Optical deflector and electronic apparatus

Abstract

The present invention broadens the range in which capacitance changes linearly with respect to changes in the deflection angle of a movable mirror. This optical deflector comprises: a mirror having a reflecting surface; a drive unit (54) for causing the mirror to oscillate; a detection unit for detecting drive unit movement by changes in capacitance (Cv); and a frame supporting the mirror, the drive unit, and the detection unit. The detection unit comprises: a movable electrode (18b, 19b) having positions that fluctuate in relation to movement of the drive unit; and a fixed electrode (18a, 19a) unrelated to movement of the drive unit. The detection unit is configured so as to produce the capacitance between the movable electrode and the fixed electrode. The frame comprises: a support layer (51) and an active layer (53) that are each a semiconductor layer; and an insulating layer (52) that is interposed between the support layer and the active layer. The layer thickness of the support layer is greater than the layer thickness of the active layer. The movable electrode and the fixed electrode are each configured as part of the support layer. The active layer comprises a conductive section (20) for ensuring electrical connection between a site constituting the drive unit and the movable electrode.

Description

Optical deflector, electronic equipment

[0001] The present disclosure relates to an optical deflector and an electronic device.

[0002] Optical deflectors that scan incident laser light in two-dimensional directions are known. A conventional example of an optical deflector is described, for example, in International Publication No. 2022 / 259912 (Patent Document 1). In such optical deflectors, comb-shaped electrodes are provided in conjunction with a movable mirror, and the deflection angle of the movable mirror is detected by detecting positional changes of the comb-shaped electrodes as changes in capacitance. However, it has been difficult to expand the range over which the capacitance changes linearly with changes in the deflection angle of the movable mirror.

[0003] International Publication No. 2022 / 259912

[0004] One of the objectives of a specific aspect of the present disclosure is to provide a technology that can widen the range in which the capacitance changes linearly with respect to changes in the deflection angle of the movable mirror.

[0005] [1] An optical deflector according to one aspect of the present disclosure includes: a mirror having a reflective surface; a driver for oscillating the mirror; a detector for detecting the movement of the driver by a change in capacitance; and a frame supporting the mirror, the driver, and the detector, wherein the detector has a movable electrode whose position changes in response to the movement of the driver and a fixed electrode that is not affected by the movement of the driver, and is configured to generate the capacitance between the movable electrode and the fixed electrode, the frame has a support layer and an active layer, each of which is a semiconductor layer, and an insulating layer interposed between the support layer and the active layer, the support layer having a thickness greater than that of the active layer, the movable electrode and the fixed electrode each being configured as a part of the support layer, and the active layer having a conductive portion for electrically connecting a portion of the driver to the movable electrode. [2] An electronic device according to one aspect of the present disclosure is an electronic device equipped with the optical deflector according to [1].

[0006] According to the above configuration, it is possible to widen the range in which the capacitance changes linearly with respect to the change in the deflection angle of the movable mirror.

[0007] FIG. 1 is a plan view showing the configuration of an optical deflector (optical scanning device) according to an embodiment. FIG. 2 is a plan view showing the configuration of an optical deflector (optical scanning device) according to an embodiment. FIGS. 3A and 3B are enlarged views of the deflection angle detection unit and its vicinity. FIG. 4 is a schematic cross-sectional view illustrating the structure of the main parts of the optical deflector. FIG. 5A is a diagram showing an electrical circuit extending from an input pad for inputting a carrier wave to a detection GND pad via electrostatic capacitances Cs and Cv. FIG. 5B is a diagram showing a more detailed electrical circuit. FIGS. 6A to 6E are diagrams illustrating a method for forming a conductive portion. FIGS. 7A to 7D are diagrams illustrating another method for forming a conductive portion. FIG. 8A is an enlarged view of a crank-shaped cut portion. FIG. 8B is a cross-sectional view taken along line B-B in FIG. 8A, and FIG. 8C is a cross-sectional view taken along line C-C in FIG. 8A. Fig. 8(D) is a cross-sectional view of a cut portion of a comparative example. Figs. 9(A) and 9(B) are diagrams showing the results of calculation of the capacitance in the deflection angle detection unit of the optical deflector of the embodiment. Fig. 10 is a diagram for explaining the lengths of the fixed electrodes and the movable electrodes in the optical deflector of the embodiment.

[0008] 1 and 2 are plan views showing the configuration of an optical deflector (optical scanning device) 1 according to one embodiment. In this embodiment, the surface on which laser light to be scanned is incident is referred to as the front surface, and the surface opposite thereto is referred to as the back surface. Fig. 1 shows a plan view from the front surface side, and Fig. 2 shows a plan view from the back surface side. As shown in the figures, the optical deflector 1 according to this embodiment has a generally bilaterally symmetrical structure in a plan view.

[0009] The optical deflector 1 mainly comprises a reflecting unit 2, a torsion bar 3, an inner piezoelectric actuator 4, an inner frame 5, an outer piezoelectric actuator (drive unit) 6, and a frame (outer frame) 7. The left-right direction in the figure is defined as the X-axis, the up-down direction as the Y-axis, and the thickness direction of the optical deflector 1 (the direction perpendicular to the paper surface) as the Z-axis. These axes are perpendicular to each other at the center of the optical deflector 1.

[0010] The reflecting unit 2 is a movable mirror having a reflecting surface that is approximately circular in plan view, and is configured to be able to swing around the X-axis and the Y-axis by the inner piezoelectric actuator 4 and the outer piezoelectric actuator 6. By reflecting the laser light by such a reflecting unit 2, the laser light incident on the reflecting unit 2 can be scanned in two dimensions.

[0011] In a plan view, one torsion bar 3 is provided above and one below the reflector 2. The torsion bars 3 extend from the reflector 2 along the Y-axis direction and are connected to the inner periphery of the inner frame 5. The torsion bars 3 are also connected to the upper and lower ends of the left and right inner piezoelectric actuators 4.

[0012] The inner piezoelectric actuator 4 and the outer piezoelectric actuator 6 are provided on the left and right sides of the reflecting section 2 in a plan view.

[0013] The inner piezoelectric actuators 4 are connected to each other and have a shape that is close to an ellipse extending along the Y axis in plan view as a whole.

[0014] The outer piezoelectric actuators 6 are provided between the inner frame 5 and the outer frame 7. Each of the outer piezoelectric actuators 6 includes a plurality of piezoelectric cantilevers.

[0015] The inner frame portion 5 surrounds the reflecting portion 2 and the torsion bar 3. The inner frame portion 5 has a shape that is close to an ellipse extending along the Y axis as a whole in a plan view.

[0016] The drive pads 14, 15, and drive GND pads 16 are provided on the upper left and right sides of the outer frame portion 7, respectively, in a plan view. The drive pads 14, 15, and drive GND pads 16 are electrically and physically connected to the outside via bonding wires (not shown) when the optical deflector 1 is packaged.

[0017] A drive voltage of a first frequency is applied to each inner piezoelectric actuator 4 via a drive pad 14 and a drive GND pad 16. Each inner piezoelectric actuator 4 is interposed between the torsion bar 3 and the inner frame portion 5, and by twisting the torsion bar 3, causes the reflecting portion 2 to oscillate around the Y axis at the first frequency. Resonance is used for this oscillation. The first frequency is, for example, 15 kHz to 25 kHz.

[0018] A drive voltage of a second frequency is applied to the outer piezoelectric actuator 6 via the drive pad 15 and the drive GND pad 16. This causes the reflecting section 2 to oscillate around the X axis at the second frequency. Resonance is not utilized for the oscillation around the X axis. The second frequency is set to be lower than the first frequency, for example, 60 Hz.

[0019] Laser light incident on the reflecting unit 2 from a light source (not shown) is reflected in directions according to the deflection angles (deflection angles) around the X-axis and the Y-axis of the reflecting unit 2. The reflection direction (deflection direction) changes from moment to moment according to changes in the deflection angles of the reflecting unit 2. As a result, the laser light reflected by the reflecting unit 2 is scanned around the Y-axis at a first frequency and around the X-axis at a second frequency.

[0020] The deflection angle detection units (detection units) 18 and 19 are each intended to detect the deflection angle of the reflecting unit 2 by detecting the movement associated with the non-resonant vibration of the outer piezoelectric actuator 6 as a change in capacitance, and each is configured to include a plurality of fixed electrodes and a plurality of movable electrodes, which are comb-shaped electrodes.

[0021] The conductive portions 20 and 21 are portions for electrically connecting the movable electrodes of the deflection angle detection portions (detection portions) 18 and 19 to the active layer 53 (details of which will be described later).

[0022] The detection pad 22 is located at the lower right end in the figure. The detection GND pad 24 is located above the detection pad 22 in the figure. The input pad 28 is located below the detection pad 22 at the left end in the figure. The input pad 28 is used to input a signal (read signal) used to read the deflection angle. A dummy detection pad 42, a dummy detection GND pad 44, and a dummy input pad 48, each having a similar structure, are provided at the lower left side in the figure.

[0023] The wiring portion 31 is a part of the support layer 51 (see FIG. 4 described later) constituting the frame 7, and functions as a wiring portion (first portion) for connecting the deflection angle detection portion 18 and the deflection angle detection portion 19 in parallel and for connecting to the capacitance Cs formed in the input pad 28 (see FIG. 5B described later). The wiring portion 31 is configured in a frame shape along the outer edge of the frame 7 in a plan view, and has a relatively narrow portion and a relatively wide portion that is connected to each of the deflection angle detection portions 18 and 19. The non-wiring portion 32 is a portion (second portion) that is a portion of the support layer 51 constituting the frame 7 and is not the wiring portion 31, and one is arranged on each of the left and right sides in the drawing.

[0024] The crank-shaped cut portions 33, 34, 35, and 36 are each formed by partially cutting a support layer 51 (described below) that constitutes the frame 7, and have a crank-like shape in plan view. These crank-shaped cut portions 33 to 36 electrically isolate the wiring portion 31 from the non-wiring portion 32, thereby eliminating the influence of parasitic capacitance in the non-wiring portion 32. The detailed configuration of the crank-shaped cut portion 33 and the like will be described later.

[0025] 3A and 3B are enlarged views showing the vicinity of the deflection angle detection units 18 and 19 as viewed from the front side. As shown in FIG. 3A, the deflection angle detection unit 18 is configured to include a plurality of fixed electrodes 18a and a plurality of movable electrodes 18b. Since labeling all of the electrodes would result in complication, only some of the fixed electrodes 18a and movable electrodes 18b are labeled with reference numerals. Similarly, as shown in FIG. 3B, the deflection angle detection unit 19 is configured to include a plurality of fixed electrodes 19a and a plurality of movable electrodes 19b. Since labeling all of the electrodes would result in complication, only some of the fixed electrodes 19a and movable electrodes 19b are labeled with reference numerals.

[0026] The fixed electrodes 18a and the movable electrodes 18b are all formed in a comb-like shape on the same layer, the support layer 51 (details of which will be described later), and are arranged alternately one by one in the left-right direction in the figure. A capacitance is formed between these fixed electrodes 18a and the movable electrodes 18b. Similarly, the fixed electrodes 19a and the movable electrodes 19b are all formed in a comb-like shape on the same layer, the support layer 51 (details of which will be described later), and are arranged alternately one by one in the left-right direction in the figure. A capacitance is formed between these fixed electrodes 19a and the movable electrodes 19b. The capacitance formed between the fixed electrodes 18a and the movable electrodes 18b and the capacitance formed between the fixed electrodes 19a and the movable electrodes 19b increase and decrease in magnitude at the same time, so they can all be used as the same capacitance to be detected.

[0027] Furthermore, a conductive portion 20 is disposed on the lower right side of the deflection angle detection portion 18 in the drawing, and a conductive portion 21 is disposed on the upper left side of the deflection angle detection portion 19 in the drawing. These conductive portions 20, 21 are portions for electrically connecting the active layer 53 and the support layer 51. A detailed structural example of the conductive portion 20 will be described later.

[0028] Fig. 4 is a schematic cross-sectional view for explaining the structure of the main parts of the optical polarizer. In Fig. 4, the structure of the optical polarizer 1 is shown in a simplified schematic form to make it easier to understand the laminated structure and the configuration of each part. The frame 7 of the optical polarizer 1 has a basic structure including a support layer 51 for holding the reflecting part 2 etc., a BOX layer 52 as an etching stop layer provided on one side (upper side in the figure) of the support layer 51, and an active layer 53 for forming elements provided on the other side. The support layer 51 is a semiconductor layer such as a Si (silicon) layer, and the BOX layer 52 is a semiconductor layer such as a SiO ２ The active layer 53 is an insulating layer such as a silicon dioxide (SiO 2 ) layer, and the active layer 54 is a semiconductor layer such as a Si layer. The piezoelectric driving unit 54 is configured to include a lower electrode layer such as a platinum (Pt) layer, a piezoelectric layer such as a lead zirconate titanate (PZT) layer, and an upper electrode layer such as a Pt layer.

[0029] As shown in the figure, the light deflector 1 can be roughly divided into frame portions 60 and 62 and a movable portion 61. The support layer 51 is cut between the movable portion 61 and the frame portion 60, and they are not electrically connected.

[0030] In the frame portion 60, a capacitance Cs is formed in a region where the support layer 51, the BOX layer 52, and the active layer 53 are laminated, and an input pad 28 is provided in the active layer 53 in this region, and a carrier wave is input using the input pad 28. A fixed electrode 18a (or 19a) is formed as a portion of the support layer 51 connected to this region. In addition, a portion of the support layer 51 where the BOX layer 52 and the active layer 53 have been removed functions as a detection pad 22. The detection pad 22 is electrically connected to the region that forms the capacitance Cs and also to the region that forms the fixed electrode 18a.

[0031] The movable portion 61 is provided with a rib 51a, which is a portion of the support layer 51 where the thickness is reduced, and a movable electrode 18b (or 19b) is formed as part of the support layer 51 on the left side of the rib 51 in the figure. The active layer 53 is also provided with a conductive portion 20 (or 21) formed by deforming a portion of the active layer 53. The conductive portion 20 is in contact with a portion of the movable electrode 18b and functions to electrically connect the movable electrode 18b and the active layer 53. A BOX layer 52 and an active layer 53 are stacked on the rib 51a. The movable portion 61 is also provided with a piezoelectric driver 54. The active layer 53 is disposed in a portion overlapping with the piezoelectric driver 54, and the BOX layer 52 and the support layer 51 are not present below the active layer 53 in the figure.

[0032] The frame portion 62 has a portion where a support layer 51, a BOX layer 52, and an active layer 53 are laminated. A detection GND pad 24 is provided in a portion of the active layer 53. This detection GND pad 24 is connected to a reference potential terminal. The detection GND pad 24 is electrically connected to the movable electrode 18b via the active layer 53 of the frame portion 62, the active layer 53 of the movable portion 61, and the conductive portion 20. The support layer 51 is cut between the movable electrode 18b and the fixed electrode 18a, so they are not connected, but a capacitance Cv to be detected is formed between them and they are electrically connected.

[0033] 5A shows an electric circuit extending from the input pad 28 for inputting a carrier wave via the electrostatic capacitances Cs and Cv to the detection GND pad 24. The electrostatic capacitances Cs and Cv are connected in series, and the carrier wave is input to these via the input pad 28 and reaches the reference potential terminal. A detection signal can be obtained via the detection pad 22 between the electrostatic capacitances Cs and Cv.

[0034] A detailed electrical circuit (equivalent circuit) is shown in FIG. 5B . As shown in the figure, the capacitance Cv is actually a parallel circuit of capacitances Ca1, Ca2, Ca3, etc. formed between the fixed electrodes 18a and the movable electrodes 18b, and capacitances Cb1, Cb2, Cb3, etc. formed between the fixed electrodes 19a and the movable electrodes 19b. The capacitance Cv is the sum of the capacitances Ca1, Ca2, Ca3, etc., and Cb1, Cb2, Cb3, etc. The movable electrodes 18b, 19b are electrically connected to each other by the conductive portions 20, 21 and the rib 51a functioning as wiring. The fixed electrodes 18a, 19a are also electrically connected to each other by the wiring portion 31 of the frame 7 functioning as wiring.

[0035] 6A to 6E are diagrams illustrating a method for forming a conductive portion. Here, the case of forming conductive portions 20 and 21 having a cantilever structure is illustrated. As shown in FIG. 6A, for example, an SOI wafer is used in which a support layer 51, a BOX layer 52, and an active layer 53 are stacked.

[0036] 6B , a part of the active layer 53 is partially removed by dry etching or the like to form a through-hole 53a that exposes the BOX layer 52. Next, isotropic etching such as wet etching using a solution such as BHF is performed through the through-hole 53a to partially remove the BOX layer 52 in a portion corresponding to the conductive portion 20 (or 21).

[0037] Next, rinsing with pure water or the like is performed, followed by drying. As a result, as shown in Fig. 6(D), the portion of the active layer 53 overlapping the portion from which the BOX layer 52 has been removed succumbs to surface tension and adheres to the support layer 51. This forms the conductive portion 20 (or 21). Note that, as shown in the plan view of Fig. 6(E), it is also preferable to provide a through-hole 53b in the portion of the active layer 53 corresponding to the conductive portion 20 (or 21), so that a hollow structure can be easily formed by wet etching when partially removing the BOX layer 52.

[0038] 7A to 7D are diagrams illustrating another method for forming the conductive portions. Here, an example is shown in which the conductive portions 20 and 21 are formed using a structure (via structure) formed by coating a conductive film, rather than a cantilever structure. As shown in FIG. 7A, for example, an SOI wafer is used in which a support layer 51, a BOX layer 52, and an active layer 53 are stacked.

[0039] 7B, a part of the active layer 53 is partially removed by dry etching or the like to form a via 53c that exposes the BOX layer 52. At this time, it is preferable that the via 53c be tapered as shown in the example.

[0040] 7C, the BOX layer 52 is partially removed through the via 53c by dry etching or the like. Next, as shown in FIG. 7D, a conductive film 60 such as an aluminum film is formed from the portion of the support layer 51 exposed at the bottom of the via 53c to the active layer 53. Even with this configuration, a conductive portion 20 (or 21) can be formed to connect the support layer 51 and the active layer 53.

[0041] Fig. 8(A) is an enlarged view of the crank-shaped cut portion. Fig. 8(B) is a cross-sectional view taken along line B-B in Fig. 8(A), and Fig. 8(C) is a cross-sectional view taken along line CC in Fig. 8(A). Fig. 8(D) is a cross-sectional view of a cut portion of a comparative example. Here, crank-shaped cut portion 33 is shown, but the other crank-shaped cut portions 34 to 36 have a similar structure.

[0042] The crank-shaped cuts 33-36 function to interrupt the electrical connection between the support layer 51 of the frame portion 60 and the support layer 51 of the frame portion 62, as described in FIG. 4 above. Without these crank-shaped cuts 33-36, the support layer 51 of the frame portion 60 and the support layer 51 of the frame portion 62 would be electrically connected through the frame 7 at another location not shown in FIG. 4. This would result in the parasitic capacitance generated by the support layer 51, BOX layer 52, and active layer 53 of the non-wiring portion 32 being connected in series with the capacitance Cs. This would significantly reduce the detection sensitivity of the output voltage. The crank-shaped cuts 33-36 are intended to prevent this problem.

[0043] Here, if the purpose is simply to achieve the above-described function, a linear cut portion may be provided instead of a crank-shaped cut portion. However, in this case, as shown in the comparative example in FIG. 8(D), the load applied during mounting and the like is supported by the active layer 53. Typically, the active layer 53 has a smaller thickness than the support layer 51, resulting in reduced mechanical strength. As an example, the active layer 53 has a thickness of approximately 50 μm, and the support layer 51 has a thickness of approximately 350 μm. In contrast, in the crank-shaped cut portion 31 and the like, as can be seen from the cross-sectional views in FIGS. 8(B) and 8(C), there is no linear portion in which only the active layer 53 crosses the frame 7. Therefore, the load can be supported for the most part by the combined thickness of the support layer 51 and the active layer 53. Therefore, the strength of the frame 7 can be maintained.

[0044] 9(A) and 9(B) show the results of calculating the capacitance in the deflection angle detection unit of the optical deflector of the embodiment. It is preferable that the thickness of the support layer be at least twice that of the active layer. In this embodiment, an optical deflector of the embodiment was used in which the active layer was a 50 μm Si layer and the support layer was a 350 μm Si layer. FIG. 9(A) shows the results of calculating the capacitance for the combination of the fixed electrode and movable electrode closest to the center of rotation. As shown in FIG. 10, the lengths of the fixed electrode and movable electrode are approximately 890 μm, and the length to the center of rotation is approximately 1240 μm. FIG. 9(B) shows the results of calculating the capacitance for the combination of the fixed electrode and movable electrode farthest from the center of rotation. As shown in FIG. 10, the lengths of the fixed electrode and movable electrode are approximately 85 μm, and the length to the center of rotation is approximately 2045 μm. As shown in each figure, it can be seen that the change in capacitance with respect to the deflection angle can be linearly detected regardless of the thickness of the active layer. The limit of linear detection was approximately 9.3°. This detectable range is sufficient for many applications, as described below. Furthermore, because the fixed electrodes and movable electrodes are connected in parallel, the greater the number of electrodes, the greater the change in capacitance. However, the fixed electrodes and movable electrodes may be thinned out to the required detectable range. For example, only the short central fixed electrodes and movable electrodes with lengths of approximately 85 μm may be used, or only the fixed electrodes and movable electrodes on both sides with lengths of approximately 890 μm may be used, or only the fixed electrodes and movable electrodes intermediate between the center and both sides may be used. However, taking into account the balance of the weights of the fixed electrodes and movable electrodes, it is preferable to arrange the fixed electrodes and movable electrodes symmetrically.

[0045] The optical deflector 1 according to the above-described embodiment can be applied to any electronic device that requires laser light scanning. For example, it can be applied to a pico-projector used in a head-up display or a wearable device. It can also be applied to a device that changes the light distribution pattern in response to the presence of an oncoming vehicle, a preceding vehicle, a pedestrian, or various objects when irradiating light ahead of a vehicle. It can also be applied to an object detection device such as LiDAR (Light Detection and Ranging). Furthermore, it can be applied to various MEMS sensors such as an acceleration sensor, an angular velocity sensor, a pressure sensor, and an electromyography sensor.

[0046] According to the above embodiment, it is possible to widen the range in which the capacitance changes linearly with respect to the change in the deflection angle of the movable mirror.

[0047] It should be noted that the present disclosure is not limited to the contents of the above-described embodiment, and various modifications can be made within the scope of the gist of the present disclosure. For example, in the above-described embodiment, the layer switch type structure and the via type structure are exemplified as configuration examples of the conductive portions 20 and 21, but the support layer and the active layer may be electrically connected by means of wire bonding or the like.

[0048] In the above embodiment, the detection signal is obtained based on the equivalent circuit shown in FIG. 5B. However, it is also possible to take the difference between the detection signal obtained by a dummy equivalent circuit using the dummy detection pad 42, the dummy detection GND pad 44, and the dummy input pad 48.

[0049] The present disclosure has the following features: (Supplementary Note 1) An optical deflector including: a mirror having a reflective surface; a driver for oscillating the mirror; a detector for detecting the movement of the driver by a change in capacitance; and a frame supporting the mirror, the driver, and the detector, wherein the detector has a movable electrode whose position changes in response to the movement of the driver and a fixed electrode that is not affected by the movement of the driver, and is configured to generate the capacitance between the movable electrode and the fixed electrode, the frame has a support layer and an active layer, each of which is a semiconductor layer, and an insulating layer interposed between the support layer and the active layer, the support layer having a thickness greater than that of the active layer, the movable electrode and the fixed electrode each being configured as part of the support layer, and the active layer having a conductive portion for electrically connecting a portion of the driver to the movable electrode. (Supplementary Note 2) The optical deflector according to Supplementary Note 1, wherein the conductive portion is a portion of the active layer configured in a cantilever structure. (Supplementary Note 3) The optical deflector according to Supplementary Note 1, wherein the conductive portion is a conductive film provided between the active layer and the movable electrode via an opening. (Supplementary Note 4) The optical deflector according to any one of Supplements 1 to 3, wherein the thickness of the support layer is at least twice the thickness of the active layer. (Supplementary Note 5) The optical deflector according to any one of Supplements 1 to 4, wherein the support layer has a cut portion for electrically isolating a first portion functioning as a wiring portion connected to the fixed electrode from a second portion other than the first portion. (Supplementary Note 6) The optical deflector according to Supplementary Note 5, wherein the cut portion is provided in a crank shape in a plan view. (Supplementary Note 7) The optical deflector according to any one of Supplements 1 to 6, wherein the active layer has an input pad used to input a signal to the detection portion, and the support layer has a detection pad for extracting a detection signal corresponding to a change in the capacitance in the detection portion. (Supplementary Note 8) An electronic device comprising the optical scanning device according to any one of Supplementary Notes 1 to 7.

[0050] 1: optical deflector, 2: reflecting section, 3: torsion bar, 4: inner piezoelectric actuator, 5: inner frame section, 6: outer piezoelectric actuator, 7: frame, 14, 15: driving pad, 16: driving GND pad, 18, 19: deflection angle detection section, 18a, 19a: fixed electrode, 18b, 19b: movable electrode, 20, 21: conducting section, 22: detection pad, 24: detection GND pad, 28: input pad, 31, 32: wiring section, 33, 34, 35, 56: crank-shaped cutting section, 51: support layer, 52: BOX layer, 53: active layer, 54: piezoelectric driving section, 60, 62: frame section, 61: movable section

Claims

1. An optical deflector comprising: a mirror having a reflective surface; a driving unit which oscillates the mirror; a detecting unit which detects the movement of the driving unit by a change in electrostatic capacitance; and a frame which supports the mirror, the driving unit and the detecting unit, wherein the detecting unit has a movable electrode whose position changes in relation to the movement of the driving unit and a fixed electrode which is not involved in the movement of the driving unit, and is configured to generate the electrostatic capacitance between the movable electrode and the fixed electrode, the frame has a support layer and an active layer, each of which is a semiconductor layer, and an insulating layer interposed between the support layer and the active layer, the thickness of the support layer being thicker than the thickness of the active layer, the movable electrode and the fixed electrode are each configured as part of the support layer, and the active layer has a conductive portion for electrically connecting a portion constituting the driving unit and the movable electrode.

2. The optical deflector according to claim 1, wherein the conductive portion is a part of the active layer configured in a cantilever structure.

3. The optical deflector according to claim 1, wherein the conductive portion is a conductive film provided between the active layer and the movable electrode via an opening.

4. The optical deflector according to claim 1, wherein the thickness of said support layer is at least twice as large as the thickness of said active layer.

5. The optical deflector according to claim 1, wherein the support layer has a first portion that functions as a wiring portion connected to the fixed electrode and a cut portion for electrically isolating a second portion other than the first portion.

6. The optical deflector according to claim 5, wherein the cut portion is provided in a crank shape in a plan view.

7. An optical deflector as described in claim 1, wherein the active layer has an input pad used to input a signal to the detection section, and the support layer has a detection pad for extracting a detection signal corresponding to a change in the capacitance in the detection section.

8. An electronic device comprising the optical deflector according to claim 1.

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