Imaging device and method of operating the same

Abstract

The present invention relates to an imaging device. The imaging device includes a Fabry-Perot interferometer (FPI) element, which includes two at least partially transmissive reflective elements defining an interferometer gap. The gap length of the interferometer gap is variable within at least a first range. The FPI element generates multiple transmission peaks when receiving light, and the peak wavelength of each transmission peak can be changed by changing the gap length of the interferometer gap. The imaging device also includes multiple optical filters, each of which allows light within a different wavelength range to pass, each wavelength range having a different average wavelength. Moreover, the wavelength ranges of the multiple optical filters are selected so that each wavelength range includes at most one peak wavelength at each gap length in the first range.

Description

Technical Field

[0001] The present invention generally relates to the field of imaging devices and, in particular, provides an imaging device and a method for operating an imaging device that can be used for hyperspectral imaging. The imaging device includes a Fabry-Perot interferometer (FPI) element that generates multiple transmission peaks when receiving light. The peak wavelength of each transmission peak can be changed by varying the gap length of the interferometer gap of the FPI element. The imaging device also includes optical filters, each of which allows at most one transmission peak to pass through at each gap length. The imaging device can generate spectral images for the hyperspectral image, and each spectral image can be generated for a specific transmission peak and a specific gap length. Background Art

[0002] Fabry-Perot interferometers (FPIs) can be used to create fixed or tunable narrowband filters (also known as "FPI filters"). However, in addition to the main transmission peak, the FPI's transmission spectrum includes several harmonic transmission peaks. In other words, the FPI generates multiple transmission peaks when receiving light. This makes it challenging to create FPI filters that can be tuned to measure multiple narrow light peaks across a large wavelength range.

[0003] For example, a typical transmission spectrum of an exemplary FPI exhibits harmonic peaks in the visible range of light—that is, it can include a primary peak and a set of harmonic peaks. For example, the primary peak can be located at λ = (2*d), where λ is the wavelength of the peak and d is the gap length of the FPI's interferometer gap. Furthermore, harmonic peaks can be generated at λ(n) = (2*d) / (n), where n is 2, 3, 4, and so on. In other words, the wavelength of each transmission peak of the FPI depends on the gap length of the interferometer gap.

[0004] Because FPI filters inevitably produce harmonic peaks in addition to the main peak, if an image sensor is used to capture light passing through the FPI filter, the measured data may include energy from several different wavelengths (i.e., the energy of the main peak and the energy of one or more harmonic peaks) - this can be a problem, especially for hyperspectral imaging, which requires narrowband spectral images.

[0005] In this regard, there is a general desire in the industry to improve imaging devices based on such FPIs, and to improve methods for operating such imaging devices. Summary of the Invention

[0006] In view of the above problems and shortcomings, embodiments of the present invention are directed to improving conventional imaging devices and methods for operating imaging devices, and in particular, to improving them for use in hyperspectral imaging.

[0007] For example, the goal is to provide an imaging device with a tunable FPI element that can measure multiple narrow light peaks from a wide range of the spectrum (i.e., over a large wavelength range). In particular, the wavelength range of interest is the range of silicon quantum efficiency, specifically from 400 nm to 950 nm, which includes visible and near-infrared electromagnetic radiation. Furthermore, the imaging device should be able to measure light peaks with specific peak widths of approximately 20 nm or even less.

[0008] This and other objects are achieved by embodiments of the present invention as set out in the appended independent claims. Advantageous implementations of the embodiments of the present invention are further defined in the dependent claims.

[0009] A first aspect of the present invention provides an imaging device, comprising an FPI element, the FPI element comprising two at least partially transmissive reflective elements defining an interferometer gap, the gap length of the interferometer gap being variable within at least a first range, the FPI element being configured to generate a plurality of transmission peaks when it receives light, the peak wavelength of each transmission peak being variable by changing the gap length of the interferometer gap; and a plurality of optical filters, each optical filter being configured to allow light within a different wavelength range to pass therethrough, each wavelength range having a different average wavelength, the wavelength ranges of the plurality of optical filters being selected such that each wavelength range includes at most one peak wavelength at each gap length within the first range.

[0010] The imaging device can be an electronic device or can be incorporated into an electronic device, which can include circuitry; the electronic device can be a digital camera, a digital video recorder, a mobile phone, a smartphone, a game station, an augmented reality device, a virtual reality device, a tablet computer or a tablet input device, etc.

[0011] An FPI element can produce multiple transmission peaks, each corresponding to a primary transmission peak or to one of one or more harmonic peaks. For a given interferometer gap length, the FPI element can have a defined transmission spectrum comprising multiple transmission peaks with different peak wavelengths. Furthermore, the transmission spectrum can be altered by varying the interferometer gap length. In particular, varying the interferometer gap length can alter the peak wavelength of each transmission peak (as described above). For example, varying the gap length can shift the peak wavelength of each transmission peak to a larger or smaller wavelength.

[0012] The imaging device also includes a plurality of optical filters, each of which can be based on an optical bandpass filter. Each optical filter passes light within a specific wavelength range having a different average wavelength (i.e., a wavelength range that is different from the average wavelength of the wavelength ranges of the other optical filters). For example, the average wavelength of a wavelength range can be the centroid wavelength of the wavelength range, etc.

[0013] In particular, the multiple optical filters are selected so that each wavelength range includes at most one peak wavelength of the transmission peak at each gap length in the first range. That is, regardless of the gap length of the interferometer gap, at least within the first range, each optical filter passes at most one of the peak wavelengths of the transmission peak. For example, each wavelength range can include exactly one peak wavelength at each gap length in the first range. Thus, the entire wavelength range covered by the FPI element can be divided into a plurality of different wavelength ranges by the optical filters. These wavelength ranges can be non-overlapping.

[0014] With this configuration of the imaging device, the gap length of the interferometer gap can be varied, for example, to scan the entire wavelength range covered by the FPI element, which wavelength range does not have two or more peak wavelengths of transmission peaks within the wavelength range of the optical filter (generated by the FPI element). Consequently, multiple narrow optical peaks (i.e., transmission peaks) can be measured over a large wavelength range, making the imaging device particularly suitable for hyperspectral imaging. At each gap length, each transmission peak can correspond to a spectral image in the hyperspectral image. Therefore, the imaging device can advantageously utilize the harmonic peaks generated by the FPI element for hyperspectral imaging.

[0015] The imaging device may further include circuitry. The circuitry may include hardware and software. The hardware may include analog or digital circuitry, or both. In some embodiments, the circuitry includes one or more processors and non-volatile memory connected to the one or more processors. The non-volatile memory may carry executable program code that, when executed by the one or more processors, may cause the device to perform the operations or methods described herein. For example, execution of the program code by the one or more processors may cause the imaging device to vary the interferometer gap within a first range and, for example, record a hyperspectral image based on spectral images generated for different transmission peaks and / or at different gap lengths within the first range.

[0016] In an implementation form of the first aspect, the wavelength ranges of the plurality of optical filters are selected such that each wavelength range includes exactly one of the peak wavelengths at each gap length of the first range.

[0017] In another implementation form of the first aspect, a wavelength interval is set between each pair of wavelength ranges.

[0018] In another implementation form of the first aspect, wavelength ranges of the plurality of optical filters do not overlap with each other.

[0019] In another implementation form of the first aspect, the wavelength range includes two overlapping wavelength ranges forming an overlapping region, and the overlapping region is:

[0020] - Each of the two overlapping wavelength ranges is less than 10%,

[0021] - preferably less than 5% of each of the two overlapping wavelength ranges,

[0022] - Most preferably, less than 3% of each of the two overlapping wavelength ranges.

[0023] That is, there can be an overlapping region between at least one pair of wavelength ranges, but each overlapping region is small compared to the wavelength ranges.

[0024] In another implementation form of the first aspect, the imaging device further includes an image sensor, wherein a plurality of optical filters are arranged between the image sensor and the FPI element; the image sensor is configured to generate a plurality of spectral images, each spectral image being generated at a specific gap length in a first range for a specific transmission peak generated by the FPI element; and the imaging device is configured to generate a hyperspectral image based on the plurality of spectral images generated for different transmission peaks and / or at different gap lengths in the first range.

[0025] In particular, the imaging device can thus be used to provide a hyperspectral camera. Despite changes in the gap length of the FPI element, at most one (e.g., exactly one) transmission peak remains within each wavelength range of the optical filter at any given time, i.e., at each gap length. At each gap length in the first range, at most one (e.g., exactly one) transmission peak can pass through each of the optical filters and reach an adjacent region of the image sensor. Thus, a hyperspectral image can be generated, which, for each gap length, can be resolved by different transmission peaks at each gap length (each transmission peak being recorded in a different region of the image sensor). That is, when the gap length is varied, multiple spectral images (e.g., dozens or hundreds of such spectral images) can be obtained. Thus, each spectral image can be obtained for the same field of view and / or having a very narrow wavelength (e.g., 20 nm). The imaging device can generate a hyperspectral image based on the multiple spectral images. For example, the imaging device can store the multiple spectral images in a hyperspectral cube (having x-coordinates, y-coordinates, and spectral curves). Furthermore, when there are two or more spectral images having the same wavelength, ie, associated with the same peak wavelength of the transmission peak, these images may be averaged to produce one spectral image.

[0026] The image sensor may be any type of image sensor. For example, it may be based on a CMOS image sensor, the sensitivity range of which may be approximately 400 nm to 1000 nm of silicon photodiodes.

[0027] In another implementation form of the first aspect, the imaging device further includes an optical array for receiving light and guiding the light to the FPI element, wherein the FPI element is disposed between the optical array and the plurality of optical filters.

[0028] In another implementation of the first aspect, the optical array includes a lens for each of the optical filters, each lens for directing light to a different region of the FPI element disposed between the lens and one of the optical filters; each lens has the same field of view.

[0029] For example, the imaging device may include four optical bandpass filters. Furthermore, four (e.g., identical) lenses may be used (i.e., the number of lenses may be equal to the number of optical filters, and therefore the number of wavelength ranges). The lenses may all have the same field of view. The identical field of view of the lenses allows for recording hyperspectral images of a particular scene.

[0030] In another implementation form of the first aspect, the plurality of optical filters are all based on optical bandpass filters, and each optical bandpass filter is configured to pass a transmission peak generated by the FPI element.

[0031] In particular, each optical bandpass filter can pass at most one transmission peak at each gap length in the first range. At a specific gap length, a specific optical bandpass filter can not pass any transmission peak.

[0032] In another implementation of the first aspect, the plurality of optical filters includes four optical bandpass filters arranged in a 2×2 two-dimensional array, each optical bandpass filter being arranged adjacent to a different region of the FPI element.

[0033] In another implementation form of the first aspect, the imaging device further includes a micro-electromechanical system (MEMS) actuator or a piezoelectric actuator, and the imaging device is further configured to change the gap length of the interferometer gap by moving one or both of the two at least partially transmissive reflective elements using the MEMS actuator or the piezoelectric actuator.

[0034] In another implementation form of the first aspect, the imaging device is further configured to direct each of the plurality of transmission peaks generated by the FPI element to a corresponding optical bandpass filter.

[0035] In another implementation of the first aspect, a gap length of the interferometer gap is variable within a movement range of at least 1100 nm to 1450 nm.

[0036] In another implementation form of the first aspect, the wavelength ranges of the plurality of optical filters are further selected such that each wavelength range includes at most one peak wavelength at the movement range of the interferometer gap.

[0037] In another implementation form of the first aspect, at least one wavelength range of the optical filter is within the following range:

[0038] 402nm to 470nm, or

[0039] 480nm to 577nm, or

[0040] 590nm to 720nm, or

[0041] 730nm to 970nm.

[0042] In yet another implementation form of the first aspect, the image sensor is a CMOS sensor.

[0043] A second aspect of the present invention provides a method for operating an imaging device, comprising: generating a plurality of transmission peaks by an FPI element of the imaging device when receiving light, the FPI element comprising two at least partially transmissive reflective elements defining an interferometer gap, the gap length of the interferometer gap being changeable at least within a first range, and changing the peak wavelength of each transmission peak by changing the gap length of the interferometer gap; and passing light within a different wavelength range through each optical filter of a plurality of optical filters from the imaging device, each wavelength range having a different average wavelength, the wavelength ranges of the plurality of optical filters being selected so that each wavelength range includes at most one peak wavelength at each gap length in the first range.

[0044] In an implementation form of the second aspect, the wavelength ranges of the plurality of optical filters are selected such that each wavelength range includes exactly one of the peak wavelengths at each gap length of the first range.

[0045] In another implementation form of the second aspect, a wavelength interval is set between each pair of wavelength ranges.

[0046] In another implementation form of the second aspect, the wavelength ranges of the multiple optical filters do not overlap with each other.

[0047] In another implementation form of the second aspect, the wavelength range includes two overlapping wavelength ranges forming an overlapping region, and the overlapping region is:

[0048] - Each of the two overlapping wavelength ranges is less than 10%,

[0049] - preferably less than 5% of each of the two overlapping wavelength ranges,

[0050] - Most preferably, less than 3% of each of the two overlapping wavelength ranges.

[0051] In another implementation form of the second aspect, the method further includes: generating a plurality of spectral images by an image sensor of an imaging device, each spectral image being generated for a specific transmission peak generated by the FPI element at a specific gap length in a first range, with a plurality of optical filters being arranged between the image sensor and the FPI element; and generating a hyperspectral image by the imaging device based on the plurality of spectral images generated for different transmission peaks and / or different gap lengths in the first range.

[0052] In another implementation form of the second aspect, the method further includes: receiving light and guiding the light to an FPI element through an optical array of an imaging device, wherein the FPI element is disposed between the optical array and the plurality of optical filters.

[0053] In another implementation of the second aspect, the optical array includes a lens for each of the optical filters, and the method further includes: directing light to different areas of the FPI element disposed between the lens and one of the optical filters; each lens has the same field of view.

[0054] In another implementation form of the second aspect, the plurality of optical filters are all based on optical bandpass filters, and the method further comprises: each optical bandpass filter passes a transmission peak generated by the FPI element.

[0055] In another implementation of the second aspect, the plurality of optical filters includes four optical bandpass filters arranged in a 2×2 two-dimensional array, each optical bandpass filter being arranged adjacent to a different region of the FPI element.

[0056] In another implementation form of the second aspect, the method further comprises: changing the gap length of the interferometer gap by the MEMS actuator or the piezoelectric actuator of the imaging device by moving one or both of the two at least partially transmissive reflective elements using the MEMS actuator or the piezoelectric actuator.

[0057] In another implementation form of the second aspect, the method further includes directing each of the plurality of transmission peaks generated by the FPI element to a corresponding optical bandpass filter.

[0058] In another implementation of the second aspect, the gap length of the interferometer gap is variable within a movement range of at least 1100 nm to 1450 nm.

[0059] In another implementation form of the second aspect, the wavelength ranges of the plurality of optical filters are further selected such that each wavelength range includes at most one peak wavelength at the movement range of the interferometer gap.

[0060] In another implementation form of the second aspect, at least one wavelength range of the optical filter is within the following range:

[0061] -402nm to 470nm, or

[0062] -480nm to 577nm, or

[0063] -590nm to 720nm, or

[0064] -730nm to 970nm.

[0065] In another implementation form of the second aspect, the image sensor is a CMOS sensor.

[0066] The method of the second aspect achieves the advantages and effects described for the imaging device of the first aspect.

[0067] It should be noted that all devices, elements, units and devices described in this application can be implemented in software or hardware elements or any type of combination thereof. All steps performed by the various entities described in this application and the functions to be performed by the various entities described are intended to represent that the corresponding entities are used to perform the corresponding steps and functions. Although in the description of the following specific embodiments, the specific functions or steps performed by the external entity are not reflected in the description of the specific detailed elements of the entity that performs the specific steps or functions, it should be clear to the technician that these methods and functions can be implemented by corresponding hardware or software elements or any combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The following description of specific embodiments with reference to the accompanying drawings will illustrate the above aspects and their implementation methods, wherein:

[0069] Figure 1 is a schematic diagram of an imaging device according to an embodiment of the present invention;

[0070] Figure 2 is an example diagram showing the range of adjustable gap lengths and the corresponding changes in the FPI transmission peaks for the ranges passing through different optical filters (i.e., different wavelength ranges);

[0071] Figure 3 is another schematic diagram of an imaging device, the imaging device also including an image sensor and an optical array;

[0072] Figure 4 is a schematic cross-sectional view of an imaging device;

[0073] Figure 5 is a schematic diagram showing a set of wavelength ranges for the optical filter, wherein an FPI peak wavelength of 1300 nm is obtained at a gap length;

[0074] Figure 6 is a schematic diagram illustrating exemplary wavelength ranges of four optical filters of an imaging device;

[0075] Figure 7 An example of the spectral response of an optical filter is shown;

[0076] Figure 8 is a schematic diagram of an exemplary imaging device for a hyperspectral camera according to an embodiment of the present invention;

[0077] Figure 9 is a flowchart of a method of operating an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0078] Figure 1 is a schematic diagram of an imaging device 100 according to an embodiment of the present invention.

[0079] The imaging device 100 comprises an FPI element 110 comprising two at least partially transflective elements 111, 112 defining an interferometer gap 113. In particular, the interferometer gap 113 is formed between the two elements 111, 112.

[0080] Furthermore, the gap length of interferometer gap 113 is variable within at least a first range, and FPI element 110 is configured to generate multiple transmission peaks when receiving light at each gap length. To change the gap length, transflective element 111 and / or transflective element 112 may be movable to reduce or increase the gap length of interferometer gap 113. Furthermore, by varying the gap length of interferometer gap 113, the peak wavelength of each transmission peak can be varied. This is due to the dependence of each transmission peak, whether a main peak or a harmonic peak, on the gap length (see above). By varying the gap length within the first range, the peak wavelength of each transmission peak can be shifted within a certain wavelength range.

[0081] The imaging device 100 also includes a plurality of optical filters 121, 122, each of which is used to allow light in a different wavelength range to pass through. For example, each wavelength range can be a different average wavelength. For example, for two different wavelength ranges, the average wavelength value of one wavelength range can be less than the average wavelength value of another wavelength range. Alternatively, or additionally, for two different wavelength ranges, the minimum value of one wavelength range can be less than the minimum value of the other wavelength range, and / or the maximum value of one wavelength range can be less than the maximum value of the other wavelength range. In addition, the wavelength ranges of the plurality of optical filters 121, 122 are selected so that each wavelength range includes at most one (i.e., 0 or 1) peak wavelength at each gap length of the first range.

[0082] Imaging device 100 may include processing circuitry (not shown) Figure 1 ) for performing, implementing, or initiating the various operations of the imaging device 100 described herein. The processing circuitry may include hardware and software. The hardware may include analog circuitry or digital circuitry, or both. The digital circuitry may include components such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or a multi-purpose processor. In one embodiment, the processing circuitry includes one or more processors and non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code that, when executed by the one or more processors, causes the imaging device 100 to perform, implement, or initiate the operations or methods described herein.

[0083] Figure 2 is a graph showing an example of the adjustable gap length range, the corresponding FPI element transmission peak, and the corresponding optical filter wavelength (pass) range.

[0084] For example, the plurality of optical filters 121, 122 of the imaging device 100 can all be based on optical bandpass filters, e.g., each optical filter 121, 122 can be a bandpass filter. Furthermore, each optical filter 121, 122 can be configured to pass one of the transmission peaks (main peak or harmonic peak) generated by the FPI element 110. The optical filters 121, 122 can be disposed adjacent to the FPI element 110, and in particular, can be disposed after the FPI element 110 relative to the direction of incident light received and transmitted by the FPI element 110. For example, the FPI element 110 can be a single-cavity FPI element 110, i.e., an FPI element 110 having a single interferometer gap 113.

[0085] Figure 2 , the transmission peak as a function of the gap length of the interferometer gap 113 and an example of the wavelength range of the four optical (bandpass) filters 121, 122 of the tunable imaging device 110 are shown. The gap length can be tuned illustratively from 1100 nm to 1450 nm. The optical filters 121, 122 (for example, four optical filters) can be arranged in a 2×2 optical array and can pass four different wavelength ranges respectively. Figure 2, the four optical filters are labeled "Filter 1" to "Filter 4." Each of the optical filters 121 and 122 is associated with one of the four transmission peaks, i.e., each optical filter 121 and 122 passes its associated transmission peak to the greatest extent at each gap length. The transmission peak as a function of the gap length associated with filter 1 is located in the wavelength range of 402 nm to 470 nm of filter 1 and is indicated by reference numeral 201. The transmission peak as a function of the gap length associated with filter 2 is located in the wavelength range of 480 nm to 577 nm of filter 2 and is indicated by reference numeral 202. The transmission peak as a function of the gap length associated with filter 3 is located in the wavelength range of 590 nm to 720 nm of filter 3 and is indicated by reference numeral 203. The transmission peak as a function of the gap length associated with filter 4 is located in the wavelength range of 730 nm to 970 nm of filter 4 and is indicated by reference numeral 204.

[0086] Can be obtained from Figure 2 It is concluded that at each gap length of the interferometer gap 113, there is at most one transmission peak in each wavelength range of each optical filter 121, 122. The gap length and wavelength range are designed so that there is always zero (0) or one (1) transmission peak in a wavelength range. When the gap length is changed, Figure 2 The four transmission peaks shown in are shifted within the wavelength range of the associated optical filters 121 , 122 .

[0087] Figure 3 30 is another schematic diagram of the imaging device 100 , which further includes an image sensor 305 and optical arrays 301 , 302 , 303 , 304 .

[0088] Figure 3 The imaging device 100 further includes an image sensor 305. Furthermore, a plurality of optical filters 121, 122, 321, 322 may be disposed between the image sensor 305 and the FPI element 110. In particular, each optical filter 121, 122, 321, 322 may be disposed between the FPI element 110 and a different region (i.e., four different regions) of the image sensor 305.

[0089] Figure 3 is a top view of the imaging device 100 . Figure 3The imaging device 100 further includes an optical array of lenses 301, 302, 303, 304, which can receive light and direct the light to the FPI element 110. Here, the imaging device 100 exemplarily includes four lenses 301, 302, 303, 304. All four optical lenses 301, 302, 303, 304 can be arranged in the same aperture 300. The FPI element 110 (not shown) Figure 3 The optical arrays 301, 302, 303, 304 are arranged between the optical arrays 301, 302, 303, 304 and the plurality of optical filters 121, 122, 321, 322. Each of the lenses 301, 302, 303, 304 may have the same field of view.

[0090] The image sensor 305 may be disposed adjacent to the FPI element 110 based on a monochrome CMOS image sensor and may receive only one narrow channel light at one gap length in four different regions thereof (in this example).

[0091] The interferometer gap 113 of the FPI element 110 can be controlled by an actuator (e.g., a MEMS actuator or a piezoelectric actuator). In addition, when the gap length of the interferometer gap 113 is changed, the position of each transmission peak changes, but each transmission peak remains within the wavelength range of its associated optical filter.

[0092] In this example, four spectral images can be captured at each gap length, that is, one spectral image is captured for each of the four transmission peaks. The spectral images for each transmission peak and each gap length can be further stored in a hyperspectral data cube. Moreover, the hyperspectral cube can be completed when the entire distance of the designed gap length is scanned. Certain transmission peak wavelengths can be measured multiple times. In this case, the data of the spectral images can be averaged. For example, some wavelength ranges of the optical filters 121, 122, 321, 322 can be scanned in two parts, for example, scanning the end of the wavelength range with one transmission peak and then scanning the beginning of the same wavelength range with another transmission peak. However, within the wavelength range of the optical filters 121, 122, 321, 322, there is always at most one transmission peak at each gap length in the first range.

[0093] The imaging device 100 can be used to scan and record full visible-near infrared (VNIR) hyperspectral images from 410 nm to 960 nm using a single FPI element 110 and can be adapted for use with a smartphone.

[0094] Imaging device 100 is capable of achieving a spectral resolution of approximately 20 nm. For example, the transmission peak width can be tuned by the reflectance value of FPI reflective element 110. When using imaging device 100, heavy system-level calibration may not be required and post-processing power starvation may not occur. However, a generally known basic calibration of FPI element 110 and image sensor 305 may be required.

[0095] Now refer to Figure 4 , which is a schematic cross-sectional view of the imaging device 100 (not to scale). Figure 4 The vertical cross-sectional views shown are exemplary and are from Figure 3 The cross-sectional view shown in line 306 is obtained.

[0096] The imaging device 100 can include four independent optical lenses 301, 302, 303, and 304 that view the same field of view. The imaging device 100 can also include four custom optical filters 121, 122, 321, and 322 that are positioned adjacent to the FPI element 110 and are used to filter out unwanted peak transmission wavelengths for each sensor region (or sensor zone) from the multiple light transmission peaks typical of FPI elements. Thus, each sensor region can record a transmission peak that can be shifted within the wavelength range of its associated optical filter.

[0097] The wavelength ranges of the plurality of optical filters 121 , 122 , 321 , 322 are selected such that each wavelength range includes at most one peak wavelength at the movement range of the interferometer gap 113 .

[0098] The imaging system 100 illustratively includes a 2×2 array of input optics (lenses) that have a relatively large field of view but are capable of directing light, for example, to illuminate the FPI element 11 at a nearly perpendicular angle. The four optical lenses 301, 302, 303, 304 can be designed to see the same (or at least similar) field of view of the scene. Light can be directed to the FPI element 110 by the optical lenses 301, 302, 303, 304. All four optical lenses 301, 302, 303, 304 can be arranged within the same aperture 300 (see FIG. 3 ). Figure 3). Thus, light can obtain similar transmission in all four paths through the FPI element 110 (each path is associated with one of the lenses 301, 302, 303, 304). Optical filters 121, 122, 321, 322 are arranged after each of the four paths through the FPI element 110 and are respectively used to filter out unwanted peaks, in particular different unwanted peaks for each path. Finally, at the bottom is an image sensor 305, for example, a monochrome CMOS image sensor that can record light intensity. For example, the image sensor 305 can therefore generate a spectral image for each gap length of the interferometer gap 113 (one for each optical path). Therefore, when scanning the entire gap length range of the interferometer gap 113 (at least within the first range), a hyperspectral data cube can be generated and stored, which in this example includes four spectral images for each gap length.

[0099] Now refer to Figure 5 , which shows a set of wavelength ranges for the optical filters 121 , 122 , 321 , 322 , and an exemplary transmission peak wavelength obtained at a gap length of 1300 nm.

[0100] In particular, it is assumed that the gap length is 1300 nm, and simulation results of four optical filters 121 , 122 , 321 , 322 having four different wavelength ranges and four transmission peak wavelengths generated by the FPI element 110 are shown.

[0101] For example, the wavelength range 511 of the optical filter 121 is selected so that the wavelength range 511 includes a first transmission peak (wavelength) 501 at a gap length of 1300 nm. Furthermore, the wavelength range 512 of the optical filter 122 is selected so that the wavelength range 512 includes a second transmission peak (wavelength) 502 at a gap length of 1300 nm. Furthermore, the wavelength range 513 of the optical filter 321 is selected so that the wavelength range 513 includes a third transmission peak (wavelength) 503 at a gap length of 1300 nm. Furthermore, the wavelength range 514 of the optical filter 322 is selected so that the wavelength range 514 includes a fourth transmission peak (wavelength) 504 at a gap length of 1300 nm.

[0102] Figure 6 is a diagram illustrating exemplary wavelength ranges 511 , 512 , 513 , 514 for selecting the four optical filters 121 , 122 , 321 , 322 of the imaging device 100 .

[0103] Can be obtained from Figure 6 It can be seen that a wavelength interval can be set between each pair of wavelength ranges 511, 512, 513, and 514.

[0104] Furthermore, the wavelength ranges 511 , 512 , 513 , 514 of the plurality of optical filters 121 , 122 , 321 , 322 may be selected such that they do not overlap with each other.

[0105] Now refer to Figure 7 , which shows examples of spectral responses 511, 512, 513, 514 of the optical filters 121, 122, 321, 322. The spectral response may define the wavelength range (pass range) of the optical filters 121, 122, 321, 322, which may be of the order of 100-150 nm.

[0106] Figure 8 is a schematic diagram of an exemplary imaging device 100 for a hyperspectral camera.

[0107] The imaging device 100 comprises optical arrays 301 , 302 , 303 , 304 for receiving light and directing the light to the FPI element 110 .

[0108] The FPI element 110 of the imaging device 100 may be disposed between the optical arrays 301 , 302 , 303 , 304 and the plurality of optical filters 121 , 122 , 321 , 322 .

[0109] Optical arrays 301, 302, 303, 304 may include a lens for each of optical filters 121, 122, 321, 322. Each lens may be used to direct light to a different region of FPI element 110 disposed between the lens and one of optical filters 121, 122, 321, 322.

[0110] Furthermore, all lenses may have the same field of view. Image sensor 305 of imaging device 100 may generate multiple spectral images. For example, each spectral image may be generated at a specific gap length 113 for a specific transmission peak generated by FPI element 110.

[0111] The imaging device 100 can further generate a hyperspectral image based on multiple spectral images generated for different transmission peaks and / or at different gap lengths 113. The image sensor 305 can be a monochrome CMOS image sensor positioned below the FPI element and can receive only a narrow optical channel at one gap length in four different regions. For example, as the gap length varies and as the interferometer gap is scanned, multiple spectral images can be acquired at each gap length within a first range. Each spectral image can be acquired for the same field of view.

[0112] Furthermore, the imaging device 100 can further combine all spectral images and can further obtain a hyperspectral data cube. Therefore, the imaging device 100 can generate a hyperspectral image based on the spectral images.

[0113] Figure 9 A method 900 of operating the imaging device 100 according to an embodiment of the present invention is shown.

[0114] Method 900 includes: step S901, when receiving light, multiple transmission peaks are generated by the FPI element 110 of the imaging device 100, and the FPI element 110 includes two at least partially transmissive reflective elements 111 and 112 that define an interferometer gap 113; the gap length of the interferometer gap 113 can be changed within at least a first range; by changing the gap length of the interferometer gap 113, the peak wavelength of each transmission peak can be changed.

[0115] Method 900 also includes: step S902, each optical filter 121, 122 from the imaging device 100 allows light in a different wavelength range to pass through, each wavelength range having a different average wavelength; the wavelength ranges of the multiple optical filters 121, 122 are selected so that each wavelength range includes at most one peak wavelength at each gap length in the first range.

[0116] The present invention has been described with reference to various embodiments as examples and implementations. However, those skilled in the art will be able to understand and implement other variations in practicing the claimed invention, based on a study of the drawings, the present invention, and the appended claims. In the claims and the specification, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfil the functions of several entities or items described in the claims. The enumeration of certain measures in different dependent claims does not indicate that a combination of these measures cannot be used effectively.

Claims

1. An imaging device (100), characterized in that include: A Fabry-Perot interferometer (FPI) element (110) comprising two at least partially transflective elements (111, 112) defining an interferometer gap (113); The gap length of the interferometer gap (113) is changeable at least within a first range, the Fabry-Perot interferometer element (110) is used to generate multiple transmission peaks when it receives light, and the peak wavelength of each transmission peak can be changed by changing the gap length of the interferometer gap (113); a plurality of optical filters (121, 122), each optical filter (121, 122) being configured to pass light within a different wavelength range, each wavelength range having a different average wavelength; The wavelength ranges of the plurality of optical filters (121, 122) are selected such that each wavelength range includes at most one peak wavelength at each gap length of the first range; When the gap length changes, each wavelength range includes at most one transmission peak corresponding to a peak wavelength at each gap length in the first range, and the transmission peak moves within the wavelength range of the relevant optical filter.

2. The imaging device (100) according to claim 1, characterized in that The wavelength ranges of the plurality of optical filters (121, 122) are selected such that each wavelength range includes exactly one of the peak wavelengths at each gap length of the first range.

3. The imaging device (100) according to claim 1 or 2, characterized in that A wavelength interval is provided between each pair of said wavelength ranges.

4. The imaging device (100) according to claim 1 or 2, characterized in that The wavelength ranges of the plurality of optical filters (121, 122, 321, 322) do not overlap with each other.

5. The imaging device (100) according to claim 1 or 2, characterized in that The wavelength range includes two overlapping wavelength ranges forming an overlapping region, and the overlapping region is: - less than 10% of each of the two overlapping wavelength ranges.

6. The imaging device (100) according to claim 1 or 2, characterized in that The wavelength range includes two overlapping wavelength ranges forming an overlapping region, and the overlapping region is: - less than 5% of each of the two overlapping wavelength ranges.

7. The imaging device (100) according to claim 1 or 2, characterized in that The wavelength range includes two overlapping wavelength ranges forming an overlapping region, and the overlapping region is: - less than 3% of each of the two overlapping wavelength ranges.

8. The imaging device (100) according to claim 1 or 2, further comprising: An image sensor (305), wherein the plurality of optical filters (121, 122, 321, 322) are arranged between the image sensor (305) and the Fabry-Perot interferometer element (110), and the image sensor (305) is used to generating a plurality of spectral images, each spectral image being generated at a specific gap length within the first range for a specific transmission peak generated by the Fabry-Perot interferometer element (110); The imaging device (100) is used to generate a hyperspectral image based on a plurality of spectral images generated for different transmission peaks in the first range and / or at different gap lengths in the first range.

9. The imaging device (100) according to claim 8, further comprising: An optical array (301, 302, 303, 304) is used to receive light and guide the light to the Fabry-Perot interferometer element (110), and the Fabry-Perot interferometer element (110) is arranged between the optical array (301, 302, 303, 304) and the plurality of optical filters (121, 122, 321, 322).

10. The imaging device (100) according to claim 9, characterized in that The optical array (301, 302, 303, 304) includes a lens for each of the optical filters (121, 122, 321, 322), each lens being configured to direct the light to a different region of the Fabry-Perot interferometer element (110) disposed between the lens and one of the optical filters (121, 122, 321, 322); each lens having the same field of view.

11. The imaging device (100) according to claim 9 or 10, characterized in that The plurality of optical filters (121, 122, 321, 322) are all based on optical bandpass filters, and each optical bandpass filter is used to pass a transmission peak generated by the Fabry-Perot interferometer element (110).

12. The imaging device (100) according to claim 11, characterized in that The plurality of optical filters (121, 122, 321, 322) include four optical bandpass filters arranged in a 2×2 two-dimensional array, each optical bandpass filter being arranged adjacent to a different region of the Fabry-Perot interferometer element (110).

13. The imaging device (100) according to claim 12, further comprising: A micro-electromechanical system (MEMS) actuator or a piezoelectric actuator, the imaging device (100) is further used to: The gap length of the interferometer gap is varied by moving one or both of the two at least partially transflective elements using the micro-electromechanical system actuator or the piezoelectric actuator.

14. The imaging device (100) according to claim 12 or 13, characterized in that Further used for: Each of the plurality of transmission peaks generated by the Fabry-Perot interferometer element (110) is directed to a corresponding optical bandpass filter.

15. The imaging device (100) according to claim 12 or 13, characterized in that The gap length of the interferometer gap (113) is variable within a movement range of at least 1100 nm to 1450 nm.

16. The imaging device (100) according to claim 15, characterized in that The wavelength ranges of the plurality of optical filters (121, 122, 321, 322) are further selected such that each wavelength range includes at most one peak wavelength within the movement range of the interferometer gap (113).

17. The imaging device (100) according to claim 16, characterized in that At least one wavelength range of the optical filter (121, 122, 321, 322) is within the following range: 402nm to 470nm, or 480nm to 577nm, or 590nm to 720nm, or 730nm to 970nm.

18. The imaging device (100) according to claim 17, characterized in that The image sensor (305) is a complementary metal-oxide-semiconductor (CMOS) sensor.

19. A method (900) of operating an imaging device (100), comprising: When receiving light, a Fabry-Perot interferometer (FPI) element (110) of the imaging device (100) generates (S901) a plurality of transmission peaks, the Fabry-Perot interferometer element (110) comprising two at least partially transmissive reflective elements (111, 112) defining an interferometer gap (113), the gap length of the interferometer gap (113) being variable within at least a first range, and the peak wavelength of each transmission peak being variable by varying the gap length of the interferometer gap (113); and Each optical filter (121, 122) of the imaging device (100) allows light in a different wavelength range to pass therethrough (S902), each wavelength range having a different average wavelength, and the multiple optical filters (121, 122) are selected so that each wavelength range includes at most one peak wavelength at each gap length in the first range; when the gap length changes, a transmission peak corresponding to a peak wavelength in each wavelength range including at most one peak wavelength at each gap length in the first range moves within the wavelength range of the relevant optical filter.

Images