Optical information acquisition device and optical information acquisition method

Abstract

A measurement system 100 comprises: two inclined dichroic mirrors 70, 71 having characteristics in which transmittance changes in accordance with a wavelength in a prescribed wavelength region; photodetectors 30, 34 for detecting first measurement light transmitted or reflected by the inclined dichroic mirror 70 based on incident light I0, and outputting a first detection signal; photodetectors 31, 34 for detecting second measurement light transmitted or reflected by the inclined dichroic mirror 71 based on the incident light I0, and outputting a second detection signal; and a computation device 5 for acquiring a standard deviation or dispersion in the wavelength spectrum of the incident light I0 on the basis of the first detection signal and the second detection signal.

Description

Optical information acquisition device and optical information acquisition method

[0001] The present invention relates to an optical information acquisition device and an optical information acquisition method.

[0002] Conventionally, measurement devices capable of detecting the centroid wavelength of incident light have been used (see, for example, Patent Document 1). In these measurement devices, an inclined dichroic mirror is used to detect light transmitted through the inclined dichroic mirror and light reflected from the inclined dichroic mirror, and the centroid wavelength of the wavelength spectrum of the incident light is calculated based on the light intensity of each light.

[0003] International Publication No. 2021 / 161684

[0004] While the conventional measurement devices described above can acquire the centroid wavelength as a characteristic related to the wavelength spectrum of incident light, there is a need for a device that can acquire characteristics related to the wavelength spectrum of incident light other than the centroid wavelength (e.g., the variance, standard deviation, skewness, or kurtosis of the wavelength spectrum of incident light).

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide an optical information acquisition device and an optical information acquisition method that can acquire characteristics related to the width of the wavelength spectrum of incident light.

[0006] An optical information acquisition device according to a first aspect of the embodiment includes a first filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range, a second filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range, a first photodetector that detects first measurement light that is transmitted through or reflected by the first filter based on incident light and outputs a first detection signal, a second photodetector that detects second measurement light that is transmitted through or reflected by the second filter based on the incident light and outputs a second detection signal, and a calculation unit that acquires the standard deviation or variance in the wavelength spectrum of the incident light based on the first detection signal and the second detection signal.

[0007] Alternatively, the optical information acquisition method according to a second aspect of the embodiment includes a first optical detection step of using a first filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range to detect first measurement light that is transmitted through or reflected by the first filter based on incident light, and outputting a first detection signal; a second optical detection step of using a second filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range to detect second measurement light that is transmitted through or reflected by the second filter based on the incident light, and outputting a second detection signal; and a calculation step of acquiring the standard deviation or variance in the wavelength spectrum of the incident light based on the first detection signal and the second detection signal.

[0008] According to either the first or second aspect, the standard deviation or variance in the wavelength spectrum of the incident light can be obtained by using a first detection signal that detects the first measurement light that has been transmitted through or reflected by the first filter based on the incident light, and a second detection signal that detects the second measurement light that has been transmitted through or reflected by the second filter based on the incident light, thereby reducing the amount of data required to measure the distribution of the wavelength spectrum of light and easily obtaining characteristics related to the width of the wavelength spectrum of the incident light.

[0009] According to any aspect of the present embodiment, it is possible to obtain characteristics related to the width of the wavelength spectrum of incident light.

[0010] FIG. 1 is a schematic diagram of a measurement system 100, which is an optical information acquisition device according to a first embodiment. FIG. 2 is a diagram showing the detailed configurations of the optical device and the detection device shown in FIG. 1. FIG. 3 is a block diagram showing the hardware configuration of the arithmetic device shown in FIG. 1. FIG. 4 is a graph showing the meaning of characteristic values ​​to be calculated by the arithmetic device, where (a) is a graph showing the meaning of standard deviation when there is one peak in the wavelength spectrum, and (b) is a graph showing the meaning of standard deviation when there are multiple peaks in the wavelength spectrum. FIG. 5 is a graph showing the meaning of characteristic values ​​to be calculated by the arithmetic device, where (a) is a graph showing the meaning of skewness, and (b) is a graph showing the meaning of kurtosis. FIG. 6 is a schematic diagram of a measurement system 100A, which is an optical information acquisition device according to a second embodiment. FIG. 7 is a diagram showing the detailed configurations of the optical device and the detection device shown in FIG. 6. FIG. 8 is a diagram showing an example configuration of the optical device shown in FIG. 6. FIG. 9 is a diagram showing the configuration of an optical device according to a first modified example. FIG. 10 is a diagram showing the configuration of an optical device and the detection device according to a second modified example. FIG. 11(a) shows the configuration of an optical device according to a second modified example. ０ 11(b) shows the use of the optical device when measuring the centroid wavelength of the wavelength spectrum of the incident light I ０ Fig. 12 is a diagram showing the configuration of an optical system constituting an optical device and a detection device according to a third modified example. Fig. 13 is a diagram showing the detailed configuration of an optical device and a detection device according to the modified example. Fig. 14 is a diagram showing the detailed configuration of an optical device and a detection device according to the modified example.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted. [First Embodiment]

[0012] 1 is a schematic diagram of a measurement system 100, which is an optical information acquisition device according to the first embodiment. The measurement system 100 of this embodiment includes an optical device 1, a detection device 3, and a calculation device 5, and detects incident light I ０ The optical device 1 is a device for measuring characteristic values ​​related to the wavelength spectrum of an incident light I from the outside. ０ When the incident light I０ The optical device 1 converts the incident light I into a plurality of measurement lights to be measured by the detection device 3. The detection device 3 detects the light intensity (light quantity) of each of the plurality of measurement lights converted by the optical device 1. The calculation device 5 calculates the incident light I using the detection signal output from the detection device 3. ０ The characteristic values ​​relating to the wavelength spectrum of the incident light I ０ is light from the object S, such as light emission, fluorescence, output light, reflected light, or transmitted light from the object S. The object S may be a semiconductor device, a semiconductor wafer, an optical integrated circuit, a light-emitting element, or a biological sample.

[0013] The detailed configurations of the optical device 1 and the detection device 3 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the detailed configurations of the optical device 1 and the detection device 3 shown in Fig. 1.

[0014] The optical device 1 includes four inclined dichroic mirrors 7 ０ , 7 １ , 7 ２ , 7 ３ The tilted dichroic mirror 7 ０ , 7 １ , 7 ２ , 7 ３ are filter members made of special optical materials, and have the property that the transmittance of light in a predetermined wavelength range changes depending on the wavelength, specifically, the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. ０ , 7 １ , 7 ２ , 7 ３ Each of these has a characteristic that the transmittance of light in a predetermined wavelength range changes monotonically according to the change in wavelength (for example, a characteristic that the transmittance in a predetermined wavelength range increases or decreases monotonically), and when the wavelength of incident light is λ, the transmittance T ０ ~T ４The inclined dichroic mirror is also called an LRG (Linear Reflectance Gradient on the wavelength axis) filter. ０ , 7 １ , 7 ２ , 7 ３ The inclined dichroic mirrors may be formed in the same film formation process. By using inclined dichroic mirrors formed in the same film formation process, it is possible to reduce variations in transmittance characteristics between inclined dichroic mirrors due to manufacturing errors, and to reduce measurement errors. ０ (λ) = a ０ λ+b ０ ... (1), T １ (λ) = a １ λ+b １ ... (2), T ２ (λ) = a ２ λ+b ２ ... (3), T ３ (λ) = a ３ λ+b ３ ... (4) In the above formulas (1) to (4), a ０ ~a ３ , b ０ ~b ３ is a known constant determined by the transmittance characteristics. The above-mentioned predetermined wavelength range is the incident light I ０ The wavelength range overlaps with the wavelength range of, for example, 400 nm or more and 800 nm or less. ０ ~a ３ , b ０ ~b ３ may differ from the design value due to manufacturing errors of the tilted dichroic mirror. Therefore, the amount of light transmitted or reflected by the tilted dichroic mirror is actually measured for each wavelength λ, and the actual constant a is calculated using a fitting method or the like. ０ ~a ３ , b ０ ~b ３ may be estimated.

[0015] The tilted dichroic mirror (first filter) 7 having the above configuration ０ is the incident light I０ is arranged so that incident light I ０ The transmitted light I １ At the same time, the incident light I ０ Reflected light I Ｒ０ Inclined dichroic mirror (second filter) 7 １ is the incident light I ０ Incident direction of the tilted dichroic mirror 7 ０ After that, transmitted light I １ is incident on the １ The transmitted light I ２ At the same time, the transmitted light I １ Reflected light I Ｒ１ Inclined dichroic mirror (third filter) 7 ２ is the incident light I ０ Incident direction of the tilted dichroic mirror 7 １ After that, transmitted light I ２ is incident on the ２ The transmitted light I ３ At the same time, the transmitted light I ２ Reflected light I Ｒ２ Inclined dichroic mirror (fourth filter) 7 ３ is the incident light I ０ Incident direction of the tilted dichroic mirror 7 ２ After that, transmitted light I ３ is incident on the ３ The transmitted light I ４ At the same time, the transmitted light I ３ Reflected light I Ｒ３ This causes

[0016] The detection device 3 includes five photodetectors 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ These photodetectors 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４is configured by a photodetector element such as an image sensor, such as a line image sensor or an area image sensor, having a plurality of pixels, or a point sensor, such as a photodiode (PD), an avalanche photodiode (APD), or a photomultiplier tube (PMT). ０ , 3 １ , 3 ２ , 3 ３ are the reflected light I Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ , and reflected light I Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ The photodetector 3 detects the light intensity (amount of light) of each of the light sources and outputs a detection signal representing the light intensity. ４ is the transmitted light I ４ In the case of an image sensor, the photodetector 3 detects the light intensity of the light and outputs a detection signal representing the light intensity. ０ , 3 １ , 3 ２ , 3 ３ is the reflected light I for each of the plurality of pixels. Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ , and reflected light I Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ The photodetector 3 detects the light intensity (amount of light) of each of the light sources and outputs a detection signal representing the light intensity. ４ For each of the plurality of pixels, ４ and outputs a detection signal representing the light intensity.

[0017] Here, the photodetector 3 ０ is an inclined dichroic mirror (first filter) 7 ０ The reflected light I is the first measurement light reflected from the Ｒ０ The first photodetector detects the １ is an inclined dichroic mirror (second filter) 7 １ The reflected light I is the second measurement light reflected from the Ｒ１The second photodetector detects the ２ is an inclined dichroic mirror (third filter) 7 ２ The reflected light I is the third measurement light reflected from the Ｒ２ The third photodetector detects the ３ is an inclined dichroic mirror (fourth filter) 7 ３ The fourth measurement light is reflected light I Ｒ３ The fourth photodetector detects the ４ is an inclined dichroic mirror (first to fourth filters) 7 ０ , 7 １ , 7 ２ , 7 ３ The fourth measurement light is transmitted through the transmitted light I ４ and a fourth photodetector for detecting

[0018] The computing device 5 has five photodetectors 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Based on the detection signal output from ０ The calculation device 5 calculates characteristic values ​​related to the wavelength spectrum of the optical fiber 1. FIG. 3 is a block diagram showing the hardware configuration of the calculation device 5. As shown in FIG. 3, the calculation device 5 is physically a computer or the like including processors such as a CPU (Central Processing Unit) 131 and a GPU (Graphic Processing Unit) 135, storage media such as a RAM (Random Access Memory) 132 and a ROM (Read Only Memory) 133, a communication module 134, and an input / output module 136, all of which are electrically connected to one another. The calculation device 5 may include input / output devices such as a display, a keyboard, a mouse, a touch panel display, or a data recording device such as a hard disk drive or semiconductor memory. The calculation device 5 may also be configured as a microcomputer or an FPGA. The calculation device 5 may also be configured by multiple computers, or may be integrated with the optical device 1 and the detection device 3.

[0019] The calculation unit 5 calculates the incident light I ０ The computing device 5 has a function of calculating the standard deviation of the wavelength spectrum, the skewness of the wavelength spectrum, and the kurtosis of the wavelength spectrum as characteristic values ​​related to the wavelength spectrum. Figure 4 is a graph for explaining the meaning of the characteristic values ​​to be calculated by the computing device 5, with part (a) being a graph for explaining the meaning of the standard deviation when the wavelength spectrum has one peak, and part (b) being a graph for explaining the meaning of the standard deviation when the wavelength spectrum has multiple peaks. Figure 5 is also a graph for explaining the meaning of the characteristic values ​​to be calculated by the computing device 5, with part (a) being a graph for explaining the meaning of the skewness, and part (b) being a graph for explaining the meaning of the kurtosis. The standard deviation σ is a characteristic value that represents the degree of variation in the distribution in the wavelength spectrum, and the larger this value, the greater the variation. In particular, as shown in part (a) of Figure 4, when the incident light I ０ In the case where there is one peak in the wavelength spectrum, the width of the wavelength spectrum is reflected in the standard deviation σ. ０ When there are multiple peaks in the wavelength spectrum, the intervals between the peaks are reflected in the standard deviation σ. Skewness is a characteristic value that represents the left-right asymmetry of the distribution in the wavelength spectrum; the larger the value, the greater the asymmetry; a positive value means that the distribution is biased toward smaller wavelengths, and a negative value means that the distribution is biased toward larger wavelengths. Kurtosis is a characteristic value that represents the sharpness of the peaks in the distribution in the wavelength spectrum; the larger the absolute value of this value, the greater the change from the sharpness of the normal distribution; a positive value means that the distribution is changing toward a sharper one, and a negative value means that the distribution is changing toward a gentler one. In the following description, the incident light I ０ The light intensity is represented by the symbol I ０ and the reflected light I Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ The light intensity of each is represented by the symbol I Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ and the transmitted light I １ , I ２ , I ３ , I ４ The light intensity of each is represented by the symbol I１ , I ２ , I ３ , I ４ Or I Ｔ０ , I Ｔ１ , I Ｔ２ , I Ｔ３ It shall be expressed as:

[0020] The calculation unit 5 calculates the incident light I ０ The centroid wavelength λ is the first moment in the wavelength spectrum of Ｇ０ That is, the calculation device 5 has a function of acquiring the light intensity from the light detector 3. ０ Based on the detection signals from the photodetectors 31, 32, 33, and 34, the incident light I ０ Calculate the first moment of the wavelength spectrum of the incident light I ０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ The principle of this function is as follows: ０ The wavelength spectrum of the function i ０ (λ) = I ０ ×f ０ (λ), and the transmitted light I １ The wavelength spectrum of the function i １ Assuming that the distribution of (λ) is: Also, according to the definition of the centroid wavelength, the following formula is established: is established, and by the definition of probability density, the following equation is obtained: Therefore, the following formula (5) holds: holds true.

[0021] According to the above principle, the calculation device 5 detects the light from the photodetector 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Light intensity I based on the detection signal output from Ｒ０ , I Ｔ０ (=I Ｒ１ +I Ｒ２ +I Ｒ３ +I Ｔ３ ) into the following formula (6); By substituting into the above, the incident light I０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ Calculate.

[0022] Furthermore, the calculation device 5 calculates the incident light I ０ The standard deviation σ, which is the second moment of the wavelength spectrum of ０ That is, the calculation device 5 also has a function of acquiring the light intensity from the light detector 3. ０ Based on the detection signals from the photodetectors 31, 32, 33, and 34, the incident light I ０ Calculate the second moment of the wavelength spectrum of the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Or variance σ ０ ２ The principle of this function is as follows: １ The wavelength spectrum of the function i １ (λ) = I １ ×f １ Assuming that the distribution of (λ) is: is established, and the following equation is obtained from equation (5): Therefore, the following equation holds: is derived, and from this equation, the following equation (7) is established as a transformation equation for lowering the order of the moment.

[0023] Furthermore, when the relationship of formula (7) is added to the definition of variance, the following formula is obtained: holds, and the distribution f ０ (λ), f １ The center of gravity of (λ) is λ Ｇ０ , λ Ｇ１ Therefore, the following formula: holds, and therefore the following equation: is derived.

[0024] According to the above principle, the calculation device 5 detects the light from the photodetector 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Light intensity I based on the detection signal output fromＲ０ , I Ｒ１ , I Ｔ１ (=I Ｒ２ +I Ｒ３ +I Ｔ３ ) into the following formula (8); By substituting into the above, the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Here, the calculation device 5 calculates the standard deviation σ ０ Instead of σ, the variance ０ ２ may be calculated.

[0025] Furthermore, the calculation device 5 calculates the incident light I ０ The skewness S is the third moment of the wavelength spectrum of ０ That is, the calculation device 5 also has a function of acquiring the light intensity from the light detector 3. ０ Based on the detection signals from the photodetectors 31, 32, 33, and 34, the incident light I ０ Calculate the third moment of the wavelength spectrum of the incident light I ０ The skewness S in the wavelength spectrum of ０ The principle of this function is as follows: When the relationship of Equation (7) is added to the definition of skewness, the following equation is obtained: Here, the following formula is satisfied: also holds true.

[0026] According to the above principle, the calculation device 5 detects the light from the photodetector 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Light intensity I based on the detection signal output from Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｔ２ (=I Ｒ３ +I Ｔ３ ) into the following formula (9); By substituting into the above, the incident light I ０ The skewness S in the wavelength spectrum of ０ Calculate.

[0027] Furthermore, the calculation device 5 calculates the incident light I ０ The kurtosis K is the fourth moment of the wavelength spectrum of ０ That is, the calculation device 5 also has a function of acquiring the light intensity from the light detector 3. ０ Based on the detection signals from the photodetectors 31, 32, 33, and 34, the incident light I ０ Calculate the fourth moment of the wavelength spectrum of the incident light I ０ Kurtosis K in the wavelength spectrum of ０ The principle of this function is as follows: When the relationship of Equation (7) is added to the definition of kurtosis, the following equation is obtained: Here, the following formula is satisfied: also holds true.

[0028] According to the above principle, the calculation device 5 detects the light from the photodetector 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Light intensity I based on the detection signal output from Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｒ３ , I Ｔ３ is expressed by the following formula (10): By substituting into the above, the incident light I ０ Kurtosis K in the wavelength spectrum of ０ Calculate.

[0029] Furthermore, the calculation device 5 calculates the centroid wavelength λ obtained by the above-mentioned calculation method. Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ), skewness S ０ , and kurtosis K ０ to a predetermined output destination. The output destination may be an output device such as a display, or a data storage device such as a semiconductor memory. Alternatively, the output may be output to the outside via the communication module 134.

[0030] Next, the procedure for measuring incident light by the measurement system 100 will be described, and the light information acquisition method of this embodiment will be described in detail.

[0031] First, the incident light I ０ The measurement process is started when the incident light I ０ is the tilted dichroic mirror 7 ０ Reflected light I generated by reflection by Ｒ０ The light intensity of the photodetector 3 ０ and the incident light I ０ is the tilted dichroic mirror 7 ０ Transmitted light I generated by being transmitted through １ The light intensity of the photodetector 3 ４ The incident light I ０ is the tilted dichroic mirror 7 ０ After being transmitted by the tilted dichroic mirror 7 １ Reflected light I generated by reflection by Ｒ１ The light intensity of the photodetector 3 １ and the incident light I ０ is the tilted dichroic mirror 7 ０ After being transmitted by the tilted dichroic mirror 7 １ Transmitted light I generated by being transmitted through ２ The light intensity of the photodetector 3 ４ Furthermore, the incident light I ０ is the tilted dichroic mirror 7 ０ After being transmitted by the tilted dichroic mirror 7 １ and is further transmitted by the inclined dichroic mirror 7 ２ Reflected light I generated by reflection by Ｒ２ The light intensity of the photodetector 3 ２ and the incident light I ０ is the tilted dichroic mirror 7 ０ After being transmitted by the tilted dichroic mirror 7 １ and is further transmitted by the inclined dichroic mirror 7 ２Transmitted light I generated by being transmitted through ３ The light intensity of the photodetector 3 ４ In addition, the incident light I ０ Three inclined dichroic mirrors 7 ０ , 7 １ , 7 ２ After being transmitted by the inclined dichroic mirror 7 ３ Reflected light I generated by reflection by Ｒ３ The light intensity of the photodetector 3 ３ and the incident light I ０ Three inclined dichroic mirrors 7 ０ , 7 １ , 7 ２ After being transmitted by the inclined dichroic mirror 7 ３ Transmitted light I generated by being transmitted through ４ The light intensity of the photodetector 3 ４ is detected by

[0032] Next, the calculation device 5 calculates the value of the photodetector 3 of the detection device 3. ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ Based on the detection signal output from the Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ), skewness S ０ , and kurtosis K ０ Finally, the arithmetic unit 5 outputs the calculated four characteristic values ​​to an output device or the like.

[0033] According to the measurement system 100 according to the first embodiment described above, the incident light I ０ Based on the inclined dichroic mirror 7 ０ Reflected light I Ｒ０ and the incident light I ０ Based on the inclined dichroic mirror 7 １ Transmitted light I transmitted and reflected ２ and reflected light I Ｒ１and the detected signal of the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Or variance σ ０ ２ This makes it possible to reduce the amount of data required to measure the distribution of the wavelength spectrum of light, and to easily obtain the incident light I ０ The characteristics related to the width of the wavelength spectrum can be obtained.

[0034] Furthermore, according to the measurement system 100, the incident light I ０ Based on the inclined dichroic mirror 7 ２ Transmitted light I transmitted and reflected ３ and reflected light I Ｒ２ The detected signal is further used to calculate the incident light I ０ The skewness S in the wavelength spectrum of ０ This makes it possible to reduce the amount of data required to measure the distribution of the wavelength spectrum of light, and to easily obtain the incident light I ０ The skewness characteristics of the wavelength spectrum can be obtained.

[0035] Furthermore, according to the measurement system 100, the incident light I ０ Based on the inclined dichroic mirror 7 ３ Transmitted light I transmitted and reflected ４ and reflected light I Ｒ３ The detected signal is further used to calculate the kurtosis K ０ This makes it possible to reduce the amount of data required to measure the distribution of the wavelength spectrum of light, and to easily obtain the kurtosis characteristics of the wavelength spectrum of incident light.

[0036] In particular, the measurement system 100 includes four tilted dichroic mirrors 7 ０ , 7 １ , 7 ２ , 7 ３ is the incident light I ０The dichroic mirror has a configuration in which the dichroic mirrors are arranged in series along the direction of incidence of the incident light. This configuration also makes it possible to easily obtain characteristics related to the width, skewness, and kurtosis of the wavelength spectrum of the incident light. In addition, since an inclined dichroic mirror having a characteristic in which the transmittance of light in a predetermined wavelength range changes linearly with wavelength can be used, it is easy to realize such transmission characteristics.

[0037] Next, simulation results of characteristic values ​​acquired by the measurement system 100 are shown. Here, the incident light I ０ Distribution of i ０ Assume that (λ) is the sum of two normal distribution functions as follows:

[0038] As a first verification calculation, the incident light I defined by the constants in Table 1 below ０ The tilted dichroic mirror 7 has the characteristics defined by the constants in Table 2 below. ０ , 7 １ , 7 ２ , 7 ３ In this case, the light intensity of the transmitted light I １ ~I ４ and the light intensity of the reflected light I Ｒ０ ~I Ｒ３ The theoretical calculated values ​​and the simulation results of the characteristic values ​​calculated by the arithmetic unit 5 are shown in Table 3 below. From this result, the calculation device 5 calculates the centroid wavelength λ Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ Since is a Gaussian, the skewness S ０ and kurtosis K ０ is calculated to be zero. Standard deviation σ ０ are calculated to the same values ​​as the parameters of the original two functions.

[0039] Similarly, the second verification calculations are shown in Tables 4 to 6 below. In this result, the calculation device 5 calculates the centroid wavelength λ Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ is the superposition of two Gaussians with different center wavelengths, and the standard deviation σ ０ is larger than the standard deviation of each Gaussian, and the kurtosis K ０ is calculated as a negative value. ０ Since is a symmetric distribution, the skewness S ０ is calculated to be zero.

[0040] The third verification calculation is shown in Tables 7 to 9 below. In this result, the calculation device 5 calculates the centroid wavelength λ Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ is a superposition of two Gaussians with different intensities, and has a standard deviation σ ０ is larger than the standard deviation of each Gaussian, and the kurtosis K ０ is calculated as a negative value. ０ Since the left-right symmetry of is broken, the skewness S ０ is calculated as a positive value.

[0041] 6 is a schematic diagram of a measurement system 100A, which is an optical information acquisition device according to the second embodiment. The measurement system 100A of this embodiment differs from the measurement system 100 according to the first embodiment in the configurations of the optical device 1A and the detection device 3A and the calculation function of the calculation device 5.

[0042] The configurations of the optical device 1A and the detection device 3A will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a diagram showing the configurations of the optical device 1A and the detection device 3A, and Fig. 8 is a diagram showing the detailed configuration of the optical device 1A.

[0043] The optical device 1A includes an inclined dichroic mirror 17 ０ , filter 17 １ , 17 ２ , 17 ３ The inclined dichroic mirror has a characteristic that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. １ , 17 ２ , 17 ３ The inclined dichroic mirror 17 has a characteristic that the transmittance of light in a predetermined wavelength range changes in a curved manner depending on the wavelength. ０ , filter 17 １ , 17 ２ , 17 ３ is the light transmittance T expressed by the following formulas (11) to (14), respectively, where λ is the wavelength of incident light. １ ~T ４ It has the following characteristics. １ (λ) = s １ λ+t １ ... (11), T ２ (λ) = r ２ λ ２ +s ２ λ+t ２ ... (12), T ３ (λ) = q ３ λ ３ +r ３ λ ２ +s ３ λ+t ３ ... (13), T ４ (λ) = p ４ λ ４ +q ４ λ ３ +r ４ λ ２ +s ４ λ+t ４ ...(14) In the above formula, t １ ~t ４ , s １ ~s ４ , r ２ ~r ４ , q ３ ~q ４ , p ４ is a known constant determined by the transmittance characteristics.１ This can be realized by stacking two inclined dichroic mirrors, each of which has a characteristic that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. Alternatively, it may be realized with a single filter. ２ This can be realized by stacking three inclined dichroic mirrors, each of which has a characteristic that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. Alternatively, it may be realized with a single filter. ３ can be realized by stacking three inclined dichroic mirrors, each of which has a characteristic that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. It can also be realized with a single filter. Note that the constant t in Equations (11) to (14) １ ~t ４ , s １ ~s ４ , r ２ ~r ４ , q ３ ~q ４ , p ４ may differ from the design value due to manufacturing errors of the inclined dichroic mirror or filter. Therefore, the amount of light transmitted or reflected by the inclined dichroic mirror or filter is actually measured for each wavelength λ, and the actual constant t １ ~t ４ , s １ ~s ４ , r ２ ~r ４ , q ３ ~q ４ , p ４ may be estimated.

[0044] The tilted dichroic mirror 17 having the above configuration ０ , filter 17 １ , 17 ２ , 17 ３ are the incident light I ０ The inclined dichroic mirror 17 is configured so that the light beam is incident on the inclined dichroic mirror 17. ０ is the incident light I ０ The transmitted light I １ Filter 17 １ , 17 ２, 17 ３ are the incident light I ０ The transmitted light I ２ ~I ４ This causes

[0045] The detection device 3A includes one photodetector 13. The photodetector 13 detects incident light I ０ , transmitted light I １ ~I ４ The photodetector 13 selectively receives either of the incident light I and detects the light intensity of either of the incident light I and outputs a detection signal. ０ is the tilted dichroic mirror 17 ０ , filter 17 １ , 17 ２ , 17 ３ Transmitted light I １ , I ２ , I ３ , I ４ The first to fourth photodetectors also serve as the first to fourth photodetectors for detecting the first to fourth measurement light beams.

[0046] 8, a specific configuration of the optical device 1A will be illustrated. The optical device 1A is configured, for example, by a filter changer 19, which is a rotatably supported disk-shaped member. The filter changer 19 has a circular tilted dichroic mirror 17 mounted around its rotation axis. ０ and a circular filter 17 １ , 17 ２ , 17 ３ The filter changer 19 having such a configuration rotates around the rotation axis, and thereby the inclined dichroic mirror 17 ０ , filter 17 １ , 17 ２ , 17 ３ , and the window portion 21 selectively receives incident light I ０ The photodetector 13 receives the incident light I via a filter changer 19 and a lens 23. ０ As a result, the photodetector 13 detects the incident light I ０ and transmitted light I １ ~I ４can be selectively detected.

[0047] The calculation device 5A calculates the incident light I output from the photodetector 13. ０ and transmitted light I １ ~I ４ Based on the detection signal of the incident light I ０ That is, the calculation device 5A calculates a characteristic value relating to the wavelength spectrum of the incident light I ０ The centroid wavelength λ of the wavelength spectrum of Ｇ０ That is, the calculation device 5A has a function of acquiring the incident light I based on the detection signal from the photodetector 13. ０ Calculate the first moment of the wavelength spectrum of the incident light I ０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ The formula that shows the principle of this function is as follows: According to the above principle, the calculation device 5A calculates the light intensity I based on the detection signal output from the photodetector 13. ０ , I １ is expressed by the following formula (15): By substituting into, the centroid wavelength λ Ｇ０ Calculate.

[0048] The calculation device 5A also calculates the incident light I ０ Standard deviation σ of the wavelength spectrum ０ That is, the calculation device 5A has a function of acquiring the incident light I based on the detection signal from the photodetector 13. ０ Calculate the second moment of the wavelength spectrum of the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Or variance σ ０ ２ The formula that shows the principle of this function is as follows: According to the above principle, the calculation device 5A calculates the light intensity I based on the detection signal output from the photodetector 13. ０ , I ２ is expressed by the following formula (16): By substituting into, the standard deviation σ ０ The calculation unit 5 calculates the standard deviation σ ０ Instead of σ, the variance０ ２ may be calculated.

[0049] Furthermore, the calculation device 5A calculates the incident light I ０ The skewness S of the wavelength spectrum ０ That is, the calculation device 5A has a function of acquiring the incident light I based on the detection signal from the photodetector 13. ０ Calculate the third moment of the wavelength spectrum of the incident light I ０ The skewness S in the wavelength spectrum of ０ The formula that shows the principle of this function is as follows: According to the above principle, the calculation device 5A calculates the light intensity I based on the detection signal output from the photodetector 13. ０ , I ３ is expressed by the following formula (17): By substituting into, the skewness S ０ Calculate.

[0050] In addition, the calculation device 5A calculates the incident light I ０ Kurtosis K for the wavelength spectrum of ０ That is, the calculation device 5A has a function of acquiring the incident light I based on the detection signal from the photodetector 13. ０ Calculate the fourth moment of the wavelength spectrum of the incident light I ０ Kurtosis K in the wavelength spectrum of ０ The formula that shows the principle of this function is as follows: According to the above principle, the calculation device 5A calculates the light intensity I based on the detection signal output from the photodetector 13. ０ , I ４ is expressed by the following formula (18): By substituting into, the kurtosis K ０ Calculate.

[0051] Here, the procedure for measuring incident light by the measurement system 100A will be described, and the light information acquisition method of this embodiment will be described in detail. ０The measurement process is started in a state where the incident light I is incident on the optical device 1A, and the filter changer 19 of the optical device 1A is rotated while the detection operation by the photodetector 13 is synchronized with the rotation. ０ , transmitted light I １ , I ２ , I ３ , I ４ The light intensities of the incident light are sequentially detected by the photodetector 13. Next, the calculation device 5A calculates the center wavelength λ of the wavelength spectrum of the incident light based on the detection signals sequentially output from the photodetector 13. Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ), skewness S ０ , and kurtosis K ０ Finally, the arithmetic unit 5 outputs the calculated four characteristic values ​​to an output device or the like.

[0052] According to the measurement system 100A according to the second embodiment described above, the incident light I ０ In addition, the number of filters through which the measurement light passes can be reduced, making it easier to realize the transmission characteristics of the filters. １ , 17 ２ , 17 ３ Since the filter has a configuration in which a plurality of tilted dichroic mirrors are combined, the configuration of the filter can be simplified.

[0053] Next, simulation results of characteristic values ​​acquired by the measurement system 100A are shown. Here, the incident light I ０ Distribution of i ０ It is assumed that (λ) is a function similar to the function used in the simulation calculation of the first embodiment. ０ , filter 17 １ , 17 ２ , 17 ３ It was assumed that the characteristics of

[0054] As a fourth verification calculation, the incident light I defined by the constants in Table 10 below ０The tilted dichroic mirror 17 has the characteristics defined by the constants in Table 11 below. ０ , filter 17 １ , 17 ２ , 17 ３ In this case, the light intensity of the transmitted light I １ ~I ４ The theoretical calculation values ​​and the simulation results of the characteristic values ​​calculated by the calculation device 5A are shown in Table 12 below. From this result, the calculation device 5A calculates the centroid wavelength λ Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ Since is a Gaussian, the skewness S ０ and kurtosis K ０ is calculated to be zero. Standard deviation σ ０ are calculated to the same values ​​as the parameters of the original two functions.

[0055] Similarly, the fifth verification calculation is shown in Tables 13 to 15 below. In this result, the centroid wavelength λ is calculated by the calculation device 5A. Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ is the superposition of two Gaussians with different center wavelengths, and the standard deviation σ ０ is larger than the standard deviation of each Gaussian, and the kurtosis K ０ is calculated as a negative value. ０ Since is a symmetric distribution, the skewness S ０ is calculated to be zero.

[0056] The sixth verification calculation is shown in Tables 16 to 18 below. In this result, the centroid wavelength λ is calculated by the calculation device 5A. Ｇ０ , standard deviation σ ０ , skewness S ０ , and kurtosis K ０ It was found that the calculated value is reasonable. Here, the incident light I ０ is a superposition of two Gaussians with different intensities, and has a standard deviation σ ０ is larger than the standard deviation of each Gaussian, and the kurtosis K ０ is calculated as a negative value. ０ Since the left-right symmetry of is broken, the skewness S ０ is calculated as a positive value.

[0057] Although various embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments.

[0058] In the measurement system 100 according to the first embodiment described above, the tilted dichroic mirror 7 ０ , 7 １ , 7 ２ , 7 ３ The light transmittance characteristics (characteristics expressed by formulas (1) to (4)) of the inclined dichroic mirrors 7 may be different from each other or may be the same. ０ , 7 １ , 7 ２ , 7 ３ When a mirror having a transmittance characteristic that increases with wavelength is used, the manufacturing cost of the filter can be reduced. Furthermore, the calculation formula for the characteristic value used in the calculation device 5 is simplified, and the calculation speed is improved. When the mirrors have different characteristics, the optical device 1 may be configured by combining a mirror having a transmittance characteristic that increases with wavelength and a mirror having a transmittance characteristic that decreases with wavelength.

[0059] In the measurement system 100A according to the second embodiment described above, the optical device 1A may be modified to have the configuration of a first modified example shown in Fig. 9. That is, the optical device 1A may be configured by a mosaic filter 25. The mosaic filter 25 has a light receiving surface on which a plurality of pixels are arranged two-dimensionally, and each pixel receives incident light I ０The mosaic filter 25 is disposed on the light receiving surface of the photodetector 13, and includes windows 21, an inclined dichroic mirror 17, and a plurality of windows 21 arranged two-dimensionally and periodically at positions corresponding to the plurality of pixels of the photodetector 13. ０ , filter 17 １ , 17 ２ According to this configuration, the incident light I ０ and transmitted light I １ , I ２ , I ３ The light intensities of the two-dimensional characteristic values ​​(standard deviation and skewness) can be detected simultaneously, and the distribution of each characteristic value (standard deviation and skewness) can be obtained immediately.

[0060] In the measurement system 100 according to the first embodiment, the optical device 1 and the detection device 3 may be modified to have a configuration according to a second modification shown in Fig. 10. The optical device 1C according to the second modification includes three inclined dichroic mirrors 37 ０ , 37 １ , 37 ２ and a depolarizing plate 31. Three inclined dichroic mirrors 37 ０ , 37 １ , 37 ２ is an inclined dichroic mirror 7 ０ , 7 １ , 7 ２ Similarly, the depolarizer 31 is a filter member having the transmittance characteristics shown in each of the formulas (1) to (3). The depolarizer 31 is an optical element that transmits incident light while changing it from polarized light to unpolarized light.

[0061] Inclined dichroic mirror 37 １ is the incident light I ０ The incident light I ０ The inclined dichroic mirror 37 transmits the light to generate transmitted light. １ is the incident light I to escape the multiple reflected light. ０ and the incident light I ０ With this configuration, the incident light I ０ is the inclined dichroic mirror 37 １and the incident light I ０ is the inclined dichroic mirror 37 １ It is possible to switch between a state in which light is not incident on the optical fiber and passes through with 100% transmittance.

[0062] Depolarizing plate 31 and tilted dichroic mirror 37 ０ is the incident light I ０ The tilted dichroic mirror 37 in the incident direction １ After that, the incident light I ０ , or tilted dichroic mirror 37 １ The dichroic mirrors 37 are arranged in this order so that transmitted light from the dichroic mirrors 37 is incident on them. ０ is designed to perform well for unpolarized light, so the tilted dichroic mirror 37 ０ A depolarizing plate 31 is placed in front of the inclined dichroic mirror 37 to prevent polarized light from entering the inclined dichroic mirror 37. ０ is the incident light I ０ When the incident light I ０ The transmitted light I １ At the same time, the incident light I ０ Reflected light I Ｒ０ The tilted dichroic mirror 37 ０ is the inclined dichroic mirror 37 １ When transmitted light is incident from the ２ At the same time, the transmitted light is reflected to produce reflected light I Ｒ１ This causes

[0063] Inclined dichroic mirror 37 ２ is the inclined dichroic mirror 37 ０ Reflected light from I Ｒ１ is directly incident on the reflector, and the reflected light I Ｒ１ The transmitted light I ３ This inclined dichroic mirror 37 ２ is the reflected light I to allow multiple reflected light to escape. Ｒ１ The reflected light I is arranged so as to be slightly tilted with respect to the optical axis of the Ｒ１ and reflected light I Ｒ０With this configuration, the reflected light I Ｒ１ The tilted dichroic mirror 37 ２ and reflected light I Ｒ０ is incident on the inclined dichroic mirror 37 ２ The inclined dichroic mirror 37 can be switched between a state in which the light is not incident on the inclined dichroic mirror 37 and a state in which the light is transmitted at a transmittance of 100%. １ and an inclined dichroic mirror 37 ２ Also, the tilted dichroic mirror 37 ０ However, these inclinations are only small enough to avoid multiple reflections, so the incident light I ０ Even when the light is polarized, the same performance as that of unpolarized light can be obtained. Therefore, if the tilted dichroic mirror is tilted to avoid multiple reflections, a depolarizer is not necessary.

[0064] The manner of use of the optical device 1C will be described with reference to Fig. 11. In Fig. 11, part (a) shows incident light I ０ The part (b) shows the usage form when measuring the centroid wavelength of the wavelength spectrum of the incident light I ０ This shows how the standard deviation and skewness of the wavelength spectrum are measured. １ , 37 ２ is the incident light I ０ Or reflected light I Ｒ０ The transmitted light I is controlled to be out of the optical axis of the optical device 1C. １ and reflected light I Ｒ０ On the other hand, when measuring the standard deviation and skewness, the tilted dichroic mirror 37 １ , 37 ２ is the incident light I ０ Or reflected light I Ｒ１ The transmitted light I is controlled to be positioned on the optical axis of the optical device 1C. ２ , I ３ will be output.

[0065] Referring again to FIG. 10, the detection device 3C according to the second modification has two photodetectors 33 ０ , 33 １ and two lenses 39 ０ , 39 １ The two lenses 39 ０ , 39 １ The optical detector 33 may be configured without including the optical detector 33. ０ Lens 39 ０ and an inclined dichroic mirror 37 ２ The photodetector 33 is disposed opposite to the ０ When the optical device 1C is set to the usage mode shown in FIG. 11(a), the reflected light I Ｒ０ When the optical device 1C is set to the usage mode shown in FIG. 11(b), the light intensity of the transmitted light I ３ The light intensity of the light detector 33 is detected. １ Lens 39 １ and an inclined dichroic mirror 37 ０ The photodetector 33 is disposed opposite to the １ When the optical device 1C is set to the usage mode shown in FIG. 11(a), the transmitted light I １ When the optical device 1C is set to the usage mode shown in FIG. 11(b), the light intensity of the transmitted light I ２ The two photodetectors 33 detect the light intensity of ０ , 33 １ is a camera that is a two-dimensional area sensor capable of detecting a two-dimensional distribution of light intensity. ０ , lens 39 １ , an optical system is provided to focus the light towards the detector 3C before it enters the optical device 1C.

[0066] The calculation function of the characteristic value of the calculation device 5C according to the second modification will be described. ０ , 33 １ Based on the light intensity distribution detected by the photodetector 33 ０ , 33 １ The calculation is performed for each corresponding pixel or pixel group to obtain a two-dimensional distribution of each characteristic value.

[0067] The formula showing the principle of the calculation function of the calculation device 5C to calculate the standard deviation in the wavelength spectrum is as follows: ０ , 33 １ Based on the detection signal from the incident light I ０ Calculate the second moment of the wavelength spectrum of the incident light I ０ The standard deviation or variance in the wavelength spectrum of the light is obtained. Here, the following formula used in the explanation of the principle of the standard deviation calculation function of the calculation device 5A: By comparing the coefficients so that they are equal, the following equation holds:

[0068] According to the above principle, the calculation device 5C detects the light from the photodetector 33 ０ , 33 １ Light intensity I based on the detection signal output from ０ , I Ｔ２ is expressed by the following formula (19): By substituting into the above, the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Calculate.

[0069] The calculation function of the calculation device 5C for calculating the skewness of the wavelength spectrum is as follows: ０ , 33 １ Based on the detection signal from the incident light I ０ Calculate the third moment of the wavelength spectrum of the incident light I ０ Obtain the skewness in the wavelength spectrum of Here, the following formula used in the explanation of the principle of the skewness calculation function of the calculation device 5A: By comparing the coefficients so that they are equal, the following equation holds:

[0070] According to the above principle, the calculation device 5C detects the light from the photodetector 33 ０ , 33 １ Light intensity I based on the detection signal output from ０ , I ３ is expressed by the following formula (20): By substituting into the above, the incident light I ０ The skewness S in the wavelength spectrum of ０ Calculate.

[0071] Furthermore, in the measurement system 100 according to the first embodiment described above, the optical device 1 and the detection device 3 may be configured as a third modified example shown in Fig. 12. In the third modified example, a part of the optical device and the detection device are integrated as a camera device. That is, an optical system 200 constituting the optical device and the detection device according to the third modified example includes two camera devices 53A and 53B, a polarizing beam splitter 61, a depolarizing plate 63, a filter 65, and two lenses 67A and 67B.

[0072] The depolarizer 63 depolarizes the light with a light intensity of (1+β)I ０ The polarizing beam splitter 61 is an optical element that is arranged so that incident light of a wavelength (λ) is incident thereon and transmits the incident light while changing it from polarized light to unpolarized light. The polarizing beam splitter 61 is arranged after the depolarizing plate 63 in the incident direction of the incident light and separates the incident light into two linearly polarized components that are orthogonal to each other. That is, the polarizing beam splitter 61 splits the incident light into two linearly polarized components with a light intensity of (1+β)I ０ From the incident light, the light intensity I ０ The linearly polarized light is separated into the incident light in the same direction as the incident light, and the light intensity βI ０ The linearly polarized light is split into two in a direction perpendicular to the optical axis of the incident light.

[0073] The filter 65 has a characteristic that the transmittance of light in a predetermined wavelength range changes in a curve according to the wavelength. Specifically, when the wavelength of incident light is λ, the filter 65 has a transmittance T Ｆ (λ) T Ｆ (λ) = c Ｆ λ ２ +a Ｆ λ+b Ｆ ...(21) The filter 65 having such characteristics is realized by overlapping two inclined dichroic mirrors. Alternatively, it may be realized by a single filter. The filter 65 is configured to divide the light intensity βI ０ The linearly polarized light is transmitted through theＦ This causes

[0074] A lens 67B is optionally disposed between the filter 65 and the camera device 53B to capture the transmitted light I Ｆ The lens 67B is disposed between the polarizing beam splitter 61 and the camera device 53A, and focuses the light intensity I ０ The linearly polarized light is focused toward the camera device 53B so that it can be detected by the camera device 53A. If the lens 67B is not provided, an optical system that focuses the light toward the camera device 53B is provided before the light is incident on the depolarizing plate 63.

[0075] The camera device 53A incorporates three prisms 69A, 71A, and 73A and three photodetectors 75A, 77A, and 79A. The three prisms 69A, 71A, and 73A are bonded together and arranged in this order along the direction of incidence of the incident light from the polarizing beam splitter 61. An inclined dichroic mirror 81A is formed on the bonding surface between the prism 69A and the prism 71A. Furthermore, an inclined dichroic mirror 83A is formed on the bonding surface between the prism 71A and the prism 73A. The inclined dichroic mirror 81A detects a light intensity I ０ The incident light is transmitted from the prism 69A to the prism 71A, and the transmitted light I １ and the light intensity I ０ The incident light is reflected into the prism 69A to form reflected light I Ｒ０ The inclined dichroic mirror 83A generates the transmitted light I transmitted through the inclined dichroic mirror 81A. １ is transmitted from the prism 71A to the prism 73A, and the transmitted light I ２ =I Ｔ１ and the transmitted light I transmitted through the inclined dichroic mirror 81A. １ is reflected into the prism 71A, and the reflected light I Ｒ１If necessary, a lens 67A is disposed between the polarizing beam splitter 61 and the camera device 53B to focus the transmitted light I toward the camera device 53A so that the transmitted light I is detected by the camera device 53A. If the lens 67A is not disposed, an optical system that focuses the light toward the camera device 53A is disposed before the light is incident on the depolarizing plate 63.

[0076] The two inclined dichroic mirrors 81A and 83A have a characteristic that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. Specifically, when the wavelength of incident light is λ, the inclined dichroic mirrors 81A and 83A have a transmittance T ０ (λ), T ０ Incidentally, the inclined dichroic mirrors 81A and 83A are set to have the above transmittance characteristics for p-polarized or s-polarized incident light.

[0077] The photodetector 75A is disposed close to the prism 69A and detects the reflected light I that is reflected twice within the prism 69A and output. Ｒ０ The photodetector 77A is disposed close to the prism 71A and detects the light intensity of the reflected light I reflected by the prism 71A. Ｒ１ The photodetector 79A is disposed close to the prism 73A and detects the light intensity of the transmitted light I that is output after passing through the prisms 69A, 71A, and 73A in this order. Ｔ１ The three photodetectors 75A, 77A, and 79A are cameras that have a plurality of pixels and are two-dimensional area sensors that can detect a two-dimensional distribution of light intensity.

[0078] In the camera device 53A configured as described above, the rotation angle around the optical axis of the incident light is adjusted so that the direction of the linearly polarized light incident from the polarizing beam splitter 61 matches the direction of the linearly polarized light of the incident light designed for the two inclined dichroic mirrors 81A and 83A.

[0079] Similar to the camera device 53A, the camera device 53B incorporates three prisms 69B, 71B, and 73B and three photodetectors 75B, 77B, and 79B. An inclined dichroic mirror 81B is formed at the joint surface between the prism 69B and the prism 71B, and an inclined dichroic mirror 83B is formed at the joint surface between the prism 71B and the prism 73B. The inclined dichroic mirror 81B reflects the light intensity βI ０ The incident light is transmitted from the prism 69B to the prism 71B, and the transmitted light is １Ｆ and the light intensity βI ０ The incident light is reflected into the prism 69B to form reflected light I Ｒ０Ｆ The inclined dichroic mirror 83B generates the transmitted light I transmitted through the inclined dichroic mirror 81B. １Ｆ is transmitted from the prism 71B to the prism 73B, and the transmitted light I ２Ｆ =I Ｔ１Ｆ and the transmitted light I transmitted through the inclined dichroic mirror 81B. １Ｆ is reflected into the prism 71B, and the reflected light I Ｒ１Ｆ This causes

[0080] The two inclined dichroic mirrors 81B and 83B have a characteristic that the transmittance of light changes linearly depending on the wavelength in a predetermined wavelength range. Specifically, when the wavelength of incident light is λ, the inclined dichroic mirrors 81B and 83B have a transmittance T ０ (λ), T ０ Incidentally, the inclined dichroic mirrors 81B and 83B are set to have the above transmittance characteristics for p-polarized or s-polarized incident light.

[0081] The photodetector 75B is disposed close to the prism 69B and detects the reflected light I that is reflected twice within the prism 69B and output. Ｒ０Ｆ The photodetector 77B is disposed close to the prism 71B and detects the light intensity of the reflected light I reflected by the prism 71B. Ｒ１ＦThe photodetector 79B is disposed close to the prism 73B and detects the intensity of the transmitted light I that is output after passing through the prisms 69B, 71B, and 73B in this order. Ｔ１Ｆ The three photodetectors 75B, 77B, and 79B are cameras that have a plurality of pixels and are two-dimensional area sensors that can detect a two-dimensional distribution of light intensity.

[0082] In the camera device 53B configured in this manner, the rotation angle around the optical axis of the incident light is adjusted so that the direction of the linearly polarized light incident from the polarizing beam splitter 61 matches the direction of the linearly polarized light of the incident light designed for the two inclined dichroic mirrors 81B and 83B.

[0083] In the third modification, the arithmetic unit 5 has a function of acquiring the centroid wavelength, standard deviation, variance, skewness, and kurtosis of the wavelength spectrum of the incident light. The arithmetic unit 5 acquires a two-dimensional distribution of each characteristic value based on the light intensity distribution detected by the two camera devices 53A and 53B. In other words, the arithmetic unit 5 acquires the two-dimensional distribution of each characteristic value based on the light intensity distribution detected by the two camera devices 53A and 53B. ０ Calculate the first, second, third and fourth moments of the wavelength spectrum of the incident light I ０ The centroid wavelength, standard deviation, variance, skewness, and kurtosis of the wavelength spectrum of the incident light I are obtained. Here, the principle of the skewness calculation function is as follows. ０ The wavelength spectrum of the function i ０ (λ) = I ０ ×f ０ (λ), and the transmitted light I Ｆ , I １ , I ２ , I １Ｆ , I ２Ｆ The wavelength spectrum of each function i Ｆ (λ), i １ (λ), i ２ (λ), i １Ｆ (λ), i ２Ｆ (λ) distribution, in which: Here, the following formula used in the explanation of the principle of the skewness calculation function of the calculation device 5A is established: By comparing the coefficients so that they are equal, the following equation holds:

[0084] According to the above principle, the calculation device 5 calculates the light intensity I based on the detection signals output from the camera devices 53A and 53B. ０ , I ３ is expressed by the following formula (22): By introducing ０ Calculate.

[0085] The formula showing the principle of the kurtosis calculation function is as follows: Here, the following formula used in the explanation of the principle of the kurtosis calculation function of the calculation device 5A: By comparing the coefficients so that they are equal, the following equation holds:

[0086] According to the above principle, the calculation device 5 calculates the light intensity I based on the detection signals output from the camera devices 53A and 53B. ０ , I ４ is expressed by the following formula (23): By introducing ０ Calculate.

[0087] In the third modified example, the configuration may be changed as follows. That is, the polarizing beam splitter 61 and the camera device 53B may be omitted, and the filter 65 may be configured to be insertable and removable between the depolarizing plate 63 and the camera device 53A on the optical axis of the incident light. According to this modified example, the calculation device 5 can acquire the centroid wavelength, standard deviation, skewness, and kurtosis of the wavelength spectrum of the incident light based on the detection signal output from the camera device 53A at the timing when the filter 65 is placed on the optical axis of the incident light and the detection signal output from the camera device 53A at the timing when the filter 65 is removed from the optical axis of the incident light.

[0088] In the measurement system 100 according to the first embodiment described above, the optical device 1 includes two inclined dichroic mirrors 7 having the same transmittance characteristics. ０ , 7 １ In this case, in the characteristics shown in the above formulas (1) and (2), a ０ = a１ , b ０ = b １ Since the above holds, the calculation device calculates the following equation (24): Using the above, the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Calculate.

[0089] In the measurement system 100 according to the first embodiment described above, the optical device 1 includes three inclined dichroic mirrors 7 having the same transmittance characteristics. ０ , 7 １ , 7 ２ In this case, in the characteristics shown in the above formulas (1) to (3), a ０ = a １ = a ２ , b ０ = b １ = b ２ Since the above holds, the calculation device calculates the following equation (25): Using the above, the incident light I ０ The skewness S in the wavelength spectrum of ０ Calculate.

[0090] In the measurement system 100 according to the first embodiment described above, the optical device 1 includes four inclined dichroic mirrors 7 having the same transmittance characteristics. ０ , 7 １ , 7 ２ , 7 ３ In this case, in the characteristics shown in the above formulas (1) to (4), a ０ = a １ = a ２ = a ３ , b ０ = b １ = b ２ = b ３ Since the above holds, the calculation device calculates the following equation (26): Using the above, the incident light I ０ Kurtosis K in the wavelength spectrum of ０ Calculate.

[0091] 2, a photodetector 3 obtained by using an optical device 1D and a detection device 3D having the configuration shown in FIG. 13 is used. ０Based on the detection signals from the photodetectors 3, 3, and 3, the calculation unit 5 calculates the incident light I ０ Calculate the second moment of the wavelength spectrum of the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Or variance σ ０ ２ The photodetector 35 may be connected to a tilted dichroic mirror (second filter) 7 １ Transmitted light I ２ Therefore, the calculation device 5 detects the photodetector 3 ０ , 3 １ , 3 ５ Light intensity I based on the detection signal output from Ｒ０ , I Ｒ１ , I Ｔ１ (=I ２ ) into the above equation (8), the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ Or variance σ ０ ２ can be calculated.

[0092] 14. It should be noted that the optical detector 3 obtained by using the optical device 1E and the detection device 3E shown in FIG. 14 instead of the optical device 1 and the detection device 3 shown in FIG. ０ detection signal from photodetector 31, detection signal from photodetector 3 ２ and the detection signal from the photodetector 3 ６ Based on the detection signal from the input, the calculation unit 5 calculates the incident light I ０ Calculate the third moment of the wavelength spectrum of the incident light I ０ The skewness S in the wavelength spectrum of ０ The photodetector 3 may acquire ６ is an inclined dichroic mirror (third filter) 7 ２ Transmitted light I ３ Therefore, the calculation device 5 detects the photodetector 3 ０ , 3 １ , 3 ２ , 3 ６ Light intensity I based on the detection signal output from Ｒ０ , I Ｒ１, I Ｒ２ , I Ｔ３ (=I ３ ) into the above equation (9), the incident light I ０ The skewness S in the wavelength spectrum of ０ can be calculated.

[0093] In the first aspect, the optical fiber may further include a third filter having a transmittance that varies depending on wavelength in a predetermined wavelength range, and a third photodetector that detects third measurement light that is transmitted through or reflected by the third filter based on incident light and outputs a third detection signal, and the calculation unit may acquire the skewness in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, and the third detection signal. In the second aspect, the optical fiber may further include a third photodetection step that uses a third filter having a transmittance that varies depending on wavelength in a predetermined wavelength range to detect third measurement light that is transmitted through or reflected by the third filter based on incident light and outputs a third detection signal, and the calculation step may acquire the skewness in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, and the third detection signal. This allows the skewness in the wavelength spectrum of the incident light to be acquired by further using the third detection signal that detects the third measurement light that is transmitted through or reflected by the third filter based on the incident light. This reduces the amount of data required to measure the distribution of the wavelength spectrum of light, and makes it possible to easily acquire the skewness characteristics of the wavelength spectrum of the incident light.

[0094] In the first aspect, the optical fiber optics may further include a fourth filter having a transmittance that varies depending on wavelength in a predetermined wavelength range, and a fourth photodetector that detects fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light and outputs a fourth detection signal, and the calculation unit may further include a fourth photodetection step of detecting fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light using a fourth filter having a transmittance that varies depending on wavelength in a predetermined wavelength range, and outputting a fourth detection signal, and the calculation step may further include a fourth photodetection step of detecting fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light and outputting a fourth detection signal, and the calculation step may obtain the kurtosis in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, the third detection signal, and the fourth detection signal. According to the above configuration, the kurtosis in the wavelength spectrum of the incident light can be obtained by further using the fourth detection signal that detects fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light. This makes it possible to reduce the amount of data required to measure the distribution of the wavelength spectrum of light, and to easily obtain the kurtosis characteristics of the wavelength spectrum of incident light.

[0095] In the first aspect, the first filter and the second filter may have a characteristic in which transmittance varies linearly with wavelength, the first photodetector may detect a first measurement light obtained by transmitting or reflecting incident light through the first filter, and the second photodetector may detect a second measurement light obtained by transmitting or reflecting incident light through the second filter after transmitting or reflecting through the first filter. According to the above configuration, characteristics related to the wavelength spectrum of the incident light can be easily acquired. Additionally, since the first filter and the second filter have a transmittance that varies linearly with wavelength, their transmission characteristics can be easily realized.

[0096] Furthermore, in the first aspect, the first filter, the second filter, and the third filter may have a characteristic in which transmittance changes linearly with wavelength, the first photodetector may detect a first measurement light obtained by transmitting or reflecting incident light through the first filter, the second photodetector may detect a second measurement light obtained by transmitting or reflecting the incident light through the first filter and then transmitting or reflecting the second filter, and the third photodetector may detect a third measurement light obtained by transmitting or reflecting the incident light through the first filter, then transmitting or reflecting the second filter, and then transmitting or reflecting the third filter. This configuration may easily obtain characteristics related to the skewness of the wavelength spectrum of the incident light. Additionally, the first filter, the second filter, and the third filter have transmittances that change linearly with wavelength, making it easy to achieve their transmission characteristics.

[0097] In the first aspect, the first filter, the second filter, the third filter, and the fourth filter may have a characteristic in which transmittance changes linearly with wavelength, the first photodetector detects a first measurement light obtained by transmitting or reflecting the first filter from incident light, the second photodetector detects a second measurement light obtained by transmitting or reflecting the first filter and then transmitting or reflecting the second filter, the third photodetector detects a third measurement light obtained by transmitting or reflecting the first filter from incident light, then transmitting or reflecting the second filter and then transmitting or reflecting the third filter, and the fourth photodetector detects a fourth measurement light obtained by transmitting or reflecting the first filter from incident light, then transmitting or reflecting the second filter, then transmitting or reflecting the third filter, and then transmitting or reflecting the fourth filter. In this case, it is possible to easily obtain a characteristic related to the kurtosis of the wavelength spectrum of the incident light. In addition, the first filter, second filter, third filter, and fourth filter are filters whose transmittance changes linearly depending on the wavelength, and therefore, it is easy to realize these transmission characteristics.

[0098] In the first aspect, the first filter may have a characteristic in which the transmittance changes linearly with wavelength, and the second filter may have a characteristic in which the transmittance changes curvedly with wavelength, the first photodetector may detect first measurement light obtained by transmitting or reflecting incident light through the first filter, and the second photodetector may detect second measurement light obtained by transmitting or reflecting incident light through the second filter. Furthermore, in the second aspect, the optical fiber may further include a detector that detects an image of the object. This configuration makes it possible to easily obtain characteristics related to the wavelength spectrum width of the incident light. Additionally, since the number of filters through which the measurement light passes can be reduced, it is easy to realize the filter transmission characteristics.

[0099] In the first aspect, the first filter may have a characteristic in which the transmittance changes linearly with wavelength, the second filter may have a characteristic in which the transmittance changes curvedly with wavelength, and the third filter may have a characteristic in which the transmittance changes curvedly with wavelength. The first photodetector may detect first measurement light obtained by transmitting or reflecting incident light through the first filter, the second photodetector may detect second measurement light obtained by transmitting or reflecting incident light through the second filter, and the third photodetector may detect third measurement light obtained by transmitting or reflecting incident light through the third filter. In this case, it is possible to easily obtain characteristics related to the skewness of the wavelength spectrum of the incident light. In addition, since the number of filters through which the measurement light passes can be reduced, it is easy to realize the transmission characteristics of the filters.

[0100] In the first aspect, the first filter may have a transmittance that varies linearly with wavelength, the second filter may have a transmittance that varies curvedly with wavelength, the third filter may have a transmittance that varies curvedly with wavelength, and the fourth filter may have a transmittance that varies curvedly with wavelength. The first photodetector may detect first measurement light that is incident light transmitted through or reflected by the first filter, the second photodetector may detect second measurement light that is incident light transmitted through or reflected by the second filter, the third photodetector may detect third measurement light that is incident light transmitted through or reflected by the third filter, and the fourth photodetector may detect fourth measurement light that is incident light transmitted through or reflected by the fourth filter. This configuration makes it possible to easily obtain characteristics related to the kurtosis of the wavelength spectrum of the incident light. Additionally, the number of filters through which the measurement light passes can be reduced, making it easier to achieve the filter transmission characteristics.

[0101] In the first aspect, the second filter may have a configuration including two filters whose transmittance varies linearly with wavelength, which can simplify the configuration of the second filter.

[0102] In the above aspect, the third filter may have a configuration including three filters whose transmittance varies linearly with wavelength, which can simplify the configuration of the third filter.

[0103] In the first aspect, the fourth filter may have a configuration including four filters each having a transmittance that changes linearly with wavelength, which can simplify the configuration of the fourth filter.

[0104] The optical information acquisition device of the embodiment is [1] "an optical information acquisition device comprising: a first filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range; a second filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range; a first photodetector that detects first measurement light that is transmitted through or reflected by the first filter based on incident light and outputs a first detection signal; a second photodetector that detects second measurement light that is transmitted through or reflected by the second filter based on the incident light and outputs a second detection signal; and a calculation unit that acquires standard deviation or variance in the wavelength spectrum of the incident light based on the first detection signal and the second detection signal."

[0105] The optical information acquisition device of the embodiment may be [2] "the optical information acquisition device described in [1] above, further including a third filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range, and a third photodetector that detects third measurement light that is transmitted through or reflected by the third filter based on incident light and outputs a third detection signal, and the calculation unit acquires the skewness in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, and the third detection signal."

[0106] The optical information acquisition device of the embodiment may be [3] "the optical information acquisition device described in [2] above, further including a fourth filter having a property that transmittance changes depending on wavelength in a predetermined wavelength range, and a fourth photodetector that detects fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light and outputs a fourth detection signal, and the calculation unit acquires the kurtosis in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, the third detection signal, and the fourth detection signal."

[0107] The optical information acquisition device of the embodiment may be [4] "the optical information acquisition device described in [1] above, wherein the first filter and the second filter have a property that the transmittance changes linearly depending on the wavelength, the first photodetector detects the first measurement light that is the incident light that has passed through or been reflected by the first filter, and the second photodetector detects the second measurement light that is the incident light that has passed through or been reflected by the second filter after passing through or being reflected by the first filter."

[0108] The optical information acquisition device of the embodiment may be [5] "the optical information acquisition device described in [2] above, wherein the first filter, the second filter, and the third filter have a property that the transmittance changes linearly depending on the wavelength, the first photodetector detects the first measurement light obtained by the incident light being transmitted through or reflected by the first filter, the second photodetector detects the second measurement light obtained by the incident light being transmitted through or reflected by the second filter after being transmitted through or reflected by the first filter, and the third photodetector detects the third measurement light obtained by the incident light being transmitted through or reflected by the second filter after being transmitted through or reflected by the first filter and further transmitted through or reflected by the third filter."

[0109] The optical information acquisition device of the embodiment may be the optical information acquisition device described in [3] above, [6] in which "the first filter, the second filter, the third filter, and the fourth filter have a property that the transmittance changes linearly depending on the wavelength, the first photodetector detects first measurement light obtained by the incident light being transmitted through or reflected by the first filter, the second photodetector detects second measurement light obtained by the incident light being transmitted through or reflected by the second filter after being transmitted through or reflected by the first filter, the third photodetector detects third measurement light obtained by the incident light being transmitted through or reflected by the second filter after being transmitted through or reflected by the first filter and further transmitted through or reflected by the third filter, and the fourth photodetector detects fourth measurement light obtained by the incident light being transmitted through or reflected by the first filter after being transmitted through or reflected by the second filter, further transmitted through or reflected by the third filter, and further transmitted through or reflected by the fourth filter."

[0110] The optical information acquisition device of the embodiment may be [7] "the optical information acquisition device described in [1] above, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light that is the incident light transmitted through or reflected by the first filter, and the second photodetector detects the second measurement light that is the incident light transmitted through or reflected by the second filter."

[0111] The optical information acquisition device of the embodiment is [8] "the optical information acquisition device described in [2] above, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the third filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light obtained by transmitting or reflecting the first filter from the incident light, the second photodetector detects the second measurement light obtained by transmitting or reflecting the second filter from the incident light, and the third photodetector detects the third measurement light obtained by transmitting or reflecting the incident light from the third filter."

[0112] The optical information acquisition device of the embodiment may be [9] "the optical information acquisition device described in [3] above, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the third filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the fourth filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light obtained by the incident light being transmitted through or reflected by the first filter, the second photodetector detects the second measurement light obtained by the incident light being transmitted through or reflected by the second filter, the third photodetector detects the third measurement light obtained by the incident light being transmitted through or reflected by the third filter, and the fourth photodetector detects the fourth measurement light obtained by the incident light being transmitted through or reflected by the fourth filter."

[0113] The optical information acquisition device of the embodiment may be

[10] "the optical information acquisition device described in [7] above, wherein the second filter has two filters having a characteristic that the transmittance changes linearly depending on the wavelength."

[0114] The optical information acquisition device of the embodiment may be

[11] "an optical information acquisition device described in [7] or [8] above, in which the third filter has three filters having a characteristic in which the transmittance changes linearly depending on the wavelength."

[0115] The optical information acquisition device of the embodiment may be

[12] "an optical information acquisition device described in any of [7] to [9] above, wherein the fourth filter has four filters having a characteristic that the transmittance changes linearly depending on the wavelength."

[0116] 100, 100A... measurement system (optical information acquisition device), 1, 1A, 1C... optical device, 3, 3A, 3C... detection device, 5, 5A, 5C... calculation device (calculation unit), 3 ０ , 3 １ , 3 ２ , 3 ３ , 3 ４ , 13, 33 ０ , 33 １ , 75A, 75B, 77A, 77B, 79A, 79B...photodetector, 17 １ , 17 ２ , 17 ３ , 37 ０ , 37 ２ , 65...filter, 7 ０ , 7 １ , 7 ２ , 7 ３ ...inclined dichroic mirror (first to fourth filters), 17 ０ , 37 ０ , 37 １ , 37 ２ , 81A, 81B, 83A, 83B... inclined dichroic mirrors, I ０ ...Incoming light.

Claims

1. An optical information acquisition device comprising: a first filter having a characteristic that transmittance changes according to wavelength in a predetermined wavelength range; a second filter having a characteristic that transmittance changes according to wavelength in a predetermined wavelength range; a first photodetector that detects a first measurement light that is based on incident light and has passed through or reflected by the first filter and outputs a first detection signal; a second photodetector that detects a second measurement light that is based on incident light and has passed through or reflected by the second filter and outputs a second detection signal; and a calculation unit that acquires the standard deviation or variance in the wavelength spectrum of the incident light based on the first detection signal and the second detection signal.

2. An optical information acquisition device as described in claim 1, further comprising: a third filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range; and a third photodetector that detects third measurement light that is transmitted through or reflected by said third filter based on incident light and outputs a third detection signal, wherein said calculation unit acquires the skewness in the wavelength spectrum of said incident light based on said first detection signal, said second detection signal, and said third detection signal.

3. The optical information acquisition device of claim 2, further comprising: a fourth filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range; and a fourth photodetector that detects fourth measurement light that is transmitted through or reflected by the fourth filter based on incident light and outputs a fourth detection signal, wherein the calculation unit acquires the kurtosis in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, the third detection signal, and the fourth detection signal.

4. The optical information acquisition device of claim 1, wherein the first filter and the second filter have a characteristic in which the transmittance changes linearly depending on the wavelength, the first photodetector detects the first measurement light that is the incident light that has been transmitted through or reflected by the first filter, and the second photodetector detects the second measurement light that is the incident light that has been transmitted through or reflected by the second filter after being transmitted through or reflected by the first filter.

5. The optical information acquisition device of claim 2, wherein the first filter, the second filter, and the third filter have a characteristic that the transmittance changes linearly depending on the wavelength, the first photodetector detects the first measurement light obtained by transmitting or reflecting the incident light through the first filter, the second photodetector detects the second measurement light obtained by transmitting or reflecting the incident light through the second filter after transmitting or reflecting the first filter, and the third photodetector detects the third measurement light obtained by transmitting or reflecting the incident light through the first filter after transmitting or reflecting the second filter and further transmitting or reflecting the third filter.

6. The optical information acquisition device according to claim 3, wherein the first filter, the second filter, the third filter, and the fourth filter have a characteristic that the transmittance changes linearly depending on the wavelength, the first photodetector detects first measurement light obtained by transmitting or reflecting the first filter from the incident light, the second photodetector detects second measurement light obtained by transmitting or reflecting the second filter from the incident light after transmitting or reflecting the first filter, the third photodetector detects third measurement light obtained by transmitting or reflecting the first filter from the incident light after transmitting or reflecting the second filter and then transmitting or reflecting the third filter, and the fourth photodetector detects fourth measurement light obtained by transmitting or reflecting the first filter from the incident light after transmitting or reflecting the second filter, then transmitting or reflecting the third filter, and then transmitting or reflecting the fourth filter.

7. The optical information acquisition device of claim 1, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light that is the incident light that has been transmitted through or reflected by the first filter, and the second photodetector detects the second measurement light that is the incident light that has been transmitted through or reflected by the second filter.

8. The optical information acquisition device of claim 2, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the third filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light obtained by transmitting or reflecting the first filter from the incident light, the second photodetector detects the second measurement light obtained by transmitting or reflecting the second filter from the incident light, and the third photodetector detects the third measurement light obtained by transmitting or reflecting the third filter from the incident light.

9. The optical information acquisition device of claim 3, wherein the first filter has a characteristic that the transmittance changes linearly depending on the wavelength, the second filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the third filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the fourth filter has a characteristic that the transmittance changes curvedly depending on the wavelength, the first photodetector detects the first measurement light obtained by transmitting or reflecting the first filter from the incident light, the second photodetector detects the second measurement light obtained by transmitting or reflecting the second filter from the incident light, the third photodetector detects the third measurement light obtained by transmitting or reflecting the third filter from the incident light, and the fourth photodetector detects the fourth measurement light obtained by transmitting or reflecting the fourth filter from the incident light.

10. The optical information acquisition device according to claim 7, wherein the second filter has two filters having a characteristic that the transmittance changes linearly depending on the wavelength.

11. The optical information acquisition device according to claim 8, wherein the third filter has three filters having the characteristic that the transmittance changes linearly depending on the wavelength.

12. The optical information acquisition device according to claim 9, wherein the fourth filter has four filters having a characteristic that the transmittance changes linearly depending on the wavelength.

13. A method for acquiring optical information comprising: a first optical detection step of detecting a first measurement light that is transmitted through or reflected by a first filter based on incident light using a first filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range, and outputting a first detection signal; a second optical detection step of detecting a second measurement light that is transmitted through or reflected by the second filter based on incident light using a second filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range, and outputting a second detection signal; and a calculation step of acquiring the standard deviation or variance in the wavelength spectrum of the incident light based on the first detection signal and the second detection signal.

14. The optical information acquisition method according to claim 13, further comprising a third optical detection step of using a third filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range to detect third measurement light that is transmitted through or reflected by the third filter based on the incident light, and outputting a third detection signal, wherein in the calculation step, the skewness in the wavelength spectrum of the incident light is acquired based on the first detection signal, the second detection signal, and the third detection signal.

15. The optical information acquisition method according to claim 14, further comprising a fourth optical detection step of using a fourth filter having a characteristic that transmittance changes depending on wavelength in a predetermined wavelength range to detect fourth measurement light that is transmitted through or reflected by the fourth filter based on the incident light, and outputting a fourth detection signal, wherein in the calculation step, kurtosis in the wavelength spectrum of the incident light is acquired based on the first detection signal, the second detection signal, the third detection signal, and the fourth detection signal.

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