Spectroscopic measurement system and spectroscopic measurement method for spectroscopic measurement system

Abstract

The present disclosure relates to a spectroscopic measurement system with which it is possible to achieve spectroscopic measurement with a high wavelength resolution using a simple device configuration, and a spectroscopic measurement method for a spectroscopic measurement system. The present invention comprises: illumination for irradiating an object with light; and an imaging element for capturing, on the basis of the light transmitted through individual bands of a plurality of bandpass filters, spectral images of the object, where the number of spectral images corresponds to the number of bandpass filters. From the spectral images, the number of which corresponds to the number of bandpass filters, spectral information having a wavelength resolution higher than the number of bandpass filters is calculated by signal processing that utilizes the wavelength characteristics of the light emitted by the illumination and the transmission characteristics of the plurality of bandpass filters. The present disclosure can be applied to a spectroscopic measurement system.

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 are capable of realizing spectroscopic measurement with high wavelength resolution using a simple device configuration.

[0002] A technology has been proposed that enables spectroscopic measurement with a simple configuration by using a spectroscopic measurement device that has bandpass filters with different wavelength transmission characteristics arranged in a line to capture images while sliding the object like a line sensor (or while sliding relative to the object) (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2022-146950

[0004] However, while the spectroscopic measurement device of Patent Document 1 can achieve spectroscopic measurement with a simple configuration, 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, resulting in low wavelength resolution and making it impossible to perform sufficient spectroscopic measurement.

[0005] The present disclosure has been made in view of the above circumstances, and in particular, aims to achieve spectroscopic measurement with high wavelength resolution using a simple device configuration.

[0006] A spectroscopic measurement system according to one aspect of the present disclosure includes an illumination device that irradiates an object with light; a plurality of band-pass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object; an image sensor that captures a number of spectral images of the object corresponding to the number of band-pass filters based on the light that has transmitted through each band of the plurality of band-pass filters; and a signal processing unit that calculates spectral information having a higher wavelength resolution than the number of band-pass filters from the number of spectral images corresponding to the number of band-pass filters by signal processing that utilizes the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of band-pass filters.

[0007] A spectroscopic measurement method according to one aspect of the present disclosure is a spectroscopic measurement method for a spectroscopic measurement system including an illumination device that irradiates an object with light, a plurality of bandpass filters that transmit different bands of light irradiated by the illumination device and reflected by the object, and an image sensor that captures a number of spectral images corresponding to the number of bandpass filters of the object based on the light that has transmitted through each band of the plurality of bandpass filters, the spectroscopic measurement method for a spectroscopic measurement system including performing signal processing that utilizes the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of bandpass filters to calculate spectral information having a higher wavelength resolution than the number of bandpass filters from the number of spectral images corresponding to the number of bandpass filters.

[0008] In one aspect of the present disclosure, there is provided an illumination device that irradiates an object with light, a plurality of band-pass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object, and an image sensor that captures a number of spectral images corresponding to the number of band-pass filters of the object based on the light that has transmitted through each band of the plurality of band-pass filters, and by signal processing that utilizes the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of band-pass filters, spectral information having a higher wavelength resolution than the number of band-pass filters is calculated from the number of spectral images corresponding to the number of band-pass filters.

[0009] FIG. 7 is a diagram illustrating an overview of a spectroscopic measurement system. FIG. 8 is a diagram illustrating a bandpass filter and a spectroscopic imaging example of the spectroscopic measurement system of FIG. 1. FIG. 9 is a diagram illustrating a configuration example of a first embodiment of a spectroscopic measurement system of the present disclosure. FIG. 10 is a diagram illustrating an imaging procedure of an object in the spectroscopic measurement system of FIG. 3. FIG. 11 is a flowchart illustrating spectral information acquisition processing by the spectroscopic measurement system of FIG. 3. FIG. 12 is a diagram illustrating that spectral information is obtained only from a range covered by the wavelength characteristics of illumination. FIG. 13 is a diagram illustrating a configuration example of a second embodiment of a spectroscopic measurement system of the present disclosure. FIG. 14 is a flowchart illustrating spectral information acquisition processing by the spectroscopic measurement system of FIG. 7. FIG. 15 is a diagram illustrating a configuration example of a general-purpose computer.

[0010] 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.

[0011] Hereinafter, embodiments of the present technology will be described in the following order: 1. Overview of the present disclosure 2. First embodiment 3. Second embodiment 4. Example of execution by software

[0012] <<1. Overview of the Present Disclosure>> The present disclosure provides a method for achieving spectroscopic measurement with high wavelength resolution using a simple device configuration. Before describing the overview of the present disclosure, the configuration of a proposed simple spectroscopic measurement device will be described.

[0013] First, with reference to FIG. 1, an example of the configuration of a simple spectroscopic measurement system will be described.

[0014] The spectroscopic measurement system 11 in FIG. 1 is composed of an illumination device 21 and a spectroscopic imaging device 22 .

[0015] The illumination 21 is an illumination having a wide wavelength characteristic such as a halogen lamp, and is a light source including at least the wavelength range required for spectroscopic imaging, and irradiates the object 20 to be subjected to spectroscopic measurement with illumination light.

[0016] The spectroscopic imaging device 22 is composed of a filter section 31 having a plurality of band-pass filters set in line units, and an imaging element 32 provided in the subsequent stage.

[0017] More specifically, as shown in the right part of Figure 1, the filter unit 31 has bandpass filters 41-1 to 41-4 arranged in a range defined by a line of pixels arranged in an array on the image sensor 32, and each filter transmits light from the object 20 in a different wavelength band, allowing the image sensor 32 to capture the light.

[0018] The image sensor 32 is composed of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and receives light that passes through bandpass filters 41-1 to 41-4, using pixels arranged in an array as units, and generates and outputs pixel signals corresponding to the amount of light.

[0019] The bandpass filters 41-1 to 41-4 transmit light in wavelength bands B1 to B4 in order from the short wavelength band, as shown in the lower left of Figure 2, to the image sensor 32, thereby capturing spectral images as shown in images PB1 to PB4 in order from top to bottom, as shown in the right part of Figure 2.

[0020] With this configuration, the imaging element 32 of the spectroscopic imaging device 22 receives light transmitted through the band-pass filters 41-1 to 41-4 in units of lines that make up the corresponding pixels, and therefore functions as a line sensor.

[0021] When spectroscopically imaging the object 20, the object 20 is moved parallel to the direction in which the bandpass filters 41-1 to 41-4 of the filter section 31 are arranged, or the spectroscopic imaging device 22 is moved in the direction in which the bandpass filters 41-1 to 41-4 of the filter section 31 of the image sensor 32 are arranged, so that each of the bandpass filters 41-1 to 41-4 receives light from the entire object 20.

[0022] As a result, the spectroscopic imaging device 22 captures a spectroscopic image of the object 20 in each band set in the band-pass filters 41-1 to 41-4.

[0023] That is, the spectroscopic imaging device 22 in FIGS. 1 and 2 captures spectral images of the object 20 in four bands set in the band-pass filters 41-1 to 41-4.

[0024] With this configuration, the spectroscopic measurement system 11 in FIG. 1 functions as a spectroscopic measurement device with a simple configuration, without using expensive optical equipment such as a prism or optical diffraction element that is required for normal spectroscopic measurement.

[0025] However, the spectroscopic imaging device 22 shown in FIGS. 1 and 2 can only acquire spectroscopic images in four bands, and can only perform spectroscopic imaging with insufficient wavelength resolution.

[0026] However, although the spectroscopic imaging device 22 in FIGS. 1 and 2 shows an example in which the number of band-pass filters in the filter section 31 is four, this is merely an example, and the number of band-pass filters can be increased.

[0027] However, increasing the number of band-pass filters may cause the boundaries of the line-unit ranges covering adjacent band-pass filters 41 on the image sensor 32 to become too close, making crosstalk more likely to occur and reducing detection accuracy. Also, if an attempt is made to provide a range on the image sensor 32 that is the boundary of the line-units covering adjacent band-pass filters 41 with a sufficient width, it is not possible to increase the number of band-pass filters that much.

[0028] That is, in the spectroscopic imaging device 22 described with reference to FIGS. 1 and 2, the number of bandpass filters cannot be increased so much, and as a result, spectroscopic measurement with sufficient wavelength resolution cannot be realized.

[0029] Therefore, in the present disclosure, spectroscopic measurement with higher wavelength resolution is realized by signal processing using the wavelength characteristics of the illumination 21 and the wavelength transmission characteristics of the bandpass filters 41-1 to 41-4 that constitute the filter unit 31 of the spectroscopic imaging device 22, with a number greater than the number of bandpass filters in the filter unit 31.

[0030] As a result, a highly accurate spectroscopic measurement system with high wavelength resolution can be realized using a simple spectroscopic imaging device.

[0031] <<2. First Embodiment>> Next, a configuration example of a spectroscopic measurement system according to a first embodiment of the present disclosure will be described with reference to FIG.

[0032] The spectroscopic measurement system 111 in FIG. 3 includes an illumination 121 , a spectroscopic imaging device 122 , an illumination information acquisition unit 123 , a filter information acquisition unit 124 , a basis function creation unit 125 , a signal processing unit 126 , a base driving unit 127 , and a base 128 .

[0033] 1, the illumination 121 is an illumination having a broadband wavelength characteristic such as a halogen lamp, and is a light source including at least the wavelength range required for spectroscopic imaging, and irradiates light onto the object 120 to be subjected to spectroscopic measurement. Therefore, if the wavelength range required for spectroscopic imaging is a specific range, it is sufficient that the illumination 121 includes the wavelength band of that specific range.

[0034] In this case, the specific range of wavelength band may be, 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.

[0035] The illumination 121 may also be configured to include a collection of LEDs (Light Emitting Diodes) that individually emit light in a plurality of wavelength bands.

[0036] The spectroscopic imaging device 122 has a configuration corresponding to the spectroscopic imaging device 22 in Fig. 1, and includes a filter unit 131 and an image sensor 132. The filter unit 131 and the image sensor 132 are configurations corresponding to the filter unit 31 and the image sensor 32 in Fig. 1, respectively.

[0037] That is, as shown in the right part of Figure 3, the filter section 131 has bandpass filters 141-1 to 141-4 provided at positions corresponding to ranges in units of lines of pixels arranged in an array on the image sensor 132, and each filter transmits light from the object 120 in a different wavelength band, allowing the image sensor 132 to capture the light.

[0038] The image sensor 132 is composed of a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and receives light that passes through bandpass filters 141-1 to 141-4 in units of pixels arranged in an array, and generates and outputs pixel signals according to the amount of light.

[0039] The transmission characteristics of the band-pass filters 141-1 to 141-4 in Fig. 3 may be similar to, for example, the bands B1 to B4 of the band-pass filters 41-1 to 41-4 described with reference to the lower left of Fig. 2. Furthermore, the images that are transmitted through each band-pass filter 141 and captured by the image sensor 132 may also be similar to the images PB1 to PB4 in Fig. 2. Furthermore, although an example in which the spectroscopic measurement system 111 in Fig. 3 has four band-pass filters 141-1 to 141-4 will be described, any number of filters may be used as long as it is three or more.

[0040] The illumination information acquisition unit 123 acquires the wavelength characteristics of the light emitted by the illumination unit 121 as illumination information, and supplies the information to the basis function creation unit 125 .

[0041] The wavelength characteristics of the irradiated light acquired by the illumination information acquisition unit 123 may be acquired by reading out information previously stored in a memory unit (not shown) of the illumination 121.

[0042] In addition, the lighting information acquisition unit 123 may be equipped with an image recognition function (not shown) and may acquire information on wavelength characteristics by reading information on a sticker attached to the exterior of the main body of the lighting 121 or information on wavelength characteristics attached to an instruction manual, etc.

[0043] Furthermore, the illumination information acquisition unit 123 may acquire, as illumination information, information on wavelength characteristics input by a user operating an operation input unit such as a keyboard (not shown).

[0044] Furthermore, the specific numerical values ​​of the wavelength characteristics of the illumination 121 may be those provided as spec data, or may be data obtained using a commercially available spectroscopic measurement device.

[0045] The filter information acquisition unit 124 acquires filter information consisting of the transmission characteristics of each of the band-pass filters 141 - 1 to 141 - 4 provided in the filter unit 131 of the spectroscopic imaging device 122 , and supplies the information to the basis function creation unit 125 .

[0046] The filter information consisting of the transmission characteristics of the bandpass filters 141-1 to 141-4 acquired by the filter information acquisition unit 124 may be obtained by reading out filter information that is stored in advance in a storage unit (not shown) of the spectroscopic imaging device 122.

[0047] In addition, the filter information acquisition unit 124 may be equipped with an image recognition function (not shown) and may acquire filter information consisting of transmission characteristics written on a sticker attached to the exterior of the main body of the spectroscopic imaging device 122 or filter information consisting of transmission characteristics attached to an instruction manual, etc.

[0048] Furthermore, the filter information acquisition unit 124 may acquire, as filter information, information on transmission characteristics input by a user operating an operation input unit such as a keyboard (not shown).

[0049] The specific numerical values ​​of the transmission characteristics of each of the bandpass filters 141-1 to 141-4 provided in the filter section 131 of the spectroscopic imaging device 122 may be provided as specification data, or may be data obtained by calibration using a commercially available spectroscopic measurement device or lighting with known wavelength characteristics.

[0050] The basis function creation unit 125 creates basis functions based on the illumination information supplied from the illumination information acquisition unit 123 and the filter information supplied from the filter information acquisition unit 124, and supplies the basis functions to the signal processing unit 126. Details of the basis functions will be described later together with the signal processing by the signal processing unit 126.

[0051] The signal processing unit 126 controls the base driving unit 127 to move the object 120 placed on the base 128 sequentially to the bases 128-1 to 128-4 at predetermined intervals in the direction of the arrow in the figure (parallel to the direction in which the band-pass filters 141-1 to 141-4 are arranged), as shown in Figure 4, while controlling the spectroscopic imaging device 122 to capture and acquire spectroscopic images PB11 to PB14 with a wavelength resolution of the number of bands corresponding to the number of band-pass filters 141.

[0052] Furthermore, the signal processing unit 126 performs signal processing based on basis functions on the spectral images PB11 to PB14, which have a wavelength resolution equivalent to the number of band-pass filters 141, to generate and output spectral information with a wavelength resolution higher than the wavelength resolution equivalent to the number of band-pass filters 141.

[0053] <Method of Creating Basis Functions by the Spectroscopic Measurement System of FIG. 3> Next, a method of creating basis functions will be described.

[0054] Here, in explaining the method of creating the basis functions, the wavelength transmission characteristics Si(λn) of the bandpass filters 141-1 to 141-4, which are the filter information acquired by the filter information acquisition unit 124, the wavelength characteristics Lk(λn) of the illumination 121, which are the illumination information acquired by the illumination information acquisition unit 123, the pixel signals Ii(xm) received by each pixel of the image sensor 132, and the spectral information f(xm, λn) of the desired wavelength resolution are respectively expressed, for example, by the following equations (1) to (4).

[0055]

[0056]

[0057]

[0058]

[0059] Here, i is an identifier for identifying the bandpass filter 141. In this example, the bandpass filter 141 is made up of four bandpass filters 141, ie, bandpass filters 141-1 to 141-4, so the maximum value t of i is 4.

[0060] Furthermore, n is an identifier for identifying each of the number N of spectral bands to be determined, which corresponds to the desired wavelength resolution (identifier for each band for the spectral resolution), and k is an identifier for identifying each of the number K of individual lights that make up the lighting 121.

[0061] That is, the lighting 121 is expressed as a collection of a plurality of small lightings such as LED lightings each having K different wavelength characteristics Lk(λn).

[0062] Therefore, for example, when the lighting 121 emits light having wavelength characteristics Lk(λn) expressed by equation (2), the light of wavelength λn emitted by the entire lighting 121 is expressed as the total amount C(λn) of light of wavelength λn from K small lighting units, as shown in the following equation (5).

[0063]

[0064] Here, C(λn) is the total amount of light of wavelength λn, expressed as the sum of the wavelength characteristics Lk(λn) of each wavelength λn of K lights that make up the light source 121 and are identified by k = 1 to K.

[0065] Furthermore, m is an identifier that identifies each of the M pixels that make up the image sensor 132, and xm represents the pixel position identified by the identifier m. In reality, a coordinate position is expressed as (x, y), but here, we will only explain the calculation method and will use the expression xm as long as it is possible to individually identify the m pixels.

[0066] In this case, the pixel signal Ii(xm) of each pixel constituting the spectral image captured by the image sensor 132 is expressed by the following equation (6) using the basis function B(i, λn) and the spectral information f(xm, λn) of the desired wavelength resolution.

[0067]

[0068] Here, B(i, λn) is a basis function. That is, the pixel signal Ii(xm) of each pixel captured by the image sensor 132 can be expressed as a product sum of the basis function B(i, λn) and the spectral information f(xm, λn) of the desired wavelength resolution. Furthermore, the basis function B(i, λn) can be expressed as in the following equation (7).

[0069]

[0070] That is, the basis function B(i, λn) is expressed as the product of the wavelength transmission coefficient of the bandpass filter 141 and the amount of light of the wavelength λn of the illumination 121.

[0071] As a result, the relationship between the pixel signal Ii(xm) and the spectral information f(xm, λn) can be expressed by the following equation (8).

[0072]

[0073] Furthermore, the basis function Si(λn)C(λn) (=B(i, λn)) can be expressed as the following equation (9) when written in a matrix.

[0074]

[0075] That is, the basis function creation unit 125 creates a basis function Si(λn)C(λn) (=B(i, λn)) by calculation as shown in equation (9) based on the wavelength transmission characteristics Si(λn) of the bandpass filters 141-1 to 141-4, which are the filter information acquired by the filter information acquisition unit 124, and the wavelength characteristics Lk(λn) of the illumination 121, which is the illumination information acquired by the illumination information acquisition unit 123, and supplies the basis function Si(λn)C(λn) (=B(i, λn)) to the signal processing unit 126.

[0076] Furthermore, the relationship of the above-mentioned equation (8) can be expressed as shown in the following equation (10) by substituting the basis function S i (λ n ) C (λ n ) (= B (i, λ n )) described with reference to equation (9).

[0077]

[0078] Incidentally, in the following, equation (10) may be simplified as I=SC·f as necessary.

[0079] That is, after determining equation (10), the signal processing unit 126 solves equation (10) by signal processing to determine the spectral information f(xm, λn).

[0080] However, since the variable N in equation (10) is much larger than the variable t (N>>t), equation (10) is an ill-posed problem, and the spectral information f(xm, λn) cannot be obtained by simply solving equation (10).

[0081] Therefore, the signal processing unit 126 uses Tikhonov's regularization method to obtain spectral information f' from equation (10) as shown in equation (11) below.

[0082]

[0083] Here, ||I-SC·f'|| ２ is a term called a data term, which represents the difference between the observed pixel signal Ii(xm) and the product of the basis function SC and the spectral information f′ of the wavelength resolution to be obtained.

[0084] ||f'・Dx|| ２ is a constraint term in the spatial direction, and represents the difference between adjacent pixels in the spatial direction of the spectral information f′ with the desired wavelength resolution.

[0085] ||f'·Dλ|| ２ is a constraint term in the wavelength direction, and the spectral information f' of the wavelength resolution to be obtained expresses the difference between adjacent wavelengths in the wavelength direction.

[0086] argmin is the data term ||I-SC·f'|| ２ , the spatial direction constraint term ||f'·Dx|| ２ , and the wavelength direction constraint term ||f'·Dλ|| ２ The spectral information f is a true value, whereas the spectral information f′ is spectral information calculated based on the observed pixel signal Ii(xm).

[0087] That is, since the spectral information f' is a continuous function in both the spatial direction and the wavelength direction, the spatial direction constraint term ||f'·Dx||, which is based on the constraint that the difference between adjacent pixels is small, is ２ , and the wavelength direction constraint term ||f'·Dλ|| ２ , the data term ||I-SC·f'|| ２is transformed into a solvable form such as equation (11), and spectral information f' with the desired wavelength resolution is obtained.

[0088] Therefore, the signal processing unit 126 solves equation (11) by signal processing based on the spectral imaging results for the number of band-pass filters 141 captured by the spectral imaging device 122 and the basis function SC (=B) supplied from the basis function creation unit 125, thereby obtaining spectral information f' with the desired wavelength resolution.

[0089] <Spectral Information Acquisition Processing by Spectroscopic Measurement System of FIG. 3> Spectral information acquisition processing by the spectroscopic measurement system 111 of FIG. 3 will be described with reference to the flowchart of FIG.

[0090] In step S31, the filter information acquisition unit 124 acquires filter information consisting of the wavelength transmission characteristics of the bandpass filters 141-1 to 141-4 provided in the filter unit 131 of the spectroscopic imaging device 122, and outputs the information to the basis function creation unit 125.

[0091] In step S32 , the illumination information acquisition unit 123 acquires illumination information consisting of the wavelength characteristics of the light emitted from the illumination unit 121 , and outputs the information to the basis function creation unit 125 .

[0092] In step S33, the basis function creation unit 125 calculates a basis function based on the filter information supplied from the filter information acquisition unit 124 and the illumination information supplied from the illumination information acquisition unit 123, and outputs the basis function to the signal processing unit 126.

[0093] In step S34, the signal processing unit 126 controls the illumination 121 to irradiate the object 120 to be subjected to spectroscopic measurement with illumination light.

[0094] In step S35, the signal processing unit 126 initializes the counter i (i=0) and controls the base driving unit 127 to set the position of the base 128 to the initial position.

[0095] In step S36, the signal processing unit 126 controls the spectroscopic imaging device 122 to cause the imaging element 132 to capture a spectroscopic image based on the light emitted by the illumination 121, reflected by the object 120, and transmitted through the band-pass filters 141-1 to 141-4 of the filter unit 131, and stores the captured spectroscopic image.

[0096] In step S37, the signal processing unit 126 determines whether or not the counter i is the number of band-pass filters 141. That is, in the configuration of Fig. 3, since there are four band-pass filters 141, it is determined whether or not the counter i is 4.

[0097] If it is determined in step S37 that the counter i is not the number of band-pass filters 141, the process proceeds to step S38.

[0098] In step S38, the signal processing unit 126 increments the counter i by 1 and controls the base driving unit 127 to move the base 128 by a predetermined distance, and the process returns to step S36.

[0099] In other words, in this process, when the base 128 is moved a predetermined distance a number of times equal to the number of band-pass filters 141, the image sensor 132 functions like a line sensor, and spectral images can be captured with the object 120 as the subject in each wavelength band of the band-pass filters 141-1 to 141-4.

[0100] Therefore, in step S37, the base 128 is moved a predetermined distance a number of times equal to the number of band-pass filters 141, and the process of capturing a spectral image of the corresponding wavelength band is repeated until the counter i reaches the number of band-pass filters 141, that is, the number of times equal to the number of band-pass filters 141.

[0101] Note that this process is repeated until a spectral image of the object 120 in each wavelength band of the bandpass filters 141-1 to 141-4 can be captured, so in reality, the movement distance of the base 128 and the number of repetitions will differ from the number of bandpass filters 141-1 to 141-4.

[0102] Then, in step S37, if it is determined that counter i is equal to the number of bandpass filters 141, that is, in this example, if it is determined that a spectral image has been captured of the object 120 in each wavelength band of bandpass filters 141-1 to 141-4, the processing proceeds to step S39.

[0103] In step S39, the signal processing unit 126 obtains a spectral image having the desired wavelength resolution by signal processing based on the spectral images of the object 120 in each wavelength band of the bandpass filter 141 and the basis functions.

[0104] Through the above processing, basis functions are calculated based on the filter information supplied from the filter information acquisition unit 124 and the illumination information supplied from the illumination information acquisition unit 123. Then, from the basis functions and the spectral images formed by the number of band-pass filters 141 of the filter unit 131 provided in the spectroscopic imaging device 122, which is a spectroscopic measurement device with a simple configuration, it is possible to acquire, through signal processing, spectral information that is greater in number than the number of band-pass filters 141, i.e., spectral information with higher wavelength resolution.

[0105] As a result, it is possible to obtain spectral information with high accuracy and higher wavelength resolution with a simple configuration.

[0106] As described above, spectral information with higher wavelength resolution is obtained from a spectral image consisting of the number of band-pass filters 141 of the filter unit 131 provided in the spectral imaging device 122 by signal processing using basis functions. Therefore, it is not possible to obtain spectral information of a wavelength band in which the wavelength band covered by the transmission characteristics of the band-pass filters 141 does not match the wavelength band covered by the wavelength characteristics of the illumination 121.

[0107] That is, for example, even if the wavelength band covered by the bandpass filters 141-1 to 141-4 constituting the filter unit 131 of the spectroscopic imaging device 122 is 400 nm to 1600 nm as shown in the left part of FIG. 6, if the wavelength characteristics of the illumination 121 are 1000 nm to 1600 nm as shown in the right part of FIG. 6, the spectral information of the wavelength resolution to be obtained will also be 1000 nm to 1600 nm, which is the same range as the wavelength characteristics of the illumination 121.

[0108] In other words, spectral information cannot be obtained unless it is within a common band range in which the wavelength bands covered by the bandpass filters 141-1 to 141-4 that constitute the filter section 131 of the spectroscopic imaging device 122 and the wavelength bands covered by the wavelength characteristics of the illumination 121 match.

[0109] <<3. Second Embodiment>> In the above, an example has been described in which basis functions are obtained based on the wavelength characteristics of the illumination 121 and the spectral transmission characteristics of the band-pass filters 141-1 to 141-4 of the filter unit 131 of the spectroscopic imaging device 122, and spectral information with a higher wavelength resolution than the number of band-pass filters 141 is obtained from the spectral images corresponding to the number of band-pass filters 141 and the basis functions.

[0110] However, it is also possible to control the wavelength characteristics (intensity for each wavelength) of the illumination 121, optimize the light of the illumination 121 to be irradiated onto the object 120, and then measure spectral information with higher wavelength resolution and higher accuracy.

[0111] FIG. 7 shows an example configuration of a spectroscopic measurement system 111′ that is capable of controlling the wavelength characteristics (intensity for each wavelength) of the illumination 121 and optimizing the light of the illumination 121 irradiated onto the object 120, thereby enabling measurement of spectroscopic information with higher wavelength resolution and higher accuracy.

[0112] In the spectroscopic measurement system 111' in FIG. 7, components having the same functions as those in the spectroscopic measurement system 111 in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0113] The spectroscopic measurement system 111′ in FIG. 7 differs from the spectroscopic measurement system 111 in FIG. 3 in that an illumination intensity optimization unit 201 and an illumination intensity control unit 202 are further provided, and illumination 121′ and a basis function creation unit 125′ are provided instead of illumination 121 and basis function creation unit 125.

[0114] The illumination intensity optimization unit 201 calculates intensity coefficients that optimize the intensity of the illumination 121′ for each wavelength based on the wavelength characteristics of the illumination 121′ and the filter information of the bandpass filters 141-1 to 141-4, and outputs the intensity coefficients to the illumination intensity control unit 202, and also outputs the intensity coefficients and wavelength characteristics to the basis function creation unit 125′.

[0115] The basis function creation unit 125' has almost the same functions as the basis function creation unit 125, but creates basis functions based on the intensity coefficient and wavelength characteristics of the illumination 121' supplied from the illumination intensity optimization unit 201. The method of creating basis functions based on the intensity coefficient and wavelength characteristics of the illumination 121' will be described in detail later.

[0116] The illumination intensity control unit 202 is controlled by the signal processing unit 126, and controls the emission intensity of the illumination 121' for each wavelength band based on the intensity coefficient of the illumination 121' supplied from the illumination intensity optimization unit 201, causing the illumination 121' to emit light.

[0117] Illumination 121' has basically the same function as illumination 121 and has similar wavelength characteristics, but emits light of each wavelength band at an intensity controlled by illumination intensity control unit 202 based on an intensity coefficient set for each wavelength, and irradiates light onto object 120.

[0118] <Method of determining intensity coefficients and creating basis functions by the spectroscopic measurement system in Fig. 7> Next, we will explain how to determine intensity coefficients and create basis functions by the spectroscopic measurement system 111' in Fig. 7. The method of determining intensity coefficients and creating basis functions by the spectroscopic measurement system 111' in Fig. 7 is basically similar to the method of creating basis functions by the spectroscopic measurement system 111 in Fig. 3, so here we will mainly explain the differences between the two.

[0119] That is, in the spectroscopic measurement system 111' in FIG. 7, the illumination 121' is configured to be able to emit light with the intensity controlled for each wavelength.

[0120] Therefore, for each wavelength characteristic Lk(λn) of the illumination 121′, which is the illumination information acquired by the illumination intensity optimization unit 201, an intensity coefficient ak (0≦ak≦1) is set.

[0121] Therefore, for example, when lighting 121′ emits light having wavelength characteristics Lk(λn) expressed by equation (2), the light of wavelength λn is expressed as shown in the following equation (12) by multiplying the total amount of light C′(λn) of wavelength λn, which is expressed as the sum of the light of wavelength λn of K small lighting units, by an intensity coefficient ak.

[0122]

[0123] Here, C'(λn) is the total amount of light of wavelength λn, which is expressed as the sum of the products of the wavelength characteristics Lk(λn) of wavelength λn of each of K lights that make up the light 121' and are identified by k = 1 to K, and the intensity coefficient ak.

[0124] Therefore, the basis function SC′ can be expressed as in the following equation (13).

[0125]

[0126] As a result, the relationship between the pixel signal Ii(xm) and the spectral information f(xm, λn) can be expressed by the following equation (14).

[0127]

[0128] Furthermore, the basis function Si(λn)C′(λn) (=B(i, λn)) can be expressed as the following equation (15) when written in a matrix.

[0129]

[0130] That is, the illumination intensity optimization unit 201 generates a basis function Si(λn)C′(λn) (=B(i, λn)) by calculation as shown in equation (15) based on the wavelength transmission characteristics Si(λn) of the bandpass filters 141-1 to 141-4, which are the filter information acquired by the filter information acquisition unit 124, and the wavelength characteristics Lk(λn) of the illumination 121, which are the illumination information acquired by the illumination information acquisition unit 123.

[0131] Furthermore, the relationship of the above-mentioned equation (14) can be expressed as shown in the following equation (16) by substituting the basis function S i (λ n ) C ′ (λ n ) described with reference to equation (15).

[0132]

[0133] Here, when solving a linear equation such as equation (16), it is known that the smaller the condition number of the basis function SC'(λn), the higher the accuracy of the calculated spectral information f(xm, λn).

[0134] Therefore, in order to obtain a basis function SC′(λn) that minimizes the condition number and maximizes the calculation accuracy of the spectral information f(xm, λn), the illumination intensity optimization unit 201 defines a cost function of the condition number cond(SC′) as shown in the following equation (17), for example, and solves the cost function of the condition number cond(SC′) defined by this equation (17) to obtain an optimized solution for the intensity coefficient a of the illumination 121′.

[0135]

[0136] Here, the condition number cond(SC') of the basis function SC' is defined as in the following equation (18).

[0137]

[0138] where σmax is the maximum singular value of the basis function SC' and σmin is the minimum singular value of the basis function SC'.

[0139] The method of solving the cost function expressed by equation (17) to obtain the intensity coefficient a k may be, for example, an optimization method called simulated annealing.

[0140] For more information on simulated annealing, please refer to https: / / ja.wikipedia.org / wiki / Simulated_annealing

[0141] The illumination intensity optimization unit 201 supplies the intensity coefficient a k thus obtained as the optimization solution to the illumination intensity control unit 202. The illumination intensity optimization unit 201 also supplies the optimized intensity coefficient a k to the basis function creation unit 125′ together with the illumination information of the illumination 121′.

[0142] The illumination intensity control unit 202 controls the emission intensity of the illumination 121′ for each band using the intensity coefficient ak as the optimization solution obtained in this manner, and irradiates the object 120 with light having optimized wavelength characteristics.

[0143] The basis function creation unit 125′ creates a basis function SC′, for example, as shown in the following equation (19), based on the illumination information of the illumination 121′, the optimized intensity coefficient a, and the filter information, and outputs it to the signal processing unit 126.

[0144]

[0145] Then, the signal processing unit 126 obtains the spectral information f(xm, λn) by solving I=SC′·f from the relationship in equation (16) using signal processing that uses Tikhonov's regularization method based on the basis function SC′ as shown in equation (19).

[0146] <Spectral Information Acquisition Processing by the Spectroscopic Measurement System of Fig. 7> The spectral information acquisition processing by the spectroscopic measurement system 111' of Fig. 7 will be described with reference to the flowchart of Fig. 8. Note that the processing of steps S57 to S61 in the flowchart of Fig. 8 is the same as the processing of steps S35 to S39 described with reference to the flowchart of Fig. 5, and therefore description thereof will be omitted.

[0147] In step S51, the filter information acquisition unit 124 acquires filter information consisting of the wavelength transmission characteristics of the bandpass filters 141-1 to 141-4 provided in the filter unit 131 of the spectroscopic imaging device 122, and outputs the filter information to the illumination intensity optimization unit 201 and the basis function creation unit 125'.

[0148] In step S52 , the illumination information acquisition unit 123 acquires illumination information consisting of wavelength characteristics of light emitted from the illumination 121 , and outputs the information to the illumination intensity optimization unit 201 .

[0149] In step S53, the illumination intensity optimization unit 201 calculates the intensity coefficient ak of the illumination 121′ as an optimization solution based on the filter information supplied from the filter information acquisition unit 124 and the illumination information supplied from the illumination information acquisition unit 123.

[0150] In step S54, the illumination intensity optimization unit 201 outputs the optimization solution for the intensity coefficient a of the illumination 121′ to the illumination intensity control unit 202. In response to this, the illumination intensity control unit 202 acquires the optimization solution for the intensity coefficient a of the illumination 121′. The illumination intensity optimization unit 201 also supplies the optimization solution for the intensity coefficient a of the illumination 121′ together with the illumination information to the basis function creation unit 125′.

[0151] In step S55, the basis function creation unit 125′ calculates a basis function based on the filter information supplied from the filter information acquisition unit 124, the optimization solution of the intensity coefficient a of the illumination 121′ supplied from the illumination intensity optimization unit 201, and the illumination information, and outputs the basis function to the signal processing unit 126.

[0152] In step S56, the signal processing unit 126 controls the illumination intensity control unit 202 to emit light having optimized wavelength characteristics based on the intensity coefficient ak with the illumination 121′ as the optimization solution, and irradiate the illumination light onto the object 120.

[0153] In the processing of steps S57 to S61, the signal processing unit 126 moves the base 128 a predetermined distance a number of times equal to the number of band-pass filters 141, and then captures spectral images of the object 120 in each wavelength band of the band-pass filters 141-1 to 141-4, and obtains a spectral image with the desired wavelength resolution by signal processing based on the spectral image and the basis function.

[0154] Through the above processing, the light emitted by the illumination 121' is emitted in an optimized state and irradiated onto the object 120, so by using a spectroscopic imaging device 122 with a simple configuration, it is possible to obtain spectroscopic information with a higher wavelength resolution and higher accuracy than the number of bandpass filters 141.

[0155] As a result, it is possible to acquire spectral information with higher wavelength resolution and higher accuracy with a simple configuration.

[0156] <<4. Example of Execution by Software>> The above-described series of processes can be executed by hardware, but can also be executed by software. When the series of processes is executed by software, the program that constitutes the software is installed from a recording medium into a computer that is built into dedicated hardware, or into, for example, a general-purpose computer that can execute various functions by installing various programs.

[0157] 9 shows an example of the configuration of a general-purpose computer. This computer has a built-in CPU (Central Processing Unit) 1001. An input / output interface 1005 is connected to the CPU 1001 via a bus 1004. A ROM (Read Only Memory) 1002 and a RAM (Random Access Memory) 1003 are connected to the bus 1004.

[0158] The input / output interface 1005 is connected to an input unit 1006 including input devices such as a keyboard and a mouse through which a user inputs operation commands, an output unit 1007 that outputs a processing operation screen and images of processing results to a display device, a storage unit 1008 including a hard disk drive or the like that stores programs and various data, and a communication unit 1009 including a LAN (Local Area Network) adapter or the like that executes communication processing via a network typified by the Internet. Also connected is a drive 1010 that reads and writes data from / to a removable storage medium 1011 such as a magnetic disk (including a flexible disk), an optical disk (including a CD-ROM (Compact Disc-Read Only Memory) and a DVD (Digital Versatile Disc)), a magneto-optical disk (including an MD (Mini Disc)), or a semiconductor memory.

[0159] The CPU 1001 executes various processes in accordance with a program stored in a ROM 1002 or a program read from a removable storage medium 1011 such as a magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, installed in a storage unit 1008, and loaded from the storage unit 1008 into a RAM 1003. The RAM 1003 also stores data necessary for the CPU 1001 to execute various processes as appropriate.

[0160] In a computer configured as described above, the CPU 1001 performs the above-described series of processes by, for example, loading a program stored in the memory unit 1008 into the RAM 1003 via the input / output interface 1005 and the bus 1004 and executing it.

[0161] The program executed by the computer (CPU 1001) can be provided by being recorded on a removable storage medium 1011 such as a package medium, for example. The program can also be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

[0162] In a computer, a program can be installed in the storage unit 1008 via the input / output interface 1005 by inserting a removable storage medium 1011 into the drive 1010. The program can also be received by the communication unit 1009 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.

[0163] 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.

[0164] 9 realizes the functions of the basis function generator 125 and signal processor 126 in FIG. 3, and the illumination intensity optimizer 201, basis function generator 125′, and signal processor 126 in FIG.

[0165] In this specification, a system refers to a collection of multiple components (devices, modules (components), etc.), regardless of whether all of the components are contained in the same housing. Therefore, multiple devices housed in separate housings and connected via a network, and a single device with multiple modules housed in a single housing, are both systems.

[0166] Furthermore, the embodiments of the present disclosure are not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present disclosure.

[0167] For example, the present disclosure can be configured as a cloud computing system in which a single function is shared and processed collaboratively by multiple devices via a network.

[0168] Furthermore, each step described in the above flowchart can be executed by one device, or can be shared and executed by a plurality of devices.

[0169] Furthermore, when one step includes multiple processes, the multiple processes included in that one step can be executed by one device or can be shared and executed by multiple devices.

[0170] The present disclosure can also be configured as follows.

[0171] <1> A spectroscopic measurement system comprising: an illumination device that irradiates an object with light; a plurality of bandpass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object; an image sensor that captures a number of spectral images of the object corresponding to the number of bandpass filters based on the light that has transmitted through each band of the plurality of bandpass filters; and a signal processing unit that calculates spectral information having a higher wavelength resolution than the number of bandpass filters from the number of spectral images corresponding to the number of bandpass filters by signal processing that utilizes wavelength characteristics of the light irradiated by the illumination device and transmission characteristics of the plurality of bandpass filters. <2> The spectroscopic measurement system according to <1>, further comprising: a basis function creation unit that creates basis functions by utilizing the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of bandpass filters, wherein the signal processing unit calculates spectral information having a higher wavelength resolution than the number of bandpass filters from the number of spectroscopic images corresponding to the number of bandpass filters based on the basis functions. <3> The spectroscopic measurement system according to <2>, wherein the signal processing unit calculates spectral information having a higher wavelength resolution than the number of band-pass filters based on the number of spectroscopic images corresponding to the number of band-pass filters by solving a relational expression utilizing that a product of the basis function multiplied by spectral information having a higher wavelength resolution than the number of band-pass filters matches the number of the spectroscopic images corresponding to the number of band-pass filters. <4> The spectroscopic measurement system according to <3>, wherein the signal processing unit calculates spectral information having a higher wavelength resolution than the number of band-pass filters based on the number of spectroscopic images corresponding to the number of band-pass filters by adding a spatial direction constraint term based on a difference in pixel values ​​between adjacent pixels constituting the image sensor and a wavelength direction constraint term based on a difference between adjacent wavelengths in the spectral information having a higher wavelength resolution than the number of band-pass filters to the relational expression and solving the relational expression.<5> The spectroscopic measurement system according to <4>, wherein the signal processing unit calculates spectral information having a wavelength resolution higher than the number of band-pass filters by solving the spatial constraint term based on the difference in pixel values ​​between adjacent pixels constituting the image sensor and the wavelength constraint term based on the difference between adjacent wavelengths in spectral information having a wavelength resolution higher than the number of band-pass filters, so as to minimize an equation obtained by adding the constraint term to the relational expression. <6> The spectroscopic measurement system according to <2>, wherein the illumination unit is configured to be able to control emission intensity for each of a plurality of wavelength bands constituting the wavelength characteristics, and the emission intensity for each wavelength band constituting the light irradiated by the illumination unit is optimized so that calculation accuracy of spectral information having a wavelength resolution higher than the number of band-pass filters, calculated from a number of spectral images corresponding to the number of band-pass filters, is higher than a predetermined value. <7> The spectroscopic measurement system according to <6>, further including an illumination intensity control unit that controls the emission intensity for each wavelength band constituting the light irradiated by the illumination unit with an intensity obtained by multiplying the wavelength characteristics of the light irradiated by the illumination unit by an intensity coefficient. <8> The spectroscopic measurement system according to <7>, wherein the intensity coefficients controlling the emission intensity for each wavelength band constituting the light irradiated by the illumination are optimized to minimize the condition number of the basis function. <9> The spectroscopic measurement system according to <8>, wherein the condition number of the basis function is the maximum singular value of the basis function divided by the minimum singular value of the basis function. <10> The spectroscopic measurement system according to <1>, wherein the plurality of band-pass filters are configured to transmit different bands in units of lines of pixels constituting the image sensor, and the image sensor captures the number of spectral images of the object corresponding to the number of band-pass filters by receiving light transmitted through the plurality of band-pass filters like a line sensor while changing its position relative to the object. <11> The spectroscopic measurement system according to <1>, wherein the spectral information having a wavelength resolution higher than the number of band-pass filters is a band common to the wavelength band of the light irradiated by the illumination and the transmittance bands of the plurality of band-pass filters.<12> A spectroscopic measurement method for a spectroscopic measurement system including: an illumination device that irradiates an object with light; a plurality of band-pass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object; and an image sensor that captures a number of spectral images of the object corresponding to the number of band-pass filters based on the light that has transmitted through each band of the plurality of band-pass filters, the spectroscopic measurement method comprising: performing signal processing that utilizes wavelength characteristics of the light irradiated by the illumination device and transmission characteristics of the plurality of band-pass filters to calculate spectral information with a higher wavelength resolution than the number of band-pass filters from the number of spectral images corresponding to the number of band-pass filters.

[0172] 111, 111' Spectroscopic measurement system, 121, 121' Illumination, 122 Spectroscopic imaging device, 123 Illumination information acquisition unit, 124 Filter information acquisition unit 125, 125' Basis function creation unit, 126 Signal processing unit, 127 Base driving unit, 128 Base, 131 Filter unit, 132 Image sensor, 141, 141-1 to 141-4 Band pass filter, 201 Illumination intensity optimization unit, 202 Illumination intensity control unit

Claims

1. A spectroscopic measurement system comprising: an illumination device that irradiates an object with light; a plurality of band-pass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object; an image sensor that captures spectral images of the object, the number of which corresponds to the number of band-pass filters, based on the light that has transmitted through each band of the plurality of band-pass filters; and a signal processing unit that calculates spectral information with a higher wavelength resolution than the number of band-pass filters from the number of spectral images corresponding to the number of band-pass filters, by signal processing that utilizes the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of band-pass filters.

2. The spectroscopic measurement system according to claim 1, further comprising a basis function creation unit that creates basis functions by utilizing the wavelength characteristics of the light irradiated by the illumination and the transmission characteristics of the plurality of band-pass filters, and wherein the signal processing unit calculates, based on the basis functions, spectral information having a wavelength resolution higher than the number of band-pass filters from the number of spectroscopic images corresponding to the number of band-pass filters.

3. The spectroscopic measurement system according to claim 2, wherein the signal processing unit calculates spectral information having a higher wavelength resolution than the number of band-pass filters based on the number of spectroscopic images corresponding to the number of band-pass filters by solving a relational equation that utilizes the fact that the basis function multiplied by spectral information having a higher wavelength resolution than the number of band-pass filters matches the number of spectroscopic images corresponding to the number of band-pass filters.

4. The spectroscopic measurement system according to claim 3, wherein the signal processing unit adds a spatial constraint term based on the difference in pixel values ​​between adjacent pixels constituting the image sensor, and a wavelength constraint term based on the difference between adjacent wavelengths in spectroscopic information having a wavelength resolution higher than the number of band-pass filters, to the relational equation and solves the equation, thereby calculating spectroscopic information having a wavelength resolution higher than the number of band-pass filters from the spectroscopic images whose number corresponds to the number of band-pass filters.

5. The spectroscopic measurement system according to claim 4, wherein the signal processing unit calculates spectral information having a higher wavelength resolution than the number of band-pass filters by solving, in a manner that minimizes an equation obtained by adding to the relational expression, a constraint term in the spatial direction based on the difference in pixel values ​​between adjacent pixels constituting the image sensor and a constraint term in the wavelength direction based on the difference between adjacent wavelengths in spectral information having a wavelength resolution higher than the number of band-pass filters.

6. The spectroscopic measurement system according to claim 2, wherein the illumination is configured to be able to control the emission intensity for each of a plurality of wavelength bands that make up the wavelength characteristics, and the emission intensity for each wavelength band that makes up the light irradiated by the illumination is optimized so that the calculation accuracy of spectral information having a wavelength resolution higher than the number of band pass filters, calculated from the number of spectral images corresponding to the number of band pass filters, is higher than a predetermined value.

7. The spectroscopic measurement system according to claim 6, further comprising an illumination intensity control unit that controls the emission intensity for each wavelength band constituting the light irradiated by the illumination with an intensity obtained by multiplying the wavelength characteristic of the light irradiated by the illumination by an intensity coefficient.

8. The spectroscopic measurement system according to claim 7, wherein the intensity coefficients that control the emission intensity for each wavelength band that constitutes the light irradiated by the illumination are optimized so as to minimize the condition number of the basis functions.

9. The spectroscopic measurement system according to claim 8, wherein the condition number of the basis function is the maximum singular value of the basis function divided by the minimum singular value of the basis function.

10. The spectroscopic measurement system according to claim 1, wherein the plurality of band-pass filters are configured to transmit different bands in units of lines of pixels constituting the image sensor, and the image sensor captures the spectral images of the object in a number corresponding to the number of band-pass filters by receiving light that passes through the plurality of band-pass filters like a line sensor while changing its position relative to the object.

11. The spectroscopic measurement system according to claim 1, wherein the spectral information having a wavelength resolution higher than the number of bandpass filters is a band common to the wavelength band of the light irradiated by the illumination and the transmittance bands of the plurality of bandpass filters.

12. A spectroscopic measurement method for a spectroscopic measurement system comprising: an illumination device that irradiates an object with light; a plurality of band-pass filters that transmit light of different bands from the light irradiated by the illumination device and reflected by the object; and an image sensor that captures spectral images of the object, the number of which corresponds to the number of band-pass filters, based on the light that has transmitted through each band of the plurality of band-pass filters, the spectroscopic measurement method comprising: performing signal processing that utilizes the wavelength characteristics of the light irradiated by the illumination device and the transmission characteristics of the plurality of band-pass filters to calculate spectral information with a wavelength resolution higher than the number of band-pass filters from the spectral images, the number of which corresponds to the number of band-pass filters.

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