SINUSOIDAL LAMP DRIVER

Abstract

A device is disclosed. The device includes a. at least one radiation emitting element configured for emitting a modulated thermal radiation as a result of its temperature; where the radiation emitting element includes at least one incandescent lamp; and b. at least one electronic circuit configured for applying a periodic time-dependent voltage to the radiation emitting element, wherein where the electronic circuit is configured for controlling one or more of an amplitude, a duty cycle and a frequency of the periodic time-dependent voltage, where a temperature of the radiation emitting element and a frequency of the modulated thermal radiation depend on the applied periodic time-dependent voltage controlled by the electronic circuit.

Claims

1. A device comprising: a) at least one radiation emitting element configured for emitting a modulated thermal radiation as a result of its temperature; wherein the radiation emitting element comprises at least one incandescent lamp; and b) at least one electronic circuit configured for applying a periodic time-dependent voltage to the radiation emitting element, wherein the electronic circuit is configured for controlling one or more of an amplitude, a duty cycle and a frequency of the periodic time-dependent voltage, wherein a temperature of the radiation emitting element and a frequency of the modulated thermal radiation depend on the applied periodic time-dependent voltage controlled by the electronic circuit.

2. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage such that the applied periodic time-dependent voltage is unipolar and sinusoidal.

3. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage such that a total harmonic distortion of the periodic time-dependent voltage is in a range from 0.01 to 0.2.

4. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage in such a way that a resulting current through the radiation emitting element is also periodic time-dependent with a total harmonic distortion in a range from 0.01 to 0.2.

5. The device of claim 1, wherein the electronic circuit comprises at least one evaluation unit configured for measuring a current flowing through the radiation emitting element, wherein an information about a current state of the current is used to configure the applied periodic time-dependent voltage.

6. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage applied to the radiation emitting element such that a total harmonic distortion of an optical output of the radiation emitting element is in a range from 0.05 to 0.4.

7. The device of claim 1, wherein the electronic circuit comprises at least one variable output buck regulator, wherein the buck regulator comprises at least one resistor network.

8. The device of claim 7, wherein the electronic circuit comprises at least one first input voltage source configured for applying a non-modulated supply voltage V.sub.Supply to the buck regulator.

9. The device of claim 7, wherein the electronic circuit comprises at least one variable electronic component configured for modulating an output of the variable buck regulator which is applied to the radiation emitting element as an applied voltage V.sub.Applied.

10. The device of claim 9, wherein the variable electronic component comprises at least one variable voltage source, wherein the variable voltage source is configured for applying a periodic time-dependent input voltage V.sub.Input to the resistor network thereby transforming the output of the variable buck regulator into a periodical time-dependent voltage, which is applied to the radiation emitting element as the applied voltage V.sub.Applied.

11. The device of claim 10, wherein the variable voltage source comprises a Digital-Analog-Converter (DAC).

12. The device of claim 9, wherein the variable electronic component comprises at least one variable resistor, wherein the variable resistor is configured for changing its resistance R.sub.Variable periodically as a function of time thereby transforming the output of the variable buck regulator into a periodic time-dependent voltage, which is applied to the radiation emitting element as the applied voltage V.sub.Applied.

13. The device of claim 12, wherein the variable resistor comprises a digital potentiometer.

14. A spectrometer device comprising i) at least one device of claim 1, wherein the device is configured for illuminating at least one measurement object; ii) at least one filter element configured to separate at least one incident light beam remitted by the measurement object into a spectrum of constituent wavelength; iii) at least one sensor element having a matrix of optical sensors, the optical sensors each having a light-sensitive area, wherein each optical sensor is configured for generating at least one sensor signal in response to an illumination of the light-sensitive area; and iv) at least one evaluation device configured for determining at least one item of information related to the spectrum by evaluating the sensor signals.

15. A method for operating a device comprising at least one radiation emitting element configured for emitting a modulated thermal radiation as a result of its temperature; wherein the radiation emitting element comprises at least one incandescent lamp, the method comprising: I) applying at least one periodic time-dependent voltage to the at least one radiation emitting element; and II) controlling one or more of an amplitude, a duty cycle, and a frequency of the periodic time-dependent voltage with electronic circuits.

16. A non-transient computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to claim 15.

17. A method of using the spectrometer device of claim 14, the method comprising using the spectrometer device for a purpose of use selected from the group consisting of: an infrared detection application; a heat detection application; a thermometer application; a heat-seeking application; a flame-detection application; a fire-detection application; a smoke-detection application; a temperature sensing application; a spectroscopy application; an exhaust gas monitoring application; a combustion process monitoring application; a pollution monitoring application; an industrial process monitoring application; a chemical process monitoring application; a food processing process monitoring application; a water quality monitoring application; an air quality monitoring application; a quality control application; a temperature control application; a motion control application; an exhaust control application; a gas sensing application; a gas analytics application; a motion sensing application; a chemical sensing application; a mobile application; a medical application; a mobile spectroscopy application; and a food analysis application.

18. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage such that a total harmonic distortion of the periodic time-dependent voltage is in a range from 0.015 to 0.15.

19. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage such that a total harmonic distortion of the periodic time-dependent voltage is in a range from 0.02 to 0.1.

20. The device of claim 1, wherein the electronic circuit is configured for controlling the periodic time-dependent voltage in such a way that a resulting current through the radiation emitting element is also periodic time-dependent with a total harmonic distortion in a range from 0.015 to 0.15.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0111] Further optional details and features of the invention are evident from the description of preferred exemplary embodiments which follows in conjunction with the dependent claims. In this context, the particular features may be implemented in an isolated fashion or in combination with other features. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are shown schematically in the figures. Identical reference numerals in the individual figures refer to identical elements or elements with identical function, or elements which correspond to one another with regard to their functions.

[0112] Specifically, in the figures:

[0113] FIG. 1 shows an exemplary embodiment of a device according to the present invention comprising at least one radiation emitting element;

[0114] FIGS. 2A-2C show experimental results;

[0115] FIG. 3 shows a further exemplary embodiment of the device according to the present invention;

[0116] FIG. 4 shows an exemplary embodiment of a spectrometer device according to the present invention;

[0117] FIG. 5 shows a flow chart of an embodiment of a method for operation a device according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0118] FIG. 1 shows an exemplary embodiment of an equivalent circuit of a device 110 according to the present invention comprising at least one radiation emitting element 112 for emitting a modulated thermal radiation as a result of its temperature. The modulated thermal radiation may be radiation having at least one modified property such as an amplitude or a frequency. The modulated thermal radiation may be electromagnetic radiation in one or more of the visible spectral range, the ultraviolet spectral range and the infrared spectral range. Preferably, radiation used for the typical purposes of the present invention is radiation in the infrared (IR) spectral range, more preferred, in the near infrared (NIR) and the mid infrared spectral range (MidIR), especially the radiation having a wavelength of 1 m to 5 m, preferably of 1 m to 3 m.

[0119] The radiation emitting element 112 comprises at least one incandescent lamp 114. The incandescent lamp 114 may be a light source based on a heated light emitting filament. The incandescent lamp 114 may comprise at least one bulb having the at least one filament positioned inside. The filament may comprise at least one wire, specifically a coiled wire. The filament may comprise tungsten. The bulb may be a glass bulb filled by an inert gas. The inert gas, e.g., may comprise a combination of argon and nitrogen. When applying the periodic time-dependent voltage across the radiation emitting element 112, electric current flows through the filament and increases the temperature of the filament such that the filament emits thermal radiation. As an example, the incandescent lamp 114 may be configured for emitting light in the infrared spectral range. The incandescent lamp 114 may be or may comprise an infrared lamp. For example, a tungsten filament with a halogen filling may be used. However, other embodiments are possible such as fillings with xenon, argon gases.

[0120] As shown in FIG. 1, the device 110 comprises at least one electronic circuit 116 configured for applying a periodic time-dependent voltage to the radiation emitting element 112. For example, the periodic time-dependent voltage may be sinusoidal or may be a square wave voltage.

[0121] The electronic circuit 116 is configured for controlling one or more of an amplitude, a duty cycle and a frequency of the periodic time-dependent voltage. The amplitude may be a local and/or a global extremum, in particular a maximum or minimum, of the periodic time-dependent voltage. The duty cycle may be a fraction of one period in which a signal or system is active. In particular, the duty cycle may be calculated as a ratio of a pulse duration divided by a period duration given the case of a periodic sequence of pulses. The frequency may be a number of occurrences of a repeating event over time and/or may be defined as the reciprocal of the period duration. The controlling of one or more of an amplitude, a duty cycle and a frequency of the periodic time-dependent voltage may be an action of at least one of monitoring and/or setting and/or regulating of one or more of the amplitude, the duty cycle and the frequency of the periodic time-dependent voltage. The controlling of one or more of the amplitude, the duty cycle and the frequency of the periodic time-dependent voltage may comprise a setting a target amplitude, target duty cycle and/or target frequency. The controlling may comprise a maintaining of one or more the target amplitude, target duty cycle and/or target frequency. A temperature of the radiation emitting element 112 and a frequency of the modulated thermal radiation depend on the applied periodic time-dependent voltage controlled by the electronic circuit 116.

[0122] The electronic circuit 116 may comprise at least one variable output buck regulator 132. The buck regulator 132 may be a DC-DC converter which is configured for modifying at least one input voltage to at least one output voltage which is smaller than or equal to the input voltage. The variable output may be a variable physical quantity such as a voltage or a current. The physical quantity may have been an input and may have subsequently been modified before the modified physical quantity may be passed on as output. As an example, an input voltage may be modified, e.g. reduced, before passing it on as output voltage. Thus, the buck regulator 132 may receive an input voltage, reduce the input voltage to a variable target voltage and provide the target voltage as output. Alternatively, the buck regulator 132 may however also leave an input, e.g. a voltage and/or a current, unmodified and simply pass it on as output.

[0123] The buck regulator 132 may comprise at least one buck converter 136. The buck converter 136 may comprise at least one of a controller, a switch, e.g. a transistor, and a diode. The buck converter 136 may comprise at least one voltage input 138. The buck converter 136 may comprise at least one of an inductor connection 140 and an output feedback connection 142. The inductor connection 140 may be configured for connecting the buck converter 136 to at least one inductor 120 of the buck regulator 132. The inductor 120 may be connected to at least one capacitor 122 of the buck regulator 132. The capacitor 122 may be grounded. In the buck converter 136, at least one controller may be configured for regularly switching at least one switch on and off, typically several thousand up to some million times per second, in order to modify at least one input voltage. Further, at least one diode of the buck converter 136 may be configured for blocking the input current, thereby forcing it to run through at least one inductor 120 of the buck regulator 132 to at least one capacitor 122 of the buck regulator 132, when the switch is switched on. The inductor 120 may be configured for storing electrical energy during the time when the switch is switched on. The capacitor 122 may be configured for storing an electrical charge during the time when the switch is switched on. The diode may further be configured for letting an electric current induced by the inductor 120 through, when the switch is switched off, wherein the electric current induced by the inductor 120 is fed by the electric charge from the capacitor 122.

[0124] The buck regulator 132, in particular the buck converter 136, may be configured for receiving at least one input voltage, in particular a non-modulated supply voltage V.sub.supply. As indicated in FIG. 1, the electronic circuit 116 may comprise at least one first input voltage source 134 configured for applying the non-modulated supply voltage V.sub.Supply to the buck regulator 132. The first input voltage source 134 may be connected with an input of the buck regulator 132 configured for receiving the at least one supply voltage, in particular the non-modulated supply voltage V.sub.supply. In particular, a constant DC supply voltage may be applied to the voltage input 138 of the buck converter 136.

[0125] The buck regulator 132 may comprise at least one resistor network 144. The resistor network 144 may be a network comprising at least one resistor 118. The resistor network 144 may for instance further comprise wires 124 and/or traces 126 for at least partially connecting resistors 118 and/or further components of the resistor network 144 with each other. For example, in the embodiment of FIG. 1, the resistor network 144 may comprise three resistors, denoted R.sub.1, R.sub.2 and R.sub.3. The first resistor R.sub.1 may be connected in parallel with the capacitor 122. The resistor R.sub.1 may be connected in series to the resistor R.sub.2. The resistor R.sub.2 may be grounded. The resistors R.sub.1 and R.sub.2 may form a voltage divider. The resistor R.sub.1 may be connected to the resistor R.sub.3, in particular an output of the voltage divider may be connected to the resistor R.sub.3.

[0126] The electronic circuit 116 may comprise at least one variable electronic component 146 configured for modulating an output of the variable buck regulator 132 which may be applied to the radiation emitting element 112 as an applied voltage V.sub.Applied. The variable electronic component 146 may be an electronic component with variable physical properties. The variable electronic component 146 may be or may comprise a variable resistance and/or a variable voltage source.

[0127] In the embodiment of FIG. 1, the variable electronic component 146 may be or may comprise a variable voltage source 148, in particular a modulated voltage source 150. The variable voltage source 148 may be configured for applying a periodic time-dependent input voltage V.sub.Input to the resistor network 144 thereby transforming the output of the variable buck regulator 132 into a periodic time-dependent voltage. The resistor R.sub.3 may be connected to the variable voltage source 148. The variable voltage source 148 may be used as a second input voltage source 152, which is configured for generating a modulated voltage also connected to the resistor network 144 in such a way that the output of the buck regulator 132, which is applied to the radiation emitting element 112, is also a modulated voltage. For example, a Digital-Analog-Converter (DAC) output 154 of a microcontroller may be used as variable voltage source 148. The output of the variable voltage source 148 may be summed into the output feedback connection 142.

[0128] FIGS. 2A-2C show experimental results regarding an exemplary embodiment of the device 110, e.g. as described with respect to FIG. 1. FIG. 2A shows the periodic time-dependent voltage V.sub.Applied in V used as input voltage for the incandescent lamp 114 as a function of time in seconds. The frequency of the periodic time-dependent voltage V.sub.Applied may be 16 Hz. As comparison in FIG. 2A a square wave voltage is applied to the incandescent lamp 114 at the same frequency, by only turning the buck converter 136 on and off via its enable pin. The periodic time-dependent voltage V.sub.Applied is denoted with reference sign 156. The square wave voltage is denoted with reference sign 158. Without any extra measures, the current flowing through the incandescent lamp 114 in the cold state is so high that the life span of the incandescent lamp 114 is reduced to some thousand pulses. Thus, a soft-start measure is taken, which decreases the slope of the rising voltage flank of the square wave as shown in FIG. 2A.

[0129] FIG. 2B shows the currents I in A corresponding to the voltages shown in FIG. 2A as a function of time in seconds. The current corresponding to the periodic time-dependent voltage V.sub.Applied is denoted with reference sign 160. The current corresponding to the square wave voltage is denoted with reference sign 162. The currents are measured across a shunt with 0.5.

[0130] Within the time scale going from 0 to 1 second, the measured currents repeatedly go from approximately 0 up to approximately 0.4 A and back again. The peaks above 0.4 A of the current corresponding to the square wave voltage indicate that there is an overshoot of current flowing through the incandescent lamp 114. Thus, regardless of the soft-start measure of the square wave voltage, an overshoot of current flowing through the incandescent lamp 114 can be seen in FIG. 2B for the square wave voltage. In contrast to the square wave voltage, the sinusoidal voltage V.sub.applied leads to a sinusoidal current without current overshoot. Since there is no overshooting of the sinusoidal current through the incandescent lamp 114 even in a cold state, a longer lifetime of the incandescent lamp 114 may be achieved.

[0131] To characterize and compare a sinusoidal wave and a square wave, total harmonic distortion (THD) can be used. Without being bound by theory, applying a sinusoidal wave to a non-linear load may cause presence of harmonics and thus, distortion of the waveform. The harmonics may be overtones which are multiples, specifically whole number multiples, of the frequency of the voltage signal. A distorted periodic voltage waveform V(t) may be written as

[00005]$V\left(t\right)=V_0+\underset{h=1}{\overset{}{.Math.}}{V}_h\sin \left(ht+{}_h\right)$

wherein V.sub.0 is a DC component voltage, voltages V.sub.h the respective voltage at a harmonic h, t is the time and is the frequency and .sub.h is the phase angle. The distortion of the waveform can be written as a single quantity/index, denoted as Total Harmonic Distortion (THD). THD is a known tool to identify how much of the distortion of a voltage or current is due to harmonics in the signal. A voltage or current that is purely sinusoidal has no harmonic distortion because it is a signal consisting of a single frequency, e.g. 16 Hz which is used in this experiment. A voltage or current that is periodic but not purely sinusoidal will have higher frequency components in it contributing to the harmonic distortion of the signal. In general, the less that a periodic signal looks like a sine wave, the stronger the harmonic components are and the more harmonic distortion it will have.

[0132] The electronic circuit 116 is configured for controlling the periodic time-dependent voltage such that a total harmonic distortion of the periodic time-dependent voltage is in a range from 0.01 to 0.2, preferably from 0.015 to 0.15, more preferably from 0.02 to 0.1. The total harmonic distortion THD of the sinusoidal voltage may be calculated as the quotient of the root-mean-square (RMS) values of the applied voltage with all of the harmonics filtered out wherein the total harmonic distortion of the sinusoidal voltage, calculated as the quotient of the RMS values of the applied voltage with all of the harmonics filtered out leaving just the fundamental frequency, denoted as V.sub.Applied,RMS,Fundemental, and the RMS value of the applied voltage with the fundamental frequency filtered out leaving all of the harmonics, denoted V.sub.Applied,RMS without Fundemental, as

[00006]$\mathrm{THD}=\frac{V_{\mathrm{Applied},\mathrm{RMS}\mathrm{without}\mathrm{Fundemental}}}{V_{\mathrm{Applied},\mathrm{RMS}\mathrm{Fundemental}}}.$

[0133] In this experiment, the THD of a pure square wave is 48.3%. Since the soft-start measure is taken, a THD of about 40% can be achieved with the suggested buck converter 136. In contrast to the square wave, the sinusoidal wave has a THD of about 5% (a perfect sine would have 0%), which means that a much higher percentage of the energy is transferred over the fundamental harmonic at the desired operation frequency. In power systems, lower THD implies lower peak currents, less heating and lower electromagnetic emissions.

[0134] FIG. 2C shows the corresponding optical output V.sub.out in V of the incandescent lamp 114 as a function of time tin seconds. The optical output corresponding to the sinusoidal voltage V.sub.Applied is denoted with reference sign 164. The optical output corresponding to the square wave voltage is denoted with reference sign 166. The optical output of the incandescent lamp 114 is measured using an indium gallium arsenide (InGaAs) detector.

[0135] FIG. 2C shows that the overshoot of current corresponding to the square wave voltage leads to a higher temperature and thus a larger dynamic range. Nevertheless, if the optical output is recorded by means of optical detectors and a data processing tools such as fast Fourier transformation (FFT) is used, the amplitude of the frequency component at the fundamental frequency is employed as signal intensity and not the dynamic range of the optical output in time domain. Thus, even though the dynamic range with the square wave is higher, the amplitude of the fundamental frequency component of the sine way may be comparable, as was the case with the experimental results.

[0136] In FIG. 3, a further exemplary embodiment of a device 110 according to the present invention is schematically depicted. For the description of FIG. 3, reference can be made to the description of FIG. 1, wherein in FIG. 3 the variable electronic component 146 may be or may comprise a variable resistor 168.

[0137] The variable resistor 168 may be configured for changing its resistance R.sub.Variable periodically as a function of time thereby transforming the output of the variable buck regulator 132 into a periodic time-dependent voltage, which may be applied to the radiation emitting element 112 as the applied voltage V.sub.Applied. The variable resistor 168 may be a resistor 118 with a variable resistance, specifically a resistance which is continuously variable over time. The variable resistor 168 may be configured to vary its resistance over a continuous resistance range. The variable resistor may be configured to vary its resistance between a plurality of discrete resistance values. The variable resistor may cause a variable voltage drop in the electronic circuit 116. As an example, a constant output voltage of the variable output buck regulator 132 may experience a variable voltage drop over the variable resistor 168 over time resulting in a periodic time-dependent voltage. The variable resistor 168 may be grounded. The variable resistor 168 may be connected in series to at least one further resistor 118 of the resistor network, specifically the resistor R.sub.2, and to the output feedback connection 142 of the buck converter 136.

[0138] The variable resistor 168 may comprise a digital potentiometer 170, wherein a potentiometer may be a three-terminal resistor with a sliding or rotating contact forming an adjustable voltage divider. Consequently, the digital potentiometer 170 may be a digitally-controlled electronic component which mimics the analog functions of a potentiometer.

[0139] In FIG. 4 an exemplary embodiment of a spectrometer device 172 according to the present invention is schematically depicted. The spectrometer device 172 comprises at least one device 110 according to the present invention, wherein the device 110 is configured for illuminating at least one measurement object 174. The device 110 may emit an illumination light beam 176 for illuminating the measurement object 174. The spectrometer device 172 may be an apparatus which is capable of recording 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, preferably, be provided as an electrical signal which may be used for further evaluation. The measurement object 174 may be an object which is to be measured, e.g. for which a spectrum is to be recorded, wherein the object has in principle arbitrary properties, e.g. arbitrary optical properties or an arbitrary shape. The object may be a sample or 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.

[0140] The spectrometer device 172 comprises at least one filter element 178. The filter element 178 is configured to separate at least one incident light beam 180 remitted by the measurement object 174 into a spectrum of constituent wavelength. The filter element 178 may be an optical element which is adapted for separating incident light into the spectrum of constituent wavelength signals. For example, the filter element 178 may be or may comprise at least one prism. For example, the filter element 178 may be and/or may comprise at least one optical filter such as a length variable filter, i.e. an optical filter which comprises a plurality of filters, preferably a plurality of interference filters, which may, in particular, be provided in a continuous arrangement of the filters. Herein, each of the filters may form a bandpass with a variable center wavelength for each spatial position on the filter, preferably continuously, along a single dimension, which is, usually, denoted by the term length, on a receiving surface of the length variable filter. In a preferred example, the variable center wavelength may be a linear function of the spatial position on the filter, in which case the length variable filter is usually referred to as a linearly variable filter or by its abbreviation LVF. However, other kinds of functions may be applicable to the relationship between the variable center wavelength and the spatial position on the filter. Herein, the filters may be located on a transparent substrate which may, in particular, comprise at least one material that may show a high degree of optical transparency within in the visual and/or infrared (IR) spectral range, especially, within the near-infrared (NIR) spectral range as described below in more detail, whereby varying spectral properties, especially continuously varying spectral properties, of the filter along length of the filter may be achieved. In particular, the filter element 178 may be a wedge filter that may be adapted to carry at least one response coating on a transparent substrate, wherein the response coating may exhibit a spatially variable property, in particular, a spatially variable thickness. However, other kinds of length variable filters which may comprise other materials or which may exhibit a further spatially variable property may also be feasible. At a normal angle of incidence of an incident light beam 180, each of the filters as comprised by the length variable filter may have a bandpass width that may amount to a fraction of the center wavelength, typically to a few percent, of the particular filter. By way of example, for a length variable filter having a wavelength range from 1400 to 1700 nm and a bandpass width of 1%, the bandpass width at the normal incidence angle might vary from 14 nm to 17 nm. However, other examples may also be feasible. As a result of this particular set-up of the length variable filter, only incident light having a wavelength which may, within a tolerance indicated by the bandpass width, equal the center wavelength being assigned to a particular spatial position on the filter is able to pass through the length variable filter at the particular spatial position. Thus, a transmitting wavelength which may be equal to the center wavelength of the bandpass width may be defined for each spatial position on the length variable filter. In other words, all light which may not pass through the length variable filter at the transmitting wavelength may be absorbed or, mostly, reflected by the receiving surface of the length variable filter. As a result, the length variable filter has a varying transmittance which may enable it for separating the incident light into a spectrum.

[0141] The spectrometer device 172 comprises at least one sensor element 182 having a matrix of optical sensors 184. The optical sensors 184 each have a light-sensitive area. Each optical sensor 184 is configured for generating at least one sensor signal in response to an illumination of the light-sensitive area. The optical sensor 184 may be a light-sensitive device for detecting a light beam, such as for detecting an illumination and/or a light spot generated by at least one light beam. The light-sensitive are may be an area of the optical sensor 184 which may be illuminated externally, by the at least one light beam, in response to which illumination at least one sensor signal is generated. The light-sensitive area may specifically be located on a surface of the respective optical sensor 184. Other embodiments, however, are feasible. Singe optical sensors 184 may each have one light sensitive area. One combined optical sensor 184 may have a plurality of light sensitive areas.

[0142] The optical sensor 184 may comprise a light-sensitive device configured to generate one output signal. In case the spectrometer device 172 comprises a plurality of optical sensors 184, each optical sensor 184 may be embodied such that precisely one light-sensitive area is present in the respective optical sensor 184, such as by providing precisely one light-sensitive area which may be illuminated, in response to which illumination precisely one uniform sensor signal is created for the whole optical sensor 184. Thus, each optical sensor 184 may be a single area optical sensor 184. The use of the single area optical sensors 184, however, renders the setup of the detector specifically simple and efficient. Thus, as an example, commercially available photo-sensors, such as commercially available silicon photodiodes, each having precisely one sensitive area, may be used in the set-up. Other embodiments, however, are feasible. The optical sensors 184 may be part of or constitute a pixelated optical device. For example, the optical sensor 184 may be and/or may comprise at least one CCD and/or CMOS device. As an example, the optical sensors 184 may be part of or constitute at least one CCD and/or CMOS device having a matrix of pixels, each pixel forming a light-sensitive area.

[0143] The optical sensors 184 specifically may be or may comprise at least one photodetector, preferably inorganic photodetectors, more preferably inorganic semiconductor photodetectors, most preferably silicon photodetectors. Specifically, the optical sensors 184 may be sensitive in the infrared spectral range. All pixels of the matrix or at least a group of the optical sensors 184 of the matrix specifically may be identical. Groups of identical pixels of the matrix specifically may be provided for different spectral ranges, or all pixels may be identical in terms of spectral sensitivity. Further, the pixels may be identical in size and/or with regard to their electronic or optoelectronic properties. Specifically, the optical sensors 184 may be or may comprise at least one inorganic photodiode which is sensitive in the infrared spectral range, preferably in the range of 700 nm to 3.0 micrometers. Specifically, the optical sensors 184 may be sensitive in the part of the near infrared region where silicon photodiodes are applicable specifically in the range of 700 nm to 1100 nm. Infrared optical sensors which may be used for optical sensors 184 may be commercially available infrared optical sensors, such as infrared optical sensors commercially available under the brand name Hertzstueck from trinamiX GmbH, D-67056 Ludwigshafen am Rhein, Germany. Thus, as an example, the optical sensors 184 may comprise at least one optical sensor 184 of an intrinsic photovoltaic type, more preferably at least one semiconductor photodiode selected from the group consisting of: a Ge photodiode, an InGaAs photodiode, an extended InGaAs photodiode, an InAs photodiode, an InSb photodiode, a HgCdTe photodiode. Additionally or alternatively, the optical sensors 184 may comprise at least one optical sensor 184 of an extrinsic photovoltaic type, more preferably at least one semiconductor photodiode selected from the group consisting of: a Ge:Au photodiode, a Ge:Hg photodiode, a Ge:Cu photodiode, a Ge:Zn photodiode, a Si:Ga photodiode, a Si:As photodiode. Additionally or alternatively, the optical sensors 184 may comprise at least one photoconductive sensor such as a PbS or PbSe sensor, a bolometer, preferably a bolometer selected from the group consisting of a VO bolometer and an amorphous Si bolometer.

[0144] The matrix may be composed of independent pixels such as of independent optical sensors 184. Thus, a matrix of inorganic photodiodes may be composed. Alternatively, however, a commercially available matrix may be used, such as one or more of a CCD detector, such as a CCD detector chip, and/or a CMOS detector, such as a CMOS detector chip. Thus, generally, the optical sensor 184 may be and/or may comprise at least one CCD and/or CMOS device and/or the optical sensors 184 of the detector may form a sensor array or may be part of a sensor array, such as the above-mentioned matrix. Thus, as an example, the optical sensors 184 may comprise and/or constitute an array of pixels, such as a rectangular array, having m rows and n columns, with m, n, independently, being positive integers. For example, the sensor element 182 may comprise at least two optical sensors 184 arranged in a row and or column such as a bi-cell. For example, the sensor element 182 may a quadrant diode system comprising a 22 matrix of optical sensors 184. For example, more than one column and more than one row is given, i.e. n>1, m>1. Thus, as an example, n may be 2 to 16 or higher and m may be 2 to 16 or higher. Preferably, the ratio of the number of rows and the number of columns is close to 1. As an example, n and m may be selected such that 0.3m/n3, such as by choosing m/n=1:1, 4:3, 16:9 or similar. As an example, the array may be a square array, having an equal number of rows and columns, such as by choosing m=2, n=2 or m=3, n=3 or the like.

[0145] The matrix specifically may be a rectangular matrix having at least one row, preferably a plurality of rows, and a plurality of columns. As an example, the rows and columns may be oriented essentially perpendicular. In order to provide a wide range of view, the matrix specifically may have at least 10 rows, preferably at least 500 rows, more preferably at least 1000 rows. Similarly, the matrix may have at least 10 columns, preferably at least 500 columns, more preferably at least 1000 columns. The matrix may comprise at least 50 optical sensors 184, preferably at least 100000 optical sensors 184, more preferably at least 5000000 optical sensors 184. The matrix may comprise a number of pixels in a multi-mega pixel range. Other embodiments, however, are feasible. Thus, in setups in which an axial rotational symmetry is to be expected, circular arrangements or concentric arrangements of the optical sensors 184 of the matrix, which may also be referred to as pixels, may be preferred.

[0146] Preferably, the light sensitive area may be oriented essentially perpendicular to an optical axis of the spectrometer device 172. The optical axis may be a straight optical axis or may be bent or even split, such as by using one or more deflection elements and/or by using one or more beam splitters, wherein the essentially perpendicular orientation, in the latter cases, may refer to the local optical axis in the respective branch or beam path of the optical setup.

[0147] The sensor signal may be a signal generated by the optical sensor 184 and/or at least one pixel of the optical sensor 184 in response to illumination. Specifically, the sensor signal may be or may comprise at least one electrical signal, such as at least one analogue electrical signal and/or at least one digital electrical signal. More specifically, the sensor signal may be or may comprise at least one voltage signal and/or at least one current signal. More specifically, the sensor signal may comprise at least one photocurrent. Further, either raw sensor signals may be used, or the detector, the optical sensor or any other element may be adapted to process or preprocess the sensor signal, thereby generating secondary sensor signals, which may also be used as sensor signals, such as preprocessing by filtering or the like.

[0148] The spectrometer device 172 comprises at least one evaluation device 186 configured for determining at least one item of information related to the spectrum by evaluating the sensor signals. The evaluation device 186 may be an arbitrary device adapted to perform the named operation, preferably by using at least one data processing device and, more preferably, by using at least one processor and/or at least one application-specific integrated circuit. Thus, as an example, the at least one evaluation device 186 may comprise at least one data processing device having a software code stored thereon comprising a number of computer commands. The evaluation device 186 may provide one or more hardware elements for performing one or more of the named operations and/or may provide one or more processors with software running thereon for performing one or more of the named operations. As an example, the evaluation device 186 may comprise one or more programmable devices such as one or more computers, application-specific integrated circuits (ASICs), Digital Signal Processors (DSPs), or Field Programmable Gate Arrays (FPGAs) which are configured to perform the evaluation. Additionally or alternatively, however, the evaluation device 186 may also fully or partially be embodied by hardware. The at least one item of information may, for example, be provided electronically, visually, acoustically or in any arbitrary combination thereof. Further, the at least one item of information may be stored in a data storage device of the spectrometer device 172 or of a separate storage device and/or may be provided via at least one interface 188, such as a wireless interface and/or a wire-bound interface. The evaluation device 186 may further be connected to the device 110 according to the present invention wirelessly and/or wire-bound.

[0149] FIG. 5 shows a flow chart of an embodiment of a method for operation a device 110 comprising at least one radiation emitting element 112 according to the present invention. The method comprises the following steps: [0150] I. (denoted with reference sign 190) applying at least one periodic time-dependent voltage to at least one of the radiation emitting elements; [0151] II. (denoted with reference sign 192) controlling one or more of the amplitude, the duty cycle and the frequency of the periodic time-dependent voltage with at least one of the electronic circuits.

[0152] The method steps may be performed in the given order. It shall be noted, however, that a different order is also possible. The method may comprise further method steps which are not listed. Further, one or more of the method steps may be performed once or repeatedly. Further, two or more of the method steps may be performed simultaneously or in a timely overlapping fashion.

LIST OF REFERENCE NUMBERS

[0153] 110 Device [0154] 112 Radiation emitting element [0155] 114 Incandescent lamp [0156] 116 Electronic circuit [0157] 118 Resistor [0158] 120 Inductor [0159] 122 Capacitor [0160] 124 Wire [0161] 126 Trace [0162] 128 Ground [0163] 130 Voltage source [0164] 132 Buck regulator [0165] 134 First input voltage source [0166] 136 Buck converter [0167] 138 Voltage input [0168] 140 Inductor connection [0169] 142 Output feedback connection [0170] 144 Resistor network [0171] R.sub.1 First resistor [0172] R.sub.2 Second resistor [0173] R.sub.3 Third resistor [0174] 146 Variable electronic component [0175] 148 Variable voltage source [0176] 150 Modulated voltage source [0177] 152 Second input voltage source [0178] 154 Digital-Analog-Converter (DAC) [0179] 156 Sinusoidal voltage [0180] 158 Square wave voltage [0181] 160 Current corresponding to the sinusoidal voltage [0182] 162 Current corresponding to the square wave voltage [0183] 164 Optical output corresponding to the sinusoidal voltage [0184] 166 Optical output corresponding to the square wave voltage [0185] 168 Variable resistor [0186] 170 Digital potentiometer [0187] 172 Spectrometer device [0188] 174 Measurement object [0189] 176 Illumination light beam [0190] 178 Filter element [0191] 180 Incident light beam [0192] 182 Sensor element [0193] 184 Optical sensor [0194] 186 Evaluation device [0195] 188 Interface [0196] 190 Method step I [0197] 192 Method step II