Optical Devices

Abstract

To provide an optical device with high reliability.SOLUTION: In an optical device, a base and a movable portion are constituted by a semiconductor substrate having a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in a predetermined direction. The base is constituted by the first semiconductor layer, the insulating layer, and the second semiconductor layer. The movable portion has an arrangement portion that is constituted by the second semiconductor layer. An optical function portion is disposed on a surface of the arrangement portion on the one side. An electrode pad is disposed on a surface of the second semiconductor layer on the one side in an opening that is formed on a surface of the first semiconductor layer on the one side so as to reach the second semiconductor layer, and is electrically connected to an actuator portion via the second semiconductor layer.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present disclosure relates to optical devices. [Background technology]

[0002] There is known an optical device in which an interference optical system is formed on an SOI (Silicon On Insulator) substrate by using MEMS (Micro Electro Mechanical Systems) technology (see, for example, Patent Document 1). Such an optical device has attracted attention because it can provide an FTIR (Fourier transform infrared spectroscopic analyzer) with a highly accurate optical arrangement. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2012-524295 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical device described above, the movable mirror constituting the interference optical system moves along the main surface of the SOI substrate. In order to increase the size of the mirror surface of the movable mirror, it is conceivable to adopt a configuration in which the movable mirror moves along a direction perpendicular to the main surface of the SOI substrate. However, simply adopting such a configuration may not provide sufficient protection for the mirror surface, which may reduce the reliability of the device.

[0005] An object of one aspect of the present disclosure is to provide a highly reliable optical device. [Means for solving the problem]

[0006] An optical device according to one aspect of the present disclosure comprises a base having a main surface, a movable part supported on the base so as to be movable along a predetermined direction intersecting the main surface, and an optical functional part arranged on the movable part, wherein the base and the movable part are constituted by a semiconductor substrate having a first semiconductor layer, an insulating layer and a second semiconductor layer in that order from one side in the predetermined direction, the base is constituted by the first semiconductor layer, the insulating layer and the second semiconductor layer, the movable part has a positioning part constituted by the second semiconductor layer, the optical functional part is arranged on a surface of one side of the positioning part, the first semiconductor layer constituting the base is thicker than the second semiconductor layer constituting the base, and the surface of one side of the base is located on one side of the optical functional part.

[0007] In this optical device, one surface of the base is located on one side of the optical function part. This allows the optical function part to be protected by the base, and for example, damage to the optical function part due to direct contact during transportation or the like can be suppressed. Furthermore, in this optical device, the first semiconductor layer constituting the base is thicker than the second semiconductor layer constituting the base. This allows the amount of protrusion of the base from the optical function part to be secured, and the optical function part can be effectively protected by the base. Therefore, this optical device can increase reliability.

[0008] The movable part further has a beam part arranged around the optical function part, and the beam part is composed of a first semiconductor layer and an insulating layer arranged on the second semiconductor layer, and an end face on one side of the beam part may be located on one side of the optical function part. In this case, the optical function part can also be protected by the beam part. Furthermore, the beam part can suppress deformation of the movable part during movement.

[0009] The beam portion may be disposed on one surface of the arrangement portion so as to extend along the outer edge of the arrangement portion when viewed from a predetermined direction. In this case, the beam portion can be disposed close to the optical function portion, and the optical function portion can be more effectively protected. Furthermore, since the beam portion is disposed on the arrangement portion, deformation of the arrangement portion can be more suitably suppressed.

[0010] The movable part may further have a frame part surrounding the arrangement part when viewed from a predetermined direction, and a connecting part connecting the arrangement part and the frame part to each other, the frame part and the connecting part being made of a second semiconductor layer, and the beam part may be arranged on a surface of one side of the frame part so as to extend along the frame part when viewed from the predetermined direction. In this case, the optical function part can be protected more effectively by the beam part. Furthermore, the beam part can suppress deformation of the frame part, and thus suppress deformation of the arrangement part caused by deformation of the frame part.

[0011] The first semiconductor layer constituting the beam may be thinner than the first semiconductor layer constituting the base. In this case, it is possible to prevent the beam from protruding from the base during movement of the movable part, and it is possible to increase the amount of movement of the movable part in a predetermined direction.

[0012] The optical device according to one aspect of the present disclosure further includes an electrode pad provided on the base, the electrode pad being disposed on one surface of the second semiconductor layer within an opening formed in the base so as to extend from one surface of the first semiconductor layer to the second semiconductor layer, and the base may be formed with a groove portion extending from one surface of the first semiconductor layer to the second semiconductor layer and surrounding the opening when viewed from a predetermined direction. In this case, the groove portion can ensure electrical insulation of the electrode pad, thereby further improving reliability.

[0013] The electrode pad may extend across the bottom and side surfaces of the opening, making it possible to increase the area of ​​the electrode pad.

[0014] Each of the electrode pads and the optical function unit is made of a metal layer, and the metal layer constituting the electrode pads may be thicker than the metal layer constituting the optical function unit. In this case, it is possible to suppress deformation of the optical function unit and to ensure electrical connection to the electrode pads.

[0015] A mirror unit according to one aspect of the present disclosure comprises the optical device described above, an optical functional member arranged on the other side in a predetermined direction relative to the optical device, and a fixed mirror arranged on the other side relative to the optical functional member, wherein the optical functional member is a mirror surface which constitutes the movable mirror together with the movable member, the optical device is provided with a first light passing portion which constitutes a first portion of the optical path between the fixed mirror and a beam splitter unit which constitutes an interference optical system together with the movable mirror and the fixed mirror, and the optical functional member is provided with a second light passing portion which constitutes a second portion of the optical path between the beam splitter unit and the fixed mirror, and the second light passing portion corrects the optical path difference occurring between the optical path between the beam splitter unit and the movable mirror and the optical path between the beam splitter unit and the fixed mirror.

[0016] This mirror unit can improve reliability for the reasons described above. Also, the second light passing portion of the optical functional member can correct the optical path length difference occurring between the optical path between the beam splitter unit and the movable mirror and the optical path between the beam splitter unit and the fixed mirror. Furthermore, in this mirror unit, the mirror surface is disposed close to the optical functional member. Such a configuration is particularly effective when the optical path length difference is corrected by the second light passing portion of the optical functional member. Effect of the Invention

[0017] According to one aspect of the present disclosure, a highly reliable optical device can be provided. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view of an optical module according to an embodiment. [Diagram 2] FIG. 2 is a plan view of the mirror unit shown in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the mirror unit taken along line III-III shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of the mirror unit taken along line IV-IV shown in FIG. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the mirror device taken along line VV shown in FIG. [Figure 6] FIG. 6 is a partial enlarged view of the mirror device shown in FIG. [Figure 7] FIG. 7 is a plan view of the optical functional member shown in FIG. [Figure 8] FIG. 8 is a cross-sectional view of the optical module taken along line VIII-VIII shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view of the optical module taken along line IX-IX shown in FIG. [Figure 10] FIG. 10 is a schematic cross-sectional view of the mirror unit and the beam splitter unit shown in FIG. [Figure 11] FIG. 11 is a schematic cross-sectional view of the mirror device taken along the line XI-XI shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and overlapping parts are omitted. [Optical module configuration]

[0020] As shown in FIG. 1, the optical module 1 includes a mirror unit 2, a beam splitter unit 3, a light input unit 4, a first photodetector 6, a second light source 7, a second photodetector 8, a support 9, a first support structure 11, and a second support structure 12. The mirror unit 2 is disposed on one side of the support 9 in the Z-axis direction (predetermined direction, first direction) and is attached to the support 9 by, for example, an adhesive. The support 9 is formed of, for example, copper tungsten, and has, for example, a rectangular plate shape. The mirror unit 2 includes a movable mirror 22 that moves along the Z-axis direction and a fixed mirror 16 whose position is fixed (details will be described later). The Z-axis direction is, for example, a vertical direction, and one side in the Z-axis direction is, for example, an upper side.

[0021] The beam splitter unit 3 is disposed on one side of the mirror unit 2 in the Z-axis direction, and is supported by a first support structure 11. The first support structure 11 is attached to the support 9, for example, by an adhesive. The light incident section 4 is disposed on one side of the beam splitter unit 3 in the X-axis direction (a third direction perpendicular to the first direction), and is supported by a second support structure 12. The first photodetector 6, the second light source 7, and the second photodetector 8 are disposed on one side of the beam splitter unit 3 in the Z-axis direction, and are supported by the second support structure 12. The second support structure 12 is attached to the support 9, for example, by a bolt.

[0022] In the optical module 1, an interference optical system for each of the measurement light L0 and the laser light L10 is configured by the beam splitter unit 3, the movable mirror 22, and the fixed mirror 16. The interference optical system configured for each of the measurement light L0 and the laser light L10 is, for example, a Michelson interference optical system.

[0023] With regard to the measurement light L0, the interference light L1 of the measurement light is detected as follows. That is, when the measurement light L0 incident from the first light source (not shown) through the measurement object (not shown) or the measurement light L0 emitted from the measurement object (for example, light emission from the measurement object itself) is incident on the beam splitter unit 3 from the light incident section 4, the measurement light L0 is split into a part and a remainder in the beam splitter unit 3. Then, a part of the measurement light L0 is reflected by the movable mirror 22 that reciprocates along the Z-axis direction and returns to the beam splitter unit 3. On the other hand, the remainder of the measurement light L0 is reflected by the fixed mirror 16 and returns to the beam splitter unit 3. The part and the remainder of the measurement light L0 that returned to the beam splitter unit 3 are emitted from the beam splitter unit 3 as interference light L1, and the interference light L1 of the measurement light is detected by the first photodetector 6.

[0024] Regarding the laser light L10, the interference light L11 of the laser light is detected as follows. That is, when the laser light L10 emitted from the second light source 7 enters the beam splitter unit 3, the laser light L10 is split into a part and a remainder in the beam splitter unit 3. Then, a part of the laser light L10 is reflected by the movable mirror 22 that reciprocates along the Z-axis direction and returns to the beam splitter unit 3. Meanwhile, the remainder of the laser light L10 is reflected by the fixed mirror 16 and returns to the beam splitter unit 3. The part and the remainder of the laser light L10 that returned to the beam splitter unit 3 are emitted from the beam splitter unit 3 as interference light L11, and the interference light L11 of the laser light is detected by the second photodetector 8.

[0025] According to the optical module 1, it is possible to measure the position of the movable mirror 22 in the Z-axis direction based on the detection result of the interference light L11 of the laser light, and it is possible to perform spectroscopic analysis of the measurement object based on the measurement result of that position and the detection result of the interference light L1 of the measurement light. [Mirror unit configuration]

[0026] 2, 3, and 4, the mirror unit 2 has a mirror device (optical device) 20, an optical functional member 13, a fixed mirror 16, and a stress relaxation substrate 17. The mirror device 20 includes a base 21, a movable mirror 22, and a drive unit 23.

[0027] The base 21 has a first surface 21a (a surface on one side in the Z-axis direction) and a second surface 21b opposite to the first surface 21a. Each of the first surface 21a and the second surface 21b is a main surface of the base 21. The base 21 has, for example, a rectangular plate shape and has a size of, for example, about 10 mm×15 mm×0.35 mm (thickness). The movable mirror 22 has a mirror surface (optical function part) 22a and a movable part 22b on which the mirror surface 22a is arranged. The movable mirror 22 (movable part 22b) is supported by the base 21 so as to be movable along the Z-axis direction (a predetermined direction perpendicular to the first surface) perpendicular to the first surface 21a. The driving part 23 moves the movable mirror 22 along the Z-axis direction.

[0028] The mirror device 20 is provided with a pair of light passing openings 24, 25. The pair of light passing openings 24, 25 are arranged on both sides of the movable mirror 22 in the X-axis direction. The light passing opening (first light passing portion) 24 forms a first portion of the optical path between the beam splitter unit 3 and the fixed mirror 16. In this embodiment, the light passing opening 25 does not function as a light passing opening.

[0029] Here, the configuration of mirror device 20 will be described in detail with reference to Fig. 2, Fig. 5, and Fig. 6. Fig. 5 is a schematic cross-sectional view of mirror device 20 shown in Fig. 3, and Fig. 5 shows mirror device 20 in a state where, for example, the dimension in the Z-axis direction is enlarged compared to the actual state.

[0030] The base 21, the movable part 22b of the movable mirror 22, and the driving part 23 are composed of an SOI (Silicon On Insulator) substrate (semiconductor substrate) 100. That is, the mirror device 20 is composed of the SOI substrate 100. The mirror device 20 is formed, for example, in a rectangular plate shape. The SOI substrate 100 has a support layer 101, a device layer 102, and an intermediate layer 103. The support layer 101 is a first silicon layer (first semiconductor layer). The device layer 102 is a second silicon layer (second semiconductor layer). The intermediate layer 103 is an insulating layer disposed between the support layer 101 and the device layer 102. The SOI substrate 100 has the support layer 101, the intermediate layer 103, and the device layer 102 in this order from one side in the Z-axis direction.

[0031] The base 21 is composed of a support layer 101, a device layer 102, and a part of the intermediate layer 103. A first surface 21a of the base 21 is a surface of the support layer 101 opposite to the intermediate layer 103. A second surface 21b of the base 21 is a surface of the device layer 102 opposite to the intermediate layer 103. The support layer 101 constituting the base 21 is thicker than the device layer 102 constituting the base 21. The thickness of the support layer 101 constituting the base 21 is, for example, about four times the thickness of the device layer 102 constituting the base 21. In the mirror unit 2, as described later, the second surface 21b of the base 21 and the third surface 13a of the optical functional member 13 are bonded to each other (see FIGS. 3 and 4).

[0032] The movable mirror 22 is disposed with its center (center of gravity) at the intersection of the axis R1 and the axis R2. The axis R1 is a straight line extending in the X-axis direction. The axis R2 is a straight line extending in the Y-axis direction (a second direction perpendicular to the first and third directions). When viewed from the Z-axis direction, the mirror device 20 has a shape that is line-symmetrical with respect to each of the axis R1 and the axis R2, except for a portion that overlaps with a sixth surface 21d of the base 21, which will be described later.

[0033] The movable mirror 22 (movable portion 22b) has a placement portion 221, a frame portion 222, a pair of connecting portions 223, and a beam portion 224. The placement portion 221, the frame portion 222, and the pair of connecting portions 223 are formed of a part of the device layer 102. The placement portion 221 has a circular shape when viewed from the Z-axis direction. The placement portion 221 has a central portion 221a and an outer edge portion 221b. A mirror surface 22a is provided on a surface 221as on one side in the Z-axis direction of the central portion 221a by forming, for example, a metal film (metal layer). The mirror surface 22a extends perpendicularly to the Z-axis direction and has a circular shape. The surface 221as of the central portion 221a is a surface on the intermediate layer 103 side of the device layer 102. The mirror surface 22a is located on the other side in the Z-axis direction from the first surface 21a of the base 21. In other words, the first surface 21a is located on one side in the Z-axis direction relative to the mirror surface 22a. The outer edge portion 221b surrounds the central portion 221a when viewed from the Z-axis direction.

[0034] When viewed from the Z-axis direction, the frame portion 222 extends in an annular shape so as to surround the arrangement portion 221 at a predetermined interval from the arrangement portion 221. The frame portion 222 has, for example, an annular shape when viewed from the Z-axis direction. Each of the pair of connecting portions 223 connects the arrangement portion 221 and the frame portion 222 to each other. The pair of connecting portions 223 are arranged on both sides of the arrangement portion 221 in the Y-axis direction.

[0035] The beam portion 224 is composed of the support layer 101 and the intermediate layer 103 arranged on the device layer 102. The beam portion 224 is arranged around the mirror surface 22a. The beam portion 224 has an inner beam portion 224a, an outer beam portion 224b, and a pair of connecting beam portions 224c. The inner beam portion 224a is arranged on the surface on one side in the Z-axis direction of the outer edge portion 221b. The inner beam portion 224a surrounds the mirror surface 22a when viewed from the Z-axis direction. For example, the outer edge of the inner beam portion 224a extends along the outer edge of the arrangement portion 221 at a predetermined interval from the outer edge of the arrangement portion 221 when viewed from the Z-axis direction. The inner edge of the inner beam portion 224a extends along the outer edge of the mirror surface 22a at a predetermined interval from the outer edge of the mirror surface 22a when viewed from the Z-axis direction. An end face 224as on one side in the Z-axis direction of the inner beam portion 224a is located on one side in the Z-axis direction with respect to the mirror surface 22a.

[0036] The outer beam portion 224b is disposed on a surface of one side in the Z-axis direction of the frame portion 222. When viewed from the Z-axis direction, the outer beam portion 224b surrounds the inner beam portion 224a, and thus surrounds the mirror surface 22a. For example, when viewed from the Z-axis direction, the outer edge of the outer beam portion 224b extends along the outer edge of the frame portion 222 at a predetermined interval from the outer edge of the frame portion 222. When viewed from the Z-axis direction, the inner edge of the outer beam portion 224b extends along the inner edge of the frame portion 222 at a predetermined interval from the inner edge of the frame portion 222. An end surface 224bs on one side in the Z-axis direction of the outer beam portion 224b is located on one side in the Z-axis direction from the mirror surface 22a.

[0037] The pair of connecting beam portions 224c are each disposed on one surface of the pair of connecting portions 223 on one side in the Z-axis direction. Each connecting beam portion 224c connects the inner beam portion 224a and the outer beam portion 224b to each other. An end surface 224cs on one side in the Z-axis direction of the connecting beam portion 224c is located on one side in the Z-axis direction of the mirror surface 22a.

[0038] The thicknesses of the inner beam portion 224a, the outer beam portion 224b, and each connecting beam portion 224c in the Z-axis direction are equal to each other. That is, the thicknesses of the support layer 101 constituting the inner beam portion 224a, the outer beam portion 224b, and each connecting beam portion 224c are equal to each other. The end face 224as of the inner beam portion 224a, the end face 224bs of the outer beam portion 224b, and the end face 224cs of each connecting beam portion 224c are located on the same plane perpendicular to the Z-axis direction. The support layer 101 constituting the inner beam portion 224a, the outer beam portion 224b, and each connecting beam portion 224c is thinner than the support layer 101 constituting the base 21. As a result, the end faces 224as, 224bs, and 224cs are located on one side in the Z-axis direction from the first surface 21a of the base 21. In other words, the first surface 21a is located on the other side in the Z-axis direction relative to the end faces 224as, 224bs, and 224cs.

[0039] When viewed from the Z-axis direction, the width of the outer beam portion 224b is wider than the width of the inner beam portion 224a. The width of the inner beam portion 224a when viewed from the Z-axis direction is the length of the inner beam portion 224a in a direction perpendicular to the extension direction of the inner beam portion 224a, and in this embodiment, is the length of the inner beam portion 224a in the radial direction of the inner beam portion 224a. This point is also the same for the width of the outer beam portion 224b when viewed from the Z-axis direction. The width of each connecting beam portion 224c is larger than the width of each of the inner beam portion 224a and the outer beam portion 224b. The width of each connecting beam portion 224c is the length of each connecting beam portion 224c along the extension direction of the inner beam portion 224a.

[0040] The driving section 23 has a first elastic support section 26, a second elastic support section 27, and an actuator section 28. The first elastic support section 26, the second elastic support section 27, and the actuator section 28 are configured by a part of the device layer 102.

[0041] Each of the first elastic support member 26 and the second elastic support member 27 is connected between the base 21 and the movable mirror 22. The first elastic support member 26 and the second elastic support member 27 support the movable mirror 22 such that the movable mirror 22 (movable portion 22b) is movable along the Z-axis direction.

[0042] The first elastic support portion 26 has a pair of levers 261, a first link member 262, a second link member 263, a pair of beam members 264, an intermediate member 265, a pair of first torsion bars (first torsion support portions) 266, a pair of second torsion bars (second torsion support portions) 267, a pair of nonlinear relaxation springs 268, and a plurality of electrode support portions 269.

[0043] The pair of levers 261 are disposed on both sides of the light passing opening 24 in the Y-axis direction and face each other in the Y-axis direction. Each lever 261 has a plate shape extending along a plane perpendicular to the Z-axis direction. Each lever 261 has a first portion 261a, a second portion 261b disposed on the opposite side of the movable mirror 22 with respect to the first portion 261a, and a third portion 261c connected to the first portion 261a and the second portion 261b. The first portion 261a and the second portion 261b extend along the X-axis direction. The length of the first portion 261a in the X-axis direction is shorter than the length of the second portion 261b in the X-axis direction. The third portions 261c of the pair of levers 261 extend at an incline so as to move away from each other as they move away from the movable mirror 22.

[0044] The first link member 262 is hung between the first end portions 261d of the pair of levers 261 on the side opposite to the movable mirror 22. The first link member 262 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The second link member 263 is hung between the second end portions 261e of the pair of levers 261 on the movable mirror 22 side. The second link member 263 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The width of the second link member 263 in the X-axis direction is narrower than the width of the first link member 262 in the X-axis direction. The length of the second link member 263 in the Y-axis direction is shorter than the length of the first link member 262 in the Y-axis direction.

[0045] The pair of beam members 264 are respectively hung between the second parts 261b of the pair of levers 261 and the first link member 262. Each beam member 264 has a plate shape extending along a plane perpendicular to the Z-axis direction. The pair of beam members 264 extend at an incline so as to approach each other as they move away from the movable mirror 22. The pair of levers 261, the first link member 262, the second link member 263, and the pair of beam members 264 define the light passing opening 24. The light passing opening 24 has a polygonal shape when viewed from the Z-axis direction. The light passing opening 24 is, for example, a cavity (hole). Alternatively, a material having optical transparency to the measurement light L0 and the laser light L10 may be disposed in the light passing opening 24.

[0046] The intermediate member 265 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The intermediate member 265 is disposed between the movable mirror 22 and the second link member 263 (in other words, between the movable mirror 22 and the light passing opening 24). The intermediate member 265 is connected to the movable mirror 22 via a nonlinearity relaxation spring 268, as described later.

[0047] The pair of first torsion bars 266 are respectively hung between the first end 261d of one lever 261 and the base 21, and between the first end 261d of the other lever 261 and the base 21. That is, the pair of first torsion bars 266 are respectively connected between the pair of levers 261 and the base 21. Each of the first torsion bars 266 extends along the Y-axis direction. The pair of first torsion bars 266 are disposed on the same center line parallel to the Y-axis direction. In this embodiment, the center line of each of the first torsion bars 266 and the center line of the first link member 262 are positioned on the same straight line. The first end 261d of each lever 261 is provided with a protruding portion 261f protruding outward in the Y-axis direction, and each of the first torsion bars 266 is connected to the protruding portion 261f.

[0048] The pair of second torsion bars 267 are respectively hung between the second end 261e of one lever 261 and one end of the intermediate member 265, and between the second end 261e of the other lever 261 and the other end of the intermediate member 265. That is, the pair of second torsion bars 267 are respectively connected between the pair of levers 261 and the movable mirror 22. Each of the second torsion bars 267 extends along the Y-axis direction. The pair of second torsion bars 267 are disposed on the same center line parallel to the Y-axis direction.

[0049] The pair of nonlinear relaxation springs 268 are connected between the movable mirror 22 and the intermediate member 265. That is, the pair of nonlinear relaxation springs 268 are connected between the movable mirror 22 and the second torsion bar 267. Each of the nonlinear relaxation springs 268 has a meandering portion 268a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 268a extends in the Y-axis direction and includes a plurality of straight portions 268b arranged in the X-axis direction, and a plurality of folded portions 268c that alternately connect both ends of the plurality of straight portions 268b. One end of the meandering portion 268a is connected to the intermediate member 265, and the other end of the meandering portion 268a is connected to the frame portion 222. The portion of the meandering portion 268a on the frame portion 222 side has a shape that follows the outer edge of the frame portion 222.

[0050] The nonlinear relaxation spring 268 is configured such that, when the movable mirror 22 moves in the Z-axis direction, the deformation amount of the nonlinear relaxation spring 268 around the Y-axis direction is smaller than the deformation amount of each of the first torsion bar 266 and the second torsion bar 267 around the Y-axis direction, and the deformation amount of the nonlinear relaxation spring 268 around the X-axis direction is larger than the deformation amount of each of the first torsion bar 266 and the second torsion bar 267 around the X-axis direction. This makes it possible to suppress nonlinearity from occurring in the torsional deformation of the first torsion bar 266 and the second torsion bar 267, and to suppress deterioration of the control characteristics of the movable mirror 22 caused by the nonlinearity. The deformation amount of the first torsion bar 266, the second torsion bar 267, and the nonlinear relaxation spring 268 around the Y-axis direction means, for example, the absolute value of the amount of twist (twist angle). The deformation amount of the first torsion bar 266, the second torsion bar 267, and the nonlinear relaxation spring 268 in the X-axis direction means, for example, the absolute value of the amount of deflection. The deformation amount of a certain member around the Y-axis direction means the deformation amount of the member in the circumferential direction of a circle that passes through the center of the member and has an axis line parallel to the Y-axis as its center. These points also apply to the first torsion bar 276, the second torsion bar 277, and the nonlinear relaxation spring 278 described later.

[0051] The electrode support parts 269 include a pair of first electrode support parts 269a, a pair of second electrode support parts 269b, and a pair of third electrode support parts 269c. Each of the electrode support parts 269a, 269b, and 269c has a plate shape extending along a plane perpendicular to the Z-axis direction and extends along the Y-axis direction. Each of the electrode support parts 269a, 269b, and 269c extends from the second part 261b of the lever 261 toward the opposite side to the light passing opening 24. The pair of first electrode support parts 269a is disposed on the same center line parallel to the Y-axis direction. The pair of second electrode support parts 269b is disposed on the same center line parallel to the Y-axis direction. The pair of third electrode support parts 269c is disposed on the same center line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portion 269a, the second electrode support portion 269b, and the third electrode support portion 269c are arranged side by side in this order from the movable mirror 22 side.

[0052] The second elastic support portion 27 has a pair of levers 271, a first link member 272, a second link member 273, a pair of beam members 274, an intermediate member 275, a pair of first torsion bars (first torsion support portion) 276, a pair of second torsion bars (second torsion support portion) 277, a pair of nonlinear relaxation springs 278, and a plurality of electrode support portions 279.

[0053] The pair of levers 271 are disposed on both sides of the light passing opening 25 in the Y-axis direction and face each other in the Y-axis direction. Each lever 271 has a plate shape extending along a plane perpendicular to the Z-axis direction. Each lever 271 has a first portion 271a, a second portion 271b disposed on the opposite side of the movable mirror 22 with respect to the first portion 271a, and a third portion 271c connected to the first portion 271a and the second portion 271b. The first portion 271a and the second portion 271b extend along the X-axis direction. The length of the first portion 271a in the X-axis direction is shorter than the length of the second portion 271b in the X-axis direction. The third portions 271c of the pair of levers 271 extend at an incline so as to move away from each other as they move away from the movable mirror 22.

[0054] The first link member 272 is hung between the first end portions 271d of the pair of levers 271 on the side opposite to the movable mirror 22. The first link member 272 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The second link member 273 is hung between the second end portions 271e of the pair of levers 271 on the movable mirror 22 side. The second link member 273 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The width of the second link member 273 in the X-axis direction is narrower than the width of the first link member 272 in the X-axis direction. The length of the second link member 273 in the Y-axis direction is shorter than the length of the first link member 272 in the Y-axis direction.

[0055] The pair of beam members 274 are respectively hung between the second parts 271b of the pair of levers 271 and the first link member 272. Each beam member 274 has a plate shape extending along a plane perpendicular to the Z-axis direction. The pair of beam members 274 extend at an incline so as to approach each other as they move away from the movable mirror 22. The pair of levers 271, the first link member 272, the second link member 273, and the pair of beam members 274 define a light passing opening 25. The light passing opening 25 has a polygonal shape when viewed from the Z-axis direction. The light passing opening 25 is, for example, a cavity (hole). Alternatively, a material having optical transparency to the measurement light L0 and the laser light L10 may be disposed in the light passing opening 25.

[0056] The intermediate member 275 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The intermediate member 275 is disposed between the movable mirror 22 and the second link member 273 (in other words, between the movable mirror 22 and the light passing opening 25). The intermediate member 275 is connected to the movable mirror 22 via a nonlinearity relaxation spring 278, as described later.

[0057] The pair of first torsion bars 276 are respectively hung between the first end 271d of one lever 271 and the base 21, and between the first end 271d of the other lever 271 and the base 21. That is, the pair of first torsion bars 276 are respectively connected between the pair of levers 271 and the base 21. Each of the first torsion bars 276 extends along the Y-axis direction. The pair of first torsion bars 276 are disposed on the same center line parallel to the Y-axis direction. In this embodiment, the center line of each of the first torsion bars 276 and the center line of the first link member 272 are positioned on the same straight line. The first end 271d of each lever 271 is provided with a protruding portion 271f protruding outward in the Y-axis direction, and each of the first torsion bars 276 is connected to the protruding portion 271f.

[0058] The pair of second torsion bars 277 are respectively hung between the second end 271e of one lever 271 and one end of the intermediate member 275, and between the second end 271e of the other lever 271 and the other end of the intermediate member 275. That is, the pair of second torsion bars 277 are respectively connected between the pair of levers 271 and the movable mirror 22. Each second torsion bar 277 extends along the Y-axis direction. The pair of second torsion bars 277 are disposed on the same center line parallel to the Y-axis direction.

[0059] The pair of nonlinear relaxation springs 278 are connected between the movable mirror 22 and the intermediate member 275. That is, the pair of nonlinear relaxation springs 278 are connected between the movable mirror 22 and the second torsion bar 277. Each of the nonlinear relaxation springs 278 has a meandering portion 278a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 278a extends in the Y-axis direction and includes a plurality of straight portions 278b arranged in the X-axis direction, and a plurality of folded portions 278c that alternately connect both ends of the plurality of straight portions 278b. One end of the meandering portion 278a is connected to the intermediate member 275, and the other end of the meandering portion 278a is connected to the frame portion 222. The portion of the meandering portion 278a on the frame portion 222 side has a shape that follows the outer edge of the frame portion 222.

[0060] The nonlinearity relaxation spring 278 is configured such that, when the movable mirror 22 moves in the Z-axis direction, the amount of deformation of the nonlinearity relaxation spring 278 around the Y-axis direction is smaller than the amount of deformation of each of the first torsion bar 276 and the second torsion bar 277 around the Y-axis direction, and the amount of deformation of the nonlinearity relaxation spring 278 in the X-axis direction is larger than the amount of deformation of each of the first torsion bar 276 and the second torsion bar 277 in the X-axis direction. This makes it possible to suppress the occurrence of nonlinearity in the torsional deformation of the first torsion bar 276 and the second torsion bar 277, and to suppress deterioration of the control characteristics of the movable mirror 22 caused by the nonlinearity.

[0061] The electrode support parts 279 include a pair of first electrode support parts 279a, a pair of second electrode support parts 279b, and a pair of third electrode support parts 279c. Each of the electrode support parts 279a, 279b, and 279c has a plate shape extending along a plane perpendicular to the Z-axis direction and extends along the Y-axis direction. Each of the electrode support parts 279a, 279b, and 279c extends from the second part 271b of the lever 271 toward the opposite side to the light passing opening 25. The pair of first electrode support parts 279a are arranged on the same center line parallel to the Y-axis direction. The pair of second electrode support parts 279b are arranged on the same center line parallel to the Y-axis direction. The pair of third electrode support parts 279c are arranged on the same center line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portion 279a, the second electrode support portion 279b, and the third electrode support portion 279c are arranged side by side in this order from the movable mirror 22 side.

[0062] The actuator section 28 moves the movable mirror 22 along the Z-axis direction. The actuator section 28 has a fixed comb tooth electrode 281, a movable comb tooth electrode 282, a fixed comb tooth electrode 283, and a movable comb tooth electrode 284. The positions of the fixed comb tooth electrodes 281 and 283 are fixed. The movable comb tooth electrodes 282 and 284 move in conjunction with the movement of the movable mirror 22.

[0063] The fixed comb electrode 281 is provided on a part of the surface of the device layer 102 of the base 21 that faces the electrode support portion 269. The fixed comb electrode 281 has a plurality of fixed comb teeth 281a extending along a plane perpendicular to the Y-axis direction. These fixed comb teeth 281a are arranged side by side at predetermined intervals in the Y-axis direction.

[0064] The movable comb electrode 282 is provided on the surface of each first electrode support portion 269a facing the movable mirror 22, on both surfaces in the X-axis direction of each second electrode support portion 269b, and on the surface of each third electrode support portion 269c facing the movable mirror 22. The movable comb electrode 282 has a plurality of movable comb teeth 282a extending along a plane perpendicular to the Y-axis direction. These movable comb teeth 282a are arranged side by side at predetermined intervals in the Y-axis direction.

[0065] In the fixed comb electrode 281 and the movable comb electrode 282, a plurality of fixed comb teeth 281a and a plurality of movable comb teeth 282a are arranged alternately. That is, each fixed comb tooth 281a of the fixed comb electrode 281 is positioned between the movable comb teeth 282a of the movable comb electrode 282. The adjacent fixed comb teeth 281a and movable comb teeth 282a face each other in the Y-axis direction. The distance between the adjacent fixed comb teeth 281a and movable comb teeth 282a is, for example, about several μm.

[0066] The fixed comb electrode 283 is provided on a part of the surface of the device layer 102 of the base 21 facing the electrode support portion 279. The fixed comb electrode 283 has a plurality of fixed comb teeth 283a extending along a plane perpendicular to the Y-axis direction. These fixed comb teeth 283a are arranged side by side at predetermined intervals in the Y-axis direction.

[0067] The movable comb electrode 284 is provided on the surface of each first electrode support portion 279a facing the movable mirror 22, on both surfaces in the X-axis direction of each second electrode support portion 279b, and on the surface of each third electrode support portion 279c facing the movable mirror 22. The movable comb electrode 284 has a plurality of movable comb teeth 284a extending along a plane perpendicular to the Y-axis direction. These movable comb teeth 284a are arranged side by side at predetermined intervals in the Y-axis direction.

[0068] In the fixed comb electrode 283 and the movable comb electrode 284, a plurality of fixed comb teeth 283a and a plurality of movable comb teeth 284a are arranged alternately. That is, each fixed comb tooth 283a of the fixed comb electrode 283 is positioned between the movable comb teeth 284a of the movable comb electrode 284. The adjacent fixed comb teeth 283a and movable comb teeth 284a face each other in the Y-axis direction. The distance between the adjacent fixed comb teeth 283a and movable comb teeth 284a is, for example, about several μm.

[0069] The base 21 is provided with a plurality of electrode pads 211. Each electrode pad 211 is disposed on the surface of the device layer 102 in an opening 213 formed in the first surface 21a of the base 21 so as to reach the device layer 102. Some of the plurality of electrode pads 211 are electrically connected to the fixed comb electrode 281 or the fixed comb electrode 283 via the device layer 102. Others of the plurality of electrode pads 211 are electrically connected to the movable comb electrode 282 or the movable comb electrode 284 via the first elastic support portion 26 or the second elastic support portion 27. The base 21 is also provided with a pair of electrode pads 212 used as ground electrodes. The pair of electrode pads 212 are disposed on the first surface 21a so as to be located on both sides of the movable mirror 22 in the Y-axis direction.

[0070] The configuration around the electrode pad 211 will be further described with reference to Fig. 11. The following description will be given with reference to one electrode pad 211, but the other electrode pads 211 are configured in the same manner. As shown in Fig. 11, each electrode pad 211 is disposed on one surface 102a in the Z-axis direction of the device layer 102, in an opening 213 formed in the surface 101a on one side in the Z-axis direction of the support layer 101 so as to reach the device layer 102.

[0071] The opening 213 has a bottom surface 214 formed by the surface 102a, and a side surface 215 formed by the support layer 101 and the intermediate layer 103. The bottom surface 214 has, for example, a rectangular shape. The side surface 215 has a first surface 215a that is continuous with the bottom surface 214 and extends substantially perpendicular to the bottom surface 214, a step surface 215b that is continuous with the first surface 215a and extends substantially parallel to the bottom surface 214, and a second surface 215c that is continuous with the step surface 215b and extends substantially perpendicular to the bottom surface 214. The step surface 215b extends in an annular shape along the edge of the opening 213 when viewed from the Z-axis direction.

[0072] The electrode pad 211 is disposed over the entire bottom surface 214. The electrode pad 211 also extends over the bottom surface 214 and the side surface 215. More specifically, the electrode pad 211 is formed so as to reach the first surface 215a of the side surface 215 but not reach the step surface 215b. The electrode pad 211 is made of, for example, a metal film (metal layer). This metal film is formed by, for example, sputtering using a hard mask. The metal film that constitutes the electrode pad 211 is thicker than the metal film that constitutes the mirror surface 22a.

[0073] The base 21 has a groove 216 formed on the surface 101a of the support layer 101 so as to reach the device layer 102. The groove 216 extends in a ring shape so as to surround the opening 213 when viewed from the Z-axis direction. The groove 216 has, for example, a rectangular ring shape when viewed from the Z-axis direction. The groove 216 ensures that the electrode pads 211 are electrically insulated from each other. That is, as in this embodiment, when the metal film constituting the electrode pad 211 is formed to reach the side surface 215 and the electrode pad 211 is in contact with the support layer 101, there is a risk that the electrode pads 211 will be electrically connected to each other via the support layer 101. In contrast, in the mirror device 20, the groove 216 ensures that the electrode pads 211 are electrically insulated from each other even in such a case.

[0074] In the mirror device 20 configured as above, an electric signal for moving the movable mirror 22 along the Z-axis direction is input to the driving unit 23 via the lead pin 113 and wires (not shown) described later. As a result, electrostatic forces are generated between the fixed comb electrode 281 and the movable comb electrode 282 facing each other, and between the fixed comb electrode 283 and the movable comb electrode 284 facing each other, so that the movable mirror 22 moves to one side in the Z-axis direction, for example. At this time, the first torsion bars 266, 276 and the second torsion bars 267, 277 are twisted in the first elastic support portion 26 and the second elastic support portion 27, and elastic forces are generated in the first elastic support portion 26 and the second elastic support portion 27. In the mirror device 20, by applying a periodic electric signal to the driving unit 23, the movable mirror 22 can be reciprocated along the Z-axis direction at its resonance frequency level. In this way, the driving unit 23 functions as an electrostatic actuator. [Other configurations of the mirror unit]

[0075] As shown in FIG. 2, FIG. 3, FIG. 4 and FIG. 7, the optical function member 13 has a third surface 13a (a surface on one side in the Z-axis direction) facing the second surface 21b of the base 21, and a fourth surface 13b on the opposite side to the third surface 13a. The optical function member 13 is disposed on the other side in the Z-axis direction with respect to the mirror device 20. When viewed from the Z-axis direction, the outer edge 13c of the optical function member 13 is located outside the outer edge 21c of the base 21. That is, when viewed from the Z-axis direction, the outer edge 13c of the optical function member 13 surrounds the outer edge 21c of the base 21. The optical function member 13 is integrally formed of a material that is transparent to the measurement light L0 and the laser light L10. The optical function member 13 is formed into a rectangular plate shape, for example, made of glass, and has a size of, for example, about 15 mm×20 mm×4 mm (thickness). The material of the optical functional member 13 is selected according to the sensitivity wavelength of the optical module 1, for example, glass when the sensitivity wavelength of the optical module 1 is in the near-infrared region, and silicon when the sensitivity wavelength of the optical module 1 is in the mid-infrared region.

[0076] The optical functional member 13 is provided with a pair of light transmitting portions 14 and 15. The light transmitting portion 14 is a portion of the optical functional member 13 facing the light passing opening 24 of the mirror device 20 in the Z-axis direction. The light transmitting portion 15 is a portion of the optical functional member 13 facing the light passing opening 25 of the mirror device 20 in the Z-axis direction. A surface 14a of the light transmitting portion 14 facing the mirror device 20 and a surface 15a of the light transmitting portion 15 facing the mirror device 20 are located on the same plane as the third surface 13a. The light transmitting portion (second light passing portion) 14 constitutes a second portion (a part) of the optical path between the beam splitter unit 3 and the fixed mirror 16. The light transmitting portion 14 is a portion that corrects the optical path difference occurring between the optical path between the beam splitter unit 3 and the movable mirror 22 and the optical path between the beam splitter unit 3 and the fixed mirror 16. In this embodiment, the light transmitting portion 15 does not function as a light transmitting portion.

[0077] The optical functional member 13 has a fifth surface 13d that faces the movable mirror 22 and the driving unit 23 of the mirror device 20. The fifth surface 13d is located closer to the fourth surface 13b than the third surface 13a. The fifth surface 13d extends to the outer edge 13c of the optical functional member 13 when viewed from the Z-axis direction. In this embodiment, the fifth surface 13d surrounds the ends of the light transmitting parts 14 and 15 on the mirror device 20 side, and extends to each of a pair of opposite sides extending in the Y-axis direction of the outer edge 13c of the optical functional member 13.

[0078] The third surface 13a of the optical functional member 13 is bonded to the second surface 21b of the base 21 by direct bonding (e.g., plasma activation bonding, surface-activated room-temperature bonding (SAB), atomic diffusion bonding (ADB), anodic bonding, fusion bonding, hydrophilic bonding, etc.). In this embodiment, the third surface 13a extends so as to face a plurality of electrode pads 211, 212 provided on the base 21 on both sides of the fifth surface 13d in the Y-axis direction. Here, since the fifth surface 13d is located closer to the fourth surface 13b than the third surface 13a, the fifth surface 13d is separated from the mirror device 20 in a region facing the movable mirror 22 and the driving unit 23. Furthermore, the surface 14a of the light transmitting portion 14 and the surface 15a of the light transmitting portion 15 face the light passing openings 24, 25 of the mirror device 20, respectively. This prevents the movable mirror 22 and the driving portion 23 from coming into contact with the optical functional member 13 in the mirror unit 2 when the movable mirror 22 moves back and forth along the Z-axis direction.

[0079] In addition, the base 21 of the mirror device 20 is provided with a sixth surface 21d that is separated from the optical functional member 13 in a state where the third surface 13a of the optical functional member 13 and the second surface 21b of the base 21 are bonded to each other. The sixth surface 21d is separated from the optical functional member 13 in a region including at least a part of the outer edge of the base 21 when viewed from the Z-axis direction. In this embodiment, the sixth surface 21d is formed by removing the device layer 102 and the intermediate layer 103 by etching along one side of the outer edge of the base 21 that extends in the Y-axis direction. In addition, a plurality of reference holes 13e are formed in the third surface 13a of the optical functional member 13. In this embodiment, the plurality of reference holes 13e are formed in the third surface 13a so as to correspond to a plurality of corners of the base 21, respectively. When the third surface 13a of the optical functional member 13 and the second surface 21b of the base 21 are joined to each other, the mirror device 20 is handled by grasping a portion of the base 21 corresponding to the sixth surface 21d, and the position of the mirror device 20 in the X-axis direction and Y-axis direction, and the angle of the mirror device 20 in a plane perpendicular to and parallel to the Z-axis direction are adjusted based on the multiple reference holes 13e formed in the third surface 13a.

[0080] As shown in FIG. 3 and FIG. 4, the fixed mirror 16 is disposed on the other side in the Z-axis direction (opposite side to the mirror device 20) with respect to the optical functional member 13, and the position of the fixed mirror 16 with respect to the base 21 of the mirror device 20 is fixed. The fixed mirror 16 is formed on the fourth surface 13b of the optical functional member 13 by, for example, vapor deposition. The fixed mirror 16 has a mirror surface 16a perpendicular to the Z-axis direction. In this embodiment, the mirror surface 22a of the movable mirror 22 and the mirror surface 16a of the fixed mirror 16 face one side in the Z-axis direction (the beam splitter unit 3 side). The fixed mirror 16 is continuously formed on the fourth surface 13b of the optical functional member 13 so as to reflect light transmitted through each light transmission portion 14, 15 of the optical functional member 13, but a fixed mirror that reflects light transmitted through the light transmission portion 14 and a fixed mirror that reflects light transmitted through the light transmission portion 15 may be provided separately.

[0081] The stress relaxation substrate 17 is attached to the fourth surface 13b of the optical function member 13 via the fixed mirror 16. The stress relaxation substrate 17 is attached to the fixed mirror 16, for example, by an adhesive. When viewed from the Z-axis direction, the outer edge of the stress relaxation substrate 17 is located outside the outer edge 13c of the optical function member 13. In other words, when viewed from the Z-axis direction, the outer edge of the stress relaxation substrate 17 surrounds the outer edge 13c of the optical function member 13. The thermal expansion coefficient of the stress relaxation substrate 17 is closer to the thermal expansion coefficient of the base 21 of the mirror device 20 (more specifically, the thermal expansion coefficient of the support layer 101) than the thermal expansion coefficient of the optical function member 13. In addition, the thickness of the stress relaxation substrate 17 is closer to the thickness of the base 21 of the mirror device 20 than the thickness of the optical function member 13. The stress relaxation substrate 17 is formed into a rectangular plate shape made of, for example, silicon, and has a size of, for example, about 16 mm×21 mm×0.65 mm (thickness).

[0082] The mirror unit 2 configured as above is attached to the support 9 by fixing the surface of the stress relaxation substrate 17 opposite to the optical function member 13 to a surface 9a (one surface in the Z-axis direction) of the support 9 with, for example, an adhesive, as shown in Fig. 1. When the mirror unit 2 is attached to the support 9, the position of the mirror device 20 in the X-axis direction and the Y-axis direction, and the angle of the mirror device 20 in a plane perpendicular to and parallel to the Z-axis direction are adjusted using a reference hole 9b formed in the support 9 as a reference, as shown in Fig. 8. Note that the second support structure 12 is omitted from Fig. 8. [Configuration of the first support structure and beam splitter unit]

[0083] 1 and 8, the first support structure 11 has a frame 111, a light transmitting member 112, and a plurality of lead pins 113. The frame 111 is formed so as to surround the mirror unit 2 when viewed from the Z-axis direction, and is attached to a surface 9a of the support 9 by an adhesive such as silver solder. The frame 111 is formed of, for example, ceramic, and has, for example, a rectangular frame shape. An end face 111a of the frame 111 opposite to the support 9 is located on the opposite side to the support 9 with respect to a first surface 21a of a base 21 of the mirror device 20.

[0084] The light transmitting member 112 is formed so as to close the opening of the frame body 111, and is attached to the end surface 111a of the frame body 111 by, for example, an adhesive. The light transmitting member 112 is formed of a material having transparency to the measurement light L0 and the laser light L10, and has, for example, a rectangular plate shape. Here, the end surface 111a of the frame body 111 is located on the opposite side to the support body 9 from the first surface 21a of the base 21 of the mirror device 20, so that the light transmitting member 112 is separated from the mirror device 20. As a result, in the optical module 1, when the movable mirror 22 reciprocates along the Z-axis direction, the movable mirror 22 and the driving unit 23 are prevented from contacting the light transmitting member 112. In the optical module 1, the support body 9, the frame body 111, and the light transmitting member 112 form a package that houses the mirror unit 2.

[0085] Each lead pin 113 is provided on the frame 111 such that one end 113a is located inside the frame 111 and the other end (not shown) is located outside the frame 111. One end 113a of the lead pin 113 is electrically connected to the electrode pads 211, 212 corresponding to the lead pin 113 in the mirror device 20 by a wire (not shown). In the optical module 1, an electric signal for moving the movable mirror 22 along the Z-axis direction is input to the driving unit 23 via the multiple lead pins 113. In this embodiment, step surfaces 111b extending in the X-axis direction on both sides of the optical functional member 13 in the Y-axis direction are formed on the frame 111, and one end 113a of each lead pin 113 is disposed on the step surfaces 111b. Each lead pin 113 extends in the Z-axis direction on both sides of the support 9 in the Y-axis direction, and the other end of each lead pin 113 is located on the other side of the support 9 in the Z-axis direction.

[0086] As shown in FIG. 10, the beam splitter unit 3 is attached to the surface 112a of the light transmitting member 112 opposite to the mirror device 20, for example, by an optical adhesive that also serves as a refractive index matching agent. The beam splitter unit 3 has a first mirror surface 31, a second mirror surface 32, and a plurality of optical surfaces 33a, 33b, 33c, and 33d. The beam splitter unit 3 is configured by bonding a plurality of optical blocks 34 and 35. Each of the optical blocks 34 and 35 is formed of a material having the same or similar refractive index as the optical functional member 13. Note that FIG. 10 is a schematic cross-sectional view of the mirror unit 2 and the beam splitter unit 3 shown in FIG. 1, and FIG. 10 shows the mirror device 20 in a state where the dimension in the Z-axis direction is enlarged compared to the actual state.

[0087] The first mirror surface 31 is a mirror surface (e.g., a half mirror surface) inclined with respect to the Z-axis direction, and is formed between the optical block 34 and the optical block 35. In this embodiment, the first mirror surface 31 is a surface parallel to the Y-axis direction and forms an angle of 45° with the Z-axis direction, and is inclined so as to move away from the light incident portion 4 as it approaches the mirror device 20. The first mirror surface 31 has a function of reflecting a part of the measurement light L0 and transmitting the remaining part of the measurement light L0, and a function of reflecting a part of the laser light L10 and transmitting the remaining part of the laser light L10. The first mirror surface 31 is formed of, for example, a dielectric multilayer film. When viewed from the Z-axis direction, the first mirror surface 31 overlaps with the light passing opening 24 of the mirror device 20, the light transmitting portion 14 of the optical functional member 13, and the mirror surface 16a of the fixed mirror 16, and when viewed from the X-axis direction, it overlaps with the light incident portion 4 (see FIG. 1). That is, the first mirror surface 31 faces the fixed mirror 16 in the Z-axis direction, and faces the light entrance portion 4 in the X-axis direction.

[0088] The second mirror surface 32 is a mirror surface (e.g., a total reflection mirror surface) parallel to the first mirror surface 31, and is formed on the optical block 35 so as to be located on the opposite side of the light entrance section 4 with respect to the first mirror surface 31. The second mirror surface 32 has a function of reflecting the measurement light L0 and a function of reflecting the laser light L10. The second mirror surface 32 is formed of, for example, a metal film. The second mirror surface 32 overlaps with the mirror surface 22a of the movable mirror 22 of the mirror device 20 when viewed from the Z-axis direction, and overlaps with the first mirror surface 31 when viewed from the X-axis direction. That is, the second mirror surface 32 faces the movable mirror 22 in the Z-axis direction, and faces the first mirror surface 31 in the X-axis direction.

[0089] The optical surface 33a is a surface perpendicular to the Z-axis direction, and is formed on the optical block 35 so as to be located on the opposite side of the mirror device 20 with respect to the first mirror surface 31. The optical surface 33b is a surface perpendicular to the Z-axis direction, and is formed on the optical block 35 so as to be located on the mirror device 20 side with respect to the second mirror surface 32. The optical surface 33c is a surface perpendicular to the Z-axis direction, and is formed on the optical block 34 so as to be located on the mirror device 20 side with respect to the first mirror surface 31. The optical surfaces 33b and 33c are located on the same plane. The optical surface 33d is a surface perpendicular to the X-axis direction, and is formed on the optical block 34 so as to be located on the light incident section 4 side with respect to the first mirror surface 31. Each of the optical surfaces 33a, 33b, 33c, and 33d has a function of transmitting the measurement light L0 and a function of transmitting the laser light L10.

[0090] The beam splitter unit 3 configured as above is attached to the light transmitting member 112 by fixing the optical surfaces 33b and 33c, which are located on the same plane, to the surface 112a of the light transmitting member 112 with, for example, an optical adhesive. When the beam splitter unit 3 is attached to the light transmitting member 112, the position of the beam splitter unit 3 in the X-axis direction and the Y-axis direction, and the angle of the beam splitter unit 3 in a plane perpendicular to and parallel to the Z-axis direction are adjusted using a reference hole 9b formed in the support 9 as a reference, as shown in Fig. 9. Note that the second support structure 12 is not shown in Fig. 9.

[0091] Here, the optical paths of the measurement light L0 and the laser light L10 in the mirror unit 2 and the beam splitter unit 3 will be described in detail with reference to FIG.

[0092] As shown in FIG. 10, when the measurement light L0 is incident on the beam splitter unit 3 along the X-axis direction through the optical surface 33d, a part of the measurement light L0 passes through the first mirror surface 31 and is reflected by the second mirror surface 32, and reaches the mirror surface 22a of the movable mirror 22 through the optical surface 33b and the light transmitting member 112. A part of the measurement light L0 is reflected by the mirror surface 22a of the movable mirror 22, travels in the opposite direction along the same optical path P1, and is reflected by the first mirror surface 31. The remaining part of the measurement light L0 is reflected by the first mirror surface 31, and travels through the optical surface 33c, the light transmitting member 112, the light passing opening 24 of the mirror device 20, and the light transmitting portion 14 of the optical function member 13 to reach the mirror surface 16a of the fixed mirror 16. The remaining part of the measurement light L0 is reflected by the mirror surface 16a of the fixed mirror 16, travels in the opposite direction along the same optical path P2, and passes through the first mirror surface 31. A portion of the measurement light L0 reflected by the first mirror surface 31 and the remaining portion of the measurement light L0 that transmits through the first mirror surface 31 become interference light L1, and the interference light L1 of the measurement light is emitted from the beam splitter unit 3 along the Z-axis direction via the optical surface 33a.

[0093] On the other hand, when the laser light L10 is incident on the beam splitter unit 3 along the Z-axis direction via the optical surface 33a, a part of the laser light L10 is reflected by the first mirror surface 31 and the second mirror surface 32, and reaches the mirror surface 22a of the movable mirror 22 via the optical surface 33b and the light transmitting member 112. A part of the laser light L10 is reflected by the mirror surface 22a of the movable mirror 22, travels in the opposite direction along the same optical path P3, and is reflected by the first mirror surface 31. The remaining part of the laser light L10 passes through the first mirror surface 31, and reaches the mirror surface 16a of the fixed mirror 16 via the optical surface 33c, the light transmitting member 112, the light passing opening 24 of the mirror device 20, and the light transmitting portion 14 of the optical function member 13. The remaining part of the laser light L10 is reflected by the mirror surface 16a of the fixed mirror 16, travels in the opposite direction along the same optical path P4, and passes through the first mirror surface 31. A portion of the laser light L10 reflected by the first mirror surface 31 and the remaining portion of the laser light L10 that passes through the first mirror surface 31 become interference light L11, and the interference light L11 of the laser light is emitted from the beam splitter unit 3 along the Z-axis direction via the optical surface 33a.

[0094] As described above, the light passing opening 24 of the mirror device 20 constitutes the first portion P2a of the optical path P2 of the measurement light L0 and the first portion P4a of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit 3 and the fixed mirror 16. In addition, the light transmitting portion 14 of the optical functional member 13 constitutes the second portion P2b of the optical path P2 of the measurement light L0 and the second portion P4b of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit 3 and the fixed mirror 16.

[0095] By forming the second portion P2b of the optical path P2 of the measurement light L0 by the light transmitting portion 14, the optical path difference between the optical paths P1 and P2 of the measurement light L0 is corrected so that the difference between the optical path length of the optical path P1 of the measurement light L0 (the optical path length taking into account the refractive index of each medium through which the optical path passes) and the optical path length of the optical path P2 of the measurement light L0 is reduced. Similarly, by forming the second portion P4b of the optical path P4 of the laser light L10 by the light transmitting portion 14, the optical path difference between the optical paths P3 and P4 of the laser light L10 is corrected so that the difference between the optical path length of the optical path P3 of the laser light L10 and the optical path P4 of the laser light L10 is reduced. In this embodiment, the refractive index of the light-transmitting section 14 is equal to the refractive index of each optical block that constitutes the beam splitter unit 3, and the distance between the first mirror surface 31 and the second mirror surface 32 along the X-axis direction is equal to the thickness of the light-transmitting section 14 along the Z-axis direction (i.e., the distance between the surface 14a of the light-transmitting section 14 and the fourth surface 13b of the optical functional member 13 along the Z-axis direction). [Configuration of the second support structure, light entrance portion, etc.]

[0096] As shown in FIG. 1, the second support structure 12 has a connecting unit 120. The connecting unit 120 includes a main body 121, a frame 122, and a fixing plate 123. The main body 121 includes a pair of side walls 124, 125, and a top wall 126. The pair of side walls 124, 125 face each other in the X-axis direction. An opening 124a is formed in the side wall 124 on one side in the X-axis direction. The top wall 126 faces the support 9 in the Z-axis direction. An opening 126a is formed in the top wall 126. The main body 121 is integrally formed of, for example, metal. The main body 121 is provided with a plurality of positioning pins 121a. The main body 121 is positioned relative to the support 9 by fitting the positioning pins 121a into the reference holes 9b and holes 9c formed in the support 9, and in this state, the main body 121 is attached to the support 9 by, for example, bolts.

[0097] The frame body 122 is disposed on the surface of the side wall portion 124 opposite to the beam splitter unit 3. The opening of the frame body 122 faces the beam splitter unit 3 via an opening 124a of the side wall portion 124. The light entrance portion 4 is disposed in the frame body 122. The fixing plate 123 is a member for fixing the light entrance portion 4 disposed in the frame body 122 to the main body portion 121 (details will be described later).

[0098] The second support structure 12 further includes a holding unit 130. The holding unit 130 includes a main body 131, a frame 132, and a fixing plate 133. The main body 131 is attached to the surface of the top wall 126 opposite to the support 9. The main body 131 is positioned with respect to the main body 121 of the connecting unit 120 by a plurality of positioning pins 131a, and in this state, is attached to the top wall 126 by, for example, bolts. A recess 134 is formed on the surface of the main body 131 opposite to the support 9. A first light passing hole 135, a second light passing hole 136, and a third light passing hole 137 are formed on the bottom surface of the recess 134. The first light passing hole 135 is formed at a position facing the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The second light passing hole 136 is formed on the other side of the first light passing hole 135 in the X-axis direction (i.e., the side opposite to the light incident portion 4). The third light passing hole 137 is formed on the other side of the second light passing hole 136 in the X-axis direction.

[0099] The frame body 132 is disposed on the bottom surface of the recess 134. An opening of the frame body 132 faces the third light passing hole 137. The second light source 7 is disposed in the frame body 132. The first light detector 6 is disposed on the bottom surface of the recess 134 in a state facing the first light passing hole 135. The second light detector 8 is disposed on the bottom surface of the recess 134 in a state facing the second light passing hole 136. The fixing plate 133 is a member for fixing the first light detector 6 and the second light detector 8 disposed on the bottom surface of the recess 134, and the second light source 7 disposed in the frame body 132, to the main body 131 (details will be described later).

[0100] The light entrance section 4 has a holder 41 and a collimator lens 42. The holder 41 holds the collimator lens 42, and is configured to enable connection of an optical fiber (not shown) that guides the measurement light L0. The collimator lens 42 collimates the measurement light L0 emitted from the optical fiber. When the optical fiber is connected to the holder 41, the optical axis of the optical fiber coincides with the optical axis of the collimator lens 42.

[0101] The holder 41 is provided with a flange portion 41a. The flange portion 41a is disposed between the frame body 122 and the fixing plate 123. In this state, the fixing plate 123 is attached to the side wall portion 124 by, for example, a bolt, so that the light incidence portion 4 disposed on the frame body 122 is fixed to the main body portion 121. In this manner, the light incidence portion 4 is disposed on one side of the beam splitter unit 3 in the X-axis direction, and is supported by the second support structure 12. The light incidence portion 4 causes the measurement light L0 incident from the first light source via the measurement object or the measurement light L0 emitted from the measurement object (in this embodiment, the measurement light L0 guided by an optical fiber) to be incident on the beam splitter unit 3.

[0102] A filter 54 is attached to the frame 122. The filter 54 has a function of cutting the laser light L10. The filter 54 is disposed in the opening 124a of the side wall 124 in a state inclined with respect to the optical axis of the light entrance portion 4. The filter 54 blocks the opening of the frame 122 when viewed from the X-axis direction. In this manner, the filter 54 is disposed between the light entrance portion 4 and the beam splitter unit 3, and is supported by the second support structure 12 in a state inclined with respect to the optical axis of the light entrance portion 4. In this embodiment, the optical surface of the filter 54 is a surface parallel to the Z-axis direction and forms an angle of 10° to 20° with the Y-axis direction. The optical axis of the light entrance portion 4 is parallel to the X-axis direction.

[0103] As a result, even if light of the same wavelength band as the laser light L10 is included in the measurement light L0, the light is prevented from entering the beam splitter unit 3, so that the position of the movable mirror 22 in the Z-axis direction can be accurately obtained based on the detection result of the interference light L11 of the laser light. Furthermore, since the filter 54 is inclined with respect to the optical axis of the light entrance part 4, the light of the same wavelength band as the laser light L10 can be reflected out of the interference optical system, and the light can be reliably prevented from becoming stray light. In this embodiment, the light of the same wavelength band as the laser light L10 emitted from the beam splitter unit 3 along the X-axis direction is reflected by the filter 54 and is sent out of the interference optical system between a pair of side walls 124, 125 of the main body part 121 of the second support structure 12. As a result, the light can be reliably prevented from becoming stray light.

[0104] The first photodetector 6 has a holder 61, a photodetection element 62, and a condenser lens 63. The holder 61 holds the photodetection element 62 and the condenser lens 63. The photodetection element 62 detects interference light L1 of the measurement light. The photodetection element 62 is, for example, an InGaAs photodiode. The condenser lens 63 condenses the interference light L1 of the measurement light incident on the photodetection element 62 onto the photodetection element 62. In the holder 61, the optical axis of the photodetection element 62 and the optical axis of the condenser lens 63 coincide with each other.

[0105] The holder 61 is provided with a flange portion 61a. The flange portion 61a is disposed between the bottom surface of the recess 134 of the main body portion 131 and the fixing plate 133. In this state, the fixing plate 133 is attached to the main body portion 131 by, for example, a bolt, so that the first photodetector 6 disposed on the bottom surface of the recess 134 is fixed to the main body portion 131. In this manner, the first photodetector 6 is disposed on one side of the beam splitter unit 3 in the Z-axis direction, and is supported by the second support structure 12. The first photodetector 6 faces the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The first photodetector 6 detects the interference light L1 of the measurement light emitted from the beam splitter unit 3.

[0106] The second photodetector 8 has a holder 81, a photodetection element 82, and a condensing lens 83. The holder 81 holds the photodetection element 82 and the condensing lens 83. The photodetection element 82 detects interference light L11 of the laser light. The photodetection element 82 is, for example, a Si photodiode. The condensing lens 83 condenses the interference light L11 of the laser light incident on the photodetection element 82 onto the photodetection element 82. In the holder 81, the optical axis of the photodetection element 82 and the optical axis of the condensing lens 83 coincide with each other.

[0107] The holder 81 is provided with a flange portion 81a. The flange portion 81a is disposed between the bottom surface of the recess 134 of the main body portion 131 and the fixing plate 133. In this state, the fixing plate 133 is attached to the main body portion 131 by, for example, a bolt, and the second photodetector 8 disposed on the bottom surface of the recess 134 is fixed to the main body portion 131. In this manner, the second photodetector 8 is disposed on one side of the beam splitter unit 3 in the Z-axis direction and is supported by the second support structure 12. The second photodetector 8 detects interference light L11 of the laser light emitted from the beam splitter unit 3.

[0108] The second light source 7 has a holder 71, a light-emitting element 72, and a collimator lens 73. The holder 71 holds the light-emitting element 72 and the collimator lens 73. The light-emitting element 72 emits laser light L10. The light-emitting element 72 is a semiconductor laser such as a VCSEL. The collimator lens 73 collimates the laser light L10 emitted from the light-emitting element 72. In the holder 71, the optical axis of the light-emitting element 72 and the optical axis of the collimator lens 73 coincide with each other.

[0109] The holder 71 is provided with a flange portion 71a. The flange portion 71a is disposed between the frame body 132 and the fixing plate 133. In this state, the fixing plate 133 is attached to the main body portion 131 by, for example, a bolt, and the second light source 7 disposed in the frame body 132 is fixed to the main body portion 131. In this manner, the second light source 7 is disposed on one side of the beam splitter unit 3 in the Z-axis direction, and is supported by the second support structure 12. The second light source 7 emits laser light L10 to be incident on the beam splitter unit 3.

[0110] As described above, the holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 so that the first photodetector (first optical device) 6, the second photodetector (second optical device) 8, and the second light source (third optical device) 7 face the same side and are arranged in the order of the first photodetector 6, the second photodetector 8, and the second light source 7. In this embodiment, the holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 on one side of the beam splitter unit 3 in the Z axis direction so that the first photodetector 6, the second photodetector 8, and the second light source 7 face the other side in the Z axis direction (i.e., the beam splitter unit 3 side). In addition, the holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 so that the first photodetector 6, the second photodetector 8, and the second light source 7 are arranged in that order from one side in the X axis direction (i.e., the light incident section 4 side).

[0111] A first mirror 51, a second mirror 52, and a third mirror 53 are attached to a main body 131 of the holding unit 130. The first mirror 51 is held by the holding unit 130 so as to be located on the opposite side of the first photodetector 6 with respect to a first light passing hole 135. The second mirror 52 is held by the holding unit 130 so as to be located on the opposite side of the second photodetector 8 with respect to a second light passing hole 136. The third mirror 53 is held by the holding unit 130 so as to be located on the opposite side of the second light source 7 with respect to a third light passing hole 137.

[0112] The first mirror 51 is a dichroic mirror that transmits the measurement light L0 and reflects the laser light L10, and is inclined with respect to the optical axis of the first photodetector 6. The first mirror 51 is disposed between the beam splitter unit 3 and the first photodetector 6. That is, the first mirror 51 is disposed so as to face the beam splitter unit 3 and the first photodetector 6. In this embodiment, the optical surface of the first mirror 51 is a surface parallel to the Y-axis direction and forms an angle of 45° with the Z-axis direction. The optical axis of the first photodetector 6 is parallel to the Z-axis direction.

[0113] The second mirror 52 has a function of reflecting a part of the laser light L10 and transmitting the remaining part of the laser light L10, and is a mirror (e.g., a half mirror) parallel to the first mirror 51. The second mirror 52 is disposed so as to overlap with the first mirror 51 when viewed from the X-axis direction, and so as to overlap with the second photodetector 8 when viewed from the Z-axis direction. In other words, the second mirror 52 is disposed so as to face the first mirror 51 and the second photodetector 8. In this embodiment, the optical surface of the second mirror 52 is a surface parallel to the Y-axis direction and forms an angle of 45° with the Z-axis direction.

[0114] The third mirror 53 has a function of reflecting the laser light L10 and is a mirror (for example, a total reflection mirror) parallel to the second mirror 52. The third mirror 53 is disposed so as to overlap with the second mirror 52 when viewed from the X-axis direction and so as to overlap with the second light source 7 when viewed from the Z-axis direction. In other words, the third mirror 53 is disposed so as to face the second mirror 52 and the second light source 7. In this embodiment, the optical surface of the third mirror 53 is a surface parallel to the Y-axis direction and forms an angle of 45° with the Z-axis direction.

[0115] An aperture 55 is attached to the main body 131 of the holding unit 130. The aperture 55 is held by the holding unit 130 so as to be located between the first mirror 51 and the first photodetector 6. The aperture 55 is a member in which an opening having a circular shape when viewed from the Z-axis direction is formed, and is disposed within the first light passing hole 135.

[0116] The interference light L1 of the measurement light emitted from the beam splitter unit 3 along the Z-axis direction passes through the first mirror 51, enters the first photodetector 6 via the aperture 55, and is detected by the first photodetector 6. On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the third mirror 53, passes through the second mirror 52, and is reflected by the first mirror 51 to enter the beam splitter unit 3 along the Z-axis direction. The interference light L11 of the laser light emitted from the beam splitter unit 3 along the Z-axis direction is reflected by the first mirror 51 and the second mirror 52 to enter the second photodetector 8, and is detected by the second photodetector 8. [Action and Effects]

[0117] In the mirror device 20 described above, the first surface 21a (surface on one side in the Z-axis direction) of the base 21 is located on one side of the mirror surface 22a. This allows the base 21 to protect the mirror surface 22a, and for example, damage to the mirror surface 22a due to direct contact during transportation or the like can be suppressed. Furthermore, in the mirror device 20, the support layer 101 constituting the base 21 is thicker than the device layer 102 constituting the base 21. This allows the amount of protrusion of the base 21 from the mirror surface 22a to be secured, and the base 21 can effectively protect the mirror surface 22a. Therefore, the mirror device 20 can improve reliability. Note that "the first surface 21a of the base 21 is located on one side of the mirror surface 22a" means that "at least a part of the first surface 21a is located on one side of the mirror surface 22a." In the mirror device 20, the entire first surface 21a is located on one side of the mirror surface 22a in the Z-axis direction. In other words, the entirety of mirror surface 22a is located on the other side in the Z-axis direction than first surface 21a. "The surface of the base on one side in the Z-axis direction" is, in other words, "the end face of the base on one side in the Z-axis direction" or "the surface of the base that is located closest to one side in the Z-axis direction."

[0118] An end face (end faces 224as, 224bs, 224cs) on one side in the Z-axis direction of the beam portion 224 is located on one side of the mirror surface 22a. This allows the mirror surface 22a to be protected by the beam portion 224. Furthermore, the beam portion 224 can also suppress deformation of the movable portion 22b during movement.

[0119] The beam portion 224 has an inner beam portion 224a arranged on one surface of the arrangement portion 221 so as to extend along the outer edge of the arrangement portion 221 when viewed from the Z-axis direction. This allows the inner beam portion 224a to be arranged close to the mirror surface 22a, so that the mirror surface 22a can be protected more effectively. Furthermore, since the inner beam portion 224a is arranged on the arrangement portion 221, deformation of the arrangement portion 221 can be more suitably suppressed.

[0120] The beam portion 224 has an outer beam portion 224b disposed on a surface on one side of the frame portion 222 so as to extend along the frame portion 222 when viewed from the Z-axis direction. This allows the mirror surface 22a to be protected more effectively by the beam portion 224. Furthermore, the outer beam portion 224b can suppress deformation of the frame portion 222, and therefore can suppress deformation of the arrangement portion 221 caused by deformation of the frame portion 222.

[0121] The support layer 101 constituting the beam portion 224 is thinner than the support layer 101 constituting the base 21. This makes it possible to prevent the beam portion 224 from protruding from the base 21 during the movement of the movable portion 22b, and to increase the amount of movement of the movable portion 22b in the Z-axis direction.

[0122] In the base 21, a groove 216 is formed which extends from the surface 101a (the surface on one side in the Z-axis direction) of the support layer 101 to the device layer 102 and surrounds the opening 213 when viewed from the Z-axis direction. This makes it possible for the groove 216 to ensure electrical insulation of the electrode pad 211, thereby further improving reliability.

[0123] The electrode pad 211 extends over the bottom surface 214 and the side surface 215 of the opening 213. This allows the electrode pad 211 to have a large area. The metal layer constituting the electrode pad 211 is thicker than the metal layer constituting the mirror surface 22a. In this case, it is possible to suppress deformation of the mirror surface 22a and ensure electrical connection to the electrode pad 211. That is, in order to suppress warping of the mirror surface 22a, it is preferable that the metal layer constituting the mirror surface 22a is thin. The thick metal layer constituting the electrode pad 211 can improve bonding performance in the wire bonding process. If the electrode pad 211 is too thin, there is a concern that it may be impossible to provide a wire or sufficient adhesion may not be obtained, but the mirror device 20 can suppress such a situation.

[0124] In the mirror unit 2, the light transmitting portion 14 of the optical functional member 13 can correct the optical path length difference occurring between the optical path between the beam splitter unit 3 and the movable mirror 22 and the optical path between the beam splitter unit 3 and the fixed mirror 16. "Correcting the optical path length difference" means reducing the difference between the optical path length of the optical path between the beam splitter unit 3 and the movable mirror 33 (the optical path length taking into account the refractive index of each medium through which the optical path passes) and the optical path length of the optical path between the beam splitter unit 3 and the fixed mirror 16. Furthermore, in the mirror unit 2, the mirror surface 22a is arranged closer to the optical functional member 13 than, for example, "a configuration in which the mirror surface 22a is arranged on the surface of the device layer 102 opposite to the intermediate layer 103, and the base 21 is bonded to the third surface 13a of the optical functional member 13 on the surface of the support layer 101 opposite to the intermediate layer 103." Such a configuration is particularly effective when the optical path length difference is corrected by the light transmitting portion 14. That is, for example, the reference position when the movable mirror 22 is reciprocated along the Z-axis direction can be easily (with a small amount of movement) aligned with the third surface 13a of the optical function member 13. Therefore, a sufficient optical interference signal can be acquired while suppressing the amount of reciprocation of the movable mirror 22 along the Z-axis direction. [Variations]

[0125] In the above embodiment, the material and shape of each component are not limited to the above-mentioned material and shape, and various materials and shapes can be adopted. For example, each of the arrangement portion 221 and the mirror surface 22a may have any shape such as a rectangular shape or an octagonal shape when viewed from the Z-axis direction. The frame portion 222 may have any ring shape such as a rectangular ring shape or an octagonal ring shape when viewed from the Z-axis direction. Each of the light passing opening 24 and the light passing opening 25 may have any shape such as a circular shape or an octagonal shape when viewed from the Z-axis direction. The mirror device 20 may have a hole or a notch formed in the base 21 as a first light passing portion instead of the light passing opening 24 or the light passing opening 25. The semiconductor substrate constituting the mirror device 20 does not necessarily have to be an SOI substrate, and may be a substrate having a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in the Z-axis direction.

[0126] Each of the inner beam portion 224a, the outer beam portion 224b, and the connecting beam portion 224c may be formed in any shape. For example, the beam portion may extend obliquely with respect to the X-axis direction or the Y-axis direction, or may extend in a zigzag shape. The arrangement, number, length, width, and thickness of each beam portion may be set arbitrarily. For example, the thicknesses of the inner beam portion 224a, the outer beam portion 224b, and the connecting beam portion 224c may be different from each other. At least one of these beam portions may be omitted. The beam portion 224 may not surround the mirror surface 22a when viewed from the Z-axis direction. The thickness of the support layer 101 constituting the beam portion 224 may be the same as the thickness of the support layer 101 constituting the base 21. The shapes of the first torsion bars 266, 276 and the second torsion bars 267, 277 are not limited, and may be any shape such as a rod shape. The electrode pad 211 may be disposed only on the bottom surface 214 of the opening 213 and may not extend to the side surface 215. In this case, the groove portion 216 may be omitted. The second surface 21b of the base 21 and the third surface 13a of the optical functional member 13 may be bonded to each other by a means other than direct bonding (for example, an adhesive such as a UV curable resin). The fixed mirror 16 may be separated from the fourth surface 13b of the optical functional member 13 as long as it is disposed on the opposite side of the optical functional member 13 to the mirror device 20.

[0127] The optical device of the present disclosure is not limited to a mirror device, and may be an optical device in which other optical functional parts than the mirror surface 22a are arranged on the movable part 22b. Examples of other optical functional parts include lenses. The driving part 23 of the mirror device 20 may have three or more elastic support parts that elastically support the movable mirror 22. The actuator part 28 is not limited to an electrostatic actuator, and may be, for example, a piezoelectric actuator, an electromagnetic actuator, or the like. In the above embodiment, the moving direction (predetermined direction) of the movable part 22b is a direction perpendicular to the first surface 21a of the base 21, but the moving direction may be any direction intersecting with the first surface 21a. The mirror device 20 is not limited to one that constitutes an FTIR, and may be one that constitutes another optical system. Each configuration in one embodiment or modified example described above can be arbitrarily applied to each configuration in another embodiment or modified example. [Explanation of symbols]

[0128] 3...beam splitter unit, 13...optical functional member, 14...light transmitting portion (second light passing portion), 16...fixed mirror, 20...mirror device (optical device), 21...base, 21a...first surface (main surface), 21b...second surface (main surface), 22a...mirror surface (optical functional portion), 22b...movable portion, 221...positioning portion, 222...frame portion, 223...connecting portion, 224...beam portion, 24...light passing opening (first light passing portion), 100...SOI substrate (semiconductor substrate), 101...support layer (first semiconductor layer), 101a...surface, 102...device layer (second semiconductor layer), 102a...surface, 103...intermediate layer (insulating layer), 211...electrode pad, 213...opening, 214...bottom surface, 215...side surface, 216...groove portion.

Claims

1. A base having a major surface; A movable part supported on the base; an optical function unit disposed on the movable unit; an actuator unit that generates a driving force for moving the movable unit; an electrode pad provided on the base and to which an electrical signal is input; the base and the movable portion are formed of a semiconductor substrate having a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in a predetermined direction; the base is composed of the first semiconductor layer, the insulating layer, and the second semiconductor layer, the movable portion has a placement portion constituted by the second semiconductor layer, the optical function portion is disposed on the surface on the one side of the arrangement portion, An optical device, wherein the electrode pad is arranged on the surface of the one side of the second semiconductor layer within an opening formed in the surface of the one side of the first semiconductor layer so as to reach the second semiconductor layer, and is electrically connected to the actuator portion via the second semiconductor layer.

2. The movable portion further includes a beam portion disposed around the optical function portion, the beam portion is formed by the first semiconductor layer and the insulating layer disposed on the second semiconductor layer, The optical device according to claim 1 , wherein the first semiconductor layer constituting the beam portion is thinner than the first semiconductor layer constituting the base.

3. The optical device according to claim 1 , wherein the electrode pad extends across a bottom surface and a side surface of the opening.

4. each of the electrode pads and the optical function portion is made of a metal layer; 4. The optical device according to claim 1, wherein the metal layer constituting the electrode pad is thicker than the metal layer constituting the optical function portion.

5. the opening has a bottom surface defined by the surface of the one side of the second semiconductor layer and a side surface defined by the first semiconductor layer and the insulating layer; The optical device according to any one of claims 1 to 4, wherein the bottom surface has a rectangular shape.

6. the opening has a bottom surface defined by the surface of the one side of the second semiconductor layer and a side surface defined by the first semiconductor layer and the insulating layer; The optical device of any one of claims 1 to 5, wherein the side surface has a first surface that is continuous with the bottom surface and extends approximately perpendicular to the bottom surface, a step surface that is continuous with the first surface and extends approximately parallel to the bottom surface, and a second surface that is continuous with the step surface and extends approximately perpendicular to the bottom surface.

7. The optical device according to claim 6 , wherein the step surface extends in an annular shape along an edge of the opening when viewed from the predetermined direction.

8. The optical device according to claim 6 , wherein the electrode pad is formed so as to reach the first surface but not to reach the step surface.

9. The optical device according to claim 1 , wherein a bottom surface of the opening is surrounded by side surfaces formed by the first semiconductor layer and the insulating layer.

10. The semiconductor device further comprises a ground electrode pad provided on the base and used as a ground electrode, The optical device according to any one of claims 1 to 9, wherein the ground electrode pad is arranged on the surface on one side of the second semiconductor layer within an opening formed on the surface on one side of the first semiconductor layer so as to reach the second semiconductor layer, and is electrically connected to the actuator portion via the second semiconductor layer.

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