Modulation Device for Periodically Modulating Light

Abstract

Described herein is a modulation device for periodically modulating light emitted by a light source. The modulation device includes at least one enclosing tube being rotatable about a cylinder axis of the enclosing tube. The enclosing tube includes at least one aperture disposed within a cylindrical wall of the enclosing tube. The modulation device further includes at least one driving system for rotating the enclosing tube about the cylinder axis. Also described herein are a modulated illumination device and a spectrometer device.

Claims

1. A modulation device for periodically modulating light emitted by a light source, the modulation device comprising at least one enclosing tube being rotatable about a cylinder axis of the enclosing tube, the enclosing tube comprising at least one aperture disposed within a cylindrical wall of the enclosing tube, the modulation device further comprising at least one driving system for rotating the enclosing tube about the cylinder axis, wherein the at least one aperture is adjustable.

2. The modulation device according to claim 1, wherein the enclosing tube has an open end and a closed end, and wherein the driving system is coupled to the closed end of the enclosing tube.

3. The modulation device according to claim 2, wherein the driving system is coupled to the closed end by an axle disposed on the cylinder axis.

4. The modulation device according to claim 1, wherein the driving system comprises at least one electrical motor.

5. The modulation device according to claim 1, wherein the at least one aperture comprises at least one of: an opening disposed at a position spaced apart from both ends of the enclosing tube; a slot in a circumferential direction in the enclosing tube; and a slot in an axial direction of the enclosing tube.

6. The modulation device according to claim 1, wherein the aperture is fully or partially filled with at least one optically transparent material, and wherein the at least one optically transparent material is transparent in one or more of an ultraviolet spectral range, a visible spectral range or an infrared spectral range.

7. The modulation device according to claim 1, wherein the enclosing tube has a reflective coating on its inside.

8. The modulation device according to claim 1, wherein the at least one aperture is adjustable in at least one of size, position, width or length.

9. The modulation device according to claim 1, wherein the enclosing tube comprises at least one movable segment for adjusting the at least one aperture.

10. The modulation device according to claim 1, wherein the enclosing tube comprises at least two concentric partial tubes, each partial tube comprising at least one partial aperture, and wherein the at least one aperture of the enclosing tube is adjustable by one or both of turning or shifting the at least two concentric partial tubes relative to one another.

11. A modulated illumination device, comprising at least one modulation device according to claim 1, further comprising at least one light source disposed at least partially within the enclosing tube of the modulation device.

12. The modulated illumination device according to claim 11, wherein the at least one light source comprises an incandescent lamp.

13. A spectrometer device for optical analysis of at least one sample, the spectrometer device comprising at least one wavelength-selective element configured for separating incident light into a spectrum of constituent wavelengths, the spectrometer device further comprising at least one detector device configured for detecting at least a portion of the constituent wavelengths, and at least one modulated illumination device according to claim 11.

14. The spectrometer device according to claim 13, wherein the spectrometer device is a hand-held spectrometer device.

15. The spectrometer device according to claim 13, wherein the spectrometer device further comprises at least one evaluation unit, wherein the at least one evaluation unit is configured for driving the modulation device, and wherein the at least one evaluation unit is further configured for analyzing at least one detector signal provided by the detector device in a frequency-selective manner.

16. A method for periodically modulating light emitted by a light source, the method comprising: i) providing the modulation device according to claim 1; ii) providing at least one light source at least partially disposed within the enclosing tube of the modulation device; iii) controlling the at least one light source to emit light; and iv) rotating the enclosing tube about the cylinder axis.

17. A method of using the modulation device according to claim 1, the method comprising using the modulation device for a purpose of use selected from the group consisting of: an infrared detection 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; a food analysis application; an agricultural application; a plant health monitoring application; a plastics identification and/or recycling application; a heat-detection application; a thermometer application; a heat-seeking application; a flame-detection application; a fire-detection application; a smoke-detection application; and a temperature sensing application.

18. The spectrometer device according to claim 13, wherein the spectrometer device further comprises at least one evaluation unit, wherein the at least one evaluation unit is configured for driving the modulation device, and wherein the at least one evaluation unit is further configured for analyzing at least one detector signal provided by the detector device by using a lock-in amplification.

19. The method of use according to claim 17, wherein the agricultural application is selected from the group consisting of characterization of soil, silage, feed, crop or produce.

Description

SHORT DESCRIPTION OF THE FIGURES

[0089] 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 embodiment. The embodiments are schematically depicted in the Figures.

[0090] In the Figures:

[0091] FIGS. 1A to 1C show various views of an embodiment of a modulation device and of a modulated illumination device; and

[0092] FIG. 2 shows a schematic view of an embodiment of a spectrometer device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0093] In FIGS. 1A to 1C, various views of an embodiment of a modulation device 110 for periodically modulating light emitted by a light source 112 as well as of a modulated illumination device 114 are shown. Therein, FIG. 1A shows a cross-sectional view through the modulation device 110, the light source 112 and the modulation illumination device 114, FIG. 1B shows a front view with the modulation device 110 in a closed position, and FIG. 1C shows a front view with the modulation device 110 in an open position. These figures, in the following, will be explained in conjunction.

[0094] The modulation device 110 comprises a enclosing tube 116, having an open end 118 as well as, optionally, a closed end 120. The enclosing tube 116 has a cylindrical wall 117. The light source 112, from the open end 118, protrudes into an inner space 122 of the enclosing tube 116. As an example and as depicted in FIG. 1A, the light source 112 may comprise an incandescent lamp 124. An inner wall 126 of the enclosing tube 116 may be coated with at least one reflective coating, such as a gold coating. The enclosing tube 116, as an example, may be made of a metallic material, such as aluminum.

[0095] The enclosing tube is rotatable about a cylinder axis 128 of the enclosing tube 116. The modulation device 110 comprises at least one driving system 130 for rotating the enclosing tube 116 about the cylinder axis 128. Thus, as an example, the driving system 130 may comprise at least one motor 132, such as at least one micro-mechanical motor. The driving system 130 may be connected to the closed end 120 of the enclosing tube 116, e.g. by at least one axle 134. A rotation, in FIGS. 1A to 1C, is symbolically depicted by reference number 136.

[0096] The enclosing tube 116 comprises at least one aperture 138, as can be seen in FIG. 1C. The aperture 138 may be disposed at the same axial position along the cylinder axis 128 as the light source 112, such that light emitted by the light source 112 in a radial direction may pass through the aperture 138. In a direction of view, e.g. in the front view shown in FIG. 1C, when the enclosing tube 116 rotates, the light beam emitted radially by the light source 112 through the aperture 118 is intermittently interrupted by the closed parts of the enclosing tube 116. Consequently, the light beam is modulated, with the rotational frequency of the rotation 136 or, in case a plurality of apertures 138 is provided, with a multiple of this rotational frequency. The enclosing tube 116 may be made of an intransparent material, and the aperture 138 may either be made of an empty opening in the enclosing tube 116 or by a transparent part of the enclosing tube 116. Thus, the aperture 138 may be left open or may fully or partially be filled with at least one optically transparent material.

[0097] The at least one aperture 138 may be fixed in size, shape and position. Still, however, the aperture 138 may also be adjustable in at least one of size, position, width or length, wherein the width, as an example, is measured along a circumferential line across the aperture 138, and wherein the length, as an example, may be defined as the extension along the cylinder axis 128. For adjustment of the aperture 138, various possibilities are given. Thus, as an example, the enclosing tube 116 may comprise one or more movable segments 140. As an example, these movable segments 140 may be concentric tubular segments of the enclosing tube 116. By changing the relative position of these movable segments 140, the aperture 138 may be adjusted.

[0098] In FIG. 2, a schematic view of an exemplary embodiment of a spectrometer device 142 for optical analysis of at least one sample 144 is shown in a cross-sectional view. The spectrometer device 142 comprises the modulation device 110 and the modulated illumination device 114 according to the embodiment shown in FIGS. 1A to 1C. Thus, for details of these elements, reference may be made to the description of FIGS. 1A to 1C above. Still, other embodiments are feasible, too. The modulated illumination device 114 is configured for illuminating the sample 144 with light 146.

[0099] Light 148 reflected by the sample 144, also denoted as incident light, enters a housing 150 of the spectrometer device 142 through an entrance window 152. Within the housing 150, a wavelength-selective element 154 is disposed, for separating incident light into a spectrum of constituent wavelengths. The spectrometer device 142 further comprises at least one detector device 156 for detecting at least a portion of the constituent wavelengths.

[0100] The spectrometer device 142 may further comprise at least one evaluation unit 158 which may be configured for analyzing at least one detector signal provided by the detector device 156. The evaluation unit 158, which may be a central evaluation unit 158 or a decentralized evaluation unit 158, may further be connected to one or more of the light source 112 and/or the driving system 130, and, as an example, may be configured for controlling one or both of these devices. Thus, as an example, the evaluation unit 158 may make use of the modulation device 110 for a frequency-selected analysis of the sample 144, e.g. by using a lock-in amplification principle. Thus, frequency-selective analysis of at least one sample 144 may be performed even when an incandescent lamp 124 is used as a light source 112, which typically is challenging specifically at high frequencies, since a modulation of the driving current of incandescent lamps 124 typically is rather difficult at high frequencies. Consequently, the setup shown in FIG. 2, as an example, may provide for the possibility of infrared spectroscopic analysis of the sample 144 in a high-frequency modulation setup, thereby being capable of providing a high signal-to-noise ratio. Still, as compared to conventional chopper wheels, the setup using the modulation device 110 with the enclosing tube 116 may be rendered rather compact and robust, such that the spectrometer device 142 may also be configured as a hand-held spectrometer device 142 which is capable of performing analysis even under rough environmental conditions in the field.

LIST OF REFERENCE NUMBERS

[0101] 110 modulation device [0102] 112 light source [0103] 114 modulated illumination device [0104] 116 enclosing tube [0105] 117 cylindrical wall [0106] 118 open end [0107] 120 closed end [0108] 122 inner space [0109] 124 incandescent lamp [0110] 126 inner wall [0111] 128 cylinder axis [0112] 130 driving system [0113] 132 motor [0114] 134 axle [0115] 136 rotation [0116] 138 aperture [0117] 140 movable segments [0118] 142 spectrometer device [0119] 144 sample [0120] 146 light [0121] 148 reflected light [0122] 150 housing [0123] 152 entrance window [0124] 154 wavelength-selective element [0125] 156 detector device [0126] 158 evaluation unit

REFERENCES

[0127] US 2014/131578 A1 [0128] US 2005/0229698 A1 [0129] U.S. Pat. No. 3,394,253 A [0130] EP 0 732 580 A2 [0131] U.S. Pat. No. 4,448,529 A [0132] GB 814 072 A [0133] U.S. Pat. No. 5,818,049 A [0134] U.S. Pat. No. 3,417,253 A