Camera

Abstract

A camera 1 includes: a prism 5 having an input surface 5a that receives incident light I0, a filter surface 5b that generates measurement light by reflecting incident light I0 and generates output light by transmitting incident light I0, and an output surface 5c that outputs the measurement light; a prism 7 having an input surface 7a that is adjacent to the filter surface 5b and that receives the output light, a filter surface 7b that generates measurement light by reflecting the output light that has passed through the input surface 7a, and generates output light by transmitting the output light, and an output surface 7c that outputs the measurement light; a prism 9 having an input surface 9a that is adjacent to the filter surface 7b and that receives the output light, and an output surface 9c that outputs the output light as measurement light; and optical detectors 11, 13, 15 that detect each measurement light. The filter surfaces 5b and 7b are provided with inclined dichroic mirrors 170 and 171, respectively, having a transmittance that changes linearly with wavelength in a predetermined wavelength region.

Description

camera

[0001] The present invention relates to a camera used to obtain characteristic information about the wavelength spectrum of incident light.

[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 such problems, and aims to provide a camera that can acquire characteristics related to the wavelength spectrum of incident light.

[0006] A camera according to a first aspect of the embodiment includes a first prism having a first input surface that receives incident light, a first filter surface that reflects a portion of the incident light that has passed through the first input surface to generate first measurement light and transmits the other portion of the incident light to generate first output light, and a first output surface that outputs the first measurement light, a second prism that is adjacent to the first filter surface and has a second input surface that receives the first output light, a second filter surface that reflects a portion of the first output light that has passed through the second input surface to generate second measurement light and transmits the other portion of the first output light to generate second output light, and a second output surface that outputs the second measurement light, and a second filter surface that outputs the second measurement light. a third prism having a third input surface adjacent to the first filter surface and a third output surface for receiving the second output light and outputting the second output light as a third measurement light; a first photodetector for detecting the first measurement light and outputting a first detection signal; a second photodetector for detecting the second measurement light and outputting a second detection signal; and a third photodetector for detecting the third measurement light and outputting a third detection signal, wherein the first filter surface is provided with a first filter having a characteristic that transmittance changes linearly with wavelength in a predetermined wavelength range, and the second filter surface is provided with a second filter having a characteristic that transmittance changes linearly with wavelength in a predetermined wavelength range.

[0007] According to the first aspect, a portion of incident light is reflected by a first filter to generate a first measurement light, and another portion of the incident light passes through the first filter and is then reflected by a second filter to generate a second measurement light. Furthermore, another portion of the incident light passes through the first filter and is then passed through the second filter to generate a third measurement light. A first detection signal that detects the first measurement light is output by the first photodetector, a second detection signal that detects the second measurement light is output by the second photodetector, and a third detection signal that detects the third measurement light is output by the third photodetector. Here, the first filter and the second filter have a characteristic in which transmittance changes linearly with wavelength in a predetermined wavelength range. Therefore, by performing an operation using the intensity of the detected light based on the first to third detection signals, a moment related to the wavelength spectrum of the incident light can be calculated, and characteristics related to the wavelength spectrum of the incident light can be easily obtained.

[0008] A camera according to a second aspect of the embodiment includes a first prism having a first input surface that receives incident light, a first filter surface that reflects a portion of the incident light that has passed through the first input surface to generate first measurement light and transmits the other portion of the incident light to generate first output light, and a first output surface that outputs the first measurement light, a second prism that is adjacent to the first filter surface and receives the first output light, a second filter surface that reflects a portion of the first output light that has passed through the second input surface to generate second measurement light and transmits the other portion of the first output light to generate second output light, and a second output surface that outputs the second measurement light, a third input surface that is adjacent to the second filter surface and receives the second output light, and a third output surface that outputs the second output light. a third prism having a third output surface that outputs the first measurement light as a third measurement light, a first photodetector that detects the first measurement light and outputs a first detection signal, a second photodetector that detects the second measurement light and outputs a second detection signal, and a third photodetector that detects the third measurement light and outputs a third detection signal, wherein the first filter surface is provided with a beam splitter that has a property of reflecting a part of the incident light in a predetermined wavelength range and transmitting the other part of the incident light, the second filter surface is provided with a first filter that has a property of transmittance that changes linearly with wavelength in the predetermined wavelength range, and the third output surface is provided with a second filter that has a property of transmittance that changes linearly with wavelength in the predetermined wavelength range.

[0009] According to the second aspect, a portion of the incident light is reflected by the beam splitter to generate a first measurement light, and another portion of the incident light passes through the beam splitter and is then reflected by the first filter to generate a second measurement light. Furthermore, another portion of the incident light passes through the beam splitter, and the other portion passes sequentially through the first filter and the second filter to generate a third measurement light. The first photodetector outputs a first detection signal detecting the first measurement light, the second photodetector outputs a second detection signal detecting the second measurement light, and the third photodetector outputs a third detection signal detecting the third measurement light. Here, the beam splitter has a characteristic of reflecting a portion of the incident light in a predetermined wavelength range and transmitting the other portion of the incident light, and the first filter and the second filter have a characteristic of having transmittance that varies linearly with wavelength in the predetermined wavelength range. Therefore, by performing an operation using the intensity of the detected light based on the first to third detection signals, a moment related to the wavelength spectrum of the incident light can be calculated, and characteristics related to the wavelength spectrum of the incident light can be easily obtained.

[0010] A camera according to a third aspect of the embodiment includes a first prism having a first input surface that receives incident light, a first filter surface that reflects a portion of the incident light that has passed through the first input surface to generate first measurement light and transmits the other portion of the incident light to generate first output light, and a first output surface that outputs the first measurement light, a second prism that is adjacent to the first filter surface and receives the first output light, a second filter surface that reflects a portion of the first output light that has passed through the second input surface to generate second measurement light and transmits the other portion of the first output light to generate second output light, and a second output surface that outputs the second measurement light, a third input surface that is adjacent to the second filter surface and receives the second output light, a third filter surface that reflects a portion of the second output light that has passed through the third input surface to generate third measurement light and transmits the other portion of the second output light to generate third output light, and a third prism that outputs the third measurement light. the third prism having a third output surface, a fourth prism having a fourth input surface adjacent to the third filter surface and receiving the third output light, and a fourth output surface outputting the third output light as fourth measurement light; a first photodetector detecting the first measurement light and outputting a first detection signal; a second photodetector detecting the second measurement light and outputting a second detection signal; a third photodetector detecting the third measurement light and outputting a third detection signal; and a fourth photodetector detecting the fourth measurement light and outputting a fourth detection signal, wherein the first filter surface is provided with a first filter having a characteristic that transmittance varies linearly with wavelength in a predetermined wavelength range, the second filter surface is provided with a second filter having a characteristic that transmittance varies linearly with wavelength in the predetermined wavelength range, and the third filter surface is provided with a third filter having a characteristic that transmittance varies linearly with wavelength in the predetermined wavelength range.

[0011] According to the third aspect, a portion of incident light is reflected by a first filter to generate a first measurement light, another portion of the incident light passes through the first filter and is then reflected by a second filter to generate a second measurement light, and another portion of the incident light passes through the second filter to generate a second output light. Also, a portion of the second output light is reflected by a third filter to generate a third measurement light, and another portion of the second output light passes through the third filter to generate a fourth measurement light. Then, a first detection signal representing the detection of the first measurement light is output by the first photodetector, a second detection signal representing the detection of the second measurement light is output by the second photodetector, a third detection signal representing the detection of the third measurement light is output by the third photodetector, and a fourth detection signal representing the detection of the fourth measurement light is output by the fourth photodetector. Here, the first filter, the second filter, and the third filter have the characteristic that the transmittance changes linearly depending on the wavelength in a predetermined wavelength range. Therefore, by performing calculations using the intensity of the detected light based on the first to fourth detection signals, the moment related to the wavelength spectrum of the incident light can be calculated, and the characteristics related to the wavelength spectrum of the incident light can be easily obtained.

[0012] A camera according to a fourth aspect of the embodiment includes a first prism having a first input surface that receives incident light, a first filter surface that reflects a portion of the incident light that has passed through the first input surface to generate first measurement light and transmits the other portion of the incident light to generate first output light, and a first output surface that outputs the first measurement light; a second input surface that is close to the first filter surface and receives the first output light, and a second filter surface that reflects a portion of the first output light that has passed through the second input surface to generate second measurement light and transmits the other portion of the first output light. a second prism having a second filter surface that transmits the remaining portion of the second output light to generate second output light, and a second output surface that outputs the second measurement light; a third input surface that is adjacent to the second filter surface and receives the second output light; a third filter surface that reflects a portion of the second output light that has passed through the third input surface to generate third measurement light and transmits the remaining portion of the second output light to generate third output light; and a third output surface that outputs the third measurement light; the fourth prism having a fourth input surface that receives the third output light and a fourth output surface that outputs the third output light as a fourth measurement light; a first photodetector that detects the first measurement light and outputs a first detection signal; a second photodetector that detects the second measurement light and outputs a second detection signal; a third photodetector that detects the third measurement light and outputs a third detection signal; and a fourth photodetector that detects the fourth measurement light and outputs a fourth detection signal; the first filter surface is provided with a beam splitter that has a characteristic of reflecting a part of the incident light in a predetermined wavelength range and transmitting the other part of the incident light; the second filter surface is provided with a first filter that has a characteristic of transmittance that varies linearly with wavelength in the predetermined wavelength range; the third filter surface is provided with a second filter that has a characteristic of transmittance that varies linearly with wavelength in the predetermined wavelength range; and the fourth output surface is provided with a third filter that has a characteristic of transmittance that varies linearly with wavelength in the predetermined wavelength range.

[0013] According to the fourth aspect, a part of the incident light is reflected by the beam splitter to generate a first measurement light, and another part of the incident light passes through the beam splitter, and then a part of the incident light is reflected by the first filter to generate a second measurement light, and the other part passes through the first filter to generate a second output light. Also, a part of the second output light is reflected by the second filter to generate a third measurement light, and the other part of the second output light passes sequentially through the second filter and the third filter to generate a fourth measurement light. Then, a first detection signal representing the detection of the first measurement light is output by the first photodetector, a second detection signal representing the detection of the second measurement light is output by the second photodetector, a third detection signal representing the detection of the third measurement light is output by the third photodetector, and a fourth detection signal representing the detection of the fourth measurement light is output by the fourth photodetector. Here, the beam splitter has the property of reflecting a portion of the incident light in a predetermined wavelength range and transmitting the other portion of the incident light, and the first filter, second filter, and third filter have the property that the transmittance changes linearly depending on the wavelength in the predetermined wavelength range. Therefore, by performing an operation using the intensity of the detected light based on the first to fourth detection signals, it is possible to calculate the moment related to the wavelength spectrum of the incident light, and it is possible to easily obtain the characteristics related to the wavelength spectrum of the incident light.

[0014] According to any aspect of the present embodiment, it is possible to obtain characteristics related to the wavelength spectrum of incident light.

[0015] FIG. 1 is a schematic configuration diagram of a measurement system 100 according to a first embodiment. FIG. 2 is a diagram showing a detailed configuration of a camera 1 shown in FIG. 1. FIG. 3 is a block diagram showing the hardware configuration of a calculation device shown in FIG. 1. FIG. 4 is a diagram showing a detailed configuration of a camera 1A according to a second embodiment. FIG. 5 is a diagram showing a detailed configuration of a camera 1B according to a first modified example. FIG. 6 is a graph showing an example of the transmission characteristics of an inclined dichroic mirror. FIG. 7 is a diagram showing a detailed configuration of a camera 1C according to a second modified example. FIG. 8 is a diagram showing a detailed configuration of a camera 1D according to a third modified example. FIG. 9 is a diagram showing a detailed configuration of a camera 1E according to a fourth modified example.

[0016] 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]

[0017] 1 is a schematic diagram of a measurement system 100 according to the first embodiment. The measurement system 100 of this embodiment includes a camera 1 and a calculation device (calculation unit) 105, and detects incident light I ０ The camera 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 I ０ The calculation device 105 converts the incident light I into a plurality of measurement lights and detects the light intensities (light amounts) of the plurality of measurement lights. 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.

[0018] The internal configuration of the camera 1 will be described with reference to Fig. 2. Fig. 2 is a diagram showing the detailed configuration of the camera 1 shown in Fig. 1.

[0019] The camera 1 incorporates a polarizing plate (polarizing element) 3, three prisms 5, 7, and 9, and three photodetectors 11, 13, and 15. The polarizing plate 3 polarizes incident light I ０ , and the incident light I ０ The polarizing plate 3 is an optical element that transmits only the linearly polarized light component (for example, p-polarized or s-polarized light) of the incident light I and makes it incident on the three prisms 5, 7, and 9. ０ The three prisms 5, 7, and 9 convert the incident light I from the polarizer 3 into linearly polarized light. ０ are arranged one on top of the other in this order along the direction of incidence.

[0020] The prism (first prism) 5 reflects the incident light I ０ An input surface (first input surface) 5a is substantially perpendicular to the incident direction of the incident light I ０The prism (second prism) 7 has an input surface (second input surface) 7a adjacent to the filter surface 5b, an output surface (first output surface) 5c, and a filter surface (first filter surface) 5b tilted from a plane perpendicular to the incident direction of the incident light I. ０ The prism (third prism) 9 has an input surface (third input surface) 9a adjacent to the filter surface 7b, and an output surface (second output surface) 7c facing the input surface 9a. ０ The prism 5 has a shape of a substantially square prism including an output surface (third output surface) 9c as a side surface, which is substantially perpendicular to the direction of incidence of the prism 7. The filter surface 5b of the prism 5 has an inclined dichroic mirror (first filter) 17 at a portion close to the prism 7. ０ In addition, an inclined dichroic mirror (second filter) 17 is formed on the filter surface 7b of the prism 7 in the vicinity of the prism 9. １ is formed.

[0021] The prisms 5, 7, and 9 configured as described above function as follows: In the prism 5, the incident light I is converted into linearly polarized light by the polarizer 3 at the input surface 5a. ０ , and the incident light I passes through the input surface 5a and passes through the medium of the prism 5. ０ A part of the reflected light (first measurement light) I is reflected on the filter surface 5b. Ｒ０ and the incident light I ０ The other part of the light is transmitted through the filter surface 5b to produce transmitted light (first output light) I Ｔ０ In addition, in the prism 5, the reflected light I reflected on the filter surface 5b is Ｒ０ is further totally reflected by the input surface 5a and emitted (output) to the outside from the output surface 5c.

[0022] In the prism 7, the transmitted light I Ｔ０ , and the transmitted light I passes through the input surface 7a and passes through the medium of the prism 7. Ｔ０ A part of the reflected light (second measurement light) I is reflected on the filter surface 7b. Ｒ１ and the transmitted light I Ｔ０The other part of the light is transmitted through the filter surface 7b to produce transmitted light (second output light) I Ｔ１ In addition, in the prism 7, the reflected light I reflected on the filter surface 7b is Ｒ１ is further totally reflected by the input surface 7a and emitted (output) to the outside from the output surface 7c. Ｒ１ The total reflection of the reflected light I at the input surface 7a occurs when an air gap is formed between the prism 5 and the prism 7, or when the reflected light I Ｒ１ This can be achieved by applying mirror processing to the reflective parts.

[0023] In the prism 9, the transmitted light I Ｔ１ , and the transmitted light I passes through the input surface 9a and passes through the medium of the prism 9. Ｔ１ is emitted (output) to the outside from the output surface 9c as the third measurement light.

[0024] Two inclined dichroic mirrors 17 formed on the filter surface 5b and the filter surface 7b ０ , 17 １ are filter members made of special optical materials, and have the property that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. ０ , 17 １ Each of the inclined dichroic mirrors 17 has a characteristic that the transmittance of light in a predetermined wavelength range changes monotonically in response to a change in wavelength (for example, a characteristic that the transmittance in a predetermined wavelength range increases or decreases monotonically). ０ , 17 １ is the transmittance T expressed by the following formulas (1) and (2), respectively, where λ is the wavelength of incident light. ０ (λ), T １ (λ) characteristics. The tilted dichroic mirror is also called an LRG (Linear Reflectance Gradient on the wavelength axis) filter. Such a tilted dichroic mirror 17 ０ , 17 １The 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) In the above formulas (1) and (2), a ０ , a １ , b ０ , b １ 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 , 17 １ is set to have the above transmittance characteristics for the incident light of linearly polarized light (for example, p-polarized light or s-polarized light) converted by the polarizer 3. Note that the constant a ０ , a １ , b ０ , b １ 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 １ , b ０ , b １ may be estimated.

[0025] The photodetector 11 is disposed close to the output surface 5c of the prism 5, and detects the reflected light I that is reflected twice within the prism 5 and output. Ｒ０ The photodetector 13 is disposed close to the output surface 7c of the prism 7 and detects the light intensity of the reflected light I that is reflected twice within the prism 7 and output, and outputs a detection signal (first detection signal). Ｒ１The photodetector 15 is disposed close to the output surface 9c of the prism 9, and detects the light intensity of the transmitted light I that has been transmitted through the prisms 5, 7, and 9 in this order and outputted as a detection signal (second detection signal). Ｔ１ The three photodetectors 11, 13, and 15 may be point sensors capable of detecting the light intensity of the spot light, line sensors capable of detecting the one-dimensional distribution of light intensity, or two-dimensional area sensors capable of detecting the two-dimensional distribution of light intensity.

[0026] Here, the reflected light I Ｒ１ Reflected light I Ｒ０ Taking into account the attenuation compared to the single reflected light I Ｒ１ The exposure time for detecting the reflected light I Ｒ０ The exposure time may be set to be longer than the exposure time for detecting the transmitted light I. Ｔ１ Reflected light I Ｒ０ Considering the attenuation compared to the light I Ｔ１ The exposure time for detecting the reflected light I Ｒ０ The exposure time may be set to be longer than the exposure time for the detection of the first light.

[0027] The calculation unit 105 calculates the incident light I based on the detection signals output from the three photodetectors 11, 13, and 15. ０The computing device 105 calculates characteristic values ​​related to the wavelength spectrum of the light. FIG. 3 is a block diagram showing the hardware configuration of the computing device 105. As shown in FIG. 3, the computing device 105 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 computing device 105 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 computing device 105 may also be configured as a microcomputer or an FPGA. The computing device 105 may also be configured by multiple computers, or may be built into the camera 1 and integrated into the camera 1.

[0028] The arithmetic unit 105 calculates the incident light I ０ The wavelength spectrum of the incident light I is calculated based on the center wavelength and standard deviation of the wavelength spectrum. ０ The light intensity is represented by the symbol I ０ and the reflected light I Ｒ０ , I Ｒ１ The light intensity of each is represented by the symbol I Ｒ０ , I Ｒ１ and the transmitted light I Ｔ０ , I Ｔ１ The light intensity of each is represented by the symbol I １ , I ２ Or I Ｔ０ , I Ｔ１ It shall be expressed as:

[0029] The arithmetic unit 105 calculates the incident light I ０ The centroid wavelength λ is the first moment 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 ×f０ (λ), and the transmitted light I Ｔ０ 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 (3) holds: holds true.

[0030] According to the above principle, the calculation device 105 calculates the light intensity I based on the detection signals output from the photodetectors 11, 13, and 15. Ｒ０ , I Ｔ０ (=I Ｒ１ +I Ｔ１ ) into the following formula (4); By substituting into the above, the incident light I ０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ That is, the calculation device 105 calculates the incident light I based on the detection signals from each photodetector. 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 Get.

[0031] Furthermore, the arithmetic unit 105 calculates the incident light I ０ The standard deviation σ, which is the second moment of the wavelength spectrum of ０ 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 (3): Therefore, the following equation holds: is derived, and from this equation, the following equation (5) is established as a transformation equation for lowering the order of the moment.

[0032] Furthermore, when the relationship of formula (5) 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.

[0033] According to the above principle, the calculation device 105 calculates the light intensity I based on the detection signals output from the photodetectors 11, 13, and 15. Ｒ０ , I Ｒ１ , I Ｔ１ is expressed by the following formula (6): By substituting into the above, the incident light I ０ Standard deviation σ in the wavelength spectrum of ０ That is, the calculation device 105 calculates the incident light I based on the detection signals from each photodetector. 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 Here, the calculation device 105 obtains the standard deviation σ ０ Instead of variance σ ０ ２ may be calculated.

[0034] Furthermore, the calculation device 105 calculates the centroid wavelength λ Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ) 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.

[0035] According to the camera 1 according to the first embodiment described above, incident light I ０ A part of the inclined dichroic mirror 17 ０ Reflected light I is reflected by Ｒ０ occurs, and the incident light I ０ The other part is an inclined dichroic mirror 17 ０After passing through the inclined dichroic mirror 17 １ Reflected light I is reflected by Ｒ１ In addition, the incident light I ０ The other part is an inclined dichroic mirror 17 ０ After passing through the inclined dichroic mirror 17, the other part １ Transmitted light I Ｔ１ Then, the reflected light I Ｒ０ The reflected light I is detected by the photodetector 13 and output as a detection signal. Ｒ１ The photodetector 15 detects the transmitted light I Ｔ１ The inclined dichroic mirror 17 outputs a detection signal that detects the ０ and tilted dichroic mirror 17 １ has the property that the transmittance changes linearly depending on the wavelength in a predetermined wavelength range, so by calculating using the intensity of the detected light based on the three detection signals, the incident light I ０ The moment of the wavelength spectrum of the incident light I can be calculated easily. ０ The wavelength spectrum characteristics can be obtained.

[0036] In the first embodiment, the incident light I ０ The calculation unit 105 is provided to obtain characteristic values ​​relating to the wavelength spectrum of the incident light, i.e., the centroid wavelength and standard deviation in the wavelength spectrum of the incident light. In this way, the incident light I can be calculated using the three detection signals. ０ In particular, by performing calculations using three detection signals, the amount of data required to measure the distribution of the wavelength spectrum of light can be reduced, and the incident light I can be easily measured. ０ The wavelength spectrum characteristics can be obtained.

[0037] In the first embodiment, the exposure time of the measurement light in the photodetector 13 is set to be longer than the exposure time of the measurement light in the photodetector 11, and the exposure time of the measurement light in the photodetector 15 is set to be even longer than the exposure time of the measurement light in the photodetector 11. In this case, the detection signal can be output taking into account the attenuation of the measurement light, so the incident light I to be acquired can be ０ This can improve the accuracy of the characteristics related to the wavelength spectrum.

[0038] In the first embodiment, the photodetectors 11, 13, and 15 are configured as point sensors, line sensors, or area sensors. ０ It is possible to obtain either a characteristic value relating to the wavelength spectrum of the light, a one-dimensional distribution of the characteristic value, or a two-dimensional distribution of the characteristic value.

[0039] In the first embodiment, a polarizing plate (polarizing element) 3 is provided. This polarizes the incident light I ０ Only the linearly polarized light component (for example, p-polarized light or s-polarized light) of the incident light I can be incident. ０ The inclined dichroic mirror 17 is not affected by the polarization state of the ０ , 17 １ Incident light I at ０ Or transmitted light I Ｔ０ The transmission characteristics of the incident light I can be stabilized. ０ The accuracy of the characteristics relating to the wavelength spectrum can be improved.

[0040] Next, the configuration of the camera 1A according to the second embodiment will be described with reference to Fig. 4, which is a diagram showing the detailed configuration of the camera 1A according to the second embodiment.

[0041] The camera 1A according to the second embodiment detects incident light I from the polarizing plate 3. ０ The second embodiment differs from the camera 1 according to the first embodiment in that it includes four prisms 5, 7, 9, and 21 and four photodetectors 11, 13, 15, and 17 that are arranged one on top of the other in this order along the direction of incidence of the light. The following description will focus on the differences between the first embodiment and the second embodiment.

[0042] The two prisms 5 and 7 and the two photodetectors 11 and 13 have the same configuration as in the first embodiment. The prism (third prism) 9 has an input surface (third input surface) 9a adjacent to the filter surface 7b, and an input surface (third input surface) 9b for inputting the incident light I ０ The prism (fourth prism) 21 has an input surface (fourth input surface) 21a adjacent to the filter surface 9b, and an output surface (third output surface) 9c facing the input surface 21a. ０ The prism 9 has a shape of a substantially square prism including an output surface (fourth output surface) 21c as a side surface, which is substantially perpendicular to the direction of incidence of the prism 21. The filter surface 9b of the prism 9 has an inclined dichroic mirror (third filter) 17 at a portion close to the prism 21. ２ is formed.

[0043] The prisms 9 and 21 configured as described above function as follows: In the prism 9, transmitted light I Ｔ１ , and the transmitted light I passes through the input surface 9a and passes through the medium of the prism 9. Ｔ１ A part of the reflected light (third measurement light) I is reflected on the filter surface 9b. Ｒ２ and the transmitted light I Ｔ１ The other part of the light is transmitted through the filter surface 9b to produce transmitted light (third output light) I Ｔ２ In addition, in the prism 9, the reflected light I reflected on the filter surface 9b is Ｒ２ is further totally reflected by the input surface 9a and emitted (output) from the output surface 9c. Ｒ２ The total reflection of the light I at the input surface 9a occurs when an air gap is formed between the prism 7 and the prism 9, or when the light I Ｒ２ This can be achieved by applying mirror processing to the reflective parts.

[0044] In the prism 21, the transmitted light I Ｔ２ , and the transmitted light I passes through the input surface 21a and passes through the medium of the prism 21. Ｔ２ is emitted (output) to the outside from the output surface 21c as the fourth measurement light.

[0045] An inclined dichroic mirror 17 formed on the filter surface 9b ２ is an inclined dichroic mirror 17 ０ , 17 １ Similarly to the inclined dichroic mirror 17, the inclined dichroic mirror 17 is a filter member made of a special optical material, and has the property that the transmittance of light in a predetermined wavelength range changes linearly depending on the wavelength. ２ is the transmittance T expressed by the following formula (7) when the wavelength of incident light is λ. ２ (λ). The inclined dichroic mirror 17 ２ is an inclined dichroic mirror 17 ０ , 17 １ By using tilted dichroic mirrors formed using the same film formation process, it is possible to reduce variations in transmittance characteristics between tilted dichroic mirrors due to manufacturing errors, and thus reduce measurement errors. ２ (λ) = a ２ λ+b ２ ... (7) In the above formula (7), a ２ , b ２ 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. ２ is set to have the above transmittance characteristics for the incident light of linearly polarized light (for example, p-polarized light or s-polarized light) converted by the polarizer 3. Note that the constant a ２ , b ２ 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. ２ , b ２ may be estimated.

[0046] The photodetector 15 is disposed close to the output surface 9c of the prism 9 and detects the reflected light IＲ２ The photodetector 17 detects the light intensity of the transmitted light I that is transmitted through the prisms 5, 7, 9, and 21 in order and outputted as a detection signal (third detection signal). Ｔ２ The photodetector 17 may be a point sensor capable of detecting the light intensity of the spot light, a line sensor capable of detecting a one-dimensional distribution of light intensity, or a two-dimensional area sensor capable of detecting a two-dimensional distribution of light intensity.

[0047] Here, the reflected light I Ｒ２ Reflected light I Ｒ０ Taking into account the attenuation compared to the single reflected light I Ｒ２ The exposure time for detecting the reflected light I Ｒ０ The exposure time may be set to be longer than the exposure time for detecting the transmitted light I. Ｔ２ Reflected light I Ｒ０ Considering the attenuation compared to the light I Ｔ２ The exposure time for detecting the reflected light I Ｒ０ The exposure time may be set to be longer than the exposure time for the detection of the first light.

[0048] In the second embodiment, the calculation device 105 calculates the incident light I based on the detection signals output from the four photodetectors 11, 13, 15, and 17. ０ The reflected light I has a function of calculating the centroid wavelength, standard deviation, and skewness of the wavelength spectrum as characteristic values ​​related to the wavelength spectrum. Ｒ２ The light intensity is represented by the symbol I Ｒ２ and the transmitted light I Ｔ２ The light intensity is represented by the symbol I ３ Or I Ｔ２ It shall be expressed as:

[0049] The calculation unit 105 calculates the light intensity I based on the detection signals output from the photodetectors 11, 13, 15, and 17. Ｒ０ , I Ｔ０ (=I Ｒ１ +I Ｒ２ +I Ｔ２ ), I Ｒ１ , IＴ１ (=I Ｒ２ +I Ｔ２ ) to calculate the centroid wavelength and standard deviation of the wavelength spectrum in the same manner as in the first embodiment. ０ The skewness S is the third moment of the wavelength spectrum of ０ The principle of this function is as follows: When the relationship of equation (5) is added to the definition of skewness, the following equation is obtained: Here, the following formula is satisfied: also holds true.

[0050] According to the above principle, the calculation device 105 calculates the light intensity I based on the detection signals output from the photodetectors 11, 13, 15, and 17. Ｒ０ , I Ｒ１ , I Ｒ２ , I Ｔ２ is expressed by the following formula (8): By substituting into the above, the incident light I ０ The skewness S in the wavelength spectrum of ０ That is, the calculation device 105 calculates the incident light I based on the detection signals from each photodetector. 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 calculation device 105 obtains the centroid wavelength λ obtained by the above-mentioned calculation method. Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ), skewness S ０ is output to the specified output destination.

[0051] According to the second embodiment, the incident light I ０ A part of the inclined dichroic mirror 17 ０ Reflected light I is reflected by Ｒ０ occurs, and the incident light I ０ The other part is an inclined dichroic mirror 17 ０ After passing through the inclined dichroic mirror 17, a part of the light passes through the inclined dichroic mirror 17. １ Reflected light I is reflected by Ｒ１ and a part of it is incident on the inclined dichroic mirror 17１ Transmitted light I Ｔ１ In addition, the transmitted light I Ｔ１ A part of the inclined dichroic mirror 17 ２ Reflected light I is reflected by Ｒ２ is generated, and the transmitted light I Ｔ１ The other part is an inclined dichroic mirror 17 ２ Transmitted light I Ｔ２ Then, the reflected light I Ｒ０ The reflected light I is detected by the photodetector 13 and output as a detection signal. Ｒ１ The reflected light I is detected by the photodetector 15 and output as a detection signal. Ｒ２ is output as a detection signal, and the transmitted light I Ｔ２ Here, the inclined dichroic mirror 17 outputs a detection signal that detects ０ , 17 １ , 17 ２ has the property that the transmittance changes linearly depending on the wavelength in a predetermined wavelength range, so by calculating using the intensity of the detected light based on the four detection signals, the incident light I ０ The moment of the wavelength spectrum of the incident light I can be calculated easily. ０ The wavelength spectrum characteristics can be obtained.

[0052] In the second embodiment, a calculation device 105 is provided that acquires, based on the four detection signals, the centroid wavelength, standard deviation, variance, and skewness of the wavelength spectrum of the incident light as characteristic values ​​related to the wavelength spectrum of the incident light. ０ In particular, by performing calculations using four detection signals, the amount of data required to measure the distribution of the wavelength spectrum of light can be reduced, and the incident light I can be easily measured. ０ The wavelength spectrum characteristics can be obtained.

[0053] In the second embodiment, the exposure time of the measurement light in the photodetector 17 is set to be longer than the exposure time of the measurement light in the photodetector 11.Ｔ２ Since the detection signal can be output taking into account the attenuation of the incident light I ０ This can improve the accuracy of the characteristics related to the wavelength spectrum.

[0054] In the second embodiment, the photodetectors 11, 13, 15, and 17 are configured as point sensors, line sensors, or area sensors. ０ It is possible to obtain either a characteristic value relating to the wavelength spectrum of the light, a one-dimensional distribution of the characteristic value, or a two-dimensional distribution of the characteristic value.

[0055] In the second embodiment, a polarizing plate (polarizing element) 3 is provided. This polarizes the incident light I ０ The inclined dichroic mirror 17 can allow only the linearly polarized light component (for example, p-polarized or s-polarized light) to enter. ０ , 17 １ , 17 ２ Incident light I at ０、 Transmitted light I Ｔ０ , or transmitted light I Ｔ１ The transmission characteristics of the incident light I can be stabilized. ０ The accuracy of the characteristics relating to the wavelength spectrum can be improved.

[0056] 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.

[0057] The tilted dichroic mirror 17 in the camera 1 according to the first embodiment described above ０ , 17 １ or the light transmittance characteristics of the inclined dichroic mirror 17 in the camera 1A according to the second embodiment. ０ , 17 １ , 17 ２The light transmittance characteristics of the inclined dichroic mirrors may be different from each other or may be the same from each other. When multiple inclined dichroic mirrors having the same transmittance characteristics are used, the calculation formula for the characteristic values ​​used by the calculation device 105 is simplified, and the calculation speed is improved. When the inclined dichroic mirrors have different characteristics from each other, the cameras 1 and 1A may be configured by combining a mirror with a transmittance characteristic that increases with wavelength and a mirror with a transmittance characteristic that decreases with wavelength.

[0058] The camera 1 according to the first embodiment described above may be modified to have the configuration of a camera 1B according to a first modified example shown in Fig. 5. That is, in the camera 1B, a depolarizing plate (depolarizing element) 33 is provided instead of the polarizing plate 3, a depolarizing plate (depolarizing element) 35 is provided on the filter surface 7b of the prism 7 so as to cover the filter surface 7b, and an inclined dichroic mirror 17 is provided on the depolarizing plate 35. １ is formed.

[0059] The depolarization plate 33 is a plate-shaped member made of quartz or the like, and depolarizes the incident light I ０ and transmits the incident light I ０ is converted into unpolarized light and made incident on the input surface 5a of the prism 5. ０ On the surface on which the incident light I ０ The optical fiber is coated with a bandpass filter that transmits only a predetermined wavelength range. Regarding the transmission characteristics of the predetermined wavelength range, if the detection sensitivity of the photodetector with respect to the wavelength is not flat, correction is made taking into account the detection sensitivity of the photodetector with respect to the wavelength, so that the centroid wavelength λ Ｇ０ , standard deviation σ ０ (or variance σ ０ ２ ), skewness S ０ can be determined more accurately.

[0060] The depolarizing plate 35 is ０ and inclined dichroic mirror 17 １ and a plate-shaped member made of quartz or the like arranged between the Ｔ０ and transmits the transmitted light I Ｔ０is converted into unpolarized light and is then incident on the inclined dichroic mirror 17 １ The depolarization plate 35 may also function as a low-pass filter that removes high-frequency components of the optical resolution by utilizing the birefringence of the crystal to prevent moiré in the pattern. Instead of being provided as a separate member, the depolarization plate 35 may be formed by the medium itself, such as the quartz prism of the prism 7.

[0061] According to the camera 1B having the above configuration, incident light I ０ is converted into unpolarized light by the depolarizing plate 33 and then directed to the inclined dichroic mirror 17 ０ Since the incident light I ０ Inclined dichroic mirror 17 ０ The transmission characteristics of the inclined dichroic mirror 17 can be stabilized. ０ 1 shows an example of the transmission characteristics of the inclined dichroic mirror 17. ０ A difference occurs in the predetermined wavelength range of 400 to 700 nm between the transmission characteristics of s-polarized light incident obliquely on the surface of the inclined dichroic mirror 17 and the transmission characteristics of p-polarized light incident obliquely on the surface of the inclined dichroic mirror 17. ０ is designed so that the transmission characteristics of obliquely incident non-polarized light change linearly with wavelength in a predetermined wavelength range (the characteristics shown as "average" in FIG. 6). ０ The incident light I is unpolarized. ０ is incident on the inclined dichroic mirror 17 ０ The transmission characteristics at the incident light I can be stabilized as designed. ０ The wavelength spectrum characteristics of the

[0062] In addition, in the camera 1B, the transmitted light I Ｔ０ is the tilted dichroic mirror 17 ０ The polarization of the light is disturbed when it passes through the depolarizing plate 35 and then passes through the inclined dichroic mirror 17. １ By making the light incident on the inclined dichroic mirror 17 without polarizing it, １ The transmission characteristics can also be stabilized as designed.

[0063] The camera 1 according to the first embodiment described above may be modified to have the configuration of a camera 1C according to a second modification shown in Fig. 7. That is, in the camera 1C, a depolarizing plate 33 is provided instead of the polarizing plate 3, and an inclined dichroic mirror 17 is provided on the filter surface 5b of the prism 5. ０ A beam splitter 37 is provided instead of the prism 7, and an inclined dichroic mirror 17 is provided on the filter surface 7b of the prism 7. ０ and an inclined dichroic mirror 17 is provided on the output surface 9c of the prism 9. １ will be established.

[0064] The beam splitter 37 is an optical element having transmission characteristics that are independent of polarization and wavelengths within a predetermined wavelength range, and is, for example, a half mirror that transmits light at a predetermined transmittance α and reflects light at a predetermined transmittance (1-α). The transmittance α of the beam splitter 37 is set to 50% or more.

[0065] In the second modification of the above configuration, the incident light I reflected by the beam splitter 37 on the filter surface 5b ０ A part of the reflected light (first measurement light) I ０Ａ The light intensity of the incident light I transmitted by the beam splitter 37 on the filter surface 5b can be detected by the photodetector 11. ０ The other transmitted light (first output light) I ０Ｂ The transmitted light I can be incident on the input surface 7a of the prism 7. ０Ｂ Theoretically, the light intensity is α×I ０ Furthermore, the transmitted light I ０Ｂ is the inclined dichroic mirror 17 on the filter surface 7b. ０ Reflected light (second measurement light) I Ｒ０ The light intensity of the transmitted light I is detected by the photodetector 13. ０Ｂ is the inclined dichroic mirror 17 on the filter surface 7b. ０ Transmitted light (second output light) I Ｔ０ The transmitted light I can be incident on the input surface 9a of the prism 9. Ｔ０ is the inclined dichroic mirror 17 on the output surface 9c １Transmitted light (third measurement light) I Ｔ１ The light intensity is detected by the photodetector 15 .

[0066] The calculation device 105 calculates the incident light I based on the three detection signals output from the camera 1C according to the second modification. ０ That is, based on the detection signal from the photodetector 11, it is possible to obtain a characteristic value relating to the wavelength spectrum of the incident light I ０ The light intensity of the transmitted light I incident on the input surface 7a can be obtained based on the light intensity and the transmittance α. ０Ｂ The light intensity of the reflected light I can be calculated based on the light intensity and the detection signals from the photodetectors 13 and 15. Ｒ１ Based on these calculation results, the calculation device 105 calculates the light intensity of the incident light I by using the same calculation function as in the first embodiment. ０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ and standard deviation σ ０ can be calculated.

[0067] The camera 1A according to the second embodiment described above may be modified to have the configuration of a camera 1D according to a third modified example shown in Fig. 8. That is, in the camera 1D, a depolarizing plate 33 is provided instead of the polarizing plate 3, and an inclined dichroic mirror 17 is provided on the filter surface 5b of the prism 5. ０ A beam splitter 37 is provided instead of the prism 7, and an inclined dichroic mirror 17 is provided on the filter surface 7b of the prism 7. ０ A depolarizing plate (depolarizing element) 41 is provided on the filter surface 9b of the prism 9 so as to cover the filter surface 9b, and an inclined dichroic mirror 17 is provided on the depolarizing plate 35. １ is formed on the output surface 21c of the prism 21, and the inclined dichroic mirror 17 ２ will be established.

[0068] The beam splitter 37 is an optical element having transmission characteristics that are independent of polarization and wavelengths within a predetermined wavelength range, and is, for example, a half mirror that transmits light at a predetermined transmittance α and reflects light at a predetermined transmittance (1-α). The transmittance α of the beam splitter 37 is set to 50% or more.

[0069] The depolarizing plate 41 is disposed on the inclined dichroic mirror 17 ０ and inclined dichroic mirror 17 １ and a plate-shaped member made of quartz or the like arranged between the Ｔ０ and transmits the transmitted light I Ｔ０ is converted into unpolarized light and is then incident on the inclined dichroic mirror 17 １ The depolarization plate 41 may also function as a low-pass filter that removes high-frequency components of the optical resolution by utilizing the birefringence of the crystal to prevent moiré in the pattern. Instead of being provided as a separate member, the depolarization plate 41 may be formed by the medium itself, such as a quartz prism of the prism 9.

[0070] In the third modification of the above configuration, the incident light I reflected by the beam splitter 37 on the filter surface 5b ０ A part of the reflected light (first measurement light) I ０Ａ The light intensity of the incident light I transmitted by the beam splitter 37 on the filter surface 5b can be detected by the photodetector 11. ０ The other transmitted light (first output light) I ０Ｂ The transmitted light I can be incident on the input surface 7a of the prism 7. ０Ｂ Theoretically, the light intensity is α×I ０ Furthermore, the transmitted light I ０Ｂ is the inclined dichroic mirror 17 on the filter surface 7b. ０ Reflected light (second measurement light) I Ｒ０ The light intensity of the transmitted light I is detected by the photodetector 13. ０Ｂ is the inclined dichroic mirror 17 on the filter surface 7b. ０ Transmitted light (second output light) I Ｔ０ The transmitted light I can be incident on the input surface 9a of the prism 9. Ｔ０ is the inclined dichroic mirror 17 on the filter surface 9b. １ Reflected light (third measurement light) I Ｒ１ is detected by the photodetector 15, and the transmitted light I Ｔ０ is the inclined dichroic mirror 17 on the filter surface 9b.１ Transmitted light (third output light) I Ｔ１ can be incident on the input surface 21a of the prism 21. Furthermore, the transmitted light I Ｔ１ is the inclined dichroic mirror 17 on the output surface 21c. ２ The transmitted light (fourth measurement light) I Ｔ２ The light intensity is detected by the photodetector 17 .

[0071] The calculation device 105 calculates the incident light I based on the four detection signals output from the camera 1D according to the third modification. ０ That is, based on the detection signal from the photodetector 11, it is possible to obtain a characteristic value relating to the wavelength spectrum of the incident light I ０ The light intensity of the transmitted light I incident on the input surface 7a can be obtained based on the light intensity and the transmittance α. ０Ｂ The light intensity of the reflected light I can be calculated based on the light intensity and the detection signals from the photodetectors 13, 15, and 17. Ｒ２ Based on these calculation results, the calculation device 105 calculates the light intensity of the incident light I by using the same calculation function as in the second embodiment. ０ The centroid wavelength λ in the wavelength spectrum of Ｇ０ , standard deviation σ ０ , and skewness S ０ can be calculated.

[0072] Furthermore, with the camera 1D having the above configuration, the incident light I ０ is converted into unpolarized light by the depolarizing plate 33 and then directed to the inclined dichroic mirror 17 ０ Since the incident light I ０ Inclined dichroic mirror 17 ０ The transmission characteristics can be stabilized.

[0073] In addition, in the camera 1D, the transmitted light I Ｔ０ is the tilted dichroic mirror 17 ０ The polarization of the light is disturbed when it passes through the depolarizing plate 41 and then passes through the inclined dichroic mirror 17. １ By making the light incident on the inclined dichroic mirror 17 without polarizing it, １The transmission characteristics can also be stabilized as designed.

[0074] In the third modified example, the inclined dichroic mirror 17 １ and inclined dichroic mirror 17 ２ A depolarizing element such as a depolarizing plate may be provided between the inclined dichroic mirror 17 and the ２ The transmission characteristics at the prism 9 can be stabilized as designed. The depolarization element may be formed by the medium itself, such as the quartz prism of the prism 9 or the quartz prism of the prism 21, instead of being provided as a separate member.

[0075] In the camera 1A according to the second embodiment, as in the third modification, the inclined dichroic mirror 17 ０ and inclined dichroic mirror 17 １ and an inclined dichroic mirror 17 １ and inclined dichroic mirror 17 ２ A depolarization element such as a depolarization plate may be provided between the prism 7 and the prism 9. In this case, the depolarization element may be formed by the medium itself, such as the quartz prism of the prism 7 or the quartz prism of the prism 9, instead of being provided as a separate member.

[0076] The camera 1D according to the third modified example described above may be modified to have the configuration of a camera 1E according to a fourth modified example shown in Fig. 9. That is, in the camera 1E, a polarizing beam splitter 43 is arranged on the filter surface 5b instead of the polarization-independent beam splitter 37 arranged on the filter surface 5b.

[0077] In the fourth modification having such a configuration, the incident light I ０ The s-polarized component of the reflected light I is reflected by the polarizing beam splitter 43 on the filter surface 5b. ０Ａ occurs, and the incident light I ０ The p-polarized light component of the polarized light is transmitted through the polarized beam splitter 43 on the filter surface 5b to form transmitted light I ０Ｂ is generated, and the transmitted light I ０Ｂ The inclined dichroic mirror 17 can be made to enter the input surface 7a of the prism 7.０ , 17 １ By designing for p-polarized light, the incident light I ０ The transmitted light I ０Ｂ Inclined dichroic mirror 17 ０ The transmission characteristics of the transmitted light I can be stabilized. Ｔ０ Inclined dichroic mirror 17 １ As a result, the transmission characteristics of the incident light I ０ This can improve the calculation accuracy of the characteristic values ​​in the wavelength spectrum.

[0078] The optical system that forms an image on each of the photodetectors included in the cameras 1, 1A, 1B, 1C, 1D, and 1E may be a telecentric optical system. ０ However, even if a telecentric optical system is not used, the influence of wavelength shift can be suppressed by taking into consideration the wavelength shift that depends on the angle of incidence of light onto the inclined dichroic mirror, which changes depending on the position of the field of view, and correcting the calculation results by the calculation device 105.

[0079] In the first aspect, a depolarizing element may be provided between the first filter and the second filter. The second prism may be a quartz prism. This allows the first output light to be incident on the second filter in an unpolarized state even if the polarization state of the first output light transmitted through the first filter is disturbed. As a result, the intensities of the second measurement light and the third measurement light can be stabilized as designed by the second filter, allowing accurate calculation of characteristics related to the wavelength spectrum of the incident light.

[0080] In the second aspect, the beam splitter may be a half mirror. In this case, the intensity of the incident light can be easily obtained based on the first detection signal, and based on this, characteristics related to the wavelength spectrum of the incident light can be obtained.

[0081] In the second aspect, the beam splitter may have a transmittance of 50% or more in a predetermined wavelength range. In this configuration, the intensities of the second measurement light and the third measurement light can be maintained, and the accuracy of the characteristics related to the wavelength spectrum of the incident light to be acquired can be improved.

[0082] In the first or second aspect, the optical fiber may further include a calculation unit that acquires a characteristic value related to the dispersion or standard deviation of the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, and the third detection signal. In this case, the characteristic value may be at least one of the centroid wavelength, the standard deviation, and the dispersion of the wavelength spectrum of the incident light. In this way, the first to third detection signals can be used to acquire any one of the centroid wavelength, the standard deviation, or the dispersion of the wavelength spectrum of the incident light. In particular, by performing calculations using the first to third detection signals, the amount of data required to measure the distribution of the wavelength spectrum of light can be reduced, and characteristics related to the wavelength spectrum of the incident light can be easily acquired.

[0083] In the first or second aspect, the exposure time of the third measurement light in the third photodetector may be longer than the exposure time of the first measurement light in the first photodetector. In this case, the third detection signal can be output taking into account the attenuation of the third measurement light, thereby improving the accuracy of the characteristics related to the wavelength spectrum of the incident light to be acquired.

[0084] In the first or second aspect, the first photodetector, the second photodetector, and the third photodetector may be a point sensor, a line sensor, or an area sensor, and it is possible to obtain a characteristic value relating to the wavelength spectrum of incident light at one point, a one-dimensional distribution of the characteristic value, or a two-dimensional distribution of the characteristic value.

[0085] In the third aspect, a depolarizing element may be provided between the first filter and the second filter and between the second filter and the third filter. In this case, the second prism and the third prism may be quartz prisms. With this configuration, even if the polarization state of the first output light transmitted through the first filter is disturbed, the first output light can be incident on the second filter without polarization. Even if the polarization state of the second output light transmitted through the second filter is disturbed, the second output light can be incident on the third filter without polarization. As a result, the intensities of the second measurement light, the third measurement light, and the fourth measurement light can be stabilized as designed for the second filter and the third filter, and characteristics related to the wavelength spectrum of the incident light can be accurately calculated.

[0086] In the fourth aspect, the beam splitter may be a half mirror, which makes it possible to easily obtain the intensity of the incident light based on the first detection signal, and based on this, to obtain characteristics related to the wavelength spectrum of the incident light.

[0087] In the fourth aspect, the beam splitter may have a transmittance of 50% or more in a predetermined wavelength range, which can maintain the intensities of the second measurement light, the third measurement light, and the fourth measurement light, thereby improving the accuracy of the acquired characteristics related to the wavelength spectrum of the incident light.

[0088] In the fourth aspect, a depolarizing element may be provided between the first filter and the second filter. In this case, the third prism may be a quartz prism. In this case, even if the polarization state of the second output light transmitted through the first filter is disturbed, the second output light can be incident on the second filter in an unpolarized state. As a result, the intensities of the third measurement light and the fourth measurement light can be stabilized as designed for the second filter, and characteristics related to the wavelength spectrum of the incident light can be accurately calculated.

[0089] In the third or fourth aspect, the optical fiber may further include a calculation unit that acquires a characteristic value related to the skewness 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. In this case, the characteristic value may be at least one of the centroid wavelength, standard deviation, variance, and skewness in the wavelength spectrum of the incident light. With this configuration, any of the centroid wavelength, standard deviation, variance, and skewness in the wavelength spectrum of the incident light can be acquired using the first to fourth detection signals. In particular, by performing calculations using the first to fourth detection signals, the amount of data required to measure the distribution of the wavelength spectrum of light can be reduced, and characteristics related to the wavelength spectrum of the incident light can be easily acquired.

[0090] In the third or fourth aspect, the exposure time of the fourth measurement light in the fourth photodetector may be longer than the exposure time of the first measurement light in the first photodetector, whereby the fourth detection signal can be output taking into account attenuation of the fourth measurement light, thereby improving the accuracy of the characteristics related to the wavelength spectrum of the incident light to be acquired.

[0091] In the third or fourth aspect, the first, second, third, and fourth photodetectors may be any of a point sensor, a line sensor, and an area sensor, and it is possible to obtain a characteristic value relating to the wavelength spectrum of incident light at one point, a one-dimensional distribution of the characteristic value, or a two-dimensional distribution of the characteristic value.

[0092] In any of the first to fourth aspects, the optical fiber may further include a polarizing element that converts incident light into linearly polarized light, and the first input surface may be configured to receive the linearly polarized light converted by the polarizing element. With this configuration, the transmission characteristics of the filter for the incident light can be stabilized without being affected by the polarization state of the incident light, so that the intensity of the measurement light can be stabilized as designed for the filter, and characteristics related to the wavelength spectrum of the incident light can be accurately calculated.

[0093] The camera of the embodiment is [1] a first prism having a first input surface that receives incident light, a first filter surface that reflects a part of the incident light that has passed through the first input surface to generate first measurement light and transmits another part of the incident light to generate first output light, and a first output surface that outputs the first measurement light; a second prism that is close to the first filter surface and receives the first output light, a second filter surface that reflects a part of the first output light that has passed through the second input surface to generate second measurement light and transmits another part of the first output light to generate second output light, and a second output surface that outputs the second measurement light; a third prism having a third input surface adjacent to a first surface and receiving the second output light, and a third output surface outputting the second output light as third measurement light; a first photodetector detecting the first measurement light and outputting a first detection signal; a second photodetector detecting the second measurement light and outputting a second detection signal; and a third photodetector detecting the third measurement light and outputting a third detection signal, wherein the first filter surface is provided with a first filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range, and the second filter surface is provided with a second filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range.

[0094] The camera of the embodiment may be [2] "the camera according to the above [1], in which a depolarizing element is provided between the first filter and the second filter."

[0095] The camera of the embodiment may be [3] "the camera according to the above [1] or [2], in which the second prism is a quartz prism."

[0096] The camera of the embodiment is [4] a first prism having a first input surface that receives incident light, a first filter surface that reflects a part of the incident light that has passed through the first input surface to generate first measurement light and transmits another part of the incident light to generate first output light, and a first output surface that outputs the first measurement light, a second prism that is close to the first filter surface and receives the first output light, a second filter surface that reflects a part of the first output light that has passed through the second input surface to generate second measurement light and transmits another part of the first output light to generate second output light, and a second output surface that outputs the second measurement light, a third input surface that is close to the second filter surface and receives the second output light, and a third output surface that outputs the second output light. a third prism having a third output surface that outputs a third measurement light as a third measurement light, a first photodetector that detects the first measurement light and outputs a first detection signal, a second photodetector that detects the second measurement light and outputs a second detection signal, and a third photodetector that detects the third measurement light and outputs a third detection signal, wherein the first filter surface is provided with a beam splitter that has a property of reflecting a part of the incident light in a predetermined wavelength range and transmitting another part of the incident light, the second filter surface is provided with a first filter that has a property of transmittance that changes linearly depending on wavelength in the predetermined wavelength range, and the third output surface is provided with a second filter that has a property of transmittance that changes linearly depending on wavelength in the predetermined wavelength range.

[0097] The camera of the embodiment may be [5] "the camera according to the above [4], in which the beam splitter is a half mirror."

[0098] The camera of the embodiment may be [6] "the camera according to the above [4] or [5], wherein the beam splitter has a transmittance of 50% or more in a predetermined wavelength range."

[0099] The camera of the embodiment may be [7] "a camera according to any one of the above [1] to [6], further comprising a calculation unit that acquires a characteristic value relating to the dispersion or standard deviation in the wavelength spectrum of the incident light based on the first detection signal, the second detection signal, and the third detection signal."

[0100] The camera of the embodiment is [8] "the camera according to the above [7], wherein the characteristic value is at least one of the centroid wavelength, the standard deviation, and the variance in the wavelength spectrum of the incident light."

[0101] The camera of the embodiment may be [9] "a camera described in any one of [1] to [8] above, in which the exposure time of the third measurement light in the third photodetector is longer than the exposure time of the first measurement light in the first photodetector."

[0102] The camera of the embodiment may be

[10] "a camera according to any one of [1] to [9] above, in which the first photodetector, the second photodetector, and the third photodetector are either a point sensor, a line sensor, or an area sensor."

[0103] The camera of the embodiment is

[11] "a first prism having a first input surface that receives incident light, a first filter surface that reflects a part of the incident light that has passed through the first input surface to generate first measurement light and transmits another part of the incident light to generate first output light, and a first output surface that outputs the first measurement light; a second prism having a second input surface that is close to the first filter surface and receives the first output light, a second filter surface that reflects a part of the first output light that has passed through the second input surface to generate second measurement light and transmits another part of the first output light to generate second output light, and a second output surface that outputs the second measurement light; a third input surface that is close to the second filter surface and receives the second output light, a third filter surface that reflects a part of the second output light that has passed through the third input surface to generate third measurement light and transmits another part of the second output light to generate third output light; and a second prism having a second input surface that is close to the second filter surface and receives the second output light, a fourth prism having a fourth input surface adjacent to the third filter surface for receiving the third output light and a fourth output surface for outputting the third output light as fourth measurement light; a first photodetector for detecting the first measurement light and outputting a first detection signal; a second photodetector for detecting the second measurement light and outputting a second detection signal; a third photodetector for detecting the third measurement light and outputting a third detection signal; and a fourth photodetector for detecting the fourth measurement light and outputting a fourth detection signal, wherein the first filter surface is provided with a first filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range, the second filter surface is provided with a second filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range, and the third filter surface is provided with a third filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range.

[0104] The camera of the embodiment may be

[12] "the camera described in

[11] above, in which a depolarizing element is provided between the first filter and the second filter, and between the second filter and the third filter."

[0105] The camera of the embodiment may be

[13] "the camera according to the above

[11] or

[12] , wherein the second prism and the third prism are quartz prisms."

[0106] The camera of the embodiment is

[14] "a first prism having a first input surface that receives incident light, a first filter surface that reflects a part of the incident light that has passed through the first input surface to generate first measurement light and transmits the other part of the incident light to generate first output light, and a first output surface that outputs the first measurement light; a second input surface that is close to the first filter surface and receives the first output light, and a second input surface that reflects a part of the first output light that has passed through the second input surface to generate second measurement light and transmits the other part of the first output light; a second prism having a second filter surface that transmits the remaining portion of the second output light to generate second output light, and a second output surface that outputs the second measurement light; a third input surface that is adjacent to the second filter surface and receives the second output light; a third filter surface that reflects a portion of the second output light that has passed through the third input surface to generate third measurement light and transmits the remaining portion of the second output light to generate third output light; and a third output surface that outputs the third measurement light; a fourth prism having a fourth input surface that receives the third output light and a fourth output surface that outputs the third output light as fourth measurement light; a first photodetector that detects the first measurement light and outputs a first detection signal; a second photodetector that detects the second measurement light and outputs a second detection signal; a third photodetector that detects the third measurement light and outputs a third detection signal; and a fourth photodetector that detects the fourth measurement light and outputs a fourth detection signal, wherein the first filter surface is provided with a beam splitter that has a property of reflecting a part of the incident light in a predetermined wavelength range and transmitting another part of the incident light; the second filter surface is provided with a first filter that has a property of transmittance that changes linearly with wavelength in the predetermined wavelength range; the third filter surface is provided with a second filter that has a property of transmittance that changes linearly with wavelength in the predetermined wavelength range; and the fourth output surface is provided with a third filter that has a property of transmittance that changes linearly with wavelength in the predetermined wavelength range.

[0107] The camera of the embodiment may be

[15] "the camera according to the above

[14] , in which the beam splitter is a half mirror."

[0108] The camera of the embodiment may be

[16] "the camera according to the above

[14] or

[15] , wherein the beam splitter has a transmittance of 50% or more in a predetermined wavelength range." The camera of the embodiment may be

[17] "the camera according to any one of the above

[14] to

[16] , wherein a depolarizing element is provided between the first filter and the second filter." The camera of the embodiment may be

[18] "the camera according to any one of the above

[14] to

[17] , wherein the third prism is a quartz prism." The camera of the embodiment may be

[19] "the camera according to any one of the above

[11] to

[18] , further comprising a calculation unit that acquires a characteristic value related to skewness 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." The camera of the embodiment may be

[20] "the camera according to the above

[19] , wherein the characteristic value is at least one of a centroid wavelength, a standard deviation, a variance, and a skewness in the wavelength spectrum of the incident light." The camera of the embodiment may be

[21] "the camera according to any one of the above

[11] to

[20] , wherein an exposure time of the fourth measurement light in the fourth photodetector is longer than an exposure time of the first measurement light in the first photodetector." The camera of the embodiment may be

[22] "the camera according to any one of the above

[11] to

[21] , wherein the first photodetector, the second photodetector, the third photodetector, and the fourth photodetector are any one of a point sensor, a line sensor, and an area sensor." The camera of the embodiment may be

[23] "the camera according to any one of the above [1], [4],

[11] , and

[14] , further comprising a polarizing element that converts the incident light into linearly polarized light, and wherein the first input surface receives the linearly polarized light converted by the polarizing element."

[0109] 100... measurement system, 1, 1A, 1B, 1C, 1D, 1E... camera, 105... calculation device (calculation unit), 3... polarizing plate (polarizing element), 5... prism (first prism), 5a... input surface (first input surface), 5b... filter surface (first filter surface), 5c... output surface (first output surface), 7... prism (second prism), 7a... input surface (second input surface), 7b... filter surface (second filter surface), 7c... output surface (second output surface), 9... prism (third prism), 9a... input surface (third input surface), 9b... filter surface (third filter surface), 9c... output surface (third output surface), 11, 13, 15, 17... photodetector, 21... prism (fourth prism), 21a... input surface (fourth input surface), 21c... output surface (fourth output surface), 17 ０ ...inclined dichroic mirror (first filter), 17 １ ...inclined dichroic mirror (second filter), 17 ２ ... inclined dichroic mirror (third filter), 33, 35, 41 ... depolarization plate (depolarization element), 37, 43 ... beam splitter, I ０ ...Incoming light.

Claims

1. A first prism having a first input surface for receiving incident light, a first filter surface for reflecting a portion of the incident light that has passed through the first input surface to generate a first measurement light and transmitting another portion of the incident light to generate a first output light, and a first output surface for outputting the first measurement light; a second prism having a second input surface adjacent to the first filter surface for receiving the first output light, a second filter surface for reflecting a portion of the first output light that has passed through the second input surface to generate a second measurement light and transmitting another portion of the first output light to generate a second output light, and a second output surface for outputting the second measurement light; a third prism having a third input surface adjacent to the second filter surface for receiving the second output light and a third output surface for outputting the second output light as a third measurement light; and a first photodetector for detecting the first measurement light and outputting a first detection signal. A camera comprising: a second photodetector that detects the second measurement light and outputs a second detection signal; and a third photodetector that detects the third measurement light and outputs a third detection signal, wherein a first filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range is provided on the first filter surface, and a second filter having a characteristic that transmittance changes linearly depending on wavelength in a predetermined wavelength range is provided on the second filter surface.

2. The camera of claim 1, wherein a depolarizing element is provided between the first filter and the second filter.

3. The camera according to claim 1 or 2, wherein the second prism is a quartz prism.

4. A first prism having a first input surface for receiving incident light, a first filter surface for reflecting a portion of the incident light that has passed through the first input surface to generate first measurement light and transmitting another portion of the incident light to generate first output light, and a first output surface for outputting the first measurement light; a second prism having a second input surface adjacent to the first filter surface for receiving the first output light, a second filter surface for reflecting a portion of the first output light that has passed through the second input surface to generate second measurement light and transmitting another portion of the first output light to generate second output light, and a second output surface for outputting the second measurement light; a third prism having a third input surface adjacent to the second filter surface for receiving the second output light and a third output surface for outputting the second output light as third measurement light; and a first photodetector for detecting the first measurement light and outputting a first detection signal. a second photodetector that detects the second measurement light and outputs a second detection signal; and a third photodetector that detects the third measurement light and outputs a third detection signal, wherein the first filter surface is provided with a beam splitter that has a property of reflecting a part of the incident light in a predetermined wavelength range and transmitting another part of the incident light, the second filter surface is provided with a first filter that has a property of transmittance that changes linearly depending on wavelength in the predetermined wavelength range, and the third output surface is provided with a second filter that has a property of transmittance that changes linearly depending on wavelength in the predetermined wavelength range.

5. The camera according to claim 4, wherein the beam splitter has a transmittance of 50% or more in a predetermined wavelength range.

6. A camera according to any one of claims 1 to 5, further comprising a calculation unit that acquires a characteristic value relating to dispersion or standard deviation in the wavelength spectrum of incident light based on the first detection signal, the second detection signal, and the third detection signal.

7. A camera according to any one of claims 1 to 6, wherein the exposure time of the third measurement light in the third photodetector is longer than the exposure time of the first measurement light in the first photodetector.

8. The camera according to any one of claims 1 to 7, wherein the first photodetector, the second photodetector, and the third photodetector are either a point sensor, a line sensor, or an area sensor.

9. A first prism having a first input surface for receiving incident light, a first filter surface for reflecting a portion of the incident light that has passed through the first input surface to generate first measurement light and transmitting another portion of the incident light to generate first output light, and a first output surface for outputting the first measurement light; a second prism having a second input surface adjacent to the first filter surface for receiving the first output light, a second filter surface for reflecting a portion of the first output light that has passed through the second input surface to generate second measurement light and transmitting another portion of the first output light to generate second output light, and a second output surface for outputting the second measurement light; a third prism having a third input surface adjacent to the second filter surface for receiving the second output light, a third filter surface for reflecting a portion of the second output light that has passed through the third input surface to generate third measurement light and transmitting another portion of the second output light to generate third output light, and a third output surface for outputting the third measurement light; a fourth prism adjacent to the third filter surface and having a fourth input surface for receiving the third output light and a fourth output surface for outputting the third output light as fourth measurement light; a first photodetector for detecting the first measurement light and outputting a first detection signal; a second photodetector for detecting the second measurement light and outputting a second detection signal; a third photodetector for detecting the third measurement light and outputting a third detection signal; and a fourth photodetector for detecting the fourth measurement light and outputting a fourth detection signal, wherein the first filter surface is provided with a first filter having a characteristic that transmittance varies linearly with wavelength in a predetermined wavelength range; the second filter surface is provided with a second filter having a characteristic that transmittance varies linearly with wavelength in a predetermined wavelength range; and the third filter surface is provided with a third filter having a characteristic that transmittance varies linearly with wavelength in a predetermined wavelength range.

10. A first prism having a first input surface for receiving incident light, a first filter surface for reflecting a portion of the incident light that has passed through the first input surface to generate a first measurement light and for transmitting the other portion of the incident light to generate a first output light, and a first output surface for outputting the first measurement light; a second prism located close to the first filter surface and having a second input surface for receiving the first output light, a second filter surface for reflecting a portion of the first output light that has passed through the second input surface to generate a second measurement light and for transmitting the other portion of the first output light to generate a second output light, and a second output surface for outputting the second measurement light; a third prism having a third input surface adjacent to the second filter surface and receiving the second output light, a third filter surface that reflects a portion of the second output light that has passed through the third input surface to generate third measurement light and transmits another portion of the second output light to generate third output light, and a third output surface that outputs the third measurement light; a fourth prism having a fourth input surface adjacent to the third filter surface and receiving the third output light, and a fourth output surface that outputs the third output light as fourth measurement light; a first photodetector that detects the first measurement light and outputs a first detection signal; a second photodetector that detects the second measurement light and outputs a second detection signal; a third photodetector that detects the third measurement light and outputs a third detection signal; and a fourth photodetector that detects the fourth measurement light and outputs a fourth detection signal, A camera in which the first filter surface is provided with a beam splitter having a characteristic of reflecting a portion of the incident light in a predetermined wavelength range and transmitting another portion of the incident light, the second filter surface is provided with a first filter having a characteristic of transmittance that varies linearly with wavelength in a predetermined wavelength range, the third filter surface is provided with a second filter having a characteristic of transmittance that varies linearly with wavelength in a predetermined wavelength range, and the fourth output surface is provided with a third filter having a characteristic of transmittance that varies linearly with wavelength in a predetermined wavelength range.

11. The camera according to claim 9 or 10, further comprising a calculation unit that acquires a characteristic value relating to the degree of distortion in the wavelength spectrum of incident light based on the first detection signal, the second detection signal, the third detection signal, and the fourth detection signal.

Images