Patent Description:
An optical device in which an interference optical system is formed on a silicon on insulator (SOI) substrate by a micro electro mechanical system (MEMS) technology is known (for example, refer to Patent Literature <NUM>). In the optical device, it is possible to provide a Fourier transformation type infrared spectral analyzer (FTIR) in which high-accuracy optical arrangement is realized, and thus the optical device has attracted attention.

Further pertinent prior art is disclosed in <CIT>.

In the above-described optical device, a movable mirror that constitutes the interference optical system moves along a main surface of an SOI substrate. In contrast, it is considered to employ a configuration in which the movable mirror moves along a direction perpendicular to a main surface of the SOI substrate to realize an increase in size of a mirror surface of the movable mirror. However, when simply employing the configuration, there is a concern that it is difficult to sufficiently protect the mirror surface, and reliability as a device deteriorates.

An object of an aspect of the present disclosure is to provide an optical device with high reliability.

The object of the invention is achieved by the subject-matter of the independent claim. According to an aspect of the present disclosure, there is provided an optical device including: a base that includes a main surface; a movable unit that is supported in the base to be movable along a predetermined direction that intersects the main surface; and an optical function unit that is disposed on the movable unit. The base and the movable unit are constituted by a semiconductor substrate that includes a first semiconductor layer, an insulating layer, and a second semiconductor layer in this 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 unit includes an arrangement portion that is constituted by the second semiconductor layer. The optical function unit is disposed on a surface of the arrangement portion on the one side. The first semiconductor layer that constitutes the base is thicker than the second semiconductor layer that constitutes the base. A surface of the base on the one side is located more to the one side than the optical function unit.

In the optical device, the surface of the base on the one side is located more to the one side than the optical function unit. Accordingly, it is possible to protect the optical function unit by the base and it is possible to prevent the optical function unit from being damaged, for example, due to direct contact in transportation or the like. In addition, in the optical device, the first semiconductor layer that constitutes the base is thicker than the second semiconductor layer that constitutes the base. Accordingly, it is possible to secure a protrusion amount of the base with respect to the optical function unit, and it is possible to effectively protect the optical function unit by the base. Accordingly, according to the optical device, it is possible to enhance reliability.

The movable unit may further include a rib portion that is disposed at the periphery of the optical function unit, the rib portion may be constituted by the first semiconductor layer and the insulating layer which are disposed on the second semiconductor layer, and an end surface of the rib portion on the one side may be located more to the one side than the optical function unit. In this case, it is also possible to protect the optical function unit by the rib portion. In addition, it is also possible to suppress deformation of the movable unit during movement by the rib portion.

The rib portion may be disposed on the surface of the arrangement portion on the one side to extend along an outer edge of the arrangement portion when viewed from the predetermined direction. In this case, it is possible to dispose the rib portion to be closer to the optical function unit, and it is possible to more effectively protect the optical function unit. In addition, the rib portion is disposed on the arrangement portion, and thus it is possible to more appropriately suppress deformation of the arrangement portion.

The movable unit may further include a frame portion that surrounds the arrangement portion when viewed from the predetermined direction, and a connection portion that connects the arrangement portion and the frame portion, the frame portion and the connection portion may be constituted by the second semiconductor layer, and the rib portion may be disposed on a surface of the frame portion on the one side to extend along the frame portion when viewed from the predetermined direction. In this case, it is possible to more effectively protect the optical function unit by the rib portion. In addition, it is possible to suppress deformation of the frame portion due to the rib portion, and it is possible to suppress deformation of the arrangement portion which is caused by the deformation of the frame portion.

The first semiconductor layer that constitutes the rib portion may be thinner than the first semiconductor layer that constitutes the base. In this case, it is possible to suppress the rib portion from protruding from the base during movement of the movable unit, and it is possible to increase a movement amount of the movable unit in a predetermined direction.

The optical device according to the aspect of the present disclosure may further include an electrode pad that is provided in the base, the electrode pad may be disposed on a surface of the second semiconductor layer on the one side in an opening that is formed in the base to reach the second semiconductor layer from a surface of the first semiconductor layer on the one side, and the base may include a groove that reaches the second semiconductor layer from the surface of the first semiconductor layer on the one side, and extends to surround the opening when viewed from the predetermined direction. In this case, it is possible to reliably secure an electrical insulation property of the electrode pad due to the groove, and it is possible to further enhance reliability.

The electrode pad may extend along a bottom surface and a lateral surface of the opening. In this case, it is possible to increase an area of the electrode pad.

Each of the electrode pad and the optical function unit may be constituted by a metal layer, and the metal layer that constitutes the electrode pad may be thicker than the metal layer that constitutes the optical function unit. In this case, it is possible to suppress deformation of the optical function unit, and it is possible to reliably secure electrical connection to the electrode pad.

According to another aspect of the present disclosure, there is provided a mirror unit including: the above-described optical device; an optical function member that is disposed on the other side in the predetermined direction with respect to the optical device; and a fixed mirror that is disposed on the other side with respect to the optical function member. The optical function unit is a mirror surface that constitutes a movable mirror in combination with the movable unit. The optical device is provided with a first light passage portion that constitutes a first portion of an optical path between a beam splitter unit that constitutes an interference optical system in combination with the movable mirror and the fixed mirror, and the fixed mirror. The optical function member is provided with a second light passage portion that constitutes a second portion of the optical path between the beam splitter unit and the fixed mirror. The second light passage portion corrects an optical path difference that occurs between an optical path between the beam splitter unit and the movable mirror, and the optical path between the beam splitter unit and the fixed mirror.

In the mirror unit, it is possible to enhance reliability due to the above-described reason. In addition, it is possible to correct an optical path length difference that occurs between an optical path between the beam splitter unit and the movable unit, and an optical path between the beam splitter unit and the fixed mirror due to the second light passage portion of the optical function member. In addition, in the mirror unit, the mirror surface is disposed to be closer to the optical function member. This configuration is particularly effective for the case of correcting the optical path length difference by the second light passage portion of the optical function member.

According to the aspect of the present disclosure, it is possible to provide an optical device with high reliability.

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. The same reference numeral will be given to the same or equivalent parts in the respective drawings, and redundant description thereof will be omitted.

As illustrated in <FIG>, an optical module <NUM> includes a mirror unit <NUM>, a beam splitter unit <NUM>, a light incident unit <NUM>, a first light detector <NUM>, a second light source <NUM>, a second light detector <NUM>, a support <NUM>, a first support structure <NUM>, and a second support structure <NUM>. The mirror unit <NUM> is disposed on one side of the support <NUM> in a Z-axis direction (a predetermined direction, a first direction), and is attached to the support <NUM>, for example, by an adhesive. For example, the support <NUM> is formed of copper tungsten, and has a rectangular plate shape. The mirror unit <NUM> includes a movable mirror <NUM> that moves in the Z-axis direction, and a fixed mirror <NUM> of which a position is fixed (details thereof will be described later). For example, the Z-axis direction is a vertical direction, and the one side in the Z-axis direction is an upper side.

The beam splitter unit <NUM> is disposed on one side of the mirror unit <NUM> in the Z-axis direction, and is supported by the first support structure <NUM>. The first support structure <NUM> is attached to the support <NUM>, for example, by an adhesive. The light incident unit <NUM> is disposed on one side of the beam splitter unit <NUM> in an X-axis direction (a third direction perpendicular to the first direction), and is supported by the second support structure <NUM>. The first light detector <NUM>, the second light source <NUM>, and the second light detector <NUM> are disposed on the one side of the beam splitter unit <NUM> in the Z-axis direction, and are supported by the second support structure <NUM>. The second support structure <NUM> is attached to the support <NUM>, for example, by a bolt.

In the optical module <NUM>, an interference optical system is constituted by the beam splitter unit <NUM>, the movable mirror <NUM>, and the fixed mirror <NUM> with respect to each of measurement light L0 and laser light L10. The interference optical system which is constituted with respect to each of the measurement light L0 and the laser light L10 is, for example, a Michelson interference optical system.

With regard to the measurement light L0, interference light L1 of measurement light is detected as follows. That is, when the measurement light L0 that is incident from a first light source (not illustrated) through a measurement target (not illustrated) or the measurement light L0 that is generated from the measurement target (for example, light emitted from the measurement target itself, or the like) is incident to the beam splitter unit <NUM> from the light incident unit <NUM>, the measurement light L0 is divided into a part and the remainder in the beam splitter unit <NUM>. The part of the measurement light L0 is reflected by the movable mirror <NUM> that reciprocates in the Z-axis direction, and returns to the beam splitter unit <NUM>. On the other hand, the remainder of the measurement light L0 is reflected by the fixed mirror <NUM> and returns to the beam splitter unit <NUM>. The part and the remainder of the measurement light L0, which return to the beam splitter unit <NUM>, are emitted from the beam splitter unit <NUM> as the interference light L1, and the interference light L <NUM> of the measurement light is detected by the first light detector <NUM>.

With regard to the laser light L10, interference light L11 of laser light is detected as follows. That is, when the laser light L10 emitted from the second light source <NUM> is incident to the beam splitter unit <NUM>, the laser light L10 is divided into a part and the remainder in the beam splitter unit <NUM>. The part of the laser light L10 is reflected by the movable mirror <NUM> that reciprocates in the Z-axis direction, and returns to the beam splitter unit <NUM>. On the other hand, the remainder of the laser light L10 is reflected by the fixed mirror <NUM> and returns to the beam splitter unit <NUM>. The part and the remainder of the laser light L10, which return to the beam splitter unit <NUM>, are emitted from the beam splitter unit <NUM> as the interference light L11, and the interference light L11 of the laser light is detected by the second light detector <NUM>.

According to the optical module <NUM>, measurement of a position of the movable mirror <NUM> in the Z-axis direction can be measured based on a detection result of the interference light L11 of the laser light, and spectral analysis with respect to the measurement target can be performed based on a measurement result of the position, and a detection result of the interference light L1 of the measurement light.

As illustrated in <FIG>, <FIG>, and <FIG>, the mirror unit <NUM> includes a mirror device (optical device) <NUM>, an optical function member <NUM>, the fixed mirror <NUM>, and a stress mitigation substrate <NUM>. The mirror device <NUM> includes a base <NUM>, the movable mirror <NUM>, and a drive unit <NUM>.

The base <NUM> includes a first surface 21a (surface on the 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 <NUM>. For example, the base <NUM> has a rectangular plate shape, and a size of approximately <NUM> × <NUM> × <NUM> (thickness). The movable mirror <NUM> includes a mirror surface (optical function member) 22a, and a movable unit 22b in which the mirror surface 22a is disposed. The movable mirror <NUM> (movable unit 22b) is supported in the base <NUM> so that the movable mirror <NUM> can move in the Z-axis direction perpendicular to the first surface 21a (a predetermined direction perpendicular to the first surface). The drive unit <NUM> moves the movable mirror <NUM> in the Z-axis direction.

A pair of light passage openings <NUM> and <NUM> are provided in the mirror device <NUM>. The pair of light passage openings <NUM> and <NUM> are respectively disposed on both sides of the movable mirror <NUM> in the X-axis direction. The light passage opening (first light passage portion) <NUM> constitutes a first portion of an optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>. In this embodiment, the light passage opening <NUM> does not function as a light passage opening.

Here, a configuration of the mirror device <NUM> will be described in detail with reference to <FIG>, <FIG>, and <FIG>. <FIG> is a schematic cross-sectional view of the mirror device <NUM> illustrated in <FIG>, and <FIG> schematically illustrates the mirror device <NUM>, for example, in a state in which dimensions in the Z-axis direction are enlarged in comparison to actual dimensions.

The base <NUM>, the movable unit 22b of the movable mirror <NUM>, and the drive unit <NUM> are constituted by a silicon on insulator (SOI) substrate (semiconductor substrate) <NUM>. That is, the mirror device <NUM> is constituted by the SOI substrate <NUM>. For example, the mirror device <NUM> is formed in a rectangular plate shape. The SOI substrate <NUM> includes a support layer <NUM>, a device layer <NUM>, and an intermediate layer <NUM>. The support layer <NUM> is a first silicon layer (a first semiconductor layer). The device layer <NUM> is a second silicon layer (a second semiconductor layer). The intermediate layer <NUM> is an insulating layer that is disposed between the support layer <NUM> and the device layer <NUM>. The SOI substrate <NUM> includes the support layer <NUM>, the intermediate layer <NUM>, and the device layer <NUM> in this order from the one side in the Z-axis direction.

The base <NUM> is constituted by a part of the support layer <NUM>, the device layer <NUM>, and the intermediate layer <NUM>. The first surface 21a of the base <NUM> is a surface of the support layer <NUM> which is opposite to the intermediate layer <NUM>. The second surface 21b of the base <NUM> is a surface of the device layer <NUM> which is opposite to the intermediate layer <NUM>. The support layer <NUM> that constitutes the base <NUM> is thicker than the device layer <NUM> that constitutes the base <NUM>. For example, the thickness of the support layer <NUM> that constitutes the base <NUM> is approximately four times the thickness of the device layer <NUM> that constitutes the base <NUM>. As will be described later, in the mirror unit <NUM>, the second surface 21b of the base <NUM> and a third surface 13a of the optical function member <NUM> are jointed to each other (refer to <FIG> and <FIG>).

The movable mirror <NUM> is disposed in a state in which an intersection between an axial line R1 and an axial line R2 is set as the central position (gravity center position). The axial line R1 is a straight line that extends in the X-axis direction. The axial line R2 is a straight line that extends in a Y-axis direction (a second direction perpendicular to the first direction and the third direction). When viewed from the Z-axis direction, in the mirror device <NUM>, a portion other than a portion that overlaps a sixth surface 21d of the base <NUM> to be described later has a shape that is linearly symmetric to each of the axial line R1 and the axial line R2.

The movable mirror <NUM> (movable unit 22b) includes an arrangement portion <NUM>, a frame portion <NUM>, a pair of connection portions <NUM>, and a rib portion <NUM>. The arrangement portion <NUM>, the frame portion <NUM>, and the pair of connection portions <NUM> are constituted by a part of the device layer <NUM>. The arrangement portion <NUM> has a circular shape when viewed from the Z-axis direction. The arrangement portion <NUM> includes a central portion 221a and an edge portion 221b. For example, the mirror surface 22a is provided on a surface 221as of the central portion 221a on the one side in the Z-axis direction by forming a metal film (metal layer) thereon. The mirror surface 22a extends perpendicular 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 <NUM> side in the device layer <NUM>. The mirror surface 22a is located on the other side in the Z-axis direction in comparison to the first surface 21a of the base <NUM>. In other words, the first surface 21a is located on the one side in the Z-axis direction in comparison to the mirror surface 22a. The edge portion 221b surrounds the central portion 221a when viewed from the Z-axis direction.

The frame portion <NUM> extends in an annular shape to surround the arrangement portion <NUM> with a predetermined gap from the arrangement portion <NUM> when viewed from the Z-axis direction. For example, the frame portion <NUM> has a circular ring shape when viewed from the Z-axis direction. Each of the pair of connection portions <NUM> connects the arrangement portion <NUM> and the frame portion <NUM> to each other. The pair of connection portions <NUM> are respectively disposed on both sides of the arrangement portion <NUM> in the Y-axis direction.

The rib portion <NUM> is constituted by the support layer <NUM> and the intermediate layer <NUM> which are disposed on the device layer <NUM>. The rib portion <NUM> is disposed at the periphery of the mirror surface 22a. The rib portion <NUM> includes an inner rib portion 224a, an outer rib portion 224b, and a pair of connection rib portions 224c. The inner rib portion 224a is disposed on a surface of the edge portion 221b on the one side in the Z-axis direction. The inner rib portion 224a surrounds the mirror surface 22a when viewed from the Z-axis direction. For example, an outer edge of the inner rib portion 224a extends along an outer edge of the arrangement portion <NUM> with a predetermined gap from the outer edge of the arrangement portion <NUM> when viewed from the Z-axis direction. An inner edge of the inner rib portion 224a extends along an outer edge of the mirror surface 22a with a predetermined gap from the outer edge of the mirror surface 22a when viewed from the Z-axis direction. An end surface 224as of the inner rib portion 224a on the one side in the Z-axis direction is located on the one side in the Z-axis direction in comparison to the mirror surface 22a.

The outer rib portion 224b is disposed on a surface of the frame portion <NUM> on the one side in the Z-axis direction. The outer rib portion 224b surrounds the inner rib portion 224a and the mirror surface 22a when viewed from the Z-axis direction. For example, an outer edge of the outer rib portion 224b extends along an outer edge of the frame portion <NUM> with a predetermined gap from the outer edge of the frame portion <NUM> when viewed from the Z-axis direction. An inner edge of the outer rib portion 224b extends along an inner edge of the frame portion <NUM> with a predetermined gap from the inner edge of the frame portion <NUM> when viewed from the Z-axis direction. An end surface 224bs of the outer rib portion 224b on the one side in the Z-axis direction is located on the one side in the Z-axis direction in comparison to the mirror surface 22a.

The pair of connection rib portions 224c are respectively disposed on surfaces of the pair of connection portions <NUM> on the one side in the Z-axis direction. The connection rib portions 224c connect the inner rib portion 224a and the outer rib portion 224b to each other. End surfaces 224cs of the connection rib portions 224c on the one side in the Z-axis direction are located on the one side in the Z-axis direction in comparison to the mirror surface 22a.

The thickness of the inner rib portion 224a, the thickness of the outer rib portion 224b, and the thickness of the respective connection rib portions 224c in the Z-axis direction are the same as each other. That is, the thickness of the support layer <NUM> that constitutes the inner rib portion 224a, the outer rib portion 224b, and the respective connection rib portions 224c is the same in each case. The end surface 224as of the inner rib portion 224a, the end surface 224bs of the outer rib portion 224b, and the end surfaces 224cs of the respective connection rib portions 224c are located on the same plane perpendicular to the Z-axis direction. The support layer <NUM> that constitutes the inner rib portion 224a, the outer rib portion 224b, and the respective connection rib portions 224c is thinner than the support layer <NUM> that constitutes the base <NUM>. Accordingly, the end surfaces 224as, 224bs, and 224cs are located on the one side in the Z-axis direction in comparison to the first surface 21a of the base <NUM>. In other words, the first surface 21a is located on the other side in the Z-axis direction in comparison to the end surfaces 224as, 224bs, and 224cs.

When viewed from the Z-axis direction, a width of the outer rib portion 224b is wider than a width of the inner rib portion 224a. The width of the inner rib portion 224a when viewed from the Z-axis direction is a length of the inner rib portion 224a in a direction perpendicular to the extending direction of the inner rib portion 224a, and is a length of the inner rib portion 224a in a radial direction of the inner rib portion 224a in this embodiment. This is also true of a width of the outer rib portion 224b when viewed from the Z-axis direction. A width of each of the connection rib portions 224c is larger than the width of each of the inner rib portion 224a and the outer rib portion 224b. The width of each of the connection rib portion 224c is a length of each of the connection rib portion 224c along the extending direction of the inner rib portion 224a.

The drive unit <NUM> includes a first elastic support unit <NUM>, a second elastic support unit <NUM>, and an actuator unit <NUM>. The first elastic support unit <NUM>, the second elastic support unit <NUM>, and the actuator unit <NUM> are constituted by a part of the device layer <NUM>.

Each of the first elastic support unit <NUM> and the second elastic support unit <NUM> is connected between the base <NUM> and the movable mirror <NUM>. The first elastic support unit <NUM> and the second elastic support unit <NUM> support the movable mirror <NUM> so that the movable mirror <NUM> (movable unit 22b) can move in the Z-axis direction.

The first elastic support unit <NUM> includes a pair of levers <NUM>, a first link member <NUM>, a second link member <NUM>, a pair of beam members <NUM>, an intermediate member <NUM>, a pair of first torsion bars (first torsion support portions) <NUM>, a pair of second torsion bars (second torsion support portions) <NUM>, a pair of non-linearity mitigation springs <NUM>, and a plurality of electrode support portions <NUM>.

The pair of levers <NUM> are respectively disposed on both sides of the light passage opening <NUM> in the Y-axis direction, and face each other in the Y-axis direction. Each of the levers <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction. The lever <NUM> includes a first portion 261a, a second portion 261b that is disposed on a side opposite to the movable mirror <NUM> with respect to the first portion 261a, and a third portion 261c that is connected to the first portion 261a and the second portion 261b. The first portion 261a and the second portion 261b extend in the X-axis direction. A length of the first portion 261a in the X-axis direction is shorter than a length of the second portion 261b in the X-axis direction. The third portions 261c of the pair of levers <NUM> obliquely extend to be spaced away from each other as going away from the movable mirror <NUM>.

The first link member <NUM> bridges first ends 261d of the pair of levers <NUM> on a side opposite to the movable mirror <NUM>. The first link member <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The second link member <NUM> bridges second ends 261e of the pair of levers <NUM> on the movable mirror <NUM> side. The second link member <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. A width of the second link member <NUM> in the X-axis direction is narrower than a width of the first link member <NUM> in the X-axis direction. A length of the second link member <NUM> in the Y-axis direction is shorter than a length of the first link member <NUM> in the Y-axis direction.

The pair of beam members <NUM> respectively bridge the second portions 261b of the pair of levers <NUM> and the first link member <NUM>. The respective beam members <NUM> have a plate shape that extends along a plane perpendicular to the Z-axis direction. The pair of beam members <NUM> obliquely extend to approach each other as going away from the movable mirror <NUM>. The pair of levers <NUM>, the first link member <NUM>, the second link member <NUM>, and the pair of beam members <NUM> define the light passage opening <NUM>. The light passage opening <NUM> has a polygonal shape when viewed from the Z-axis direction. For example, the light passage opening <NUM> is a cavity (hole). Alternatively, a material having optical transparency with respect to the measurement light L0 and the laser light L10 may be disposed in the light passage opening <NUM>.

The intermediate member <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The intermediate member <NUM> is disposed between the movable mirror <NUM> and the second link member <NUM> (in other words, between the movable mirror <NUM> and the light passage opening <NUM>). The intermediate member <NUM> is connected to the movable mirror <NUM> through the non-linearity mitigation springs <NUM> as to be described later.

The pair of first torsion bars <NUM> respectively bridge the first end 261d of one lever <NUM> and the base <NUM>, and the first end 261d of the other lever <NUM> and the base <NUM>. That is, the pair of first torsion bars <NUM> are respectively connected between the pair of levers <NUM> and the base <NUM>. The first torsion bars <NUM> extend in the Y-axis direction. The pair of first torsion bars <NUM> are disposed on the same central line parallel to the Y-axis direction. In this embodiment, the central line of the first torsion bars <NUM> and the central line of the first link member <NUM> are located on the same straight line. A protrusion 261f that protrudes outward in the Y-axis direction is provided in each of the first ends 261d of the levers <NUM>, and each of the first torsion bars <NUM> is connected to the protrusion 261f.

The pair of second torsion bars <NUM> respectively bridge the second end 261e of one lever <NUM> and one end of the intermediate member <NUM>, and the second end 261e of the other lever <NUM> and the other end of the intermediate member <NUM>. That is, the pair of second torsion bars <NUM> are respectively connected between the pair of levers <NUM> and the movable mirror <NUM>. The respective second torsion bars <NUM> extend in the Y-axis direction. The pair of second torsion bars <NUM> are disposed on the same central line parallel to the Y-axis direction.

The pair of non-linearity mitigation springs <NUM> are connected between the movable mirror <NUM> and the intermediate member <NUM>. That is, the pair of non-linearity mitigation springs <NUM> are connected between the movable mirror <NUM> and the second torsion bar <NUM>. Each of the non-linearity mitigation springs <NUM> includes a meandering portion 268a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 268a includes a plurality of straight portions 268b which extend in the Y-axis direction and are aligned in the X-axis direction, and a plurality of folded portions 268c which alternately connect both ends of the plurality of straight portions 268b. One end of the meandering portion 268a is connected to the intermediate member <NUM>, and the other end of the meandering portion 268a is connected to the frame portion <NUM>. In the meandering portion 268a, a portion on the frame portion <NUM> side has a shape along the outer edge of the frame portion <NUM>.

The non-linearity mitigation spring <NUM> is constituted as follows. In a state in which the movable mirror <NUM> has moved in the Z-axis direction, the amount of deformation of the non-linearity mitigation spring <NUM> around the Y-axis direction becomes smaller than the amount of deformation of each of the first torsion bar <NUM> and the second torsion bar <NUM> around the Y-axis direction, and the amount of deformation of the non-linearity mitigation spring <NUM> in the X-axis direction becomes larger than the amount of deformation of each of the first torsion bar <NUM> and the second torsion bar <NUM> in the X-axis direction. Accordingly, it is possible to suppress occurrence of non-linearity in twist deformation of the first torsion bar <NUM> and the second torsion bar <NUM>, and it is possible to suppress deterioration of control characteristics of the movable mirror <NUM> due to the non-linearity. The amount of deformation of the first torsion bar <NUM>, the second torsion bar <NUM>, and the non-linearity mitigation spring <NUM> around the Y-axis direction represents, for example, an absolute value of a twist amount (twist angle). The amount of deformation of the first torsion bar <NUM>, the second torsion bar <NUM>, and the non-linearity mitigation spring <NUM> in the X-axis direction represents, for example, an absolute value of a deflection amount. The amount of deformation of a member around the Y-axis direction represents the amount of deformation of the member in a peripheral direction of a circle of which the center is set to an axial line that passes through the center of the member and is parallel to the Y-axis. This is also true of first torsion bars <NUM>, second torsion bars <NUM>, and a non-linearity mitigation spring <NUM> to be described later.

The plurality of electrode support portions <NUM> include a pair of first electrode support portions 269a, a pair of second electrode support portions 269b, and a pair of third electrode support portions 269c. Each of the electrode support portions 269a, 269b, and 269c has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. Each of the electrode support portions 269a, 269b, and 269c extends from the second portion 261b of the lever <NUM> toward a side opposite to the light passage opening <NUM>. The pair of first electrode support portions 269a are disposed on the same central line parallel to the Y-axis direction. The pair of second electrode support portions 269b are disposed on the same central line parallel to the Y-axis direction. The pair of third electrode support portions 269c are disposed on the same central line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portions 269a, the second electrode support portions 269b, and the third electrode support portions 269c are aligned in this order from the movable mirror <NUM> side.

The second elastic support unit <NUM> includes a pair of levers <NUM>, a first link member <NUM>, a second link member <NUM>, a pair of beam members <NUM>, an intermediate member <NUM>, a pair of first torsion bars (first torsion support portions) <NUM>, a pair of second torsion bars (second torsion support portions) <NUM>, a pair of non-linearity mitigation springs <NUM>, and a plurality of electrode support portions <NUM>.

The pair of levers <NUM> are respectively disposed on both sides of the light passage opening <NUM> in the Y-axis direction, and face each other in the Y-axis direction. Each of the levers <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction. The lever <NUM> includes a first portion 271a, a second portion 271b that is disposed on a side opposite to the movable mirror <NUM> with respect to the first portion 271a, and a third portion 271c that is connected to the first portion 271a and the second portion 271b. The first portion 271a and the second portion 271b extend in the X-axis direction. A length of the first portion 271a in the X-axis direction is shorter than a length of the second portion 271b in the X-axis direction. The third portions 271c of the pair of levers <NUM> obliquely extend to be spaced away from each other as going away from the movable mirror <NUM>.

The first link member <NUM> bridges first ends 271d of the pair of levers <NUM> on a side opposite to the movable mirror <NUM>. The first link member <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. The second link member <NUM> bridges second ends 271e of the pair of levers <NUM> on the movable mirror <NUM> side. The second link member <NUM> has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. A width of the second link member <NUM> in the X-axis direction is narrower than a width of the first link member <NUM> in the X-axis direction. A length of the second link member <NUM> in the Y-axis direction is shorter than a length of the first link member <NUM> in the Y-axis direction.

The pair of beam members <NUM> respectively bridge the second portions 271b of the pair of levers <NUM> and the first link member <NUM>. The respective beam members <NUM> have a plate shape that extends along a plane perpendicular to the Z-axis direction. The pair of beam members <NUM> obliquely extend to approach each other as going away from the movable mirror <NUM>. The pair of levers <NUM>, the first link member <NUM>, the second link member <NUM>, and the pair of beam members <NUM> define the light passage opening <NUM>. The light passage opening <NUM> has a polygonal shape when viewed from the Z-axis direction. For example, the light passage opening <NUM> is a cavity (hole). Alternatively, a material having optical transparency with respect to the measurement light L0 and the laser light L10 may be disposed in the light passage opening <NUM>.

The pair of first torsion bars <NUM> respectively bridge the first end 271d of one lever <NUM> and the base <NUM>, and the first end 271d of the other lever <NUM> and the base <NUM>. That is, the pair of first torsion bars <NUM> are respectively connected between the pair of levers <NUM> and the base <NUM>. The first torsion bars <NUM> extend in the Y-axis direction. The pair of first torsion bars <NUM> are disposed on the same central line parallel to the Y-axis direction. In this embodiment, the central line of the first torsion bars <NUM> and the central line of the first link member <NUM> are located on the same straight line. A protrusion 271f that protrudes outward in the Y-axis direction is provided in each of the first ends 271d of the levers <NUM>, and each of the first torsion bars <NUM> is connected to the protrusion 271f.

The pair of second torsion bars <NUM> respectively bridge the second end 271e of one lever <NUM> and one end of the intermediate member <NUM>, and the second end 271e of the other lever <NUM> and the other end of the intermediate member <NUM>. That is, the pair of second torsion bars <NUM> are respectively connected between the pair of levers <NUM> and the movable mirror <NUM>. The respective second torsion bars <NUM> extend in the Y-axis direction. The pair of second torsion bars <NUM> are disposed on the same central line parallel to the Y-axis direction.

The pair of non-linearity mitigation springs <NUM> are connected between the movable mirror <NUM> and the intermediate member <NUM>. That is, the pair of non-linearity mitigation springs <NUM> are connected between the movable mirror <NUM> and the second torsion bar <NUM>. Each of the non-linearity mitigation springs <NUM> includes a meandering portion 278a that extends in a meandering manner when viewed from the Z-axis direction. The meandering portion 278a includes a plurality of straight portions 278b which extend in the Y-axis direction and are aligned in the X-axis direction, and a plurality of folded portions 278c which alternately connect both ends of the plurality of straight portions 278b. One end of the meandering portion 278a is connected to the intermediate member <NUM>, and the other end of the meandering portion 278a is connected to the frame portion <NUM>. In the meandering portion 278a, a portion on the frame portion <NUM> side has a shape along the outer edge of the frame portion <NUM>.

The non-linearity mitigation spring <NUM> is constituted as follows. In a state in which the movable mirror <NUM> has moved in the Z-axis direction, the amount of deformation of the non-linearity mitigation spring <NUM> around the Y-axis direction becomes smaller than the amount of deformation of each of the first torsion bar <NUM> and the second torsion bar <NUM> around the Y-axis direction, and the amount of deformation of the non-linearity mitigation spring <NUM> in the X-axis direction becomes larger than the amount of deformation of each of the first torsion bar <NUM> and the second torsion bar <NUM> in the X-axis direction. Accordingly, it is possible to suppress occurrence of non-linearity in twist deformation of the first torsion bar <NUM> and the second torsion bar <NUM>, and it is possible to suppress deterioration of control characteristics of the movable mirror <NUM> due to the non-linearity.

The plurality of electrode support portions <NUM> includes a pair of first electrode support portions 279a, a pair of second electrode support portions 279b, and a pair of third electrode support portions 279c. Each of the electrode support portions 279a, 279b, and 279c has a plate shape that extends along a plane perpendicular to the Z-axis direction, and extends in the Y-axis direction. Each of the electrode support portions 279a, 279b, and 279c extends from the second portion 271b of the lever <NUM> toward a side opposite to the light passage opening <NUM>. The pair of first electrode support portions 279a are disposed on the same central line parallel to the Y-axis direction. The pair of second electrode support portions 279b are disposed on the same central line parallel to the Y-axis direction. The pair of third electrode support portions 279c are disposed on the same central line parallel to the Y-axis direction. In the X-axis direction, the first electrode support portions 279a, the second electrode support portions 279b, and the third electrode support portions 279c are aligned in this order from the movable mirror <NUM> side.

The actuator unit <NUM> moves the movable mirror <NUM> in the Z-axis direction. The actuator unit <NUM> includes a fixed comb electrode <NUM>, a movable comb electrode <NUM>, a fixed comb electrode <NUM>, and a movable comb electrode <NUM>. Positions of the fixed comb electrodes <NUM> and <NUM> are fixed. The movable comb electrodes <NUM> and <NUM> move in accordance with movement of the movable mirror <NUM>.

The fixed comb electrode <NUM> is provided on a part of a surface, which faces the electrode support portions <NUM>, of the device layer <NUM> of the base <NUM>. The fixed comb electrode <NUM> includes a plurality of fixed comb fingers 281a which extend along a plane perpendicular to the Y-axis direction. The fixed comb fingers 281a are aligned in the Y-axis direction with a predetermined gap therebetween.

The movable comb electrode <NUM> is provided on a surface of each of the first electrode support portions 269a on the movable mirror <NUM> side, on surfaces of each of the second electrode support portions 269b on both sides in the X-axis direction, and on a surface of each of the third electrode support portion 269c on the movable mirror <NUM> side. The movable comb electrode <NUM> includes a plurality of movable comb fingers 282a which extend along a plane perpendicular to the Y-axis direction. The movable comb fingers 282a are aligned in the Y-axis direction with a predetermined gap therebetween.

In the fixed comb electrode <NUM> and the movable comb electrode <NUM>, the plurality of fixed comb fingers 281a and the plurality of movable comb fingers 282a are alternately arranged. That is, each of the fixed comb fingers 281a of the fixed comb electrode <NUM> is located between the movable comb fingers 282a of the movable comb electrode <NUM>. The fixed comb fingers 281a and the movable comb fingers 282a, which are adjacent to each other, face each other in the Y-axis direction. A distance between the fixed comb finger 281a and the movable comb finger 282a, which are adjacent to each other, is approximately several µm.

The fixed comb electrode <NUM> is provided on a part of a surface, which faces the electrode support portions <NUM>, of the device layer <NUM> of the base <NUM>. The fixed comb electrode <NUM> includes a plurality of fixed comb fingers 283a which extend along a plane perpendicular to the Y-axis direction. The fixed comb fingers 283a are aligned in the Y-axis direction with a predetermined gap therebetween.

The movable comb electrode <NUM> is provided on a surface of each of the first electrode support portion 279a on the movable mirror <NUM> side, on surfaces of each of the second electrode support portions 279b on both sides in the X-axis direction, and on a surface of each of the third electrode support portion 279c on the movable mirror <NUM> side. The movable comb electrode <NUM> includes a plurality of movable comb fingers 284a which extend along a plane perpendicular to the Y-axis direction. The movable comb fingers 284a are aligned in the Y-axis direction with a predetermined gap therebetween.

In the fixed comb electrode <NUM> and the movable comb electrode <NUM>, the plurality of fixed comb fingers 283a and the plurality of movable comb fingers 284a are alternately arranged. That is, each of the fixed comb fingers 283a of the fixed comb electrode <NUM> is located between the movable comb fingers 284a of the movable comb electrode <NUM>. The fixed comb fingers 283a and the movable comb fingers 284a, which are adjacent to each other, face each other in the Y-axis direction. For example, a distance between the fixed comb finger 283a and the movable comb finger 284a, which are adjacent to each other, is approximately several µm.

A plurality of electrode pads <NUM> are provided in the base <NUM>. The electrode pads <NUM> are disposed on a surface of the device layer <NUM> in an opening <NUM> formed in the first surface 21a of the base <NUM> to reach the device layer <NUM>. Some of the plurality of electrode pads <NUM> are electrically connected to the fixed comb electrode <NUM> or the fixed comb electrode <NUM> via the device layer <NUM>. Several other electrode pads <NUM> among the plurality of electrode pads <NUM> are electrically connected to the movable comb electrode <NUM> or the movable comb electrode <NUM> via the first elastic support unit <NUM> or the second elastic support unit <NUM>. In addition, a pair of electrode pads <NUM> which can be used as ground electrodes are provided in the base <NUM>. The pair of electrode pads <NUM> are disposed on the first surface 21a to be located on both sides of the movable mirror <NUM> in the Y-axis direction.

A configuration of the periphery of the electrode pads <NUM> will be described with reference to <FIG>. Hereinafter, description will be made with reference to one electrode pad <NUM>, but other electrode pads <NUM> also have the same configuration. As illustrated in <FIG>, each of the electrode pads <NUM> is disposed on a surface 102a of the device layer <NUM> on one side in the Z-axis direction in an opening <NUM> formed in a surface 101a of the support layer <NUM> on one side in the Z-axis direction to reach the device layer <NUM>.

The opening <NUM> includes a bottom surface <NUM> constituted by the surface 102a, and a lateral surface <NUM> constituted by the support layer <NUM> and the intermediate layer <NUM>. For example, the bottom surface <NUM> has a rectangular shape. The lateral surface <NUM> includes a first surface 215a that extends continuously from the bottom surface <NUM> and approximately vertically to the bottom surface <NUM>, a stepped surface 215b that extends continuously from the first surface 215a and in approximately parallel to the bottom surface <NUM>, and a second surface 215c that extends continuously from the stepped surface 215b and approximately vertically to the bottom surface <NUM>. The stepped surface 215b extends in an annular shape along an edge of the opening <NUM> when viewed from the Z-axis direction.

The electrode pad <NUM> is disposed along an entire surface of the bottom surface <NUM>. In addition, the electrode pad <NUM> extends along the bottom surface <NUM> and the lateral surface <NUM>. More specifically, the electrode pad <NUM> is formed so that the electrode pad <NUM> reaches the first surface 215a of the lateral surface <NUM> and does not reach the stepped surface 215b of the lateral surface <NUM>. For example, the electrode pad <NUM> is constituted by a metal film (metal layer). For example, the metal film is formed by sputtering using a hard mask. The metal film that constitutes the electrode pad <NUM> is thicker than a metal film that constitutes the mirror surface 22a.

The base <NUM> includes a groove <NUM> that is formed in the surface 101a of the support layer <NUM> to reach the device layer <NUM>. The groove <NUM> extends in an annular shape to surround the opening <NUM> when viewed from the Z-axis direction. For example, the groove <NUM> has a rectangular shape when viewed from the Z-axis direction. Because the groove <NUM> is formed, it is possible to reliably electrically insulate the electrode pads <NUM> from each other. That is, as in this embodiment, in a case where the metal film that constitutes the electrode pad <NUM> is formed to reach the lateral surface <NUM>, and the electrode pad <NUM> is in contact with the support layer <NUM>, there is a concern that the electrode pads <NUM> may be electrically connected to each other through the support layer <NUM>. In contrast, in the mirror device <NUM>, because the groove <NUM> is provided, even in the above-described case, it is possible to reliably electrically insulate the electrode pads <NUM> from each other.

In the mirror device <NUM> configured as described above, an electric signal for moving the movable mirror <NUM> in the Z-axis direction, is input to the drive unit <NUM> through a lead pin <NUM> to be described later and a wire (not illustrated). Accordingly, for example, an electrostatic force is generated between the fixed comb electrode <NUM> and the movable comb electrode <NUM> which face each other, and the fixed comb electrode <NUM> and the movable comb electrode <NUM> which face each other so that the movable mirror <NUM> moves to one side in the Z-axis direction. At this time, the first torsion bars <NUM> and <NUM> and the second torsion bars <NUM> and <NUM> in the first elastic support unit <NUM> and the second elastic support unit <NUM> are twisted, and an elastic force is generated in the first elastic support unit <NUM> and the second elastic support unit <NUM>. In the mirror device <NUM>, when a periodic electric signal is applied to the drive unit <NUM>, it is possible to reciprocate the movable mirror <NUM> in the Z-axis direction at a resonance frequency level. In this manner, the drive unit <NUM> functions as an electrostatic actuator.

As illustrated in <FIG>, <FIG>, <FIG>, and <FIG>, the optical function member <NUM> includes the third surface 13a (a surface on the one side in the Z-axis direction) that faces the second surface 21b of the base <NUM>, and a fourth surface 13b opposite to the third surface 13a. The optical function member <NUM> is disposed on the other side in the Z-axis direction with respect to the mirror device <NUM>. When viewed from the Z-axis direction, an outer edge 13c of the optical function member <NUM> is located outside of an outer edge 21c of the base <NUM>. That is, when viewed from the Z-axis direction, the outer edge 13c of the optical function member <NUM> surrounds the outer edge 21c of the base <NUM>. The optical function member <NUM> is integrally formed by a material having transparency with respect to the measurement light L0 and the laser light L10. For example, the optical function member <NUM> is formed in a rectangular plate shape by glass, and has a size of approximately <NUM> × <NUM> × <NUM> (thickness). For example, the material of the optical function member <NUM> is selected in accordance with a sensitivity wavelength of the optical module <NUM>. For example, the material is set to glass in a case where the sensitivity wavelength of the optical module <NUM> is a near infrared region, and the material is set to silicon in a case where the sensitivity wavelength of the optical module <NUM> is an intermediate infrared region.

A pair of light transmitting portions <NUM> and <NUM> are provided in the optical function member <NUM>. The light transmitting portion <NUM> is a portion, which faces the light passage opening <NUM> of the mirror device <NUM> in the Z-axis direction, in the optical function member <NUM>. The light transmitting portion <NUM> is a portion, which faces the light passage opening <NUM> of the mirror device <NUM> in the Z-axis direction, in the optical function member <NUM>. A surface 14a of the light transmitting portion <NUM> on the mirror device <NUM> side, and a surface 15a of the light transmitting portion <NUM> on the mirror device <NUM> side are located on the same plane as the third surface 13a. The light transmitting portion (second light passage portion) <NUM> constitutes a second portion (partial portion) of an optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>. The light transmitting portion <NUM> is a portion that corrects an optical path difference that occurs between an optical path between the beam splitter unit <NUM> and the movable mirror <NUM>, and an optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>. In this embodiment, the light transmitting portion <NUM> does not function as a light transmitting portion.

The optical function member <NUM> includes a fifth surface 13d that faces the movable mirror <NUM> and the drive unit <NUM> of the mirror device <NUM>. The fifth surface 13d is located on the fourth surface 13b side in comparison to the third surface 13a. The fifth surface 13d extends to the outer edge 13c of the optical function member <NUM> when viewed from the Z-axis direction. In this embodiment, the fifth surface 13d extends to a pair of opposite sides which extend in the Y-axis direction in the outer edge 13c of the optical function member <NUM> while surrounding ends of the respective light transmitting portions <NUM> and <NUM> on the mirror device <NUM> side.

The third surface 13a of the optical function member <NUM> is joined to the second surface 21b of the base <NUM> by direct bonding (for example, plasma activation bonding, surface-activated room-temperature bonding (SAB), atomic diffusion bonding (ADB), anodic bonding, fusion bonding, hydrophilic bonding, and the like). In this embodiment, the third surface 13a extends to face a plurality of the electrode pads <NUM> and <NUM> provided in the base <NUM> on both sides of the fifth surface 13d in the Y-axis direction. Here, the fifth surface 13d is located on the fourth surface 13b side in comparison to the third surface 13a, and thus the fifth surface 13d is separated from the mirror device <NUM> in a region where the fifth surface 13d faces the movable mirror <NUM> and the drive unit <NUM>. In addition, the surface 14a of the light transmitting portion <NUM> and the surface 15a of the light transmitting portion <NUM> respectively face the light passage openings <NUM> and <NUM> of the mirror device <NUM>. Accordingly, in the mirror unit <NUM>, when the movable mirror <NUM> reciprocates in the Z-axis direction, the movable mirror <NUM> and the drive unit <NUM> are prevented from coming into contact with the optical function member <NUM>.

A sixth surface 21d, which is separated from the optical function member <NUM> in a state in which the third surface 13a of the optical function member <NUM> and the second surface 21b of the base <NUM> are joined to each other, is provided in the base <NUM> of the mirror device <NUM>. The sixth surface 21d is separated from the optical function member <NUM> in a region that includes at least a part of an outer edge of the base <NUM> when viewed from the Z-axis direction. In this embodiment, the sixth surface 21d is formed by removing the device layer <NUM> and the intermediate layer <NUM> along one side, which extends in the Y-axis direction, in the outer edge of the base <NUM> by etching. In addition, a plurality of reference holes 13e are formed in the third surface 13a of the optical function member <NUM>. In this embodiment, the plurality of reference holes 13e are formed in the third surface 13a to correspond to a plurality of corners of the base <NUM>. When the third surface 13a of the optical function member <NUM> and the second surface 21b of the base <NUM> are joined to each other, handling of the mirror device <NUM> is performed in a state in which a portion of the base <NUM> which corresponds to the sixth surface 21d is gripped, and thus a position of the mirror device <NUM> in the X-axis direction and the Y-axis direction, and an angle of the mirror device <NUM> in a horizontal plane perpendicular to the Z-axis direction are adjusted based on of the plurality of reference holes 13e formed in the third surface 13a.

As illustrated in <FIG> and <FIG>, the fixed mirror <NUM> is disposed on the other side (side opposite to the mirror device <NUM>) in the Z-axis direction with respect to the optical function member <NUM>, and a position of the mirror device <NUM> with respect to the base <NUM> is fixed. For example, the fixed mirror <NUM> is formed on the fourth surface 13b of the optical function member <NUM> by vapor deposition. The fixed mirror <NUM> includes a mirror surface 16a perpendicular to the Z-axis direction. In this embodiment, the mirror surface 22a of the movable mirror <NUM>, and the mirror surface 16a of the fixed mirror <NUM> face one side (beam splitter unit <NUM> side) in the Z-axis direction. The fixed mirror <NUM> is formed continuously with the fourth surface 13b of the optical function member <NUM> to reflect light that is transmitted through the respective light transmitting portions <NUM> and <NUM> of the optical function member <NUM>. However, a fixed mirror that reflects light transmitted through the light transmitting portion <NUM>, and a fixed mirror that reflects light transmitted through the light transmitting portion <NUM> may be provided, respectively.

The stress mitigation substrate <NUM> is attached to the fourth surface 13b of the optical function member <NUM> via the fixed mirror <NUM>. For example, the stress mitigation substrate <NUM> is attached to the fixed mirror <NUM>, for example, by an adhesive. When viewed from the Z-axis direction, an outer edge of the stress mitigation substrate <NUM> is located outside of the outer edge 13c of the optical function member <NUM>. That is, when viewed from the Z-axis direction, the outer edge of the stress mitigation substrate <NUM> surrounds the outer edge 13c of the optical function member <NUM>. A thermal expansion coefficient of the stress mitigation substrate <NUM> is closer to a thermal expansion coefficient of the base <NUM> of the mirror device <NUM> (more specifically, a thermal expansion coefficient of the support layer <NUM>) in comparison to a thermal expansion coefficient of the optical function member <NUM>. In addition, the thickness of the stress mitigation substrate <NUM> is closer to the thickness of the base <NUM> of the mirror device <NUM> in comparison to the thickness of the optical function member <NUM>. For example, the stress mitigation substrate <NUM> is formed in a rectangular plate shape by silicon, and has a size of approximately <NUM> × <NUM> × <NUM> (thickness).

As illustrated in <FIG>, the mirror unit <NUM> configured as described above is attached to the support <NUM> by fixing a surface of the stress mitigation substrate <NUM> on a side opposite to the optical function member <NUM> to a surface 9a of the support <NUM> (surface on the one side in the Z-axis direction), for example, by an adhesive. When the mirror unit <NUM> is attached to the support <NUM>, as illustrated in <FIG>, a position of the mirror device <NUM> in the X-axis direction and the Y-axis direction and an angle of the mirror device <NUM> in a horizontal plane perpendicular to the Z-axis direction are adjusted based on a reference hole 9b that is formed in the support <NUM>. In <FIG>, the second support structure <NUM> is not illustrated.

As illustrated in <FIG> and <FIG>, the first support structure <NUM> includes a frame body <NUM>, a light transmitting member <NUM>, and a plurality of lead pins <NUM>. The frame body <NUM> is formed so as to surround the mirror unit <NUM> when viewed from the Z-axis direction, and is attached to the surface 9a of the support <NUM>, for example, by an adhesive such as silver solder. For example, the frame body <NUM> is formed of ceramic, and has a rectangular frame shape. An end surface 111a of the frame body <NUM> on a side opposite to the support <NUM> is located on a side opposite to the support <NUM> in comparison to the first surface 21a of the base <NUM> of the mirror device <NUM>.

The light transmitting member <NUM> is formed so as to close an opening of the frame body <NUM>, and is attached to the end surface 111a of the frame body <NUM>, for example, with an adhesive. The light transmitting member <NUM> is formed of a material having transparency with respect to the measurement light L0 and the laser light L10, and has a rectangular plate shape for example. Here, the end surface 111a of the frame body <NUM> is located on a side opposite to the support <NUM> in comparison to the first surface 21a of the base <NUM> of the mirror device <NUM>, and thus the light transmitting member <NUM> is separated from the mirror device <NUM>. Accordingly, in the optical module <NUM>, when the movable mirror <NUM> reciprocates in the Z-axis direction, the movable mirror <NUM> and the drive unit <NUM> are prevented from coming into contact with the light transmitting member <NUM>. In the optical module <NUM>, the support <NUM>, the frame body <NUM>, and the light transmitting member <NUM> constitute a package that accommodates the mirror unit <NUM>.

The respective lead pins <NUM> are provided in the frame body <NUM> in such a manner that one end 113a is located inside of the frame body <NUM>, and the other end (not illustrated) is located outside of the frame body <NUM>. The one ends 113a of the lead pins <NUM> are electrically connected to the electrode pads <NUM> and <NUM> corresponding to the lead pins <NUM> in the mirror device <NUM> by wires (not illustrated). In the optical module <NUM>, an electric signal for moving the movable mirror <NUM> in the Z-axis direction is input to the drive unit <NUM> through the plurality of lead pins <NUM>. In this embodiment, a stepped surface 111b that extends in the X-axis direction on both sides of the optical function member <NUM> in the Y-axis direction is formed in the frame body <NUM>, and one end 113a of each of the lead pins <NUM> is disposed on the stepped surface 111b. The lead pin <NUM> extends in the Z-axis direction on both sides of the support <NUM> in the Y-axis direction, and the other end of the lead pin <NUM> is located on the other side in the Z-axis direction in comparison to the support <NUM>.

As illustrated in <FIG>, the beam splitter unit <NUM> is attached to a surface 112a of the light transmitting member <NUM> on a side opposite to the mirror device <NUM>, for example, by an optical adhesive that also functions as a refractive index matching agent. The beam splitter unit <NUM> includes a first mirror surface <NUM>, a second mirror surface <NUM>, and a plurality of optical surfaces 33a, 33b, 33c, and 33d. The beam splitter unit <NUM> is constituted by joining a plurality of optical blocks <NUM> and <NUM>. The respective optical blocks <NUM> and <NUM> are formed of a material having a refractive index that is the same as or similar to that of the optical function member <NUM>. <FIG> is a schematic cross-sectional view of the mirror unit <NUM> and the beam splitter unit <NUM> illustrated in <FIG>, and in <FIG>, the mirror device <NUM> is schematically illustrated, for example, in a state in which dimensions in the Z-axis direction are enlarged in comparison to actual dimensions.

The first mirror surface <NUM> is a mirror surface (for example, a half mirror surface) that is inclined with respect to the Z-axis direction, and is formed between the optical block <NUM> and the optical block <NUM>. In this embodiment, the first mirror surface <NUM> is a surface that is parallel to the Y-axis direction, has an angle of <NUM>° with respect to the Z-axis direction, and is inclined to be spaced away from the light incident unit <NUM> as it approaches the mirror device <NUM>. The first mirror surface <NUM> has a function of reflecting a part of the measurement light L0 and allowing the remainder of the measurement light L0 to be transmitted therethrough, and a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough. For example, the first mirror surface <NUM> is formed of a dielectric multi-layer film. The first mirror surface <NUM> overlaps the light passage opening <NUM> of the mirror device <NUM>, the light transmitting portion <NUM> of the optical function member <NUM>, and the mirror surface 16a of the fixed mirror <NUM> when viewed from the Z-axis direction, and overlaps the light incident unit <NUM> when viewed form the X-axis direction (refer to <FIG>). That is, the first mirror surface <NUM> faces the fixed mirror <NUM> in the Z-axis direction, and faces the light incident unit <NUM> in the X-axis direction.

The second mirror surface <NUM> is a mirror surface (for example, a total reflection mirror surface) that is parallel to the first mirror surface <NUM>, and is formed in the optical block <NUM> to be located on a side opposite to the light incident unit <NUM> with respect to the first mirror surface <NUM>. The second mirror surface <NUM> has a function of reflecting the measurement light L0 and a function of reflecting the laser light L10. For example, the second mirror surface <NUM> is formed of a metal film. The second mirror surface <NUM> overlaps the mirror surface 22a of the movable mirror <NUM> of the mirror device <NUM> when viewed from the Z-axis direction, and overlaps the first mirror surface <NUM> when viewed from the X-axis direction. That is, the second mirror surface <NUM> faces the movable mirror <NUM> in the Z-axis direction, and faces the first mirror surface <NUM> in the X-axis direction.

The optical surface 33a is a surface perpendicular to the Z-axis direction, and is formed in the optical block <NUM> to be located on a side opposite to the mirror device <NUM> with respect to the first mirror surface <NUM>. The optical surface 33b is a surface perpendicular to the Z-axis direction, and is formed in the optical block <NUM> to be located on the mirror device <NUM> side with respect to the second mirror surface <NUM>. The optical surface 33c is a surface perpendicular to the Z-axis direction, and is formed in the optical block <NUM> to be located on the mirror device <NUM> side with respect to the first mirror surface <NUM>. The optical surface 33b and the optical surface 33c are located on the same plane. The optical surface 33d is a surface perpendicular to the X-axis direction, and is formed in the optical block <NUM> to be located on the light incident unit <NUM> side with respect to the first mirror surface <NUM>. The respective optical surfaces 33a, 33b, 33c, and 33d have a function of allowing the measurement light L0 to be transmitted therethrough, and a function of allowing the laser light L10 to be transmitted therethrough.

The beam splitter unit <NUM> configured as described above is attached to the light transmitting member <NUM> by fixing the optical surface 33b and the optical surface 33c which are located on the same plane to the surface 112a of the light transmitting member <NUM>, for example, by an optical adhesive. When the beam splitter unit <NUM> is attached to the light transmitting member <NUM>, as illustrated in <FIG>, a position of the beam splitter unit <NUM> in the X-axis direction and the Y-axis direction, and an angle of the beam splitter unit <NUM> in a horizontal plane perpendicular to the Z-axis direction are adjusted based on the reference hole 9b formed in the support <NUM>. In <FIG>, the second support structure <NUM> is not illustrated.

Here, the optical path of the measurement light L0 and the optical path of the laser light L10 in the mirror unit <NUM> and the beam splitter unit <NUM> will be described in detail with reference to <FIG>.

As illustrated in <FIG>, when the measurement light L0 is incident to the beam splitter unit <NUM> in the X-axis direction through the optical surface 33d, a part of the measurement light L0 is transmitted through the first mirror surface <NUM>, is reflected by the second mirror surface <NUM>, and reaches the mirror surface 22a of the movable mirror <NUM> through the optical surface 33b and the light transmitting member <NUM>. The part of the measurement light L0 is reflected by the mirror surface 22a of the movable mirror <NUM>, and proceeds on the same optical path P1 in an opposite direction, and is reflected by the first mirror surface <NUM>. The remainder of the measurement light L0 is reflected by the first mirror surface <NUM>, and reaches the mirror surface 16a of the fixed mirror <NUM> through the optical surface 33c, the light transmitting member <NUM>, the light passage opening <NUM> of the mirror device <NUM>, and the light transmitting portion <NUM> of the optical function member <NUM>. The remainder of the measurement light L0 is reflected by the mirror surface 16a of the fixed mirror <NUM>, proceeds on the same optical path P2 in an opposite direction, and is transmitted through the first mirror surface <NUM>. The part of the measurement light L0 which is reflected by the first mirror surface <NUM>, and the remainder of the measurement light L0 which is transmitted through the first mirror surface <NUM> become interference light L1, and the interference light L1 of the measurement light is emitted from the beam splitter unit <NUM> through the optical surface 33a along the Z-axis direction.

On the other hand, when the laser light L10 is incident to the beam splitter unit <NUM> in the Z-axis direction through the optical surface 33a, a part of the laser light L10 is reflected by the first mirror surface <NUM> and the second mirror surface <NUM>, and reaches the mirror surface 22a of the movable mirror <NUM> through the optical surface 33b and the light transmitting member <NUM>. The part of the laser light L10 is reflected by the mirror surface 22a of the movable mirror <NUM>, proceeds on the same optical path P3 in an opposite direction, and is reflected by the first mirror surface <NUM>. The remainder of the laser light L10 is transmitted through the first mirror surface <NUM>, and reaches the mirror surface 16a of the fixed mirror <NUM> through the optical surface 33c, the light transmitting member <NUM>, the light passage opening <NUM> of the mirror device <NUM>, and the light transmitting portion <NUM> of the optical function member <NUM>. The remainder of the laser light L10 is reflected by the mirror surface 16a of the fixed mirror <NUM>, proceeds on the same optical path P4 in an opposite direction, and is transmitted through the first mirror surface <NUM>. The part of the laser light L10 which is reflected by the first mirror surface <NUM>, and the remainder of the laser light L10 which is transmitted through the first mirror surface <NUM> become interference light L11, and the interference light L11 of the laser light is emitted from the beam splitter unit <NUM> through the optical surface 33a along the Z-axis direction.

As described above, the light passage opening <NUM> of the mirror device <NUM> constitutes a first portion P2a of the optical path P2 of the measurement light L0 and a first portion P4a of the optical path P4 of the laser light L10 in an optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>. In addition, the light transmitting portion <NUM> of the optical function member <NUM> constitutes a second portion P2b of the optical path P2 of the measurement light L0 and a second portion P4b of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>.

The second portion P2b of the optical path P2 of the measurement light <NUM> is constituted by the light transmitting portion <NUM>, thus an optical path difference between both the optical paths P1 and P2 is corrected so that a difference between an optical path length (optical path length in consideration of a refractive index of respective media through which the optical path passes) of the optical path P1 of the measurement light L0, and an optical path length of the optical path P2 of the measurement light L0 decreases. Similarly, the second portion P4b of the optical path P4 of the laser light L10 is constituted by the light transmitting portion <NUM>, thus an optical path difference between both the optical paths P3 and P4 is corrected so that a difference between an optical path length of the optical path P3 of the laser light L10 and an optical path length of the optical path P4 of the laser light L10 decreases. In this embodiment, a refractive index of the light transmitting portion <NUM> is the same as a refractive index of the respective optical blocks which constitute the beam splitter unit <NUM>, and a distance between the first mirror surface <NUM> and the second mirror surface <NUM> in the X-axis direction is the same as the thickness of the light transmitting portion <NUM> in the Z-axis direction (that is, a distance between the surface 14a of the light transmitting portion <NUM> and the fourth surface 13b of the optical function member <NUM> in the Z-axis direction).

As illustrated in <FIG>, the second support structure <NUM> includes a connection unit <NUM>. The connection unit <NUM> includes a main body portion <NUM>, a frame body <NUM>, and a fixing plate <NUM>. The main body portion <NUM> includes a pair of side wall portions <NUM> and <NUM>, and a ceiling wall portion <NUM>. The pair of side wall portions <NUM> and <NUM> face each other in the X-axis direction. An opening 124a is formed in the side wall portion <NUM> on one side in the X-axis direction. The ceiling wall portion <NUM> faces the support <NUM> in the Z-axis direction. An opening 126a is formed in the ceiling wall portion <NUM>. For example, the main body portion <NUM> is integrally formed of a metal. A plurality of positioning pins 121a are provided in the main body portion <NUM>. The main body portion <NUM> is positioned with respect to the support <NUM> by inserting the positioning pins 121a into the reference hole 9b and the hole 9c which are formed in the support <NUM>, and is attached to the support <NUM> in this state, for example, by a bolt.

The frame body <NUM> is disposed on a surface of the side wall portion <NUM> on a side opposite to the beam splitter unit <NUM>. An opening of the frame body <NUM> faces the beam splitter unit <NUM> through the opening 124a of the side wall portion <NUM>. The light incident unit <NUM> is disposed in the frame body <NUM>. The fixing plate <NUM> is a member that fixes the light incident unit <NUM> disposed in the frame body <NUM> to the main body portion <NUM> (details will be described later).

The second support structure <NUM> further includes a holding unit <NUM>. The holding unit <NUM> includes a main body portion <NUM>, a frame body <NUM> and a fixing plate <NUM>. The main body portion <NUM> is attached to a surface of the ceiling wall portion <NUM> which is opposite to the support <NUM>. The main body portion <NUM> is positioned with respect to the main body portion <NUM> of the connection unit <NUM> by a plurality of positioning pins 131a, and is attached to the ceiling wall portion <NUM> in this state, for example, by a bolt. A concave portion <NUM> is formed in a surface of the main body portion <NUM> which is opposite to the support <NUM>. A first light passage hole <NUM>, a second light passage hole <NUM>, and a third light passage hole <NUM> are formed in a bottom surface of the concave portion <NUM>. The first light passage hole <NUM> is formed at a position that faces the first mirror surface <NUM> of the beam splitter unit <NUM> in the Z-axis direction. The second light passage hole <NUM> is formed on the other side of the first light passage hole <NUM> in the X-axis direction (that is, on a side opposite to the light incident unit <NUM>). The third light passage hole <NUM> is formed on the other side of the second light passage hole <NUM> in the X-axis direction.

The frame body <NUM> is disposed on the bottom surface of the concave portion <NUM>. An opening of the frame body <NUM> faces the third light passage hole <NUM>. The second light source <NUM> is disposed in the frame body <NUM>. The first light detector <NUM> is disposed on the bottom surface of the concave portion <NUM> in a state of facing the first light passage hole <NUM>. The second light detector <NUM> is disposed on the bottom surface of the concave portion <NUM> in a state of facing the second light passage hole <NUM>. The fixing plate <NUM> is a member that fixes the first light detector <NUM> and the second light detector <NUM> which are disposed on the bottom surface of the concave portion <NUM>, and the second light source <NUM> that is disposed in the frame body <NUM> to the main body portion <NUM> (details will be described later).

The light incident unit <NUM> includes a holder <NUM> and a collimator lens <NUM>. The holder <NUM> holds the collimator lens <NUM>, and is configured so that an optical fiber (not illustrated) that guides the measurement light L0 can be connected to the holder <NUM>. The collimator lens <NUM> collimates the measurement light L0 emitted from the optical fiber. When the optical fiber is connected to the holder <NUM>, an optical axis of the optical fiber matches an optical axis of the collimator lens <NUM>.

A flange portion 41a is provided in the holder <NUM>. The flange portion 41a is disposed between the frame body <NUM> and the fixing plate <NUM>. In this state, fixing plate <NUM> is attached to the side wall portion <NUM>, for example, by a bolt, and the light incident unit <NUM> disposed in the frame body <NUM> is fixed to the main body portion <NUM>. In this manner, the light incident unit <NUM> is disposed on one side of the beam splitter unit <NUM> in the X-axis direction, and is supported by the second support structure <NUM>. The light incident unit <NUM> allows measurement light L0 that is incident from the first light source through a measurement target or measurement light L0 that is generated from the measurement target (in this embodiment, the measurement light L0 guided by the optical fiber) to be incident to the beam splitter unit <NUM>.

A filter <NUM> is attached to the frame body <NUM>. The filter <NUM> has a function of cutting off the laser light L10. The filter <NUM> is disposed in the opening 124a of the side wall portion <NUM> in a state of being inclined with respect to an optical axis of the light incident unit <NUM>. The filter <NUM> closes the opening of the frame body <NUM> when viewed form the X-axis direction. In this manner, the filter <NUM> is disposed between the light incident unit <NUM> and the beam splitter unit <NUM>, and is supported by the second support structure <NUM> in a state of being inclined with respect to an optical axis of the light incident unit <NUM>. In this embodiment, an optical surface of the filter <NUM> is a surface that is parallel to the Z-axis direction and has an angle of <NUM>° to <NUM>° with respect to the Y-axis direction. The optical axis of the light incident unit <NUM> is parallel to the X-axis direction.

Accordingly, even when light in the same wavelength range as the laser light L10 is included in the measurement light L0, the light is prevented from being incident to the beam splitter unit <NUM>, and thus it is possible to obtain a position of the movable mirror <NUM> in the Z-axis direction with accuracy based on a detection result of the interference light L11 of the laser light. In addition, because the filter <NUM> is inclined with respect to the optical axis of the light incident unit <NUM>, light in the same wavelength range as the laser light L10 is reflected to the outside of an interference optical system, and thus it is possible to reliably prevent the light from being stray light. In this embodiment, light in the same wavelength range as the laser light L10 emitted from the beam splitter unit <NUM> in the X-axis direction is reflected by the filter <NUM>, and is emitted to the outside of the interference optical system from between the pair of side wall portions <NUM> and <NUM> in the main body portion <NUM> of the second support structure <NUM>. Accordingly, it is possible to reliably prevent the light from being stray light.

The first light detector <NUM> includes a holder <NUM>, a light detection element <NUM>, and a condensing lens <NUM>. The holder <NUM> holds the light detection element <NUM> and the condensing lens <NUM>. The light detection element <NUM> detects the interference light L1 of the measurement light. For example, the light detection element <NUM> is an InGaAs photodiode. The condensing lens <NUM> condenses the interference light L1 of the measurement light incident to the light detection element <NUM> to the light detection element <NUM>. In the holder <NUM>, an optical axis of the light detection element <NUM> and an optical axis of the condensing lens <NUM> match each other.

A flange portion 61a is provided in the holder <NUM>. The flange portion 61a is disposed between the bottom surface of the concave portion <NUM> of the main body portion <NUM>, and the fixing plate <NUM>. In this state, the fixing plate <NUM> is attached to the main body portion <NUM>, for example, by a bolt, and thus the first light detector <NUM> disposed on the bottom surface of the concave portion <NUM> is fixed to the main body portion <NUM>. In this manner, the first light detector <NUM> is disposed on one side of the beam splitter unit <NUM> in the Z-axis direction, and is supported by the second support structure <NUM>. The first light detector <NUM> faces the first mirror surface <NUM> of the beam splitter unit <NUM> in the Z-axis direction. The first light detector <NUM> detects the interference light L1 of the measurement light emitted from the beam splitter unit <NUM>.

The second light detector <NUM> includes a holder <NUM>, a light detection element <NUM>, and a condensing lens <NUM>. The holder <NUM> holds the light detection element <NUM> and the condensing lens <NUM>. The light detection element <NUM> detects the interference light L11 of the laser light. For example, the light detection element <NUM> is a Si photodiode. The condensing lens <NUM> condenses the interference light L11 of the laser light incident to the light detection element <NUM> to the light detection element <NUM>. In the holder <NUM>, an optical axis of the light detection element <NUM> and an optical axis of the condensing lens <NUM> match each other.

A flange portion 81a is provided in the holder <NUM>. The flange portion 81a is disposed between the bottom surface of the concave portion <NUM> of the main body portion <NUM>, and the fixing plate <NUM>. In this state, the fixing plate <NUM> is attached to the main body portion <NUM>, for example, by a bolt, and thus the second light detector <NUM> disposed on the bottom surface of the concave portion <NUM> is fixed to the main body portion <NUM>. In this manner, the second light detector <NUM> is disposed on one side of the beam splitter unit <NUM> in the Z-axis direction, and is supported by the second support structure <NUM>. The second light detector <NUM> detects the interference light L11 of the laser light emitted from the beam splitter unit <NUM>.

The second light source <NUM> includes a holder <NUM>, a light-emitting element <NUM>, and a collimator lens <NUM>. The holder <NUM> holds the light-emitting element <NUM> and the collimator lens <NUM>. The light-emitting element <NUM> emits the laser light L10. For example, the light-emitting element <NUM> is a semiconductor laser such as a VCSEL. The collimator lens <NUM> collimates the laser light L10 emitted from the light-emitting element <NUM>. In the holder <NUM>, an optical axis of the light-emitting element <NUM> and an optical axis of the collimator lens <NUM> match each other.

A flange portion 71a is provided in the holder <NUM>. The flange portion 71a is disposed between the frame body <NUM> and the fixing plate <NUM>. In this state, the fixing plate <NUM> is attached to the main body portion <NUM>, for example, by a bolt, and thus the second light source <NUM> disposed in the frame body <NUM> is fixed to the main body portion <NUM>. In this manner, the second light source <NUM> is disposed on one side of the beam splitter unit <NUM> in the Z-axis direction, and is supported by the second support structure <NUM>. The second light source <NUM> emits the laser light L10 that is to be incident to the beam splitter unit <NUM>.

As described above, the holding unit <NUM> holds the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> so that the first light detector (first optical device) <NUM>, the second light detector (second optical device) <NUM>, and the second light source (third optical device) <NUM> face the same side, and the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> are aligned in this order. In this embodiment, on one side of the beam splitter unit <NUM> in the Z-axis direction, the holding unit <NUM> holds the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> so that the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> face the other side in the Z-axis direction (that is, the beam splitter unit <NUM> side). In addition, the holding unit <NUM> holds the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> so that the first light detector <NUM>, the second light detector <NUM>, and the second light source <NUM> are aligned in this order from one side (that is, the light incident unit <NUM> side) in the X-axis direction.

A first mirror <NUM>, a second mirror <NUM>, and a third mirror <NUM> are attached to the main body portion <NUM> of the holding unit <NUM>. The first mirror <NUM> is held by the holding unit <NUM> to be located on a side opposite to the first light detector <NUM> with respect to the first light passage hole <NUM>. The second mirror <NUM> is held by the holding unit <NUM> to be located on a side opposite to the second light detector <NUM> with respect to the second light passage hole <NUM>. The third mirror <NUM> is held by the holding unit <NUM> to be located on a side opposite to the second light source <NUM> with respect to the third light passage hole <NUM>.

The first mirror <NUM> is a dichroic mirror that has a function of allowing the measurement light L0 to be transmitted therethrough and of reflecting the laser light L10, and is inclined with respect to the optical axis of the first light detector <NUM>. The first mirror <NUM> is disposed between the beam splitter unit <NUM> and the first light detector <NUM>. That is, the first mirror <NUM> is disposed to face the beam splitter unit <NUM> and the first light detector <NUM>. In this embodiment, an optical surface of the first mirror <NUM> is a surface that is parallel to the Y-axis direction and has an angle of <NUM>° with respect to the Z-axis direction. The optical axis of the first light detector <NUM> is parallel to the Z-axis direction.

The second mirror <NUM> is a mirror (for example, a half mirror) that has a function of reflecting a part of the laser light L10 and allowing the remainder of the laser light L10 to be transmitted therethrough, and is parallel to the first mirror <NUM>. The second mirror <NUM> is disposed to overlap the first mirror <NUM> when viewed from the X-axis direction, and to overlap the second light detector <NUM> when viewed from the Z-axis direction. That is, the second mirror <NUM> is disposed to face the first mirror <NUM> and the second light detector <NUM>. In this embodiment, an optical surface of the second mirror <NUM> is a surface that is parallel to the Y-axis direction, and has an angle of <NUM>° with respect to the Z-axis direction.

The third mirror <NUM> is a mirror (for example, a total reflection mirror) that has a function of reflecting the laser light L10 and is parallel to the second mirror <NUM>. The third mirror <NUM> is disposed to overlap the second mirror <NUM> when viewed from the X-axis direction, and overlap the second light source <NUM> when viewed from the Z-axis direction. That is, the third mirror <NUM> is disposed to face the second mirror <NUM> and the second light source <NUM>. In this embodiment, an optical surface of the third mirror <NUM> is a surface that is parallel to the Y-axis direction, and has an angle of <NUM>° with respect to the Z-axis direction.

An aperture <NUM> is attached to the main body portion <NUM> of the holding unit <NUM>. The aperture <NUM> is held by the holding unit <NUM> to be located between the first mirror <NUM> and the first light detector <NUM>. The aperture <NUM> is a member in which an opening having a circular shape is formed when viewed from the Z-axis direction, and is disposed in the first light passage hole <NUM>.

The interference light L1 of the measurement light, which is emitted from the beam splitter unit <NUM> in the Z-axis direction, is transmitted through the first mirror <NUM>, is incident to the first light detector <NUM> through the aperture <NUM>, and is detected by the first light detector <NUM>. On the other hand, the laser light L10 emitted from the second light source <NUM> is reflected by the third mirror <NUM>, is transmitted through the second mirror <NUM>, is reflected by the first mirror <NUM>, and is incident to the beam splitter unit <NUM> in the Z-axis direction. The interference light L11 of the laser light, which is emitted from the beam splitter unit <NUM> in the Z-axis direction, is reflected by the first mirror <NUM> and the second mirror <NUM>, is incident to the second light detector <NUM>, and is detected by the second light detector <NUM>.

In the above-described mirror device <NUM>, the first surface 21a of the base <NUM> (a surface on one side in the Z-axis direction) is located more to the one side than the mirror surface 22a. Accordingly, it is possible to protect the mirror surface 22a by the base <NUM> and it is possible to prevent the mirror surface 22a from being damaged, for example, due to direct contact in transportation or the like. In addition, in the mirror device <NUM>, the support layer <NUM> that constitutes the base <NUM> is thicker than the device layer <NUM> that constitutes the base <NUM>. Accordingly, it is possible to secure a protrusion amount of the base <NUM> with respect to the mirror surface 22a, and it is possible to effectively protect the mirror surface 22a by the base <NUM>. Accordingly, according to the mirror device <NUM>, it is possible to enhance reliability. A "configuration in which the first surface 21a of the base <NUM> is located more to the one side than the mirror surface 22a" represents that "at least a part of the first surface 21a is located more to the one side than the mirror surface 22a". In the mirror device <NUM>, the entirety of the first surface 21a is located more to the one side in the Z-axis direction than the mirror surface 22a. In other words, the entirety of the mirror surface 22a is located more tothe other side in the Z-axis direction than the first surface 21a. In other words, the "surface of the base on the one side in the Z-axis direction" is an "end surface of the base on the one side in the Z-axis direction" or a "surface located on the most one side in the Z-axis direction among surfaces of the base".

End surfaces (end surfaces 224as, 224bs, and 224cs) of the rib portion <NUM> on one side in the Z-axis direction are located more to the one side than the mirror surface 22a. Accordingly, it is also possible to protect the mirror surface 22a by the rib portion <NUM>. In addition, it is also possible to suppress deformation of the movable unit 22b during movement by the rib portion <NUM>.

The rib portion <NUM> includes the inner rib portion 224a that is disposed on a surface on one side in the arrangement portion <NUM> to extend along an outer edge of the arrangement portion <NUM> when viewed from the Z-axis direction. Accordingly, the inner rib portion 224a is disposed to be closer to the mirror surface 22a, and thus it is possible to more effectively protect the mirror surface 22a. In addition, the inner rib portion 224a is disposed on the arrangement portion <NUM>, and thus it is possible to more appropriately suppress deformation of the arrangement portion <NUM>.

The rib portion <NUM> includes the outer rib portion 224b that is disposed on a surface on one side in the frame portion <NUM> to extend along the frame portion <NUM> when viewed from the Z-axis direction. Accordingly, it is possible to more effectively protect the mirror surface 22a due to the rib portion <NUM>. In addition, it is possible to suppress deformation of the frame portion <NUM> due to the outer rib portion 224b, and it is possible to suppress deformation of the arrangement portion <NUM> which is caused by deformation of the frame portion <NUM>.

The support layer <NUM> that constitutes the rib portion <NUM> is thinner than the support layer <NUM> that constitutes the base <NUM>. Accordingly, it is possible to suppress the rib portion <NUM> from protruding from the base <NUM> during movement of the movable unit 22b, and it is possible to increase a movement amount of the movable unit 22b in the Z-axis direction.

The groove <NUM> that reaches the device layer <NUM> from the surface 101a (surface on one side in the Z-axis direction) of the support layer <NUM> and extends to surround the opening <NUM> when viewed from the Z-axis direction is formed in the base <NUM>. Accordingly, it is possible to reliably secure an electrical insulation property of the electrode pads <NUM> due to the groove <NUM>, and it is possible to further enhance reliability.

The electrode pads <NUM> extend along the bottom surface <NUM> and the lateral surface <NUM> of the opening <NUM>. Accordingly, it is possible to increase an area of the electrode pads <NUM>. A metal layer that constitutes the electrode pads <NUM> is thicker than a metal layer that constitutes the mirror surface 22a. In this case, it is possible to suppress deformation of the mirror surface 22a, and it is possible to reliably secure electrical connection to the electrode pads <NUM>. That is, bending of the mirror surface 22a is suppressed, and thus it is preferable that the metal layer that constitutes the mirror surface 22a is thin. Because the metal layer that constitutes the electrode pads <NUM> is thick, it is possible to enhance bonding performance in a wire bonding process. If the electrode pads <NUM> are excessively thin, there is a concern that it is difficult to provide a wire or a sufficient adhesive force is not obtained, but in the mirror device <NUM>, it is possible to suppress the problem.

In the mirror unit <NUM>, it is possible to correct an optical path length difference that occurs between the optical path between the beam splitter unit <NUM> and the movable mirror <NUM>, and the optical path between the beam splitter unit <NUM> and the fixed mirror <NUM> due to the light transmitting portion <NUM> of the optical function member <NUM>. "Correction of the optical path length difference" represents reduction of a difference between an optical path length of the optical path between the beam splitter unit <NUM> and the movable mirror <NUM> (optical path length in consideration of a refractive index of respective media through which the optical path passes), and an optical path length of the optical path between the beam splitter unit <NUM> and the fixed mirror <NUM>. In addition, in the mirror unit <NUM>, for example, the mirror surface 22a is disposed to be closer to the optical function member <NUM> in comparison to a "configuration in which the mirror surface 22a is disposed on a surface of the device layer <NUM> which is opposite to the intermediate layer <NUM>, and the base <NUM> is joined to the third surface 13a of the optical function member <NUM> in a surface the support layer <NUM> which is opposite to the intermediate layer <NUM>". This configuration is particularly effective for a case where the optical path length difference is corrected by the light transmitting portion <NUM>. That is, for example, it is possible to align the reference position in the case of reciprocating the movable mirror <NUM> along the Z-axis direction to the third surface 13a of the optical function member <NUM> in an easy manner (in a small operation amount). Accordingly, it is possible to acquire sufficient optical interference signals while suppressing a reciprocation movement amount of the movable mirror <NUM> along the Z-axis direction.

In the above-described embodiment, materials and shapes of respective configurations are not limited to the above-described materials and shapes, and various materials and shapes can be employed. For example, each of the arrangement portion <NUM> and the mirror surface 22a may have any shape such as a rectangular shape and an octagonal shape when viewed from the Z-axis direction. The frame portion <NUM> may have any ring shape such as a rectangular ring shape and an octagonal ring shape when viewed from the Z-axis direction. Each of the light passage opening <NUM> and the light passage opening <NUM> may have any shape such as a circular shape and an octagonal shape when viewed from the Z-axis direction. The mirror device <NUM> may include a hole or a notch that is formed in the base <NUM> as a first light passage portion instead of the light passage opening <NUM> or the light passage opening <NUM>. The semiconductor substrate that constitutes the mirror device <NUM> may not be the SOI substrate, and may be a substrate including a first semiconductor layer, an insulating layer, and a second semiconductor layer in this order from one side in the Z-axis direction.

Each of the inner rib portion 224a, the outer rib portion 224b, and the connection rib portion 224c (beam portions) may be formed in any shape. For example, the rib portions may extend obliquely with respect to X-axis direction or the Y-axis direction, or may extend in a zigzag shape. The arrangement, the number, the length, the width, and the thickness of the rib portions may be arbitrarily set. For example, the thicknesses of the inner rib portion 224a, the outer rib portion 224b, and the connection rib portion 224c may be different from each other. At least one of the rib portions may be omitted. The rib portion <NUM> may do not surround the mirror surface 22a when viewed from the Z-axis direction. The thickness of the support layer <NUM> that constitutes the rib portion <NUM> may be the same as the thickness of the support layer <NUM> that constitutes the base <NUM>. The shape of the first torsion bars <NUM> and <NUM> and the second torsion bars <NUM> and <NUM> is not limited and may be any shape such as a rod shape. The electrode pads <NUM> may be disposed only on the bottom surface <NUM> of the opening <NUM>, and may do not reach the lateral surface <NUM>. In this case, the groove <NUM> may be omitted. The second surface 21b of the base <NUM> and the third surface 13a of the optical function member <NUM> may be joined to each other with means (for example, an adhesive such as a UV-curable resin) other than the direct bonding. In a case where the fixed mirror <NUM> is disposed on a side opposite to the mirror device <NUM> with respect to the optical function member <NUM>, the fixed mirror <NUM> may be separated from the fourth surface 13b of the optical function member <NUM>.

The optical device of the present disclosure is not limited to the mirror device, and may be an optical device in which another optical function unit other than the mirror surface 22a is disposed on the movable unit 22b. Examples of the other optical function unit include a lens and the like. The drive unit <NUM> of the mirror device <NUM> may include three or more elastic support portions which elastically support the movable mirror <NUM>. The actuator unit <NUM> is not limited to the electrostatic actuator, and may be, for example, a piezoelectric type actuator, an electromagnetic type actuator, or the like. In the above-described embodiment, the movement direction (predetermined direction) of the movable unit 22b is a direction perpendicular to the first surface 21a of the base <NUM>, but the movement direction may be any direction as long as the direction intersects the first surface 21a. The mirror device <NUM> is not limited to constitute the FTIR, and may constitute another optical system. The respective configurations in one embodiment or one modification example as described above can be arbitrarily applied to respective configurations in other embodiments or modification examples.

Claim 1:
An optical module (<NUM>) comprising a mirror unit (<NUM>) and a beam splitter unit (<NUM>);
the mirror unit (<NUM>) comprising:
an optical device (<NUM>) comprising:
a base (<NUM>) that includes a main surface (21a, 21b);
a movable unit (22b) that is supported in the base (<NUM>) to be movable along a predetermined direction (Z) that intersects the main surface (21a, 21b);
an actuator unit (<NUM>) for moving the movable unit (22b) along the predetermined direction (Z); and
an optical function unit (22a) that is disposed on the movable unit (22b),
wherein the base (<NUM>) and the movable unit (22b) are constituted by a semiconductor substrate that includes a first semiconductor layer (<NUM>), an insulating layer (<NUM>), and a second semiconductor layer (<NUM>) in this order from one side in the predetermined direction (Z),
the base (<NUM>) is constituted by the first semiconductor layer (<NUM>), the insulating layer (<NUM>), and the second semiconductor layer (<NUM>),
the movable unit (22b) includes an arrangement portion that is constituted by the second semiconductor layer (<NUM>),
the optical function unit (22a) is disposed on a surface of the arrangement portion on the one side,
the first semiconductor layer (<NUM>) that constitutes the base (<NUM>) is thicker than the second semiconductor layer (<NUM>) that constitutes the base (<NUM>), and
a surface of the base (<NUM>) on the one side is located over the optical function unit (22a) in the predetermined direction (Z);
the mirror unit (<NUM>) further comprising:
an optical function member (<NUM>) that is disposed on the other side in the predetermined direction (Z) with respect to the optical device (<NUM>), the optical function member (<NUM>) being transparent and having a plate shape; and
a fixed mirror (<NUM>) that is disposed on the other side, which is the side opposite to the optical device (<NUM>), in the Z-axis direction, with respect to the optical function member (<NUM>);
wherein the optical function unit (22a) is a mirror surface that constitutes a movable mirror in combination with the movable unit (22b); and
wherein the beam splitter unit (<NUM>) constitutes an interference optical system in combination with the movable mirror and the fixed mirror (<NUM>).