Spectrometer and spectroscopic measurement system

Abstract

This spectrometer comprises: a spectroscopic unit; a light separation unit that separates light dispersed by the spectroscopic unit into first light in a first wavelength range and second light in a second wavelength range that is shorter than the first wavelength range; and a light detection unit that detects N-th order diffracted light included in the first light separated by the light separation unit and detects M-th order diffracted light included in the second light separated by the light separation unit. N and M are integers other than 0 where the absolute value of N is less than the absolute value of M.

Description

Spectrometers and spectroscopic measurement systems

[0001] One aspect of the present disclosure relates to a spectrometer and a spectroscopic measurement system.

[0002] Patent Documents 1 and 2 describe spectroscopic devices that use a diffraction grating to separate incident light and a light detecting section to detect the separated light.

[0003] JP-A No. 57-111422 JP-A No. 8-254464

[0004] The spectroscopic device described above may be required to have a wide detectable wavelength range. However, it is difficult to make a diffraction grating capable of diffracting light in a wide wavelength range. Even if a diffraction grating capable of diffracting light in a wide wavelength range could be realized, the diffraction efficiency may be low.

[0005] Therefore, an object of one aspect of the present disclosure is to provide a spectroscope and a spectroscopic measurement system that can disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0006] A spectrometer according to one aspect of the present disclosure is [1] "a spectrometer comprising: a spectrometer unit; a light separation unit that separates light separated by the spectrometer unit into a first light in a first wavelength range and a second light in a second wavelength range shorter than the first wavelength range; and a light detection unit that detects N-th order diffracted light contained in the first light separated by the light separation unit, and detects M-th order diffracted light contained in the second light separated by the light separation unit, wherein N and M are integers other than 0 and the absolute value of N is smaller than the absolute value of M."

[0007] In this spectrometer, the light separating unit separates the light separated by the spectroscopic unit into a first light in a first wavelength range and a second light in a second wavelength range. The light detecting unit then detects the Nth-order diffracted light contained in the first light and the Mth-order diffracted light contained in the second light. This allows the light detecting unit to detect the Nth-order diffracted light contained in the first light and the Mth-order diffracted light contained in the second light, which have relatively high diffraction efficiency. As a result, it becomes possible to separate and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0008] A spectrometer according to one aspect of the present disclosure may be [2] "the spectrometer according to [1], wherein the light detection unit has a first photodetector that detects the N-th order diffracted light and a second photodetector that detects the M-th order diffracted light." In this case, the N-th order diffracted light contained in the first light and the M-th order diffracted light contained in the second light can be suitably detected by the light detection unit.

[0009] A spectrometer according to one aspect of the present disclosure may be [3] "the spectrometer according to [2], in which the first photodetector and the second photodetector are configured by two detectors having substantially different wavelength sensitivity ranges." In this case, for example, the Nth-order diffracted light included in the first light can be detected by a first photodetector having a wavelength sensitivity range suitable for detecting the Nth-order diffracted light, and the Mth-order diffracted light can be detected by a second photodetector having a wavelength sensitivity range suitable for detecting the Mth-order diffracted light included in the second light.

[0010] A spectrometer according to one aspect of the present disclosure may be [4] "the spectrometer according to [2], wherein the first photodetector and the second photodetector are configured by two detectors having substantially the same wavelength sensitivity range." In this case, the first photodetector and the second photodetector may be configured by, for example, the same detector.

[0011] A spectrometer according to one aspect of the present disclosure may be [5] "the spectrometer according to any one of [1] to [4], further including a filter disposed between the light separating unit and the light detecting unit, which attenuates at least one of diffracted light other than the N-th order diffracted light contained in the first light and diffracted light other than the M-th order diffracted light contained in the second light." In this case, the N-th order diffracted light contained in the first light and the M-th order diffracted light contained in the second light can be more reliably detected by the light detecting unit.

[0012] A spectrometer according to one aspect of the present disclosure may be [6] "the spectrometer according to any one of [1] to [5], wherein the light separating unit has a dichroic surface that transmits one of the first light and the second light and reflects the other of the first light and the second light." In this case, the light separating unit can be suitably configured.

[0013] A spectrometer according to one aspect of the present disclosure may be [7] "the spectrometer according to [6], wherein the light separation unit has a prism including the dichroic surface, and the light detection unit is fixed directly or indirectly to the prism." In this case, it is possible to easily position the light detection unit relative to the dichroic surface.

[0014] A spectrometer according to one aspect of the present disclosure may be [8] "the spectrometer according to any one of [1] to [7], wherein the photodetector detects Nth-order diffracted light included in the second light in addition to the Mth-order diffracted light included in the second light." In this case, for example, when the diffraction efficiency of the Nth-order diffracted light of the spectrometer is higher than the diffraction efficiency of the Mth-order diffracted light in a portion of the second wavelength range, the diffraction efficiency in the portion can be improved by detecting the Nth-order diffracted light included in the second light in the portion. Alternatively, when the quantum efficiency of the photodetector is low in a portion of the second wavelength range, the amount of signal acquired in the portion can be increased by detecting both the Nth-order diffracted light and the Mth-order diffracted light included in the second light in the portion.

[0015] A spectrometer according to one aspect of the present disclosure may be [9] "the spectrometer according to [8], wherein the light detection unit detects the N-th order diffracted light contained in the second light for a first portion in the second wavelength range, and detects the M-th order diffracted light contained in the second light for a second portion in the second wavelength range." In this case, for example, by detecting the N-th order diffracted light contained in the second light for a first portion in which the diffraction efficiency of the N-th order diffracted light of the spectroscopic unit is higher than the diffraction efficiency of the M-th order diffracted light, the diffraction efficiency in the first portion can be improved.

[0016] A spectrometer according to an aspect of the present disclosure may be

[10] "the spectrometer according to [9], wherein the diffraction efficiency of the N-order diffracted light of the spectroscopic unit in the first portion is higher than the diffraction efficiency of the M-order diffracted light of the spectroscopic unit in the first portion." In this case, for the first portion in which the diffraction efficiency of the N-order diffracted light of the spectroscopic unit is higher than the diffraction efficiency of the M-order diffracted light, the diffraction efficiency of the first portion can be improved by detecting the N-order diffracted light included in the second light.

[0017] A spectrometer according to one aspect of the present disclosure may be

[11] "the spectrometer according to [8], wherein the light detection unit detects both the N-th order diffracted light and the M-th order diffracted light contained in the second light for a first portion in the second wavelength range, and detects the M-th order diffracted light contained in the second light for a second portion in the second wavelength range." In this case, for example, by detecting both the N-th order diffracted light and the M-th order diffracted light contained in the second light for a first portion in which the quantum efficiency of the photodetector is low, the amount of signal acquired for the first portion can be increased.

[0018] A spectrometer according to one aspect of the present disclosure may be

[12] "the spectrometer according to

[11] , wherein the first portion is on the longer wavelength side than the second portion." In this case, even if the quantum efficiency of the photodetector on the longer wavelength side is lower than the quantum efficiency on the shorter wavelength side, for example, the first portion with the lower quantum efficiency of the photodetector can detect both the Nth-order diffracted light and the Mth-order diffracted light contained in the second light, thereby increasing the amount of signal acquired for the first portion.

[0019] A spectrometer according to one aspect of the present disclosure may be

[13] "the spectrometer according to any one of [1] to

[12] , wherein the absolute value of N is 1 and the absolute value of M is 2." In this case, it becomes possible to disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0020] A spectrometer according to one aspect of the present disclosure may be

[14] "the spectrometer according to any one of [1] to

[13] , wherein the spectroscopic unit includes a spectroscopic element capable of separating light in a wavelength range of at least 1000 nm to 1500 nm into first-order diffracted light." In this case, the diffraction efficiency of the diffraction grating is high on the long wavelength side while the diffraction efficiency of the diffracted light is low on the short wavelength side. However, by detecting N-order diffracted light included in the first light in a first wavelength range on the long wavelength side and M-order diffracted light included in the second light in a second wavelength range on the short wavelength side, the spectrometer can separate and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0021] A spectrometer according to one aspect of the present disclosure may be

[15] "the spectrometer according to any one of [1] to

[14] , wherein the spectroscopic unit includes a spectroscopic element made of a blazed diffraction grating, and the blazed diffraction grating has a blaze wavelength of 1000 nm or more." In this case, the diffraction efficiency of the diffraction grating is high on the long wavelength side, while the diffraction efficiency of diffracted light is low on the short wavelength side. However, by detecting N-order diffracted light included in first light in a first wavelength range on the long wavelength side and M-order diffracted light included in second light in a second wavelength range on the short wavelength side, this spectrometer can disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0022] A spectrometer according to one aspect of the present disclosure may be

[16] "the spectrometer according to any one of [1] to

[15] , wherein the light detection unit has a plurality of pixels arranged along a first direction corresponding to the spectroscopic direction of the spectroscopic unit and a direction intersecting with the first direction." In this case, for example, it is possible to acquire not only wavelength information, which is information along the spectroscopic direction, but also position information, which is information along a direction intersecting with the spectroscopic direction.

[0023] A spectroscopic measurement system according to one aspect of the present disclosure is

[17] "a spectroscopic measurement system including the spectroscope according to any one of [1] to

[16] and a light irradiation unit that irradiates an object with light, wherein light irradiated from the light irradiation unit and reflected or scattered by the object is dispersed by the spectroscopic unit and detected by the light detection unit." For the reasons described above, this spectroscopic measurement system allows the spectroscope to disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0024] According to one aspect of the present disclosure, it is possible to provide a spectroscope and a spectroscopic measurement system that can disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0025] FIG. 1 is a configuration diagram of a spectroscopic measurement system according to an embodiment; FIG. 2 is a diagram illustrating a guide member; FIG. 3 is a configuration diagram of a spectroscope; FIG. 4 is a diagram illustrating the characteristics of a dichroic surface; FIG. 5 is a diagram illustrating diffracted light detected by a first photodetector; FIG. 6 is a diagram illustrating diffracted light detected by a second photodetector; FIG. 7 is a diagram illustrating the characteristics of a filter; (a) and (b) are diagrams illustrating improvement in diffraction efficiency by a spectroscopic unit; (a) is a configuration diagram of a spectroscope according to a first modified example; (b) is a diagram illustrating the characteristics of a dichroic surface in the first modified example; (c) is a diagram illustrating diffracted light detected by a first photodetector in the first modified example; (d) is a diagram illustrating diffracted light detected by a second photodetector in the first modified example; (e) is a diagram illustrating an example of diffracted light detected by a second photodetector in the second modified example; (f) is a diagram illustrating the characteristics of a filter in the second modified example; (f) is a diagram illustrating an example of diffracted light detected by a second photodetector in the third modified example; (f) is a configuration diagram of a spectroscope according to a fourth modified example; (f) is a diagram illustrating the characteristics of a dichroic surface in the fourth modified example; (g) is a diagram illustrating diffracted light detected by a first photodetector in the fourth modified example. 10 is a diagram for explaining diffracted light detected by a second photodetector in a fourth modified example. FIG. 11 is a diagram showing the configuration of a spectroscope according to a fifth modified example.

[0026] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and redundant description will be omitted. [Spectroscopic Measurement System]

[0027] As shown in FIG. 1 , a spectroscopic measurement system 1 according to an embodiment includes a conveying unit 2, a light irradiating unit 3, a spectroscope 4, and a processing unit 5. In the spectroscopic measurement system 1, light is irradiated from the light irradiating unit 3 onto an object B being conveyed by the conveying unit 2 along a conveying direction A. The light irradiated from the light irradiating unit 3 and reflected or scattered by the object B is incident on the spectroscope 4, where it is dispersed and detected. Based on this detection result, a spectral image is generated in the processing unit 5. The spectral image is an image that includes not only position information on the object B but also wavelength information (spectral information) at that position. As such, in the spectroscopic measurement system 1, the spectroscope 4 is configured as a hyperspectral camera, and hyperspectral observation of the object B is performed. The spectroscope 4 can also be considered as a camera module or a spectroscopic measurement module.

[0028] In this example, the transport unit 2 is a belt conveyor, and transports the object B placed on a transport surface 2a (mounting surface), which is the surface of the belt, along a transport direction A. When observing the object B (when the spectroscopic measurement system 1 is in operation), light is irradiated from the light irradiation unit 3 onto the object B being transported by the transport unit 2. This allows observation to be performed while changing the irradiation position of light on the object B, and allows the entire object B to be observed.

[0029] The light irradiation unit 3 has a light source 11, a lens 12, a guide member 13, and a pair of lenses 14. The light source 11 is a wide wavelength range light source configured, for example, by a halogen lamp light source, a super continuum light source (SC light source), etc. The light source 11 outputs irradiation light P1, which is light in a wavelength range of 200 nm to 1700 nm, for example.

[0030] The illumination light P1 is focused by the lens 12 and enters the guide member 13. The guide member 13 has a first portion 131, a second portion 132, and a third portion 133. Each of the portions 131 to 133 is tubular. One end of the first portion 131 constitutes a light entrance portion 13a, which is the portion through which the illumination light P1 enters the guide member 13. One ends of the second portion 132 and the third portion 133 are connected to the other end of the first portion 131. That is, the guide member 13 has a structure in which the other end of the first portion 131 branches into the second portion 132 and the third portion 133. The other ends of the second portion 132 and the third portion 133 each have a light exit portion 13b ( FIG. 2 ), which is the portion through which the illumination light P1 exits the guide member 13. In the guide member 13, the irradiation light P1 incident from the light incident portion 13a is guided to be emitted from each light exit portion 13b. Note that Fig. 2 shows an example of the guide member 13 in which the light exit portion 13b is provided at one end of the first portion 131 and does not have the second portion 132 or the third portion 133.

[0031] The light emitting portion 13b is formed in a flattened rectangular parallelepiped shape and has a rectangular light emitting opening 13c. Therefore, if the direction parallel to the long side of the light emitting opening 13c is defined as direction D, then irradiation light P1 spreading in direction D is emitted from the light emitting portion 13b. The light emitting portion 13b is disposed so that direction D is parallel to the conveying surface 2a and perpendicular to the conveying direction A. As a result, the object B is irradiated with irradiation light P1 spreading in a direction perpendicular to the conveying direction A (a direction perpendicular to the plane of the paper in FIG. 1 ).

[0032] If the position where the irradiation light P1 is irradiated onto the object B is defined as irradiation position X1, the pair of light emitting units 13b are respectively disposed on one side and the other side of the irradiation position X1 in the conveying direction A. The irradiation light P1 emitted from one light emitting unit 13b is focused by one of the pair of lenses 14 and irradiated onto the object B at the irradiation position X1 from one side (e.g., the upstream side) in the conveying direction A. The irradiation light P1 emitted from the other light emitting unit 13b is focused by the other of the pair of lenses 14 and irradiated onto the object B at the irradiation position X1 from the other side (e.g., the downstream side) in the conveying direction A. Each lens 14 is configured, for example, by a cylindrical lens to focus the irradiation light P1 that spreads in a direction perpendicular to the conveying direction A. By irradiating the object B with light from both sides in the conveying direction A in this manner, light can be suitably irradiated onto an object B having a three-dimensional shape.

[0033] Irradiation light P1 irradiated from the light irradiation unit 3 and reflected or scattered by the object B is incident on the spectroscope 4. As shown in Figures 1 and 3, the spectroscope 4 has a slit unit 21, a lens 22, a spectroscopic unit 23, a lens 24, a light separation unit 25, a filter 26, a light detection unit 27, and a housing 28. The housing 28 is formed, for example, in a box shape, and houses the slit unit 21, the lens 22, the spectroscopic unit 23, the lens 24, the light separation unit 25, the filter 26, and the light detection unit 27. The light detection unit 27 has a first photodetector 27a and a second photodetector 27b.

[0034] Irradiation light P1 is incident on the slit section 21. The slit section 21 is, for example, a rectangular flat plate-shaped member with a slit 21a formed therein. The slit section 21 is arranged so that the extension direction of the slit 21a is parallel to the conveying surface 2a and perpendicular to the conveying direction A. The slit 21a transmits at least a portion of the irradiation light P1 and emits it toward the lens 22. In the irradiation light P1 from the slit 21a, the position in the extension direction of the slit 21a represents position information of the object B along the direction perpendicular to the conveying direction A. The irradiation light P1 from the slit 21a is collected by the lens 22 and enters the spectroscopic section 23.

[0035] The spectroscopic unit 23 disperses the illumination light P1 from the lens 22 and outputs light P2. The spectroscopic unit 23 is, for example, a reflective spectroscopic element made of a blazed diffraction grating. The spectroscopic unit 23 is configured to be able to disperse light in at least a wavelength range of 1000 nm to 1500 nm into first-order diffracted light. "Able to disperse light in a certain wavelength range into first-order diffracted light" means, for example, that the diffraction efficiency of first-order diffracted light in that wavelength range is 30% or higher. In this example, the spectroscopic unit 23 is able to disperse illumination light P1 in a wavelength range of 800 nm to 1800 nm into first-order diffracted light. The blazed wavelength of the blazed diffraction grating constituting the spectroscopic unit 23 is, for example, 1000 nm or higher, and in this example, is 1200 nm. The light P2 dispersed by the spectroscopic unit 23 includes diffracted light of the illumination light P1, such as zeroth-order diffracted light, first-order diffracted light, second-order diffracted light, third-order diffracted light, etc. Hereinafter, zeroth-order diffracted light, first-order diffracted light, second-order diffracted light, third-order diffracted light, etc. will also be referred to as zeroth-order light, first-order light, second-order light, third-order light, etc. The light from the spectroscopic unit 23 is collected by a lens 24 and enters the light separation unit 25. Note that the spectroscopic unit 23 may be a transmission type spectroscopic element made of a prism or the like, or a spectroscopic element made of a holographic diffraction grating, depending on the design.

[0036] The light splitting unit 25 splits the light P2 split by the spectroscopic unit 23 into a first light L1 in a first wavelength range and a second light L2 in a second wavelength range shorter than the first wavelength range. In this example, the light splitting unit 25 is configured by a prism 31 (optical element) including a dichroic surface 31a. The dichroic surface 31a is configured, for example, by a dielectric multilayer film or a periodic nanostructure. In addition to the dichroic surface 31a formed inside, the prism 31 has a first surface 31b, a second surface 31c, and a third surface 31d as external surfaces. The light P2 from the spectroscopic unit 23 enters the prism 31 from the first surface 31b and then enters the dichroic surface 31a. The dichroic surface 31a transmits the first light L1 in the first wavelength range while reflecting the second light L2 in a second wavelength range shorter than the first wavelength range. The first light L1 transmitted through the dichroic surface 31a travels within the prism 31 along the optical axis AX1 and is incident on the first photodetector 27a of the photodetection unit 27 fixed on the second surface 31c. The second light L2 reflected by the dichroic surface 31a travels within the prism 31 along the optical axis AX2 and is reflected by the first surface 31b and is incident on the filter 26. The second light L2 transmitted through the filter 26 is incident on the second photodetector 27b of the photodetection unit 27 fixed on the third surface 31d.

[0037] An example of the characteristics of the dichroic surface 31a will be described with reference to Fig. 4. The horizontal axis of the graph in Fig. 4 represents the position in the direction of light splitting by the spectroscopic section 23, and the vertical axis represents the wavelength. This also applies to Figs. 5 and 6, which will be described later. Fig. 4 shows first to fourth order light. As shown in Fig. 4, when the position in the direction of light splitting is the same, the wavelength of the Lth order light (L is an integer equal to or greater than 1) is 1 / L of the wavelength of the first order light.

[0038] In the example of Figure 4, the dichroic surface 31a transmits light of 950 nm or more (transmission band) as a first wavelength range and reflects light of 900 nm or less (reflection band) as a second wavelength range. In this way, the dichroic surface 31a has long-pass characteristics. The dichroic surface 31a also partially transmits light in the 900 nm to 950 nm range (transition band) between the transmission band and the reflection band. From the perspective of smoothly realizing the generation process (stitching) of spectral images (described later) without any steps, a wider transition band is preferable.

[0039] In this example, irradiation light P1 in the wavelength range of 200 nm to 1700 nm is split by the splitting unit 23, and of the split light P2, first light L1 having a wavelength of 950 nm to 1700 nm (first wavelength range) is transmitted through the dichroic surface 31 a, and second light L2 having a wavelength of 200 nm to 900 nm (second wavelength range) is reflected by the dichroic surface 31 a. In the transition band of 900 nm to 950 nm, the characteristics of the dichroic surface 31 a switch between transmission characteristics and reflection characteristics.

[0040] Returning to FIG. 3 , the filter 26 is disposed between the prism 31 (light separating unit 25) and the second photodetector 27b of the photodetector 27. In this example, the filter 26 is fixed on the third surface 31d of the prism 31, and the second photodetector 27b is fixed on the third surface 31d via the filter 26. The filter 26 has a plate-shaped main body 26a and a filter portion 26b formed in a layer on the main body 26a. The filter 26 is disposed so that the filter portion 26b faces the prism 31. In this example, the filter portion 26b functions as an order sorting filter that transmits second-order light contained in the second light L2 and blocks diffracted light (higher-order light than the second order) other than the second-order light contained in the second light L2. Details of the filter 26 will be described later.

[0041] The first light L1 and the second light L2 separated by the light separating unit 25 are detected by the light detecting unit 27. The light detecting unit 27 has a first light detector 27a that detects the first light L1 and a second light detector 27b that detects the second light L2. Each of the first light detector 27a and the second light detector 27b is, for example, an image sensor or a line sensor configured with a single sensor element.

[0042] The light detection unit 27 is fixed to the prism 31. In this example, the first light detector 27a is fixed on the second surface 31c of the prism 31 so that the first light L1 emitted from the prism 31 is incident thereon. In this example, the first light detector 27a is indirectly fixed to the second surface 31c of the prism 31 via a metal part (not shown). The first light detector 27a may also be directly fixed to the second surface 31c of the prism 31. The second light detector 27b is fixed on the third surface 31d of the prism 31 via the filter 26 so that the second light L2 emitted from the prism 31 is incident thereon.

[0043] The first photodetector 27a and the second photodetector 27b are configured with two detectors having substantially different wavelength sensitivity ranges. That is, the wavelength sensitivity range of the detector constituting the first photodetector 27a is substantially different from the wavelength sensitivity range of the detector constituting the second photodetector 27b. The term "two detectors having substantially different wavelength sensitivity ranges" includes, for example, cases where the two detectors are of different types. Furthermore, the term "two detectors having substantially different wavelength sensitivity ranges" also includes cases where the two detectors are of the same type, and the overlapping wavelength ranges of the two detectors are defined as overlapping wavelength ranges, and the ratio of the overlapping wavelength range to the wavelength sensitivity ranges of the two detectors is 90% or less. In this example, the first photodetector 27a is, for example, an InGaAs image sensor. The second photodetector 27b is, for example, a charge-coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor. That is, in this example, the first photodetector 27a and the second photodetector 27b are detectors of different types. The wavelength range of sensitivity of the first photodetector 27a is, for example, 900 nm to 1700 nm, and overlaps with at least a portion (in this example, the entirety) of the first wavelength range. The wavelength range of sensitivity of the second photodetector 27b is, for example, 300 nm to 1000 nm, and overlaps with at least a portion (in this example, a portion on the long wavelength side) of the second wavelength range. As in this example, the wavelength ranges of sensitivity of the first photodetector 27a and the second photodetector 27b may overlap.

[0044] The first photodetector 27a has a plurality of pixels arranged in a first direction D1 corresponding to the spectral direction determined by the spectroscopic unit 23 and a direction perpendicular to the first direction D1. In this example, the first photodetector 27a is arranged so that the first direction D1 is parallel to the spectral direction determined by the spectroscopic unit 23. The second photodetector 27b has a plurality of pixels arranged in a second direction D2 corresponding to the spectral direction determined by the spectroscopic unit 23 and a direction perpendicular to the second direction D2. In this example, the second photodetector 27b is arranged so that the second direction D2 is inclined with respect to the spectral direction determined by the spectroscopic unit 23. That is, in each of the first photodetector 27a and the second photodetector 27b, a plurality of pixels are arranged two-dimensionally in a matrix. In each of the first photodetector 27a and the second photodetector 27b, the position in the direction corresponding to the spectral direction (first direction D1 or second direction D2) represents wavelength information, and the position in the direction perpendicular to that direction represents position information of the object B along the direction perpendicular to the conveying direction A. In the following description, the positions in the spectral direction will be explained in association with the positions on the detection surfaces of the first photodetector 27a and the second photodetector 27b.

[0045] The diffracted light detected by the first photodetector 27a will be described with reference to FIG. 5. As shown in FIG. 5, the first photodetector 27a detects light in the transmission band shown in FIG. 4. In FIG. 5, a detection region R1 indicating the position and wavelength range detected by the first photodetector 27a is indicated by a rectangular dotted line. In this example, the first photodetector 27a detects light in the wavelength range of 900 nm to 1700 nm that is incident at a position between approximately 14 mm and approximately 28 mm. Only the primary light contained in the first light L1 is incident on the first photodetector 27a, and only this primary light is detected by the first photodetector 27a.

[0046] Referring to FIG. 6, the diffracted light detected by the second photodetector 27b will be described. As shown in FIG. 6, the second photodetector 27b detects light in the reflection band shown in FIG. 4. In FIG. 6, a detection region R2 indicating the position and wavelength range detected by the second photodetector 27b is indicated by a rectangular dotted line. Furthermore, a blocking region R3 indicating the position and wavelength range where the filter 26 (filter portion 26b) blocks light is indicated by a trapezoidal dashed-dotted line. In this example, the second photodetector 27b detects light in the wavelength range of 300 nm to 1000 nm incident at a position between approximately 15 mm and approximately 31 mm. The filter portion 26b is positioned so that the wavelength of the transmitted light continuously changes between approximately 15 mm and approximately 31 mm so as to block the tertiary and quaternary light contained in the second light L2. As a result, only the secondary light contained in the second light L2 is incident on the second photodetector 27b, and only this secondary light is detected by the second photodetector 27b.

[0047] An example of the characteristics of the filter 26 (filter portion 26b) will be described with reference to FIG. 7 . The filter portion 26b is a filter whose transmittable wavelength changes along the second direction D2. In FIG. 7 , each position of the filter portion 26b in the second direction D2 and the wavelength of light transmittable by the filter portion 26b at each position are shown in grayscale. For example, at one end of the filter portion 26b (a position relatively closer to white), the filter portion 26b transmits light with a wavelength of 300 nm or more and blocks light with a wavelength of less than 300 nm. At the other end of the filter portion 26b (a position relatively closer to black), the filter portion 26b transmits light with a wavelength of 800 nm or more and blocks light with a wavelength of less than 800 nm. By arranging such a filter portion 26b in a predetermined positional relationship with the second photodetector 27b, it is possible to block light at a target position and wavelength range, as shown in FIG. 6 . In Figure 7, the characteristics of each position of the filter section are long-pass characteristics that transmit wavelengths longer than a certain wavelength, but the characteristics of each position of the filter section may also be, for example, band-pass characteristics that transmit only a certain wavelength width.

[0048] The processing unit 5 is communicatively connected to the light detection unit 27 and generates a spectral image based on the detection results of the light detection unit 27. The processing unit 5 is configured, for example, by a computer including a processor (CPU) and recording media such as RAM and ROM. In this example, the processing unit 5 generates a spectral image based on the detection results of the first light detector 27a and the second light detector 27b (by combining the detection results of the first light detector 27a and the second light detector 27b). As described above, the first light detector 27a detects primary light contained in the first light L1, and the second light detector 27b detects secondary light contained in the second light L2. Based on these detection results, the processing unit 5 generates a spectral image indicating intensities in, for example, a first wavelength band and a second wavelength band.

[0049] A method for observing the object B in the spectroscopic measurement system 1 will be described. As described above, first, the light irradiating unit 3 irradiates the object B being transported along the transport direction A by the transport unit 2 with irradiation light P1. Next, the irradiation light P1 irradiated from the light irradiating unit 3 and reflected or scattered by the object B is dispersed by the spectroscopic unit 23 and detected by the light detecting unit 27. At this time, the light P2 dispersed by the spectroscopic unit 23 is separated into first light L1 and second light L2 by the light separating unit 25, and the primary light contained in the first light L1 is detected by the first photodetector 27a, and the secondary light contained in the second light L2 is detected by the second photodetector 27b. Next, a spectral image is generated in the processing unit 5 based on the detection results of the first photodetector 27a and the second photodetector 27b. [Operation and Effects]

[0050] As described above, in the spectrometer 4, the light separating unit 25 separates the light P2 separated by the spectroscopic unit 23 into the first light L1 in the first wavelength range and the second light L2 in the second wavelength range. Then, the primary light contained in the first light L1 and the secondary light contained in the second light L2 are detected by the light detecting unit 27. This allows the primary light contained in the first light L1 and the secondary light contained in the second light L2, which have relatively high diffraction efficiency, to be detected by the light detecting unit 27. As a result, it becomes possible to separate and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0051] This point will be further explained with reference to FIG. 8 . FIG. 8( a) shows an example of a simulation result of the diffraction efficiency of a diffraction grating with a blaze wavelength of 600 nm, and FIG. 8( b) shows an example of a simulation result of the diffraction efficiency of a diffraction grating with a blaze wavelength of 1200 nm. For example, when light is dispersed using the diffraction grating shown in FIG. 8( a) and the resulting first-order light is detected, the diffraction efficiency is low in the long-wavelength region. In contrast, by dispersing light using the diffraction grating shown in FIG. 8( b), for example, and using the first-order light for a first wavelength range on the long-wavelength side (e.g., 800 nm or more) and the second-order light for a second wavelength range on the short-wavelength side (e.g., 800 nm or less), the first-order light contained in the first light L1 and the second-order light contained in the second light L2, which have relatively high diffraction efficiencies, can be detected by the light detection unit 27. This makes it possible to disperse and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0052] In the spectrometer 4, the light detection unit 27 has a first light detector 27a that detects the primary light and a second light detector 27b that detects the secondary light. This allows the light detection unit 27 to suitably detect the primary light contained in the first light L1 and the secondary light contained in the second light L2.

[0053] In the spectrometer 4, the first photodetector 27a and the second photodetector 27b are configured as two detectors having substantially different sensitivity wavelength ranges. This makes it possible, for example, to detect the primary light contained in the first light L1 using the first photodetector 27a having a sensitivity wavelength range suitable for detecting the primary light, and to detect the secondary light contained in the second light L2 using the second photodetector 27b having a sensitivity wavelength range suitable for detecting the secondary light. For example, in the above example, the first photodetector 27a is configured as an InGaAs image sensor, and the second photodetector 27b is configured as a CMOS image sensor.

[0054] The spectrometer 4 includes a filter 26 (filter section 26b) disposed between the light separating section 25 and the second photodetector 27b, which blocks diffracted light other than the secondary light contained in the second light L2. This allows the second photodetector 27b to more reliably detect the secondary light contained in the second light L2.

[0055] In the spectrometer 4, the light separating section 25 has a dichroic surface 31a that transmits the first light L1 and reflects the second light L2. This allows the light separating section 25 to be configured appropriately.

[0056] In the spectrometer 4, the light splitting unit 25 is a prism 31 including a dichroic surface 31a, and the first photodetector 27a and the second photodetector 27b are fixed to the prism 31. This makes it possible to easily position the first photodetector 27a and the second photodetector 27b with respect to the dichroic surface 31a. For example, in the above example, by fixing the first photodetector 27a to the second surface 31c of the prism 31 and fixing the second photodetector 27b to the third surface 31d of the prism 31, it is possible to easily position the first photodetector 27a and the second photodetector 27b with respect to the dichroic surface 31a.

[0057] In the spectrometer 4, the spectroscopic unit 23 includes a spectroscopic element capable of separating light in at least a wavelength range of 1000 nm to 1500 nm into primary light. When the spectroscopic unit 23 is configured in this manner, as shown in FIG. 8B , for example, the diffraction efficiency of the spectroscopic unit 23 for primary light is high on the long wavelength side, while the diffraction efficiency of the primary light is low on the short wavelength side. Furthermore, on the short wavelength side, the diffraction efficiency of the primary light is higher than the diffraction efficiency of the secondary light. Therefore, the spectrometer 4 uses such a spectroscopic element and detects primary light contained in the first light L1 in a first wavelength range on the long wavelength side, and detects secondary light contained in the second light L2 in a second wavelength range on the short wavelength side. This allows light in a wide wavelength range to be separated and detected with sufficient diffraction efficiency.

[0058] In the spectrometer 4, the spectroscopic unit 23 includes a spectroscopic element made of a blazed diffraction grating, and the blaze wavelength of the blazed diffraction grating is 1000 nm or more, for example, 1200 nm. When the blaze wavelength is set to the long wavelength side in this manner, as shown in FIG. 8B , for example, the diffraction efficiency of the spectroscopic unit 23 for first-order light is high on the long wavelength side, while the diffraction efficiency of first-order light is low on the short wavelength side. Furthermore, on the short wavelength side, the diffraction efficiency of first-order light is higher than the diffraction efficiency of second-order light. Therefore, the spectrometer 4 uses such a spectroscopic element and detects first-order light contained in the first light L1 in a first wavelength range on the long wavelength side, and detects second-order light contained in the second light L2 in a second wavelength range on the short wavelength side. This allows light in a wide wavelength range to be dispersed and detected with sufficient diffraction efficiency.

[0059] In the spectrometer 4, the first photodetector 27a has a plurality of pixels arranged along a first direction D1 corresponding to the spectroscopic direction of the spectroscopic unit 23 and a direction perpendicular to the first direction D1. The second photodetector 27b has a plurality of pixels arranged along a second direction D2 corresponding to the spectroscopic direction of the spectroscopic unit 23 and a direction perpendicular to the second direction D2. This makes it possible to acquire, for example, not only wavelength information, which is information along the spectroscopic direction, but also position information, which is information along the direction perpendicular to the spectroscopic direction.

[0060] The spectroscopic measurement system 1 includes a spectroscope 4 and a light irradiation unit 3 that irradiates light onto an object B. In the spectroscopic measurement system 1, light irradiated from the light irradiation unit 3 and reflected or scattered by the object B is dispersed by a spectroscopic unit 23 and detected by a light detection unit 27. For the reasons described above, this spectroscopic measurement system 1 allows the spectroscope 4 to disperse and detect light in a wide wavelength range with sufficient diffraction efficiency. [Modification]

[0061] In a first modified example shown in FIG. 9 , the prism 31 includes a dichroic surface 131a with different characteristics from the dichroic surface 31a of the above embodiment. The dichroic surface 131a reflects the first light L1 while transmitting the second light L2. The dichroic surface 131a is formed, for example, of a dielectric multilayer film. As shown in FIG. 10 , the dichroic surface 131a reflects light in a first wavelength range of 950 nm or more (reflection band) and transmits light in a second wavelength range of 900 nm or less (transmission band). In this way, the dichroic surface 131a has short-pass characteristics. In this example, irradiation light P1 in the wavelength range of 200 nm to 1700 nm is split by the splitting unit 23, and of the split light P2, first light L1 having a wavelength of 950 nm to 1700 nm (first wavelength range) is reflected by the dichroic surface 131a, and second light L2 having a wavelength of 200 nm to 900 nm (second wavelength range) is transmitted through the dichroic surface 131a. In the transition band of 900 nm to 950 nm, the characteristics of the dichroic surface 131a switch between transmission characteristics and reflection characteristics.

[0062] Therefore, in the first modified example, the relative positions of the filter 26, the first photodetector 27a, and the second photodetector 27b are different from those in the above embodiment. In this example, the first photodetector 27a is fixed on the third surface 31d of the prism 31 so that the first light L1 emitted from the prism 31 is incident thereon. In this example, the first photodetector 27a is indirectly fixed to the third surface 31d of the prism 31 via a metal part (not shown). The first photodetector 27a may also be directly fixed to the third surface 31d of the prism 31. The second photodetector 27b is fixed on the second surface 31c of the prism 31 via the filter 26 so that the second light L2 emitted from the prism 31 is incident thereon. In other words, in the first modified example, the relative positions of the filter 26, the second photodetector 27b, and the first photodetector 27a are reversed from those in the above embodiment.

[0063] Diffracted light detected by each of the first photodetector 27a and the second photodetector 27b in the first modified example will be described with reference to Figures 11 and 12. As shown in Figure 11, the first photodetector 27a, unlike the above embodiment, detects light in the reflection band rather than light in the transmission band. As shown in Figure 12, the second photodetector 27b, unlike the above embodiment, detects light in the transmission band rather than light in the reflection band. As with the above embodiment, this first modified example also makes it possible to separate and detect light in a wide wavelength range with sufficient diffraction efficiency.

[0064] 13 differs from the above embodiment in the blocking region of the filter 26 and the detection region of the photodetector 27. In this example, the filter 26 has a first filter portion 126b and a second filter portion 126c instead of the filter portion 26b, and the photodetector 27 has a second photodetector 127b instead of the second photodetector 27b.

[0065] The first filter portion 126b and the second filter portion 126c are formed in layers on the main body portion 26a. The first filter portion 126b is formed on one surface of the main body portion 26a, and the second filter portion 126c is formed on the other surface of the main body portion 26a. The filter 26 is arranged so that the first filter portion 126b faces the prism 31 and the second filter portion 126c faces the opposite side from the prism 31. The first filter portion 126b is arranged so that all of the light traveling to the second photodetector 127b is incident on the first filter portion 126b. In contrast, the second filter portion 126c is arranged so that only a portion of the light traveling to the second photodetector 127b is incident on the second filter portion 126c. In this example, the first filter portion 126b transmits the first and second light contained in the second light L2 and blocks diffracted light other than the first and second light contained in the second light L2. The second filter portion 126c transmits first-order light contained in the second light L2 and blocks diffracted light (higher-order light than the first-order light) other than the first-order light contained in the second light L2. Details of the first filter portion 126b and the second filter portion 126c will be described later.

[0066] The second photodetector 127b differs from the second photodetector 27b of the above embodiment in that it is configured to detect primary and secondary light contained in the second light L2. In FIG. 14 , the detection region R4 of the second photodetector 127b is indicated by a rectangular dotted line. The blocking region R5 of the first filter unit 126b is indicated by a trapezoidal dashed line. The blocking region R6 of the second filter unit 126c is indicated by a rectangular dashed double-dashed line. In this example, the second photodetector 127b detects light in the wavelength range of 300 nm to 1000 nm incident at a position between approximately 12.5 mm and approximately 26 mm. The first filter unit 126b is positioned so that the wavelength of the transmitted light continuously changes between approximately 12.5 mm and approximately 26 mm to block tertiary and quaternary light contained in the second light L2. The second filter portion 126c is positioned to block second-order, third-order, and fourth-order light contained in the second light L2 from approximately 12.5 mm to approximately 15 mm, but does not block diffracted light from approximately 15 mm to approximately 26 mm. As a result, first-order light contained in the second light L2 is incident on the second photodetector 127b from approximately 12.5 mm to approximately 15 mm, and second-order light contained in the second light L2 is incident on the second photodetector 127b from approximately 15 mm to approximately 26 mm. As a result, in the example of FIG. 14, first-order light is detected for a first portion C1 of the second wavelength range (wavelength range of 800 nm to 900 nm), and second-order light is detected for a second portion C2 of the second wavelength range (wavelength range of approximately 450 nm to 800 nm). The first portion C1 is longer wavelength than the second portion C2.

[0067] Such detection is effective when the diffraction efficiency of the first-order light in the first portion C1 (wavelength range of 800 nm to 900 nm) in the second wavelength range is higher than the diffraction efficiency of the second-order light in the first portion C1, as shown in Figure 8(b), for example.

[0068] An example of the characteristics of the filter 26 in the second modified example will be described with reference to FIG. 15 . The characteristics of the first filter portion 126b are similar to those of the filter portion 26b. The first filter portion 126b is provided on the entire surface of one side of the main body portion 26a, and the second filter portion 126c is provided on a portion of the surface of the other side of the main body portion 26a. The second filter portion 126c is capable of transmitting light with a wavelength of 500 nm or more that is incident on that portion and blocks light with a wavelength of less than 500 nm. Note that the characteristics of the second filter portion 126c shown in FIG. 15 are different from those shown in FIG. 14 . In the example of FIG. 14 , the second filter portion 126c is capable of transmitting light with a wavelength of approximately 650 nm or more.

[0069] As with the above embodiment, this second modification also allows light in a wide wavelength range to be dispersed and detected with sufficient diffraction efficiency. Furthermore, the light detection unit 27 detects not only the secondary light contained in the second light L2 but also the primary light contained in the second light L2. In this example, the light detection unit 27 detects the primary light contained in the second light L2 for the first portion C1 (800 nm to 900 nm) of the second wavelength range, and detects the secondary light contained in the second light L2 for the second portion C2 (approximately 450 nm to 800 nm) of the second wavelength range. Thus, when the diffraction efficiency of the primary light of the spectroscopic unit 23 in the first portion C1 of the second wavelength range is higher than the diffraction efficiency of the secondary light, the diffraction efficiency in the first portion C1 can be improved by detecting the primary light contained in the second light L2 for the first portion C1.

[0070] Furthermore, the diffraction efficiency of the first-order light of the spectroscopic unit 23 in the first portion C1 is higher than the diffraction efficiency of the second-order light of the spectroscopic unit 23 in the first portion C1. As a result, for the first portion C1 in which the diffraction efficiency of the first-order light of the spectroscopic unit 23 is higher than the diffraction efficiency of the second-order light, the diffraction efficiency of the first portion C1 can be improved by detecting the first-order light contained in the second light L2. For example, when the blaze wavelength of the spectroscopic unit 23 is 1200 nm, the diffraction efficiency of the first-order light in the first portion C1 (800 nm to 900 nm) is higher than the diffraction efficiency of the second-order light, as shown in FIG. 8B .

[0071] In the second modification described above, secondary light is not detected for the first portion C1 in the second wavelength band. However, in the third modification shown in FIG. 16, the detection region of the second photodetector 127b is set so that secondary light is also detected for the first portion C1. In FIG. 16, the detection region R7 of the second photodetector 127b is indicated by a rectangular dotted line, and the blocking region R8 of the first filter unit 126b is indicated by a trapezoidal dot-dash line. In FIG. 16, the ranges of the detection region R7 and the blocking region R8 are approximately 12.5 mm to 30 mm, which is wider than the ranges of the detection region R4 and the blocking region R5 shown in FIG. 15. By widening the range of the detection region R7 in this way, both primary and secondary light can be detected for the first portion C1.

[0072] In this example, the processing unit 5 acquires the intensity in the first portion C1 in the second wavelength band by adding up the signal amounts acquired in ranges C3 and C4 corresponding to the first portion C1. In the example of Fig. 16, the ranges C3 and C4 correspond to approximately 12.5 mm to approximately 15 mm and approximately 26 mm to approximately 30 mm, respectively.

[0073] In the third modified example described above, for the first portion C1 in the second wavelength range, both the primary light and the secondary light contained in the second light L2 are detected, and for the second portion C2 in the second wavelength range, the secondary light contained in the second light L2 is detected. For example, for the first portion C1 in which the quantum efficiency of the second photodetector 127b is low, detecting both the primary light and the secondary light contained in the second light L2 can increase the amount of signal acquired for the first portion C1.

[0074] Furthermore, the first portion C1 is on the longer wavelength side than the second portion C2. In this example, the first portion C1 is 800 nm to 900 nm, and the second portion C2 is approximately 450 nm to 800 nm. As a result, even if the quantum efficiency of the second photodetector 127b on the longer wavelength side is lower than the quantum efficiency on the shorter wavelength side, the first portion C1, where the quantum efficiency of the second photodetector 127b is low, can detect both the primary light and the secondary light contained in the second light L2, thereby increasing the amount of signal acquired for the first portion C1.

[0075] The above-described functions and effects are supplemented. For example, a CMOS image sensor is used as the second photodetector 127b. The quantum efficiency of a CMOS image sensor may decrease toward the longer wavelength side. Therefore, there is a risk that the quantum efficiency will decrease for the first portion C1, which is on the relatively longer wavelength side in the second wavelength range. In contrast, in the third modification described above, the amount of signal acquired for the first portion C1 can be increased, so that a spectral image can be generated with high accuracy even if the quantum efficiency for the first portion C1 is low.

[0076] 17, the wavelength of light detected by the light detection unit 27 differs from that of the above embodiment. In the fourth modification, light in the ultraviolet to visible range is mainly detected. In this example, the light source 11 outputs irradiation light P1, which is light in the wavelength range of 170 nm to 900 nm, for example.

[0077] In this example, the prism 31 includes a dichroic surface 231a with different characteristics from the dichroic surface 31a of the above-described embodiment. As shown in FIG. 18 , the dichroic surface 231a transmits light in a first wavelength range of 500 nm or more (transmission band) and reflects light in a second wavelength range of 450 nm or less (reflection band). The dichroic surface 231a is formed, for example, of a dielectric multilayer film. In this example, the wavelength range of the illumination light P1 is 170 nm to 900 nm, so that the first light L1 having a wavelength of 500 nm to 900 nm (first wavelength range) is transmitted through the dichroic surface 231a, and the second light L2 having a wavelength of 170 nm to 450 nm (second wavelength range) is reflected by the dichroic surface 231a.

[0078] The photodetector unit 27 includes a first photodetector 227a having a wavelength sensitivity range different from that of the first photodetector 27a of the above embodiment, and a second photodetector 227b having a wavelength sensitivity range different from that of the second photodetector 27b of the above embodiment. The first photodetector 227a and the second photodetector 227b are configured as two detectors having substantially the same wavelength sensitivity range. The term "the two detectors have substantially the same wavelength sensitivity range" includes, for example, cases where the two detectors are of the same type. Furthermore, the term "the two detectors have substantially the same wavelength sensitivity range" also includes cases where the two detectors are of different types, and the overlapping wavelength ranges of the two detectors are defined as overlapping wavelength ranges, and the overlapping wavelength ranges account for 90% or more of the wavelength sensitivity ranges of the two detectors. In this example, the first photodetector 227a and the second photodetector 227b are each a CMOS image sensor. That is, in this example, the first photodetector 227a and the second photodetector 227b are the same type (identical) detectors. The wavelength range of sensitivity of the first photodetector 227a and the second photodetector 227b is, for example, 170 nm to 900 nm. The wavelength range of sensitivity of the first photodetector 227a overlaps with at least a part (all of the first wavelength range in this example) and the wavelength range of sensitivity of the second photodetector 227b overlaps with at least a part (all of the second wavelength range in this example).

[0079] Diffracted light detected by each of the first photodetector 227a and the second photodetector 227b in the fourth modified example will be described with reference to FIGS. 19 and 20. In FIG. 19, the detection region R9 of the first photodetector 227a is indicated by a rectangular dotted line. In this example, a portion of the wavelength sensitivity range of the first photodetector 227a (450 nm to 900 nm) that overlaps with the first wavelength range (500 nm to 900 nm) is indicated as the detection region R9. In this example, the first photodetector 227a detects light in the wavelength range of 450 nm to 900 nm that is incident at a position approximately 14 mm to approximately 28 mm away. In FIG. 20, the detection region R10 of the second photodetector 227b is indicated by a rectangular dotted line. In this example, a portion of the wavelength sensitivity range of the second photodetector 227b (170 nm to 500 nm) that overlaps with the second wavelength range (170 nm to 450 nm) is indicated as the detection region R10. The filter 26 has a filter portion 226b (FIG. 17) with a different blocking region from the filter portion 26b of the above embodiment. In FIG. 20, the blocking region R11 of the filter 26 is indicated by a trapezoidal dashed line. In this example, the second photodetector 227b can detect light in the wavelength range of 170 nm to 500 nm that is incident at a position between approximately 15 mm and approximately 30 mm. The filter portion 226b is configured so that the wavelength of the light that is transmitted changes continuously between approximately 15 mm and approximately 30 mm so as to block the tertiary and quaternary light contained in the second light L2. As described above, as in the above embodiment, only the primary light contained in the first light L1 is detected by the first photodetector 227a, and only the secondary light contained in the second light L2 is detected by the second photodetector 227b.

[0080] As with the above embodiment, this fourth modification also allows light in a wide wavelength range to be dispersed and detected with sufficient diffraction efficiency. Furthermore, in the fourth modification, the first photodetector 227a and the second photodetector 227b are configured as two detectors having substantially the same wavelength sensitivity range. This allows the first photodetector 227a and the second photodetector 227b to be configured, for example, as the same detector. For example, in the fourth modification, the first photodetector 227a and the second photodetector 227b are configured as the same CMOS image sensor.

[0081] 21 , the light separating unit 25 may be configured with a dichroic mirror 32 including a dichroic surface 32a, and the prism 31 may be omitted. The characteristics of the dichroic surface 32a are the same as, for example, the characteristics of the dichroic surface 31a in the above embodiment. In this example, the filter 26 and the second photodetector 27b are arranged so that the second light L2 reflected by the dichroic surface 32a is directly incident on the filter 26.

[0082] The present disclosure is not limited to the above-described embodiments and modifications. For example, the materials and shapes of the components are not limited to those described above, and various materials and shapes can be adopted.

[0083] In the above embodiment, the first-order light contained in the first light L1 and the second-order light contained in the second light L2 are detected. However, the light detection unit 27 may also detect the N-order diffracted light (N-order light) contained in the first light L1 and the M-order diffracted light (M-order light) contained in the second light L2. Here, N and M are integers other than 0, with the absolute value of N being smaller than the absolute value of M. For example, the light detection unit 27 may detect the second-order light contained in the first light L1 and the third-order light contained in the second light L2. That is, N and M are not limited to 1 and 2, but may be 2 and 3. Alternatively, N and M may be −1 and −2. That is, the light detection unit 27 may detect the −1-order light contained in the first light L1 and the −2-order light of the second light L2.

[0084] In the above embodiment, the filter 26 blocks diffracted light other than the second-order light contained in the second light L2. However, the filter 26 may attenuate the diffracted light. However, if the filter 26 blocks the diffracted light, the second-order light contained in the second light L2 can be detected more reliably. The filter 26 may attenuate diffracted light other than the first-order light contained in the first light L1. In the above embodiment, the filter 26 is fixed on the third surface 31 d of the prism 31. However, the filter 26 may be fixed to the second photodetector 27 b. Furthermore, the filter 26 may be a component of the light separating unit 25 or the photodetector 27.

[0085] In the above embodiment, the primary light contained in the first light L1 and the secondary light contained in the second light L2 are detected by the first photodetector 27 a and the second photodetector 27 b, respectively, but the primary light and the secondary light may be detected by a single photodetector. For example, the primary light contained in the first light L1 may be detected by a first detection region of the photodetector, and the secondary light contained in the second light L2 may be detected by a second detection region of the photodetector that is separate from the first detection region.

[0086] The wavelength range of the illumination light P1 and the first and second wavelength ranges are not limited to the above examples. Furthermore, the sensitivity wavelength range of the first photodetector 27a and the sensitivity wavelength range of the second photodetector 27b are not limited to the above examples. In the above embodiment, the first photodetector 27a and the second photodetector 27b each have a plurality of pixels aligned along a direction corresponding to the spectral direction and a direction perpendicular to that direction. However, the first photodetector 27a and the second photodetector 27b may each have a plurality of pixels aligned only along the direction corresponding to the spectral direction.

[0087] 1...spectroscopic measurement system, 3...light irradiation unit, 4...spectroscope, 23...spectrometry unit, 25...light separation unit, 26...filter, 27...light detection unit, 27a, 227a...first photodetector, 27b, 127b, 227b...second photodetector, 31...prism, 31a, 32a, 131a, 231a...dichroic surface, B...object, C1...first part, C2...second part, D1...first direction, D2...second direction, L1...first light, L2...second light, P2...light.

Claims

1. A spectrometer comprising: a spectroscopic unit; a light separation unit that separates the light separated by the spectroscopic unit into a first light in a first wavelength range and a second light in a second wavelength range shorter than the first wavelength range; and a light detection unit that detects Nth-order diffracted light contained in the first light separated by the light separation unit, and detects Mth-order diffracted light contained in the second light separated by the light separation unit, wherein N and M are integers other than 0 and the absolute value of N is smaller than the absolute value of M.

2. The spectrometer according to claim 1, wherein the light detection section comprises a first photodetector that detects the Nth-order diffracted light and a second photodetector that detects the Mth-order diffracted light.

3. The spectrometer according to claim 2, wherein the first photodetector and the second photodetector are constituted by two detectors having wavelength sensitivity ranges that are substantially different from each other.

4. The spectrometer according to claim 2, wherein the first photodetector and the second photodetector are constituted by two detectors having substantially the same wavelength sensitivity range.

5. A spectrometer according to any one of claims 1 to 4, further comprising a filter disposed between the light separation unit and the light detection unit, which attenuates at least one of diffracted light other than the Nth-order diffracted light contained in the first light and diffracted light other than the Mth-order diffracted light contained in the second light.

6. A spectroscope according to any one of claims 1 to 5, wherein the light separation section has a dichroic surface that transmits one of the first light and the second light and reflects the other of the first light and the second light.

7. The spectrometer according to claim 6, wherein the light separating section has a prism including the dichroic surface, and the light detecting section is fixed directly or indirectly to the prism.

8. A spectrometer according to any one of claims 1 to 7, wherein the light detection unit detects the Nth-order diffracted light contained in the second light in addition to the Mth-order diffracted light contained in the second light.

9. A spectrometer as described in claim 8, wherein the light detection unit detects the Nth-order diffracted light contained in the second light for a first portion in the second wavelength range, and detects the Mth-order diffracted light contained in the second light for a second portion in the second wavelength range.

10. The spectrometer according to claim 9, wherein the diffraction efficiency of the Nth-order diffracted light of the spectroscopic section in the first portion is higher than the diffraction efficiency of the Mth-order diffracted light of the spectroscopic section in the first portion.

11. A spectrometer as described in claim 8, wherein the light detection unit detects both the Nth-order diffracted light and the Mth-order diffracted light contained in the second light for a first portion in the second wavelength range, and detects the Mth-order diffracted light contained in the second light for a second portion in the second wavelength range.

12. The spectrometer of claim 11, wherein the first portion is longer wavelength than the second portion.

13. A spectrometer according to any one of claims 1 to 12, wherein the absolute value of N is 1 and the absolute value of M is 2.

14. A spectroscope according to any one of claims 1 to 13, wherein the spectroscopic section includes a spectroscopic element capable of separating light in a wavelength range of at least 1000 nm to 1500 nm into first-order diffracted light.

15. A spectrometer according to any one of claims 1 to 14, wherein the spectroscopic section includes a spectroscopic element made of a blazed diffraction grating, and the blaze wavelength of the blazed diffraction grating is 1000 nm or more.

16. A spectrometer according to any one of claims 1 to 15, wherein the light detection unit has a plurality of pixels arranged along a first direction corresponding to the direction of light splitting by the spectroscopic unit and a direction intersecting the first direction.

17. A spectroscopic measurement system comprising: a spectroscope according to any one of claims 1 to 16; and a light irradiation unit that irradiates an object with light, wherein the light irradiated from the light irradiation unit and reflected or scattered by the object is dispersed by the spectroscopic unit and detected by the light detection unit.

Images