Spectroscopic module
The use of thin, plate-shaped beam splitters with precise support grooves in the spectroscopic module addresses optical axis shifts, improving signal-to-noise ratio and reducing stray light, resulting in a more efficient and compact design.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HAMAMATSU PHOTONICS KK
- Filing Date
- 2024-10-02
- Publication Date
- 2026-05-27
AI Technical Summary
In existing spectroscopic modules, the accumulation of optical axis shifts due to beam splitters causes a decrease in signal-to-noise ratio and generates stray light, particularly in light receiving regions further along the optical path.
The spectroscopic module employs plate-shaped beam splitters with a thickness of 1 mm or less, supported by grooves in a support structure, ensuring accurate positioning and minimizing optical axis shifts, thereby reducing stray light and improving signal-to-noise ratio.
This configuration enhances the signal-to-noise ratio and reduces stray light, allowing for a more compact module design while maintaining positional accuracy and effective light reception.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a spectroscopic module.
Background Art
[0002] As a spectroscopic module that splits measurement light into lights in a plurality of wavelength bands and detects the lights in each wavelength band, there is known one in which a plurality of beam splitters and a plurality of band-pass filters are arranged in a housing (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the spectroscopic module as described above, when each beam splitter has a plate shape, refraction occurs in each beam splitter, and the optical axis of the transmitted light shifts to the side away from the band-pass filter with respect to the optical axis of the incident light. Therefore, the more the beam splitters are arranged in the subsequent stage, the more the optical axis of the incident light shifts to the side away from the band-pass filter. The amount by which the optical axis of the incident light shifts accumulates according to the number of beam splitters not only on the side away from the band-pass filter but also on the subsequent stage side in the direction in which the plurality of beam splitters are arranged. From this, among the plurality of light receiving regions for detecting lights in a plurality of wavelength bands, in the light receiving regions other than the light receiving region arranged in the forefront stage, the optical path length of the optical path reaching the light receiving region becomes long depending on the thickness of the beam splitter arranged in the previous stage of the beam splitter corresponding to the light receiving region. When the optical path length of the optical path reaching the light receiving region becomes long, it leads to a decrease in the light reception amount in the light receiving region and the generation of stray light in the optical path, and the S / N ratio tends to decrease. Such a phenomenon becomes remarkable in the light receiving region arranged in the more subsequent stage. The present invention aims to provide a spectroscopic module that can improve the signal-to-noise ratio (S / N ratio). [Means for solving the problem]
[0005] The spectroscopic module of the present invention comprises M beam splitters (where M is a natural number greater than or equal to 2) arranged along a first direction, M bandpass filters arranged on one side in a second direction intersecting the first direction with respect to the M beam splitters, each facing each of the M beam splitters, a photodetector arranged on one side in the second direction with respect to the M bandpass filters, each having M light-receiving regions, and a support for supporting the M beam splitters and the M bandpass filters, wherein each of the N beam splitters (where N is a natural number greater than or equal to 2 and less than or equal to M) is plate-shaped and has a thickness of 1 mm or less.
[0006] In this spectroscopic module, each of the N beam splitters out of the M beam splitters is plate-shaped and has a thickness of 1 mm or less. As a result, in each of the N beam splitters, the amount by which the optical axis of the transmitted light shifts away from the bandpass filter relative to the optical axis of the incident light (amount of light refraction) is reduced. Therefore, for the N beam splitters as a whole, the sum of the accumulated amount of light refraction is sufficiently small both on the side away from the bandpass filter and on the downstream side in the direction in which the N beam splitters are arranged. A small sum of accumulated light refraction means that the optical path length to the light-receiving regions other than the one located at the very front of the multiple light-receiving regions is suppressed. This reduces the amount of light received in the light-receiving region and suppresses the generation of stray light in the optical path. Therefore, this spectroscopic module can improve the signal-to-noise ratio.
[0007] In the spectroscopic module of the present invention, each of the N beam splitters may have a thickness of 0.5 mm or less. This further suppresses the length of the optical path leading to the light-receiving regions other than the one located at the front of the multiple light-receiving regions, thereby enabling an even greater improvement in the signal-to-noise ratio of the entire module.
[0008] In the spectroscopic module of the present invention, the support has a support portion in which N grooves are formed, and each of the N grooves in the support portion is arranged in a set of N beam splitters, so that there are N combinations of grooves and beam splitters, and in each of the N combinations, the groove may have a width of at least twice the thickness of the beam splitter. This makes it possible to easily and accurately form the grooves in which the beam splitters are arranged during the manufacturing of the spectroscopic module, thereby ensuring the positional accuracy of each of the N beam splitters.
[0009] In the spectroscopic module of the present invention, in each of the N combinations, the groove has a pair of sides with light-passing apertures formed therein, and a bottom surface, and in each of the N combinations, the beam splitter may be positioned in the groove so as to be in contact with the side located on one side of the pair of sides in the second direction, and the bottom surface. This ensures the positional accuracy of each of the N beam splitters and allows for stable support of each of the N beam splitters.
[0010] The spectroscopic module of the present invention further comprises a light incidence section that defines the light incident on M beam splitters along a first direction, and the N beam splitters are supported by a support such that the center of each of the N beam splitters is located on a line parallel to the first direction, and the optical axis of the light incidence section may be located on one side in the second direction with respect to the line. With this, for example, when each of the N beam splitters has the same shape, it is possible to miniaturize each of the N beam splitters while effectively utilizing the clear aperture of each of the N beam splitters.
[0011] In the spectroscopic module of the present invention, each of the N beam splitters has the same thickness and is arranged so that light is incident at an incident angle of 45° along a first direction. The array pitch of the N beam splitters may be the sum of the array pitch of the N light-receiving regions corresponding to the N beam splitters out of M light-receiving regions, and the amount of refraction of light in each of the N beam splitters. This allows the light reflected by each of the N beam splitters to be accurately incident on each of the N light-receiving regions.
[0012] In the spectroscopic module of the present invention, each of the N beam splitters is elongated when viewed from the thickness direction of each of the N beam splitters, and the direction perpendicular to the longitudinal direction of each of the N beam splitters may be perpendicular to both the first and second directions. This makes it possible to miniaturize each of the N beam splitters in the direction perpendicular to both the first and second directions while effectively utilizing the clear aperture of each of the N beam splitters.
[0013] In the spectroscopic module of the present invention, each of the N beam splitters may have the same shape. This allows for the commonality of components among the N beam splitters. [Effects of the Invention]
[0014] According to the present invention, it is possible to provide a spectroscopic module that can improve the signal-to-noise ratio. [Brief explanation of the drawing]
[0015] [Figure 1] This is a cross-sectional view of a spectroscopic module according to one embodiment. [Figure 2] This is a cross-sectional view taken along the line II-II shown in Figure 1. [Figure 3] This is a plan view of a portion of the first support shown in Figure 1. [Figure 4] It is a cross-sectional view of a part of the second support shown in FIG. 1. [Figure 5] It is a cross-sectional view along the V-V line shown in FIG. 4. [Figure 6] It is a cross-sectional view along the VI-VI line shown in FIG. 4. [Figure 7] It is a diagram showing the relationship of the arrangement of a plurality of beam splitters with respect to the optical axis of the light incident portion.
Embodiments for Carrying Out the Invention
[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. [Configuration of Spectroscopic Module]
[0017] As shown in FIGS. 1 and 2, the spectroscopic module 1 includes a housing 2, a plurality of beam splitters 3, a plurality of band-pass filters 4, a first support (support, support portion) 5, a second support (support) 6, a photodetector 7, and a light shielding member 8. The plurality of beam splitters 3 are arranged along the X direction (first direction). The plurality of band-pass filters 4 are arranged on one side in the Z direction (second direction intersecting the first direction) perpendicular to the X direction with respect to the plurality of beam splitters 3. The photodetector 7 is arranged on one side in the Z direction with respect to the plurality of band-pass filters 4. The photodetector 7 has a plurality of light receiving regions 7a.
[0018] Each beam splitter 3 is, for example, a half mirror, which reflects part of the light incident along the X direction to one side in the Z direction and transmits the light other than part of the incident light to one side in the X direction. Each band-pass filter 4 faces each beam splitter 3 in the Z direction, and transmits the light in a predetermined wavelength band among the light incident along the Z direction from each beam splitter 3 to one side in the Z direction. Each band-pass filter 4 transmits light in different wavelength bands. Each light receiving region 7a faces each band-pass filter 4 in the Z direction and detects the light incident along the Z direction from each band-pass filter 4. Each light receiving region 7a constitutes different light detection channels. In the spectroscopic module 1, the measurement light L is split into lights in a plurality of wavelength bands by the plurality of beam splitters 3 and the plurality of band-pass filters 4, and the lights in each wavelength band are detected by the photodetector 7. [Configuration of the housing]
[0019] As shown in FIGS. 1 and 2, the housing 2 houses a plurality of beam splitters 3, a plurality of band-pass filters 4, a first support 5, a second support 6, a photodetector 7, and a light shielding member 8. The housing 2 has a main body portion 20. The main body portion 20 is constituted by a first wall portion 21, a second wall portion 22, a third wall portion 23, and a fourth wall portion 24. The first wall portion 21 and the second wall portion 22 face each other in the X direction. The second wall portion 22 is located on one side in the X direction with respect to the first wall portion 21. The third wall portion 23 is located on one side in the Y direction perpendicular to both the X direction and the Z direction with respect to the first wall portion 21 and the second wall portion 22. The fourth wall portion 24 is located on the other side (the side opposite to the one side) in the Z direction with respect to the first wall portion 21, the second wall portion 22, and the third wall portion 23.
[0020] The first wall portion 21 has a first light incidence hole 2a formed along the X direction for injecting measurement light L into the housing 2. The third wall portion 23 has an inner surface 2b formed parallel to both the X and Z directions. Each of the multiple positioning holes 2c formed in the third wall portion 23 opens onto the inner surface 2b. The third wall portion 23 is integrally formed with the second support 6. The main body portion 20 and the second support 6 constitute a recess 9 with the inner surface 2b of the third wall portion 23 as its bottom surface 91. That is, the housing 2 defines a recess 9 with the inner surface 2b of the third wall portion 23 as its bottom surface 91. The main body portion 20 and the second support 6 are integrally formed from, for example, metal.
[0021] The housing 2 further includes a lid 25 and a shield cover 26. The lid 25 is attached to the main body 20 and the second support 6 so as to close the opening of the recess 9. The shield cover 26 is attached to the main body 20 and the lid 25 so as to cover the photodetector 7 from one side in the Z direction. [Configuration of the beam splitter and first support]
[0022] As shown in Figures 1 and 2, the first support 5 supports a plurality of beam splitters 3. Each beam splitter 3 is plate-shaped and has a thickness of 1 mm or less. Each beam splitter 3 is elongated when viewed from the thickness direction, and the direction perpendicular to the longitudinal direction of each beam splitter 3 is parallel to the Y direction. Each beam splitter 3 has the same shape. Each beam splitter 3 is, for example, rectangular plate-shaped.
[0023] The beam splitter 3 is constructed, for example, by forming a dielectric multilayer film on the order of several nanometers in thickness, on the surface of a glass layer of about 0.5 to 1 mm, with multiple dielectric films having a thickness of several angstroms stacked on top of each other. Although refraction of light occurs within the dielectric multilayer film, considering the difference in thickness between the glass layer and the dielectric multilayer film, most of the refraction generated in the beam splitter 3 occurs in the glass layer. In this embodiment, the total thickness of the glass layer and the dielectric multilayer film is defined as the thickness of the beam splitter 3. The material used for the beam splitter 3 is, for example, a light-transmitting material such as optical glass or plastic.
[0024] The first support 5 is composed of a first wall portion 51, a second wall portion 52, a third wall portion 53, a fourth wall portion 54, and a fifth wall portion 55. The first wall portion 51 and the second wall portion 52 face each other in the X direction. The second wall portion 52 is located on one side of the first wall portion 51 in the X direction. The third wall portion 53 and the fourth wall portion 54 face each other in the Y direction. The third wall portion 53 is located on one side of the first wall portion 51 and the second wall portion 52 in the Y direction. The fourth wall portion 54 is located on the other side of the first wall portion 51 and the second wall portion 52 in the Y direction. The fifth wall portion 55 is located on the other side of the first wall portion 51, the second wall portion 52, the third wall portion 53, and the fourth wall portion 54 in the Z direction. The first support 5 is integrally formed from, for example, metal.
[0025] The first wall portion 51 has a second light incidence hole 5a formed therein, which causes measurement light L to be incident on a plurality of beam splitters 3 along the X direction. The third wall portion 53 has an outer surface 5b formed therein, which is parallel to both the X and Z directions. A plurality of positioning pins 5c are provided on the outer surface 5b. The first support 5 is attached to the third wall portion 23 such that the outer surface 5b is in contact with the inner surface 2b of the housing 2, with the position of the first support 5 in a plane parallel to both the X and Z directions (along that plane) defined by fitting each positioning pin 5c into each positioning hole 2c of the housing 2.
[0026] The first support 5 is positioned within the recess 9 with its outer surface 5b in contact with the inner surface 2b of the housing 2 (i.e., the bottom surface 91 of the recess 9). The side surface 92 of the recess 9 includes a plurality of spaced-out regions 92a. Each spaced-out region 92a is spaced apart from the first support 5. In this embodiment, the side surface 92 is composed of the inner surfaces of the first wall 21, second wall 22, and fourth wall 24 of the main body 20, and the surface of the second support 6 on the fourth wall 24 side. Note that the side surface 92 only needs to include at least one spaced-out region 92a. Alternatively, the spaced-out region 92a may be the entire side surface 92.
[0027] Multiple grooves 56 are formed in the first support 5. Each beam splitter 3 is positioned in each groove 56. As a result, the first support 5 is provided with multiple combinations, each consisting of a groove 56 and a beam splitter 3. Hereinafter, each of these multiple combinations will be referred to as the "corresponding groove 56 and beam splitter 3".
[0028] As shown in Figures 1 and 3, each groove 56 opens onto the outer surface of the fifth wall 55. The extension direction of each groove 56 is parallel to the Y direction. The depth direction of each groove 56 is inclined at 45° in the direction perpendicular to the Y direction, such that deeper grooves are located on one side in the X direction. Each groove 56 has a pair of side surfaces 56a and 56b and a bottom surface 56c. The pair of side surfaces 56a and 56b face each other in the width direction of each groove 56 (a direction perpendicular to both the extension direction and the depth direction). A light-passing aperture 57a is formed on side surface 56a, and a light-passing aperture 57b is formed on side surface 56b.
[0029] In this embodiment, each groove 56 is formed such that both ends of each groove 56 in the extending direction are located at the third wall portion 53 and the fourth wall portion 54, respectively. The light-passing aperture 57a is formed on the side surface 56a by the space between the third wall portion 53 and the fourth wall portion 54 facing each other in the Y direction, and the light-passing aperture 57b is formed on the side surface 56b by the space, which cuts out the side surface 56b. The bottom surface 56c is also separated into two regions in the Y direction.
[0030] In the corresponding groove 56 and beam splitter 3, the groove 56 has a width of at least twice the thickness of the beam splitter 3 (i.e., the distance between the pair of sides 56a and 56b). For example, the thickness of the beam splitter 3 is 0.5 mm, and the width of the groove 56 is 2.5 mm to 3.0 mm. In the corresponding groove 56 and beam splitter 3, the beam splitter 3 is positioned in the groove 56 so as to contact the side 56a located on one side of the pair of sides 56a and 56b in the Z direction, and the bottom surface 56c. In this state, the beam splitter 3 is fixed to the side 56a and bottom surface 56c, for example, by adhesive.
[0031] As shown in Figure 1, the optical incident section 10 of the spectroscopic module 1 is composed of a first optical incident hole 2a and a second optical incident hole 5a. The optical incident section 10 defines the light incident on multiple beam splitters 3 along the X direction. The second optical incident hole 5a includes the first optical incident hole 2a when viewed from the X direction. In this case, the center line of the first optical incident hole 2a becomes the optical axis A of the optical incident section 10. For example, when viewed from the X direction, the first optical incident hole 2a has a circular shape, and the second optical incident hole 5a has an oval shape with the Z direction as its longitudinal direction. For example, when viewed from the X direction, the first optical incident hole 2a overlaps with one side of the second optical incident hole 5a in the Z direction. This allows the center of the beam splitter 3 to be identified through the second optical incident hole 5a when the beam splitter 3 is placed on the first support 5. [Bandpass filter and second support configuration]
[0032] As shown in Figures 4 and 5, the second support 6 supports a plurality of bandpass filters 4. Each bandpass filter 4 has a light-transmitting substrate 41, an interference film 42, and a light-shielding film 43. The light-transmitting substrate 41 is, for example, a rectangular plate. The interference film 42 is provided on the light-incident surface 41a of the light-transmitting substrate 41. The interference film 42 is, for example, a dielectric multilayer film. The light-shielding film 43 is provided on the side surface 41b of the light-transmitting substrate 41. The light-shielding film 43 is, for example, a black painted film. In each bandpass filter 4, the surface of the interference film 42 opposite to the light-transmitting substrate 41 is the light-incident surface 4a of the bandpass filter 4, the surface of the light-transmitting substrate 41 opposite to the interference film 42 is the light-emitting surface 4b of the bandpass filter 4, and the outer surface of the light-shielding film 43 is the side surface 4c of the bandpass filter 4. Note that in Figures 1 and 2, each bandpass filter 4 is shown in a simplified configuration.
[0033] The second support 6 has a support portion 61. The support portion 61 has a support surface 61a formed thereon that is open to one side in the Z direction. The fact that the support surface 61a is open to one side in the Z direction means that when the support portion 61 is viewed from one side in the Z direction with only the second support 6 present, the support surface 61a is exposed (i.e., the support surface 61a is visible). Multiple bandpass filters 4 are arranged on the support surface 61a so as to be aligned along the X direction. The support surface 61a is a plane perpendicular to the Z direction, and the support portion 61 is formed such that the area outside the clear aperture 40 of the light incident surface 4a of each bandpass filter 4 is in contact with the support surface 61a. The clear aperture 40 is an effective aperture region in which the function of the bandpass filter 4 is guaranteed. The support portion 61 has a single light-passing aperture 61b formed thereon through which multiple optical paths (dashed lines shown in Figure 1) from multiple beam splitters 3 to multiple bandpass filters 4 pass. As a result, the support surface 61a is separated into two regions in the Y direction.
[0034] The second support 6 further includes a restricting portion 62. The restricting portion 62 is provided on the second support 6 so as to be located on one side in the Z direction relative to the support portion 61. The restricting portion 62 restricts each bandpass filter 4 from moving in a direction perpendicular to the Z direction. The restricting portion 62 is composed of a plurality of contact portions 62a provided so as to contact the side surface 4c of each bandpass filter 4, and a plurality of separating portions 62b provided so as to be separated from the side surface 4c of each bandpass filter 4. The restricting portion 62 does not completely separate the plurality of bandpass filters 4. In other words, the plurality of bandpass filters 4 are separated from each other through space, with their movement in the direction perpendicular to the Z direction restricted by the restricting portion 62.
[0035] As shown in Figures 1 and 2, the second support 6 has a recess 63 that opens on one side in the Z direction. The bottom surface 63a of the recess 63 is the surface of the regulating portion 62 opposite to the support portion 61. The distance between the support surface 61a and the bottom surface 63a in the Z direction is smaller than the thickness of each bandpass filter 4 (i.e., the distance between the light incident surface 4a and the light emission surface 4b in the Z direction). As a result, a portion of each bandpass filter 4 opposite to the support portion 61 protrudes from the bottom surface 63a, and the light emission surface 4b of each bandpass filter 4 is located on one side in the Z direction relative to the bottom surface 63a (see Figure 4). Multiple positioning pins 6a are provided on the bottom surface 63a. [Configuration of photodetector and light-shielding member]
[0036] As shown in Figures 1 and 2, the photodetector 7 includes a wiring board 71, a plurality of photodetectors 72, and a connector 73. The plurality of photodetectors 72 are mounted on the surface 71a of the wiring board 71 on the side of the plurality of bandpass filters 4, so as to be arranged along the X direction. Each photodetector 72 is a discrete semiconductor element such as a PD chip and has a light-receiving area 7a. The connector 73 is attached to the surface 71b of the wiring board 71 opposite to the surface 71a. The connector 73 is a port for inputting and outputting electrical signals to and from each photodetector 72. The connector 73 extends to the outside of the housing 2 through an opening 26a formed in the shield cover 26. The photodetector 7 is attached to the second support 6 so as to close the opening of the recess 63. In this embodiment, the wiring board 71 is attached to the second support 6 so as to close the opening of the recess 63, and the plurality of photodetectors 72 are located within the recess 63.
[0037] The light-shielding member 8 is positioned between the multiple bandpass filters 4 and the photodetector 7. The light-shielding member 8 is made of an elastic material and is positioned in a compressed state in the recess 63 of the second support 6. In this state, the multiple bandpass filters 4 are sandwiched between the support portion 61 of the second support 6 and the light-shielding member 8. The light-shielding member 8 has multiple light-passing apertures 8a. Each of the multiple optical paths from the multiple bandpass filters 4 to the multiple light-receiving regions 7a passes through each of the multiple light-passing apertures 8a. In other words, the multiple optical paths from the multiple bandpass filters 4 to the multiple light-receiving regions 7a are separated from each other by the light-shielding member 8. In this embodiment, each photodetector element 72 of the photodetector 7 is located within each light-passing aperture 8a of the light-shielding member 8. Within each light-passing aperture 8a, the terminals of the photodetector element 72 and the terminals of the wiring board 71 are electrically connected by wires 74, and the wires 74 are covered by a resin member 75.
[0038] As shown in Figure 6, each light-passing aperture 8a is formed in the light-shielding member 8 such that the area of the light-emitting surface 4b of each bandpass filter 4 that is outside the clear aperture 40 contacts the light-shielding member 8. In other words, the light-shielding member 8 is configured such that the area of the light-emitting surface 4b of each bandpass filter 4 that is outside the clear aperture 40 contacts the light-shielding member 8. Note that in Figure 6, the bandpass filter 4 is shown by a dashed line.
[0039] As shown in Figure 2, the light-shielding member 8 has a plurality of positioning holes 8b. The wiring board 71 has a plurality of positioning holes 7b. Each positioning hole 7b overlaps with each positioning hole 8b when viewed from the Z direction. The light-shielding member 8 is positioned in the recess 63 such that the position of each light-passing aperture 8a in the direction perpendicular to the Z direction is defined by fitting each positioning pin 6a of the second support 6 into each positioning hole 8b. The photodetector 7 is attached to the second support 6 such that the position of each light-receiving region 7a in the direction perpendicular to the Z direction is defined by fitting each positioning pin 6a that penetrates each positioning hole 8b of the light-shielding member 8 into each positioning hole 7b. [Arrangement of multiple beam splitters]
[0040] As shown in Figure 7, the multiple beam splitters 3 are arranged such that the center 3a of each beam splitter 3 lies on a line α parallel to the X direction. The center 3a of the beam splitter 3 is the center (centroid) of the beam splitter 3 when viewed from the thickness direction of the beam splitter 3. Each beam splitter 3 has the same thickness of 1 mm or less and is arranged so that light is incident on it at an incident angle of 45° along the X direction. The optical axis A of the light incident section 10 is located on one side in the Z direction with respect to the line α passing through the center 3a of each beam splitter 3. Note that the light incident section 10 is schematically illustrated in Figure 7.
[0041] In each beam splitter 3, refraction occurs, causing the optical axis of the transmitted light to shift away from the optical axis A of the light incident section 10 relative to the optical axis of the incident light. In the spectroscopic module 1, each beam splitter 3 has the same thickness and is arranged so that light is incident at an incident angle of 45° along the X direction, so the amount of refraction of light is equal in each beam splitter 3. The amount of refraction of light refers to the amount by which the optical axis of the transmitted light shifts away from the optical axis A of the light incident section 10 relative to the optical axis of the incident light in the beam splitter 3.
[0042] If the amount of refraction of light in each beam splitter 3 is ΔZ, and the number of beam splitters 3 is M, then the distance between the optical axis of the incident light in the foremost beam splitter 3 and the optical axis of the incident light in the last beam splitter 3 in the Z direction is ΔZ(M-1). The foremost beam splitter 3 refers to the beam splitter 3 located furthest forward (upstream in the direction of light propagation), and the last beam splitter 3 refers to the beam splitter 3 located furthest backward (downstream in the direction of light propagation).
[0043] In the spectral module 1, multiple beam splitters 3 are arranged with respect to the optical axis A of the light incident section 10 such that the distance between the optical axis A and line α in the Z direction is ΔZ(M-1) / 2. As a result, in the beam splitter 3 located in the middle section (midstream side in the direction of light propagation), the optical axis of the incident light passes through the center 3a or near the center 3a of the beam splitter 3.
[0044] For example, if each beam splitter 3 has a thickness of 0.5 mm, a refractive index of 1.5, an incident angle to the beam splitter 3 of 45°, and 10 beam splitters 3 are arranged, the value of the refraction amount ΔZ of light will be 0.165 mm. Therefore, the distance between the optical axis A and line α in the Z direction is ΔZ(M-1) / 2 = 0.165 × (10-1) / 2 = approximately 0.74 mm. In this case, the optical axis of the incident light will pass near the center 3a of each beam splitter 3, for the 5th and 6th beam splitters 3 from the front. If the diameter of the measurement light L defined by the light incident section 10 (i.e., the diameter of the incident light at the frontmost beam splitter 3) is 4 mm, then if the length of each beam splitter 3 in the longitudinal direction is 10 mm, the incident light will be contained within the clear aperture at all beam splitters 3.
[0045] In the spectroscopic module 1, the array pitch of the multiple beam splitters 3 is the sum of the array pitch of the multiple light-receiving regions 7a and the amount of light refraction in each beam splitter 3. The array pitch of the multiple beam splitters 3 refers to the distance between the centers 3a of adjacent beam splitters 3 when the multiple beam splitters 3 are arranged at equal intervals along the X direction. The array pitch of the multiple light-receiving regions 7a refers to the distance between the centers of adjacent light-receiving regions 7a when the multiple light-receiving regions 7a are arranged at equal intervals along the X direction. If the array pitch of the multiple beam splitters 3 is P1 and the array pitch of the multiple light-receiving regions 7a is P2, then P1 = P2 + ΔZ. Therefore, if the number of beam splitters 3 is M, the distance between the "frontmost beam splitter 3" and the "last beam splitter 3" in the X direction is P1(M-1)=(P2+ΔZ)(M-1)=P2(M-1)+ΔZ(M-1). In this way, the array pitch of the multiple beam splitters 3 is cumulatively affected not only by the array pitch of the multiple light-receiving regions 7a, but also by the amount of light refraction in each beam splitter 3.
[0046] Based on the above, in order to "miniaturize the entire module by sufficiently reducing the total amount of accumulated light refraction on both the side away from the bandpass filter 4 and the downstream side in the direction in which the multiple beam splitters 3 are lined up," it is preferable that each beam splitter 3 has a thickness of 1 mm or less, and more preferably 0.5 mm or less. However, in order to ensure the strength of the beam splitter 3, it is preferable that each beam splitter 3 has a thickness of 0.1 mm or more. [Mechanism of Action and Effects]
[0047] In the spectroscopic module 1, each beam splitter 3 is plate-shaped and has a thickness of 1 mm or less. This reduces the amount by which the optical axis of the transmitted light shifts away from the bandpass filter 4 relative to the optical axis of the incident light (amount of light refraction) in each beam splitter 3. Therefore, for the entire group of beam splitters 3, the sum of the accumulated amount of light refraction is sufficiently small both on the side away from the bandpass filter 4 and on the downstream side in the direction in which the beam splitters 3 are aligned (X direction). A small sum of the accumulated amount of light refraction means that the optical path length to the light-receiving regions 7a other than the first-most light-receiving region 7a is suppressed. This reduces the amount of light received in the light-receiving region 7a and suppresses the generation of stray light in the optical path. Therefore, the signal-to-noise ratio can be improved with this spectroscopic module 1. Specifically, by suppressing the length of the optical path and thereby suppressing the reduction in the amount of light received in the subsequent light-receiving area 7a, the amplification factor of the electrical signal in the circuit of the wiring board 71 can be suppressed. Furthermore, by suppressing the length of the optical path, diffuse reflection and scattering of light in the optical path can be suppressed, thus suppressing the generation of stray light in the optical path. In addition, with the spectroscopic module 1, the total sum of the accumulated amount of refraction of light is sufficiently small both on the side away from the bandpass filter 4 and on the downstream side in the direction in which the multiple beam splitters 3 are aligned (X direction), so the overall size of the module can be reduced.
[0048] Furthermore, if each beam splitter 3 has a thickness of 0.5 mm or less, the length of the optical path leading to the subsequent light-receiving area 7a is further suppressed, thus enabling a further improvement in the signal-to-noise ratio of the entire spectroscopic module 1. In addition, the spectroscopic module 1 can be made even more compact.
[0049] Furthermore, in the spectroscopic module 1, each plate-shaped beam splitter 3 is arranged in each groove 56 formed in the first support 5, and in the corresponding groove 56 and beam splitter 3, the groove 56 has a width of more than twice the thickness of the beam splitter 3. This makes it possible to easily and accurately form the grooves 56 in which the beam splitters 3 are arranged during the manufacturing of the spectroscopic module 1, thereby ensuring the positional accuracy of each beam splitter 3. For example, when forming the grooves 56 in the first support 5 using an end mill, the wobble of the end mill tip is suppressed during processing, so that the grooves 56 can be easily and accurately formed in the first support 5.
[0050] Furthermore, in the spectroscopic module 1, the beam splitter 3 is positioned in the groove 56 such that it contacts the side 56a located on one side in the Z direction of the pair of side surfaces 56a and 56b, and the bottom surface 56c. This ensures the positional accuracy of each beam splitter 3 and allows for stable support of each of the multiple beam splitters 3.
[0051] Furthermore, in the spectroscopic module 1, multiple beam splitters 3 are arranged such that the center 3a of each beam splitter 3 lies on a line α parallel to the X direction. The optical axis A of the light incidence section 10, which defines the light incident on the multiple beam splitters 3 along the X direction, is located on one side in the Z direction relative to line α. This allows for miniaturization of each beam splitter 3, which have the same shape, while effectively utilizing the clear aperture of each beam splitter 3.
[0052] Furthermore, in the spectroscopic module 1, each beam splitter 3 has the same thickness and is arranged so that light is incident at an incidence angle of 45° along the X direction. The array pitch of the multiple beam splitters 3 is the sum of the array pitch of the multiple light-receiving regions 7a and the amount of refraction of light in each beam splitter 3. This allows the light reflected by each beam splitter 3 to be accurately incident into each light-receiving region 7a. In addition, in the spectroscopic module 1, the array pitch P1 of the multiple beam splitters 3 is constant (P1 = P2 + ΔZ). This makes it possible to keep the array pitch between multiple adjacent light-receiving regions 7a in the X direction constant, thereby simplifying manufacturing.
[0053] Furthermore, in the spectral module 1, each beam splitter 3 is elongated when viewed from the thickness direction, and the direction perpendicular to the longitudinal direction of each beam splitter 3 is the Y direction (perpendicular to both the X and Z directions). This allows for miniaturization of each beam splitter 3 in the Y direction while effectively utilizing the clear aperture of each beam splitter 3. In addition, miniaturization of each beam splitter 3 in the Y direction also allows for miniaturization of the housing 2.
[0054] Furthermore, in the spectroscopic module 1, each beam splitter 3 has the same shape. This allows for the commonality of components among multiple beam splitters 3. [Differentiation]
[0055] The present invention is not limited to the above embodiments. For example, in the above embodiment, a plurality of beam splitters 3 are arranged along the first direction (X direction), and a plurality of bandpass filters 4 etc. are arranged on one side of the plurality of beam splitters 3 in the second direction (Z direction). In other words, in the above embodiment, the second direction (Z direction) was perpendicular to the first direction (X direction), but the second direction can be any direction that intersects the first direction. Also, in the above embodiment, the meaning of "so as to be in contact" is not limited to the contact between certain members, but also includes the case where a film such as an adhesive is placed between certain members.
[0056] Furthermore, the housing 2 only needs to accommodate at least a plurality of beam splitters 3 and a plurality of bandpass filters 4. Also, a portion of the housing 2 may be formed by at least one part of the first support 5, the second support 6, and the photodetector 7. Furthermore, the first support 5 and the second support 6 may be integrally formed. In addition, although the light incident surface 4a of each bandpass filter 4 was located on one side in the Z direction of the bottom surface 63a of the recess 63 where the light-shielding member 8 is placed, it may also be located at the same position as the bottom surface 63a.
[0057] Furthermore, each beam splitter 3 may be a dichroic mirror that reflects light of different wavelength bands and transmits light of other wavelength bands. Also, each beam splitter 3 may have a specific shape, such as a polygon or ellipse, as long as it is elongated when viewed from the thickness direction of each beam splitter 3. Furthermore, the multiple bandpass filters 4 may be composed of, for example, at least two dielectric multilayer films formed on a single substrate. In other words, there should be multiple parts, each functioning as a bandpass filter 4, and the substrates on which each of these multiple parts is arranged do not need to be separated from each other. Furthermore, the photodetector 7 may be a PD array or the like, in which multiple light-receiving regions 7a are formed on a single semiconductor substrate. Furthermore, the photodetector 7 may be a photomultiplier tube.
[0058] Furthermore, in the above embodiment, the housing 2 had a plurality of positioning holes 2c as a defining portion, but it is sufficient if at least one of the second support 6 and the housing 2 has a defining portion that defines the position of the first support 5 in a plane parallel to both the X and Z directions. Examples of defining portions of the second support 6 and the housing 2 include contact areas provided on the side surface 92 of the recess 9 so as to contact the first support 5 located within the recess 9. Alternatively, the first support 5 may have a first engaging portion, and the housing 2 may have a second engaging portion that engages with the first engaging portion as a defining portion. In that case, one of the first and second engaging portions may be a plurality of positioning holes, and the other of the first and second engaging portions may be positioning pins fitted into each of the plurality of positioning holes.
[0059] Furthermore, in the above embodiment, the second support 6 has a positioning pin 6a and the light-shielding member 8 has a positioning hole 8b. However, the second support 6 may have a first engaging portion and the light-shielding member 8 may have a second engaging portion that engages with the first engaging portion. In that case, one of the first engaging portion and the second engaging portion may be a plurality of positioning holes, and the other of the first engaging portion and the second engaging portion may each be a positioning pin fitted into each of the plurality of positioning holes 0.
[0060] Furthermore, if the beam splitter 3 is plate-shaped and has a thickness of 1 mm or less (more preferably 0.5 mm or less), then if the total number of beam splitters 3 is M (where M is a natural number greater than or equal to 2), then it is sufficient that each of the N beam splitters 3 (where N is a natural number greater than or equal to 2 and less than or equal to M) is plate-shaped and has a thickness of 1 mm or less (more preferably 0.5 mm or less). Note that all beam splitters 3 may be plate-shaped and have a thickness of 1 mm or less (more preferably 0.5 mm or less) (when M=N). [Explanation of Symbols]
[0061] 1...Spectroscopic module, 3...Beam splitter, 3a...Center, 4...Bandpass filter, 5...First support (support, support part), 6...Second support (support), 7...Photodetector, 7a...Light receiving area, 10...Light incident part, 56...Groove, 56a, 56b...Side, 56c...Bottom, 57a, 57b...Light passing aperture, A...Optical axis, α...Line.
Claims
1. M beam splitters (where M is a natural number greater than or equal to 2) are arranged along the first direction, With respect to the M beam splitters, M bandpass filters are arranged on one side in a second direction intersecting the first direction, each facing each of the M beam splitters, A photodetector is provided, which is positioned on one side in the second direction relative to the M bandpass filters, and each of the M light-receiving regions is positioned opposite each of the M bandpass filters. The system comprises a support for the M beam splitters, Each of the N beam splitters (where N is a natural number between 2 and M) out of the M beam splitters has a plate-like shape with a pair of main surfaces and a thickness of 1 mm or less. The support has a support portion in which N grooves are formed, The support portion is provided with N combinations of grooves and beam splitters, each of which is arranged in each of the N grooves, and each of the N beam splitters is arranged in each of the N grooves. In each of the N combinations, the groove has a pair of sides, In each of the N combinations, one of the pair of main faces faces one of the pair of side faces, and the other of the pair of main faces faces the other of the pair of side faces. In each of the N combinations, the beam splitter is fixed in the groove such that at least one main surface is in contact with one side surface. A spectroscopic module wherein the groove further has a bottom surface, and the beam splitter is fixed to the groove by an adhesive arranged to be in contact with the beam splitter and the bottom surface.
2. In each of the N combinations, a light-transmitting region is formed on each of the pair of sides. In each of the N combinations, the one side surface includes a first region and a second region located on both sides of the light-transmitting region in a third direction that intersects both the first and second directions, The spectroscopic module according to claim 1, wherein in each of the N combinations, the beam splitter is fixed in the groove such that at least one of the main surfaces is in contact with the first region and the second region.
3. In each of the N combinations, the beam splitter is fixed to the groove by at least one main surface being bonded to one side surface, as described in claim 1 or 2.
4. The spectroscopic module according to any one of claims 1 to 3, wherein the support portion is formed of metal.
5. The support portion includes a wall portion located on one side in a third direction that intersects both the first and second directions with respect to the N grooves. The spectroscopic module according to any one of claims 1 to 4, wherein, when viewed from the first direction, the thickness of the wall in the third direction is smaller than the thickness of each of the M bandpass filters in the second direction.
6. The spectroscopic module according to any one of claims 1 to 5, wherein, when viewed from the first direction, the width of the N beam splitters in the second direction is greater than the thickness of each of the M bandpass filters in the second direction.
7. The aforementioned one side includes a third region located between the first region and the second region in the third direction, The spectroscopic module according to claim 2, wherein in each of the N combinations, the beam splitter is fixed in the groove such that at least one of the main surfaces is in contact with the first region, the second region, and the third region.
8. In each of the N combinations, the groove further has the bottom surface, In each of the N combinations, the beam splitter is fixed in the groove so as to be in contact with one side and the bottom surface, the spectroscopic module according to any one of claims 1 to 7.
9. The spectroscopic module according to claim 8, wherein a light-transmitting region is formed on the bottom surface such that the bottom surface is separated into two regions in a third direction intersecting both the first and second directions.
10. The device further comprises light-shielding portions disposed between the M bandpass filters and the M light-receiving regions in the second direction, The spectroscopic module according to any one of claims 1 to 9, wherein the light-shielding portion has a plurality of light-passing apertures through which each of the plurality of optical paths from the M bandpass filters to the M light-receiving regions passes.
11. The spectral module according to claim 10, wherein the width of each of the plurality of light-passing apertures in the first direction is greater than the length of each of the plurality of light-passing apertures in the second direction.
12. The spectral module according to claim 10 or 11, wherein the width between adjacent optical apertures in the first direction is smaller than the width of each of the M bandpass filters in the first direction.
13. The spectral module according to any one of claims 1 to 12, wherein the distance between each of the light-emitting surfaces of the M bandpass filters and each of the M light-receiving regions in the second direction is smaller than the width of each of the M bandpass filters in the first direction.
14. The aforementioned photodetector has a photodetector element, The spectroscopic module according to any one of claims 1 to 13, wherein the photodetector includes a semiconductor substrate on which a plurality of light-receiving regions included in the M light-receiving regions are formed.
15. The aforementioned photodetector has a plurality of photodetectors, The spectroscopic module according to any one of claims 1 to 13, wherein each of the plurality of photodetectors includes a semiconductor substrate on which a single light-receiving region is formed, which is included in the M light-receiving regions.