Disclosure of Invention
This problem is solved by a spectrometer device, a corresponding method, a computer program, a computer readable storage medium and a non-transitory computer readable medium for obtaining spectroscopic information about at least one object having the features of the independent claims. Advantageous embodiments that can be realized in a separate manner or in any arbitrary combination are listed in the dependent claims and throughout the description.
In a first aspect, a spectrometer apparatus for obtaining spectroscopic information about at least one object is disclosed.
As used herein, the term "spectrometer device" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, an optical device configured for acquiring at least one item of spectral information about at least one object. In particular, the at least one item of spectral information may be at least one optical property or an optically measurable property that is determined as a function of wavelength for one or more different wavelengths. More particularly, the optical or optically measurable property and the at least one item of spectral information may relate to at least one property characterizing at least one of transmission, absorption, reflection and emission of the at least one object itself or after external light irradiation. At least one optical characteristic may be determined for one or more wavelengths. The spectrometer device may in particular form a device capable of recording signal intensities with respect to corresponding wavelengths of the spectrum or a partition thereof, such as a wavelength interval, wherein the signal intensities may in particular be provided as electrical signals which may be used for further evaluation.
As an example, the spectrometer device may be or may comprise a device allowing measuring at least one spectrum (e.g. for measuring spectral flux, in particular as a function of wavelength or detection wavelength). As an example, the spectrum may be acquired in absolute units or relative units (e.g., relative to at least one reference measurement). Thus, as an example, the acquisition of the at least one spectrum may be performed in particular for a measurement of the spectral flux (in W/nm) or a measurement of the spectrum (in 1) with respect to at least one reference material, which may describe a property of the material (e.g. the change of reflectivity with wavelength). Additionally or alternatively, the reference measurement may be based on a reference light source, an optical reference path, a calculated reference signal (e.g., a calculated reference signal from the literature), and/or a reference device.
In particular, the at least one spectrometer device may be a diffuse reflectance spectrometer device configured to obtain spectral information from light diffusely reflected by the at least one object (e.g., the at least one sample). Additionally or alternatively, the at least one spectrometer device may be or may comprise an absorption spectrometer and/or a transmission spectrometer. In particular, measuring the spectrum with the spectrometer device may comprise measuring the absorption in a transmissive configuration. In particular, the spectrometer device may be configured for measuring absorption in a transmissive configuration. However, as outlined above, other types of spectrometer devices are also possible.
In particular and as will be outlined in further detail below, the at least one spectrometer device may comprise at least one light source, which may be, as an example, at least one of a tunable light source, a light source having at least one fixed emission wavelength, and a broadband light source. As will be outlined in further detail below, the spectrometer device further comprises at least one detector device configured for detecting light, such as at least one of light transmitted, reflected or emitted from the at least one object. As will be outlined in further detail below, the spectrometer device may further comprise at least one wavelength selective element, such as at least one of a grating, a prism and a filter (e.g. a variable length filter with varying transmission characteristics over its lateral extension). The wavelength selective element may be used to separate the incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector, such as a detector having a detector array as described in more detail below.
The spectrometer device may in particular be a portable spectrometer device. As used herein, the term "portable" 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 custom meaning. The term may particularly refer to, but is not limited to, the property that at least one object is moved by human force, such as by a single user. In particular, the weight of the object characterized by the term "portable" may not exceed 10 kg, in particular not exceed 5 kg, more in particular not exceed 1 kg or even not exceed 500 g. Additionally or alternatively, the size of the object characterized by the term "portable" may be such that the object extends no more than 0.3 m to any dimension, in particular no more than 0.2 m to any dimension. In particular, the volume of the object may not exceed 0.03 m3, in particular not exceed 0.01 m3, more in particular not exceed 0.001 m3 or even not exceed 500 mm3. In particular, as an example, the portable spectrometer device may have dimensions of, for example, 10 mm ×10 mm ×5 mm. In particular, the portable spectrometer device may be part of, or may be attachable to, a mobile device, such as a notebook computer, a tablet computer, a cell phone (such as a smartphone), a smart watch, and/or a wearable computer (also referred to as a "wearable device", e.g., a body worn computer (such as a wristband or watch)). In particular, the weight of the spectrometer device, in particular the portable spectrometer device, may be in the range of 1g to 100 g, more particularly in the range of 1g to 10 g.
As used herein, the term "spectroscopic information" (also referred to as "spectroscopic information" or "item of spectroscopic information") is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, for example, an information item about at least one object and/or radiation emitted by at least one object, which characterizes at least one optical property of the object, more particularly characterizes at least one information item, for example, at least one of a transmission, an absorption, a reflection and an emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one item of intensity information, e.g. information about the intensity of light transmitted, absorbed, reflected or emitted by the object, e.g. as a function of wavelength or wavelength sub-ranges within one or more wavelengths (e.g. within a wavelength range). In particular, the intensity information may correspond to or be derived from a signal intensity (in particular an electrical signal) recorded by the spectrometer device in relation to the wavelength or wavelength range of the spectrum.
The spectrometer device may in particular be configured for acquiring at least one spectrum or at least a part of a spectrum of detection light propagating from the object to the spectrometer. The spectrum may describe the units of radiation measurement of the spectral flux, for example given in watts per nanometer (W/nm), or in other units, for example as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, for example, in the NIR spectral range, in a particular band. The spectrum may contain one or more optical variables that are a function of wavelength, such as power spectral densityAn electrical signal obtained by optical measurement, and the like. As an example, a spectrum may indicate a power spectral density of an object (e.g., a sample), e.g., relative to a reference sampleAnd/or spectral flux, such as transmittance and/or reflectance of an object, in particular a sample.
As an example, the spectrum may comprise at least one measurable optical variable or property of the detection light and/or the object, which optical variable or property is in particular a function of the illumination light and/or the detection light. As an example, the at least one measurable optical variable or characteristic may include at least one radiation dose, such as spectral density, power spectral densityAt least one of spectral flux, radiant intensity, spectral radiant intensity, irradiance, spectral irradiance. Specifically, as an example, a spectrometer device (specifically a detector) may measure irradiance in watts per square meter (W/m2), more specifically spectral irradiance in watts per square meter per nanometer (W/m2/nm). Based on the measured quantities, the spectral flux in watts per nanometer (W/nm) and/or the radiant flux in watts (W) may be determined (e.g., calculated) by taking into account the area of the detector.
As used herein, the term "object" 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 custom meaning. The term may particularly refer to, but is not limited to, any body selected from the group consisting of living and inanimate objects. Thus, as an example, at least one object may comprise one or more items and/or one or more portions of items, wherein at least one item or at least one portion thereof may comprise at least one component that may provide a spectrum suitable for investigation. Additionally or alternatively, the subject may be or may include one or more living beings and/or one or more portions thereof, such as one or more body parts of a human (e.g., user) and/or animal. In particular, the object may comprise at least one sample, which may be wholly or partly analyzed by spectroscopic methods. By way of example, the object may be or may include at least one of human or animal skin, edibles such as fruit, plastics and textiles.
The spectrometer apparatus includes:
(i) At least one light source configured to generate illumination light for illuminating the object, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, wherein the spectrometer device is configured to drive the light source in such a way that a driving state of the light source is changed at least once;
(ii) At least one detector configured to detect light and thereby generate at least one detector signal when a driving state of the light source changes, wherein the detector signal is time resolved;
(iii) At least one evaluation unit configured for deriving the spectroscopic information about the object by detecting detection light from the object using the detector, and further configured for deriving at least one time constant of the light source from a time resolved detector signalThe at least one time constant describing characteristics of the light source when the driving state is changed, wherein the at least one time constant is used when obtaining the spectroscopic information about the objectTaking into account.
The spectrometer device comprises at least one light source configured for generating illumination light for illuminating an object. The light source further comprises at least one light emitting diode and at least one luminescent material for light conversion of primary light generated by the light emitting diode, wherein the spectrometer device is configured for driving the light source in such a way that the driving state of the light source is changed at least once.
As further used herein, the term "light" as used herein is a broad term and is to be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, electromagnetic radiation in one or more of the infrared, visible and ultraviolet spectral ranges. In this context, the term "ultraviolet spectral range" generally refers to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably 100 nm to 380 nm. Further, the term "visible spectral range" generally refers to the spectral range of 380 nm to 760 nm, in part according to standard ISO-21348, an active version of the date of this document. The term "infrared spectral range" (IR) generally refers to electromagnetic radiation of 760 nm to 1000 μm, with the range 760 nm to 1.5 μm generally referred to as the "near infrared spectral range" (NIR), while the range 1.5 μm to 15 μm is referred to as the "mid-infrared spectral range" (MidIR), and the range 15 μm to 1000 μm is referred to as the "far infrared spectral range" (FIR). Preferably, the light used for the typical purposes of the present invention is light in the Infrared (IR) spectral range, more preferably in the Near Infrared (NIR) and/or mid infrared spectral range (MidIR), especially light having a wavelength of 1 μm to 5 μm, preferably 1 μm to 3 μm. This is because the material properties of many objects or properties concerning chemical composition can be derived from the near infrared spectrum. However, it should be noted that spectral analysis of other spectral ranges is also applicable and within the scope of the present invention.
Thus, as used herein, the term "light source" (also referred to as an "illumination source") is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device configured to generate or provide light in the sense of the definition above. The light source may in particular be or may comprise at least one electric light source, such as an electrically driven light source.
As will be outlined in further detail below, the light source may generally be implemented in various ways. Thus, the light source may be, for example, a part of the spectrometer device in a housing of the spectrometer device. Alternatively or additionally, however, the at least one light source may also be arranged outside the housing, for example as a separate light source. The light source may be arranged separately from the object and illuminate the object from a distance.
In spectroscopy, various light sources and light paths are distinguished. In the context of the present invention, the nomenclature used first refers to the light propagating from the light source to the object as "illumination light" (illuminating light or illumination light). Second, light propagating from the object to the detector is referred to as "detection light". The detection light may comprise at least one of illumination light reflected by the object, illumination light scattered by the object, illumination light transmitted by the object, luminescence light generated by the object (e.g. phosphorescence or fluorescence generated by the object after optical, electrical or acoustic excitation of the object by the illumination light, etc.). Thus, the detection light may be generated directly or indirectly by illumination of the object by the illumination light.
Further, as will be outlined in detail below, within the light source itself, a distinction can be made between various light sources (such as primary and secondary light sources). Thus, as will be outlined in further detail below, the "primary light" (also referred to as "pump light") may be generated by a primary light source, such as at least one light emitting diode, and may then be converted into "secondary light", such as by using light conversion (e.g. by one or more phosphor materials). The illumination light may be or may comprise at least one of primary light or a part thereof, secondary light or a part thereof, or a mixture of primary light and secondary light.
Thus, as used herein, the term "illumination" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of exposing at least one element to light.
As outlined above, the light source comprises at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, wherein in particular the illumination light may be a combination of the primary light and light generated by light converting of the luminescent material or light generated by light converting of the luminescent material (also referred to as secondary light).
As used herein, the term "light emitting diode" or simply "LED" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, an optoelectronic semiconductor device which is capable of emitting light when a current flows through the device. The optoelectronic semiconductor device may be configured to generate light as a result of various physical processes including one or more of spontaneous radiation, induced radiation, decay of metastable excited states, and the like. Thus, by way of example, the light emitting diode may comprise one or more of a light emitting diode based on spontaneous emission of light (in particular an organic light emitting diode), a super-emission based light emitting diode (sLED), or a Laser Diode (LD). In the following, the abbreviation "LED" will be used for any type of light emitting diode without shrinking the possible embodiments of the light emitting diode to any of the aforementioned physical principles or arrangements. In particular, the LED may comprise at least two layers of semiconductor material, wherein light may be generated at least one interface between the at least two layers of semiconductor material, in particular due to recombination of positive and negative charges (e.g. electron-hole recombination). The at least two layers of semiconductor material may have different electrical properties, such as at least one of the layers being an n-doped semiconductor material and at least one of the layers being a p-doped semiconductor material. Thus, as an example, the LED may comprise at least one pn junction and/or at least one pin structure. However, it should be noted that other device configurations are possible. The at least one semiconductor material may in particular be or may comprise at least one inorganic semiconductor material. However, it should be noted that organic semiconductor materials may additionally or alternatively be used.
Generally, as will be outlined in further detail below, the LEDs may convert a current into light, in particular into primary light, more in particular into blue primary light. Thus, the LED may in particular be a blue LED. The LEDs may be configured to generate primary light, also referred to as "pump light". Thus, the LED may also be referred to as a "pump LED". The LEDs may in particular comprise at least one LED chip and/or at least one LED die. Accordingly, the semiconductor element of the LED may include an LED bare chip.
Various types of LEDs suitable for generating primary light are known to the skilled person and can also be applied in the present invention. In particular, a p-n junction diode may be used. As an example, one or more LEDs selected from the group of indium gallium nitride (InGaN) based LEDs, gaN based LEDs, inGaN/GaN alloy based LEDs, or combinations thereof, and/or other LEDs may be used. Additionally or alternatively, quantum well LEDs, such as one or more InGaN-based quantum well LEDs, may also be used. Additionally or alternatively, super-radiating LEDs (slds) and/or quantum cascade lasers may be used.
As used herein, the term "light emitting" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process in which a substance spontaneously radiates light that is not caused by heat. In particular, luminescence may refer to cold body radiation. More specifically, luminescence may be initiated or excited by irradiation of light, in which case luminescence is also referred to as "photoluminescence". In the context of the present invention, the properties of a material capable of emitting light are referred to by the adjective "luminescent". The at least one luminescent material may in particular be a photoluminescent material, i.e. a material that is capable of emitting light after absorption of photons or excitation light. In particular, the luminescent material may have a positive stokes shift, which may generally refer to the fact that the secondary light is red shifted with respect to the primary light.
Thus, the at least one luminescent material may form at least one converter (also referred to as a light converter) that converts the primary light into secondary light having different spectral properties than the primary light. In particular, the spectral width of the secondary light may be larger than the spectral width of the primary light and/or the emission center of the secondary light may be shifted (in particular red shifted) compared to the primary light. In particular, the at least one luminescent material may have an absorption in the ultraviolet and/or blue spectral range and an emission in the near infrared and/or infrared spectral range. Thus, in general, the luminescent material or the converter may form at least one component of the phosphor LED that concentrates primary light or pump light, in particular in the blue spectral range, into light with a longer wavelength, for example in the near infrared or infrared spectral range.
Various types of conversion and/or luminescence are known and may be used in the context of the present invention. Thus, in particular, the conversion may occur via a dipole-allowed transition in the luminescent material (also referred to as fluorescence) and/or via a dipole-forbidden, thus longer-lived transition in the luminescent material (also commonly referred to as phosphorescence).
The luminescent material may thus particularly form at least one converter or light converter. The luminescent material may form at least one of a conversion plate, a luminescent coating (in particular a fluorescent coating) on the LED, and a phosphor coating on the LED. By way of example, the luminescent material may comprise one or more of cerium doped YAG (YAG: ce3+ or Y3Al5O12:Ce3+), rare earth doped Sialon, copper aluminum co-doped zinc sulfide (ZnS: cu, al).
The LED and the luminescent material together may form a so-called "phosphor LED". Thus, as used herein, the term "phosphor light emitting diode" or simply "phosphor LED" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a combination of at least one light emitting diode configured for generating primary light or pump light and at least one luminescent material (also referred to as "phosphor") configured for light conversion of the primary light generated by the light emitting diode. Phosphor LEDs may form a packaged LED light source comprising an LED die (e.g. a blue LED emitting blue pump light) and a phosphor, for example, fully or partially coating the LED, and being configured for converting primary light or blue light into light having different spectral characteristics (in particular into near infrared light), as an example. In general, phosphor LEDs may be packaged in a housing or may be unpackaged. The LED and the at least one luminescent material for light conversion of the primary light generated by the light emitting diode may thus be accommodated in particular in a common housing. Alternatively, however, the LEDs may also be unpackaged or bare LEDs, which may be fully or partially covered with luminescent material, such as by providing one or more layers of luminescent material on the LED die. Phosphor LEDs may generally themselves form the emitter or light source.
In a light source, in particular a phosphor LED, at least one luminescent material may in particular be positioned relative to the light emitting diode such that heat transfer from the light emitting diode to the luminescent material is possible. More specifically, the luminescent material may be positioned such that heat transfer may be by one or both of heat radiation and heat conduction (more preferably by heat conduction). Thus, as an example, the luminescent material may be in thermal and/or physical contact with the light emitting diode. As an example, the luminescent material may form one or more coatings or layers in contact with or in close proximity to the light emitting diode, such as in contact with one or more of the semiconductor materials of the light emitting diode. Thus, in general, the temperature of the luminescent material and the temperature of the light emitting diode may be coupled.
The at least one luminescent material may in particular form at least one layer. In general, various alternatives for positioning the luminescent material relative to the light emitting diode are possible, which may be used alone or in combination. First, the luminescent material (e.g., at least one layer of luminescent material, such as a phosphor) may be positioned directly on the light emitting diode, also referred to as "direct attachment", e.g., with no material between the LED and the luminescent material, or with one or more transparent materials between the two, such as with one or more transparent materials (especially transparent to primary light) between the LED and the luminescent material. Thus, as an example, a coating of luminescent material may be placed directly or indirectly on the LED. Additionally or alternatively, as an example, the luminescent material may form at least one conversion body, such as at least one conversion disc, which conversion body may be placed on top of the LED, for example by attaching the conversion body to the LED with an adhesive. Additionally or alternatively, the luminescent material may also be placed in a remote manner, such that the primary light from the LED has to pass through an intermediate light path before reaching the luminescent material. Such placement may also be referred to as "remote placement" or "remote phosphor. Also, as an example, the remotely located luminescent material may form a solid or conversion body, such as a disk or conversion disk. Further, in case of remote placement, the luminescent material may also be a coating. In particular, light-transmitting objects (e.g. thin glass substrates, module windows) may be coated with phosphors, which objects comprise and/or are made of glass or plastic. Alternatively, the reflective surface may be coated with a phosphor. This may be a flat or rough mirror, which may comprise and/or be made of a high reflectivity material substrate (e.g. silicon), or a flat or rough surface (e.g. glass or plastic) coated with gold, silver, aluminium or chromium. In the intermediate optical path, one or more optical elements, such as one or more of lenses, prisms, gratings, mirrors, apertures, or combinations thereof, may be placed. Thus, in particular, an optical system with imaging properties may be placed in the intermediate light path, between the LED and the luminescent material. Thus, as an example, the primary light may be focused or concentrated onto the conversion body.
Power spectral density of illumination light generated by a light sourceGenerally depending on the temperature of the light source, in particular of the light emitting diode and/or to a large extent of the light emitting material. To be able to compensate for the power spectral density due to the change in temperatureDrift of the corresponding temperature is required.
As used herein, the term "drive" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. For driving the at least one light source, the spectrometer device may comprise a driving unit. The term may particularly refer to, but is not limited to, a process of providing one or both of at least one control parameter and/or electrical power to another device. Thus, as used herein, the term "drive unit" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device or combination of devices configured to provide one or both of at least one control parameter and/or electrical power to another device (e.g., to at least one light source in this example). For example, the drive unit may in particular be configured for at least one of measuring and controlling one or more electrical parameters of the electrical power provided to the light source (in particular to the at least one light emitting diode). As an example, the driving unit may be configured for providing a current to the LED, in particular for controlling the current through the LED. Wherein, as an example, the driving unit may be configured to adapt and measure the voltage provided to the LED, which is required to achieve a specific current through the LED. The drive unit may in particular comprise one or more of a current source, a voltage source, a current measuring device (such as an ammeter), a voltage measuring device (such as a voltmeter), a power measuring device. In particular, the driving unit may comprise at least one current source for providing at least one predetermined current to the LED, wherein the current source may in particular be configured for adjusting or controlling the voltage applied to the LED in order to generate the predetermined current. As an example, the drive unit may comprise one or more electrical components (such as an integrated circuit) for driving the light source. The drive unit may be fully or partially integrated into the light source or may be separate from the light source.
As used herein, the term "driving state" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, at least one specific condition under which the light source operates. The at least one specific condition may be directly and/or indirectly related to at least one and/or any specific electrical parameter of the electrical power provided to the light source. Alternatively, the at least one specific condition may be at least one of the electrical power supplied to the light source and/or any specific electrical parameter. The driving state may be changed by changing at least one of the specific conditions, in particular the electric power supplied to the light source, and/or any specific electric parameter. Thus, the light source may be driven under a first specific condition and then driven under a second specific condition different from the first specific condition. The driving state may be further affected by at least one pressure and/or at least one temperature associated with the light source. Optical feedback may also have an effect on the light source. The driving state may be changed by modulating the light source, in particular the light emitting diode, in particular by applying a pulse modulation scheme, in particular a pulse width modulation scheme.
As further summarized above, the spectrometer device further comprises at least one detector configured to detect light and thereby generate at least one detector signal when the driving state of the light source is changed, wherein the detector signal is time resolved.
As further summarized above, the spectrometer device includes at least one detector configured to detect light. As used herein, the verb "detect" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of at least one operation of qualitatively and/or quantitatively determining, measuring and monitoring at least one parameter, such as at least one of a physical parameter, a chemical parameter and a biological parameter. In particular, the physical parameter may be or may comprise an electrical parameter. Thus, the term "detector" as used herein is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device configured for detecting, i.e. qualitatively and/or quantitatively determining, measuring and monitoring at least one of the at least one parameter, such as at least one of the physical parameter, the chemical parameter and the biological parameter. The detector may be configured for generating at least one detector signal, more particularly at least one electrical detector signal, such as an analog and/or digital detector signal, the detector signal providing information about at least one parameter measured by the detector. The detector signal may be provided directly or indirectly by the detector to the evaluation unit, so that the detector and the evaluation unit may be connected directly or indirectly. The detector signal may be used as a "raw" detector signal and/or may be processed or pre-processed (e.g., by filtering, etc.) prior to further use. Thus, the detector may comprise at least one processing device and/or at least one preprocessing device, such as at least one of an amplifier, an analog/digital converter, an electrical filter and a fourier transform.
In this example, the detector is configured to detect light. Thus, in particular, the detector may be or may comprise at least one optical detector. The optical detector may be configured for determining at least one optical parameter, such as the intensity and/or power of light irradiating at least one sensitive area of the detector. More specifically, the optical detector may comprise at least one photosensitive element and/or at least one optical sensor, such as at least one of a photodiode, a photocell, a photoresistor, a phototransistor, a thermopile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier, and a bolometer. Thus, the detector may be configured for generating at least one detector signal, more particularly at least one electrical detector signal in the above sense, which provides information about at least one optical parameter, such as the power and/or intensity of the light illuminating the detector or a sensitive area of the detector.
The detector may comprise a single optical sensor or area or a plurality of optical sensors or areas. In particular, the detector may be or may comprise at least one detector array (more particularly an array of light sensitive elements), as will be outlined in further detail below. Each light sensitive element may comprise at least a light sensitive area, which may be adapted to generate an electrical signal depending on the intensity of the incident light, wherein the electrical signal may in particular be provided to an evaluation unit, as will be outlined in further detail below.
The photosensitive area comprised by each optical sensor may in particular be a single, uniform photosensitive area configured to receive incident light impinging on the respective optical sensor. However, other arrangements of the optically sensitive elements are also conceivable.
The array of optical sensing elements may be designed to generate detector signals, preferably electronic signals, associated with the intensity of incident light impinging on the respective optical sensing elements. The detector signal may be an analog signal and/or a digital signal. Accordingly, the electronic signals of adjacent pixelated sensors may be generated simultaneously or in a temporally continuous manner. For example, during a row scan or line scan, a series of electrical signals corresponding to a series of individual optical sensing elements arranged in a row may be generated. In addition, these individual optical sensitive elements may preferably be active pixel sensors, which may be adapted to amplify the electronic signals before they are provided to the evaluation unit. For this purpose, the detector may comprise one or more signal processing devices, such as one or more filters and/or analog-to-digital converters, for processing and/or preprocessing the electronic signals.
Where the detector comprises an array of optically sensitive elements, the detector may be selected from any known pixel sensor, in particular from a pixelated organic camera element, preferably a pixelated organic camera chip, or from a pixelated inorganic camera element, preferably a pixelated inorganic camera chip, more preferably from a CCD chip or CMOS chip, as examples, of the type commonly used in the types of cameras currently available. Alternatively, the detector may generally be or include a photoconductor, particularly an inorganic photoconductor, particularly PbS, pbSe, ge, inGaAs, extended InGaAs, inSb, or HgCdTe. As a further alternative, the detector may comprise at least one of a pyroelectric element, a bolometer element or a thermopile detector element. Thus, a camera chip having a matrix of 1×n pixels or m×n pixels may be used herein, where, as an example, M may be <10, and N may be in the range from 1 to 50, preferably from 2 to 20, more preferably from 5 to 10. Further, a monochrome camera element, preferably a monochrome camera chip, may be used, wherein the monochrome camera element may be selected differently for each optically sensitive element, in particular according to a wavelength that varies over a range of optical sensors.
Thus, the array may be adapted to provide a plurality of electrical signals, which may be generated by the photosensitive areas of the optically sensitive elements comprised by the array. The electrical signals provided by the array of spectrometer devices may be forwarded to an evaluation unit.
As used herein, the term "time resolved detector signal" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, capturing a time-evolving detector signal of at least one process, in particular in such a way that the process may be resolved in time. The time-resolved detector signal may be configured for monitoring at least one change in an operating parameter, in particular by monitoring at least one illumination light generated by the light source, in particular at least indirectly.
As further outlined above, the spectrometer device comprises at least one evaluation unit configured for deriving the spectroscopic information about the object by detecting detection light from the object using the detector, and further configured for deriving at least one time constant of the light source from a time resolved detector signalThe at least one time constant describing characteristics of the light source when the driving state is changed, wherein the at least one time constant is used when obtaining the spectroscopic information about the objectTaking into account.
In this example, the detector is configured to detect light (such as diffusely reflected light) propagating from the object to the spectrometer device or more specifically to the detector of the spectrometer device, which light is referred to as "detected light" according to the above nomenclature. The time resolved detector signals or time dependent detector signals may be used to obtain spectroscopic information about the object. Alternatively, the time-resolved detector signal and the detector signal (also referred to as "spectral detector signal") used to obtain the spectroscopic information about the object may be different signals, such as by being generated by different detectors and/or detector arrays.
As further described above, the spectrometer device comprises at least one evaluation unit for evaluating at least one detector signal generated by the detector and for deriving spectroscopic information about the object from the detector signal. As used herein, the term "evaluate" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, a process of processing at least one first information item in order to thereby generate at least one second information item. Thus, as used herein, the term "evaluation unit" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any device or combination of devices configured to evaluate or process at least one first information item in order to generate at least one second information item thereof. Thus, in particular, the evaluation unit may be configured for processing the at least one input signal and generating at least one output signal thereof. As an example, the at least one input signal may comprise at least one detector signal provided directly or indirectly by the at least one detector, and additionally at least one signal provided directly or indirectly by a measuring unit, which may for example be an element of the drive unit, which signal comprises at least one information item about the at least one electrically measurable quantity, in particular the forward voltage.
By way of example, the evaluation unit may be or may comprise one or more integrated circuits, such as one or more Application Specific Integrated Circuits (ASICs), and/or one or more data processing devices, such as one or more of a computer, a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), preferably one or more microcomputers and/or microcontrollers. Additional components may be included, such as one or more preprocessing devices and/or data acquisition devices, such as one or more devices for receiving and/or preprocessing detector signals, such as one or more AD converters and/or one or more filters. Further, the evaluation unit may comprise one or more data storage devices. Further, the evaluation unit may comprise one or more interfaces, such as one or more wireless interfaces and/or one or more wired interfaces.
The at least one evaluation unit may be adapted to execute at least one computer program, such as at least one computer program that performs or supports the information item generating step. As an example, one or more algorithms may be implemented that may perform a predetermined transformation to obtain spectroscopic information about the object, such as for obtaining at least one item of spectroscopic information describing at least one characteristic of the object, by using at least one detector signal, such as a time resolved detector signal and/or a spectroscopic detector signal, as an input variable. For this purpose, the evaluation unit may particularly comprise at least one data processing device (also referred to as a processor, in particular an electronic data processing device) which may be designed to generate the desired information by evaluating the detector signal. The evaluation unit may use any procedure to generate the desired information, such as by calculating and/or using at least one stored and/or known relationship. The evaluation unit may in particular be configured for performing at least one Digital Signal Processing (DSP) technique, in particular at least one fourier transformation, on the primary detector signal or any secondary detector signal derived therefrom. Additionally or alternatively, the evaluation unit may be configured to perform one or more further digital signal processing techniques, such as windowing, filtering, goertzel algorithms, cross-correlation and auto-correlation, on the primary detector signal or any secondary detector signal derived therefrom. In addition to the detector signal, one or more further parameters and/or information items may also influence the relation. The relationship may be determined or determinable by empirical, analytical or semi-empirical methods. As an example, the relationship may comprise at least one of a model or a calibration curve, at least one set of calibration curves, at least one function, or a combination of the mentioned possibilities. The one or more calibration curves may be stored, for example, in the form of a set of values and their associated function values, for example, in a data storage device and/or table. Alternatively or additionally, however, the at least one calibration curve may also be stored, for example, in parameterized form and/or as a function equation. A separate relationship for processing the detector signals into information items may be used. Alternatively, at least one combination for processing the detector signals is possible. Various possibilities are conceivable and these may also be combined.
As an example, the detector signal may comprise a plurality of detector signals (such as time resolved detector signals and/or spectral detector signals) which are at least a function of the wavelength of the detected light and optionally also a function of time, in particular for time dependent detector signals. The plurality of detector signals (such as spectral detector signals) may form a spectrum, including the option of a digital spectrum or an analog spectrum. Thus, as an example, each detector signal may summarize information from a predetermined spectral range defined by the spectral resolution of the detector. As will be outlined in further detail below, the detector may comprise a plurality of photosensitive elements, each photosensitive element being sensitive in a different spectral range and/or being exposed to a different part of the spectrum of the detection light. All detector signals of the photosensitive element may form the detector signal or, as an example, define the spectral information, a part thereof or a precursor thereof as a whole. Since the spectral range of the sensitivity of each photosensitive element may be known, in particular by taking into account the time-resolved detector signal, the intensity of the detection light as a function of the detection wavelength may be derived from this detector signal by combining the data pairs of the photosensitive elements, each data pair comprising the corresponding signal of the photosensitive element and the sensitivity wavelength. However, it should be noted that other ways of generating spectral information are possible, such as by sequentially exposing the same detector to different spectral portions of the detection light, for example by using a scannable wavelength selective element.
As an example, the detector may be configured for generating a detector signal (in particular a spectral detector signal) for at least one spectral range (in particular for at least two different spectral ranges) of the light from the object, in particular at least one of sequentially and simultaneously. For example, as outlined above, the detector may comprise an array of photosensitive elements, wherein each photosensitive element may be sensitive in a different spectral range and/or may be exposed to light in a different spectral range.
As used herein, the term "time constant"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 custom meaning. The term may particularly refer to, but is not limited to, typical time intervals describing the reorganization of the state of equilibrium (in particular of the luminescent material) when at least one operating parameter is changed. Time constantA delay that occurs between the absorption of at least one primary photon by the luminescent material and the emission of at least one secondary photon by the luminescent material may be described. This delay may be defined by a so-called "characteristic time constant"(Also referred to as a "time constant", "decay time", or "saturation time"). When used in the context of a process in which the rate or probability of a process (such as photon emission) is proportional to the population of one or more states or process states, the population typically varies exponentially. In these processes, time constantThe 1/e time of the process can be determined. Two different time constants may occur for the luminescent material or the converter, in particular for the phosphor. First, the first time constant may describe a typical time for the emission of converted light to reach saturation, such as a "growth constant", which may depend on the intensity of the pump light. Second, the second time constant may describe a typical time of afterglow of the luminescent material or the converter, such as a "decay constant" or "decay".
Time constantMay be related to the properties of the light source, in particular to the material properties of the light source, more in particular to the material properties of the luminescent material used in the light source. As used herein, the term "characteristic of a light source" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, at least one property of a material of the light source, particularly at least one property of a luminescent material. Thus, the "property" of the light source may be a "material property" of the light source, in particular a "material property" of the luminescent material. The properties of the material of the light source may be related to the structure of at least one molecule of the light source, in particular the luminescent material. The characteristics of the light source may be described by using a temperature coefficient. The temperature coefficient may be different for different wavelengths, and thus may depend on the wavelength. The temperature coefficient associated with a particular wavelength may be positive or negative, and its absolute value may vary based on the distribution of the various energy states and the einstein coefficient.
At least one time constant of the light source is typically dependent on the light emitting diode and the luminescent material. Time constant of light sourceBy taking into account the time constant of the light emitting diodeAnd time constant of luminescent materialIs obtained. These time constantsDepending on the respective temperature and wavelength. In general, the number of the devices used in the system,Ratio ofMuch smaller, in such a way that, on a smaller time scale,Is subject toIs dominant in (2). Within this range, the determination of the time scale is particularly important.
Thus, the time constant of the light sourceCan be derived from the time constant of the light emitting diodeAnd time constant of luminescent materialObtained, for example, by determining the convolution of。Possibly byDominant, especially because ofIn general, possibly toMuch larger.
Typical time constant of phosphor converterIn the range of 0.1 ms to <10 ms. At least one detector may be configured to generate time resolved detector signals to monitor the time constants. In general, the temporal resolution of the detector may be less than 1 ms, preferably less than 0.1 ms, more preferably less than 0.01 ms.
These time constants are typically different between different phosphor LEDs and/or between different types of luminescent materials or phosphors. In general, phosphors that emit short wavelengths exhibit smaller time constants. In addition, the damping constantConstant of growthMay depend on the wavelength. These time constants are typically extracted from the step response of the light signal by applying/switching off the forward current required to drive the light source in such a way that primary light is generated by the light emitting diode.
After switching off the forward current, the signal or emission generally decays according to equation (1):
(1)
after switching on the forward current, the signal or emission generally increases according to equation (2):
(2)
For equations (1) and (2),Is when the forward current is applied/switched off,Optical signal level at that time.Is thatThe optical signal level reached at that time.
The light emitting diode may have a primary emission range at least partially within the spectral range of 420 nm to 460 nm, more specifically within the range of 440 nm to 455 nm, more specifically at 440 nm. The luminescent material may be a phosphor. The illumination light may have a spectral range at least partly within the near infrared spectral range, in particular within a spectral range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.
The driving state of the light source may be at least one of a first driving state in which the light emitting diode generates the primary light, or a second driving state in which the light emitting diode does not generate the primary light. To switch between the first driving state and the second driving state, the driving unit may switch the current and/or voltage, such as the forward voltage, provided to the LEDs.
The light emitting diode may irradiate the light emitting material when the light emitting diode is switched to the first driving state. Thus, the excited state in the luminescent material can be populated, such as the growth constant of the excited state in the luminescent materialDescribed. When the light emitting diode is switched from the first driving state to the second driving state, the light emitting diode may no longer irradiate the light emitting material. The excited state in the luminescent material can thus be decolonized, e.g. the decay constant of the excited state in the luminescent materialDescribed.
The at least one spectrometer device may be configured for operating the light source in a pulsed mode in such a way that the driving state of the light source is repeatedly changed, in particular between a first driving state and a second driving state. As used herein, the term "pulse mode" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, driving the light source in such a way that the illumination light is generated in a plurality of pulses having a predetermined duration, a predetermined repetition rate.
The at least one spectrometer device may be configured for being in a particular driving state (in particular the first driving state and/or the second driving state) at a time constant greater thanOperating the light source within a predetermined time span, in particular the time constantOr at least 10 times greater than the time constant. The pulse duration (especially when the light source is operated in pulsed mode) may be greater than the time constantIn particular at least 5 times the time constant, or a time constantIs at least 10 times larger. In general, the pulse duration may range from 1 ms to 100 ms, typically depending on the time constant of the luminescent material。
The detector may be configured for generating the detector signal for at least two different spectral ranges of the light from the object, in particular at least one of sequentially and simultaneously, to obtain the spectroscopic information. The detector may comprise an array of photosensitive elements, wherein each photosensitive element is configured to generate at least one detector signal to obtain the spectroscopic information. The spectrometer device may be configured such that the photosensitive element is sensitive to different spectral ranges of light from the object. The spectrometer device may comprise at least one filter element arranged in a beam path of light from the object, wherein the filter element is configured such that each photosensitive element is exposed to a separate spectral range of the light from the object.
The spectrometer device may further comprise at least one wavelength selective element comprising at least one of a wavelength selective element arranged in the beam path of the illumination light and a wavelength selective element arranged in the beam path of the detection light. The wavelength selective element may be selected from the group of tunable wavelength selective elements and wavelength selective elements having a fixed transmission spectrum.
As outlined above, the light sensitive element may be sensitive to different spectral ranges of the light from the object. The different spectral sensitivities may be implemented by using photosensitive elements with inherently different spectral sensitivities, such as by using different integrated filters and/or different sensitive materials, such as semiconductor materials. Additionally or alternatively, the different spectral sensitivities may be achieved by using one or more wavelength selective elements (such as one or more of filters, gratings, prisms, etc.) in one or more beam paths of the detection light, the one or more wavelength selective elements being configured to allow forward different spectral portions of the detection light from the object to reach the respective photosensitive elements sequentially or simultaneously.
Thus, in general, the spectrometer device may further comprise at least one wavelength selective element. As used herein, the term "wavelength selective element" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, any optical element that interacts with different spectral portions of incident light in different ways, for example by having at least one wavelength dependent optical property, such as at least one wavelength dependent optical property selected from the list consisting of reflectance, reflectance direction, refraction direction, absorption, transmission, refraction index.
Wherein the wavelength selection by the at least one wavelength selective element may be performed in at least one beam path of the illumination light, thereby selecting and/or modifying the illumination wavelength of the object, and/or in a detection beam path of the detection light, thereby selecting and/or modifying the detection wavelength, e.g. typically for the detector and/or for each photosensitive element. Thus, as an example, the at least one wavelength selective element may comprise at least one of a wavelength selective element arranged in the beam path of the illumination light and a wavelength selective element arranged in the beam path of the detection light.
The wavelength selective element may in particular be selected from the group of tunable wavelength selective elements and wavelength selective elements having a fixed transmission spectrum. By way of example, by using tunable wavelength selective elements, different wavelength ranges may be sequentially selected, while by using wavelength selective elements with a fixed transmission spectrum, the selection of wavelength ranges may be fixed, but may depend on e.g. the detection position, allowing e.g. simultaneous exposure of different detectors and/or different photosensitive elements of the detectors to light of different spectral ranges in the beam path of the detection light.
Thus, as outlined above and as an example, the at least one wavelength selective element may comprise at least one of a filter, a grating, a prism, a plasma filter, a diffractive optical element and a metamaterial. More specifically, the spectrometer device may comprise at least one filter element arranged in the beam path of the light from the object (i.e. arranged in the beam path of the detection light), wherein the filter element may in particular be configured such that each photosensitive element is exposed to a separate spectral range of the light from the object. As an example, a variable filter element may be used, the transmission of which depends on the position on the filter element, such that when the variable filter element is placed on top of the array of light sensitive elements, the individual light sensitive elements are exposed to different spectral ranges of the incident light, in particular the detection light from the object. Additionally or alternatively, the at least one wavelength selective element may comprise at least one of an array of individual bandpass filters, a patterned filter array, a MEMS interferometer, a MEMS fabry-perot interferometer. Additional elements are also possible.
The evaluation unit may be configured for deriving at least part of the spectroscopic information from the time-resolved detector signal. Thus, the time resolved detector signal may be used as a spectral detector signal. Alternatively, the time resolved detector signal may be different from the spectral detector signal. The spectral detector signals may be time resolved.
The detector may be configured to generate a time resolved detector signal in response to detecting at least a portion of at least one of:
Illumination light that does not interact with the object and/or the at least one reference target;
detection light from an object, or
Light from at least one reference target.
As used herein, the term "not interacting with an object and/or at least one reference object" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, light propagating from a light source to a spectrometer device, or more particularly to a detector of a spectrometer device. Thus, the detected illumination light may particularly have a spectrum that is not affected by the object and/or the reference target. As used herein, the term "light from at least one reference target" is a broad term and will be given its ordinary and customary meaning to those skilled in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, light propagating from a reference target to a spectrometer device, or more particularly to a detector of a spectrometer device, such as diffusely reflected light. The detection light may include at least one of illumination light reflected by the reference object, illumination light scattered by the reference object, illumination light transmitted by the reference object, luminescence light generated by the reference object (e.g., phosphorescence or fluorescence generated by the reference object after optical, electrical, or acoustic excitation of the reference object by the illumination light, etc.). The reference target may have a known effect on the spectrum of the illumination light. The reference target may comprise a material having a known optical influence on the detected light from the reference target. Such a material may be barium sulfate or the like. Additional materials may be present.
The at least one detector may generate at least one further detector signal from the detected detection light from the object, the detector signal comprising at least a part of the spectroscopic information. The further detector signal may be used as a spectral detector signal. The further detector signal and/or the spectral detection signal may be time resolved.
The at least one detector generating the time-resolved detector signal may be comprised by a first detector module and/or the at least one detector generating the further detector signal may be comprised by a second detector module, in particular wherein the first detector module and the second detector module may be different detector modules. As used herein, the term "detector module" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to physically and/or functionally separate units comprising at least one detector.
Time constantMay be at least one of the following:
Decay constant of excited state in luminescent materialEither (or)
Growth constant of excited state in luminescent material。
As used herein, the term "decay constant" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, constants describing the attenuation of signals and/or emissions (especially of luminescent materials). As used herein, the term "growth constant" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, constants describing the increase of the signal and/or emission (especially of the luminescent material).
Time constantMay depend on at least one of the following wavelengths of the illumination lightTemperature of or of the light source, in particular of the luminescent material. The time constant can be setTaking into account by evaluating the time constantTo determine the temperature of a light source, in particular a luminescent materialIn particular, a temperature dependent drift of the light source, in particular the luminescent material, is determined. By taking into account the determined temperature of the light sourceThe power spectral density of the light source, in particular of the luminescent material, can be obtainedWherein the power spectral density of the light source can be used in obtaining the spectroscopic information about the objectTaking into account.
Power spectral densityMay depend on at least one of the following wavelengths of the illumination lightTemperature of or of the light source, in particular of the luminescent material. Time constants can be consideredSo that the power spectral density of the light source, in particular of the luminescent material, can be obtainedIs the absolute value of (c). By assuming that all wavelengths are in thermal equilibrium, one can determine the thermal balance by taking into account at least one time constant for the different wavelengthsAnd/or a plurality of time constantsTo determine the power spectral density of a light source。
Can determine the time constantTo match the power spectral density of the light source, in particular of the luminescent materialTaking into account the relative values of (2). By taking into account the fact that for at least two different wavelengths、Determining a plurality of time constantsCan determine the power spectral density of the light sourceIs a variation of (c). By taking into accountProportional quotientThe comparison is performed by a change in the ratio of (a).
For determining the power spectral density of a light source, in particular a light emitting diodeAt least one information item concerning an electronic characteristic, in particular an electronic characteristic of a light emitting diode, is considered. As used herein, the term "electronic property" is a broad term and will be given its ordinary and customary meaning to those of ordinary skill in the art and is not limited to a special or custom meaning. The term may particularly refer to, but is not limited to, the electronic properties of the light source, particularly the light emitting diode. The electronic properties may be determined by taking into account a change in at least one electronic value that is indirectly and/or directly related to the at least one light source. Such characteristics may be the current and/or the voltage of the light source, in particular the light emitting diode. The spectrometer device may comprise at least one measurement unit for generating at least one information item about the electronic property. The measuring unit may be comprised by the driving unit.
By taking into account the power spectral density of the luminescent materialAnd power spectral density of light emitting diodesTo determine the total power spectral density of the light source. As used herein, the term "total power spectral density"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 custom meaning. The term may particularly refer to, but is not limited to, the power spectral density of a light emitting diodeAnd the power spectral density of the luminescent materialGenerated power spectral density. Thus, stray light generated by the at least one light source may be considered when obtaining spectroscopic information about the object.
In another aspect, a method of obtaining spectroscopic information about at least one object is disclosed. The method comprises the following steps that may be performed in a given order. However, different sequences are also possible. In particular, one, more than one or even all method steps may be performed once or repeatedly. Further, the method steps may be performed sequentially or, alternatively, one or more method steps may be performed in a timely overlapping manner or even in parallel and/or in a combined manner. The method may further comprise additional method steps not listed.
The method comprises the following steps:
(a) Illuminating the object with illumination light generated by at least one light source, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, and driving the light source in such a way that a driving state of the light source is changed at least once;
(b) Detecting light by using at least one detector and thereby generating at least one detector signal when the driving state of the light source is changed, wherein the detector signal is time resolved, and
(C) Obtaining the spectroscopic information about the object by detecting detection light from the object by using the detector by using at least one evaluation unit, and further obtaining a time constant of the light source from a time resolved detector signalThe time constant describing characteristics of the light source when the driving state is changed, wherein the at least one time constant is used when obtaining the spectroscopic information about the objectTaking into account.
As further summarized above, the method according to any of the above embodiments and/or according to any of the embodiments described in further detail below may be wholly or partially at least one of computer-controlled, computer-implemented and computer-aided, e.g. by using one or more computer programs running on at least one processor (e.g. at least one processor of a spectrometer device (e.g. at least one processor integrated within a detector and/or within an evaluation unit)). In particular, as outlined above, at least step c. Of the method may be at least one of computer controlled, computer implemented and computer assisted. It should be noted, however, that other steps of the method may also be wholly or partially at least one of computer-controlled, computer-implemented and computer-aided, such as one or more of steps a, b and c.
The method can be performed on-site and on-line. In particular, the spectrometer device may be a portable spectrometer device that may particularly be used in the field. In particular, the spectrometer device may be part of, or may be attachable to, a mobile device, such as a notebook computer, a tablet computer, a cellular phone (such as a smart phone), a smart watch, and/or a wearable computer (also referred to as a "wearable device", e.g., a body worn computer).
At least step c. Of the method may be computer implemented.
A computer program comprising instructions which, when executed by an evaluation unit of a spectrometer device, cause the evaluation unit to perform the method. A computer readable storage medium comprising instructions which, when executed by an evaluation unit of a spectrometer device, cause the evaluation unit to perform the method. A non-transitory computer readable medium comprising instructions that, when executed by an evaluation unit of the spectrometer device, cause the evaluation unit to perform the method. As used herein, the terms "computer-readable data carrier," "computer-readable storage medium," and "non-transitory computer-readable medium" are broad terms and are to be given their ordinary and customary meaning to those of ordinary skill in the art and are not limited to a special or custom meaning. These terms may particularly refer to, but are not limited to, data storage devices, particularly non-transitory data storage devices such as hardware storage media having computer-executable instructions stored thereon. The computer-readable data carrier or storage medium or computer-readable medium may in particular be or may comprise a storage medium such as a Random Access Memory (RAM) and/or a Read Only Memory (ROM).
As used herein, the terms "having," "including," or "containing," or any grammatical variation thereof, are used in a non-exclusive manner. Thus, these terms may refer to both the absence of an additional feature in the entity described in this context and the presence of one or more additional features in addition to the features introduced by these terms. As an example, the expressions "a has B", "a includes B" and "a includes B" may refer to both a case where no other element is present in a except B (i.e., a case where a is composed of B only and alone) and a case where one or more additional elements (such as elements C, C and D, or even additional elements) are present in an entity a in addition to B.
Further, it should be noted that the terms "at least one," "one or more," or the like, indicating that a feature or element may appear one or more times, typically are used only once when introducing the corresponding feature or element. In most cases, the expression "at least one" or "one or more" is not repeated when referring to the corresponding feature or element, but in fact the corresponding feature or element may appear one or more times.
Further, as used herein, the terms "preferably," "more preferably," "particularly," "more particularly," "specifically," "more specifically," or similar terms are used in combination with optional features without limiting the alternatives. Thus, 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 appreciate, the invention may be implemented using alternative features. Similarly, features introduced by "in embodiments of the invention" or similar expressions are intended to be optional features, without any limitation to alternative embodiments of the invention, without any limitation to the scope of the invention, and without any limitation to the possibility of combining features introduced in this way with other optional or non-optional features of the invention.
The spectrometer device and method according to the invention provide a number of advantages over known devices and methods of similar type in one or more of the above-described embodiments and/or in one or more of the embodiments described in further detail below. In particular, at least one time constant for determining at least one temperature of the light source is obtainedRepeatability and/or accuracy of the spectroscopic information about the object can be significantly improved. In particular, the temperature of the luminescent material can be reliably determined, in particular without having to take into account information items about the electronic properties.
Further, the use of phosphor LEDs may provide several advantages in lieu of or in addition to conventional heat emitters, such as incandescent lamps having tungsten filaments as the light source. Thus, in general, even thermal emitters can provide flat spectra, low temperature dependence and high power spectral density even at long wavelengths (such as in the NIR range)But thermal emitters are generally not well suited for mass spectrometer production. Thus, in general, disadvantages of the thermal emitter include high complexity of the manufacturing process, low efficiency of conversion of electric power to optical power, and physical limitation of miniaturization. These drawbacks can be overcome by using LEDs, in particular phosphor LEDs. LEDs have proven to be reliable light sources, such as standardized light sources in the visible light regime.
In the context of the present invention, a broadband light source may be provided by using one or more phosphor LEDs in a spectrometer device, the one or more phosphor LEDs comprising at least one light emitting diode and at least one luminescent material or phosphor. Thus, as an example, a white light source and/or a broadband light source in the infrared range, in particular in the NIR range, may be produced. The phosphor may convert photons having a shorter wavelength and thus a higher energy into photons having a longer wavelength or lower energy, for example by transferring a portion of the primary photon energy to a phosphor material, such as to a phosphor lattice. The remaining lower energy may result in the emission of long wavelength photons.
Thus, the luminescent material may be configured to absorb one or more primary photons generated by the light emitting diode and may emit one or more secondary photons in response to such absorption. The emission of the secondary photons may occur instantaneously or after a delay or decay time. Thus, as outlined above, the luminescent material may be or may comprise at least one of a phosphorescent material and a fluorescent material. Phosphorescence may result in the effect that after switching off the primary light, such as short wavelength or high energy pump light, the luminescent material may be at a characteristic lifetime(Tau) internally emits secondary light (such as long wavelength light) due to, for example, forbidden quantum optical transitions or forbidden dipole transitions. Thus, in particular, in luminescent materials, the emission of secondary light may occur through forbidden transitions (such as forbidden dipole transitions), which have a longer lifetime than allowed by spontaneous dipoles, as may be the case for many fluorescent materials.
In particular, as outlined above, luminescent materials, in particular phosphorescent materials, may be used, which have an absorption in the blue spectral range and an emission in the infrared spectral range. As an example, luminescent materials may be used which have the ability to convert blue primary light or pump light having a wavelength of e.g. 440 nm into near infrared secondary light, e.g. secondary light having a wavelength in the range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm. Additionally or alternatively, the primary light or pump light may be generated by an infrared LED having a wavelength in the range of 850 nm to 940 nm, and then the primary light or pump light may be converted by the luminescent material into near infrared secondary light having a wavelength in the range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.
A phosphor LED comprising at least one light emitting diode and at least one luminescent material may be implemented as a single element. Thus, in the state of the art, a phosphor LED may comprise a plurality of sub-components.
First, the phosphor LED may comprise one or more functional components, such as an LED die comprising at least one junction, such as at least one p-n junction, between at least two semiconductor regions. In an LED die, primary light, such as short wavelength pump light, for example, in the blue spectral range may be generated.
Further, the phosphor LED may comprise at least one luminescent material, in particular at least one phosphorescent material, which may in particular be placed directly on top of the LED die and which may convert primary light (in particular pump light) into secondary light (in particular into long wavelength near infrared light).
Further, the phosphor LED may comprise one or more substrates, in particular one or more electrically insulating substrates. Thus, as an example, a phosphor LED may comprise one or more ceramic substrates. The at least one substrate may be configured to hold at least one LED die and at least one luminescent material. Further, at least one substrate may hold or include one or more electrical connection components, such as one or more contact pads and/or one or more electrical leads, such as one or more metal contacts and/or one or more metal leads. In addition, the substrate (e.g., ceramic substrate) may be configured to act as a heat sink. For example, during the conversion process, heat may be generated in both the LED die and the luminescent material (e.g., due to limited conversion of electrical energy to photon energy), as well as in the luminescent material. The heat may be dissipated in a substrate, such as a ceramic substrate.
A spectrometer device using at least one LED may be configured to apply a Continuous Wave (CW) mode and/or preferably at least one modulation driving scheme to improve the accuracy and reliability of the measurement. Thus, for example, the at least one driving unit may be configured for applying a modulation driving scheme to the LEDs, and the evaluation device may be configured for taking into account the modulation driving scheme to derive the at least one item of spectroscopic information from the at least one detector signal. As an example, phase lock techniques, filtering techniques, etc. may be applied, as known to those skilled in the art.
Thus, the spectrometer device may be configured to apply a modulation drive scheme to the LEDs to compensate for the DC background of the detector and/or reduce detector noise. Thus, as an example, a band pass filter may be applied to the detector signal in order to eliminate the DC component.
Illumination light generated by a light source, in particular a phosphor LED, may be directed to illuminate the sample. To direct the illumination light, as an example, one or more mirrors may optionally be used. Detection light (e.g., reflected light) from the object may be directed to the detector, wherein optionally one or more optical components may be used. As an example, one or more wavelength selective elements, such as one or more dispersive elements, may be used, for example, for separating the detection light into its spectral components.
By means of the detector, one or more detector signals may be recorded, for example by using readout electronics comprised by the spectrometer device, which readout electronics may in particular be comprised by one or both of the detector and the evaluation device. As an example, the readout electronics may comprise one or more signal processing devices. Thus, as outlined above, for evaluation by the evaluation device, the "raw" detector signal and/or one or more secondary detector signals derived therefrom (such as one or more filtered detector signals) may be used. Further, at least one detector signal (primary or secondary) may also be combined with further information, such as information about the wavelength, e.g. derived from the number of the photosensitive element of the array of photosensitive elements from which the detector signal was derived, which photosensitive element is known to be exposed to a specific wavelength within a certain wavelength range. In the context of the present invention, in particular in the context of the evaluation unit evaluating the detector signals, it is possible to evaluate the option of the original detector signals and/or the option of the secondary detector signals, such as the preprocessed detector signals, the processed detector signals or the combined detector signals. However, the invention is still significant in particular for determining a "raw" detector signal, in particular a detector signal indicative of the change in signal strength with the detection wavelength. However, other options are also possible.
As an example, the detector signal may be processed or preprocessed (e.g. by the detector itself and/or by the evaluation unit) into a secondary detector signal by applying one or more fourier transforms. As an example, a fast fourier transform may be applied. From the processed secondary detector signal, at least one item of spectroscopic information may be obtained, for example by software executed by the evaluation unit. Thus, as an example, the fourier transform of the detector signal may be read out by the software of the spectroscopic device (in particular the evaluation device) and post-processed into spectroscopic information about the object.
Thus, as outlined above, LEDs and phosphor LEDs may provide an efficient light source that may be modulated in order to perform a specific evaluation scheme and to reduce noise and artifacts. By taking into account at least one time constant describing the characteristics of the light source when the driving state is changedThe temperature variation within the light source, in particular within the luminescent material, may be compensated completely or partly. Thus, for a typical LED as used herein, the temperature of the various components of the light source (in particular, the temperature of the LED) may vary over a large temperature range when operating at the maximum voltage and current that the LED may withstand. As an example, the standard operating current may range from 2 mA to 1000 mA, typically from 10 mA to 300 mA. As an example, the forward voltage may be in the range of 1.5V to 3.5V, typically in the range of 2.25V to 3V. Thus, as an example, under maximum operating conditions, the junction temperature of the emitter may be 135 ℃. The operating envelope temperature may vary from-40 ℃ to 135 ℃ and the storage temperature of the emitter may vary from-40 ℃ to 125 ℃. The ESD sensitivity of the led may be 250V according to the standard ANSI/ESDA/JEDEC JS-001-2012. These typical parameters show a large range of temperature variations, which may have an effect on the spectroscopic information about the object obtained by the spectrometer device. It should be noted that other parameters and other parameter ranges are also possible.
It is generally known that phosphor LEDs generate different spectra in the case of different compositions of the luminescent material, such as different compositions of the phosphor. Typically, each phosphor LED has multiple peaks in the spectrum, where the spectrum is typically distributed over a broad wavelength range. However, even if the same current is supplied to the phosphor LED, the spectral characteristics or spectrum may vary with temperature. These changes may include shifts in emission peaks, broadening or narrowing of the spectrum, increases or decreases in emission, and the like. However, in many cases, the emissions at some wavelengths are affected to a greater extent than the emissions at other wavelengths. Thus, typically, there is a specific center wavelength within the spectrum where the power (specifically the power spectral density) Typically not with temperature. Thus, with respect to the increment/decrement of power, each wavelength typically has its own temperature coefficient. Thus, the shape of the spectrum varies with temperature. By using at least one time constantSeparate temperatures of the spectra at different wavelengths can be generated. Thus, as outlined above, the evaluation unit may be configured for individually determining detector signals in different spectral ranges and for combining the individual detector signals to obtain the spectroscopic information. More specifically, as also outlined above, this may be performed by using an array of photosensitive elements, wherein each photosensitive element may be configured for generating at least one detector signal. Finally, the corrected detector signals may be combined to obtain the spectroscopy information.
By using at least one time constantThe temperature change and the respective characteristics of the phosphor LED can be determined. Thus, as an example, when the same current is applied to an LED, the forward voltage of the LED generally decreases with increasing temperature. Each type of LED has its own forward voltage-temperature characteristic. Typically, the forward voltage of an LED decreases linearly with increasing temperature, e.g., withTo the point ofSlope in the range of V/K.
Another characteristic of LEDs is that the light output power varies with forward current. Thus, in general, by increasing the input current, the allowable power of the LED increases. The shape (e.g., slope) of the curve of light output as a function of forward current is a characteristic of each LED.
As outlined above, at least one time constant is usedAs a control parameter for spectroscopic analysis purposes, efficient and reliable online correction or online calibration can be achieved. Thus, various challenges of a typical spectrometer and its corresponding calibration can be overcome. In particular, during a typical spectroscopic analysis, the reference measurement of the spectrometer allows the calibration instrument to respond, so the measurement only provides information about the sample. However, if the optical components of the spectrometer device change between the reference measurement and the sample measurement, the sample information may be affected by the system change, and thus the information about the sample may be distorted. In particular, when the spectrum of the light sourceDuring reference measurement (during which the light source has a spectrum) And actual sample measurement (during which the light source has a spectrum) When the spectrum is changed, the spectrum information about the image or sample is distorted, because the spectrum is generally based on two spectra、Is biased by the ratio of (c). In phosphor LEDs, the situation is often even more complicated, as the spectrum of a phosphor LED is a combination of the spectra of the LED and the luminescent material. Both components of the phosphor LED may be affected by temperature variations in different ways. Thus, for phosphor LEDs, the spectrum can be generally described by equation (3):
(3)
Wherein, theRepresenting the spectrum of the light source LS as wavelengthP-n junction temperature of LEDAnd the temperature of the phosphorIs a function of (2).Representing the spectrum of an LED (e.g., blue LED), andRepresenting the spectrum of the luminescent material, e.g. phosphor.
Both the LED and the luminescent material sub-components show separate temperature responses. Thus, a system temperature change or shift or an ambient temperature change or shift (particularly between a reference measurement and a sample measurement) will typically affect the spectrum by affecting both the LED junction and the luminescent material. The present invention can solve this problem in an efficient and reliable manner.
In summary, and without excluding further possible embodiments, the following embodiments are conceivable:
embodiment 1a spectrometer apparatus for obtaining spectroscopic information about at least one object, the spectrometer apparatus comprising:
(i) At least one light source configured to generate illumination light for illuminating the object, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, wherein the spectrometer device is configured to drive the light source in such a way that a driving state of the light source is changed at least once;
(ii) At least one detector configured to detect light and thereby generate at least one detector signal when a driving state of the light source changes, wherein the detector signal is time resolved;
(iii) At least one evaluation unit configured for deriving the spectroscopic information about the object by detecting detection light from the object using the detector, and further configured for deriving at least one time constant of the light source from a time resolved detector signalThe at least one time constant describing characteristics of the light source when the driving state is changed, wherein the at least one time constant is used when obtaining the spectroscopic information about the objectTaking into account.
Embodiment 2 the spectrometer device according to the previous embodiment, wherein the light emitting diode has a primary emission range at least partly within the spectral range 420 nm to 460 nm, more particularly within the range 440 nm to 455 nm, more particularly at 440 nm.
Embodiment 3 the spectrometer device according to any of the preceding embodiments, wherein the luminescent material is a phosphor.
Embodiment 4 the spectrometer device according to any of the preceding embodiments, wherein the illumination light has a spectral range at least partly within the near infrared spectral range, in particular within a spectral range of 1 to 3 μm, preferably 1.3 to 2.5 μm, more preferably 1.5 to 2.2 μm.
Embodiment 5 the spectrometer device according to any of the preceding embodiments, wherein the driving state of the light source is at least one of:
A first driving state in which the light emitting diode generates the primary light;
and a second driving state in which the light emitting diode does not generate primary light.
Embodiment 6 the spectrometer device according to the previous embodiment, wherein the at least one spectrometer device is configured for operating the light source in a pulsed mode in such a way that the driving state of the light source is repeatedly changed, in particular between the first driving state and the second driving state.
Embodiment 7 the spectrometer device according to any of the two previous embodiments, wherein the at least one spectrometer device is configured for being in a specific driving state, in particular the first driving state and/or the second driving state, being greater than the time constantOperating the light source within a predetermined time span, in particular at least 5 times the time constant, or the time constantIs at least 10 times larger.
Embodiment 8 the spectrometer device according to any of the preceding embodiments, wherein the detector is configured for generating detector signals for at least two different spectral ranges of the light from the object, in particular at least one of sequentially and simultaneously, to obtain the spectroscopic information.
Embodiment 9 the spectrometer device according to any of the preceding embodiments, wherein the detector comprises an array of photosensitive elements, wherein each photosensitive element is configured to generate at least one detector signal to obtain the spectroscopic information.
Embodiment 10 the spectrometer device according to the previous embodiment, wherein the spectrometer device is configured such that the light sensitive elements are sensitive to different spectral ranges of the light from the object.
Embodiment 11 the spectrometer device according to the previous embodiment, wherein the spectrometer device comprises at least one filter element arranged in a beam path of light from the object, wherein the filter element is configured such that each photosensitive element is exposed to a separate spectral range of light from the object.
Embodiment 12 the spectrometer device according to any of the preceding embodiments, further comprising at least one wavelength selective element comprising at least one of a wavelength selective element arranged in a beam path of the illumination light and a wavelength selective element arranged in a beam path of the detection light.
Embodiment 13 the spectrometer device according to the previous embodiment, wherein the wavelength selective element is selected from the group of tunable wavelength selective elements and wavelength selective elements having a fixed transmission spectrum.
Embodiment 14 the spectrometer device according to any of the preceding embodiments, wherein the evaluation unit is configured to derive at least a part of the spectroscopic information from the time resolved detector signal.
Embodiment 15 the spectrometer device according to any of the preceding embodiments, wherein the detector is configured to generate the time resolved detector signal in response to detecting at least a portion of at least one of:
the illumination light not interacting with the object and/or at least one reference target;
the detection light from the object, or
Light from the at least one reference target.
Embodiment 16 the spectrometer device according to any of the preceding embodiments, wherein the at least one detector generates at least one further detector signal from the detected detection light from the object, the detector signal comprising at least a part of the spectroscopy information.
Embodiment 17 the spectrometer device according to the previous embodiment,
Wherein the at least one detector generating the time resolved detector signal is comprised by a first detector module;
wherein the at least one detector generating the further detector signal is comprised by a second detector module;
Wherein the first detector module and the second detector module are different detector modules.
Embodiment 18 the spectrometer device according to any of the preceding embodiments, wherein the time constantIs at least one of the following:
Decay constant of excited state in the luminescent materialEither (or)
Growth constant of excited state in the luminescent material。
Embodiment 19 the spectrometer device according to any of the preceding embodiments, wherein the time constantDepending on at least one of the wavelength of the illumination lightOr the temperature of the light source, in particular the luminescent material。
Embodiment 20 the spectrometer device according to any of the preceding embodiments, wherein the time constantIs taken into account by evaluating the time constantTo determine the temperature of the light source, in particular the luminescent materialIn particular a temperature dependent drift of the light source, in particular the luminescent material, is determined.
Embodiment 21 the spectrometer device according to the previous embodiment, wherein the determined temperature of the light source is taken into accountObtaining the power spectral density of the light source, in particular of the luminescent materialWherein the power spectral density of the light source is used in obtaining the spectral information about the objectTaking into account.
Embodiment 22 the spectrometer apparatus according to the previous embodiment, wherein the power spectral densityDepending on at least one of the wavelength of the illumination lightOr the temperature of the light source, in particular the luminescent material。
Embodiment 23 the spectrometer device according to any of the two previous embodiments, wherein the time constant is consideredSuch that the power spectral density of the light source, in particular of the luminescent material, is reduced when the spectroscopic information about the object is obtainedTaking into account the absolute value of (a).
Embodiment 24 the spectrometer device according to any of the three previous embodiments, wherein the time constant is determinedSuch that the power spectral density of the light source, in particular of the luminescent material, is reduced when the spectroscopic information about the object is obtainedTaking into account the relative values of (2).
Embodiment 25 the spectrometer device according to any of the four previous embodiments, wherein for determining the power spectral density of the light source, in particular the light emitting diodeAt least one information item concerning an electronic property, in particular an electronic property of the light emitting diode, is considered.
Embodiment 26 the spectrometer device according to any of the five previous embodiments, wherein the spectral density of the luminescent material is determined by considering the power of the luminescent materialAnd the power spectral density of the light emitting diodeTo determine the total power spectral density of the light source。
Embodiment 27 a method of obtaining spectroscopic information about at least one object, the method comprising:
(a) Illuminating the object with illumination light generated by at least one light source, the light source comprising at least one light emitting diode and at least one luminescent material for light converting primary light generated by the light emitting diode, and driving the light source in such a way that a driving state of the light source is changed at least once;
(b) Detecting light by using at least one detector and thereby generating at least one detector signal when the driving state of the light source is changed, wherein the detector signal is time resolved, and
(C) Obtaining the spectroscopic information about the object by detecting detection light from the object by using the detector by using at least one evaluation unit, and further obtaining a time constant of the light source from a time resolved detector signalThe time constant describes the characteristics of the light source when the driving state is changed, wherein the time constant is used when obtaining the spectroscopic information about the objectTaking into account.
Embodiment 28 the method according to the previous embodiment, wherein a spectrometer device according to any of the previous embodiments relating to spectrometer devices is used.
Embodiment 29 the method of any of the preceding method embodiments, wherein the method is performed on-site on-line.
Embodiment 30 the method according to any of the preceding method embodiments, wherein at least step c. Of the method is computer implemented.
Embodiment 31: a computer program comprising instructions which, when executed by an evaluation unit of a spectrometer device according to any of the previous embodiments relating to a spectrometer device, cause the evaluation unit to perform the method according to any of the previous embodiments relating to a method, in particular to perform at least step c.
Embodiment 32 a computer-readable storage medium comprising instructions which, when executed by an evaluation unit of a spectrometer device according to any of the previous embodiments of the spectrometer device, cause the evaluation unit to perform the method according to any of the previous embodiments of the method, in particular to perform at least step c.
Embodiment 33. A non-transitory computer-readable medium comprising instructions that, when executed by an evaluation unit of a spectrometer device according to any of the previous embodiments of the spectrometer device, cause the evaluation unit to perform the method according to any of the previous embodiments of the method, in particular to perform at least step c.
Detailed Description
In fig. 1, a schematic overview of a spectrometer device 110 for obtaining spectroscopic information about at least one object 112 is shown. The spectrometer device 110 may include a number of components as illustrated in fig. 1. Possible components of the spectrometer device 110 and their interactions will be described below with specific reference to fig. 1. The spectrometer device 110 comprises at least one light source 114 for generating illumination light 116 for illuminating the object 112. The light source 114 may be at least one of a tunable light source, a light source having at least one fixed emission wavelength, and a broadband light source. The light source 114 may specifically be or may comprise at least one electric light source. The light source 114 comprises at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118. By way of example, the light emitting diode 118 may include one or more of a Light Emitting Diode (LED) based on light spontaneous emission, a light emitting diode (sLED) based on superemission, a laser diode (LLED).
The LED 118 may in particular comprise at least two layers of semiconductor material 121, wherein light may be generated at least one interface between the at least two layers of semiconductor material 121, in particular due to recombination of positive and negative charges. The at least two layers of semiconductor material 121 may have different electrical properties, such as at least one of the layers being an n-doped semiconductor material 121 and at least one of the layers being a p-doped semiconductor material 121. Thus, as an example, the LED 118 may comprise at least one pn junction and/or at least one pin structure. However, it should be noted that other device configurations are possible.
The light emitting diode 118 may generate primary light, which may also be referred to as "pump light". The primary light may then be converted into "secondary light", such as by using light conversion (e.g., by one or more luminescent materials 120, such as phosphor materials). Thus, the at least one luminescent material 120 may form at least one converter (also referred to as a light converter) that converts the primary light into secondary light having different spectral properties than the primary light. In particular, the spectral width of the secondary light may be larger than the spectral width of the primary light and/or the emission center of the secondary light may be shifted (in particular red shifted) compared to the primary light. In particular, the at least one luminescent material 120 may be absorbing in the ultraviolet and/or blue spectral range and emissive in the near infrared and/or infrared spectral range. The illumination light 116 may be or may include at least one of primary light or a portion thereof, secondary light or a portion thereof, or a mixture of primary and secondary light.
As indicated in fig. 1, the light source 114 may specifically comprise a phosphor light emitting diode 122, also referred to as a phosphor LED 122. The phosphor LED 122 may be a combination of at least one light emitting diode 118 configured to generate primary light or pump light and at least one luminescent material 120 (also referred to as "phosphor") configured to light convert the primary light generated by the light emitting diode 118. The phosphor LED 122 may form a packaged LED light source comprising an LED die 124 (e.g., a blue LED that emits blue pump light) and a phosphor, for example, that completely or partially coats the LED 118 and is configured to convert primary or blue light into light having different spectral characteristics (specifically into near infrared light), as examples. Fig. 2 shows a more detailed view of the light source 114 implemented as a phosphor LED 122.
In general, the light source 114 may be implemented in various ways. Thus, the light source 114 may be, for example, a portion of the spectrometer device 110 in a housing 126 of the spectrometer device 110, as illustrated in fig. 1. Alternatively or additionally, however, the at least one light source 114 may also be arranged outside the housing 126, for example as a separate light source 114 (not shown). The light source 114 may be arranged separately from the object 110 and illuminate the object 110 from a distance, as indicated in fig. 1.
Illumination light 116 as generated by light source 114 may propagate from light source 114 to object 112. In fig. 1, illumination light 116 generated by light source 114 and propagating to object 112 is shown by arrows. In particular, the object 112 may comprise at least one sample, which may be wholly or partially analyzed by spectroscopic methods.
As is apparent from fig. 1, the spectrometer device 110 further comprises at least one detector 128 configured for detecting detection light 130 from the object 112. Light propagating from the light source 114 to the object 112 may be referred to as illumination light 116, while light propagating from the object 112 to the detector 128 may be referred to as "detection light" 130. In fig. 1, detection light 130 is shown by an arrow. The detection light 130 may include at least one of illumination light 116 reflected by the object 112, illumination light 116 scattered by the object 112, illumination light 116 transmitted by the object 112, luminescence light generated by the object 112 (e.g., phosphorescence or fluorescence generated by the object 112 after optical, electrical, or acoustic excitation of the object 112 by the illumination light 116, etc.). Thus, the detection light 130 may be generated directly or indirectly by illumination of the object 112 by the illumination light 116.
The detector 128 is further configured to detect light and thereby generate at least one detector signal when the driving state of the light source 114 is changed, wherein the detector signal is time resolved. The detector 128 may be configured to generate a time-resolved detector signal in response to detecting at least a portion of at least one of illumination light that does not interact with the object 116 and/or the at least one reference target, detection light 130 from the object, or light 250 from the at least one reference target 248 (as further depicted in fig. 11). The time resolved detector signals may be used to obtain spectroscopic information about the object 112. Thus, the evaluation unit 136 may be configured for deriving at least a part of the spectroscopic information from the time-resolved detector signal. Alternatively, the time-resolved detector signal and the detector signal (also referred to as "spectral detector signal") used to obtain the spectroscopic information about the object may be different signals, such as by being generated by different detectors 128. Thus, the at least one detector 128 may not only generate a time resolved detector signal, but may also generate at least one further detector signal (comprising at least part of the spectroscopic information) from the detected light from the object 112. The further detector signal may be used as a spectral detector signal. The further detector signal and/or the spectral detection signal may be time resolved. In the exemplary spectrometer device 110 depicted in fig. 1, at least one detector that generates a time resolved detector signal and that generates additional detector signals is comprised by the same detector module 135.
The detector 128 may be or may include at least one optical detector 132. The optical detector 132 may be configured to determine at least one optical parameter, such as the intensity and/or power of light irradiating at least one sensitive area of the detector 132. More specifically, the optical detector 132 may include at least one photosensitive element and/or at least one optical sensor, such as at least one of a photodiode, a photocell, a photoresistor, a phototransistor, a thermopile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier, and a bolometer. Thus, the detector 128 may be configured for generating at least one detector signal, more particularly at least one electrical detector signal in the above sense, providing information about at least one optical parameter, such as power and/or intensity of light illuminating the detector 128 or a sensitive area of the detector 128.
The detector 128 may include a single optical sensor or region or multiple optical sensors or regions. As indicated in fig. 1, the detector 130 may comprise at least one detector array, more particularly an array of photosensitive elements 134. Each photosensor 134 can be configured to generate at least one detector signal. In particular, each light sensitive element 134 may comprise at least a light sensitive region, which may be adapted to generate an electrical signal depending on the intensity of the incident light, wherein the electrical signal may in particular be provided to an evaluation unit 136 of the spectrometer device, as will be outlined in further detail below.
Where the detector 128 comprises an array of optically sensitive elements 134, the detector 128 may for example be selected from any known pixel sensor, in particular from a CCD chip or a CMOS chip. Alternatively, the detector 128 may generally be or include a photoconductor, particularly an inorganic photoconductor, particularly PbS, pbSe, ge, inGaAs, extended InGaAs, inSb, or HgCdTe. As a further alternative, the detector may comprise at least one of a pyroelectric element, a bolometer element or a thermopile detector element.
The spectrometer apparatus 110 comprises at least one evaluation unit 136 for evaluating at least one detector signal (such as a spectral detector signal and/or a time-resolved detector signal) generated by the detector 128 and for deriving spectroscopic information about the object 112 from the detector signal. The detector 128 may directly or indirectly provide the detector signal to the evaluation unit 136. Thus, the detector 128 and the evaluation unit 136 may be directly or indirectly connected, as indicated by the arrow in fig. 1. The detector signal may be used as a "raw" detector signal and/or may be processed or pre-processed (e.g., by filtering, etc.) prior to further use. Thus, the detector 128 may include at least one processing device and/or at least one preprocessing device, such as at least one of an amplifier, an analog/digital converter, an electrical filter, and a fourier transform.
As shown in fig. 1, the spectrometer device 110 further comprises at least one drive unit 138 for electrically driving the light source 114. The spectrometer device 110 comprises at least one measurement unit 139 for generating at least one information item about the electronic properties. Information items about the electronic properties can be taken into account to determine the power spectral density of the light source, in particular a light emitting diode. The measurement unit 139 may be an element of the drive unit 138, as indicated in fig. 1. In particular, the drive unit 138 may be configured for providing a current to the LED 118, in particular for controlling the current through the LED 118. Therein, as an example, the drive unit 138 may be configured to adapt and measure the voltage provided to the LED 118, which is required to achieve a specific current through the LED 118. The drive unit 138 may specifically include one or more of a current source 140, a voltage source, a current measurement device (such as an ammeter), a voltage measurement device 142 (such as a voltmeter), a power measurement device. In particular, the drive unit 138 may comprise at least one current source 140 for providing at least one predetermined current to the LED 118, wherein the current source 140 may in particular be configured for adjusting or controlling the voltage applied to the LED 118 in order to generate the predetermined current. As an example, the drive unit 138 may include one or more electrical components (such as an integrated circuit) for driving the light source 114. The drive unit 138 may be fully or partially integrated into the light source 114 or may be separate from the light source 114, the latter configuration being illustrated in fig. 1.
The forward voltage may be applied to the LED in the forward direction, i.e., a positive contact of a voltage or current source 140 is applied to the p-layer of the LED 118 and a negative contact is applied to the n-layer of the LED 118, so as to generate a predetermined current through the LED 118. Thus, the LED may generate primary light. As an example, the predetermined current defining the forward voltage may be a current known to generate a predetermined light output of the light source 114 and/or the light emitting diode 118.
The spectrometer device 110 is configured to drive the light source 114 in such a way that the driving state of the light source 114 is changed at least once. The driving state of the light source may be at least one of a first driving state in which the light emitting diode 118 generates the primary light, or a second driving state in which the light emitting diode 118 does not generate the primary light. The at least one spectrometer device 110 may be configured for operating the light source 114 in a pulsed mode in such a way that the driving state of the light source 114 is repeatedly changed, in particular between a first driving state and a second driving state. The at least one spectrometer device 110 may be configured for driving in a specific driving state, in particular a first driving state and/or a second driving state, at a time constant larger thanThe light source 114 is operated within a predetermined time span, in particular at least 5 times the time constant, or the time constantIs at least 10 times larger.
As outlined above, and as shown in fig. 1, the spectrometer apparatus 110 comprises at least one evaluation unit 136 for evaluating at least one detector signal (such as a spectral detector signal) generated by the detector 128 and for deriving spectroscopic information about the object 112 from the detector signal. The evaluation unit 136 is configured for deriving a time constant of the light source by evaluating the time resolved detector signalThe time constant describes the characteristics of the light source when the driving state changes. Time constant considered in obtaining spectroscopic information about object 110。
Time constantMay be at least one of the decay constants of the excited states in the luminescent materialOr the growth constant of the excited state in the luminescent material。
Time constantMay depend on at least one of the wavelength of the illumination light 116Or the temperature of the light source 114 (particularly the luminescent material 120). The time constant can be setTaking into account by evaluating the time constantTo determine the temperature of the light source 114, in particular the luminescent material 120In particular, a temperature dependent drift of the light source 114, in particular the luminescent material 120, is determined. By taking into account the determined temperature of the light source 114The power spectral density of the light source 114, in particular the luminescent material 120, can be obtainedWherein the power spectral density of the light source 114 can be used when the spectroscopic information about the object 112 is availableTaking into account. Power spectral densityDepending on at least one of the wavelength of the illumination light 116Or the temperature of the light source 114 (particularly the luminescent material 120)。
Time constants can be consideredSuch that the power spectral density of the light source 114, in particular of the luminescent material 120, can be used when obtaining the spectroscopic information about the object 112Taking into account the absolute value of (a). Can determine the time constantSuch that the power spectral density of the light source 114, in particular the luminescent material 120, is reduced when the spectroscopic information about the object 112 is availableTaking into account the relative values of (2).
By taking into account the power spectral density of the luminescent material 120And the power spectral density of the light emitting diode 118To determine the total power spectral density of the light source。
In particular, the evaluation unit 136 may be configured for processing at least one input signal and generating at least one output signal thereof. As an example, the at least one input signal may include at least one detector signal provided directly or indirectly by at least one detector 128. The arrow between the drive unit 138 (which comprises the measuring unit 139 in the embodiment illustrated in fig. 1) and the evaluation unit 136 in fig. 1 illustrates the process of providing a signal to the evaluation unit 136 and/or retrieving a signal by the evaluation unit 136, which signal comprises at least one information item about the electronic properties.
The evaluation unit 136 may be or include one or more integrated circuits, such as one or more Application Specific Integrated Circuits (ASICs), and/or one or more data processing devices 144, such as one or more of a computer, a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), preferably one or more microcomputers and/or microcontrollers. Additional components may be included, such as one or more preprocessing devices 146 and/or data acquisition devices, such as one or more devices for receiving and/or preprocessing detector signals, such as one or more AD converters and/or one or more filters. Further, the evaluation unit may comprise one or more data storage devices 148, as shown in fig. 1. Further, the evaluation unit 136 may comprise one or more interfaces, such as one or more wireless interfaces and/or one or more wired interfaces.
As described in more detail above, the detector 128 may specifically include an array of photosensitive elements 134. Each photosensitive element may be configured to generate at least one detector signal. The evaluation unit 136 may be configured to take into account each of these detector signals to obtain the spectroscopic information. The spectrometer device 110 may be configured such that the photosensitive elements of the detector 128 are sensitive to different spectral ranges of light from the object 112. In particular, the detector 128 may be configured for generating detector signals for at least two different spectral ranges of light from the object, in particular at least one of sequentially and simultaneously. The spectrometer 110 may in particular comprise at least one filter element 150 arranged in the beam path of the light from the object. The filter element 150 may in particular be configured such that each photosensitive element is exposed to a separate spectral range of light from the object 112.
The spectrometer device 110 can further include one or more optical components 151, such as one or more of at least one mirror, at least one lens, at least one aperture, and at least one wavelength selective element 152. Specifically, one or more optical components 151 may be disposed in at least one of the beam path of the illumination light 116 and the beam path of the detection light 130. The spectrometer device 110 may in particular comprise at least one wavelength selective element 152. The wavelength selective element 152 may in particular be selected from the group comprising a tunable wavelength selective element 152 and a wavelength selective element 152 having a fixed transmission spectrum. By way of example, by using a tunable wavelength selective element 152, different wavelength ranges may be sequentially selected, while by using a wavelength selective element 152 with a fixed transmission spectrum, the selection of wavelength ranges may be fixed, but may also depend on the detector position, for example. The wavelength selective element 152 may be used to separate the incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector, such as the detector 128 of the spectrometer device 110, which may include an array of photosensitive elements 134. The at least one wavelength selective element 152 may, for example, comprise at least one of a filter, a grating, and a prism. The wavelength selective element 152 may specifically include at least one of a wavelength selective element 152 disposed in a beam path of the illumination light 116 and a wavelength selective element 152 disposed in a beam path of the detection light 130. Fig. 1 illustrates an embodiment of a spectrometer device 110 having one wavelength selective element 152 arranged in the beam path of illumination light 116 and one wavelength selective element 152 arranged in the beam path of detection light 130.
The spectrometer device 110 as schematically represented in fig. 1 is configured for obtaining spectroscopic information about at least one object 112. In particular, the spectrometer device may be configured for obtaining an information item, for example, about at least one object and/or radiation emitted by at least one object, the information item characterizing at least one optical property of the object, more particularly at least one information item, for example, characterizing and/or quantifying at least one of transmission, absorption, reflection and emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one item of intensity information, e.g. information about the intensity of light transmitted, absorbed, reflected or emitted by the object, e.g. as a function of wavelength or wavelength sub-ranges within one or more wavelengths (e.g. within a wavelength range). Accordingly, the spectrometer device 110 may be configured to acquire at least one spectrum or at least a portion of a spectrum of the detection light 130 propagating from the object 112 to the detector 128. The spectrum may describe the units of radiation measurement of the spectral flux, for example given in watts per nanometer (W/nm), or in other units, for example as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, for example, in the NIR spectral range, in a particular band. The spectrum may contain one or more optical variables that are a function of wavelength, such as power spectral densityAn electrical signal obtained by optical measurement, and the like. Examples of spectra are shown, for example, in fig. 4, 7A and 7B. The spectrometer device 110 may in particular be a portable spectrometer device 110, which may in particular be used in the field.
A schematic cross-sectional view of the light source 114 is shown in fig. 2. The at least one light source 114 of the spectrometer device 110 may be configured to generate or provide electromagnetic radiation in one or more of the infrared, visible, and ultraviolet spectral ranges. Because many material properties or chemical composition properties of many objects 112 are available from the near infrared spectrum, light used for typical purposes of the present invention is light in the Infrared (IR) spectrum, more preferably in the Near Infrared (NIR) and/or mid-infrared (MidIR) spectrum, especially light having a wavelength of 1 to 5 μm, preferably 1 to 3 μm. The light source 114 comprises at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118. As described above, the LED 118 and the luminescent material 120 together may form a phosphor LED 122.
As illustrated in fig. 2, the phosphor LED 122 may include one or more functional components. In particular, the phosphor LED 122 may comprise one or more substrates 154, in particular one or more electrically insulating substrates 154. In particular, the phosphor LED 122 may include one or more ceramic substrates 156, as shown in fig. 2. The substrate 154 may be configured to hold the at least one LED die 124 and the at least one luminescent material 120. Further, the at least one substrate 154 may hold or include one or more electrical connection components, such as one or more contact pads 158 and/or one or more electrical leads, such as one or more metal contacts and/or one or more metal leads, as shown in fig. 2. The substrate 154 may be configured to act as a heat sink. For example, during the conversion process, heat may be generated in the LED die 124 (e.g., due to limited conversion of electrical energy to photon energy) and in the luminescent material 120. The heat may be dissipated in the substrate 154, such as in a ceramic substrate.
As shown in fig. 2, the phosphor LED 122 may include a light emitting diode 118. The light emitting diode 118 may be configured to convert current into primary light, such as blue primary light, using at least one LED chip and/or at least one LED die 124 as illustrated in fig. 2. In particular, a p-n junction diode may be used. As an example, one or more LEDs 118 selected from the group of indium gallium nitride (InGaN) based LEDs 118, gaN based LEDs 118, inGaN/GaN alloy based LEDs 118, or combinations thereof, and/or other LEDs 118 may be used. Additionally or alternatively, quantum well LEDs 118 may also be used, such as one or more InGaN-based quantum well LEDs 118. Additionally or alternatively, super-radiating LEDs (slds) and/or quantum cascade lasers may be used. As is further apparent from fig. 2, the phosphor LED may comprise at least one luminescent material 120 configured for light conversion of primary light generated by the light emitting diode 118. Various types of conversion and/or luminescence are known and may be used in the context of the present invention. Specifically, the luminescent material 120 may include at least one of cerium doped YAG (YAG: ce3+ or Y3Al5O12:Ce3+), rare earth doped Sialon, copper aluminum co-doped zinc sulfide (ZnS: cu, al).
The luminescent material 120 may in particular form at least one layer. In general, various alternatives for positioning the luminescent material 120 relative to the light emitting diode 118 are possible, which may be used alone or in combination. First, the luminescent material 120 (e.g., at least one layer of luminescent material 120, such as a phosphor) may be positioned directly on the light emitting diode 118, e.g., with no material between the LED 118 and the luminescent material 120, or with one or more transparent materials therebetween, such as with one or more transparent materials (particularly transparent to primary light) between the LED and the luminescent material 120. Thus, as an example, a coating of luminescent material 120 may be placed directly or indirectly on the LEDs 118 (not shown). Additionally or alternatively, as an example, the luminescent material 120 may form at least one conversion body 160, such as at least one conversion plate, which may also be referred to as conversion plate. The conversion body 160 may be placed on top of the LED 118, for example, as illustrated in fig. 2, by adhesively attaching the conversion body 160 to the LED 118. Additionally or alternatively, the luminescent material 120 may also be placed in a remote manner such that the primary light from the LED 118 has to pass through an intermediate light path before reaching the luminescent material 120 (not shown). Also, as an example, the remotely located luminescent material may form a solid or conversion body 160, such as a disk or conversion disk. In the intermediate optical path, one or more optical elements, such as one or more of lenses, prisms, gratings, mirrors, apertures, or combinations thereof, may be placed. Thus, in particular, an optical system with imaging properties may be placed in the intermediate light path between the LED 118 and the luminescent material 120. Thus, as an example, the primary light may be focused or focused onto the conversion body 160.
In the light source 114, in particular the phosphor LED 122, at least one luminescent material 120 may be positioned relative to the light emitting diode 118 such that heat transfer from the light emitting diode 118 to the luminescent material 120 is possible. More specifically, the luminescent material 120 may be positioned such that heat transfer may be by one or both of thermal radiation and thermal conduction (more preferably by thermal conduction). Thus, as an example, the luminescent material 120 may be in thermal and/or physical contact with the light emitting diode 118, as shown in fig. 2. Thus, in general, the temperature of the luminescent material 120 and the temperature of the light emitting diode 118 may be coupled.
As shown in fig. 2, the light source 114 (and in particular the phosphor LED 122) may include further components such as at least one side coating 162 covering at least one side (such as a top surface, a bottom surface, and/or one or more lateral sides) of at least one of the substrate 154, the contact pads 158, the light emitting diode 118, and the luminescent material 120. In particular, the side coating 162 may cover voids and/or gaps that may be present in a layered arrangement of the light sources 114, as shown in fig. 2. Other components of the light source 114, in particular components not shown in fig. 2, are possible. In general, the light sources 114 (and in particular the phosphor LEDs 122) may be packaged in a housing (not shown in fig. 2) or may be unpackaged. Thus, the LED 118 and the at least one luminescent material 120 for light conversion of the primary light generated by the light emitting diode 118 may in particular be accommodated in a common housing. Alternatively, however, the LEDs 118 may also be shell-less or bare LEDs 118, as illustrated in fig. 2.
The schematic flow chart of fig. 3 shows a process of generating and processing detector signals. In particular, a hardware component 164 that may participate in the process or in the generation and/or preprocessing of the detector signals and a software component 166 that may participate in the processing of the detector signals are illustrated in fig. 3. The hardware component 164 (also referred to simply as "hardware" 164) may specifically include at least one light emitting diode 118 (particularly a blue LED 118) of the spectrometer device 110 configured to emit blue primary light. The hardware component 164 may further include a luminescent material 120 (also referred to as an LED phosphor), an object 112, and one or more optical components 151 (e.g., at least one wavelength-selective element 152) and a detector 128.
The evaluation unit 136 may take into account temperature variations (even local temperature variations inside the light source 114) which may have an influence on the emission characteristics of the light source 114. In addition to the hardware component 164, the temperature of the selected hardware component 164 is indicated in FIG. 3. For example, depending on the arrangement of hardware components 164 (such as the relative position and distance of the hardware components in spectrometer device 110), hardware components 164 may have different or the same temperatures. Specifically, as described above, the temperature of the light emitting material 120 and the temperature of the light emitting diode 118 may be coupled, for example, due to heat transfer caused by one or both of heat radiation and heat conduction between the light emitting diode 118 and the light emitting material 120. Thus, in particular, the temperature of the LED 118 (which may also be referred to as "Tpn") and the temperature of the luminescent material 120 (which may also be referred to as "TPh") may be similar. In fig. 3, the temperature of the LED 118 is indicated by reference numeral 168, the temperature of the luminescent material 120 is indicated by reference numeral 170, and the temperature of the detector 128 (also referred to as "TD") is indicated by reference numeral 172.
When a current flows through the LED 118 (e.g., due to the drive unit 138 applying an appropriate voltage to the LED), the LED 118 may emit primary light to generate a particular current (e.g., a predetermined current). The target signal St, as indicated by reference numeral 174 in fig. 3, may be provided to, for example, the drive unit 138 to drive the LED 118 to emit blue primary light. In particular, the target signal St 174 may be a predetermined current value through the LED 118 to be generated, for example, by applying an appropriate voltage. In particular, the predetermined current value may be in the range of 10mA to 500 mA, more particularly in the range of 100 mA to 300 mA, for example a current value of 50 mA. Thus, the known predetermined current may generate a predetermined light output of the LED 118, such as blue primary light. LED 118 may be at a temperature "Tpn" indicated by reference numeral 168. The blue primary light may be converted by the luminescent material 120 into secondary light, such as into light in the infrared spectral range. The luminescent material 120 may be at a temperature "Tph" indicated by reference numeral 170. The illumination light 116 generated by the light source 114 may illuminate the object 112, which may include at least one of primary light or a portion thereof, secondary light or a portion thereof, or a mixture of primary light and secondary light. To direct the illumination light 116, one or more optical components 151 (such as one or more mirrors, lenses, wavelength-selective elements 152, or other optical components 151) may be used, for example, by placing the optical components 151 in the beam path of the illumination light 116. Detection light (e.g., reflected light) from the object 112 may be directed to the detector 128. In the beam path of the detection light 130, also optionally, one or more optical components 151 may be used. As an example, one or more wavelength selective elements 152, such as one or more dispersive elements, may be used, for example, to separate the detection light 130 into its spectral components.
As described in more detail above, the detector 128 may, for example, include an array of photosensitive elements 134. In particular, the detector 128 may be or may include a pixel sensor, such as a CCD chip or a CMOS chip, including a plurality of pixels arranged on the chip. As an example, each pixel may correspond to a predetermined spectral range, for example by being sensitive to the predetermined spectral range. Thus, the detector 128 may generate a detector signal Spx,i, 176, as indicated by reference numeral 176 in fig. 3, comprising a plurality of detector signals. Thus, each of the plurality of detector signals may correspond to an electronic signal generated by one of the plurality of pixels of the detector 128. Each of the plurality of detector signals may be given, for example, as a value corresponding to a count number of the respective pixels measured, for example, during a predetermined time span. Thus, the detector signal Spx,i 176,176 may specifically be a function of the wavelength of the detection light 130, as indicated by the index "px". The signal Spx,i 176,176 may further be a function of time (e.g. in the case of a time dependent detector signal or a time resolved detector signal), as indicated by the index "i".
The plurality of signals comprised by the detector signal Spx,i 176,176 may be generated simultaneously or in a time-sequential manner. The detector signal Spx、i 176,176 may be determined using readout electronics 178 as shown in fig. 3. The detector signal Spx、i 176,176 may be processed, for example as part of a pre-processing and/or as part of a further processing step. As an example, the pixels comprised by the detector 128 may in particular be active pixel sensors, which may be adapted to amplify the electronic detector signal Spx,i 176,176, e.g. as part of a pre-processing procedure before further processing, which may be performed, e.g., by one or more of the software components 166.
The signal Spx,i 176 generated by the detector 128 may also be referred to as "frame signal Spx,i 176". Fig. 3 illustrates with an arrow the process of providing a signal Spx,i 176,176 to one of the software components 166. In particular, the software component 166 configured for processing the detector signal Spx,i 176,176 may include at least one first software 180 (which may also be referred to as "software 1") and at least one second software 182 (which may also be referred to as "software 2"). The first software 180 may be configured to perform at least one first processing step 184 (also referred to as "process 1") on the detector signal Spx,i 176, such as by applying at least one algorithm to the detector signal Spx,i 176. Specifically, the first processing step 184 may include at least one correction for transient effects or time-dependent effects. Thus, as an example, the first processing step 184 may include one or more of correction for dark signals, correction for dark signal drift, correction for wave effects, correction for photo-detector response of individual detector elements or individual time steps, correction for photo-detector response variations caused by the environment (e.g., caused by temperature), extraction of information for subsequent processing, addition or multiplication with parameters, correction for detector responsiveness variations generated from information about at least one electrical characteristic or about device temperature. The first software 180 may be configured to perform at least one further step comprising performing at least one fast fourier transform 186 on the detector signal. Thus, as a result of the application of the first processing step 184 and/or the fast fourier transform 186 to the detector signal Spx,i, a signal Spx 188 (also referred to as "pixel signal Spx 188") may be generated, which may no longer be a function of time. In particular, the time dependence of the frame signal Spx,i 176,176 may be eliminated by one or more of the steps forming part of the first software component 1, while the wavelength dependence may still be present in the turn-on signal Spx 188, as indicated by the index "pn". Fig. 3 further illustrates the process of providing the signal Spx 188,188 to the second software 182 with an arrow. The second software 182 may be configured to perform at least one second processing step 190 (also referred to as "process 2") on the signal Spx 188,188, such as by applying at least one algorithm to the signal Spx 188,188, thereby generating at least one corrected signal Spx,corr 191. In particular, the second processing step 190 may include one or more of correction of dark signals, correction of dark signal drift, correction of wave effects, correction of photo-detector response to individual detector elements or individual time steps, correction of photo-detector response variations caused by the environment (e.g., caused by temperature), extraction of information for subsequent processing, addition or multiplication with parameters generated from information about at least one electrical characteristic or about device temperature. In particular, corrected signal Spx,corr 191 may include a plurality of corrected signals, such as a plurality of corrected electronic signals. Each of the plurality of corrected signals may specifically correspond to a correction count number of the respective pixel.
For example, as described in more detail above, both the light emitting diode 118 and the light emitting material 120 may be based on different materials and/or different material compositions, which typically affect the spectrum 192 of the phosphor LED 122. However, the spectrum 192 or spectral characteristics of a particular phosphor LED 122 may vary with temperature even when operated at a particular predetermined current. These changes may include shifts in emission peaks 193, broadening or narrowing of spectrum 192, increases or decreases in emission, and the like. However, in many cases, the emissions at some wavelengths are affected to a greater extent than the emissions at other wavelengths. This effect is illustrated by the graph shown in fig. 4, which represents the superposition of the infrared radiation spectra 192 of the phosphor LED 122 at various temperatures. Specifically, the plot in FIG. 4 shows the power spectral density in microwatts per nanometer (μW/nm) on the y-axis 196194 Vary with wavelength 198 given in nanometers on the x-axis 200. For the spectrum 192 represented, the temperature range at which the phosphor LED 122 generates the illumination light 116 is from 25 ℃ to 50 ℃. Typically, there is a specific center wavelength within spectrum 192, where the power spectral densityTypically not with temperature. Thus, with respect to the increment/decrement of power, each wavelength typically has its own temperature coefficient. Thus, as is apparent from fig. 4, the shape of the spectrum 192 varies with temperature. To more clearly visualize this effect, a number of four specific wavelength intervals are indicated in fig. 4, each centered on one of the four specific wavelengths within the spectrum 192 range. The wavelength interval is delimited by a dashed line. Specifically, the following four wavelengths and their corresponding intervals are labeled with reference numeral 1643 nm as indicated by reference numeral 202, 1750 nm as indicated by reference numeral 204, 1802 nm as indicated by reference numeral 206, and 1950 nm as indicated by reference numeral 208. For each of these wavelengths, the variation of the transmit power with temperature normalized to the variation of the transmit power at 25 ℃ over the temperature range from 25 ℃ to 50 ℃ is shown in the graph of fig. 5. In the graph of fig. 5, the transmit power variation (given in percent) normalized to the transmit power variation at 25 ℃ is shown on the y-axis 196 and indicated by reference numeral 219, while the temperature in units of ℃ is indicated on the x-axis 200 (indicated by reference numeral 220). The line in the graph in fig. 5 indicates a fitted curve 236. As is apparent from fig. 5, the transmit power at the center wavelength of 1802 nm may have very little variation (i.e., transmit power variation to zero or near zero) over the observed temperature range, while for other wavelengths (e.g., for 1643 nm or 1953 nm) the transmit power variation may have significant variation.
When a particular current (such as a particular predefined value of current) through the light emitting diode 118 is generated by applying a forward voltage to the light emitting diode 118, the appropriate forward voltage may be a function of the temperature of the light emitting diode 118. Thus, when the same current is applied to the light emitting diode 118, the forward voltage of the LED 118 generally decreases with increasing temperature. Each type of LED 118 has its own forward voltage-temperature characteristic. Typically, the forward voltage of the LED 118 decreases linearly with increasing temperature, such as withTo the point ofSlope in the range of V/K. Fig. 6 illustrates this relationship for a particular LED 118. In particular, the graph of fig. 6 shows a forward voltage applied to the LED 118 for generating a direct current through 150 mA of the LED 118 that varies with the temperature of the LED 118. The forward voltage in volts is represented by reference numeral 224 on the y-axis 196. The temperature in degrees Celsius is indicated by reference numeral 220 on the x-axis 200. As is apparent from fig. 6, in this case, the forward voltage linearly decreases with an increase in temperature. The curve in fig. 5 can be described by the following equation:
Wherein, theRepresenting forward voltageIndicating temperature. In the graph of fig. 6, the measurement points 221 represented by gray solid circles and the dashed lines corresponding to the given fitting curve 236 described above are shown. Instead of the relation and/or curve between forward voltage and temperature as described above in an exemplary manner, another relation between an electrically measurable quantity required to drive the light source and temperature may be used, such as feeding in electrical power, current, resistance, inductance, capacitance, etc.
Thus, by taking into account at least one time constant when obtaining the spectroscopic information about the object 112The spectrum 192 of the luminescent material at different wavelengths for the respective temperatures may be generated and/or corrected to the first operating state in such a way that a reference spectrum is generated. In particular, the evaluation unit 136 may be configured for taking into account the spectrum 192 by a plurality of the detector signals Spx,i. The detector signals Spx,i may be combined to obtain the spectroscopic information.
In order to obtain spectroscopic information (in particular a spectrum) about the object 112, the spectrometer device 110 (in particular the evaluation unit 136) may in particular take into account the characteristics of the luminescent material 120 used in the light source 114. As outlined in more detail above, the luminescent material 120 may be configured to absorb primary photons generated by the light emitting diode 118 and, in response, may emit secondary photons instantaneously or after a delay or decay time. The signal or emission of the phosphor LED 122 after turning off the forward current may be described using equations (1) and (2) as described above.
Thus, the characteristics of the luminescent material 120 may be in particular the decay constant228 And growth constantThe decay constant may describe a typical time for afterglow of luminescent material 120 and the increase constant may describe a typical time to reach emission saturation of the converted light. Time constantAndTypically different between different phosphor LEDs 122 and/or between different types of luminescent materials 120. In addition, the damping constantConstant of growthMay depend on the wavelength. The time constant is typically extracted from the step response of the optical signal by applying/switching off a forward current. Fig. 7A and 7B show spectra 192 of two different types of phosphor LEDs 122 that emit light in the near infrared range. Specifically, the power spectral densityShown as a function of wavelength, given in nm. As is apparent from fig. 7A and 7B, the spectra 192 of the two different phosphor LEDs 122 are different. Thus, by way of example, the spectrum 192 shown in fig. 7A reflects a high emission in the range from 1400 nm to 1600 nm, while the emission in this region is negligible for the phosphor LED 122, whose spectrum 192 is shown in fig. 7B. Decay constant of phosphor LED 122 (the spectrum of which is shown in fig. 7A)Constant of growthAre given as a function of wavelength in fig. 8A and 8B, respectively. Decay constant of phosphor LED 122 (the spectrum of which is shown in fig. 7B)Constant of growthAre given as a function of wavelength in fig. 9A and 9B, respectively. In particular, FIGS. 8A and 9A show the corresponding decay constant in ms on the y-axis 196(Indicated by reference numeral 228) with wavelength 198 in nm on x-axis 200, and FIGS. 8B and 9B show the corresponding growth constant in ms on y-axis 196Relationship (indicated by reference numeral 230) to wavelength 198 in nm on the x-axis 200. Data points from different repeated measurements are marked with different shades of gray.
Another characteristic of the LED 118 is that the light output power varies with forward current. Thus, in general, by increasing the forward current (specifically the input current), the power emitted by the LED 118 will increase. The shape (e.g., slope) of the curve of light output as a function of forward current is a characteristic of each LED 118. An example of such a curve is shown in fig. 10. Specifically, in the graph of fig. 10, the normalized light output 232 of the phosphor LED is shown as a function of forward current 234, which is given in amperes.
Another exemplary spectrometer device 110 is shown in fig. 11. The at least one detector 128 that generates the time resolved detector signal may be comprised by a first detector module 244 and the at least one detector 128 that generates the further detector signal may be comprised by a second detector module 246, wherein the first detector module 244 and the second detector module 246 may be different detector modules. The first detector module 244 may detect light 250 from at least one reference target 248.
In fig. 12, an exemplary method 236 of obtaining spectroscopic information about at least one object 112 is illustrated. The method 236 includes the steps of:
(a) Step (a) 238 of illuminating the object 112 with illumination light 116 generated by at least one light source 114, the light source 114 comprising at least one light emitting diode 118 and at least one luminescent material 120 for light converting primary light generated by the light emitting diode 118, and driving the light source 114 in such a way that the driving state of the light source 114 is changed at least once;
(b) Step (b) 240 of detecting light by using at least one detector 128 and thereby generating at least one detector signal upon a change in the driving state of the light source 114, wherein the detector signal is time resolved, and
(C) Step (c) 242 of obtaining spectroscopic information about the object 112 by detecting the detected light from the object 112 using the detector 128 using the at least one evaluation unit 136 and further obtaining the time constant of the light source 114 from the time resolved detector signalThe time constant describes the characteristics of the light source 114 when the driving state is changed, wherein the time constant is to be used when obtaining the spectroscopic information about the object 112Taking into account.
Spectrometer device 110 as described elsewhere herein may be used. The method 236 may be performed in-situ and online. At least step c of method 236 may be computer-implemented.
List of reference numerals
110 Spectrometer apparatus
112 Object
114 Light source
116 Illumination light
118 Light emitting diode
120 Luminescent material
121 Semiconductor material
122 Phosphor light emitting diode
124LED die
126 Shell
128 Detector
130 Detection light
132 Optical detector
134 Array of photosensitive elements
135 Detector module
136 Evaluation unit
138 Drive unit
139 Measuring unit
140 Current source
142 Voltage measuring device
144 Data processing apparatus
146 Pretreatment equipment
148 Data storage device
150 Filter element
151 Optical component
152 Wavelength selective element
154 Substrate
156 Ceramic substrate
158 Contact pad
160 Switch body
162 Side coating
164 Hardware component
166 Software component
Temperature of 168LED
170 Temperature of luminescent material
172 Temperature of detector
174 Target signal St
176 Electronic detector signal Spx,i
178 Readout electronic device
180 Software 1
182 Software 2
184 First processing step
186 Fast fourier transform
188 Pixel signal Spx
190 Second process step
191 Signal Spx,corr
192 Spectrum
193 Peak value
194 Power spectral density PSD in microwatts per nanometer
196Y axis
198 Wavelength, unit: nm
200X axis
2021643 nm
2041750 nm
2061802 nm
2081950 nm
219 Normalized to 25 ℃ transmit power variation (given in percent)
220 Temperature in degrees C
221 Measuring point
224 Forward voltage in volts
226 Signals, expressed in count number
228 Decay constantUnit of ms
230 Growth constantUnit of ms
232 Normalized light output
234 Forward current in amperes
236 Method for obtaining spectroscopic information about at least one object
238 Step (a) of irradiating the object
240 Step (b) of detecting light
242 Step (c) of obtaining spectroscopic information about the object
244 First detector module
246 Second detector module
248 Reference targets
250 Light from a reference target