Mirror device and optical scanning device

Abstract

This mirror device comprises: a mirror unit that reflects incident light; a drive unit that is connected to the mirror unit and swings the mirror unit around at least one swing axis; an annular damping member that is connected to the drive unit and disposed so as to surround the drive unit; and a fixed frame that is connected to the damping member and disposed so as to surround the damping member.

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-mentioned object, the mirror device of the present disclosure comprises a movable part including a mirror part that reflects incident light, a drive part connected to the movable part and that causes the mirror part to oscillate around at least one oscillation axis, an annular vibration-damping member connected to the drive part and arranged to surround the drive part, and a fixed frame connected to the vibration-damping member and arranged to surround the vibration-damping member.

[0009] The movable part includes a pair of first support parts connected to the mirror part and arranged on a first axis, and a pair of movable frames connected to the pair of first support parts and facing each other across the first axis, and it is preferable that the oscillation axis is the first axis or a second axis intersecting the first axis.

[0010] The vibration-damping member is preferably connected to the drive unit and the fixed frame on the first axis or the second axis.

[0011] It is preferable that the drive unit includes a pair of second support parts connected to the movable frame on the second axis and supporting the movable unit, and that the pair of second support parts are arranged on the second axis.

[0012] 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.

[0013] 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.

[0014] When the mirror portion swings, the vibration-damping member and the driving portion are preferably displaced in the thickness direction of the fixed frame in an opposite phase relationship.

[0015] 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.

[0016] 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.

[0017] 4 is a diagram schematically illustrating an optical scanning device according to an 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 an embodiment. FIG. 7 is a plan view of the micromirror device according to an embodiment, 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 portion 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 the micromirror device. FIG. 12 is a plan view of a micromirror device according to a first comparative example, viewed from the light incident side. FIG. 13 is a plan view of a micromirror device according to a second comparative example, viewed from the light incident side. FIG. 14 is a diagram illustrating simulation results. FIG. 15 is a diagram illustrating simulation results. FIG. 16 is a graph illustrating the relationship between the measured Q value and the degree of vacuum. FIG. 17 is a graph illustrating the relationship between the measured Q value and the degree of vacuum.

[0018] An example of an embodiment of the technology of the present disclosure will be described with reference to the accompanying drawings.

[0019] 1 is a schematic diagram of an optical scanning device 10 according to an 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 is 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.

[0020] 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.

[0021] 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 (not shown).

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 2.

[0030] 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.

[0031] Next, the configuration of the MMD 2 according to the 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.

[0032] 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, a pair of third connection sections 27C, a fixed frame 27, and a vibration damping member 60. The MMD 2 is a so-called MEMS scanner.

[0033] 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

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] The pair of second support portions 23 and the first actuator 24 are connected to each other, thereby surrounding the movable portion 50 .

[0042] 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 actuator.

[0043] 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).

[0044] 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.

[0045] The second actuator 25 surrounds the pair of movable frames 22 and the first actuator 24. The pair of second support parts 23, the first actuator 24, and the second actuator 25 constitute a drive part that is arranged surrounding the pair of movable frames 22.

[0046] 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 the second axis a ２ The second actuator 25 and the vibration damping member 60 are connected to the pair of second connecting portions 26B. ２ It is supported so that it can swing around.

[0047] The vibration damping member 60 is an annular member disposed around the second actuator 25 and is axially aligned with the first axis a. １ and the second axis a ２ The vibration damping member 60 has a shape that is symmetrical about the second axis a. ２ A pair of slits 60A is provided on the first axis a. １ The slits 60A are arranged at positions facing each other with the second axis a ２ The shape is symmetrical about the center.

[0048] The vibration damping member 60 also has a first axis a １ A pair of protrusions 60B is provided on the second axis a. ２The protrusions 60B are arranged at positions facing each other with the first axis a １ Each of the protrusions 60B is wider than the other portions of the vibration damping member 60. The pair of protrusions 60B are arranged along the first axis a. １ Moment of inertia around the second axis a ２ The pair of protrusions 60B are provided to adjust the moment of inertia of the surroundings. The protrusion amount of the pair of protrusions 60B may be changed as appropriate.

[0049] The pair of third connection portions 26C are connected to the first axis a １ The third connection portions 26C are arranged at positions facing each other with the second axis a ２ Each of the third connection portions 26C has a shape that is line-symmetrical about the second axis a ２ and arranged along the second axis a ２ The pair of third connecting portions 26C connect the vibration damping member 60 to the fixed frame 27. ２ It is supported so that it can swing around.

[0050] The pair of third connecting portions 26C are provided with a pair of slits 26D. The pair of slits 26D are １ The slits 26D are arranged at positions facing each other with the second axis a ２ The shape is symmetrical about the center.

[0051] The pair of second connecting portions 26B and the pair of third connecting portions 26C are connected to the second axis a ２ Not limited to the above, the first axis a １ That is, the drive unit, the vibration damping member 60, and the fixed frame 27 may be arranged on the second axis a ２ Not limited to the above, the first axis a １ may be connected above.

[0052] 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 is parallel to the second axis a ２Two 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.

[0053] 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.

[0054] The vibration-damping member 60 is displaceable in the thickness direction (i.e., Z direction) of the fixed frame 27 in a state where the portions connected to the pair of second connecting portions 26B and the pair of third connecting portions 26C are fixed. １ Circumference or second axis a ２ The vibration damping member 60 has the effect of canceling out vibrations caused by the MMD 2 swinging around, thereby suppressing the vibrations from propagating to the outside world.

[0055] In FIG. 4, the imaginary line L indicates the boundary between the pair of third connection portions 26C and the fixed frame 27.

[0056] 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.

[0057] The pair of connecting portions 21B are connected to the first axis a １ and are arranged at positions facing each other across the first axis a １The 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.

[0058] 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.

[0059] 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 second 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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, the pair of third connection portions 27C, and the vibration-damping member 60 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.

[0064] 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, the pair of third connecting sections 27C, and the vibration damping member 60 are each thinner than the fixed frame 27. In the present disclosure, the term "thickness" refers to the width in the Z direction.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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

[0070] 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.

[0071] 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°).

[0072] 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.

[0073] 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°).

[0074] 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.

[0075] 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)

[0076] Here, V １ is the amplitude voltage. V ｏｆｆ１ is the bias voltage. ｄ１ is 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°.

[0077] Drive voltage waveform V １Ａ (t) and V１Ｂ When the second actuator 25 is applied with the first drive frequency f ｄ１ The first axis a １ Swinging around.

[0078] 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)

[0079] 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).

[0080] 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.

[0081] Drive voltage waveform V ２Ａ (t) and V ２Ｂ When the first actuator 24 is applied with the second drive frequency f ｄ２ and the second axis a ２ Swinging around.

[0082] First drive frequency f ｄ１ is the first axis a of the mirror part 20 １The 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 ｄ１ is the second driving frequency f ｄ２ Greater than.

[0083] The mirror portion 20 is aligned along the first axis a １ When the first axis a swings around the first axis a, the vibration is cancelled out by the vibration damping member 60 and the drive unit being displaced in the thickness direction of the fixed frame 27 in an opposite phase relationship. １ The directions of displacement of the vibration-damping member 60 and the drive unit are opposite, with this as the center. In the region where the drive unit displaces in the +Z direction (positive direction), the vibration-damping member 60 displaces in the -Z direction (negative direction). Conversely, in the region where the drive unit displaces in the -Z direction (negative direction), the vibration-damping member 60 displaces in the +Z direction (positive direction).

[0084] Similarly, the mirror portion 20 is ２ When the second axis a swings around the second axis a, the vibration is cancelled out by the vibration damping member 60 and the drive unit being displaced in the thickness direction of the fixed frame 27 in an opposite phase relationship. ２ The directions of displacement of the vibration-damping member 60 and the drive unit are opposite, with this as the center. In the region where the drive unit displaces in the +Z direction (positive direction), the vibration-damping member 60 displaces in the -Z direction (negative direction). Conversely, in the region where the drive unit displaces in the -Z direction (negative direction), the vibration-damping member 60 displaces in the +Z direction (positive direction).

[0085] In order to enhance the vibration damping effect of the vibration damping member 60, the first axis a １ Around and second axis a ２ It is preferable that the resonance frequency of the mirror portion 20 and the resonance frequency of the vibration damping member 60 are close to each other for each of the peripheral oscillations.

[0086] FIG. 8 shows an example of the operation of the MMD 2. In FIG. 8, the first axis a １ The mirror part 20 is oscillated around the first axis a. １ 8, it can be seen that the vibration damping member 60 is displaced in the Z direction in an anti-phase relationship with the driving unit.

[0087] 9 shows an example of the operation of the MMD 2. In FIG. ２ The mirror part 20 is oscillated around the second axis a. ２ 9, it can be seen that the vibration damping member 60 is displaced in the Z direction in an anti-phase relationship with the driving unit.

[0088] [Comparative Example] Next, a comparative example will be described. Fig. 10 is a plan view of an MMD 2A according to a first comparative example, viewed from the light incident side. The MMD 2A basically differs from the MMD 2 according to the embodiment only in that it does not include a vibration damping member 60. In the MMD 2A, a pair of second connection portions 26B connect the second actuator 25 and the fixed frame 27.

[0089] 11 is a plan view of an MMD 2B according to a second comparative example, viewed from the light incident side. The MMD 2B basically differs from the MMD 2 according to the embodiment only in that it does not include a vibration damping member 60. In the MMD 2B, a pair of second connectors 26B connect the second actuator 25 and the fixed frame 27.

[0090] The MMD 2A according to the first comparative example and the MMD 2B according to the second comparative example have the same configuration except for the shape of the drive unit, which is the same as the shape of the MMD 2 according to the embodiment.

[0091] [Simulation Results] FIG. 12 shows the results of simulations of the first comparative example, the second comparative example, and the MMD according to the embodiment, which are not fixed but are moved independently along the first axis a １ The simulation results are shown for the case where the mirror unit 20 is swung around the first axis a. １ The amount of displacement of the fixed frame 27 in the Z direction (hereinafter referred to as fixed frame Z displacement amount) was evaluated when the mirror unit 20 was swung so that the maximum value of the deflection angle around the mirror unit 20 was 7.5° (i.e., the total optical angle was 30°). In the embodiment, it can be seen that the amount of fixed frame Z displacement is significantly lower than in the first and second comparative examples, and vibration is suppressed.

[0092] FIG. 13 shows the first comparative example, the second comparative example, and the MMD according to the embodiment, which is not fixed but is moved independently along the second axis a ２ The simulation results are shown for the case where the mirror unit 20 is swung around the second axis a. ２ The amount of Z displacement of the fixed frame was evaluated when the mirror unit 20 was swung so that the maximum value of the deflection angle around the mirror unit 20 was 7.5° (i.e., the total optical angle was 30°). In the embodiment, it can be seen that the amount of Z displacement of the fixed frame is significantly reduced compared to the first and second comparative examples, and vibration is suppressed.

[0093] FIG. 14 shows a state in which a package accommodating an MMD according to the first comparative example, the second comparative example, and the embodiment is fixed to a substrate (PCB), and the substrate is screwed to a base material, and the first axis a １ The simulation results are shown for the case where the mirror unit 20 is swung around the first axis a. １ The displacement amount of the substrate in the Z direction (hereinafter referred to as the substrate Z displacement amount) and the displacement amount of the base material in the Z direction (hereinafter referred to as the base material Z displacement amount) were evaluated when the mirror unit 20 was swung so that the maximum deflection angle around the mirror unit 20 was 7.5° (i.e., the total optical angle was 30°). In the embodiment, it can be seen that the substrate Z displacement amount and the base material Z displacement amount are each significantly smaller than in the first and second comparative examples, and vibration is suppressed.

[0094] FIG. 15 shows a state in which a package accommodating an MMD according to the first comparative example, the second comparative example, and the embodiment is fixed to a substrate (PCB), and the substrate is screwed to the base material, and the second axis a ２ The simulation results are shown for the case where the mirror unit 20 is swung around the second axis a. ２ The Z displacement amount of the substrate and the Z displacement amount of the base material were evaluated when the mirror unit 20 was swung so that the maximum deflection angle around the mirror unit 20 was 7.5° (i.e., the total optical angle was 30°). In the embodiment, it can be seen that the Z displacement amount of the substrate and the Z displacement amount of the base material are each significantly lower than in the first and second comparative examples, and vibration is suppressed.

[0095] 16 and 17, the relationship between the Q value and the degree of vacuum was evaluated with an MMD 2A according to the first comparative example and an MMD 2 according to the embodiment, each mounted in a clamshell in a vacuum chamber. The Q value is a value that represents the resonance characteristics of the mirror portion 20. FIG. 16 shows the relationship between the Q value and the degree of vacuum with the first axis a １ 17 shows the measurement results of the Q value when the mirror section 20 is oscillated around the second axis a. ２ 16 and 17 show the measurement results of the Q value when the mirror part 20 is oscillated around the oscillation axis. It can be seen from Figures 16 and 17 that the Q value of the MMD 2 according to the embodiment is larger than the Q value of the MMD 2A according to the first comparative example. This means that in the embodiment, energy dissipation during resonance due to vibration leaking to the outside of the MMD 2 is suppressed.

[0096] As described above, according to this embodiment, it is possible to suppress vibrations caused by the swinging of the mirror unit 20. This suppresses the generation of noise caused by vibrations. Furthermore, according to this embodiment, differences in the drive state that depend on the fixed state of the MMD 2 are reduced. In other words, the reproducibility of the drive state is improved. Specifically, in this embodiment, a large deflection angle can be obtained regardless of the fixed state of the MMD 2.

[0097] [Modifications] Various modifications of the above embodiment will be described below.

[0098] In the above embodiment, the MMD 2 is a two-axis mirror device in which the mirror portion oscillates around two intersecting axes, but the MMD 2 may also be a one-axis mirror device in which the mirror portion oscillates around one axis.

[0099] 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.

[0100] The above description allows the understanding of the following technology. [Supplementary Item 1] A mirror device comprising: a movable section including a mirror section that reflects incident light; a drive section connected to the movable section and that causes the mirror section to swing around at least one swing axis; an annular vibration-damping member connected to the drive section and arranged to surround the drive section; and a fixed frame connected to the vibration-damping member and arranged to surround the vibration-damping member. [Supplementary Item 2] The mirror device described in Supplementary Item 1, wherein the movable section includes: a pair of first support sections connected to the mirror section and arranged on a first axis; and a pair of movable frames connected to the pair of first support sections and facing each other across the first axis, wherein the swing axis is the first axis or a second axis that intersects the first axis. [Supplementary Item 3] The mirror device described in Supplementary Item 2, wherein the vibration-damping member is connected to the drive section and the fixed frame on the first axis or the second axis. [Supplementary Item 4] The mirror device according to Supplementary Item 2 or Supplementary Item 3, wherein the driver includes a pair of second support parts connected to the movable frame on the second axis and supporting the movable part, and the pair of second support parts are arranged on the second axis. [Supplementary Item 5] The mirror device according to Supplementary Item 4, wherein the driver includes 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 6] The mirror device according to Supplementary Item 5, wherein the driver includes a second actuator arranged to surround the first actuator and having a pair of second piezoelectric elements facing each other across the first axis. [Supplementary Item 7] The mirror device according to any one of Supplementary Items 1 to 6, wherein the vibration damping member and the driver are displaced in opposite phases in the thickness direction of the fixed frame when the mirror part oscillates. [Supplementary Item 8] An optical scanning device comprising: the mirror device according to any one of Supplementary Items 1 to 7; 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 movable section including a mirror section that reflects incident light; a drive section connected to said movable section and that causes said mirror section to swing around at least one swing axis; an annular vibration-damping member connected to said drive section and disposed surrounding said drive section; and a fixed frame connected to said vibration-damping member and disposed surrounding said vibration-damping member.

2. The mirror device according to claim 1, wherein the movable section comprises: a pair of first support sections connected to the mirror section and arranged on a first axis; and a pair of movable frames connected to the pair of first support sections and facing each other across the first axis, and the oscillation axis is the first axis or a second axis intersecting the first axis.

3. The mirror device according to claim 2, wherein the vibration-damping member is connected to the drive unit and the fixed frame on the first axis or the second axis.

4. The mirror device according to claim 3, wherein the drive unit is connected to the movable frame on the second axis and comprises a pair of second support parts that support the movable unit, and the pair of second support parts are arranged on the second axis.

5. The mirror device according to claim 4, wherein the drive section includes a first actuator connected to a pair of the second support sections and having a pair of first piezoelectric elements facing each other across the second axis.

6. The mirror device according to claim 5, 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.

7. A mirror device according to any one of claims 1 to 6, wherein when the mirror section oscillates, the vibration-damping member and the drive section are displaced in the thickness direction of the fixed frame in an anti-phase relationship.

8. An optical scanning device comprising the mirror device according to claim 1 and a processor that drives the drive unit, wherein the drive unit oscillates the mirror unit in response to a drive signal given by the processor.

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