Micromirror device and optical scanning device

Abstract

A micromirror device includes: a mirror portion; a first support portion that supports the mirror portion so as to be able to oscillate around a first axis; a movable frame that is connected to the first support portion; a second support portion that supports the mirror portion, the first support portion, and the movable frame so as to be able to oscillate around a second axis; a pair of first actuators that are connected to the second support portion and are opposed across the second axis; a second actuator that is disposed so as to surround the first actuators; a first connection portion that connects the first actuators and the second actuator; a fixed frame that is disposed so as to surround the second actuator; and a second connection portion that connects the second actuator and the fixed frame. The second actuator causes a torque around the first axis to act on the mirror portion. The first actuators cause a torque around the second axis to act on the movable frame.

Description

Technical Field

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

[0002] Micromirror devices (also known as microscanners) are one type of microelectromechanical systems (MEMS) devices fabricated using silicon (Si) microfabrication technology. Due to their compact size and low power consumption, these devices are expected to find widespread application in laser displays, laser projectors, optical coherence tomography scanners, and other applications.

[0003] There are various driving methods for micromirror devices. For example, Japanese Patent Application Laid-Open No. 2003-117897 discloses an electrostatically driven micromirror device. Furthermore, Japanese Patent Application Laid-Open No. 07-027989 discloses an electromagnetically driven micromirror device. Furthermore, Japanese Patent Application Laid-Open No. 2010-060688 discloses a piezoelectrically driven micromirror device.

[0004] Piezoelectric drive has gained attention for its ability to generate higher torque and achieve higher scanning angles than other drive methods. In particular, when a large scanning angle is required, such as in laser displays, piezoelectric micromirror devices can be driven by resonant drive to achieve even higher scanning angles.

[0005] Conventional micromirror devices used in laser displays include a reflector portion, a first piezoelectric actuator, and a second actuator (e.g., see Japanese Patent Application Publication No. 2010-060688). The reflector portion is capable of swinging freely about a first axis and a second axis that are orthogonal to each other. The first actuator swings the reflector portion about the first axis based on an externally supplied drive voltage. The second actuator swings the reflector portion about the second axis based on an externally supplied drive voltage. The scanning angle corresponds to the maximum value of the deflection angle of the reflector portion (hereinafter referred to as the maximum deflection angle).

[0006] Furthermore, it is known to perform two-dimensional optical scanning by causing a reflective mirror to resonate about a first axis and a second axis (for example, see Japanese Patent Application Laid-Open No. 2010-060688). This type of two-dimensional optical scanning is called Lissajous scanning.

[0007] The micromirror device described in Japanese Patent Application Laid-Open No. 2010-060688 includes a mirror portion, a first actuator connected to the mirror portion via a first support portion, a frame connected to the first actuator via a second support portion, and a second actuator connected to the frame via a third support portion.

[0008] In the micromirror device described in Japanese Patent Application Laid-Open No. 2010-060688, a first actuator swings the reflector portion using a first support portion as a first axis, and a second actuator swings the reflector portion using a second support portion as a second axis. Therefore, the first actuator swings only the reflector portion, while the second actuator swings the reflector portion, the first actuator, and the frame.

[0009] In the micromirror device described in Japanese Patent Application Laid-Open No. 2010-060688, it is impossible to independently determine the maximum deflection angle around the first axis of the first actuator and the weight of the swinging portion (i.e., the reflector portion, the first actuator, and the housing) of the second actuator. For example, if the maximum deflection angle around the first axis is to be increased, the first actuator needs to be enlarged in order to increase the torque around the first axis of the first actuator. If the first actuator is enlarged, the resonant frequency around the second axis will decrease due to the increased weight of the first actuator. Summary of the Invention

[0010] The technical object of the present invention is to provide a micromirror device and an optical scanning device that can increase the maximum deflection angle around the first axis without reducing the resonance frequency around the second axis.

[0011] In order to achieve the above-mentioned object, the micromirror device of the present invention comprises: a reflector portion having a reflective surface for reflecting incident light; a first support portion connected to the reflector portion on a first axis located in 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 support portion and opposed to each other across the first axis; a second support portion connected to the movable frame on a second axis located in a plane including the reflective surface when the reflector portion is stationary 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 pair of movable frames connected to the first support portion and opposed to each other across the first axis; a second support portion connected to the movable frame on a second axis located in a plane including the reflective surface when the reflector portion is stationary 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 first actuator is connected to the second supporting portion and is opposed to the second axis, the first actuator having a piezoelectric element; a pair of second actuators are arranged to surround the first actuator and are opposed to each other with the first axis, the second actuator having a piezoelectric element; a first connecting portion connects the first actuator and the second actuator; a fixed frame is arranged to surround the second actuator; and a second connecting portion connects the second actuator and the fixed frame, the second actuator applies a torque around the first axis to the reflector portion, and the first actuator applies a torque around the second axis to the movable frame, thereby causing the reflector portion to swing around the first axis and the second axis, respectively.

[0012] Preferably, the first connecting portion connects the first actuator and the second actuator in the vicinity of either or both of the first axis and the second axis, the second connecting portion connects the fixed frame and the second actuator in the vicinity of either or both of the first axis and the second axis, and includes a 2A connecting portion connected on the same axis as the first connecting portion, constituting a virtual extension portion that virtually extends the first connecting portion along the first axis to the end portion of the second actuator on the side opposite to the reflector portion, when the reflector portion, the first supporting portion, the movable frame, the second supporting portion, the first actuator, the first connecting portion, the virtual extension portion, and the 2A connecting portion are connected. The part is set as the first structural part, the second actuator and the second connecting part are set as the second structural part, the resonance frequency of the first resonance mode in which the reflector part swings around the first axis in the resonance mode of the first structural part when the end part on the fixed frame side of the second connecting part is fixed is set as fm, and the resonance frequency of the second resonance mode in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical in the resonance mode of the second structural part on the fixed frame side to which the second connecting part is fixed is set as fa, then the relationship |fm-fa| / fm≤0.03 is satisfied.

[0013] Preferably, the first connecting portion connects the first actuator and the second actuator near either the first axis or the second axis, and the second connecting portion connects the fixed frame and the second actuator near an axis orthogonal to the axis on which the first connecting portion is arranged, forming a virtual extension portion that virtually extends the first connecting portion along the first axis to the end portion of the second actuator on the side opposite to the reflector portion. When the reflector portion, the first supporting portion, the movable frame, the second supporting portion, the first actuator, the first connecting portion, and the virtual extension portion are set as the first structural portion, the second actuator The device and the second connecting portion are set as the second structural portion, the resonance frequency of the first resonance mode in which the reflector portion swings around the first axis in the resonance mode of the first structural portion when the end portion on the fixed frame side of the virtual extension portion is fixed is set as fm, and the resonance frequency of the second resonance mode in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis becomes symmetrical in the resonance mode of the second structural portion on the fixed frame side to which the second connecting portion is fixed is set as fa, the relationship of 0≤(fm-fa) / fm≤0.14 is satisfied.

[0014] Preferably, the first connecting portion connects the first actuator and the second actuator in the vicinity of either or both of the first axis and the second axis, the second connecting portion connects the fixed frame and the second actuator in the vicinity of either or both of the first axis and the second axis, and includes a 2A connecting portion connected on the same axis as the first connecting portion, constituting a virtual extension portion that virtually extends the first connecting portion along the first axis to the end portion of the second actuator on the side opposite to the reflector portion, when the reflector portion, the first supporting portion, the movable frame, the second supporting portion, the first actuator, the first connecting portion, the virtual extension portion, and the 2A connecting portion are connected. The part is set as the first structural part, the second actuator and the second connecting part are set as the second structural part, the resonance frequency of the first resonance mode in which the reflector part swings around the first axis in the resonance mode of the first structural part when the end part on the fixed frame side of the second connecting part is fixed is set as fm, and the resonance frequency of the second resonance mode in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical in the resonance mode of the second structural part on the fixed frame side to which the second connecting part is fixed is set as fa, then the relationship |fm-fa| / fm>0.03 is satisfied.

[0015] Preferably, the first connecting portion connects the first actuator and the second actuator near either the first axis or the second axis, and the second connecting portion connects the fixed frame and the second actuator near an axis orthogonal to the axis on which the first connecting portion is arranged, forming a virtual extension portion that virtually extends the first connecting portion along the first axis to the end portion of the second actuator on the side opposite to the reflector portion. When the reflector portion, the first supporting portion, the movable frame, the second supporting portion, the first actuator, the first connecting portion and the virtual extension portion are set as the first structural portion, the second actuator and the second connecting portion are connected. The part is set as the second structural part, the resonance frequency of the first resonance mode in which the reflector part swings around the first axis in the resonance mode of the first structural part when the end part on the fixed frame side of the virtual extension part is fixed is set as fm, and the resonance frequency of the second resonance mode in which the first axis is located at the node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis becomes symmetrical in the resonance mode of the second structural part on the fixed frame side to which the second connecting part is fixed is set as fa, then the relationship of (fm-fa) / fm<0 or (fm-fa) / fm>0.14 is satisfied.

[0016] Preferably, the first actuator and the mirror portion have the same thickness, and the second actuator is thinner than the first actuator.

[0017] Preferably, the first connecting portion is arranged along the first supporting portion.

[0018] Preferably, each of the pair of first actuators has a semi-annular shape.

[0019] Preferably, each of the pair of second actuators has a semi-annular shape.

[0020] The optical scanning device of the present invention comprises: any one of the above-mentioned micromirror devices; and a processor that drives the first actuator and the second actuator. In the optical scanning device, the processor applies a driving signal to the first actuator and the second actuator, causing the reflective mirror to resonate around the first axis and the second axis respectively.

[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 increase the maximum deflection angle around the first axis without reducing the resonance frequency around the second axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of an optical 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 This is a three-dimensional diagram of the appearance of a micromirror device.

[0026] Figure 4 This is a top view of the micromirror device as viewed from the light incident side.

[0027] Figure 5 It is along Figure 4 Cross-sectional view of the AA line cutting.

[0028] Figure 6 It is along Figure 4 Cross-sectional view of BB line cutting.

[0029] Figure 7 It is a diagram showing an example of driving the second actuator.

[0030] Figure 8 It is a diagram showing an example of driving the first actuator.

[0031] Figure 9 This is a diagram showing an example of the first driving signal.

[0032] Figure 10 This is a diagram showing an example of the second driving signal.

[0033] Figure 11 It is a top view showing the first structural part.

[0034] Figure 12 This is a diagram showing an example of a resonance mode in which only the first structural portion is targeted.

[0035] Figure 13 It is a top view showing the second structural part.

[0036] Figure 14This is a diagram showing an example of a resonance mode in which only the second structural portion is targeted.

[0037] Figure 15 It is a cross-sectional view illustrating the dimensions of a micromirror device.

[0038] Figure 16 It is a graph showing the results of the simulation experiment.

[0039] Figure 17 It is a graph showing the simulation test results for Models 1 to 7.

[0040] Figure 18 It is a graph showing the simulation test results for Models 8 to 15.

[0041] Figure 19 It is a top view of the micromirror device involved in the first modification.

[0042] Figure 20 It is a plan view showing the first structural portion according to the first modification.

[0043] Figure 21 It is a plan view showing the second structural portion according to the first modification.

[0044] Figure 22 It is a graph showing the results of the simulation experiment.

[0045] Figure 23 This is a graph showing the simulation results for Models 16 to 23.

[0046] Figure 24 It is a top view of the micromirror device involved in the second modification.

[0047] Figure 25 It is a plan view showing the first structural portion according to the second modification.

[0048] Figure 26 It is a plan view showing the second structural portion according to the second modification.

[0049] Figure 27 It is a graph showing the results of the simulation experiment.

[0050] Figure 28 It is a graph showing the results of simulation experiments on models 24 to 30.

[0051] Figure 29 1 is a diagram showing a modified example of the shape of the first connecting portion and the second connecting portion. Figure 29 (A) represents the first shape, Figure 29 (B) represents the second shape, Figure 29 (C) shows the third shape. DETAILED DESCRIPTION

[0052] An example of an embodiment according to the technology of the present invention will be described with reference to the drawings.

[0053] [First embodiment]

[0054] Figure 1 The following diagram schematically illustrates an optical scanning device 10 according to one embodiment. The optical scanning device 10 includes a micromirror device (hereinafter referred to as an MMD) 2, a light source 3, and a drive control unit 4. Under control of the drive control unit 4, the optical scanning device 10 reflects a light beam L emitted from the light source 3 via the MMD 2, thereby optically scanning a scanned surface 5. The scanned surface 5 is, for example, a screen.

[0055] MMD2 is a device that can make the reflector portion 20 (refer to Figure 3 A piezoelectric two-axis driven micromirror device is described, which oscillates (i.e., performs reciprocating motion) about a first axis a1 and a second axis a2 perpendicular to the first axis a1. Hereinafter, the direction parallel to the first axis a1 is referred to as the X direction, the direction parallel to the second axis a2 is referred to as the Y direction, and the direction perpendicular to the first axis a1 and the second axis a2 is referred to as the Z direction.

[0056] The light source 3 is a laser device that emits a laser beam as a light beam L. The light source 3 preferably emits a light beam to the reflective surface 20A (refer to FIG. 2 ) of the reflective mirror 20 when the reflective mirror 20 of the MMD 2 is stationary. Figure 3 ) is vertically irradiated with the light beam L. In addition, the angle at which the light beam L emitted from the light source 3 is irradiated on the reflecting surface 20A is not limited to being vertical, and the light beam L may be irradiated on the reflecting surface 20A obliquely.

[0057] The drive control unit 4 outputs a drive signal to the light source 3 and the MMD 2 based on the light scanning information. The light source 3 generates a light beam L based on the input drive signal and irradiates the light beam L to the MMD 2. The MMD 2 swings the mirror unit 20 around the first axis a1 and the second axis a2 based on the input drive signal.

[0058] Although details will be described later, the drive control unit 4 causes the mirror unit 20 to resonate about the first axis a1 and the second axis a2, respectively, so that the light beam L reflected by the mirror unit 20 is scanned so as to draw a Lissajous waveform on the scanned surface 5. This optical scanning method is called a Lissajous scanning method.

[0059] The optical scanning device 10 is applicable to, for example, a Lissajous scanning laser display. Specifically, the optical scanning device 10 can be applied to laser scanning displays such as AR (Augmented Reality) glasses or VR (Virtual Reality) glasses.

[0060] Figure 2 The figure shows an example of the hardware configuration 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 reads programs and data from a storage device such as the ROM 41 into the RAM 42 and executes these programs, thereby realizing the overall functions of the drive control unit 4. The CPU 40 is an example of a processor involved in the technology of the present invention.

[0061] The ROM 41 is a nonvolatile storage device and stores programs for execution by the CPU 40 and data such as the aforementioned light scanning information. The RAM 42 is a nonvolatile storage device that temporarily stores programs and data.

[0062] 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.

[0063] The MMD driver 44 is a circuit that outputs a drive signal to the MMD 2 under 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 oscillation of the mirror unit 20 of the MMD 2.

[0064] 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 L for scanning the scanned surface 5 and the emission timing of the light source 3.

[0065] Next, use Figures 3 to 6 An example of MMD2 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 It is along Figure 4 Cross-sectional view of the AA line cutting. Figure 6 It is along Figure 4 Cross-sectional view of BB line cutting.

[0066] like Figure 3 As shown, the MMD 2 includes a mirror unit 20, a pair of first support units 21, a pair of movable frames 22, a pair of second support units 23, a pair of first actuators 24, a pair of second actuators 25, a pair of first connecting units 26A, a pair of second connecting units 26B, and a fixed frame 27. The MMD 2 is a so-called MEMS scanner.

[0067] The reflector 20 has a reflective surface 20A that reflects 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 reflective surface 20A is shaped, for example, circularly centered at the intersection of the first axis a1 and the second axis a2.

[0068] The first axis a1 and the second axis a2 exist in a plane including the reflecting surface 20A when the mirror unit 20 is stationary. The planar shape of the MMD 2 is rectangular and is line-symmetric about the first axis a1 and the second axis a2.

[0069] The pair of first support portions 21 are disposed at opposing positions across the second axis a2 and are line-symmetrical about the second axis a2. Furthermore, each first support portion 21 is line-symmetrical about the first axis a1. The first support portions 21 are connected to the reflector portion 20 along the first axis a1 and support the reflector portion 20 so that it can swing about the first axis a1.

[0070] A pair of movable frames 22 are positioned opposite each other across the first axis a1 and are symmetrical about the first axis a1. Each movable frame 22 is symmetrical about the second axis a2. Furthermore, each movable frame 22 is semi-annular, curved in an arc along the outer circumference of the reflector portion 20. Both ends of the movable frame 22 are connected to the first support portion 21.

[0071] The first support portion 21 and the movable frame 22 are connected to each other, thereby surrounding the reflector portion 20. The movable frame 22 and the first support portion 21 are formed as a continuous integral structure. In addition, the shape formed by the pair of movable frames 22 includes an annular shape such as a ring.

[0072] A pair of second support portions 23 are disposed at opposing positions across the first axis a1 and are symmetrical about the first axis a1. Each second support portion 23 is symmetrical about the second axis a2. The second support portions 23 are connected to the movable frame 22 along the second axis a2 and support the mirror portion 20, the first support portion 21, and the movable frame 22 so that they can swing about the second axis a2. Furthermore, each end of the second support portion 23 is connected to the first actuator 24.

[0073] The pair of first actuators 24 are disposed at opposing positions across the second axis a2 and are symmetrical about the second axis a2. Furthermore, each first actuator 24 is symmetrical about the first axis a1. Furthermore, each first actuator 24 has a semi-annular shape that curves along the outer circumference of the first support portion 21.

[0074] The pair of first actuators 24 are connected to each other via a pair of second support portions 23, thereby surrounding the mirror portion 20, the first support portion 21, and the movable frame 22. The first actuator 24 and the second support portion 23 are continuously formed into an integral structure. The shape formed by the pair of first actuators 24 includes an annular shape such as a ring.

[0075] The pair of second actuators 25 are positioned opposite each other across the first axis a1 and are symmetrical about the first axis a1. Furthermore, each second actuator 25 is symmetrical about the second axis a2. Furthermore, each second actuator 25 has a semi-annular shape that curves along the outer circumference of the first actuator 24 and the second support portion 23. Furthermore, the second actuators 25 are connected to the pair of first connecting portions 26A.

[0076] The pair of first connecting portions 26A are disposed at opposing positions across the second axis a2 and are symmetrical about the second axis a2. Furthermore, each first connecting portion 26A is symmetrical about the first axis a1. The first connecting portions 26A are disposed along the first axis a1 and connect the first actuator 24 and the second actuator 25 along the first axis a1.

[0077] The pair of second actuators 25 are connected to each other, thereby surrounding the mirror portion 20, the first support portion 21, the movable frame 22, and the first actuator 24. The shape formed by the pair of second actuators 25 includes an annular shape such as a ring.

[0078] The fixed frame 27 is a rectangular frame-shaped member having a line-symmetric shape about the first axis a1 and the second axis a2. The fixed frame 27 is arranged to surround the outer periphery of the second actuator 25. The fixed frame 27 is connected to the second actuator 25 via the second connecting portion 26B.

[0079] The pair of second connecting portions 26B are positioned opposite each other across the second axis a2 and are symmetrical about the second axis a2. Furthermore, each second connecting portion 26B is symmetrical about the first axis a1. The second connecting portions 26B are arranged along the first axis a1 and connect the second actuator 25 and the fixed frame 27 along the first axis a1.

[0080] The first actuator 24 and the second actuator 25 are piezoelectric actuators each including a piezoelectric element. The pair of first actuators 24 apply a torque about the second axis a2 to the movable frame 22, thereby causing the mirror portion 20 to oscillate about the second axis a2. The pair of second actuators 25 apply a torque about the first axis a1 to the mirror portion 20, thereby causing the mirror portion 20 to oscillate about the first axis a1.

[0081] like Figure 4As shown, 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 so-called torsion bar extending along the first axis a1. 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.

[0082] The pair of connecting portions 21B are arranged at opposing positions across the first axis a1 and are line-symmetrical about the first axis a1. One end of the connecting portion 21B is connected to the swing shaft 21A, and the other end is connected to the movable frame 22. The connecting portion 21B has a foldable structure. This foldable structure provides elasticity to the connecting portion 21B, thereby alleviating internal stress applied to the swing shaft 21A when the reflector portion 20 swings about the first axis a1.

[0083] 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 so-called torsion bar extending along the second axis a2. 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.

[0084] The pair of connecting portions 23B are arranged at opposing positions across the second axis a2 and are line-symmetrical about the second axis a2. One end of the connecting portion 23B is connected to the swing shaft 23A, and the other end is connected to the first actuator 24. The connecting portion 23B has a foldable structure. The foldable structure provides elasticity to the connecting portion 23B, thereby alleviating internal stress applied to the swing shaft 23A when the reflector portion 20 swings about the second axis a2.

[0085] The first actuator 24 is composed of an arcuate portion 24A and a pair of fan-shaped portions 24B. The arcuate portion 24A is line-symmetrical about the first axis a1. Both ends of the arcuate portion 24A are connected to the fan-shaped portions 24B.

[0086] The pair of fan-shaped portions 24B are arranged at opposing positions across the first axis a1 and are line-symmetrical about the first axis a1. One end of the fan-shaped portion 24B is connected to the arc-shaped portion 24A, and the other end is connected to the connecting portion 23B of the second support portion 23. The first actuator 24 has a large fan-shaped portion 24B, so the area of ​​the piezoelectric element is large. As a result, a large driving torque is obtained around the second axis a2 by the first actuator 24.

[0087] Furthermore, the reflector portion 20 has a plurality of slits 20B and 20C formed along the outer periphery of the reflective surface 20A outside the reflective surface 20A. The slits 20B and 20C are arranged at positions that are line-symmetrical about the first axis a1 and the second axis a2. The slits 20B suppress deformation of the reflective surface 20A caused by the oscillation of the reflector portion 20.

[0088] exist Figure 3 and Figure 4In 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.

[0089] like Figure 5 and Figure 6 As shown, the MMD 2 is formed, for example, by etching an SOI (Silicon On Insulator) substrate 30. The SOI substrate 30 comprises a first silicon active layer 31 made of single crystal silicon, a silicon oxide layer 32 provided on top of the first silicon active layer 31, and a second silicon active layer 33 made of single crystal silicon provided on the silicon oxide layer 32.

[0090] The mirror portion 20, first support portion 21, movable frame 22, second support portion 23, first actuator 24, second actuator 25, first connecting portion 26A, and second connecting portion 26B are formed from the second silicon active layer 33 remaining after etching away the first silicon active layer 31 and silicon oxide layer 32 from the SOI substrate 30. The second silicon active layer 33 functions as a resilient elastic portion. The fixed frame 27 is formed from three layers: the first silicon active layer 31, the silicon oxide layer 32, and the second silicon active layer 33.

[0091] The first actuator 24 has a thickness equal to that of the mirror portion 20. The second actuator 25 is formed by etching the second silicon active layer 33 so that the thickness of the second silicon active layer 33 is thinner than that of the first actuator 24. In other words, the second actuator 25 is thinner in the Z direction than the first actuator 24.

[0092] The first actuator 24 and the second actuator 25 include a piezoelectric element 28 on the second silicon active layer 33. The piezoelectric element 28 has a stacked structure in which a lower electrode 51, a piezoelectric film 52, and an upper electrode 53 are stacked in this order on the second silicon active layer 33. An insulating film is provided on the upper electrode 53, but this is not shown in the figure.

[0093] The upper electrode 53 and the lower electrode 51 are formed of, for example, gold (Au) or platinum (Pt). The piezoelectric film 52 is formed of, for example, PZT (lead zirconate titanate), a piezoelectric material. The upper electrode 53 and the lower electrode 51 are electrically connected to the aforementioned drive control unit 4 via wiring and electrode pads.

[0094] A driving voltage is applied to the upper electrode 53 from the driving control unit 4. The lower electrode 51 is connected to the driving control unit 4 via wiring and electrode pads, and a reference potential (for example, ground potential) is applied thereto.

[0095] When a positive or negative voltage is applied to the piezoelectric film 52 in its polarization direction, it deforms (e.g., expands and contracts) in proportion to the applied voltage. In other words, the piezoelectric film 52 exhibits the so-called inverse piezoelectric effect. The piezoelectric film 52 exhibits the inverse piezoelectric effect when a drive voltage is applied to the upper electrode 53 by the drive control unit 4, causing the first actuator 24 and the second actuator 25 to displace.

[0096] Figure 7 The example shows a method of generating torque about the first axis a1 in the second actuator 25 by expanding the piezoelectric film 52 of one of the pair of second actuators 25 and contracting the piezoelectric film 52 of the other. In this manner, one and the other of the pair of second actuators 25 are displaced in opposite directions relative to each other, causing the mirror portion 20 to rotate about the first axis a1.

[0097] and, Figure 7 This example shows that the second actuators 25 are driven in an anti-phase resonance mode in which the displacement directions of the pair of second actuators 25 and the rotational direction of the mirror unit 20 are opposite to each other. Alternatively, the second actuators 25 may be driven in an in-phase resonance mode in which the displacement directions of the pair of second actuators 25 and the rotational direction of the mirror unit 20 are the same.

[0098] The deflection angle of the mirror portion 20 around the first axis a1 is controlled by a drive signal (hereinafter referred to as a first drive signal) applied 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 opposite phases (i.e., a phase difference of 180°).

[0099] The deflection angle of the mirror portion 20 about the first axis a1 refers to an angle at which the normal line of the reflecting surface 20A is inclined with respect to the Z direction on the YZ plane.

[0100] Figure 8 The example shows a method of generating torque about the second axis a2 in the first actuator 24 by expanding the piezoelectric film 52 of one of the pair of first actuators 24 and contracting the piezoelectric film 52 of the other. In this manner, one and the other of the pair of first actuators 24 are displaced in opposite directions relative to each other, causing the mirror portion 20 to rotate about the second axis a2.

[0101] and, Figure 8The example in which the first actuators 24 are driven in an in-phase resonance mode in which the displacement directions of the pair of first actuators 24 and the rotational direction of the mirror unit 20 are in the same direction is shown. Alternatively, the first actuators 24 may be driven in an anti-phase resonance mode in which the displacement directions of the pair of first actuators 24 and the rotational direction of the mirror unit 20 are in opposite directions.

[0102] The deflection angle of the reflector portion 20 around the second axis a2 is controlled by a drive signal (hereinafter referred to as a second drive signal) applied 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 opposite phases (i.e., a phase difference of 180°).

[0103] The deflection angle of the mirror portion 20 about the second axis a2 refers to an angle at which the normal line of the reflecting surface 20A is inclined with respect to the Z direction on the XZ plane.

[0104] Figure 9 and Figure 10 An example of the first drive signal and the second drive signal is shown. Figure 9 The driving voltage waveform V included in the first driving signal is shown as 1A (t) and V 1B (t). Figure 10 The driving voltage waveform V included in the second driving signal is shown in FIG. 2A (t) and V 2B (t).

[0105] Driving voltage waveform V 1A (t) and V 1B (t) are expressed as follows.

[0106] V 1A (t) = V off1 +V1sin(2πf d1 t)

[0107] V 1B (t) = V off1 +V1sin(2πf d1 t+α)

[0108] Here, V1 is the amplitude voltage. 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 V1A (t) and V 1B In this embodiment, for example, α is set to 180°.

[0109] Driving voltage waveform V 1A (t) and V 1B (t) is applied to the pair of second actuators 25, whereby the mirror portion 20 is driven at the first driving frequency f d1 To swing around the first axis a1 (refer to Figure 7 ).

[0110] Driving voltage waveform V 2A (t) and V 2B (t) are expressed as follows.

[0111] V 2A (t) = V off2 +V2sin(2πf d2 t+φ)

[0112] V 2B (t) = V off2 +V2sin(2πf d2 t+β+φ)

[0113] Here, V2 is the amplitude voltage. 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°. And 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, it is set to V off1 =V off2 =0V.

[0114] Driving voltage waveform V 2A (t) and V 2B (t) is applied to the pair of first actuators 24, whereby the mirror portion 20 is driven at the second driving frequency f d2 To swing around the second axis a2 (refer to Figure 8 ).

[0115] First driving frequency f d1 The second driving frequency f is set to coincide with the resonance frequency of the mirror portion 20 about the first axis a1 (hereinafter referred to as the first resonance frequency). d2It is set to coincide with the resonance frequency of the mirror portion 20 about the second axis a2 (hereinafter referred to as the second resonance frequency). In this embodiment, it is set to f d1 >f d2 That is, the oscillation frequency of the mirror portion 20 around the first axis a1 is higher than the oscillation frequency around the second axis a2. d1 and the second driving frequency f d2 It does not have to be consistent with the resonance frequency. For example, the first drive frequency f d1 and the second driving frequency f d2 Each frequency may be within a frequency range near the resonance frequency (for example, a range of the half-value width of a frequency distribution with the resonance frequency as a peak).

[0116] In the resonance of the mirror portion 20, in addition to the aforementioned phase (in phase or in reverse phase), there are multiple resonance modes with different orders. For example, the first driving frequency f d1 The first drive frequency f is set to a value that matches the resonance frequency of the resonance mode that obtains the maximum deflection angle from the anti-phase resonance mode group around the first axis a1. d1 The resonance frequency coincides with the resonance frequency of the second resonance mode from the lowest order in the anti-phase resonance mode group. Hereinafter, the resonance mode around the first axis a1 is referred to as a high-speed scanning mode.

[0117] Furthermore, for example, the second driving frequency f d2 The second drive frequency f is set to a value that matches the resonance frequency of the resonance mode that obtains the maximum deflection angle from the resonance mode group with the same phase around the second axis a2. d2 The resonant frequency of the second resonant mode from the lowest order in the resonant mode group with the same phase coincides with the resonant frequency of the second resonant mode. Hereinafter, the resonant mode around the second axis a2 is referred to as a low-speed scanning mode.

[0118] In addition, the order of the resonance mode that obtains the maximum deflection angle varies depending on the shapes of the first actuator 24 and the second actuator 25. Therefore, the first drive frequency f d1 and the second driving frequency f d2 The frequencies are consistent with those of the resonance modes of other orders.

[0119] Next, the resonance mode around the first axis a1 will be described. Figure 11FIG2 shows a portion of the structure of the MMD2, namely the first structure 60A. The first structure 60A includes the mirror section 20, the first support section 21, the movable frame 22, the second support section 23, the first actuator 24, the first connection section 26A, the virtual extension section 26C, and the second connection section 26B. The virtual extension section 26C is formed by virtually extending the first connection section 26A along the first axis a1 to the end 25B of the second actuator 25 on the side opposite to the mirror section 20 (see FIG2 ). Figure 13 ) is formed. Furthermore, the second connection portion 26B of this embodiment is an example of the "2A connection portion" involved in the technology of the present invention. The 2A connection portion connects the fixed frame 27 and the second actuator 25 on the same axis as the first connection portion 26A.

[0120] Figure 12 1 shows an example of a resonance mode in which only the first structural portion 60A is targeted. Specifically, Figure 12 The end portion 61 on the fixing frame 27 side to which the second connecting portion 26B is fixed is shown (see FIG. Figure 11 ), a resonance mode in which the mirror portion 20 oscillates about the first axis a1 (hereinafter referred to as a first resonance mode) among the resonance modes of the first structural portion 60A when φ(φ)=φ(φ)=φ(φ).

[0121] Figure 13 The second structural part 60B which is a partial structural part of the MMD 2 is shown. The second structural part 60B includes the second actuator 25 and the second connecting part 26B.

[0122] Figure 14 : shows an example of a resonance mode in which only the second structural part 60B is the target. Specifically, Figure 14 The figure shows a resonance mode (hereinafter referred to as the second resonance mode) in which the first axis a1 is located at a node of vibration and the displacement distribution of the second actuator 25 in the out-of-plane direction (i.e., the plate thickness direction) with respect to the first axis a1 when the second connection portion 26B is fixed to the fixing frame 27 side. Figure 14 In the embodiment, the displacement distribution of the second actuator 25 in the out-of-plane direction is rotationally symmetric with respect to the first axis a1.

[0123] Only the first structural portion 60A is used as the object, and the first resonance mode (refer to Figure 12 ) is set as the resonance frequency fm. And, only the second structural part 60B is set as the object, and the displacement distribution of the second actuator 25 in the out-of-plane direction with respect to the first axis a1 is made into the second resonance mode (reference Figure 14 ) is set to fa.

[0124] The present applicant has discovered that the closer the resonant frequency fm of the first resonant mode is to the resonant frequency fa of the second resonant mode, the greater the maximum deflection angle θm of the reflector portion 20 about the first axis a1 (hereinafter referred to as the maximum deflection angle). Specifically, to increase the maximum deflection angle θm, the resonant frequencies fm and fa preferably satisfy the relationship expressed by the following equation (1).

[0125] -0.03≤Δf / fm≤0.03……(1)

[0126] Here, Δf is the difference between the resonant frequency fm and the resonant frequency fa, and is expressed as Δf=fm-fa. Δf / fm is the matching ratio indicating the degree of matching between the resonant frequency fm and the resonant frequency fa.

[0127] This indicates that even if the amplitude voltage V1 of the first drive signal is constant, the maximum deflection angle θm is maximized when the resonant frequencies fm and fa satisfy the above equation (1), that is, when |fm-fa| / fm≤0.03. By increasing the maximum deflection angle θm, the scanning angle of the light beam L reflected by the reflector unit 20 can be increased.

[0128] In addition, there are a plurality of candidate modes for each of the first resonance mode and the second resonance mode, and therefore it is preferable to select an appropriate mode from these modes in consideration of the target driving frequency, stability, displacement, and the like.

[0129] [Example 1]

[0130] Next, the results of simulations conducted to confirm the above formula (1) will be described as Example 1. The present applicants conducted vibration analysis simulations based on the finite element method and studied the relationship between the matching ratio Δf / fm and the maximum deflection angle θm while varying the dimensions of the MMD 2.

[0131] (MMD size)

[0132] First, the size of the MMD2 used in this embodiment is described. Figure 13 In FIG. 1 , Wx represents the width of the second actuator 25 in the X direction near the first axis a1. Wy represents the width of the second actuator 25 in the Y direction on the second axis a2. L represents the length of one side of the fixed frame 27. The length L of one side of the fixed frame 27 is equal in the X and Y directions.

[0133] H represents the width of the fixed frame 27. The width H of the fixed frame 27 is equal in the X direction and the Y direction. Figure 11 In FIG. 2 , D represents the diameter of the reflecting surface 20A of the reflector portion 20. In this embodiment, the diameter D and the width H are fixed. Specifically, D = 1.5 mm and H = 0.5 mm.

[0134] In this embodiment, the widths Wx and Wy are changed as parameters, and the length L is a value that changes in conjunction with the change in the widths Wx and Wy.

[0135] Figure 15 It is a cross-sectional view showing the thickness of MMD2. Figure 15 In the figure, T1 represents the first structural part 60A (refer to Figure 11 ) thickness. T2 represents the second structural portion 60B (reference Figure 13 T1 corresponds to the thickness of the second silicon active layer 33 constituting the first actuator 24 and the mirror portion 20. T2 corresponds to the thickness of the second silicon active layer 33 constituting the second actuator 25.

[0136] The applicant prepared multiple simulation models (hereinafter referred to as models) by changing the widths Wx, Wy and thicknesses T1, T2, and obtained the matching ratio Δf / fm and the maximum deflection angle θm for each model. Here, the amplitude voltage V1 of the first drive signal is set to 5V (i.e., Vpp = 10V). Vpp represents the difference between the maximum voltage and the minimum voltage of the first drive signal. In addition, the first drive frequency f d1 Set to approximately 35kHz.

[0137] Figure 16 Shows the simulation results of each model. Figure 16 In the figure, models 1-7 are created by varying widths Wx and Wy while setting T1 = T2. Model 1 has the smallest widths Wx and Wy, while model 7 has the largest. Models 8-15 are created by varying widths Wx and Wy while setting T1 > T2. Model 8 has the smallest widths Wx and Wy, while model 15 has the largest.

[0138] Figure 17 and Figure 18 : is a graph showing the relationship between the matching ratio Δf / fm and the maximum deflection angle θm. Figure 17 The simulation results of models 1 to 7 are shown. Figure 18 The simulation results for models 8 to 15 are shown.

[0139] from Figures 16 to 18 The simulation results show that, in both the case where T1 = T2 and the case where T1 > T2, when the matching ratio Δf / fm satisfies the above equation (1), the maximum deflection angle θm is maximized. Furthermore, a comparison between the case where T1 = T2 and the case where T1 > T2 shows that the case where T1 > T2 allows for smaller widths Wx and Wy (i.e., a smaller size of the second actuator 25).

[0140] As described above, according to the technology of the present invention, by configuring MMD2 as described above, the shapes of the first actuator 24 and the second actuator 25 can be optimized for driving about the second axis a2 and the first axis a1, respectively. This allows the maximum deflection angle θm of the reflector unit 20 to be set to a desired angle, while also ensuring the stability of the oscillation of the reflector unit 20. More specifically, by fine-tuning the resonant frequency of the second structural unit 60B by varying the dimensions of the second actuator 25, the deflection angle of the reflector unit 20 per unit amplitude voltage of the first drive signal that applies torque about the first axis a1 can be freely set. Furthermore, robustness against dimensional variations can be freely designed within a wide range.

[0141] Furthermore, by adjusting the size of the second actuator 25 to keep the matching ratio Δf / fm within the range of equation (1), the maximum deflection angle θm of the reflector portion 20 about the first axis a1 can be increased. Furthermore, there is no need to increase the size of the first actuator 24 to increase the maximum deflection angle θm. Therefore, a decrease in the resonant frequency about the second axis a2, which would otherwise be caused by the increase in weight associated with the size of the first actuator 24, can be suppressed. Therefore, according to the technology of the present invention, the maximum deflection angle θm about the first axis a1 can be increased without lowering the resonant frequency about the second axis a2.

[0142] And, from Figures 16 to 18 The simulation results show that when the matching ratio Δf / fm satisfies the following equation (2) or (3), the change rate of the maximum deflection angle θm relative to the change of the matching ratio Δf / fm is small.

[0143] Δf / fm>0.03……(2)

[0144] Δf / fm<-0.03……(3)

[0145] This corresponds to the fact that when the matching ratio Δf / fm satisfies equation (2) or equation (3), that is, when the relationship |fm-fa| / fm>0.03 is satisfied, the rate of change of the maximum deflection angle θm with respect to changes in widths Wx and Wy (i.e., changes in the dimensions of the second actuator 25) is small. In other words, when the matching ratio Δf / fm satisfies equation (2) or equation (3), a stable deflection angle can be achieved (i.e., manufacturing robustness is high) even if errors occur in the dimensions of the second actuator 25 due to errors in the manufacturing process.

[0146] How to design the matching ratio Δf / fm to satisfy any of the above equations (1) to (3) can be freely selected based on major factors such as system requirements and manufacturing process accuracy.

[0147] [First Modification]

[0148] Next, a first modification of the micromirror device will be described. Figure 19 FIG2 shows an MMD2A according to a first modification. The shape of the first support portion 21 of the MMD2A is different from the shape of the first support portion 21 of the MMD2 according to the first embodiment. The shape of the first support portion 21 of the MMD2A is the same as the shape of the second support portion 23 .

[0149] Furthermore, in the MMD2A according to the first modification, the second connection portion 26B is disposed near the first axis a1 and near the second axis a2. Specifically, a pair of second connection portions 26B are disposed at positions opposing each other across the second axis a2, and a pair of second connection portions 26B are disposed at positions opposing each other across the first axis a1. The second connection portions 26B connect the second actuator 25 and the fixed frame 27 along the first axis a1 and the second axis a2. In the first modification, the pair of second connection portions 26B disposed at positions opposing each other across the second axis a2 are an example of the "2A connection portion" involved in the technology of the present invention.

[0150] Figure 20 1 shows a first structure portion 70A according to a first modification. The structure of the first structure portion 70A is the same as the structure of the first structure portion 60A according to the first embodiment. Figure 20 In FIG. 1 , reference numeral 71 denotes an end portion on the fixing frame 27 side of the second connecting portion 26B fixed when the first structural portion 70A is caused to resonate in the first resonance mode.

[0151] Figure 21 FIG2 shows a second structural portion 70B according to a first modification. The second structural portion 70B differs from the second structural portion 60B according to the first embodiment in that second connecting portions 26B are provided near the first axis a1 and near the second axis a2. In this modification, the second structural portion 60B is resonantly driven by fixing the second connecting portion 26B provided near the first axis a1 to the fixed frame 27 side.

[0152] [Example 2]

[0153] The present applicant also conducted a vibration analysis simulation experiment on the MMD 2A according to the first modification, similar to that of Example 1. The dimensions of the MMD 2A are the same as those of the MMD 2 according to the first embodiment.

[0154] Figure 22 Shows the simulation results of each model. Figure 22 In the figure, models 16 to 23 are models created by setting T1 = T2 and changing widths Wx and Wy. Model 16 has the smallest width Wx and model 23 has the largest width Wx and Wy.

[0155] Figure 23 is a graph showing the relationship between the matching rate Δf / fm and the maximum deflection angle θm. Figure 23It can be seen that when the matching ratio Δf / fm satisfies the above equation (1), the maximum deflection angle θm is maximized. It can also be seen that when the matching ratio Δf / fm satisfies the above equation (2) or (3), the manufacturing robustness is improved.

[0156] [Second Modification]

[0157] Next, a second modification of the micromirror device will be described. Figure 24 This figure shows the MMD2B according to the second modification. In the MMD2B, each corner of the second actuator 25 is cut at a 45° angle to the X and Y directions. The shape of the first support portion 21 is the same as that of the first support portion 21 of the MMD2A according to the first modification.

[0158] Furthermore, in the MMD2B according to the second modification, the second connection portion 26B is provided only near the second axis a2. That is, a pair of second connection portions 26B are arranged at positions opposing each other across the first axis a1. The second connection portion 26B connects the second actuator 25 and the fixed frame 27 along the second axis a2. In the second modification, the second connection portion 26B is an example of a "2B connection portion" that connects the fixed frame 27 and the second actuator 25 near an axis perpendicular to the axis on which the first connection portion 26A is arranged.

[0159] Figure 25 1 shows a first structural portion 80A according to a second modified example. The first structural portion 80A includes the reflector portion 20, the first support portion 21, the movable frame 22, the second support portion 23, the first actuator 24, the first connecting portion 26A, and the dummy extension portion 26C. The dummy extension portion 26C is formed by extending the first connecting portion 26A along the first axis a1 to the end portion 25B of the second actuator 25 on the side opposite to the reflector portion 20 (see FIG. 1 ). Figure 26 ) and the parts formed. Figure 25 In FIG. 8 , reference numeral 81 denotes an end portion of the dummy extension portion 26C on the fixing frame 27 side that is fixed when the first structure portion 80A is caused to resonate in the first resonance mode.

[0160] Figure 26 The second structural portion 80B according to the second modification is shown. Unlike the second structural portion 70B according to the first modification, the second structural portion 80B has a second connecting portion 26B provided only near the second axis a2. Furthermore, as described above, each corner of the second actuator 25 is cut away. The second structural portion 80B is resonantly driven by fixing the second connecting portion 26B to the fixed frame 27.

[0161] [Example 3]

[0162] The applicant also conducted the same vibration analysis simulation experiments as in Example 1 on the MMD2B according to the second modification. The dimensions of the MMD2B were the same as those of the MMD2 according to the first embodiment. Furthermore, in this modification, in addition to the widths Wx and Wy, the length Wz of the notch of the second actuator 25 was varied, resulting in the production of multiple models 24 to 30.

[0163] Figure 27 Shows the simulation results of each model. Figure 27 In the models 24 to 30, T1>T2 is set and the length Wz of the notch portion of the second actuator 25 is changed in addition to the widths Wx and Wy (refer to Figure 26 ) The models thus produced. More specifically, models 24 to 27 are models produced by setting widths Wx and Wy constant and varying length Wz. Models 28 to 30 are models produced by setting Wz = 0 and varying widths Wx and Wy.

[0164] Figure 28 is a graph showing the relationship between the matching rate Δf / fm and the maximum deflection angle θm. Figure 28 It can be seen that when the matching ratio Δf / fm satisfies the following formula (4), the maximum deflection angle θm is maximized.

[0165] 0≤Δf / fm≤0.14……(4)

[0166] On the other hand, when the matching ratio Δf / fm satisfies the following equation (5) or (6), the change rate of the maximum deflection angle θm with respect to the change of the matching ratio Δf / fm is small, and manufacturing robustness is improved.

[0167] Δf / fm<0……(5)

[0168] Δf / fm>0.14……(6)

[0169] [Other modifications]

[0170] In the first embodiment and the modifications, the first support portion 21 is provided with the connecting portion 21B having a folding structure, but the folding structure is not essential. Similarly, the second support portion 23 is provided with the connecting portion 23B having a folding structure, but the folding structure is not essential.

[0171] Furthermore, in the first embodiment and the modifications, a plurality of first connection portions 26A and second connection portions 26B are provided. However, the number of first connection portion 26A and second connection portion 26B may be one (single).

[0172] Furthermore, in the first embodiment and the various modifications, the shapes of the first connecting portion 26A and the second connecting portion 26B are respectively set to be rectangular, but they are not limited to rectangular. The first connecting portion 26A and the second connecting portion 26B may be any shape as long as they are along the first axis a1 or the second axis a2 and function as spring elements with respect to the rotational motion. For example, as the shapes of the first connecting portion 26A and the second connecting portion 26B, Figure 29 The shapes shown in (A) to (C). Figure 29 (A) shows a first shape consisting of a plurality of rods arranged in parallel. Figure 29 (B) shows the second shape in which one end of the rod is branched. Figure 29 (C) shows a third shape in which both ends of the rod are branched.

[0173] Furthermore, the first connecting portion 26A only needs to connect the first actuator 24 and the second actuator 25 near either or both of the first axis a1 and the second axis a2. Similarly, the second connecting portion 26B only needs to connect the fixed frame 27 and the second actuator 25 near either or both of the first axis a1 and the second axis a2. Furthermore, the second connecting portion 26B includes at least one of a 2A connecting portion and a 2B connecting portion. The 2A connecting portion connects the fixed frame 27 and the second actuator 25 on the same axis as the first connecting portion 26A. The 2B connecting portion connects the fixed frame 27 and the second actuator 25 near an axis orthogonal to the axis on which the first connecting portion 26A is located.

[0174] The first embodiment is an example of a method in which the second connecting portion 26B includes only the 2A connecting portion. The first modified example is an example of a method in which the second connecting portion 26B includes both the 2A connecting portion and the 2B connecting portion. The second modified example is an example of a method in which the second connecting portion 26B includes only the 2B connecting portion. In the first embodiment and the first modified example, the 2A connecting portion is included in the first structural portion.

[0175] Furthermore, the hardware structure of the drive control unit 4 can be modified in various ways. The processing unit of the drive control unit 4 can be composed of one processor, or can be composed of 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, a CPU is a general-purpose processor that executes software (programs) and functions as a variety of processing units. PLD is a processor such as FPGA (Field Programmable Gate Array) that can change its circuit structure after manufacture. A dedicated circuit is a processor such as ASIC (Application Specific Integrated Circuit) that has a circuit structure specially designed to perform specific processing.

[0176] All documents, patent applications, and technical standards cited in this specification are incorporated herein by reference to the same extent as if each document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A micromirror device comprising: a reflector portion having a reflective surface for reflecting incident light; a first support portion connected to the reflector portion on a first axis located 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 shaft; a second support portion connected to the movable frame about a second axis, the second support portion supporting the reflector portion, the first support portion, and the movable frame so as to be swingable about the second axis, the second axis being located in a plane including the reflecting surface of the reflector portion when the reflector portion is stationary and being orthogonal to the first axis; a pair of first actuators connected to the second support portion, opposed to each other across the second axis, and having piezoelectric elements; a pair of second actuators disposed so as to surround the first actuator and opposed to each other across the first axis, each having a piezoelectric element; a first connecting portion connecting the first actuator and the second actuator; a fixed frame configured to surround the second actuator; and a second connecting portion connecting the second actuator and the fixing frame, The second actuator applies a torque about the first axis to the reflector portion, and the first actuator applies a torque about the second axis to the movable frame, thereby causing the reflector portion to swing about the first axis and the second axis, respectively. The first connecting portion connects the first actuator and the second actuator in the vicinity of one or both of the first shaft and the second shaft. The second connection portion connects the fixed frame and the second actuator near one or both of the first axis and the second axis, and includes a 2A connection portion connected on the same axis as the first connection portion. A virtual extension portion is formed by virtually extending the first connection portion along the first axis to an end portion of the second actuator on the side opposite to the reflector portion. The reflector portion, the first support portion, the movable frame, the second support portion, the first actuator, the first connection portion, the dummy extension portion, and the 2A connection portion are set as a first structural portion, and the second actuator and the second connection portion are set as a second structural portion. Let fm be the resonance frequency of a first resonance mode in which the reflector portion oscillates about the first axis in a resonance mode of the first structural portion when the end portion of the second connection portion on the fixing frame side is fixed, In the resonance mode of the second structural portion on the fixed frame side to which the second connecting portion is fixed, the resonance frequency in the second resonance mode in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical is denoted as fa. At this time, the relationship of |fm-fa| / fm≤0.03 is satisfied.

2. A micromirror device comprising: a reflector portion having a reflective surface for reflecting incident light; a first support portion connected to the reflector portion on a first axis located 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 shaft; a second support portion connected to the movable frame about a second axis, the second support portion supporting the reflector portion, the first support portion, and the movable frame so as to be swingable about the second axis, the second axis being located in a plane including the reflecting surface of the reflector portion when the reflector portion is stationary and being orthogonal to the first axis; a pair of first actuators connected to the second support portion, opposed to each other across the second axis, and having piezoelectric elements; a pair of second actuators disposed so as to surround the first actuator and opposed to each other across the first axis, each having a piezoelectric element; a first connecting portion connecting the first actuator and the second actuator; a fixed frame configured to surround the second actuator; and a second connecting portion connecting the second actuator and the fixing frame, The second actuator applies a torque about the first axis to the reflector portion, and the first actuator applies a torque about the second axis to the movable frame, thereby causing the reflector portion to swing about the first axis and the second axis, respectively. The first connecting portion connects the first actuator and the second actuator in the vicinity of either the first shaft or the second shaft. The second connecting portion connects the fixed frame and the second actuator in the vicinity of an axis perpendicular to the axis on which the first connecting portion is arranged, of the first axis and the second axis. A virtual extension portion is formed by virtually extending the first connection portion along the first axis to an end portion of the second actuator on the side opposite to the reflector portion. The reflector portion, the first support portion, the movable frame, the second support portion, the first actuator, the first connection portion, and the dummy extension portion are set as a first structural portion, and the second actuator and the second connection portion are set as a second structural portion. Let fm be the resonance frequency of a first resonance mode in which the reflector portion oscillates about the first axis in a resonance mode of the first structural portion when the end portion of the dummy extension portion on the fixing frame side is fixed, Assuming that the resonance frequency in the second resonance mode of the second structural portion on the fixed frame side to which the second connecting portion is fixed is fa, in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical, At this time, the relationship of 0≤(fm-fa) / fm≤0.14 is satisfied.

3. A micromirror device comprising: a reflector portion having a reflective surface for reflecting incident light; a first support portion connected to the reflector portion on a first axis located 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 shaft; a second support portion connected to the movable frame about a second axis, the second support portion supporting the reflector portion, the first support portion, and the movable frame so as to be swingable about the second axis, the second axis being located in a plane including the reflecting surface of the reflector portion when the reflector portion is stationary and being orthogonal to the first axis; a pair of first actuators connected to the second support portion, opposed to each other across the second axis, and having piezoelectric elements; a pair of second actuators disposed so as to surround the first actuator and opposed to each other across the first axis, each having a piezoelectric element; a first connecting portion connecting the first actuator and the second actuator; a fixed frame configured to surround the second actuator; and a second connecting portion connecting the second actuator and the fixing frame, The second actuator applies a torque about the first axis to the reflector portion, and the first actuator applies a torque about the second axis to the movable frame, thereby causing the reflector portion to swing about the first axis and the second axis, respectively. The first connecting portion connects the first actuator and the second actuator in the vicinity of one or both of the first shaft and the second shaft. The second connection portion connects the fixed frame and the second actuator near one or both of the first axis and the second axis, and includes a 2A connection portion connected on the same axis as the first connection portion. A virtual extension portion is formed by virtually extending the first connection portion along the first axis to an end portion of the second actuator on the side opposite to the reflector portion. The reflector portion, the first support portion, the movable frame, the second support portion, the first actuator, the first connection portion, the dummy extension portion, and the 2A connection portion are set as a first structural portion, and the second actuator and the second connection portion are set as a second structural portion. Let fm be the resonance frequency of a first resonance mode in which the reflector portion oscillates about the first axis in a resonance mode of the first structural portion when the end portion of the second connection portion on the fixing frame side is fixed, Assuming that the resonance frequency in the second resonance mode of the second structural portion on the fixed frame side to which the second connecting portion is fixed is fa, in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical, At this time, the relationship of |fm-fa| / fm>0.03 is satisfied.

4. A micromirror device comprising: a reflector portion having a reflective surface for reflecting incident light; a first support portion connected to the reflector portion on a first axis located 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 shaft; a second support portion connected to the movable frame about a second axis, the second support portion supporting the reflector portion, the first support portion, and the movable frame so as to be swingable about the second axis, the second axis being located in a plane including the reflecting surface of the reflector portion when the reflector portion is stationary and being orthogonal to the first axis; a pair of first actuators connected to the second support portion, opposed to each other across the second axis, and having piezoelectric elements; a pair of second actuators disposed so as to surround the first actuator and opposed to each other across the first axis, each having a piezoelectric element; a first connecting portion connecting the first actuator and the second actuator; a fixed frame configured to surround the second actuator; and a second connecting portion connecting the second actuator and the fixing frame, The second actuator applies a torque about the first axis to the reflector portion, and the first actuator applies a torque about the second axis to the movable frame, thereby causing the reflector portion to swing about the first axis and the second axis, respectively. The first connecting portion connects the first actuator and the second actuator in the vicinity of either the first shaft or the second shaft. The second connecting portion connects the fixed frame and the second actuator in the vicinity of an axis perpendicular to the axis on which the first connecting portion is arranged, of the first axis and the second axis. A virtual extension portion is formed by virtually extending the first connection portion along the first axis to an end portion of the second actuator on the side opposite to the reflector portion. The reflector portion, the first support portion, the movable frame, the second support portion, the first actuator, the first connection portion, and the dummy extension portion are set as a first structural portion, and the second actuator and the second connection portion are set as a second structural portion. Let fm be the resonance frequency of a first resonance mode in which the reflector portion oscillates about the first axis in a resonance mode of the first structural portion when the end portion of the dummy extension portion on the fixing frame side is fixed, Assuming that the resonance frequency in the second resonance mode of the second structural portion on the fixed frame side to which the second connecting portion is fixed is fa, in which the first axis is located at a node of vibration and the displacement distribution of the second actuator in the out-of-plane direction with respect to the first axis is symmetrical, At this time, the relationship of (fm-fa) / fm<0 or (fm-fa) / fm>0.14 is satisfied.

5. The micromirror device according to claim 1, wherein: The thickness of the first actuator is equal to the thickness of the mirror portion, and the second actuator is thinner than the first actuator. The micromirror device according to claim 1 , wherein: The first connecting portion is arranged along the first supporting portion.

7. The micromirror device according to claim 1, wherein: The pair of first actuators are each semi-annular.

8. The micromirror device according to claim 1, wherein: The pair of second actuators are each semi-annular.

9. An optical scanning device comprising: The micromirror device according to any one of claims 1 to 8; and a processor that drives the first actuator and the second actuator, In the optical scanning device, The processor applies drive signals to the first actuator and the second actuator to cause the mirror portion to resonate around the first axis and the second axis, respectively.

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