Imaging device with spectroscopic function and manufacturing method thereof, manufacturing method of pixelated optical filter array and product equipped with imaging device with spectroscopic function.

Abstract

Provided are a spectral function-equipped imaging element and a manufacturing method therefor, the imaging element incorporating a plurality of spectral-use pixelated optical filters by which a spectrum in a target wavelength region can be obtained continuously in one direction of the imaging element, without substantially affecting the imaging function of the imaging element. Also provided is a manufacturing method for a pixelated optical filter array which is suitable for use as a spectral-use optical filter for the spectral function-equipped imaging element.

Description

[Technical Field]

[0001] The present invention relates to an imaging device with spectroscopic capabilities and a method for manufacturing the same, a method for manufacturing a pixelated optical filter array, a product incorporating the pixelated optical filter array, and a product including an imaging device with spectroscopic capabilities. [Background technology]

[0002] Spectrometers are instruments that measure the energy intensity of light wavelengths. Recently, their applications have expanded beyond academic fields, from everyday life to industrial applications. For example, by obtaining the spectrum of fresh food using a spectrometer, it is possible to obtain information such as freshness and sugar content. Other promising applications include using skin spectra obtained with a spectrometer to provide beauty advice, and using spectra obtained from spectrometers mounted on endoscopes to monitor the condition of living organs and tissues. Furthermore, obtaining spectra of finished or semi-finished products during the manufacturing process of processed foods and industrial products can enable the identification of defective products that cannot be identified with conventional cameras. Furthermore, by installing spectrometers on drones, airplanes, and satellites, they can be used to survey light environments over a wide area. Furthermore, by installing spectrometers on wearable devices, it is possible to obtain information about the light environment in which one is exposed. Thus, spectrometers are expected to be applied in a variety of fields.

[0003] Diffraction grating spectrometers are widely used as spectrometers. For example, in a Czerny-Turner diffraction grating spectrometer, incident light passes through an entrance slit, reflects off a collimator mirror, and then strikes a diffraction grating. The light incident on the diffraction grating is resolved into its wavelength components and detected by a photodetector. However, diffraction grating spectrometers require a certain amount of space for the diffraction of the incident light, which limits their miniaturization. On the other hand, there has been a demand for smaller spectrometers that people can carry around comfortably on a daily basis and that can be installed in small precision instruments.

[0004] An image sensor is a device that converts an image into an electrical signal. CMOS image sensors and CCD image sensors are used as image sensors in digital still cameras, digital video cameras, etc. Recently, in response to the need for higher pixel count image sensors, several imaging devices have been proposed that use multispectral sensors that increase the number of wavelength bands they disperse, thereby more accurately detecting the color components of a subject and improving color reproducibility (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-87806 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-44519 [Patent Document 3] Japanese Patent Application Publication No. 2020-27980 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 proposes a technology using 16 types of color filters, but because the pixel arrangement in the image sensor is not a Bayer array, it is not possible to output a color image as the actual output image. Patent Document 2 describes an image sensor using multiple color filters with bandwidths narrower than the bandwidths of each RGB color in a Bayer array, but it is only able to obtain information in 12 wavelength bands. Patent Document 3 proposes a technology in which two regions corresponding to the second color in a Bayer array consisting of first, second, and third colors have different spectral characteristics, thereby increasing the number of wavelength bands from which information is obtained and enabling finer spectral separation, but it is still not possible to obtain sufficient information.

[0007] To realize widespread adoption of spectrometers, the inventors conceived the idea that if a portion of an image sensor already built into a portable, compact device, such as a smartphone or digital camera, could be used as a spectrometer, the portable device could also incorporate spectroscopic functionality without compromising its existing imaging function or device size. Even if a pixel in an image sensor is missing, the missing pixel is corrected by averaging the data surrounding the missing pixel to replace the missing pixel. Therefore, by arranging multiple spectroscopic pixelated optical filters continuously along one direction of the image sensor, covering the entire wavelength range of interest, without substantially affecting the image sensor's imaging function, a compact device can be realized that combines existing imaging and spectroscopic functions. For example, if a high-resolution 1980 x 1080 pixel image sensor is used for one row, the number of missing pixels that need to be corrected by the spectrometer is only 1980 out of approximately 2 million pixels, or approximately 0.09% of the total pixels.

[0008] An object of the present invention is to provide an image sensor with a spectroscopic function that incorporates a spectroscopic function without compromising the imaging function and size of the image sensor, and a method for manufacturing the same. Another object of the present invention is to provide a pixelated optical filter array that is suitable as a spectroscopic optical filter for the image sensor with a spectroscopic function. [Means for solving the problem]

[0009] The above-mentioned problems of the present invention have been solved by the following means. [1] An image sensor with a spectroscopic function that incorporates a plurality of pixelated spectroscopic optical filters to enable acquisition of a spectrum of a target wavelength range continuously in one direction of the image sensor without substantially affecting the image capturing function of the image sensor. [2] The image sensor with spectroscopic function described in [1], wherein a plurality of spectroscopic pixelated optical filters are incorporated so that a spectrum of a target wavelength range can be acquired continuously in one direction of the image sensor by replacing some of the pixelated color filters of the image sensor with the spectroscopic pixelated optical filters. [3] The image sensor with spectroscopic function according to [1] or [2], wherein the target wavelength range includes at least a wavelength range of 400 to 700 nm. [4] The image sensor with spectroscopic function according to any one of [1] to [3], wherein the wavelengths of transmitted light of the plurality of spectroscopic pixelated optical filters arranged continuously in one direction are continuously shifted from short wavelengths to long wavelengths from one end to the other end in the one direction. [5] [5] The image sensor with spectroscopic function according to [4], wherein each of the plurality of spectroscopic pixelated optical filters continuously arranged in one direction has a reflective layer A, an optical waveguide layer on the reflective layer A, and a reflective layer B on the optical waveguide layer, the plurality of spectroscopic pixelated optical filters being continuously arranged in one direction, and a thickness of the optical waveguide layer continuously increasing from one end to the other end in the one direction. [6] The spectroscopic imaging element according to [5], wherein the reflective layer A and / or the reflective layer B is a layer containing a metal. [7] The image sensor with spectroscopic capabilities according to any one of [1] to [6], wherein the spectroscopic pixelated optical filters are not adjacent to each other in a plan view from a side where the spectroscopic pixelated optical filters are arranged. [8] forming a reflective layer A on a transparent substrate, then arranging a mask on the reflective layer A at a distance from the surface of the reflective layer A and sputtering an optical waveguide layer forming material toward the surface of the reflective layer A to form an optical waveguide layer on the reflective layer A having a sloped portion whose thickness continuously increases in one direction, and then forming a reflective layer B on the optical waveguide layer to obtain an optical filter with a sloped thickness; forming a photoresist film on the reflective layer B, then masking the photoresist film in the inclined portions corresponding to portions where a plurality of pixelated optical filters are to be formed, then exposing the photoresist film, and then removing the photoresist film in the unmasked portions; scraping off the gradient thickness optical filter corresponding to the portion where the photoresist film has been removed; and removing the remaining photoresist film to obtain a spectroscopic pixelated optical filter array in which the transmitted light wavelength is gradually shifted from shorter wavelengths to longer wavelengths from one end to the other end in said one direction. [9] The method for manufacturing a spectroscopic pixelated optical filter array according to [8], wherein the spectroscopic pixelated optical filters constituting the spectroscopic pixelated optical filter array are not adjacent to each other in a plan view.

[10] A method for manufacturing an image sensor with spectroscopic function according to any one of [1] to [7], comprising incorporating a pixelated optical filter array obtained by the method for manufacturing a spectroscopic pixelated optical filter array according to [8] or [9] into an image sensor.

[11] A product including the imaging element with spectroscopic function according to any one of [1] to [7]. [Effects of the Invention]

[0010] According to the present invention, there is provided an image sensor with a spectroscopic function that incorporates a spectroscopic function without compromising the imaging function or size of the image sensor, and a method for manufacturing the same. Furthermore, the image sensor with a spectroscopic function described in the present invention can increase the number of wavelength divisions almost continuously, thereby not only obtaining fine spectroscopic data but also preventing the obtained image from becoming coarse. Furthermore, according to the present invention, there is provided a method for manufacturing a pixelated optical filter array suitable as a spectroscopic optical filter for the image sensor with a spectroscopic function. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is an explanatory diagram illustrating an example of a spectroscopic principle achieved by incorporating a spectroscopic pixelated optical filter into an image sensor. [Figure 2] FIG. 10 is an explanatory diagram showing a mechanism for correcting defects caused by incorporating spectral pixelated color filters. [Figure 3] FIG. 1 is a schematic diagram illustrating one embodiment of a spectroscopic pixelated light filter array. [Figure 4] 1A to 1C are explanatory diagrams schematically illustrating an example of a process from the fabrication of a gradient thickness optical filter to pixelation. [Figure 5] FIG. 1 is an explanatory diagram (schematic cross-sectional view) showing an example in which the amount of sputtered atoms reaching the Ag film surface can be controlled by the arrangement of a mask. [Figure 6] 1 is an example of a photograph of a gradient thickness filter produced in an example, observed from the SiO2 substrate side. [Figure 7] 1 shows the transmission spectrum of the gradient thickness filter produced in the example when the thickness is increased by 320 μm. [Figure 8] This is a graph showing an approximation line obtained by the least squares method for the transmission spectrum shown in Figure 7, with the vertical axis representing the peak wavelength and the horizontal axis representing the position (at 320 μm intervals) where the peak wavelength is observed. The coefficient of determination R2 is also shown. [Figure 9] 1 is a diagram showing an example of the arrangement of pixel regions of a photomask employed in an example. [Figure 10] 1 is a photograph illustrating an evaluation method for a spectroscopic pixelated optical filter array according to an embodiment. [Figure 11] 1 shows the transmission spectrum of the gradient thickness filter produced in the example when the thickness is increased by 50 μm. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Image sensor with spectroscopic function] The image sensor with spectroscopic capabilities (image sensor with spectroscopic capabilities) of the present invention has a structure in which multiple spectroscopic pixelated optical filters are incorporated into the image sensor in one direction, allowing for continuous acquisition of a spectrum in a desired wavelength range, without substantially affecting the image sensor's imaging function. The phrase "multiple spectroscopic pixelated optical filters are incorporated into the image sensor in one direction, allowing for continuous acquisition of a spectrum in a desired wavelength range" does not necessarily mean that the multiple spectroscopic pixelated optical filters are linearly arranged in one direction. It means that, when the image sensor is viewed from the side, focusing on the arrangement of only the spectroscopic pixelated optical filters, the multiple spectroscopic pixelated optical filters are continuously arranged in one direction, allowing for acquisition of a spectrum in a desired wavelength range. This state will be described with reference to FIG. 1. Note that FIG. 1 is merely an explanatory diagram of the spectroscopic principle achieved by incorporating pixelated spectroscopic filters into the image sensor, and the present invention should not be construed as being limited in any way by the configuration of FIG. 1 other than as defined in the present invention. Furthermore, the term "continuously" can be explained by the following formula: y=aX+b Here, y represents the peak transmission wavelength of the spectral pixelated optical filter, X represents an arbitrary position (length, for example, expressed in μm) in the direction in which the thickness of the spectral pixelated optical filter increases from the starting point where the thickness begins to increase, a is a coefficient, and b represents the peak transmission wavelength of the spectral pixelated optical filter when X is zero. A specific example will be described later with reference to FIG.

[0013] FIG. 1 is a schematic diagram of spectroscopy using pixelated spectral filters. FIG. 1 shows pixels (8 pixels, 12 pixels) that make up an image sensor 1. The pixel in the first column from the left and second row from the top in FIG. 1 of this image sensor 1 is a spectral pixelated optical filter 2 that selectively transmits light with the shortest wavelength among all the spectral pixelated optical filters arranged in this image sensor 1. The second row from the bottom in the second column is a spectral pixelated optical filter 3 that selectively transmits light with wavelengths longer than those of the spectral pixelated optical filter 2, and the third row from the top in the third column is a spectral pixelated optical filter 4 that selectively transmits light with wavelengths longer than those of the spectral pixelated optical filter 3. In this way, each column from left to right contains only one spectral pixelated optical filter that selectively transmits light with longer wavelengths. In other words, when viewed from the top of FIG. 1 (or from the bottom, similarly), the multiple spectral pixelated optical filters are arranged continuously in the horizontal direction of FIG. 1. By aggregating the data collected through the pixels with these spectral pixelated optical filters into a single row of data as shown in the bottom of Figure 1, it is possible to obtain a spectrum over the entire desired wavelength range. Note that, as long as the intended effect is not impaired, multiple spectral pixelated optical filters may be arranged intermittently in one direction. For example, in FIG. 1, spectral pixelated optical filters may be arranged in every other row (e.g., one spectral pixelated optical filter may be arranged every two rows). Even in this configuration, it is possible to acquire a spectrum in a desired wavelength range, and this configuration is included in the configuration defined in the present invention as "continuously arranged in one direction of the image sensor" and "incorporating multiple spectral pixelated optical filters."

[0014] The multiple spectroscopic pixelated optical filters arranged continuously in one direction may typically be configured such that the transmission wavelengths of the spectroscopic pixelated optical filters continuously shift from the short wavelength side (or long wavelength side) to the long wavelength side (or short wavelength side) from one end to the other end in the one direction. However, the present invention is not limited to such a configuration except as defined in the present invention. The arrangement of the transmission wavelengths of the multiple spectroscopic pixelated optical filters is not particularly limited as long as the energy intensity for each wavelength across the entire wavelength range of interest can be obtained when the data is aggregated into one row or one column. For example, the transmission wavelengths of the spectroscopic pixelated optical filters arranged in the "first column, second column, third column, fourth column, etc." in FIG. 1 may be configured such that the transmission wavelengths continuously shift from the short wavelength side to the long wavelength side, such as "400 nm, 410 nm, 420 nm, 430 nm, etc.", or may be randomly arranged, such as "410 nm, 430 nm, 400 nm, 420 nm, etc." In essence, it is sufficient to incorporate a plurality of pixelated spectroscopic optical filters covering a desired wavelength range in a continuous manner in one direction.

[0015] Fig. 1 is an explanatory diagram for facilitating understanding of the present invention, and an actual image sensor is usually composed of far more pixels than those shown in Fig. 1. For example, since the resolution (number of pixels) of Full HD is 1980 x 1080, theoretically, 1980 pixelated spectral optical filters can be arranged in one row.

[0016] In the image sensor with spectroscopic function of the present invention, the spectroscopic pixelated optical filter is arranged so as not to substantially affect the imaging function of the image sensor. "Substantially not affecting the imaging function" means that the influence of defective pixels is not discernible when an image obtained by the image sensor is visually observed. That is, to eliminate the influence of defective pixels on an image, it is preferable that the spectroscopic pixelated optical filter be designed so that defective pixels of the image sensor caused by the spectroscopic pixelated optical filter can be corrected using data surrounding the defective pixels. More specifically, it is preferable that the defective pixels can be corrected by using an average value of the data surrounding the defective pixels as data for the defective pixels, and as a result, the influence of the defective pixels is not discernible when an image obtained by the image sensor is visually observed. To enable defective pixels to be corrected using data from their surroundings, the spectral pixelated optical filters can be arranged so that they are not adjacent to (discontinuous with) each other in a planar view from the side where the spectral pixelated optical filters are arranged (FIG. 1 corresponds to this planar view). This is the arrangement shown in FIG. 1. By arranging the spectral pixelated optical filters so that the defective pixels of the image sensor are not adjacent to each other, correction of the defective pixels can be more reliably performed. In the present invention, "spectroscopy pixelated optical filters are not adjacent to each other" means that the spectral pixelated optical filters are not adjacent to each other in either the vertical or horizontal directions of the pixel arrangement (the column and row directions in FIG. 1). Furthermore, it is preferable that the spectral pixelated optical filters are not adjacent to each other in diagonal directions (the pixel diagonal directions). In addition, "does not substantially affect the imaging function" means that the imaging function of the imaging element is at a level that does not impair the functions provided to digital cameras and smartphone cameras, such as autofocus, white balance, zoom, image format for saving, and size (pixel loss of the image due to the addition of the spectral function). The mechanism for correcting defects caused by incorporating spectral color filters is outlined in Figure 2. Light (including reflected light) emitted from an object passes through RGB color filters and enters a color imaging element (color image sensor), forming an image. Some pixels of the RGB color filter are replaced with spectral color filters, and the RGB information in these areas is corrected, for example, by averaging the data of the surrounding pixels.

[0017] The imaging element constituting the spectroscopic imaging element of the present invention may be a color imaging element having a color filter, or a monochrome (black and white) imaging element without a color filter. When incorporating a spectral pixelated optical filter into a color imaging element in which color filters such as RGB color filters are arranged on the pixels of the sensor, some of the color filters on the pixels are replaced with the spectral pixelated optical filters. In addition, in the case of a monochrome imaging element without a color filter, the spectral pixelated optical filters can be arranged on some of the pixels of the monochrome imaging element.

[0018] In the image sensor with spectroscopic function of the present invention, the wavelength range of the obtainable spectroscopic spectrum can be appropriately set depending on the purpose. For example, if a spectroscopic spectrum in the visible light range is to be obtained, spectroscopic pixelated optical filters can be continuously incorporated in one direction on the pixels of the image sensor so as to cover a wavelength range of at least 400 to 700 nm. Furthermore, if light energy information from the near-ultraviolet to near-infrared ranges is also to be obtained, spectroscopic pixelated optical filters can be incorporated so as to cover a wavelength range of, for example, 350 to 1100 nm. This wavelength range can be appropriately set within the detectable wavelength range, taking into account the quantum efficiency of the image sensor, etc. Therefore, a spectroscopic function specialized for a limited wavelength range within the above wavelength range can also be used.

[0019] In the image sensor with spectroscopic function of the present invention, among the plurality of spectroscopic pixelated optical filters continuously assembled in one direction, the difference in transmitted light wavelength between adjacent spectroscopic pixelated optical filters in the same direction is preferably 20 nm or less, more preferably 10 nm or less, also preferably 5 nm or less, still preferably 4 nm or less, still preferably 3 nm or less, and still preferably 2 nm or less.

[0020] The spectral pixelated optical filter used in the present invention can be obtained by individually fabricating pixelated filters for each wavelength. Alternatively, a gradient thickness optical filter with a Fabry-Perot structure can be fabricated, pixelated, and incorporated into an image sensor as a spectral pixelated optical filter array. For details about the Fabry-Perot structure, see, for example, ACS Photonics, Vol. 2, pp. 183-188, (2015). Considering manufacturing efficiency and mass production, it is preferable to use a spectral pixelated optical filter array as the spectral pixelated optical filter. A spectral pixelated optical filter array is described below.

[0021] <Pixelated optical filter array for spectroscopy> Figure 3 shows a schematic diagram of a pixelated optical filter array for spectroscopy. Figure 3(a) shows a three-dimensional diagram, Figure 3(b) shows a cross-sectional view along the A-A' plane in Figure 3(a) and pixelated sections (1) to (3), and Figure 3(c) shows an enlarged view of pixelated section (2). An interferometer using an optical system with two reflecting mirrors (reflecting layers) like the one shown in Figure 3(c) is called a Fabry-Perot interferometer, and the structure of this optical system is called a Fabry-Perot structure. Figure 3 shows a three-layer Fabry-Perot structure using silver (Ag) films as the two reflecting mirrors and a silicon dioxide (SiO2) optical waveguide layer. The Fabry-Perot structure can control the transmission wavelength by adjusting the spacing between the reflecting mirrors. In a film-thickness-graded optical filter with linearly varying mirror spacing, if the tilt direction is the X-axis and the in-plane direction perpendicular to the tilt direction is the Y-axis, the optical transmission wavelength changes linearly along the X-axis, while the optical transmission characteristics along the Y-axis are constant. Therefore, the pixelated spectroscopic optical filter array obtained by pixelating the gradient thickness optical filter exhibits light transmission characteristics corresponding to the positions of the pixelated portions (1) to (3), as shown in Figure 3(d). Therefore, when all the pixels in Figure 3(a) are combined, they become a filter that transmits wavelengths that vary in stages, and can function as a spectroscopic filter. The material constituting the reflecting mirror is not particularly limited as long as it functions as a reflecting mirror. Generally, a film formed of a material containing metal (preferably a metal or alloy) is used as the reflecting mirror. Examples of metals constituting such metals or alloys include silver (Ag), aluminum (Al), and gold (Au). Furthermore, a multilayer mirror or photonic crystal that does not contain metal can also be used as the reflecting mirror. The material of the optical waveguide layer is not particularly limited as long as it is optically transparent, and examples thereof include silicon dioxide (SiO2), hafnium oxide (HfO2), and resins (e.g., acrylic resin, polystyrene resin, polycarbonate resin, and polyolefin resin).

[0022] Regarding the manufacturing of a pixelated spectroscopic optical filter array, the process from fabricating a gradient thickness optical filter to pixelation is shown in a schematic side view in Fig. 4. Fig. 4 shows an embodiment in which the reflecting mirror is an Ag film and the optical waveguide layer is an SiO2 film, but as mentioned above, the materials for forming the pixelated spectroscopic optical filter array in the present invention are not limited to these.

[0023] Figure 4(a) shows the process of forming a reflecting mirror made of an Ag film by sputtering Ag onto a SiO2 substrate. The thickness of the SiO2 substrate is set appropriately depending on the purpose. For example, it can be about 10 to 1000 nm. The thickness of the reflecting mirror can also be set appropriately depending on the purpose, for example, it can be about 5 to 100 nm.

[0024] In Figure 4(b), a mask is placed at a distance above the Ag film formed in Figure 4(a), and SiO2 is sputtered toward the Ag film surface, forming an optical waveguide layer made of SiO2 on the Ag film. When SiO2 is sputtered, the presence of the mask makes it difficult for sputtered atoms to reach the area below the mask (see Figure 5). Therefore, the amount of sputtered atoms reaching the Ag film surface can be controlled by the mask positioning, and a gradient SiO2 film can be formed, as shown in Figures 4(b) and 5. Furthermore, the gradient angle and width of the gradient SiO2 film can be controlled by the distance between the Ag film and the mask, making it possible to freely create gradients ranging from gentle and long to steep and narrow.

[0025] Figure 4(c) shows the process of forming a reflecting mirror made of Ag film by sputtering Ag on the SiO2 film formed in Figure 4(b). This results in a gradient thickness optical filter. The thickness of this reflecting mirror can also be set appropriately depending on the purpose, for example, to about 5 to 100 nm. The maximum film thickness of this gradient thickness optical filter can be designed according to the desired transmitted light wavelength. For example, the thickness of the SiO2 film (optical waveguide layer) that achieves transmission of the visible light range of 400 to 700 nm is 75 to 185 nm, so to cover the visible light range, the maximum film thickness in sputtering is 185 nm or more. The gradient thickness optical filter is subjected to a pixelation process described below.

[0026] Figure 4(d) shows the process of applying photoresist by spin coating or the like onto the gradient thickness optical filter obtained in Figure 4(c). As the photoresist, any existing photoresist used for forming fine patterns can be used as appropriate.

[0027] FIG. 4(e) shows a process of aligning a photomask with a desired pixel area for the photoresist formed in FIG. 4(d) and exposing the area other than the pixel area.

[0028] Figure 4(f) shows the step of removing the photoresist exposed in Figure 4(e) using an alkaline developer. The alkaline developer can be any developer commonly used for removing photoresist, such as an aqueous solution of tetramethylammonium hydroxide (TMAH). After treatment with the alkaline developer, it is preferable to wash with pure water and dry.

[0029] Figure 4(g) shows the process of removing (scraping off) the part of the gradient thickness optical filter where the photoresist has been removed (non-pixelated area) after removing the photoresist in Figure 4(f). Ion beam milling is usually used.

[0030] Figure 4(h) shows the process of removing the photoresist remaining in the pixelated regions after removing the non-pixelated regions from the gradient thickness optical filter in Figure 4(g). Although the method depends on the type of photoresist, the photoresist can be removed by, for example, immersing the filter in a solvent such as acetone. After removing the photoresist, rinse with alcohol (e.g., isopropanol) if necessary, and then dry to obtain a pixelated spectroscopic optical filter array.

[0031] For convenience of explanation, FIG. 4 shows the spectral pixelated optical filters in the form of an array in which the spectral pixelated optical filters are arranged in a row in the horizontal direction. However, the arrangement of the spectral pixelated optical filters in the spectral pixelated optical filter array can be appropriately designed by controlling the arrangement of the mask in SiO2 sputtering and the arrangement of the photomask on the photoresist.

[0032] That is, the present invention provides the following method for manufacturing a pixelated spectroscopic optical filter array.

[0033] forming a reflective layer A on a transparent substrate, then arranging a mask on the reflective layer A at a distance from the surface of the reflective layer A and sputtering an optical waveguide layer forming material toward the surface of the reflective layer A to form an optical waveguide layer on the reflective layer A having a sloped portion whose thickness continuously increases in one direction, and then forming a reflective layer B on the optical waveguide layer to obtain an optical filter with a sloped thickness; forming a photoresist film on the reflective layer B, then masking the photoresist film in the inclined portions corresponding to portions where a plurality of pixelated light filters will be formed, then exposing the photoresist film, and then removing the photoresist film in the unmasked portions; scraping off the gradient thickness optical filter corresponding to the portion where the photoresist film has been removed; and removing the remaining photoresist film to obtain a spectroscopic pixelated optical filter array in which the transmitted light wavelength is gradually shifted from shorter wavelengths to longer wavelengths from one end to the other end in said one direction.

[0034] In the above-described spectroscopic pixelated optical filter array or its manufacturing method, the transparent substrate and reflective layer A, the reflective layer A and the optical waveguide layer, and the optical waveguide layer and reflective layer B may be in direct contact with each other, or may be in contact with each other via another layer such as an adhesive layer (e.g., a layer made of chromium or titanium). In addition, a protective film that transmits visible light may be provided on the surface of reflector B.

[0035] By incorporating the above-obtained pixelated optical filter array for spectral analysis into an imaging device, the imaging device with spectral function of the present invention can be obtained. [Example]

[0036] The present invention will be described in more detail based on examples, but the present invention is not limited to these forms except as defined in the present invention.

[0037] [Fabrication of gradient thickness optical filter] An SiO2 substrate measuring 9mm wide x 2.5mm long x 0.5mm thick was prepared, and a three-layer gradient film consisting of an Ag film (reflector A) / SiO2 gradient film (optical waveguide layer) / Ag film (reflector B) was formed on this substrate to create a gradient film thickness optical filter that covers the visible light wavelength range of 400 to 700nm. The size of the SiO2 substrate was determined taking into consideration the size of the sensor of an existing image sensor, the S10420-1006-01 manufactured by Hamamatsu Photonics KK The specific fabrication method is described below.

[0038] The thickness of the optical waveguide layer of the Fabry-Perot structure, which transmits light in the visible range of 400 to 700 nm, is 75 to 185 nm. By forming a gradient SiO2 film with this thickness range, it is possible to obtain a gradient optical filter that covers the visible range of 400 to 700 nm. Therefore, we decided to form a gradient SiO2 film (2.6 mm long) with a maximum thickness of 280 nm, which is significantly larger than 185 nm. In addition, the two Ag films sandwiching the optical waveguide layer each have a thickness of 30 nm. First, an optical filter with a gradient thickness was obtained through the steps shown in FIGS. 4(a) to 4(c).

[0039] <Formation of Ag film> The SiO2 substrate was ultrasonically cleaned with ethanol, and Ag was sputtered using a sputtering apparatus QUICKCOATER (SC-701HMCII) manufactured by Sunyu Electronics to form an Ag film with a thickness of 30 nm on the SiO2 substrate (Fig. 4(a)).

[0040] <Formation of SiO2 inclined film> A mask with a thickness of 1 mm (material: SS400) was placed on the surface of the above Ag film at a certain distance from the Ag film surface, and SiO2 was sputtered using an RF magnetron SputterCFS-4ES manufactured by Shibaura Mechatronics to form a SiO2 inclined film with a thickness of 280 nm on the Ag film (Fig. 4(b)).

[0041] <Formation of Ag film> Ag was sputtered using a sputtering apparatus QUICKCOATER (SC-701HMCII) manufactured by Sunyu Electronics to form an Ag film with a thickness of 30 nm on the SiO2 inclined film (Fig. 4(c)). In this way, a film thickness inclined optical filter was obtained.

[0042] Fig. 6 shows the state of the obtained film thickness inclined filter observed from the SiO2 substrate side. In the above <Formation of SiO2 inclined film>, during SiO2 sputtering, the mask was arranged at the upper part of the left half of Fig. 6. It can be seen that the color changes (spectroscopy) as the film thickness increases from the left side to the right side where the mask is arranged.

[0043] [Evaluation of film thickness inclined optical filter] A film thickness inclined filter obtained in the same manner as above except that the size of the SiO2 substrate was 2 cm square was subjected to transmission measurement from the SiO2 substrate side in the wavelength range of 400 nm to 700 nm using a microscope spectrometer. The angle of the color fringes was visually confirmed, and each time transmission measurement was performed, the filter was moved perpendicular to the color fringes visually confirmed to examine the change in the spectrum of the transmission characteristics depending on the position. Figure 7 shows the transmission spectrum for every 320 μm shift in the direction in which the film thickness increases (corresponding to X (μm) in Figure 8). The peak wavelength of the spectrum (the peak transmission wavelength y at X) and the coordinate of X (x axis) were approximated by the least squares method, and the coefficient of determination R 2 As shown in Figure 7, the spectrum transitions depending on the position of the gradient film thickness optical filter. 2 = 0.9991, which means that the graph is highly linear. In other words, it can be seen that the change in peak wavelength is linear. In this way, the spectroscopic imaging element of the present invention can greatly increase the number of wavelength divisions, thereby enabling the acquisition of detailed spectroscopic data and preventing the resulting image from becoming coarse. In other words, in the above description, the image sensor has a structure in which "multiple spectroscopic pixelated optical filters are incorporated so that a spectrum in a target wavelength range can be acquired continuously in one direction of the image sensor." In other words, for example, the technology of Patent Document 3 can only divide the wavelength of visible light into a maximum of 16 parts, but the present invention can be designed to divide the wavelength into more than 16 parts. In the present invention, although it depends on the maximum number of pixels in one direction of the imaging element, it is not limited. For example, when the number of pixels in one direction is N pixels (N: integer), the wavelength of visible light can be divided into at least 20 or more, preferably 20 to N divisions, and more preferably 30 to N x 0.8 divisions. N is in the range of 50 to 8000. By dividing N into 20 or more divisions, a clearer image can be obtained. At most, the image sensor can be divided into one horizontal or vertical row, whichever is greater. For example, a 4K-compatible image sensor has approximately 4,000 horizontal pixels, each consisting of 2 x 2 pixels, allowing for approximately 8,000 (4,000 x 2) divisions. This increases the variety of wavelength bands available, enabling much more detailed spectral data to be obtained than with the technology of Patent Document 3. Furthermore, with the technology of Patent Document 3, each RGB pixel is further divided into four, typically resulting in four (2 x 2) pixels per pixel, requiring 16 (4 x 4) pixels per pixel. For example, even when the technology of Patent Document 3 is applied to a 4K-compatible image sensor, it can only obtain images with a resolution equivalent to 2K, resulting in a grainy image. However, when applied to a 4K-compatible image sensor, the image sensor with spectral function of the present invention can obtain images with a resolution equivalent to 4K without the image becoming grainy. In this gradient thickness optical filter fabricated on a 2cm square SiO2 substrate, the distance X at which the peak wavelength effectively functions as a spectroscopic filter in the range from 400nm to 700nm was 1600µm. Furthermore, based on the correlation between the peak wavelength and the distance X, it is possible to design and manufacture an image sensor with a spectroscopic function for peak wavelengths outside the range of 400nm to 700nm.

[0044] [Fabrication of pixelated optical filter arrays for spectroscopy] The gradient thickness optical filter (SiO2 substrate size: width 9 mm × length 2.5 mm × thickness 0.5 mm) obtained in the above [Fabrication of gradient thickness optical filter] was subjected to the pixelation process shown in Figure 4(d) to (h) to obtain a pixelated optical filter array for spectroscopy.

[0045] <Photoresist film formation> Since the equipment used in the following processes is not suitable for small substrates less than 2 cm square, photoresist OFPR-800LB-200cp was spin-coated onto a 2 cm square glass substrate at 3000 rpm for 20 seconds, and the gradient thickness optical filter was placed on top of it and baked in a 90°C oven for 60 minutes. In this way, the gradient thickness optical filter was attached to the 2 cm square glass substrate. In this process, the photoresist OFPR-800LB-200cp was used as an adhesive. Next, the photoresist OFPR-800LB-200cp was spin-coated at 3500 rpm for 30 seconds onto the gradient thickness optical filter on a 2 cm square glass substrate to form a photoresist film on the Ag film (Fig. 4(d)).

[0046] <Photomask alignment> Using a mask aligner MA6 manufactured by SUSS MicroTec, the gradient optical filter attached to a 2 cm square glass substrate was aligned with the pixel area of ​​the photomask, and exposure was performed for 20 seconds (Figure 4(e)). Here, to verify the principle, the pixels in the pixel area of ​​the photomask were not arranged randomly, but were arranged at equal intervals as shown in Fig. 9. The pixel area size shown in Fig. 9 is smaller than the light-receiving surface of, for example, Hamamatsu Photonics S10420-1006-01, and can cover the entire gradient length of the film thickness gradient optical filter.

[0047] <Developing> The gradient filter was immersed in NMD-3 (2.38% TMAH) at 26°C for 90 seconds, then rinsed twice with pure water for 30 seconds each to develop the film (Fig. 4(f)). After development, the film was dried by dry spin for 180 seconds.

[0048] <Milling> After development, the photoresist-removed portion (non-pixelated area) of the gradient thickness optical filter was removed by ion beam milling using an IBE-KDC 75 manufactured by Hakuto Co., Ltd. for 10 minutes (Fig. 4(g)).

[0049] <Removal of residual photoresist> The remaining photoresist in the pixelated area was removed by immersing it in acetone for 5 min, rinsing it once with IPA, and then air-drying it (Figure 4(h)). Thus, a pixelated optical filter array for spectroscopic use was obtained.

[0050] [Evaluation of pixelated optical filter arrays for spectroscopy] For each pixel row (a row of pixels aligned in the film thickness gradient direction) of the pixelated optical filter array for spectroscopic use obtained above, one pixel was selected from every two pixels, as shown in Figure 10, and the selected pixels were designated p1, p2, p3, p4, ..., p14, p15, p16, and p17. Transmission measurements were taken from the filter surface (Ag film side) for these pixels p1 to p17. As a result, it was confirmed that the peak wavelength changed linearly with pixel position. Furthermore, transmission measurements were taken from the filter surface (Ag film side) under conditions exceeding pixel p17 (see Figure 11). [Industrial Applicability]

[0051] The spectroscopic imaging element of the present invention can continuously and significantly increase the number of wavelength divisions, thereby achieving the effect of obtaining sharper images. Therefore, the spectroscopic imaging element of the present invention is incorporated into products in a wide range of industrial fields. Examples of applicable products and industrial fields include optical communication equipment, optical measurement equipment, optical information equipment (including information terminal devices), automobiles, mobility, artificial satellites, robots, tracking systems (equipment), and wearable devices. Examples of information terminal devices include mobile terminal devices such as small laptops, smartphones, and tablet devices. Other examples include devices for managing food freshness and flavor factors, devices for managing color and quality, printing equipment, ink and paint management equipment, beauty diagnostic equipment, and entertainment equipment. [Explanation of symbols]

[0052] 1. Image sensor 2,3,4 Pixelated optical filters for spectroscopy

Claims

1. An image sensor with a spectroscopic function, in which a plurality of spectroscopic pixelated optical filters are incorporated into the image sensor so that the image sensor can acquire a spectrum in a target wavelength range continuously in one direction of the image sensor without substantially affecting an image capturing function of the image sensor for obtaining an image, The spectroscopic imaging device, wherein the spectroscopic pixelated optical filter has a Fabry-Perot structure.

2. 2. The image sensor with spectroscopic function according to claim 1, wherein the spectroscopic pixelated optical filters are incorporated into the image sensor such that a spectrum in the target wavelength range can be acquired continuously in the one direction of the image sensor by replacing a part of pixelated color filters of the image sensor with the spectroscopic pixelated optical filters.

3. 3. The image sensor with spectroscopic function according to claim 1, wherein the target wavelength range includes at least a wavelength range of 400 to 700 nm.

4. 4. The image sensor with spectroscopic function according to claim 1, wherein the wavelengths of transmitted light of the plurality of spectroscopic pixelated optical filters arranged continuously in the one direction continuously increase from a short wavelength side to a long wavelength side from one end to the other end in the one direction.

5. 5. The image sensor with spectroscopic function according to claim 4, wherein each of the plurality of spectroscopic pixelated optical filters continuously arranged in the one direction includes a reflective layer A, an optical waveguide layer on the reflective layer A, and a reflective layer B on the optical waveguide layer, the plurality of spectroscopic pixelated optical filters being continuously arranged in the one direction, and a thickness of the optical waveguide layer continuously increasing from one end to the other end in the one direction.

6. The image sensor with spectroscopic function according to claim 5 , wherein the reflective layer A and / or the reflective layer B is a layer containing a metal.

7. 7. The image sensor with spectroscopic function according to claim 1, wherein the spectroscopic pixelated optical filters are not adjacent to each other in a plan view from a side on which the spectroscopic pixelated optical filters are arranged.

8. A method for manufacturing a spectroscopic pixelated optical filter array for use as the plurality of spectroscopic pixelated optical filters in the spectroscopic imaging device according to claim 2, comprising: a step of forming a reflective layer A on a transparent substrate, then arranging a mask on the reflective layer A at a distance from the surface of the reflective layer A and sputtering an optical waveguide layer forming material toward the surface of the reflective layer A to form an optical waveguide layer on the reflective layer A having a sloped portion whose thickness continuously increases in one direction, and then forming a reflective layer B on the optical waveguide layer to obtain an optical filter with a sloped thickness; forming a photoresist film on the reflective layer B, masking the photoresist film on the inclined portions corresponding to the portions where the plurality of spectral pixelated light filters are to be formed, exposing the photoresist film to light, and removing the photoresist film on the unmasked portions; scraping off the gradient thickness optical filter corresponding to the portion where the photoresist film has been removed; and removing the remaining photoresist film to obtain a spectroscopic pixelated optical filter array in which the transmitted light wavelength is gradually shifted from shorter wavelengths to longer wavelengths from one end to the other end in said one direction.

9. The method for manufacturing a spectroscopic pixelated light filter array according to claim 8 , wherein the spectroscopic pixelated light filters constituting the spectroscopic pixelated light filter array are not adjacent to each other in a plan view.

10. A method for manufacturing an imaging element with spectroscopic function described in any one of claims 1 to 7, comprising incorporating a spectroscopic pixelated optical filter array obtained by the following method for manufacturing a spectroscopic pixelated optical filter array into an imaging element. <Method of manufacturing a pixelated optical filter array for spectroscopy> a step of forming a reflective layer A on a transparent substrate, then arranging a mask on the reflective layer A at a distance from the surface of the reflective layer A and sputtering an optical waveguide layer forming material toward the surface of the reflective layer A to form an optical waveguide layer on the reflective layer A having a sloped portion whose thickness continuously increases in one direction, and then forming a reflective layer B on the optical waveguide layer to obtain an optical filter with a sloped thickness; forming a photoresist film on the reflective layer B, then masking the photoresist film in the inclined portions corresponding to portions where a plurality of spectral pixelated light filters are to be formed, then exposing the photoresist film, and then removing the photoresist film in the unmasked portions; scraping off the gradient thickness optical filter corresponding to the portion where the photoresist film has been removed; and removing the remaining photoresist film to obtain a spectroscopic pixelated optical filter array in which the transmitted light wavelength is gradually shifted from shorter wavelengths to longer wavelengths from one end to the other end in said one direction.

11. A product comprising the imaging element with spectroscopic function according to any one of claims 1 to 7.

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