Light deflector and electronic apparatus
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- STANLEY ELECTRIC CO LTD
- Filing Date
- 2023-08-24
- Publication Date
- 2026-07-17
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present disclosure relates to an optical deflector and an electronic device. [Background technology]
[0002] An optical deflector that scans an incident laser beam in a two-dimensional direction is known. A conventional example of an optical deflector is described in, for example, International Publication No. 2022 / 259912 (Patent Document 1). In such an optical deflector, for example, a comb electrode is provided so as to move in conjunction with a movable mirror, and the deflection angle of the movable mirror is detected by detecting the position change of the comb electrode as a change in capacitance. However, it has been difficult to expand the range in which the capacitance changes linearly with respect to the change in the deflection angle of the movable mirror. [Prior art documents] [Patent documents]
[0003] [Patent Document 1] International Publication No. 2022 / 259912 Summary of the Invention [Problem to be solved by the invention]
[0004] An object of a specific aspect of the present disclosure is to provide a technique capable of expanding the range in which the capacitance changes linearly with respect to a change in the deflection angle of the movable mirror. [Means for solving the problem]
[0005] [1] An optical deflector according to one aspect of the present disclosure, A mirror having a reflective surface; A drive unit that swings the mirror; A detection unit that detects the movement of the drive unit based on a change in capacitance; a frame supporting the mirror, the driving unit, and the detection unit; Including, the detection unit has a movable electrode whose position varies in accordance with the movement of the drive unit and a fixed electrode that is not involved in the movement of the drive unit, 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 thickness of the support layer being greater than the thickness of the active layer, the movable electrode and the fixed electrode are each configured as a part of the support layer; the active layer has a conductive portion for establishing an electrical connection between a portion constituting the driving portion and the movable electrode; It is an optical deflector. [2] An electronic device according to one aspect of the present disclosure is an electronic device including the optical deflector described above in [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. [Brief description of the drawings]
[0007] [Figure 1] FIG. 1 is a plan view showing a configuration of an optical deflector (optical scanning device) according to an embodiment. [Diagram 2] FIG. 2 is a plan view showing a configuration of an optical deflector (optical scanning device) according to an embodiment. [Diagram 3] 3A and 3B are enlarged views showing the vicinity of the deflection angle detection unit. [Figure 4] FIG. 4 is a schematic cross-sectional view for explaining the structure of the main part of the optical deflector. [Diagram 5] Fig. 5(A) is a diagram showing an electric circuit from an input pad for inputting a carrier wave to a detection GND pad via electrostatic capacitances Cs and Cv, and Fig. 5(B) is a diagram showing a more detailed electric circuit. [Figure 6] 6(A) to 6(E) are diagrams for explaining a method of forming the conductive portion. [Figure 7]7(A) to 7(D) are diagrams for explaining another method for forming the conductive portion. [Figure 8] Fig. 8(A) is an enlarged view of the crank-shaped cut portion. Fig. 8(B) is a cross-sectional view taken along line BB 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 the cut portion of a comparative example. [Figure 9] 9A and 9B are diagrams showing the calculation results of the electrostatic capacitance in the deflection angle detection unit of the optical deflector according to the embodiment. [Figure 10] FIG. 10 is a diagram for explaining the lengths of the fixed electrodes and the movable electrodes in the optical deflector of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0008] 1 and 2 are plan views showing the configuration of an optical deflector (optical scanning device) 1 according to an embodiment. In this embodiment, the surface on the side where the laser light to be scanned is incident is called the front surface, and the surface on the opposite side is called 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 when viewed from a plane.
[0009] The optical deflector 1 mainly comprises a reflecting section 2, a torsion bar 3, an inner piezoelectric actuator 4, an inner frame section 5, an outer piezoelectric actuator (driving section) 6, and a frame (outer frame section) 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 (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 substantially circular in plan view, and is configured to be oscillated 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-dimensional directions.
[0011] The torsion bars 3 are provided above and below the reflector 2 in plan view. The torsion bars 3 extend from the reflector 2 along the Y-axis direction and are coupled to the inner periphery of the inner frame 5. The torsion bars 3 are also coupled 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 as a whole in a plan view.
[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 reflector 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 driving pads 14, 15, and driving GND pads 16 are provided on the upper left and right sides, respectively, of the outer frame portion 7 in a plan view. The driving pads 14, 15, and driving GND pads 16 are electrically / 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 utilized 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 lower than the above-mentioned first frequency, and is set to, for example, 60 Hz.
[0019] Laser light incident on the reflecting unit 2 from a light source (not shown) is reflected in a direction according to the deflection angles (deflection angles) around the X-axis and Y-axis of the reflecting unit 2. The reflection direction (deflection direction) changes from moment to moment according to the change in the deflection angle 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 at the same time scanned around the X-axis at a second frequency.
[0020] The deflection angle detection units (detection units) 18, 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-tooth 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 an active layer 53 (to be described in detail later).
[0022] The detection pad 22 is disposed at the end on the lower right side in the figure. The detection GND pad 24 is disposed above the detection pad 22 in the figure. The input pad 28 is disposed below the detection pad 22 on the left end side 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, which have similar structures, are provided on the lower left side in the figure.
[0023] The wiring section 31 is a part of the support layer 51 (see FIG. 4 described later) constituting the frame 7, and functions as a wiring section (first section) for connecting the deflection angle detection section 18 and the deflection angle detection section 19 in parallel and connecting to the capacitance Cs formed in the input pad 28 (see FIG. 5(B) described later). The wiring section 31 is configured in a frame shape along the outer edge of the frame 7 in a plan view, and has a relatively narrow section and a relatively wide section that connects to each of the deflection angle detection sections 18 and 19. The non-wiring section 32 is a part of the support layer 51 constituting the frame 7, and is a section (second section) that is not the wiring section 31, and one is disposed on each of the left and right sides in the drawing.
[0024] The crank-shaped cut portions 33, 34, 35, and 36 are each a portion of a support layer 51 (described below) constituting the frame 7, and have a crank-like shape in plan view. The crank-shaped cut portions 33 to 36 electrically isolate the wiring portion 31 from the non-wiring portion 32, eliminating the effect 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] 3(A) and 3(B) are enlarged views of the deflection angle detection units 18 and 19 as viewed from the front side. As shown in FIG. 3(A), the deflection angle detection unit 18 includes a plurality of fixed electrodes 18a and a plurality of movable electrodes 18b. Since it would be cumbersome to label everything in the figure, only some of the fixed electrodes 18a and movable electrodes 18b are labeled with reference numerals. Similarly, as shown in FIG. 3(B), the deflection angle detection unit 19 includes a plurality of fixed electrodes 19a and a plurality of movable electrodes 19b. Since it would be cumbersome to label everything in the figure, 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 in 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 in 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] Moreover, a conductive portion 20 is disposed on the lower right side of the deflection angle detection portion 18 in the figure, and a conductive portion 21 is disposed on the upper left side of the deflection angle detection portion 19 in the figure. 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 simplified and shown in a schematic manner 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 having a support layer 51 for holding the reflecting part 2 and the like, 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 one side. The support layer 51 is a semiconductor layer such as a Si (silicon) layer, the BOX layer 52 is an insulating layer such as a SiO2 (silicon dioxide) layer, and the active layer 53 is a semiconductor layer such as a Si layer. The piezoelectric driving part 54 is configured to include a lower electrode layer such as a Pt (platinum) layer, a piezoelectric layer such as a PZT (lead zirconate titanate) 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 section 60, a capacitance Cs is formed in a portion 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 portion, and a carrier wave is input using the input pad 28. A fixed electrode 18a (or 19a) is formed as a part of the support layer 51 connected to this portion. In addition, a part 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 portion that forms the capacitance Cs, and is also electrically connected to the portion that forms the fixed electrode 18a.
[0031] The movable part 61 is provided with a rib 51a which is a portion where the thickness of the support layer 51 is reduced, and the movable electrode 18b (or 19b) is formed as a part of the support layer 51 on the left side of the rib 51 in the figure. The active layer 53 is provided with a conductive part 20 (or 21) formed by deforming a part of the active layer 53. The conductive part 20 is in contact with a part constituting the movable electrode 18b, and serves to electrically connect the movable electrode 18b and the active layer 53. The BOX layer 52 and the active layer 53 are laminated on the rib 51a. The movable part 61 is provided with a piezoelectric driving part 54. The active layer 53 is disposed in a portion overlapping with the piezoelectric driving part 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 section 62 is provided with a portion in which the support layer 51, the BOX layer 52, and the active layer 53 are laminated. In addition, a detection GND pad 24 is provided on a part 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 section 62, the active layer 53 of the movable section 61, and the conductive section 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] 5(A) shows an electric circuit from the input pad 28 for inputting a carrier wave to the detection GND pad 24 via the electrostatic capacitances Cs and Cv. 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 electric circuit (equivalent circuit) is shown in FIG. 5(B). The capacitance Cv is actually a parallel circuit of capacitances Ca1, Ca2, Ca3... formed between the fixed electrodes 18a and the movable electrodes 18b, and capacitances Cb1, Cb2, Cb3... formed between the fixed electrodes 19a and the movable electrodes 19b. The capacitance Cv is the sum of capacitances Ca1, Ca2, Ca3..., Cb1, Cb2, Cb3... The movable electrodes 18b, 19b are electrically connected to each other by the conductive parts 20, 21 and the rib 51a functioning as wiring. The fixed electrodes 18a, 19a are electrically connected to each other by the wiring part 31 of the frame 7 functioning as wiring.
[0035] 6(A) to 6(E) are diagrams for explaining a method for forming a conductive part. Here, a case where conductive parts 20, 21 having a cantilever structure are formed is illustrated. As shown in Fig. 6(A), for example, an SOI wafer in which a support layer 51, a BOX layer 52, and an active layer 53 are laminated is used.
[0036] 6(B), a part of the active layer 53 is partially removed by dry etching or the like to form a through hole 53a exposing 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, and drying causes the portion of active layer 53 overlapping the portion from which BOX layer 52 has been removed to adhere to support layer 51 due to surface tension, as shown in Fig. 6(D). As a result, conductive portion 20 (or 21) is formed. Note that, as shown in the plan view of Fig. 6(E), it is also preferable to provide through-holes 53b in the portion of active layer 53 corresponding to conductive portion 20 (or 21) so that a hollow structure can be easily formed by wet etching when partially removing BOX layer 52.
[0038] 7(A) to 7(D) are diagrams for explaining another method for forming the conductive parts. Here, an example is shown in which the conductive parts 20, 21 are formed using a structure (via structure) formed by coating a conductive film, rather than a cantilever structure. As shown in Fig. 7(A), for example, an SOI wafer in which a support layer 51, a BOX layer 52, and an active layer 53 are laminated is used.
[0039] 7(B), a portion 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 is tapered as shown in the example.
[0040] 7(C), the BOX layer 52 is partially removed through the via 53c by dry etching or the like. Next, as shown in FIG. 7(D), 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. With this configuration as well, the conductive portion 20 (or 21) for connecting the support layer 51 and the active layer 53 can be formed.
[0041] Fig. 8(A) is an enlarged view of a crank-shaped cut portion. Fig. 8(B) is a cross-sectional view taken along line BB 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 illustrated, but the other crank-shaped cut portions 34 to 36 have the same structure.
[0042] The crank-shaped cuts 33-36 function to cut off the electrical connection between the support layer 51 of the frame portion 60 and the support layer 51 of the frame portion 62 described in FIG. 4 above. If these crank-shaped cuts 33-36 did not exist, 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, and the parasitic capacitance generated by the support layer 51, BOX layer 62, and active layer 53 of the non-wiring portion 31 described above would be connected in series with the above-mentioned capacitance Cs. This would significantly reduce the detection sensitivity of the output voltage. The crank-shaped cuts 33-36 are intended to prevent such inconvenience.
[0043] Here, in order to simply realize the above-mentioned function, a straight cut portion may be provided instead of a crank-shaped cut portion. However, in this case, as in the comparative example shown in FIG. 8(D), the load applied during mounting and the like is supported by the active layer 53. Normally, the active layer 53 has a smaller layer thickness than the support layer 51, and therefore the mechanical strength is reduced. As an example, the active layer 53 has a layer thickness of about 50 μm, and the support layer 51 has a layer thickness of about 350 μm. In contrast, in the crank-shaped cut portion 31 and the like, as can be seen from the cross-sectional views shown in FIG. 8(B) and FIG. 8(C), there is no part in which only the active layer 53 is straight so as to cross the frame 7, so that the load can be supported by the combined layer thickness of the support layer 51 and the active layer 53 in most parts. Therefore, the strength of the frame 7 can be maintained.
[0044] 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. The thickness of the support layer is preferably at least twice the thickness of the active layer, and in this embodiment, the optical deflector of the embodiment was used in which the active layer is a Si layer of 50 μm and the support layer is a Si layer of 350 μm. FIG. 9(A) shows the results of calculation of the capacitance by the combination of the fixed electrode and the movable electrode closest to the center of rotation. As shown in FIG. 10, the length of the fixed electrode and the movable electrode is about 890 nm, and the length to the center of rotation is about 1240 μm. FIG. 9(B) shows the results of calculation of the capacitance by the combination of the fixed electrode and the movable electrode farthest from the center of rotation. As shown in FIG. 10, the length of the fixed electrode and the movable electrode is about 85 nm, and the length to the center of rotation is about 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 about 9.3°. This detectable range is sufficient for many applications, as described below. Since the fixed electrodes and the movable electrodes are connected in parallel, the greater the number of electrodes, the greater the change in capacitance. However, the fixed electrodes and the movable electrodes may be thinned out to the required detectable range. For example, only the short central fixed electrodes and the movable electrodes may be used, which are short in length, approximately 85 nm, or only the fixed electrodes and the movable electrodes on both sides may be used, which are long in length, approximately 890 nm, or only the intermediate fixed electrodes and the movable electrodes between the center and both sides. However, it is better to arrange the fixed electrodes and the movable electrodes symmetrically, taking into account the balance of the weights of the fixed electrodes and the movable electrodes.
[0045] The optical deflector 1 according to the above-described embodiment can be applied to any electronic device that requires scanning with laser light. For example, the optical deflector 1 can be applied to a pico-projector used in a head-up display or a wearable device. The optical deflector 1 can also be applied to a device that changes a light distribution pattern in response to the presence of an oncoming vehicle, a preceding vehicle, a pedestrian, or various objects when irradiating light forward of a vehicle. Alternatively, the optical deflector 1 can be applied to an object detection device such as LiDAR (Light Detection And Ranging). Furthermore, the optical deflector 1 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 embodiment described above, 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] The present disclosure is not limited to the contents of the above-mentioned embodiment, and various modifications can be made within the scope of the gist of the present disclosure. For example, in the above-mentioned embodiment, the layer switch type structure and the via type structure are exemplified as configuration examples of the conductive parts 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 was obtained based on the equivalent circuit shown in FIG. 5(B), but the difference may be taken between the detection signal obtained based on 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. (Appendix 1) A mirror having a reflective surface; A drive unit that swings the mirror; A detection unit that detects the movement of the drive unit based on a change in capacitance; a frame supporting the mirror, the driving unit, and the detection unit; Including, the detection unit has a movable electrode whose position varies in accordance with the movement of the drive unit and a fixed electrode that is not involved in the movement of the drive unit, 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 thickness of the support layer being greater than the thickness of the active layer, the movable electrode and the fixed electrode are each configured as a part of the support layer; the active layer has a conductive portion for establishing an electrical connection between a portion constituting the driving portion and the movable electrode; light deflector. (Appendix 2) The conductive portion is a part of the active layer configured in a cantilever structure. 2. The optical deflector according to claim 1. (Appendix 3) the conductive portion is formed by providing a conductive film between the active layer and the movable electrode via an opening; 2. The optical deflector according to claim 1. (Appendix 4) The thickness of the support layer is at least twice the thickness of the active layer. 4. An optical deflector according to any one of claims 1 to 3. (Appendix 5) 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; 5. The optical deflector according to claim 1. (Appendix 6) The cutting portion is provided in a crank shape in a plan view. 6. The optical deflector according to claim 5. (Appendix 7) the active layer has an input pad used for inputting a signal to the detection unit, the support layer has a detection pad for extracting a detection signal corresponding to a change in the capacitance at the detection unit; 7. An optical deflector according to any one of claims 1 to 6. (Appendix 8) An electronic device comprising the optical scanning device according to any one of claims 1 to 7. [Explanation of symbols]
[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 electrodes, 18b, 19b: movable electrodes, 20, 21: conductive section, 22: detection pad, 24: detection GND pad, 28: input pad, 31, 32: wiring section, 33, 34, 35, 56: crank-shaped cut section, 51: support layer, 51: BOX layer, 53: active layer, 54: piezoelectric driving section, 60, 62: frame section, 61: movable section
Claims
1. A mirror having a reflective surface, A drive unit for swinging the aforementioned mirror, A detection unit that detects the movement of the drive unit by a change in capacitance, A frame supporting the mirror, the drive unit and the detection unit, Includes, The detection unit has a movable electrode whose position changes in relation to the movement of the drive unit and a fixed electrode that does not change in relation to the movement of the drive unit, and is configured to generate the capacitance between the movable electrode and the fixed electrode. The frame comprises a support layer and an active layer, each being a semiconductor layer, and an insulating layer interposed between the support layer and the active layer, wherein the thickness of the support layer is greater than the thickness of the active layer. The movable electrode and the fixed electrode are each configured as part of the support layer. The active layer has a conductive portion for providing an electrical connection between the portion constituting the drive unit and the movable electrode. The support layer has a first portion that functions as a wiring portion connected to the fixed electrode and a second portion other than the first portion, with a cutting portion for electrically separating them. light deflector.
2. The conductive portion is configured as a cantilever structure in which a part of the active layer is electrically connected to the support layer. The optical deflector according to claim 1.
3. The conductive portion is provided with a conductive film between the active layer and the movable electrode via an opening. The optical deflector according to claim 1.
4. The thickness of the support layer is at least twice the thickness of the active layer. The optical deflector according to claim 1.
5. Torsion bars extending in the vertical direction of the mirror, The inner frame portion surrounding the mirror and the torsion bar, It further includes, The movable electrode is formed to extend from the inner frame portion toward the frame, The fixed electrode is formed to extend from the frame side toward the inner frame portion. The drive unit is an actuator that swings the mirror in a direction perpendicular to the torsion bar. The optical deflector according to claim 1.
6. The aforementioned cutting portion is arranged in a crank shape in a plan view. The optical deflector according to claim 5.
7. The active layer has an input pad used for signal input to the detection unit, The support layer has a detection pad for extracting a detection signal corresponding to the change in capacitance at the detection unit. The optical deflector according to claim 1.
8. An electronic device comprising the optical deflector described in claim 1.