Mirror device and optical scanning device

Abstract

This mirror device is provided with: a mirror unit that reflects incident light; a drive unit that is connected to the mirror unit and that oscillates the mirror unit around at least one oscillation axis; a fixed frame that is connected to the drive unit and that is disposed so as to surround the drive unit; and a vibration control unit that is disposed in the fixed frame, that is thinner than the fixed frame, and that includes a plurality of vibration members that vibrate in the thickness direction of the fixed frame in conjunction with the oscillation of the mirror unit.

Description

Mirror device and optical scanning device

[0001] The technology of the present disclosure relates to a mirror device and an optical scanning device.

[0002] Micromirror devices (also called microscanners) are known as one type of microelectromechanical systems (MEMS) device fabricated using silicon (Si) microfabrication technology. Because these micromirror devices are small and consume little power, they are expected to be widely used in laser displays, laser projectors, optical coherence tomography, and other applications.

[0003] There are various drive methods for micromirror devices, but the piezoelectric drive method, which uses the deformation of a piezoelectric material, is considered promising because it generates a higher torque than other methods and can achieve a wide scan angle. In particular, when a wide scan angle is required, such as in laser displays, a wider scan angle can be achieved by resonantly driving a piezoelectric micromirror device.

[0004] A typical micromirror device used in a laser display includes a mirror portion and a piezoelectric actuator (see, for example, Japanese Patent Application Laid-Open No. 2023-039221). The mirror portion is freely oscillating around a first axis and a second axis that are orthogonal to each other. The actuator is a driving unit that oscillates the mirror portion around the first axis and the second axis in response to an externally supplied driving voltage.

[0005] The above-described micromirror device is housed in a package, and the package housing the micromirror device is fixed to a substrate such as a PCB (Printed Circuit Board).

[0006] However, when the mirror part of a micromirror device oscillates, vibrations are generated in the package, substrate, etc., which can cause fluctuations in the device's characteristics. For example, the vibrations propagate to the outside world, dissipating energy during resonance and reducing the mirror part's deflection angle. The amount of such fluctuations in characteristics varies greatly depending on factors such as the state of fixation of the micromirror device. Furthermore, if the sound generated by the vibrations is within the human audible range, it can be unpleasant for humans.

[0007] The technique of the present disclosure aims to provide a mirror device and an optical scanning device that can suppress vibrations caused by swinging of a mirror portion.

[0008] In order to achieve the above object, the mirror device of the present disclosure comprises a mirror section that reflects incident light, a drive section connected to the mirror section and that causes the mirror section to oscillate around at least one oscillation axis, a fixed frame connected to the drive section and arranged to surround the drive section, and a vibration control section provided within the fixed frame, that is thinner than the fixed frame, and that has multiple vibration members that vibrate in the thickness direction of the fixed frame in response to the oscillation of the mirror section.

[0009] It is preferable that the fixed frame has a rectangular outer shape, and that each of the plurality of vibration members extends along one of the plurality of sides of the fixed frame.

[0010] When the resonance frequency related to the oscillation of the mirror portion around the oscillation axis is fm and the resonance frequency related to the vibration of the multiple vibration members in the thickness direction is fs, it is preferable to satisfy the relationship 0.9<fs / fm<1.1.

[0011] The plurality of vibration members are preferably arranged at positions facing each other across the oscillation axis or an axis intersecting the oscillation axis.

[0012] The drive unit is connected to the mirror unit via a pair of first support units arranged on a first axis, and the oscillation axis is preferably the first axis or a second axis intersecting the first axis.

[0013] The drive unit is connected to the fixed frame via a pair of connecting parts that are thinner than the fixed frame, and the pair of connecting parts are preferably arranged on the first axis or the second axis.

[0014] The drive unit includes a pair of movable frames connected to the first support unit and facing each other across the first axis, and a pair of second support units connected to the movable frames on the second axis and supporting the mirror unit, the pair of first support units, and the pair of movable frames, and it is preferable that the pair of second support units be arranged on the second axis.

[0015] The driving section preferably includes a first actuator connected to the pair of second support sections and having a pair of first piezoelectric elements facing each other across the second axis.

[0016] The driving section preferably includes a second actuator that is disposed surrounding the first actuator and has a pair of second piezoelectric elements that face each other across the first axis.

[0017] The optical scanning device of the present disclosure is an optical scanning device including the mirror device described above and a processor that drives a drive unit, and the drive unit oscillates the mirror unit in response to a drive signal provided by the processor.

[0018] According to the technique of the present disclosure, it is possible to provide a mirror device and an optical scanning device that are capable of suppressing vibrations caused by the swinging of a mirror portion.

[0019] 4 is a diagram schematically illustrating an optical scanning device according to a first embodiment. FIG. 5 is a block diagram illustrating an example of the hardware configuration of a drive control unit. FIG. 6 is a perspective view of the appearance of a micromirror device according to the first embodiment. FIG. 7 is a plan view of the micromirror device according to the first embodiment, as viewed from the light incident side. FIG. 8 is a cross-sectional view taken along line AA in FIG. 4. FIG. 9 is a cross-sectional view illustrating a state in which the mirror unit has rotated around a first axis. FIG. 10 is a diagram illustrating an example of a first drive signal and a second drive signal. FIG. 11 is a diagram illustrating an example of the operation of a micromirror device according to a second embodiment. FIG. 12 is a plan view of a micromirror device according to a third embodiment, as viewed from the light incident side. FIG. 13 is a diagram illustrating an example of the operation of a micromirror device according to the third embodiment. FIG. 14 is a plan view of a micromirror device according to a fourth embodiment, as viewed from the light incident side. FIG. 15 is a diagram illustrating an example of the operation of a micromirror device according to the fourth embodiment. FIG. 16 is a plan view of a micromirror device according to a fifth embodiment, as viewed from the light incident side. FIG. 17 is a diagram illustrating an example of the operation of a micromirror device according to the fifth embodiment. FIG. 18 is a plan view of a micromirror device according to a sixth embodiment, as viewed from the light incident side. FIG. 19 is a diagram illustrating an example of the operation of a micromirror device according to the sixth embodiment. FIG. 19 is a plan view of a micromirror device according to a seventh embodiment, as viewed from the light incident side. FIG. 19 is a diagram illustrating an example of the operation of a micromirror device according to the seventh embodiment. Fig. 10 is a plan view of a micromirror device according to a comparative example, as viewed from the light incident side; Fig. 11 is a diagram showing simulation results when the mirror portion is oscillated around a first axis as the oscillation axis in the micromirror devices according to the first to fourth embodiments and the comparative example; Fig. 12 is a diagram showing simulation results when the mirror portion is oscillated around a second axis as the oscillation axis in the micromirror devices according to the fifth to seventh embodiments and the comparative example.

[0020] An example of an embodiment of the technology of the present disclosure will be described with reference to the accompanying drawings.

[0021] First Embodiment Fig. 1 schematically illustrates an optical scanning device 10 according to a first embodiment. The optical scanning device 10 includes a micro mirror device (MMD) 2, a light source 3, and a drive controller 4. The optical scanning device 10 optically scans a surface 5 to be scanned by reflecting a light beam LB emitted from the light source 3 by the MMD 2 under the control of the drive controller 4. The surface 5 to be scanned may be a screen, the retina of an eye, or the like. The MMD 2 is an example of a "mirror device" according to the technology of the present disclosure.

[0022] MMD2 is the first axis a １ and the first axis a １ A second axis a perpendicular to ２ The micromirror device is a piezoelectric two-axis drive type that can oscillate the mirror portion 20 (see FIG. 3) around the first axis a. １ The direction parallel to this is the X direction, and the second axis a ２ The direction parallel to the axis a is the Y direction. １ and the second axis a ２ In this embodiment, the direction perpendicular to the first axis a is called the Z direction. １ and the second axis a ２ The example shows an example in which the first axis a and the second axis b are perpendicular to each other. １ and the second axis a ２ The angles may intersect at an angle other than 90°. Here, "perpendicular" means that the angles intersect within a certain angle range including a tolerance, with 90° as the center.

[0023] The MMD 2 is housed in a package (not shown) made of ceramic or the like. The package housing the MMD 2 is fixed to a substrate (not shown) such as a PCB, and the substrate is screwed to a base material (not shown).

[0024] The light source 3 is a laser device that emits, for example, laser light as the light beam LB. It is preferable that the light source 3 irradiates the light beam LB perpendicularly to a reflecting surface 20A (see FIG. 3 ) of the mirror portion 20 when the mirror portion 20 of the MMD 2 is stationary.

[0025] The drive control unit 4 outputs drive signals to the light source 3 and the MMD 2 based on the optical scanning information. The light source 3 generates a light beam LB based on the input drive signal and irradiates the MMD 2 with the light beam LB. The MMD 2 rotates the mirror unit 20 along the first axis a based on the input drive signal. １ and the second axis a ２ Rock it around.

[0026] Although the details will be described later, for example, the drive control unit 4 rotates the mirror unit 20 along the first axis a １ and the second axis a ２ , and the light beam LB reflected by the mirror portion 20 is scanned so as to trace a Lissajous waveform on the surface to be scanned 5. This optical scanning method is called a Lissajous scanning method.

[0027] The optical scanning device 10 is applicable to, for example, a Lissajous scanning laser display. Specifically, the optical scanning device 10 is applicable to a laser scanning display such as an augmented reality (AR) glass or a virtual reality (VR) glass.

[0028] 2 shows an example of the hardware configuration of the drive control unit 4. The drive control unit 4 has 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 storage devices such as the ROM 41 into the RAM 42 and executing processing.

[0029] The ROM 41 is a non-volatile storage device that stores programs for the CPU 40 to execute processes and data such as the optical scanning information described above. The RAM 42 is a volatile storage device that temporarily stores programs and data.

[0030] The light source driver 43 is an electric circuit that outputs a drive signal to the light source 3 under 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.

[0031] The MMD driver 44 is an electric 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, period, and deflection angle of the oscillation of the mirror portion 20 of the MMD driver 44.

[0032] The CPU 40 controls the light source driver 43 and the MMD driver 44 based on the optical scanning information. The optical scanning information includes the scanning pattern of the light beam LB that scans the surface 5 to be scanned and the light emission timing of the light source 3.

[0033] Next, the configuration of the MMD 2 according to the first embodiment will be described with reference to Figs. 3 to 6. Fig. 3 is an external perspective view of the MMD 2. Fig. 4 is a plan view of the MMD 2 as seen from the light incident side. Fig. 5 is a cross-sectional view taken along line AA in Fig. 4. Fig. 6 is a cross-sectional view of the MMD 2 as seen from the light incident side. １ 10 is a cross-sectional view showing a state in which the rotational movement is performed around the center of the shaft.

[0034] 3, the MMD 2 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 first actuator 24, a second actuator 25, a pair of first connection sections 26A, a pair of second connection sections 26B, and a fixed frame 27. The MMD 2 is a so-called MEMS scanner.

[0035] The mirror section 20 has a reflecting surface 20A that reflects incident light. The reflecting surface 20A is formed of a thin metal film such as gold (Au) or aluminum (Al) provided on one surface of the mirror section 20. The shape of the reflecting surface 20A is, for example, a first axis a １ and the second axis a ２ It is a circle with the intersection point of

[0036] 1st axis a １ and the second axis a ２For example, when the mirror unit 20 is stationary, the first axis a is present in a plane including the reflecting surface 20A. １ and is symmetrical about the second axis a ２ It is symmetrical about the center.

[0037] The pair of first support portions 21 are ２ and the second axis a ２ Each of the first support portions 21 has a shape that is line-symmetrical about the first axis a. １ Each of the first support portions 21 has a shape that is line-symmetrical about the first axis a １ The mirror section 20 is connected to the first axis a １ It is supported so that it can swing around.

[0038] The pair of movable frames 22 are arranged along a first axis a １ and are arranged at positions facing each other across the first axis a １ Each of the movable frames 22 has a shape that is line-symmetrical about the second axis a ２ The movable frames 22 are shaped to be line-symmetrical about the center. Each movable frame 22 is curved along the outer periphery of the mirror section 20. Both ends of the movable frame 22 are connected to the first support section 21.

[0039] The pair of first support parts 21 and the pair of movable frames 22 are connected to each other to surround the mirror part 20. The mirror part 20, the pair of first support parts 21, and the pair of movable frames 22 constitute the movable part 50.

[0040] The pair of second support portions 23 are １ and are arranged at positions facing each other across the first axis a １ Each of the second support portions 23 has a shape that is line-symmetrical about the second axis a ２ Each of the second support portions 23 has a shape that is line-symmetrical about the second axis a ２ The movable portion 50 having the mirror portion 20 is connected to the movable frame 22 on the second axis a. ２ Both ends of each of the second support portions 23 are connected to a first actuator 24.

[0041] The first actuator 24 is ２ The piezoelectric element 24A is configured by a pair of first piezoelectric elements 24A facing each other with the second axis a ２ The first actuator 24 has a shape that is symmetrical about the first axis a. １ The first actuator 24 is disposed along the outer periphery of the pair of movable frames 22 and the pair of first support portions 21. The first actuator 24 is a piezoelectric drive type actuator.

[0042] 3 and 4, the first piezoelectric element 24A constituting the first actuator 24 is aligned with the first axis a １ It appears to be separated by the first axis a １ The two first piezoelectric elements 24A facing each other with the first piezoelectric element 24A sandwiched therebetween are electrically connected by metal wiring (not shown).

[0043] The pair of second support portions 23 and the first actuator 24 are connected to each other, thereby surrounding the movable portion 50 .

[0044] The second actuator 25 is １ The piezoelectric element 25A is configured by a pair of second piezoelectric elements 25A facing each other with the first axis a １ The second actuator 25 has a shape that is symmetrical about the second axis a. ２ The second actuator 25 is formed along the outer periphery of the first actuator 24 and the pair of second support portions 23. The second actuator 25 is a piezoelectric drive type actuator.

[0045] 3 and 4, the second piezoelectric element 25A constituting the second actuator 25 is ２ It appears to be separated by the second axis a ２ The two second piezoelectric elements 25A facing each other with the second piezoelectric element 25A sandwiched therebetween are electrically connected by metal wiring (not shown).

[0046] The pair of first connecting portions 26A are connected to the second axis a ２ and the second axis a２ Each of the first connection portions 26A has a shape that is line-symmetrical about the first axis a. １ Each of the first connection portions 26A has a shape that is line-symmetrical about the first axis a. １ and arranged along a first axis a １ Above, the first actuator 24 and the second actuator 25 are connected.

[0047] The pair of second connection portions 26B are connected to the first axis a １ The second connection portions 26B are arranged at positions facing each other with the second axis a ２ Each of the second connection portions 26B has a shape that is line-symmetrical about the second axis a ２ and arranged along a second axis a ２ The second actuator 25 and the fixed frame 27 are connected to each other by the pair of second connecting portions 26B. ２ The pair of second connecting portions 26B are supported so as to be swingable around the first axis a. １ The pair of second connecting portions 26B is an example of a "pair of connecting portions" according to the technology of the present disclosure.

[0048] The second actuator 25 and the pair of second connection portions 26B are connected to each other, thereby surrounding the pair of movable frames 22 and the first actuator 24. The first actuator 24 and the second actuator 25 constitute a drive unit disposed surrounding the pair of movable frames 22.

[0049] The fixed frame 27 is a frame-shaped member having a rectangular outer shape, and has a first axis a １ and the second axis a ２ The outer shape of the fixed frame 27 is symmetrical about the first axis a １ Parallel to the second axis a ２ Two opposing sides at the center and the second axis a ２ is parallel to the first axis a １ The fixed frame 27 surrounds the outer periphery of the pair of second actuators 25 and the second connection portion 26B. In other words, the fixed frame 27 is disposed to surround the drive portion.

[0050] The first actuator 24 is connected to the mirror unit 20 and the pair of movable frames 22 by a second axis a ２ By applying a rotational torque around the second axis a ２ The second actuator 25 rotates the mirror unit 20, the pair of movable frames 22, and the first actuator 24 around the first axis a. １ By applying a rotational torque around the first axis a １ Swing it around.

[0051] A vibration suppressing section 60 is provided inside the fixed frame 27. In this embodiment, the vibration suppressing section 60 is configured by a pair of vibration members 61. The pair of vibration members 61 are arranged in the fixed frame 27 along the first axis a １ The pair of vibration members 61 are housed in openings 62 provided at positions facing each other with the first axis a at the center. １ are arranged at positions facing each other with the center at the center.

[0052] Each of the vibration members 61 is oriented along a second axis a ２ The vibration members 61 are each symmetrical about the first axis a and have a rectangular shape extending in the X direction. Each vibration member 61 is connected to the fixed frame 27 at its center, and both ends are free ends. Each vibration member 61 is movable in the thickness direction of the fixed frame 27 (i.e., in the Z direction) while its center is fixed. The vibration suppression unit 60 is configured such that the mirror unit 20 is moved along the first axis a １ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0053] 3 and 4, an imaginary line L1 indicates the boundary between the pair of second connection portions 26B and the fixed frame 27, and an imaginary line L2 indicates the boundary between the pair of vibration members 61 and the fixed frame 27.

[0054] As shown in Fig. 4, each of the first support parts 21 is composed of a shaft part 21A and a pair of connecting parts 21B. １ The shaft portion 21A is a so-called torsion bar that extends along the mirror portion 20. One end of the shaft portion 21A is connected to the mirror portion 20, and the other end is connected to the connecting portion 21B.

[0055] The pair of connecting portions 21B are connected to the first axis a１ and are arranged at positions facing each other across the first axis a １ The connecting portions 21B have a shape that is line-symmetrical about the first axis a. One end of each connecting portion 21B is connected to the shaft portion 21A, and the other end is connected to the movable frame 22. Each connecting portion 21B has a folded structure. Since each connecting portion 21B has elasticity due to the folded structure, the mirror portion 20 can be moved around the first axis a. １ When the shaft portion 21A swings around, the internal stress acting on the shaft portion 21A is alleviated.

[0056] Each of the second support parts 23 is composed of a shaft part 23A and a pair of connecting parts 23B. ２ The shaft portion 23A is a so-called torsion bar that extends along the axis of the movable frame 22. One end of the shaft portion 23A is connected to the movable frame 22, and the other end is connected to the pair of connecting portions 23B.

[0057] The pair of connecting portions 23B are connected to the second axis a ２ and the second axis a ２ The connecting portions 23B have a shape that is line-symmetrical about the axis a. One end of each connecting portion 23B is connected to the shaft portion 23A, and the other end is connected to the first actuator 24. Each connecting portion 23B has a folded structure. Since each connecting portion 23B has elasticity due to the folded structure, the mirror portion 20 can be moved along the second axis a. ２ When the shaft portion 23A swings around, the internal stress acting on the shaft portion 23A is alleviated.

[0058] Furthermore, in the mirror section 20, a plurality of slits 20B and 20C are formed on the outer side of the reflecting surface 20A along the outer periphery of the reflecting surface 20A. The plurality of slits 20B and 20C are aligned along the first axis a １ and the second axis a ２ The slits 20B and 20C are arranged at positions that are line-symmetrical with respect to the center of the mirror 20. The slits 20B and 20C have the effect of suppressing distortion that occurs in the reflecting surface 20A when the mirror portion 20 swings.

[0059] 3 and 4 , metal wiring and metal pads for applying drive signals to the first actuator 24 and the second actuator 25 are not shown. A plurality of metal pads are provided on the fixed frame 27. The metal pads are also called electrode pads.

[0060] 5, the MMD 2 is formed, for example, by 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 silicon support layer 31 made of single crystal silicon, and a silicon active layer 33 made of single crystal silicon is provided on the silicon oxide layer 32.

[0061] The mirror portion 20, the pair of first support portions 21, the pair of movable frames 22, the pair of second support portions 23, the first actuator 24, the second actuator 25, the pair of first connection portions 26A, the pair of second connection portions 26B, and the pair of vibration members 61 are formed by removing the silicon support layer 31 and the silicon oxide layer 32 from the SOI substrate 30 by etching, and then patterning the remaining silicon active layer 33.

[0062] The fixed frame 27 is formed of three layers: a silicon support layer 31, a silicon oxide layer 32, and a silicon active layer 33. That is, the mirror section 20, the pair of first support sections 21, the pair of movable frames 22, the pair of second support sections 23, the first actuator 24, the second actuator 25, the pair of first connecting sections 26A, the pair of second connecting sections 26B, and the pair of vibration members 61 are each thinner than the fixed frame 27. In the present disclosure, thickness refers to the width in the Z direction.

[0063] The first piezoelectric element 24A and the second piezoelectric element 25A described above have a laminated structure in which a lower electrode, a piezoelectric film, and an upper electrode are laminated in this order on a silicon active layer 33.

[0064] The lower electrode and the upper electrode are made of a metal such as gold (Au) or platinum (Pt). The piezoelectric film is made of a piezoelectric material such as PZT (lead zirconate titanate). The lower electrode and the upper electrode are electrically connected to the drive control unit 4 via wiring and electrode pads.

[0065] The lower electrode is connected to the drive control unit 4 via wiring and an electrode pad, and is supplied with a ground potential. A drive voltage is applied from the drive control unit 4 to the upper electrode.

[0066] When a positive or negative voltage is applied to the piezoelectric film in the polarization direction, the piezoelectric film undergoes deformation (e.g., expansion and contraction) proportional to the applied voltage. In other words, the piezoelectric film exhibits the so-called inverse piezoelectric effect. When a drive voltage is applied to the upper electrode from the drive control unit 4, the piezoelectric film exhibits the inverse piezoelectric effect, displacing the first actuator 24 and the second actuator 25.

[0067] 6 shows a state in which one of the pair of second piezoelectric elements 25A constituting the second actuator 25 is expanded and the other is contracted, whereby the second actuator 25 is caused to move along the first axis a １ In this way, one of the pair of second piezoelectric elements 25A is displaced in the opposite directions, so that the mirror section 20 rotates around the first axis a. １ rotates around the

[0068] 6 shows an example in which the second actuator 25 is driven in an anti-phase resonance mode (hereinafter referred to as an anti-phase rotation mode) in which the displacement direction of the pair of piezoelectric actuators and the rotation direction of the mirror section 20 are opposite to each other. In contrast, an in-phase resonance mode in which the displacement direction of the pair of piezoelectric actuators and the rotation direction of the mirror section 20 are the same is called an in-phase rotation mode. In this embodiment, the second actuator 25 is driven in the anti-phase rotation mode.

[0069] The first axis a of the mirror section 20 １ The deflection angle θ is controlled by a drive signal (hereinafter referred to as a first drive signal) that the drive control unit 4 provides to the second actuator 25. The first drive signal is, for example, a sinusoidal AC voltage. The first drive signal is a drive voltage waveform V applied to one of the pair of piezoelectric actuators. １Ａ (t) and the driving voltage waveform V applied to the other １Ｂ (t) and the driving voltage waveform V １Ａ (t) and the driving voltage waveform V １Ｂ(t) are in opposite phase to each other (i.e., a phase difference of 180°).

[0070] The first axis a of the mirror part 20 １ The deflection angle θ corresponds to the angle at which the normal N of the reflecting surface 20A is tilted with respect to the Z direction in the YZ plane.

[0071] The first actuator 24 is driven in an anti-phase resonance mode in the same manner as the second actuator 25. ２ The deflection angle around the piezoelectric actuator 24 is controlled by a drive signal (hereinafter referred to as a second drive signal) that the drive control unit 4 supplies to the first actuator 24. The second drive signal is, for example, a sinusoidal AC voltage. The second drive signal is a drive voltage waveform V ２Ａ (t) and the driving voltage waveform V applied to the other ２Ｂ (t) and the driving voltage waveform V ２Ａ (t) and the driving voltage waveform V ２Ｂ (t) are in opposite phase to each other (i.e., a phase difference of 180°).

[0072] 7A and 7B show examples of the first and second drive signals. Fig. 7A shows a drive voltage waveform V １Ａ (t) and V １Ｂ FIG. 7B shows the drive voltage waveform V ２Ａ (t) and V ２Ｂ (t) is shown.

[0073] Drive voltage waveform V １Ａ (t) and V １Ｂ (t) are expressed as follows: V １Ａ (t) = V ｏｆｆ１ +V １ sin(2πf ｄ１ t) V １Ｂ (t) = V ｏｆｆ１ +V １ sin(2πf ｄ１ t + α)

[0074] Here, V １ is the amplitude voltage. V ｏｆｆ１ is the bias voltage. ｄ１is the drive frequency (hereinafter referred to as the first drive frequency), t is time, and α is the drive voltage waveform V １Ａ (t) and V １Ｂ In this embodiment, for example, α=180°.

[0075] Drive voltage waveform V １Ａ (t) and V １Ｂ When the second actuator 25 is applied with the first drive frequency f ｄ１ The first axis a １ Swinging around.

[0076] Drive voltage waveform V ２Ａ (t) and V ２Ｂ (t) are expressed as follows: V ２Ａ (t) = V ｏｆｆ２ +V ２ sin(2πf ｄ２ t+φ) V ２Ｂ (t) = V ｏｆｆ２ +V ２ sin(2πf ｄ２ t + β + φ)

[0077] Here, V ２ is the amplitude voltage. V ｏｆｆ２ is the bias voltage. ｄ２ is the drive frequency (hereinafter referred to as the second drive frequency). t is time. β is the drive voltage waveform V ２Ａ (t) and V ２Ｂ In this embodiment, for example, β is set to 180°. φ is the phase difference of the driving voltage waveform V １Ａ (t) and V １Ｂ (t) and the driving voltage waveform V ２Ａ (t) and V ２Ｂ (t) is the phase difference with respect to (t).

[0078] In this embodiment, V ｏｆｆ１ ≧V １ and V ｏｆｆ２ ≧V ２ That is, the first drive signal and the second drive signal are set to positive voltages.

[0079] Drive voltage waveform V ２Ａ (t) and V ２ＢWhen the first actuator 24 is applied with the second drive frequency f ｄ２ and the second axis a ２ Swinging around.

[0080] First drive frequency f ｄ１ is the first axis a of the mirror part 20 １ The second drive frequency f is set to match the surrounding resonant frequency. ｄ２ is the second axis a of the mirror part 20 ２ In this embodiment, the first driving frequency f is set to match the surrounding resonant frequency. ｄ１ is the second driving frequency f ｄ２ Greater than.

[0081] In this embodiment, the first driving frequency f ｄ１ The first axis a of the mirror part 20 １ When set to match the surrounding resonant frequency, the pair of vibrating members 61 that make up the vibration suppression unit 60 vibrate in the thickness direction of the fixed frame 27, thereby consuming the vibration energy generated in the fixed frame 27. This suppresses the vibration generated in the fixed frame 27.

[0082] 1st axis a １ When the mirror section 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping section 60, the first axis a of the mirror section 20 is １ It is preferable that the resonance frequency fm related to the circumferential oscillation is close to the resonance frequency fs related to the thickness direction of the pair of vibration members 61. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0083] 8 shows an example of the operation of the MMD 2 according to the first embodiment. １ The mirror part 20 is oscillated around the first axis a. １ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0084] Second Embodiment Next, a second embodiment will be described. Fig. 9 is a plan view of an MMD 2A according to the second embodiment, as viewed from the light incident side. The MMD 2A differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60A.

[0085] In this embodiment, the vibration suppression unit 60A is composed of four vibration members 61A. The four vibration members 61A are arranged in the fixed frame 27 along the first axis a １ In this embodiment, the opening 62A is provided at a position facing the second axis a. ２ The four vibration members 61A are divided into two parts with the first axis a １ At positions facing each other with the second axis a ２ Each of the vibration members 61A has a rectangular shape extending in the X direction and is arranged at a position facing each other with the second axis a ２ The end on the far side is connected to a fixed frame 27, and the end on the near side is a free end.

[0086] Each of the vibrating members 61A, with its end portion fixed, is displaceable in the thickness direction (i.e., Z direction) of the fixed frame 27. The vibration suppressing section 60A has the effect of suppressing vibrations that occur in the fixed frame 27 when the mirror section 20 swings.

[0087] 1st axis a １ When the mirror section 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping section 60A, １ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the four vibration members 61A are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0088] 10 shows an example of the operation of the MMD 2A according to the second embodiment. １ The mirror part 20 is oscillated around the first axis a. As the mirror part 20 oscillates, the four vibration members 61A are oscillated around the first axis a. １ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0089] 11 is a plan view of an MMD 2B according to the third embodiment, as viewed from the light incident side. The MMD 2B differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60B.

[0090] In this embodiment, the vibration suppression unit 60B is configured by a pair of vibration members 61B. The pair of vibration members 61B are arranged in the fixed frame 27 along the first axis a １ The pair of vibration members 61B are housed in openings 62B that are provided at positions facing each other with the first axis a at the center. １ are arranged at positions facing each other with the center at the center.

[0091] Each of the vibration members 61B is ２ The vibration members 61B are rectangular and symmetrical about the first axis a and extend in the X direction. Both ends of each of the vibration members 61B are connected to the fixed frame 27. With both ends fixed, each of the vibration members 61B is displaceable in the thickness direction of the fixed frame 27 (i.e., the Z direction). The vibration suppression unit 60B is configured such that the mirror unit 20 is moved in the direction perpendicular to the first axis a. １ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0092] 1st axis a １ When the mirror part 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping part 60B, １ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the pair of vibration members 61B are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0093] 12 shows an example of the operation of the MMD 2B according to the third embodiment. １ The mirror part 20 is oscillated around the first axis a. １ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0094] 13 is a plan view of an MMD 2C according to the fourth embodiment, as viewed from the light incident side. The MMD 2C differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60C.

[0095] In this embodiment, the vibration suppression unit 60C is configured by four vibration members 61C. The four vibration members 61C are arranged in the fixed frame 27 along the second axis a ２ In this embodiment, the opening 62C is provided at a position facing the first axis a. １ The four vibration members 61C are divided around the first axis a １ At positions facing each other with the second axis a ２ Each of the vibration members 61C has a rectangular shape extending in the Y direction and is arranged at a position facing each other with the first axis a １ The end on the far side is connected to a fixed frame 27, and the end on the near side is a free end.

[0096] Each of the vibration members 61C is displaceable in the thickness direction (i.e., Z direction) of the fixed frame 27 with its end portion fixed. １ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0097] 1st axis a １ When the mirror section 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping section 60C, the first axis a of the mirror section 20 is １ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the four vibration members 61C are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0098] 14 shows an example of the operation of the MMD 2C according to the fourth embodiment. １ The mirror part 20 is oscillated around the first axis a. As the mirror part 20 oscillates, the four vibration members 61C are oscillated around the first axis a. １ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0099] Fifth Embodiment Next, a fifth embodiment will be described. Fig. 15 is a plan view of an MMD 2D according to the fifth embodiment, as viewed from the light incident side. The MMD 2D differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60D.

[0100] In this embodiment, the vibration suppression unit 60D is configured by a pair of vibration members 61D. The pair of vibration members 61D are arranged in the fixed frame 27 along the second axis a ２ That is, the pair of vibration members 61D are housed in openings 62D provided at positions facing each other with the second axis a at the center. ２ are arranged at positions facing each other with the center at the center.

[0101] Each of the vibration members 61D is １ The vibration members 61D are rectangular and symmetrical about the second axis a and extend in the Y direction. Each of the vibration members 61D is connected to the fixed frame 27 at its center, and both ends are free ends. Each of the vibration members 61D is displaceable in the thickness direction of the fixed frame 27 (i.e., the Z direction) while its center is fixed. The vibration suppression unit 60D is configured such that the mirror unit 20 is moved in the direction of the second axis a. ２ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0102] 2nd axis a ２ When the mirror section 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping section 60D, ２ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the pair of vibration members 61D are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0103] 16 shows an example of the operation of the MMD 2D according to the fifth embodiment. ２ The mirror part 20 is oscillated around the second axis a. ２ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0104] Sixth Embodiment Next, a sixth embodiment will be described. Fig. 17 is a plan view of an MMD 2E according to the sixth embodiment, as viewed from the light incident side. The MMD 2E differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60E.

[0105] In this embodiment, the vibration suppression unit 60E is configured by a pair of vibration members 61E. The pair of vibration members 61E are arranged in the fixed frame 27 along the first axis a １ The pair of vibration members 61E are housed in openings 62E that are provided at positions facing each other with the first axis a at the center. １ are arranged at positions facing each other with the center at the center.

[0106] Each of the vibration members 61E is oriented along the second axis a ２ The vibration members 61E are rectangular and symmetrical about the second axis a and extend in the X direction. Each of the vibration members 61E is connected to the fixed frame 27 at its center, and both ends are free ends. Each of the vibration members 61E is movable in the thickness direction of the fixed frame 27 (i.e., the Z direction) while its center is fixed. The vibration suppression unit 60E is configured such that the mirror unit 20 is moved in the thickness direction of the fixed frame 27 (i.e., the Z direction) when the mirror unit 20 is rotated along the second axis a. ２ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0107] 2nd axis a ２ When the mirror section 20 is oscillated around the second axis a of the mirror section 20, in order to enhance the vibration damping effect of the vibration damping section 60E, ２ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the pair of vibration members 61E are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0108] 18 shows an example of the operation of the MMD 2E according to the sixth embodiment. ２ The mirror part 20 is oscillated around the second axis a. ２ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0109] Seventh Embodiment Next, a seventh embodiment will be described. Fig. 19 is a plan view of an MMD 2F according to the seventh embodiment, as viewed from the light incident side. The MMD 2F differs from the MMD 2 according to the first embodiment only in the configuration of the vibration suppression section 60F.

[0110] In this embodiment, the vibration suppression unit 60F is configured by a pair of vibration members 61F. The pair of vibration members 61F are arranged in the fixed frame 27 along the first axis a １ The pair of vibration members 61F are housed in openings 62F that are provided at positions facing each other with the first axis a at the center. １ are arranged at positions facing each other with the center at the center.

[0111] Each of the vibration members 61F is oriented along the second axis a ２ The vibration members 61F are symmetrical about the center, and each of the portions extending in the X direction is connected to a portion extending in the Y direction. The ends of the portions extending in the Y direction are free ends. Each of the vibration members 61F is displaceable in the thickness direction of the fixed frame 27 (i.e., the Z direction) while its center is fixed. The vibration suppression unit 60F is configured such that the mirror unit 20 is moved in the direction of the second axis a. ２ This has the effect of suppressing vibrations that occur in the fixed frame 27 due to the swinging motion around the frame.

[0112] 2nd axis a ２ When the mirror section 20 is oscillated around the oscillation axis, in order to enhance the vibration damping effect of the vibration damping section 60F, ２ It is preferable that the resonance frequency fm related to the circumferential oscillation and the resonance frequency fs related to the thickness direction of the pair of vibration members 61F are close to each other. Specifically, it is preferable that the relationship 0.9<fs / fm<1.1 is satisfied.

[0113] 20 shows an example of the operation of the MMD 2F according to the seventh embodiment. In FIG. 20, the second axis a ２ The mirror part 20 is oscillated around the second axis a. ２ By vibrating so as to displace in opposite directions on either side of the fixed frame 27, vibrations occurring in the fixed frame 27 are suppressed.

[0114] In the MMDs according to the first to seventh embodiments, each of the multiple vibration members extends along one of the multiple sides of the fixed frame, so the mass of each vibration member can be increased, thereby enhancing the vibration suppression effect. Furthermore, by changing the length of each vibration member in the extension direction, the resonance frequency of the multiple vibration members can be easily adjusted. This makes it easy to control the vibration suppression effect.

[0115] 21 is a plan view of an MMD 2G according to the comparative example, viewed from the light incident side. The MMD 2G differs from the MMD 2 according to the first embodiment only in that the fixed frame 27 does not have a vibration damping section.

[0116] [Simulation Results] FIG. 22 shows the results of simulations of the first axis a １ The simulation results are shown for the case where the mirror unit 20 is oscillated around the first axis a. １ The resonance frequency fm for the circumferential oscillation is 28810.32 Hz. The resonance frequency fs differs depending on the embodiment, but satisfies the relationship 0.9<fs / fm<1.1.

[0117] In this simulation, the Z displacement amount and the Q value were evaluated for the first to fourth embodiments and the comparative example. １ The Q value is the maximum displacement of the fixed frame 27 in the Z direction when the mirror unit 20 is swung so that the maximum value of the deflection angle around the first axis a of the mirror unit 20 is 7.5°. １ This is a value that represents the surrounding resonance characteristics. The Q value when the MMD is in fixed state A and the Q value when the MMD is in fixed state B were obtained, and the difference between the two values ​​was calculated.

[0118] According to this simulation, it can be seen that the MMDs according to the first to fourth embodiments, which have vibration-damping units, have smaller Z displacement amounts than the MMD according to the comparative example, and also have smaller differences in the Q values ​​between fixed states A and B. That is, in the first to fourth embodiments, the difference in the drive state that depends on the fixed state of the MMD is reduced compared to the comparative example, that is, the reproducibility of the drive state is improved. Specifically, in the first to fourth embodiments, a large deflection angle can be obtained regardless of the fixed state of the MMD.

[0119] FIG. 23 shows the second axis a in the MMDs according to the fifth to seventh embodiments and the comparative example. ２ The simulation results are shown for the case where the mirror unit 20 is oscillated around the second axis a. ２ The resonance frequency fm for the circumferential oscillation is 14177.5 Hz. The resonance frequency fs differs depending on the embodiment, but satisfies the relationship 0.9<fs / fm<1.1.

[0120] In this simulation, the Z displacement amount and the Q value were evaluated for the fifth to seventh embodiments and the comparative example. ２ The Q value is the maximum displacement of the fixed frame 27 in the Z direction when the mirror unit 20 is swung so that the maximum value of the deflection angle around the second axis a of the mirror unit 20 is 7.5°. ２ This is a value that represents the surrounding resonance characteristics. The Q value when the MMD was in fixed state A and the Q value when the MMD was in fixed state B were obtained, and the difference between the two was calculated. In this simulation, the sound generated by the resonance frequency fm is in the human audible range, so the amount of noise generated during operation was evaluated.

[0121] According to this simulation, it can be seen that the MMDs according to the fifth to seventh embodiments, which have a vibration-damping portion, have a smaller Z displacement amount than the MMD according to the comparative example, and also have a smaller difference in the Q value between fixed state A and fixed state B. That is, in the fifth to seventh embodiments, the difference in the drive state depending on the fixed state of the MMD is reduced compared to the comparative example, that is, the reproducibility of the drive state is improved. Specifically, in the fifth to seventh embodiments, a large deflection angle can be obtained regardless of the fixed state of the MMD. Furthermore, in the fifth to seventh embodiments, the amount of noise is reduced compared to the comparative example.

[0122] [Modifications] Various modifications of the above embodiments will be described below.

[0123] In each of the above embodiments, the vibration damping portion is １ and the second axis a ２ Alternatively, the vibration suppressing unit may be configured to suppress vibrations that occur in the fixed frame 27 when the mirror unit 20 swings around either the first axis a or the second axis a. １ The vibration generated in the fixed frame 27 due to the mirror part 20 swinging around the second axis a ２ The vibration damping unit may be configured to suppress both vibrations that occur in the fixed frame 27 due to the swinging of the mirror unit 20 around the mirror unit 20. For example, the vibration damping unit may be a combination of the vibration damping unit according to any one of the first to fourth embodiments and the vibration damping unit according to any one of the fifth to seventh embodiments.

[0124] In each of the above embodiments, the MMD is a two-axis mirror device in which the mirror portion oscillates around two intersecting axes, but the MMD may also be a one-axis mirror device in which the mirror portion oscillates around one axis.

[0125] Furthermore, in the above embodiment, the hardware configuration of the drive control unit 4 can be modified in various ways. The processing unit of the drive control unit 4 may be configured with a single processor, or may be configured with a combination of two or more processors of the same or different types. Processors include CPUs, programmable logic devices (PLDs), dedicated electrical circuits, etc. As is well known, a CPU is a general-purpose processor that executes software (programs) to function as various processing units. A PLD is a processor, such as an FPGA (Field Programmable Gate Array), whose circuit configuration can be changed after manufacturing. A dedicated electrical circuit is a processor, such as an ASIC (Application Specific Integrated Circuit), that has a circuit configuration designed specifically to execute specific processing.

[0126] The above description allows the understanding of the following technology. [Supplementary Item 1] A mirror device comprising: a mirror unit that reflects incident light; a driver connected to the mirror unit and that oscillates the mirror unit around at least one oscillation axis; a fixed frame connected to the driver and disposed surrounding the driver; and a vibration control unit provided within the fixed frame, thinner than the fixed frame, and having a plurality of vibration members that vibrate in the thickness direction of the fixed frame in conjunction with the oscillation of the mirror unit. [Supplementary Item 2] The mirror device according to Supplementary Item 1, wherein the fixed frame has a rectangular outer shape, and each of the plurality of vibration members extends along one of a plurality of sides of the fixed frame. [Supplementary Item 3] The mirror device according to Supplementary Item 1 or Supplementary Item 2, wherein, where fm is a resonance frequency related to the oscillation of the mirror unit around the oscillation axis and fs is a resonance frequency related to the vibration of the plurality of vibration members in the thickness direction, the relationship 0.9<fs / fm<1.1 is satisfied. [Supplementary Item 4] The mirror device according to any one of Supplementary Items 1 to 3, wherein the plurality of vibration members are arranged at positions opposing each other across the oscillation axis or an axis intersecting the oscillation axis. [Supplementary Item 5] The mirror device according to any one of Supplementary Items 1 to 4, wherein the drive unit is connected to the mirror unit via a pair of first support units arranged on a first axis, and the oscillation axis is the first axis or a second axis intersecting the first axis. [Supplementary Item 6] The mirror device according to Supplementary Item 5, wherein the drive unit is connected to the fixed frame via a pair of connection units thinner than the fixed frame, and the pair of connection units are arranged on the first axis or the second axis. [Supplementary Item 7] The mirror device according to Supplementary Item 5 or Supplementary Item 6, wherein the drive unit comprises: a pair of movable frames connected to the first support parts and facing each other across the first axis; and a pair of second support parts connected to the movable frame on the second axis and supporting the mirror part, the pair of first support parts, and the pair of movable frames, and the pair of second support parts are arranged on the second axis. [Supplementary Item 8] The mirror device according to Supplementary Item 7, wherein the drive unit comprises a first actuator connected to the pair of second support parts and having a pair of first piezoelectric elements facing each other across the second axis.[Supplementary Item 9] The mirror device according to Supplementary Item 7 or Supplementary Item 8, wherein the drive unit includes a second actuator that is disposed surrounding the first actuator and has a pair of second piezoelectric elements that face each other across the first axis. [Supplementary Item 10] An optical scanning device comprising: the mirror device according to any one of Supplementary Items 1 to 9; and a processor that drives the drive unit, wherein the drive unit oscillates the mirror unit in response to a drive signal provided by the processor.

Claims

1. A mirror device comprising: a mirror section that reflects incident light; a drive section connected to said mirror section and that causes said mirror section to swing around at least one swing axis; a fixed frame connected to said drive section and disposed surrounding said drive section; and a vibration control section provided within said fixed frame, having a thickness thinner than said fixed frame, and having a plurality of vibration members that vibrate in the thickness direction of said fixed frame in response to the swing of said mirror section.

2. The mirror device according to claim 1, wherein the fixed frame has a rectangular outer shape, and each of the multiple vibration members extends along one of multiple sides of the fixed frame.

3. The mirror device according to claim 1, wherein the resonant frequency related to the oscillation of the mirror section around the oscillation axis is fm and the resonant frequency related to the vibration of the multiple vibration members in the thickness direction is fs, satisfying the relationship 0.9<fs / fm<1.

1.

4. A mirror device according to any one of claims 1 to 3, wherein the plurality of vibration members are arranged in opposing positions across the oscillation axis or an axis intersecting the oscillation axis.

5. The mirror device according to claim 4, wherein the drive unit is connected to the mirror unit via a pair of first support parts arranged on a first axis, and the oscillation axis is the first axis or a second axis intersecting the first axis.

6. The mirror device according to claim 5, wherein the drive unit is connected to the fixed frame via a pair of connecting parts that are thinner than the fixed frame, and the pair of connecting parts are arranged on the first axis or the second axis.

7. The mirror device described in claim 6, wherein the drive unit comprises: a pair of movable frames connected to the first support part and facing each other across the first axis; and a pair of second support parts connected to the movable frames on the second axis and supporting the mirror unit, the pair of first support parts, and the pair of movable frames, and the pair of second support parts are arranged on the second axis.

8. The mirror device according to claim 7, wherein the driving section comprises a first actuator connected to a pair of the second support sections and having a pair of first piezoelectric elements opposed to each other across the second axis.

9. The mirror device according to claim 8, wherein the driving section includes a second actuator having a pair of second piezoelectric elements arranged to surround the first actuator and facing each other across the first axis.

10. An optical scanning device comprising: a mirror device according to claim 1; and a processor that drives said drive unit, wherein said drive unit oscillates said mirror unit in response to a drive signal provided by said processor.

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