MODULATION OF A MOVABLE IR EMITTER THROUGH A DIAPHRAGM STRUCTURE

Abstract

The invention relates to a modulatable infrared emitter comprising an aperture structure, a structured micro-heating element, and an actuator, wherein the aperture structure and the structured micro-heating element are movable relative to each other in parallel planes by means of the actuator to modulate the intensity of emitted infrared radiation. The invention further relates to methods of manufacturing the infrared emitter, a method of modulating emission of infrared radiation using the infrared emitter, and preferred uses of the infrared emitter. In further aspects the invention relates to a system comprising the infrared emitter and a control device for regulating the actuator.

Claims

1. Modulatable infrared emitter comprising an aperture structure, a structured micro-heating element and an actuator, wherein the micro-heating element exhibits in a first plane heatable and non-heatable regions, the aperture structure exhibits in a second plane transmissive regions and non-transmissive regions for infrared radiation, the two planes being parallel to one another, the aperture structure and the micro-heating element are movable in the parallel planes relative to each other, and the actuator is configured for a relative movement of the aperture structure and the micro-heating element between at least a first and a second position, such that an extinction ratio of at least 2 is achievable for the infrared radiation emittable by the micro-heating element through the aperture structure between the first and second position, wherein in the first position the IR radiation emittable by the heatable regions is predominantly absorbed and/or reflected by the non-transmissive regions of the aperture structure, while in the second position the IR radiation emittable by the heatable regions predominantly radiates through the transmissive regions of the aperture structure.

2. Modulatable infrared emitter according to claim 1, wherein the actuator is coupled to the heating element and is configured for translational movement of the heating element relative to the aperture structure, or the actuator is coupled to the aperture structure and is configured for translational movement of the aperture structure relative to the heating element.

3. Modulatable infrared emitter according to claim 1, wherein the infrared emitter comprises a housing in which the aperture structure, the micro-heating element and the actuator are installed,

4. Modulatable infrared emitter according to claim 1, wherein the micro-heating element comprises a substrate on which at least partially a heatable layer of a conductive material is deposited, on which contacts for a current and/or voltage source are present.

5. Modulatable infrared emitter according to claim 1, wherein the micro-heating element comprises a lamellar structure, a meander structure and/or a grid structure

6. Modulatable infrared emitter according to claim 1, wherein the actuator is a MEMS actuator,

7. Modulatable infrared emitter according to claim 1, wherein the non-transmissive regions of the aperture structure exhibit a transmittance of less than 0.1 in a wavelength range within 780 nm to 1 mm and the transmissive regions of the aperture structure exhibit a transmittance of more than 0.9.

8. Manufacturing method for an infrared emitter according to claim 1, wherein the manufacture of the micro-heating element comprises the following steps: etching of the substrate; deposition of a conductive material on the substrate; optionally, patterning the conductive material to form a heatable layer; and contacting the conductive material.

9. Manufacturing method according to claim 8, wherein etching and/or patterning is selected from the group consisting of dry etching, wet chemical etching, plasma etching, reactive ion etching, and reactive ion deep etching (Bosch process); or the deposition is selected from the group consisting of physical vapor deposition (PVD), thermal evaporation, laser beam evaporation, arc evaporation, molecular beam epitaxy, sputtering, chemical vapor deposition (CVD) and atomic layer deposition (ALD).

10. A system comprising: a) a modulatable infrared emitter according to claim 1, and b) a control device, wherein the control device is configured for regulating the actuator for relative movement of the heating element and the aperture structure between a first and a second position.

11. System according to claim 10, wherein the control device is configured to regulate the temperature of the heatable regions of the micro-heating element,

12. Method for a modulated emission of infrared radiation comprising: providing a modulatable infrared emitter according to claim 1; heating the heatable regions of the micro-heating element to emit an infrared radiation; and controlling the actuator for relative movement of the aperture structure and the micro-heating element between at least a first position and a second position to modulate the radiant power of the emitted infrared radiation.

13. A method of performing photoacoustic spectroscopy and/or infrared spectroscopy comprising using a modulatable infrared emitter according to claim 1.

14. Photoacoustic spectroscope for the analysis of gas, comprising: a modulatable infrared emitter according to claim 1, an analysis volume fillable with gas, and an acoustic detector, wherein the analysis volume is positioned between the infrared emitter and the acoustic detector so that the infrared radiation modulatably emitted by the infrared emitter can be used for photoacoustic spectroscopy of the gas.

15. Modulatable infrared emitter according to claim 1, wherein the infrared emitter comprises a housing in which the aperture structure, the micro-heating element and the actuator are present installed, wherein the aperture structure is thermally decoupled from the housing or wherein the housing comprises a cover element in which the aperture structure is present fixated and at least one optical filter is additionally installed in the cover element.

16. Modulatable infrared emitter according to claim 1, wherein with respect to the possible relative movement between the micro-heating element and the aperture structure, in the first plane the heatable regions and non-heatable regions of the micro-heating element and in the second plane the transmissive regions and non-transmissive regions of the aperture structure are arranged periodically.

17. Modulatable infrared emitter according to claim 1, the actuator is a MEMS actuator selected from the group comprising electrostatic actuator, piezoelectric actuator, electromagnetic actuator.

18. Modulatable infrared emitter according to claim 1, the actuator is an electrostatic MEMS actuator in the form of a comb drive based on a variation of the comb overlap and/or the comb spacing.

19. System according to claim 10 wherein the control device is configured to regulate the actuator for an oscillating relative movement of the heating element and the aperture structure, wherein during a period of the oscillation at least a first and a second position are passed,

20. System according to claim 10 wherein the control device is configured to regulate the actuator for an oscillating relative movement of the heating element and the aperture structure such that a modulation frequency of the radiant power of the emitted infrared radiation between 10 Hz and 100 kHz is achieved.

Description

SHORT DESCRIPTION OF THE IMAGES

[0175] FIG. 1 shows a schematic diagram of the IR emitter.

[0176] FIG. 2 shows a schematic representation of the IR emitter during a translation period of the heating element to modulate the IR beam at time T=0.

[0177] FIG. 3 shows a schematic representation of the IR emitter during a translation period of the heating element to modulate the IR beam at time T=¼.

[0178] FIG. 4 shows a schematic representation of the IR emitter during a translation period of the heating element to modulate the IR beam at time T= 2/4.

[0179] FIG. 5 shows a schematic representation of the IR emitter during a translation period of the heating element to modulate the IR beam at time T=¾.

[0180] FIG. 6 shows a schematic representation of the IR emitter during a translation period of the heating element to modulate the IR beam at time T=1.

DETAILED DESCRIPTION OF THE IMAGE

[0181] FIG. 1 shows a schematic cross-sectional view of the modulatable infrared emitter 1. The IR emitter is accommodated in a housing 18, which consists of a lower support 19, side parts 23 and a cover element 21. Sealing elements 25 may be present between the support 19, cover element 21 and side parts 23, respectively. These sealing elements 21 are used to reduce thermal exchange of the interior of the emitter 1, in which the micro-heating element 5 is present, with the external environment of the IR emitter 1. The cover element 21 comprises an applied aperture structure 3 at the top. The structured micro-heating element 5 within the housing 18 comprises individual, parallel heating lamellae 17. The surfaces of the heating lamellae 17 oriented in the direction of the aperture structure 3 represent heatable regions 9 in a first plane 10. Along said first plane 10, periodically arranged non-heatable regions 11 are located between the periodically arranged heatable regions 9. The aperture structure is arranged along a second plane 12, which is parallel to the first plane 10 and consists of regions 13 which are transmissive (transparent) to infrared radiation and regions 15 which are non-transmissive (opaque). These are also arranged periodically and have the same period. The relative movement between the heating element 5 and the aperture structure 3 is realized by an actuator 7 in the form of a comb drive, which is directly coupled to the micro-heating element 5. The actuator 7 is in turn attached to a side part 23 of the housing 18. The micro-heating element 5 is free-standing except for the connection to the actuator 7.

[0182] The number of non-transmissive regions 15 of the aperture structure 3 is equal to the number of heatable regions 9 of the micro-heating element 5. The width of the non-transmissive regions 15 is slightly wider than that of the heatable regions 9 so that their IR radiation is substantially blocked when the heatable regions 9 are positioned in a first position directly below the non-transmissive regions 15 by means of the actuator 7. In said first position, the radiation emitted from the IR emitter 1 exhibits a minimum intensity. By moving the heatable regions 9 to a second position (not shown) below the transmissive regions 13 of the aperture structure 3, a maximum intensity of the emitted beam can be set. In this case, the regions are designed in such a way that an extinction ratio between the intensity of the radiation emitted in the first position and the intensity of the radiation emitted in the second position of at least 2 is achieved.

[0183] FIG. 2 shows the modulatable infrared emitter 1 of FIG. 1 during a translation period, at time T=0, at the beginning of the period. Here, all heatable regions 9 of the micro-heating element 5, which is directly coupled to the actuator 7, are positioned by the latter in a first position directly below the non-transmissive (opaque) regions 15 of the aperture structure 3. In this case, the unmodulated radiation 29 emitted by the heatable regions 9 is substantially absorbed and/or reflected by the non-transmissive regions 15 and the emitted intensity of the IR beam is minimal. In the embodiment shown, a lens 27 is present on the emitter above the aperture structure 3 and used to collimate the modulated infrared beam.

[0184] FIG. 3 shows the modulatable infrared emitter 1 during the translation period at time T=¼, after one quarter of the period length. Here, all heatable regions 9 of the micro-heating element 5 are positioned by the actuator 7 in a second position directly below the transmissive regions 13 of the aperture structure 3. The translational movement of the micro-heating element 5 by the actuator 7 proceeds to the right. Thereby, the unmodulated radiation 29 essentially radiates through the transmissive regions 13 and the emitted intensity of the IR beam is maximal.

[0185] FIG. 4 is a representation of the modulatable infrared emitter 1 during the translation period at time T= 2/4, after half of the full period duration. The micro-heating element 5 has been translated back to the initial position to the left. As at time T=0 in FIG. 2, all heatable regions 9 of the micro-heating element 5 are positioned by the actuator 7 in the (same) first position directly below the non-transmissive regions 15 of the aperture structure 3 and the unmodulated radiation 29 is substantially absorbed and/or reflected. The emitted intensity of the IR beam is again minimal.

[0186] FIG. 5 shows the modulatable infrared emitter 1 during the translation period at time T=¾, after three quarters of the period length has passed. The heatable regions 9 of the micro-heating element 5 have been translated further to the left by the actuator 7 to another second position directly below the transmissive regions 13 of the aperture structure 3. The unmodulated radiation 29 now again radiates essentially through the transmissive regions 13, and the emitted intensity of the IR beam is again at a maximum.

[0187] In FIG. 6, at the end of the translation period, the modulatable infrared emitter 1 has translated back to the right, to the starting point of the movement. The heatable regions 9 are again in the first position, just below the non-transmissive regions 15. The unmodulated radiation 29 is essentially absorbed and/or reflected and the intensity of the IR beam is minimal. Now a new translation period can start anew with the same sequence. The end time of the shown period coincides with the start time of the following period.

[0188] In a traversed translation period, as shown in FIGS. 3-6, the first position was passed twice and two different second positions passed once. The end point of the period is assigned to the next period, whose starting point it represents. Thus, the intensity was twice minimum and maximum within one translation period. At a translation frequency of f, the IR beam is thus modulated with an average frequency of about 2.Math.f.

[0189] It is noted that various alternatives to the described embodiments of the invention may be used to carry out the invention and arrive at the solution according to the invention. Thus, the infrared emitter according to the invention, the system, and methods and uses thereof are not limited in their embodiments to the foregoing preferred embodiments. Rather, a multitude of embodiments is conceivable, which may deviate from the solution presented. The aim of the claims is to define the scope of protection of the invention. The scope of protection of the claims is directed to covering the infrared emitter according to the invention, the system, methods of their use as well as equivalent embodiments thereof.

LIST OF REFERENCE SIGNS

[0190] 1 modulating infrared emitter [0191] 3 aperture structure [0192] 5 structured micro-heating element [0193] 7 actuator [0194] 9 heatable regions [0195] 10 first state [0196] 11 non-heatable regions [0197] 12 second state [0198] 13 transmissive (transparent) regions [0199] 15 non-transmissive (opaque) regions [0200] 17 heating lamella [0201] 18 housing [0202] 19 support [0203] 21 cover element [0204] 23 side parts [0205] 25 sealing elements [0206] 27 lens [0207] 29 unmodulated radiation