Spectroscopic measurement system and spectroscopic measurement method for spectroscopic measurement system

Abstract

The present disclosure pertains to: a spectroscopic measurement system that makes it possible to realize high-speed spectroscopic measurement in various bands with an inexpensive device configuration; and a spectroscopic measurement method for a spectroscopic measurement system. By causing an object to pass in front of a spectral filter which has arranged therein filters having a plurality of different transmission characteristics, an imaging element captures images of the object with different transmission characteristics on the basis of the entire light of the object, which enters the imaging element after having transmitted through the respective filters, and spectroscopic information of the object is calculated through signal processing on the basis of the images of the object with different transmission characteristics and information on the transmission characteristics. The present disclosure can be applied to spectroscopic measurement systems.

Description

Spectroscopic measurement system and spectroscopic measurement method for spectroscopic measurement system

[0001] The present disclosure relates to a spectroscopic measurement system and a spectroscopic measurement method for the spectroscopic measurement system, and more particularly to a spectroscopic measurement system and a spectroscopic measurement method for the spectroscopic measurement system that can perform spectroscopic measurements in various bands at high speed with an inexpensive device configuration.

[0002] Image sensors that can capture images from visible light to near-infrared light using a single camera (hereinafter referred to as SWIR (Short-Wave Infrared) image sensors) can capture not only information visible to the human eye, but also information on the molecular vibrations of substances present in near-infrared light and the light of high-temperature substances.

[0003] For this reason, SWIR image sensors are particularly effective in non-contact identification of materials that appear to be the same on the surface but are actually different, and are expected to be used in fields such as inspection.

[0004] However, a SWIR image sensor alone can only obtain an image that is an integration of information from multiple wavelengths, so spectral information across multiple wavelengths is required to accurately identify materials.

[0005] In order to obtain spectral information that is an image of multiple wavelengths, a hyper-multispectral camera has traditionally been used with a scanning mechanism in the wavelength or spatial direction, but this makes the system complex and expensive.

[0006] Therefore, a technology has been proposed that enables spectroscopic measurement with a simple configuration by using a spectroscopic imaging device that has bandpass filters with different wavelength transmission characteristics arranged in a line to image the object while sliding it like a line sensor (or while sliding relative to the object) (see Patent Document 1).

[0007] Japanese Patent Application Laid-Open No. 2022-146950

[0008] However, although the spectroscopic measurement device of Patent Document 1 can achieve spectroscopic measurement with a simple configuration, once the combination of bandpass filters is set, it is not easy to change the band to be measured by spectroscopic measurement, and there is a limit to the number of bandpass filters with different wavelength transmission characteristics that can be set on a line-by-line basis.

[0009] The present disclosure has been made in view of the above circumstances, and in particular aims to realize high-speed spectroscopic measurement of various bands using an inexpensive device configuration.

[0010] A spectroscopic measurement system according to one aspect of the present disclosure includes a spectral filter consisting of a plurality of filters that transmit light from an object with different transmission characteristics, and an image sensor that captures images of the object with a number of different transmission characteristics corresponding to the number of filters based on light that has passed through the spectral filters, wherein the plurality of filters are arranged in a predetermined direction, and the image sensor captures images of the object with a number of different transmission characteristics corresponding to the number of filters based on the entire light of the object that passes through each of the plurality of filters and is incident thereon as the relative position between the image sensor and the object changes.

[0011] A spectroscopic measurement method according to one aspect of the present disclosure is a spectroscopic measurement method for a spectroscopic measurement system including a spectral filter consisting of a plurality of filters that transmit light from an object with different transmission characteristics, and an image sensor that captures images of the object with a number of different transmission characteristics corresponding to the number of filters based on the light that has passed through the spectral filters, wherein the plurality of filters are arranged in a predetermined direction, and the image sensor captures images of the object with a number of different transmission characteristics corresponding to the number of filters based on the entire light of the object that passes through each of the plurality of filters and is incident thereon as the relative position between the image sensor and the object changes.

[0012] In one aspect of the present disclosure, there is provided a spectral filter consisting of a plurality of filters that transmit light from an object with different transmission characteristics, and an image sensor that captures images of the object with different transmission characteristics, the number of which corresponds to the number of filters, based on the light that has passed through the spectral filters, wherein the plurality of filters are arranged in a predetermined direction, and the image sensor changes the relative position between the image sensor and the object, thereby capturing images of the object with different transmission characteristics, the number of which corresponds to the number of filters, based on the entire light of the object that passes through each of the plurality of filters and is incident thereon.

[0013] 15 is a diagram illustrating a configuration example of a first embodiment of a spectroscopic measurement system according to the present disclosure. FIG. 16 is a diagram illustrating the spectral filter of FIG. 1 . FIG. 17 is a diagram illustrating the transmission characteristics of the spectral filter. FIG. 18 is a diagram illustrating a procedure for generating spectral information by the spectroscopic measurement system of FIG. 1 . FIG. 19 is a flowchart illustrating a spectral information acquisition process by the spectroscopic measurement system of FIG. 1 . FIG. 19 is a diagram illustrating a first modified example of the first embodiment of the spectral filter. FIG. 20 is a diagram illustrating a second modified example of the first embodiment of the spectral filter. FIG. 21 is a diagram illustrating the spectral characteristics of the second modified example of the first embodiment of the spectral filter. FIG. 22 is a diagram illustrating a third modified example of the first embodiment of the spectral filter. FIG. 23 is a diagram illustrating a fourth modified example of the first embodiment of the spectral filter. FIG. 24 is a diagram illustrating a first application example of the first embodiment of the spectral filter. FIG. 25 is a diagram illustrating a first application example of the first embodiment of the spectral filter. FIG. 26 is a diagram illustrating a second application example of the first embodiment of the spectral filter. FIG. 27 is a diagram illustrating a configuration example of an object recognition system that is a third application example of the first embodiment of the present disclosure. FIG. 28 is a diagram illustrating a configuration example of a second embodiment of the spectroscopic measurement system according to the present disclosure. FIG. 29 is a diagram illustrating the spectral filter of FIG. 15 . FIG. 29 is a diagram illustrating the transmission characteristics of the spectral filter of FIG. 15 . Fig. 16 is a flowchart illustrating a spectral information acquisition process performed by the spectroscopic measurement system of Fig. 15. Fig. 17 is a diagram illustrating a first modified example of the second embodiment of the spectral filter. Fig. 18 is a diagram illustrating a second modified example of the second embodiment of the spectral filter. Fig. 19 is a diagram illustrating an example of the configuration of a computer.

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0015] Hereinafter, embodiments for implementing the present technology will be described. The description will be given in the following order: 1. First embodiment 2. First modified example of the first embodiment 3. Second modified example of the first embodiment 4. Third modified example of the first embodiment 5. Fourth modified example of the first embodiment 6. First applied example of the first embodiment 7. Second applied example of the first embodiment 8. Third applied example of the first embodiment 9. Second embodiment 10. First modified example of the second embodiment 11. Second modified example of the second embodiment 12. Description of a computer to which the present technology is applied

[0016] <<1. First Embodiment>> <Outline of the Present Disclosure> The present disclosure is directed to realizing high-speed spectroscopic measurement of various bands with an inexpensive device configuration. Before describing the details of the present disclosure, the outline of the present disclosure will first be described.

[0017] In the present disclosure, a spectral filter is configured by combining a polarizer and a liquid crystal element between a lens and an image sensor. The transmission characteristics of the liquid crystal element that configures the spectral filter can be changed by changing the applied voltage.

[0018] This makes it possible to acquire multiple spectral images by changing the applied voltage, and spectral information in a wide range from visible light to near-infrared light is calculated through signal processing based on the transmission characteristics corresponding to the applied voltage that have been recorded in advance.

[0019] The various ranges from visible light to near-infrared light referred to here may include, for example, the NIR (Near Infrared) wavelength band, the SWIR (Short Wavelength Infrared) wavelength band, the MWIR (Mid Wavelength Infrared) wavelength band, the LWIR (Long Wavelength Infrared), and the FIR (Far Infrared) wavelength band, etc. Furthermore, in addition to the various ranges from visible light to near-infrared light, the range may also be from ultraviolet light to visible light.

[0020] In addition, the liquid crystal elements that make up the spectral filter have transmission characteristics that change depending on the wavelength of the incident light, and by arranging them in multiple rectangular divided regions, it is possible to set regions to which multiple different voltages can be applied, in other words, regions with multiple different transmission characteristics.

[0021] This makes it possible to efficiently capture images of objects with multiple different transmission characteristics, like a line sensor, by capturing an image of the object while moving it in front of the strip-shaped divided areas with different transmission characteristics in a direction parallel to the direction in which the strip-shaped areas are arranged.

[0022] As a result, it becomes possible to acquire images of multiple transmission characteristics more quickly and in a shorter time, and by signal processing using the acquired images of multiple transmission characteristics and information on previously known transmission characteristics, it becomes possible to acquire highly accurate spectroscopic information with higher wavelength resolution at high speed.

[0023] <Configuration Example of First Embodiment of Spectroscopic Measurement System of the Present Disclosure> Next, a configuration example of a first embodiment of a spectroscopic measurement system of the present disclosure will be described with reference to FIG.

[0024] The spectroscopic measurement system 111 in FIG. 1 captures an image of an object 121 to be spectroscopically measured, and acquires highly accurate spectroscopic information 122 with high wavelength resolution at high speed by signal processing based on the image capture result.

[0025] The spectroscopic measurement system 111 includes a power supply 130, a lens 131, a spectral filter 132, an image sensor 133, and a signal processing unit 134.

[0026] The power supply 130 is a power supply that is controlled by the signal processing unit 134 and applies different voltages to the respective rectangular strip regions that are set in the vertical direction in the figure and are set in the spectral filter 132. The method for setting the voltages to the respective regions will be described in detail later.

[0027] The lens 131 collects light from the object 121 so that the light is focused on the imaging surface of the imaging element 133 .

[0028] As shown in the right part of Figure 2, the spectral filter 132 is configured by stacking a polarizer 171, a liquid crystal element 172, and a polarizer 173 in this order from the front toward the direction of incidence of light from the object 121, and converts the light from the object 121 into light having transmission characteristics that correspond to the voltage applied by the power supply 130.

[0029] Furthermore, as indicated by the dotted arrows on the right side of Figure 2, the polarization axis Ax-Pf of polarizer 171 and the polarization axis Ax-Pr of polarizer 173 are set to form +45 degrees and -45 degrees, respectively, with respect to the fast axis Ax-LC of liquid crystal element 172.

[0030] The angles of the polarization axis Ax-Pf of the polarizer 171 and the polarization axis Ax-Pr of the polarizer 173 relative to the fast axis Ax-LC of the liquid crystal element 172 may be set to +45 degrees and −45 degrees, respectively, as shown in Fig. 2, or may be set to other angles. For example, the angles of the polarization axis Ax-Pf of the polarizer 171 and the polarization axis Ax-Pr of the polarizer 173 relative to the fast axis Ax-LC of the liquid crystal element 172 may be configured to be −45 degrees and +45 degrees, respectively, or may be other angles.

[0031] However, in this embodiment, as shown in Figure 2, the angles of the polarization axis Ax-Pf of polarizer 171 and the polarization axis Ax-Pr of polarizer 173 relative to the fast axis Ax-LC of liquid crystal element 172 are +45 degrees and -45 degrees, respectively.

[0032] 2, the spectral filter 132 has divided regions 151-1 to 151-7, to which voltages can be applied, arranged in strips in the vertical direction of the figure, and can be set to have different transmission characteristics by applying different voltages from the power supply 130. More specifically, the liquid crystal element 172 of the spectral filter 132 has divided regions 172a-1 to 172a-7, which correspond to the divided regions 151-1 to 151-7, and the power supply 130 applies a voltage set for each divided region 172a. As a result, the spectral filter 132 functions as an individual filter in accordance with the voltage applied by the power supply 130 in each of the divided regions 151-1 to 151-7.

[0033] For this reason, since the divided areas 151-1 to 151-7 are individual filters corresponding to the voltage applied by the power supply 130, they will hereinafter also be referred to simply as filters 151-1 to 151-7, and when there is no need to distinguish them individually, they will also be simply referred to as divided areas 151 or filters 151.

[0034] In the spectral filter 132 of Figures 1 and 2, an example is shown in which seven rectangular divided regions (filters) 151-1 to 151-7 are set to which different voltages can be applied, but the filter may be divided into a number of regions (filters) other than seven.

[0035] However, it is assumed that the horizontal width of each region (filter) 151 in the drawing is set to a width of at least several pixels set on the image sensor 133 .

[0036] The transmission characteristics of the divided region (filter) 151 with respect to the applied voltage may be, for example, as shown in FIG.

[0037] In FIG. 3, the horizontal axis represents wavelength (nm), the vertical axis represents applied voltage (V), and the transmittance, which is a transmission characteristic, is expressed by density.

[0038] That is, for example, when the applied voltage is Va in Fig. 3, the transmittance changes periodically for each wavelength as shown in the range surrounded by the dotted line. More specifically, in Fig. 3, the transmittance changes periodically like a trigonometric function in proportion to the inverse of the wavelength, and in Fig. 3, the period becomes shorter as the voltage increases.

[0039] Due to these characteristics, as shown in FIG. 3, for example, when the applied voltage is voltage Va, as shown in the area surrounded by the dotted line, the transmittance changes from a state close to 0 to a state close to 1 from the short wavelength side to the long wavelength side, and this change is repeated for about two periods.

[0040] In contrast, when the applied voltage is Vb (>Va), the transmittance for each wavelength changes in a shorter cycle than when the voltage is Va, as shown by the range enclosed by the dotted line. As a result, from the short wavelength side to the long wavelength side, the transmittance changes between a state close to 0 and a state close to 1, which is repeated for about four cycles.

[0041] In this way, the spectral filter 132 has a transmission characteristic in which the transmittance of incident light is proportional to the inverse of the wavelength and changes periodically like a trigonometric function in response to the applied voltage.

[0042] In other words, the spectral filter 132 transmits the wavelength components that make up the incident light with a transmittance that changes periodically according to the applied voltage, as shown in FIG. 3, and converts the light into light with transmission characteristics that are the integration of all of these characteristics.

[0043] The image sensor 133 is composed of a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor), or the like, and receives light from the object 121 that has been converted into spectral characteristics corresponding to the applied voltage by passing through the spectral filter 132, and outputs a pixel signal corresponding to the amount of light to the signal processing unit 134.

[0044] The signal processing unit 134 sets the voltage to be applied to each of the divided regions (filters) 151 based on the wavelength range to be determined for the object 121 .

[0045] Then, the signal processing unit 134 controls the power supply 130 to apply a voltage set for each divided region (filter) 151 of the spectral filter 132 .

[0046] Furthermore, the signal processing unit 134 drives the base unit 120 on which the object 121 is placed, thereby controlling the object 121 to pass in front of each of the divided areas (filters) 151-11 to 151-14 along the direction in which the divided areas (filters) 151 are arranged, for example, as shown in the left part of Figure 4, and causes the image sensor 133 to capture images Pr for the number of divided areas (filters) 151 that have been converted into the transmission characteristics of each divided area (filter) 151.

[0047] Then, as shown in the center of Figure 4, the signal processing unit 134 corrects positional shifts and distortions in the images Pr for the number of divided areas (filters) 151 captured by the image sensor 133, and then calculates spectral information Ps with higher wavelength resolution that is at least greater than the number of divided areas (filters) 151 by signal processing that utilizes the transmission characteristics F1 corresponding to the applied voltage to each divided area (filter) 151.

[0048] <Method of Setting Applied Voltage for Each Divided Region and Method of Calculating Spectral Information by Signal Processing> Next, a method of setting applied voltage for each divided region and a method of calculating spectral information by signal processing will be described.

[0049] First, when light emitted from the object 121 passes through the spectral filter 132 (each divided area (filter) 151) to which a voltage v is applied, and is received at a pixel position (x, y) on the image sensor 133, a pixel signal i ｖ (x, y) is defined as in the following equation (1).

[0050]

[0051] Here, the coordinate position on the spectrum filter 132 and the coordinate position on the image sensor 133 are expressed by corresponding (x, y) positions. ｖ (x, y) is the pixel signal of the pixel at the position (x, y) on the image sensor 133, and S ｖ (x, y, λ) is the transmittance of light of wavelength λ when voltage v is applied to position (x, y) on the spectral filter 132, and h(x, y, λ) is the spectral reflectance (spectral information) of light of wavelength λ at position (x, y).

[0052] In addition, the transmittance S ｖ (x, y, λ) depends on the configuration of the spectral filter 132 (each divided region (filter) 151), and for example, in the case of the polarizer 171, liquid crystal element 172, and polarizer 173 as described with reference to Figure 2, it is expressed as the following equation (2).

[0053]

[0054] Here, Δn(v) is the refractive index difference between the fast axis and the slow axis of the liquid crystal element 172 at voltage v (birefringence between the fast axis and the slow axis), and d ＬＣ is the thickness of the liquid crystal element 172.

[0055] More specifically, the liquid crystal element 172 functions as a variable wave plate depending on the applied voltage due to the liquid crystal molecules. The liquid crystal element 172 also has birefringence and optical anisotropy.

[0056] Therefore, for incident light, a phase difference φ(λ) occurs between the fast axis and the slow axis as shown in the following equation (3).

[0057]

[0058] On the other hand, the polarizer 171, the liquid crystal element 172, and the polarizer 173 can be expressed by the following equations (4) to (6) using the Jones calculation method.

[0059]

[0060]

[0061]

[0062] Here, Vp1, VLC, and Vp2 are the Jones matrices of the polarizer 171, the liquid crystal element 172, and the polarizer 173, respectively.

[0063] Therefore, the Jones vector when the incident light passes through the spectral filter 132 is the product of Vp1, VLC, and Vp2, and is expressed as the following equation (7).

[0064]

[0065] Furthermore, the intensity of transmitted light, that is, the transmittance Sv(λ), is expressed as the square of the magnitude of the Jones vector, and is calculated as in the following equation (8).

[0066]

[0067] As a result, when a voltage v is applied to the spectral filter 132 (each divided region (filter) 151), the transmittance Sv(λ) at the corresponding position (x, y) is expressed by equation (2) (= equation (8)).

[0068] Returning to the explanation of formula (1), the spectral reflectance h(x, y, λ) in formula (1) is a continuous variable, but the data cube H to be found that corresponds to the spectral reflectance h is expressed as a discrete variable. Therefore, by discretizing and then vectorizing the data, formula (1) can be replaced with formula (9) below.

[0069]

[0070] Here, H is a data cube that corresponds to the spectral reflectance h and is the spectral information of the object 121 to be obtained, and Nx, Ny, and Nλ are the coordinates x, y and the number of wavelengths λ, respectively.

[0071] That is, in formula (9), i ｖ(x, y) is the pixel signal of the pixel at position (x, y) on the imaging element 133, in other words, it is information on the image signal captured at position (x, y) on the imaging element 133 when light passes through with a transmittance Sv when a voltage v is applied to the spectral filter 132. Furthermore, the transmittance Sv is a known value based on the applied voltage v. From this, based on the relationship in equation (9), the desired data cube H can be found by solving the following equation (10).

[0072]

[0073] where R(H) is the regularization term and N ｆｉｌｔｅｒｓ is the number of divided regions (filters) 151.

[0074] Since Equation (10) is a linear problem, it can be solved by a least squares method. However, Equation (10) can be solved by a method other than the least squares method, for example, by using a neural network.

[0075] That is, the signal processing unit 134 applies a voltage set according to the number of filters (divided areas) 151 to each of the filters (divided areas) 151, and solves equation (10) based on the image captured by the imaging element 133, which has transmission characteristics set by each applied voltage, and the transmittance Sv determined from the applied voltage, thereby obtaining a data cube H that represents the spectral information of the object 121.

[0076] Furthermore, the set V of voltages v applied to each of the filters (division regions) 151 can be optimized by solving the following equation (11).

[0077] Here, N ａｌｌ is the total number of voltage sets V that can be set as combinations of voltages v applied to each filter (division area 151).

[0078] That is, the signal processing unit 134 calculates the total number N that can be set as the voltage set V based on the above-mentioned equation (11). ａｌｌ Among them, pixel signal i ｖ and H.S. ｖIn other words, a voltage set V is set in advance so that the difference between the voltages V and H is minimized, that is, the voltage set V is obtained as an optimal solution for the data cube H.

[0079] In addition, the signal processing unit 134 applies each voltage that makes up the set voltage set V to each of the divided areas (filters) 151, and while the object 121 passes in front of each of the divided areas (filters) 151, the image sensor 133 captures an image having transmission characteristics that are transmitted at a transmittance for each wavelength according to the applied voltage of each divided area (filter) 151.

[0080] Then, the signal processing unit 134 outputs a pixel signal i having a transmission characteristic set for each divided area (filter) 151 captured. ｖ and the transmittance Sv, which is a transmission characteristic specified by the applied voltage v, a data cube H is calculated by signal processing.

[0081] In addition, the pixel signal i ｖ For transmittance S ｖ By setting the above, a telecentric optical system is not required, and therefore, for example, a configuration for producing parallel light is not required in an optical system corresponding to the lens 131, and a cheaper optical system can be achieved.

[0082] Furthermore, the signal processing unit 134 is generally premised on obtaining a voltage set V that is optimized for obtaining a data cube H, which is ultimately desired spectral information over a relatively wide band from the visible light region to the infrared light region, but may also obtain a voltage set that will obtain an optimal data cube depending on the application. That is, when a specific wavelength band is the only band required for comparison of some object, the signal processing unit 134 may obtain a voltage set V that will obtain an optimal data cube H only for the specific wavelength band.

[0083] <Spectral Information Acquisition Processing> Next, the spectral information acquisition processing will be described with reference to the flowchart of FIG.

[0084] In step S31, the signal processing unit 134 sets a voltage set by calculation using the above-mentioned equation (11) based on the number of divided regions (filters).

[0085] In step S32 , the signal processing unit 134 controls the power supply 130 to apply a voltage set that has been set for each divided region (filter) 151 of the spectral filter 132 .

[0086] In step S33, the signal processing unit 134 drives the base unit 120 on which the object 121 is placed, causing the object 121 to pass in front of each divided region (filter) 151 of the spectral filter 132, and also controls the image sensor 133 to capture images, thereby capturing images of the object 121 having the transmission characteristics (transmittance) of the divided regions (filters) 151, as many as the number of divided regions (filters) 151, and acquires and stores the captured images. At this time, the signal processing unit 134 corrects positional deviations and the like as necessary for the images of the object 121 corresponding to the multiple transmission characteristics.

[0087] In step S34, the signal processing unit 134 calculates spectral information with high wavelength resolution, which is at least greater than the number of divided regions (filters) 151, by, for example, solving the above-mentioned equation (10) based on images of the object 121 having the transmission characteristics (transmittance) of the divided regions (filters) 151 captured by the image sensor 133 and the transmission characteristics of each divided region (filter) 151 according to the applied voltage.

[0088] In step S35, the signal processing unit 134 outputs spectral information with high wavelength resolution, which is at least greater than the number of divided areas (filters) 151, calculated by signal processing based on images for the number of divided areas (filters) 151 captured by the image sensor 133 and the transmission characteristics of each divided area (filter) 151 according to the applied voltage.

[0089] By the above processing, it is possible to set the applied voltage so that each divided region (filter) 151 set in the spectral filter 132 provided in front of the image sensor 133 has optimal transmission characteristics depending on the band of the spectral information to be obtained, and therefore it is possible to obtain the spectral information that is ultimately generated with high accuracy.

[0090] Furthermore, in the present disclosure, in a state where a voltage is applied so as to provide optimal transmission characteristics for each divided region (filter) 151 set in the spectral filter 132, the base 120 is driven to cause the object 121 to pass in front of the spectral filter 132, and images of the object 121 with multiple transmission characteristics can be acquired in a single image capture by the image sensor 133. This reduces the effort and time required for image capture, and makes it possible to acquire highly accurate spectral information at high speed.

[0091] As a result, it is possible to realize high-speed spectroscopic measurements in various bands using an inexpensive device configuration.

[0092] Furthermore, by applying a voltage to the entire spectral filter 132 so that it has uniform transmission characteristics, and then imaging the object 121 multiple times while sequentially switching the overall applied voltage, it is possible to obtain objects 121 with multiple transmission characteristics and use them to obtain spectral information.

[0093] However, in this case, multiple imaging operations are required, and if, for example, near-infrared light is required as the final spectroscopic information, the thickness of the spectral filter 132 needs to be increased. However, the increased thickness reduces the response time for switching the applied voltage.

[0094] Therefore, if imaging is repeated multiple times while switching the voltage applied to the spectral filter 132, this may increase the effort and time required for imaging.

[0095] In contrast, in the spectroscopic measurement system 111 of Figure 1 of the present disclosure, an image with multiple transmission characteristics can be acquired in a single imaging session, thereby reducing the time required for imaging and enabling images with multiple transmission characteristics to be acquired at high speed.

[0096] Furthermore, in this disclosure, an example has been described in which the object 121 is placed on the base 120 and the imaging element 133 images the object 121 while the object 121 passes in front of the spectral filter 132. However, the object 121 does not necessarily need to move as long as the relative positions of the object 121, the spectral filter 132, and the imaging element 133 can be changed so that the object 121 can be imaged as if it had passed in front of the spectral filter 132 from the perspective of the imaging element 133. For example, the imaging element 133 and the spectral filter 132 may pass in front of the object 121.

[0097] <<2. First Modification of the First Embodiment>> In the above, an example has been described in which the polarization axis Ax-Pf of the polarizer 171 and the polarization axis Ax-Pr of the polarizer 173 that constitute the spectral filter 132 are set to form +45 degrees and −45 degrees, respectively, with respect to the fast axis Ax-LC of the liquid crystal element 172.

[0098] However, the polarization axis Ax-Pf of the polarizer 171 and the polarization axis Ax-Pr of the polarizer 173 may be set to form +45 degrees with respect to the fast axis Ax-LC of the liquid crystal element 172 .

[0099] The upper part of Figure 6 shows an example of the configuration of a spectral filter in which the polarization axis Ax-Pf and the polarization axis Ax-Pr of the polarizer 173 are both set to form +45 degrees with respect to the fast axis Ax-LC of the liquid crystal element 172.

[0100] That is, in the upper part of Fig. 6, the same components as those of the spectral filter 132 in Fig. 2 are denoted by the same reference numerals. Also, in the upper part of Fig. 6, the spectral filter is referred to as a spectral filter 132A in order to distinguish it from the spectral filter 132 in Fig. 2.

[0101] The spectral filter 132A in the upper part of FIG. 6 differs from the spectral filter 132 in FIG. 2 in that a polarizer 173LU is provided instead of the polarizer 173.

[0102] 6, for comparison, only the polarizer 171, the liquid crystal element 172, and the polarizer 173 that constitute the spectral filter 132 are shown. Here, the polarizer 173 will also be referred to as polarizer 173RU hereinafter for comparison with the upper part of FIG.

[0103] That is, as shown in the upper part of Figure 6, the polarization axis Ax-PrA of the polarizer 173LU is set to be at +45 degrees with respect to the fast axis Ax-LC of the liquid crystal element 172, and is parallel to the polarization axis Ax-Pf of the polarizer 171.

[0104] With this configuration, the transmittance of the spectral filter 132A can be expressed by the following equation (12).

[0105]

[0106] More specifically, the polarizer 173LU can be expressed by the following equation (13) using the Jones matrix.

[0107]

[0108] where Vp2A is the Jones matrix of the polarizer 173LU.

[0109] Therefore, the Jones vector when the incident light passes through the spectral filter 132A is the product of Vp1, VLC, and Vp2A, and is expressed as in the following equation (14).

[0110]

[0111] Furthermore, the intensity of transmitted light, that is, the transmittance Sv(λ), is expressed as the square of the magnitude of the Jones vector, and is therefore calculated as in the following equation (15).

[0112]

[0113] As a result, the transmittance Sv(λ) is expressed by equation (12) (=equation (15)).

[0114] In this way, the polarization axis Ax-Pf of the polarizer 171 and the polarization axis Ax-PrA of the polarizer 173A may be set to form +45 degrees with respect to the fast axis Ax-LC of the liquid crystal element 172, respectively.

[0115] In this case, however, the transmittance Sv(λ) is expressed by equation (12).

[0116] Also, although not shown, the polarization axis Ax-Pf of polarizer 171 and the polarization axis Ax-Pr of polarizer 173 may both be at -45 degrees with respect to the fast axis Ax-LC of liquid crystal element 172, in which case the corresponding transmittance Sv(λ) is set.

[0117] In addition, when the polarization axis Ax-Pr of the polarizer 173 forms an angle of θ degrees with respect to the fast axis Ax-LC of the liquid crystal element 172, the generalized Jones matrix Vp2J has the relationship shown in the following equation (16).

[0118] Therefore, the Jones vector when transmitted through the generalized spectral filter 132J is the product of Vp1, VLC, and Vp2J, and is expressed as in the following equation (17).

[0119]

[0120] Furthermore, the intensity of transmitted light, that is, the transmittance Sv(λ), is expressed as the square of the magnitude of the Jones vector, and is therefore calculated as in the following equation (18).

[0121]

[0122] As a result, the generalized transmittance Sv(λ) is expressed by equation (18).

[0123] <<3. Second Modification of First Embodiment>> In the above, an example has been described in which the transmission characteristics are changed by changing the applied voltage for each divided region (filter) 151 of the spectral filter 132.

[0124] However, the transmission characteristics may be changed by providing variations in the thickness or medium characteristics of the liquid crystal element 172 for each divided region (filter) 151 of the spectral filter 132 .

[0125] The upper part of FIG. 7 shows an example of the configuration of a spectral filter when at least one of the thickness and medium characteristics of the divided region 172Da corresponding to the divided region (filter) 151 of the liquid crystal element 172 is changed.

[0126] That is, in the upper part of Fig. 7, the same components as those of the spectral filter 132 in Fig. 2 are denoted by the same reference numerals. Also, in the upper part of Fig. 7, the spectral filter is referred to as a spectral filter 132D in order to distinguish it from the spectral filter 132 in Fig. 2.

[0127] The spectral filter 132D of FIG. 7 differs from the spectral filter 132 of FIG. 2 in that a liquid crystal element 172D is provided instead of the liquid crystal element 172.

[0128] 7, for comparison, only the polarizer 171, the liquid crystal element 172, and the polarizer 173 that constitute the spectral filter 132 in FIG. 2 are shown.

[0129] That is, as shown in the upper part of Figure 7, the liquid crystal element 172D is divided into divided regions 172Da-1 to 172Da-7 to correspond to the divided regions (filters) 151-1 to 151-7, and at least one of the thickness and medium characteristics is set so that each has the required transmission characteristics (transmittance).

[0130] The liquid crystal element 172D is divided into divided regions 172Da-1 to 172Da-7 corresponding to the divided regions (filters) 151-1 to 151-7, and each has a thickness, at least one of the medium characteristics, and a transmission characteristic (transmittance) according to the voltage. Therefore, for example, even if the same voltage is applied to all, it is possible to configure them to have different transmission characteristics.

[0131] Therefore, even if the same voltage is applied to the divided regions 172Da-1 to 172Da-4 so as to correspond to the divided regions (filters) 151-1 to 151-4, it is possible to set different transmittances, for example, as shown by the transmission characteristics F11 to F14 in Figure 8.

[0132] In Figure 8, transmission characteristics F11 to F14 are displayed in order from left to right, and examples of distributions in which the period of the transmitted light intensity relative to the wavelength becomes shorter in the order of transmission characteristics F11 to F14 at the same voltage are shown.

[0133] Furthermore, with this configuration, the parameters for changing the transmission characteristics for each divided region (filter) 151 include not only voltage but also thickness and medium characteristics, thereby increasing the variation in transmission characteristics.

[0134] This makes it possible to set the transmission characteristics of the divided region (filter) 151 from a variety of parameters, including not only voltage but also thickness and medium characteristics, when finding the optimal solution for the voltage set V using equation (11).

[0135] As a result, for example, when optimized transmission characteristics are required for each divided region (filter) 151 of the spectral filter 132, the voltage applied by the power supply 130 may be set to a common value and either the thickness or the medium characteristics may be changed, thereby making it possible to easily control the voltage of the power supply 130.

[0136] <<4. Third Modification of First Embodiment>> In the above, an example has been described in which the transmission characteristics are changed by varying the thickness and medium characteristics of the liquid crystal element 172 for each divided region (filter) 151 of the spectral filter 132.

[0137] However, the second polarizer 173 may be omitted, and a polarizer may be provided instead of the color filter of the image sensor 133 .

[0138] The upper part of Figure 9 shows an example of the configuration of an image sensor-integrated spectral filter, in which the second polarizer 173 is omitted and an image sensor 133A is provided with a polarizer instead of the color filter of the image sensor 133.

[0139] That is, in the upper part of Fig. 9, the same components as those of the spectral filter 132 in Fig. 2 are denoted by the same reference numerals. Also, in the upper part of Fig. 9, the spectral filter is designated as a spectral filter 132E to distinguish it from the spectral filter 132 in Fig. 2.

[0140] The spectral filter 132E in Figure 9 differs from the spectral filter 132 in Figure 2 in that the second polarizer 173 is omitted and, further, the spectral filter 132E is integrated with an image sensor 133A that is provided with a polarizer filter instead of a color filter.

[0141] That is, as shown in the upper part of Figure 9, the spectral filter 132E has an integrated configuration in which the second polarizer 173 is replaced by an image sensor 133A in which a polarizer filter 173PF is provided instead of a color filter.

[0142] The polarizer filter 173PF provided in place of a color filter in the image sensor 133A is, as shown in the lower left of Figure 9, a polarizer filter P11 to P14 provided for an arrangement of four pixels where R, Gr, Gb, and B color filters are generally arranged.

[0143] In FIG. 9, the polarizer filters P11 and P14 have polarization axes Ax-LU oriented upward to the left, and the polarizer filters P12 and P13 have polarization axes Ax-RU oriented upward to the right.

[0144] Therefore, by generating different images for each of the polarization axes Ax-RU and Ax-LU through demosaic processing, it is possible to capture images with two types of transmission characteristics F21 and F22 for the same applied voltage, as shown in the lower right corner of Figure 9.

[0145] In this case, it is possible to set two types of transmission characteristics F21 and F22 even at the same voltage, and therefore, even in the parameters used to find the optimal solution for the voltage set V using equation (11), different transmission characteristics can be set at a single voltage. This increases the variety of transmission characteristics that can be set, thereby increasing the possibility of setting more optimized transmission characteristics.

[0146] <<5. Fourth Modification of First Embodiment>> Furthermore, as shown in the upper right part of FIG. 10 , for an arrangement of four pixels in which R, Gr, Gb, and B color filters are generally arranged, a polarizer 173PF′ in which polarizer filters P21 to P24 having polarization axes Ax1 to Ax4 are provided may be provided together with the image sensor 133A in a state inclined by an angle θ with respect to the optical axis of the polarizer 171 and the liquid crystal element 172.

[0147] 10, by tilting polarizer 173PF' and image sensor 133A by angle θ with respect to the optical axis of polarizer 171 and liquid crystal element 172, the polarization axes Ax1 to Ax4 of polarizer filters P21 to P24 are at different angles, and therefore, by demosaicing, it is possible to set, for example, four types of transmission characteristics F31 to F34, as shown in the lower part of Fig. 10. Therefore, even in the parameters used to find the optimal solution for voltage set V using equation (11), it is possible to set more different transmission characteristics with a single voltage, thereby increasing the variety of settable transmission characteristics and increasing the possibility of setting more optimized transmission characteristics.

[0148] In the above, we have described an example in which the polarizer 173PF' and the image sensor 133A are tilted by an angle θ with respect to the optical axis of the polarizer 171 and the liquid crystal element 172, but conversely, the polarizer 171 and the liquid crystal element 172 may be configured to be tilted by an angle θ with respect to the optical axis of the polarizer 173PF' and the image sensor 133A.

[0149] <<6. First Application Example of First Embodiment>> In the above, an example has been described in which processing is performed with the aim of acquiring spectral information about a predetermined wide wavelength band, such as from visible light to infrared light.

[0150] However, in reality, once it has been determined that desired information can be obtained in a specific wavelength band through analysis based on the spectral information, spectral information other than that specific wavelength band becomes unnecessary. In such a case, it is possible to save storage resources and calculation resources by extracting only the spectral information of the required wavelength band from the multiple images obtained.

[0151] For example, pixel signal i ｖ can be expressed by the following equation (19) based on equation (1).

[0152]

[0153] where v is the voltage applied to the divided region (filter) 151, and i ｖ is the pixel signal of the pixel on the image sensor 133 when light transmitted through the divided region (filter) 151 to which the voltage v is applied is received, and s ｖλ is the transmittance (transmission characteristic) at the corresponding position, and h λ is the spectral reflectance (spectral information).

[0154] Here, the pixel signal i of the light transmitted through the divided region (filter) 151 is ｖ , a predetermined coefficient w ｖ When multiplied by this, it can be expressed by the following equation (20).

[0155]

[0156] Furthermore, the coefficient w expressed by the above equation (20) ｖ The pixel signal i multiplied by ｖ When the sum of pixel signals having the transmission characteristics of all divided regions (filters) 151 of the spectral filter 132 is calculated, it can be expressed as the following equation (21).

[0157]

[0158] Here, m is the total number of divided regions (filters) 151 set in the spectral filter 132 .

[0159] The coefficient w in equation (21) ｖ By adjusting the wavelength λ, it is possible to obtain a value only for a specific wavelength λ.

[0160] FIG. 11 shows the case where the total number of m is 15, the total number of wavelengths λ is 15, and the coefficient w １ ~w １５ When a predetermined value is assigned to the pixel signal i at wavelength λ=1, 2, . . . 15, １ ~i １５ The coefficient w １ ~w １５ 10 shows the results of a simulation of the sum of products of the above and a bandpass filter for each wavelength λ.

[0161] That is, the pixel signal i shown in the upper left of FIG. １ ~i １５ , the coefficient w as shown in the upper center of FIG. １ ~w １５ is set and the sum of products is calculated, the wavelength λ １ The value (bpf gen) obtained for the sum corresponding to the wavelength λ １ The value (bpf) is approximately the same as the value when the light passes through the band pass filter of FIG. 1, and the values ​​for other wavelengths are approximately 0.

[0162] Also, the pixel signal i shown in the lower left portion of FIG. １ ~i １５ , the coefficient w as shown in the lower center of FIG. １ ~w １５ is set and the sum of products is calculated, the wavelength λ １５ The value (bpf gen) obtained for the sum corresponding to the wavelength λ １５ The value (bpf) is approximately the same as the value when the light passes through the band pass filter of FIG. 1, and the values ​​for other wavelengths are approximately 0.

[0163] That is, for each wavelength λ, the coefficient w １ ~w １５is appropriately set, the sum of the products of the coefficients and the transmittance can be calculated to have the same value as that of a bandpass filter at the corresponding wavelength λ.

[0164] The signal processing unit 134 processes the signal to obtain the coefficient w ｖ may be multiplied to realize substantially the same function as the band pass filter as described above.

[0165] Also, the coefficient w ｖ can be considered to be substantially a transmission coefficient, so the coefficient w ｖ A new polarizer whose transmission characteristics can be changed so as to correspond to the value of the coefficient w is provided in front of the polarizer 171, and the signal processing unit 134 ｖ The control may be performed in accordance with the above.

[0166] 12 shows the coefficient w ｖ This is an example of the configuration of a spectral filter provided with a new polarizer whose transmission characteristics can be changed to correspond to the value of

[0167] In FIG. 12, the spectral filter is designated as a spectral filter 132F to distinguish it from the spectral filter 132 in FIG.

[0168] That is, in the spectral filter 132F of FIG. 12, a coefficient w ｖ A new polarizer 201 is provided that can change the transmission characteristics to correspond to the value of . The polarizer 201 is controlled by the signal processing unit 134, and is configured so that the polarization axis is variable for each of the divided regions (filters) 151.

[0169] When it is desired to acquire spectral information of a specific wavelength λ like a band-pass filter from a plurality of images formed by the transmission characteristics of the respective filters captured by the spectral filter 132F, the signal processing unit 134 calculates a coefficient w that enables the signal processing unit 134 to function as a band-pass filter for the desired wavelength λ, as described with reference to FIG. ｖ Then, the signal processing unit 134 calculates the coefficient w ｖ The polarization axis of the polarizer 171 is adjusted to achieve transmission characteristics corresponding to the above.

[0170] With this configuration, it is possible to obtain spectral information of a specific wavelength λ, like a bandpass filter, simply by adding and subtracting each pixel signal of multiple images consisting of the transmission characteristics of each of the multiple filters captured by the spectral filter 132F.

[0171] <<7. Second Application Example of the First Embodiment>> In addition, the coefficient w ｖ To realize the corresponding transmission characteristics, the coefficient w ｖ Since it is sufficient to adjust the sensitivity for each divided region (filter) 151 so as to correspond to the coefficient w ｖ For example, the exposure time of the image sensor 133 may be adjustable for each divided area (filter) 151 so as to realize transmission characteristics corresponding to the above.

[0172] Figure 13 shows the coefficient w ｖ 15 shows an example of the configuration of a spectral filter 132G integrated with an image sensor 133G that allows the exposure time of the image sensor 133 to be adjusted for each divided region (filter) 151 so as to realize transmission characteristics corresponding to the above.

[0173] In FIG. 13, the spectral filter is denoted as a spectral filter 132G in order to distinguish it from the spectral filter 132 in FIG.

[0174] The spectral filter 132G is configured such that an image sensor 133B capable of adjusting exposure time for each pixel belonging to the divided region (filter) 151 is integrated with the polarizer 173 in the spectral filter 132 of FIG.

[0175] In this example, the signal processing unit 134 determines the coefficient w , which enables the signal processing unit 134 to function as a band-pass filter for the desired wavelength λ, as described with reference to FIG. ｖ When we calculate the coefficient w ｖ The image sensor 133B is controlled to realize transmission characteristics corresponding to the above, and an exposure time of each pixel in the divided region (filter) 151 is adjusted to capture an image.

[0176] Even with this configuration, it is possible to obtain spectral information of a specific wavelength λ, just like a bandpass filter, by simply adding and subtracting each pixel signal of multiple images consisting of the transmission characteristics of each of the multiple filters captured by the spectral filter 132G.

[0177] <<8. Third Application Example of First Embodiment>> In the above, an example has been described in which spectral information with high wavelength resolution is acquired from images with a plurality of transmission characteristics. However, in cases where object recognition is performed using spectral information, object recognition processing may be performed directly from images with a plurality of transmission characteristics without calculating higher spectral information.

[0178] FIG. 14 shows an example of the configuration of an object recognition system 221 that realizes object recognition processing directly from an image having a plurality of transmission characteristics without generating spectral information.

[0179] In the object recognition system 221 of FIG. 14, components having the same functions as those in the spectroscopic measurement system 111 of FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0180] That is, the object recognition system 221 in FIG. 14 differs from the spectroscopic measurement system 111 in FIG. 1 in that an object recognition unit 231 is provided instead of the signal processing unit 134 .

[0181] The object recognition unit 231 has the same functions as the signal processing unit 134 regarding the operation control of the power supply 130 , the drive unit 127 , and the image sensor 133 .

[0182] Similar to the signal processing unit 134, the object recognition unit 231 controls the image sensor 133 and the drive unit 127 to capture multiple images with multiple transmission characteristics, then performs object recognition processing based on the multiple images with multiple transmission characteristics and outputs the object recognition results that are the processing results.

[0183] In other words, the images of multiple transmission characteristics obtained by passing through the spectral filter 132 of the present disclosure are not images for multiple wavelength bands obtained by a bandpass filter set for each different band, but multiple images containing multiple overlapping wavelength bands at various sensitivities, so that spectral information with high wavelength resolution can be generated by signal processing.

[0184] Therefore, even if an image with multiple different transmission characteristics is used for object recognition processing as is, without the need for signal processing, it is possible to achieve highly accurate object recognition processing, just as when spectral information with high wavelength resolution is used.

[0185] <<9. Second Embodiment>> In the above-described spectral filter 132, an example has been described in which a liquid crystal element 172 having birefringence, optical anisotropy, and functioning as a variable wavelength plate in response to an applied voltage, and provided with a plurality of segmented regions (filters) 151, is sandwiched between polarizers 171 and 173.

[0186] In this case, by providing a plurality of divided regions (filters) 151 in the liquid crystal element 172, different voltages are applied to each divided region (filter) 151, thereby setting different transmission characteristics for each divided region (filter).

[0187] However, a plurality of transmission characteristics may be set by using a spectral filter that combines one liquid crystal element that functions as a variable wave plate with wave plates that provide a plurality of different fixed phase differences.

[0188] FIG. 15 shows an example configuration of a second embodiment of the spectroscopic measurement system of the present disclosure, in which a plurality of transmission characteristics are set by using a spectral filter that combines a liquid crystal element that functions as a variable wavelength plate and does not have a division region 151 set therein with wavelength plates that impart a plurality of different fixed phase differences.

[0189] The spectroscopic measurement system 311 in FIG. 15 captures an image of an object 321 to be spectroscopically measured, and acquires highly accurate spectroscopic information 322 with high wavelength resolution at high speed by signal processing based on the image capture result.

[0190] The spectroscopic measurement system 311 includes a power supply 330 , a lens 331 , a spectral filter 332 , an image sensor 333 , and a signal processing unit 334 .

[0191] The power supply 330, lens 331, spectral filter 332, image sensor 333, and signal processing unit 334 in the spectroscopic measurement system 311 in FIG. 15 basically correspond to the power supply 130, lens 131, spectral filter 132, image sensor 133, and signal processing unit 134 in the spectroscopic measurement system 111 in FIG. 1, and have the same basic functions.

[0192] However, while the spectral filter 112 has a configuration in which a plurality of liquid crystal elements 172 are sandwiched between polarizers 171 and 173, the spectral filter 332 has a configuration in which a liquid crystal element that functions as a variable wave plate and does not have a configuration corresponding to the divided region 151 is combined with a wave plate that provides a plurality of different fixed phase differences. Furthermore, the signal processing unit 334 acquires spectral information of the object 321 by signal processing different from that of the signal processing unit 114, depending on the configuration of the spectral filter 332.

[0193] More specifically, as shown in the right part of Figure 16, the spectral filter 332 is configured by stacking, from the front toward the incident direction of light from the object 321, a polarizer 371, a wave plate 381 that imparts a plurality of different fixed phase differences, a liquid crystal element 372, and a polarizer 373 in this order.

[0194] The polarizers 371 and 373 have the same configuration as the polarizers 171 and 173 in FIG.

[0195] The liquid crystal element 372 has basically the same configuration as the liquid crystal element 172, but does not have the divided regions 151 and has a configuration in which the entire surface has a unified birefringence at a single applied voltage. However, the liquid crystal element 372 can change the birefringence over the entire surface by changing the applied voltage.

[0196] As shown in the lower right of Figure 16, the wave plate 381 is configured by repeating wave plate units 381u in the horizontal and vertical directions, each of which has a 2 x 2 fixed pattern of small wave plates 381a-1 to 381a-4 that provide different fixed phase differences. The fixed pattern of the small wave plates 381a-1 to 381a-4 is a pattern set using pixels in the image sensor 333 as units, such as a Bayer array. Note that hereinafter, when there is no need to distinguish between the small wave plates 381a-1 to 381a-4 individually, they will simply be referred to as small wave plates 381a. Here, the size set for one small wave plate 381a only needs to be equal to or greater than one pixel in the image sensor 333, and may be, for example, 2 pixels x 2 pixels or 3 pixels x 3 pixels.

[0197] With this configuration, the spectral filter 332 converts the light from the object 321 into light having the transmission characteristics of each of the small wavelength plates 381a-1 to 381a-4.

[0198] Here, an example is shown in which the wave plate unit 381u is composed of small wave plates 381a-1 to 381a-4 arranged in a 2 x 2 fixed pattern, but the number of small wave plates 381a that make up the wave plate unit 381u may be other than four, as long as the phase differences provided by each small wave plate are different, and may be, for example, 3 x 3, 4 x 4, 2 x 3, 3 x 2, etc.

[0199] However, in this embodiment, as shown in Figure 16, the explanation will be given assuming that the wave plate unit 381u constituting the wave plate 381 is composed of four small wave plates 381a-1 to 381a-4 arranged in a grid pattern with a fixed 2 x 2 pattern.

[0200] Furthermore, as shown in the right part of Figure 16, the liquid crystal element 372 that constitutes the spectral filter 332 does not have a divided region 151 set, unlike the spectral filter 132 of Figure 2. Therefore, the number of output channels of the power supply 330 is only one, which allows for a single wiring, and also allows for a relatively simple power supply itself to be used, allowing for a simpler device configuration and making it possible to reduce costs.

[0201] However, in the spectral filter 332 of Figure 16, the liquid crystal element 372 that functions as a variable wavelength plate does not have a divided region 151 set, so the transmission characteristics cannot be changed locally as with the divided region 151, but it is possible to make one transmission characteristic variable over the entire surface by applying one unified voltage.

[0202] On the other hand, in the spectral filter 332 of FIG. 16, the wave plate 381 has local transmission characteristics in each of the small wave plates 381a-1 to 381a-4 that make up the wave plate unit 381u.

[0203] The transmission characteristics of each combination of the small wavelength plates 381a-1 to 381a-4 and the liquid crystal element 372 may be, for example, as shown in FIG.

[0204] 17 shows, from top to bottom, the transmission characteristics when each of the small wave plates 381a-1 to 381a-4 is combined with the liquid crystal element 372. In the transmission characteristic distribution diagram on the left side of the diagram, the horizontal axis is wavelength (wavelength (nm)) and the vertical axis is applied voltage (voltage (V)), and transmittance, which is the transmission characteristic, is expressed by density. Furthermore, to the right of the transmission characteristic distribution diagram for each of the small wave plates 381a-1 to 381a-4, waveform diagrams of the transmission characteristics when the voltages applied to the liquid crystal element 372 are Vx and Vy are shown above and below, respectively.

[0205] That is, for example, in the transmission characteristic distribution diagram when each of small wave plates 381a-1 to 381a-4 in Fig. 17 is combined with liquid crystal element 372, when the applied voltage is voltage Vx, the transmittance changes periodically for each wavelength as shown by the waveform diagram in the upper right of each transmission characteristic distribution diagram. Also, in the transmission characteristic distribution diagram of small wave plates 381a-1 to 381a-4 in Fig. 17, when the applied voltage is voltage Vy, the transmittance changes periodically for each wavelength as shown by the waveform diagram in the lower right of each transmission characteristic distribution diagram.

[0206] The transmittance is proportional to the inverse of the wavelength and changes periodically like a trigonometric function, and the period becomes shorter as the voltage decreases.

[0207] In addition, in FIG. 17, the small wave plates 381a-1 to 381a-4 are set so that the period of the change in transmittance becomes longer in this order.

[0208] In other words, in FIG. 17, the small wavelength plates 381a-1 to 381a-4 are configured to have mutually different transmission characteristics when combined with the liquid crystal element 372.

[0209] 17, the configurations including small wave plates 381a-1 to 381a-4 and liquid crystal element 372 all have a characteristic in which the period shortens as the voltage drops. Furthermore, the transmission characteristic Pmax1 at the maximum voltage when small wave plate 381a-1 is combined with liquid crystal element 372 is substantially the same as the transmission characteristic Pmin2 at the minimum voltage when small wave plate 381a-2 is combined with liquid crystal element 372.

[0210] Furthermore, the transmission characteristic Pmax2 at the maximum voltage when the small wavelength plate 381a-2 is combined with the liquid crystal element 372 is approximately the same as the transmission characteristic Pmin3 at the minimum voltage when the small wavelength plate 381a-3 is combined with the liquid crystal element 372.

[0211] Furthermore, the transmission characteristic Pmax3 at the maximum voltage when the small wavelength plate 381a-3 is combined with the liquid crystal element 372 is approximately the same as the transmission characteristic Pmin4 at the minimum voltage when the small wavelength plate 381a-4 is combined with the liquid crystal element 372.

[0212] In this way, by combining the small wavelength plates 381a-1 to 381a-4 with the liquid crystal element 372, the small wavelength plates 381a-1 to 381a-4 have the transmission characteristics shown in Figure 17, so that no matter what voltage is applied to the liquid crystal element 372, the light passing through the small wavelength plates 381a-1 to 381a-4 can always have different transmission characteristics, and the spectroscopic information Ps can be appropriately determined by the signal processing unit 374.

[0213] The conditions for the small wavelength plates 381a-1 to 381a-4 to have the transmission characteristics shown in FIG. 17 will be described in detail later.

[0214] The signal processing unit 334 sets the applied voltage based on the wavelength range to be determined for the object 321 , and controls the power supply 330 to apply the set applied voltage to the spectral filter 332 .

[0215] Furthermore, the signal processing unit 334 controls the image pickup element 333 to pick up an image converted to have the transmission characteristics of the spectral filter 332 .

[0216] The signal processing unit 334 then performs demosaic processing on the image captured by the image sensor 333 for each of the small wavelength plates 381a-1 to 381a-4 of the wavelength plate 381 to generate four images corresponding to the number of small wavelength plates 381a, each with the transmission characteristics of the small wavelength plates 381a-1 to 381a-4, and calculates spectral information with higher wavelength resolution, which is at least greater than the number of the small wavelength plates 381a-1 to 381a-4, through signal processing that utilizes the applied voltage and the respective transmission characteristics.

[0217] 15, the wave plate 381 is divided into small wave plates 381a-1 to 381a-4 in units of pixels within a 2 x 2 array, and by demosaicing the image signals of each small wave plate 381a-1 to 381a-4, it is possible to obtain images of four objects 321 with different optical properties. This eliminates the need for a configuration such as the base 120 for moving the object 321, making it possible to reduce device costs and simplifying processing by eliminating the need for processing to move the object 321.

[0218] In addition, in the spectroscopic measurement system 311 of Figure 15, a spectral filter 332 is used that combines one liquid crystal element that functions as a wave plate whose transmission characteristics can be changed by an applied voltage with wave plates having multiple different fixed transmission characteristics.By using this, image signals captured for each of the small wave plates 381a-1 to 381a-4 with different transmission characteristics in pixel units are demosaic processed to generate images with multiple transmission characteristics, and spectral information is generated based on the images with the multiple transmission characteristics.

[0219] In contrast, in the spectroscopic measurement system 111 of Figure 1, the rectangular divided area 151 of the spectral filter 132 functions as a line sensor, thereby capturing an image with multiple transmission characteristics, and generating spectral information based on the image with the multiple transmission characteristics.

[0220] That is, although the spectroscopic measurement system 111 in FIG. 1 and the spectroscopic measurement system 311 in FIG. 15 have different configurations and signal processing, they are common in that they are equipped with filters having different transmission characteristics, and multiple images having different transmission characteristics are generated from image signals captured using these filters, thereby generating spectral information.

[0221] <Method for calculating spectral information by signal processing by the signal processing unit in FIG. 15> Next, a method for calculating spectral information by signal processing by the signal processing unit 334 in FIG. 15 will be described.

[0222] First, when light emitted from the object 321 passes through the spectral filter 332 to which a voltage v is applied and is received at a pixel position (x, y) on the image sensor 333, a pixel signal i ｖ As in the first embodiment, (x, y) is defined as in the following equation (1).

[0223]

[0224] Here, the coordinate position on the spectrum filter 332 and the coordinate position on the image sensor 333 are expressed by corresponding (x, y) positions. ｖ (x, y) is the pixel signal of the pixel at the position (x, y) on the image sensor 133, and S ｖ (x, y, λ) is the transmittance of light of wavelength λ when voltage v is applied to position (x, y) on the spectral filter 332, and h(x, y, λ) is the spectral reflectance (spectral information) of light of wavelength λ at position (x, y).

[0225] In addition, the transmittance S ｖ (x, y, λ) corresponds to the transmission characteristics of each of the small wavelength plates 381a-m (m = 1, 2, 3, 4) that make up the wavelength plate unit 381u of the wavelength plate 381 that makes up the spectral filter 332. For example, in the case of the polarizer 371, wavelength plate 381, liquid crystal element 372, and polarizer 373 described with reference to Figure 16, each of the small wavelength plates 381a-m is expressed as in the following equations (22) to (25).

[0226]

[0227] Here, the transmittance S ｍｖ (x, y, λ) is the transmission characteristic of each of the small wave plates 381a-m (m=1, 2, 3, 4) that constitute the wave plate unit 381u of the wave plate 381 that constitutes the spectral filter 332. Ｒｍ is the refractive index difference between the fast axis and the slow axis of the small wavelength plate 381a-m (birefringence between the fast axis and the slow axis), and d Ｒｍ is the thickness of the small wave plate 381a-m. LC(v) is the refractive index difference between the fast axis and the slow axis of the liquid crystal element 372 at voltage v (birefringence between the fast axis and the slow axis), and d ＬＣ is the thickness of the liquid crystal element 372.

[0228] As described above, the spectral reflectance h(x, y, λ) in equation (1) is a continuous variable, but the data cube H to be obtained, which corresponds to the spectral reflectance h, is expressed as a discrete variable. Therefore, by discretizing and then vectorizing the data cube H, equation (1) can be replaced with equation (9) below.

[0229]

[0230] Here, H is a data cube that corresponds to the spectral reflectance h and is the spectral information of the object 321 to be obtained, and Nx, Ny, and Nλ are the coordinates x, y, and the number of wavelengths λ, respectively.

[0231] That is, in formula (9), i ｖ (x, y) is the pixel signal of the pixel at the position (x, y) on the image sensor 333. In other words, when a voltage v is applied to the spectral filter 332, the transmittance S on the demosaic-processed image for each of the small wave plates 381a-1 to 381a-4 is １ v~S ４ The transmittance S is information on an image signal captured at a position (x, y) on the image sensor 333 when light passes through the image sensor 333 at a transmittance S １ v~S ４ v is a known value based on the transmission characteristics of each of the small wavelength plates 381a-1 to 381a-4 and the liquid crystal element 372 at the applied voltage v. From this, based on the relationship in equation (9), the desired data cube H can be found by solving the following equation (26).

[0232]

[0233] where R(H) is a regularization term and m is the identifier of the sub-waveplates 381a-m with different transmission characteristics.

[0234] Since Equation (26) is a linear problem, it can be solved by a least squares method. However, Equation (29) can be solved by a method other than the least squares method, for example, by using a neural network.

[0235] That is, the signal processing unit 334 performs demosaic processing on the image captured by the image sensor 333 for the number of small wave plates 381a-m, and generates an image having the transmission characteristics of each small wave plate 381a-m and the transmittance S of each small wave plate 381a-m. １ v~S ４ By solving equation (26) based on v, a data cube H that is the spectral information of the object 321 can be obtained.

[0236] Furthermore, the voltage v applied to the liquid crystal element 372 can be optimized by solving the following equation (27).

[0237]

[0238] Here, N ａｌｌ is the total number of voltages that can be applied to the liquid crystal element 372.

[0239] That is, the signal processing unit 334 calculates the total number N that can be set as the voltage V based on the above-mentioned equation (27). ａｌｌ Among them, pixel signal i ｖ and H.S. ｍｖ In other words, the voltage V at which the data cube H is obtained as an optimal solution is set in advance.

[0240] In addition, the signal processing unit 334 applies a voltage to the liquid crystal element 372 at the set voltage V, and causes the light from the object 321 to pass through each of the small wavelength plates 381a-1 to 381a-4 that make up the wavelength plate unit 381u of the wavelength plate 381, while causing the image pickup element 333 to capture an image having transmission characteristics transmitted at the transmittance of each of the small wavelength plates 381a-1 to 381a-4.

[0241] The signal processing unit 334 then demosaics the captured image for each of the small wavelength plates 381a-1 to 381a-4 to generate pixel signals i ｍｖand the transmittance S ｍｖ Based on this, a data cube H is calculated by signal processing.

[0242] In addition, the pixel signal i ｍｖ For transmittance S ｍｖ By setting the above, a telecentric optical system is not required, and therefore, for example, a configuration for producing parallel light is not required in an optical system corresponding to the lens 331, and a cheaper optical system can be achieved.

[0243] Furthermore, the signal processing unit 334 is generally premised on determining a voltage V optimized for determining a data cube H, which is ultimately desired spectral information over a relatively wide band from the visible light region to the infrared light region, but may also determine a voltage that will determine an optimal data cube depending on the application. That is, when a specific wavelength band is the only band required for comparing some object, the signal processing unit 334 may determine a voltage V that will determine an optimal data cube H only for the specific wavelength band.

[0244] As described with reference to FIG. 17, in order to make the transmission characteristics combined with each of the small wave plates 381a-1 to 381a-4 different regardless of the voltage V set in the liquid crystal element 372, Δn Ｒ ≒Δn ＬＣ In the case of (0), the relationship between the thickness of each of the small wavelength plates 381a-1 to 381a-4 and the thickness of the liquid crystal element 372 must satisfy the conditions expressed by the following expressions (28) to (30).

[0245]

[0246]

[0247]

[0248] With this setting, the transmission characteristics that are generated by combining the small wavelength plates 381a-1 to 381a-4 with the liquid crystal element 372 are different from each other, as shown in Figure 17, making it possible to more appropriately determine the spectral information of the object 321.

[0249] The transmission characteristics that are produced by combining the small wavelength plates 381a-1 to 381a-4 with the liquid crystal element 372 do not necessarily have to be completely independent of each other as shown in FIG. 17, as long as they are not identical to each other.

[0250] <Spectral Information Acquisition Processing> Next, the spectral information acquisition processing will be described with reference to the flowchart of FIG.

[0251] In step S51, the signal processing unit 334 sets the voltage V by calculation using the above-mentioned equation (27).

[0252] In step S 52 , the signal processing unit 334 controls the power supply 330 to apply the set voltage V to the liquid crystal element 372 of the spectral filter 332 .

[0253] In step S53, the signal processing unit 334 controls the image sensor 333 to capture an image of the object 321 having the transmission characteristics (transmittance) resulting from the combination of the small wavelength plates 381a-1 to 381a-4 and the liquid crystal element 372, and acquires and stores the captured image.

[0254] In step S54, the signal processing unit 334 controls the image sensor 333 to individually demosaic the captured images for each of the small wavelength plates 381a, thereby generating a number of images corresponding to the number of small wavelength plates 381a.

[0255] In step S55, the signal processing unit 334 calculates spectral information with high wavelength resolution, which is at least greater than the number of small wavelength plates 381a, by, for example, solving the above-mentioned equation (26) based on the demosaiced images of the object 321 with different transmission characteristics (transmittances) of a number corresponding to the number of small wavelength plates 381a, the transmission characteristics of the liquid crystal element 372 according to the applied voltage, and the fixed transmission characteristics of each small wavelength plate 381a.

[0256] In step S56, the signal processing unit 334 outputs spectral information with high wavelength resolution, which is at least greater than the number of small wavelength plates 381a, calculated by signal processing based on the transmission characteristics of the liquid crystal element 372 according to the applied voltage and the fixed transmission characteristics of each small wavelength plate 381a, using a number of images equivalent to the number of small wavelength plates 381a that have been demosaiced.

[0257] By the above processing, it is possible to set the applied voltage so that the liquid crystal element 372 set in the spectral filter 332 provided in front of the image sensor 333 has optimal transmission characteristics depending on the band of the spectral information to be obtained, and therefore it is possible to obtain the spectral information that is ultimately generated with high accuracy.

[0258] Furthermore, in the present disclosure, images of the object 321 having a plurality of transmission characteristics can be acquired in a single image capture by the image capture element 333 while a voltage is applied so that the transmission characteristics of the combination of the small wave plates 381a-1 to 381a-4 set in the spectral filter 332 and the liquid crystal element 372 are optimal. This reduces the cost of the device configuration, as well as the effort and time required for imaging, and makes it possible to acquire highly accurate spectral information at high speed.

[0259] As a result, it is possible to realize high-speed spectroscopic measurements in various bands using an inexpensive device configuration.

[0260] Furthermore, by capturing an image of the object 321 multiple times while sequentially switching the voltage applied to the liquid crystal element 372 of the spectral filter 332, it is possible to obtain a larger number of objects 321 with multiple transmission characteristics and use them to acquire spectral information.

[0261] However, in this case, imaging will be performed multiple times, and if, for example, near-infrared light is required as the final spectroscopic information, the thickness of the spectral filter 332 will need to be increased, and the increased thickness will result in a decrease in the response time related to switching the applied voltage.

[0262] Therefore, if imaging is repeated multiple times while switching the voltage applied to the spectral filter 332, this may increase the effort and time required for imaging.

[0263] In contrast, in the spectroscopic measurement system 311 of Figure 15 of the present disclosure, an image with multiple transmission characteristics can be obtained by demosaic processing in a single image capture, thereby reducing the time required for image capture and enabling images with multiple transmission characteristics to be obtained quickly.

[0264] Furthermore, in the present disclosure, there is no need to place the object 321 on something like a base 120 and pass it in front of the spectral filter 332, which reduces the cost of the device configuration and eliminates the need to move the object 321.

[0265] Although not shown, in the spectroscopic measurement system 311 of FIG. 15 , in the same way as in the third application example of the first embodiment, when object recognition is performed using spectral information, it is possible to provide a configuration corresponding to the object recognition unit 231 instead of the signal processing unit 334, and perform object recognition processing directly from images with a plurality of transmission characteristics, without calculating higher spectral information.

[0266] <<10. First Modification of Second Embodiment>> In the above, an example has been described in which the fast axes of the wave plate 381 and the liquid crystal element 372 are aligned, but they do not necessarily have to be aligned.

[0267] 19, a liquid crystal element 372' may be provided whose fast axis is offset from the fast axis of the wave plate 381. Conversely, although not shown, a wave plate 381 may be provided whose fast axis is offset from the fast axis of the liquid crystal element 372.

[0268] <<11. Second Modification of Second Embodiment>> In the above, an example has been described in which signal processing is performed after demosaicing is performed for each of the small wavelength plates 381 a-1 to 381 a-4 based on the image signals captured in the signal processing unit 334. However, signal processing may also be performed by directly utilizing the transmission characteristics of each of the small wavelength plates 381 a-1 to 381 a-4 using the following equation (31) without demosaicing.

[0269]

[0270] In this case, however, it is necessary to grasp in advance the arrangement of the small wave plates 381a-1 to 381a-4 configured in the wave plate 381 by calibration or the like.

[0271] Furthermore, as long as the arrangement of the small wavelength plates 381a can be determined in advance by calibration or the like, the positions of the small wavelength plates 381a do not need to be fixed, as in the wavelength plate unit 381u of the wavelength plate 381. For example, as shown in Figure 20, instead of the wavelength plate 381, a wavelength plate 381' in which small wavelength plates 381a with various transmission characteristics are randomly arranged may be used.

[0272] As a result, for the wave plate 381', for example, quartz crystal, which exists in nature, may be used, which makes it possible to further reduce costs.

[0273] <<12. Description of Computer to which the Present Technology is Applied>>

[0274] The above-described series of processes can be executed by hardware or software. When the series of processes is executed by software, the programs constituting the software are installed on a computer. Here, the term "computer" includes computers built into dedicated hardware, and general-purpose personal computers, etc., that can execute various functions by installing various programs.

[0275] FIG. 21 is a block diagram showing an example of the hardware configuration of a computer that executes the above-described series of processes by a program.

[0276] In the computer, a processing circuit 1001 , a ROM (Read Only Memory) 1002 , and a RAM (Random Access Memory) 1003 are interconnected by a bus 1004 .

[0277] An input / output interface 1005 is further connected to the bus 1004. An input unit 1006, an output unit 1007, a storage unit 1008, a communication unit 1009, and a drive 1010 are connected to the input / output interface 1005.

[0278] The input unit 1006 may include physical or virtual operating means, such as a keyboard, mouse, or touch panel, that a user operates to input information, as well as means for the user to input information by voice, gaze, or the like. Furthermore, the input unit 1006 may include sensors for inputting various physical quantities to the computer. For example, the input unit 1006 may include sensors, such as a camera or microphone, that acquire physical quantities such as light (including infrared light other than visible light) and sound. Furthermore, the input unit 1006 may include sensors that acquire other physical quantities such as temperature, moisture content, acceleration, and distance. The output unit 1007 may include means, such as a display, speaker, or haptic device, that present information to a user by stimulating the user's perception. The storage unit 1008 may be composed of a hard disk, non-volatile or volatile memory, or the like, and stores various information (including programs). The communication unit 1009 may be a network interface or the like, and may communicate with the outside world via wired or wireless connections. The drive 1010 drives a removable medium 1011 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

[0279] The processing circuit 1001 includes a processor that executes a program, such as a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The processing circuit 1001 (the processor) performs the above-described series of processes by loading a program stored in a storage unit 1008 into a RAM 1003 via an input / output interface 1005 and a bus 1004 and executing the program. The processing circuit 1001 can output the results of the series of processes from an output unit 1007, for example, via the bus 1004 and the input / output interface 1005, as necessary. The processing circuit 1001 can also store the processing results in the storage unit 1008 or transmit them from a communication unit 1009.

[0280] The program executed by the computer (processing circuit 1001) can be provided by being recorded on removable media 1011 such as package media, for example. The program can also be provided via wired or wireless transmission media such as a local area network, the Internet, or digital satellite broadcasting.

[0281] In a computer, the program can be installed in the storage unit 1008 via the input / output interface 1005 by inserting the removable medium 1011 into the drive 1010. The program can also be received by the communication unit 1009 from another device such as a server via a wired or wireless transmission medium and installed in the storage unit 1008. Alternatively, the program can be installed in advance in the ROM 1002 or the storage unit 1008.

[0282] The program executed by the computer may be a program that processes in chronological order according to the order described in this specification, or may be a program that processes in parallel or at the required timing, such as when called.

[0283] The processing performed by a computer according to a program does not necessarily have to be performed in chronological order according to the order described in the flowchart. In other words, the processing performed by a computer according to a program also includes processing that is executed in parallel or individually (for example, parallel processing or processing by objects).

[0284] The program may be processed by a single computer (processor), or may be distributed among multiple computers. Furthermore, the program may be transferred to and executed on a remote computer.

[0285] When the above-described series of processes are performed by a computer executing a program, the processing circuit 1001 (its processor) executes the program to function as the signal processing unit 134 in FIG. 1, the object recognition unit 231 in FIG. 14, and the signal processing unit 334 in FIG. 15.

[0286] In this specification, a system refers to one component or a collection of multiple components (devices, modules (components), etc.). Therefore, one or multiple components of a computer, for example, only a processor, or a combination of a processor and memory, for example, only the processing circuit 1001, or a combination of the processing circuit 1001 and bus 1004, etc., is a system. With respect to a collection of multiple components, it does not matter whether all the components are in the same housing. Therefore, multiple devices housed in separate housings and connected via a network, or a single device housed in a single housing with multiple modules, are both systems. Furthermore, for example, an entire computer or a combination of a computer and another device, such as a server (not shown), is also a system.

[0287] Also, for example, each step of a single flowchart may be executed by a single device, or may be shared and executed by multiple devices. Furthermore, when a single step includes multiple processes, the multiple processes may be executed by a single device, or may be shared and executed by multiple devices. In other words, multiple processes included in a single step can be executed as multiple step processes. Conversely, processes described as multiple steps can be executed collectively as a single step.

[0288] For example, the steps of a program executed by a computer may be executed in chronological order in the order described herein, or may be executed in parallel or individually at the required timing, such as when a call is made. In other words, as long as no contradiction occurs, the steps may be executed in an order different from the order described above. Furthermore, the steps of this program may be executed in parallel with the processing of another program, or may be executed in combination with the processing of another program.

[0289] Furthermore, for example, the multiple technologies related to the present disclosure can be implemented independently and singly, as long as no contradiction occurs. Of course, any multiple technologies of the present disclosure can also be implemented in combination. For example, part or all of the present disclosure described in any embodiment can be implemented in combination with part or all of the present disclosure described in another embodiment. Furthermore, part or all of any of the above-mentioned present disclosures can be implemented in combination with other technologies not described above.

[0290] The present disclosure can also be configured as follows.

[0291] <1> A spectroscopic measurement system comprising: a spectral filter including a plurality of filters that transmit light from an object with different transmission characteristics; and an image sensor that captures images of the object with a number of different transmission characteristics corresponding to the number of filters based on light that has passed through the spectral filters, wherein the plurality of filters are arranged in a predetermined direction, and the image sensor captures images of the object with a plurality of different transmission characteristics corresponding to the number of filters based on the entire light of the object that passes through each of the plurality of filters and is incident thereon as a relative position between the image sensor and the object changes. <2> The spectroscopic measurement system described in <1>, wherein the plurality of filters that constitute the spectral filter are each configured by stacking a first polarizer, a liquid crystal element, and a second polarizer different from the first polarizer in this order from the front to the back with respect to the direction of incidence of light from the object. <3> The spectroscopic measurement system described in <2>, wherein the liquid crystal element of each of the plurality of filters changes its transmittance for each wavelength as a transmission characteristic in response to an applied voltage. <4> The spectroscopic measurement system according to <3>, wherein the transmittance of the liquid crystal element changes for each wavelength in proportion to the inverse of the wavelength in a period expressed by a trigonometric function in response to the applied voltage. <5> The spectroscopic measurement system according to <2>, wherein the polarization axes of the first polarizer and the second polarizer are at angles of +45 degrees and −45 degrees, or −45 degrees and +45 degrees, respectively, with respect to the fast axis of the liquid crystal element. <6> The spectroscopic measurement system according to <2>, wherein the polarization axes of the first polarizer and the second polarizer are both at +45 degrees or −45 degrees with respect to the fast axis of the liquid crystal element. <7> The spectroscopic measurement system according to <2>, wherein the liquid crystal element of each of the plurality of filters changes its transmittance for each wavelength as a transmission characteristic in accordance with at least one of the thickness of the liquid crystal element and the characteristics of the medium. <8> The spectroscopic measurement system according to <2>, wherein the second polarizer is configured to replace a color filter in units of pixels in the image sensor.<9> The spectroscopic measurement system according to <8>, wherein when the second polarizer is configured to replace a color filter in units of pixels in the image sensor, two or more types of polarization axes are set in the second polarizer. <10> The spectroscopic measurement system according to <1>, further including a signal processing unit that calculates spectral information by signal processing based on an image of the object having a plurality of different transmission characteristics and the transmission characteristics of the plurality of filters. <11> The spectroscopic measurement system according to <1>, further including a signal processing unit that calculates spectral information of a predetermined wavelength band by signal processing based on pixel signals of the image of the object having a plurality of different transmission characteristics and a product-sum of predetermined coefficients corresponding to the pixel signals. <12> The spectroscopic measurement system according to <11>, wherein each of the plurality of filters constituting the spectral filter is configured to have a first polarizer, a liquid crystal element, and a second polarizer different from the first polarizer stacked in this order with respect to the incident direction of light from the object, and further includes a third polarizer, located before the first polarizer, that is adjustable to have transmission characteristics corresponding to a predetermined coefficient corresponding to the pixel signal, and the signal processing unit calculates spectral information in a predetermined wavelength band by signal processing that adds together pixel signals of an image of the object having a plurality of different transmission characteristics, the image being captured using light that has transmitted through the third polarizer, the first polarizer, the liquid crystal element, the second polarizer, and the image capture element in that order. <13> The spectroscopic measurement system according to <11>, wherein the image capture element captures an image by controlling an exposure time of a region having a transmission characteristic corresponding to the pixel signal so as to correspond to the predetermined coefficient corresponding to the pixel signal, and the signal processing unit calculates spectral information in the predetermined wavelength band by signal processing that adds together pixel signals of the image of the object having a plurality of different transmission characteristics. <14> The spectroscopic measurement system according to <1>, further including an object recognition unit that performs object recognition processing of the object by signal processing based on pixel signals of an image of the object having a plurality of different transmission characteristics. <15> The spectroscopic measurement system according to <1>, further including a drive unit that changes the relative position between the image sensor and the object so that the image sensor can capture images of the object having a plurality of different transmission characteristics corresponding to the number of filters based on the entire light of the object that is transmitted through each of the plurality of filters and incident thereon.<16> The spectroscopic measurement system according to <2>, wherein the spectral filter further includes a wave plate, which functions as the plurality of filters and provides a plurality of different fixed-value phase differences, located between the first polarizer and the liquid crystal element. <17> The spectroscopic measurement system according to <16>, wherein the wave plate is composed of a plurality of small wave plates, which function as the plurality of filters and provide a plurality of different fixed-value phase differences, for each pixel of the image sensor. <18> The spectroscopic measurement system according to <17>, wherein the plurality of small wave plates which provide a phase difference of different fixed values ​​are repeatedly arranged in the horizontal and vertical directions on the wave plate, for each wave plate unit arranged in a predetermined pattern. <19> The spectroscopic measurement system according to <17>, wherein the plurality of small wave plates which provide a phase difference of different fixed values ​​are arranged randomly. <20> A spectroscopic measurement method for a spectroscopic measurement system including: a spectral filter consisting of a plurality of filters that transmit light from an object with different transmission characteristics; and an image sensor that captures images of the object with a number of different transmission characteristics corresponding to the number of the filters based on light that has transmitted through the spectral filters, wherein the plurality of filters are arranged side by side in a predetermined direction, and the image sensor captures images of the object with a number of different transmission characteristics corresponding to the number of the filters based on the entire light of the object that has passed through each of the plurality of filters and is incident thereon as a relative position between the image sensor and the object changes.

[0292] 111 Spectroscopic measurement system, 130 Power supply, 131 Lens, 132, 132A to 132E Spectral filter, 133, 133A, 133B Imaging element, 134 Signal processing unit, 151, 151-1 to 151-7 Divided region (filter), 171 Polarizer, 172, 172D Liquid crystal element, 173, 173RU, 173LU Polarizer, 173PF, 173PF' Polarizer filter, 201 Polarizer, 221 Object recognition system, 231 Object recognition unit, 311 Spectroscopic measurement system, 330 Power supply, 331 Lens, 332 Spectral filter, 333 Imaging element, 334 Signal processing unit, 371 Polarizer, 372 Liquid crystal element, 173 Polarizer, 381 Wave plate, 381u Wave plate unit, 381a, 381a-1 to 381a-4 Small wave plate

Claims

a spectral filter including a plurality of filters that transmit light from an object with different transmission characteristics; an image pickup element configured to capture images of the object having different transmission characteristics, the number of which corresponds to the number of the filters, based on light transmitted through the spectral filters; The plurality of filters are arranged in a predetermined direction, The imaging element captures images of the object with a plurality of different transmission characteristics corresponding to the number of filters, based on the entire light of the object that is transmitted through each of the plurality of filters and incident thereon as the relative position between the imaging element and the object changes. Spectroscopic measurement system. 　 The plurality of filters constituting the spectral filter are each configured such that a first polarizer, a liquid crystal element, and a second polarizer different from the first polarizer are stacked in this order from the front to the back with respect to the incident direction of light from the object. The spectroscopic measurement system according to claim 1 . 　 The liquid crystal elements of each of the plurality of filters change their transmittance for each wavelength as a transmission characteristic in response to an applied voltage. The spectroscopic measurement system according to claim 2 . 　 The transmittance of the liquid crystal element varies for each wavelength in proportion to the inverse of the wavelength in accordance with the applied voltage, with a period expressed by a trigonometric function. The spectroscopic measurement system according to claim 3 . 　 The polarization axis of the first polarizer and the polarization axis of the second polarizer are at angles of +45 degrees and −45 degrees, or −45 degrees and +45 degrees, respectively, with respect to the fast axis of the liquid crystal element. The spectroscopic measurement system according to claim 2 . 　 The polarization axis of the first polarizer and the polarization axis of the second polarizer are both at +45 degrees or -45 degrees with respect to the fast axis of the liquid crystal element. The spectroscopic measurement system according to claim 2 . 　 The liquid crystal element of each of the plurality of filters changes the transmittance for each wavelength as a transmission characteristic in accordance with at least one of the thickness of the liquid crystal element and the characteristics of the medium. The spectroscopic measurement system according to claim 2 . 　 The second polarizer is configured to replace a color filter in units of pixels in the image sensor. The spectroscopic measurement system according to claim 2 . 　 When the second polarizer is configured to replace a color filter in units of pixels in the image sensor, two or more types of polarization axes are set in the second polarizer. The spectroscopic measurement system according to claim 8 . 　 The image processing device further includes a signal processing unit that calculates spectral information by signal processing based on images of the object having a plurality of different transmission characteristics and the transmission characteristics of the plurality of filters. The spectroscopic measurement system according to claim 1 . 　 The image processing device further includes a signal processing unit that calculates spectral information of a predetermined wavelength band by signal processing based on the sum of products of pixel signals of the image of the object having a plurality of different transmission characteristics and predetermined coefficients corresponding to the pixel signals. The spectroscopic measurement system according to claim 1 . 　 each of the plurality of filters constituting the spectral filter is configured such that a first polarizer, a liquid crystal element, and a second polarizer different from the first polarizer are stacked in this order from the front to the back with respect to the incident direction of light from the object; a third polarizer, which is adjustable to have a transmission characteristic corresponding to a predetermined coefficient corresponding to the pixel signal, located before the first polarizer; The signal processing unit calculates spectral information of a predetermined wavelength band by signal processing that adds up pixel signals of images of the object having a plurality of different transmission characteristics, the images being captured using light that has been transmitted through the third polarizer, the first polarizer, the liquid crystal element, the second polarizer, and the image sensor in that order. The spectroscopic measurement system according to claim 11 . 　 the imaging element controls an exposure time of an area having a corresponding transmission characteristic so as to correspond to a predetermined coefficient corresponding to the pixel signal, and captures an image; The signal processing unit calculates spectral information of a predetermined wavelength band by signal processing that adds up pixel signals of the image of the object having a plurality of different transmission characteristics. The spectroscopic measurement system according to claim 11 . 　 The image processing device further includes an object recognition unit that performs object recognition processing of the object by signal processing based on pixel signals of images of the object having a plurality of different transmission characteristics. The spectroscopic measurement system according to claim 1 . 　 The imaging device further includes a driving unit that changes the relative position between the imaging device and the object so that the imaging device can capture images of the object with a plurality of different transmission characteristics corresponding to the number of filters based on the entire light of the object that is transmitted through each of the plurality of filters and incident thereon. The spectroscopic measurement system according to claim 1 . 　 The spectral filter further includes a wave plate between the first polarizer and the liquid crystal element, the wave plate functioning as the plurality of filters and providing a plurality of different fixed retardation values. The spectroscopic measurement system according to claim 2 . 　 The wave plate is composed of a plurality of small wave plates that function as the plurality of filters and provide phase differences of different fixed values, with the pixels of the image sensor as units. The spectroscopic measurement system according to claim 16. 　 The plurality of small wave plates that give phase differences of different fixed values ​​are arranged repeatedly in the horizontal and vertical directions on the wave plate, with wave plate units arranged in a predetermined pattern as units. The spectroscopic measurement system according to claim 17. 　 The plurality of small wave plates that provide phase differences of different fixed values ​​are randomly arranged. The spectroscopic measurement system according to claim 17. 　 a spectral filter including a plurality of filters that transmit light from an object with different transmission characteristics; and an image sensor configured to capture images of the object having different transmission characteristics, the number of which corresponds to the number of the filters, based on light transmitted through the spectral filters, the spectroscopic measurement method comprising: The plurality of filters are arranged in a predetermined direction, The imaging element captures images of the object with a plurality of different transmission characteristics corresponding to the number of filters, based on the entire light of the object that is transmitted through each of the plurality of filters and incident thereon as the relative position between the imaging element and the object changes. A spectroscopic measurement method for a spectroscopic measurement system.

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