Spectroscopic imaging system, method for manufacturing a spectroscopic imaging system

Abstract

This suppresses variations in the wavelength dependence of transmittance caused by differences in etching rates across different parts of the optical filter. [Solution] The spectroscopic imaging system according to the present invention comprises a plurality of optical filters whose light transmittance has different wavelength dependences, the optical filters are composed of through holes smaller than the pixel size of the image sensor, the optical filters are supported by a transparent material that transmits incident light, and the arithmetic mean roughness on the transparent material side of the interface between the optical filters and the transparent material is 10 nm or less.

Description

Technical Field

[0001] The present invention relates to a spectroscopic imaging system that spectroscopically detects incident light.

Background Art

[0002] When observing substances or objects with a camera or microscope, the reflected or transmitted light from the substances or objects is detected by a detector (such as an image sensor) of the camera or microscope and imaged. The detector captures all light with wavelengths for which it has sensitivity. For example, a Si CMOS image sensor has sensitivity to light with wavelengths of about 0.4 to 1 μm, and for light within that wavelength range, it integrates and detects. On the other hand, the spectroscopic imaging method involves obtaining an image at a specific wavelength by spectroscopically separating the reflected or transmitted light and detecting the light of a specific wavelength with a detector. When the number of wavelengths (number of bands) is several to about a dozen, that is, when the corresponding number of images is several to about a dozen, it is sometimes called multispectral imaging, and when it is more than that, it is called hyperspectral imaging. Generally, since the wavelengths absorbed by substances or objects to be observed vary depending on their types, it is possible to classify the types of substances or objects or determine the amount of contained moisture by using the images obtained by spectroscopic imaging.

[0003] Multispectral imaging can be realized by methods such as arranging multiple types of optical filters that only transmit light of specific wavelengths on an image sensor. For example, a color image sensor arranges color filters that transmit red, green, and blue respectively, so it can be said to be a type of multispectral imaging. On the other hand, when using a similar method in hyperspectral imaging, since the spatial resolution decreases as the number of optical filters increases, a method may be adopted in which the light dispersed by a spectroscopic element such as a diffraction grating is irradiated onto the image sensor. However, since the light is dispersed and irradiated in the x - direction or y - direction with respect to an image sensor composed of a two - dimensional array, the remaining number of dimensions becomes 1, that is, it becomes a line sensor, and the entire image cannot be acquired at once.

[0004] In contrast, a compressed sensing technique is known that utilizes optical filters but significantly reduces the number of filters to less than the desired number of bands. This technique uses multiple types of optical filters that transmit various wavelengths of light, but with different transmittances depending on the wavelength, rather than just optical filters that transmit only light of a specific wavelength. The intensity of the light transmitted through each filter is detected by an image sensor through integration in the wavelength direction, and the spectrum of the incident light is reconstructed from this intensity information. To improve the accuracy of the reconstructed spectrum, it is desirable that the wavelength dependence of the transmittance differs as much as possible between different types of filters. Although this technique also uses multiple types of filters, resulting in lower spatial resolution compared to images without filters, it can significantly improve spatial resolution compared to the case where there are as many filters as there are bands to be measured.

[0005] Non-patent document 1 below describes a technique for acquiring spectral images using compressed sensing. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Single-shot on-chip spectral sensors based on photonic crystal slabs, Zhu Wang et al., NATURE COMMUNICATIONS (2019) 10:1020 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] A known method for forming multiple types of optical filters with different wavelength dependencies of transmittance on the same plane involves forming an array of structures (including structures with wavelength-like dimensions, collectively referred to as subwavelength structures) with dimensions approximately equal to or shorter than the wavelength to be measured. Since the wavelength dependency of transmittance can be modulated according to the shape, dimensions, and period on a two-dimensional plane (such as a circle or square), multiple regions with different wavelength dependencies of transmittance can be formed on the same plane by changing these parameters for each region, i.e., by forming multiple types of patterns. These optical filters will be referred to as photonic crystal filters below.

[0008] While conventional semiconductor manufacturing processes are used to form subwavelength structures, the aspect ratio cannot be made very high, making single-film formation difficult; therefore, they are formed on a support substrate. Since the formed nanostructures are stacked on an image sensor, a material transparent in the wavelength range to be measured is used as the substrate. When forming subwavelength structures by etching a film deposited on the substrate, if various dimensions and periods are mixed in the plane, the etching rate will differ for each structure due to the loading effect. This can result in some patterns being etched only partway through the film, while others are etched all the way to the substrate. Even in these states, it is possible to modulate the wavelength dependence of the transmittance, but the wavelength dependence of the transmittance will differ compared to a structure etched to the depth of the film thickness. Furthermore, if in-plane distributions generated by semiconductor manufacturing equipment and variations during repeated processing are superimposed, the wavelength dependence of the transmittance will deviate from the value assumed in the design, even if the same pattern is intended to be formed.

[0009] When reconstructing the spectrum of incident light, information on the wavelength dependence of the photonic crystal filter's transmittance is needed, either directly or indirectly. In principle, it is possible to measure the wavelength dependence of transmittance at each location and use that information to correct the reconstruction model. However, this presents challenges such as the time required to retrain the reconstruction model, the enormous amount of information needed for correction straining memory, and the time required for correction. Furthermore, if the wavelength dependence of transmittance at a specific location is used as a representative value and applied to the entire region to reduce the amount of information, there is a problem in that the reconstructed spectrum does not faithfully reproduce the spectrum of the incident light.

[0010] This invention has been made in view of the above-mentioned problems, and aims to suppress variations in the wavelength dependence of transmittance caused by differences in etching rates for each part of the optical filter. [Means for solving the problem]

[0011] The spectroscopic imaging system according to the present invention comprises a plurality of optical filters whose light transmittance has wavelength dependences that differ from each other, wherein the optical filters are composed of through holes smaller than the pixel size of the image sensor, the optical filters are supported by a transparent material that transmits incident light, and the arithmetic mean roughness on the transparent material side of the interface between the optical filters and the transparent material is 10 nm or less. [Effects of the Invention]

[0012] The spectroscopic imaging system according to the present invention can suppress variations in the wavelength dependence of transmittance caused by differences in etching rates at different parts of the optical filter. Other problems, configurations, and advantages of the present invention will become clear from the following description of embodiments. [Brief explanation of the drawing]

[0013] [Figure 1] This is an overall configuration diagram of the spectroscopic imaging system according to Embodiment 1. [Figure 2] This is a top view showing a magnified portion of the photonic crystal filter 11. [Figure 3] This shows an example of the transmittance when light passes through the photonic crystal filter 11, and information on the wavelength dependence of the transmittance extracted from it. [Figure 4] This is a schematic diagram illustrating the procedure by which the computing unit 24 reconstructs hyperspectral image data. [Figure 5] This is a side cross-sectional view of the photonic crystal filter 11. [Figure 6] An example of data structure describing the wavelength dependence of transmittance is shown. [Figure 7] This is a side cross-sectional view illustrating a conventional process for manufacturing a photonic crystal filter 11. [Figure 8] This is a side cross-sectional view illustrating the process for manufacturing the photonic crystal filter 11 according to Embodiment 1. [Figure 9] This is a side cross-sectional view illustrating the process for manufacturing the photonic crystal filter 11 according to Embodiment 2. [Figure 10] This shows an example of forming a tapered SiN film during the manufacturing process of the photonic crystal filter 11. [Figure 11] This is a side cross-sectional view illustrating another problem that occurs when the SiN film has a tapered shape. [Figure 12] This is a side cross-sectional view illustrating the process for manufacturing the photonic crystal filter 11 according to Embodiment 3. [Modes for carrying out the invention]

[0014] <Embodiment 1> Figure 1 is an overall configuration diagram of a spectral imaging system according to Embodiment 1 of the present invention. The spectral imaging system is a system for acquiring spectral images of an object to be measured 3, and comprises a filter 21, a lens 22, a camera 1, a cable 23, a computing device 24, and a light source 25. Reflected light from the object to be measured 3, illuminated by the light source 25, is focused through the filter 21 and lens 22 to the camera 1, and the camera 1 captures a spectral image.

[0015] The filter 21 is composed of either one or both of a short wavelength cut-off filter and a long wavelength cut-off filter for restricting the wavelength range to be measured. If there is no need to restrict the wavelength range, the filter 21 may be omitted. The filter 21 is usually composed of a laminated film. The lens 22 is selected according to the spatial region to be measured, and the distance from the measurement object 3 is set so as to be in focus.

[0016] The camera 1 includes a photonic crystal filter 11 (optical filter), an image sensor 12, a readout circuit 13, and a casing 14. A configuration example of the photonic crystal filter 11 will be described later. The light transmitted through the photonic crystal filter 11 is detected by the image sensor 12, and the readout circuit 13 further acquires the detection signal. The detection signal acquired by the readout circuit 13 is subjected to arithmetic processing by the arithmetic device 24 and recorded as a spectroscopic image. Although a microlens array may be arranged on the image sensor 12, it is omitted in FIG. 1 for convenience of explanation.

[0017] FIG. 2 is a top view showing an enlarged part of the photonic crystal filter 11. The photonic crystal filter 11 is an optical filter in which sub-wavelength structures having dimensions comparable to or shorter than the wavelength to be measured are formed in an array. Only some of the holes constituting the sub-wavelength structure are shown in FIG. 2, but actually a large number of holes are formed. The shape of the holes is not limited to circles or squares.

[0018] On the upper layer of the photonic crystal filter 11, there is a base material for supporting the photonic crystal filter 11, and an antireflection film may be formed on the upper layer thereof. Since the photonic crystal filter 11 needs to transmit light to a certain extent, it is formed thinly, and the film thickness is, for example, from 100 nm to 500 nm. The photonic crystal filter 11 is manufactured separately from the image sensor 12, and the two are integrated by bonding them together.

[0019] In Figure 2, nine different hole shapes are arranged in a repeating pattern. Each pattern may correspond to one pixel of the image sensor 12 directly below it, or one pattern may be formed over multiple pixels. The dimensions of each pattern are formed to be an integer multiple of the pixel size of the image sensor 12. In Figure 2, a filter is formed by nine different hole shapes, but there may be any number of patterns.

[0020] Figure 3 shows an example of transmittance when light passes through the photonic crystal filter 11, and information on the wavelength dependence of the transmittance extracted therefrom. The pattern and material of the photonic crystal filter 11 are designed so that the light transmittance of each pattern is as different as possible from one another in the target wavelength range to be measured. The wavelength dependence of the transmittance is continuous, but the values ​​are extracted discretely according to the wavelength resolution to be measured, such as every 1 nm or every 10 nm. In the case of nine types of patterns repeated as shown in Figure 2, there are ideally nine types of transmittance, so nine types of transmittance values ​​are extracted for each discretely set wavelength value.

[0021] For each wavelength of light that passes through a given pattern, the transmittance value when light of that wavelength passes through the pattern can be obtained discretely. For example, the transmittance of the first wavelength number among the wavelengths of light that pass through pattern 1 can be expressed as T11, for example.

[0022] In addition, the effective transmittance may be used as the transmittance, which is a superposition of values ​​related to the characteristics of objects present in the path of light, such as the quantum efficiency of the image sensor 12 and the transmittance of the lens 22.

[0023] Figure 4 is a schematic diagram showing the procedure by which the computing unit 24 reconstructs hyperspectral image data. The computing unit 24 creates an encoded image as an image captured by the image sensor 12 through the photonic crystal filter 11. The computing unit 24 further stores the wavelength dependence of the transmittance of each pattern in the photonic crystal filter 11 in a storage device beforehand and reads it out. The computing unit 24 creates a hyperspectral image by inputting these into the reconstruction model. Note that by training the reconstruction model in advance using the wavelength dependence of the transmittance of each pattern in the photonic crystal filter 11, it is also possible to configure the system to use only encoded images as input data.

[0024] When a 3x3 pattern is considered as one pattern set, if the pattern set is manufactured uniformly regardless of its planar position on the photonic crystal filter 11, the transmittance characteristics will be common to all pattern sets (they will all be the same). Therefore, the data describing the wavelength dependence (e.g., the matrix shown in the lower part of Figure 4) can be composed of nine pieces of information for each wavelength.

[0025] Figure 5 is a side cross-sectional view of the photonic crystal filter 11. To form the photonic crystal filter 11, holes of various sizes and densities must be formed. Generally, when forming holes, a film such as SiN is formed on a transparent substrate, a resist pattern is formed on top of it, and then the holes are formed by etching. At this time, the etching rate differs depending on the size and density of the holes, so as shown in Figure 5, there are regions where the rate of hole formation is relatively fast and regions where it is slow. As a result, the depth of the holes will differ from hole to hole. For example, as shown in Figure 5, there will be a mixture of regions where the holes do not penetrate the film on the transparent substrate and regions where the holes penetrate to the transparent substrate.

[0026] Figure 6 shows an example of data structure describing the wavelength dependence of transmittance. As shown in Figure 5, if the hole depth differs for each planar position on the photonic crystal filter 11, the transmittance will differ for each pattern set, as shown in Figure 6. Furthermore, if the in-plane distribution of film thickness of the deposition apparatus before hole formation and the in-plane etching distribution of the hole formation apparatus are superimposed, the transmittance will exhibit location dependence even if the same pattern is intended to be formed on the photonic crystal filter 11. This also contributes to the difference in transmittance for each pattern set.

[0027] Even in such cases, it is possible to make the transmittance different for each pattern. However, if a hyperspectral image is created using information from only a single pattern set as the wavelength dependence of transmittance, as shown in Figure 4, the hyperspectral image will not faithfully reproduce the actual spectrum. Therefore, in order to faithfully reproduce the actual spectrum of the object being measured 3, it is necessary to input the wavelength dependence of transmittance for each location into the reconstruction model. This leads to problems such as the reconstruction model taking a long time to retrain, or the amount of information required for correction becoming enormous and putting a strain on memory, or the correction taking a long time.

[0028] In view of the above-mentioned problems, this embodiment proposes a method in which the hole formation is allowed to continue without stopping midway, thereby ensuring that the hole depth equals the film thickness and improving the uniformity of the depth.

[0029] Figure 7 is a side cross-sectional view illustrating a conventional process for manufacturing a photonic crystal filter 11. A film (in this case, a SiN film) for forming a hole pattern is deposited on a transparent substrate for transmitting light (1). A resist pattern is formed on the SiN film (2), and the SiN film is patterned by etching (3). Through these steps, a photonic crystal filter 11 with a hole pattern is completed. However, according to this process, as explained in Figure 5, the hole formation rate differs depending on the position, so even if the same pattern set is formed, the wavelength dependence of the transmittance will differ for each pattern set.

[0030] Figure 8 is a side cross-sectional view illustrating the process for manufacturing a photonic crystal filter 11 according to Embodiment 1. A film for forming a hole pattern (in this case, a SiN film) is deposited on a substrate such as a Si substrate (1). A resist pattern is formed on the SiN film (2), and the SiN film is patterned by etching (3). A transparent substrate is attached to the side of the SiN film opposite to the substrate (the top surface in Figure 8) by, for example, surface plasma treatment (4). The substrate is ground from the back side (the side opposite to the transparent substrate) to the extent that it does not reach the bottom surface of the hole pattern (5). Finally, the substrate is removed from the back side by etching (e.g., wet etching) (6).

[0031] In the above process, since there are no holes created by the etching process at the interface between the transparent substrate and the SiN film (the upper surface of the SiN film in Figure 8), the transmittance does not differ from place to place due to differences in hole formation speed, as shown in Figure 7. Furthermore, the interface between the transparent substrate and the SiN film is a surface formed by the process of depositing the SiN film, and since deposition generally provides better in-plane uniformity than etching, this surface has a smaller arithmetic mean roughness than the surface formed by etching. Therefore, although the in-plane thickness distribution of the SiN film still remains, the in-plane uniformity of the depth of the hole pattern can be improved compared to the conventional technique. As a result, the in-plane uniformity of the wavelength dependence of transmittance can also be improved compared to the conventional technique.

[0032] <Embodiment 1: Summary> In the spectroscopic imaging system according to Embodiment 1, the photonic crystal filter 11 is equipped with a subwavelength structure consisting of numerous holes, and the dimensions and periods of the hole patterns of the subwavelength structure are different from each other. The arithmetic mean roughness of the interface between the SiN film constituting the hole pattern of the photonic crystal filter 11 and the transparent substrate supporting the SiN film is smaller than when the hole pattern is formed by etching. As a result, the transmittance when light passes through the photonic crystal filter 11 is approximately uniform across each planar position of the photonic crystal filter 11. Therefore, the processing load for correction when reconstructing hyperspectral image data and the storage capacity for data describing wavelength dependence can be suppressed. Furthermore, it is possible to further improve the reconstruction accuracy of hyperspectral image data by correcting the in-plane distribution of transmittance that remains slightly due to the in-plane thickness distribution of the SiN film, but since the in-plane distribution of transmittance is small, it is sufficient to simply fine-tune the existing model, and this can be done with low computational cost.

[0033] <Embodiment 2> Figure 9 is a side cross-sectional view illustrating the process for manufacturing a photonic crystal filter 11 according to Embodiment 2 of the present invention. Compared to the process described in Embodiment 1, steps (4) and (5) are different, while the other steps are the same. In step (4), a transparent substrate is attached to the SiN film with an adhesive such as an organic material. This fills the SiN film with the organic material in the same layer. In step (5), the substrate is removed by grinding from the back side. By doing so, a photonic crystal filter 11 can be manufactured, and similar to Embodiment 1, the depth of the pore pattern is approximately uniform across each planar position of the photonic crystal filter 11.

[0034] <Embodiment 3> Figure 10 shows an example of forming a tapered SiN film during the manufacturing process of the photonic crystal filter 11. When etching the SiN film, it is desirable to etch it as vertically as possible, but this does not prevent it from forming a tapered shape. For example, the SiN film may be etched into a tapered shape in step (3) described in Figure 8.

[0035] However, as shown in Figure 10, etching the hole pattern so that it tapers from the Si substrate towards the opening is prone to collapse of the SiN film pattern. If areas where the pattern has collapsed and areas where it has not coexist within the plane of the photonic crystal filter 11, the wavelength dependence of the transmittance will differ between areas with a lot of collapse and areas with little collapse, which is undesirable.

[0036] Figure 11 is a side cross-sectional view illustrating another problem when the SiN film has a tapered shape. In this example, the photonic crystal filter 11 and the image sensor 12 are bonded together with the transparent substrate facing the image sensor 12, and the pore pattern in the SiN film is configured to taper from the image sensor 12 towards the opening. In this case, because the transparent substrate is relatively thick, the incident light diffracted by the photonic crystal filter 11 may incident on adjacent pixels instead of the intended pixels. This results in an unclear image.

[0037] Figure 12 is a side cross-sectional view illustrating the process for manufacturing a photonic crystal filter 11 according to Embodiment 3 of the present invention. In step (3), when etching the SiN film, the etching is performed so that the hole pattern tapers from the opening toward the Si substrate. The rest is the same as in Embodiment 1. The image sensor 12 is attached to the completed photonic crystal filter 11 so that it is in contact with the SiN film (7). By following these steps, the problems described in Figures 10 to 11 can be suppressed.

[0038] <Regarding variations of the present invention> The present invention is not limited to the embodiments described above, and various modifications are included. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment without departing from the spirit of the invention, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0039] The positions, sizes, and ranges of the components shown in the drawings and other illustrations of this specification may not represent their actual positions, sizes, and ranges for the sake of ease of understanding. Therefore, the present invention is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings and other illustrations.

[0040] In the embodiments described above, it was explained that the interface between the SiN film (optical filter) of the photonic crystal filter 11 and the transparent substrate is flatter than when formed by an etching process. Specifically, it is desirable that the arithmetic mean roughness on the transparent substrate side of the interface be about 10 nm or less, and more preferably about 1 nm or less.

[0041] In the embodiments described above, the spectroscopic imaging system needs to be able to detect the wavelength range of the reflected light from the object to be measured 3. Therefore, the image sensor 12 needs to have detection sensitivity to incident light in that wavelength range. Furthermore, the photonic crystal filter 11 needs to be able to modulate its transmittance by its hole pattern when incident light in that wavelength range is incident on it. For example, it can be configured as follows: (a) When the image sensor 12 has detection sensitivity to incident light with a wavelength of 500 nm, the refractive index of the material constituting the photonic crystal filter 11 is 1.5 or more and 2.8 or less at room temperature (e.g., 25°C, the same applies below) and a wavelength of 500 nm; (b) When the image sensor 12 has detection sensitivity to incident light with a wavelength of 1500 nm, the refractive index of the material constituting the photonic crystal filter 11 is 1.9 or more and 3.5 or less at room temperature (e.g., 25°C, the same applies below) and a wavelength of 1500 nm; (c) When the image sensor 12 has detection sensitivity to incident light with a wavelength of 2500 nm, the refractive index of the material constituting the photonic crystal filter 11 is 2.5 or more and 4.5 or less at room temperature (e.g., 25°C, the same applies below) and a wavelength of 2500 nm.

[0042] In the embodiments described above, the material constituting the photonic crystal filter 11 may include, for example, one or more of silicon nitride, titanium oxide, silicon carbide, silicon, germanium, and gallium nitride. The transparent substrate material may include, for example, at least one of glass or quartz.

[0043] In Embodiment 2, the organic material constituting the adhesive needs to transmit incident light. For example, to transmit incident light with a wavelength of 500 nm, the refractive index of the organic material is 1.4 to 1.7 at 25°C and a wavelength of 500 nm. The same organic material can be used even when the wavelength is greater than this.

[0044] In the embodiments described above, for example, it is assumed that all nine types of hole patterns shown in Figure 2 have the same hole depth. However, if each hole pattern has different transmittance characteristics with respect to incident light, the hole depth of one of the hole patterns may differ from that of the other hole patterns. Even in this case, however, it is still desirable that the transmittance characteristics be the same across the pattern sets, regardless of their planar position.

[0045] This invention relates to a spectroscopic imaging system, which can be used to classify the types of objects and substances, or to determine the amount of moisture they contain, in locations ranging from factory production lines to farms and forests. [Explanation of Symbols]

[0046] 1: Camera 11: Photonic crystal filter 12: Image Sensor 13:Readout circuit 14: Casing 21: Filter 22: Lens 23: Cable 24: Arithmetic device 25: Light source 3: Object to be measured

Claims

1. A spectral imaging system that detects incident light by spectrally analyzing it, Multiple optical filters with different wavelength dependencies on light transmittance, An image sensor that detects the intensity of incident light transmitted through the optical filter, A computing device that calculates the spectrum of the incident light based on the intensity, Equipped with, The optical filter is composed of through-holes smaller than the pixel size of the image sensor. The optical filter is supported by a transparent material that transmits the incident light. The arithmetic mean roughness of the interface between the optical filter and the transparent material on the transparent material side is 10 nm or less. A spectroscopic imaging system characterized by the following features.

2. The arithmetic mean roughness of the interface on the transparent material side is 1 nm or less. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

3. The refractive index of the material constituting the optical filter is 1.5 or more and 2.8 or less at 25°C and a wavelength of 500 nm. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

4. The image sensor is sensitive to the incident light with a wavelength of 500 nm. The spectroscopic imaging system according to claim 3, characterized in that it is the same as described in claim 3.

5. The refractive index of the material constituting the optical filter is 1.9 or more and 3.5 or less at 25°C and a wavelength of 1500 nm. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

6. The image sensor is sensitive to the incident light with a wavelength of 1500 nm. The spectroscopic imaging system according to claim 5, characterized in that it is the same as described in claim 5.

7. The refractive index of the material constituting the optical filter is 2.5 or more and 4.5 or less at 25°C and a wavelength of 2500 nm. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

8. The image sensor is sensitive to the incident light with a wavelength of 2500 nm. The spectroscopic imaging system according to claim 7, characterized in that it is a spectral imaging system.

9. The material constituting the optical filter includes one or more of the following: silicon nitride, titanium oxide, silicon carbide, silicon, germanium, and gallium nitride. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

10. The transparent material includes at least one of glass or quartz. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

11. The transparent material is an inorganic material that transmits the incident light, The optical filter and the inorganic material are joined to each other by an organic material that transmits the incident light. The refractive index of the aforementioned organic material is 1.4 or more and 1.7 or less at 25°C and a wavelength of 500 nm. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

12. The aperture size of the through-hole on the side furthest from the image sensor is greater than or equal to the aperture size on the side closer to the image sensor. The spectroscopic imaging system according to claim 1, characterized in that it is the same as described in claim 1.

13. A method for manufacturing a spectral imaging system that detects incident light by spectrally analyzing it, The step of forming multiple optical filters whose light transmittance has different wavelength dependencies from each other, A step of bonding the optical filter to an image sensor that detects the intensity of incident light transmitted through the optical filter, It has, In the step of forming the optical filter, the optical filter is formed by forming through holes smaller than the pixel size of the image sensor. In the step of forming the optical filter, after forming the material for the optical filter on a temporary substrate, the through-holes are formed by dry etching. In the step of forming the optical filter, after forming the through hole, the optical filter is bonded to the transparent material, and then the temporary substrate is removed. The arithmetic mean roughness of the interface between the optical filter and the transparent material on the transparent material side is 10 nm or less. A manufacturing method characterized by the following features.

Images