding embodiments.

[0178] Embodiment 19: The method of the preceding embodiment, wherein the calibrated optical properties of the sample include one or more of light absorptivity and light reflectivity of the sample.

[0179] Embodiment 20: The method according to any of the preceding embodiments relating to a method of determining at least one calibrated optical characteristic of at least one sample, wherein the operational calibration information includes information about the first detector signal The reference signal of the second optical path The information of the first relationship between them.

[0180] Embodiment 21: The method according to the previous embodiment, wherein the first relationship is given by the following formula:

[0181]

[0182] in, is a constant, .

[0183] Embodiment 22: The method according to any of the preceding embodiments relating to a method of determining at least one calibrated optical characteristic of at least one sample, wherein the operational calibration information includes information about the first detector signal With open port detector signal The information of the second relationship between them.

[0184] Embodiment 23: The method according to the previous embodiment, wherein the second relationship is given by the following formula:

[0185]

[0186] in, is a constant, .

[0187] Embodiment 24: The method of embodiments 19 and 21, wherein the calibrated optical property of the sample is the light reflectivity of the sample ,in,

[0188]

[0189] Embodiment 25: The method according to any of the preceding embodiments relating to a method for determining at least one calibrated optical property of at least one sample, wherein steps iii. and iv. are performed using at least one multiplexing method selected from the group consisting of: a time multiplexing method; a frequency multiplexing method.

[0190] Embodiment 26: The method according to any of the preceding embodiments involving a method of determining at least one calibrated optical characteristic of at least one sample, further comprising re-determining the operational calibration information.

[0191] Example 27: A method according to the previous embodiment, wherein the sensing device further includes at least one monitoring device, which is used to monitor at least one operating condition of the sensing device, specifically for monitoring the ambient temperature of the sensing device, wherein the operating information is re-determined when the monitored operating condition deviates from the nominal value by more than a given threshold.

[0192] Embodiment 28: The method according to any one of the two preceding embodiments, wherein re-determining the operational calibration information comprises executing the method for calibrating the sensing device according to any one of the preceding embodiments involving methods for calibrating the sensing device.

[0193] Embodiment 29: A sensing device comprising:

[0194] a. at least one detector element configured to generate at least one detector signal in response to incident light irradiating the detector element;

[0195] b. at least one light source configured to emit light within at least one optical spectral range;

[0196] c. at least one sample interface configured to allow light from the light source to illuminate at least one sample and to allow light from the sample to propagate to the detector element, in particular via at least one wavelength selective element;

[0197] d. at least one first optical path, wherein the first optical path is configured to allow light emitted from the light source to propagate to the detector element specifically via the wavelength selective element without passing through the sample interface;

[0198] e. at least one second optical path, wherein the second optical path is configured to allow light emitted from the light source to propagate to the detector element by passing through the sample interface at least once, in particular via the wavelength selective element; and

[0199] f. At least one evaluation unit configured to determine at least one calibrated optical property of the sample by using the method for determining at least one calibrated optical property of at least one sample according to any of the aforementioned embodiments relating to a method for determining at least one calibrated optical property of the sample.

[0200] Embodiment 30: The sensing device according to the preceding embodiment, further comprising at least one wavelength selective element configured to pass incident light within at least one selected wavelength range onto the detector element.

[0201] Embodiment 31: The sensing device according to any one of the two preceding embodiments, wherein the sensing device further comprises at least one monitoring device for monitoring at least one operating condition of the sensing device, specifically for monitoring the ambient temperature of the sensing device.

[0202] Embodiment 32: A computer program for calibrating a sensing device, the computer program comprising instructions which, when executed by a computer or a computer network, cause the computer or computer network to perform at least step III of the method for calibrating a sensing device according to any one of the aforementioned embodiments relating to methods for calibrating a sensing device.

[0203] Embodiment 33: The computer program according to the previous embodiment further comprises instructions which, when executed by the computer or computer network, cause the computer or computer network to control the execution of steps I. and II. of the method for calibrating a sensing device according to any one of the previous embodiments relating to methods for calibrating a sensing device.

[0204] Embodiment 34: A computer-readable storage medium, specifically a non-transitory computer-readable storage medium, comprising instructions which, when executed by a computer or a computer network, cause the computer or computer network to perform at least step III of the method for calibrating a sensing device according to any one of the aforementioned embodiments of the method for calibrating a sensing device.

[0205] Embodiment 35: The computer-readable storage medium according to the previous embodiment further includes instructions, which, when executed by the computer or computer network, cause the computer or computer network to control the execution of steps I. and II. of the method for calibrating a sensing device according to any one of the aforementioned embodiments involving methods for calibrating a sensing device.

[0206] Embodiment 36: A computer program for determining at least one calibrated optical property of at least one sample, the computer program comprising instructions which, when executed by a computer or a computer network, cause the computer or computer network to perform at least step v. of the method for determining at least one calibrated optical property of at least one sample according to any of the aforementioned embodiments relating to the method for determining at least one calibrated optical property of at least one sample.

[0207] Embodiment 37: The computer program according to the previous embodiment further comprises instructions which, when the program is executed by a computer or a computer network, cause the computer or computer network to control the execution of steps iii. and iv. of the method for determining at least one calibrated optical property of at least one sample according to any one of the previous embodiments involving methods for determining at least one calibrated optical property of at least one sample.

[0208] Embodiment 38: The computer program according to any one of the two preceding embodiments further comprises instructions which, when the program is executed by a computer or a computer network, cause the computer or computer network to prompt a user to perform steps i. and ii. of the method for determining at least one calibrated optical property of at least one sample according to any one of the preceding embodiments involving methods for determining at least one calibrated optical property of at least one sample.

[0209] Embodiment 39: A computer-readable storage medium, specifically a non-transitory computer-readable storage medium, comprising instructions which, when executed by a computer or a computer network, cause the computer or computer network to perform at least step v. of the method for determining at least one calibrated optical property of at least one sample according to any one of the aforementioned embodiments involving methods for determining at least one calibrated optical property of at least one sample.

[0210] Embodiment 40: The computer-readable storage medium according to the previous embodiment further includes instructions, which, when executed by a computer or a computer network, cause the computer or computer network to control the execution of steps iii. and iv. of the method for determining at least one calibrated optical characteristic of at least one sample according to any one of the aforementioned embodiments involving methods for determining at least one calibrated optical characteristic of at least one sample.

[0211] Embodiment 41: The computer-readable storage medium according to any one of the two preceding embodiments further comprises instructions which, when executed by a computer or a computer network, cause the computer or computer network to prompt a user to perform steps i. and ii. of the method for determining at least one calibrated optical property of at least one sample according to any one of the preceding embodiments involving methods for determining at least one calibrated optical property of at least one sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0212] Additional optional features and embodiments will be disclosed in more detail in the subsequent description of the embodiments, preferably in conjunction with the dependent claims. As will be appreciated by those skilled in the art, the respective optional features can be implemented independently and in any feasible combination. The scope of the present invention is not limited by the preferred embodiment. The embodiments are schematically depicted in the accompanying drawings. Identical reference numerals in these drawings represent identical or functionally equivalent elements.

[0213] In the attached figure:

[0214] Figures 1 to 3 Schematic diagrams showing different embodiments of sensing devices;

[0215] Figure 4 a flow chart illustrating an embodiment of a method of calibrating a sensing device; and

[0216] Figure 5 A flow chart illustrating an embodiment of a method of determining at least one calibrated optical property of at least one sample is shown. DETAILED DESCRIPTION

[0217] Figure 1 Schematic diagram of a first exemplary embodiment of the sensing device 110 is shown. Figures 1 to 3In an embodiment of the present invention, the sensing device 110 may be a spectral sensing device 111. The sensing device 110 includes at least one detector element 112 configured to generate at least one detector signal in response to incident light irradiating the detector element 112. Specifically, the sensing device 110 may include a plurality of detector elements 112 arranged in a detector array 114. Each of the plurality of detector elements 112 may include at least one photosensitive element 116 having at least one photosensitive region 118 configured to record a light response in response to irradiation of the corresponding detector element 112.

[0218] The sensing device 110 may further include at least one wavelength selective element 120 configured to pass incident light within at least one selected wavelength range to the detector element 112. For example, the wavelength selective element 120 may include a filter element 122, such as a linear gradient filter or an optical filter, particularly a narrow bandpass filter. However, other wavelength selective elements 120, such as a prism or a grating, are also feasible.

[0219] The sensing device 110 includes at least one light source 124 configured to emit light within at least one optical spectral range. Figure 1 As shown, the sensing device 110 may include two light sources 124. The sensing device 110 further includes at least one sample interface 126 configured to allow light from the light sources 124 to illuminate at least one sample 127 and to allow light from the sample 127 to propagate to the detector element 112 via the wavelength selective element 120.

[0220] The sensing device 110 includes at least one first optical path 128 and at least one second optical path 130. The first optical path 128 is configured to allow light emitted from the light source 124 to propagate to the detector element 112 via the wavelength selection element 120 without passing through the sample interface 126. The second optical path 130 is configured to allow light emitted from the light source 124 to propagate to the detector element 112 via the wavelength selection element 120 by passing through the sample interface 126 at least once.

[0221] As outlined above, the sensing device 110 may include two light sources 124. In this example, a first light source 132 may be arranged to illuminate a first light path 128 and a second light source 134 may be arranged to illuminate a second light path 130. The sensing device 110 may further include at least one reflective element 136 on the first light path 128. The first light source 132 may be arranged to illuminate the reflective element 136. The reflective element 136 may reflect incident light onto the wavelength selective element 120. The reflective element 136 may include at least one reflective surface 138. The reflective surface 138 may be one or more of a metal reflective surface and a polymer reflective surface. The reflection at the reflective element 136 may be a specular reflection of light. The reflection at the reflective element 136 may be a broadband reflection, specifically a uniform reflection of multiple wavelengths within at least one wavelength range. As seen from Figure 1 As can be further seen in FIG, the second light source 134 may be arranged to illuminate the sample interface 126 .

[0222] The sensing device 110 further comprises at least one evaluation unit 140. The evaluation unit 140 is configured to evaluate the sensor data by using the sensor data according to the present invention (e.g. according to the present invention). Figure 5 The method for determining at least one calibrated optical property of at least one sample 127 according to the exemplary embodiment shown in FIG. 1 and described in further detail below, determines at least one calibrated optical property of the sample 127. Figure 1 As shown, the evaluation unit 140 can be configured to receive and / or retrieve detector signals from the detector elements 112. The evaluation unit 140 can be specifically configured to evaluate the received and / or retrieved detector signals (e.g., by determining at least one operational calibration information and determining a calibrated optical characteristic). Specifically, the evaluation unit 140 can include one or more processors 142, wherein the one or more processors 142 can be configured, such as by software programming, to perform one or more evaluation operations.

[0223] The sensing device 110 may further include at least one monitoring device 143, which is used to monitor at least one operating condition of the sensing device 110, specifically for monitoring one or more of the ambient temperature, the temperature of one or more components of the sensing device 110 (such as the light source 124 and / or the detector element 112), the ambient humidity, etc.

[0224] exist Figure 2 , a schematic diagram of a second exemplary embodiment of a sensing device 110 is shown. Figure 2 The embodiment of the sensing device 110 shown generally corresponds to Figure 1 Therefore, reference is made to Figure 1 However, as from Figure 2, the sensing device 110 may be devoid of the reflective element 136. The first light source 132 may be arranged to directly illuminate the wavelength selective element 120. Thus, in this example, the first light source 132 may directly illuminate the detector element 112 without any other optical components on the first optical path 128.

[0225] Figure 3 A schematic diagram of a third exemplary embodiment of a sensing device 110 is shown. Figure 3 The embodiment of the sensing device 110 shown generally corresponds to Figure 1 Therefore, reference is made to Figure 1 In this exemplary embodiment, the sensing device 110 includes only one light source 124. The light source 124 may be specifically arranged to illuminate a first light path 128 and a second light path 130.

[0226] like Figure 3 As shown, the sensing device 110 may further include: at least one first optical modulator 144 arranged on the first optical path 128, the first optical modulator configured to modulate light on the first optical path 128; and at least one second optical modulator 146 arranged on the second optical path 130, the second optical modulator configured to modulate light on the second optical path 130. The first optical modulator 144 may be configured to modulate the light on the first optical path 128 at a first modulation frequency, and the second optical modulator 146 may be configured to modulate light at a second modulation frequency. The evaluation unit 140 may be configured to distinguish detector signals obtained by illumination via the first optical path 128 and the second optical path 130 by distinguishing detector signals associated with the first modulation frequency and the second modulation frequency, respectively. As an example, the first optical modulator 144 and the second optical modulator 146 may include mechanical modulators 148, such as choppers and / or slits. However, other optical modulators, such as acousto-optic modulators, electro-optic modulators, spatial light modulators, or liquid crystal light modulators, may also be feasible.

[0227] Figure 4 A flow chart of an embodiment of a method for calibrating the sensing device 110 is shown. In the method, the sensing device 110 to be calibrated may be calibrated according to Figures 1 to 3 Any of the embodiments shown and / or implemented according to any other embodiment disclosed herein. Therefore, with respect to the description of the sensing device 110, reference is made to Figures 1 to 3 Description.

[0228] The method includes the following steps, which may be performed in the order given by way of example. However, it should be noted that different orders are also possible. Furthermore, one, more than one, or even all of the method steps may be performed once or repeatedly. Furthermore, two or more method steps may be performed simultaneously or in a timely overlapping manner. The method may include additional method steps not listed.

[0229] The method includes:

[0230] I. (denoted by reference numeral 150 ) Illuminating the detector element 112 via at least one first optical path 128 to obtain at least one first detector signal ;

[0231] II. (Indicated by reference numeral 152 ) Illuminating the detector element 112 via the at least one second optical path 130 without the sample 127 being applied to the sample interface 126 to obtain at least one open port detector signal ;as well as

[0232] III. (Indicated by reference numeral 154) by using the first detector signal , open port detector signal and at least one piece of factory calibration information to determine at least one piece of operational calibration information, wherein the factory calibration information includes an open port detector signal and a predefined relationship between the reference signal of the second optical path 130 .

[0233] Predefined relationships can include linear functions ,in, represents the reference signal of the second optical path 130, and wherein, is a constant, .like Figure 4 As shown, the predefined relationship may be determined before step I., specifically, in a factory calibration performed on the sensing device 110 before step I. (indicated by reference numeral 156 ).

[0234] Further, the operational calibration information may include information about the first detector signal The first relationship between the reference signal of the second optical path 130 and the first detector signal With open port detector signal In this exemplary embodiment, both the first relationship and the second relationship may include linear functions, wherein the first relationship may be represented by Given, where is a constant, , and wherein the second relation can be given by Given, where is a constant, However, other mathematical functions for the first and second relations are also feasible. In this exemplary embodiment, step III. may include determining the first and second relations, specifically determining the factor and .

[0235] Figure 5 A flow chart showing an embodiment of a method for determining at least one calibrated optical characteristic of at least one sample 127 is shown. The sensing device 110 to be used in the method may be configured according to Figures 1 to 3 Any of the embodiments shown and / or implemented according to any other embodiment disclosed herein. Therefore, with respect to the description of the sensing device 110, reference is made to Figures 1 to 3 Description.

[0236] The method includes the following steps, which may be performed in the order given by way of example. However, it should be noted that different orders are also possible. Furthermore, one, more than one, or even all of the method steps may be performed once or repeatedly. Furthermore, two or more method steps may be performed simultaneously or in a timely overlapping manner. The method may include additional method steps not listed.

[0237] The method includes:

[0238] i. (denoted by reference numeral 158) providing according to the present invention (such as according to Figures 1 to 3 The sensing device 110 of any of the embodiments described in and / or according to any other embodiments disclosed herein;

[0239] ii. (indicated by reference numeral 160 ) providing at least one sample 127 , specifically providing at least one sample 127 to the sample interface 126 ;

[0240] iii. (indicated by reference numeral 162 ) illuminating the detector element 112 via at least one first optical path 128 to obtain at least one first detector signal ;

[0241] iv. (denoted by reference numeral 164 ) illuminating the detector element 112 via at least one second optical path 130 to obtain at least one second detector signal ;as well as

[0242] v. (denoted by reference numeral 166) by using the first detector signal , the second detector signal and at least one operational calibration information to determine at least one calibrated optical characteristic of the sample 127, the at least one calibration information being obtained by using a method according to the present invention (e.g., according to Figure 4 The method of calibrating the sensing device 110 according to the illustrated embodiment and / or any other embodiment disclosed herein is determined.

[0243] In this exemplary embodiment, the calibrated optical properties of the sample 127 may include the light reflectivity of the sample 127. . As about Figure 4 As outlined in the exemplary embodiment of the present invention, the operational calibration information may include linear functions and The information about the first relationship and the second relationship is given. In this example, the light reflectance of sample 127 is It can be determined in step v. according to the following formula:

[0244]

[0245] The method may further include re-determining the operational calibration information (indicated by reference numeral 168). Specifically, in the case where the sensing device 110 further includes a monitoring device 143 for monitoring at least one operational condition of the sensing device 110, the operational information may be re-determined when the monitored operational condition deviates from the nominal value by more than a given threshold. Re-determining the operational calibration information may include performing the operation according to the present invention (e.g., according to Figure 4

[0026] A method of calibrating the sensing device 110 according to the exemplary embodiment shown in the drawings and / or according to any other embodiment disclosed herein. Figure 5 As can be seen in , the optional step of re-determining the calibration information may be performed before step v.

[0246] Example 1:

[0247] In Example 1, these methods can be based on Figure 4 and Figure 5 Factory calibration can be performed at 20°C and can yield factors that are assumed to be constant. During operation of the sensing device at 30°C, the user may need to recalibrate the factor and In this example, the sensing device includes two light sources, wherein the light source includes a temperature coefficient of The temperature coefficient of the first LED is Therefore, at 20°C, the signal of 1000 counts can be reduced to and Therefore, the reference signal of the second optical path can be:

[0248]

[0249] Therefore, the re-determined factors b and c can be:

[0250]

[0251]

[0252] The measurement of a sample with a reflectance of 60% at 32°C can be performed as follows:

[0253] At 32°C, the responsivity of the detector element will decrease , so the total reduction Therefore, the expected signal is 0.52 times the initial value at 20°C. In addition, the light source can be and- And drift.

[0254] The measured signal at a given temperature is as follows:

[0255]

[0256]

[0257] Therefore, in this example, the reflectivity of the sample can be determined using Equation 11:

[0258]

[0259] List of Reference Numerals

[0260]

[0261]

Claims

1. A method of calibrating a sensing device (110), the sensing device (110) comprising: a. at least one detector element (112) configured to generate at least one detector signal in response to incident light impinging upon the detector element (112); b. at least one light source (124) configured to emit light within at least one optical spectral range; c. at least one sample interface (126) configured to allow light from the light source (124) to illuminate at least one sample (127) and to allow light from the sample (127) to propagate to the detector element (112); d. at least one first optical path (128), wherein the first optical path (128) is configured to allow light emitted from the light source (124) to propagate to the detector element (112) without passing through the sample interface (126); e. at least one second optical path (130), wherein the second optical path (130) is configured to allow light emitted from the light source (124) to propagate to the detector element (112) by passing through the sample interface (126) at least once; The method includes: I. Illuminating the detector element (112) via the at least one first optical path (128) to obtain at least one first detector signal ; II. Illuminating the detector element (112) via the at least one second optical path (130) without applying a sample to the sample interface (126) to obtain at least one open port detector signal ;as well as III. By using the first detector signal , the open port detector signal and at least one piece of factory calibration information to determine at least one piece of operational calibration information, wherein the factory calibration information includes the open port detector signal A predefined relationship between the reference signal of the second optical path (130) and the reference signal of the second optical path (130).

2. The method according to the preceding claim, wherein This predefined relationship is represented by the following mathematical function gives: in, Represents a reference signal of the second optical path (130).

3. The method according to the preceding claim, wherein This predefined relationship is given by: in, is a constant, .

4. A method according to any one of the preceding claims, wherein The operational calibration information includes information about the first detector signal and a reference signal of the second optical path (130), wherein the first relationship is given by the following mathematical function gives: in, Represents a reference signal of the second optical path (130).

5. The method according to the preceding claim, wherein This first relationship is given by: in, is a constant, .

6. The method according to any one of the two preceding claims, wherein The method includes, at step III. determining the first relationship, wherein determining the first relationship includes using the factory calibration information.

7. A method according to any one of the preceding claims, wherein The operational calibration information includes information about the first detector signal With the open port detector signal The information of the second relationship between gives: 。 8. The method according to the preceding claim, wherein This second relationship is given by: in, is a constant, .

9. The method according to any one of the two preceding claims, wherein The method includes, at step III, determining the second relationship.

10. A method of determining at least one calibrated optical property of at least one sample (127), the method comprising: i. Providing a sensing device (110) as defined in claim 1; ii. providing the at least one sample (127); iii. Illuminating the detector element (112) via the at least one first optical path (128) to obtain at least one first detector signal ; iv. illuminating the detector element (112) via the at least one second optical path (130) to obtain at least one second detector signal ;as well as v. By using the first detector signal , the second detector signal and the at least one piece of operational calibration information for determining at least one calibrated optical property of the sample (127), the at least one piece of calibration information being determined by using the method of calibrating a sensing device (110) according to any one of the preceding claims.

11. The method according to the preceding claim, wherein The operational calibration information includes information about the first detector signal and the reference signal of the second optical path (130) Information about a first relationship between , wherein the first relationship is given by: in, is a constant, The operational calibration information includes information about the first detector signal With open port detector signal , wherein the second relationship is given by: in, is a constant, , wherein the calibrated optical property of the sample (127) is the light reflectivity of the sample (127) ,in, 12. The method according to any of the preceding claims relating to a method of determining at least one calibrated optical property of at least one sample (127), further comprising re-determining the operational calibration information, wherein The sensing device (110) further comprises at least one monitoring device (143) for monitoring at least one operating condition of the sensing device (110), wherein the operating information is re-determined in case the monitored operating condition deviates from a nominal value by more than a given threshold.

13. The method according to the preceding claim, wherein Re-determining the operational calibration information comprises performing a method of calibrating a sensing device (110) according to any of the preceding claims relating to a method of calibrating a sensing device (110).

14. A sensing device (110), comprising: a. at least one detector element (112) configured to generate at least one detector signal in response to incident light impinging upon the detector element (112); b. at least one light source (124) configured to emit light within at least one optical spectral range; c. at least one sample interface (126) configured to allow light from the light source (124) to illuminate at least one sample (127) and to allow light from the sample (127) to propagate to the detector element (112); d. at least one first optical path (128), wherein the first optical path (128) is configured to allow light emitted from the light source (124) to propagate to the detector element (112) without passing through the sample interface (126); e. at least one second optical path (130), wherein the second optical path (130) is configured to allow light emitted from the light source (124) to propagate to the detector element (112) by passing through the sample interface (126) at least once; and f. At least one evaluation unit (140) configured to determine at least one calibrated optical property of at least one sample (127) by using the method for determining at least one calibrated optical property of at least one sample (127) according to any of the preceding claims relating to a method for determining at least one calibrated optical property of at least one sample (127).

15. The sensing device (110) according to the preceding claim, wherein The sensing device (110) further comprises at least one monitoring device (143) for monitoring at least one operating condition of the sensing device (110).

16. A computer program for calibrating a sensing device (110), the computer program comprising instructions which, when executed by a computer or a computer network, cause the computer or computer network to perform at least step III. of the method for calibrating a sensing device (110) according to any one of the preceding claims relating to a method for calibrating a sensing device (110).

17. A computer program for determining at least one calibrated optical property of at least one sample (127), the computer program comprising instructions which, when the program is executed by a computer or a computer network, cause the computer or computer network to perform at least step v. of the method for determining at least one calibrated optical property of at least one sample (127) according to any of the preceding claims relating to a method for determining at least one calibrated optical property of at least one sample (127).

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