Illumination unit comprising a plurality of illumination channels

Abstract

An illumination unit (110) is disclosed, comprising a plurality of illumination channels (112), wherein the plurality of illumination channels (112) comprises at least one first channel (114) comprising at least one first light source (116) for generating illumination light (178), wherein the plurality of illumination channels (112) comprises at least one second channel (120) comprising at least one second light source (122) for generating illumination light (178), wherein the illumination unit (110) comprises at least one driving unit (126) configured for electrically driving the first light source (116) and the second light source (122), wherein the driving unit (126) comprises at least one electronic component (128) configured for operating the first light source (116) by using a first enabling signal having a first enabling frequency f1 and the second light source (122) by using a second enabling signal having a second enabling frequency f2, wherein the driving unit (126) comprises at least one power supply (130) configured for supplying a first current to the first channel (114) and for supplying a second current to the second channel (120), wherein the driving unit (126) comprises at least one switching circuitry (132) configured for switching between supply from the power supply (130) to the first channel (114) and supply from the power supply (130) to the second channel (120).

Description

[0001] Illumination unit comprising a plurality of illumination channels

[0002] Technical Field

[0003] The invention relates to an Illumination unit comprising a plurality of illumination channels, a method for driving the illumination unit, a spectrometer device for obtaining spectroscopic information on at least one object and to a method of obtaining spectroscopic information on at least one object by using the spectrometer device. The invention further relates to a computer program and a computer-readable storage medium. Such devices and methods can, in general, be used for investigating or monitoring purposes, in particular, in the infrared (I R) spectral region, especially in the near-infrared (NIR) spectral region, and in the visible (VIS) spectral region, e.g. in a spectral region allowing to mimic a human's ability of color sight. However, further applications are feasible.

[0004] Background art

[0005] Spectrometer devices are known to be efficient tools for obtaining information on the spectral properties of an object, when emitting, irradiating, reflecting and / or absorbing light. Spectrometer devices, thus, may assist in analyzing samples or other tasks in which information on the spectral properties of an object is of interest.

[0006] Usually, in spectrometer devices, spectral information is obtained via one or more detectors and one or more wavelength-selective optical elements, such as one or more dispersive optical elements, filters such as bandpass filters, prisms, gratings, interferometers, or the like. The detectors may comprise any type of light-sensitive element, such as one or more single or multiple pixel detectors, line detectors or array detectors having one- or two-dimensional arrays of pixels. Further, spectrometer devices may comprise one or more light sources. Thus, in spectroscopy, typically, tunable light sources, e.g. lasers, and / or broadband emitting light sources are used, such as halogen-gas filled light bulbs and / or hot filaments. However, additionally or alternatively, other light sources, such as light emitting diodes have also been proposed for the visible spectral region.

[0007] Some spectrometer devices employ two light sources, e.g. at least one first light emitting diode (LED) for interacting with the sample and at least one second LED used for reference measurements. In general, multiple light sources are driven by using the same driving unit in order to save costs and to ensure that the light sources are driven by equal hardware running at the same temperature. Driving multiple light sources with the same driving unit may also reduce de- vice-to-device deviations. The driving unit may regulate a current and / or a voltage applied to each of the light sources individually but usually employs the same power source.

[0008] The shared power source may need to supply different currents depending on the number of light sources driven at a given time. Thus, the shared power source may experience different load. This different load may lead to a voltage drop on the output of the power source which can be seen in the current supplied to the light sources and consequently in the light output of the light sources, too.

[0009] Since multiple light sources are usually keying modulated with different frequencies, the driving currents for the light sources are visibly distorted when another light source is turned on. This effect is also referred to as “driver crosstalk”. The driver crosstalk may amount up to 10% of the current and may differ for different light sources, driving units and / or driving currents. The driver crosstalk may affect voltage- and / or current-based compensation schemes at the light sources and may reduce the overall performance of the spectrometer device. Additionally, high currents may cause the light sources to impact behavior of the driving unit. For example, drive currents may be different if more than one light source is activated at the same time.

[0010] Problem to be solved

[0011] It is therefore desirable to provide methods and devices which at least partially address the above-mentioned technical challenges and at least substantially avoid the disadvantages of known methods and devices. Specifically, it is an object of the present invention to provide an illumination unit comprising a plurality of illumination channels and a method for driving the illumination unit which allow for simultaneous operation of multiple light sources using the same driving unit with reduced or avoided driver crosstalk.

[0012] Summary

[0013] This problem is addressed by an Illumination unit comprising a plurality of illumination channels, a method for driving the illumination unit, a spectrometer device for obtaining spectroscopic information on at least one object, a method of obtaining spectroscopic information on at least one object by using the spectrometer device, a computer program and by a computer-readable storage medium with the features of the independent claims. Advantageous embodiments which might be realized in an isolated fashion or in any arbitrary combinations are listed in the dependent claims as well as throughout the specification.

[0014] In a first aspect, an illumination unit comprising a plurality of illumination channels is disclosed. The plurality of illumination channels comprises at least one first channel comprising at least one first light source for generating illumination light. The plurality of illumination channels comprises at least one second channel comprising at least one second light source for generating illumination light. The illumination unit comprises at least one driving unit configured for electrically driving the first light source and the second light source. The driving unit comprises at least one electronic component configured for operating the first light source by using a first enabling signal having a first enabling frequency and the second light source by using a second enabling signal having a second enabling frequency f2. The driving unit comprises at least one power supply configured for supplying a first current to the first channel and for supplying a second current to the second channel. The driving unit comprises at least one switching circuitry configured for switching between supply from the power supply to the first channel and supply from the power supply to the second channel.

[0015] The term “illumination unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a device or combination of devices configured for controlling operation of light sources. The illumination unit may be a single device or an arbitrary set of interacting or interdependent devices forming a whole, wherein, specifically, the single device or the set of interacting or interdependent devices in interaction with each other may be configured for controlling operation of light sources. The at least two devices may be handled independently and / or may be coupled or connectable in order to provide a single functional unit. The illumination unit may specifically comprise the light sources to be operated. For example, as will be outlined in further detail below, the illumination unit may comprise two or more light emitting diodes (LED). The illumination unit may specifically comprise a plurality of light sources, e.g. a plurality of LEDs. The illumination unit may be configured for individually controlling operation of the light sources. The illumination unit may comprise at least one electrical circuit configured for powering the light sources, specifically the LEDs. The illumination unit may specifically be configured for controlling operation of the plurality of light source using a single driving unit, in particular by providing current to one light source at a time. The illumination unit may comprise at least one switching circuitry for controlling operation of the plurality of light sources, e.g. a physical electronic switch, as will be outlined in further detail below. The illumination unit may further be configured for modulating the light signals from the plurality of light source with different modulation signal, e.g. in order to match light signals to a specific light source.

[0016] The term “illumination channel", also referred to as “channel”, as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a physical or logical path configured for transmitting at least one electronic signal to a light source. The illumination channel may further comprise at least one of the light sources to be operated by the illumination unit, specifically one of the LEDs. Each illumination channel may specifically comprise a single light source, e.g. a single LED. Alternatively, each illumination channel may comprise a plurality of light sources, e.g. two or more first light sources in the first illumination channel and / or two or more second light sources in the second illumination channel. For example, each illumination channel may comprise more than one light source to increase spectral bandwidth and / or optical output power, e.g. two or more light sources, such as two or more low power LEDs having different spectral bandwidths. The illumination channel may be configured for transmitting the at least one electronic signal used for controlling operation of the light source to the light source. The illumination channel may be at least partially separated from the other illumination channels of the illumination unit. Thus, specifically, at least the light source of each illumination channel may be separated from each other. The illumination channel may have one or more elements in common with the other illumination channels. For example, the illumination channels may share one or more common signal transmission means and / or signal processing means, such as a logic circuitry. Alternatively, the illumination channels may be completely separated from each other, e.g. by having signal transmission means and / or signal processing means fixedly associated with each illumination channel.

[0017] The term “plurality of illumination channels" as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a number of two or more illumination channels. As an example, as outlined above, the illumination unit comprises the first channel comprising the first light source and the second illumination channel comprising the second light source. Alternatively, as another example, the illumination unit may comprise more than two channels each comprising at least one light source. For example, the illumination unit may comprise two or more first illumination channels and two or more second illumination channels. The number of first and second channels may be equal or, alternatively, may be different from each other, e.g. by having two first illumination channels and only one second illumination channel. Each channel of the plurality of illumination channels may be operated differently and / or independently from each other. The first channel and the second channel may be phase shifted by 180°, as will be outlined in further detail below.

[0018] The terms “first” and “second” as used herein are used for nomenclature only, without indicating an order or ranking. Thus, it may be possible to have one or more first devices or elements and / or one or more second devices or elements. The first and second device or element may be of the same type and / or may be of different type.

[0019] As further used herein, the term “light” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to electromagnetic radiation in one or more of the infrared, the visible and the ultraviolet spectral range. Herein, the term “ultraviolet spectral range”, generally, refers to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably of 100 nm to 380 nm. Further, in partial accordance with standard ISO-21348 in a valid version at the date of this document, the term “visible spectral range”, generally, refers to a spectral range of 380 nm to 760 nm. The term “infrared spectral range” (IR) generally refers to electromagnetic radiation of 760 nm to 1000 pm, wherein the range of 760 nm to 1 .5 pm is usually denominated as “near infrared spectral range” (NI ) while the range from 1 .5 p to 15 pm is denoted as “mid infrared spectral range” (MidlR) and the range from 15 pm to 1000 pm as “far infrared spectral range” (FIR). Preferably, light used for the typical purposes of the present invention is light in the infrared (IR) spectral range, more preferred, in the near infrared (NIR) and / or the mid infrared spectral range (MidlR), especially the light having a wavelength of 1 pm to 5 pm, preferably of 1 pm to 3 pm. This is due to the fact that many material properties or properties on the chemical constitution of many objects may be derived from the near infrared spectral range. It shall be noted, however, that spectroscopy in other spectral ranges is also feasible and within the scope of the present invention. The term “light source” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device configured for generating or providing light in the sense of the above-mentioned definition. The light source specifically may be or may comprise at least one electrical light source, such as an electrically driven light source. Specifically, the light source may be operated by applying at least one voltage and / or current. The first light source and the second light source may be operated with an identical or different voltages and / or currents.

[0020] In spectroscopy, various sources and paths of light are to be distinguished. In the context of the present invention, a nomenclature is used which, firstly, denotes light propagating from the light source to an object as “illuminating light” or “illumination light”. Secondly, light propagating from the object to the detector is denoted as “detection light”, as will be outlined further detail below. The detection light may comprise at least one of illumination light reflected by an object, illumination light scattered by the object, illumination light transmitted by the object, luminescence light generated by the object, e.g. phosphorescence or fluorescence light generated by the object after optical, electrical or acoustic excitation of the object by the illumination light or the like. Thus, the detection light may directly or indirectly be generated through the illumination of the object by the illumination light. The illumination light may have a spectral range at least partially located in the near-infrared spectral range.

[0021] The first light source and / or the second light source may comprise at least one first light emitting diode and / or the at least one second light emitting diode, respectively. The term “light-emitting diode” or briefly “LED” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an optoelectronic semiconductor device capable of emitting light when an electrical current flows through the device. The optoelectronic semiconductor device may be configured for generating the light due to various physical processes, including one or more of spontaneous emission, induced emission, decay of metastable excited states and the like. Thus, as an example, the light-emitting diode, may comprise one or more of: a light-emitting diode based on spontaneous emission of light, in particular an organic light emitting diode, a light-emitting diode based on superluminescence (sLED), or a laser diode (LD) In the following, without narrowing the possible embodiments of the light-emitting diode to any of the before-mentioned physical principles or setups, the abbreviation “LED” will be used for any type of light-emitting diode. Specifically, the LED may comprise at least two layers of semiconductor material, wherein light may be generated at at least one interface between the at least two layers of semiconductor material, specifically due to a recombination of positive and negative electrical charges, e.g. due to electron-hole recombination. The at least two layers of semiconductor material may have differing electrical properties, such as at least one of the layers being an n-doped semiconductor material and at least one of the layers being a p-doped semiconductor material. Thus, as an example, the LED may comprise at least one pn-junction and / or at least one pin-set up. It shall be noted, however, that other device structures are feasible, too. The at least one semiconductor material may specifically be or may comprise at least one inorganic semiconducting material. It shall be noted, however, that organic semiconducting materials may be used additionally or alternatively.

[0022] Various types of LEDs suitable for generating light are known to the skilled person and may also be applied in the present invention. Specifically, p-n-diodes may be used. As an example, one or more LEDs selected from the group of an LED on the basis of indium gallium nitride (InGaN), an LED on the basis of GaN, an LED on the basis of InGaN / GaN alloys or combinations thereof and / or other LEDs may be used. Additionally or alternatively, quantum well LEDs may also be used, such as one or more quantum well LEDs on the basis of InGaN. Additionally or alternatively, superluminescence LEDs (sLED) and / or Quantum cascade lasers may be used.

[0023] The first light-emitting diode and the second light-emitting diode may have a primary emission range at least partially located in the spectral range of 420 nm to 460 nm, more specifically in the range of 440 nm to 455 nm, more specifically at 440 nm.

[0024] Generally, the LED may convert electrical current into light, specifically into light, more into one of illumination light and / or primary light, specifically into blue primary light, as will be outlined in further detail below. The LED, thus, specifically may be a blue LED. The LED may be configured for generating primary light, also referred to as the “pump light”. Thus, the LED may also be referred to as the “pump LED”. The LED specifically may comprise at least one LED chip and / or at least one LED die. Thus, the semiconductor element of the LED may comprise a LED bare chip.

[0025] The first light source and / or the second light source each may comprise a LED bare chip. Alternatively or additionally, the first light source may further comprise at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode and the second light source may further comprise at least one second luminescent material for lightconversion of primary light generated by the second light-emitting diode.

[0026] Thus, in this example, a distinction may be made between various light sources, such as primary light sources and secondary light sources. “Primary light”, also referred to as “pump light”, may be generated by a primary light source, such as at least one of the first and second lightemitting diode, and may subsequently be transformed into “secondary light”, such as by using light conversion at the first and / or second luminescent material, e.g. through one or more phosphor materials. The illumination light may be or may comprise at least one of the primary light or a part thereof, the secondary light or a part thereof, or a mixture of both.

[0027] The term “luminescence” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of spontaneous emission of light by a substance not resulting from heat. Specifically, luminescence may refer to a cold-body radiation. More specifically, the luminescence may be initiated or ex- cited by irradiation of light, in which case the luminescence is also referred to as “photoluminescence”. The property of a material being capable of performing luminescence, in the context of the present invention, is referred to by the adjective “luminescent”. The at least one luminescent material specifically may be a photoluminescent material, i.e. a material which is capable of emitting light after absorption of photons or excitation light. Specifically, the luminescent material may have a positive Stokes shift, which generally may refer to the fact that the secondary light is red-shifted with respect to the primary light.

[0028] The at least one first and / or second luminescent material, thus, may form at least one converter, also referred to as a light converter, transforming primary light into secondary light having different spectral properties as compared to the primary light. Specifically, a spectral width of the secondary light may be larger than a spectral width of the primary light, and / or a center of emission of the secondary light may be shifted, specifically red-shifted, compared to the primary light. Specifically, the at least one first and / second luminescent material may have an absorption in the ultraviolet and / or blue spectral range and an emission in the near-infrared and / or infrared spectral range. Thus, generally, the first and / or second luminescent material or converter may form at least one component of the phosphor LED converging primary light or pump light, specifically in the blue spectral range, into light having a longer wavelength, e.g. in the near-infrared or infrared spectral range.

[0029] Various types of conversion and / or luminescence are known and may be used in the context of the present invention. Thus, specifically, the conversion can occur via a dipole-allowed transition in the luminescent material, also referred to as fluorescence, and / or via a dipole-forbidden, thus long-lived, transition in the first and / or second luminescent material, often also referred to as phosphorescence. Light conversion and / or luminescence may lead to secondary light reacting on a different time scale compared to the primary light. Thus, a modulation above a certain threshold frequency of the primary light may not be followed by the secondary light. For example, a pulse width modulation of the primary light may lead to changes in the average light output of the secondary light without instantaneous changes visible in the primary light.

[0030] The first and / or second luminescent material, specifically, may, thus, form at least one converter or light converter. The first and / or second luminescent material may form at least one of a converter platelet, a luminescent and specifically a fluorescent coating on the LED and phosphor coating on the LED. The first and / or second luminescent material may, as an example, comprise one or more of the following materials: Cerium-doped YAG (YAG:Ce3+, or Y3AI50i2:Ce3+); rare-earth-doped Sialons; copper- and aluminum-doped zinc sulfide (ZnS:Cu,AI).

[0031] The first light source and the second light source may comprise at least one phosphor lightemitting diode. The first and / or second LED and the first and / or second luminescent material, respectively, may form together a so-called “phosphor LED”. Consequently, the term “phosphor light-emitting diode” or briefly “phosphor LED”, as used herein, is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a combination of at least one light-emitting diode configured for generating primary light or pump light, and at least one luminescent material, also referred to as a “phosphor”, configured for light-conversion of the primary light generated by the light-emitting diode. The phosphor LED may form a packaged LED light source, including the LED die, e.g. a blue LED emitting blue pump light, as well as the phosphor, which, as an example, fully or partially coats the LED, which is, as an example, configured for converting the primary light or blue light into light having differing spectral properties, specifically into near-infrared light. Generally, the phosphor LED may be packaged in one housing or may be unpackaged. Thus, the first and / or second LED and the first and / or second at least one luminescent material for light-conversion of the primary light generated by the light-emitting diode may specifically be housed in a common housing, respectively. Alternatively, however, the first and / or second LED may also be an unhoused or bare LED which may fully or partially be covered with the first and / or second luminescent material, respectively, such as by disposing one or more layers of the first and / or second luminescent material on the LED die. The phosphor LED, generally, may form an emitter or light source by itself.

[0032] The at least one first and / or second luminescent material specifically may form at least one layer. Generally, various alternatives of positioning the first and / or second luminescent material with respect to the first and / or second light-emitting diode are feasible, alone or in combination. Firstly, the first and / or second luminescent material, e.g., at least one layer of the first and / or second luminescent material, such as the phosphor, may be positioned directly on the first and / or second light-emitting diode, respectively, which is also referred to as a “direct attach”, e.g. with no material in between the first and / or second LED and the first and / or second luminescent material or with one or more transparent materials in between, such as with one or more transparent materials, specifically transparent for the primary light, in between the first and / or second LED and the first and / or second luminescent material, respectively. Thus, as an example, a coating of the first and / or second luminescent material may be placed directly or indirectly on the first and / or second LED, respectively. Additionally or alternatively, the first and / or second luminescent material, as an example, may form at least one converter body, such as at least one converter disk, which may be placed on top of the first and / or second LED, respectively, e.g. by adhesive attachment of the converter body to the first and / or second LED. Additionally or alternatively, the first and / or second luminescent material may also be placed in a remote fashion, such that the primary light from the first and / or second LED has to pass an intermediate optical path before reaching the first and / or second luminescent material. This placement may also be referred to as a “remote placement” or as a “remote phosphor”. Again, as an example, the first and / or second luminescent material in the remote placement may form a solid body or converter body, such as a disk or converter disk.

[0033] Further, in case of the remote placement, the first and / or second luminescent material may also be a coating. In particular, an object which is transmitting light, e.g. a thin glass substrate, module window, comprising and / or being made of glass or plastics, may be coated with the phosphor. Alternatively, a reflective surface may be coated with the phosphor. This could be a flat or rough mirror, which may comprise and / or be made of a high-reflective index material substrate, e.g. silicon, or a gold, silver, aluminum or chromium coated flat or rough surface, e.g. glass, or a plastic. In the intermediate optical path, one or more optical elements may be placed, such as one or more of a lens, a prism, a grating, a mirror, an aperture or a combination thereof. Thus, in the intermediate optical path, an optical system having imaging properties may specifically be placed in between the first and / or second LED and the first and / or second luminescent material, respectively. Thereby, as an example, the primary light may be focused, or bundled onto the converter body.

[0034] As outlined above, the illumination unit comprises the at least one driving unit configured for electrically driving the first light source and the second light source. The term “driving” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of providing one or both of at least one control parameter and / or electrical power to another device. Consequently, the term “driving unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device or a combination of devices configured for providing one or both of at least one control parameter and / or electrical power to another device, such as, in the present case, to at least one of the first light source and the second light source. For example, the driving unit specifically may be configured for controlling one or more electrical parameters of an electrical power provided to at least one of the first light source and the second light source, specifically to at least one of the first light-emitting diode and the second light-emitting diode. As an example, the driving unit may be configured for providing an electrical current to at least one of the first and second LED, specifically for controlling an electrical current through at least one of the first and second LED. Therein, as an example, the driving unit may be configured for adapting a voltage provided to at least one of the first and second LED, the voltage being required for achieving a specific electrical current through the first or second LED. The driving unit, as an example, may comprise one or more electrical components, such as integrated circuits, for driving the first light source and the second light source. The driving unit may fully or partially be integrated into the first light source and / or the second light source or may be separated from the first light source and / or the second light source.

[0035] As outlined above, the driving unit comprises the at least one electronic component configured for operating the first light source by using the first enabling signal having the first enabling frequency frand the second light source by using the second enabling signal having the second enabling frequency f2. The driving unit comprises the at least one power supply configured for supplying the first current to the first channel and for supplying the second current to the second channel. The driving unit comprises the at least one switching circuitry configured for switching between supply from the power supply to the first channel and supply from the power supply to the second channel. The term “operating” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of controlling one or more process parameter of another device. Consequently, the term “electronic component” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device or a combination of devices configured for controlling one or more process parameter of another device, such as, in the present case, of at least one of the first light source and the second light source. The electronic component may specifically be configured for modulating at least one process parameter provided to at least one of the first light source and the second light source. The electronic component may be configured for at least one of an analog modulation and a digital modulation. For example, the electronic component may be configured for analog modulation of at least one of a voltage and a current provided to at least one of the first light source and the second light source, such as by applying one or more of an amplitude modulation, a frequency modulation, a phase modulation and a pulse-width modulation. As an example, the electronic component may comprise at least one switch, such as at least one electronic switch, e.g. at least one of a diode, a transistor, specifically a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor (BJT), a thyristor. For example, the electronic component may comprise at least one transistor, such as a MOSFET or a BJT.

[0036] The term “enabling signal” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary signal causing operation of a device. Specifically, the enabling signal may cause operation of the light source. Thus, specifically, the first enabling signal may cause operation of the first light source and the second enabling signal may cause operation of the second light source. The first and / or second enabling signal may comprise at least one modulation signal. The first and / or second enabling signal may specifically provide the modulation signal when using keying modulation, e.g. ON-OFF keying. For example, the first and / or second enabling signal may comprise a pulse-width modulation signal modulating at least one of the voltage and the current provided to at least one the first light source and the second light source. The enabling signal may decide if there is an electric connection between the power supply over the illumination channel to the light source. The current may be supplied to the light source only if a product of the switching frequency and the enabling frequency is a logical 1 . The first and / or second enabling signal may comprise a periodic signal having at least one frequency. The frequency of the periodic enabling signal may also be referred to as “enabling frequency”. The first and / or second enabling frequency may be in the range of 1 Hz to 10 kHz, specifically in the range of 8 Hz to 800 Hz, more specifically in the range of 15 Hz to 100 Hz. The first light source and the second light source may be enabled with different enabling frequencies. The term “supplying” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of providing electrical power to another device. Consequently, the term “power supply” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrical device configured for providing electrical power to another device. The power supply may specifically be configured for providing electrical power to at least one of the first light source and the second light second, more specifically to both of the first light source and the second light source. The power supply may be configured for converting electric current from a source to a desired voltage, current and / or frequency to power the other device, in this case at least one of the first light source and the second light source. Alternatively or additionally, the power supply may comprise a voltage or current source providing the desired voltage or current to at least one of the first light source and the second light source.

[0037] The term “current” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a flow of charge carriers, such as electrons or ions, moving through an electrical conductor or circuit. In this example, the first current and / or the second current may comprise the flow of charge carriers, such as electrons or ions, moving through the first channel and / or the second channel, respectively.

[0038] The term “switching” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of disconnecting, connecting, interrupting and / or diverting a conducting path in an electrical circuit. Consequently, the term “switching circuitry” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrical device or combination of electrical devices configured for disconnecting, connecting, interrupting and / or diverting a conducting path in an electrical circuit. Specifically, in this case, the switching circuit may be configured for disconnecting, connecting, interrupting and / or diverting the current in between the plurality of illumination channels. The switching circuit may specifically be configured for selectively connecting one of the illumination channels to the power supply. For example, in case the illumination unit comprises two illumination channels, the switching circuit may be configured for connecting either the first channel or the second illumination channel to the power supply. The switching between illumination channels by using the switching circuitry may specifically avoid simultaneous connection of multiple light sources in multiple illumination channels to the power supply and, thus, may avoid optical crosstalk. Additionally, the switching circuit may be configured for disconnecting all of the illumination channels from the power supply. A phase of having none of the illumination channels connected to the power supply may be referred to as “downtime”, as will be outlined in further detail below. Downtime may also be achieved by turning the current flow off through the enabling signal followed by switching to other illumination channels. The switching circuitry may be actively electronically controllable. For example, the switching circuitry may comprise at least one electronic switch. Additionally or alternatively, the switching circuit may comprise at least one logic circuit, specifically a digital logic circuit, configured for processing one or more signals, such as modulation signals, e.g. at least one of the switching signal, the first enabling signal and the second enabling signal, in order to derive one or more control signal for controlling electrical devices. The logic circuit may, as an example, be implemented in at least one microcontroller.

[0039] The switching of the multiple light source may result in a pulsing of the light source. Pulse-width modulation may be used during pulsing of the respective light source.

[0040] The term “supply” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the electrical power provided by the power supply. The supply may specifically comprise current provided by the power supply to the first channel or the second channel.

[0041] The supply from the power supply may be time multiplexed between the channels according to a predefined switching signal, specifically a predefined switching signal having a predefined switching frequency fswitCh- The switching frequency may be at least one magnitude, specifically at least two magnitudes, more specifically at least three magnitudes, higher than the first enabling frequency and the second enabling frequency.

[0042] The term “time multiplexed” or “time multiplexing” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a plurality of signals sharing the same information channel by dividing the information channel into a plurality of time slots. The illumination unit may comprise the first light source and the second light source, wherein the at least one driving unit may be configured for sequentially switching an operation state of the first light source and the second light source. Time multiplexing may comprise using time for separating the illumination light emitted by the first light source and the second light source. Particularly, each illumination light generated by the first light source and the second light source may be transmitted during its own time slot, which specifically can allow differentiating between the illumination light generated by the first light source and the second light source. For example, the driving unit may be configured for generating at least one item of switch-on information indicating at which point in time in which one of the first light source and the second light source is turned on. An evaluation unit may be configured for taking into consideration the item of switch-on information, e.g. when deriving the spectroscopic information from the detector signal, as will be outlined in further detail below.

[0043] The enabling signals, specifically the first enabling signal and the second enabling signal, may be superpositioned with the switching signal, thereby generating a first superpositioned signal for operating the first light source and a second superpositioned signal for operating the second light source. As an example and as outlined above, the first light source may further comprise the at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode and / or the second light source may further comprise the at least one second luminescent material for light-conversion of primary light generated by the second lightemitting diode. In this example, an optical output of the first light source may be an envelope of the first superpositioned signal and an optical output of the second light source may be an envelope of the second superpositioned signal. Thus, even though the switching circuitry may avoid simultaneous connection of multiple illumination channels to the power supply, the optical output of multiple light source, e.g. the optical output of the first light source and the optical output of the second optical light source, may overlap. Specifically, the envelope of the optical output of the respective light source may be generated due to a limited bandwidth of the luminescent material. In other words, the luminescent material may provide an averaging effect to the primary light generated by the respective LED. Thus, the illumination light of the respective light source may be the envelope of the respective superimposed signal. Alternatively or additionally, in case the illumination unit is used in a spectrometer device or the like, the averaging effect may also be provided by a detector, e.g. due to a limited lifetime of light generated charge carriers in a photomaterial of the detector, and / or due to the detector's read-out electronics. Thus, in these cases, the light sources of the illumination unit may be embodied without luminescent coating.

[0044] Additionally or alternatively, a duty cycle of the switching frequency for each channel may be selected as < 100% / number of channels. Optionally, downtimes between switching in between the illumination channels may be considered. The supplied current Isupgenerated by the power supply may be selected as Isup> ILS* - - - . The light source current ILSmay represent an average light source current, e.g. a light source current corresponding to an average light output of a light source without switching.

[0045] As an example, the driving unit may comprise a single voltage or current source. The driving unit may comprise a switch configured for switching between the first channel and the second channel based on a predefined switching signal, specifically a predefined switching signal with a predefined switching frequency. The driving unit may comprise the electronic component configured for operating the first light source by using the first enabling signal and the second light source by using the second enabling signal. The switching signal may specifically comprise a downtime between switching between the first channel and the second channel. Thus, in the example of two light sources, the downtime in the switching signal may result in a duty cycle of the driving unit below 50%. Additionally or alternatively, the driving unit may comprise at least two electronic components. A first electronic component may be configured for operating the first light source by using the first enabling signal having the first enabling frequency . A second electronic component may be configured for operating the second light source by using the second enabling signal having the second enabling frequency f2. The first electronic component and the second electronic component each may comprise a switch, e.g. an electronic switch. For example, the driving unit may comprise the switch configured for switching the supply between the illumination channels. Additionally, the electronic component may comprise at least one switch for each illumination channel, specifically one switch being arranged in the respective illumination channel. The switches in the illumination channel may be configured for frequency modulation of the respective light source. In this example, the switching and enabling signals may be directly provided to the electronic components, specifically without the need for additional digital circuitry.

[0046] Alternatively or additionally, the driving unit may comprise a single voltage or current source. The voltage or current source may be driven by using a combined switching and enabling signal. The combined switching and enabling signal may comprise a digital signal being derived from the first enabling signal, the second enabling signal and a predefined switching signal at a switch for time multiplexing the supply from the power supply between the channels.

[0047] For example, the driving unit may comprise a switch configured for switching the supply between the illumination channels. Further, the electronic may comprise a single enable switch driving the light sources. A logic circuit may provide the combined switching and enabling signal, such as a digital signal for enabling from the switching signal, the first enabling signal and the second enabling signal. The illumination unit may specifically require only two signals at minimum, e.g. in case two light sources are used, and may still be scalable to a plurality of light sources of three of more light sources.

[0048] Alternatively or additionally, the driving unit may comprise at least two power supplies. A first power supply may be assigned to the first channel and a second power supply may be assigned to the second channel. The driving unit may be configured for individually turn the channels on and off. The signals for operating the first channel and the second channel may be: first channel: F(f = fswitch,<p = 0) ■ G(f = second channel: F(f = fswitch,(p = 180°) ■ G(f = f2), wherein F denotes a periodic signal, optionally including downtimes between switching, and G denotes a modulation signal.

[0049] The periodic signal may comprise at least one square wave signal. Additionally or alternatively, the periodic signal may comprise a representation of at least one of a sine wave signal, a triangular signal and a sawtooth signal. The modulation signal may comprise at least one of a sine wave signal, a square wave signal, a triangular signal and a sawtooth signal. Additionally or alternatively, the modulation signal may comprise a representation of at least one of a sine wave signal, a triangular signal and a sawtooth signal.

[0050] For example, the illumination unit may comprise a dual channel driver. At least two signals may be used for the first enabling signal of the first light source and the second enabling signal of the second light source. The signals may be derived from the switching signal, the first enabling signal and the second enabling signal via a digital logic circuit. Alternatively or additionally, the driving unit may comprise at least one DC current source. The driving unit may comprise a totem pole circuit. The first light source and the second light source may have different polarizations.

[0051] The term “totem pole circuit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an electrical circuit configured for alternately providing and absorbing current from a connected load. The totem pole circuit may specifically comprise an electrical circuit in the form of a bridge circuit, e.g. in the form of an H-bridge, having at least two totem pole outputs. The outputs may be connected to the first light and the second light source, respectively. The totem pole circuit may comprise an arrangement of transistors. The totem pole circuit may be for changing a direction of current flow, e.g. a current flow via the first channel or the second channel. The totem pole circuit may be configured for providing current to one of the first and second light sources with different current flow direction, i.e. with different current polarity. Thus, as an example, by using light sources with different polarity, e.g. LEDs with diode behavior, the totem pole circuit may be configured for preventing simultaneous operation of the light sources.

[0052] For example, the illumination unit may comprise the driving unit comprising an analog totem pole circuit having the first light source and the second light source arranged with different polarities. The analog totem pole circuit may comprise four transistors having logic signal inputs, e.g. denoted as QA,SA, QBand SBderived from the switching signal, the first enabling signal and the second enabling signal via a digital logic circuit.

[0053] In a further aspect of the present invention, a method for driving an illumination unit according to the present invention, such as according to any one of the embodiment disclosed above and / or according to any of the embodiments disclosed in further detail below, is disclosed. Thus, for definitions of terms and possible embodiments, reference is made to the description of the illumination unit above.

[0054] The method comprises the following steps that may be performed in the given order. However, a different order may also be possible. In particular, one, more than one or even all of the method steps may be performed once or repeatedly. Further, the method steps may be performed successively or, alternatively, one or more of the method steps may be performed in a timely overlapping fashion or even in a parallel fashion and / or in a combined fashion. The method may further comprise additional method steps that are not listed.

[0055] The method comprises: i. supplying, by using at least one power supply of the driving unit, a first current to the first channel and a second current to the second channel, wherein at least one switching circuitry switches between supply from the power supply to the first channel and supply from the power supply to the second channel; and ii. operating the first light source by using a first enabling signal having a first enabling frequency / i and the second light source by using a second enabling signal having second enabling frequency f2by using at least one electronic component of the driving unit

[0056] In a further aspect of the present invention, a spectrometer device for obtaining spectroscopic information on at least one object is disclosed. The spectrometer device comprises: at least one illumination unit according to the present invention, such as according to any one of the embodiment disclosed above and / or according to any of the embodiments disclosed in further detail below; at least one detector for detecting detection light from the object and for generating at least one detector signal for each of the first light source and the second light source thereby; and at least one evaluation unit for evaluating the detector signals generated by the detector and for deriving the spectroscopic information on the object from the detector signals.

[0057] The term “spectrometer device” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an optical device configured for acquiring at least one item of spectral information on at least one object. Specifically, the at least one item of spectral information may refer to at least one optical property or optically measurable property which is determined as a function of a wavelength, for one or more different wavelengths. More specifically, the optical property or optically measurable property, as well as the at least one item of spectral information, may relate to at least one property characterizing at least one of a transmission, an absorption, a reflection and an emission of the at least one object, either by itself or after illumination with external light. The at least one optical property may be determined for one or more wavelengths. The spectrometer device specifically may form an apparatus which is capable of recording a signal intensity with respect to the corresponding wavelength of a spectrum or a partition thereof, such as a wavelength interval, wherein the signal intensity may, specifically, be provided as an electrical signal which may be used for further evaluation.

[0058] The spectrometer device, as an example, may be or may comprise a device which allows for a measurement of at least one spectrum, e.g. for the measurement of a spectral flux, specifically as a function of a wavelength or detection wavelength. The spectrum may be acquired, as an example, in absolute units or in relative units, e.g. in relation to at least one reference measurement. Thus, as an example, the acquisition of the at least one spectrum specifically may be performed either for a measurement of the spectral flux (unit W / nm) or for a measurement of a spectrum relative to at least one reference material (unit 1), which may describe the property of a material, e.g., reflectance over wavelength. Additionally or alternatively, the reference measurement may be based on a reference light source, an optical reference path, a calculated reference signal, e.g. a calculated reference signal from literature, and / or on a reference device. Specifically, the at least one spectrometer device may be a diffusive reflective spectrometer device configured for acquiring spectral information from the light which is diffusively reflected by the at least one object, e.g. the at least one sample. Additionally or alternatively, the at least one spectrometer device may be or may comprise an absorption- and / or transmission spectrometer. In particular, measuring a spectrum with the spectrometer device may comprise measuring absorption in a transmission configuration. Specifically, the spectrometer device may be configured for measuring absorption in a transmission configuration. As outlined above, however, other types of spectrometer devices are also feasible.

[0059] The at least one spectrometer device, specifically, may comprise at least one light source which, as an example, may be at least one of a tunable light source, a light source having at least one fixed emission wavelength and a broadband light source. The spectrometer device, as will be outlined above, further comprises the at least one detector configured for detecting light, such as light which is at least one of transmitted, reflected or emitted from the at least one object. The spectrometer device further may comprise, as will be outlined in further detail below, at least one wavelength-selective element, such as at least one of a grating, a prism and a filter, e.g. a length variable filter having varying transmission properties over its lateral extension. The wavelength-selective element may be used for separating incident light into a spectrum of constituent wavelength signals whose respective intensities are determined by employing a detector such as a detector having a detector array as described below in more detail.

[0060] The spectrometer device, specifically, may be a portable spectrometer device. The term “portable” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the property of at least one object of being moved by human force, such as by a single user. Specifically, the object characterized by the term “portable” may have a weight not exceeding 10 kg, specifically not exceeding 5 kg, more specifically not exceeding 1 kg or even not exceeding 500 g. Additionally or alternatively, the dimensions of the object characterized by the term “portable” may be such that the object extends by no more than 0.3 m into any dimension, specifically by no more than 0.2 m into any dimension. The object, specifically, may have a volume of no more than 0.03 m3, specifically of no more than 0.01 m3, more specifically no more than 0.001 m3or even no more than 500 mm3. In particular, as an example, the portable spectrometer device may have dimensions of e.g.

[0061] 10 mm by 10 mm by 5 mm. Specifically, the portable spectrometer device may be part of a mobile device or may be attachable to a mobile device, such as a notebook computer, a tablet, a cell phone, such as a smart phone, a smartwatch and / or a wearable computer, also referred to as “wearable”, e.g. a body borne computer such as a wrist band or a watch. In particular, the a weight of the spectrometer device, specifically the portable spectrometer device, may be in the range from 1 g to 100 g, more specifically in the range from 1 g to 10 g.

[0062] The term “spectroscopic information”, also referred to as “spectral information” or as “item of spectral information”, as used herein is a broad term and is to be given its ordinary and custom- ary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an item of information, e.g. on at least one object and / or radiation emitted by at least one object, characterizing at least one optical property of the object, more specifically at least one item of information characterizing, e.g. qualifying and / or quantifying, at least one of a transmission, an absorption, a reflection and an emission of the at least one object. As an example, the at least one item of spectral information may comprise at least one intensity information, e.g. information on an intensity of light being at least one of transmitted, absorbed, reflected or emitted by the object, e.g. as a function of a wavelength or wavelength sub-range over one or more wavelengths, e.g. over a range of wavelengths. Specifically, the intensity information may correspond to or be derived from the signal intensity, specifically the electrical signal, recorded by the spectrometer device with respect to a wavelength or a range of wavelengths of the spectrum.

[0063] The spectrometer device specifically may be configured for acquiring at least one spectrum or at least a part of a spectrum of detection light propagating from the object to the spectrometer. The spectrum may describe the radiometric unit of spectral flux, e.g. given in units of watt per nanometer (W I nm), or other units, e.g. as a function of the wavelength of the detection light. Thus, the spectrum may describe the optical power of light, e.g. in the NIR spectral range, in a specific wavelength band. The spectrum may contain one or more optical variables as a function of the wavelength, e.g. the power spectral density, electric signals derived by optical measurements and the like. The spectrum may indicate, as an example, the power spectral density and / or the spectral flux of the object, e.g. of a sample, e.g. relative to a reference sample, such as a transmittance and / or a reflectance of the object, specifically of the sample

[0064] The spectrum, as an example, may comprise at least one measurable optical variable or property of the detection light and / or of the object, specifically as a function of the illumination light and / or the detection light. As an example, the at least one measurable optical variable or property may comprise at least one at least one radiometric quantity, such as at least one of a spectral density, a power spectral density, a spectral flux, a radiant flux, a radiant intensity, a spectral radiant intensity, an irradiance, a spectral irradiance. Specifically, as an example, the spectrometer device, specifically the detector, may measure the irradiance in Watt per square meter (W I m2), more specifically the spectral irradiance in Watt per square meter per nanometer (W / m2 / nm). Based on the measured quantity the spectral flux in Watt per nanometer (W / nm) and / or the radiant flux in Watt (W) may be determined, e.g. calculated, by taking into account an area of the detector.

[0065] The term “object” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary body, chosen from a living object and a non-living object. Thus, as an example, the at least one object may comprise one or more articles and / or one or more parts of an article, wherein the at least one article or the at least one part thereof may comprise at least one component which may provide a spectrum suitable for investigations. Additionally or alternatively, the object may be or may comprise one or more living beings and / or one or more parts thereof, such as one or more body parts of a human being, e.g. a user, and / or an animal. The object specifically may comprise at least one sample which may fully or partially be analyzed by spectroscopic methods. As an example, the object may be or may comprise at least one of: human or animal skin; edibles, such as fruits; plastics and textile.

[0066] The term “detecting” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of at least one of determining, measuring and monitoring at least one parameter, qualitatively and / or quantitatively, such as at least one of a physical parameter, a chemical parameter and a biological parameter. Specifically, the physical parameter may be or may comprise an electrical parameter. Consequently, the term “detector” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device configured for detecting, i.e. for at least one of determining, measuring and monitoring, at least one parameter, qualitatively and / or quantitatively, such as at least one of a physical parameter, a chemical parameter and a biological parameter. The detector may be configured for generating at least one detector signal, more specifically at least one electrical detector signal, such as an analogue and / or a digital detector signal, the detector signal providing information on the at least one parameter measured by the detector. The detector signal may directly or indirectly be provided by the detector to the evaluation unit, such that the detector and the evaluation unit may be directly or indirectly connected. The detector signal may be used as a “raw” detector signal and / or may be processed or preprocessed before further used, e.g. by filtering and the like. Thus, the detector may comprise at least one processing device and / or at least one preprocessing device, such as at least one of an amplifier, an analogue / digital converter, an electrical filter and a Fourier transformation.

[0067] In the present case, the detector is configured for detecting light propagating from the object to the spectrometer device or more specifically to the detector of the spectrometer device, which, according to the above-mentioned nomenclature, is referred to as “detection light”. Thus, specifically, 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 an intensity and / or a power of light by which at least one sensitive area of the detector is irradiated. 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 photosensitive resistor, a phototransistor, a thermophile sensor, a photoacoustic sensor, a pyroelectric sensor, a photomultiplier and a bolometer. The detector, thus, may be configured for generating at least one detector signal, more specifically at least one electrical detector signal, in the above-mentioned sense, providing information on at least one optical parameter, such as the power and / or intensity of light by which the detector or a sensitive area of the detector is illuminated. The detector may comprise one single optically sensitive element or area or a plurality of optically sensitive elements or areas. Specifically, the detector may be or may comprise at least one detector array, more specifically an array of photosensitive elements. Each of the photosensitive elements may comprise at least a photosensitive area which may be adapted for generating an electrical signal depending on the intensity of the incident light, wherein the electrical signal may, in particular, be provided to the evaluation unit.

[0068] The photosensitive area as comprised by each of the optically sensitive elements may, especially, be a single, uniform photosensitive area which is configured for receiving the incident light which impinges on the individual optically sensitive elements. However, other arrangements of the optically sensitive elements may also be conceivable.

[0069] The array of optically sensitive elements may be designed to generate detector signals, preferably electronic signals, associated with the intensity of the incident light which impinges on the individual optically sensitive elements. The detector signal may be an analogue and / or a digital signal. The electronic signals for adjacent pixelated sensors can, accordingly, be generated simultaneously or else in a temporally successive manner. By way of example, during a row scan or line scan, it is possible to generate a sequence of electronic signals which correspond to the series of the individual optically sensitive elements which are arranged in a line. In addition, the individual optically sensitive elements may, preferably, be active pixel sensors which may be adapted to amplify the electronic signals prior to providing it to the evaluation unit. For this purpose, the detector may comprise one or more signal processing devices, such as one or more filters and / or analogue-digital-converters for processing and / or preprocessing the electronic signals.

[0070] In case the detector comprises an array of optically sensitive elements, the detector, as an example, may be selected from any known pixel sensor, in particular, from a pixelated organic camera element, preferably, a pixelated organic camera chip, or from a pixelated inorganic camera element, preferably, a pixelated inorganic camera chip, more preferably from a CCD chip or a CMOS chip, which are, commonly, used in various cameras nowadays. As an alternative, the detector generally may be or comprise a photoconductor, in particular an inorganic photoconductor, especially PbS, PbSe, Ge, InGaAs, ext. InGaAs, InSb, or HgCdTe. As a further alternative, the detector may comprise at least one of pyroelectric, bolometer or thermophile detector elements. Thus, a camera chip having a matrix of 1 x N pixels or of M x N pixels may be used here, wherein, as an example, M may be < 10 and N may be in the range from 1 to 50, preferably from 2 to 20, more preferred from 5 to 10. Further, a monochrome camera element, preferably a monochrome camera chip, may be used, wherein the monochrome camera element may be differently selected for each optically sensitive element, especially, in accordance with the varying wavelength along the series of the optical sensors.

[0071] Thus, the array may be adapted to provide a plurality of the electrical signals which may be generated by the photosensitive areas of the optically sensitive elements comprised by the array. The electrical signals as provided by the array of the spectrometer device may be forwarded to the evaluation unit.

[0072] The term “evaluating” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the process of processing at least one first item of information in order to generate at least one second item of information thereby. Consequently, the term “evaluation unit”, as used herein, is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary device or a combination of devices configured to evaluate or process at least one first item of information, in order to generate at least one second item of information thereof. Thus, specifically, the evaluation unit may be configured for processing at least one input signal and to generate at least one output signal thereof. The at least one input signal, as an example, may comprise at least one detector signal provided directly or indirectly by the at least one detector and, optionally, at least one signal directly or indirectly provided by the driving unit.

[0073] As an example, the evaluation unit may be or may comprise one or more integrated circuits, such as one or more application-specific integrated circuits (ASICs), and / or one or more data processing devices, such as one or more of computers, digital signal processors (DSP), field programmable gate arrays (FPGA) preferably one or more microcomputers and / or microcontrollers. Additional components may be comprised, such as one or more preprocessing devices and / or data acquisition devices, such as one or more devices for receiving and / or preprocessing of the detector signals, such as one or more AD-converters and / or one or more filters. Further, the evaluation unit may comprise one or more data storage devices. Further, the evaluation unit may comprise one or more interfaces, such as one or more wireless interfaces and / or one or more wire-bound interfaces.

[0074] The at least one evaluation unit may be adapted to execute at least one computer program, such as at least one computer program performing or supporting the step of generating the items of information. As an example, one or more algorithms may be implemented which, by using the at least one detector signal as an input variable, may perform a predetermined transformation for deriving the spectroscopic information on the object, such as for deriving a spectrum and / or for deriving at least one spectroscopic information describing at least one property of the object. For this purpose, the evaluation unit may, particularly, comprise at least one data processing device, also referred to as a processor, in particular an electronic data processing device, which can be designed to generate the desired information by evaluating the detector signal. The evaluation unit may use an arbitrary process for generating the required information, such as by calculation and / or using at least one stored and / or known relationship. The evaluation unit specifically may be configured for performing at least one digital signal processing (DSP) technique on the primary detector signal or any secondary detector signal derived thereof, in particular at least one Fourier transformation. Additionally or alternatively, the evalua- tion unit may be configured for performing one or more further digital signal processing techniques on the primary detector signal or any secondary detector signal derived thereof, e.g. windowing, filtering, Goertzel algorithm, crosscorrelation and autocorrelation. Besides the detector signal, one or a plurality of further parameters and / or items of information can influence said relationship. The relationship can be determined or determinable empirically, analytically or else semi-empirically. As an example, the relationship may comprise at least one of a model or calibration curve, at least one set of calibration curves, at least one function or a combination of the possibilities mentioned. One or a plurality of calibration curves can be stored for example in the form of a set of values and the associated function values thereof, for example in a data storage device and / or a table. Alternatively or additionally, however, the at least one calibration curve can also be stored for example in parameterized form and / or as a functional equation. Separate relationships for processing the detector signals into the spectroscopic information may be used. Alternatively, at least one combined relationship for processing the detector signals is feasible. Various possibilities are conceivable and can also be combined.

[0075] The spectrometer device may specifically comprise two or more illumination units according to any one of the embodiment disclosed above and / or according to any of the embodiments disclosed in further detail below. For definitions of terms and possible embodiments, reference is made to the description of the illumination unit above.

[0076] The evaluation unit may be configured for generating at least one first output comprising an envelope of a first superpositioned signal from the first enabling signal being superpositioned with a switching signal. The evaluation unit may further be configured for generating at least one second output comprising an envelope of a second superpositioned signal from the second enabling signal being superpositioned with the switching signal. In the spectrometer device, for example, the first light source may comprise at least one first light-emitting diode and the second light source may comprise at least one second light-emitting diode. The first light source may further comprise at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode and the second light source may further comprise at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode. The first luminescent material and the second luminescent material may provide an averaging effect over time to the primary light generated by the first LED and the second LED, respectively. Alternatively or additionally to the configuration of the light source with the luminescent materials, the detector, specifically at least one of the photosensitive element and / or the readout electronics, may provide an averaging effect over time. In these examples, the evaluation unit may be further configured for deriving the spectroscopic information on the object using the first output and the second output. For example, the spectrometer may be configured for generating detector signals at the enabling signal frequencies fi and f2. Thus, the signals may facilitate averaging over time with respect to at least one of the illumination unit, specifically the first and second light sources with the first and second luminescent materials, respectively, the detector, specifically the photosensitive element and / or the readout electronics. In a further aspect of the present invention, a method of obtaining spectroscopic information on at least one object is disclosed. The method comprises using at least one spectrometer device according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below.

[0077] The method comprises the following steps that may be performed in the given order. However, a different order may also be possible. In particular, one, more than one or even all of the method steps may be performed once or repeatedly. Further, the method steps may be performed successively or, alternatively, one or more of the method steps may be performed in a timely overlapping fashion or even in a parallel fashion and / or in a combined fashion. The method may further comprise additional method steps that are not listed.

[0078] The method comprises: a. driving the illumination unit according to a method for driving an illumination unit according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below; b. illuminating the object with illumination light generated by at least one of the first light source and the second light source; c. detecting, by the detector, detection light from the object and generating at least one detector signal for each of the first light source and the second light source thereby; and d. evaluating the detector signals generated by the detector by using the evaluation unit and deriving the spectroscopic information on the object from the detector signals, by using the evaluation unit.

[0079] As outlined above, the detector may comprise an array of photosensitive elements. Each of the photosensitive elements may be configured for generating at least one detector signal. The method may comprise combining the detector signals for deriving the spectroscopic information, specifically combining the detector signals from the array of photosensitive elements for deriving the spectroscopic information.

[0080] In step b., the illumination light generated by the first light source and the second light source may be used to illuminate the object. Alternatively or additionally, the illumination light from one of the light sources may be used as a reference, e.g. by illuminating an internal reflection target of the spectrometer device. Thus, in this case, the detection light detected by the detector may be received from the internal reflection target.

[0081] In a further aspect of the present invention, a computer program for obtaining spectroscopic information on at least one object is disclosed, comprising instructions which, when the program is executed by a spectrometer device according to the present invention, such as according to any one of the embodiment disclosed above and / or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method of obtaining spectroscopic information on at least one object according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below.

[0082] In a further aspect of the present invention, a computer-readable storage medium, specifically a non-transient computer-readable storage medium, is disclosed, comprising instructions which, when the instructions are executed by a spectrometer device according to the present invention, such as according to any one of the embodiment disclosed above and / or according to any one of the embodiments disclosed in further detail below, cause the spectrometer device to perform the method of obtaining spectroscopic information on at least one object according to the present invention, such as according to any one of the embodiments disclosed above and / or according to any one of the embodiments disclosed in further detail below.

[0083] As used herein, the term “computer-readable storage medium” specifically may refer to non- transitory data storage means, such as a hardware storage medium having stored thereon computer-executable instructions. The computer-readable storage medium specifically may be or may comprise a storage medium such as a random-access memory (RAM) and / or a read-only memory (ROM). The computer-readable storage medium specifically may be or may comprise a computer-readable data carrier.

[0084] Referring to the computer-implemented aspects of the invention, one or more of the method steps or even all of the method steps of the method according to one or more of the embodiments disclosed herein may be performed by using a computer or computer network. Thus, generally, any of the method steps including provision and / or manipulation of data may be performed by using a computer or computer network. Generally, these method steps may include any of the method steps, typically except for method steps requiring manual work, such as providing the samples and / or certain aspects of performing the actual measurements.

[0085] In a further aspect of the present invention, a method for driving an illumination unit comprising a plurality of illumination channels is disclosed. The plurality of illumination channels comprises at least one first channel comprising at least one first light source for generating illumination light, wherein, as an example, the first light source may comprise at least one first light-emitting diode and, optionally, at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode. The plurality of illumination channels comprises at least one second channel comprising at least one second light source for generating illumination light, wherein, as an example, the second light source may comprise at least one second light-emitting diode and, optionally, at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode. The illumination unit comprises at least one driving unit configured for electrically driving the first light source and the second light source. The method comprises the following steps: i. supplying, by using at least one power supply of the driving unit, a first current to the first channel and a second current to the second channel, wherein at least one switching circuitry switches between supply from the power supply to the first channel and supply from the power supply to the second channel, wherein the supply is time multiplexed between the channels according to switching signal having a predefined switching frequency fswitch; and ii. operating the first light source by using a first enabling signal having a first enabling frequency and the second light source by using a second enabling signal having second enabling frequency f2by using at least one electronic component of the driving unit.

[0086] The methods and devices according to the present invention, in one or more of the above-mentioned embodiments and / or in one or more of the embodiments described in further detail below, may provide a large number of advantages over known methods and devices of similar kind. For example, the methods and devices according to the present invention may allow using multiple light sources with a single driving unit, specifically reducing and / or avoiding LED driver crosstalk. Thus, the methods and devices according to the present invention may improve performance of spectrometer devices by preventing driver crosstalk on light sources. Additionally, the illumination unit may allow using different light sources with different driving voltages. The illumination unit can specifically be implemented using and / or repurposing available circuitry which may simplify construction and implementation of these illumination units. Further, the methods and devices according to the present invention may avoid driver crosstalk and may simultaneously reduce hardware effort, e.g. by using a single driving unit instead of a dual channel driving unit, and, thus, save costs. The illumination unit may be potentially usable for any spectrometer device using more than one light source.

[0087] The illumination unit may specifically ensure that the two light sources can be driven simultaneously without simultaneous supply from the power source and, thus may eliminate the driver crosstalk effectively. Further, the illumination unit may employ a trigger pattern which prevents that both light sources are supplied with current from the power source at the same time.

[0088] As an example, the illumination unit may comprise two light sources. The switching signal having the switching frequency fswitchmay be a square waveform with 50% duty cycle. With two light sources, other duty cycles may be possible. With more light sources having two states, off- time with delay may be implemented between switching in order to avoid switching under load. Further, the first enabling signal and the second enabling signal may also be square waveforms with their respective frequencies. Alternatively or additionally, analog waveforms may be supported, too, specifically modulating the duty cycle and / or the current from the power source.

[0089] The illumination unit may specifically provide the possibility of operating a plurality of illumination channels with at least one light source with a single driving unit having one power source, such as a current or voltage source. The electronic component, specifically comprising a logic unit, may provide a logic function to modulate the illumination channels with signal of arbitrary phase and frequency. The switching circuitry may provide a switching function for simultaneous operation of the light source and still avoid driver crosstalk. The logic function may be realized via a circuit in hard- or software, e.g. via a logic circuit. Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0090] Embodiment 1 : An illumination unit comprising a plurality of illumination channels, wherein the plurality of illumination channels comprises at least one first channel comprising at least one first light source for generating illumination light, wherein the plurality of illumination channels comprises at least one second channel comprising at least one second light source for generating illumination light, wherein the illumination unit comprises at least one driving unit configured for electrically driving the first light source and the second light source, wherein the driving unit comprises at least one electronic component configured for operating the first light source by using a first enabling signal having a first enabling frequency and the second light source by using a second enabling signal having a second enabling frequency f2, wherein the driving unit comprises at least one power supply configured for supplying a first current to the first channel and for supplying a second current to the second channel, wherein the driving unit comprises at least one switching circuitry configured for switching between supply from the power supply to the first channel and supply from the power supply to the second channel.

[0091] Embodiment 2: The illumination unit according to the preceding embodiment, wherein the supply from the power supply is time multiplexed between the channels according to a predefined switching signal, specifically a predefined switching signal having a predefined switching frequency fswitch.

[0092] Embodiment 3: The illumination unit according to the preceding embodiment, wherein the enabling signals are superpositioned with the switching signal, thereby generating a first superpositioned signal for operating the first light source and a second superpositioned signal for operating the second light source.

[0093] Embodiment 4: The illumination unit according to the preceding embodiment, wherein the first light source comprises at least one first light-emitting diode, wherein the second light source comprises at least one second light-emitting diode.

[0094] Embodiment 5: The illumination unit according to the preceding embodiment, wherein the first light source further comprises at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode, wherein the second light source further comprises at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode, wherein an optical output of the first light source is an envelope of the first superpositioned signal and an optical output of the second light source is an envelope of the second superpositioned signal. Embodiment 6: The illumination unit according to any one of the four preceding embodiments, wherein the switching frequency is at least one magnitude, specifically at least two magnitudes, more specifically at least three magnitudes, higher than the first enabling frequency and the second enabling frequency.

[0095] Embodiment 7: The illumination unit according to any one of the preceding embodiments, wherein pulse-width modulation is used during pulsing of the respective light source.

[0096] Embodiment 8: The illumination unit according to any one of the preceding embodiments, wherein the first light source and the second light source are enabled with different enabling frequencies.

[0097] Embodiment 9: The illumination unit according to any one of the preceding embodiments, wherein the first channel and the second channel are phase shifted by 180°.

[0098] Embodiment 10: The illumination unit according to any one of the preceding embodiments, wherein the illumination unit comprises more than two channels each comprising at least one light source.

[0099] Embodiment 11 : The illumination unit according to any one of the eight preceding embodiments, wherein a duty cycle of the switching frequency for each channel is selected as < 100% / number of channels, wherein the supplied current Isupgenerated by the power supply is selected

[0100] Embodiment 12: The illumination unit according to any one of the preceding embodiments, wherein the first light source and the second light source are operated with an identical or different forward voltages.

[0101] Embodiment 13: The illumination unit according to any one of the preceding embodiments, wherein the electronic component comprises at least one transistor.

[0102] Embodiment 14: The illumination unit according to any one of the preceding embodiments, wherein the first light source comprises at least one first light-emitting diode, wherein the second light source comprises at least one second light-emitting diode, wherein the first light source further comprises at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode, wherein the second light source further comprises at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode.

[0103] Embodiment 15: The illumination unit according to the preceding embodiment, wherein the first light source and the second light source comprise at least one phosphor light-emitting diode. Embodiment 16: The illumination unit according to any one of the two preceding embodiments, wherein the first light-emitting diode and the second light-emitting diode have a primary emission range at least partially located in the spectral range of 420 nm to 460 nm, more specifically in the range of 440 nm to 455 nm, more specifically at 440 nm.

[0104] Embodiment 17: The illumination unit according to any one of the preceding embodiments, wherein the illumination light has a spectral range at least partially located in the near-infrared spectral range.

[0105] Embodiment 18: The illumination unit according to any one of the preceding embodiments, wherein the driving unit comprises a single voltage or current source, wherein the driving unit comprises a switch configured for switching between the first channel and the second channel based on a predefined switching signal, specifically a predefined switching signal with a predefined switching frequency, wherein the driving unit comprises the electronic component configured for operating the first light source by using the first enabling signal and the second light source by using the second enabling signal.

[0106] Embodiment 19: The illumination unit according to the preceding embodiment, wherein the switching signal comprises a downtime between switching between the first channel and the second channel.

[0107] Embodiment 20: The illumination circuit according to any one of the two preceding embodiments, wherein the driving unit comprises at least two electronic components, wherein a first electronic component is configured for operating the first light source by using the first enabling signal having the first enabling frequency , wherein a second electronic component is configured for operating the second light source by using the second enabling signal having the second enabling frequency ^.

[0108] Embodiment 21 : The illumination circuit according to the preceding embodiment, wherein the first electronic component and the second electronic component each comprise a switch.

[0109] Embodiment 22: The illumination unit according to any one of embodiments 1 to 17, wherein the driving unit comprises a single voltage or current source, wherein the voltage or current source is driven by using a combined switching and enabling signal.

[0110] Embodiment 23: The illumination unit according to the preceding embodiment, wherein the combined switching and enabling signal comprises a digital signal being derived from the first enabling signal, the second enabling signal and a predefined switching signal at a switch for time multiplexing the supply from the power supply between the channels.

[0111] Embodiment 24: The illumination unit according to any one of embodiments 1 to 17, wherein the driving unit comprises at least two power supplies, wherein a first power supply is assigned to the first channel and a second power supply is assigned to the second channel, wherein the driving unit is configured for individually turn the channels on and off, wherein the signals for operating the first channel and the second channel are: first channel: F(f = fswitch, p = 0) ■ = / second channel: F(f = fswitch,(p = 180°) ■ G(f = f2~), wherein F denotes a periodic signal, optionally including downtimes between switching, and G denotes a modulation signal.

[0112] Embodiment 25: The illumination unit according to the preceding embodiment, wherein the periodic signal comprises at least one of a sine wave signal, a square wave signal, a triangular signal and a sawtooth signal.

[0113] Embodiment 26: The illumination unit according to any one of the two preceding embodiments, wherein the modulation signal comprises at least one of a sine wave signal, a square wave signal, a triangular signal and a sawtooth signal.

[0114] Embodiment 27: The illumination unit according to any one of embodiments 1 to 17, wherein the driving unit comprises at least one DC current source, wherein the driving unit comprises a totem pole circuit, wherein the first light source and the second light source have different polarizations.

[0115] Embodiment 28: A method for driving an illumination unit according to any one of the preceding embodiments referring to an illumination unit, wherein the method comprises i. supplying, by using at least one power supply of the driving unit, a first current to the first channel and a second current to the second channel, wherein at least one switching circuitry switches between supply from the power supply to the first channel and supply from the power supply to the second channel; and ii. operating the first light source by using a first enabling signal having a first enabling frequency fi and the second light source by using a second enabling signal having second enabling frequency f2by using at least one electronic component of the driving unit.

[0116] Embodiment 29: A spectrometer device for obtaining spectroscopic information on at least one object, the spectrometer device comprising: at least one illumination unit according to any one of the preceding embodiments referring to an illumination unit; at least one detector for detecting detection light from the object and for generating at least one detector signal for each of the first light source and the second light source thereby; and at least one evaluation unit for evaluating the detector signals generated by the detector and for deriving the spectroscopic information on the object from the detector signals. Embodiment 30: The spectrometer device according to the preceding embodiment, wherein the spectrometer device comprises two or more illumination units according to any one of the preceding embodiments referring to an illumination unit.

[0117] Embodiment 31 : The spectrometer device according to any one of the two preceding embodiments, wherein the evaluation unit is configured for generating at least one first output comprising an envelope of a first superpositioned signal from the first enabling signal being superpositioned with a switching signal, wherein the evaluation unit is further configured for generating at least one second output comprising an envelope of a second superpositioned signal from the second enabling signal being superpositioned with the switching signal, wherein the first light source comprises at least one first light-emitting diode, wherein the second light source comprises at least one second light-emitting diode, wherein the first light source further comprises at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode, wherein the second light source further comprises at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode, wherein the first luminescent material and the second luminescent material provide an averaging effect over time to the primary light generated by the first LED and the second LED, respectively, and / or wherein the detector, specifically at least one of the photosensitive element and / or the readout electronics, provide an averaging effect over time, wherein the evaluation unit is further configured for deriving the spectroscopic information on the object using the first output and the second output.

[0118] Embodiment 32: A method of obtaining spectroscopic information on at least one object by using at least one spectrometer device according to the preceding embodiment, the method comprising: a. driving the illumination unit according to a method for driving an illumination unit according to embodiment 28; b. illuminating the object with illumination light generated by at least one of the first light source and the second light source; c. detecting, by the detector, detection light from the object and generating at least one detector signal for each of the first light source and the second light source thereby; and d. evaluating the detector signals generated by the detector by using the evaluation unit and deriving the spectroscopic information on the object from the detector signals, by using the evaluation unit.

[0119] Embodiment 33: The method according to the preceding embodiment, wherein the detector comprises an array of photosensitive elements, wherein each of the photosensitive elements is configured for generating at least one detector signal, wherein the method comprises combining the detector signals for deriving the spectroscopic information. Embodiment 34: A computer program for obtaining spectroscopic information on at least one object comprising instructions which, when the program is executed by a spectrometer device according to embodiment 29 to 31 , cause the spectrometer device to perform the method of obtaining spectroscopic information on at least one object according to any one of the preceding embodiments referring to a method of obtaining spectroscopic information on at least one object.

[0120] Embodiment 35: A computer-readable storage medium, specifically a non-transient computer- readable storage medium, comprising instructions which, when the instructions are executed by a spectrometer device according to embodiment 29 to 31 , cause the spectrometer device to perform the method of obtaining spectroscopic information on at least one object according to any one of the preceding embodiments referring to a method of obtaining spectroscopic information on at least one object.

[0121] Short description of the Figures

[0122] Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

[0123] In the Figures:

[0124] Figures 1A to 1C show a first embodiment of an illumination unit;

[0125] Figures 2A and 2B show a second embodiment of an illumination unit;

[0126] Figures 3A and 3B show a third embodiment of an illumination unit;

[0127] Figures 4A to 4C show a fourth embodiment of an illumination unit;

[0128] Figure 5 shows a flow chart of an embodiment of a method for driving an illumination unit;

[0129] Figure 6 shows an embodiment of a spectrometer device in a schematic view; and

[0130] Figure 7 shows a flow chart of an embodiment of a method of obtaining spectroscopic information. Detailed description of the embodiments

[0131] Figure 1A to 1C show a first embodiment of an illumination unit 110 comprising a plurality of illumination channels 112. Specifically, Figure 1 A shows a circuit diagram of the illumination unit 110, Figure 1 B shows a schematic overview on the illumination unit 110 and Figure 1 C shows an exemplary optical output of the illumination unit 110.

[0132] As can be seen best in Figures 1 A and 1 B, the plurality of illumination channels 112 comprises at least one first channel 114 comprising at least one first light source 116 for generating illumination light. In the exemplary first embodiment of Figures 1A to 1C, the first light source 116 may comprise at least one first light-emitting diode 118. The plurality of illumination channels 112 comprises at least one second channel 120 comprising at least one second light source 122 for generating illumination light. In the exemplary first embodiment of Figures 1A to 1C, the second light source 122 may comprise at least one second light-emitting diode 124. However, in principle, other light sources are also feasible, e.g. electrically driven light sources, such as incandescent light sources, electric discharge lambs or laser or the like. Fuhrter, in this example, the first light source 116 may comprise at least one first luminescent material (not shown in the Figures) for light-conversion of primary light generated by the first light-emitting diode 118 and the second light source 122 may further comprise at least one second luminescent material (not shown in the Figures) for light-conversion of primary light generated by the second light-emitting diode 124. However, other examples of light sources, such as LED bare chips, are also feasible.

[0133] Further, the illumination unit 110 comprises at least one driving unit 126 configured for electrically driving the first light source 116 and the second light source 122. The driving unit 126 comprises at least one electronic component 128 configured for operating the first light source 116 by using a first enabling signal having a first enabling frequency and the second light source 122 by using a second enabling signal having a second enabling frequency f2. The driving unit 126 comprises at least one power supply 130 configured for supplying a first current to the first channel 114 and for supplying a second current to the second channel 120. The driving unit 126 comprises at least one switching circuitry 132 configured for switching between supply from the power supply 130 to the first channel 114 and supply from the power supply 130 to the second channel 120.

[0134] In this exemplary embodiment, the driving unit 126 may comprise a single voltage or current source 134. The driving unit 126 may comprise a switch 136 configured for switching between the first channel 114 and the second channel 120 based on a switching signal with a predefined switching frequency. For example, as shown in Figure 1A, the switching circuitry 132 may be or may comprise the switch 136. The switching signal may be provided to the switch 136, as denoted by reference number 138. The switching signal may specifically comprise a downtime between switching between the first channel 114 and the second channel 120. Thus, in the example of two light sources 116, 122, the downtime in the switching signal may result in a duty cycle of the driving unit 126 below 50%. Further, the driving unit 126 may comprise the electronic component 128 configured for operating the first light source 116 by using the first enabling signal and the second light source 122 by using the second enabling signal. As shown in Figures 1 A and 1 B, the driving unit 126, in this example, may comprise at least two electronic components 128. A first electronic component 140 may be configured for operating the first light source 116 by using the first enabling signal having the first enabling frequency . A second electronic component 142 may be configured for operating the second light source 122 by using the second enabling signal having the second enabling frequency f2. The first electronic component 140 and the second electronic component 142 each may comprise a switch 144, e.g. an electronic switch. The first enabling signal and the second enabling signal may be provided to the first electronic component 140 and the second electronic component 142, respectively, as denoted by reference numbers 146 and 148 in Figures 1 A and 1 B.

[0135] As can be seen in the schematic overview of Figure 1 B, the power supply 130 may provide a constant voltage, e.g. a constant voltage over time as shown in diagram 1 , to the switching circuitry 132. The supply from the power supply 130 may be time multiplexed between the channels 112 according to a predefined switching signal (denoted by reference number 138), specifically a predefined switching signal having a predefined switching frequency fswitCh- The switching frequency may be at least one magnitude, specifically at least two magnitudes, more specifically at least three magnitudes, higher than the first enabling frequency and the second enabling frequency. The first channel 114 and the second channel 120 may be phase shifted by 180°, as can be seen in the upper and lower diagram 2. At the electronic component 128, specifically at the first electronic component 140 and the second electronic component 142, e.g. embodied by transistors, the enabling signals, specifically the first enabling signal (denoted by reference number 146) and the second enabling signal (denoted by reference number 148), may be superpositioned with the switching signal, thereby generating a first superpositioned signal for operating the first light source 116 and a second superpositioned signal for operating the second light source 122. The superpositioned signals are represented by the dashed lines in the upper and lower diagram 3. The optical output of the first light source 116 (shown in the upper diagram 4) may be an envelope of the first superpositioned signal and an optical output of the second light source 122 (shown in the lower diagram 4) may be an envelope of the second superpositioned signal. Specifically, since the LED semiconductor chips may be fast components with high bandwidth in MHz range compared to the luminescent coating. The LED semiconductor chips may be turned on and off with the switching frequency fswitCh- The slower luminescent coating, or alternatively a slower detector, may be illuminated with the superpositioned frequency and may experience the envelope of the superpositioned signal as shown in the upper and lower diagram 4. The frequencies of the first and second enabling signals may be chosen freely. Independent of the envelope signals, the first and second LED 118, 124 may not draw current from the power supply 130 at the same time. In order to maintain radiant power compared with a continuous operation, the current supplied to the first and second LED 118, 124 may be doubled compared with the continuous operation. Figure 1C shows a time course of the optical output 150 of the first LED 118 and the second LED 124 (top diagram) and the course of the current 152 (bottom diagram) as a function of time 154. In the top diagram, the optical output 150 of the first LED 118 is denoted by reference number 149 and the optical output 150 of the second LED 124 is denoted by reference number 151 . In the bottom diagram, the current 152 of the first LED 118 is denoted by reference number 153 and the current 152 of the second LED 124 is denoted by reference number 155. As can be seen in Figure 1C, the illumination circuit 110 may prevent providing the supply to both LEDs 118, 124 at the same time and may still allow for simultaneous optical output of the LEDs 118, 124. Additionally, since the LEDs 118, 124 may not be driven at the same time, the LEDs 118, 124 may be provided with different forward voltages, e.g. for different wavelength ranges. Additionally, even if the LEDs 118, 124 are of the same wavelength, the illumination unit 110 may avoid having to use expensive binning of LEDs 118,124.

[0136] Both LEDs 118, 124 may optionally be modulated with different modulation frequencies for frequency-division multiplexing. Using pulse-width modulation during a LED-ON pulse may reduce the duty cycle while maintaining a comparable average output power. As outlined above, both LEDs 118, 124 may comprise a luminescent material, e.g. phosphor. The luminescent material may have a much slower maximum modulation frequency than the bare LED itself. The light radiated from the luminescent material may thus still behave like in the normal ON-OFF keying case. Advantageously, the pulsed operation with reduced duty cycle may avoid to drive current through both LEDs 118, 124 at the same time. Specifically, as the driving unit 126 may be fast compared to the optical output of the light sources 116, 122 and the bare LED chips may be fast compared to the luminescent coating, pulse width modulation may be used to adjust optical power of the first and second light sources 116, 122. The duty cycle and frequency can be controlled much better than current which may specifically suffer from quantization error and / or noise at lower power. The pulse width modulation signal of both light sources 116, 122 may be designed so that the PWM pulses never overlap thus avoiding LED driver crosstalk.

[0137] Thus, in the first exemplary embodiment shown in Figures 1 A to 1C, a single channel light source driver may be used, e.g. the voltage or current source 134, wherein the switch 136 may switch between the first LED 118 and the second LED 124 based on the predefined switching signal with the switching frequency fswitcflexceeding the first and second enabling frequencies by at least one magnitude. Driving of the first LED 118 and the second LED 124 may be further enabled by the switches 144 for each LED 118, 124 with their respective frequency signal. The duty cycle may be below 50% to prevent switching under load

[0138] Figures 2A and 2B show a second exemplary embodiment of the illumination unit 110. The illumination unit 110 according to this second embodiment widely correspond to the first exemplary embodiment shown in Figures 1A to 1C. Thus, for a detailed description of the second exemplary embodiment of the illumination unit 110 and it's functionality, reference is made to the description of Figures 1A to 1C. As can be seen in Figure 2A, the driving unit 126 may comprise the single voltage or current source 134. The voltage or current source 134 may be driven by using a combined switching and enabling signal (denoted by reference number 156). The combined switching and enabling signal may comprise a digital signal being derived from the first enabling signal, the second enabling signal and the predefined switching signal at the switch 136 for time multiplexing the supply from the power supply 130 between the channels 112. Specifically, an example of a logic circuit for obtaining the combined switching and enabling signal is shown in Figure 2B. This logic circuit, as an example, may be realized by using a microcontroller.

[0139] Thus, in this example, the illumination unit 110 may comprise only a single enable switch used to directly turn the driver ON and OFF instead of having an enable switch for each channel 112. The switching and enabling signals may comprise square wave signals. Thus, the combined switching and enabling signal may comprise the addition of the multiplication of the square wave function of frequency fswitcfltimes the square wave function of frequency plus the multiplication of the square wave function of frequency fswitCh being phase shifted by 180° times the square wave function of frequency f2

[0140] SQR(J fswitch* P 0) ■ SQRCf = fi) + SQR(f fswitch* P = 180°) ■ SQR(f = / 2)

[0141] Figures 3A and 3B show a third exemplary embodiment of the illumination unit 110. The illumination unit 110 according to this third embodiment widely correspond to the first exemplary embodiment shown in Figures 1A to 1C. Thus, for a detailed description of the third exemplary embodiment of the illumination unit 110 and it's functionality, reference is made to the description of Figures 1 A to 1C.

[0142] As shown in Figure 3A, as an example, the driving unit 126 may comprise at least two power supplies 130. A first power supply 158 may be assigned to the first channel 114 and a second power supply 160 may be assigned to the second channel 120. The driving unit 126 may be configured for individually turn the channels 112 on and off. For example, a dual channel driver may be used which allows to individually turn the channels on and off. The signals for operating the first channel 114 and the second channel 120 may be: first channel (denoted by reference number 162): F(f = fSWitCh><P = 0) ■ G(f = f^) second channel 120 (denoted by reference number 164): F(f = fswitch, P = 180°) ■ G f = f2~), wherein F denotes a periodic signal, optionally including downtimes between switching, and G denotes a modulation signal. The digital signals 162, 164 may be obtained via a logic circuit, specifically an exemplary logic circuit as shown in Figure 3B. This logic circuit, as an example, may be realized by using a microcontroller.

[0143] Figures 4A to 4C show a fourth exemplary embodiment of the illumination unit 110. The illumination unit 110 according to this fourth embodiment widely correspond to the first exemplary embodiment shown in Figures 1A to 1C. Thus, for a detailed description of the fourth exemplary embodiment of the illumination unit 110 and it's functionality, reference is made to the description of Figures 1A to 1C. In this exemplary embodiment, the driving unit 126 may comprise at least one DC current source 166. The driving unit 126 may comprise a totem pole circuit 168. The first light source 116 and the second light source 122 may have different polarizations. For example, as shown in Figure 4A, the illumination unit 110 may comprise the driving unit 126 comprising the analog totem pole circuit 168 having the first light source 116, e.g. the first LED 118, and the second light source 122, e.g. the second LED 124, arranged with different polarities. The analog totem pole circuit 168 may comprise four transistors having logic signal inputs, e.g. denoted as

[0144] QA,SA, QB and SBderived from the switching signal, the first enabling signal and the second enabling signal via a digital logic circuit, e.g. via the digital logic circuit shown in Figure 4B. This exemplary embodiment may assume ON / OFF keying modulation. The switching and enabling signals may specifically be similar to the signals shown in Figures 2A and 2B.

[0145] In the fourth embodiment, the DC current source 168 may be switched via the totem pole circuit 168. The totem pole circuit 168 may be known and available, e.g. from power electronics and / or from power factor corrections (PFCs). The transistor pairs may be used to switch the polarity from the DC current source 168 to the LEDs 118, 124 thereby switching between the LEDs 118, 124. Specifically, using the LEDs 118, 124 in opposite polarity may ensure that only one LED is on at a time. By also applying the enabling signals to the switches via a logic gate, the luminescent material may be modulated according to their frequency. In this exemplary embodiment, there may be three different states:

[0146] 1 .) LED1 118 ON and LED2 124 OFF (denoted as A in Figure 4C) a. Qa ON; Sa OFF; Qb OFF; Sb ON

[0147] 2.) LED1 118 OFF and LED2 124 ON -> (denoted as B in Figure 4C) a. Qa OFF; Sa ON; Qb ON; Sb OFF

[0148] 3.) LED1 118 OFF and LED2 124 OFF -> (denoted as 0 in Figure 4C) a. Qa OFF; Sa OFF; Qb OFF; Sb OFF

[0149] Specifically, either only one of the first and second LED 118, 124 may be ON or both LEDs 118, 124 may be OFF. Signal A may turn Qa ON and Sa OFF. Signal B may turn Qb ON and Sb OFF. The switching circuitry 132 may be realized by alternating between signals A and B, effectively alternating between the first LED 118 and the second LED 124. The single enable switch to turn the source ON and OFF may be realized by turning all gates OFF, when the enable is not positive, realizing the state where both LEDs 118, 124 are OFF. Figure 4C shows the optical output 150 of the first LED 118 and the second LED 124 as a function of time 154 together with the corresponding states of the circuit.

[0150] Figure 5 shows a flow chart of an exemplary embodiment method for driving the illumination unit 110. The illumination unit 110 may be embodied according to any one of the exemplary embodiments shown in Figures 1 A to 4C and / or according to any other embodiment disclosed herein.

[0151] The method comprises the following steps that may be performed in the given order. However, a different order may also be possible. In particular, one, more than one or even all of the method steps may be performed once or repeatedly. Further, the method steps may be performed successively or, alternatively, one or more of the method steps may be performed in a timely overlapping fashion or even in a parallel fashion and / or in a combined fashion. The method may further comprise additional method steps that are not listed.

[0152] The method comprises: i. (denoted by reference number 170) supplying, by using the at least one power supply 130 of the driving unit 126, a first current to the first channel 114 and a second current to the second channel 120, wherein the at least one switching circuitry 132 switches between supply from the power supply 130 to the first channel 114 and supply from the power supply 130 to the second channel 120; and ii. (denoted by reference number 172) operating the first light source 116 by using a first enabling signal having a first enabling frequency i and the second light source 122 by using a second enabling signal having second enabling frequency f2by using the at least one electronic component 128 of the driving unit 126.

[0153] Figure 6 shows an exemplary embodiment of a spectrometer device 174 for obtaining spectroscopic information on at least one object 176 in a schematic view. The spectrometer device 174 comprises at least one illumination unit 110 according to the present invention, such as according to any one of the exemplary embodiments disclosed in Figures 1A to 4C and / or according to any other embodiment disclosed herein. As shown in Figure 6, the illumination unit 110 may be arranged to illuminate the object 176 with illumination light 178. The spectrometer device 174 further comprises at least one detector 180 for detecting detection light 182 from the object 176 and for generating at least one detector signal for each of the first light source 116 and the second light source 122 thereby. The spectrometer device 174 further comprises at least one evaluation unit 184 for evaluating the detector signals generated by the detector 180 and for deriving the spectroscopic information on the object 176 from the detector signals.

[0154] Figure 7 shows a flow chart of an exemplary embodiment of a method of obtaining spectroscopic information. The method comprises using at least one spectrometer device 174 according to the present invention, such as according to the exemplary embodiment shown in Figure 6 and / or according to any other embodiment disclosed herein.

[0155] The method comprises the following steps that may be performed in the given order. However, a different order may also be possible. In particular, one, more than one or even all of the method steps may be performed once or repeatedly. Further, the method steps may be performed successively or, alternatively, one or more of the method steps may be performed in a timely overlapping fashion or even in a parallel fashion and / or in a combined fashion. The method may further comprise additional method steps that are not listed.

[0156] The method comprises: a. (denoted by reference number 170, 172) driving the illumination unit 110 according to a method for driving an illumination unit 110 according to the present invention, such as according to the exemplary embodiment shown in Figure 5 and / or according to any other embodiment disclosed herein; b. (denoted by reference number 186) illuminating the object 176 with illumination light 178 generated by at least one of the first light source 116 and the second light source 122; c. (denoted by reference number 188) detecting, by the detector 180, detection light 182 from the object 176 and generating at least one detector signal for each of the first light source 116 and the second light source 122 thereby; and d. (denoted by reference number 190) evaluating the detector signals generated by the detector 180 by using the evaluation unit 184 and deriving the spectroscopic information on the object 176 from the detector signals, by using the evaluation unit 184.

[0157] In step b., the illumination light 178 generated by the first light source 116 and the second light source 122 may be used to illuminate the object 176. Alternatively or additionally, the illumination light from one of the light sources 116, 122 may be used as a reference, e.g. by illuminating an internal reflection target (not shown in the Figures) of the spectrometer device 174. Thus, in this case, the detection light 182 detected by the detector 180 may be received from the internal reflection target.

[0158] List of reference numbers illumination unit illumination channel first channel first light source first light-emitting diode second channel second light source second light-emitting diode driving unit electronic component power supply switching circuitry voltage or current source switch switching signal first electronic component second electronic component switch first enabling signal second enabling signal optical output of the first LED optical output optical output of the second LED current current of the first LED time current of the second LED combined switching and enabling signal first power supply second power supply first digital signal second digital signal

[0159] DC current source totem pole circuit supplying current operating the first and second light source spectrometer device object illumination light detector detection light evaluation unit illuminating the object with illumination light detecting detection light evaluating the detector signals

Claims

Claims1. An illumination unit (110) comprising a plurality of illumination channels (112), wherein the plurality of illumination channels (112) comprises at least one first channel (114) comprising at least one first light source (116) for generating illumination light (178), wherein the plurality of illumination channels (112) comprises at least one second channel (120) comprising at least one second light source (122) for generating illumination light (178), wherein the illumination unit (110) comprises at least one driving unit (126) configured for electrically driving the first light source (116) and the second light source (122), wherein the driving unit (126) comprises at least one electronic component (128) configured for operating the first light source (116) by using a first enabling signal having a first enabling frequency fi and the second light source (122) by using a second enabling signal having a second enabling frequency f2, wherein the driving unit (126) comprises at least one power supply (130) configured for supplying a first current to the first channel (114) and for supplying a second current to the second channel (120), wherein the driving unit (126) comprises at least one switching circuitry (132) configured for switching between supply from the power supply (130) to the first channel (114) and supply from the power supply (130) to the second channel (120).

2. The illumination unit (110) according to the preceding claim, wherein the supply from the power supply (130) is time multiplexed between the channels (112, 114, 120) according to a predefined switching signal.

3. The illumination unit (110) according to the preceding claim, wherein the enabling signals are superpositioned with the switching signal, thereby generating a first superpositioned signal for operating the first light source (116) and a second superpositioned signal for operating the second light source (122).

4. The illumination unit (110) according to the preceding claim, wherein the first light source (116) comprises at least one first light-emitting diode (118), wherein the second light source (122) comprises at least one second light-emitting diode (124), wherein the first light source (116) further comprises at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode (118), wherein the second light source (122) further comprises at least one second luminescent material for lightconversion of primary light generated by the second light-emitting diode (124), wherein an optical output (149, 150) of the first light source (116) is an envelope of the first superpositioned signal and an optical output (150, 151 ) of the second light source (122) is an envelope of the second superpositioned signal.

5. The illumination unit (110) according to any one of the four preceding claims, wherein a duty cycle of the switching frequency for each channel (112, 114, 120) is selected as< 100% / number of channels, wherein the supplied current Isupgenerated by the powersupply (130) is selected as Isup> ILS*duty cycle-. wherein ILSdenotes the light source current.

6. The illumination unit (110) according to any one of the preceding claims, wherein pulsewidth modulation is used during pulsing of the respective light source (116, 122).

7. The illumination unit (110) according to any one of the preceding claims, wherein the driving unit (126) comprises a single voltage or current source (134), wherein the driving unit (126) comprises a switch (136) configured for switching between the first channel (114) and the second channel (120) based on a predefined switching signal, wherein the driving unit (126) comprises the electronic component (128) configured for operating the first light source (116) by using the first enabling signal and the second light source (122) by using the second enabling signal.

8. The illumination unit (110) according to any one of claims 1 to 7, wherein the driving unit (126) comprises a single voltage or current source (134), wherein the voltage or current source (134) is driven by using a combined switching and enabling signal.

9. The illumination unit (110) according to any one of claims 1 to 7, wherein the driving unit (126) comprises at least two power supplies (130, 158, 160), wherein a first power supply (158) is assigned to the first channel (114) and a second power supply (160) is assigned to the second channel (120), wherein the driving unit (126) is configured for individually turn the channels (112, 114, 120) on and off, wherein the signals for operating the first channel (114) and the second channel (120) are: first channel: F(f = fswitch, (p = 0) ■ G f = second channel: F f = fswitch, (p = 180°) ■ G(f = f2), wherein F denotes a periodic signal, optionally including downtimes between switching, and G denotes a modulation signal.

10. The illumination unit (110) according to any one of claims 1 to 7, wherein the driving unit (126) comprises at least one DC current source (166), wherein the driving unit (126) comprises a totem pole circuit (168), wherein the first light source (116) and the second light source (122) have different polarizations.

11. A method for driving an illumination unit (110) according to any one of the preceding claims referring to an illumination unit (110), wherein the method comprises i. supplying, by using at least one power supply (130) of the driving unit (126), a first current to the first channel (114) and a second current to the second channel (122), wherein at least one switching circuitry (132) switches between supply from the power supply (130) to the first channel (114) and supply from the power supply (130) to the second channel (120); andII. operating the first light source (116) by using a first enabling signal having a first enabling frequency / ! and the second light source (122) by using a second enablingsignal having second enabling frequency f2by using at least one electronic component (128) of the driving unit (126).

12. A spectrometer device (174) for obtaining spectroscopic information on at least one object (176), the spectrometer device (174) comprising: at least one illumination unit (110) according to any one of the preceding claims referring to an illumination unit (110); at least one detector (180) for detecting detection light (182) from the object (176) and for generating at least one detector signal for each of the first light source (116) and the second light source (122) thereby; and at least one evaluation unit (184) for evaluating the detector signals generated by the detector (180) and for deriving the spectroscopic information on the object (176) from the detector signals.

13. The spectrometer device (174) according to the preceding claim, wherein the evaluation unit (184) is configured for generating at least one first output comprising an envelope of a first superpositioned signal from the first enabling signal being superpositioned with a switching signal, wherein the evaluation unit (184) is further configured for generating at least one second output comprising an envelope of a second superpositioned signal from the second enabling signal being superpositioned with the switching signal, wherein the first light source (116) comprises at least one first light-emitting diode (118), wherein the second light source (122) comprises at least one second lightemitting diode (124), wherein the first light source (116) further comprises at least one first luminescent material for light-conversion of primary light generated by the first light-emitting diode (118), wherein the second light source (122) further comprises at least one second luminescent material for light-conversion of primary light generated by the second light-emitting diode (124), wherein the first luminescent material and the second luminescent material provide an averaging effect over time to the primary light generated by the first LED (118) and the second LED (124), respectively, and / or wherein the detector (180), specifically at least one of the photosensitive element and / or the readout electronics, provide an averaging effect over time, wherein the evaluation unit (184) is further configured for deriving the spectroscopic information on the object using the first output and the second output.

14. A method of obtaining spectroscopic information on at least one object (176) by using at least one spectrometer device (174) according to the preceding claim, the method comprising: a. driving the illumination unit (110) according to a method for driving an illumination unit (110) according to claim 11 ; b. illuminating the object (176) with illumination light (178) generated by at least one of the first light source (116) and the second light source (122);c. detecting, by the detector (180), detection light (182) from the object (178) and generating at least one detector signal for each of the first light source (116) and the second light source (122) thereby; and d. evaluating the detector signals generated by the detector (180) by using the evalua- tion unit (184) and deriving the spectroscopic information on the object (176) from the detector signals, by using the evaluation unit (184).

15. A computer program for obtaining spectroscopic information on at least one object (176) comprising instructions which, when the program is executed by a spectrometer device (174) according to claim 12 or 13, cause the spectrometer device (174) to perform the method of obtaining spectroscopic information on at least one object (176) according to the preceding claim referring to a method of obtaining spectroscopic information on at least one object (176).

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