Light deflector

Abstract

To provide a light deflector capable of suppressing a decrease in swing angle efficiency of a mirror part and increasing a frequency (primary resonance frequency) of a primary mode (shifting to a high-frequency side).SOLUTION: A light deflector 10 includes at least one of second actuators 53, 54 for rocking a mirror part 2 relative to a second support part 6 with a second axis X as a center, the second actuators include multiple piezoelectric cantilevers 53A to 53G, 54A to 54G disposed in a direction of the second axis, the multiple piezoelectric cantilevers are connected in a bellows shape, and distance D3 between a fold-back end of at least one piezoelectric cantilever from among piezoelectric cantilevers other than the piezoelectric cantilevers 53G, 54G farthest from the mirror part and the second axis is shorter than distance D2 between a fold-back end of a piezoelectric cantilever farthest from the mirror part and the second axis.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an optical deflector, and particularly to an optical deflector capable of increasing the frequency of the primary mode (primary resonance frequency) (shifting it to the high-frequency side) while suppressing a decrease in the swing angle efficiency of the mirror portion.

Background Art

[0002] An optical deflector including a mirror portion and an actuator including a plurality of piezoelectric cantilevers connected in a bellows shape as an actuator for swinging the mirror portion is known (see, for example, Patent Document 1).

[0003] On the other hand, the inventors of the present invention considered shortening the length of the piezoelectric cantilever(s) connected in a bellows shape in order to suppress the optical deflector from being affected by external vibration even when external vibration is applied to the optical deflector.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, as a result of the inventors' study, although it is possible to increase the frequency of the primary mode (primary resonance frequency) (shift it to the high-frequency side) by shortening the length of the piezoelectric cantilever(s) connected in a bellows shape, a problem has been found that the swing angle efficiency of the mirror portion is greatly reduced.

[0006] The present invention has been made to solve such problems, and an object thereof is to provide an optical deflector that can increase the frequency of the first mode (first resonance frequency) (shift it to the high-frequency side) while suppressing a decrease in the swing angle efficiency of the mirror unit.

Means for Solving the Problems

[0007] The optical deflector according to the present invention includes a mirror unit, a first support unit that supports the mirror unit so as to be swingable about a first axis, a second support unit that supports the first support unit so as to be swingable about a second axis that intersects the first axis, at least one first actuator that swings the mirror unit about the first axis with respect to the first support unit, and at least one second actuator that swings the first support unit and the mirror unit supported by the first support unit about the second axis with respect to the second support unit. The second actuator includes a plurality of piezoelectric cantilevers arranged in the direction of the second axis, and the plurality of piezoelectric cantilevers are connected in a bellows shape such that each piezoelectric cantilever folds back with respect to an adjacent piezoelectric cantilever. A free end of the piezoelectric cantilever closest to the mirror unit among the piezoelectric cantilevers is connected to the first support unit, a free end of the piezoelectric cantilever farthest from the mirror unit among the piezoelectric cantilevers is connected to the second support unit, and a distance between a folded end of at least one piezoelectric cantilever among the piezoelectric cantilevers other than the piezoelectric cantilever farthest from the mirror unit and the second axis is shorter than a distance between a folded end of the piezoelectric cantilever farthest from the mirror unit and the second axis.

[0008] With such a configuration, it is possible to increase the frequency of the first mode (first resonance frequency) (shift it to the high-frequency side) while suppressing a decrease in the swing angle efficiency of the mirror unit.

[0009] The ability to increase the frequency of the first mode (first resonance frequency) (shift it to the high-frequency side) is due to making the distance between the folded end of at least one of the piezoelectric cantilevers other than the piezoelectric cantilever farthest from the mirror portion and the second axis shorter than the distance between the folded end of the piezoelectric cantilever farthest from the mirror portion and the second axis. That is, this is because the rigidity of at least one of the piezoelectric cantilevers other than the piezoelectric cantilever farthest from the mirror portion becomes relatively higher than the rigidity of the piezoelectric cantilever farthest from the mirror portion.

[0010] The ability to suppress the decrease in the swing angle efficiency of the mirror portion is due to the fact that the farther the piezoelectric cantilever is from the mirror portion, the relatively lower its rigidity (easier to bend and deform).

[0011] Also, in the above optical deflector, the distance between the folded end of the piezoelectric cantilever closer to the mirror portion among the plurality of piezoelectric cantilevers and the second axis may be shorter.

[0012] Also, the second support portion is provided so as to surround the first support portion, the first actuator, and the second actuator, and includes a plurality of portions facing the folded ends of the plurality of piezoelectric cantilevers. The plurality of portions may each extend to the vicinity of the folded end of the piezoelectric cantilever facing the portion.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide an optical deflector capable of increasing the frequency of the first mode (first resonance frequency) (shifting it to the high-frequency side) while suppressing the decrease in the swing angle efficiency of the mirror portion.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0015] Hereinafter, the optical deflector 10 according to the embodiment of the present invention will be described with reference to the accompanying drawings. In each figure, corresponding components are denoted by the same reference numerals, and redundant explanations are omitted.

[0016] The optical deflector 10 of the present embodiment is a piezoelectric type (uniaxial non-resonant · uniaxial resonant type) optical deflector, for example, a MEMS scanner.

[0017] Hereinafter, for convenience of explanation, the basic configuration of a piezoelectric type (uniaxial non-resonant · uniaxial resonant type) optical deflector will be described, and then the optical deflector 10 of the present embodiment will be described. <Basic Configuration of the Optical Polarizer> FIG. 1 is a perspective view of an optical deflector 1 (basic configuration).

[0018] As shown in Fig. 1, the optical deflector 1 includes a mirror section 2, a pair of first piezoelectric actuators 31 and 32, a first support section 4, a pair of second piezoelectric actuators 51 and 52, and a second support section 6.

[0019] The mirror section 2 includes a circular reflecting surface 2a that reflects incident light, and a circular reflecting surface support 2b that supports the reflecting surface 2a.

[0020] The reflecting surface support 2b is made of a silicon substrate. A pair of torsion bars 21 and 22 extending outward from both ends thereof are connected to the reflecting surface support 2b.

[0021] The first piezoelectric actuators 31 and 32 are each formed in a semi-circular arc shape and are arranged with a gap therebetween so as to surround the mirror section 2. One end of each of the first piezoelectric actuators 31 and 32 is connected in opposition across one torsion bar 21, and the other end of each is connected in opposition across the other torsion bar 22.

[0022] The first support section 4 is formed in a rectangular frame shape and is provided so as to surround the mirror section 2 and the first piezoelectric actuators 31 and 32. The first support section 4 is connected to the outside of the center position of the arc portions of the first piezoelectric actuators 31 and 32 and supports the mirror section 2 via the first piezoelectric actuators 31 and 32.

[0023] The second piezoelectric actuators 51 and 52 are arranged to face each other with the first support section 4 therebetween. The tip portions of the second piezoelectric actuators 51 and 52 are respectively connected to both sides in a direction orthogonal to the torsion bars 21 and 22 of the first support section 4.

[0024] The second support portion 6 is formed in a rectangular frame shape and is provided so as to surround the first support portion 4 and the second piezoelectric actuators 51 and 52. A pair of other ends of the second piezoelectric actuators 51 and 52, which are not connected to the first support portion 4, are respectively connected to the second support portion 6. Thereby, the second support portion 6 supports the first support portion 4 via the second piezoelectric actuators 51 and 52.

[0025] Next, the detailed configuration of the first piezoelectric actuators 31 and 32 will be described. The first piezoelectric actuators 31 and 32 each include first piezoelectric cantilevers 31A and 32A configured to bend and deform by piezoelectric driving. Specifically, one of the first piezoelectric actuators 31 of the first piezoelectric actuators 31 and 32 includes one of the first piezoelectric cantilevers 31A, and the other of the first piezoelectric actuators 31 and 32, the other first piezoelectric actuator 32, includes the other first piezoelectric cantilever 32A. The first piezoelectric actuators 31 and 32 can swing the mirror unit 2 around the first axis Y with respect to the first support portion 4 via the torsion bars 21 and 22 due to the bending deformation of the first piezoelectric cantilevers 31A and 32A.

[0026] Next, the detailed configuration of the second piezoelectric actuators 51 and 52 will be described. The second piezoelectric actuators 51 and 52 each include a pair of second piezoelectric cantilevers 51A to 51D and 52A to 52D configured to bend and deform by piezoelectric driving. Specifically, one of the pair of second piezoelectric actuators 51, the second piezoelectric actuator 51, is composed of one of the second piezoelectric cantilevers 51A to 51D, which are composed of four piezoelectric cantilevers. Also, the other of the pair of second piezoelectric actuators 51 and 52, the other second piezoelectric actuator 52, is composed of the other second piezoelectric cantilever 52A to 52D, which are composed of four piezoelectric cantilevers.

[0027] One of the second piezoelectric cantilevers 51A to 51D is arranged such that both ends of each are adjacent to each other with their longitudinal directions being the same, and are arranged at a predetermined interval so as to be swingable around the second axis X (an axis orthogonal to the first axis Y. However, it is not necessary to be exactly orthogonal). And one of the second piezoelectric cantilevers 51A to 51D is connected so as to be folded back with respect to the adjacent piezoelectric cantilevers. The second axis X is an example of the swing axis of the present invention.

[0028] The other second piezoelectric cantilevers 52A to 52D are arranged in the same manner as the one second piezoelectric cantilevers 51A to 51D, such that both ends of each are adjacent to each other with their longitudinal directions being the same, and are arranged at a predetermined interval so as to be swingable around the second axis X. And the other second piezoelectric cantilevers 52A to 52D are connected so as to be folded back with respect to the adjacent piezoelectric cantilevers.

[0029] Thus, in one of the second piezoelectric actuators 51 and the other second piezoelectric actuator 52, the one second piezoelectric cantilevers 51A to 51D and the other second piezoelectric cantilevers 52A to 52D forming the same are formed in a so-called meander shape (or bellows shape).

[0030] The cantilevers (hereinafter referred to as "first second piezoelectric cantilevers") 51A and 52A arranged on the mirror part 2 side (first support part 4 side) among the one second piezoelectric cantilevers 51A to 51D and the other second piezoelectric cantilevers 52A to 52D are each connected at one end (free end) of the side not connected to the adjacent second piezoelectric cantilever (hereinafter referred to as "second second piezoelectric cantilever") 51B and 52B to the outer peripheral part of the first support part 4.

[0031] Similarly, the piezoelectric cantilevers (hereinafter referred to as "the fourth second piezoelectric cantilevers") 51D and 52D disposed on the second support portion 6 side among one set of second piezoelectric cantilevers 51A to 51D and the other set of second piezoelectric cantilevers 52A to 52D are each connected at one end (free end) on the side not connected to the adjacent second piezoelectric cantilevers (hereinafter referred to as "the third second piezoelectric cantilevers") 51C and 52C to the inner peripheral portion of the second support portion 6.

[0032] Thereby, the first support portion 4 can swing around the second axis X with respect to the second support portion 6 due to the bending deformation of the second piezoelectric cantilevers 51A to 51D and 52A to 52D that constitute the second piezoelectric actuators 51 and 52.

[0033] Hereinafter, among the pair of second piezoelectric cantilevers 51A to 51D and 52A to 52D, the respective piezoelectric cantilevers arranged in odd numbers when counted from the mirror portion 2 (the first second piezoelectric cantilevers 51A and 52A and the third second piezoelectric cantilevers 51C and 52C) are referred to as the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, and 52C.

[0034] Among the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, and 52C, those included in one set of second piezoelectric cantilevers 51A to 51D are referred to as one set of odd-numbered second piezoelectric cantilevers 51A and 51C, and those included in the other set of second piezoelectric cantilevers 52A to 52D are referred to as the other set of odd-numbered second piezoelectric cantilevers 52A and 52C.

[0035] Similarly, among the pair of second piezoelectric cantilevers 51A to 51D and 52A to 52D, the respective piezoelectric cantilevers arranged in even numbers when counted from the mirror portion 2 (the second second piezoelectric cantilevers 51B and 52B and the fourth second piezoelectric cantilevers 51D and 52D) are referred to as the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, and 52D.

[0036] Among the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, and 52D, those included in one of the second piezoelectric cantilevers 51A to 51D are referred to as one of the even-numbered second piezoelectric cantilevers 51B and 51D, and those included in the other second piezoelectric cantilevers 52A to 52D are referred to as the other even-numbered second piezoelectric cantilevers 52B and 52D.

[0037] FIG. 2 shows a schematic end view of the optical deflector 1. FIG. 2(a) shows an end view taken along line I-I of FIG. 1. However, in FIG. 2(a), the second support portion 6 is shown omitted. FIG. 2(b) shows an end view taken along line II-II of FIG. 1. However, in FIG. 2(b), the second support portion 6 and the third second piezoelectric cantilevers 51C, 52C and the fourth second piezoelectric cantilevers 51D, 52D among the pair of second piezoelectric cantilevers 51A to 51D, 52A to 52D are shown omitted.

[0038] The third second piezoelectric cantilevers 51C, 52C have the same configuration as the first second piezoelectric cantilevers 51A, 52A. Similarly, the fourth second piezoelectric cantilevers 51D, 52D have the same configuration as the second second piezoelectric cantilevers 51B, 52B.

[0039] Each of the first piezoelectric cantilevers 31A, 32A constituting the first piezoelectric actuators 31, 32 and each of the pair of second piezoelectric cantilevers 51A to 51D, 52A to 52D constituting the second piezoelectric actuators 51, 52 are piezoelectric cantilevers having a structure in which a lower electrode L1, a piezoelectric body L2, and an upper electrode L3 are laminated on a support B as a strain generating body (cantilever body).

[0040] Note that in the detailed structure of the piezoelectric cantilever, a lower electrode L1, a piezoelectric body L2, and an upper electrode L3 are laminated on the support B layer, and an interlayer insulating film M1 is provided so as to surround these lower electrode L1, piezoelectric body L2, and upper electrode L3. Then, an upper electrode wiring W is laminated on the interlayer insulating film M1, and a passivation film M2 is provided so as to surround this upper electrode wiring W.

[0041] Note that, as will be described later, the upper electrode wiring W includes a first driving upper electrode wiring Wy, a second driving odd upper electrode wiring Wo, a second driving even upper electrode wiring We, a first detection upper electrode wiring Wmy, and a second detection upper electrode wiring Wmx. When there is no need to particularly distinguish them, they are referred to as the upper electrode wiring W.

[0042] When a driving voltage is applied between the upper electrode L3 and the lower electrode L1 of the piezoelectric bodies L2 of these piezoelectric cantilevers 31A, 32A, 51A to 51D, 52A to 52D, they are bent and deformed by piezoelectric driving. These piezoelectric cantilevers 31A, 32A, 51A to 51D, 52A to 52D are bent and deformed as the piezoelectric bodies L2 are bent and deformed.

[0043] Note that the connecting portions of adjacent piezoelectric cantilevers of the pair of second piezoelectric cantilevers 51A to 51D, 52A to 52D that constitute the second piezoelectric actuators 51, 52 are portions where the respective supports B of the adjacent piezoelectric cantilevers are integrally connected, and the layers of the piezoelectric body L2 and the upper electrode L3 are not provided at the connecting portions.

[0044] On the first support portion 4, a first detection portion 71y, 72y and a second detection portion 71x, 72x are provided. The first detection portions 71y, 72y are arranged at the central portions of the sides parallel to the second axis X of the first support portion 4 (sides orthogonal to the longitudinal sides of the respective piezoelectric cantilevers of the second piezoelectric cantilevers 51A to 51D, 52A to 52D) along the sides on the first support portion 4.

[0045] The second detection portions 71x, 72x are arranged at the central portions of the sides parallel to the first axis Y of the first support portion 4 along the sides on the first support portion 4. The first detection portions 71y, 72y and the second detection portions 71x, 72x are provided separately from each other in a planar manner.

[0046] The first detection units 71y and 72y are provided as sensors for detecting the first vibration transmitted to the first support unit 4 when the mirror unit 2 is swung around the first axis Y by the piezoelectric driving of the first piezoelectric actuators 31 and 32. The second detection units 71x and 72x are provided as sensors for detecting the second vibration transmitted to the first support unit 4 when the first support unit 4 is swung around the second axis X with respect to the second support unit 6 by the piezoelectric driving of the second piezoelectric actuators 51 and 52.

[0047] Similar to the first piezoelectric cantilevers 31A and 32A and the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the first detection units 71y and 72y and the second detection units 71x and 72x have a structure in which a lower electrode L1, a piezoelectric body L2, and an upper electrode L3 are laminated on the layer of the support B constituting the first support unit 4. Also, in the first detection units 71y and 72y and the second detection units 71x and 72x, an interlayer insulating film M1, an upper electrode wiring W, and a passivation film M2 are provided, similar to the piezoelectric cantilevers 31A, 32A, 51A to 51D, and 52A to 52D.

[0048] When the first vibration or the second vibration is transmitted to the first support unit 4 and the first support unit 4 is bent and deformed, the piezoelectric bodies L2 of the first detection units 71y and 72y and the second detection units 71x and 72x output a voltage corresponding to the amount of deformation of this bending deformation. The optical deflector 1 can detect the vibration transmitted to the first support unit 4 based on the voltage value at this time.

[0049] It has been found by a previously conducted experiment that in the first support unit 4 of the optical deflector 1 of the present embodiment, when the mirror unit 2 is swinging around the first axis Y, the central portions of the two sides parallel to the second axis X are likely to be bent and deformed. For this reason, the first detection units 71y and 72y are arranged at the central portions of the two sides. Also, it has been found by a previously conducted experiment that when the first support unit 4 is swinging around the second axis X, the central portions of the two sides parallel to the first axis Y are likely to be bent and deformed. For this reason, the second detection units 71x and 72x are arranged at the central portions of the two sides.

[0050] The optical deflector 1 includes, on the second support portion 6, lower electrode pads 61a and 62a, first upper electrode pads 61b and 62b, second upper electrode pads 61c and 62c for odd numbers, second upper electrode pads 61d and 62d for even numbers, a first detection electrode pad 61e, and a second detection electrode pad 62e.

[0051] One of the lower electrode pads 61a and 62a, i.e., the lower electrode pad 61a, is electrically connected to the lower electrode L1 of one first piezoelectric cantilever 31A, the lower electrodes L1 of one second piezoelectric cantilevers 51A to 51D, and the lower electrodes L1 of the first detection portions 71y and 72y. The other lower electrode pad 62a of the lower electrode pads 61a and 62a is electrically connected to the lower electrode L1 of the other first piezoelectric cantilever 32A, the lower electrodes L1 of the other second piezoelectric cantilevers 52A to 52D, and the lower electrodes L1 of the second detection portions 71x and 72x.

[0052] Thus, the lower electrode pads 61a and 62a serve as common electrode pads for the first piezoelectric actuators 31 and 32, the second piezoelectric actuators 51 and 52, the first detection portions 71y and 72y, and the second detection portions 71x and 72x.

[0053] One of the first upper electrode pads 61b and 62b, i.e., the first upper electrode pad 61b, is electrically connected to the upper electrode L3 of one first piezoelectric cantilever 31A. The other first upper electrode pad 62b of the first upper electrode pads 61b and 62b is electrically connected to the upper electrode L3 of the other first piezoelectric cantilever 32A.

[0054] One of the second upper electrode pads 61c and 62c for odd numbers, i.e., the second upper electrode pad 61c for odd numbers, is electrically connected to the upper electrodes L3 of one odd-numbered second piezoelectric cantilevers 51A and 51C. The other second upper electrode pad 62c for odd numbers of the second upper electrode pads 61c and 62c for odd numbers is electrically connected to the upper electrodes L3 of the other odd-numbered second piezoelectric cantilevers 52A and 52C.

[0055] Of the second upper electrode pads 61d and 62d for even numbers, one second upper electrode pad 61d for even numbers is electrically connected to the upper electrode L3 of one of the second piezoelectric cantilevers 51B and 51D with even numbers. The other second upper electrode pad 62d for even numbers is electrically connected to the upper electrode L3 of the other second piezoelectric cantilevers 52B and 52D with even numbers.

[0056] The first detection electrode pad 61e is electrically connected to the upper electrode L3 of the first detection units 71y and 72y. The second detection electrode pad 62e is electrically connected to the upper electrode L3 of the second detection units 71x and 72x.

[0057] Due to the electrical connection as described above, when a driving voltage is applied between the upper electrode L3 and the lower electrode L1, the piezoelectric body L2 laminated between the applied upper electrode L3 and the lower electrode L1 bends and deforms by piezoelectric driving. As a result, the support B (piezoelectric cantilever) corresponding to the bent and deformed piezoelectric body L2 bends and deforms.

[0058] Also, as will be described later, due to the piezoelectric effect caused by the bending deformation due to the transmitted vibration, the voltage generated from the first detection units 71y and 72y is output as the potential difference between the first detection electrode pad 61e and one of the lower electrode pads 61a. Similarly, the voltage generated from the second detection units 71x and 72x due to the piezoelectric effect caused by the bending deformation of the first support portion 4 is output as the potential difference between the second detection electrode pad 62e and one of the lower electrode pads 61a.

[0059] A pair of lower electrode pads 61a and 62a, the lower electrodes L1 of the first piezoelectric cantilevers 31A and 32A, the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the first detection units 71y and 72y, and the second detection units 71x and 72x are formed by shaping a metal thin film (in this embodiment, a two-layer metal thin film, hereinafter also referred to as a lower electrode layer) on a silicon substrate (a silicon substrate with a thermal oxide film) using a semiconductor planar process. As the material of this metal thin film, for example, titanium (Ti), titanium dioxide (TiO2), or titanium oxide with an adjusted oxidation amount (TiOx) is used for the first layer (lower layer), Pt (the main electrode) is used for the second layer, and LaNiO3·SrRuO3 is used for the third layer.

[0060] In this case, the lower electrodes L1 of the first piezoelectric cantilevers 31A and 32A are formed on substantially the entire surface of the support B of the first piezoelectric cantilevers 31A and 32A. The lower electrodes L1 of the second piezoelectric cantilevers 51A to 51D and 52A to 52D are formed on substantially the entire surface of the support B of the second piezoelectric cantilevers 51A to 51D and 52A to 52D (the entire part including the straight part and the connecting part where each piezoelectric cantilever extends).

[0061] The lower electrodes L1 of the first detection units 71y and 72y are formed in the portions of the support B of the first support portion 4 where the first detection units 71y and 72y are disposed. The lower electrodes L1 of the second detection units 71x and 72x are formed in the portions of the support B of the first support portion 4 where the second detection units 71x and 72x are disposed. Similarly, on the second support portion 6, a lower electrode L1, an interlayer insulating film M1, an upper electrode wiring W, and a passivation film M2 are provided.

[0062] Then, the lower electrode pads 61a and 62a are electrically connected to the lower electrodes L1 of the first piezoelectric cantilevers 31A and 32A, the lower electrodes L1 of the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the lower electrodes L1 of the first detection units 71y and 72y, and the lower electrodes L1 of the second detection units 71x and 72x through the lower electrodes L1 formed on the second support portion 6 and the first support portion 4 as described above.

[0063] The piezoelectric bodies L2 of the first piezoelectric cantilevers 31A and 32A, the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the first detection units 71y and 72y, and the second detection units 71x and 72x are each formed separately on the lower electrodes L1 of the respective piezoelectric cantilevers by shaping a single layer of piezoelectric film (hereinafter also referred to as a piezoelectric body layer) on the lower electrode layer using a semiconductor planar process. As the material of this piezoelectric film, for example, lead zirconate titanate (PZT), which is a piezoelectric material, is used.

[0064] In this case, the piezoelectric bodies L2 of the first piezoelectric cantilevers 31A and 32A are formed substantially over the entire surface on the lower electrodes L1 for each of the first piezoelectric cantilevers 31A and 32A. The piezoelectric bodies L2 of the second piezoelectric cantilevers 51A to 51D and 52A to 52D are formed substantially over the entire surface on the lower electrodes L1 in the extending portions (linear portions) of the respective second piezoelectric cantilevers 51A to 51D and 52A to 52D. The piezoelectric bodies L2 of the first detection units 71y and 72y are formed substantially over the entire surface on the lower electrodes L1 for each of the first detection units 71y and 72y. The piezoelectric bodies L2 of the second detection units 71x and 72x are formed substantially over the entire surface on the lower electrodes L1 for each of the second detection units 71x and 72x.

[0065] The "first upper electrode pads 61b and 62b, odd-numbered second upper electrode pads 61c and 62c, even-numbered second upper electrode pads 61d and 62d, first detection electrode pads 61e, and second detection electrode pads 62e", the "upper electrodes L3 of the first piezoelectric cantilevers 31A and 32A, the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the first detection units 71y and 72y, and the second detection units 71x and 72x", and the upper electrode wirings W that conduct these are formed by shaping a metal thin film (a single layer of metal thin film in this embodiment; hereinafter also referred to as an upper electrode layer) on the piezoelectric body layer using a semiconductor planar process. As the material of this metal thin film, for example, platinum (Pt), gold (Au), aluminum (Al), or an aluminum alloy (Al alloy) is used.

[0066] In this case, the upper electrodes L3 of the first piezoelectric cantilevers 31A and 32A, the second piezoelectric cantilevers 51A to 51D and 52A to 52D, the first detection units 71y and 72y, and the second detection units 71x and 72x are formed substantially over the entire surface of the piezoelectric body L2 for each piezoelectric cantilever or each detection unit.

[0067] Then, the first upper electrode pads 61b and 62b are electrically connected to the upper electrodes L3 of the first piezoelectric cantilevers 31A and 32A via the first driving upper electrode wiring Wy as described above. Also, the second upper electrode pads 61c and 62c for odd numbers are electrically connected to the upper electrodes L3 of the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, and 52C via the second driving odd upper electrode wiring Wo as described above. Further, the second upper electrode pads 61d and 62d for even numbers are electrically connected to the upper electrodes L3 of the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, and 52D via the second driving even upper electrode wiring We as described above.

[0068] Also, the first detection electrode pad 61e is electrically connected to the upper electrodes L3 of the first detection units 71y and 72y via the first detection upper electrode wiring Wmy as described above. Further, the second detection electrode pad 62e is electrically connected to the upper electrodes L3 of the second detection units 71x and 72x via the second detection upper electrode wiring Wmx as described above.

[0069] As shown in FIG. 2, the first driving upper electrode wiring Wy, the second driving odd upper electrode wiring Wo, the second driving even upper electrode wiring We, the first detection upper electrode wiring Wmy, and the second detection upper electrode wiring Wmx are provided separately from each other in a plane. Also, the upper electrode wiring W is insulated by an interlayer insulating film M1 formed between the upper electrode wiring W and the upper electrode L3. When electrically connecting the upper electrode wiring W to the upper electrode L3, a conducting member (for example, an electrode via or the like) is formed in the interlayer insulating film M1 so that the upper electrode wiring W and the upper electrode L3 can be electrically connected.

[0070] Further, the passivation film M2 is formed on the upper electrode wiring W using a semiconductor planar process so as to surround the upper electrode wiring W.

[0071] Further, the reflection surface support 2b, the torsion bars 21 and 22, the support B, the first support portion 4, and the second support portion 6 are integrally formed by shaping a semiconductor substrate (silicon substrate) composed of a plurality of layers. As a method for shaping the semiconductor substrate, a semiconductor planar process and a MEMS process using photolithography technology, dry etching technology, or the like are used.

[0072] Next, the operation of the optical deflector 1 of the present embodiment will be described. First, the case where the mirror portion 2 is swung around the first axis Y with respect to the first support portion 4 by the first piezoelectric actuators 31 and 32 will be described.

[0073] In this case, a drive voltage is applied to the first piezoelectric actuators 31 and 32 of the optical deflector 1. Specifically, in one of the first piezoelectric actuators 31, a first drive voltage Vy1 is applied between one of the first upper electrode pads 61b and one of the lower electrode pads 61a to drive one of the first piezoelectric cantilevers 31A. In the other first piezoelectric actuator 32, a second drive voltage Vy2 is applied between the other first upper electrode pad 62b and the other lower electrode pad 62a to drive the other first piezoelectric cantilever 32A. Here, the first drive voltage Vy1 and the second drive voltage Vy2 are AC voltages (for example, sine waves, sawtooth waves, etc.) having opposite phases or a phase shift with respect to each other.

[0074] At this time, the voltage components for swinging of the first drive voltage Vy1 and the second drive voltage Vy2 are applied such that angular displacements of one of the first piezoelectric cantilevers 31A and the other first piezoelectric cantilever 32A occur in opposite directions with respect to the vertical direction (the upward direction U in FIG. 1 and the downward direction opposite thereto) of the first piezoelectric actuators 31 and 32.

[0075] For example, when swinging around the first axis Y, when displacing one of the first piezoelectric actuators 31 upward, one of the first piezoelectric cantilevers 31A is displaced upward. To displace one of the first piezoelectric actuators 31 downward, one of the first piezoelectric cantilevers 31A is displaced downward.

[0076] Also, regarding the other first piezoelectric actuator 32, similar to one of the first piezoelectric actuators 31, when displacing the other first piezoelectric actuator 32 upward, the other first piezoelectric cantilever 32A is displaced upward. To displace the other first piezoelectric actuator 32 downward, the other first piezoelectric cantilever 32A is displaced downward.

[0077] In the optical deflector 1 of the present embodiment, by "displacing one of the first piezoelectric actuators 31 upward and displacing the other first piezoelectric actuator 32 downward" or "displacing one of the first piezoelectric actuators 31 downward and displacing the other first piezoelectric actuator 32 upward", when swinging around the first axis Y, a large deflection angle is obtained. Here, the first drive voltage Vy1 and the second drive voltage Vy2 can be swung by resonance drive by having frequencies near the frequencies of higher-order modes of the second-order mode or higher. In this way, in the present embodiment, the mirror unit 2 can be swung around the first axis Y, and optical scanning with a predetermined first deflection angle at a predetermined first frequency Fy can be performed.

[0078] Next, the case of swinging the first support portion 4 around the second axis X with respect to the second support portion 6 by the second piezoelectric actuators 51 and 52 will be described.

[0079] In this case, the optical deflector 1 applies drive voltages to the second piezoelectric actuators 51 and 52. Specifically, in one of the second piezoelectric actuators 51, a third drive voltage Vx1 is applied between one of the second upper electrode pads 61c for odd numbers and one of the lower electrode pads 61a to drive one of the odd-numbered second piezoelectric cantilevers 51A and 51C. At the same time, in one of the second piezoelectric actuators 51, a fourth drive voltage Vx2 is applied between one of the second upper electrode pads 61d for even numbers and one of the lower electrode pads 61a to drive one of the even-numbered second piezoelectric cantilevers 51B and 51D.

[0080] Furthermore, in the other second piezoelectric actuator 52, a third drive voltage Vx1 is applied between the other second upper electrode pad 62c for odd numbers and the other lower electrode pad 62a to drive the other odd-numbered second piezoelectric cantilevers 52A and 52C. At the same time, in the other second piezoelectric actuator 52, a fourth drive voltage Vx2 is applied between the other second upper electrode pad 62d for even numbers and the other lower electrode pad 62a to drive the other even-numbered second piezoelectric cantilevers 52B and 52D.

[0081] Here, the third drive voltage Vx1 and the fourth drive voltage Vx2 are AC voltages (e.g., sine wave, sawtooth wave, etc.) with opposite phases. FIG. 3 shows an example of the third drive voltage Vx1 and the fourth drive voltage Vx2. In FIG. 3, the sawtooth wave depicted by the solid line is an example of the third drive voltage Vx1. Hereinafter, the third drive voltage Vx1 is also referred to as the first drive signal P. Also, in FIG. 3, the sawtooth wave depicted by the dashed-dotted line is an example of the fourth drive voltage Vx2. Hereinafter, the fourth drive voltage Vx2 is also referred to as the second drive signal N. Note that the third drive voltage Vx1 and the fourth drive voltage Vx2 may be AC voltages (e.g., sine wave, sawtooth wave, etc.) with a phase shift from each other. The picture angle and the deflection direction of the image projected by the optical deflector 1 can be made variable by changing at least one of the amplitudes and the offset amounts of the two drive signals (the first drive signal P and the second drive signal N). Thereby, the angle of swing and the offset angle can be controlled.

[0082] At this time, the voltage components for swinging the third drive voltage Vx1 and the fourth drive voltage Vx2 are set such that the angular displacements of the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D occur in opposite directions with respect to the vertical direction (the upward direction U in FIG. 1 and the downward direction opposite thereto) of the second piezoelectric actuators 51 and 52.

[0083] For example, when swinging around the second axis X, when the tip portions of the second piezoelectric actuators 51 and 52 are displaced upward (in the direction U shown in FIG. 1), the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C are displaced upward, and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D are displaced downward. To displace the tip portions of the second piezoelectric actuators 51 and 52 downward, the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C are displaced downward, and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D are displaced upward.

[0084] As a result, the odd-numbered second piezoelectric cantilevers 51A, 51C, 52A, 52C and the even-numbered second piezoelectric cantilevers 51B, 51D, 52B, 52D are bent and deformed in opposite directions to each other.

[0085] FIG. 4 is a diagram showing the operation of one of the second piezoelectric actuators 51 of the optical deflector 1. FIG. 4(a) shows a state in which one of the second piezoelectric actuators 51 is not operating, and FIG. 4(b) shows a state in which one of the second piezoelectric actuators 51 is operating.

[0086] As shown in FIG. 4(b), the fourth one of the second piezoelectric cantilevers 51D has a downward angular displacement at its tip with the base end connected to the second support portion 6 as a fulcrum. The third one of the second piezoelectric cantilevers 51C has an upward angular displacement at its tip with the base end connected to the tip of the fourth one of the second piezoelectric cantilevers 51D as a fulcrum.

[0087] The base end of the second one of the second piezoelectric cantilevers 51B, which is connected to the tip of the third one of the second piezoelectric cantilevers 51C, serves as a fulcrum, and a downward angular displacement is generated at its tip. The base end of the first one of the second piezoelectric cantilevers 51A, which is connected to the tip of the second one of the second piezoelectric cantilevers 51B, serves as a fulcrum, and an upward angular displacement is generated at its tip (which is connected to the first support portion 4). As a result, in one of the second piezoelectric actuators 51, an angular displacement of a magnitude obtained by adding up the magnitudes of the bending deformations of the respective second piezoelectric cantilevers 51A to 51D occurs.

[0088] Therefore, the first support portion 4 can swing around the second axis X, and light scanning with a predetermined second deflection angle can be performed at a predetermined second frequency Fx.

[0089] Also, when the first support portion 4 swings around the second axis X, as described above, it is not necessary to apply an alternating voltage, and a direct current voltage may be applied. In this case, the magnitudes of the bending deformations generated in the second piezoelectric cantilevers 51A to 51D and 52A to 52D change linearly according to the magnitude of the direct current voltage. Therefore, an arbitrary output can be obtained from the second piezoelectric actuators 51 and 52 by controlling the magnitude of the direct current voltage.

[0090] In this way, in the optical deflector 1, when swinging around the second axis X, the deflection angle can be linearly controlled according to the magnitude of the direct current voltage applied as the driving voltage, so that an arbitrary deflection angle can be obtained at an arbitrary speed.

[0091] Also, the second piezoelectric actuators 51 and 52 are each formed in a meander shape (or bellows shape). As a result, the bending deformations of the respective piezoelectric cantilevers are formed so as to be accumulated. For this reason, the second piezoelectric actuators 51 and 52 are more likely to obtain a larger deflection angle than the first piezoelectric actuators 31 and 32.

[0092] Therefore, in this embodiment, when swinging by the first piezoelectric actuators 31 and 32, in order to obtain a deflection angle as large as possible, the frequency for changing the upward or downward displacement of the first piezoelectric actuators 31 and 32, that is, the first frequency Fy, is set to be the resonance frequency determined by the structure, material, etc. of the optical deflector 1 (particularly, a piezoelectric cantilever or the like).

[0093] Further, the second piezoelectric actuators 51 and 52 are formed in a meander shape (or bellows shape) and are easier to swing than the first piezoelectric actuators 31 and 32. For this reason, the second frequency Fx is set to be sufficiently lower than the first frequency Fy. In this embodiment, for example, the first frequency Fy is set to 30 kHz and the second frequency Fx is set to 60 Hz. Note that the first frequency is not limited to 30 kHz, and the second frequency Fx is not limited to 60 Hz, but it is preferable that the first frequency Fy is 20 kHz to 40 kHz and the second frequency Fx is 120 Hz or less. <Optical deflector 10 of this embodiment> Next, the optical deflector 10 of this embodiment will be described.

[0094] FIG. 5 is an example of the optical deflector 10 of this embodiment.

[0095] As shown in FIG. 5, the optical deflector 10 of this embodiment is an optical deflector of a piezoelectric method (uniaxial non-resonance · uniaxial resonance type), similar to the optical deflector 1 (see FIG. 1). The size of the optical deflector 10 is, for example, a height H of 5 mm and a width W of 11 mm.

[0096] Hereinafter, the optical deflector 10 will be described centering on the differences while comparing with the optical deflector 1. Note that the same components as those of the optical deflector 1 are denoted by the same reference numerals, and the description will be omitted as appropriate.

[0097] As shown in FIG. 5, the optical deflector 10 of the present embodiment includes a mirror unit 2, a first support unit 4 that supports the mirror unit 2 so as to be swingable about a first axis Y, a second support unit 6 that supports the first support unit 4 so as to be swingable about a second axis X that intersects (for example, is orthogonal to) the first axis Y, two first piezoelectric actuators 31 and 32 that swing the mirror unit 2 about the first axis Y with respect to the first support unit 4, and two second piezoelectric actuators 53 and 54 that swing the first support unit 4 and the mirror unit 2 supported by the first support unit 4 about the second axis X with respect to the second support unit 6.

[0098] The second piezoelectric actuators 53 and 54 have the same configuration as the second piezoelectric actuators 51 and 52 (see FIG. 1), except that the number and length are different as described later.

[0099] The second piezoelectric actuator 53 includes a plurality of piezoelectric cantilevers 53A to 53G arranged in the direction of the second axis X. The piezoelectric cantilevers 53A to 53G are connected in a bellows shape so that each piezoelectric cantilever folds back with respect to an adjacent piezoelectric cantilever. The free end of the piezoelectric cantilever 53A closest to the mirror unit 2 among the piezoelectric cantilevers 53A to 53G is connected to the first support unit 4. The free end of the piezoelectric cantilever 53G farthest from the mirror unit 2 among the piezoelectric cantilevers 53A to 53G is connected to the second support unit 6.

[0100] Similarly, the second piezoelectric actuator 54 includes a plurality of piezoelectric cantilevers 54A to 54G arranged in the direction of the second axis X. The piezoelectric cantilevers 54A to 54G are connected in a bellows shape such that each piezoelectric cantilever folds back with respect to an adjacent piezoelectric cantilever. The free end of the piezoelectric cantilever 54A closest to the mirror unit 2 among the piezoelectric cantilevers 54A to 54G is connected to the first support portion 4. The free end of the piezoelectric cantilever 54G farthest from the mirror unit 2 among the piezoelectric cantilevers 54A to 54G is connected to the second support portion 6. Both the second piezoelectric actuators 53 and 54 are shaped such that the respective piezoelectric cantilevers 53A to 53G and 54A to 54G extend in the direction of the first axis Y. The connecting portions that connect adjacent piezoelectric cantilevers 53A to 53G and 54A to 54G to each other at the folding portions extend in the direction of the second axis X that is orthogonal thereto.

[0101] The optical deflector 10 of the present embodiment is mainly different from the optical deflector 1 (see FIG. 1) in the following points.

[0102] First, the number of the second piezoelectric cantilevers is different. Specifically, in the optical deflector 1 (see FIG. 1), one second piezoelectric cantilever 51A to 51D composed of four piezoelectric cantilevers and the other second piezoelectric cantilever 52A to 52D composed of four piezoelectric cantilevers are provided, whereas in the optical deflector 10 of the present embodiment, one second piezoelectric cantilever 53A to 53G composed of seven piezoelectric cantilevers and the other second piezoelectric cantilever 54A to 54G composed of seven piezoelectric cantilevers are provided.

[0103] Second, the lengths of the second piezoelectric cantilevers, that is, the distances between the folded ends of the second piezoelectric cantilevers and the second axis X are different. Specifically, in the optical deflector 1 (see FIG. 1), the distances between the folded ends of one set of second piezoelectric cantilevers 51A to 51D and the other set of second piezoelectric cantilevers 52A to 52D and the second axis X are all the same, which is D1. In contrast, as shown in FIG. 5, in the optical deflector 10 of the present embodiment, the closer the second piezoelectric cantilever is to the mirror unit 2, the shorter the distance between the folded end of the second piezoelectric cantilever and the second axis X. That is, the distance D2 between the folded ends of the piezoelectric cantilevers 53G and 54G, which are the farthest from the mirror unit 2, and the second axis X is the longest, and the distance D3 between the folded ends of the piezoelectric cantilevers 53A and 54A, which are the closest to the mirror unit 2, and the second axis X is the shortest. Among the second piezoelectric cantilevers, 53A and 54A are connected to the first support portion 4 on the second axis X, and 53G and 54G are connected to the second support portion 6 on the second axis X. Therefore, among the second piezoelectric cantilevers, 53A, 54A, 53G, and 54G extend only above or below the second axis X. The second piezoelectric cantilevers 53B to 53E and 54B to 54E extend above and below the second axis X, but their lengths from the second axis X are different, and they have an asymmetric shape. The second piezoelectric cantilevers 53F and 54F extend above and below the second axis X, and their lengths from the second axis X are the same. The total lengths of the second piezoelectric cantilevers 53A to 53G and 54A to 54G are made the same by adding the lengths of the odd-numbered second piezoelectric cantilevers from the mirror unit 2 side and adding the lengths of the even-numbered second piezoelectric cantilevers from the mirror unit 2 side. Each of one set of second piezoelectric cantilevers 53A to 53G and the other set of second piezoelectric cantilevers 54A to 54G consists of seven, an odd number of cantilevers. The second piezoelectric cantilevers are shorter the closer they are to the mirror unit 2. Since there are an odd number of cantilevers, there are more odd-numbered second piezoelectric cantilevers than even-numbered second piezoelectric cantilevers from the mirror unit 2 side, and adjustments are made to make the lengths the same.

[0104] In other words, as shown in FIG. 5, in the optical deflector 10 of the present embodiment, the folded ends of one of the second piezoelectric cantilevers 53A to 53G are arranged along straight lines L1 and L2 inclined toward the mirror unit 2. Similarly, the folded ends of the other second piezoelectric cantilevers 54A to 54G are arranged along straight lines L3 and L4 inclined toward the mirror unit 2.

[0105] Next, the effect of shortening the distance between the folded end of the second piezoelectric cantilever and the second axis X as the second piezoelectric cantilever is closer to the mirror unit 2 as described above will be described while comparing with a comparative example.

[0106] FIG. 6(a) shows an optical deflector 10A of a first comparative example.

[0107] As shown in FIG. 6(a), in the optical deflector 10A of the first comparative example, the lengths of the second piezoelectric cantilevers 53A to 53G and 54A to 54G are all D2, that is, the distances between the folded ends of the second piezoelectric cantilevers 53A to 53G and 54A to 54G and the second axis X are all the same at D2. Otherwise, the configuration is the same as that of the optical deflector 10.

[0108] FIG. 6(b) shows an optical deflector 10B of a second comparative example.

[0109] As shown in FIG. 6(b), in the optical deflector 10B of the second comparative example, the lengths of the second piezoelectric cantilevers 53A to 53G and 54A to 54G are shorter than those of the optical deflector 10A of the first comparative example. Specifically, in the optical deflector 10B of the second comparative example, the lengths of the second piezoelectric cantilevers 53A to 53G and 54A to 54G are all D4 (D4 < D2), that is, the distances between the folded ends of the second piezoelectric cantilevers 53A to 53G and 54A to 54G and the second axis X are all the same at D4 (D4 < D2). Otherwise, the configuration is the same as that of the optical deflector 10 and the optical deflector 10A of the first comparative example.

[0110] The inventors confirmed the frequency of the first mode (first resonance frequency) of the optical deflector 10A of the first comparative example, the optical deflector 10B of the second comparative example, and the optical deflector 10 of the present embodiment by simulation using predetermined software.

[0111] FIG. 7 is a table summarizing the simulation results.

[0112] In FIG. 7, “bellows length” represents the ratio of the total length of the second piezoelectric actuators 53 and 54 of each of the optical deflectors 10, 10A, and 10B to the total length of the second piezoelectric actuators 53 and 54 of the first comparative example. “First mode (Hz)” represents the frequency of the first mode (first resonance frequency) of each of the optical deflectors 10, 10A, and 10B. Note that the actual frequency of the first mode (first resonance frequency) can be measured, for example, using a laser Doppler vibrometer (manufactured by Polytec). “Oscillation angle efficiency (deg / V)” represents the oscillation angle of the mirror unit 2 when a unit voltage is applied to the second piezoelectric actuators 53 and 54 of each of the optical deflectors 10, 10A, and 10B.

[0113] Referring to “Second Comparative Example” in FIG. 7, it can be seen that the optical deflector 10B of the second comparative example has a higher frequency of the first mode (first resonance frequency) and a lower oscillation angle efficiency than the optical deflector 10A of the first comparative example.

[0114] In the optical deflector 10B of the second comparative example, by further shortening the lengths D4 of the second piezoelectric cantilevers 53A to 53G and 54A to 54G, the frequency of the first mode (first resonance frequency) can be further increased, but the oscillation angle efficiency also further decreases.

[0115] On the other hand, referring to “Embodiment” in FIG. 7, it can be seen that in the optical deflector 10 of the present embodiment, the frequency of the first mode (first resonance frequency) is higher without a decrease in the oscillation angle efficiency compared to the optical deflector 10B of the second comparative example.

[0116] In the optical deflector 10 of the present embodiment, compared with the optical deflector 10B of the second comparative example, the frequency of the first mode (first resonance frequency) is higher because the optical deflector 10 of the present embodiment has a second piezoelectric cantilever (for example, the second piezoelectric cantilevers 53A and 54A closest to the mirror unit 2) that is shorter (relatively higher in rigidity) than the second piezoelectric cantilevers 53A to 53G and 54A to 54G of the optical deflector 10B of the second comparative example.

[0117] On the other hand, in the optical deflector 10 of the present embodiment, compared with the optical deflector 10B of the second comparative example, the swing angle efficiency does not decrease because the optical deflector 10 of the present embodiment has a second piezoelectric cantilever (for example, the second piezoelectric cantilevers 53G and 54G farthest from the mirror unit 2) that is longer (relatively lower in rigidity. That is, relatively easier to bend and deform) than the second piezoelectric cantilevers 53A to 53G and 54A to 54G of the optical deflector 10B of the second comparative example.

[0118] Note that when the optical deflector 10 of the present embodiment is designed to have the same frequency of the first mode as in Comparative Example 2, the swing angle efficiency of the optical deflector 10 can be made larger than that of Comparative Example 2.

[0119] The optical deflector 10 of the present embodiment can be applied to all applications of laser scan type mirror devices. For example, it can be applied to smart glasses, ultra-small projectors, and interactive projectors.

[0120] As described above, according to the present embodiment, it is possible to increase the frequency of the first mode (first resonance frequency) (shift it to the high frequency side) while suppressing the decrease in the swing angle efficiency of the mirror unit 2.

[0121] The reason why the frequency of the first mode (the first resonance frequency) can be increased (shifted to the high-frequency side) is that the distance between the folded end of at least one of the piezoelectric cantilevers 53A to 53F and 54A to 54F other than the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2 and the second axis X (for example, refer to the distance indicated by reference symbol D3 in FIG. 5) is made shorter than the distance D2 between the folded end of the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2 and the second axis X. That is, this is because the rigidity of at least one of the piezoelectric cantilevers 53A to 53F and 54A to 54F other than the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2 becomes relatively higher than the rigidity of the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2.

[0122] The reason why it is possible to suppress the decrease in the swing angle efficiency of the mirror unit 2 is that the farther the piezoelectric cantilever is from the mirror unit 2, the relatively lower its rigidity becomes (the easier it is to bend and deform). Further, according to the present embodiment, since the frequency of the first mode (the first resonance frequency) can be increased (shifted to the high-frequency side), an optical deflector that is resistant to external vibration can be realized. External vibration is, for example, vibration caused by a person wearing the optical deflector walking or vibration caused by a vehicle on which the optical deflector is mounted traveling.

[0123] Next, a modified example will be described.

[0124] FIG. 8 is a diagram for explaining a modified example of the optical deflector 10.

[0125] In the above embodiment, in the optical deflector 10 of the present embodiment, an example in which the closer the second piezoelectric cantilever is to the mirror unit 2, the shorter the distance between the folded end of the second piezoelectric cantilever and the second axis X has been described (see FIG. 5), but the present invention is not limited to this.

[0126] Basically, the distance between the folding end of at least one of the piezoelectric cantilevers 53A to 53F and 54A to 54F other than the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2 and the second axis X (for example, the distance D5 between the folding ends of the piezoelectric cantilevers 53C, 53D, 54C, and 54D and the second axis X) may be shorter than the distance D2 between the folding ends of the piezoelectric cantilevers 53G and 54G that are farthest from the mirror unit 2 and the second axis X.

[0127] Also according to this modification, the same effects as those of the above-described embodiment can be achieved.

[0128] Note that the number of the second piezoelectric cantilevers may be a plurality, and is not limited to four (see FIG. 1) or seven (see FIG. 5).

[0129] FIG. 9 is a diagram for explaining another modification of the optical deflector 10.

[0130] As shown in FIG. 9, the second support portion 6 is provided so as to surround the first support portion 4, the first piezoelectric actuators 31 and 32, and the second piezoelectric actuators 53 and 54, and includes a plurality of portions facing the folding ends of the plurality of piezoelectric cantilevers 53A to 53F and 54A to 54F. Each of these plurality of portions may extend to the vicinity of the folding end of the piezoelectric cantilever facing the portion.

[0131] In this way, compared with the case where the plurality of portions are not provided (see FIG. 5, for example), the strength of the optical deflector 10 can be increased, so that the optical deflector 10 is less likely to be damaged.

[0132] All the numerical values shown in the above embodiments are merely examples, and it goes without saying that appropriate different numerical values can be used.

[0133] The above-described embodiments are merely illustrative in every respect. The present invention is not to be construed as being limited by the description of the above embodiments. The present invention can be implemented in various other forms without departing from its spirit or main features.

Description of Reference Numerals

[0134] 1… Light deflector, 2… Mirror section, 2a… Reflective surface, 2b… Reflective surface support, 4… First support section, 6… Second support section, 10… Light deflector, 10A… Light deflector, 10B… Light deflector, 21… Torsion bar, 22… Torsion bar, 31… First piezoelectric actuator, 31A… First piezoelectric cantilever, 32… First piezoelectric actuator, 32A… First piezoelectric cantilever, 51… Second piezoelectric actuator, 51A to 51D… Second piezoelectric cantilevers, 52… Second piezoelectric actuator, 52A to 52D… Second piezoelectric cantilevers, 53… Second piezoelectric actuator, 53A to 53G, 54A to 54G… Second piezoelectric cantilevers, 54… Second piezoelectric actuator, 61a… Lower electrode pad, 61b… First upper electrode pad, 61c… Second upper electrode pad for odd numbers, 61d… Second upper electrode pad for even numbers, 61e… First detection electrode pad, 62a… Lower electrode pad, 62b… First upper electrode pad, 62c… Second upper electrode pad for odd numbers, 62d… Second upper electrode pad for even numbers, 62e… Second detection electrode pad, 71x… Second detection section, 71y… First detection section, 72x… Second detection section, 72y… First detection section, L1… Lower electrode, L2… Piezoelectric body, L3… Upper electrode, M1… Interlayer insulating film, M2… Passivation film, W… Upper electrode wiring, We… Second driving even upper electrode wiring, Wmx… Second detection upper electrode wiring, Wmy… First detection upper electrode wiring, Wo… Second driving odd upper electrode wiring, Wy… First driving upper electrode wiring

Claims

1. a mirror section; a first support section that supports the mirror section so as to be swingable about a first axis; a second support section that supports the first support section so as to be swingable about a second axis intersecting the first axis; at least one first actuator that swings the mirror section about the first axis with respect to the first support section; at least one second actuator that swings the first support section and the mirror section supported by the first support section about the second axis with respect to the second support section, and the second actuator includes a plurality of piezoelectric cantilevers arranged in the direction of the second axis, the plurality of piezoelectric cantilevers are connected in a bellows shape such that each piezoelectric cantilever folds back with respect to an adjacent piezoelectric cantilever, a free end of the piezoelectric cantilever closest to the mirror section among the piezoelectric cantilevers is connected to the first support section, a free end of the piezoelectric cantilever farthest from the mirror section among the piezoelectric cantilevers is connected to the second support section, a distance between a folded end of at least one piezoelectric cantilever among the piezoelectric cantilevers other than the piezoelectric cantilever farthest from the mirror section and the second axis is shorter than a distance between a folded end of the piezoelectric cantilever farthest from the mirror section and the second axis, the piezoelectric cantilever closest to the mirror section, the piezoelectric cantilever farthest from the mirror section, and all the piezoelectric cantilevers between the piezoelectric cantilever closest to the mirror section and the piezoelectric cantilever farthest from the mirror section each extend in a shape parallel to the first axis, a connecting section that connects the piezoelectric cantilevers in the bellows shape so as to fold back extends in a shape parallel to the second axis, further comprising a torsion bar that connects the mirror section and the first actuator, the free end of the piezoelectric cantilever closest to the mirror section is connected to the first support section at a connecting section extending on the second axis, and the first support section is connected to the second support section only via the second actuator. A light deflector

2. The light deflector according to claim 1, wherein, among the plurality of piezoelectric cantilevers, the closer the piezoelectric cantilever is to the mirror section, the shorter the distance between the folded end of the piezoelectric cantilever and the second axis.

3. The second support portion is provided so as to surround the first support portion, the first actuator, and the second actuator, and includes a plurality of portions facing the folded ends of the plurality of piezoelectric cantilevers. The optical deflector according to claim 1, wherein the plurality of portions each extend to the vicinity of the folded end of the piezoelectric cantilever facing the portion.

4. The optical deflector according to claim 1, wherein the sum of the lengths of the odd-numbered piezoelectric cantilevers from the mirror portion is equal to the sum of the lengths of the even-numbered piezoelectric cantilevers from the mirror portion.

5. The optical deflector according to claim 1, wherein the second support portion has a rectangular frame-shaped portion and a protruding portion that extends from a connection portion with the piezoelectric cantilever farthest from the mirror portion inside the frame-shaped portion and is connected to two sides perpendicular to the frame-shaped portion.

6. The optical deflector according to claim 1, wherein the piezoelectric cantilever farthest from the mirror portion is wider in the direction of the second axis than the piezoelectric cantilever closest to the mirror portion.

7. The optical deflector according to claim 1, wherein the plurality of piezoelectric cantilevers become narrower in the direction of the second axis from the piezoelectric cantilever farthest from the mirror portion toward the piezoelectric cantilever closest to the mirror portion.

8. The optical deflector according to claim 1, wherein the folded ends of the plurality of piezoelectric cantilevers are arranged along a straight line inclined toward the mirror portion.

9. The optical deflector according to claim 1, wherein the width of all the connecting portions that connect the piezoelectric cantilevers to fold back in the direction of the first axis is narrower than the width of all the plurality of piezoelectric cantilevers in the direction of the second axis.

10. The optical deflector according to claim 7, wherein the width of all the connecting portions that connect the piezoelectric cantilevers to fold back in the direction of the first axis is narrower than the width of the piezoelectric cantilever closest to the mirror portion in the direction of the second axis.

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