RADIATION SENSING APPARATUS AND METHOD OF SENSING RADIATION CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority of U.S. provisional patent application 63/357,071, filed June 30, 2022, the disclosure content of which is hereby incorporated by reference.

FIELD OF THE INVENTION

A radiation sensing apparatus and a method of sensing radiation are provided.

BACKGROUND OF THE INVENTION

For sensing and detecting thermal radiation an array of mirrors can be employed that is sensitive to the intensity of impinging thermal radiation. The resolution of sensing thermal radiation from a distinct area or volume can be improved by increasing the number of mirrors or by decreasing the size of the mirrors. However, both might not be feasible since an increase of the number of mirrors leads to an increase of the size of the whole device which might not be desired. On the other hand, decreasing the size of the mirrors has technical limits.

SUMMARY OF THE INVENTION

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus comprises a radiation source. The radiation source can be configured to emit electromagnetic radiation. The radiation source can comprise a light emitting diode. The radiation source can be configured to emit electromagnetic radiation within a wavelength range.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus comprises an optical element. The optical element can be configured to deflect electromagnetic radiation. This can mean, that the optical element is configured to change a main propagation direction of electromagnetic radiation impinging on the optical element. The optical element can be translucent for electromagnetic radiation emitted by the radiation source. The optical element can face the radiation source. This can mean, that at least a part of the electromagnetic radiation emitted by the radiation source propagates towards the optical element. The optical element can be arranged within a main propagation path of electromagnetic radiation emitted by the radiation source. The radiation source can comprise a further optical element. The radiation source with the further optical element can be configured to emit focused, dispersed, or patterned light.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus comprises an array of mirrors that are arranged on a carrier. The array of mirrors can be a two-dimensional array. The mirrors can be arranged within the array in a regular way. For example, the mirrors are arranged at nodes of a two-dimensional lattice, for example a square lattice or a rectangular lattice. This can mean, that each mirror is arranged at one node of a two- dimensional lattice, respectively. Each mirror can have a first surface that faces the optical element. Each mirror can have a second surface that faces away from the optical element. At the first surface each mirror can have a reflection coefficient of at least 0.4. For each mirror, at the second surface a material that is configured to absorb thermal radiation can be arranged. The carrier can have a main plane of extension. The carrier can comprise a material that is translucent.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus comprises an actuator that is connected with the carrier. The actuator can be a device that is configured to move a device connected with the actuator. The actuator can be configured to move the carrier. The carrier can be fixed to the actuator. The actuator can be configured to move the carrier spatially. The actuator can be configured to move the carrier relative to the optical element. The actuator can be configured to move the carrier relative to the radiation source. The actuator can be a controllable device. This can mean that the actuator is configured to move the carrier in a controllable way. The actuator can be arranged next to or adjacent to the carrier in at least one lateral direction, wherein the lateral direction extends parallel to the main plane of extension of the carrier.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus comprises a radiation sensor. The radiation sensor can be configured to detect electromagnetic radiation. The radiation sensor can be configured to detect electromagnetic radiation emitted by the radiation source. The radiation sensor can be configured to detect electromagnetic radiation within a wavelength range. The optical element can be arranged between the array of mirrors and the radiation sensor. The radiation sensor can have a main plane of extension that extends parallel to the main plane of extension of the carrier.

According to at least one embodiment of the radiation sensing apparatus the optical element is configured to direct electromagnetic radiation emitted by the radiation source towards the array of mirrors. For directing electromagnetic radiation emitted by the radiation source towards the array of mirrors, the optical element can change a main propagation direction of electromagnetic radiation emitted by the radiation source. The optical element can be configured to change the main propagation direction of electromagnetic radiation emitted by the radiation source by at least 80° and at most 100°. The optical element can be configured to change the main propagation direction of electromagnetic radiation emitted by the radiation source by 90°. For this purpose, the optical element can comprise a deflection surface that encloses an angle of at least 30° and at most 60° with the main plane of extension of the carrier. The deflection surface can enclose an angle of 45° with the main plane of extension of the carrier. At the deflection surface the optical element can have a reflectivity of at least 0.2 or at least 0.4. Thus, the optical element can be configured to reflect electromagnetic radiation emitted by the radiation source towards the array of mirrors.

According to at least one embodiment of the radiation sensing apparatus the radiation sensor is configured to detect electromagnetic radiation reflected by the array of mirrors. At least a part of the electromagnetic radiation reaching the array of mirrors is reflected at the mirrors. The radiation sensor can face the array of mirrors. This can mean, that the main plane of extension of the radiation source extends parallel to the main plane of extension of the carrier. The radiation sensor and the carrier can have a connecting axis that extends from the carrier to the radiation sensor, wherein the connecting axis extends perpendicular to the main plane of extension of the radiation source. The connecting axis is an imaginary axis. Due to this arrangement, electromagnetic radiation that is reflected at the mirrors propagates in the direction of the radiation sensor. In this way, the radiation sensor can detect electromagnetic radiation reflected by the array of mirrors.

The radiation sensing apparatus can be employed to detect thermal radiation. For this purpose, thermal radiation can be provided at a side of the array of mirrors facing away from the optical element. At this side, the mirrors are sensitive to thermal radiation. This can mean, that the mirrors can absorb thermal radiation. Due to the absorption of the thermal radiation, the mirrors can bend or be deflected. The bending or deflection of the mirrors can be detected by the radiation sensor. For this purpose, electromagnetic radiation is emitted by the radiation source and directed towards the side of the mirrors facing the optical element. This electromagnetic radiation is at least partially reflected at the mirrors towards the radiation sensor. A bending or deflection of the mirrors can be detected by the change in the pattern that is detected by the radiation sensor.

The thermal radiation can be provided at a first frame rate. The radiation sensor can detect electromagnetic radiation at a second frame rate which can be significantly higher than the first frame rate. The difference between the first frame rate and the second frame rate is employed in the radiation sensing apparatus for improving the spatial resolution of sensing thermal radiation. For this purpose, the actuator changes the position of the carrier at least once during one period of the first frame rate. It is also possible that the actuator changes the position of the carrier several times during one period of the first frame rate. For each change of the position of the carrier, for each mirror the region from which it receives thermal radiation changes. This can mean that for each different position of the carrier each mirror receives thermal radiation from a different area or volume. The different areas or volumes can overlap. If the intensity of thermal radiation changes for different areas or volumes, the bending of the mirrors changes. Thus, also the pattern detected by the radiation sensor changes. In this way, the spatial resolution of detecting thermal radiation can be improved.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus further comprises an aperture that is arranged adjacent to a surrounding of the radiation sensing apparatus. The aperture can connect the surrounding of the radiation sensing apparatus with an inside of the radiation sensing apparatus. The aperture can be arranged at an outer side of the radiation sensing apparatus. The aperture can face the array of mirrors. The aperture can face the side of the array of mirrors facing away from the optical element. Via the aperture thermal radiation can reach the array of mirrors. In this way, the thermal radiation can be sensed by the radiation sensing apparatus. The thermal radiation can originate from an area or a volume that is to be observed. According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus further comprises a lens arranged between the aperture and the array of mirrors. The lens can be configured to direct thermal radiation entering the radiation sensing apparatus through the aperture towards the array of mirrors. In this way, the thermal radiation can be sensed.

According to at least one embodiment of the radiation sensing apparatus the actuator comprises a piezoelectric element. The piezoelectric element can comprise a piezoelectric material. This has the advantage that by applying a voltage to the piezoelectric element the actuator can move the carrier.

According to at least one embodiment of the radiation sensing apparatus the actuator is configured to move the carrier along at least one axis. The actuator can be configured to move the carrier in two opposite directions along the at least one axis. This can mean that the actuator can be configured to move the carrier in two opposite directions that extend parallel to the at least one axis. For each point in time, the actuator can be configured to move the carrier in one of the two opposite directions. Since the array of mirrors is arranged on the carrier, with this a movement of the array of mirrors along the at least one axis is enabled. Each mirror can have an extension along the least one axis. The actuator can be configured to move the carrier by less than the extension of one mirror along the at least one axis. The actuator can be configured to move the carrier several steps along the at least one axis. The extension of each of the steps can be smaller than the extension of one mirror along the at least one axis. The actuator can be configured to move the carrier by a maximum distance along the at least one axis. The maximum distance can be smaller than the extension of one mirror along the at least one axis. The movement of the carrier with the array of mirrors along the at least one axis allows to increase the resolution of sensing thermal radiation along the at least one axis.

According to at least one embodiment of the radiation sensing apparatus the actuator is configured to move the carrier along at least two axes that extend perpendicular to each other. The actuator can be configured to move the carrier in two opposite directions along each of the at least two axes. The actuator can thus move the carrier in four different directions within a plane. Each mirror can have an extension along each of the at least two axes. For each axis, the actuator can be configured to move the carrier by less than the extension of one mirror along the respective axis. For each axis, the actuator can be configured to move the carrier several steps along the respective axis. The extension of each of the steps can be smaller than the extension of one mirror along the respective axis. The actuator can be configured to move the carrier by a maximum distance along the respective axis. The maximum distance can be smaller than the extension of one mirror along the respective axis. Since the array of mirrors is arranged on the carrier, with this a movement of the array of mirrors along the at least two axes is enabled. Therefore, the resolution of sensing thermal radiation can be improved along the at least two axes.

According to at least one embodiment of the radiation sensing apparatus the two axes each extend parallel to a main plane of extension of the carrier. This means, the mirrors can be moved by the actuator within the main plane of extension of the carrier. This enables to improve the spatial resolution of the pattern of the electromagnetic radiation detected by the radiation sensor, since the main plane of extension of the radiation sensor extends parallel to the main plane of extension of the carrier.

According to at least one embodiment of the radiation sensing apparatus each mirror comprises a first layer comprising a metal and a second layer comprising a metal that is different from the metal of the first layer. The following can be true for at least one of the mirrors, several of the mirrors or each of the mirrors. The first layer and the second layer can each extend parallel to the main plane of extension of the carrier. The first layer can be arranged at the side of the mirror facing the optical element. The second layer can be arranged at the side of the mirror facing the aperture. The first layer can be arranged at the first side of the mirror. The second layer can be arranged at the second side of the mirror. The first layer can have a reflection coefficient of at least 0.4 or at least 0.6. The second layer can be configured to absorb thermal radiation. In this way, the mirrors can be employed in the radiation sensing apparatus for sensing thermal radiation.

According to at least one embodiment of the radiation sensing apparatus the radiation source is configured to emit electromagnetic radiation of at least two different wavelengths. The radiation source can be configured to emit electromagnetic radiation of a first wavelength and electromagnetic radiation of a second wavelength, wherein the first wavelength is different from the second wavelength. It is also possible that the radiation source is configured to emit electromagnetic radiation of a first wavelength range and of a second wavelength range, wherein the first wavelength range is different from the second wavelength range. The radiation source can for example be configured to emit electromagnetic radiation of different colors. The different wavelengths of the electromagnetic radiation emitted by the radiation source can be employed to differentiate between different spatial positions of the carrier. For this purpose, the wavelength of electromagnetic radiation emitted by the radiation source can be changed at the same time as the position of the carrier is changed.

According to at least one embodiment of the radiation sensing apparatus the radiation sensor is configured to detect electromagnetic radiation of at least two different wavelengths. The radiation sensor can be sensitive to at least two different wavelengths. The radiation sensor can be configured to detect electromagnetic radiation of the first wavelength and of the second wavelength. The radiation sensor can be configured to detect electromagnetic radiation of the first wavelength range and of the second wavelength range. In this way, the radiation sensor can be configured to detect electromagnetic radiation emitted by the radiation source. Furthermore, with the different wavelengths detected by the radiation sensor it can be differentiated between different spatial positions of the carrier.

According to at least one embodiment of the radiation sensing apparatus the optical element comprises a beamsplitter that is arranged between the array of mirrors and the radiation sensor, wherein the beamsplitter comprises a beam splitting element that is translucent and has a reflection coefficient of larger than 0. The beamsplitter can be translucent and can have a reflection coefficient of at least 0.2 or at least 0.4. The beamsplitter can be translucent and can have a reflection coefficient of at least 0.2 or at least 0.4 for electromagnetic radiation emitted by the radiation source. The beamsplitter enables that electromagnetic radiation emitted by the radiation source is directed towards the array of mirrors.

The radiation sensor can be arranged on a printed circuit board (PCB). The beamsplitter can be arranged on the radiation sensor. The array of mirrors can be arranged on the beamsplitter. The beamsplitter can be translucent for electromagnetic radiation reflected at the array of mirrors. In this way, electromagnetic radiation reflected at the array of mirrors can reach the radiation sensor.

The beam splitting element can have a reflection coefficient of at least 0.2 or at least 0.4. The beam splitting element can have a reflection coefficient of larger than 0, for example at least 0.2 or at least 0.4, for electromagnetic radiation emitted by the radiation source. The beam splitting element can comprise a layer that comprises a metal. Since the beam splitting element is translucent and has a reflection coefficient of larger than 0, a part of electromagnetic radiation reaching the beam splitting element is reflected at the beam splitting element and another part of electromagnetic radiation reaching the beam splitting element is transmitted by the beam splitting element. With this, the beam splitting element enables that electromagnetic radiation emitted by the radiation source is reflected at the beam splitting towards the array of mirrors. Furthermore, electromagnetic radiation reflected at the array of mirrors can propagate through the beam splitting element towards the radiation sensor. According to at least one embodiment of the radiation sensing apparatus the beam splitting element has a main plane of extension that encloses an angle of more than 0 degrees with a main plane of extension of the radiation sensor. The main plane of extension of the beam splitting element can enclose an angle of at least 30° and at most 60° with the main plane of extension of the radiation sensor. The main plane of extension of the beam splitting element can enclose an angle of 45° with the main plane of extension of the radiation sensor. With this, the beam splitting element enables that electromagnetic radiation emitted by the radiation source is reflected at the beam splitting element towards the array of mirrors. Furthermore, electromagnetic radiation reflected at the array of mirrors can propagate through the beam splitting element towards the radiation sensor.

According to at least one embodiment of the radiation sensing apparatus the beam splitting element has a main plane of extension that encloses an angle of more than 0 degrees with a main plane of extension of the carrier. The main plane of extension of the beam splitting element can enclose an angle of at least 30° and at most 60° with the main plane of extension of the carrier. The main plane of extension of the beam splitting element can enclose an angle of 45° with the main plane of extension of the carrier. With this, the beam splitting element enables that electromagnetic radiation emitted by the radiation source is reflected at the beam splitting element towards the array of mirrors. Furthermore, electromagnetic radiation reflected at the array of mirrors can propagate through the beam splitting element towards the radiation sensor. According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus further comprises a control unit that is configured to control the radiation source and the actuator in a synchronized way. The control unit can be configured to control the emission of electromagnetic radiation of the radiation source. For example, the control unit is configured to control the wavelength of electromagnetic radiation emitted by the radiation source. The control unit can be configured to control a pulse duration of electromagnetic radiation emitted by the radiation source. The control unit can be configured to control the actuator. This can mean, that the control unit is configured to control how far the actuator moves the carrier. The control unit can be configured to control in which direction the actuator moves the carrier. That the control unit is configured to control the radiation source and the actuator in a synchronized way can mean, that the control unit can be configured to control the radiation source and the actuator at the same time. For example, the control unit is configured to control the radiation source in such a way that the wavelength of electromagnetic radiation emitted by the radiation source is changed at the same time as the actuator moves the position of the carrier. The control unit can thus control the radiation source to change the wavelength of electromagnetic radiation emitted by the radiation source and the control unit can control the actuator to move the position of the carrier at the same time as the control unit controls the radiation source to change the wavelength of electromagnetic radiation emitted by the radiation source. This has the advantage that for different positions of the carrier, the mirrors are illuminated by electromagnetic radiation of different wavelengths by the radiation source. In this way, by detecting the electromagnetic radiation of different wavelengths by the radiation sensor, it can be differentiated between different spatial positions of the carrier. Thus, the spatial resolution of sensing thermal radiation can be increased.

According to at least one embodiment of the radiation sensing apparatus, the radiation sensing apparatus further comprises a processing chip that is connected with the control unit and the radiation sensor. The processing chip can be configured to process data received from the control unit and the radiation sensor. The control unit can provide data about controlling the emission of electromagnetic radiation by the radiation source to the processing chip. The control unit can provide data about controlling the movement of the carrier by the actuator to the processing chip. The radiation sensor can provide data about electromagnetic radiation detected by the radiation sensor to the processing chip. The processing chip can be configured to determine a spatial distribution of the intensity of thermal radiation within the area or volume that is exposed to the aperture. For this, the processing chip takes into account to which spatial positions the carrier is moved by the actuator. The processing chip can also take into account the wavelength of electromagnetic radiation emitted by the radiation source. The processing chip further takes into account the distribution of electromagnetic radiation detected by the radiation sensor. Since the carrier can be moved to different positions during one exposure time frame of the thermal radiation, the spatial distribution of thermal radiation can be sensed with an increased resolution.

Furthermore, a method of sensing radiation is provided. The radiation sensing apparatus can preferably be employed for the method of sensing radiation described herein. This means all features disclosed for the radiation sensing apparatus are also disclosed for the method of sensing radiation and vice-versa.

According to at least one embodiment of the method of sensing radiation, the method comprises exposing a radiation sensing apparatus to thermal radiation. The radiation sensing apparatus can comprise an aperture that is exposed to the thermal radiation. The aperture can be an opening in the radiation sensing apparatus. The thermal radiation can be thermal radiation originating from an area or a volume to be observed. The radiation sensing apparatus can be exposed to thermal radiation at an exposure rate.

According to at least one embodiment of the method of sensing radiation, the method comprises emitting electromagnetic radiation by a radiation source of the radiation sensing apparatus. The radiation source can emit electromagnetic radiation at the same time as the radiation sensing apparatus is exposed to thermal radiation.

According to at least one embodiment of the method of sensing radiation, the method comprises directing electromagnetic radiation emitted by the radiation source towards an array of mirrors of the radiation sensing apparatus by an optical element of the radiation sensing apparatus, wherein the array of mirrors is arranged on a carrier and an actuator is connected with the carrier. This can mean, that electromagnetic radiation emitted by the radiation source is directed towards the array of mirrors by the optical element. The first sides of the mirrors can face the optical element. Thus, electromagnetic radiation emitted by the radiation source can be directed towards the first sides of the mirrors by the optical element. The second sides of the mirrors can face the aperture.

According to at least one embodiment of the method of sensing radiation, the method comprises detecting electromagnetic radiation reflected by the array of mirrors with a radiation sensor of the radiation sensing apparatus. This can mean, that electromagnetic radiation emitted by the radiation source, deflected by the optical element and reflected by the mirrors can be detected by the radiation sensor.

According to at least one embodiment of the method of sensing radiation, the method comprises moving the carrier along at least one direction by the actuator. The at least one direction can extend parallel to the main plane of extension of the carrier. The actuator can move the carrier at least once during one period of the exposure rate of thermal radiation. It is also possible that the actuator moves the carrier several times during one period of the exposure rate of thermal radiation. The actuator can move the carrier several steps along the at least one direction. The actuator can move the carrier at a constant rate. This can mean, that the actuator moves the carrier at points in time that are equally spaced from each other. The actuator can move the carrier at least twice by the same distance. It is also possible that the actuator moves the carrier several times by the same distance. The actuator can move the carrier along at least two axes that extend perpendicular to each other. The two axes can extend parallel to the main plane of extension of the carrier. Thus, the carrier can be moved within a two- dimensional space. The method of sensing radiation enables to sense thermal radiation with an increased resolution. For this purpose, the carrier is moved by the actuator to different positions during one period of the exposure rate of thermal radiation.

According to at least one embodiment of the method of sensing radiation a change of a wavelength of electromagnetic radiation emitted by the radiation source is synchronized with a movement of the carrier along the at least one direction by the actuator. This can mean, that the wavelength of electromagnetic radiation emitted by the radiation source is changed at the same time as the carrier is moved along the at least one direction by the actuator. This enables to differentiate the different spatial positions of the carrier since the radiation sensor detects electromagnetic radiation of different wavelengths for different spatial positions of the carrier.

According to at least one embodiment of the method of sensing radiation a side of the mirrors facing away from the optical element is exposed to the thermal radiation. The side of the mirrors facing away from the optical element can face the aperture. It is also possible that thermal radiation entering the radiation sensing apparatus through the aperture is directed towards the side of the mirrors facing away from the optical element. The mirrors can absorb thermal radiation at the sides that are exposed to thermal radiation. This can lead to a bending of the mirrors depending on the intensity of absorbed radiation. The bending of the mirrors can be observed by detecting the change of the pattern of electromagnetic radiation reflected at the sides of the mirrors facing the optical element. In this way, thermal radiation can be sensed. According to at least one embodiment of the method of sensing radiation an exposure rate of the thermal radiation is lower than a rate at which the carrier is moved by the actuator. This can mean, that the exposure rate of the thermal radiation is smaller than the rate at which the carrier is moved by the actuator. That the radiation sensing apparatus is exposed to the thermal radiation at the exposure rate can mean that the intensity and distribution of the thermal radiation that the mirrors are exposed to does not change within one period of the exposure rate. The rate at which the radiation sensor detects electromagnetic radiation can be at least as high as the rate at which the carrier is moved by the actuator. In this way, during one period of the exposure rate of thermal radiation, the radiation sensor is oversampled. During one period of the exposure rate of thermal radiation the radiation sensor can detect electromagnetic radiation reflected at the mirrors for different positions of the carrier and thus the mirrors. This means, during one period of the exposure rate of thermal radiation the area or volume to be observed is scanned with a higher resolution than it is possible without the movement of the carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description of figures may further illustrate and explain exemplary embodiments. Components that are functionally identical or have an identical effect are denoted by identical references. Identical or effectively identical components might be described only with respect to the figures where they occur first. Their description is not necessarily repeated in successive figures. Figure 1 shows an exemplary embodiment of the radiation sensing apparatus.

Figure 2 shows a top view on an array of mirrors.

Figure 3 shows a side view on a mirror.

DETAILED DESCRIPTION

In figure 1 an exemplary embodiment of the radiation sensing apparatus 20 is shown. The radiation sensing apparatus 20 comprises a radiation source 21. The radiation source 21 is configured to emit electromagnetic radiation. As an example, figure 1 shows that the radiation source 21 is configured to emit electromagnetic radiation of three different wavelengths. The radiation source 21 is configured to emit electromagnetic radiation in the direction of an optical element 22 of the radiation sensing apparatus 20. The optical element 22 is configured to change the main propagation direction of electromagnetic radiation reaching the optical element 22 by 90°. Thus, the main propagation direction of electromagnetic radiation emitted by the radiation source 21 and impinging on the optical element 22 is changed by 90° by the optical element 22. In figure 1, this means that electromagnetic radiation leaves the optical element 22 to the left side of figure 1. For changing the main propagation direction of electromagnetic radiation the optical element 22 can comprise a beamsplitter 33 that comprises a beam splitting element 34 that is translucent and has a reflection coefficient of larger than 0. The beam splitting element 34 can be embedded in a translucent or a transparent material. The radiation sensing apparatus 20 further comprises an array of mirrors 23 that are arranged on a carrier 24. The array of mirrors 23 faces the optical element 22. The optical element 22 is configured to direct electromagnetic radiation emitted by the radiation source 21 towards the array of mirrors 23. Thus, electromagnetic radiation whose main propagation direction is changed by 90° by the optical element 22 leaves the optical element 22 towards the array of mirrors 23. The radiation sensing apparatus 20 further comprises an actuator 25 that is connected with the carrier 24 on which the array of mirrors 23 is arranged. The actuator 25 can be translucent for electromagnetic radiation or different from what is shown in figure 1 it is possible that the actuator 25 is arranged adjacent to the carrier 24 in a lateral direction, wherein the lateral direction extends parallel to a main plane of extension of the carrier 24.

The actuator 25 can comprise a piezoelectric element. The actuator 25 can be configured to move the carrier 24 along at least one axis or along at least two axes that extend perpendicular to each other, wherein the two axes each extend parallel to the main plane of extension of the carrier 24.

Each mirror 23 comprises a first layer 29 comprising a metal and a second layer 30 comprising a metal that is different from the metal of the first layer 29. For each mirror 23 the first layer 29 is arranged at a first side 31 of the mirror 23. For each mirror 23 the second layer 30 is arranged at a second side 32 of the mirror 23. For each mirror 23 the first side 31 faces the optical element 22. For each mirror 23 the second side 32 faces away from the optical element 22. The radiation sensing apparatus 20 further comprises a radiation sensor 26. The radiation sensor 26 is configured to detect electromagnetic radiation reflected by the array of mirrors 23. In particular, the radiation sensor 26 is configured to detect electromagnetic radiation reflected at the first sides 31 of the mirrors 23. The optical element 22 is arranged between the array of mirrors 23 and the radiation sensor 26. The radiation sensor 26 can be arranged on a printed circuit board or another type of carrier. The radiation source 21 can also be arranged on the printed circuit board or other type of carrier. The radiation sensor 26 can be configured to detect electromagnetic radiation of at least two different wavelengths, for example three different wavelengths.

The beamsplitter 33 can be arranged between the array of mirrors 23 and the radiation sensor 26. The beam splitting element 34 has a main plane of extension that encloses an angle of more than 0 degrees with a main plane of extension of the radiation sensor 26. For example, the beam splitting element 34 has a main plane of extension that encloses an angle of 45° with the main plane of extension of the radiation sensor 26.

The radiation sensing apparatus 20 further comprises an aperture 27 that is arranged adjacent to a surrounding of the radiation sensing apparatus 20. The radiation sensing apparatus 20 further comprises a lens 28 arranged between the aperture 27 and the array of mirrors 23. Via the lens 28 thermal radiation from the surrounding of the radiation sensing apparatus 20 can be directed towards the array of mirrors 23. The radiation sensing apparatus 20 further comprises a control unit 35 that is configured to control the radiation source 21 and the actuator 25 in a synchronized way. The control unit 35 is connected with the radiation source 21 and with the actuator 25. The radiation sensing apparatus 20 further comprises a processing chip 36 that is connected with the control unit 35 and the radiation sensor 26. The processing chip 36 can be arranged on or in the same printed circuit board or carrier as the radiation sensor 26.

With figure 1 also an exemplary embodiment of the method of sensing radiation is described. According to the method the radiation sensing apparatus 20 is exposed to thermal radiation via the aperture 27. This means, thermal radiation is directed towards the second side 32s of the mirrors 23. Thus, a side of the mirrors 23 facing away from the optical element 22 is exposed to the thermal radiation. At the same time the radiation source 21 emits electromagnetic radiation. Electromagnetic radiation emitted by the radiation source 21 is directed towards the array of mirrors 23 by the optical element 22. Electromagnetic radiation reflected by the array of mirrors 23 is detected with the radiation sensor 26.

During the exposure to thermal radiation the carrier 24 is moved along the at least one direction by the actuator 25.

A change of a wavelength of electromagnetic radiation emitted by the radiation source 21 can be synchronized with a movement of the carrier 24 along the at least one direction by the actuator 25. An exposure rate of the thermal radiation is lower than a rate at which the carrier 24 is moved by the actuator 25.

Figure 2 shows a top view on the array of mirrors 23 according to an exemplary embodiment. As an example, 16 mirrors 23 are shown. It is however also possible that the array of mirrors 23 comprises less than 16 or more than 16 mirrors 23. The mirrors 23 are arranged at nodes of a two- dimensional lattice.

Figure 3 shows a side view on one mirror 23 according to an exemplary embodiment. The mirror 23 comprises the first layer 29 and the second layer 30. The first layer 29 is arranged at the first side 31 of the mirror 23 and the second layer 30 is arranged at the second side 32 of the mirror 23. The mirror 23 can be fixed to the carrier 24 via an anchoring structure 37 that is shown at the left side in figure 3. The part of the mirror 23 that is not in direct contact with the anchoring structure 3/ can freely move. In this way, a bending or a deflection of the mirror 23 is possible once the second side 32 is exposed to thermal radiation.

It will be appreciated that the disclosure is not limited to the disclosed embodiments and to what has been particularly shown and described hereinabove. Rather, features recited in separate dependent claims or in the description may advantageously be combined. Furthermore, the scope of the disclosure includes those variations and modifications, which will be apparent to those skilled in the art. The term "comprising", insofar it was used in the claims or in the description, does not exclude other elements or steps of a corresponding feature or procedure. In case that the terms "a" or "an" were used in conjunction with features, they do not exclude a plurality of such features. Moreover, any reference signs in the claims should not be construed as limiting the scope. References

20 radiation sensing apparatus

21 radiation source

22 optical element

23 mirror

24 carrier

25 actuator

26 radiation sensor

27 aperture

28 lens

29 first layer

30 second layer

31 first side

32 second side

33 beamsplitter

34 beam splitting element

35 control unit

36 processing chip

37 anchoring structure