Light deflector

Abstract

To provide an optical deflector that can alleviate a stress applied during the drive of a piezoelectric actuator and improve the limit deflection angle of the piezoelectric actuator.SOLUTION: An optical deflector comprises: a mirror unit 2 including a reflection surface; a piezoelectric actuator 4 located on the periphery of the mirror unit 2 and oscillating the mirror unit 2 around a central axis; an inner frame 6 connected to one end of the piezoelectric actuator 4; and an outer frame 7 connected to the other end of the piezoelectric actuator 4. The piezoelectric actuator 4 includes a piezoelectric cantilever unit 34 driven by a piezoelectric element 31c provided between the inner frame 6 and the outer frame 7. At a position where the inner frame 6 and the piezoelectric cantilever unit 34 are connected to each other, a projection 6d at which part of the inner frame 6 projects is provided in a direction intersecting the central axis of the piezoelectric cantilever unit 34.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical deflector. [Background technology]

[0002] Conventionally, galvanometer mirrors and polygon mirrors are commonly used as examples of optical deflectors that deflect and scan light beams such as laser light. Of these, galvanometer mirrors are optical deflectors in which a plane mirror for polarization is attached to a rotating shaft, and the rotation angle of the mirror is made variable by driving an electromagnetic motor in response to an electric signal. This galvanometer mirror is a non-resonant optical deflector, so it can be driven by sawtooth or random electric signals. On the other hand, polygon mirrors are optical deflectors in which a multi-faceted mirror for polarization is attached to a rotating shaft, and can scan faster than galvanometer mirrors.

[0003] However, since galvanometer mirrors and polygon mirrors use electromagnetic motors as their drive sources, it is difficult to reduce their size and weight, and it is difficult to use them in applications that require space saving.

[0004] In response to this, an optical deflector (also called a micromirror) has been proposed in which mechanical components such as mirrors and elastic bodies are integrally formed on a semiconductor substrate using micromachining technology (so-called MEMS technology), which applies semiconductor manufacturing technology to finely process silicon or glass (see, for example, Patent Documents 1 and 2 below).

[0005] Specifically, this optical deflector uses a piezoelectric actuator in which multiple piezoelectric elements with electrodes on the top and bottom of the piezoelectric body are arranged on a support plate and an elastic body is connected to the top of the piezoelectric elements. The piezoelectric actuator generates a linear reciprocating vibration up and down in the piezoelectric body by applying an AC voltage between the top and bottom electrodes, and this vibration is transmitted to the reflector plate via the elastic body, deflecting the reflector plate left and right around the rotating support.

[0006] Such optical deflectors are MEMS devices composed entirely of tiny mechanical structures, making them easy to miniaturize and reduce weight. Furthermore, multiple devices can be fabricated simultaneously from a single wafer, just like in semiconductor processes, making mass production easy and reducing costs. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2008-040240 A [Patent Document 2] JP 2019-144416 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in a non-resonant type piezoelectric actuator, the deflection angle efficiency per drive voltage is poorer than in a resonant type piezoelectric actuator.

[0009] On the other hand, in order to improve the deflection angle efficiency, it is necessary to reduce the thickness of the Si substrate that serves as the support for the non-resonant piezoelectric actuator. However, if the thickness of the Si substrate is reduced, the structure becomes fragile, making the device itself more susceptible to damage. In addition, the limit deflection angle of the non-resonant piezoelectric actuator decreases.

[0010] The limiting deflection angle refers to the deflection angle at which, during testing of an optical deflector, the driving voltage of the piezoelectric actuator is gradually increased at a reference frequency to gradually increase the deflection angle of the mirror section, at which point any part of the optical deflector is damaged and it becomes difficult to increase the deflection angle any further.

[0011] In particular, in a non-resonant piezoelectric actuator, stress is easily applied to the connection position between the tip of the cantilever and the inner frame, making it prone to breakage due to repeated application of stress.

[0012] The present invention has been proposed in view of the above-mentioned conventional circumstances, and has an object to provide an optical deflector that makes it possible to reduce the stress applied to a piezoelectric actuator when it is driven, and improve the limit deflection angle of the piezoelectric actuator. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention provides the following means. [1] A mirror portion including a reflective surface; a piezoelectric actuator positioned around the mirror portion to swing the mirror portion around a central axis; an inner frame connected to one end side of the piezoelectric actuator; an outer frame connected to the other end side of the piezoelectric actuator; the piezoelectric actuator includes a piezoelectric cantilever portion driven by a piezoelectric element provided between the inner frame and the outer frame, An optical deflector characterized in that at a position where the inner frame and the piezoelectric cantilever portion are connected, a protrusion is provided in which a part of the inner frame protrudes in a direction intersecting a central axis of the piezoelectric cantilever portion. [2] The inner frame is connected to the piezoelectric cantilever portion via an extension portion extending in a direction intersecting a central axis of the piezoelectric cantilever portion, The optical deflector described in [1] above, wherein the protrusion is provided protruding from the extension portion in a direction in which the extension portion extends. [3] A mirror portion including a reflective surface; a first piezoelectric actuator located around the mirror portion and configured to oscillate the mirror portion around a first central axis; a second piezoelectric actuator located around the first piezoelectric actuator and configured to oscillate the mirror portion around a second central axis perpendicular to the first central axis; a torsion bar connecting the mirror portion and one end of the first piezoelectric actuator; an inner frame connecting the other end of the first piezoelectric actuator and one end of the second piezoelectric actuator; an outer frame located around the second piezoelectric actuator and connected to the other end of the second piezoelectric actuator; the first piezoelectric actuator includes a first piezoelectric cantilever portion that is driven in a resonant state by a piezoelectric element provided between the torsion bar and the inner frame, the second piezoelectric actuator includes a second piezoelectric cantilever portion that is driven in a non-resonant state by a piezoelectric element provided between the inner frame and the outer frame, An optical deflector characterized in that at a position where the inner frame and the second piezoelectric cantilever portion are connected, a protrusion is provided in which a part of the inner frame protrudes in a direction intersecting a central axis of the second piezoelectric cantilever portion. [4] The inner frame is connected to the second piezoelectric cantilever portion via an extension portion extending in a direction intersecting a central axis of the second piezoelectric cantilever portion, The optical deflector described in [3] above, wherein the protrusion is provided protruding from the extension portion in a direction in which the extension portion extends. [5] The optical deflector described in any one of [1] to [4], wherein the protrusion is provided so as to protrude in a direction perpendicular to the central axis. Effect of the Invention

[0014] As described above, according to the present invention, it is possible to provide an optical deflector that can reduce the stress applied to the piezoelectric actuator when it is driven, thereby improving the limit deflection angle of the piezoelectric actuator. [Brief description of the drawings]

[0015] [Figure 1] 1 is a plan view showing a configuration of an optical deflector according to a first embodiment of the present invention. [Diagram 2]2A and 2B show the cross-sectional structure of the optical deflector shown in FIG. 1, where FIG. 2A is a cross-sectional view of the optical deflector taken along line AA in FIG. 1, and FIG. 2B is a cross-sectional view showing the layered structure of each layer constituting the optical deflector. [Diagram 3] 13 is a diagram showing the stress distribution at the connection position between the inner frame and the second piezoelectric cantilever portion when there is a protrusion. FIG. [Figure 4] 13 is a diagram showing the stress distribution at the connection position between the inner frame and the second piezoelectric cantilever portion when there is no protrusion. FIG. [Diagram 5] FIG. 11 is a plan view showing a configuration of an optical deflector according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a plan view showing a configuration of an optical deflector according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, the dimensions of the components may be shown at different scales to make each component easier to see, and the dimensional ratios of each component may not necessarily be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and may be appropriately modified and implemented within the scope of the present invention.

[0017] In addition, in the drawings shown below, an XYZ Cartesian coordinate system is set, and the X-axis direction is the direction of the second central axis in the plane of the optical deflector (horizontal direction), the Y-axis direction is the direction of the first central axis perpendicular to the second direction in the plane of the optical deflector (vertical direction), and the Z-axis direction is the thickness direction (height direction) perpendicular to the plane of the optical deflector.

[0018] (First embodiment) First, as a first embodiment of the present invention, an optical deflector 1 shown in, for example, FIGS. 1 and 2 will be described.

[0019] Fig. 1 is a plan view showing the configuration of the optical deflector 1. Fig. 2 shows a cross-sectional structure of the optical deflector 1, where (A) is a cross-sectional view of the optical deflector 1 taken along line segment AA shown in Fig. 1, and (B) is a cross-sectional view showing the laminated structure of each layer constituting the optical deflector 1.

[0020] As shown in Figures 1 and 2, the optical deflector 1 of this embodiment includes a mirror portion 2, a first piezoelectric actuator 3 located around the mirror portion 2 and oscillating the mirror portion 2 around a first central axis AY (in this embodiment, a direction along the Y-axis), a second piezoelectric actuator 4 located around the first piezoelectric actuator 3 and oscillating the mirror portion 2 around a second central axis AX (in this embodiment, a direction along the X-axis) perpendicular to the first central axis AY, a torsion bar 5 connecting the mirror portion 2 and the first piezoelectric actuator 3, an inner frame 6 connecting the first piezoelectric actuator 3 and the second piezoelectric actuator 4, and an outer frame 7 located around the second piezoelectric actuator 4 and connected to the second piezoelectric actuator 4.

[0021] Moreover, the optical deflector 1 of this embodiment is composed of a micromirror in which a mirror portion 2, first and second piezoelectric actuators 3, 4, a torsion bar 5, an inner frame 6, and an outer frame 7 are integrally formed on a semiconductor substrate serving as a support using MEMS technology.

[0022] For example, the optical deflector 1 of this embodiment is formed by forming a SiO 2 Layer 12 and Si / SiO 2 On the other surface (upper surface) of the Si substrate 11, a Pt layer 14, a PZT (lead zirconate titanate) layer 15, and a Pt layer 16 are laminated in this order.

[0023] Of these, the mirror part 2 is made of Si / SiO 2 Layer 13, SiO 2The first and second piezoelectric actuators 3 and 4 are each composed of a laminate of a Si substrate 11, a Pt layer 14, a PZT layer 15 and a Pt layer 16. The torsion bar 5 and the inner frame 6 are each composed of a Si / SiO 2 Layer 13, SiO 2 The outer frame 7 is made of a laminate of a Si / SiO 2 Layer 13, SiO 2 The mirror section 2, the first and second piezoelectric actuators 3 and 4, the torsion bar 5 and the inner frame 6 are made of a Si / SiO 2 The thickness of the layer 13 is determined by the thickness of the Si / SiO 2 It is thinner than the thickness of layer 13.

[0024] The mirror section 2 has a reflecting surface 2a that is circular in plan view and is made of a Pt layer 14 that serves as a reflector, a Si substrate 11, a SiO 2 Layer 12 and Si / SiO 2 and a mirror frame 2b formed by a layer 13.

[0025] The optical deflector 1 of this embodiment has a space K between the mirror section 2 and a substantially rectangular outer frame 7 surrounding the mirror section 2. The optical deflector 1 of this embodiment has a structure in which a pair of first piezoelectric actuators 3 arranged symmetrically in the direction of the second central axis AX across the mirror section 2 are connected to the mirror section 2 via a pair of torsion bars 5, and a pair of second piezoelectric actuators 4 arranged symmetrically in the direction of the second central axis AX across the mirror section 2 are connected to the pair of first piezoelectric actuators 3 via an inner frame 6.

[0026] Therefore, in the optical deflector 1 of this embodiment, a pair of torsion bars 5, a pair of first piezoelectric actuators 3, an inner frame 6 and a pair of second piezoelectric actuators 4 are arranged symmetrically on either side of the mirror portion 2.

[0027] The connection positions between the pair of second piezoelectric actuators 4 and the outer frame 7 are arranged symmetrically in the diagonal direction of the outer frame 7, but this is not necessarily limited to such a configuration and may be arranged symmetrically in the direction of the first central axis AY.

[0028] A pair of first piezoelectric actuators 3 are each formed in a long semicircular arc shape extending in the direction of a first central axis AY when viewed in a plane, and with both ends connected to a pair of torsion bars 5, the actuators are formed overall in the shape of an oval ring that surrounds the mirror portion 2.

[0029] The pair of torsion bars 5 are each formed linearly and extending in the direction of the first central axis AY in a plan view, and connect the mirror portion 2 and the pair of first piezoelectric actuators 3 along the first central axis AY.

[0030] Each of the first piezoelectric actuators 3 has a first piezoelectric cantilever portion 32 provided with a driving piezoelectric element 31a and a detecting piezoelectric element 31b.

[0031] The piezoelectric elements 31a and 31b are constructed by laminating a Pt layer 14 serving as a lower electrode, a PZT layer 15 serving as a piezoelectric body, and a Pt layer 16 serving as an upper electrode on a Si substrate 11 serving as a vibration plate.

[0032] A plurality of (three in this embodiment) driving piezoelectric elements 31a are arranged side by side in the extending direction of the first piezoelectric cantilever portion 32. The three piezoelectric elements 31a are arranged symmetrically in the direction of the first central axis AY with the central piezoelectric element 31a sandwiched between the piezoelectric elements 31a at both ends.

[0033] Between a pair of first piezoelectric actuators 3, the central piezoelectric element 31a provided on one of the first piezoelectric cantilever portions 32 and the piezoelectric elements 31a at both ends provided on the other first piezoelectric cantilever portion 32 are electrically connected via a pair of connecting wiring 33a.

[0034] The detection piezoelectric element 31b is arranged alongside the multiple piezoelectric elements 31a at one end side (−Y axis side) in the direction in which the first piezoelectric cantilever portion 32 extends.

[0035] The inner frame 6 is formed in a long semicircular arc shape extending in the direction of the first central axis AY in a plan view, and with both ends connected to a pair of torsion bars 5, the inner frame 6 is formed in an oval ring shape overall so as to surround the pair of first piezoelectric actuators 3.

[0036] In addition, the inner frame 6 connects the pair of first piezoelectric actuators 3 and the inner frame 6 along the first central axis AY via a pair of connecting portions 6a that are formed linearly and extend in the direction of the first central axis AY when viewed in a plane.

[0037] In addition, the inner frame 6 connects the pair of first piezoelectric actuators 3 and the inner frame 6 along the second central axis AX via a pair of connecting portions 6b that are formed linearly and extend in the direction of the second central axis AX in a planar view.

[0038] In addition, the inner frame 6 is connected to a pair of second piezoelectric actuators 4 via a pair of extension portions 6c that are formed linearly and extend in opposite directions from both ends in the direction of the first central axis AY in a planar view while being aligned in the direction of the second central axis AX.

[0039] The pair of second piezoelectric actuators 4 each extend in the direction of the first central axis AY in a plan view and connect the inner frame 6 and the outer frame 7 together.

[0040] Each second piezoelectric actuator 4 has a second piezoelectric cantilever portion 34 provided with a driving piezoelectric element 31c. That is, the second piezoelectric actuator 4 has a structure in which a pair of second piezoelectric cantilever portions 34 formed linearly while extending in the direction of the first central axis AY are disposed between the inner frame 6 and the outer frame 7.

[0041] Like the above-mentioned piezoelectric elements 31a and 31b, the piezoelectric element 31c is configured by laminating a Pt layer 14 serving as a lower electrode, a PZT layer 15 serving as a piezoelectric body, and a Pt layer 16 serving as an upper electrode on a Si substrate 11 serving as a vibration plate. The piezoelectric element 31c is provided across one end side and the other end side in the direction in which the second piezoelectric cantilever portion 34 extends.

[0042] A plurality of electrode pads 35a, 35b, and 35c (six in this embodiment) corresponding to the piezoelectric elements 31a, 31b, and 31c are provided on the surface of the outer frame 7. The electrode pads 35a, 35b, and 35c are located on both sides in the direction of the second central axis AX and are arranged side by side in the direction of the first central axis AY.

[0043] The driving piezoelectric element 31a is electrically connected to a pair of connection wires 33a, and is also electrically connected to a pair of electrode pads 35a via a pair of connection wires 33b routed from one connecting portion 6b to one inner frame 6, one second piezoelectric actuator 4, and on the surface of the outer frame 7. This makes it possible to apply a driving voltage (e.g., an AC voltage such as a sine wave) to the piezoelectric element 31a via the pair of electrode pads 35a, the pair of connection wires 33b, and the pair of connection wires 33a.

[0044] The detection piezoelectric element 31b is electrically connected to a pair of electrode pads 35b via a pair of connection wires 33c routed from one connecting portion 6a to the other inner frame 6, the other second piezoelectric actuator 4, and on the surface of the outer frame 7. This makes it possible to detect a voltage output from the piezoelectric element 31b in response to deformation of the first piezoelectric cantilever portion 32 via the pair of connection wires 33c and the pair of electrode pads 35b.

[0045] The driving piezoelectric element 31c is electrically connected to a pair of electrode pads 35c via a pair of connection wires 33d routed on the surface of the outer frame 7. This makes it possible to apply a driving voltage (e.g., an AC voltage such as a sine wave) to the piezoelectric element 31c via the pair of electrode pads 35c and the pair of connection wires 33d.

[0046] In the optical deflector 1 of this embodiment having the above-mentioned configuration, the mirror portion 2 can be swung around the first central axis AY by piezoelectric driving of the pair of first piezoelectric actuators 3.

[0047] Specifically, by applying a drive voltage to the driving piezoelectric element 31a and bending the first piezoelectric cantilever portion 32, it is possible to oscillate the mirror portion 2 around the first central axis AY.

[0048] In the optical deflector 1 of this embodiment, the first piezoelectric actuator 3 is a resonant type piezoelectric actuator, and applies a drive voltage near the resonant frequency to the driving piezoelectric element 31a. At this time, the detection piezoelectric element 31b detects the bending state of the first piezoelectric cantilever portion 32, while controlling the drive voltage applied to the driving piezoelectric element 31a so that the first piezoelectric cantilever portion 32 resonates. This makes it possible to oscillate the mirror portion 2 at a larger deflection angle while driving the first piezoelectric cantilever portion 32 (first piezoelectric actuator 3) in a resonant state (resonant drive).

[0049] On the other hand, in the optical deflector 1 of this embodiment, the mirror portion 2 can be swung around the second central axis AX by the piezoelectric driving of the pair of second piezoelectric actuators 4.

[0050] Specifically, by applying a drive voltage to the driving piezoelectric element 31c to bend the second piezoelectric cantilever portion 34, it is possible to oscillate the mirror portion 2 around the second central axis AX.

[0051] In the optical deflector 1 of this embodiment, the second piezoelectric actuator 4 is a non-resonant piezoelectric actuator, and a drive voltage is applied to the driving piezoelectric element 31c at a frequency at which the second piezoelectric cantilever portion 34 does not resonate. This makes it possible to oscillate the mirror portion 2 around the second central axis AX while driving the second piezoelectric cantilever portion 34 (second piezoelectric actuator 4) in a non-resonant state (non-resonant drive).

[0052] In the optical deflector 1 of this embodiment, at the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected, a protrusion 6d is provided in which a part of the inner frame 6 protrudes in a direction intersecting the central axis of the second piezoelectric cantilever portion 34.

[0053] Specifically, this protrusion 6d is continuous with the extending portion 6c of the inner frame 6 and protrudes in a direction perpendicular to the central axis of the second piezoelectric cantilever portion 34 extending in the direction of the first central axis AY (in the direction of the second central axis AX).

[0054] In the optical deflector 1 of this embodiment, by providing such a protrusion 6d, it is possible to alleviate the stress in the direction of the first central axis AY that is applied to the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected when the non-resonant second piezoelectric actuator 4 is driven.

[0055] As a result, in the optical deflector 1 of this embodiment, the second piezoelectric actuator 4 is made less susceptible to damage, and the limit deflection angle of the second piezoelectric actuator 4 can be improved.

[0056] Here, the effect of stress relaxation due to the presence or absence of the protrusion 6d was obtained by simulation, and the simulation results are shown in Figs. Fig. 3 is a diagram showing the stress distribution at the connection position between the inner frame 6 and the second piezoelectric cantilever part 34 when there is a protrusion 6d. Fig. 4 is a diagram showing the stress distribution at the connection position between the inner frame 6 and the second piezoelectric cantilever part 34 when there is no protrusion 6d.

[0057] It can be seen that, when there is no protrusion 6d, as shown in FIG. 4, stress is concentrated at the connection position between the inner frame 6 and the second piezoelectric cantilever portion 34 (enclosed portion B in FIG. 4).

[0058] In contrast, when the protrusion 6d is provided, it is found that the stress is alleviated in the direction of the first central axis AY, as shown in Fig. 3. As a result, it was found that the maximum stress is reduced by approximately 20% and the limit swing angle is improved by approximately 20% compared to when the protrusion 6d is not provided.

[0059] In addition, the above-mentioned Patent Document 2 discloses an optical deflector that can increase the limit deflection angle of the reflecting part while ensuring the bonding strength of the outer piezoelectric actuator by providing a protruding rib that reaches the corner of the tip end of the piezoelectric cantilever.

[0060] In the invention described in Patent Document 2, the stress in the X direction transmitted from the outer piezoelectric actuator to the inner frame and the outer piezoelectric actuator is alleviated by providing such a protruding rib. Therefore, the invention described in Patent Document 2 is different in the direction of stress alleviation from the optical deflector 1 of this embodiment, which alleviates the stress in the direction of the first central axis AY applied to the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected.

[0061] Second embodiment Next, as a second embodiment of the present invention, an optical deflector 1A shown in FIG. 5 will be described.

[0062] 5 is a plan view showing the configuration of the optical deflector 1 A. In the following explanation, the explanation of the same parts as those in the optical deflector 1 will be omitted and the same reference numerals will be used in the drawings.

[0063] 5, the optical deflector 1A of this embodiment has a configuration in which the connection position between the inner frame 6 and the pair of second piezoelectric actuators 4 and the connection position between the pair of second piezoelectric actuators 4 and the outer frame 7 are arranged symmetrically in the direction of the first central axis AY across the direction of the second central axis AX. Otherwise, the optical deflector 1A has basically the same configuration as the optical deflector 1 described above.

[0064] In the optical deflector 1A of this embodiment, similarly to the above-described optical deflector 1, at the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected, a protrusion 6d is provided in which a part of the inner frame 6 protrudes in a direction intersecting (orthogonal in this embodiment) the central axis of the second piezoelectric cantilever portion 34.

[0065] In the optical deflector 1A of this embodiment, by providing such a protrusion 6d, it is possible to alleviate the stress applied to the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected when the non-resonant second piezoelectric actuator 4 is driven.

[0066] As a result, in the optical deflector 1A of this embodiment, the second piezoelectric actuator 4 can be made less susceptible to damage, and the limit deflection angle of the second piezoelectric actuator 4 can be improved.

[0067] (Third embodiment) Next, as a third embodiment of the present invention, an optical deflector 1B shown in FIG. 6 will be described.

[0068] 6 is a plan view showing the configuration of the optical deflector 1B. In the following description, the description of the same parts as those in the optical deflector 1 will be omitted and the same reference numerals will be used in the drawings.

[0069] 6, the optical deflector 1B of this embodiment has a second piezoelectric cantilever portion 34 constituting the second piezoelectric actuator 4 that has a curved shape in accordance with the curved shape of the inner frame 6. Other than that, the optical deflector 1B has basically the same configuration as the optical deflector 1 described above.

[0070] Specifically, the inner frame 6 has a linear region E1 that extends linearly and a curved region E2 that curves in an arc shape from the linear region E1 toward both ends. The second piezoelectric cantilever portion 34 has a linear region E3 that extends linearly along the shape of the inner frame 6 and a curved region E4 that curves in an arc shape from the linear region E3 toward both ends.

[0071] Furthermore, the distance W1 between the inner frame 6 and the second piezoelectric cantilever portion 34 in the straight line regions E1 and E3 is constant, and the distance W2 between the inner frame 6 and the second piezoelectric cantilever portion 34 in the curved regions E2 and E4 is constant. Furthermore, in this embodiment, W1=W2. In the curved regions E2 and E4, the width in the direction perpendicular to the tangent of the inner frame 6 or the second piezoelectric cantilever portion 34 is set as the distance W2.

[0072] Furthermore, in the optical deflector 1B of this embodiment, the first piezoelectric cantilever portion 32 (first piezoelectric actuator 3) has a curved shape in accordance with the curved shape of the inner frame 6 described above.

[0073] Specifically, the first piezoelectric cantilever portion 32 has a straight line region E5 that extends linearly along the shape of the inner frame 6, and a curved region E6 that is curved in an arc shape from this straight line region E5 toward both ends.

[0074] Furthermore, the distance W3 between the inner frame 6 and the first piezoelectric cantilever portion 32 in the straight line regions E1 and E5 is constant, and the distance W4 between the inner frame 6 and the first piezoelectric cantilever portion 32 in the curved regions E2 and E6 is constant. Furthermore, in this embodiment, W3=W4. In the curved regions E2 and E6, the width in the direction perpendicular to the tangent of the inner frame 6 or the second piezoelectric cantilever portion 34 is set as the distance W4.

[0075] In the optical deflector 1B of this embodiment, the above-mentioned inner frame 6 includes the curved region E2, which makes it possible to reduce stress and reduce chip size more than when the inner frame 6 is composed of only the straight region E1.

[0076] Furthermore, in the optical deflector 1B of this embodiment, the second piezoelectric cantilever portion 34 (second piezoelectric actuator 4) has a curved shape that follows the curved shape of the inner frame 6 described above, so that the distance W2 in the curved regions E2, E4 between the inner frame 6 and the second piezoelectric cantilever portion 34 can be narrowed while maintaining the length of the second piezoelectric cantilever portion 34.

[0077] As a result, in the optical deflector 1B of this embodiment, it is possible to improve the deflection angle efficiency per drive voltage of the second piezoelectric actuator 4 and increase the primary resonance frequency, compared to the case where the second piezoelectric cantilever portion 34 (second piezoelectric actuator 4) is composed of only the linear region E3. Also, it is possible to reduce the chip size.

[0078] In the optical deflector 1B of this embodiment, similarly to the above-described optical deflector 1, at the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected, a protrusion 6d is provided in which a part of the inner frame 6 protrudes in a direction intersecting the central axis of the second piezoelectric cantilever portion 34.

[0079] In this embodiment, the central axis of the second piezoelectric cantilever portion 34 is an extension of the center of the curved region E4 with the same curvature.

[0080] In the optical deflector 1B of this embodiment, by providing such a protrusion 6d, it is possible to alleviate the stress applied to the position where the extension portion 6c of the inner frame 6 and the second piezoelectric cantilever portion 34 are connected when the non-resonant second piezoelectric actuator 4 is driven.

[0081] As a result, in the optical deflector 1B of this embodiment, the second piezoelectric actuator 4 is made less susceptible to damage, and the limit deflection angle of the second piezoelectric actuator 4 can be improved.

[0082] As described above, in the above embodiment, the protrusion 6d is provided to protrude from the extension portion 6c that intersects with the second piezoelectric cantilever portion 34 in the extension direction of the extension portion 6c.

[0083] The present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the protrusion 6d has an angular tip, but the tip may be rounded or pointed. Also, the corner at the connection position between the protrusion 6d and the second piezoelectric cantilever portion 34 is connected at a right angle, but it may be connected at an angle or curved.

[0084] Furthermore, the optical deflector to which the present invention is applied is not necessarily limited to a two-axis type in which the above-mentioned mirror portion 2 is oscillated around the first central axis AY and the second central axis AX, but may also be a single-axis type.

[0085] That is, the present invention is applicable to an optical deflector including at least a mirror portion including a reflective surface, a piezoelectric actuator located around the mirror portion and swinging the mirror portion around a central axis, an inner frame connected to one end of the piezoelectric actuator, and an outer frame connected to the other end of the piezoelectric actuator. In this case, a protrusion may be provided in which a part of the inner frame protrudes in a direction intersecting with the central axis of the piezoelectric cantilever portion at a position where the inner frame and the piezoelectric cantilever portion of the piezoelectric actuator are connected.

[0086] Furthermore, the second piezoelectric actuator 4 may have a meandering structure in which a plurality of second piezoelectric cantilever portions 34 are arranged side by side toward the direction of the second central axis AX, and one end and the other end of adjacent second piezoelectric cantilever portions 34 are folded back and connected via a connecting portion extending in the direction of the second central axis AX. [Explanation of symbols]

[0087] REFERENCE SIGNS LIST 1, 1A... Optical deflector 2... Mirror portion 2a... Reflecting surface 3... First piezoelectric actuator 4... Second piezoelectric actuator 5... Torsion bar 6... Inner frame 6d... Protruding portion 7... Outer frame 11... Si substrate 12... SiO 2 Layer 13…Si / SiO 2 Layer 14...Pt layer 15...PZT layer 16...Pt layer 31a, 31b, 31c...piezoelectric element 32...first piezoelectric cantilever portion 33a, 33b, 33c, 33d...connecting wiring 34...second piezoelectric cantilever portion 35a, 35b, 35c...electrode pads AX...second central axis AY...first central axis K...space

Claims

1. A mirror portion including a reflective surface; a piezoelectric actuator positioned around the mirror portion to swing the mirror portion around a central axis; an inner frame connected to one end side of the piezoelectric actuator; an outer frame connected to the other end side of the piezoelectric actuator; the piezoelectric actuator includes a piezoelectric cantilever portion driven by a piezoelectric element provided between the inner frame and the outer frame, An optical deflector characterized in that at a position where the inner frame and the piezoelectric cantilever portion are connected, a protrusion is provided in which a part of the inner frame protrudes in a direction intersecting a central axis of the piezoelectric cantilever portion.

2. the inner frame is connected to the piezoelectric cantilever portion via an extension portion that extends in a direction intersecting a central axis of the piezoelectric cantilever portion, 2. The optical deflector according to claim 1, wherein the protrusion is provided so as to protrude from the extending portion in a direction in which the extending portion extends.

3. A mirror portion including a reflective surface; a first piezoelectric actuator located around the mirror portion and configured to swing the mirror portion around a first central axis; a second piezoelectric actuator located around the first piezoelectric actuator and configured to oscillate the mirror portion around a second central axis perpendicular to the first central axis; a torsion bar connecting the mirror portion and one end of the first piezoelectric actuator; an inner frame connecting the other end of the first piezoelectric actuator and one end of the second piezoelectric actuator; an outer frame located around the second piezoelectric actuator and connected to the other end of the second piezoelectric actuator; the first piezoelectric actuator includes a first piezoelectric cantilever portion that is driven in a resonant state by a piezoelectric element provided between the torsion bar and the inner frame, the second piezoelectric actuator includes a second piezoelectric cantilever portion that is driven in a non-resonant state by a piezoelectric element provided between the inner frame and the outer frame, An optical deflector characterized in that at a position where the inner frame and the second piezoelectric cantilever portion are connected, a protrusion is provided in which a part of the inner frame protrudes in a direction intersecting the central axis of the second piezoelectric cantilever portion.

4. the inner frame is connected to the second piezoelectric cantilever portion via an extension portion extending in a direction intersecting a central axis of the second piezoelectric cantilever portion, 4. The optical deflector according to claim 3, wherein the protrusion is provided so as to protrude from the extending portion in a direction in which the extending portion extends.

5. 5. The optical deflector according to claim 1, wherein the protrusion is provided so as to protrude in a direction perpendicular to the central axis.

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