Photodetector

Abstract

To provide a light detector that can increase an imaging characteristic.SOLUTION: The light detector includes: a filter array including a plurality of filters, each filter having a light entrance surface and a light projection surface and being arranged in a two-dimensional plane, wherein the plurality of filers have mutually different transmittance spectrums; and an image sensor having a light detection surface facing the light projection surface and including a plurality of light detection elements arranged in the two-dimensional plane along the light detection surface. A distance between the light projection surface and the light detection surface is different for each of the filters, and the smallest distance between the light projection surface and the light detection surface is larger than 0.1 μm and is not larger than 200 μm.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present disclosure relates to a light detection device. [Background technology]

[0002] By utilizing spectral information from many narrow bands, for example several dozen bands, it is possible to grasp detailed physical properties of objects that were not possible with conventional RGB images. A camera that obtains such multi-wavelength information is called a "hyperspectral camera." Hyperspectral cameras are used in various fields such as food inspection, biological testing, pharmaceutical development, and mineral component analysis.

[0003] Patent Document 1 discloses an example of a hyperspectral imaging device using compressed sensing. The imaging device includes an encoding element, which is an array of multiple optical filters with different wavelength dependencies of light transmittance, an image sensor that detects light transmitted through the encoding element, and a signal processing circuit. The encoding element is disposed on an optical path connecting a subject and the image sensor. The image sensor simultaneously detects light in which components of multiple wavelength regions are superimposed for each pixel to obtain one wavelength-multiplexed image. The signal processing circuit generates image data for each of the multiple wavelength regions by applying compressed sensing to the obtained wavelength-multiplexed image using information on the spatial distribution of the spectral transmittance of the encoding element. In the imaging device disclosed in Patent Document 1, an optical filter array having two or more transmittance peaks (i.e., local maximum values) within the target wavelength region is used as the encoding element.

[0004] Patent Document 2 discloses an example of a filter array including a Fabry-Perot resonator using a dielectric multilayer film as a reflective layer. Patent Documents 3 to 5 disclose examples of the arrangement of a filter array and an image sensor. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 9,599,511 [Patent Document 2] U.S. Pat. No. 9,466,628 [Patent Document 3] Special Publication No. 2013-512445 [Patent Document 4] Japanese Patent Application Publication No. 63-151076 [Patent Document 5] Japanese Patent Application Publication No. 59-218770 Summary of the Invention

[0006] The present disclosure provides a light detection device capable of improving imaging characteristics.

[0007] An optical detection device according to one embodiment of the present disclosure comprises a filter array including a plurality of filters arranged two-dimensionally, each having a light entrance surface and a light exit surface, the plurality of filters including a plurality of types of filters having different transmission spectra from each other, and an image sensor having a light detection surface facing the light exit surface, the image sensor including a plurality of optical detection elements arranged two-dimensionally along the light detection surface, wherein a distance between the light exit surface and the light detection surface varies for each filter.

[0008] A comprehensive or specific aspect of the present disclosure may be realized in a system, an apparatus, a method, an integrated circuit, a computer program, or a computer-readable recording medium, or in any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a computer-readable recording medium. A computer-readable recording medium includes a non-volatile recording medium such as a compact disc-read only memory (CD-ROM). An apparatus may be composed of one or more apparatuses. When an apparatus is composed of two or more apparatuses, the two or more apparatuses may be arranged in one device, or may be arranged separately in two or more separate devices. In this specification and the claims, an "apparatus" may mean not only one apparatus, but also a system consisting of multiple apparatuses.

[0009] According to the technology of the present disclosure, it is possible to improve the imaging characteristics of a light detection device such as a hyperspectral camera. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a light detection system in accordance with an exemplary embodiment. [Figure 2A] FIG. 2A is a schematic diagram of an example filter array in accordance with an example embodiment. [Figure 2B] FIG. 2B is a diagram showing an example of a spatial distribution of the transmittance of light in each of a plurality of wavelength ranges included in the target wavelength range. [Figure 2C] FIG. 2C is a diagram showing an example of the transmission spectrum of a filter included in the filter array shown in FIG. 2A. [Figure 2D] FIG. 2D is a diagram showing an example of the transmission spectrum of another filter included in the filter array shown in FIG. 2A. [Figure 3A] FIG. 3A is a diagram for explaining an example of the relationship between a target wavelength range and a plurality of wavelength ranges included therein. [Figure 3B]FIG. 3B is a diagram for explaining another example of the relationship between the target wavelength range and a plurality of wavelength ranges included therein. [Figure 4A] FIG. 4A is a diagram for explaining the characteristics of the transmission spectrum of a filter in a filter array. [Figure 4B] FIG. 4B is a diagram showing the results of averaging the transmission spectrum shown in FIG. 4A for each wavelength range. [Figure 5A] FIG. 5A is a schematic cross-sectional view of a first example of a filter array according to an embodiment of the present disclosure. [Figure 5B] FIG. 5B is a schematic cross-sectional view of a second example of a filter array according to an embodiment of the present disclosure. [Figure 5C] FIG. 5C is a cross-sectional view that illustrates a schematic of a third example of a filter array according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a diagram showing examples of light transmission spectra of a double-sided DBR structure and a single-sided DBR structure when light is vertically incident. [Figure 7] FIG. 7 is a cross-sectional view illustrating a schematic diagram of a first example of a photodetector according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a graph showing the transmission spectrum of a configuration having two media with the same refractive index and an air gap layer positioned between them. [Figure 9A] FIG. 9A is a diagram illustrating a modified example of the photodetector shown in FIG. [Figure 9B] FIG. 9B is a diagram illustrating a schematic diagram of another modified example of the photodetector shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view illustrating a schematic diagram of a second example of the photodetector. [Figure 11] FIG. 11 is a cross-sectional view illustrating a schematic diagram of a third example of the photodetector. [Figure 12] FIG. 12 is a cross-sectional view illustrating a schematic diagram of a fourth example of the photodetector. [Figure 13] FIG. 13 is a plan view illustrating a schematic view of a fifth example of the photodetector. [Figure 14]FIG. 14 is a plan view that shows a schematic configuration in which the filter array is rotated at angles from 0° to 45° in 5° increments with respect to the image sensor on the XY plane. [Figure 15A] FIG. 15A is a cross-sectional view diagrammatically illustrating a sixth example of the photodetector. [Figure 15B] FIG. 15B is a cross-sectional view showing the photodetector shown in FIG. 15A with the filter array and the substrate removed. [Figure 15C] FIG. 15C is a plan view that illustrates another example of the arrangement of the double-sided tape 30 shown in FIG. 15B. [Figure 16A] FIG. 16A is a cross-sectional view diagrammatically illustrating a seventh example of a photodetector. [Figure 16B] FIG. 16B is a plan view showing the photodetector device shown in FIG. 16A with the filter array and the substrate removed. [Figure 16C] FIG. 16C is a plan view diagrammatically illustrating another example of the arrangement of the plurality of spacers shown in FIG. 16B. [Figure 16D] FIG. 16D is a plan view diagrammatically illustrating yet another example of the arrangement of the plurality of spacers shown in FIG. 16B. [Figure 16E] FIG. 16E is a plan view diagrammatically illustrating yet another example of the arrangement of the plurality of spacers shown in FIG. 16B. [Figure 17A] FIG. 17A is a diagram for explaining an example of a process in a method of forming a spacer. [Figure 17B] FIG. 17B is a diagram for explaining an example of a process in a method of forming a spacer. [Figure 17C] FIG. 17C is a view for explaining an example of a process in a method of forming a spacer. [Figure 17D] FIG. 17D is a diagram for explaining an example of a process in a method of forming a spacer. [Figure 18A] FIG. 18A is a diagram for explaining an example of a process in a method for bonding a filter array and an image sensor. [Figure 18B]FIG. 18B is a diagram for explaining an example of a process in a method for bonding a filter array and an image sensor. [Figure 18C] FIG. 18C is a diagram for explaining an example of a process in a method for bonding a filter array and an image sensor. [Figure 19] FIG. 19 is a cross-sectional view diagrammatically illustrating an eighth example of a photodetector. [Figure 20] FIG. 20 is a cross-sectional view illustrating a schematic diagram of a ninth example of a photodetector. [Figure 21] FIG. 21 is a diagram showing schematic transmission spectra of a red filter, a green filter, and a blue filter. [Figure 22] FIG. 22 is a cross-sectional view diagrammatically illustrating a tenth example of the photodetector. [Figure 23A] FIG. 23A is a cross-sectional view illustrating a schematic modification of the photodetector shown in FIG. [Figure 23B] FIG. 23B is a cross-sectional view that typically shows another modified example of the photodetector shown in FIG. [Figure 24A] FIG. 24A is a cross-sectional view diagrammatically illustrating an eleventh example of a photodetector. [Figure 24B] FIG. 24B is a cross-sectional view diagrammatically illustrating a twelfth example of the photodetector. [Figure 24C] FIG. 24C is a cross-sectional view diagrammatically illustrating a thirteenth example of the photodetector. [Diagram 25] FIG. 25 is a cross-sectional view illustrating a schematic diagram of a fourteenth example of the photodetector. [Figure 26] FIG. 26 is a cross-sectional view diagrammatically illustrating a fifteenth example of the photodetector. [Figure 27] FIG. 27 is a cross-sectional view diagrammatically illustrating a sixteenth example of the photodetector. [Figure 28] FIG. 28 is a cross-sectional view diagrammatically illustrating a seventeenth example of the photodetector. [Figure 29] FIG. 29 is a cross-sectional view diagrammatically illustrating an eighteenth example of the photodetector. [Diagram 30] FIG. 30 is a cross-sectional view illustrating a schematic diagram of a nineteenth example of a photodetector. [Diagram 31] FIG. 31 is a cross-sectional view illustrating a schematic diagram of a twentieth example of the photodetector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present disclosure will be described. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, arrangement and connection forms of components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components that are not described in an independent claim showing the highest concept are described as optional components. In addition, each figure is a schematic diagram and is not necessarily illustrated strictly. Furthermore, in each figure, substantially the same components are given the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0012] Before describing the embodiments of the present disclosure, the findings on which the present disclosure is based will be described.

[0013] Patent Document 1 discloses an imaging device capable of generating a high-resolution multi-wavelength image, i.e., an image for each of a plurality of wavelength regions. In the imaging device, an image of light from an object is encoded and imaged by an optical element called an "encoding element." The encoding element has, for example, a plurality of regions arranged two-dimensionally. The transmission spectrum of each of at least two of the plurality of regions has a maximum value of transmittance in a plurality of wavelength regions within the wavelength region of the imaging object. The plurality of regions may be arranged, for example, corresponding to a plurality of pixels of an image sensor. In imaging using the encoding element, data of each pixel includes information of a plurality of wavelength regions. That is, image data acquired by imaging is compressed image data in which wavelength information is compressed. Therefore, it is necessary to hold only two-dimensional data, and the amount of data can be reduced. For example, even if the capacity of a recording medium is limited, it is possible to acquire data of a long-term moving image. A multi-wavelength image is generated by reconstructing a plurality of images corresponding to a plurality of wavelength regions from an image acquired by imaging.

[0014] The encoding element may be realized, for example, by a filter array including a plurality of filters arranged two-dimensionally. Each of the plurality of filters may have, for example, a so-called Fabry-Perot resonator structure including an interference layer. As the Fabry-Perot resonator, for example, the structure disclosed in Patent Document 2 may be adopted. The plurality of filters may be designed such that the transmission spectrum of each filter has a plurality of peaks in the wavelength range of the imaging target. The plurality of filters having different thicknesses of the interference layer have different transmission spectra from each other.

[0015] The light transmitted through the filter array is detected by the image sensor. Patent documents 3 to 5 disclose examples of arrangements of the filter array and the image sensor. In the arrangement disclosed in Patent document 3, the filter array is integrated on the image sensor. In such a configuration, changing the configuration of the filter array also changes the manufacturing process, which results in higher costs. In the arrangement disclosed in Patent document 4, the filter array and the image sensor are bonded with a gap between them. In such a configuration, interference fringes such as Newton's rings appear in the captured image due to the interference of light between the filter array and the image sensor. As a result, the imaging characteristics are degraded. In the arrangement disclosed in Patent document 5, the filter array and the image sensor are bonded with no gap between them. However, if the filter array and / or the image sensor are warped, there is a possibility that a gap will be created even if an attempt is made to bond them without a gap.

[0016] From the above considerations, the inventors have come up with an arrangement of a filter array and an image sensor that can suppress the deterioration of imaging characteristics due to light interference at a low cost. A light detection device according to an embodiment of the present disclosure includes a filter array having a light incident surface and a light exit surface on the opposite side, and an image sensor having a light detection surface facing the light exit surface. The filter array includes a plurality of types of filters having different transmission spectra from each other within a specific wavelength range. The distance between the light exit surface and the light detection surface varies according to the transmission spectrum of the filter. Since the distance between the light exit surface and the light detection surface is non-uniform, the effect of interference fringes on the captured image can be suppressed. As a result, the imaging characteristics can be improved. Furthermore, since there is no need to integrate a filter array on the image sensor, the light detection device can be manufactured at a low cost. The light detection device according to the embodiment of the present disclosure can be applied not only to a hyperspectral camera but also to a general color camera that captures an image of three primary colors, for example. The light detection device according to the embodiment of the present disclosure will be briefly described below.

[0017] The photodetector according to the first aspect includes a filter array including a plurality of filters arranged two-dimensionally, each having a light entrance surface and a light exit surface, the plurality of filters including a plurality of types of filters having different transmission spectra, and an image sensor having a light detection surface facing the light exit surface, the image sensor including a plurality of light detection elements arranged two-dimensionally along the light detection surface. The distance between the light exit surface and the light detection surface is different for each filter.

[0018] This light detection device can suppress the appearance of interference fringes in a captured image.

[0019] The photodetector according to the second aspect is the photodetector according to the first aspect, wherein each of the plurality of types of filters has a resonant structure including an interference layer having a first surface and a second surface opposite to each other, and a reflective layer provided on the first surface. The thickness of the interference layer varies according to the transmission spectrum of the filter. The transmission spectrum of each of the plurality of types of filters has a maximum value of transmittance at each of two or more wavelengths included in a specific wavelength range. The image sensor has sensitivity to the specific wavelength range.

[0020] This light detection device is capable of acquiring a multi-wavelength image.

[0021] A photodetection device according to a third aspect is the photodetection device according to the first aspect, wherein the plurality of types of filters include two or more types of color filters.

[0022] This light detection device is capable of acquiring a multi-wavelength image.

[0023] A photodetector according to a fourth aspect is the photodetector according to the third aspect, wherein at least one of the plurality of types of color filters has an anti-reflection film on the light exit surface.

[0024] This light detection device can further suppress the appearance of interference fringes in a captured image.

[0025] A photodetector according to a fifth aspect is the photodetector according to any one of the first to fourth aspects, wherein the plurality of types of filters are arranged irregularly.

[0026] In this light detection device, the appearance of interference fringes in a captured image can be further suppressed, and in the case of acquiring a multi-wavelength image, restoration errors in the multi-wavelength image can be reduced.

[0027] A photodetector according to a sixth aspect is the photodetector according to any one of the first to fifth aspects, wherein the minimum distance between the light exit surface and the light detection surface is 0.1 μm or more and 200 μm or less.

[0028] In this photodetector, most of the light passing through each filter can be made to enter an area located directly below each filter within the photodetection surface.

[0029] A photodetector according to a seventh aspect is the photodetector according to any one of the first to sixth aspects, wherein the filters face the photodetecting elements, respectively.

[0030] In this photodetector, the light that has passed through each filter can be made incident on one photodetector element.

[0031] The photodetection device according to the eighth item is a photodetection device according to any one of the first to sixth items, wherein at least one of the plurality of filters has a portion facing each of a part of two adjacent photodetection elements among the plurality of photodetection elements.

[0032] In this photodetection device, the randomness of the spectrum of light detected by the multiple photodetection elements can be improved.

[0033] A photodetector according to a ninth aspect is the photodetector according to any one of the first to eighth aspects, wherein the light incident surfaces and the light detection surfaces of the plurality of filters are parallel to each other.

[0034] In this light detection device, the distance between the filter array and the image sensor can be made small without them contacting each other.

[0035] A photodetector according to a tenth aspect is the photodetector according to any one of the first to eighth aspects, wherein the light incident surfaces and the light detection surfaces of the plurality of filters are not parallel to each other.

[0036] This light detection device can further suppress the appearance of interference fringes in a captured image.

[0037] The photodetector according to an eleventh aspect is the photodetector according to any one of the first to tenth aspects, wherein, when viewed from the light incident surface side, the filters are two-dimensionally arranged along a first direction and a second direction rotated counterclockwise from the first direction by a predetermined angle, and the photodetector elements are two-dimensionally arranged along a third direction and a fourth direction rotated counterclockwise from the third direction by the predetermined angle. An angle between the first direction and the third direction is ¼ to ½ of the predetermined angle.

[0038] In this light detection device, it is possible to suppress moire and improve imaging characteristics.

[0039] A photodetector according to a twelfth aspect is the photodetector according to the eleventh aspect, wherein the predetermined angle is 90 degrees.

[0040] In this light detection device, the range of angles over which moire can be suppressed is increased.

[0041] A photodetection device according to a thirteenth aspect is the photodetection device according to any one of the first to twelfth aspects, wherein the filter array and the image sensor have warpage of the same tendency.

[0042] In this light detection device, the distance between the filter array and the image sensor can be made small without them contacting each other.

[0043] A photodetection device according to a fourteenth aspect is the photodetection device according to any one of the first to twelfth aspects, wherein the filter array and the image sensor have warps in opposite directions.

[0044] This light detection device can further suppress the appearance of interference fringes in a captured image.

[0045] A photodetector according to a fifteenth aspect is the photodetector according to any one of the first to fourteenth aspects, further comprising a substrate on the light incident surfaces of the plurality of filters.

[0046] In this photodetector, the substrate on which the filter array is provided is used as a constituent element, so that the step of removing the substrate can be omitted.

[0047] A photodetector according to a sixteenth aspect is the photodetector according to the fifteenth aspect, wherein the substrate has an anti-reflection film on a surface opposite to the surface on which the filter array is formed.

[0048] In this light detection device, the light detection efficiency can be improved.

[0049] The photodetection device according to a seventeenth item is a photodetection device according to any one of the first to sixteenth items, further comprising double-sided tape that bonds at least a portion of a peripheral region located around the light emission surfaces of the plurality of filters to at least a portion of a peripheral region located around the light detection surface of the image sensor.

[0050] In this light detection device, the arrangement of the filter array and the image sensor can be fixed.

[0051] The photodetector according to an eighteenth aspect is the photodetector according to any one of the first to sixteenth aspects, further comprising a plurality of spacers sandwiched between the filter array and the image sensor and defining the distance between the light exit surface of each filter and the light detection surface. At least a part of the light exit surface of each filter and at least a part of the light detection surface are bonded with a transparent adhesive.

[0052] In this light detection device, the arrangement of the filter array and the image sensor can be fixed.

[0053] The photodetector according to a nineteenth aspect is the photodetector according to the eighteenth aspect, wherein at least one of the spacers is arranged at a position overlapping at least one of the photodetector elements in a plan view.

[0054] In this photodetection device, the randomness of the spectrum of light detected by the multiple photodetection elements can be improved.

[0055] A photodetection device according to a twentieth item is the photodetection device according to any one of the first to nineteenth items, wherein the image sensor includes a plurality of first microlenses arranged on the plurality of photodetection elements, respectively.

[0056] In this light detection device, the light transmitted through the filter can be efficiently made incident on the light detection element by the first microlens.

[0057] The photodetection device according to a 21st item is the photodetection device according to any one of the 1st to 20th items, wherein the filter array includes a plurality of second microlenses respectively arranged on the light exit surfaces of the plurality of filters.

[0058] In this photodetection device, the light transmitted through the filter can be efficiently made incident on the photodetection element by the second microlens.

[0059] A photodetector according to a twenty-second item is the photodetector according to any one of the first to twenty-first items, wherein the minimum distance between the light emitting surface and the light detecting surface is greater than 0.1 μm.

[0060] This photodetector can reduce the influence of interference near a wavelength of 400 nm in the target wavelength range.

[0061] The photodetector according to the 23rd item is a photodetector according to any one of the 1st to 21st items, wherein when the target wavelength range is λ1 or more and λ2 or less, the minimum distance between the light emission surface and the light detection surface is greater than λ1 / 4.

[0062] In this light detection device, the imaging characteristics in the target wavelength range can be improved.

[0063] The photodetector according to the 24th item is a photodetector according to any one of the 1st to 21st items, wherein when the target wavelength range is greater than or equal to λ1 and less than or equal to λ2, the minimum distance between the light emission surface and the light detection surface is greater than λ2 / 4.

[0064] With this light detection device, the imaging characteristics in the target wavelength range can be further improved.

[0065] The photodetector according to a twenty-fifth item is the photodetector according to any one of the first to twenty-fourth items, and further includes a transparent cover supporting the filter array, a package including a bottom having a first region in which the image sensor is provided, and a sidewall extending from a second region of the bottom located around the first region and surrounding the image sensor. The transparent cover and the package seal the filter array and the image sensor.

[0066] This light detection device can prevent dust, dirt, or moisture from entering the interior of the light detection device.

[0067] A photodetector according to a twenty-sixth aspect is the photodetector according to any one of the first to twenty-fifth aspects, further comprising a signal processing circuit. The signal processing circuit restores a plurality of spectral images for four or more wavelength ranges from the compressed image encoded by the filter array.

[0068] This photodetection device can obtain an image that contains more wavelength information than an RGB color image.

[0069] A method for manufacturing a structure according to the 27th item includes the steps of: preparing a filter array including a plurality of filters arranged two-dimensionally and having an uneven surface, the plurality of filters having different transmission spectra from one another; forming a photoresist on the uneven surface of the filter array by spin coating; and forming a plurality of spacers on the uneven surface of the filter array by patterning the photoresist.

[0070] This method of manufacturing a filter array makes it possible to form a plurality of spacers with the same height on the uneven surface of the filter array.

[0071] The manufacturing method for a photodetection device according to the 28th item includes the steps of preparing a structure manufactured by the manufacturing method for a structure according to the 27th item, and an image sensor having a photodetection surface, and bonding the filter array and the image sensor via the multiple spacers while arranging the uneven surface of the filter array and the photodetection surface of the image sensor facing each other.

[0072] In this method of manufacturing a photodetector, the filter array and the image sensor can be attached to each other in a substantially parallel state.

[0073] A manufacturing method for a photodetection device according to a 29th item is the manufacturing method for a photodetection device according to the 28th item, wherein a plurality of adhesives are arranged on the photodetection surface of the image sensor and / or on a peripheral region located around the photodetection surface, and the step of bonding the filter array to the image sensor includes pressing the filter array against the image sensor via the plurality of spacers and the plurality of adhesives.

[0074] In this method of manufacturing a photodetector, the filter array and the image sensor can be bonded together by hardening a plurality of adhesives.

[0075] In the present disclosure, all or part of a circuit, unit, device, member or part, or all or part of a functional block in a block diagram may be implemented by one or more electronic circuits including, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). The LSI or IC may be integrated into one chip, or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated into one chip. Here, although it is called an LSI or an IC, the name may change depending on the degree of integration, and it may be called a system LSI, a VLSI (very large scale integration), or an ULSI (ultra large scale integration). A Field Programmable Gate Array (FPGA), which is programmed after the manufacture of the LSI, or a reconfigurable logic device, which can reconfigure the junction relationship inside the LSI or set up the circuit partition inside the LSI, can also be used for the same purpose.

[0076] Furthermore, all or part of the functions or operations of a circuit, unit, device, member, or part can be executed by software processing. In this case, the software is recorded in one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, etc., and when the software is executed by a processor, the functions specified in the software are executed by the processor and peripheral devices. The system or device may include one or more non-transitory recording media on which the software is recorded, a processor, and necessary hardware devices, such as interfaces.

[0077] (Embodiment) <Optical detection system> FIG. 1 is a schematic diagram of a light detection system 400 according to an exemplary embodiment of the present disclosure. The light detection system 400 includes an optical system 40, a filter array 10, an image sensor 60, and a signal processing circuit 200. The filter array 10 has a function similar to that of the "encoding element" disclosed in Patent Document 1. For this reason, the filter array 10 can also be called the "encoding element." The optical system 40 and the filter array 10 are disposed in the optical path of light incident from an object 70. In the example shown in FIG. 1, the filter array 10 is disposed between the optical system 40 and the image sensor 160.

[0078] In FIG. 1, an apple is illustrated as an example of the object 70. The object 70 is not limited to an apple, and may be any object. The signal processing circuit 200 generates image data for each of a plurality of wavelength ranges included in a specific wavelength range (hereinafter also referred to as a "target wavelength range") based on the image data generated by the image sensor 60. This image data is referred to as "spectral image data" in this specification. Here, the number of wavelength ranges included in the target wavelength range is N (N is an integer equal to or greater than 4). In the following description, the generated spectral image data for the plurality of wavelength ranges is referred to as separated images 220W1, 220W2, . . . , 220W Nand these are collectively referred to as separated images 220. In this specification, a signal representing an image, that is, a set of signals representing pixel values ​​of a plurality of pixels that constitute an image, is also simply referred to as an "image".

[0079] The filter array 10 includes a plurality of light-transmitting filters arranged in rows and columns. The filter array 10 is an optical element in which the light transmission spectrum, i.e., the wavelength dependency of light transmittance, differs from filter to filter. The filter array 10 modulates the intensity of incident light for each wavelength range before allowing it to pass.

[0080] 1, the filter array 10 is disposed in the vicinity of the image sensor 60. Here, "in the vicinity" means close enough that an image of light from the optical system 40 is formed on the surface of the filter array 10 with a certain degree of clarity. In this specification, an apparatus including the filter array 10 and the image sensor 60 is referred to as "photodetection apparatus 300."

[0081] The optical system 40 includes at least one lens. Although one lens is shown in Fig. 1, the optical system 40 may be configured by a combination of multiple lenses. The optical system 40 forms an image on the imaging surface of the image sensor 60 through the filter array 10.

[0082] The image sensor 60 includes a plurality of photodetection elements arranged two-dimensionally. The image sensor 60 may be, for example, a charge-coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, or an infrared array sensor. The photodetection elements may include, for example, photodiodes. The image sensor 60 may be, for example, a monochrome type sensor or a color type sensor. The target wavelength range may be determined arbitrarily. The target wavelength range is not limited to the visible wavelength range, and may be an ultraviolet, near infrared, mid infrared, far infrared, or microwave wavelength range.

[0083] In the example shown in FIG. 1, each of the multiple photodetection elements is disposed facing one of the multiple filters. Each of the multiple photodetection elements has sensitivity to light in the wavelength range of the image capture target. Specifically, each of the multiple photodetection elements has a substantial sensitivity required to detect light in the wavelength range of the image capture target. For example, the external quantum efficiency of the photodetection element in the wavelength range may be 1% or more. The external quantum efficiency of the photodetection element may be 10% or more. The external quantum efficiency of the photodetection element may be 20% or more. In the following description, the photodetection element is also referred to as a "pixel."

[0084] The signal processing circuit 200 may be an integrated circuit including, for example, a processor and a storage medium such as a memory. The signal processing circuit 200 generates data of a plurality of separated images 220 each including information of a plurality of wavelength ranges based on the image 120 acquired by the image sensor 60. Details of the plurality of separated images 220 and the image signal processing method of the signal processing circuit 200 will be described later. The signal processing circuit 200 may be incorporated in the photodetection device 300, or may be a component of a signal processing device electrically connected to the photodetection device 300 by wire or wirelessly.

[0085] <Filter array> The filter array 10 according to this embodiment will be described below. The filter array 10 is disposed in the optical path of light incident from an object, and modulates the intensity of the incident light for each wavelength and outputs the modulated light. This process by the filter array, i.e., the encoding element, is referred to as "encoding" in this specification.

[0086] 2A is a diagram showing a schematic example of a filter array 10. The filter array 10 includes a plurality of filters arranged two-dimensionally. Each filter has an individually set transmission spectrum. The transmission spectrum is expressed by a function T(λ), where λ is the wavelength of incident light. The transmission spectrum T(λ) can take a value between 0 and 1.

[0087] In the example shown in Fig. 2A, the filter array 10 has 48 rectangular filters arranged in 6 rows and 8 columns. This is merely an example, and in actual applications, more filters may be provided. The number of filters may be approximately the same as the number of pixels of the image sensor 60, for example. The number of filters included in the filter array 10 is determined depending on the application and may range from several tens to several tens of millions.

[0088] FIG. 2B shows multiple wavelength bands W1, W2, . . . , W i 2B is a diagram showing an example of the spatial distribution of the light transmittance of each filter. In the example shown in FIG. 2B, the difference in the shade of each filter represents the difference in the transmittance. The lighter the filter, the higher the transmittance, and the darker the filter, the lower the transmittance. As shown in FIG. 2B, the spatial distribution of the light transmittance differs depending on the wavelength range.

[0089] 2C and 2D are diagrams showing examples of the transmission spectra of the filter A1 and the filter A2 included in the multiple filters of the filter array 10 of FIG. 2A, respectively. The transmission spectrum of the filter A1 and the transmission spectrum of the filter A2 are different from each other. In this way, the transmission spectrum of the filter array 10 differs depending on the filter. However, it is not necessary that the transmission spectra of all the filters are different. In the filter array 10, the transmission spectra of at least two or more filters among the multiple filters are different from each other. That is, the filter array 10 includes two or more filters whose transmission spectra are different from each other. In an example, the number of patterns of the transmission spectra of the multiple filters included in the filter array 10 may be the same as or greater than the number i of wavelength ranges included in the target wavelength range. The filter array 10 may be designed so that the transmission spectra of more than half of the filters are different.

[0090] 3A and 3B show a target wavelength range W and a number of wavelength ranges W1, W2, . . . , W iFIG. 1 is a diagram for explaining the relationship between the wavelength range W and the visible light wavelength range. The target wavelength range W may be set to various ranges depending on the application. The target wavelength range W may be, for example, a visible light wavelength range of about 400 nm to about 700 nm, a near-infrared wavelength range of about 700 nm to about 2500 nm, or a near-ultraviolet wavelength range of about 10 nm to about 400 nm. Alternatively, the target wavelength range W may be a radio wave range such as mid-infrared, far-infrared, terahertz waves, or millimeter waves. Thus, the wavelength range used is not limited to the visible light range. In this specification, not only visible light, but also non-visible light such as near-ultraviolet light, near-infrared light, and radio waves are referred to as "light" for convenience.

[0091] In the example shown in FIG. 3A, the target wavelength range W is divided into i equal parts, i being an arbitrary integer equal to or greater than 4, and each part is designated as wavelength range W1, wavelength range W2, . . . , wavelength range W i However, the present invention is not limited to this example. The multiple wavelength ranges included in the target wavelength range W may be set arbitrarily. For example, the bandwidth may be non-uniform depending on the wavelength range. There may be a gap between adjacent wavelength ranges. In the example shown in FIG. 3B, the bandwidth differs depending on the wavelength range, and there is a gap between two adjacent wavelength ranges. In this way, the multiple wavelength ranges may be different from each other, and the method of determining the number of wavelength divisions may be arbitrary. The number of wavelength divisions i may be 3 or less.

[0092] 4A is a diagram for explaining the characteristics of the transmission spectrum of a filter in the filter array 10. In the example shown in FIG. 4A, the transmission spectrum has multiple maximum values ​​P1 to P5 and multiple minimum values ​​for wavelengths in the target wavelength range W. In the example shown in FIG. 4A, the optical transmittance in the target wavelength range W is normalized so that the maximum value is 1 and the minimum value is 0. In the example shown in FIG. 4A, the optical transmittance in the wavelength range W2 and the wavelength range W3 is normalized so that the optical transmittance in the wavelength range W4 is normalized so that the optical transmittance in the wavelength range W5 is normalized so that the optical transmittance in the wavelength range W6 is normalized so that the optical transmittance in the wavelength range W7 is normalized so that the optical transmittance in the wavelength range W8 is normalized so that the optical transmittance in the wavelength range W9 is normalized so that the optical transmittance in the wavelength range W10 is normalized so that the optical transmittance in the wavelength range W110 is normalized so that the optical transmittance in the wavelength range W120 is normalized so that the optical transmittance in the wavelength range W130 is normalized so that the optical transmittance in the wavelength range W140 is normalized so that the optical transmittance in the wavelength range W150 is normalized so that the optical transmittance in the wavelength range W160 is normalized so that the optical transmittance in the wavelength range W170 is normalized so that the optical transmittance in the wavelength range W180 is normalized so that the optical transmittance in the wavelength range W190 is normalized so that the optical transmittance in the wavelength range W210 is normalized so that the optical transmittance in the wavelength range W220 is normalized so that the optical transmittance in the wavelength range W230 is normalized so that the optical transmittance in the wavelength range W240 is normalized so that the optical transmittance in the wavelength range W250 is normalized so that the optical transmittance in the wavelength range W i-1 In this manner, in this embodiment, the transmission spectrum of each filter has a maximum value in a wavelength range from a wavelength range W1 to a wavelength range W i As can be seen from Fig. 4A, the local maximum value P1, the local maximum value P3, the local maximum value P4, and the local maximum value P5 are 0.5 or more.

[0093] As described above, the light transmittance of each filter varies with wavelength. Therefore, the filter array 10 transmits a larger proportion of the components in a certain wavelength range of the incident light and less of the components in other wavelength ranges. For example, for the light in k of the i wavelength ranges, the transmittance can be greater than 0.5, and for the light in the remaining i - k wavelength ranges, the transmittance can be less than 0.5. k is an integer satisfying 2 ≤ k < i. If the incident light is white light that equally contains the wavelength components of all visible light, the filter array 10 modulates the incident light into light having a plurality of intensity peaks discrete with respect to wavelength for each filter, and superimposes and outputs these multi-wavelength lights.

[0094] FIG. 4B shows, as an example, the result of averaging the transmittance spectrum shown in FIG. 4A for each of the wavelength ranges W1, W2, ···, W i FIG. 4B is a diagram showing the result of averaging the transmittance spectrum shown in FIG. 4A for each of the wavelength ranges W1, W2, ···, W. The averaged transmittance is obtained by integrating the transmittance spectrum T(λ) for each wavelength range and dividing by the bandwidth of that wavelength range. In this specification, the value of the transmittance averaged in this way for each wavelength range is referred to as the transmittance in that wavelength range. In this example, the transmittance is prominently high in three wavelength ranges taking the maximum values P1, P3, and P5. In particular, in the two wavelength ranges taking the maximum values P3 and P5, the transmittance exceeds 0.8.

[0095] The resolution in the wavelength direction of the transmittance spectrum of each filter can be set to about the bandwidth of the desired wavelength range. In other words, the width of the range that takes a value equal to or greater than the average value of the minimum value closest to the maximum value and the maximum value among the wavelength ranges including one maximum value in the transmittance spectrum curve can be set to about the bandwidth of the desired wavelength range. In this case, if the transmittance spectrum is decomposed into frequency components by, for example, Fourier transform, the value of the frequency component corresponding to that wavelength range becomes relatively large.

[0096] The filter array 10 typically has a plurality of filters divided into a grid pattern as shown in Fig. 2A. Some or all of these filters have different transmission spectra. The wavelength distribution and spatial distribution of the light transmittance of the plurality of filters included in the filter array 10 may be, for example, a random distribution or a quasi-random distribution.

[0097] The concept of random distribution and quasi-random distribution is as follows. First, each filter in the filter array 10 can be considered as a vector element having a value of, for example, 0 to 1 according to the light transmittance. Here, when the transmittance is 0, the value of the vector element is 0, and when the transmittance is 1, the value of the vector element is 1. In other words, a set of filters arranged in a row or column direction can be considered as a multidimensional vector having a value of 0 to 1. Therefore, it can be said that the filter array 10 has a plurality of multidimensional vectors in the column or row direction. In this case, the random distribution means that any two multidimensional vectors are independent, that is, not parallel. Moreover, the quasi-random distribution means that a configuration in which some multidimensional vectors are not independent from each other is included. Therefore, in the random distribution and the quasi-random distribution, a vector whose elements are the values ​​of the transmittance of light in the first wavelength range in each filter belonging to a set of filters arranged in one row or column included in a plurality of filters and a vector whose elements are the values ​​of the transmittance of light in the first wavelength range in each filter belonging to a set of filters arranged in another row or column are independent of each other. Similarly, for a second wavelength range different from the first wavelength range, a vector whose elements are the transmittance values ​​of light in the second wavelength range for each filter belonging to a set of filters arranged in one row or column included in the multiple filters, and a vector whose elements are the transmittance values ​​of light in the second wavelength range for each filter belonging to a set of filters arranged in another row or column are independent of each other.

[0098] When the filter array 10 is disposed near the image sensor 60, the mutual intervals between the multiple filters included in the filter array 10 may be approximately equal to the pixel pitch of the image sensor 60. In this way, the resolution of the encoded light image emitted from the filter array 10 approximately equals the pixel resolution. By making the light transmitted through each cell incident on a corresponding pixel, it is possible to facilitate the calculation described below. When the filter array 10 is disposed away from the image sensor 60, the cell pitch may be made finer depending on the distance.

[0099] In the examples shown in FIGS. 2A to 2D, the filter array 10 has a grayscale transmittance distribution in which the transmittance of each filter can take any value between 0 and 1. However, the transmittance distribution does not necessarily have to be a grayscale one. For example, a binary scale transmittance distribution in which the transmittance of each filter can take a value of either approximately 0 or approximately 1 may be adopted. In a binary scale transmittance distribution, each filter transmits most of the light in at least two wavelength ranges among a plurality of wavelength ranges included in the target wavelength range, and does not transmit most of the light in the remaining wavelength ranges. Here, "most of the light" refers to approximately 80% or more.

[0100] A part of all the filters, for example half of the filters, may be replaced with transparent filters. Such transparent filters transmit light from all wavelength ranges W1 to Wi included in the target wavelength range with high transmittance. The high transmittance is, for example, 0.8 or more. In such a configuration, the multiple transparent filters may be arranged, for example, in a checkerboard pattern. That is, in two arrangement directions of the multiple filters in the filter array 10, filters whose light transmittance varies depending on the wavelength and transparent filters may be arranged alternately. In the example shown in FIG. 2A, the two arrangement directions are the horizontal direction and the vertical direction.

[0101] Such data indicating the spatial distribution of the spectral transmittance of the filter array 10 is acquired in advance based on design data or actual measurement calibration, and is stored in a storage medium provided in the signal processing circuit 200. This data is used in the arithmetic processing described later.

[0102] The filter array 10 may be configured using, for example, a multilayer film, an organic material, a diffraction grating structure, or a microstructure containing a metal. When configured using a multilayer film, for example, a dielectric multilayer film or a multilayer film containing a metal layer may be used. In this case, at least one of the thickness, material, and stacking order of each multilayer film may be formed differently for each cell. This allows different spectral characteristics to be realized for each cell. By using a multilayer film, sharp rises and falls in the spectral transmittance can be realized. A configuration using an organic material can be realized by making the pigment or dye contained differently depending on the cell, or by stacking different materials. A configuration using a diffraction grating structure can be realized by providing a diffraction structure with a different diffraction pitch or depth for each cell. When using a microstructure containing a metal, it can be created by utilizing spectrum due to the plasmon effect.

[0103] <Signal processing circuit> Next, a method for reconstructing a multi-wavelength separated image 220 by the signal processing circuit 200 will be described. Here, multi-wavelength means more wavelength ranges than the wavelength ranges of the three colors of RGB captured by a normal color camera, that is, four or more wavelength ranges. The number of wavelength ranges can be, for example, about 4 to 100. The number of wavelength ranges is also referred to as the "number of spectral bands." Depending on the application, the number of spectral bands may exceed 100.

[0104] The desired data is the separated image 220, and the data is represented as f. If the number of spectral bands is w, f is the image data of each band, f1, f2, . . . , f w Here, as shown in Fig. 1, the horizontal direction of the image is the x direction, and the vertical direction of the image is the y direction. If the number of pixels in the x direction of the image data to be obtained is n, and the number of pixels in the y direction is m, then the image data f1, f2, ..., fw Each of the elements f is two-dimensional data of n×m pixels. Therefore, the data f is three-dimensional data of n×m×w elements. On the other hand, the number of elements of the data g of the image 120 obtained by encoding and multiplexing by the filter array 10 is n×m. The data g can be expressed by the following formula (1).

[0105]

number

[0106] where f1, f2, . . . , f w is a data set with n × m elements. Therefore, the vector on the right side is strictly a one-dimensional vector with n × m × w rows and 1 column. The vector g is converted to a one-dimensional vector with n × m rows and 1 column, and then calculated. The matrix H is the components f1, f2, ..., f of the vector f. w This represents a conversion in which each wavelength band is encoded with different encoding information, intensity-modulated, and then added together. Therefore, H is a matrix with n × m rows and n × m × w columns.

[0107] Given vector g and matrix H, it seems possible to calculate f by solving the inverse problem of equation (1). However, since the number of elements n×m×w of the desired data f is greater than the number of elements n×m of the acquired data g, this problem is an ill-posed problem and cannot be solved as is. Therefore, the signal processing circuit 200 uses the image redundancy contained in the data f to find a solution using a compressed sensing technique. Specifically, the desired data f is estimated by solving the following equation (2).

[0108]

number

[0109] Here, f' represents the estimated f data. The first term in the brackets in the above formula represents the deviation between the estimated result Hf and the acquired data g, that is, the residual term. Here, the sum of squares is used as the residual term, but the absolute value or the square root of the sum of squares, etc. may be used as the residual term. The second term in the brackets is a regularization term or stabilization term, which will be described later. Equation (2) means to find f that minimizes the sum of the first and second terms. The signal processing circuit 200 can converge the solution by recursive iterative calculations and calculate the final solution f'.

[0110] The first term in the parentheses in formula (2) means an operation to obtain the sum of squares of the difference between the acquired data g and Hf obtained by system-transforming f in the estimation process by the matrix H. The second term Φ(f) is a constraint condition in the regularization of f, and is a function reflecting the sparse information of the estimation data. Its function is to smooth or stabilize the estimation data. The regularization term can be expressed by, for example, the discrete cosine transform (DCT) of f, the wavelet transform, the Fourier transform, or the total variation (TV). For example, when the total variation is used, stable estimation data that suppresses the influence of noise in the observation data g can be obtained. The sparsity of the object 70 in the space of each regularization term differs depending on the texture of the object 70. A regularization term that makes the texture of the object 70 sparser in the space of the regularization term may be selected. Alternatively, multiple regularization terms may be included in the operation. τ is a weighting coefficient. The larger the weighting factor τ, the more redundant data is reduced, and the higher the compression ratio. The smaller the weighting factor τ, the weaker the convergence to a solution. The weighting factor τ is set to an appropriate value that allows f to converge to a certain extent, but does not result in over-compression.

[0111] Although an example of calculation using compressed sensing shown in Equation (2) is shown here, other methods may be used for the solution. For example, other statistical methods such as maximum likelihood estimation or Bayesian estimation may be used. In addition, the number of separated images 220 may be any number, and each wavelength range may be set arbitrarily. Details of the reconstruction method are disclosed in Patent Document 1. The entire disclosure of Patent Document 1 is incorporated herein by reference.

[0112] <Filter array including Fabry-Perot filters> Next, with reference to FIG. 5A to FIG. 5C, a specific structural example of the filter array 10 according to the embodiment of the present disclosure will be described. FIG. 5A to FIG. 5C are cross-sectional views each showing a first to third example of the filter array 10 according to the embodiment of the present disclosure. In these cross-sectional views, five filters 100 included in one row are shown for simplicity. In the examples shown in FIG. 5A to FIG. 5C, the filter array 10 is supported by a substrate 20. As shown in FIG. 2A, the filter array 10 includes a plurality of filters 100 arranged two-dimensionally in a square lattice shape. In the first example shown in FIG. 5A to the third example shown in FIG. 5C, all of the filters 100 included in the filter array 10 have a resonant structure. A resonant structure means a structure in which light of a certain wavelength forms a standing wave inside and exists stably.

[0113] In the first example shown in FIG. 5A, a first reflective layer 14a, an interference layer 12, and a second reflective layer 14b are laminated in this order on a substrate 20. Each resonant structure shown in FIG. 5A includes an interference layer 12 having a first surface 12s1 and a second surface 12s2 located opposite each other, a first reflective layer 14a provided on the first surface 12s1, and a second reflective layer 14b provided on the second surface 12s2. The reflectance of each of the first surface 12s1 and the second surface 12s2 for light in the target wavelength range W may be, for example, 80% or more. The reflectance may be lower than 80% but may be designed to be 40% or more. The thickness of the first reflective layer 14a and the thickness of the second reflective layer 14b may be designed to be equal. A plurality of filters 100 having different thicknesses of the interference layer 12 have different transmission spectra in the target wavelength range W. The transmission spectrum of each resonant structure shown in FIG. 5A has two or more sharp peaks in the target wavelength range W as described later.

[0114] In the first example shown in Fig. 5A, each of the first reflective layer 14a and the second reflective layer 14b is formed of a distributed Bragg reflector (DBR) in which a plurality of high refractive index layers and a plurality of low refractive index layers are alternately stacked. Each of the first reflective layer 14a and the second reflective layer 14b may be formed of a metal thin film.

[0115] A DBR includes one or more pairs of layers, a high refractive index layer and a low refractive index layer, which have different refractive indices. The refractive index of the high refractive index layer is higher than that of the low refractive index layer. The DBR has a wavelength range in which the reflectance is high due to Bragg reflection caused by the periodic stack structure. This wavelength range is called the stop band. By increasing the number of the above pair layers, the reflectance of the stop band approaches 100%.

[0116] The wavelength in the target wavelength range W is λ, and the refractive index of the high refractive index layer is n H , the refractive index of the low refractive index layer is n L The thickness is λ / (4n H ), and a high refractive index layer having a thickness of λ / (4n L A DBR that includes one or more pairs of low refractive index layers having a wavelength of λ efficiently reflects light having a wavelength of λ. i wavelength λ f In the following range, by gradually changing the thicknesses of the multiple high refractive index layers and multiple low refractive index layers, the DBR can i From the pair layer corresponding to the wavelength λ f As a result, the DBR can efficiently reflect all light in the wavelength range W of interest.

[0117] The high and low refractive index layers included in each of the first and second reflective layers 14a and 14b, as well as the interference layer 12, may be made of, for example, a material that has a low absorption rate for light in the target wavelength range W. When the target wavelength range W is within the visible light region, such a material may be, for example, SiO2, Al2O3, SiO x N y, Si3N4, Ta2O5, and TiO2. When the wavelength range W of interest is within the infrared region, such a material may be, for example, the above-mentioned SiO2, Al2O3, SiO x N y , Si3N4, Ta2O5, and TiO2, and may be at least one selected from the group consisting of single crystal Si, polycrystalline Si, and amorphous Si. Similarly, the substrate 20 may be formed of, for example, a material with low absorption for light in the target wavelength range W. When the target wavelength range W is in the visible light range, such a material may be at least one selected from the group consisting of SiO2, ITO, Al2O3, GaN, Nb2O5, Ta2O5, and SiC. When the target wavelength range W is in the infrared range, such a material may be at least one selected from the group consisting of single crystal Si, polycrystalline Si, amorphous Si, and InP, in addition to the above-mentioned SiO2, ITO, Al2O3, GaN, Nb2O5, Ta2O5, and SiC. The thickness of each of the first reflective layer 14a and the second reflective layer 14b may be, for example, 100 nm or more and 900 nm or less. The thickness of the interference layer 12 may be, for example, 10 nm or more and 500 nm or less. The thickness of the substrate 20 may be, for example, not less than 0.1 mm and not more than 1 mm.

[0118] In the second example shown in FIG. 5B, a first reflective layer 14a and an interference layer 12 are laminated in this order on a substrate 20. Each resonant structure shown in FIG. 5B includes an interference layer 12 and a first reflective layer 14a provided on a first surface 12s1. The second example shown in FIG. 5B differs from the first example shown in FIG. 5A in that a second reflective layer 14b is not provided on a second surface 12s2. The transmission spectrum of each resonant structure shown in FIG. 5B has two or more broad peaks in a target wavelength range W, as described below.

[0119] In the example shown in FIG. 5B, the second surface 12s2 is exposed to the outside and in contact with air. A transparent layer may be further laminated on the second surface 12s2 of the interference layer 12. The reflectance of the first surface 12s1 for light in the target wavelength range W (hereinafter referred to as the "first reflectance") may be, for example, 80% or more. The first reflectance may be lower than 80% but may be designed to be 40% or more. The reflectance of the second surface 12s2 for light in the target wavelength range W (hereinafter referred to as the "second reflectance") may be lower than the first reflectance, for example, 1% or more and less than 30%. There is a certain difference of 10% or more between the first reflectance and the second reflectance.

[0120] In this specification, the resonant structure shown in FIG. 5A is referred to as a "double-sided DBR structure," and the resonant structure shown in FIG. 5B is referred to as a "single-sided DBR structure." In this specification, in the double-sided DBR structure and the single-sided DBR structure, the light in the interference layer 12 is reflected by the first surface 12s1 and the second surface 12s2, unless the exact position of the surface that reflects the light is an issue. In this embodiment, a part of the light that enters the first reflection layer 14a or the second reflection layer 14b from the interference layer 12 actually penetrates into the first reflection layer 14a or the second reflection layer 14b and is reflected by the interfaces of the multiple high refractive index layers and the multiple low refractive index layers. The interfaces at which the light is reflected vary depending on the wavelength. However, for convenience of explanation, these lights are treated as being reflected by the first surface 12s1 and the second surface 12s2.

[0121] In a third example shown in FIG. 5C, some of the filters 100 have a double-sided DBR structure, and other filters 100 have a single-sided DBR structure. The ratio of the single-sided DBR structures to all the DBR structures included in the filter array 10 may be, for example, 10% or more and 90% or less. The ratio of the single-sided DBR structures may be smaller than the ratio of the double-sided DBR structures, may be equal to the ratio of the double-sided DBR structures, or may be larger than the ratio of the double-sided DBR structures. The arrangement of the double-sided DBR structures and the single-sided DBR structures may be regular or irregular. By mixing the double-sided DBR structures and the single-sided DBR structures, the randomness of the transmission spectra of the multiple filters 100 included in the filter array 10 can be improved. As a result, multiple more accurate separated images 220 can be obtained.

[0122] Next, an example of the transmission spectrum of the filter 100 will be described with reference to FIG. 6. FIG. 6 is a diagram showing an example of the transmission spectrum of light of a double-sided DBR structure and a single-sided DBR structure when light is incident perpendicularly. In the example shown in FIG. 6, the target wavelength range W is 450 nm or more and 850 nm or less. The solid line shown in FIG. 6 represents the transmission spectrum of the double-sided DBR structure, and the dashed line shown in FIG. 6 represents the transmission spectrum of the single-sided DBR structure. As shown in FIG. 6, the transmission spectra of the double-sided DBR structure and the single-sided DBR structure have a maximum value of transmittance at each of two or more wavelengths within the target wavelength range W. In this specification, a filter having such a transmission spectrum is called a "multimode filter." The wavelength at which the transmittance shows a maximum value shifts to the short wavelength side when the interference layer 12 is made thinner, and shifts to the long wavelength side when the interference layer 12 is made thicker.

[0123] The characteristics of the double-sided DBR structure and the single-sided DBR structure differ in the following points. In the transmission spectrum of the double-sided DBR structure, each peak is sharp, and the maximum transmittance is about 1.0, and the minimum transmittance is about 0.02. In contrast, in the transmission spectrum of the single-sided DBR structure, each peak is broad, and the maximum transmittance is about 0.5, and the minimum transmittance is about 0.1. In the single-sided DBR structure, the baseline of the transmittance is higher than that of the double-sided DBR structure. In the example shown in FIG. 6, the average transmittance in the target wavelength range W of the single-sided DBR structure is about 26%, and the average transmittance in the target wavelength range W of the double-sided DBR structure is about 14%. In the single-sided DBR structure, the average transmittance is about twice that of the double-sided DBR structure. In this way, the single-sided DBR structure can suppress the loss of light during imaging.

[0124] In the filter array 10 according to the present embodiment, a plurality of types of multimode filters having different transmission spectra from each other within the target wavelength range W may be irregularly arranged. An irregular arrangement is an arrangement that does not show clear regularity or periodicity, and is also aperiodic. The irregular arrangement may be, for example, an arrangement according to the above-mentioned random distribution or quasi-random distribution concept. In one example, the filter array 10 includes millions of filters 100 arranged two-dimensionally, and the millions of filters 100 include nine types of multimode filters arranged irregularly. The nine types of multimode filters may be arranged with high randomness. The filter array 10 having such a highly random filter arrangement can reduce the restoration error of the separated image 220. Since the arrangement is irregular, adjacent filters may be the same type of filters. However, such cases are considered to be rare, and do not pose a major problem.

[0125] The filter array 10 according to the present embodiment may include a filter that does not have the above-mentioned resonant structure. The filter array 10 according to the present embodiment may include a filter that does not have wavelength dependency of light transmittance, such as a transparent filter or an ND filter (Neutral Density Filter).

[0126] In this specification, the filter 100 having a double-sided DBR structure and / or a single-sided DBR structure is also referred to as a "Fabry-Perot filter." A Fabry-Perot filter is a type of interference filter. Instead of a Fabry-Perot filter, other types of interference filters, such as a color separation filter composed of a diffraction grating, can be used.

[0127] <Layout of filter array and image sensor> Next, an example of the arrangement relationship between the filter array 10 and the image sensor 60 will be described with reference to Fig. 7 to Fig. 14. In the examples shown in Fig. 7 and the following figures, for simplicity, the filter array 10 and the image sensor 60 are each described as including 5 x 5 unit cells arranged two-dimensionally. However, in reality, the filter array 10 and the image sensor 60 may each include, for example, several million unit cells arranged two-dimensionally. The illustrated structures are merely examples, and the number and arrangement of the unit cells may be determined arbitrarily.

[0128] FIG. 7 is a cross-sectional view showing a first example of a photodetection device 300 according to an embodiment of the present disclosure. The cross-sectional view is a cross-sectional view of the filter array 10 and the image sensor 60 for one row. The structure shown in FIG. 7 is a partial structure of the photodetection device 300. For convenience of explanation, FIG. 7 shows an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other. The direction of the X-axis arrow is referred to as the +X direction, and the opposite direction is referred to as the -X direction. The same applies to the directions of the Y-axis and Z-axis arrows and their opposite directions. The +Z direction side is also referred to as "upper", and the -Z direction side is also referred to as "lower". These axes do not limit the arrangement and posture of the photodetection device 300, and the arrangement and posture of the actual photodetection device 300 are arbitrary. The photodetection device 300 according to this embodiment includes a filter array 10, a substrate 20 that supports the filter array 10, and an image sensor 60.

[0129] The configurations of the filter array 10 and the substrate 20 shown in Fig. 7 are the same as those of the filter array 10 and the substrate 20 shown in Fig. 5C, except that they are inverted. Instead of the configuration shown in Fig. 5C, the configuration shown in Fig. 5A or 5B may be adopted. The substrate 20 is used in the process of manufacturing the photodetector 300. The substrate 20 is not necessarily required, but if the substrate 20 is not removed in the manufacture of the photodetector 300, the substrate 20 is included in the photodetector 300.

[0130] The filter array 10 includes a plurality of filters 100 arranged two-dimensionally in a square lattice pattern along the XY plane. The plurality of filters 100 include a plurality of types of multimode filters having different transmission spectra in a target wavelength range W. The thickness of the interference layer 12 varies according to the transmission spectra of the multimode filters. The arrangement pitches of the plurality of filters 100 in the X and Y directions are all equal. The plurality of types of multimode filters are irregularly arranged, for example, according to the above-mentioned random distribution or quasi-random distribution concept.

[0131] The filter array 10 has a light incident surface 10s1 and a light exit surface 10s2 on the opposite side. The light incident surface 10s1 is formed by a collection of the light incident surfaces of the multiple filters 100. The light exit surface 10s2 is formed by a collection of the light exit surfaces of the multiple filters 100. In the example shown in FIG. 7, the light incident surface 10s1 is flat. In other words, the light incident surfaces of the multiple filters 100 form flat surfaces without steps. In contrast, the light exit surface 10s2 has irregularities, i.e. steps. In other words, the light exit surfaces of the multiple filters 100 form uneven surfaces. This unevenness occurs due to differences in thickness between the filters 100. The difference in thickness between the filters 100 occurs due to differences in thickness between the interference layers or the presence or absence of the second reflective layer 14b. The substrate 20 is provided on the light incident surface 10s1 of the filter array 10.

[0132] The image sensor 60 has a light detection surface 60s facing the light emission surface 10s2, and includes a plurality of light detection elements 60a arranged two-dimensionally in a square lattice pattern along the light detection surface 60s. The light detection surface 60s is flat. The plurality of light detection elements 60a are sensitive to the target wavelength range W. The plurality of light detection elements 60a face a plurality of filters 100, respectively. In the first example shown in FIG. 7, the arrangement pitches of the plurality of light detection elements 60a in the X direction and the Y direction are all equal. The arrangement pitches of the light detection elements 60a in the X direction and the Y direction may be different. The arrangement pitch of the light detection elements 60a may be, for example, 1 μm or more and 10 μm or less. In the first example shown in FIG. 7, the arrangement pitch of the filters 100 is designed to be equal to the arrangement pitch of the light detection elements 60a. Each of the plurality of light detection elements 60a has a plurality of microlenses 40a directly above it. The microlens 40a efficiently allows the light transmitted through the filter 100 to enter the light detection element 60a. The light incident surface 10s1 and the light detection surface 60s are parallel to each other. "The light incident surface 10s1 and the light detection surface 60s are parallel to each other" does not mean that they are strictly parallel, but means that the angle between the normal direction of the light incident surface 10s1 and the normal direction of the light detection surface 60s is 10° or less. The normal direction of the light incident surface 10s1 is perpendicular to the light incident surface 10s1 and is a direction away from the filter array 10. The normal direction of the light detection surface 60s is perpendicular to the light detection surface 60s and is a direction away from the image sensor 60.

[0133] The light reflected by the object 70 is incident on the light incident surface 10s1 of the filter array 10 through the substrate 20 mainly along the -Z direction, passes through the filter array 10, and exits from the light exit surface 10s2 of the filter array 10. The light exiting from the light exit surface 10s2 of the filter array 10 is incident on the light detection surface 60s of the image sensor 60.

[0134] The distance between the light exit surface 10s2 and the light detection surface 60s is different for each multimode filter. The light detection device 300 of this embodiment is manufactured by fixing the structure shown in FIG. 5C and the image sensor 60 so that the uneven surface of the filter array 10 faces the light detection surface 60s. Since the distance between the light exit surface 10s2 and the light detection surface 60s is non-uniform, even if multiple reflections of light occur between the light exit surface 10s2 and the light detection surface 60s, the appearance of interference fringes due to light interference in the captured image can be suppressed. Therefore, the imaging characteristics of the light detection device 300 can be improved. The irregular arrangement of multiple types of multimode filters not only reduces the restoration error of the multiple separated images 220, but also further suppresses the appearance of interference fringes in the captured image.

[0135] Furthermore, in this embodiment, the second reflective layer 14b, rather than the substrate 20, is disposed so as to face the light detection surface 60s of the image sensor 60, thereby allowing the filter array 10 and the image sensor 60 to be brought closer to each other. m ". The distance .gamma. between the light-emitting surface 10s2 and the light-detecting surface 60s may be, for example, 0.1 μm or more and 200 μm or less. In this embodiment, the F-number of the optical system 40 shown in FIG. 1 is 16 or less, and the arrangement pitch of the light-detecting elements 60a may be about 6 μm. In this case, since the focal depth is about 200 μm, if the minimum distance between the light-emitting surface 10s2 and the light-detecting surface 60s is within the above range, most of the light passing through each filter 100 can be made to enter an area located directly below each filter 100 in the light-detecting surface 60s. In the first example shown in FIG. 7, one light-detecting element 60a is located in that area.

[0136] Depending on the distance between the light exit surface 10s2 and the light detection surface 60s, optical interference may occur between them. Due to the influence of this interference, the spectrum of the light detected by the light detection element 60a may deviate from the transmission spectrum of the multimode filter. The interference that may occur here depends on the distance d between the light exit surface 10s2 and the light detection surface 60s. When the round-trip distance 2d between the light exit surface 10s2 and the light detection surface 60s is an integer multiple of the wavelength λ, that is, when the distance d = m1 λ / 2, the light is constructively interfered with, and as a result, the transmittance is maximized at the wavelength λ = 2d / m1. m1 is an integer of 1 or more. On the other hand, when the round-trip distance 2d between the light exit surface 10s2 and the light detection surface 60s is a half-integer multiple of the wavelength λ, that is, when the distance d = (m2 + 1 / 2) λ / 2, the light is destructively interfered with, and as a result, the transmittance is minimized at the wavelength λ = 2d / (m2 + 1 / 2). m2 is an integer of 0 or more. The maximum wavelength at which the transmittance becomes minimal due to interference is when m2 = 0, that is, λ = 4d. In this specification, the interference occurring at a distance d = λ / 4 is referred to as "fundamental mode interference".

[0137] FIG. 8 is a graph showing the transmission spectrum in a configuration including two media with the same refractive index and an air gap layer between them. The solid line, dotted line, and dashed line in FIG. 8 represent the cases where the thickness d of the gap layer is 100 nm, 125 nm, and 150 nm, respectively. The two media are SiO2, and the refractive index of each is n=1.5. As shown in FIG. 8, at a distance d=100 nm, fundamental mode interference occurs for light with a wavelength λ=400 nm, and the transmittance becomes minimal near a wavelength λ=400 nm. Similarly, at a distance d=125 nm, the transmittance becomes minimal near a wavelength λ=500 nm, and at a distance d=150 nm, the transmittance becomes minimal near a wavelength λ=600 nm. As shown in FIG. 8, when the wavelength becomes longer than the wavelength at which fundamental mode interference occurs, the transmittance increases gradually, and when the wavelength becomes shorter than the wavelength at which fundamental mode interference occurs, the transmittance increases steeply toward a maximum value.

[0138] The photodetector element of each pixel detects light in which the transmission spectrum of the multimode filter is affected by the above-mentioned interference. That is, the spectrum of light detected at each pixel may be significantly different from the transmission spectrum of the multimode filter. As a result, there is a possibility that the imaging characteristics may be deteriorated, such as an increase in the reconstruction error of the separated image 220.

[0139] The target wavelength range is the visible light wavelength range, i.e., from about 400 nm to about 700 m. Minimum distance d m If the minimum distance d is less than 0.1 μm, the transmittance may be low due to interference over the entire wavelength range of interest. m is greater than 0.1 μm, i.e., the distance d m If there are no pixels with a minimum distance d of 0.1 μm or less, the effect of interference near a wavelength of 400 nm in the target wavelength range can be reduced. m In this case, the imaging characteristics can be improved as compared with the case where the thickness is 0.1 μm or less.

[0140] Similarly, the minimum distance d m When the minimum distance d is greater than 0.125 μm, the influence of interference in the wavelength range of 400 nm to 500 nm inclusive of the target wavelength range can be reduced, and the imaging characteristics can be further improved. m When is larger than 0.150 μm, the influence of interference in the wavelength range of 400 nm or more and 600 nm or less in the target wavelength range can be reduced, and the imaging characteristics can be further improved.

[0141] In general, when the wavelength range of interest is λ1≦λ≦λ2, the minimum distance d m By making the minimum distance d larger than λ1 / 4, the imaging characteristics can be improved. m By making it larger than λ2 / 4, the imaging characteristics can be further improved.

[0142] minimum distance d mThe larger the transmittance is, the shorter the period of oscillation in the transmittance shown in FIG. 8 becomes due to the effect of interference as the wavelength changes in the target wavelength range. The oscillation width is, for example, the wavelength range W i When the wavelength is sufficiently smaller than i Since the interference is averaged and cancelled out in , the multiple separated images 220 are hardly affected by interference, and the imaging characteristics can be further improved.

[0143] The lower limit wavelength λ1 and the upper limit wavelength λ2 of the target wavelength range may be the lower limit wavelength and the upper limit wavelength, respectively, of the wavelength component included in the separated image 220. Alternatively, the lower limit wavelength λ1 and the upper limit wavelength λ2 of the target wavelength range may be the lower limit wavelength and the upper limit wavelength, respectively, of the light that can be detected by the image sensor 60 in the photodetection device 300. Alternatively, the lower limit wavelength λ1 and the upper limit wavelength λ2 of the target wavelength range may be the lower limit wavelength and the upper limit wavelength, respectively, of the light that is incident on the image sensor 60 in the photodetection device 300.

[0144] The filter array 10 and the image sensor 60 may have warpage. The substrate 20 supporting the filter array 10 may also have warpage in the same direction as the filter array 10. For example, when the side of the filter array 10 or the image sensor 60 is 10 mm, the warpage may cause a difference of about 1 μm in the Z direction between the center and the end. The filter array 10 and the image sensor 60 may have warpage with the same tendency. That is, the filter array 10 and the image sensor 60 may both have warpage that is convex upward or convex downward. Alternatively, the filter array 10 and the image sensor 60 may have warpage with opposite tendencies. That is, one of the filter array 10 and the image sensor 60 may have warpage that is convex upward and the other may have warpage that is convex downward. In particular, when the filter array 10 and the image sensor 60 have warpage with opposite tendencies, the distance between the light emitting surface 10s2 and the light detecting surface 60s becomes more non-uniform, so that the appearance of interference fringes in the captured image can be further suppressed. In addition, when it is stated in this specification that "the light incident surface 10s1 and the light detection surface 60s are flat," warping of the filter array 10 and the image sensor 60 is ignored.

[0145] As a modification of the photodetector 300 shown in FIG. 7, a plurality of microlenses may be arranged on the light exit surface of each of the filters 100 in the filter array 10. FIG. 9A is a diagram showing a schematic diagram of a modification of the photodetector 300 shown in FIG. 7. The photodetector 300 shown in FIG. 9A is different from the photodetector 300 shown in FIG. 7 in that the filter array 10 includes a plurality of microlenses 40b arranged on the light exit surface of each of the filters 100. The plurality of microlenses 40b arranged on the light exit surface 10s2 face the plurality of microlenses 40a arranged on the light detection surface 60s. With such a configuration, most of the light passing through each filter 100 can be collected or collimated by the microlens 40b and can be incident on the photodetector element 60a through the microlens 40a below it. By using the microlenses 40a and 40b in combination, the light passing through each filter 100a can be more efficiently incident on the corresponding photodetector element 60a.

[0146] Fig. 9B is a diagram showing a schematic diagram of another modified example of the photodetector 300 shown in Fig. 7. The photodetector 300 shown in Fig. 9B differs from the photodetector 300 shown in Fig. 9A in that the multiple microlenses 40a are not arranged on the photodetection surface 60s. As in this modified example, the multiple microlenses 40a are not arranged, and instead, the multiple microlenses 40b arranged on the light exit surface 10s2 are used to allow light to be efficiently incident on the photodetector element 60a.

[0147] In this specification, the multiple microlenses 40a arranged on the light detection surface 60s are also referred to as "multiple first microlenses," and the multiple microlenses 40b provided on the light emission surface 10s2 are also referred to as "multiple second microlenses."

[0148] Other components may be added to the structure shown in FIG. 7. FIG. 10 is a cross-sectional view showing a second example of the photodetector 300. The structure shown in FIG. 10 is different from the structure shown in FIG. 7 in that the substrate 20 has an antireflection film 22 on the surface opposite to the surface supporting the filter array 10. The antireflection film 22 can suppress the reflection of light that occurs at the interface between the substrate 20 and air in the first example shown in FIG. 7. Therefore, the light detection efficiency of the photodetector 300 can be improved. Furthermore, the antireflection film 22 can ease the warping of the filter array 10 and the substrate 20 or reverse the direction of the warping. By adjusting the warping of the filter array 10 and the substrate 20 with the antireflection film 22, the appearance of interference fringes in the captured image can be further suppressed.

[0149] The arrangement of the configuration shown in FIG. 7 may be changed. FIG. 11 is a cross-sectional view showing a third example of the photodetection device 300. The structure shown in FIG. 11 differs from the structure shown in FIG. 7 in that the arrangement relationship between the filter array 10 and the image sensor 60 is shifted along one direction parallel to the photodetection surface 60s. In the third example shown in FIG. 11, the direction is the X direction. The magnitude of the shift is smaller than the arrangement pitch of the filters 100 or the arrangement pitch of the photodetection elements 60a. In the third example shown in FIG. 11, the filters 100 and the photodetection elements 60a do not face each other one-to-one. Except for the filters 100 located at the ends, each of the filters 100 overlaps two adjacent photodetection elements 60a when viewed from the Z direction. In other words, each of the filters 100 has a portion facing each of the two adjacent photodetection elements 60a. In this case, part of the light transmitted through each filter 100 is incident on a certain photodetection element 60a, and the other part is incident on another adjacent photodetection element 60a. Therefore, the randomness of the spectrum of the light detected by the multiple photodetection elements 60a can be improved. As a result, the multiple separated images 220 can be restored more accurately.

[0150] In the example shown in FIG. 11, the arrangement pitch of the filters 100 and the arrangement pitch of the photodetector elements 60a are equal, but these arrangement pitches may be different. Alternatively, the arrangement pitch of the filters 100 and / or the arrangement pitch of the photodetector elements 60a may be non-uniform. By such an arrangement, when the light emission surface 0s2 of the filter array 10 and the photodetector surface 60s of the image sensor 60 are opposed to each other, a configuration in which the filters 100 and the photodetector elements 60a do not face each other one-to-one can be obtained. In such a configuration, some of the filters 100 and some of the photodetector elements 60a may face each other one-to-one. In this embodiment, at least one of the filters 100 may have a portion facing each of two adjacent photodetector elements 60a.

[0151] FIG. 12 is a cross-sectional view showing a fourth example of the light detection device 300. The fourth example shown in FIG. 12 is different from the first example shown in FIG. 7 in that the light incident surface 10s1 of the filter array 10 and the light detection surface 60s of the image sensor 60 are not parallel to each other. The normal direction of the light incident surface 10s1 and the normal direction of the light detection surface 60s intersect. The angle at which these normal directions intersect may be, for example, 30° or more and 45° or less. In a configuration in which the light incident surface 10s1 and the light detection surface 60s are not parallel as in this embodiment, the distance between the light exit surface 10s2 and the light detection surface 60s becomes more non-uniform. As a result, it is possible to further suppress the appearance of interference fringes in the captured image.

[0152] FIG. 13 is a plan view showing a schematic diagram of a fifth example of the photodetector 300. The plan view shows the photodetector 300 from the light incident surface 10s1 side of the filter array 10. The substrate 20 is not shown in the plan view. In the fifth example shown in FIG. 13, the thick lines represent the filter array 10 including the 5×5 filters 100, and the thin lines represent the image sensor 60 including the 5×5 photodetector elements 60a. The fifth example shown in FIG. 13 is different from the first example shown in FIG. 7 in that the filter array 10 is rotated by a certain angle with respect to the image sensor 60 in the XY plane. The filters 100 included in the filter array 10 are two-dimensionally arranged along the directions of the fundamental vectors, which are a first vector D1 and a second vector D2 obtained by rotating the first vector D1 by 90° counterclockwise. The photodetecting elements 60a in the image sensor 60 are two-dimensionally arranged along the directions of the third vector D3 and the fourth vector D4 obtained by rotating the third vector D3 counterclockwise by 90°, which are used as the basic vectors. The magnitudes of the first and second vectors D1 and D2 are equal to the arrangement pitch of the filters 100 in the directions of the first and second vectors D1 and D2, respectively. The magnitudes of the third and fourth vectors D3 and D4 are equal to the arrangement pitch of the photodetecting elements 60a in the directions of the third and fourth vectors D3 and D4, respectively. The magnitudes of the first vector D1 to the fourth vector D4 are all equal. In the first example shown in FIG. 7, the first vector D1 and the third vector D3 are parallel to each other, and the second vector D2 and the fourth vector D4 are parallel to each other. In contrast, in the fifth example shown in FIG. 13, the third vector D3 intersects the first vector D1, and the fourth vector D4 intersects the second vector D2.

[0153] FIG. 14 is a plan view showing a configuration in which the filter array 10 is rotated in 5° increments from 0° to 45° with respect to the image sensor 60 in the XY plane. The configuration of rotation angles from 45° to 90° is equivalent to the configuration of rotation angles from 45° to 0° shown in FIG. 14. For example, the configuration of a rotation angle of 55° is equivalent to the configuration of a rotation angle of 35°, and the configuration of a rotation angle of 80° is equivalent to the configuration of a rotation angle of 10°. As shown in FIG. 14, at rotation angles other than 0°, moire, i.e., regular light and dark, appears in the overlapping portion of the filter array 10 and the image sensor 60. As the rotation angle increases, the moire pattern becomes finer. Moire is difficult to see when the rotation angle is in the range of 25° to 45°.

[0154] In order to obtain a higher quality hyperspectral image, moire may be suppressed as much as possible. Even if the filter array 10 and the image sensor 60 are arranged without being rotated, an error of a rotation angle of several degrees may actually occur. As shown in FIG. 14, a noticeable moire appears even at a rotation angle of 5°. In contrast, when the filter array 10 and the image sensor 60 are arranged at a rotation angle of 25° or more and 45° or less, even if an error of a rotation angle of several degrees occurs, the moire hardly changes and is difficult to see as shown in FIG. 14. Therefore, an increase in moire caused by arrangement errors can be suppressed.

[0155] Furthermore, in the fifth example shown in Fig. 13, similarly to the third example shown in Fig. 11, the filters 100 and the photodetection elements 60a are not opposed to each other in a one-to-one relationship. Therefore, the randomness of the spectrum of the light detected by the photodetection elements 60a can be improved. As a result, the separated images 220 can be restored more accurately.

[0156] In the example shown in FIG. 13, the angle between the first vector D1 and the second vector D2, and the angle between the third vector D3 and the fourth vector are 90°. These angles correspond to a square lattice arrangement. The angle between the first vector D1 and the second vector D2, and the angle between the third vector D3 and the fourth vector may be a predetermined angle other than 90°. For example, an angle of 60° corresponds to a triangular lattice arrangement. The rotation angle at which moire is less visible is between ¼ and ½ of the predetermined angle.

[0157] <Fixing the arrangement of filter arrays and image sensors> Next, with reference to FIGS. 15A to 16E, an example of a structure for fixing the filter array 10 and the image sensor 60 to each other will be described.

[0158] FIG. 15A is a cross-sectional view showing a sixth example of the photodetector 300. FIG. 15B is a plan view showing a state in which the filter array 10 and the substrate 20 are removed from the photodetector 300 shown in FIG. 15A. In the sixth example shown in FIG. 15A, the filter array 10 has a peripheral region 10p located around the light emission surface 10s2, and the image sensor 60 has a peripheral region 60p located around the light detection surface 60s. The peripheral region 10p of the filter array 10 and the peripheral region 60p of the image sensor 60 are flat. In the sixth example shown in FIG. 15A, the photodetector 300 includes a double-sided tape 30 that bonds the peripheral region 10p of the filter array 10 and the peripheral region 60p of the image sensor 60 together. The double-sided tape 30 has a shape extending along a direction perpendicular to the light detection surface 60s as shown in FIG. 15A, and has a shape surrounding the space between the light emission surface 10s2 and the light detection surface 60s as shown in FIG. 15B. The double-sided tape 30 defines the distance between the light emission surface of each filter 100 and the light detection surface 60s. The height of the double-sided tape 30 can be designed so that the distance between the light emission surface 10s2 and the light detection surface 60s satisfies the minimum distance described above. By fixing the arrangement of the filter array 10 and the image sensor 60 with the double-sided tape 30, the light detection device 300 can be manufactured at low cost through a simple process.

[0159] Fig. 15C is a plan view showing a schematic diagram of another example of the arrangement of the double-sided tape 30 shown in Fig. 15B. In the example shown in Fig. 15C, the four corners of the peripheral region 10p of the filter array 10 and the four corners of the peripheral region 60p of the image sensor 60 are attached together with the double-sided tape 30. In this embodiment, at least a part of the peripheral region 10p of the filter array 10 and at least a part of the peripheral region 60p of the image sensor 60 are attached together with the double-sided tape 30. As a result, the arrangement of the filter array 10 and the image sensor 60 can be fixed.

[0160] Fig. 16A is a cross-sectional view that shows a schematic diagram of a seventh example of the photodetector 300. Fig. 16B is a plan view that shows a state in which the filter array 10 and the substrate 20 are removed from the photodetector 300 shown in Fig. 16A. In the seventh example shown in Fig. 16A, the photodetector 300 includes a plurality of spacers 32 sandwiched between the filter array 10 and the image sensor 60. The light emission surface 10s2 and the light detection surface 60s are bonded with a transparent adhesive 34. The transparent adhesive 34 is formed to cover all wavelength ranges W1 to W3 included in the target wavelength range. i The transparent adhesive 34 transmits light with high transmittance. The high transmittance is, for example, 0.8 or more. The spacers 32 have rigidity and more accurately define the distance between the light emission surface of each filter 100 and the light detection surface 60s. The spacers 32 may be, for example, photospacers that define the height of a space in a liquid crystal display into which liquid crystal material is injected. The photospacer may be formed, for example, from negative photoresist SU8 (manufactured by Nippon Kayaku Co., Ltd.). The transparent adhesive 34 may be formed, for example, from optical path coupling adhesive GA700L (manufactured by NTT Advanced Technology Corporation). A method for forming the spacers 32 will be described later.

[0161] When the cross-sectional size of each spacer 32 in the XY plane is larger than the size of the photodetection element 60a, each spacer 32 is supported by the light exit surface of the filter 100 and the top of the microlens 40a. Even when the cross-sectional size of each spacer 32 is approximately the same as the size of the photodetection element 60a, some of the spacers 32 are supported by the light exit surface of the filter 100 and the top of the microlens 40a. In either case, the spacer 32 can more accurately define the distance between the light exit surface of each filter 100 and the photodetection surface 60s.

[0162] In the example shown in FIG. 16B, the spacers 32 are irregularly arranged. The distribution density of the spacers 32 can be designed to be uniform for each region of a predetermined size (e.g., a region corresponding to a 3×3 unit cell). The cross-sectional size of the spacers 32 may be uniform or non-uniform. The cross-sectional size of the spacers 32 may be larger than or approximately equal to the size of the photodetector element 60a. The cross-sectional size of some of the spacers 32 may be smaller than the size of the photodetector element 60a. The spacers 32 may or may not have light-transmitting properties. In a plan view, at least one of the spacers 32 may be arranged at a position overlapping the microlens 40a.

[0163] The spacers 32, whether located near the peripheral region 60p or on the photodetection surface 60s of the image sensor 60, serve to more accurately define the distance between the light exit surface of each filter 100 and the photodetection surface 60s. The spacers 32 located on the photodetection surface 60s and overlapping the microlenses 40a also serve to improve the randomness of the spectrum of light detected by the photodetection elements 60a. If the refractive index of the spacers 32 is different from that of the transparent adhesive 34, part of the light incident on the photodetection elements 60a is modulated by the spacers 32.

[0164] In the example shown in FIG. 16A and FIG. 16B, the space between the light emitting surface 10s2 and the light detecting surface 60s is filled with the transparent adhesive 34. Therefore, the mechanical strength of the light detecting device 300 can be improved. As a result, the reliability of the light detecting device 300 can be improved. Furthermore, since the heat generated from the image sensor 60 is transferred to the filter array 10 and the substrate 20 via the transparent adhesive 34, the heat can be efficiently released to the outside. In this embodiment, at least a part of the light emitting surface 10s2 and at least a part of the light detecting surface 60s are bonded with the transparent adhesive 34. Alternatively, as shown in FIG. 15A to FIG. 15C, at least a part of the peripheral region 10p of the filter array 10 and at least a part of the peripheral region 60p of the image sensor 60 may be bonded with an adhesive. In this case, the adhesive does not need to be transparent.

[0165] Fig. 16C is a plan view showing a schematic diagram of another example of the arrangement of the plurality of spacers 32 shown in Fig. 16B. In the example shown in Fig. 16C, the plurality of spacers 32 are provided on the light detection surface 60s of the image sensor 60, not on the peripheral region 60p of the image sensor 60. When it is necessary to further improve the randomness of the spectrum of light detected by the light detection element 60a, the arrangement of the plurality of spacers 32 shown in Fig. 16C is effective.

[0166] Fig. 16D is a plan view showing a schematic diagram of yet another example of the arrangement of the plurality of spacers 32 shown in Fig. 16B. In the example shown in Fig. 16D, the plurality of spacers 32 are provided near the peripheral region 60p of the image sensor 60 rather than on the light detection surface 60s of the image sensor 60. When it is not necessary to improve the randomness of the spectrum of the light detected by the light detection element 60a and it is necessary to more accurately define the distance between the light emission surface of each filter 100 and the light detection surface 60s, the arrangement of the plurality of spacers 32 shown in Fig. 16D is effective.

[0167] FIG. 16E is a plan view showing a schematic diagram of yet another example of the arrangement of the plurality of spacers 32 shown in FIG. 16B. In the example shown in FIG. 16E, the plurality of spacers 32 and the plurality of adhesives 35 are arranged in the peripheral region 60p of the image sensor 60. The adhesives 35 have a columnar shape similar to the spacers 32. The adhesives 35 arranged in the peripheral region 60p do not need to be transparent. This is because the peripheral region 60p does not contribute to light detection. When viewed from the normal direction of the light incident surface 10s1, the adhesives 35 and the spacers 32 do not overlap each other. Therefore, the distance between the light exit surface 10s2 of the filter array 10 and the light detection surface 60s of the image sensor 60 can be accurately defined, and the filter array 10 and the image sensor 60 can be attached in a state closer to parallel. Furthermore, since the spacers 32 and the transparent adhesives 34 are not arranged on the light detection surface 60s, there is no attenuation of light due to the spacers 32 and the transparent adhesives 34. When there is no need to improve the randomness of the spectrum of the light detected by the photodetection element 60a, no need to improve the mechanical strength by the transparent adhesive 34, and it is necessary to more accurately specify the distance between the light emission surface 10s2 and the photodetection surface 60s, the arrangement of multiple spacers 32 shown in Figure 16E is effective.

[0168] In the example shown in FIG. 16E, a plurality of spacers 32 and a plurality of adhesives 35 are alternately arranged in the peripheral region 60p of the image sensor 60. The plurality of spacers 32 and the plurality of adhesives 35 do not need to be alternately arranged, and two or more spacers 32 may be continuously arranged, or two or more adhesives 35 may be continuously arranged. Alternatively, four spacers 32 may be arranged at the four corners of the peripheral region 60p of the image sensor 60, and a plurality of adhesives 35 may be arranged in other parts. In the example shown in FIG. 16E, the spacers 32 have a rectangular cross-sectional shape, but may also have a circular cross-sectional shape. The adhesive 35 has a circular shape, but may also be elliptical. When it is not necessary to precisely define the distance between the light emission surface 10s2 and the light detection surface 60s, the adhesives 35 and the spacers 32 may overlap each other when viewed from the normal direction of the light incidence surface 10s1.

[0169] <Method of forming spacers> As a method for forming the spacers 32, for example, a method of forming a plurality of spacers 32 on the light detection surface 60s of the image sensor 60 is considered. However, this method may cause the following problems. Assume that an image sensor 60 having a plurality of spacers 32 formed on the light detection surface 60s is bonded to a filter array 10 having a light exit surface 10s2 that is an uneven surface. In this case, since the distance between the light detection surface 60s of the image sensor 60 and the light exit surface 10s2 of the filter array 10 varies for each pixel, or the distance between the peripheral region 10p of the filter array 10 and the peripheral region 60p of the image sensor 60 varies for each location, some of the spacers 32 may not contact the light exit surface 10s2 of the filter array 10. In such a configuration, problems may occur such as a decrease in the mechanical strength of the bonded filter array 10 and image sensor 60, or a decrease in the accuracy of defining the distance between the light exit surface 10s2 and the light detection surface 60s. In order to solve this problem, the present inventors have come up with a method of forming a plurality of spacers 32 on the light exit surface 10s2 of the filter array 10.

[0170] 17A to 17D, a method for forming a plurality of spacers 32 on the light exit surface 10s2 of the filter array 10 will be described below. Figures 17A to 17D are diagrams for explaining an example of steps in the method for forming spacers.

[0171] In a first step, a filter array 10 having a textured surface is prepared, as shown in Figure 17 A. In the example shown in Figure 17 A, the filter array 10 is supported by a substrate 20, but the substrate 20 may be omitted.

[0172] In the next step, as shown in Fig. 17B, a liquid photoresist 32A is applied to the light output surface 10s2 of the filter array 10 by, for example, spin coating. The spin-coated photoresist 32A absorbs or fills in the irregular asperities of the light output surface 10s2, so that the top surface of the photoresist 32A becomes flat. The photoresist can be formed on the asperity surface of the filter array 10 by the steps described with reference to Fig. 17B.

[0173] In the next step, as shown in FIG. 17C or FIG. 17D, a photoresist is patterned to form a plurality of spacers 32 having the same height on the light emission surface 10s2 of the filter array 10. Here, the uniform height means that the ends of the plurality of spacers 32 are located at approximately the same height in the vertical direction. As shown in FIG. 17C, when the cross-sectional size of each spacer 32 is equal to or smaller than the size of one pixel, the vertical length of the spacer differs for each pixel, but the heights of the plurality of spacers 32 are uniform in the filter array 10. As shown in FIG. 17D, even when the cross-sectional size of each spacer 32 is larger than the size of one pixel, the heights of the plurality of spacers 32 are uniform in the filter array 10. A plurality of spacers can be formed on the uneven surface of the filter array 10 by the steps described with reference to FIG. 17C or FIG. 17D.

[0174] 17A to 17D, a plurality of spacers 32 are formed on the light exit surface 10s2 of the filter array 10. Without being limited to this example, a plurality of spacers 32 may be formed on the light exit surface 10s2 and / or the peripheral region 10p of the filter array 10. In this specification, the filter array 10 on which a plurality of spacers 32 are formed is also referred to as a "structure."

[0175] <Bonding the Filter Array 10 and the Image Sensor 60> 18A to 18C, a method for bonding the filter array 10 and the image sensor 60 together will be described. Figures 18A to 18C are views for explaining an example of steps in the method for bonding the filter array 10 and the image sensor 60 together.

[0176] In the first step, as shown in FIG. 18A, a filter array 10 having a plurality of spacers 32 formed on a light emitting surface 10s2 and an image sensor 60 having a plurality of adhesives 35 arranged in dots on a light detecting surface 60s are prepared. The adhesive 35 may be made of, for example, a photocurable resin or a thermosetting resin. The photocurable resin may be an ultraviolet curable resin or a visible light curable resin. In the example shown in FIG. 18A, the adhesive 35 has a roughly semi-elliptical spherical shape. The shape of the adhesive 35 is arbitrary.

[0177] In the next step, as shown in FIG. 18B, the filter array 10 is pressed against the image sensor 60 via a plurality of spacers 32 and a plurality of adhesives 35, with the light emission surface 10s of the filter array 10 and the light detection surface 60s of the image sensor 60 facing each other. As shown in FIG. 18B, the spacers 32 and the adhesives 35 may be arranged so as not to overlap each other when viewed from a direction perpendicular to the light incidence surface 10s1. In this step, the adhesive 35 is pressed by the filter array 10 to have a roughly cylindrical shape. By pressing, the diameter of the adhesive 35 shown in FIG. 18B becomes larger than the diameter of the adhesive 35 shown in FIG. 18A.

[0178] In the next step, when the adhesive 35 is made of a photocurable resin, the adhesives 35 are irradiated with light through the filter array 10 and the substrate 20 as shown in FIG. 18C. The arrows in FIG. 18C show the state of light irradiation. When the photocurable resin is an ultraviolet curable resin, the irradiated light is ultraviolet light, and when the photocurable resin is a visible light curable resin, the irradiated light is visible light. The adhesives 35 are hardened by the light irradiation, and the filter array 10 and the image sensor 60 are bonded together in a state where they are almost parallel to each other. This bonding can accurately define the distance between the light emission surface of each filter 100 and the light detection surface of the corresponding light detection element 60a. When the adhesive 35 is made of a thermosetting resin, the adhesives 35 are hardened by heating, and the filter array 10 and the image sensor 60 are bonded together in a state where they are almost parallel to each other.

[0179] In the example shown in Figures 18A to 18C, a filter array 10 having a plurality of spacers 32 formed on a light emitting surface 10s2 is bonded to an image sensor 60 having a plurality of adhesives 35 arranged on a light detection surface 60s. The present invention is not limited to this example, and a filter array 10 having a plurality of spacers 32 formed on a light emitting surface 10s2 and / or a peripheral region 10p may be bonded to an image sensor 60 having a plurality of adhesives 35 arranged on a light detection surface 60s and / or a peripheral region 60p. Although not shown in Figures 18A to 18C, the peripheral region 10p of the filter array 10 and the peripheral region 60p of the image sensor 60 face each other.

[0180] <Sealing of filter arrays and image sensors> Next, with reference to FIGS. 19 and 20, an example of sealing the filter array 10 and the image sensor 60 in a package will be described.

[0181] 19 is a cross-sectional view showing a schematic diagram of an eighth example of a photodetector 300. The eighth example shown in FIG. 19 is different from the seventh example shown in FIG. 16A in that the photodetector 300 includes a transparent cover 50 and a package 80, and does not include a transparent adhesive 34 between the light exit surface 10s2 and the light detection surface 60s. The transparent cover 50 covers all wavelength ranges W1 to W2 included in the target wavelength range. i The transparent cover 50 transmits light of a wavelength of 100 nm to the transparent cover 50 at a high transmittance. The high transmittance is, for example, 0.8 or more. The transparent cover 50 has a convex portion 50p. The convex portion 50p of the transparent cover 50 supports the filter array 10 and the substrate 20 via the transparent adhesive 36. The transparent cover 50 may be formed of, for example, glass or plastic. If the refractive index of the transparent adhesive 36 is close to the refractive index of the transparent cover 50, reflection of light at the interface between the transparent cover 50 and the transparent adhesive 36 can be suppressed. The package 80 includes a bottom 82, a sidewall 84, and a plurality of pairs of lead electrodes 80a penetrating the bottom 82. The bottom 82 has a first region 82a in which the image sensor 60 is provided. The sidewall 84 extends from a second region 82b located around the first region 82a of the bottom 82 in a direction perpendicular to the bottom 82, and has a shape surrounding the image sensor 60. The plurality of pairs of lead electrodes 80a are electrically connected to the plurality of photodetection elements 60a included in the image sensor 60. A photocurrent generated in each of the photodetection elements 60a can be extracted from the pair of lead electrodes 80a.

[0182] The upper surface of the side wall 84 of the package 80 is joined to the peripheral region of the transparent cover 50 facing the upper surface. For example, a soldering material or a brazing material, or a photocurable resin or a thermosetting resin may be used for this joining. As shown in FIG. 19, the transparent cover 50 and the package 80 seal the filter array 10 and the image sensor 60. This sealing can prevent dust, dirt, or moisture from entering the inside of the light detection device 300. As a result, the reliability of the light detection device 300 can be improved.

[0183] The photodetector 300 shown in FIG. 19 can be manufactured by covering the package 80 including the image sensor 60 and the multiple pairs of lead electrodes 80a with the transparent cover 50 that supports the filter array 10 and the substrate 20 via the transparent adhesive 36. Since the package 80 is covered with the transparent cover 50, the photodetector 300 can be manufactured at low cost and through a simple process. The multiple spacers 32 are provided on the light exit surface 10s2 before the package 80 is covered with the transparent cover 50. The thickness of the convex portion 50p of the transparent cover 50 and the thickness of the transparent adhesive 36 are designed so that the multiple spacers 32 come into contact with the light detection surface 60s when the package 80 is covered with the transparent cover 50. When the package 80 is covered with the transparent cover 50, the transparent adhesive 36 before hardening is compressed and the thickness of the transparent adhesive 36 is reduced. As a result, the distance between the light exit surface of each filter 100 and the light detection surface 60s is more accurately defined by the multiple spacers 32. If there is a manufacturing error in the height of the sidewall 84 of the package 80, the size of the gap between the substrate 20 and the transparent cover 50 may vary from package to package. The manufacturing error may be, for example, 100 μm to 300 μm. If the transparent adhesive 36 is made of a photocurable resin, even if the size of the gap between the substrate 20 and the transparent cover 50 varies from package to package, the gap can be filled with the transparent adhesive 36 that expands and contracts before curing. The transparent adhesive 36 is then irradiated with light or heated to be cured. Unlike the embodiment shown in FIG. 19, the substrate 20 and the transparent cover 50 located above the filter array 10 may not be bonded to each other by the transparent adhesive 36. In this case, there is a gap between the substrate 20 and the transparent cover 50, so that the two do not come into contact with each other. The filter array 10 is fixed to the image sensor 60 by the adhesive 35.

[0184] Fig. 20 is a cross-sectional view showing a ninth example of the photodetector 300. The ninth example shown in Fig. 20 differs from the eighth example shown in Fig. 19 in the following three points. The protrusion 50p of the transparent cover 50 directly supports the filter array 10 without the substrate 20. The side wall 84 of the package 80 is lower by the amount of the substrate 20 not present. The upper surface of the side wall 84 of the package 80 and the peripheral region of the transparent cover 50 facing the upper surface are joined with an adhesive 38 made of a photocurable resin or a thermosetting resin.

[0185] As shown in FIG. 20, the filter array 10 may be directly laminated on the convex portion 50p of the transparent cover 50. Compared with the eighth example shown in FIG. 19, the number of parts can be reduced by the absence of the substrate 20. Even if there is a manufacturing error in the height of the sidewall 84 of the package 80, the gap between the upper surface of the sidewall 84 of the package 80 and the peripheral region of the transparent cover 50 can be filled with the elastic adhesive 38 before hardening. The adhesive 38 is then hardened by irradiating it with light or by heating. As a result, the transparent cover 50 is bonded to the package 80. The adhesive 38 does not need to be transparent.

[0186] <Arrangement of the filter array including the color filter and the image sensor> In the above-mentioned example, the filter array 10 includes a Fabry-Perot filter. Such a filter array 10 can be used in a hyperspectral camera. The filter array of the present disclosure can be used not only in a hyperspectral camera but also in a general camera (i.e., an imaging device) that acquires color images of three primary colors (red, green, and blue). In that case, the filter array 10 can include a color filter instead of a Fabry-Perot filter. The effect of reducing the influence of the interference fringes described above can be obtained not only in a Fabry-Perot filter but also in a filter array using a color filter. A filter array including a color filter can also be used in a hyperspectral camera. Hereinafter, an example of a configuration for acquiring a hyperspectral image, i.e., the above-mentioned separation image 220, using such a filter array will be described.

[0187] FIG. 21 is a diagram showing the transmission spectra of a red filter, a green filter, and a blue filter. In FIG. 21, "R", "G", and "B" represent red, green, and blue, respectively. In this specification, the red, green, and blue color filters are referred to as "R filter", "G filter", and "B filter", respectively. The transmission spectrum of the R filter has a maximum value at a wavelength in the range of 600 nm to 700 nm, and has a peak width equivalent to this range. The transmission spectrum of the G filter has a maximum value at a wavelength in the range of 500 nm to 600 nm, and has a peak width equivalent to this range. The transmission spectrum of the B filter has a maximum value at a wavelength in the range of 400 nm to 500 nm, and has a peak width equivalent to this range. The transmission spectrum of each color filter has a single broad peak within the target wavelength range W. This peak width is determined by dividing the wavelength ranges W1, W2, ..., W included in the target wavelength range W. i If the transmission spectrum of each color filter has such a wide peak, it is possible that one of the color filters has a peak in the adjacent wavelength range W within the target wavelength range W. i and wavelength range W i+1 In this case, even if the transmission spectrum of each color filter does not have two or more peaks in the target wavelength range W, multiple separated images 220 can be obtained.

[0188] Therefore, the filter array 10 including the Fabry-Perot filter in the first example shown in Fig. 7 to the ninth example shown in Fig. 20 may be replaced with a filter array 10 including a color filter. By using a color filter, the filter array 10 can be manufactured at low cost.

[0189] 22 to 31, an example of the arrangement relationship between the filter array 10 including color filters and the image sensor 60 will be described. Descriptions that overlap with the above description will be omitted.

[0190] FIG. 22 is a cross-sectional view showing a tenth example of the light detection device 300 according to the embodiment of the present disclosure. The tenth example shown in FIG. 22 is different from the first example shown in FIG. 7 in that the filter array 10 includes a filter 100 that is a color filter. The color filter may be formed of, for example, a color resist. The filter array 10 includes a plurality of R filters, a plurality of G filters, and a plurality of B filters that are irregularly arranged on the substrate 20, such as a random distribution or a quasi-random distribution. The thicknesses of the R filters, the G filters, and the B filters are different from each other. The thickness of each filter may be, for example, 100 nm or more and 5 μm or less. The distance between the light exit surface 10s2 and the light detection surface 60s is different for each of the R filters, the G filters, and the B filters. Since the distance between the light exit surface 10s2 and the light detection surface 60s is non-uniform, even if multiple reflection of light occurs between the light exit surface 10s2 and the light detection surface 60s, it is possible to suppress the appearance of interference fringes in the captured image. If the distance between the light emitting surface 10s2 and the light detecting surface 60s is not uniform, the appearance of interference fringes in the captured image can be suppressed even if the filter array 10 includes color filters in a normal Bayer array. Unlike the filter array 10 including Fabry-Perot filters, the filter array 10 including color filters does not have substantial warping. Therefore, the effect of the filter array 10 on the warping of the substrate 20 is sufficiently small.

[0191] The filter array 10 according to the present embodiment includes two or more types of color filters having different transmission spectra in the target wavelength range W. The distance between the light exit surface 10s2 and the light detection surface 60s is different for each of the two or more types of color filters. The color filters may be primary color filters such as an R filter, a G filter, and a B filter. Alternatively, the color filters may be complementary color filters such as a cyan filter, a magenta filter, and a yellow filter. Alternatively, the color filters may be a mixture of primary color filters and complementary color filters. The filter array 10 according to the present embodiment may include a filter that does not have wavelength dependency of light transmittance, such as a transparent filter or an ND filter.

[0192] Figures 23A and 23B are cross-sectional views that typically show modified examples of the photodetector shown in Figure 22. The modified examples shown in Figures 23A and 23B correspond to the modified examples shown in Figures 9A and 9B, respectively.

[0193] 24A to 24C are cross-sectional views each showing an eleventh to thirteenth example of a photodetector 300 according to an embodiment of the present disclosure. The eleventh example shown in Fig. 24A corresponds to the second example shown in Fig. 10. The twelfth example shown in Fig. 24B and the thirteenth example shown in Fig. 24C are configurations specific to a filter array 10 including a color filter.

[0194] The twelfth example shown in FIG. 24B differs from the tenth example shown in FIG. 22 in that each of the multiple filters 100 has an anti-reflection film 22 on the light exit surface. At least one of the filters 100 may have the anti-reflection film 22, not all of the filters 100. If the anti-reflection film 22 is provided directly on the Fabry-Perot filter, the transmission spectrum of the Fabry-Perot filter may change. In contrast, if the anti-reflection film 22 is provided directly on the color filter, the transmission spectrum of the color filter does not change. Therefore, in the filter array 10 including the color filter, the anti-reflection film 22 can be provided on the light exit surface 10s2. The anti-reflection film 22 can suppress the reflection of light that occurs at the interface between the filter array 10 and the air in the tenth example shown in FIG. 22. Therefore, the multiple reflection of light that occurs between the light exit surface 10s2 and the light detection surface 60s can be suppressed. As a result, the appearance of interference fringes in the captured image can be further suppressed. The thirteenth example shown in Fig. 24C differs from the twelfth example shown in Fig. 24B in that the substrate 20 further includes an antireflection film 22 on the surface opposite to the surface supporting the filter array 10. The two antireflection films 22 can further improve the light detection efficiency of the light detection device 300.

[0195] 25 and 26 are cross-sectional views each showing a schematic diagram of a fourteenth and a fifteenth example of a photodetector 300 according to an embodiment of the present disclosure. The fourteenth example shown in Fig. 25 corresponds to the third example shown in Fig. 11. The fifteenth example shown in Fig. 26 corresponds to the fourth example shown in Fig. 12.

[0196] 27 is a plan view diagrammatically illustrating a sixteenth example of a photodetector 300 according to an embodiment of the present disclosure. The sixteenth example illustrated in FIG. 27 corresponds to the fifth example illustrated in FIG.

[0197] Fig. 28 is a cross-sectional view that illustrates a schematic diagram of a 17th example of a photodetector 300 according to an embodiment of the present disclosure. The 17th example illustrated in Fig. 28 corresponds to the 6th example illustrated in Fig. 15A. The peripheral region 10p of the filter array 10 illustrated in Fig. 28 may be, for example, the surface of any one of the R filter, G filter, and B filter.

[0198] 29 to 31 are cross-sectional views each showing a schematic diagram of an 18th to 20th example of a photodetector 300 according to an embodiment of the present disclosure. The 18th example shown in FIG. 29 corresponds to the 7th example shown in FIG. 16A. The 19th example shown in FIG. 30 corresponds to the 8th example shown in FIG. 19. The 20th example shown in FIG. 31 corresponds to the 9th example shown in FIG. 20.

[0199] In addition, some or all of the above-mentioned examples of the photodetector 300 may be combined in any way depending on the purpose or application. For example, the anti-reflection film 22 in the second example shown in Fig. 10 may be applied to any of the third example shown in Fig. 11 to the ninth example shown in Fig. 20. Alternatively, the filter array 10 and the image sensor 60 in the fifth example shown in Fig. 13 may be sealed by the transparent cover 50 and the package 80 in the eighth example shown in Fig. 19 or the ninth example shown in Fig. 20. [Industrial Applicability]

[0200] The optical detection device and the filter array in the present disclosure are useful, for example, in cameras and measuring instruments that acquire two-dimensional images of multiple wavelengths. The optical detection device and the filter array in the present disclosure can also be applied to sensing for biological, medical, and cosmetic purposes, foreign matter and pesticide residue inspection systems for food, remote sensing systems, and vehicle-mounted sensing systems. [Explanation of symbols]

[0201] 10 Filter Array 10s1 light incidence surface 10s2 light exit surface 10p Filter array edge area 12 Interference Layer 14a 1st reflective layer 14b 2nd reflective layer 20 Substrate 22 Anti-reflection coating 30 Double-sided tape 32 Spacer 32A Photoresist 34, 36 Transparent adhesive 35 Adhesive 38 Adhesive 40 Optical system 40a Micro Lens 50 Transparent Cover 50p Transparent cover protrusion 60 Image Sensor 60s Light detection surface 60a Photodetector element 60p image sensor edge area 70 Objects 80 packages 82 Bottom 82a Bottom first area 82b Bottom second area 84 Side wall 100 Filters 120 images 200 Signal Processing Circuit 220 Separate Images 300 Photodetector 400 Optical Detection System

Claims

1. a filter array including a plurality of filters arranged in a two-dimensional plane, each of the filters having a light input surface and a light output surface, the plurality of filters having different transmission spectra; an image sensor having a light detection surface facing the light emission surface, the image sensor including a plurality of light detection elements arranged in a two-dimensional plane along the light detection surface; Equipped with a gap exists between the light emission surface and the light detection surface; the gap distance is different for each of the filters; The minimum distance of the gap is greater than 0.1 μm and less than or equal to 200 μm; the gap contains air; Light detection device.

2. At least a part of the light emitting surface and at least a part of the light detecting surface are bonded together with a transparent adhesive.

2. The optical detection device according to claim 1.

3. At least a part of a peripheral region located around the light emission surface of each of the filters and at least a part of a peripheral region located around the light detection surface are bonded together with an adhesive.

2. The optical detection device according to claim 1.

4. further comprising a plurality of spacers positioned between the filter array and the image sensor.

4. The optical detection device according to claim 3.

5. When viewed from a normal direction of the light incident surface, the adhesive and the spacers do not overlap each other.

5. The optical detection device according to claim 4.

6. The thicknesses of the plurality of filters are different from one another, so that the distance of the gap is different for each of the filters.

2. The optical detection device according to claim 1.

7. A signal processing circuit is further provided, The signal processing circuit generates a multi-wavelength image based on the light detected by the image sensor.

2. The optical detection device according to claim 1.

8. Further, an anti-reflection film is provided between the light emitting surface and the light detecting surface.

2. The optical detection device according to claim 1.

Images