Photodetector and spectrometric measurement device

Abstract

This photodetector detects primary light from among light to be measured dispersed in the X-axis direction. A photodetector is provided with: a package having an opening; a window that seals the opening and allows the primary light to pass therethrough; and a light detection element that is disposed in the package, has a light receiving region facing the window, and detects primary light. The light receiving region includes a plurality of light detection channels arranged in the X-axis direction. The window portion includes: a light transmitting member having a light incident surface and a light exit surface; and a linear variable filter coating layer that is formed on one of the light incident surface and the light exit surface, and that transmits a wavelength change in the X-axis direction.

Description

Technical Field

[0001] The present invention relates to a light detector and a spectrophotometric device. Background Art

[0002] A spectrophotometric device is known, which includes: a light incident portion that allows light to be measured to be incident; a diffraction grating that separates the light to be measured incident from the light incident portion; and a photodetector that detects the light to be measured separated by the diffraction grating. In such a spectrophotometric device, even if light of a predetermined order (e.g., primary light) is detected among the separated light to be measured, light other than the fixed order (e.g., higher-order light than secondary light) may overlap with the light of the predetermined order. Therefore, a filter member for removing light other than the predetermined order is sometimes arranged at the front stage of the photodetector (e.g., refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-76712 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] However, if a filter is placed in front of the photodetector, stray light may increase. For example, stray light may increase due to multiple reflections of the light being measured inside the filter or between the filter and the window of the photodetector. Suppressing the influence of such stray light is extremely important in generating accurate spectral data.

[0008] An object of the present disclosure is to provide a photodetector and a spectroscopic measurement device capable of detecting light of a predetermined order among the spectroscopically measured light.

[0009] Technical means of solving problems

[0010] An optical detector according to one aspect of the present disclosure is, [1] "an optical detector, wherein it is an optical detector for detecting a predetermined number of lights in a measured light dispersed along a predetermined direction, comprising: a package having an opening; a window portion, which seals the opening and allows the predetermined number of lights to pass through; and an optical detection element, which is arranged in the package, has a light receiving area opposite to the window portion, and detects the predetermined number of lights, the light receiving area comprising: a plurality of light detection channels arranged in the predetermined direction, the window portion comprising: a light transmitting member having a light incident surface and a light exiting surface; and a linear variable filter coating, which is formed on one of the light incident surface and the light exiting surface and transmits a wavelength change along the predetermined direction".

[0011] In the spectrophotometric device described in [1] above, the window portion that seals the opening of the package body includes: a light-transmitting member; and a linear variable filter coating whose transmission wavelength changes along a predetermined direction of the spectroscopic light to be measured. Thus, for each of the plurality of wavelength components included in the light to be measured, light of a number other than a predetermined number can be suppressed from entering the light detection element. In addition, in the photodetector described in [1] above, the linear variable filter coating is formed on one of the light incident surface and the light exit surface of the light-transmitting member. For example, when a filter coating of a single transmission wavelength is formed on each of the light incident surface and the light exit surface of the light-transmitting member, the light to be measured may be reflected multiple times between the filter coating formed on the light incident surface and the filter coating formed on the light exit surface. However, in the photodetector described in [1] above, the generation of stray light due to the multiple reflections can be suppressed. As described above, according to the photodetector described in [1] above, light of a predetermined number in the spectroscopic light to be measured can be detected.

[0012] The photodetector according to one aspect of the present disclosure may also be, [2] "the photodetector according to the above [1], wherein the linear variable filter coating is formed on the light incident surface". According to the photodetector described in [2], compared with the case where the linear variable filter coating is arranged on the light exit surface, the package body and the window portion can be easily and reliably joined.

[0013] The photodetector according to one aspect of the present disclosure may be [3] "a photodetector according to [1] or [2] above, wherein the light of the predetermined order is primary light". According to the photodetector described in [3], the linear variable filter coating can function as a high-order light cutoff filter for transmitting primary light in the measured light, thereby generating spectral data with excellent S / N.

[0014] The photodetector according to one aspect of the present disclosure may also be [4] "a photodetector according to any one of [1] to [3] above, wherein the linear variable filter coating is a linear variable long-pass filter coating whose cutoff wavelength varies along the specified direction, or a linear variable band-pass filter coating whose transmission wavelength varies along the specified direction". According to the photodetector described in [4], since the transmission of high-order light is suppressed based on light of a specified order, it is possible to suppress unnatural peaks caused by the high-order light from appearing in the spectral data.

[0015] The photodetector according to one aspect of the present disclosure may be, [5] "a photodetector as described in any one of [1] to [4] above, wherein the window portion further includes: a reflection reducing layer formed on the other of the light incident surface and the light exit surface". According to the photodetector described in [5], stray light generated by multiple reflections of the light to be measured between the light exit surface and the light receiving area can be reduced.

[0016] The spectroscopic measurement device of one aspect of the present disclosure may also be, [6] "a spectroscopic measurement device comprising: a light incident portion, which allows the measured light to be incident; a diffraction grating, which disperses the measured light incident from the light incident portion; an analysis portion, which generates spectral data of the measured light; and a light detector described in any one of [1] to [5] above."

[0017] According to the spectrophotometric measurement device described in [6], the light of a predetermined number of times in the spectroscopically measured light can be detected by the photodetector.

[0018] Effects of the Invention

[0019] According to the present disclosure, it is possible to provide a photodetector and a spectroscopic measurement device capable of detecting light of a predetermined order in the spectroscopically measured light. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a diagram showing the structure of a spectrophotometer according to one embodiment.

[0021] Figure 2 It is shown Figure 1 A diagram showing the structure of a photodetector.

[0022] Figure 3 is along Figure 2 A cross-sectional view of the photodetector along line III-III is shown.

[0023] Figure 4 It is shown Figure 2 A graph showing the transmission wavelength characteristics of a linear variable filter coat.

[0024] Figure 5 It shows the light transmission once Figure 2 A diagram showing the manner of the window portion shown.

[0025] Figure 6 It is shown in Figure 2 The diagram shows the shape of stray light generated by the window shown.

[0026] Figure 7 This is a diagram showing the transmission wavelength characteristics of the filter coating included in the window portion of the first comparative example.

[0027] Figure 8 It shows the light transmission once Figure 7 The shape of the window shown in Figure 7 The diagram shows the shape of stray light generated by the window shown.

[0028] Fig. 9 It is a diagram showing the state in which stray light is generated in the window portion of the second comparative example.

[0029] Fig.10 It is a diagram showing a state in which the measurement light is transmitted through the window portion of the modification example. DETAILED DESCRIPTION

[0030] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in each figure, and repeated descriptions are omitted.

[0031] [Structure of Spectrophotometer]

[0032] like Figure 1 As shown, the spectrometer 1 includes a light incident unit 2, a diffraction grating 3, a photodetector 10, a lens 5, and an analysis unit 6. The spectrometer 1 generates spectrum data of a plurality of wavelength components L2 included in the light L1 by splitting the light L1 to be measured.

[0033] The light incident portion 2, the diffraction grating 3 and the lens 5 constitute an optical system (so-called Dyson optical system) for guiding the measured light L1 to the light receiving area 13a of the light detection element 13 included in the light detector 10, and forming the spectral images of the multiple wavelength components L2 of the measured light L1 on the light receiving area 13a of the light detector 10 along the wavelength axis. In the present embodiment, the diffraction grating 3 is a reflective diffraction grating. The measured light L1 passes through the diffraction grating 3 and is split in a direction perpendicular to the direction in which the measured light L1 is incident. Here, the direction in which the measured light L1 is split (that is, the direction parallel to the wavelength axis) is called the X-axis direction, the direction perpendicular to the X-axis direction is called the Y-axis direction, and the direction perpendicular to the X-axis direction and the Y-axis direction is called the Z-axis direction. In addition, the light detector 10 blocks the secondary light in the measured light L1 and detects the primary light. The secondary light sometimes appears as an unnatural peak in the spectral data. Therefore, in order to extract the light of a specified order (primary light), the secondary light must be blocked. The details will be described later.

[0034] The light incident part 2 is configured to allow the measured light L1 to be incident into the spectroscopic measurement device 1. The light incident part 2 adjusts the incident amount of the measured light L1. The light incident part 2 is, for example, a slit member. The slit formed in the slit member opens in a rectangular shape with the X-axis direction as the short side and the Z-axis direction as the long side when viewed from the Y-axis direction. If the width of the short side is increased, the incident amount of the measured light L1 increases, so that spectral data with less noise but low wavelength resolution is obtained in the analysis part 6. On the other hand, if the width of the short side is narrowed, the incident amount of the measured light L1 decreases, so that spectral data with improved wavelength resolution but more noise is obtained in the analysis part 6. The light incident part 2 may also be composed of, for example, a slit member and an optical fiber that transmits the measured light L1 to the slit member. Alternatively, the light incident part 2 may also be composed of, for example, a slit member and a lens structure that focuses the measured light L1 from the outside of the slit member.

[0035] The diffraction grating 3 is opposite to the light incident portion 2 in the Y-axis direction. Since the diffraction grating 3 is a reflection type, the measured light L1 is split to the opposite side of the direction in which the measured light L1 is incident. The diffraction grating 3 is composed of a plurality of grating grooves (not shown). The plurality of grating grooves are arranged in the direction perpendicular to the incident direction of the measured light L1, that is, the X-axis direction, and extend in the direction perpendicular to the arrangement direction, that is, the Z-axis direction. The measured light L1 incident on the diffraction grating 3 is split corresponding to the plurality of wavelength components L2 along the direction in which the plurality of grating grooves are arranged, that is, the X-axis direction.

[0036] The photodetector 10 is opposite to the diffraction grating 3 in the Y-axis direction. The photodetector 10 has a photodetection element 13. The photodetection element 13 includes a light receiving area 13a that receives a plurality of wavelength components L2. In the photodetector 10, a spectral image having a wavelength axis along the X-axis direction is formed on the light receiving area 13a. The light receiving area 13a is in a strip shape with the X-axis direction as the long side direction, and has a plurality of light detection channels arranged along the X-axis direction (predetermined direction). That is, the arrangement direction of the plurality of light detection channels is consistent with the direction in which the measured light L1 is spectrally dispersed. Therefore, each wavelength component L2 is incident on a different position (different light detection channel) at a certain interval along the long side direction of the light receiving area 13a. Each light detection channel is composed of a plurality of pixels along the Z-axis direction. The photodetector 10 receives the spectral image in the light receiving area 13a over a predetermined exposure time, and outputs the spectrum data S of each wavelength component L2. The photodetection element 13 is, for example, a CCD image sensor or a CMOS image sensor formed on a semiconductor substrate. The CCD image sensor may be any of an interline type, a frame transfer type, and a full frame transfer type.

[0037] In the present embodiment, the position of the photodetector 10 in the Y-axis direction is consistent with the light incident portion 2. The photodetector 10 is arranged on the incident side of the multiple wavelength components L2 at a certain distance from the light incident portion 2 in the Z-axis direction. In other words, the photodetector 10 is offset toward the incident side of the multiple wavelength components L2 relative to the light incident portion 2 in the direction perpendicular to the wavelength axis (Z-axis direction).

[0038] The lens 5 is arranged between the light incident portion 2 and the photodetector 10 and the diffraction grating 3 in the Y-axis direction. The lens 5 guides the measured light L1 incident from the light incident portion 2 to the diffraction grating 3, and forms a spectroscopic image of a plurality of wavelength components L2 in the light receiving area 13a of the photodetector 10. The lens 5 is a convex lens having a surface 5a and a convex surface 5b on the opposite side of the surface 5a. The surface 5a faces the light incident portion 2 and the photodetector 10. The surface 5a is a flat surface, a concave surface, or a convex surface. The convex surface 5b is a surface facing the diffraction grating 3 and convexly curved to the opposite side of the surface 5a.

[0039] The analyzing unit 6 generates the spectrum data S of the measured light L1 based on the data obtained from the photodetector 10. The content of the analysis by the analyzing unit 6 will be described later. The analyzing unit 6 includes: a storage unit for storing the data obtained from the photodetector 10 and the analysis results. In addition, the analyzing unit 6 can also control the photodetector 4. The analyzing unit 6 can also be a computer or a tablet terminal having a processor such as a CPU (Central Processing Unit) and a storage medium such as a RAM (Random Access Memory) or a ROM (Read Only Memory). In addition, the analyzing unit 6 can also be composed of a microcomputer or an FPGA (Field Programmable Gate Array).

[0040] In the spectroscopic measurement device 1 configured as described above, the light to be measured L1 incident from the light incident portion 2 is incident with respect to the surface 5a at a certain incident angle. The light to be measured L1 incident on the surface 5a is refracted on the surface 5a according to the difference between the refractive index of air and the refractive index of the lens 5, travels in the lens 5, and is emitted from the convex surface 5b. The light to be measured L1 emitted from the convex surface 5b is refracted on the convex surface 5b according to the difference between the refractive index of the lens 5 and the refractive index of air, and is guided to the diffraction grating 3 at the subsequent stage.

[0041] The multiple wavelength components L2 separated by the diffraction grating 3 are incident on the lens 5. The lens 5 allows the multiple wavelength components L2 to be incident at a certain incident angle relative to the convex surface 5b. The multiple wavelength components L2 incident on the convex surface 5b are refracted on the convex surface 5b according to the difference between the refractive index of the air and the refractive index of the lens 5, and travel in the lens 5 to be emitted from the surface 5a. The multiple wavelength components L2 emitted from the surface 5a are refracted on the surface 5a according to the difference between the refractive index of the lens 5 and the refractive index of the air, and are imaged on the photodetector 4 at the rear stage, forming a spectroscopic image on the light receiving area 13a.

[0042] [Structure of Photodetector]

[0043] like Figure 2 and Figure 3 As shown, the photodetector 10 further includes: a package 11, and a window portion 12. The package 11 is composed of a bottom wall 111, a side wall 112, and a top wall 113. The bottom wall 111 is in the shape of a flat plate. The side wall 112 is in the shape of a frame having an opening in a rectangular shape. The top wall 113 is in the shape of a cap having an opening in a rectangular shape. The side wall 112 is arranged on the bottom wall 111 and is joined to the bottom wall 111. The top wall 113 is arranged on the side wall 112 and is joined to the side wall 112. Thus, a space SP is formed in the package 11. As an example, the bottom wall 111, the side wall 112, and the top wall 113 are respectively made of metal.

[0044] A light detecting element 13 is arranged on the bottom wall 111. The light detecting element 13 is arranged in the space SP in the package 11. An opening 11a is formed in the package 11. Specifically, the opening 11a is formed on the top wall 113 in a manner facing the light detecting element 13. When viewed from the Y-axis direction, the inner edge of the top wall 113 forming the opening 11a is smaller than the inner edges of the side walls 112 and the top wall 113 forming the space SP. That is, the top wall 113 forms a stepped shape when viewed from the Z-axis direction in a manner in which the area of ​​the inner edge decreases from the inner edge forming the space SP to the inner edge forming the opening 11a. The opening 11a allows multiple wavelength components L2 to be incident into the package 11.

[0045] The window portion 12 is arranged on the top wall 113 in a manner to seal the opening 11a. The window portion 12 is opposite to the light receiving area 13a of the light detection element 13 arranged in the package 11 in the Y-axis direction. The window portion 12 includes: a light transmitting component 121, and a linear variable filter coat 122. The light transmitting component 121 includes: a light incident surface 121a and a light emitting surface 121b that are opposite to each other in the Y-axis direction. In the present embodiment, the light emitting surface 121b of the window portion 12 is joined to the surrounding portion of the opening 11a of the top wall 113 to ensure the airtightness of the space SP. The light transmitting component 121, when observed from the Y-axis direction, is in the shape of a rectangle with the X-axis direction as the long side and the Z-axis direction as the short side. The light transmitting component 121 is made of, for example, glass, quartz, silicon, germanium, plastic, etc.

[0046] The linear variable filter coating 122 is formed on the light incident surface 121a. Like the light transmitting component 121, the linear variable filter coating 122 is in a rectangular shape with the long side in the X-axis direction and the short side in the Z-axis direction when observed from the Y-axis direction. The outer edge of the linear variable filter coating 122 is not completely consistent with the outer edge of the light transmitting component 121, and there is a portion 123 where the linear variable filter coating 122 and the light incident surface 121a do not overlap. Specifically, the length of the short side of the linear variable filter coating 122 is the same as the length of the short side of the light transmitting component 121, and the length of the long side of the linear variable filter coating 122 is shorter than the length of the long side of the light transmitting component 121. Therefore, in Figure 2 and Figure 3 In the example of FIG. 1 , one short side of the linear variable filter coating 122 is consistent with one short side of the light-transmitting member 121, but the other short side of the linear variable filter coating 122 is located inside the other short side of the light-transmitting member 121. The linear variable filter coating 122 is a coating formed by applying an insulating multilayer film on the light incident surface 121a by evaporation or the like, and is continuously formed without a gap. For example, the thickness of the linear variable filter coating 122 gradually increases in a slope from one short side along the X-axis direction.

[0047] When viewed from the Y-axis direction, the inner edge of the top wall 113 forming the opening 11a is larger than the outer edge of the light detecting element 13. Furthermore, the outer edge of the light transmitting member 121 is larger than the inner edge of the top wall 113 forming the opening 11a. In addition, a portion of the outer edge of the light detecting element 13 overlaps with a portion 123 where the linear variable filter coating 122 and the light incident surface 121a do not overlap. Specifically, the other short side of the light detecting element 13 is located outside the other short side of the linear variable filter coating 122.

[0048] The transmission wavelength of the linear variable filter coating 122 changes along the X-axis direction (predetermined direction). Specifically, as the linear variable filter coating 122 and the light incident surface 121a do not overlap, the transmission wavelength gradually changes to a high wavelength band. In other words, the blocked wavelength band gradually increases. Figure 4 As an example, an example of the characteristics of the transmission wavelength of the linear variable filter coating 122 is described. The transmission wavelength characteristic T1 of the portion closest to the portion 123 where the linear variable filter coating 122 and the light incident surface 121a do not overlap is that the transmittance starts to rise from about 430nm, the transmittance is about 0.9 at about 460nm, and the cut-off wavelength (the wavelength at which the transmittance reaches 50%) is about 450nm. On the other hand, the transmission wavelength characteristic T2 of the portion farthest from the portion 123 where the linear variable filter coating 122 and the light incident surface 121a do not overlap is that the transmittance starts to rise from about 780nm, the transmittance is about 0.9 at about 830nm, and the cut-off wavelength is about 810nm. The transmission wavelength of the linear variable filter coating 122 gradually changes to a high wavelength band between T1 and T2. In this embodiment, a plurality of wavelength components L2 are incident along the direction in which the transmission wavelength of the linear variable filter coating 122 changes. Therefore, in each wavelength component L2 , the primary light is transmitted, while the secondary light is suppressed from being incident on the photodetection element 13 .

[0049] Reference Figure 5 , the relationship between each wavelength component L2 and the transmission wavelength is described in more detail. Figure 5 As shown, the plurality of wavelength components L2 are set to include a wavelength component having λ1 1 ~λ1 5 The wavelength component of the central wavelength. λ1 1 ~λ1 5 Here, for example, let λ1 1 :300nm、λ1 2 :450nm、λ1 3 :600nm、λ1 4 :750nm、λ1 5 :900nm.λ1 1 ~λ1 5 According to the above sequence, the diffraction angle becomes larger, and according to the above sequence, it is incident on the linear variable filter coating 122 along the direction of the change of the transmission wavelength. 1 The secondary light is set to λ2 1 , change λ1 2 The secondary light is set to λ2 2 λ2 1 The value of the central wavelength is related to λ1 1 Same as 300nm, but λ2 1 The diffraction angle is related to λ1 1The diffraction angles are different. 1 The diffraction angle is equal to λ1 1 The central wavelength is twice that of λ1 3 The same diffraction angle. That is, at the same 3 The incident position of λ2 is also incident at the same position as the incident position of 1 Similarly, λ1 2 The secondary light λ2 2 (Center wavelength 450nm) incident on λ1 2 The central wavelength is twice that of λ1 5 The linear variable filter coating 122 is used to convert the primary light (λ1 1 ~λ1 5 ) is transmitted, so that the secondary light (λ2 1 ,λ2 2 ) and functions as a filter that blocks the primary light. Therefore, the window 12 allows the primary light in each wavelength component L2 to pass through, and the photodetector 10 detects the primary light. The linear variable filter coating 122 functions as a long pass filter by allowing the wavelength components above the central wavelength of the primary light to pass through. In other words, the linear variable filter coating 122 is a linear variable long pass filter coating whose cutoff wavelength changes along the X-axis direction (predetermined direction). In addition, λ1 1 The light enters the part 123 of the linear variable filter coating 122 which does not overlap with the light incident surface 121a. This is because, due to λ1 1 The central wavelength of is 300 nm, and thus is blocked by the linear variable filter coating 122 .

[0050] Here, λ1 1 ~λ1 5 The wavelengths of the light incident on the linear variable filter coating 122 are the corresponding transmission wavelengths. 3 The characteristic of the transmission wavelength corresponding to the incident position is that the primary light, i.e., λ1 3 (Central wavelength 600nm) is transmitted, while the secondary light, λ2 1 (Central wavelength 300nm) is blocked. In addition, 5 The characteristic of the transmission wavelength corresponding to the incident position is that the primary light, i.e., λ1 5 (central wavelength 900nm) is transmitted, while the secondary light, λ2 2 (Central wavelength 450nm) blocked.

[0051] [Function and Effect]

[0052] In the photodetector 10, the window portion 12 that seals the opening 11a of the package 11 includes: a light transmitting member 121; and a linear variable filter coating 122, whose transmission wavelength changes along the X-axis direction, that is, the direction in which the measured light L1 is split. Thus, for each of the multiple wavelength components L2 included in the measured light L1, the secondary light (λ2 1 ,λ2 2 ) is incident on the light detecting element 13. In addition, in the light detector 10, the linear variable filter coating 122 is formed on the light incident surface 121a of the light transmitting member 121. For example, in the case where a filter coating of a single transmission wavelength is formed on each of the light incident surface 121a and the light exit surface 121b of the light transmitting member 121, the measured light L1 may be multiply reflected between the filter coating formed on the light incident surface 121a and the filter coating formed on the light exit surface 121b. However, in the light detector 10, the generation of stray light due to the multiply reflection can be suppressed. As described above, according to the light detector 10, the primary light (λ1 1 ~λ1 5 ).

[0053] In the photodetector 10, the linear variable filter coating 122 is formed on the light incident surface 121a. Therefore, compared with the case where the linear variable filter coating 122 is arranged on the light exit surface 121b, the package 11 can be easily and reliably joined to the window portion 12. In addition, compared with the case where the linear variable filter coating 122 is arranged on the light exit surface 121b, it is easy to join the light exit surface 121b of the window portion 12 to the surrounding portion of the opening 11a of the top wall 113, and the airtightness of the space SP can be easily ensured.

[0054] In the photodetector 10, the light of a predetermined number is the primary light (λ1 1 ~λ1 5 ). Primary light (λ1 1 ~λ1 5 ) compared to the secondary light (λ2 1 ,λ2 2 ), the light intensity is high. Therefore, according to the light detector 10, by making the linear variable filter coating 122 as the primary light (λ1 1 ~λ1 5 ) by functioning as a secondary light cutoff filter that transmits light, thereby generating spectral data S with excellent S / N.

[0055] In the optical detector 10, the linear variable filter coating 122 is a linear variable long-pass filter coating whose cut-off wavelength varies along the X-axis direction. 1 ~λ1 5 ) as a reference to suppress secondary light (λ2 1 ,λ22 ) can suppress the secondary light (λ2 1 ,λ2 2 ) causes unnatural peaks to appear in the spectral data S.

[0056] According to the spectroscopic measurement device 1, the photodetector 10 can detect the primary light (λ1 1 ~λ1 5 ).

[0057] [Comparative Example]

[0058] like Figure 6 As shown in FIG. 1 , a part of the measured light L1 incident on the window portion 12 may be reflected by the light exit surface 121b of the light transmitting member 121, and then reflected by the surface of the linear variable filter coating 122, thereby becoming stray light L3. The stray light L3 may appear as an unnatural peak in the spectrum data, and therefore should be suppressed. However, compared with the comparative example described later, the linear variable filter coating 122 can reduce the cause of the generation of the stray light L3.

[0059] Reference Figure 7 , Figure 8 , the window portion 12a of the first comparative example will be described. Figure 7 As shown in (a), in the window portion 12a, a filter coating 122a is formed on the light incident surface 121a of the light transmitting member 121, and a filter coating 122b is formed on the light emitting surface 121b of the light transmitting member 121. The filter coating 122a and the filter coating 122b, when observed from the Y-axis direction, are in a rectangular shape with the X-axis direction as the long side and the Z-axis direction as the short side. One short side of the filter coating 122a is consistent with one short side of the light transmitting member 121 and one short side of the filter coating 122b. The other short side of the filter coating 122a is located on the inner side than the other short side of the light transmitting member 121, and is located on the outer side than the other short side of the filter coating 122b. As shown Figure 7 As shown in (b), the filter coating 122a and the filter coating 122b have a single transmission wavelength characteristic that is different from each other. An example of the transmission wavelength characteristic is as follows. The transmission wavelength characteristic T3 of the filter coating 122a is that the transmittance starts to increase from about 420nm and the transmittance is about 0.9 at about 450nm. The cut-off wavelength is about 440nm. On the other hand, the transmission wavelength characteristic T4 of the filter coating 122b is that the transmittance starts to increase from about 520nm and the transmittance is about 0.9 at about 570nm. The cut-off wavelength is about 550nm.

[0060] Reference Figure 8 , the relationship between each wavelength component L2 and the transmission wavelength is described in more detail. 1 ~λ15 The values ​​of the respective central wavelengths are the same as those in the embodiment. The filter coatings 122a and 122b are similar to the linear variable filter coating 122 as a means for converting the primary light (λ1 1 ~λ1 5 ) is transmitted, so that the secondary light (λ2 1 ,λ2 2 ) blocks the light and functions as a filter. For example, λ1 3 Through the filter coatings 122a and 122b, but λ2 1 The light is blocked by the filter coating 122a. Here, when the filter coating 122a and the filter coating 122b are used, stray light is generated due to various factors. For example, since the other short side of the filter coating 122b is located on the inner side than the other short side of the filter coating 122a, the other short side of the filter coating 122b becomes an end face when viewed from the Z-axis direction. Sometimes, any wavelength component among the plurality of wavelength components L2 is scattered at the end face of the filter coating 122b, and becomes a cause of stray light L3. Furthermore, sometimes, any wavelength component among the plurality of wavelength components L2 is multiply reflected between the filter coating 122a and the filter coating 122b, and becomes a cause of stray light L3. These are all stray lights L3 that are unlikely to be generated when the linear variable filter coating 122 of the embodiment is used as a part of the window portion 12. Therefore, in the light detector 10 of the embodiment, the stray light L3 caused by scattering or multiply reflection can be suppressed from entering the light detection element 13.

[0061] Next, refer to Fig. 9 , the window portion 12b of the second comparative example is described. In the window portion 12b, instead of forming a filter coating on the light-transmitting member 121, a filter member 122c having a thickness greater than that of the filter coating is disposed on the light incident surface 121a. The filter member 122c is combined with the light-transmitting member 121 to form the window portion 12b. In this case, stray light L3 is generated due to various factors. For example, stray light L3 is generated due to multiple reflections inside the filter member 122c, or multiple reflections between the filter member 122c and the light incident surface 121a or the light exit surface 121b. That is, compared with the linear variable filter coating 122 of the embodiment, the number of locations where stray light may be generated is significantly increased.

[0062] [Example of variation]

[0063] The present disclosure is not limited to the above-mentioned embodiments. The linear variable filter coating 122 may also be a linear variable band pass filter coating (linear variable band pass filter coat) whose transmission band changes along the X-axis direction. In this case, the linear variable filter coating 122 functions as a filter that transmits only a certain range of wavelength components including the central wavelength of the primary light for each wavelength component L2. Thus, since the transmission of the secondary light is suppressed based on the primary light, it is possible to suppress the unnatural peak caused by the secondary light from appearing in the spectrum data S. In addition, the spectroscopic measurement device 1 of the embodiment is a Dyson optical system having a light incident part 2, a diffraction grating 3, a photodetector 10, a lens 5, and an analysis part 6, but it may also be a different optical system. For example, it may also be a Zenittana optical system. Furthermore, when an optical system different from the Dyson optical system is adopted, the diffraction grating 3 may also be a transmission type diffraction grating. In addition, the linear variable filter coating 122 may also be formed on the light exit surface 121b. In addition, the light blocked by the linear variable filter coating 122 is not limited to the secondary light. For example, higher-order light (third-order light or fourth-order light, etc.) than the secondary light may be blocked, diffracted light of a negative order may be blocked, and reflected light (zero-order light) may be blocked. On the other hand, the linear variable filter coating 122 may transmit light of an order other than the primary light (for example, light of the above-mentioned order) as a predetermined order, and block the primary light.

[0064] like Fig.10 As shown, the window portion 12 may also include a reflection reducing layer 124 . Fig.10 The window portion 12 shown includes a light-transmitting member 121, a linear variable filter coating 122, and a reflection-reducing layer 124. Fig.10 In the window portion 12 shown in FIG. 1 , a linear variable filter coating 122 is formed on the light incident surface 121a of the light transmitting member 121, and a reflection reducing layer 124 is formed on the light exiting surface 121b of the light transmitting member 121. The reflection reducing layer 124 is made of, for example, magnesium fluoride (MgF 2 ), silicon dioxide (SiO 2 ), titanium oxide (TiO 2 )、ZrO 2 ) or tantalum pentoxide (Ta 2 O 5 ) or a stack of these multiple substances.

[0065] exist Fig.10In the window portion 12 shown, the reflection reducing layer 124 is formed on the entire surface of the light exit surface 121b. That is, when viewed from the Y-axis direction, the outer edge of the reflection reducing layer 124 coincides with the outer edge of the light transmitting member 121. However, the reflection reducing layer 124 may be formed on a portion of the light exit surface 121b. For example, the reflection reducing layer 124 may be formed so as to overlap at least the linear variable filter coating 122 when viewed from the Y-axis direction. In this case, the outer edge of the reflection reducing layer 124 may also coincide with the outer edge of the linear variable filter coating 122 when viewed from the Y-axis direction.

[0066] The reflection reducing layer 124 is, for example, an AR coating (Anti-Reflection coating). In this case, if the reflected light L4 of the measured light L1 reflected in the light receiving area 13a enters the reflection reducing layer 124, the reflected light L4 is canceled out by light interference in the reflection reducing layer 124. For example, in the reflection reducing layer 124, the reflected light L4 is canceled out by interference between the light reflected from the surface of the light transmitting component 121 side of the reflection reducing layer 124 and the light reflected from the surface of the reflection reducing layer 124 on the light receiving area 13a side. In the case where the reflection reducing layer 124 is not formed, the reflected light L4 is reflected from the light emitting surface 121b of the light transmitting component 121, and multiple reflections occur between the light emitting surface 121b and the light receiving area 13a, and may become stray light. Fig.10 The window portion 12 shown in the figure can reduce stray light caused by the reflected light L4 by forming a reflection reducing layer 124 on the light emitting surface 121b.

[0067] The reflection reducing layer 124 is not limited to an AR coating. The reflection reducing layer 124 may be, for example, a multilayer film. In this case, the refractive index of the reflection reducing layer 124 changes layer by layer. For example, the refractive index of the reflection reducing layer 124 may also change in stages from the refractive index of the gap between the reflection reducing layer 124 and the light receiving area 13a (refractive index of air) to the refractive index of the light transmitting member 121. In this case, the reflected light L4 is not reflected at the light emitting surface 121b of the light transmitting member 121, but is emitted to the outside via the light transmitting member 121 and the linear variable filter coating 122.

[0068] Alternatively, the linear variable filter coating 122 may be formed on the light exit surface 121b of the light transmitting member 121, and the reflection reducing layer 124 may be formed on the light incident surface 121a of the light transmitting member 121. In this case, for example, in the reflection reducing layer 124, light reflected from the surface of the reflection reducing layer 124 on the light transmitting member 121 side interferes with light reflected from the surface of the reflection reducing layer 124 on the opposite side to the light transmitting member 121, thereby canceling out the reflected light L4.

[0069] [Explanation of symbols]

[0070] 1…spectrometric measuring device, 2…light incident portion, 3…diffraction grating, 10…photodetector, 6…analyzing portion, 11…package, 11a…opening, 12…window portion, 13…photodetecting element, 13a…light receiving region, 121…light transmitting member, 121a…light incident surface, 121b…light emitting surface, 122…linear variable filter coating, 124…reflection reducing layer, L1…measured light, S…spectral data

Claims

1. A light detector, wherein: A photodetector for detecting light of a predetermined number of times in the light to be measured that is dispersed in a predetermined direction. have: a package having an opening; a window portion that seals the opening and allows the predetermined number of times of light to pass therethrough; and a light detecting element disposed in the package, having a light receiving area facing the window portion and detecting the light of the predetermined number of times, The light receiving area includes: a plurality of light detection channels arranged in the specified direction, The window portion comprises: a light-transmitting member having a light-incident surface and a light-exiting surface; and A linear variable filter coating is formed on one of the light incident surface and the light emitting surface and changes the transmission wavelength along the specified direction.

2. The optical detector according to claim 1, wherein The linear variable filter coating is formed on the light incident surface.

3. The light detector according to claim 1, wherein The light of the predetermined number of times is the light of one time.

4. The light detector according to claim 1, wherein The linear variable filter coating is a linear variable long-pass filter coating whose cutoff wavelength varies along the specified direction, or a linear variable band-pass filter coating whose transmission wavelength varies along the specified direction.

5. The light detector according to claim 1, wherein The window portion further includes a reflection reducing layer formed on the other of the light incident surface and the light emitting surface.

6. A spectrophotometric measuring device comprising: a light incident portion for causing the light to be measured to be incident; a diffraction grating for splitting the light to be measured incident from the light incident portion; an analyzing unit that generates spectrum data of the light to be measured; and The photodetector according to any one of claims 1 to 5.

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