Micromirror device and optical scanning device

Abstract

This micromirror device (2) is provided with a mirror section (20), a pair of first support sections (21), a pair of movable frames (22), a pair of second support sections (23), a drive section, a fixed frame (27), and a pair of connection sections (26B). The first support section (21) has a shape that is line-symmetric about a first axis (a1). The second support section (23) has a line-symmetric shape centered on the second shaft (a2), and has a second swing shaft (23A) disposed on the second shaft (a2), and a pair of second connection sections (23B) disposed at positions facing each other across the second shaft (a2). One end of the second swing shaft (23A) is connected to the movable frame (22), and the other end is connected to a second connection part (23B), which extends from the outer end of the second swing shaft (23A) on the second shaft (a2) in the direction toward the mirror part, and which is connected to the drive part in a region adjacent to the movable frame (22). The connection part (26B) has a line-symmetric shape about the second shaft (a2), and supports the drive part so as to be swingable about the second shaft (a2).

Description

Technical Field

[0001] The technology of the present invention relates to a micromirror device and a light scanning device. Background Art

[0002] As one of the MEMS devices made using silicon (Si) microfabrication technology, a micromirror device (also called a microscanner) is known. The micromirror device is small and consumes little power, so it is expected to be widely used in laser displays, laser projectors, optical coherence tomography scanners, etc.

[0003] There are many ways to drive a micromirror device, but the piezoelectric drive method that uses the deformation of a piezoelectric body generates a higher torque than other methods and can achieve a high scanning angle, so it is considered to be very promising. In particular, in the case where a high scanning angle is required, such as in a laser display, a higher scanning angle can be achieved by resonantly driving a piezoelectric drive micromirror device.

[0004] A common micromirror device used in a laser display includes a reflector and a piezoelectric actuator (for example, see Japanese Patent Application Publication No. 2017-132281). The reflector can swing freely around a first axis and a second axis that are orthogonal to each other. The actuator is a driving unit that swings the reflector around the first axis and the second axis according to a driving voltage supplied from the outside. Summary of the invention

[0005] Technical issues to be solved by the invention

[0006] As performance indicators of laser displays, resolution and viewing angle can be cited. Resolution and viewing angle are greatly affected by the swing frequency and deflection angle of the reflector. For example, in a Lissajous scan type laser display, two-dimensional light scanning is performed by swinging the reflector at different frequencies around the first axis and the second axis at the same time. At this time, the larger the deflection angle of the reflector, the larger the scanning area of ​​the light becomes, and a larger image can be displayed with a shorter optical path length.

[0007] In order to increase the deflection angle of the reflector, the simplest method is to increase the area of ​​the drive unit to increase the driving torque. However, increasing the area of ​​the drive unit will lead to a larger micromirror device, which goes against the miniaturization required for micromirror devices used in laser displays.

[0008] In order to solve this problem, in a micromirror device using resonance drive, the deflection angle of the reflector portion is usually improved by adjusting the resonance mode. For example, regarding the resonance mode in which the reflector portion and the drive portion are swung in opposite phases to each other, the gain of the deflection angle relative to the voltage applied to the drive portion is large. However, in the resonance mode of the opposite phase, a large stress is applied to the swing axis, so from the viewpoint of durability, it is not easy to increase the deflection angle.

[0009] The technical object of the present invention is to provide a micromirror device and an optical scanning device that can achieve a large deflection angle without increasing the area of ​​a drive unit.

[0010] Means for solving technical problems

[0011] In order to achieve the above-mentioned purpose, the micromirror device of the present invention comprises: a reflector portion having a reflective surface for reflecting incident light; a pair of first supporting portions connected to the reflector portion on a first axis within a plane including the reflective surface when the reflector portion is stationary, and supporting the reflector portion so as to be able to swing around the first axis; a pair of movable frames connected to the first supporting portions and opposed to each other across the first axis; a pair of second supporting portions connected to the movable frame on a second axis within the plane and orthogonal to the first axis, and supporting the reflector portion, the first supporting portion and the movable frame so as to be able to swing around the second axis; a driving portion connected to the second supporting portion and configured to surround the movable frame; and a fixed frame configured to surround the driving portion. ; and a pair of connecting parts, connecting the driving part and the fixed frame, the first supporting part is a shape that is line symmetrical about the first axis as the center, the second supporting part is a shape that is line symmetrical about the second axis as the center, and has a second swing axis arranged on the second axis, and a pair of second connecting parts arranged at positions opposite to each other across the second axis, one end of the second swing axis is connected to the movable frame and the other end is connected to the second connecting part, the second connecting part extends from the outer end of the second swing axis on the second axis in a direction toward the reflector part, and is connected to the driving part in a region adjacent to the movable frame, the connecting part is a shape that is line symmetrical about the second axis as the center, and supports the driving part so that it can swing around the second axis.

[0012] The driving portion preferably comprises: a pair of first actuators connected to the second supporting portion and opposed to each other via the second axis, the first actuators having piezoelectric elements; and a pair of second actuators arranged to surround the first actuators and opposed to each other via the first axis, the second actuators having piezoelectric elements.

[0013] Preferably, the connection portion is arranged on the second axis.

[0014] Preferably, the first support portion has a shape that is line-symmetrical about the first axis, and includes a first swing axis disposed on the first axis, and a pair of first connection portions disposed at positions opposing each other across the first axis.

[0015] Preferably, one end of the first swing shaft is connected to the reflector portion and the other end is connected to the first connecting portion, the first connecting portion extends from the outer end portion of the first swing shaft on the first axis toward the reflector portion, bends in the outer peripheral direction in an area adjacent to the reflector portion, and bends again in an area adjacent to the driving portion to be connected to the movable frame.

[0016] Preferably, one end of the first swing shaft is connected to the mirror portion and the other end is connected to the first connecting portion, the first connecting portion extending from the outer end of the first swing shaft on the first axis toward the mirror portion and connected to the movable frame in a region adjacent to the mirror portion.

[0017] Preferably, the first connection portion extends from a portion connected to the movable frame in the direction of the first axis to an outer end portion of the first swing shaft on the first axis.

[0018] Preferably, the first connecting portion bends outward from the outer end of the first shaft of the first swing shaft to form an annular region in a region adjacent to the movable frame, further extends from the annular region along the first shaft, and extends along the driving portion in a region adjacent to the driving portion to be connected to the movable frame.

[0019] Preferably, the pair of first connection parts are connected in a region adjacent to the driving part.

[0020] The optical scanning device of the present invention includes the above-mentioned micromirror device and a processor for driving a driving unit, wherein the processor causes the reflection mirror unit to swing around the first axis and the second axis respectively by giving a driving signal to the driving unit.

[0021] Effects of the Invention

[0022] According to the technology of the present invention, it is possible to provide a micromirror device and an optical scanning device that can achieve a large deflection angle without increasing the area of ​​a drive unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of a light scanning device.

[0024] Figure 2 This is a block diagram showing an example of the hardware configuration of the drive control unit.

[0025] Figure 3 It is a perspective view of the appearance of the micromirror device according to the first embodiment.

[0026] Figure 4 This is a plan view of the micromirror device according to the first embodiment as viewed from the light incident side.

[0027] Figure 5 is along Figure 4 Sectional view taken along line AA.

[0028] Figure 6It is a cross-sectional view showing a state where the reflector portion rotates around the first axis.

[0029] Figure 7 It is a diagram showing an example of the first drive signal and the second drive signal.

[0030] Figure 8 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0031] Fig. 9 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0032] Fig.10 This is a diagram showing specific setting values ​​of parameters.

[0033] Fig.11 This is a plan view of the micromirror device according to the second embodiment when viewed from the light incident side.

[0034] Fig.12 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0035] Fig.13 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0036] Fig.14 This is a diagram showing specific setting values ​​of parameters.

[0037] Fig.15 This is a plan view of the micromirror device according to the third embodiment when viewed from the light incident side.

[0038] Fig.16 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0039] Fig.17 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0040] Fig.18 This is a diagram showing specific setting values ​​of parameters.

[0041] Fig.19 This is a plan view of the micromirror device according to the fourth embodiment when viewed from the light incident side.

[0042] Fig. 20 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0043] Fig.21 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0044] Fig. 22 This is a diagram showing specific setting values ​​of parameters.

[0045] Fig.23 This is a plan view of the micromirror device according to the fifth embodiment as viewed from the light incident side.

[0046] Fig.24 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0047] Fig.25 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0048] Fig.26 This is a diagram showing specific setting values ​​of parameters.

[0049] Fig. 27 This is a plan view of the micromirror device according to the first comparative example when viewed from the light incident side.

[0050] Fig.28 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0051] Fig.29 This is a diagram showing specific setting values ​​of parameters.

[0052] Fig.30 This is a plan view of the micromirror device according to the second comparative example when viewed from the light incident side.

[0053] Fig.31 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0054] Fig.32 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0055] Fig.33 It is a diagram showing parameters related to the dimensions of components of a micromirror device.

[0056] Fig.34 This is a diagram showing specific setting values ​​of parameters.

[0057] Fig.35 The following are diagrams showing the results of experiments and simulations related to the respective embodiments and comparative examples. DETAILED DESCRIPTION

[0058] An example of an embodiment according to the technology of the present invention will be described with reference to the drawings.

[0059] [First embodiment]

[0060] exist Figure 11 and 2 schematically show an optical scanning device 10 according to the first embodiment. The optical scanning device 10 includes a micromirror device (hereinafter referred to as MMD (Micro Mirror Device)) 2, a light source 3, and a drive control unit 4. The optical scanning device 10 reflects the light beam LB irradiated from the light source 3 by the MMD 2 under the control of the drive control unit 4, thereby optically scanning a scanned surface 5. The scanned surface 5 is, for example, a screen.

[0061] MMD2 is a device capable of making the reflector portion 20 (refer to Figure 3 ) around the first axis a 1 and the first axis a 1 Orthogonal second axis a 2 The following is a micromirror device with a piezoelectric dual-axis drive mode for swinging. 1 The direction parallel to the second axis a is called the X direction. 2 The direction parallel to the first axis a is called the Y direction. 1 and the second axis a 2 The orthogonal direction is called the Z direction.

[0062] The light source 3 is, for example, a laser device that emits a laser beam as the light beam LB. The light source 3 preferably projects a laser beam toward a reflective surface 20A (see FIG. 2A ) provided on the reflector portion 20 when the reflector portion 20 of the MMD 2 is stationary. Figure 3 )Vertical irradiation beam LB.

[0063] The drive control unit 4 outputs a drive signal to the light source 3 and the MMD 2 according to the light scanning information. The light source 3 generates a light beam LB according to the input drive signal and irradiates the light beam LB to the MMD 2. The MMD 2 makes the reflector unit 20 rotate around the first axis a according to the input drive signal. 1 and the second axis a 2 swing.

[0064] The details will be described later, but the drive control unit 4 causes the mirror unit 20 to rotate around the first axis a. 1 and the second axis a 2 The light beam LB reflected by the mirror unit 20 resonates and scans in a manner that a Lissajous waveform is drawn on the scanned surface 5. This optical scanning method is called a Lissajous scanning method.

[0065] The optical scanning device 10 is applicable to, for example, a laser display of a Lissajous scanning method. Specifically, the optical scanning device 10 can be applied to a laser scanning display such as AR (Augmented Reality) glasses or VR (Virtual Reality) glasses.

[0066] exist Figure 24 shows an example of the hardware structure of the drive control unit 4. The drive control unit 4 includes a CPU (Central Processing Unit) 40, a ROM (Read Only Memory) 41, a RAM (Random Access Memory) 42, a light source driver 43, and an MMD driver 44. The CPU 40 is a computing device that realizes the overall function of the drive control unit 4 by reading programs and data from a storage device such as the ROM 41 to the RAM 42 and executing processing. The CPU 40 is an example of a processor involved in the technology of the present invention.

[0067] The ROM 41 is a nonvolatile storage device, and stores a program for the CPU 40 to execute a process and data such as the aforementioned light scanning information. The RAM 42 is a volatile storage device that temporarily stores the program and data.

[0068] The light source driver 43 is a circuit that outputs a drive signal to the light source 3 according to the control of the CPU 40. In the light source driver 43, the drive signal is a drive voltage for controlling the irradiation timing and irradiation intensity of the light source 3.

[0069] The MMD driver 44 is a circuit that outputs a drive signal to the MMD 2 according to the control of the CPU 40. In the MMD driver 44, the drive signal is a drive voltage for controlling the timing, cycle, and deflection angle of the MMD driver 44 to oscillate the mirror unit 20.

[0070] The CPU 40 controls the light source driver 43 and the MMD driver 44 based on the light scanning information. The light scanning information is information including the scanning pattern of the light beam LB for scanning the scanned surface 5 and the light emission timing of the light source 3.

[0071] Next, use Figure 3 to Figure 5 The structure of the MMD 2 according to the first embodiment will be described. Figure 3 This is a three-dimensional image of the appearance of MMD2. Figure 4 This is a top view of the MMD2 as viewed from the light incident side. Figure 5 is along Figure 4 Sectional view taken along line AA.

[0072] like Figure 3 As shown, MMD2 has a mirror section 20, a pair of first support sections 21, a pair of movable frames 22, a pair of second support sections 23, a pair of first actuators 24, a pair of second actuators 25, a pair of first connecting sections 26A, a pair of second connecting sections 26B, and a fixed frame 27. MMD2 is a so-called MEMS scanner.

[0073] The reflector 20 has a reflective surface 20A for reflecting incident light. The reflective surface 20A is formed of a metal thin film such as gold (Au) or aluminum (Al) provided on one surface of the reflector 20. The shape of the reflective surface 20A is, for example, 1 With the second axis a 2 A circle with the intersection point as its center.

[0074] Axis 1 1 and the second axis a 2 For example, the MMD 2 exists in a plane including the reflecting surface 20A when the reflecting mirror portion 20 is stationary. 1 The axis is symmetrical with the second axis a 2 Symmetrical about the center.

[0075] The pair of first support parts 21 are arranged on both sides of the second axis a. 2 The second axis a is located opposite to the 2 The first support portion 21 is a shape that is line symmetrical with the first axis a as the center. 1 The first support portion 21 is symmetrical about the first axis a. 1 The reflector unit 20 is connected to the reflector unit 20 and supports the reflector unit 20 so that it can rotate around the first axis a 1 swing.

[0076] The pair of movable frames 22 are arranged on both sides of the first axis a 1 The first axis a is located opposite to the first axis a. 1 The movable frame 22 is a shape that is line symmetrical with the second axis a as the center. 2 The movable frame 22 is formed to be line-symmetrical about the center. The movable frame 22 is bent along the outer periphery of the reflector portion 20. Both ends of the movable frame 22 are connected to the first support portion 21, respectively.

[0077] The first support portion 21 and the movable frame 22 are connected to each other, and surround the mirror portion 20. The mirror portion 20, the first support portion 21, and the movable frame 22 constitute a movable portion 60.

[0078] The pair of second support parts 23 are arranged on both sides of the first axis a 1 The first axis a is located opposite to the first axis a. 1 The second support parts 23 are respectively symmetrical about the second axis a 2 The second support portion 23 is symmetrical about the second axis a. 2 The movable frame 22 is connected to the movable frame 22, and supports the movable portion 60 having the reflector portion 20 so as to be movable around the second axis a. 2 Furthermore, both ends of the second support portion 23 are connected to the first actuator 24, respectively.

[0079] The pair of first actuators 24 are arranged across the second axis a 2 The second axis a is located opposite to the 2 The first actuator 24 is a shape that is line symmetrical with the first axis a as the center. 1 The first actuator 24 is formed along the outer periphery of the movable frame 22 and the first support portion 21. The first actuator 24 is a piezoelectric drive type actuator including a piezoelectric element.

[0080] The first actuator 24 is connected to the first shaft a by wiring (not shown). 1 Electrical connection. Across the second axis a 2 The pair of first actuators 24 are arranged to be electrically isolated from each other.

[0081] The second support portion 23 and the first actuator 24 are connected to each other so as to surround the movable portion 60 .

[0082] The pair of second actuators 25 are arranged across the first axis a 1 The first axis a is located opposite to the first axis a. 1 The second actuator 25 is a shape that is line symmetrical with the second axis a as the center. 2 The second actuator 25 is formed along the outer periphery of the first actuator 24 and the second support portion 23. The second actuator 25 is a piezoelectric drive type actuator including a piezoelectric element.

[0083] The second actuator 25 is connected to the second shaft a by wiring (not shown). 2 Electrical connection. Across the first axis a 1 The pair of second actuators 25 are arranged to be electrically isolated from each other.

[0084] The pair of first connection parts 26A are arranged on both sides of the second axis a. 2 The second axis a is located opposite to the 2 The first connecting portion 26A is a shape that is line symmetrical with the first axis a as the center. 1 The first connecting portion 26A is symmetrical about the center. 1 Configuration, and on the 1st axis a 1 The first actuator 24 and the second actuator 25 are connected thereto.

[0085] The pair of second connection parts 26B are arranged on both sides of the first axis a 1 The first axis a is located opposite to the first axis a. 1 The second connecting portion 26B extends in the Y direction and is symmetrical with the second axis a. 2The second connecting portion 26B is symmetrical about the center. 2 configuration, and on the second axis a 2 The second connecting portion 26B connects the second actuator 25 and the fixed frame 27. The second connecting portion 26B supports the second actuator 25 so that it can move around the second axis a. 2 The second connection portion 26B corresponds to the "connection portion" involved in the technology of the present invention.

[0086] The second actuator 25 surrounds the first actuator 24. The first actuator 24 and the second actuator 25 constitute a driving unit that is arranged to surround the movable frame 22.

[0087] The fixing frame 27 is a frame-shaped member having a rectangular outer shape and is respectively 1 and the second axis a 2 The fixing frame 27 surrounds the outer periphery of the second actuator 25 and the second connecting portion 26B. That is, the fixing frame 27 is arranged to surround the driving portion.

[0088] The first actuator 24 and the second actuator 25 are piezoelectric actuators each having a piezoelectric element. 2 The rotation torque acts on the reflector portion 20 and the movable frame 22 to move the movable portion 60 around the second axis a. 2 The pair of second actuators 25 swing around the first axis a 1 The rotation torque of 20 acts on the mirror portion 20, the movable frame 22 and the first actuator 24 to move the mirror portion 20 around the first axis a. 1 swing.

[0089] like Figure 4 As shown in FIG. 1 , the first support portion 21 is composed of a swing shaft 21A and a pair of connecting portions 21B. The swing shaft 21A is a first support portion 21A extending along the first axis a. 1 One end of the swing shaft 21A is connected to the reflector portion 20 and the other end is connected to the connecting portion 21B.

[0090] The pair of connecting portions 21B are arranged across the first axis a 1 The first axis a is located opposite to the first axis a. 1 One end of the connecting portion 21B and the swing shaft 21A are aligned with the first axis a. 1 The connecting portion 21B is connected to the outer end E1 on the first axis a and the other end is connected to the movable frame 22. The connecting portion 21B has a folded structure. Specifically, the connecting portion 21B extends from the swing shaft 21A to the first axis a. 1The outer end E1 on the connecting portion 21B extends in the direction toward the reflector portion 20, is bent in the outer peripheral direction in the region adjacent to the reflector portion 20, and is bent again in the region adjacent to the first actuator 24 to be connected to the movable frame 22. In this way, the connecting portion 21B has elasticity due to the folded structure, so that the connecting portion 21B can be bent around the first axis a at the reflector portion 20. 1 During the swing, the internal stress applied to the swing shaft 21A is relieved. The swing shaft 21A and the connection portion 21B correspond to the "first swing shaft" and the "first connection portion" according to the technique of the present invention, respectively.

[0091] The second support portion 23 is composed of a swing shaft 23A and a pair of connecting portions 23B. The swing shaft 23A is a 2 One end of the swing shaft 23A is connected to the movable frame 22 and the other end is connected to the connecting portion 23B.

[0092] The pair of connecting parts 23B are arranged across the second axis a 2 The second axis a is located opposite to the 2 One end of the connecting portion 23B and the swing shaft 23A are aligned with the second axis a. 2 The outer end E2 on the first actuator 24 is connected to the connecting portion 23B. The connecting portion 23B has a folded structure. Specifically, the connecting portion 23B extends from the swing shaft 23A to the second axis a. 2 The outer end portion E2 on the upper side of the connecting portion 23B extends in the direction toward the reflector portion 20 and is connected to the first actuator 24 in the region adjacent to the movable frame 22. In this way, the connecting portion 23B has elasticity due to the folded structure, so that the connecting portion 23B can be adjusted around the second axis a at the reflector portion 20. 2 During the swing, the internal stress applied to the swing shaft 23A is relieved. The swing shaft 23A and the connection portion 23B correspond to the "second swing shaft" and the "second connection portion" according to the technique of the present invention, respectively.

[0093] Furthermore, in the reflector portion 20, a plurality of slits 20B and 20C are formed outside the reflective surface 20A along the outer periphery of the reflective surface 20A. The plurality of slits 20B and 20C are arranged at the positions respectively aligned with the first axis a. 1 and the second axis a 2 The slit 20B has a function of suppressing deformation of the reflecting surface 20A caused by the swing of the reflector unit 20 .

[0094] exist Figure 3 and Figure 4 In the figure, wiring and electrode pads for applying drive signals to the first actuator 24 and the second actuator 25 are omitted from the figure. A plurality of electrode pads are provided on the fixing frame 27.

[0095] like Figure 5As shown, the MMD 2 is formed by, for example, etching an SOI (Silicon On Insulator) substrate 30. The SOI substrate 30 is a substrate in which a silicon oxide layer 32 is provided on a first silicon active layer 31 made of single crystal silicon, and a second silicon active layer 33 made of single crystal silicon is provided on the silicon oxide layer 32.

[0096] The mirror section 20, the first support section 21, the movable frame 22, the second support section 23, the first actuator 24, the second actuator 25, the first connection section 26A, and the second connection section 26B are formed by the second silicon active layer 33 remaining after the first silicon active layer 31 and the silicon oxide layer 32 are removed from the SOI substrate 30 by etching. The second silicon active layer 33 functions as an elastic part having elasticity. The fixed frame 27 is formed by three layers of the first silicon active layer 31, the silicon oxide layer 32, and the second silicon active layer 33. That is, the thickness of the mirror section 20, the first support section 21, the movable frame 22, the second support section 23, the first actuator 24, the second actuator 25, the first connection section 26A, and the second connection section 26B are thinner than the fixed frame 27. In the present invention, the thickness refers to the width in the Z direction.

[0097] The first actuator 24 includes a piezoelectric element (not shown) formed on the second silicon active layer 33. The piezoelectric element has a stacked structure in which a lower electrode, a piezoelectric film, and an upper electrode are stacked in this order on the second silicon active layer 33. The second actuator 25 has the same structure as the first actuator 24.

[0098] The lower electrode and the upper electrode are formed of metals such as gold (Au) or platinum (Pt). The piezoelectric film is formed of PZT (lead zirconate titanate) as a piezoelectric material. The lower electrode and the upper electrode are electrically connected to the drive control unit 4 via wiring and electrode pads.

[0099] The lower electrode is connected to the drive control unit 4 via wiring and an electrode pad, and a ground potential is applied thereto. A drive voltage is applied from the drive control unit 4 to the upper electrode.

[0100] When a positive or negative voltage is applied in the polarization direction, the piezoelectric film deforms (e.g., expands and contracts) in proportion to the applied voltage. That is, the piezoelectric film exerts the so-called inverse piezoelectric effect. The piezoelectric film exerts the inverse piezoelectric effect by applying a driving voltage from the drive control unit 4 to the upper electrode, so that the first actuator 24 and the second actuator 25 are displaced.

[0101] exist Figure 6 FIG. 2 shows a diagram of a second actuator 25 that generates a rotation about the first axis a by extending one piezoelectric film and contracting the other piezoelectric film in a pair of second actuators 25. 1Thus, one of the pair of second actuators 25 is displaced in opposite directions to the other, so that the reflector portion 20 is rotated around the first axis a. 1 Rotate.

[0102] and, Figure 6 This is an example of driving the second actuator 25 in an anti-phase resonance mode (hereinafter referred to as an anti-phase rotation mode) in which the displacement direction of a pair of second actuators 25 and the rotation direction of the mirror unit 20 are opposite to each other. In contrast, a resonance mode in which the displacement direction of a pair of second actuators 25 and the rotation direction of the mirror unit 20 are the same in phase is referred to as an in-phase rotation mode. In this embodiment, the second actuator 25 is driven in the anti-phase rotation mode.

[0103] Regarding the mirror portion 20 around the first axis a 1 The deflection angle θ is controlled according to a drive signal (hereinafter referred to as a first drive signal) given to the second actuator 25 by the drive control unit 4. The first drive signal is, for example, a sinusoidal AC voltage. The first drive signal includes a drive voltage waveform V applied to one of the pair of second actuators 25. 1A (t) and the driving voltage waveform V applied to the other 1B (t). Driving voltage waveform V 1A (t) and driving voltage waveform V 1B (t) are in anti-phase with each other (ie, out of phase by 180°).

[0104] In addition, the mirror portion 20 has a 1 The deflection angle θ corresponds to the angle at which the normal line N of the reflecting surface 20A is inclined relative to the Z direction on the YZ plane.

[0105] The first actuator 24 is driven in the reverse phase rotation mode similarly to the second actuator 25. 2 The deflection angle of the first actuator 24 is controlled according to a drive signal (hereinafter referred to as a second drive signal) given to the first actuator 24 by the drive control unit 4. The second drive signal is, for example, a sinusoidal AC voltage. The second drive signal includes a drive voltage waveform V applied to one of the pair of first actuators 24. 2A (t) and the driving voltage waveform V applied to the other 2B (t). Driving voltage waveform V 2A (t) and driving voltage waveform V 2B (t) are in anti-phase with each other (ie, out of phase by 180°).

[0106] exist Figure 7 An example of the first drive signal and the second drive signal is shown in FIG. Figure 7(A) shows the driving voltage waveform V included in the first driving signal. 1A (t) and V 1B (t). Figure 7 (B) shows the driving voltage waveform V included in the second driving signal. 2A (t) and V 2B (t).

[0107] Driving voltage waveform V 1A (t) and V 1B (t) are expressed as follows.

[0108] V 1A (t) = V off1 +V 1 sin(2πf d1 t)

[0109] V 1B (t) = V off1 +V 1 sin(2πf d1 t+α)

[0110] Here, V 1 is the amplitude voltage. V off1 is the bias voltage. d1 is the driving frequency (hereinafter referred to as the first driving frequency). t is the time. α is the driving voltage waveform V 1A (t) and V 1B In this embodiment, for example, α is set to 180°.

[0111] By applying the driving voltage waveform V to the pair of second actuators 25 1A (t) and V 1B (t), the mirror unit 20 is driven at the first driving frequency f d1 Around the first axis a 1 swing.

[0112] Driving voltage waveform V 2A (t) and V 2B (t) are expressed as follows.

[0113] V 2A (t) = V off2 +V 2 sin(2πf d2 t+φ)

[0114] V 2B (t) = V off2 +V 2 sin(2πf d2 t+β+φ)

[0115] Here, V 2 is the amplitude voltage. V off2 is the bias voltage. d2 is the driving frequency (hereinafter referred to as the second driving frequency). t is the time. β is the driving voltage waveform V 2A (t) and V 2B In this embodiment, for example, β is set to 180°. Also, φ is the driving voltage waveform V 1A (t) and V 1B (t) and driving voltage waveform V 2A (t) and V 2B (t) phase difference. And, in this embodiment, for example, V off1 =V off2 =0V.

[0116] By applying the driving voltage waveform V to the pair of first actuators 24 2A (t) and V 2B (t), the movable portion 60 including the reflector portion 20 is driven at the second driving frequency f d2 Around the second axis a 2 swing.

[0117] First driving frequency f d1 The first axis a of the reflector portion 20 is set to 1 The second driving frequency f d2 The second axis a of the reflector portion 20 is set to 2 For example, the first drive frequency f d1 Greater than the second drive frequency f d2 .

[0118] The applicant has found that by configuring the MMD2 as described above, a large deflection angle can be achieved without increasing the area of ​​the drive unit by using the reverse phase rotation mode. In addition, in the MMD2, the first support portion 21 and the second support portion 23 are separated from the drive unit at the outer ends E1 and E2, respectively, thereby suppressing the stress concentration at one point during driving. Thus, the first support portion 21 and the second support portion 23 are suppressed from causing the Si structure to be damaged, and a large deflection angle can be achieved.

[0119] In order to verify the above effects, the applicant prepared samples of MMD2 and conducted experiments. Figure 8 and Fig. 9 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.10 The specific setting values ​​of the parameters are shown in .

[0120] Furthermore, the diameter of the mirror portion 20 was set to 1.5 mm, the thickness of the SOI substrate 30 was set to 430 μm, and the thickness of the second silicon active layer 33 was set to 100 μm. Furthermore, the length of one side of the fixing frame 27 was set to 5.5 mm.

[0121] In this experiment, the mirror unit 20 is rotated in a reverse phase mode around the second axis a in a vacuum (less than 50 Pa). 2 Resonant driving was performed and the driving voltage required for θ = 11.25° (i.e., the amplitude voltage V 2 ). In the scanning angle (full angle) of the light beam LB, θ=11.25° corresponds to 45°. The experimental result shows that the driving voltage required for θ=11.25° is 3.8V.

[0122] Furthermore, a resonance mode analysis simulation based on the finite element method was performed. Specifically, the reflector unit 20 was caused to rotate around the second axis a in a reverse phase rotation mode. 2 Resonance driving was performed, and the von Mises stress applied to the second support portion 23 at θ=11.25° was calculated. The calculated value of the von Mises stress was 1.79 GPa.

[0123] [Second embodiment]

[0124] Next, a second embodiment will be described. Fig.11 This is a plan view of the MMD2A according to the second embodiment as viewed from the light incident side. The MMD2A is different from the MMD2 according to the first embodiment only in the structure of the first supporting portion 21 .

[0125] In this embodiment, the first support portion 21 is composed of a swing shaft 21A and a pair of connecting portions 21B. One end of the swing shaft 21A is connected to the reflector portion 20 and the other end is connected to the connecting portion 21B. One end of the connecting portion 21B is connected to the swing shaft 21A at the first axis a. 1 The outer end E1 on the first axis a is connected to the connecting portion 21B and the other end is connected to the movable frame 22. In the present embodiment, the connecting portion 21B does not have a folded structure. That is, the connecting portion 21B extends from the swing shaft 21A to the first axis a. 1 An outer end portion E1 on the upper portion extends in a direction toward reflector portion 20 , and is connected to movable frame 22 in a region adjacent to reflector portion 20 .

[0126] The applicant also conducted the same experiments and simulations as above for the MMD2A involved in the second embodiment. Fig.12 and Fig.13 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.14 The specific setting values ​​of the parameters are shown in .

[0127] The experimental results showed that the driving voltage required for θ=11.25° was 3.7 V. The results of the resonance mode analysis simulation showed that the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 1.77 GPa.

[0128] [Third Embodiment]

[0129] Next, a third embodiment will be described. Fig.15 This is a plan view of the MMD2B according to the third embodiment as viewed from the light incident side. The MMD2B is different from the MMD2 according to the first embodiment only in the structure of the first supporting portion 21 .

[0130] In this embodiment, the first support portion 21 is composed of a swing shaft 21A and a pair of connecting portions 21B. One end of the swing shaft 21A is connected to the reflector portion 20 and the other end is connected to the connecting portion 21B. One end of the connecting portion 21B is connected to the swing shaft 21A at the first axis a. 1 The outer end E1 on the connecting portion 21B is connected to the movable frame 22. In the present embodiment, the connecting portion 21B has a folded structure.

[0131] Specifically, similarly to the first embodiment, the connecting portion 21B extends from the swing shaft 21A to the first axis a. 1 The outer end E1 on the movable frame 22 extends in the direction toward the reflector portion 20, is bent in the outer peripheral direction in the region adjacent to the reflector portion 20, and is bent again in the region adjacent to the first actuator 24 to be connected to the movable frame 22. The connection portion 21B of this embodiment is different from the connection portion 21B of the first embodiment in that the connection portion 21B extends from the portion connected to the movable frame 22 along the first axis a. 1 The swing axis 21A extends in the direction of the first axis a 1 The symbol P indicates that the connecting portion 21B is located along the first axis a. 1 The area extending in the direction of

[0132] The applicant has also carried out the same experiments and simulations as above for the MMD2B involved in the third embodiment. Fig.16 and Fig.17 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.18 The specific setting values ​​of the parameters are shown in .

[0133] The experimental results showed that the driving voltage required for θ=11.25° was 3.5 V. The results of the resonance mode analysis simulation showed that the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 1.77 GPa.

[0134] [Fourth embodiment]

[0135] Next, a fourth embodiment will be described. Fig.19 This is a plan view of the MMD2C according to the fourth embodiment as viewed from the light incident side. The MMD2C is different from the MMD2 according to the first embodiment only in the structure of the first supporting portion 21 .

[0136] In this embodiment, the first support portion 21 is composed of a swing shaft 21A and a pair of connecting portions 21B. One end of the swing shaft 21A is connected to the reflector portion 20 and the other end is connected to the connecting portion 21B. One end of the connecting portion 21B is connected to the swing shaft 21A at the first axis a. 1 The outer end E1 on the connecting portion 21B is connected to the movable frame 22. In the present embodiment, the connecting portion 21B has a folded structure.

[0137] Specifically, similarly to the first embodiment, the connecting portion 21B extends from the swing shaft 21A to the first axis a. 1 The outer end E1 on the upper side is directed outward (ie, the second axis a 2 The connecting portion 21B is bent in the first direction and forms an annular region C in the region adjacent to the movable frame 22. 1 The movable frame 22 extends along the driving portion in a region adjacent to the driving portion.

[0138] The applicant has also carried out the same experiments and simulations as above for the MMD2C involved in the fourth embodiment. Fig. 20 and Fig.21 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig. 22 The specific setting values ​​of the parameters are shown in .

[0139] The experimental results showed that the driving voltage required for θ=11.25° was 3.8 V. The results of the resonance mode analysis simulation showed that the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 1.79 GPa.

[0140] [Fifth embodiment]

[0141] Next, a fifth embodiment will be described. Fig.23 This is a plan view of the MMD 2D according to the fifth embodiment as viewed from the light incident side. The MMD 2D is different from the MMD 2 according to the first embodiment only in the structure of the first supporting portion 21 .

[0142] In this embodiment, the first support portion 21 is composed of a swing shaft 21A and a pair of connecting portions 21B. One end of the swing shaft 21A is connected to the reflector portion 20 and the other end is connected to the connecting portion 21B. One end of the connecting portion 21B is connected to the swing shaft 21A at the first axis a.1 The outer end E1 on the connecting portion 21B is connected to the movable frame 22. In the present embodiment, the connecting portion 21B has a folded structure.

[0143] In this embodiment, in addition to the structure of the fourth embodiment, the first support portion 21 is further connected to a pair of connecting portions 21B in a region adjacent to the drive portion. The first support portion 21 of this embodiment has the same structure as the first support portion 21 of the fourth embodiment except that the pair of connecting portions 21B are connected.

[0144] The applicant has also carried out the same experiments and simulations as above for the MMD2D involved in the fifth embodiment. Fig.24 and Fig.25 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.26 The specific setting values ​​of the parameters are shown in .

[0145] The experimental results showed that the driving voltage required for θ=11.25° was 3.8 V. The results of the resonance mode analysis simulation showed that the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 1.80 GPa.

[0146] [Comparative Example 1]

[0147] Next, a first comparative example will be described. Fig. 27 1 is a top view of the MMD2E according to the first comparative example when viewed from the light incident side. The difference between the MMD2E and the MMD2 according to the first embodiment is that the first support portion 21 and the second support portion 23 do not have a folded structure, and the first support portion 21 and the second support portion 23 are directly connected to the driving portion. In addition, in the first comparative example, the first support portion 21 is disposed on the second axis a. 2 The upper part is connected to the fixed frame 27 via the connecting portion 26. In the first comparative example, the movable frame 22 is not provided, and the first actuator 24 is arranged so as to surround the second actuator 25.

[0148] The applicant also conducted the same experiments and simulations as above for MMD2E involved in the first comparative example. Fig.28 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.29 The specific setting values ​​of the parameters are shown in .

[0149] The diameter of the mirror portion 20 was set to 1.5 mm, the thickness of the SOI substrate 30 was set to 430 μm, and the thickness of the second silicon active layer 33 was set to 100 μm. The lengths of the fixing frame 27 in the X direction and the Y direction were set to 6.2 mm and 8.6 mm, respectively.

[0150] The experimental results showed that the driving voltage required for θ=11.25° was 3.2 V. Furthermore, the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 2.155 GPa according to the results of the resonance mode analysis simulation.

[0151] [Comparative Example 2]

[0152] Next, a second comparative example will be described. Fig.30 1 is a top view of the MMD2F according to the second comparative example when viewed from the light incident side. In the MMD2F, the first support portion 21 and the second support portion 23 have a folded structure, but the structure of the second support portion 23 is different from that of the MMD2 according to the first embodiment. In the second comparative example, the connecting portion 23B of the second support portion 23 extends from the swing axis 23A to the second axis a. 2 The outer end portion E2 on the movable frame 22 extends in the direction toward the reflector portion 20, bends in the region adjacent to the movable frame 22, and extends in the direction toward the second actuator 25. In addition, the connecting portion 23B is connected to the first actuator 24 in the region adjacent to the second actuator 25. In the second comparative example, the first actuator 24 is connected to the first axis a. 1 The upper portion is connected to the second actuator 25 and the fixed frame 27 via the connecting portion 26 .

[0153] The applicant also conducted the same experiments and simulations as above for the MMD2F involved in the second comparative example. Figure 31 to Figure 33 Parameters related to the width and length of each component of the sample used in the experiment are shown in FIG. Fig.34 The specific setting values ​​of the parameters are shown in .

[0154] Furthermore, the diameter of the mirror portion 20 was set to 1.5 mm, the thickness of the SOI substrate 30 was set to 350 μm, and the thickness of the second silicon active layer 33 was set to 60 μm. Furthermore, the length of one side of the fixing frame 27 was set to 6.1 mm.

[0155] In addition, in the structure of the MMD2F according to the second comparative example, the mirror portion 20 cannot be rotated around the second axis a in the reverse phase rotation mode. 2 The mirror portion 20 is resonantly driven so as to rotate about the second axis a in the same phase. 2 Resonant drive was performed.

[0156] The experimental results showed that the driving voltage required for θ=11.25° was 18 V. The results of the resonance mode analysis simulation showed that the calculated value of the normative equivalent stress applied to the second supporting portion 23 at θ=11.25° was 1.225 GPa.

[0157] [Summarize]

[0158] exist Fig.35 The results of experiments and simulations involved in the above-mentioned embodiments and comparative examples are shown. In the application of laser display, θ=11.25° (i.e., optical full angle 45°) is an indicator that can reduce the optical system to a level that allows the MMD to be mounted on AR glasses. Considering the power consumption when driving the MMD for a long time with AR glasses, the driving voltage required for θ=11.25° is preferably less than 10V. In addition, in order to prevent structural damage to the swing shaft 23A, the paradigm equivalent stress applied to the second support portion 23 at θ=11.25° is preferably less than 2GPa.

[0159] In the first comparative example, the second support portion 23 does not have a folding structure and is directly connected to the driving portion, so when the mirror portion 20 and the first actuator 24 swing in opposite phases, the second support portion 23 is greatly twisted, thereby generating a large stress. In the first comparative example, the paradigm equivalent stress applied to the second support portion 23 becomes 2 GPa or more when θ = 11.25°, so the risk of structural damage to the second support portion 23 is high.

[0160] In the second comparative example, the reflector portion 20 and the first actuator 24 do not swing in opposite phases, but swing in the same phase. At this time, the internal energy loss of the second support portion 23 in the Si structure during resonance becomes larger, so the Q value is not improved even in a vacuum, and the driving voltage required for θ=11.25° becomes more than 10V. Considering power consumption, it is preferred to suppress the driving voltage to less than 10V, but if the driving voltage is set to less than 10V, a sufficiently large deflection angle cannot be achieved in the second comparative example.

[0161] Thus, in the first and second comparative examples, although the device size is large and the area of ​​the driving portion is large, a large deflection angle cannot be achieved. In contrast, in the above-mentioned embodiments, the driving voltage required for θ=11.25° is less than 10V, and the paradigm equivalent stress applied to the second supporting portion 23 is less than 2GPa when θ=11.25°, so a large deflection angle can be achieved without increasing the area of ​​the driving portion.

[0162] In addition, in the above-mentioned embodiment, the hardware structure of the drive control unit 4 can be variously modified. The processing unit of the drive control unit 4 can be composed of one processor, or a combination of two or more processors of the same type or different types. The processor includes a CPU, a programmable logic device (PLD) and a dedicated circuit. As is well known, the CPU is a general-purpose processor that executes software (programs) to function as various processing units. PLD is a processor that can change the circuit structure after manufacturing, such as FPGA (Field Programmable Gate Array). A dedicated circuit is a processor with a circuit structure specially designed to perform specific processing, such as ASIC (Application Specific Integrated Circuit).

[0163] All documents, Japanese patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, Japanese patent application, and technical standard were specifically and individually described.

Claims

1. A micromirror device, comprising: a reflector portion having a reflective surface for reflecting incident light; a pair of first support portions connected to the reflector portion on a first axis within a plane including the reflecting surface when the reflector portion is stationary, and supporting the reflector portion so as to be swingable about the first axis; a pair of movable frames connected to the first support portion and opposed to each other across the first axis; a pair of second support portions connected to the movable frame on a second axis that is within the plane and orthogonal to the first axis, and supporting the reflector portion, the first support portion, and the movable frame so as to be able to swing around the second axis; a driving portion connected to the second supporting portion and arranged to surround the movable frame; a fixing frame configured to surround the driving portion; and a pair of connecting parts, which connect the driving part and the fixing frame, The first support portion has a shape that is line-symmetrical about the first axis. The second support portion is in a line-symmetrical shape with the second axis as the center, and includes a second swing axis disposed on the second axis, and a pair of second connecting portions disposed at positions opposite to each other across the second axis. One end of the second swing shaft is connected to the movable frame, and the other end is connected to the second connecting portion. The second connecting portion extends from an outer end portion of the second swing shaft on the second axis in a direction toward the reflector portion and is connected to the driving portion in a region adjacent to the movable frame. The connecting portion has a shape that is line-symmetrical about the second axis, and supports the driving portion so as to be swingable about the second axis.

2. The micromirror device according to claim 1, wherein: The driving unit comprises: a pair of first actuators connected to the second support portion and opposed to each other across the second axis, the first actuators having piezoelectric elements; and A pair of second actuators are arranged to surround the first actuator and face each other across the first axis, wherein the second actuators include piezoelectric elements.

3. The micromirror device according to claim 2, wherein: The connection portion is arranged on the second shaft.

4. The micromirror device according to any one of claims 1 to 3, wherein: The first support portion has a shape that is line-symmetrical about the first axis, and includes a first swing axis disposed on the first axis, and a pair of first connection portions disposed at positions opposing each other across the first axis.

5. The micromirror device according to claim 4, wherein: One end of the first swing shaft is connected to the reflector portion, and the other end is connected to the first connecting portion. The first connection portion extends from an outer end portion of the first swing shaft on the first axis toward the mirror portion, bends toward the outer circumferential direction in a region adjacent to the mirror portion, bends again in a region adjacent to the drive portion, and is connected to the movable frame.

6. The micromirror device according to claim 4, wherein: One end of the first swing shaft is connected to the reflector portion, and the other end is connected to the first connecting portion. The first connection portion extends from an outer end portion of the first swing shaft on the first axis in a direction toward the reflector portion, and is connected to the movable frame in a region adjacent to the reflector portion.

7. The micromirror device according to claim 5, wherein: The first connection portion extends from a portion connected to the movable frame in the direction of the first axis to an outer end portion of the first swing axis on the first axis.

8. The micromirror device according to claim 4, wherein: The first connecting portion is bent outward from the outer end of the first shaft of the first swing shaft to form an annular area in an area adjacent to the movable frame, further extends from the annular area along the first shaft, and extends along the driving portion in an area adjacent to the driving portion to be connected to the movable frame.

9. The micromirror device according to claim 8, wherein: The pair of first connection parts are connected in a region adjacent to the driving part.

10. An optical scanning device comprising the micromirror device according to claim 1 and a processor for driving the driving unit, wherein: The processor supplies a driving signal to the driving unit to cause the mirror unit to swing around the first axis and the second axis.

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