Spectroscopic analysis device and spectroscopic analysis method

Abstract

Disclosed is a spectroscopic analysis device which comprises an imaging element, a transmission wavelength-tunable FP optical filter A, and a film thickness gradient FP spectral filter B, wherein some of the incident light passes through both the optical filter A and the spectral filter B and reaches the imaging element, and the remaining incident light reaches the imaging element without passing through the spectral filter B. Also disclosed is a spectroscopic analysis method in which, in spectroscopic analysis of the incident light of the optical filter A, some of the light transmitted through the optical filter A is made incident on the spectral filter B, and the transmission peak wavelength of the optical filter A is detected using, as an index, the transmission peak wavelength of the spectroscopic filter B, or the transmission peak wavelength of the optical filter A of some of the incident light that is dispersed and transmitted by the spectral filter B and is subsequently made incident on the optical filter A.

Description

Spectroscopic analysis device and spectroscopic analysis method

[0001] The present invention relates to a spectroscopic analysis device and a spectroscopic analysis method.

[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 using a spectrometer to obtain the spectrum of fresh food, it is possible to obtain information such as freshness and sugar content. Furthermore, it is being considered to use the skin spectrum obtained by a spectrometer for beauty advice, and to capture the condition of biological organs and tissues based on the spectrum obtained by a spectrometer mounted on an endoscope. Furthermore, in the manufacturing process of processed foods and industrial products, obtaining the spectrum of finished or semi-finished products can enable the identification of defective products that cannot be identified with conventional cameras. Furthermore, when mounted on drones, airplanes, and satellites, spectrometers can be used to survey light environments over a wide area. Furthermore, when mounted on wearable devices, spectrometers can provide information on the light environment in which one is exposed. Thus, spectrometers are expected to be applied in a variety of fields.

[0003] Hyperspectral imaging is an advanced spectroscopic analysis technology that can obtain image information with high wavelength resolution. For example, while an RGB camera can only distinguish three bands, a hyperspectral camera can obtain detailed wavelength information in more than 100 bands. This makes it possible to visualize information that is invisible to the naked eye, and it is used in a wide range of fields, from food to agriculture to space.

[0004] Conventional hyperspectral cameras are divided into two types: a line-based method, which measures one line at a time while moving the measurement target or the camera itself, and a filter array method, which captures images for each wavelength simultaneously using a mosaic filter array. Line-based hyperspectral cameras require the measurement target and camera to be moved, limiting the device's miniaturization. Figure 1 shows an example of the mechanism of a filter array-based hyperspectral camera. A filter array-based hyperspectral camera places optical filters for each band on the sensor, enabling hyperspectral imaging with a single camera without moving parts. However, because optical filters are placed on the sensor for each band, there is a trade-off between increasing the number of bands and improving spatial resolution. Figure 2 shows schematic diagrams of optical filter arrays for (a) low wavelength resolution and high spatial resolution, and (b) high wavelength resolution and low spatial resolution. The number of squares indicated by dashed lines corresponds to the spatial resolution. Increasing the number of optical filters to improve wavelength resolution on the same imaging element (CMOS image sensor or CCD image sensor) reduces the spatial resolution of the image, as shown in Figure 2(b). Therefore, the wavelength resolution of the filter array-based hyperspectral cameras currently in practical use is relatively low, with many of them only covering a dozen or so bands. As such, it is difficult to realize a hyperspectral camera using the filter array method that can obtain more detailed wavelength information by increasing the wavelength resolution while also having high spatial resolution.

[0005] A hyperspectral camera using a wavelength-tunable optical filter with variable transmission characteristics has been proposed as a hyperspectral camera that increases both the number of bands and spatial resolution while also aiming to reduce the size of the device. Figure 3 shows the mechanism of a wavelength-tunable optical filter-based hyperspectral camera. In this method, the transmission characteristics of the optical filter are variable, and by controlling the transmission characteristics, imaging can be performed for each wavelength. Therefore, hyperspectral imaging is possible with a single camera without moving parts like in the line method, and high wavelength resolution can be achieved without sacrificing spatial resolution.

[0006] One of the principles of currently proposed wavelength-tunable optical filters is the Fabry-Perot (FP) interferometer using a multilayer film. A schematic diagram of an FP interferometer is shown in Figure 4. The FP interferometer is an optical system consisting of a multilayer film made of two mirrors (reflective layers (R)) and a transparent medium (M) between them. The transmitted light of a specific wavelength is intensified depending on the refractive index of the transparent medium and the distance between the mirrors. In other words, when the phase difference between the zeroth-order transmitted light and higher-order transmitted light at a certain wavelength λ becomes zero, that wavelength λ is selectively transmitted. This allows the Fabry-Perot (FP) interferometer to function as a wavelength-tunable optical filter. The FP interferometer itself is well known; see, for example, Non-Patent Document 1. As an example of a hyperspectral camera using an FP interferometer, HinaLea Imaging has launched a hyperspectral camera (4200C) with 300 bands, a full width at half maximum of 4 nm, and dimensions of 85 mm x 59 mm x 70 mm, which uses an FP structure to cover the visible-near-infrared range from 400 to 1000 nm. As an example of research into a wavelength-tunable optical filter using an FP interferometer, an air-gap FP optical filter has been reported, in which air is used as the transparent medium and the air gap between metal thin films is controlled using Micro Electro Mechanical Systems (MEMS) technology (Non-Patent Document 2). An example of this air-gap FP optical filter is shown in Figure 5. The upper side of Figure 5 is a cross-sectional view, and the lower side is a top view. This air-gap FP optical filter has two glass substrates (1) each with an Ag alloy film (2) formed on it to form a mirror, and air as the transparent medium (4, the transparent medium filling the gap) between the two mirrors. The peak wavelength of transmitted light is controlled by changing the air gap (4) between the two Ag alloy films (2) using an electrostatic actuator (3) with indium tin oxide (ITO) electrodes on the inside of the two glass substrates (1). Another example of an air-gap FP optical filter for the far infrared has been proposed: an air-gap FP optical filter using a distributed Bragg reflector mirror made of alternating layers of Ge, a high-refractive index material, and ZnS, a low-refractive index material (Non-Patent Document 3).In this air gap FP optical filter, the air gap or transmission peak wavelength is controlled by an electrostatic actuator using a driving Au electrode formed around the mirror.

[0007] A wavelength-tunable optical filter using an FP interferometer can use liquid crystal as the transparent medium instead of air. In this case, the molecular orientation of the liquid crystal is controlled by adjusting the voltage. This molecular orientation control changes the refractive index of the transparent medium, allowing the transmission peak wavelength to be adjusted to the desired wavelength.

[0008] To commercialize a hyperspectral camera using the air-gap FP optical filter, it is necessary to incorporate a function to monitor the accuracy of the air gap (the distance between the two mirrors) control of the air-gap FP optical filter, either before measurement begins or in real time. For example, when controlling the air gap using the electrostatic actuator, the driving performance of the electrostatic actuator may change due to the influence of the measurement environment (e.g., temperature, humidity, etc.). That is, the relationship between the applied voltage and the air gap changes, which in turn changes the relationship between the applied voltage and the light transmission characteristics of the air-gap FP optical filter. By detecting the change in the relationship between the applied voltage and the air gap, for example, calibration can be performed before measurement, allowing the transmission wavelength of the wavelength-tunable optical filter to be accurately controlled to the desired wavelength. To achieve this, it has been proposed to incorporate a capacitive displacement sensor into the air-gap FP optical filter to monitor the accuracy of gap control. However, this method requires dedicated wiring and a capacitance detection circuit for the capacitive displacement sensor, which limits the miniaturization of the hyperspectral camera.

[0009] Furthermore, when liquid crystal is used instead of air as the transparent medium of a transmission wavelength tunable optical filter, the relationship between the applied voltage and the liquid crystal orientation or refractive index may change due to the influence of the measurement environment, etc.

[0010] Techniques for calibrating wavelength-tunable optical filters using optical techniques have also been proposed. For example, Patent Document 1 (JP-A-2005-102626) describes a self-calibration method for a tunable Fabry-Perot cavity, comprising: step S1 of irradiating incident light onto a filter glass, transmitting the incident light through a calibration filter film on the filter glass, and obtaining calibration light having a fixed wavelength; step S2 of strobing the calibration light through the Fabry-Perot cavity, transmitting the calibration light through the Fabry-Perot cavity, and obtaining strobe light; and step S3 of irradiating the strobe light onto an imaging chip (image sensor) to perform imaging and obtain an output signal. According to the calibration method described in Patent Document 1, the calibration light reaches the imaging chip (image sensor) only when the air gap of the Fabry-Perot cavity, which is a wavelength-tunable optical filter, matches the wavelength of the calibration light, thereby enabling self-calibration of the relationship between the applied voltage and the air gap in real time.

[0011] Japanese Patent Application Laid-Open No. 2022-524361

[0012] ACS Photonics, 2015, Vol. 2, pp. 183-188; IEEJ Transactions on Sensors and Micromachines, 2012, Vol. 132, No. 2, pp. 25-30; JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, 2016, Vol. 25, No. 1, pp. 227-235

[0013] The self-calibration method for a Fabry-Perot cavity described in Patent Document 1 performs calibration using calibration light obtained by selectively transmitting light of a specific wavelength from incident light, without using a capacitive displacement sensor. Therefore, this technology can also be said to be a feasible technology for miniaturizing hyperspectral cameras. However, this calibration method calibrates the drive voltage or air gap based on the wavelength of calibration light of several fixed wavelengths. In other words, the drive voltage of the transmission wavelength tunable optical filter is controlled to match the air gap with the wavelength of the calibration light, and the deviation in the relationship between the drive voltage and the air gap is calibrated based on this. However, it is not possible to directly, instantaneously, or accurately capture the wavelength of the transmission light itself of the transmission wavelength tunable optical filter.

[0014] An object of the present invention is to provide a spectroscopic analysis device that obtains the spectrum of an analyte using a transmission wavelength-tunable optical filter with an FP structure, and that can directly detect the actual transmission peak wavelength of the transmission wavelength-tunable optical filter in spectroscopic analysis.An object of the present invention is to provide a spectroscopic analysis method that obtains the spectrum of an analyte using a transmission wavelength-tunable optical filter with an FP structure, and that can directly detect the actual transmission peak wavelength of the transmission wavelength-tunable optical filter in spectroscopic analysis.

[0015] The above-mentioned object of the present invention has been achieved by the following means: [1] An imaging device, a transmission wavelength tunable optical filter A, and a film thickness gradient spectral filter B, wherein the transmission wavelength tunable optical filter A has a reflective layer R on the light incident side. ａ１ and the reflective layer R on the light exit side. ａ２ and are arranged in parallel, and the reflective layer R ａ１ and the reflective layer R ａ２ and the gradient thickness spectral filter B has a Fabry-Perot structure in which the distance or the refractive index between the reflective layer R ｂ１ and the reflective layer R on the light exit side. ｂ２a spectroscopic analysis device having a thickness-gradient Fabry-Perot structure in which the distance between the transmission wavelength tunable optical filter A and the thickness-gradient spectral filter B increases continuously in one direction, so that a portion of incident light passes through both the transmission wavelength tunable optical filter A and the thickness-gradient spectral filter B to reach the image sensor, and the remaining incident light passes through the transmission wavelength tunable optical filter A but reaches the image sensor without passing through the thickness-gradient spectral filter B. [2] The spectroscopic analysis device according to [1], wherein the spectroscopic analysis device detects the peak transmission wavelength of the transmission wavelength tunable optical filter A in spectroscopic analysis using as an index the peak transmission wavelength of the thickness-gradient spectral filter B onto which a portion of the transmitted light of the transmission wavelength tunable optical filter A is incident, or [3] The spectroscopic analysis device according to [2], wherein the peak transmission wavelength of the tunable optical filter A is detected based on a position at which light having the peak transmission wavelength that has passed through both the tunable optical filter A and the gradient thickness spectral filter B reaches the image sensor. ａ２ is disposed on the substrate a2, and the reflective layer R ａ２ [5] The spectroscopic analyzer according to any one of [1] to [3], wherein the gradient thickness spectral filter B is disposed on a part of the surface opposite to the reflection layer R. [6] The spectroscopic analyzer according to any one of [1] to [3], wherein the gradient thickness spectral filter B is disposed on the imaging element. [7] The spectroscopic analyzer according to any one of [1] to [3], wherein the gradient thickness spectral filter B is disposed on the imaging element. [8] The spectroscopic analyzer according to any one of [1] to [3], wherein the gradient thickness spectral filter B is disposed on the reflection layer R at least in the wavelength range of 400 to 700 nm. ｂ１ and the reflective layer R ｂ２ [7] The spectroscopic analysis device according to any one of [1] to [5], wherein the reflective layer R transmits light of a specific wavelength selectively at a position in a film thickness gradient direction depending on the distance between the reflective layer R and the target object. ｂ１ and the reflective layer R ｂ２ Between ２ [8] The spectroscopic analyzer according to any one of [1] to [6], wherein the reflective layer R ａ１ and the reflective layer R ａ２[9] The spectroscopic analyzer according to any one of [1] to [7], wherein an air layer is formed between the reflective layer R and the transmission wavelength tunable optical filter A. ａ１ and the reflective layer R ａ２

[10] The spectroscopic analysis device according to [8], wherein the reflecting layer R ａ１ and the reflective layer R ａ２

[11] The spectroscopic analysis device according to any one of [1] to [7], wherein a liquid crystal layer is disposed between the reflective layer R on the light incident side and the reflective layer R on the light incident side.

[12] The spectroscopic analysis device according to

[10] , wherein a refractive index of the liquid crystal layer is detected by detecting a transmission peak wavelength of the transmission wavelength tunable optical filter A.

[13] The spectroscopic analysis device according to

[12] , wherein a refractive index of the liquid crystal layer is detected by detecting a transmission peak wavelength of the transmission wavelength tunable optical filter A. ａ１ and the reflective layer R on the light exit side. ａ２ and are arranged in parallel, and the reflective layer R ａ１ and the reflective layer R ａ２ When spectroscopically analyzing light incident on a transmission wavelength tunable optical filter A having a Fabry-Perot structure in which the distance or refractive index between the reflective layer R on the light incident side is variable, ｂ１ and the reflective layer R on the light exit side. ｂ２ a spectroscopic analysis method comprising: making a portion of the transmitted light of the tunable transmission wavelength optical filter A incident on a gradient thickness spectral filter B having a gradient thickness Fabry-Perot structure in which the distance between the filter and the incident light is continuously increased in one direction, and detecting the peak transmission wavelength of the tunable transmission wavelength optical filter A in the spectroscopic analysis using the peak transmission wavelength of the gradient thickness spectral filter B as an index, or separating a portion of the incident light into wavelengths by the gradient thickness spectral filter B and transmitting the separated transmitted light, and using the peak transmission wavelength of the tunable transmission wavelength optical filter A as an index.

[13] The spectroscopic analysis method according to

[12] , wherein the peak transmission wavelength of the tunable transmission wavelength optical filter A is detected based on a position at which light of the peak transmission wavelength that has passed through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B reaches the image sensor.

[0016] The spectroscopic analysis device of the present invention obtains a spectrum of an analyte using a transmission wavelength-tunable optical filter with an FP structure, and can directly detect the actual transmission peak wavelength of the transmission wavelength-tunable optical filter during spectroscopic analysis. Therefore, when the environment in which the spectroscopic analysis is performed (such as the installation location of the device) changes, it is possible to calibrate the spectroscopic analysis device before performing the spectroscopic analysis and accurately control the transmission wavelength of the transmission wavelength-tunable optical filter to a desired wavelength. It is also possible to check in real time the accuracy of the control of the transmission wavelength by the transmission wavelength-tunable optical filter during spectroscopic analysis. Furthermore, the spectroscopic analysis method of the present invention obtains a spectrum of an analyte using a transmission wavelength-tunable optical filter with an FP structure, and can directly detect the actual transmission peak wavelength of the transmission wavelength-tunable optical filter during spectroscopic analysis.

[0017] FIG. 1 is an explanatory diagram showing the mechanism of a filter array type hyperspectral camera. FIG. 2 is a schematic diagram of an optical filter array in the case where (a) wavelength resolution is low and spatial resolution is high, and in the case where (b) wavelength resolution is high and spatial resolution is low. FIG. 3 is an explanatory diagram showing the mechanism of a transmission wavelength tunable optical filter type hyperspectral camera. FIG. 4 is a schematic diagram of a Fabry-Perot (FP) interferometer. FIG. 5 is a cross-sectional view and a top view showing an example of an air-gap FP optical filter. FIG. 6 is a schematic diagram of a gradient thickness spectral filter B and an explanatory diagram showing the film formation principle of a gradient film. FIG. 7 is a cross-sectional view showing an example of the layer structure of a first embodiment of the spectroscopic analysis device of the present invention. FIG. 8 is an explanatory diagram showing the optical principle of a spectroscopic analysis device when the air-gap FP optical filter is driven. In the design of the gradient thickness spectral filter B, the reflective layer R ｂ１ and the reflective layer R ｂ２ The thickness of the reflective layer R ｂ１ and the reflective layer R ｂ２ Between them, SiO ２ 10 is a graph showing the results of a rigorous coupled wave analysis of the optical transmittance of an FP structure with a gradient film. ａ１ and the reflective layer R ａ２1 is a graph showing the results of a rigorous coupled wave analysis of the light transmittance of an FP structure in which an air gap is movable in the range of 130 to 300 nm and an Ag alloy is used to form a reflective layer R. FIG. 2 is a diagram showing a cross section of the optical system of a spectroscopic analyzer designed in an example. FIG. 3 is a diagram showing the film formation range (multilayer film formation area) for forming a gradient thickness spectral filter B on a lower substrate. ａ１ 1 is an explanatory diagram showing a manufacturing process of the upper substrate; ａ２ 1 is an explanatory diagram showing a manufacturing process of the lower substrate with the gradient thickness spectral filter B and the reflective layer R. ａ２ 10 is an explanatory diagram showing the manufacturing process of the lower substrate with the gradient thickness spectral filter B. ａ２ 16 is a graph showing the relationship between the position x and the peak wavelength when the position x shown in FIG. 16 is between 0.00 mm (the right end of the arrow) and 2.50 mm (the left end of the arrow). 17 is an explanatory diagram showing the assembly process (optical system formation) of an optical filter using the fabricated upper and lower substrates and piezoelectric elements.

[0018] [Spectroscopic Analysis Apparatus] The spectroscopic analysis apparatus of the present invention includes an image sensor, a transmission wavelength tunable optical filter A, and a thickness gradient spectral filter B. The transmission wavelength tunable optical filter A has a reflective layer R, which is a mirror on the light incident side. ａ１ and a reflective layer R which is a mirror on the light exit side. ａ２ and are arranged parallel (including a state in which they are approximately parallel within a range that does not impair the effects of the present invention), and the reflective layer R ａ１ and the reflective layer R ａ２ The gradient thickness spectral filter B has an FP structure in which the distance or the refractive index between the reflective layer R and the incident light is variable. ｂ１ and the reflective layer R on the light exit side. ｂ２The spectroscopic analysis device of the present invention has a gradient thickness FP structure in which the distance between the transmission wavelength tunable optical filter A and the gradient thickness spectral filter B (the thickness of the transparent medium) and the filter B increases continuously in one direction. The spectroscopic analysis device of the present invention has an imaging element, a tunable wavelength transmission optical filter A, and a gradient thickness spectral filter B arranged so that a portion of the incident light passes through both the tunable wavelength transmission optical filter A and the gradient thickness spectral filter B before reaching the imaging element, and the remaining incident light passes through the tunable wavelength transmission optical filter A but does not pass through the gradient thickness spectral filter B before reaching the imaging element. There is no particular restriction on the order in which a portion of the incident light passes through both the tunable wavelength transmission optical filter A and the gradient thickness spectral filter B. The transmitted light from the tunable wavelength transmission optical filter A may be incident on the gradient thickness spectral filter B, or the transmitted light from the gradient thickness spectral filter B may be incident on the gradient thickness spectral filter A. Furthermore, although there are no particular restrictions on the location of the gradient thickness spectral filter B, it is preferable to provide it at or near the end row of the imaging element so as not to interfere with imaging. Furthermore, two or more gradient thickness spectral filters B may be provided, rather than one. In particular, providing them on both ends of the image sensor is desirable, since it makes it possible to detect any inclination of the transmission wavelength tunable optical filter A or the like.

[0019] The transmission wavelength tunable optical filter A has the reflective layer R ａ１ and the reflective layer R ａ２ While maintaining the parallel state with the reflective layer R ａ１ and the reflective layer R ａ２ By controlling the distance or refractive index to a desired level, the device functions as a wavelength-tunable optical filter that transmits light of a wavelength corresponding to the distance or refractive index and blocks light of other wavelengths.

[0020] In the spectroscopic analysis device of the present invention, the gradient thickness spectral filter B is a linear color filter provided to check whether the transmission wavelength tunable optical filter A functions as an optical filter that selectively transmits a desired wavelength. Therefore, the gradient thickness spectral filter B itself is not directly involved in spectroscopic analysis, but is a spectral filter for detecting whether the transmitted light of the transmission wavelength tunable optical filter A is of a desired wavelength. As described above, the gradient thickness spectral filter B has a reflective layer R on the light incident side. ｂ１ and the reflective layer R on the light exit side. ｂ２ The gradient thickness spectral filter B has a film thickness gradient FP structure in which the distance between the film thickness and the substrate increases continuously in one direction, and functions as a linear color filter. The use of a gradient thickness FP structure as a linear color filter is known, and for details of its fabrication method, etc., reference can be made to, for example, International Publication No. 2023 / 032146. Figure 6 shows a schematic diagram of the gradient thickness spectral filter B and the film formation principle of the gradient film. The gradient thickness spectral filter B shown in Figure 6 is shown in a form provided on an image sensor (13). In addition, the gradient thickness spectral filter B can be, for example, an Ag-SiO ２ The FP structure is shown as a multilayer film consisting of three layers of Ag and SiO. ２ The thickness of the layer is continuously increased in one direction (from left to right in FIG. 6). ２ When forming the layer by sputtering, a shadow mask (11) is placed above the substrate (12) at a distance, allowing the amount of sputtered atoms to be controlled. For example, a 30 nm thick Ag film (reflective layer) and a 75 to 185 nm thick SiO ２ It has been reported that a gradient thickness spectral filter was formed using a gradient film, resulting in a linear color filter with a wavelength resolution of 15 nm and a wavelength range of 400 to 700 nm. As the thickness of gradient thickness spectral filter B increases in one direction, the transmission peak wavelength shifts to the longer wavelength side.

[0021] In one form (referred to as "first form") of the spectroscopic analysis device of the present invention, the peak transmission wavelength of the gradient thickness spectral filter B, onto which a portion of the transmitted light of the tunable transmission wavelength optical filter A is incident, is used as an index for detecting whether or not the transmitted light of the tunable transmission wavelength optical filter A has a desired wavelength. In this case, the analysis device of the present invention can employ a structure in which, in a spectroscopic analysis device having the tunable transmission wavelength optical filter A and an image sensor that detects the light transmitted through the tunable transmission wavelength optical filter A, the gradient thickness spectral filter B is disposed somewhere between the image sensor and the tunable transmission wavelength optical filter A so that a portion of the transmitted light of the tunable transmission wavelength optical filter A is incident thereon.

[0022] 7 is an explanatory diagram (cross-sectional view) for explaining an example of the structure of the first embodiment of the spectroscopic analyzer of the present invention. Note that each drawing for explaining the present invention is a schematic diagram for facilitating understanding of the present invention, and the size or relative size relationship of each member may be changed for the sake of convenience of explanation, and does not directly represent the actual relationship.

[0023] In the spectroscopic analyzer shown in Fig. 7, the transmission wavelength tunable optical filter A (21) is a so-called air-gap FP optical filter. This air-gap FP optical filter has two reflective layers R ａ１ and the reflective layer R ａ２ The reflective layer R has a silver alloy (Ag alloy) layer as a reflecting layer, and the transparent medium between these reflective layers is air. ａ１ and the reflective layer R ａ２ are all SiO ２ A reflective layer R is disposed on the substrate. ａ１ and the reflective layer R ａ２ The distance (air gap, indicated by the arrow in the figure) between the reflective layer R and the spectral filter B (22) is variable. ａ２ SiO ２ Reflective layer R of the substrate ａ２The area where the gradient thickness spectral filter B (22) is disposed is preferably small so as not to interfere with the intended spectral analysis (it is disposed in a part of the depth direction in FIG. 7, see FIG. 8). The gradient thickness spectral filter B (22) is disposed on a part of the surface opposite to the reflective layer R. ｂ１ and the reflective layer R ｂ２ SiO as a transparent medium between ２ Reflective layer R ｂ１ and the reflective layer R ｂ２ The spectroscopic analyzer shown in Fig. 7 employs a CMOS sensor as an imaging element. A cover glass (24) is placed on the pixels (23) of the CMOS sensor, and a SiO ２ 7, incident light (25) enters from the top and passes through the bottom. The light that passes through both the wavelength-tunable optical filter A and the graded-thickness spectral filter B is indicated by the black arrows.

[0024] Figure 8 shows the optical principle of the spectroscopic analysis device when the air-gap FP optical filter is operating. Most of the light incident on the air-gap FP optical filter from the top of Figure 8 passes only through the air-gap FP optical filter in a wavelength-selective manner and reaches the CMOS sensor, but some also passes through the gradient thickness spectral filter B. The gradient thickness spectral filter B transmits light of specific wavelengths selectively in a position in the thickness gradient direction. The position on the CMOS sensor of light with a peak transmission wavelength that passes through the gradient thickness spectral filter B and reaches the CMOS sensor (the position of light transmitted through the gradient thickness spectral filter B that corresponds to the transmission position of the gradient thickness spectral filter B) and the corresponding peak transmission wavelength of the gradient thickness spectral filter B theoretically correspond one-to-one. Therefore, the peak transmission wavelength of the light transmitted through the gradient thickness spectral filter B can be determined based on the position on the CMOS sensor of the light with the peak transmission wavelength that passes through the gradient thickness spectral filter B and reaches the CMOS sensor. Furthermore, since the transmission peak wavelength of this gradient thickness spectral filter B theoretically matches the transmission peak wavelength of the air-gap FP optical filter, it is possible to directly detect the transmission peak wavelength of light that has actually passed through the air-gap FP optical filter. In this way, the transmission peak wavelength of light that has actually passed through the air-gap FP optical filter can be detected simply by detecting the position of light that has passed through the gradient thickness spectral filter B on the CMOS sensor. Therefore, a measuring device for detecting the wavelength of transmitted light is not required, and the transmission peak wavelength of the actual transmitted light can be easily detected by, for example, borrowing part of the image sensor of a spectroscopic analysis device. Figure 8(a) shows the case where, when white light is incident, the air gap of the air-gap FP optical filter is made small (the reflective layer R ａ１ and the reflective layer R ａ２FIG. 8( b ) shows a state in which, when white light is incident, the air gap of the air-gap FP optical filter is made larger than that of FIG. 8( a ) to transmit medium-wavelength light, which then passes through the gradient-thickness spectral filter B and reaches the CMOS sensor, which is an image sensor. FIG. 8( c ) shows a state in which, when white light is incident, the air gap of the air-gap FP optical filter is made larger than that of FIG. 8( b ) to transmit long-wavelength light, which then passes through the gradient-thickness spectral filter B and reaches the CMOS sensor, which is an image sensor. As shown in each figure, the position of the light passing through the gradient-thickness spectral filter B changes depending on the wavelength of the light passing through the air-gap FP optical filter. In each figure, 23 indicates a pixel of the image sensor. Note that the smaller the tilt angle of the gradient-thickness spectral filter B, the more improved the spectral accuracy. The length of the direction in which the thickness of the gradient thickness spectral filter B changes and tilts is determined by the length of one side of the imaging area of ​​the imaging element, so the longer the length, the smaller the tilt angle of the gradient thickness spectral filter can be, which is preferable.

[0025] In the first embodiment, as an example, referring to FIG. 7, a gradient thickness spectral filter B is provided with a reflective layer R ａ２ SiO ２ Reflective layer R of the substrate ａ２ The gradient thickness spectral filter B is fixed to a part of the surface opposite to the reflective layer R. ａ２ SiO ２ The imaging element may be fixed on the imaging element without being in contact with the substrate. "Fixed on the imaging element" includes both a form in which the imaging element is fixed in contact with the imaging element and a form in which the imaging element is fixed to a substrate or the like disposed on the imaging element.

[0026] In another embodiment (referred to as the "second embodiment") of the spectroscopic analysis device of the present invention, the positional relationship between the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B relative to the direction of light incidence is reversed compared to the first embodiment. That is, a portion of the incident light is dispersed into wavelengths by the gradient thickness spectral filter B and transmitted, and the dispersed transmitted light is detected at the transmission peak wavelength of the tunable transmission wavelength optical filter A upon which the incident light is incident. In this case, the analysis device of the present invention is provided with the gradient thickness spectral filter B on the light incident side relative to the tunable transmission wavelength optical filter A and so as to cover a portion of the tunable transmission wavelength optical filter A in a planar view. In this second embodiment, most of the incident light passes wavelength-selectively only through the tunable transmission wavelength optical filter A to reach the imaging element, but a portion of the incident light is incident on the gradient thickness spectral filter B, and the transmitted light dispersed by the gradient thickness spectral filter B is incident on the tunable transmission wavelength optical filter A. As described above, the gradient thickness spectral filter B transmits light of a specific wavelength selectively in a position in the thickness gradient direction. There is a theoretical one-to-one correspondence between the position on the imaging element of light of a peak transmission wavelength that has passed through gradient thickness spectral filter B and then also passed through transmission wavelength-tunable optical filter A, and the peak transmission wavelength of gradient thickness spectral filter B that corresponds to that position. Therefore, based on the position on the imaging element of light of a peak transmission wavelength that has passed through gradient thickness spectral filter B and transmission wavelength-tunable optical filter A in this order and reached the imaging element, it is possible to directly detect the peak transmission wavelength of light that has passed through gradient thickness spectral filter B and transmission wavelength-tunable optical filter A in this order and reached the imaging element, i.e., the peak transmission wavelength of light that has actually passed through transmission wavelength-tunable optical filter A.

[0027] In either of the spectroscopic analyzers of the first and second embodiments described above, it is possible to directly detect the actual transmission peak wavelength of the transmission wavelength tunable optical filter A in spectroscopic analysis.

[0028] 7 and 8, the transmission wavelength tunable optical filter A is formed by using the reflective layer R ａ１ and the reflective layer R ａ２Although an example using an air-gap FP optical filter with an air layer between the reflective layer R and the reflective layer R is shown, the transmission wavelength tunable optical filter A is not limited to the air-gap FP optical filter. ａ１ and the reflective layer R ａ２ A liquid crystal layer FP optical filter can also be used, in which the transparent medium between the first and second electrodes is a liquid crystal layer.

[0029] When an air-gap FP optical filter is used as the transmission wavelength tunable optical filter A, the size of the air gap (the above-mentioned reflective layer R ａ１ and the reflective layer R ａ２ The peak transmission wavelength of the air-gap FP optical filter can be controlled by controlling the distance between the air gap and the peak transmission wavelength of the air-gap FP optical filter, for example, using an electrostatic actuator. In this case, since there is a theoretical one-to-one correspondence between the size of the air gap and the peak transmission wavelength of the air-gap FP optical filter, the state of the air gap can also be known by detecting the peak transmission wavelength of the air-gap FP optical filter.

[0030] When a liquid crystal layer FP optical filter is used as the transmission wavelength tunable optical filter A, the refractive index of the liquid crystal layer can be controlled by controlling the orientation of the liquid crystal molecules according to the level of the applied voltage, and as a result, the transmission peak wavelength of the liquid crystal layer FP optical filter can be controlled. In this case, since the orientation or refractive index of the liquid crystal molecules and the transmission peak wavelength of the liquid crystal layer FP optical filter have a theoretical one-to-one correspondence, the refractive index of the liquid crystal layer can also be known by detecting the transmission peak wavelength of the liquid crystal layer FP optical filter.

[0031] In this way, the spectroscopic analysis device of the present invention can detect the peak transmission wavelength of the transmission wavelength-tunable optical filter A based on the position where light of the peak transmission wavelength that has passed through both the transmission wavelength-tunable optical filter A and the gradient thickness spectral filter B reaches the imaging element, and based on this detected peak transmission wavelength, can detect the state of the air gap if the transmission wavelength-tunable optical filter A is an air-gap FP optical filter, or the refractive index of the liquid crystal layer if the transmission wavelength-tunable optical filter A is a liquid crystal layer FP optical filter. Note that, as described above, the position where light of the peak transmission wavelength that has passed through both the transmission wavelength-tunable optical filter A and the gradient thickness spectral filter B reaches the imaging element can be associated in advance with the size of the air gap of the air-gap FP optical filter, or the position can be associated in advance with the refractive index of the liquid crystal layer of the liquid crystal layer FP optical filter, so it is also possible to detect the size of the air gap of the air-gap FP optical filter or the refractive index of the liquid crystal layer of the liquid crystal layer FP optical filter from the position where light of the peak transmission wavelength that has passed through both the transmission wavelength-tunable optical filter A and the gradient thickness spectral filter B reaches the imaging element. However, even in this case, the detected size of the air gap and the refractive index of the liquid crystal layer are closely related to the peak transmission wavelength transmitted through both the transmission wavelength tunable optical filter A and the gradient thickness spectral filter B. Therefore, in the present invention, a form in which the size of the air gap and the refractive index of the liquid crystal layer are detected from "the position where light of the peak transmission wavelength transmitted through both the transmission wavelength tunable optical filter A and the gradient thickness spectral filter B reaches the imaging element" is also included in the form of "detecting the peak transmission wavelength of the transmission wavelength tunable optical filter A."

[0032] The spectroscopic analysis device of the present invention is a spectroscopic analysis device that obtains the spectrum of an analyte using a transmission wavelength-tunable optical filter A, and as described above, can directly detect the actual transmission peak wavelength of the transmission wavelength-tunable optical filter A in spectroscopic analysis. Therefore, it becomes possible to calibrate the spectroscopic analysis device before spectroscopic analysis when the environment in which the spectroscopic analysis is performed (such as the installation location of the device) changes. It also becomes possible to check in real time the accuracy of the control of the transmission light wavelength by the transmission wavelength-tunable optical filter A during spectroscopic analysis.

[0033] The spectroscopic analyzer of the present invention is not particularly limited in wavelength range for spectroscopic analysis, and can be designed to perform spectroscopic analysis over a wide range from ultraviolet light to infrared light. It can also be designed to perform spectroscopic analysis over a specific, limited wavelength range. For example, the spectroscopic analyzer of the present invention can be designed to perform spectroscopic analysis over a wavelength range of at least 400 to 700 nm (the visible light range). In this case, the gradient thickness spectral filter B can be configured to reflect the reflective layer R at least in the wavelength range of 400 to 700 nm. ｂ１ and the reflective layer R ｂ２ It is possible to provide a configuration in which light of a specific wavelength is transmitted selectively at a position in the film thickness gradient direction depending on the distance between the film and the target.

[0034] [Spectroscopic Analysis Method] The spectroscopic analysis method of the present invention can be carried out using the spectroscopic analysis device of the present invention described above. That is, in one aspect, the spectroscopic analysis method of the present invention includes, when spectroscopically analyzing light incident on the transmission wavelength-tunable optical filter A, making a portion of the transmitted light of the transmission wavelength-tunable optical filter A incident on the gradient thickness spectral filter B, and detecting the peak transmission wavelength of the transmission wavelength-tunable optical filter A in the spectroscopic analysis using the peak transmission wavelength of the gradient thickness spectral filter B as an index. In another aspect, the spectroscopic analysis method of the present invention includes dispersing a portion of the incident light into wavelengths by the gradient thickness spectral filter B and transmitting the separated transmitted light, and detecting the peak transmission wavelength of the transmission wavelength-tunable optical filter A in the spectroscopic analysis using the peak transmission wavelength of the transmission wavelength-tunable optical filter A as an index. In both of the above aspects, the peak transmission wavelength of the transmission wavelength-tunable optical filter A can be detected based on the position at which light of the peak transmission wavelength that has transmitted through both the transmission wavelength-tunable optical filter A and the gradient thickness spectral filter B reaches an image sensor.

[0035] An optical system equipped in a spectroscopic analysis device of the present invention was fabricated using an air-gap FP optical filter as the transmission wavelength tunable optical filter A, and its performance was verified, which will be described below as an example. Note that the following example does not use an imaging element, and is merely an experiment for verifying the principles of the optical system equipped in a spectroscopic analysis device of the present invention. The present invention should not be construed as being limited by the following example, except as defined in the present invention.

[0036] [Design of the Thickness Gradient Spectral Filter B] In order to design the thickness gradient spectral filter B whose transmission characteristics change linearly in the visible light range, a reflective layer R is formed using an Ag alloy. ｂ１ and the reflective layer R ｂ２ and forming SiO ２ The optical transmittance of the FP structure having the reflective layer R as a transparent medium layer was calculated. The calculation was performed using rigorous coupled wave analysis (RCWA). The calculation software Diffract MOD from Synopsys was used. As a result, ｂ１ and the reflective layer R ｂ２ The thickness of the SiO ２ When a gradient film is used, it is found that the transmittance peak shifts in the wavelength range of 400 to 700 nm, as shown in FIG.

[0037] [Design of Transmission Wavelength Tunable Optical Filter A] An air-gap FP optical filter was adopted as the transmission wavelength tunable optical filter A, and the size of the air gap (the reflection layer R ａ１ and the reflective layer R ａ２ As a result, the reflective layer R ａ１ and the reflective layer R ａ２ By forming the film with a thickness of 30 nm from an Ag alloy and making the air gap movable in the range of 130 to 300 nm, it was found that the transmittance peak shifts in the wavelength range of 400 to 700 nm, as shown in FIG. 10.

[0038] [Fabrication of the optical system of the spectroscopic analyzer] Figure 11 shows a schematic cross section of the optical system of the designed spectroscopic analyzer. The upper substrate supporting the air-gap FP optical filter is made of SiO２ A substrate was used, and a 30 nm thick Ag alloy film (reflective layer R ａ１ A 2.0 mm thick SiO ２ The substrate was used, and a 30 nm thick Ag alloy film (reflective layer R ａ２ ) was deposited on the upper and lower substrates. The thickness of the upper and lower substrates may be thinner than in the examples, provided that the substrates do not warp. The gradient thickness spectral filter B designed above was then formed on the back surface by film deposition. The film deposition range (multilayer film deposition area) for forming the gradient thickness spectral filter B was the entire area shown as 2.7 mm wide in Figure 12, but for ease of explanation, Figure 11 omits areas other than the gradient (areas with constant film thickness) (the same applies to Figure 18 described below). A piezoelectric element (41, PA1CEW manufactured by THORLABS) was used to drive the air gap. The maximum displacement of this piezoelectric element was 2.0 μm, which is sufficient for driving the air gap of 130 to 300 nm in the air gap FP optical filter designed above. The piezoelectric element (41) and the lower substrate were covered with a 0.5 mm thick SiO ２ The piezoelectric element (41) was fixed on a substrate, and the upper surface of the piezoelectric element was fixed to the upper substrate. The piezoelectric element (41) was fixed using adhesive (42), and the lower substrate was fixed using carbon tape (43). The manufacturing process is explained below.

[0039] <Reflection layer R ａ１ Fabrication of the upper substrate > Reflective layer R ａ１ The manufacturing process of the upper substrate will be described with reference to FIG.

[0040] (a) SiO2 measuring 20 mm in length, 20 mm in width, and 0.5 mm in thickness ２ Photoresist (51, OFPR-800LB 200 cp) was spin-coated onto the substrate at 3000 rpm for 20 seconds. (b) A 4.5 mm x 3.5 mm photomask (not shown) was placed on the photoresist, and exposure was performed using a mask aligner MA6 manufactured by SUSS Microtec. (c) The photoresist was immersed in a solution containing 2.38 mass% TMAH (tetramethylammonium hydroxide) for 150 seconds, and then rinsed twice with pure water for 30 seconds each time for development. (d) The photoresist was developed using an Elionix ion beam milling system EIS-220P at 1.02 mA / cm２ (e) The resist was removed by Piranha cleaning. (f) An Ag alloy (52, Ag purity 99.5%, Tanaka Kikinzoku Kogyo K.K.) was milled at 1.47 mA / cm for 75 minutes. ２ The film was formed by sputtering for 5 minutes at an Ar gas pressure of 0.65 Pa. The sputtering rate of the Ag alloy was 6 nm / min, and an Ag alloy film having a thickness of 30 nm was formed.

[0041] <Reflection layer R ａ２ and Fabrication of Lower Substrate with Thickness Gradient Spectral Filter B> Reflective Layer R ａ２ The manufacturing process of the lower substrate with the gradient thickness spectral filter B will be described with reference to Figures 14 and 15. Figure 14 is a top view of the lower substrate. Figure 15 is a cross-sectional view taken along the line A-A' in Figure 14. That is, Figure 15 shows cross sections of both the area masked with polyimide tape (61) during the process and the multilayer film deposition area (62), divided into left and right sections.

[0042] (a) SiO2 measuring 10 mm in length, 10 mm in width, and 2.0 mm in thickness ２ As shown in Figures 14 and 15, a polyimide tape (61) was attached to the substrate as a mask. (b) A Ag alloy (63, Ag purity 99.5%, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was sputtered to a thickness of 30 nm. Sputtering was performed at 83 W for 50 seconds in Ar gas at 0.6 Pa. (c) A metal mask (64) was set 2.0 mm away from the sample, and SiO was deposited on the sample using a Shibaura Mechatronics CFS-4ES. ２ A gradient film was formed by sputtering to a maximum thickness of 190 nm. Sputtering was performed at 300 W for 23.5 seconds in 0.5 Pa Ar gas. (d) Ag alloy (63, Ag purity 99.5%, Tanaka Kikinzoku Kogyo Co., Ltd.) was sputtered to a thickness of 30 nm. Sputtering was performed at 83 W for 50 seconds in 0.6 Pa Ar gas. (e) SiO was sputtered using a CFS-4ES from Shibaura Mechatronics. ２ (f) The polyimide tape was removed and ultrasonic cleaning was performed with acetone. (g) A 0.5 mm thick SiO film was applied to the bottom surface of the substrate (the side on which the gradient film was formed) using carbon tape (65).２ (h) Using an Elionix ECR ion beam sputtering system EIS-220P, a 30 nm thick Ag alloy (63) was sputtered. The sputtering current was 1.47 mA / cm. ２ The treatment was carried out at 0.65 Pa of Ar gas for 5 minutes.

[0043] The reflective layer R that was created ａ２ Photographs of the lower substrate with gradient thickness spectral filter B taken after step (g) and before step (h) are shown in Figure 16. The rainbow-colored stripes in the center of Figure 16 are the sloped portions of gradient thickness spectral filter B (described as gradient thickness optical filter in Figure 16). In order to evaluate gradient thickness spectral filter B itself, after step (g) of the above manufacturing process, the reflective layer R ａ２ Before depositing the film, transmission microspectroscopic measurements were performed while moving the position on the gradient thickness spectral filter B in 0.25 mm intervals. Figure 17 shows the relationship between the position x and the peak wavelength for positions x = 0.00 to 2.50 mm, which includes the peak wavelength range of 400 to 700 nm. Figure 17 shows that a gradient thickness spectral filter B with a filter length of 2.0 mm was successfully fabricated, covering the transmission peak wavelength range of 400 to 700 nm.

[0044] <Assembly of the Optical System of the Spectroscopic Analysis Apparatus> The assembly process of the filter using the manufactured upper and lower substrates and piezoelectric elements will be described with reference to FIG.

[0045] (a) The piezoelectric element was attached to the base substrate with a cyanoacrylate adhesive. The piezoelectric element was attached at the position corresponding to the reflective layer R. ａ２ The position was 1 mm away from the lower substrate with the gradient thickness spectral filter B. (b) A reflective layer R was attached to the upper surface of the piezoelectric element with epoxy adhesive. ａ１ (c) Under a microscope, the sloped portion of the film thickness gradient spectral filter B was aligned so that the transmitted light of the air gap FP optical filter was incident, and the reflective layer R ａ１ The upper substrate and the reflective layer R ａ２ The substrates were then pressed against the lower substrate with the gradient thickness spectral filter B to achieve parallelism between them. (d) The substrates were left for half a day to allow the epoxy adhesive to harden completely. In this way, the optical system of the spectroscopic analyzer was assembled.

[0046] <Verification of the Optical System of the Spectroscopic Analysis Device> To examine whether light transmitted through the air-gap FP optical filter can be dispersed by the gradient-thickness spectral filter B, the transmission peak wavelengths of a portion where incident light passes only through the air-gap FP optical filter (single filter area) and a portion where incident light passes through the air-gap FP optical filter and the gradient-thickness spectral filter in that order (double filter area) were measured by transmission microspectroscopic measurement. Specifically, with the applied voltage to the piezoelectric element at 0.0 V, transmission microspectroscopic measurement was performed at positions X of 0.00 mm, 0.25 mm, and 0.50 mm in Figure 16, and in the single filter area (the area other than the multilayer film molding area in Figure 16), and the average of the transmission peak wavelengths at the three locations was calculated to be 557.6 nm. Furthermore, when the applied voltage to the piezoelectric element was 5.0 V, transmission microspectroscopic measurements were performed at positions X of 0.00 mm, 0.25 mm, and 0.50 mm in Figure 16, and in the single filter area. The average transmission peak wavelength at these three locations was calculated to be 589.3 nm. The difference between the two transmission peak wavelengths was 31.7 nm. Next, when the applied voltage to the piezoelectric element was 0.0 V, the transmission peak wavelength of light transmitted through the gradient thickness spectral filter B in the double filter area was 550.2 nm. Furthermore, when the applied voltage to the piezoelectric element was 5.0 V, the transmission peak wavelength of light transmitted through the gradient thickness spectral filter B in the double filter area was 580.6 nm. The difference between the two transmission peak wavelengths was 30.4 nm.

[0047] As described above, when the voltage applied to the piezoelectric element was 0.0 V and 5.0 V, the transmission peak wavelength of the air-gap FP optical filter shifted by 31.7 nm, whereas the transmission peak wavelength in the double filter area also shifted by 30.4 nm, which is almost the same as 31.7 nm, indicating that the transmission peak wavelength of the air-gap FP optical filter can be detected from the transmission peak wavelength of the gradient thickness spectral filter B. Note that although the transmission peak wavelength of the air-gap FP optical filter and the transmission peak wavelength in the double filter area differ slightly in absolute value (557.6 nm vs. 550.2 nm, and 589.3 nm vs. 580.6 nm), this difference is due to the positional accuracy of the transmission microspectroscopy measurement; if transmission microspectroscopy could be performed at finer positional increments, the difference would disappear, and the transmission peak wavelength of the air-gap FP optical filter and the transmission peak wavelength in the double filter area would match.

[0048] As described above, it has been demonstrated that it is possible to construct an optical system in accordance with theory, in which incident light is wavelength-selectively transmitted through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B. Therefore, it can be understood that by using an imaging element such as a CMOS sensor or a CCD image sensor as the photodetector element of the optical system, the peak transmission wavelength of the tunable transmission wavelength optical filter A can be detected based on the position at which light of the peak transmission wavelength that has transmitted through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B reaches the imaging element.

[0049] The spectroscopic analysis device of the present invention can be suitably used, for example, as a compact hyperspectral imaging device with improved wavelength resolution and spatial resolution. For example, it can be used as a portable compact spectroscopic analysis device. The spectroscopic analysis device of the present invention can also be incorporated into a smartphone, tablet, wristwatch, etc.

[0050] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0051] This application claims priority based on Japanese Patent Application No. 2024-086545, filed on May 28, 2024, the contents of which are incorporated herein by reference.

[0052] R: Reflective layer M: Transparent medium 1: Glass substrate 2, 52, 63: Ag alloy film 3: Electrostatic actuator 4: Air gap 11, 64: Shadow mask 12: Substrate 13: Image sensor 21: Tunable transmission wavelength optical filter A 22: Thickness gradient spectral filter B 23: Pixel 24: Cover glass 25: Incident light 41: Piezo element 42: Adhesive 43, 65: Carbon tape 51: Photoresist 61: Polyimide tape 62: Multilayer film deposition area

Claims

1. An imaging device, a wavelength-tunable optical filter A, and a thickness-gradient spectral filter B, wherein the wavelength-tunable optical filter A has a reflective layer R on the light-incident side. ａ１ and the reflective layer R on the light exit side. ａ２ and are arranged in parallel, and the reflective layer R ａ１ and the reflective layer R ａ２ and the gradient thickness spectral filter B has a Fabry-Perot structure in which the distance or the refractive index between the reflective layer R and the gradient thickness spectral filter B is variable. ｂ１ and the reflective layer R on the light exit side. ｂ２ a Fabry-Perot structure with a gradient thickness in which the distance between the filter A and the gradient thickness spectral filter B is continuously increased in one direction, and a portion of the incident light passes through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B to reach the image sensor, and the remaining incident light passes through the tunable transmission wavelength optical filter A but reaches the image sensor without passing through the gradient thickness spectral filter B.

2. The spectroscopic analysis device according to claim 1, wherein the peak transmission wavelength of the transmission wavelength tunable optical filter A in spectroscopic analysis is detected using as an index the peak transmission wavelength of the gradient thickness spectral filter B onto which a portion of the transmitted light of the transmission wavelength tunable optical filter A is incident, or a portion of the incident light is dispersed into wavelengths by the gradient thickness spectral filter B and transmitted, and the peak transmission wavelength of the transmission wavelength tunable optical filter A onto which this dispersed transmitted light is incident is used as an index.

3. The spectroscopic analysis device according to claim 2, wherein the peak transmission wavelength of the tunable transmission wavelength optical filter A is detected based on the position at which light of the peak transmission wavelength that has passed through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B reaches the imaging element.

4. The reflective layer R ａ２ is disposed on the substrate a2, and the reflective layer R ａ２ 4. The spectroscopic analyzer according to claim 3, wherein the gradient thickness spectral filter B is disposed on a part of the surface opposite to the surface of the spectroscopic analyzer.

5. The spectroscopic analysis device according to claim 3, wherein the gradient thickness spectral filter B is disposed on the imaging element.

6. The thickness gradient spectral filter B has the reflecting layer R ｂ１ and the reflective layer R ｂ２ 4. The spectroscopic analyzer according to claim 3, wherein light of a specific wavelength is transmitted selectively at a position in a film thickness gradient direction depending on the distance between the film thickness gradient direction and the target.

7. The reflective layer R ｂ１ and the reflective layer R ｂ２ Between ２ The spectroscopic analyzer of claim 3 , wherein the spectroscopic analyzer is a layer.

8. The reflective layer R ａ１ and the reflective layer R ａ２ The spectroscopic analyzer according to claim 3 , wherein an air layer is provided between the 9. By detecting the transmission peak wavelength of the transmission wavelength tunable optical filter A, the reflection layer R ａ１ and the reflective layer R ａ２ The spectroscopic analyzer according to claim 8, wherein the spectroscopic analyzer detects a distance between the 10. The reflective layer R ａ１ and the reflective layer R ａ２ The spectroscopic analyzer according to claim 3 , wherein a liquid crystal layer is provided between the first and second electrodes.

11. The spectroscopic analyzer according to claim 10, wherein the refractive index of said liquid crystal layer is detected by detecting the peak transmission wavelength of said transmission wavelength tunable optical filter A.

12. Reflective layer R on the light incident side ａ１ and the reflective layer R on the light exit side. ａ２ and are arranged in parallel, and the reflective layer R ａ１ and the reflective layer R ａ２ When spectroscopically analyzing light incident on a transmission wavelength tunable optical filter A having a Fabry-Perot structure in which the distance or refractive index between the reflective layer R on the light incident side is variable, ｂ１ and the reflective layer R on the light exit side. ｂ２ a spectral analysis method including: making a portion of the transmitted light of the tunable transmission wavelength optical filter A incident on a gradient thickness spectral filter B having a gradient thickness Fabry-Perot structure in which the distance between the filter A and the incident light is continuously increased in one direction, and detecting the peak transmission wavelength of the gradient thickness spectral filter B as an index; or separating a portion of the incident light into wavelengths by the gradient thickness spectral filter B and transmitting the separated transmitted light, and detecting the peak transmission wavelength of the tunable transmission wavelength optical filter A as an index.

13. The spectroscopic analysis method according to claim 12, wherein the peak transmission wavelength of the tunable transmission wavelength optical filter A is detected based on the position at which light of the peak transmission wavelength that has passed through both the tunable transmission wavelength optical filter A and the gradient thickness spectral filter B reaches the image sensor.

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