Optical reflection element and optical reflection device

Abstract

An optical reflection element (1) according to the present invention is characterized by comprising: a movable part (10) provided with a reflection surface (11); drive parts (20, 30) that rotate the movable part (10) about a rotation axis (R10); piezoelectric bodies (22, 24, 31, 33) that generate electric power corresponding to distortion caused by the rotation of the movable part (10); and resistors (65, 75) that are connected to the piezoelectric bodies (22, 24, 31, 33) and consume the electric power generated by the piezoelectric bodies (22, 24, 31, 33), the resistors (65, 75) each having a resistance value corresponding to a frequency to be suppressed.

Description

Optical reflection element and optical reflection device

[0001] The present invention relates to an optical reflection element including a movable part having a reflection surface, and an optical reflection device including the optical reflection element.

[0002] An optical reflection element including a movable part having a reflection surface is known. In this type of optical reflection element, for example, a reflection surface is disposed on a movable part that rotates about a rotation axis, and a beam incident on the reflection surface is scanned as the movable part rotates. Patent Document 1 below describes a mirror drive mechanism including a movable part having a reflection surface, a drive part that supports the movable part so as to be swingable, and a resistor connected to the outer edge of the movable part. The resistor connected to the movable part functions as an air damper by increasing the air resistance during the swinging of the movable part. Thereby, attenuation of unnecessary vibrations generated by the drive part is promoted.

[0003] Japanese Patent Application Laid-Open No. 2021-107877

[0004] In the optical reflection element as described above, in order to cause air resistance in the air damper, it is necessary to dispose the air damper at a limited position with respect to the rotation axis. Therefore, the degree of freedom in the design of the optical reflection element is reduced.

[0005] In view of such problems, an object of the present invention is to provide an optical reflection element and an optical reflection device capable of effectively suppressing unnecessary vibrations while increasing the degree of freedom in design.

[0006] A first aspect of the present invention relates to an optical reflection element. The optical reflection element according to this aspect includes a movable part provided with a reflection surface, a drive part that rotates the movable part about a rotation axis, a piezoelectric body that generates electric power according to distortion generated by the rotation of the movable part, and a resistor connected to the piezoelectric body that consumes the electric power generated by the piezoelectric body, and the resistor has a resistance value corresponding to a frequency to be suppressed.

[0007] Generally, the Q-factor decreases when energy generated by rotational motion is consumed. In contrast, according to the optical reflective element of this embodiment, the energy generated by rotational motion is consumed by a resistor having a resistance value corresponding to the frequency to be suppressed. That is, electricity is generated from the piezoelectric element in response to the rotation of the movable part, and the electricity generated from the piezoelectric element is consumed as heat by the resistor. This suppresses unwanted vibrations based on the frequency to be suppressed. Furthermore, according to the optical reflective element of this embodiment, the piezoelectric element and the resistor only need to be set and arranged so that electricity is consumed in response to the rotation of the movable part. Therefore, unwanted vibrations can be effectively suppressed while increasing the degree of design freedom.

[0008] A second aspect of the present invention relates to an optical reflective element. The optical reflective element according to this aspect comprises a movable part provided with a reflective surface, a drive unit that rotates the movable part about a pivot axis, a piezoelectric element disposed in the drive unit and serving as a drive source for the drive unit, and a resistor that consumes power generated by the distortion of the piezoelectric element due to the drive of the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0009] In the optical reflective element according to this embodiment, the energy generated by the rotational movement is consumed by a resistor having a resistance value corresponding to the frequency to be suppressed. This suppresses unwanted vibrations based on the frequency to be suppressed. Furthermore, in the optical reflective element according to this embodiment, the piezoelectric element is used not only as a driving piezoelectric element (driving source for the driving unit) but also as a damping piezoelectric element. Therefore, by arranging the piezoelectric element as a driving source, it becomes unnecessary to arrange a separate piezoelectric damper. Thus, unwanted vibrations can be effectively suppressed while increasing the degree of design flexibility.

[0010] A third aspect of the present invention relates to an optical reflective device. The optical reflective device according to this aspect comprises an optical reflective element having a movable part provided with a reflective surface, a drive unit that rotates the movable part about a pivot axis, and a piezoelectric body disposed in the drive unit and serving as a drive source for the drive unit, and a resistor disposed outside the optical reflective element and consuming power generated by the distortion of the piezoelectric body due to the drive of the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0011] The optical reflective device according to this embodiment provides the same effects as the second embodiment. Furthermore, since the resistor is not provided on the optical reflective element, the manufacturing process of the optical reflective element becomes simpler compared to the case where the resistor is provided on the optical reflective element.

[0012] As described above, the present invention provides an optical reflective element and an optical reflective device that can effectively suppress unwanted vibrations while increasing the degree of design freedom.

[0013] The effects and significance of the present invention will become even clearer from the description of the embodiments shown below. However, the embodiments shown below are merely examples of how to implement the present invention, and the present invention is not limited in any way to those described in the embodiments below.

[0014] Figure 1 is a schematic plan view showing the configuration of an optical reflective element according to Embodiment 1. Figure 2 is a schematic diagram showing the end face when the optical reflective element is cut by a plane passing through the pivot axis and parallel to the X-Z plane, according to Embodiment 1. Figure 3 is a schematic plan view showing the configuration of the drive unit, wiring unit, and electrode unit according to Embodiment 1. Figure 4 is a schematic diagram showing the end face near the electrode unit when the optical reflective element is cut by a plane parallel to the Y-Z plane at the position C1-C2 in Figure 3, according to Embodiment 1. Figure 5 is a circuit diagram composed of the optical reflective element according to Embodiment 1. Figure 6(a) is a graph to explain the shape of the sawtooth wave of the oscillation angle. Figure 6(b) is a graph to explain that the amount of vibration becomes excessively large in accordance with the resonance of a predetermined frequency. Figures 7(a) to 7(c) are schematic cross-sectional views showing a piezoelectric body according to a comparative example. Figures 8(a) to 8(c) are schematic cross-sectional views showing a piezoelectric body according to Embodiment 1. Figure 9 is a diagram showing the configuration of a circuit model consisting of a piezoelectric element and a resistor according to Embodiment 1. Figure 10(a) is an experimental result showing the Q value corresponding to each resistance value in an experiment of the circuit model of Figure 9 according to Embodiment 1. Figure 10(b) is a simulation result showing the power consumption corresponding to each resistance value in the circuit model of Figure 9 according to Embodiment 1. Figure 11 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 1. Figure 12 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 1. Figure 13 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 2. Figure 14 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 2. Figure 15 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 3. Figure 16 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 4. Figure 17 is a schematic plan view showing the configuration of an optical reflective element according to Modified Example 4. Figure 18 is a schematic plan view showing the configuration of the optical reflective element according to Modification Example 4. Figure 19 is a schematic plan view showing the configuration of the optical reflective element according to Modification Example 5. Figure 20 is a schematic plan view showing the phase of the piezoelectric cantilever when the movable part rotates about the pivot axis according to Modification Example 5. Figure 21 is a schematic plan view showing the phase of the piezoelectric cantilever when the movable part resonates in a direction perpendicular to the reflective surface according to Modification Example 5.Figures 22(a) to (c) are schematic diagrams illustrating how electric charge is generated in the piezoelectric element for the damper according to Modification Example 5. Figure 23 is a schematic plan view showing the configuration of the optical reflective element according to Modification Example 5. Figure 24(a) is a schematic diagram showing the end face when the piezoelectric cantilever is cut in a plane parallel to the Y-Z plane according to Modification Example 6. Figure 24(a) is a schematic diagram showing the end face when the piezoelectric cantilever is cut in a plane parallel to the X-Z plane according to Modification Example 6. Figure 25 is a schematic diagram showing the configuration of the optical reflective device according to Embodiment 2. Figure 26 is a circuit diagram composed of the optical reflective device according to Embodiment 2. Figure 27 is a circuit diagram composed of the optical reflective device according to Modification Example 7. Figures 28(a) and (b) are diagrams showing the driving voltages applied to the first group and the second group, respectively, according to Modification Example 7. Figure 29 is a schematic plan view showing the configuration of the optical reflective element according to Embodiment 3. Figure 30 is a circuit diagram comprising optical reflective elements according to Embodiment 3. Figure 31 is a diagram showing the configuration of a circuit model comprising a piezoelectric element and a resistor according to Embodiment 3. Figure 32 is an experimental result showing the Q value corresponding to each resistance value in an experiment of the circuit model of Figure 31 according to Embodiment 3. Figure 33 is a circuit diagram comprising optical reflective elements according to Modified Example 8. Figure 34 is a circuit diagram comprising an optical reflective device according to Embodiment 4.

[0015] However, the drawings are for illustrative purposes only and do not limit the scope of this invention.

[0016] Embodiments of the present invention will be described below with reference to the figures. For convenience, mutually orthogonal X, Y, and Z axes are indicated in each figure. The positive Z-axis direction is the vertically upward direction and is the thickness direction (height direction) of the optical reflective element 1. The X-axis is parallel to the rotation axis R10 of the optical reflective element 1.

[0017] The following embodiments describe an optical reflective element that scans a beam incident on a reflective surface by rotating the reflective surface. This optical reflective element is mounted, for example, in an optical reflective device that displays a predetermined image by scanning a beam. However, the optical reflective device on which the optical reflective element is mounted is not limited to this. For example, an optical reflective element with the following configuration may be mounted in an object detection device that detects the presence or absence of an object in the direction of beam projection and the distance to the object.

[0018] <Embodiment 1> Figure 1 is a schematic plan view showing the configuration of the optical reflective element 1.

[0019] The optical reflective element 1 comprises a movable part 10, drive parts 20 and 30, a plurality of wiring parts 40, a fixed part 50, and electrode parts 60 and 70. In a plan view, the optical reflective element 1 has a shape that is point-symmetric with respect to the center C10, except for the electrode parts 60 and 70.

[0020] The movable part 10 is circular in plan view. A reflective surface 11 is formed on the upper surface of the movable part 10. The reflective surface 11 may be formed by mirror-finishing the upper surface of the movable part 10, or by forming a reflective film on the upper surface of the movable part 10.

[0021] The drive unit 20 is positioned on the negative X-axis side of the movable part 10 and supports the movable part 10 from the negative X-axis side. The drive unit 30 is positioned on the positive X-axis side of the movable part 10 and supports the movable part 10 from the positive X-axis side. In a plan view, the drive units 20 and 30 have a meander shape that serpentine in the Y-axis direction.

[0022] The drive unit 20 has four piezoelectric cantilevers 20a, which are rectangles with their longer sides parallel to the Y-axis in a plan view, and a connecting part 20b arranged in the X-axis direction. Two adjacent piezoelectric cantilevers 20a are connected at either the positive or negative Y-axis end so that the drive unit 20 has a meander shape in a plan view. Similarly, the drive unit 30 has four piezoelectric cantilevers 30a, which are rectangles with their longer sides parallel to the Y-axis in a plan view, and a connecting part 30b arranged in the X-axis direction. Two adjacent piezoelectric cantilevers 30a are connected at either the positive or negative Y-axis end so that the drive unit 30 has a meander shape in a plan view.

[0023] In the drive unit 20, the four piezoelectric cantilevers 20a have rectangular piezoelectric elements 21 to 24 arranged sequentially in the negative X-axis direction, with their longer sides parallel to the Y-axis direction in a plan view. In the drive unit 30, the four piezoelectric cantilevers 30a have rectangular piezoelectric elements 31 to 34 arranged sequentially in the positive X-axis direction, with their longer sides parallel to the Y-axis direction in a plan view.

[0024] As shown in Figure 2, piezoelectric elements 21-24 and 31-34 all have a configuration in which a piezoelectric layer 112 is sandwiched between a lower electrode layer 111 and an upper electrode layer 113. Piezoelectric elements 21-24 are connected to the corresponding electrode pads of the electrode section 60 by a plurality of wiring sections 40, and piezoelectric elements 31-34 are connected to the corresponding electrode pads of the electrode section 70 by a plurality of wiring sections 40. In this embodiment, piezoelectric elements 21, 23, 32, and 34 are used as driving piezoelectric elements to rotate the movable section 10, and piezoelectric elements 22, 24, 31, and 33 are used as damper piezoelectric elements to suppress unwanted vibrations generated in the movable section 10.

[0025] Piezoelectric elements 21 and 23 are driving piezoelectric elements to which a driving voltage of the same phase is applied, and are connected to the electrode section 60. Piezoelectric elements 22 and 24 are damper piezoelectric elements installed on the piezoelectric cantilever 20a that vibrates in the same phase, and are connected to the electrode section 60. Piezoelectric elements 31 and 33 are driving piezoelectric elements to which a driving voltage of the same phase is applied, and are connected to the electrode section 70. Piezoelectric elements 32 and 34 are damper piezoelectric elements installed on the piezoelectric cantilever 20a that vibrates in the same phase, and are connected to the electrode section 70.

[0026] In Figure 1, for convenience, piezoelectric elements connected to each other by the wiring section 40 are shown with the same diagonal pattern, while the driving piezoelectric element and the damping piezoelectric element are shown with different diagonal patterns. Also, for convenience, in Figure 1, only the wiring 41, which will be described later, is shown from the wiring section 40.

[0027] The fixed part 50 has a rectangular frame shape with an opening 51 in a plan view. Drive units 20 and 30 are connected to the negative X-axis end and the positive X-axis end of the opening 51, respectively. In other words, the fixed part 50 supports the movable part 10 via the drive units 20 and 30.

[0028] The electrode sections 60 and 70 are installed on the upper surfaces of the negative and positive ends of the fixed section 50, respectively. The electrode section 60 includes electrode pads 61 and 62 connected to the driving piezoelectric elements (piezoelectric elements 21 and 23), and electrode pads 63 and 64 and a resistor 65 connected to the damper piezoelectric elements (piezoelectric elements 22 and 24). Similarly, the electrode section 70 includes electrode pads 71 ​​and 72 connected to the driving piezoelectric elements (piezoelectric elements 32 and 34), and electrode pads 73 and 74 and a resistor 75 connected to the damper piezoelectric elements (piezoelectric elements 31 and 33).

[0029] Figure 2 schematically shows the end face when the optical reflective element 1 is cut by a plane passing through the pivot axis R10 and parallel to the X-Z plane. For convenience, Figure 2 shows the piezoelectric elements 21 and 31, the piezoelectric cantilevers 20a and 30a on which the piezoelectric elements 21 and 31 are respectively arranged, and the connecting parts 20b and 30b of the drive units 20 and 30.

[0030] The movable part 10, the drive parts 20 and 30, and the fixed part 50 are connected by a common active layer 101. The outline of the optical reflective element 1 in plan view is made up of an active layer 101 made of silicon (Si) and silicon dioxide (SiO ２ An SOI wafer is formed by etching an intermediate oxide film 102 made of ) and a base layer 103 made of silicon (Si) which are stacked in order from top to bottom.

[0031] Furthermore, the base layer 103 and the intermediate oxide film 102 are removed from the SOI wafer by etching. At this time, the base layer 103 and the intermediate oxide film 102 remain on the fixed portion 50 to ensure thickness. The base layer 103 and the intermediate oxide film 102 remain on the drive portions 20 and 30 so that ribs are formed at the positive and negative ends of the Y axis. The base layer 103 and the intermediate oxide film 102 also remain on the connecting portions 20b and 30b. The base layer 103 and the intermediate oxide film 102 remain on the outer circumference of the movable portion 10 so that ribs are formed.

[0032] Piezoelectric elements 21-24 are formed on a piezoelectric cantilever 20a made of an active layer 101, and piezoelectric elements 31-34 are formed on a piezoelectric cantilever 30a made of an active layer 101. Piezoelectric elements 21-24 and 31-34 all have a laminated structure in which a lower electrode layer 111, a piezoelectric layer 112, and an upper electrode layer 113 are stacked in order from bottom to top. The lower electrode layer 111 is made of, for example, platinum (Pt). The piezoelectric layer 112 is made of, for example, PZT (lead zirconate titanate: Pb(Zr,Ti)O ３ The upper electrode layer 113 is made of, for example, gold (Au). However, the materials constituting the lower electrode layer 111, the piezoelectric layer 112, and the upper electrode layer 113 are not limited to these.

[0033] In addition, electrode portions 60 and 70 and wiring portion 40, as shown in Figure 1, are formed on the upper surface of the active layer 101.

[0034] Figure 3 is a schematic plan view showing the configuration of the drive unit 20, the wiring unit 40, and the electrode unit 60.

[0035] At the positive and negative Y-axis ends of the piezoelectric elements 21-24, the upper electrode layer 113 and the piezoelectric layer 112 have been removed, exposing the lower electrode layer 111 upwards. In Figure 3, for convenience, the upper electrode layer 113 and the lower electrode layer 111 are shown with different diagonal patterns.

[0036] The wiring section 40 is composed of wires 41 and 42 arranged with gaps between them. Wire 41 is connected to the upper electrode layer 113, and wire 42 is connected to the lower electrode layer 111. Near the connection point between wire 41 and the upper electrode layer 113, wire 41 is installed on piezoelectric elements 21 to 24 via an insulating film to prevent a short circuit between wire 41 and the lower electrode layer 111.

[0037] The upper electrode layer 113 of piezoelectric element 21, the upper electrode layer 113 of piezoelectric element 23, and the electrode pad 61 are connected in series by wiring 41, and the lower electrode layer 111 of piezoelectric element 21, the lower electrode layer 111 of piezoelectric element 23, and the electrode pad 62 are connected in series by wiring 42. The upper electrode layer 113 of piezoelectric element 22, the upper electrode layer 113 of piezoelectric element 24, the resistor 65, and the electrode pad 63 are connected in series by wiring 41, and the lower electrode layer 111 of piezoelectric element 22, the lower electrode layer 111 of piezoelectric element 24, and the electrode pad 64 are connected in series by wiring 42.

[0038] The configuration of the drive unit 30, the wiring unit 40, and the electrode unit 70 is the same as in Figure 3. Specifically, the upper electrode layer 113 of the piezoelectric body 32, the upper electrode layer 113 of the piezoelectric body 34, and the electrode pad 71 are connected in series by wiring 41, and the lower electrode layer 111 of the piezoelectric body 32, the lower electrode layer 111 of the piezoelectric body 34, and the electrode pad 72 are connected in series by wiring 42. The upper electrode layer 113 of the piezoelectric body 31, the upper electrode layer 113 of the piezoelectric body 33, the resistor 75, and the electrode pad 73 are connected in series by wiring 41, and the lower electrode layer 111 of the piezoelectric body 31, the lower electrode layer 111 of the piezoelectric body 33, and the electrode pad 74 are connected in series by wiring 42.

[0039] Figure 4 schematically shows the end face near the electrode portion 60 when the optical reflective element 1 is cut by a plane parallel to the Y-Z plane at the position C1-C2 in Figure 3.

[0040] The electrode pads 61 to 64 and the wirings 41 and 42 are constituted by a wiring layer 121. The wiring layer 121 is made of, for example, gold (Au). In the present embodiment, since the electrode pads 61 to 64 and the wirings connected to these electrode pads are made of the same material as each other, they are integrally formed. The resistor 65 is a thin film resistor. The material of the resistor 65 is made of a conductive metal or the like having a resistance value described later, and is made of, for example, nichrome. When the resistor 65 is made of nichrome, another metal may be further added to the nichrome. The resistor 65 and the wiring 41 are connected by, for example, solder 122. Note that the configuration of the electrode portion 70 is the same as that of the electrode portion 60.

[0041] FIG. 5 is a circuit diagram constituted by the optical reflection element 1.

[0042] The optical reflection element 1 is connected to an external control circuit and used. The external control circuit includes power supplies 201 and 202 for applying drive voltages to the drive units 20 and 30, respectively. The electrode pads 61 to 64 and 71 to 74 of the optical reflection element 1 are electrically connected to the external control circuit. The external control circuit will be described later by referring to Embodiment 2 of FIG. 25.

[0043] In the drive unit 20, the upper electrode layers 113 of the piezoelectric bodies 21 and 23 are connected to one end of the power supply 201, and the lower electrode layers 111 of the piezoelectric bodies 21 and 23 are connected to the other end of the power supply 201 and the ground. The upper electrode layers 113 of the piezoelectric bodies 22 and 24 are connected to the ground via the resistor 65, and the lower electrode layers 111 of the piezoelectric bodies 22 and 24 are connected to the ground.

[0044] In the drive unit 30, the upper electrode layers 113 of the piezoelectric bodies 32 and 34 are connected to one end of the power supply 202, and the lower electrode layers 111 of the piezoelectric bodies 32 and 34 are connected to the other end of the power supply 202 and the ground. The upper electrode layers 113 of the piezoelectric bodies 31 and 33 are connected to the ground via the resistor 75, and the lower electrode layers 111 of the piezoelectric bodies 31 and 33 are connected to the ground.

[0045] When the optical reflection element 1 is driven, driving voltages of the same phase are applied from the power supplies 201 and 202 to the piezoelectric bodies 21, 23, 32, and 34. As a result, these piezoelectric bodies are deformed by the inverse piezoelectric effect, and the piezoelectric cantilevers 20a formed by these piezoelectric bodies vibrate in the same phase, and the movable part 10 rotates about the rotation axis R10 (see FIG. 1). Thereby, the light incident on the movable part 10 is reflected by the reflection surface 11 of the movable part 10, and the reflected light is scanned in the scanning region.

[0046] When the movable part 10 rotates during the driving of the optical reflection element 1, the piezoelectric cantilevers 20a and 30a vibrate, so that the piezoelectric bodies 22, 24, 31, and 33 are deformed in the same phase, and charges are generated in these piezoelectric bodies due to the piezoelectric effect. The electric energy based on the charges generated in these piezoelectric bodies is consumed as heat in the resistors 65 and 75. Thereby, as will be described later, unnecessary vibrations in the rotation operation of the movable part 10 are suppressed.

[0047] Incidentally, the movable part 10 is repeatedly rotated at a substantially constant angular velocity, for example, between the maximum deflection angles of positive and negative as shown by the solid line in FIG. 6(a). In this case, a sawtooth wave-shaped driving voltage is applied to the driving parts 20 and 30. However, the optical reflection element 1 has an unnecessary resonance point (resonance frequency) f1 with a high Q value as shown in FIG. 6(b) in addition to the frequency corresponding to the rotation operation of the movable part 10. Therefore, when some frequency components constituting the sawtooth wave overlap with this frequency f1, the resonance at the frequency f1 becomes large, and an unnecessary vibration component is superimposed on the rotation of the movable part 10 as shown by the dotted line in FIG. 6(a). Therefore, means for suppressing unnecessary resonance at the frequency f1 is required.

[0048] In contrast, in this embodiment, resistors 65 and 75 are arranged to suppress such unwanted resonances. More specifically, the mechanical energy based on unwanted resonances is converted into electrical energy by the piezoelectric dampers 22, 24, 31, and 33, and this electrical energy is consumed by the resistors 65 and 75, thereby lowering the Q value of the optical reflector 1 at frequency f1. This suppresses unwanted resonances at frequency f1. The resistance values ​​of the resistors 65 and 75 are set to values ​​that can effectively suppress resonances at frequency f1, that is, values ​​that can effectively consume electrical energy based on unwanted resonances, as will be explained below. As a result, resonances at frequency f1 are effectively suppressed, and the movable part 10 can be rotated stably at an ideal angular velocity.

[0049] Next, the charge states resulting from the deformation of the piezoelectric material will be explained with reference to Figures 7(a) to 7(c) and 8(a) to 8(c).

[0050] Figures 7(a) to 7(c) are schematic cross-sectional views showing a piezoelectric body according to a comparative example. In the comparative example, the upper electrode layer 113 and the lower electrode layer 111 are short-circuited by wiring.

[0051] Figure 7(a) shows the piezoelectric element in its lowest downward position, Figure 7(b) shows the piezoelectric element in an unbent position, and Figure 7(c) shows the piezoelectric element in its highest upward position. As shown in Figures 7(a) to (c), when the piezoelectric element vibrates periodically in the vertical direction, an electric charge is generated in the piezoelectric element.

[0052] In the state shown in Figure 7(a), a positive charge is generated on the upper electrode layer 113 and a negative charge is generated on the lower electrode layer 111. At this time, the electrical energy of the piezoelectric material is at its maximum, and the kinetic energy of the piezoelectric material is zero. In the state shown in Figure 7(b), no charge is generated on the piezoelectric material. At this time, the electrical energy of the piezoelectric material is zero, and the kinetic energy of the piezoelectric material is at its maximum. In the state shown in Figure 7(c), a negative charge is generated on the upper electrode layer 113 and a positive charge is generated on the lower electrode layer 111. At this time as well, the electrical energy of the piezoelectric material is at its maximum, and the kinetic energy of the piezoelectric material is zero.

[0053] In the comparative example, since the upper electrode layer 113 and the lower electrode layer 111 are electrically connected, the electrical energy generated by the vibration of the piezoelectric body is hardly consumed, and the sum of the electrical and kinetic energy of the piezoelectric body remains almost constant. Therefore, even if an electric charge is generated as shown in Figures 7(a) and 7(c), the vibration state of the piezoelectric body does not change significantly.

[0054] Figures 8(a) to 8(c) are schematic cross-sectional views showing a piezoelectric element and a resistor according to Embodiment 1. In Embodiment 1, the upper electrode layer 113 and the lower electrode layer 111 are connected via a resistor.

[0055] Figure 8(a) shows the piezoelectric material in its lowest downward position, Figure 8(b) shows the piezoelectric material in an unbent position, and Figure 8(c) shows the piezoelectric material in its highest upward position. As shown in Figures 8(a) to (c), when the piezoelectric material vibrates periodically in the vertical direction, an electric charge is generated in the piezoelectric material, similar to the comparative example.

[0056] In Embodiment 1, current flows through the circuit connecting the upper electrode layer 113 and the lower electrode layer 111 in response to the periodic vibrations shown in Figures 8(a) to 8(c), and the electrical energy based on the current is consumed as heat by the resistor. When Joule heat is generated during this conversion of electrical energy to kinetic energy, the total energy decreases, and the vibration of the piezoelectric material is dampened.

[0057] Here, if the resistance value of the resistor is excessively large, the current flowing through the resistor will be small, and the Joule heat generated in the resistor will be small. On the other hand, if the resistance value of the resistor is excessively small, the current flowing through the resistor will be large, but the Joule heat generated in the resistor will be small. Furthermore, the vibrations damped by the resistor are unwanted resonances superimposed on the ideal waveform, as shown in Figure 6(a). Therefore, in order to effectively suppress unwanted resonances, it is necessary to set the resistance value of the resistor appropriately.

[0058] Therefore, the inventor considered a circuit model consisting of a piezoelectric element and a resistor, as shown in Figure 9, and investigated the resistance value of the resistor that would generate Joule heat most effectively in this circuit.

[0059] In the circuit model shown in Figure 9, a closed circuit is formed by a piezoelectric element and a resistor. Let Z be the internal impedance of the piezoelectric element, and V be the voltage generated by the piezoelectric effect of the piezoelectric element. ＰＺＴ The resistance of the resistor was denoted as R, and the power consumed by the resistor as P. When a piezoelectric element vibrates, an AC voltage is normally generated, but in this circuit model, for convenience, it is assumed that a DC voltage is generated. In this case, the power consumption P is expressed by the following equation (1).

[0060]

[0061] Differentiating equation (1) with respect to R yields equation (2). From equation (2), it can be seen that the power consumption P is maximized when the resistance R is equal to the impedance Z.

[0062]

[0063] Here, the impedance Z changes depending on the frequency f of the vibration generated in the piezoelectric material. Therefore, if the capacitance of the piezoelectric material is C, the impedance Z is expressed by the following equation (3).

[0064]

[0065] Therefore, the value of the resistance R when the power consumption P is maximum is calculated by the following equation (4). In other words, if the frequency of an unwanted resonance is f, the resistance R should be set as shown in equation (4) to effectively suppress this resonance.

[0066]

[0067] Next, the inventor actually constructed the circuit model shown in Figure 9, and in the constructed circuit model, he vibrated the piezoelectric element with predetermined frequencies f and capacitance C, changed the resistance R to nine different values, and conducted an experiment to calculate the Q value for each resistance R.

[0068] Figure 10(a) shows the experimental results of the circuit model in Figure 9, illustrating the Q value corresponding to each resistance value R.

[0069] The vertical axis represents the Q value (%) normalized to 100% when the resistor is omitted and both poles of the piezoelectric element are short-circuited. The horizontal axis represents the resistance value (%) of the resistor normalized to 100% when the resistance value R obtained in equation (4) above is set to 100%. The black circles represent the values ​​obtained in this experiment, and adjacent plots along the horizontal axis are connected by straight lines.

[0070] As shown in Figure 10(a), it was found that the Q value is almost minimized when the resistance value R of the resistor is set to the value obtained by equation (4) above. Therefore, it can be said that by setting the resistance value R of the resistor as shown in equation (4) above, the vibration of the frequency f to be suppressed that occurs in the piezoelectric material having capacitance C can be effectively suppressed.

[0071] In the configuration of Embodiment 1 shown in Figure 5, since the piezoelectric elements 22 and 24 are connected in parallel, the resistance value R of the resistor 65 can be calculated by using the capacitance C in equation (4) as the sum of the capacitances of the piezoelectric elements 22 and 24. Similarly, since the piezoelectric elements 31 and 33 are connected in parallel, the resistance value R of the resistor 75 can be calculated by using the capacitance C in equation (4) as the sum of the capacitances of the piezoelectric elements 31 and 33. This makes it possible to effectively suppress unwanted frequency f vibrations among the vibrations generated in the movable part 10.

[0072] In Figure 5, resistors 65 and 75 are placed for the left and right drive units 20 and 30, respectively. However, a single resistor common to both the left and right drive units 20 and 30 may also be placed. In this case, piezoelectric elements 22, 24, 31, and 33 are arranged in parallel, and the resistance value R of the resistor can be calculated by taking the capacitance C in equation (4) above as the sum of the capacitances of piezoelectric elements 22, 24, 31, and 33.

[0073] Next, the inventors conducted a simulation to determine a preferred range of resistance values ​​R by calculating multiple combinations of power consumption P and resistance value R based on equation (1) above, since increasing the power consumption P in the resistor can suppress the Q value.

[0074] Figure 10(b) shows the simulation results of the power consumption P corresponding to each resistance value R in the circuit model of Figure 9.

[0075] The vertical axis represents the Q value (%) normalized to 100% when the resistor's resistance is 100%. The horizontal axis represents the resistor's resistance (%) normalized to 100% when the resistance R obtained from equation (4) above is 100%. The black circles represent the values ​​obtained in this simulation, and adjacent plots along the horizontal axis are connected by straight lines. The position where power consumption is 60% is indicated by a dotted line.

[0076] As shown in Figure 10(b), when the power consumption is 60% or more, it can be assumed that the Q value of unwanted vibrations can be suppressed to a certain extent. When the range of resistance R when the power consumption is approximately 60% or more is calculated based on the above equation (1), it was found that the ratio of resistance R to impedance Z is between 0.2 and 4.5. In other words, by setting the ratio X in the following equation (5) to between 0.2 and 4.5, it can be said that the power consumption P can be set to approximately 60% or more compared to the maximum value.

[0077] R=X / (2πfC)...(5)

[0078] Furthermore, the power consumption P is maximized when the resistance R is 100%. The resistance R is 100% when equation (4) above is satisfied. Therefore, in equation (5) above, the power consumption P can be maximized by setting the ratio X to 1. Note that even if the ratio X deviates slightly from 1, the power consumption P will be almost maximized. In other words, if the ratio X is effectively set to 1, the power consumption P can be effectively maximized.

[0079] <Effects of Embodiment 1> According to Embodiment 1, the following effects are achieved.

[0080] The optical reflective element 1 comprises a movable part 10 on which a reflective surface 11 is provided, drive units 20 and 30 that rotate the movable part 10 about a pivot axis R10, piezoelectric elements 22, 24, 31 and 33 that generate power corresponding to the strain caused by the rotation of the movable part 10, and resistors 65 and 75 connected to the piezoelectric elements 22, 24, 31 and 33 that consume the power generated by the piezoelectric elements 22, 24, 31 and 33. The resistors 65 and 75 have a resistance value R corresponding to the frequency f to be suppressed.

[0081] Generally, the Q value decreases when energy generated by rotational motion is consumed. In contrast, with the above configuration, the energy generated by rotational motion is consumed by resistors 65 and 75 having a resistance R corresponding to the frequency f to be suppressed. That is, electricity is generated from piezoelectric elements 22, 24, 31, and 33 (damper piezoelectric elements) in response to the rotation of the movable part 10, and the electricity generated from the piezoelectric elements 22, 24, 31, and 33 is consumed as heat by the resistors 65 and 75. As a result, unwanted vibrations based on the frequency f to be suppressed are suppressed. Furthermore, in the above configuration, the piezoelectric elements 22, 24, 31, and 33 and the resistors 65 and 75 only need to be set and arranged so that electricity corresponding to the rotation of the movable part 10 is consumed. Therefore, unwanted vibrations can be effectively suppressed while increasing the degree of design freedom.

[0082] The piezoelectric elements 22, 24, 31, and 33 are installed in the drive units 20 and 30.

[0083] With this configuration, the piezoelectric elements 22, 24, 31, and 33 (damper piezoelectric elements) are installed in the drive units 20 and 30, which are distorted more significantly than other parts of the optical reflective element 1 when the movable part 10 rotates. As a result, the piezoelectric elements 22, 24, 31, and 33 can generate relatively large amounts of power. This effectively suppresses unwanted vibrations.

[0084] The drive units 20 and 30 include piezoelectric elements 21, 23, 32, and 34 that drive the drive units 20 and 30. The piezoelectric elements 22, 24, 31, and 33 for power generation and the piezoelectric elements 21, 23, 32, and 34 for driving each include a lower electrode layer 111, a piezoelectric layer 112, and an upper electrode layer 113. Each layer of the piezoelectric elements 22, 24, 31, and 33 for power generation and each layer of the piezoelectric elements 21, 23, 32, and 34 for driving are made of the same material.

[0085] With this configuration, the piezoelectric elements 22, 24, 31, and 33 for power generation (damper piezoelectric elements) and the piezoelectric elements 21, 23, 32, and 34 for driving (driving piezoelectric elements) can be formed using the same process during manufacturing.

[0086] The optical reflective element 1 includes a fixed part 50 that supports the drive units 20 and 30, and the resistors 65 and 75 are thin-film resistors installed on the fixed part 50.

[0087] This configuration prevents the resistors 65 and 75 from affecting the operation of the movable part 10 and the drive parts 20 and 30. Furthermore, by performing laser trimming on the resistors installed in the fixed part 50 during manufacturing, the resistance values ​​R of the resistors 65 and 75 can be adjusted easily and with high precision.

[0088] When the resistance of resistor 65 is R, the frequency to be suppressed is f, and the capacitance based on piezoelectric elements 22 and 24 (capacitance of piezoelectric elements) is C, the ratio X in the following equation is set to be between 0.2 and 4.5. Similarly, when the resistance of resistor 75 is R, the frequency to be suppressed is f, and the capacitance based on piezoelectric elements 31 and 33 (capacitance of piezoelectric elements) is C, the ratio X in the following equation is set to be between 0.2 and 4.5. R = X / (2πfC)

[0089] With this configuration, the power consumption P dissipated as heat in the resistors 65 and 75 can be set to approximately 60% or more of its maximum value. This effectively suppresses unwanted vibrations.

[0090] The above ratio X is effectively set to 1.

[0091] This configuration allows for the most effective suppression of unwanted vibrations based on the target frequency f.

[0092] The piezoelectric elements 22, 24, 31, and 34 are installed in piezoelectric cantilevers 20a and 30a (regions) that vibrate with substantially the same phase in the resonant mode based on the frequency f to be suppressed.

[0093] With this configuration, in each piezoelectric element 22, 24, 31, 34 (damper piezoelectric element), the cancellation of charges generated in the damper piezoelectric element within the element is suppressed, allowing for efficient charge generation. Therefore, the electrical energy based on the charge can be efficiently consumed in the resistors 65 and 75.

[0094] The piezoelectric elements 22 and 24 are respectively installed in two piezoelectric cantilevers 20a (regions) that vibrate with substantially the same phase in a resonant mode based on the frequency f to be suppressed, and the piezoelectric elements 22 and 24 located in the two piezoelectric cantilevers 20a (regions) are electrically connected to each other. Similarly, the piezoelectric elements 31 and 33 are respectively installed in two piezoelectric cantilevers 30a (regions) that vibrate with substantially the same phase in a resonant mode based on the frequency f to be suppressed, and the piezoelectric elements 31 and 33 located in the two piezoelectric cantilevers 30a (regions) are electrically connected to each other.

[0095] In this configuration, multiple piezoelectric dampers, each placed in multiple regions vibrating in the same phase, are electrically connected to one another. This allows the electrical energy generated by the charges produced by the multiple piezoelectric dampers to be efficiently dissipated by the resistor. Furthermore, since there is no need to place a resistor for each of the multiple piezoelectric dampers, the optical reflective element can be constructed simply.

[0096] <Example of modification 1> In Embodiment 1, as shown in Figure 1, piezoelectric elements 21, 23, 32, and 34 were used as driving piezoelectric elements, and piezoelectric elements 22, 24, 31, and 33 were used as damping piezoelectric elements. However, the arrangement of piezoelectric elements 21-24 and 31-34 remains the same as in Figure 1, and these eight piezoelectric elements may be changed to either driving or damping piezoelectric elements.

[0097] Figures 11 and 12 are schematic plan views showing the configuration of the optical reflective element 1 according to this modified example, respectively.

[0098] In this modified example, compared to Embodiment 1 in Figure 1, two electrode portions 60 and two electrode portions 70 are arranged on the upper surface of the fixed portion 50. Note that in Figures 11 and 12, the wiring portion 40 is omitted for convenience. Furthermore, the driving piezoelectric elements to which driving voltages with a phase difference of 180° (opposite phase) are applied are indicated by a pattern of diagonal lines that are reversed left and right, and the damper piezoelectric elements that vibrate with a phase difference of 180° (opposite phase) are indicated by a pattern of diagonal lines that are reversed left and right. In Figures 13 and onward, the wiring portion 40 is also omitted, and the diagonal lines on the piezoelectric elements are similarly indicated.

[0099] In the example shown in Figure 11, piezoelectric elements 21, 24, 31, and 34 are used as driving piezoelectric elements, and piezoelectric elements 22, 23, 32, and 33 are used as damping piezoelectric elements. In this case, piezoelectric elements 21 and 24 vibrate in opposite phases and are therefore connected to different electrode sections 60 (electrode pads 61 and 62), respectively, and piezoelectric elements 22 and 23 vibrate in opposite phases and are therefore connected to different electrode sections 60 (electrode pads 63 and 64 and resistors 65), respectively. Similarly, piezoelectric elements 31 and 34 vibrate in opposite phases and are therefore connected to different electrode sections 70 (electrode pads 71 ​​and 72), respectively, and piezoelectric elements 32 and 33 vibrate in opposite phases and are therefore connected to different electrode sections 70 (electrode pads 73 and 74 and resistors 75), respectively.

[0100] In the example shown in Figure 12, piezoelectric elements 21, 22, 31, and 32 are used as driving piezoelectric elements, and piezoelectric elements 23, 24, 33, and 34 are used as damping piezoelectric elements. In this case as well, piezoelectric elements 21 and 22 are connected to different electrode sections 60, piezoelectric elements 23 and 24 are connected to different electrode sections 60, piezoelectric elements 31 and 32 are connected to different electrode sections 70, and piezoelectric elements 33 and 34 are connected to different electrode sections 70.

[0101] <Example of modification 2> In Embodiment 1, as shown in Figure 1, the shapes of the drive units 20 and 30 in plan view were point-symmetric with respect to the center C10, but they may also be line-symmetric with respect to a straight line parallel to the Y-axis passing through the center C10.

[0102] Figures 13 and 14 are schematic plan views showing the configuration of the optical reflective element 1 according to this modified example, respectively. In this modified example, compared to modified example 1 shown in Figures 11 and 12, the shapes of the drive units 20 and 30 in plan view are symmetrical with respect to a straight line parallel to the Y-axis passing through the center C10.

[0103] In the example shown in Figure 13, piezoelectric elements 21, 22, 31, and 32 are used as driving piezoelectric elements, and piezoelectric elements 23, 24, 33, and 34 are used as damping piezoelectric elements. In this case as well, piezoelectric elements 21-24 and 31-34 are connected to electrode sections 60 and 70, similar to the modified example 1 in Figure 12. In the example shown in Figure 14, piezoelectric elements 21, 24, 31, and 34 are used as driving piezoelectric elements, and piezoelectric elements 22, 23, 32, and 33 are used as damping piezoelectric elements. In this case as well, piezoelectric elements 21-24 and 31-34 are connected to electrode sections 60 and 70, similar to the modified example 1 in Figure 11.

[0104] <Example of modification 3> In Embodiment 1, one piezoelectric element was placed on one piezoelectric cantilever, but multiple piezoelectric elements may be placed on it.

[0105] Figure 15 is a schematic plan view showing the configuration of the optical reflective element 1 according to this modified example.

[0106] In this modified example, compared to Modified Example 2 shown in Figures 13 and 14, piezoelectric elements 81 to 84 are arranged on each of the four piezoelectric cantilevers 20a where piezoelectric elements 21 to 24 are arranged, and piezoelectric elements 91 to 94 are arranged on each of the four piezoelectric cantilevers 30a where piezoelectric elements 31 to 34 are arranged. Piezoelectric elements 81 to 84 are each positioned with a gap in the negative X-axis direction relative to piezoelectric elements 21 to 24, and piezoelectric elements 91 to 94 are each positioned with a gap in the positive X-axis direction relative to piezoelectric elements 31 to 34.

[0107] In this case, piezoelectric elements 21-24 and 31-34 are used as driving piezoelectric elements, and piezoelectric elements 81-84 and 91-94 are used as damper piezoelectric elements.

[0108] Piezoelectric elements 21 and 23 are connected to each other and to the electrode pads 61 and 62 of one electrode section 60, while piezoelectric elements 22 and 24 are connected to each other and to the electrode pads 61 and 62 of the other electrode section 60. Piezoelectric elements 81 and 83 are connected to each other and to the electrode pads 63 and 64 and resistor 65 of one electrode section 60, while piezoelectric elements 82 and 84 are connected to each other and to the electrode pads 63 and 64 and resistor 65 of the other electrode section 60. Similarly, piezoelectric elements 31 to 34 and 91 to 94 are also connected to the two electrode sections 70.

[0109] <Example of modification 4> In Embodiment 1, the piezoelectric element for the damper was placed on the piezoelectric cantilevers 20a and 30a of the drive units 20 and 30, but it is not limited to this and may be placed in other locations as shown in Figures 16 to 18.

[0110] In the example shown in Figure 16, compared to the modified example 1 in Figure 11, a plate-shaped portion 210 is connected to the portion of the drive unit 20 where the two central piezoelectric cantilevers 20a are connected in the X-axis direction, and a piezoelectric body 211 is formed on the plate-shaped portion 210 as a piezoelectric damper. A plate-shaped portion 220 is connected to the portion of the drive unit 30 where the two central piezoelectric cantilevers 30a are connected in the X-axis direction, and a piezoelectric body 221 is formed on the plate-shaped portion 220 as a piezoelectric damper. The plate-shaped portions 210 and 220 are composed of an active layer 101 (see Figure 2) and are integrally formed with the piezoelectric cantilevers 20a and 30a, respectively. The piezoelectric bodies 211 and 221 have the same laminated structure as the piezoelectric bodies 21-24 and 31-34. In this case as well, the shapes of the drive units 20 and 30 in plan view are point-symmetric with respect to the center C10.

[0111] Furthermore, compared to the modified example 1 in Figure 11, the piezoelectric element 211 is connected to the electrode pads 63, 64 and resistor 65 of one electrode section 60, while the electrode pads 63, 64 and resistor 65 are omitted from the other electrode section 60. Similarly, the piezoelectric element 221 is connected to the electrode pads 73, 74 and resistor 75 of one electrode section 70, while the electrode pads 73, 74 and resistor 75 are omitted from the other electrode section 70.

[0112] In the example shown in Figure 16, the piezoelectric elements 211 and 221 deform in accordance with the rotational movement of the movable part 10, and the power generated from the piezoelectric elements 211 and 221 is consumed as heat by the resistors 65 and 75. Therefore, by setting the resistance values ​​R of the resistors 65 and 75 in the same manner as in Embodiment 1, unwanted vibrations based on the frequency f to be suppressed can be suppressed.

[0113] Furthermore, as shown in the example in Figure 16, the piezoelectric elements 211 and 221 can be easily arranged by utilizing the space around the drive units 20 and 30. In addition, air resistance is generated on the plate-shaped parts 210 and 220 when the movable part 10 rotates, which can further effectively suppress unwanted vibrations.

[0114] In the example shown in Figure 17, compared to the example in Figure 16, the plate-like portions 210 and 220 are connected to the negative and positive ends of the movable portion 10. The plate-like portions 210 and 220 and the piezoelectric bodies 211 and 221 are formed to extend long in the X-axis direction, and the shapes of the plate-like portions 210 and 220 and the piezoelectric bodies 211 and 221 in plan view are symmetric with respect to the rotation axis R10 and with respect to a line parallel to the Y-axis passing through the center C10. The piezoelectric body 211 is connected to the electrode pads 63 and 64 and the resistor 65 by wiring that passes through the upper surfaces of the movable portion 10 and the drive portion 20, and the piezoelectric body 221 is connected to the electrode pads 73 and 74 and the resistor 75 by wiring that passes through the upper surfaces of the movable portion 10 and the drive portion 30.

[0115] In the example shown in Figure 17, the piezoelectric elements 211 and 221 deform in accordance with the rotational movement of the movable part 10, and the power generated from the piezoelectric elements 211 and 221 is consumed as heat by the resistors 65 and 75. Therefore, by setting the resistance values ​​R of the resistors 65 and 75 in the same manner as in Embodiment 1, unwanted vibrations based on the frequency f to be suppressed can be suppressed.

[0116] Furthermore, as shown in the example in Figure 17, the piezoelectric elements 211 and 221 can be easily arranged by utilizing the space around the movable part 10. In addition, since relatively large piezoelectric elements 211 and 221 can be arranged in the space around the movable part 10, air resistance is generated on the plate-shaped parts 210 and 220 when the movable part 10 rotates, which can further effectively suppress unwanted vibrations.

[0117] In the example shown in Figure 18, compared to Embodiment 1 in Figure 1, plate-like portions 230 extending in the positive and negative Y-axis directions are formed near the X-axis positive end of the connecting portion 20b, and plate-like portions 230 extending in the positive and negative Y-axis directions are formed near the X-axis negative end of the connecting portion 30b. The four plate-like portions 230 extend in the Y-axis direction from the connecting portion 20b or the connecting portion 30b and are connected to the inner surface of the fixing portion 50. In plan view, the plate-like portions 230 have a rectangular portion on the fixing portion 50 side and a meandering meandering portion in the Y-axis direction. In plan view, the four plate-like portions 230 are symmetrical with respect to the rotation axis R10 and with respect to a line passing through the center C10 and parallel to the Y-axis.

[0118] The plate-shaped portion 230 is composed of an active layer 101 (see Figure 2), and the active layer 101 of the connecting portion 20b or connecting portion 30b and the active layer 101 of the fixed portion 50 are integrally formed. Piezoelectric bodies 231 to 234 are formed on the upper surface of each of the four plate-shaped portions 230. Piezoelectric bodies 231 to 234 have the same laminated structure as piezoelectric bodies 21 to 24 and 31 to 34.

[0119] Piezoelectric element 231 is connected to the electrode pads 63, 64 and resistor 65 of one electrode section 60 by wiring that passes over the top surface of the fixed section 50, and piezoelectric element 232 is connected to the electrode pads 63, 64 and resistor 65 of the other electrode section 60 by wiring that passes over the top surface of the fixed section 50. Similarly, piezoelectric element 233 is connected to the electrode pads 73, 74 and resistor 75 of one electrode section 70 by wiring that passes over the top surface of the fixed section 50, and piezoelectric element 234 is connected to the electrode pads 73, 74 and resistor 75 of the other electrode section 70 by wiring that passes over the top surface of the fixed section 50.

[0120] Here, the resonance modes of the movable part 10 may include an R mode for causing the movable part 10 to rotate, and a P mode in which the movable part 10 resonates in a direction perpendicular to the reflective surface 11. If the resonance frequencies of the P mode and the R mode are close together, the P mode will be excited at the same time as the R mode, and the resonant motion of the P mode will have a significant effect on the rotational motion of the R mode.

[0121] In the example shown in Figure 18, in each plate-like portion 230, the bending rigidity of the rectangular portion on the fixed portion 50 side is higher than the bending rigidity of the meander-shaped portion on the connecting portion 20b or connecting portion 30b side. This makes it possible to maintain the R-mode resonance frequency while moving the P-mode resonance frequency away from the R-mode resonance frequency, thereby stabilizing the rotational movement of the movable portion 10.

[0122] Furthermore, the piezoelectric elements 231 to 234 deform in accordance with the rotational movement of the movable part 10, and the power generated from the piezoelectric elements 231 to 234 is consumed as heat by the resistors 65 and 75. Therefore, by setting the resistance values ​​R of the resistors 65 and 75 in the same manner as in Embodiment 1, unwanted vibrations based on the frequency f to be suppressed can be suppressed.

[0123] <Example of modification 5> In Embodiment 1, the piezoelectric elements 21-24 and 31-34 were arranged in the piezoelectric cantilevers 20a and 30a so as to straddle the pivot axis R10 in the Y-axis direction. However, they may be arranged on the positive or negative Y-axis side of the pivot axis R10 without straddling the pivot axis R10.

[0124] Figure 19 is a schematic plan view showing the configuration of the optical reflective element 1 according to this modified example.

[0125] In this modified example, compared to Embodiment 1, the piezoelectric element 24 is formed on the negative Y-axis side of the pivot axis R10 in the piezoelectric cantilever 20a, and the piezoelectric element 34 is formed on the positive Y-axis side of the pivot axis R10 in the piezoelectric cantilever 30a. In this case as well, the shapes of the drive units 20 and 30 in plan view are point-symmetric with respect to the center C10.

[0126] Piezoelectric elements 21 and 23 are connected to electrode pads 61 and 62 of one electrode section 60, and piezoelectric element 22 is connected to electrode pads 61 and 62 of the other electrode section 60, with electrode pads 63 and 64 and resistor 65 omitted from the other electrode section 60. Piezoelectric element 24 is connected to electrode pads 63 and 64 and resistor 65 of one electrode section 60. Similarly, piezoelectric elements 31 and 33 are connected to electrode pads 71 ​​and 72 of one electrode section 70, and piezoelectric element 32 is connected to electrode pads 71 ​​and 72 of the other electrode section 70, with electrode pads 73 and 74 and resistor 75 omitted from the other electrode section 70. Piezoelectric element 34 is connected to electrode pads 73 and 74 and resistor 75 of one electrode section 60.

[0127] In this case, when the movable part 10 rotates around the pivot axis R10 (R mode), as shown in Figure 20, the piezoelectric cantilevers 20a and 30a vibrate in a first phase and a second phase that are 180° apart in phase (opposite phase) from each other. In this case, the regions of the first phase and the second phase are both distributed so as to straddle the pivot axis R10. Therefore, if the goal is to suppress unwanted resonance in the R mode, the piezoelectric damper should be positioned so as to straddle the pivot axis R10.

[0128] On the other hand, when the movable part 10 resonates in a direction perpendicular to the reflective surface 11 (P mode), as shown in Figure 21, the piezoelectric cantilevers 20a and 30a vibrate in a first phase and a second phase that are 180° apart in phase (opposite phase) from each other. In this case, the regions of the first phase and the second phase are distributed on the positive or negative side of the Y axis of the pivot axis R10. Therefore, if the goal is to suppress unwanted resonance in the P mode, the piezoelectric damper should be positioned on the positive or negative side of the Y axis of the pivot axis R10.

[0129] Figures 22(a) to 22(c) are schematic diagrams illustrating how electric charge is generated in a piezoelectric material used for dampers.

[0130] When suppressing vibrations of the same phase in a single piezoelectric cantilever, as shown in Figure 22(a), for example, a piezoelectric damper is positioned so as to straddle the rotation axis R10 in the piezoelectric cantilever. In this case, due to the resonance of the vibration to be suppressed, the same charge is generated on the upper electrode layer 113 of the piezoelectric damper, regardless of its position in the Y-axis direction. In this case, power can be appropriately consumed in the resistor.

[0131] When suppressing vibrations of different phases in a single piezoelectric cantilever, as shown in Figure 22(b), if the piezoelectric damper is positioned so as to straddle the rotation axis R10 in the piezoelectric cantilever, the resonance of the suppressed element will generate different charges on the upper electrode layers 113 on the positive and negative sides of the Y-axis, causing the positive and negative charges generated on the upper electrode layers 113 to cancel each other out. In this case, the resistor will not be able to properly dissipate power.

[0132] In contrast, when suppressing vibrations of different phases in a single piezoelectric cantilever, as shown in Figure 22(c), if damper piezoelectric elements are arranged on the positive and negative Y-axis sides of the rotation axis R10 in the piezoelectric cantilever, the different charges generated in each damper piezoelectric element do not cancel each other out. In this case, power can be appropriately consumed in the resistors corresponding to each damper piezoelectric element.

[0133] For these reasons, the piezoelectric damper should be positioned according to whether the resonance to be suppressed is R-mode or P-mode. For example, if the piezoelectric damper is positioned so as not to straddle the rotation axis R10 as shown in Figure 22(c), power can be appropriately consumed in both unwanted vibrations based on the R-mode as shown in Figure 22(a) and unwanted vibrations based on the P-mode as shown in Figure 22(c).

[0134] In the configuration shown in Figure 19, the piezoelectric elements 24 and 34, which are damper piezoelectric elements, are positioned on the negative and positive sides of the Y-axis of the rotation axis R10, respectively. This allows for the suppression of multiple resonance modes based on the frequency f to be suppressed, regardless of whether the vibration based on the frequency f to be suppressed is in the R-mode or P-mode.

[0135] As shown in Figure 23, in a piezoelectric cantilever, damper piezoelectric elements may be arranged on both the positive and negative Y-axis sides of the rotation axis R10. In the example shown in Figure 23, compared to the example in Figure 19, in the piezoelectric cantilever 20a where piezoelectric element 24 is arranged, piezoelectric element 25 is arranged as a damper piezoelectric element on the positive Y-axis side of the rotation axis R10, and in the piezoelectric cantilever 30a where piezoelectric element 34 is arranged, piezoelectric element 35 is arranged as a damper piezoelectric element on the negative Y-axis side of the rotation axis R10.

[0136] In the configuration shown in Figure 23, the piezoelectric elements 24 and 25 are installed in the first and second regions (corresponding to the first and second phases in Figure 21) respectively, where they vibrate at different phases in the P mode (one resonant mode) and at substantially the same phase in the R mode (another resonant mode), among a plurality of resonant modes based on the frequency f to be suppressed. Similarly, the piezoelectric elements 34 and 35 are installed in the first and second regions (corresponding to the first and second phases in Figure 21) respectively, where they vibrate at different phases in the P mode (one resonant mode) and at substantially the same phase in the R mode (another resonant mode), among a plurality of resonant modes based on the frequency f to be suppressed.

[0137] With this configuration, in the case of the P mode, the Q value for the P mode can be suppressed by consuming the power generated from the damping piezoelectric elements installed in the first and second regions, respectively, which vibrate at different phases, and in the case of the R mode, the Q value for the R mode can be suppressed by consuming the power generated from the damping piezoelectric elements installed in the first and second regions, respectively, which vibrate at substantially the same phase. In other words, with the above configuration, multiple resonance modes based on the frequency f to be suppressed can be suppressed.

[0138] <Modification Example 6> In the configuration of Modification Example 5 shown in Figure 23, the piezoelectric elements 24 and 25 are arranged separately with a predetermined gap between them and the pivot shaft R10, and the piezoelectric elements 34 and 35 are arranged separately with a predetermined gap between them and the pivot shaft R10. However, the configuration is not limited to this, and as shown in Figure 24(a), the lower electrode layer 111 and the piezoelectric layer 112 of two adjacent damper piezoelectric elements may be common to each other.

[0139] In other words, as shown in Figure 24(a), the piezoelectric damper is composed of a piezoelectric material including a lower electrode layer 111, a piezoelectric layer 112, and an upper electrode layer 113, and multiple dampers are arranged adjacent to each other with gaps between them. Among adjacent piezoelectric dampers, the upper electrode layer 113 of one piezoelectric damper is spaced apart with a gap between them. The piezoelectric layer 112 and lower electrode layer 111 of one piezoelectric damper are integrally formed with the piezoelectric layer 112 and lower electrode layer 111 of the other piezoelectric damper, respectively.

[0140] With this configuration, two adjacent piezoelectric dampers can be formed simply by processing the upper electrode layer 113 of a piezoelectric damper, which includes an upper electrode layer 113, a piezoelectric layer 112, and a lower electrode layer 111, so that they are spaced apart from each other. Therefore, two adjacent piezoelectric dampers can be formed with high precision.

[0141] In the configuration of the modified example 3 shown in Figure 15, the driving piezoelectric element and the damping piezoelectric element are arranged separately with a predetermined gap between them in a single piezoelectric cantilever. However, the configuration is not limited to this, and as shown in Figure 24(b), the lower electrode layer 111 and the piezoelectric element layer 112 of adjacent driving piezoelectric elements and damping piezoelectric elements may be common to each other.

[0142] In other words, in the configuration shown in Figure 24(b), the damper piezoelectric element (a piezoelectric element for generating power) and the drive piezoelectric element (a piezoelectric element for driving) are arranged adjacent to each other with a gap between them. The upper electrode layer 113 of the damper piezoelectric element and the upper electrode layer 113 of the drive piezoelectric element are spaced apart with a gap between them, and the piezoelectric layer 112 and lower electrode layer 111 of the damper piezoelectric element are integrally formed with the piezoelectric layer 112 and lower electrode layer 111 of the drive piezoelectric element, respectively.

[0143] With this configuration, by processing the upper electrode layer 113 of a piezoelectric body consisting of an upper electrode layer 113, a piezoelectric layer 112, and a lower electrode layer 111 so that they are spaced apart from each other, adjacent damper piezoelectric bodies and drive piezoelectric bodies can be formed. Therefore, adjacent damper piezoelectric bodies and drive piezoelectric bodies can be formed with high precision.

[0144] <Embodiment 2> In Embodiment 1, the resistors 65 and 75 were provided on the fixed portion 50 of the optical reflective element 1. In contrast, in Embodiment 2, the resistor for consuming power is provided outside the optical reflective element 1.

[0145] Figure 25 is a schematic diagram showing the configuration of the optical reflector 2 according to this embodiment.

[0146] The optical reflective device 2 comprises an optical reflective element 1, a substrate 300, and a control circuit 400. The optical reflective device 2 is, for example, a device that displays a predetermined image by scanning a beam.

[0147] The substrate 300 has an opening 300a for installing the optical reflective element 1. In a plan view, the opening 300a is smaller than the outer shape of the optical reflective element 1 and larger than the opening 51 of the fixing part 50. The opening 300a penetrates the substrate 300 in the Z-axis direction. In a plan view, the optical reflective element 1 is installed on the substrate 300 such that the movable part 10 is positioned at the center of the opening 300a. The optical reflective element 1 of this embodiment has the same configuration as, for example, Embodiment 1 in Figure 1. However, in the optical reflective element 1 of this embodiment, the resistors 65 and 75 on the fixing part 50 are omitted, and the electrode pads 63 and 73 are directly connected to the piezoelectric damper.

[0148] The substrate 300 includes electrode pads 301-304 and 311-314, resistors 321 and 322, and a connector 330. The electrode pads 301-304 are electrically connected to the electrode pads 61-64 of the optical reflective element 1 by wire bonding or the like, and the electrode pads 311-314 are electrically connected to the electrode pads 71-74 of the optical reflective element 1 by wire bonding or the like.

[0149] Electrode pads 301-304 and 311-314 are connected to connector 330 via wiring 340. A resistor 321 is placed in the wiring 340 between electrode pad 303 and connector 330, and a resistor 322 is placed in the wiring 340 between electrode pad 313 and connector 330. Resistors 321 and 322 are configured in the same way as resistors 65 and 75 in Embodiment 1.

[0150] The control circuit 400 comprises a control unit 401 and power supplies 201 and 202, and is connected to the connector 330. The control unit 401 controls the power supplies 201 and 202.

[0151] Figure 26 is a circuit diagram of the optical reflector 2 according to this embodiment.

[0152] In this embodiment, resistors 321 and 322 are provided on the substrate 300, and power supplies 201 and 202 are provided on the control circuit 400. In this embodiment as well, the same circuit as in Embodiment 1 of Figure 5 is configured.

[0153] <Effects of Embodiment 2> According to Embodiment 2, the following effects are achieved.

[0154] The optical reflective device 2 comprises an optical reflective element 1 and resistors 321 and 322 arranged outside the optical reflective element 1, connected to piezoelectric elements 22, 24, 31, and 33, and consuming the power generated by the piezoelectric elements 22, 24, 31, and 33. The resistors 321 and 322 have a resistance value R corresponding to the frequency f to be suppressed.

[0155] This configuration provides the same effects as in Embodiment 1. Furthermore, since the resistors 321 and 322 are not provided on the optical reflective element 1, the manufacturing process of the optical reflective element 1 becomes easier compared to the case where the resistors 321 and 322 are provided on the optical reflective element 1.

[0156] The optical reflective device 2 includes a substrate 300 on which the optical reflective element 1 is installed, and the resistors 321 and 322 are installed on the substrate 300.

[0157] With this configuration, the resistors 321 and 322 are provided on a substrate 300 which is relatively larger than the optical reflective element 1, making it easier to install the resistors 321 and 322.

[0158] <Example of modification 7> In Embodiment 2, the functions of the piezoelectric elements 21-24 and 31-34 were fixedly set as either driving piezoelectric elements or damping piezoelectric elements. However, the invention is not limited to this, and may be periodically switched between driving piezoelectric elements and damping piezoelectric elements.

[0159] Figure 27 is a circuit diagram of the optical reflector 2 according to this modified example.

[0160] In this modified example, compared to Embodiment 2 shown in Figure 26, resistors 321 and 322 are provided in the control circuit 400, and switching circuits 411, 412, 421, and 422 are provided in the control circuit 400. The connection state of the switching circuits 411, 412, 421, and 422 is switched by the control unit 401 (see Figure 25).

[0161] Switching circuits 411 and 412 switch the connection state between the first group consisting of piezoelectric elements 21 and 23 and the second group consisting of piezoelectric elements 22 and 24 between a state in which the first group is connected to the power supply 201 and the second group is connected to the resistor 321, and a state in which the first group is connected to the resistor 321 and the second group is connected to the power supply 201. Similarly, switching circuits 421 and 422 switch the connection state between the first group consisting of piezoelectric elements 32 and 34 and the second group consisting of piezoelectric elements 31 and 33 between a state in which the first group is connected to the power supply 202 and the second group is connected to the resistor 322, and a state in which the first group is connected to the resistor 322 and the second group is connected to the power supply 202.

[0162] Figures 28(a) and 28(b) show the drive voltages applied to the first group (piezoelectric elements 21, 23, 32, 34) and the second group (piezoelectric elements 22, 24, 31, 33), respectively.

[0163] In Figure 28(a), during the section where a driving voltage is applied to the first group of piezoelectric elements, the first group of piezoelectric elements functions as driving piezoelectric elements, and the driving units 20 and 30 are driven. On the other hand, during the section where no driving voltage is applied to the first group of piezoelectric elements, the first group of piezoelectric elements functions as damper piezoelectric elements, and the power generated by the first group of piezoelectric elements is consumed as heat by the resistors 321 and 322. Similarly, in Figure 28(b), during the section where a driving voltage is applied to the second group of piezoelectric elements, the second group of piezoelectric elements functions as driving piezoelectric elements, and the driving units 20 and 30 are driven. On the other hand, during the section where no driving voltage is applied to the second group of piezoelectric elements, the second group of piezoelectric elements functions as damper piezoelectric elements, and the power generated by the second group of piezoelectric elements is consumed as heat by the resistors 321 and 322. Furthermore, as shown in Figures 28(a) and (b), driving voltages are applied to the first group of piezoelectric elements and the second group of piezoelectric elements at alternating timings.

[0164] In this modified configuration, the optical reflector 2 includes a control circuit 400 that controls the drive units 20 and 30, and the resistors 321 and 322 are installed in the control circuit 400. The control circuit 400 also includes switching circuits 411, 412, 421, and 422, which switch between electrically connecting the piezoelectric elements 21-24 and 31-34 to the resistors 321 and 322 and connecting them to the power supplies 201 and 202.

[0165] With this configuration, the switching circuits 411, 412, 421, and 422 control the piezoelectric elements 21-24 and 31-34, which can be periodically set to either damper piezoelectric elements or drive piezoelectric elements. Therefore, compared to the case where a drive voltage is applied only to the first group of piezoelectric elements as shown in Figure 28(a), for example, the driving efficiency of the movable part 10 can be increased.

[0166] <Embodiment 3> In the above embodiment, the piezoelectric element for the damper was arranged separately from the piezoelectric element for the drive. In contrast, in Embodiment 3, the piezoelectric element for the drive is used not only as a drive source for the drive unit but also as a piezoelectric element for the damper.

[0167] Figure 29 is a schematic plan view showing the configuration of the optical reflective element 1 according to Embodiment 3.

[0168] In Embodiment 3, compared to Embodiment 1 in Figure 1, electrode pads 501, 502, 511, 512 and resistors 503, 513 are arranged on the electrode section 60, and electrode pads 521, 522, 531, 532 and resistors 523, 533 are arranged on the electrode section 70. The resistors 503, 513, 523, and 533 are thin-film resistors.

[0169] The upper electrode layers 113 of piezoelectric elements 21 and 23 are connected to electrode pad 501 via resistor 503, and the upper electrode layers 113 of piezoelectric elements 22 and 24 are connected to electrode pad 511 via resistor 513. Electrode pads 501 and 511 are connected to external power supplies 201 and 203 (see Figure 30), respectively, and electrode pads 502 and 512 are connected to ground. The upper electrode layers 113 of piezoelectric elements 32 and 34 are connected to electrode pad 521 via resistor 523, and the upper electrode layers 113 of piezoelectric elements 31 and 33 are connected to electrode pad 531 via resistor 533. Electrode pads 521 and 531 are connected to external power supplies 202 and 204 (see Figure 30), respectively, and electrode pads 522 and 532 are connected to ground.

[0170] Figure 30 is a circuit diagram comprising an optical reflective element 1 according to Embodiment 3.

[0171] In Embodiment 3, compared to Embodiment 1 in Figure 5, power supply 201 is connected to a circuit including piezoelectric elements 21, 23 and resistor 503, and power supply 203 is connected to a circuit including piezoelectric elements 22, 24 and resistor 513. Power supply 202 is connected to a circuit including piezoelectric elements 32, 34 and resistor 523, and power supply 204 is connected to a circuit including piezoelectric elements 31, 33 and resistor 533. Power supplies 201 and 202 apply AC voltages with the same phase to the circuits, and power supplies 203 and 204 apply AC voltages with the same phase to the circuits. The magnitude (amplitude) of the driving voltages of power supplies 201 to 204 is adjusted so that the movable part 10 rotates at a desired swing angle.

[0172] As shown in Figures 29 and 30, in Embodiment 3, the piezoelectric elements 21-24 and 31-34 are all placed within circuits that include resistors, and these circuits are all connected to an external power source. As a result, a voltage is applied to each piezoelectric element, and the movable part 10 rotates in the same manner as in the above embodiment. In addition, in response to the periodic vibration of each piezoelectric element (see Figures 8(a) to (c)), current flows through the circuits that include the piezoelectric elements, and the electrical energy based on the current is consumed as heat by the resistors. In other words, the piezoelectric elements 21-24 and 31-34 in Embodiment 3 function as both driving piezoelectric elements and damping piezoelectric elements.

[0173] In Figure 30, resistors are placed in each of the four circuits described above, but it is not necessary for resistors to be placed in all circuits; resistors may be placed in only some of the circuits. For example, either resistor 503 or 513 may be omitted, or either resistor 523 or 533 may be omitted. In this case, considering the symmetry in the X-axis direction, it is preferable that resistors 503 and 523 are omitted from the configuration of Figure 30, or that resistors 513 and 533 are omitted. When resistors are omitted, the magnitude (amplitude) of the drive voltage of the power supply in the circuit without resistors is adjusted to be smaller than the magnitude (amplitude) of the drive voltage of the power supply in the circuit with resistors, compared to the configuration of Figure 30, so that the movable part 10 rotates at the desired swing angle. Furthermore, the resistors are not limited to being placed between the power supply and the upper electrode layer 113 in each circuit, but may also be placed between the power supply and the lower electrode layer 111.

[0174] Figure 31 is a diagram showing the configuration of a circuit model consisting of a piezoelectric element and a resistor according to Embodiment 3.

[0175] In the circuit model of Embodiment 3, compared to Embodiment 1 in Figure 9, the power supply is located in a closed circuit consisting of a piezoelectric element and a resistor. In the circuit model of Figure 31, a voltage is applied to the piezoelectric element by the voltage V of the power supply, and the piezoelectric element vibrates due to the inverse piezoelectric effect.

[0176] In this case, the piezoelectric material acts as a capacitance, so the same voltage as the power supply is generated between the two electrodes of the piezoelectric material. However, unwanted bending may occur in the piezoelectric material in addition to the deformation of the piezoelectric material due to the inverse piezoelectric effect caused by the power supply voltage V. For example, if no unwanted bending occurs in the piezoelectric material, i.e., if the amount of superimposed deformation is 0, then the voltage V generated in the piezoelectric material due to the piezoelectric effect is present. ＰＺＴ This becomes V. In this case, the potential V1 between the power source and the resistor is equal to the potential V2 between the piezoelectric material and the resistor, and the current I flowing through the resistor becomes 0. On the other hand, if there is unwanted bending in the piezoelectric material, that is, if the superimposed amount of deformation is not 0, the voltage V generated in the piezoelectric material due to the piezoelectric effect becomes V. ＰＺＴ The equation becomes V + δ. Here, δ is an unwanted voltage generated in the piezoelectric material due to the piezoelectric effect, and is a voltage corresponding to the amount of deformation superimposed on the piezoelectric material. In this case, a difference is created between the potentials V1 and V2, and a current I flows through the resistor according to this difference, and the electrical energy based on the current I is consumed as heat in the resistor.

[0177] Therefore, in the circuit model of Embodiment 3, the power consumption P is also expressed by the above equation (1). In this case as well, by setting the resistance value R as shown in the above equation (4), the voltage generated in the piezoelectric element due to unwanted resonance can be consumed by the resistor, and the Q value of the optical reflector 1 at the frequency f corresponding to the resonance can be reduced. This makes it possible to suppress unwanted resonance at frequency f.

[0178] Next, the inventor actually constructed the circuit model shown in Figure 31, and in the constructed circuit model, he oscillated the piezoelectric element with predetermined frequencies f and capacitance C, varied the resistance R to several values, and conducted an experiment to calculate the Q value for each resistance R.

[0179] Figure 32 shows the experimental results for the circuit model in Figure 31, illustrating the Q value corresponding to each resistance value R.

[0180] The vertical axis represents the Q value (%) normalized to 100% when the resistor is omitted and both poles of the piezoelectric element are connected to the power supply. The horizontal axis represents the resistance value (%) of the resistor normalized to 100% when the resistance value R obtained in equation (4) above is set to 100%.

[0181] As shown in Figure 32, it was found that the Q value is almost minimized when the resistance value R of the resistor is set to the value obtained by equation (4) above. Therefore, it can be said that by setting the resistance value R of the resistor as shown in equation (4) above, the vibration of the frequency f to be suppressed that occurs in the piezoelectric material having capacitance C can be effectively suppressed.

[0182] Furthermore, the inventors experimentally calculated the amplitude of the swing of the movable part 10 based on the circuit model in Figure 31. In this experiment, the optical reflective element 1 shown in Figure 29 was actually constructed, laser light was incident on the reflective surface 11 of the movable part 10, and the reflected laser light was received by a position detection element (PSD). The amplitude of the swing of the movable part 10 was calculated from the length of the scan line on the light-receiving surface of the position detection element and the distance between the reflective surface 11 and the position detection element. As a result, when the resistance value R was set to the value obtained by the above formula (4), the amplitude was 99.4% of the amplitude when the resistor was omitted. From this, it can be said that even if both the power supply and the resistor are provided in a common circuit as in Embodiment 3, the amplitude of the movable part 10 can be sufficiently maintained.

[0183] In the configuration of Embodiment 3 shown in Figures 29 and 30, since the piezoelectric elements 21 and 23 are connected in parallel, the resistance R of the resistor 503 can be calculated by using the capacitance C in formula (4) above as the sum of the capacitances of the piezoelectric elements 21 and 23. Similarly, the resistance R of the resistor 513 is calculated based on the sum of the capacitances of the piezoelectric elements 22 and 24, the resistance R of the resistor 523 is calculated based on the sum of the capacitances of the piezoelectric elements 32 and 34, and the resistance R of the resistor 533 is calculated based on the sum of the capacitances of the piezoelectric elements 31 and 33.

[0184] Furthermore, since the experimental results in Figure 32 are the same as those in Figure 10(a), it is expected that the simulation results showing the power consumption P for each resistance value R in the circuit model of Figure 31 will be the same as those in Figure 10(b). In other words, in Embodiment 3 as well, similar to Figure 10(b), the power consumption is maximum when the resistance value R is 100%, and when the power consumption is 60% or more, it is expected that the preferred range of resistance value R will be around 20% to 450%. Therefore, in Embodiment 3 as well, by setting the ratio X in the above formula (5) to 0.2 or more and 4.5 or less, it can be said that the power consumption P can be set to approximately 60% or more compared to the maximum value.

[0185] Furthermore, in Embodiment 3, the power consumption P is maximized when the resistance R is 100%, and the resistance R is 100% when equation (4) above is satisfied. Therefore, in equation (5) above, the power consumption P can be maximized by setting the ratio X to 1. Note that even if the ratio X deviates slightly from 1, the power consumption P will be almost maximized. In other words, if the ratio X is substantially set to 1, the power consumption P can be substantially maximized.

[0186] Furthermore, from the viewpoint of efficiently applying the applied voltage to the piezoelectric element and improving the driving efficiency of the movable part 10, it is preferable that the resistance value R of the resistor be as small as possible. In particular, when the movable part 10 is rotated at a high frequency, if the resistance value R is large, the applied voltage distributed to the piezoelectric element decreases and the driving force decreases, making it difficult to improve the responsiveness of the movable part 10. From these viewpoints, it is preferable that the resistance value R be as small as possible, and from the above formula (5), it is preferable that the ratio X is 1 or less.

[0187] However, if the ratio X is small, it becomes difficult to efficiently dissipate the power generated by unwanted vibrations with the resistor, making it difficult to lower the Q value. For this reason, the lower limit of the ratio X needs to be set to a value that can provide a Q value capable of effectively suppressing unwanted vibrations. From this viewpoint, in the configuration of Embodiment 3, it is preferable to set the value of the ratio X in the range of 0.2 or more and 1 or less.

[0188] <Effects of Embodiment 3> According to Embodiment 3, the following effects are achieved.

[0189] The optical reflective element 1 comprises a movable part 10 on which a reflective surface 11 is provided, drive units 20 and 30 that rotate the movable part 10 about a pivot axis R10, piezoelectric elements 21 to 24 and 31 to 34 arranged in the drive units 20 and 30 and serving as the driving source for the drive units 20 and 30, and resistors 503, 513, 523, and 533 that consume the power generated by the distortion of the piezoelectric elements 21 to 24 and 31 to 34 due to the driving of the drive units 20 and 30. The resistors 503, 513, 523, and 533 have a resistance value R corresponding to the frequency f to be suppressed.

[0190] In this configuration, the energy generated by the rotational movement is consumed by resistors 503, 513, 523, and 533 having a resistance R corresponding to the frequency f of the object to be suppressed. This suppresses unwanted vibrations based on the frequency f of the object to be suppressed. Furthermore, in the above configuration, piezoelectric elements 21 to 24 are used not only as driving piezoelectric elements (driving sources for the driving units 20 and 30) but also as damper piezoelectric elements. Therefore, by arranging piezoelectric elements 21 to 24 as driving sources, it becomes unnecessary to arrange separate damper piezoelectric elements. Thus, unwanted vibrations can be effectively suppressed while increasing the degree of design freedom.

[0191] The optical reflective element 1 includes a fixed part 50 that supports the drive units 20 and 30, and the resistors 503, 513, 523, and 533 are thin-film resistors installed on the fixed part 50.

[0192] This configuration prevents the resistors 503, 513, 523, and 533 from affecting the operation of the movable part 10 and the drive parts 20 and 30. Furthermore, by performing laser trimming on the resistors installed in the fixed part 50 during manufacturing, the resistance values ​​R of the resistors 503, 513, 523, and 533 can be adjusted easily and with high precision.

[0193] When the resistance of resistor 503 is R, the frequency to be suppressed is f, and the capacitance based on piezoelectric elements 21 and 23 (capacitance of piezoelectric elements) is C, the ratio X in the following equation is set to be between 0.2 and 4.5. Similarly, for resistor 513 and piezoelectric elements 22 and 24, resistor 523 and piezoelectric elements 32 and 34, and resistor 533 and piezoelectric elements 31 and 33, the ratio X in the following equation is set to be between 0.2 and 4.5. R = X / (2πfC)

[0194] With this configuration, the power consumption P dissipated as heat in resistors 503, 513, 523, and 533 can be set to approximately 60% or more of the maximum value. This effectively suppresses unwanted vibrations.

[0195] The above ratio X is effectively set to 1 or less.

[0196] According to this technology, by setting the ratio X to 1, unwanted vibrations based on the frequency f to be suppressed can be suppressed most effectively. Furthermore, by setting the ratio X to a small value of 1 or less, the applied voltage can be efficiently applied to the piezoelectric body, thereby increasing the driving efficiency of the movable part 10.

[0197] <Example of modification 8> In Embodiment 3, one resistor was placed for each pair of piezoelectric elements, but a resistor may be placed individually for each piezoelectric element.

[0198] Figure 33 is a circuit diagram comprising the optical reflective element 1 according to this modified example.

[0199] In this modified example, compared to Embodiment 3 of Figure 30, resistors 541 and 542 are connected to piezoelectric elements 21 and 23, respectively, and resistors 541 and 542 are connected to the power supply 201. Resistors 551 and 552 are connected to piezoelectric elements 22 and 24, respectively, and resistors 551 and 552 are connected to the power supply 203. Resistors 561 and 562 are connected to piezoelectric elements 32 and 34, respectively, and resistors 561 and 562 are connected to the power supply 202. Resistors 571 and 572 are connected to piezoelectric elements 31 and 33, respectively, and resistors 571 and 572 are connected to the power supply 204. The resistance value R of each resistor is calculated by taking the capacitance C in the above formula (4) as the capacitance of the corresponding piezoelectric element.

[0200] In this way, by individually placing resistors for each piezoelectric element, it becomes possible to flexibly suppress unwanted vibrations by adjusting the resistance value of each resistor. This allows for the suppression of unwanted vibrations not only at the frequency to be suppressed, but also by targeting specific other vibration modes.

[0201] For example, in the optical reflective element 1, there may be other vibration modes in which only the piezoelectric cantilever on which the piezoelectric elements 22, 23, 32, and 33 are arranged moves, while the piezoelectric cantilever on which the piezoelectric elements 21, 24, 31, and 34 are arranged does not move. Even in such cases, according to this modified example, since resistors are individually arranged for each piezoelectric element, these other vibration modes can be appropriately suppressed by adjusting the resistance values ​​R of the resistors 542, 551, 561, and 572.

[0202] In other words, as shown in Figure 32, by setting the resistance value R based on the above equation (4), the Q value based on the frequency f to be suppressed can be effectively suppressed by about 40%. However, even when a resistance value that is shifted by about 20% to 500% from this resistance value R is set, the Q value based on the oscillation of frequency f can be suppressed by about 40% to 60%. Furthermore, when the resistance value fluctuates by about 20% to 500% from the above resistance value R, the frequency f' that can be most suppressed by this resistance value also fluctuates by about 20% to 500% from frequency f.

[0203] Therefore, if the frequency f' of other vibration modes is within a range of approximately 20% to 500% of the frequency f of the vibration to be suppressed, both the Q value based on the vibration at frequency f and the Q value based on the other vibration modes at frequency f' can be suppressed to a range of approximately 60% or less. Thus, by individually adjusting the resistance value of the resistor according to the frequencies f and f' to be suppressed, as described above, it is possible to suppress the frequency f of the vibration to be suppressed while also suppressing specific vibration modes.

[0204] In addition, in embodiments 1 and 2 and modifications 1 to 7, resistors may be individually placed on the piezoelectric element for the damper, and the resistance value of each resistor may be adjusted based on equation (4) above, according to either the frequency f of the suppression target or the frequency f' of other vibration modes.

[0205] <Embodiment 4> In Embodiment 3, the resistors 503, 513, 523, and 533 were provided on the fixed portion 50 of the optical reflective element 1. In contrast, in Embodiment 4, these resistors are provided on the outside of the optical reflective element 1 (for example, on the substrate 300).

[0206] Figure 34 is a circuit diagram of the optical reflector 2 according to this embodiment.

[0207] In this embodiment, resistors 503, 513, 523, and 533 are provided on the substrate 300, and power supplies 201 to 204 are provided on the control circuit 400. Similar to Embodiment 2 shown in Figure 25, the optical reflective device 2 is composed of the optical reflective element 1, the substrate 300, and the control circuit 400. In this embodiment as well, the same circuit as in Embodiment 3 shown in Figure 30 is configured.

[0208] <Effects of Embodiment 4> According to Embodiment 4, the following effects are achieved.

[0209] The optical reflective device 2 comprises an optical reflective element 1 similar to that in Embodiment 3, and resistors 503, 513, 523, and 533 arranged outside the optical reflective element 1, which consume power generated by the distortion of piezoelectric elements 21-24 and 31-34 due to the driving of drive units 20 and 30. The resistors 503, 513, 523, and 533 have a resistance value R corresponding to the frequency f to be suppressed.

[0210] This configuration provides the same effects as in Embodiment 3. Furthermore, since the resistors 503, 513, 523, and 533 are not provided on the optical reflective element 1, the manufacturing process of the optical reflective element 1 becomes easier compared to the case where these resistors are provided on the optical reflective element 1.

[0211] In Embodiment 4, as in Modified Example 8, resistors may be individually placed on each piezoelectric element, and the resistance value of each resistor may be adjusted based on equation (4) according to either the frequency f of the suppression target or the frequency f' of the other vibration mode.

[0212] <Other Modification Examples> In the above embodiments and modifications, the layout of the electrode sections 60 and 70 is not limited to those described above. For example, the electrode sections 60 and 70 may be arranged together on the negative or positive side of the X-axis of the fixed section 50. In this case, in embodiments 1 and 2 and modifications 1 to 7, the piezoelectric driving elements driven in the same phase may be connected to each other, and piezoelectric damper elements driven in the same phase may be connected to each other. In embodiments 3 and 4 and modification 8, piezoelectric elements driven in the same phase may be connected to each other.

[0213] In the above embodiment 2 and modified example 7, if the circuits in Figures 26 and 27 are configured, the power supplies 201 and 202, resistors 321 and 322, and switching circuits 411, 412, 421 and 422 may be provided on either the circuit board 300 or the control circuit 400. In the above embodiment 4, if the circuit in Figure 34 is configured, the power supplies 201 and 202 and resistors 503, 513, 523 and 533 may be provided on either the circuit board 300 or the control circuit 400.

[0214] In Embodiment 2 and Modified Example 7 described above, the optical reflective device 2 is equipped with an optical reflective element 1 similar to that of Embodiment 1 in Figure 1, but it may also be equipped with an optical reflective element 1 of Modified Examples 1 to 6.

[0215] In the above embodiments and modifications, the piezoelectric body consisted only of a lower electrode layer 111, a piezoelectric layer 112, and an upper electrode layer 113, but other layers may be included between each layer. Also, in plan view, the drive units 20 and 30 had meander shapes, but they may have other shapes.

[0216] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea set forth in the claims.

[0217] (Note) The above description of embodiments discloses the following technologies.

[0218] (Technology 1) An optical reflective element comprising: a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element that generates power corresponding to the strain caused by the rotation of the movable part; and a resistor connected to the piezoelectric element and consuming the power generated by the piezoelectric element, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0219] Generally, the Q-factor decreases when energy generated by rotational motion is consumed. In contrast, according to the above technology, the energy generated by rotational motion is consumed by a resistor having a resistance value corresponding to the frequency to be suppressed. That is, electricity is generated from the piezoelectric element in response to the rotation of the movable part, and the electricity generated from the piezoelectric element is consumed as heat by the resistor. This suppresses unwanted vibrations based on the frequency to be suppressed. Furthermore, in the above technology, the piezoelectric element and the resistor only need to be set and arranged so that electricity is consumed in response to the rotation of the movable part. Therefore, unwanted vibrations can be effectively suppressed while increasing the degree of design freedom.

[0220] (Technology 2) An optical reflective element as described in Technology 1, characterized in that the piezoelectric element is installed in the drive unit.

[0221] According to this technology, the piezoelectric element is installed in the drive unit, which is subjected to greater distortion than other parts of the optical reflective element during rotation of the movable part. Therefore, the piezoelectric element can generate a relatively large amount of power. This effectively suppresses unwanted vibrations.

[0222] (Technology 3) An optical reflective element according to Technology 1 or 2, characterized in that the piezoelectric material is installed on a plate-shaped portion connected to the drive unit.

[0223] This technology allows for easy placement of piezoelectric elements by utilizing the space surrounding the drive unit. Furthermore, air resistance is generated on the plate-like portion during the rotation of the movable part, which can more effectively suppress unwanted vibrations.

[0224] (Technical 4) An optical reflective element according to any one of Technical 1 to 3, characterized in that the piezoelectric material is installed on a plate-shaped part connected to the movable part.

[0225] This technology allows for easy placement of piezoelectric elements by utilizing the space surrounding the movable part. Furthermore, because relatively large piezoelectric elements can be placed in the space surrounding the movable part, air resistance is generated on the plate-like portion when the movable part rotates, which can more effectively suppress unwanted vibrations.

[0226] (Technology 5) An optical reflective element according to any one of Technology 1 to 4, wherein the drive unit includes a piezoelectric body for driving the drive unit, the piezoelectric body for power generation and the piezoelectric body for driving each include a lower electrode layer, a piezoelectric body layer and an upper electrode layer, and each layer of the piezoelectric body for power generation and each layer of the piezoelectric body for driving are made of the same material.

[0227] This technology allows for the formation of both the piezoelectric element for power generation and the piezoelectric element for driving during manufacturing using the same process.

[0228] (Technical 6) An optical reflective element according to any one of Technical 1 to 5, characterized in that it comprises a fixed part that supports the drive unit, and the resistor is a thin film resistor installed on the fixed part.

[0229] This technology prevents the resistor from affecting the operation of the movable and drive parts. Furthermore, by performing laser trimming on the resistor installed in the fixed part during manufacturing, the resistance value of the resistor can be adjusted easily and with high precision.

[0230] (Technology 7) An optical reflective element according to any one of Technology 1 to 6, wherein when the resistance value of the resistor is R, the frequency to be suppressed is f, and the capacitance of the piezoelectric element is C, the ratio X in the following formula is set to 0.2 or more and 4.5 or less, characterized in that R = X / (2πfC).

[0231] This technology allows the power consumption dissipated as heat in the resistor to be set to approximately 60% or more of its maximum value. This effectively suppresses unwanted vibrations.

[0232] (Technical 8) An optical reflective element as described in Technical 7, characterized in that the ratio X is set to substantially 1.

[0233] This technology allows for the most effective suppression of unwanted vibrations based on the target frequency f.

[0234] (Technical 9) An optical reflective element according to any one of Technical 1 to 8, characterized in that the piezoelectric material is installed in a region that vibrates with substantially the same phase in a resonance mode based on the frequency to be suppressed.

[0235] This technology suppresses the cancellation of charges within a piezoelectric material, allowing for efficient charge generation. Therefore, the electrical energy based on these charges can be efficiently dissipated in the resistor.

[0236] (Technical 10) An optical reflective element according to any one of Technical 1 to 9, wherein the piezoelectric material is installed in multiple regions that vibrate with substantially the same phase in a resonance mode based on the frequency to be suppressed, and the multiple piezoelectric materials installed in the multiple regions are electrically connected to each other.

[0237] According to this technology, multiple piezoelectric elements, each positioned in multiple regions vibrating with the same phase, are electrically connected to one another. This allows the electrical energy generated by the charges produced by the multiple piezoelectric elements to be efficiently dissipated in the resistor. Furthermore, since there is no need to place a resistor for each of the multiple piezoelectric elements, the optical reflective element can be constructed simply.

[0238] (Technical 11) An optical reflective element according to any one of Technical 1 to 10, characterized in that the piezoelectric material is installed in a first region and a second region, respectively, in which, among a plurality of resonance modes based on the frequency to be suppressed, the piezoelectric material vibrates with different phases in one of the resonance modes and vibrates with substantially the same phase in the other resonance modes.

[0239] According to this technology, in the case of one resonance mode, the Q value for that resonance mode can be suppressed by consuming the power generated by piezoelectric elements installed in the first and second regions, respectively, which vibrate at different phases. In the case of other resonance modes, the Q value for those other resonance modes can be suppressed by consuming the power generated by piezoelectric elements installed in the first and second regions, respectively, which vibrate at substantially the same phase. In other words, according to the above technology, multiple resonance modes based on the frequency to be suppressed can be suppressed.

[0240] (Technical 12) An optical reflective element according to any one of Technical 1 to 11, wherein the piezoelectric body includes a lower electrode layer, a piezoelectric layer, and an upper electrode layer, and a plurality of piezoelectric bodies are arranged adjacent to each other with a gap between them, and the upper electrode layer of one piezoelectric body and the upper electrode layer of the other piezoelectric body are separated by the gap, and the piezoelectric layer and the lower electrode layer of one piezoelectric body are integrally formed with the piezoelectric layer and the lower electrode layer of the other piezoelectric body, respectively.

[0241] According to this technology, two adjacent piezoelectric elements can be formed in a piezoelectric material, which includes an upper electrode layer, a piezoelectric layer, and a lower electrode layer, simply by processing the upper electrode layer so that it is spaced apart from each other. Therefore, two adjacent piezoelectric elements can be formed with high precision.

[0242] (Technical 13) An optical reflective element according to any one of Technical 1 to 12, wherein the drive unit includes a piezoelectric body for driving the drive unit, the piezoelectric body for power generation and the piezoelectric body for driving each include a second piezoelectric body including a lower electrode layer, a piezoelectric layer and an upper electrode layer, the piezoelectric body for power generation and the piezoelectric body for driving are arranged adjacent to each other with a gap between them, the upper electrode layer of the piezoelectric body for power generation and the upper electrode layer of the piezoelectric body for driving are separated by the gap, and the piezoelectric layer and the lower electrode layer of the piezoelectric body for power generation are integrally formed with the piezoelectric layer and the lower electrode layer of the piezoelectric body for driving, respectively.

[0243] According to this technology, by processing a piezoelectric material consisting of an upper electrode layer, a piezoelectric layer, and a lower electrode layer so that the upper electrode layer is spaced apart from each other, adjacent piezoelectric elements for power generation and driving can be formed. Therefore, adjacent piezoelectric elements for power generation and driving can be formed with high precision.

[0244] (Technical 14) An optical reflective device comprising: an optical reflective element having a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element that generates power corresponding to the strain caused by the rotation of the movable part; and a resistor disposed outside the optical reflective element, connected to the piezoelectric element, and consuming the power generated by the piezoelectric element, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0245] This technology eliminates the need for a resistor in the optical reflective element, thus simplifying the manufacturing process for the optical reflective element compared to cases where a resistor is present.

[0246] (Technical 15) An optical reflective device as described in Technical 14, characterized in that it comprises a substrate on which the optical reflective element is installed, and the resistor is installed on the substrate.

[0247] This technology allows the resistor to be mounted on a relatively large substrate compared to an optical reflective element, making the installation of the resistor easier.

[0248] (Technical 16) An optical reflective device as described in Technical 14, characterized in that it comprises a control circuit for controlling the drive unit, and the resistor is installed in the control circuit.

[0249] (Technical 17) An optical reflective device according to Technical 15 or 16, wherein the control circuit comprises a switching circuit, a plurality of piezoelectric elements are arranged in the drive unit, and the switching circuit switches the piezoelectric elements between a state in which they are electrically connected to the resistor and a state in which they are connected to a power supply.

[0250] This technology allows each piezoelectric element to be periodically set to either a power-generating piezoelectric element or a driving piezoelectric element by controlling the switching circuit. Therefore, the driving efficiency of the movable parts can be improved.

[0251] (Technical 18) An optical reflective element comprising: a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element disposed in the drive unit and serving as a drive source for the drive unit; and a resistor that consumes power generated by the distortion of the piezoelectric element due to the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0252] According to this technology, the energy generated by rotational motion is consumed by a resistor having a resistance value corresponding to the frequency to be suppressed. This suppresses unwanted vibrations based on the frequency to be suppressed. Furthermore, in the above technology, the piezoelectric element is used not only as a driving piezoelectric element (the driving source for the driving unit) but also as a damping piezoelectric element. Therefore, by arranging the piezoelectric element as a driving source, it becomes unnecessary to arrange a separate piezoelectric damper. Thus, unwanted vibrations can be effectively suppressed while increasing the degree of design flexibility.

[0253] (Technical 19) An optical reflective element as described in Technical 18, characterized in that it comprises a fixed part that supports the drive unit, and the resistor is a thin-film resistor installed on the fixed part.

[0254] This technology prevents the resistor from affecting the operation of the movable and drive parts. Furthermore, by performing laser trimming on the resistor installed in the fixed part during manufacturing, the resistance value of the resistor can be adjusted easily and with high precision.

[0255] (Technical 20) An optical reflective element according to Technical 18 or 19, characterized in that when the resistance value of the resistor is R, the frequency to be suppressed is f, and the capacitance of the piezoelectric element is C, the ratio X in the following formula is set to 0.2 or more and 4.5 or less: R = X / (2πfC).

[0256] This technology allows the power consumption dissipated as heat in the resistor to be set to approximately 60% or more of its maximum value. This effectively suppresses unwanted vibrations.

[0257] (Technical 21) An optical reflective element as described in Technical 20, characterized in that the ratio X is set to substantially 1 or less.

[0258] According to this technology, setting the ratio X to 1 allows for the most effective suppression of unwanted vibrations based on the target frequency f. Furthermore, setting the ratio X to a small value less than 1 allows for efficient application of the voltage to the piezoelectric element, thereby increasing the driving efficiency of the movable part.

[0259] (Technical 22) An optical reflective device comprising: an optical reflective element having a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element disposed in the drive unit and serving as a drive source for the drive unit; and a resistor disposed outside the optical reflective element and consuming power generated by the distortion of the piezoelectric element due to the drive of the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

[0260] This technology eliminates the need for a resistor in the optical reflective element, thus simplifying the manufacturing process for the optical reflective element compared to cases where a resistor is present.

[0261] 1 Optical reflective element 2 Optical reflective device 10 Movable part 11 Reflective surface 20, 30 Drive unit 20a, 30a Piezoelectric cantilever (region) 21-24, 31-34, 81-84, 91-94, 211, 221, 231-234 Piezoelectric body 50 Fixed part 65, 75 Resistor 111 Lower electrode layer 112 Piezoelectric layer 113 Upper electrode layer 201, 202, 203, 204 Power supply 210, 220 Plate-shaped part (region) 230 Plate-shaped part 300 Substrate 321, 322 Resistor 400 Control circuit 411, 412, 421, 422 Switching circuit 503, 513, 523, 533, 541, 542, 551, 552, 561, 562, 571, 572 Resistor R10 Rotary shaft

Claims

1. An optical reflective element comprising: a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element that generates power corresponding to the strain caused by the rotation of the movable part; and a resistor connected to the piezoelectric element and consuming the power generated by the piezoelectric element, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

2. An optical reflective element according to claim 1, characterized in that the piezoelectric element is installed in the drive unit.

3. An optical reflective element according to claim 1, characterized in that the piezoelectric material is installed on a plate-shaped portion connected to the drive unit.

4. An optical reflective element according to claim 1, characterized in that the piezoelectric element is installed on a plate-shaped portion connected to the movable portion.

5. An optical reflective element according to claim 1, wherein the drive unit includes a piezoelectric body for driving the drive unit, and both the piezoelectric body for power generation and the piezoelectric body for driving include a lower electrode layer, a piezoelectric body layer, and an upper electrode layer, and each layer of the piezoelectric body for power generation and each layer of the piezoelectric body for driving are made of the same material.

6. An optical reflective element according to claim 1, wherein it comprises a fixed portion that supports the drive portion, and the resistor is a thin-film resistor installed on the fixed portion.

7. An optical reflective element according to claim 1, wherein when the resistance value of the resistor is R, the frequency to be suppressed is f, and the capacitance of the piezoelectric element is C, the ratio X in the following formula is set to be 0.2 or more and 4.5 or less: R = X / (2πfC).

8. An optical reflective element according to claim 7, characterized in that the ratio X is set to substantially 1.

9. An optical reflective element according to claim 1, characterized in that the piezoelectric element is installed in a region that vibrates with substantially the same phase in a resonance mode based on the frequency to be suppressed.

10. An optical reflective element according to claim 1, wherein the piezoelectric elements are arranged in multiple regions that vibrate with substantially the same phase in a resonance mode based on the frequency to be suppressed, and the multiple piezoelectric elements arranged in the multiple regions are electrically connected to each other.

11. An optical reflective element according to claim 1, wherein the piezoelectric material is installed in a first region and a second region, respectively, in which, among a plurality of resonance modes based on the frequency to be suppressed, the piezoelectric material vibrates with different phases in one of the resonance modes and vibrates with substantially the same phase in the other resonance modes.

12. An optical reflective element according to claim 1, wherein the piezoelectric body includes a lower electrode layer, a piezoelectric layer, and an upper electrode layer, and a plurality of piezoelectric bodies are arranged adjacent to each other with a gap between them, the upper electrode layer of one piezoelectric body and the upper electrode layer of the other piezoelectric body are separated by the gap, and the piezoelectric layer and the lower electrode layer of one piezoelectric body are integrally formed with the piezoelectric layer and the lower electrode layer of the other piezoelectric body.

13. An optical reflective element according to claim 1, wherein the drive unit includes a piezoelectric body for driving the drive unit, the piezoelectric body for power generation and the piezoelectric body for driving each include a second piezoelectric body including a lower electrode layer, a piezoelectric layer, and an upper electrode layer, the piezoelectric body for power generation and the piezoelectric body for driving are arranged adjacent to each other with a gap between them, the upper electrode layer of the piezoelectric body for power generation and the upper electrode layer of the piezoelectric body for driving are separated by the gap, and the piezoelectric layer and the lower electrode layer of the piezoelectric body for power generation are integrally formed with the piezoelectric layer and the lower electrode layer of the piezoelectric body for driving, respectively.

14. An optical reflective element comprising: a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element disposed in the drive unit and serving as a drive source for the drive unit; and a resistor that consumes power generated by the distortion of the piezoelectric element due to the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

15. An optical reflective element according to claim 14, wherein it comprises a fixed portion that supports the drive portion, and the resistor is a thin-film resistor installed on the fixed portion.

16. An optical reflective element according to claim 14, wherein when the resistance value of the resistor is R, the frequency to be suppressed is f, and the capacitance of the piezoelectric element is C, the ratio X in the following formula is set to be 0.2 or more and 4.5 or less: R = X / (2πfC).

17. An optical reflective element according to claim 16, characterized in that the ratio X is set to substantially 1 or less.

18. An optical reflective device comprising: an optical reflective element having a movable part provided with a reflective surface; a drive unit for rotating the movable part about a pivot axis; a piezoelectric element disposed in the drive unit and serving as a drive source for the drive unit; and a resistor disposed outside the optical reflective element and consuming power generated by the distortion of the piezoelectric element due to the drive of the drive unit, wherein the resistor has a resistance value corresponding to the frequency to be suppressed.

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