Optical detector and spectroscopic measuring device

Abstract

An optical detector detects primary light in a light to be measured that is dispersed in an X-axis direction. The optical detector comprises: a housing having an opening; a window that closes the opening and allows the passage of light of a predetermined order; and a light-sensing element arranged in the housing, comprising a light-receiving area facing the window and configured to detect the predetermined order of light. The light-receiving area comprises a plurality of light-sensing channels arranged in the X-axis direction. The window comprises: a light-transmitting element having an incidence surface and a light-emission surface; and a linear variable filter coating formed on the incidence surface or the light-emission surface, having a transmitted wavelength that changes along the X-axis direction.

Description

Technical field

[0001] The present invention relates to an optical detector and a spectroscopic measuring device. State of the art

[0002] A spectroscopic measuring device is known comprising a light entrance section onto which light to be measured can be incident, a diffraction grating that disperses the light to be measured incident on the light entrance section, and an optical detector that detects the light to be measured dispersed by the diffraction grating. If, in such a spectroscopic measuring device, an attempt is made to detect light of a predetermined order (for example, primary light) from the dispersed light to be measured, light of a different order than the predetermined one (for example, secondary light or light of a higher order) can be superimposed on the light of the predetermined order. Therefore, a filter element for removing light of a different order than the predetermined one can be arranged at an upstream stage of the optical detector (see, for example, patent reference 1). Reference list patent literature

[0003] Patent literature 1: Unexamined Japanese patent with publication number 2020-76712 Summary of the invention Problem statement

[0004] However, if the filter element is located on an upstream side of the optical detector, more stray light may be generated. For example, more stray light can be caused by multiple reflections of the light being measured within the filter element or between the filter element and a window of the optical detector. Suppressing the effects of such stray light is extremely important for generating accurate spectral data.

[0005] It is an object of the invention to provide an optical detector and a spectroscopic measuring device that can detect light of a predetermined order from the dispersed light to be measured. Problem solving

[0006] An optical detector according to one aspect of the invention is [1] “an optical detector for detecting light of a predetermined order in light to be measured dispersed in a predetermined direction, wherein the optical detector comprises: a housing having an opening; a window closing the opening and allowing the passage of light of the predetermined order; and a light-sensing element arranged in the housing, comprising a light-receiving area facing the window and configured to detect light of the predetermined order; wherein the light-receiving area comprises a plurality of light-sensing channels arranged in the predetermined direction; and wherein the window comprises: a light-transmitting element with a light-incidence surface and a light-emitting surface;and a linear variable filter coating formed on the light incidence surface or the light emission surface and having a transmitted wavelength that changes along the predetermined direction.

[0007] In the optical detector of [1], the window closing the opening of the housing comprises the light transmitting element and the linear variable filter coating, which has a transmitted wavelength that changes along the predetermined direction in which the light to be measured is dispersed. In this way, the incident of light of a different order than the predetermined order onto the light detection element can be prevented for each of the multitude of wavelength components in the light to be measured. Furthermore, in the optical detector of [1], the linear variable filter coating is formed on the light-incidence surface or the light-emission surface of the light transmitting element.For example, if a filter coating of a single transmitted wavelength is formed on both the light-incidence and light-emission surfaces of the light-transmitting element, the light to be measured can be reflected multiple times between the filter coating formed on the light-incidence surface and the filter coating formed on the light-emission surface. However, in the optical detector of [1], the generation of scattered light due to multiple reflections can be prevented. As described above, the optical detector of [1] can detect the predetermined order of the light in the dispersed light to be measured.

[0008] An optical detector according to one aspect of the invention can [2] be “the optical detector of [1] wherein the linear variable filter coating is formed on the light incidence surface.” In the optical detector of [2], the housing and the window can be connected more easily and reliably than in a case where the linear variable filter coating is arranged on the light emission surface.

[0009] An optical detector according to one aspect of the invention can be [3] “the optical detector of [1] or [2], wherein the light of the predetermined order is a primary light.” The primary light has a higher light intensity than a secondary light. In the optical detector of [3], spectral data with an excellent signal-to-noise (S / N) ratio can be generated by causing the linear variable filter coating to act as a clipping filter for higher-order light that transmits the primary light in the light to be measured.

[0010] An optical detector according to one aspect of the invention can [4] “be the optical detector of one of [1] to [3], wherein the linear variable filter coating is a linear variable longpass filter coating in which the cut-on wavelength changes along the predetermined direction, or a linear variable bandpass filter coating in which a transmitted wavelength band changes along the predetermined direction.” In the optical detector of [4], transmission of higher-order light is suppressed based on the light of a predetermined order, so that the occurrence of an unnatural peak in the spectral data caused by higher-order light can be suppressed.

[0011] An optical detector according to one aspect of the invention can [5] “be the optical detector of one of [1] to [4], wherein the window further comprises a reflection reduction layer formed on the opposite side of the light incidence surface and the light emission surface.” In the optical detector of [5], a scattered light which is generated when the light to be measured is reflected multiple times between the light emission surface and the light reception area can be reduced.

[0012] A spectroscopic measuring device according to one aspect of the invention is [6] “a spectroscopic measuring device comprising: a light entrance part onto which light to be measured can be incident; a diffraction grating configured to disperse the light to be measured incident from the light entrance part; an analyzer configured to generate spectral data of the light to be measured; and the optical detector according to one of [1] to [5].

[0013] With the spectroscopic measuring device of [6], the light of the predetermined order in the dispersed light to be measured can be detected in the optical detector. Advantageous effects of the invention

[0014] According to the invention, an optical detector and a spectroscopic measuring device, which can detect light of a predetermined order from the dispersed light to be measured, can be provided. Brief description of the drawings Fig. Figure 1 is a schematic view showing a configuration of a spectroscopic measuring device of one embodiment. Fig. 2 is a top view of an optical detector of Fig. 1. Fig. Figure 3 is a cross-sectional view of the optical detector along line III-III of Fig. 2. Fig. Figure 4 is a schematic view showing the properties of a transmitted wavelength of a linear variable filter coating of Fig. 2 shows. Fig. 5 is a schematic view showing a state in which a primary light passes through a Fig. The second window shown works. Fig. Figure 6 is a schematic view showing a state in which scattered light is present in the Fig. The 2 windows shown are created. Fig. Figure 7 is a schematic view showing the properties of a transmitted wavelength of a filter coating contained in a window of a first comparative example. Fig. Figure 8 is a schematic view showing a state in which a primary light passes through the in Fig. The seven windows shown are involved, and a condition in which scattered light is present in the window. Fig. The window shown in section 7 is generated. Fig. Figure 9 is a schematic view showing a state in which scattered light is generated in a window of a second comparative example. Fig. Figure 10 is a schematic view showing a state in which light to be measured passes through a window of a modified example. Description of embodiments

[0015] The following section describes embodiments of the invention in detail with reference to the drawings. It should be noted that identical or corresponding parts in the drawings are consistently indicated by the same reference numerals, and repeated descriptions of these parts are omitted below. [Configuration of the spectroscopic measuring device]

[0016] As in Fig. As shown in Figure 1, a spectroscopic measuring device 1 comprises a light entrance part 2, a diffraction grating 3, an optical detector 10, a lens 5, and an analyzer 6. The spectroscopic measuring device 1 is a device that generates spectral data of a plurality of wavelength components L2 in the light L1 to be measured by dispersing the light L1 to be measured.

[0017] The light entrance part 2, the diffraction grating 3, and the lens 5 are contained in an optical system (a so-called Dyson optical system) for guiding the light L1 to be measured to a light receiving area 13a of a light receiving element 13 contained in the optical detector 10 and for generating a spectral image of the plurality of wavelength components L2 of the light L1 to be measured at the light receiving area 13a of the optical detector 10 along a wavelength axis A. In this embodiment, the diffraction grating 3 is a reflective diffraction grating. The light L1 to be measured is dispersed by the diffraction grating 3 in a direction perpendicular to the direction in which the light L1 to be measured is incident. The direction in which the light L1 to be measured is dispersed (i.e.,The direction parallel to the wavelength axis A) is designated as the X-axis direction, the direction perpendicular to the X-axis direction is designated as the Y-axis direction, and the direction perpendicular to both the X-axis and Y-axis directions is designated as the Z-axis direction. Furthermore, the optical detector blocks secondary light and detects primary light in the light being measured, L1. The secondary light can appear as an unnatural peak in spectral data. For this reason, the secondary light must be blocked to extract light of a predetermined order (primary light). Details on this are described below.

[0018] The light entrance section 2 is arranged such that the light L1 to be measured can fall onto the inside of the spectroscopic measuring device 1. The light entrance section 2 controls the amount of incident light L1. The light entrance section 2 is, for example, a slot element. Viewed from the Y-axis, a rectangular slot opens in the slot element, having a short side in the X-axis direction and a long side in the Z-axis direction. Increasing the width of the short side increases the amount of incident light L1, resulting in spectral data with lower noise and lower wavelength resolution being obtained in the analyzer 6.Conversely, if the width of the short side is reduced, the amount of incident light L1 to be measured decreases, resulting in spectral data with improved wavelength resolution and high noise levels in the analyzer 6. For example, the light entrance section 2 can comprise a slot element and an optical waveguide that transmits the light L1 to be measured to the slot element. Alternatively, the light entrance section 2 can, for example, comprise a slot element and a lens that collects the light L1 to be measured from outside the slot element.

[0019] The diffraction grating 3 faces the light entrance 2 in the Y-axis direction. The diffraction grating 3 is reflective and thus disperses the light L1 to be measured in a direction opposite to the direction in which the light L1 to be measured is incident. The diffraction grating 3 comprises a plurality of diffraction grooves (not shown). The plurality of diffraction grooves extend along the Z-axis direction, which is perpendicular to the orientation direction, and are aligned along the X-axis direction, which is perpendicular to the direction in which the light L1 to be measured is incident. The light L1 to be measured, incident on the diffraction grating 3, is dispersed according to the plurality of wavelength components L2 along the X-axis direction, which is the direction in which the plurality of diffraction grooves are aligned.

[0020] The optical detector 10 faces the diffraction grating 3 in the Y-axis direction. The optical detector 10 includes the light-sensing element 13. The light-sensing element 13 comprises the light-receiving area 13a, which receives the plurality of wavelength components L2. In the optical detector 10, a spectral image with a wavelength axis in the X-axis direction is formed at the light-receiving area 13a. The light-receiving area 13a has an elongated shape with the X-axis direction as its longitudinal direction and contains a plurality of light-sensing channels arranged along the X-axis direction (a predetermined direction). That is, the direction in which the plurality of light-sensing channels are arranged coincides with the direction in which the light L1 to be measured is dispersed.Therefore, each wavelength component L2 is incident at a different position (a different light detection channel) at a specific interval along the longitudinal direction of the light reception area 13a. Each light reception channel comprises a plurality of pixels along the Z-axis. The optical detector 10 receives a spectral image in the light reception area 13a over a predetermined exposure time and outputs spectral data S for each wavelength component L2. The light detection element 13 is, for example, a CCD image sensor or a CMOS image sensor formed on a semiconductor substrate. The CCD image sensor can be of any interline, frame-transfer, or full-frame-transfer type.

[0021] In this embodiment, the optical detector 10 is arranged in the same position along the Y-axis as the light entrance part 2. The optical detector 10 is located at a specific distance from the light entrance part 2 along the Z-axis on the side where the plurality of wavelength components L2 are incident. In other words, the optical detector 10 is offset from the light entrance part 2 to the side where the plurality of wavelength components L2 are incident along the direction perpendicular to the wavelength axis (the Z-axis direction).

[0022] The lens 5 is arranged along the Y-axis between the positions of the light entrance part 2 and the optical detector 4 and the position of the reflective diffraction grating 3. The lens 5 directs the light L1 incident from the light entrance part 2 to be measured to the diffraction grating 3 and forms a spectral image of the multitude of wavelength components L2 in the light receiving area 13a of the optical detector 10. The lens 5 is a convex lens with a surface 5a and a convex surface 5b opposite surface 5a. Surface 5a faces the light entrance part 2 and the optical detector 10. Surface 5a can be flat, concave, or convex. The convex surface 5b faces the diffraction grating 3 and is convex on the side opposite surface 5a.

[0023] The analyzer 6 generates spectral data S of the light L1 to be measured, based on data received from the optical detector 10. The analysis performed by the analyzer 6 is described below. The analyzer 6 includes a memory unit that stores data received from the optical detector 10, an analysis result, etc. Furthermore, the analyzer 6 can control the optical detector 4. The analyzer 6 can be, for example, a computer or a tablet with a processor such as a CPU (Central Processing Unit) and a storage medium such as RAM (Random Access Memory) or ROM (Read Only Memory). The analyzer 6 can be a microcomputer or an FPGA (Field Programmable Gate Array).

[0024] In the spectroscopic measuring device 1 with the configuration described above, the light to be measured L1 incident from the light entrance part 2 strikes surface 5a at a constant angle. The light to be measured L1 incident on surface 5a is refracted at surface 5a according to the difference between the refractive index of air and the refractive index of lens 5, travels within the lens 5, and exits from the convex surface 5b. The light to be measured L1 exiting the convex surface 5b is refracted at the convex surface 5b according to the difference between the refractive index of lens 5 and the refractive index of air and is guided to the diffraction grating 3 in a downstream stage.

[0025] The multitude of wavelength components L2 dispersed by the diffraction grating 3 incident on the lens 5. This multitude of wavelength components L2 incident on the lens 5 occurs at a specific angle of incidence with respect to the convex surface 5b. The multitude of wavelength components L2 incident on the convex surface 5b is refracted at the convex surface 5b according to the difference between the refractive index of air and the refractive index of the lens 5, travels within the lens 5, and exits from surface 5a. The multitude of wavelength components L2 exiting from surface 5a is refracted at surface 5a according to the difference between the refractive index of the lens 5 and the refractive index of air and is imaged at the optical detector 4 in a downstream stage to form a spectral image in the light receiving section 13a. [Optical detector configuration]

[0026] As in Fig. 2 and Fig. As shown in Figure 3, the optical detector 10 further comprises a housing 11 and a window 12. The housing 11 includes a lower wall 111, a side wall 112, and an upper wall 113. The lower wall 111 has a flat plate shape. The side wall 112 has a frame shape with a rectangular opening. The upper wall 113 has a cap shape with a rectangular opening. The side wall 112 is located on and connected to the lower wall 111. The upper wall 113 is located on and connected to the side wall 112. This results in a space SP being formed within the housing 11. For example, the lower wall 111, the side wall 112, and the upper wall 113 are all made of metal.

[0027] The light-sensing element 13 is arranged on the lower wall 111. The light-sensing element 13 is located in the space SP within the housing 11. An opening 11a is formed in the housing 11. In particular, the opening 11a in the upper wall 113 is configured to face the light-sensing element 13. Viewed from the Y-axis direction, an inner edge of the upper wall 113 forming the opening 11a is smaller than the inner edge of the side wall 112 forming the space SP, and an inner edge of the upper wall 113 forming the space SP together with the inner edge of the side wall 112 is also smaller. In other words, viewed from the Z-axis direction, the upper wall 113 has a stepped shape, such that 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 the multitude of wavelength components L2 to fall upon the housing 11.

[0028] The window 12 is arranged on the upper wall 113 to close the opening 11a. The window 12 faces the light-receiving area 13a of the light-sensing element 13 arranged in the housing 11 in the Y-axis direction. The window 12 comprises a light-transmitting element 121 and a linear variable filter coating 122. The light-transmitting element 121 comprises a light-incidence surface 121a and a light-emission surface 121b, which face each other in the Y-axis direction. In this embodiment, the light-emission surface 121b of the window 12 is connected to a circumferential portion of the opening 11a in the upper wall 113 to ensure the airtightness of the room SP. Viewed from the Y-axis direction, the light-transmitting element 121 has a rectangular shape with one long side in the X-axis direction and one short side in the Z-axis direction. The light transmitting element 121 is made, for example, of glass, quartz, silicon, germanium, plastic, etc.

[0029] The linear variable filter coating 122 is formed on the light-incidence surface 121a. Similar to the light-transmitting element 121, the linear variable filter coating 122 has a rectangular shape as viewed from the Y-axis direction, with a long side in the X-axis direction and a short side in the Z-axis direction. An outer edge of the linear variable filter coating 122 does not completely coincide with an outer edge of the light-transmitting element 121, and there is a portion 123 where the linear variable filter coating 122 and the light-incidence surface 121a do not overlap. In particular, the length of the short side of the linear variable filter coating 122 is equal to the length of the short side of the light-transmitting element 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 element 121. For this reason, in the examples of Fig. 2 and Fig. 3. Although one short side of the linear variable filter coating 122 coincides with one short side of the light transmittance 121, the other short side of the linear variable filter coating 122 is located within the other short side of the light transmittance 121. The linear variable filter coating 122 is formed continuously without gaps by coating the light-incidence surface 121a with an insulating multilayer film by deposition, etc. For example, the thickness of the linear variable filter coating 122 gradually increases in an oblique shape from one short side along the X-axis direction.

[0030] Viewed from the Y-axis direction, the inner edge of the upper wall 113 forming the opening 11a is larger than an outer edge of the light-sensing element 13. Furthermore, the outer edge of the light-transmitting element 121 is larger than the inner edge of the upper wall 113 forming the opening 11a. Additionally, a portion of the outer edge of the light-sensing element 13 overlaps the portion 123 where the linear variable filter coating 122 and the light-incidence surface 121a do not overlap. In particular, the other short side of the light-sensing element 13 is located outside the other short side of the linear variable filter coating 122.

[0031] The linear variable filter coating 122 has a transmitted wavelength that changes along the x-axis direction (predetermined direction). In particular, the transmitted wavelength gradually shifts to a higher wavelength band with increasing distance from the part 123 where the linear variable filter coating 122 and the light-entry surface 121a do not overlap. In other words, the blocked wavelength band gradually increases. An example of the transmitted wavelength characteristic of the linear variable filter coating 122 is given with reference to Fig. Figure 4 is described as an example. In a characteristic curve T1 of a transmitted wavelength of a section nearest to part 123, where the linear variable filter coating 122 and the light-incidence area 121a do not overlap, the transmittance begins to increase from approximately 430 nm, reaches a value of approximately 0.9 at approximately 460 nm, and a cut-on wavelength (the wavelength at which the transmittance reaches 50%) is located at approximately 450 nm. Furthermore, in a characteristic curve T2 of a transmitted wavelength of a section furthest from part 123, where the linear variable filter coating 122 and the light-incidence area 121a do not overlap, the transmittance begins to increase from approximately 780 nm, reaches a value of 0.9 at approximately 830 nm, and a cut-on wavelength is located at approximately 810 nm.The transmitted wavelength of the linear variable filter coating 122 gradually changes to a higher wavelength band between T1 and T2. In this embodiment, the multitude of wavelength components L2 occur along a direction in which the transmitted wavelength of the linear variable filter coating 122 changes. Therefore, primary light is transmitted in each wavelength component L2, while secondary light is prevented from reaching the light-sensing element 13.

[0032] The relationship between each wavelength component L2 and a transmitted wavelength is discussed in greater detail below with reference to Fig. 5 described. As in Fig. As shown in Figure 5, the multitude of wavelength components L2 comprises wavelength components with center wavelengths from λ11 to λ15. The wavelengths from λ11 to λ15 are all primary light. For example, λ11 is 300 nm, λ12 is 450 nm, λ13 is 600 nm, λ14 is 750 nm, and λ15 is 900 nm. λ11 to λ15 exhibit increasing diffraction angles in the aforementioned order and are incident on the linear variable filter coating 122 along a direction in which the transmitted wavelengths change in the order mentioned above. Secondary light is set from λ11 to λ21, and secondary light is set from λ12 to λ22. The center wavelength of λ21 is 300 nm, which is the same as that of λ11, while the diffraction angle of λ21 is different from that of λ11. The diffraction angle of λ21 is equal to the diffraction angle of λ13, which has a center wavelength twice that of λ11.In other words, λ21 arrives at the same position as λ13. Similarly, the secondary light λ22 (center wavelength 450 nm) from λ12 arrives at the same position as that from λ15, which has a center wavelength twice that of λ12. The linear variable filter coating 122 acts as a filter that transmits primary light (λ11 to λ15) of the multitude of wavelength components L2 and blocks the secondary light (λ21 and λ22). Therefore, the window 12 transmits primary light of each wavelength component L2, and the optical detector 10 detects primary light. The linear variable filter coating 122 transmits a wavelength component with a wavelength equal to or greater than the center wavelength of the primary light and thus acts as a long-pass filter.In other words, the linear variable filter coating 122 is a linear variable longpass filter coating whose cut-on wavelength changes along the X-direction (predetermined direction). It should be noted that λ11 is incident on the part 123 where the linear variable filter coating 122 and the light-incidence surface 121a do not overlap. One reason for this is that the center wavelength of λ11 is 300 nm and is therefore blocked by the linear variable filter coating 122.

[0033] Here, wavelengths λ11 to λ15 are incident on the linear variable filter coating 122, becoming the corresponding transmitted wavelengths. For example, in a characteristic curve for a transmitted wavelength corresponding to an incidence position of λ13, the primary light λ13 (center wavelength 600 nm) is transmitted, while the secondary light λ21 (center wavelength 300 nm) is blocked. Furthermore, in a characteristic curve for a transmitted wavelength corresponding to an incidence position of λ15, the primary light λ15 (center wavelength 900 nm) is transmitted, while the secondary light λ22 (center wavelength 450 nm) is blocked. [Operation and Effects]

[0034] In the optical detector 10, the window 12, which closes the opening 11a of the housing 11, comprises the light transmitting element 121 and the linear variable filter coating 122, in which a transmitted wavelength changes along the X-axis direction, i.e., the direction in which the light L1 to be measured is dispersed. In this way, the incident secondary light (λ21 and λ22) on the light detection element 13 can be suppressed for each of the multiple wavelength components L2 in the light L1 to be measured. Furthermore, in the optical detector 10, the linear variable filter coating 122 is formed on the light-incident surface 121a of the light transmitting element 121.For example, if a filter coating of a single transmitted wavelength is formed on both the light-incidence surface 121a and the light-exit surface 121b of the light-transmitting element 121, the light L1 to be measured can be reflected multiple times between the filter coating formed on the light-incidence surface 121a and the filter coating formed on the light-exit surface 121b. However, the optical detector 10 can suppress the occurrence of scattered light due to multiple reflections. As described above, the primary light (λ11 to λ15) of the dispersed light L1 to be measured can be detected with the optical detector 10.

[0035] In the optical detector 10, the linear variable filter coating 122 is formed on the light-incidence surface 121a. This allows the housing 11 and the window 12 to be connected more easily and reliably than if the linear variable filter coating 122 were located on the light-emission surface 121b. Furthermore, compared to a case where the linear variable filter coating 122 is located on the light-emission surface 121b, the light-emission surface 121b of the window 12 can be more easily connected to the perimeter of the opening 11a in the upper wall 113, thus ensuring a more airtight seal for the room SP.

[0036] In the optical detector 10, a predetermined order of light is a primary light (λ11 to λ15). The primary light (λ11 to λ15) has a higher luminous intensity than the secondary light (λ21 and λ22). Therefore, spectral data S with an excellent signal-to-noise (S / N) ratio can be generated with the optical detector 10 by ensuring that the linear variable filter coating 122 functions as a secondary light cutoff filter for the transmission of the primary light (λ11 to λ15) in the light L1 to be measured.

[0037] In the optical detector 10, the linear variable filter coating 122 is a linear variable longpass filter coating whose cut-on wavelength changes along the X-axis direction. This suppresses the transmission of secondary light (λ21 and λ22) based on the primary light (λ11 to λ15), thus suppressing the occurrence of an unnatural peak due to the secondary light (λ21 and λ22) in the spectral data S.

[0038] In the spectroscopic measuring device 1, the optical detector 10 can detect the primary light (λ11 to λ15) in the dispersed light L1 to be measured. [Comparative examples]

[0039] As in Fig. As shown in Figure 6, some of the light L1 incident on window 12 to be measured can be reflected by the light exit surface 121b of the light transmitting element 121 and then reflected by the surface of the linear variable filter coating 122, resulting in stray light L3. This stray light L3 can appear as an unnatural peak in the spectral data and therefore must be suppressed. However, in comparison to a further example described below, the linear variable filter coating 122 can reduce one cause of the stray light L3.

[0040] Window 12a of a first comparative example will be discussed below with reference to Fig. 7 and Fig. 8 described. As in Fig. As shown in Figure 7(a), a filter coating 122a is formed on the light-incidence surface 121a of the light-transmitting element 121 in window 12a, and a filter coating 122b is formed on the light-emission surface 121b of the light-transmitting element 121. Viewed from the Y-axis direction, the filter coating 122a and the filter coating 122b each have a rectangular shape with one long side in the X-axis direction and one short side in the Z-axis direction. One short side of the filter coating 122a thus coincides with one short side of the light-transmitting element 121 and one short side of the filter coating 122b. The other short side of the filter coating 122a is located inside the other short side of the light-transmitting element 121 and outside the other side of the filter coating 122b. As shown in Fig. As shown in Figure 7(b), filter coating 122a and filter coating 122b each exhibit a different transmitted wavelength characteristic. An example of the transmitted wavelength characteristic is as follows. In characteristic curve T3 of a transmitted wavelength of filter coating 122a, the transmittance begins to increase from approximately 420 nm and reaches a value of approximately 0.9 at approximately 450 nm. A cut-on wavelength is at approximately 440 nm. Furthermore, in characteristic curve T4 of a transmitted wavelength of filter coating 122b, the transmittance begins to increase from approximately 520 nm and reaches a value of approximately 0.9 at approximately 570 nm. A cut-on wavelength is at approximately 550 nm.

[0041] The relationship between each wavelength component L2 and a transmitted wavelength is discussed in greater detail below with reference to Fig. 8 described. The center wavelengths from λ11 to λ15 are similar to those in the embodiment. And similarly to the linear variable filter coating 122, the filter coating 122a and the filter coating 122b each function as a filter that transmits the primary light (λ11 to λ15) of the multitude of wavelength components L2 and blocks the secondary light (λ21 and λ22). For example, λ13 passes through the filter coatings 122a and 122b, while λ21 is blocked by the filter coating 122a. When the filter coatings 122a and 122b are used, scattered light occurs due to various factors. For example, because the other short side of the filter coating 122b is located inside the other short side of the filter coating 122a, the other short side of the filter coating 122b acts as an end face viewed from the Z-axis direction.Any one of the wavelength components L2 can be scattered at the end surface of the filter coating 122b and cause the scattered light L3. Furthermore, any one of the wavelength components L2 can be reflected multiple times between the filter coating 122a and the filter coating 122b and cause the scattered light L3. In any case, the scattered light L3 is not generated if the linear variable filter coating 122 of the embodiment is used as part of the window 12. Therefore, the incident of the scattered light caused by scattering or by multiple reflections at the light-sensing element 13 can be suppressed in the optical detector 10 of the embodiment.

[0042] The following is a window 12b of a second comparison example with reference to Fig. As described in Figure 9, in window 12b, no filter coating is formed on the light transmitting element 121, and a filter element 122c, which is thicker than the filter coating, is arranged at the light incidence surface 121a. The filter element 122c and the light transmitting element 121 are collectively referred to as window 12b. In this case, the scattered light L3 is generated by various factors. For example, the scattered light L3 is generated by multiple reflections within the filter element 122c or by multiple reflections between the filter element 122c and the light incidence surface 121a or the light emission surface 121b. In other words, the number of positions at which scattered light can be generated is significantly greater than with the linear variable filter coating 122 of the embodiment. [Modified example]

[0043] The invention is not limited to the embodiment described above. The linear variable filter coating 122 can be a linear variable bandpass filter coating in which a transmitted wavelength band changes along the X-axis direction. In this case, the linear variable filter coating 122 functions as a filter that transmits only a specific range of wavelength components, including a center wavelength of a primary light for each wavelength component L2. In this way, the transmission of secondary light based on the primary light is suppressed, thus preventing the appearance of an unnatural peak in the spectral data S caused by the secondary light. Furthermore, the spectroscopic measuring device 1 of the embodiment is a Dyson optical system comprising the light entrance part 2, the diffraction grating 3, the optical detector 10, the lens 5, and the analyzer 6.However, the spectroscopic measuring device 1 can also be a different optical system. For example, the spectroscopic measuring device 1 can be a Czerny-Turner optical system. And if an optical system other than a Dyson optical system is used, the diffraction grating 3 can be a transparent diffraction grating. Furthermore, the linear variable filter coating 122 can be formed on the light exit surface 121b. Moreover, the light blocked by the linear variable filter coating 122 is not limited to secondary light. For example, higher-order light (such as third-order or fourth-order light) can be blocked, diffracted light of negative orders can be blocked, or reflected light (zero-order light) can be blocked.The linear variable filter coating 122 can transmit light of orders other than the (predetermined) first order (for example, light of the above-mentioned orders) and block primary light.

[0044] As in Fig. As shown in Figure 10, the window 12 can further include a reflection reduction layer 124. The in Fig. The window 12 shown comprises the light transmitting element 121, the linear variable filter coating 122, and the reflection reduction layer 124. In the Fig. In the window 12 shown in Figure 10, the linear variable filter coating 122 is formed on the light-incidence surface 121a of the light-transmitting element 121, and the reflection-reducing layer 124 is formed on the light-exiting surface 121b of the light-transmitting element 121. For example, the reflection-reducing layer 124 is formed by a single layer of magnesium fluoride (MgF2), silicon dioxide (SiO2), titanium oxide (TiO2), zirconia (ZrO2), or tantalum pentoxide (Ta2O5), or a laminate of several of these substances.

[0045] In the Fig. In the window 12 shown in Figure 10, the reflection-reducing layer 124 extends over the entire surface of the light-exiting surface 121b. In other words, viewed along the Y-axis, an outer edge of the reflection-reducing layer 124 coincides with the outer edge of the light-transmitting element 121. However, the reflection-reducing layer 124 can also be formed only on a portion of the light-exiting surface 121b. For example, the reflection-reducing layer 124 can be designed such that it overlaps at least the linear variable filter coating 122 when viewed along the Y-axis. In this case, the outer edge of the reflection-reducing layer 124, viewed along the Y-axis, can coincide with the outer edge of the linear variable filter coating 122.

[0046] The reflection-reducing layer 124 is, for example, an antireflective coating (AR coating). If, in this case, light L4 of the light to be measured, reflected by the light receiving area 13a, is incident on the reflection-reducing layer 124, the reflected light L4 is canceled out by optical interference within 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 by a surface of the reflection-reducing layer 124 on the side of the light transmitting element 121 and the light reflected by a surface of the reflection-reducing layer 124 on the side of the light receiving area 13a.If the reflection-reducing layer 124 is not provided, the reflected light L4 can become scattered light by being reflected at the light-emitting surface 121b of the light-transmitting element 121 and by being reflected multiple times between the light-emitting surface 121b and the light-receiving area 13a. In the Fig. In window 12 shown in Figure 10, the reflection reduction layer 124 is formed on the light exit surface 121b, so that stray light caused by the reflected light L4 can be reduced.

[0047] The reflection reduction layer 124 is not limited to the AR coating. For example, the reflection reduction layer 124 can be a multilayer film. In this case, the refractive index of the reflection reduction layer 124 changes at each layer. For example, the refractive index of the reflection reduction layer 124 can change stepwise from the refractive index of an intermediate space between the reflection reduction layer 124 and the light receiving area 13a (refractive index of air) to the refractive index of the light transmittance 121. In this case, the reflected light L4 is not reflected at the light exit surface 121b of the light transmittance 121 and is emitted outwards through the light transmittance 121 and the linear variable filter coating 122.

[0048] The linear variable filter coating 122 can be formed on the light-exit surface 121b of the light-transmitting element 121, and the reflection-reducing layer 124 can be formed on the light-incidence surface 121a of the light-transmitting element 121. In this case, for example, in the reflection-reducing layer 124, the reflected light L4 is canceled out by interference between the light reflected from a surface of the reflection-reducing layer 124 on the side of the light-transmitting element 121 and the light reflected from a surface of the reflection-reducing layer 124 opposite the light-transmitting element 121. List of reference symbols

[0049] 1: spectroscopic measuring device; 2: light entrance part; 3: diffraction grating; 10: optical detector; 6: analyzer; 11: housing; 11a: aperture; 12: window; 13: light detection element; 13a: light reception area; 121: light transmission element; 121a: light incidence surface; 121b: light exit surface; 122: linear variable filter coating; 124: reflection reduction layer; L1: light to be measured; S: spectral data. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-76712

[0003]

Claims

[1] An optical detector for detecting light of a predetermined order in a light to be measured dispersed in a predetermined direction, the optical detector comprising: a housing having an opening, a window that closes the opening and allows the passage of light of the predetermined order, and a light detecting element arranged in the housing, comprising a light receiving area facing the window and configured to detect the light of the predetermined order, wherein the light receiving area comprises a plurality of light detection channels arranged in the predetermined direction, and where the window includes: a light transmitting element with a light incidence surface and a light exit surface, and a linear variable filter coating arranged on the light incident surface or the light exit surface and having a transmitted wavelength changing along the predetermined direction. [2] The optical detector according to claim 1, wherein the linear variable filter coating is formed on the light incident surface. [3] An optical detector according to claim 1, wherein the predetermined order of light is a primary light. [4] The optical detector according to claim 1, wherein the linear variable filter coating is a linear variable long-pass filter coating in which a cut-on wavelength changes along the predetermined direction, or a linear variable band-pass filter coating in which a transmitted wavelength band changes along the predetermined direction. [5] The optical detector according to claim 1, wherein the window further comprises a reflection reduction layer formed on the other of the light incident surface and the light exit surface. [6] Spectroscopic measuring device comprising: a light entry part onto which the light to be measured can fall, a diffraction grating configured to disperse the light to be measured incident from the light entrance part, an analyzer configured to generate spectral data of the light to be measured, and the optical detector according to one of claims 1 to 5.

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