Vibration module and light deflector

Abstract

A drive element (1) is provided with: a movable part (11); a drive part (12); a fixing part (15); and a plurality of electrode pads (16a) that are installed on the upper surface of the fixing part (15) and connected to the drive part (12). A plurality of electrode pads (21a) are arranged at positions facing the plurality of electrode pads (16a) on the lower surface of a support substrate (2). The upper surface of the fixing part (15) is fixed to the lower surface of the support substrate (2) by an adhesive (23) in which elastic modulus decreases as the temperature rises in a plurality of portions that are discrete from each other. The plurality of portions include a portion corresponding to an antinode of vibrations of the fixing part (15) that occur during the resonant drive of the movable part (11). The electrode pads (16a, 21a) serving as a set are connected to each other at any of the plurality of portions.

Description

Vibration module and optical deflector

[0001] The present invention relates to a vibration module that rotates a movable part about a rotation axis, and an optical deflector that includes the vibration module.

[0002] In recent years, drive elements that rotate a movable part using MEMS (Micro Electro Mechanical System) technology have been developed. In this type of drive element, a reflective surface is disposed on the movable part, so that light incident on the reflective surface can be scanned at a predetermined deflection angle. This type of drive element is mounted, for example, on image display devices such as head-up displays and head-mounted displays. In addition, this type of drive element can also be used in laser radars that detect objects using laser light.

[0003] The following Patent Document 1 describes a driving element that rotates a movable part using a so-called tuning fork vibrator. In this driving element, a piezoelectric element is disposed on each of a pair of arms extending along a rotation axis. When AC voltages with a phase difference of 180° (opposite phases) are applied to the piezoelectric elements, the pair of arms expand and contract in opposite directions. This causes the movable part to rotate about the rotation axis, and accordingly, a reflecting surface disposed on the movable part rotates. The tuning fork vibrator is connected to a frame-shaped fixed part via a connecting part extending along the rotation axis.

[0004] Patent No. 5045470

[0005] In the driving element having the above configuration, the piezoelectric element is driven so that the movable part rotates repeatedly at a natural resonant frequency. However, the driving amount (static displacement) of the piezoelectric element when a constant voltage is applied changes with temperature. Therefore, even if the same driving voltage is applied to the piezoelectric element, the deflection angle of the movable part during resonant driving changes with temperature.

[0006] Furthermore, in the drive element having the above configuration, for example, the lower surface of the frame-shaped fixing part is fixed to the substrate, and the drive element is installed on the substrate. Then, the connection terminals of the drive element are connected to the circuit on the substrate by wire bonding. However, in this case, the arrangement of the wire bonding increases the size of the entire configuration.

[0007] In view of these problems, the present invention aims to provide a vibration module and an optical deflector that can reduce the size of the overall configuration while suppressing changes in the swing angle of the movable part due to changes in the static displacement of the piezoelectric element caused by temperature changes.

[0008] A first aspect of the present invention relates to a vibration module. The vibration module according to this aspect includes a drive element and a support substrate supporting the drive element. The drive element includes a movable part, a drive unit that rotates the movable part about a rotation axis, a fixed part that supports the movable part and the drive unit and is fixed to the support substrate, and a plurality of first electrode pads installed on an upper surface of the fixed part and connected to the drive unit by a wiring pattern. A plurality of second electrode pads are arranged on a lower surface of the support substrate at positions facing the plurality of first electrode pads, respectively. The upper surface of the fixed part is fixed to the lower surface of the support substrate at a plurality of mutually separated portions with an adhesive whose elastic modulus decreases with increasing temperature, the plurality of portions including portions corresponding to antinodes of vibration generated on the fixed part when the movable part is resonantly driven, and each pair of the first electrode pad and the second electrode pad are connected to each other at any of the plurality of portions.

[0009] In the vibration module according to this aspect, the elastic modulus of the adhesive decreases with increasing temperature, making the portion of the fixed portion fixed with the adhesive corresponding to the vibration antinode more susceptible to vibration with increasing temperature. Therefore, with increasing temperature, the loss of vibration energy at the vibration antinode increases, reducing the Q value of the vibration module. As a result, the increase in static displacement and the decrease in Q value with increasing temperature act in opposite directions, thereby suppressing changes in the output of the vibration module with temperature changes. This suppresses changes in the deflection angle of the movable portion due to temperature changes. Furthermore, because the first electrode pad and the second electrode pad are connected to each other, the support substrate and the fixed portion can be electrically connected without using a separate wiring method such as wire bonding. This allows the overall configuration of the vibration module to be miniaturized.

[0010] A second aspect of the present invention relates to an optical deflector, which includes the vibration module according to the first aspect and a reflecting surface disposed on the movable part.

[0011] Since the optical deflector according to this aspect includes the vibration module according to the first aspect, the optical deflector according to this aspect can suppress changes in the deflection angle of the movable part and the reflecting surface due to temperature changes, thereby enabling the light incident on the reflecting surface to be stably deflected and scanned at a predetermined deflection angle.

[0012] As described above, according to the present invention, it is possible to provide a vibration module and an optical deflector that can suppress changes in the swing angle of the movable part due to changes in the static displacement of the piezoelectric element caused by temperature changes while miniaturizing the overall configuration.

[0013] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0014] FIG. 1 is a perspective view showing the configuration of a drive element according to the first embodiment. FIG. 2 is a perspective view of the drive element according to the first embodiment, as viewed from the bottom side. FIG. 3 is a perspective view showing the configuration of a support substrate according to the first embodiment. FIG. 4 is a perspective view showing the assembly of a vibration module according to the first embodiment. FIG. 5 is a plan view showing an example of mounting a vibration module (optical deflector) according to the first embodiment. FIG. 6 is a cross-sectional view of a cross section of a vibration module (optical deflector) installed in a housing according to the first embodiment, viewed in the negative X-axis direction. FIG. 7 is a perspective view showing an example of a usage form of the vibration module (optical deflector) of FIG. 5 according to the first embodiment. FIG. 8 is a graph showing measurement results of static displacement of a piezoelectric body for each temperature according to the first embodiment. FIG. 9 is a diagram showing simulation results of vibration in the Z-axis direction generated in a fixed part when a movable part is resonantly driven according to the first embodiment. FIG. 10 is a plan view showing the configuration of a vibration module (optical deflector) according to the first embodiment. FIG. 11 is a cross-sectional view of the C1-C2 cross section shown in FIG. 10 as viewed in the negative X-axis direction, according to the first embodiment. FIGS. 12(a) and 12(b) are diagrams illustrating a verification example in which vibrations in the Z-axis direction occurring in the fixed portion are measured when a drive element secured by the securing method shown in FIGS. 10 and 11 according to the first embodiment is actually resonantly driven. FIG. 13(a) is a graph schematically illustrating the ideal relationship between the change in static displacement of the vibration module with temperature and the change in the Q value of the vibration module with temperature, according to the first embodiment. FIG. 13(b) is a graph schematically illustrating the temperature characteristics of the deflection angle of the movable portion and the reflecting surface during resonant driving when the static displacement and the Q value have the ideal relationship shown in FIG. 13(a), according to the first embodiment. FIG. 14 is a cross-sectional view of the C1-C2 cross section shown in FIG. 10 as viewed in the negative X-axis direction, according to a modification of the securing method of the first embodiment. FIG. 15 is a plan view illustrating the configuration of a vibration module (optical deflector) according to a first modification of the first embodiment. Fig. 16 is a plan view showing the configuration of a vibration module (optical deflector) according to Modification 2 of Embodiment 1. Fig. 17 is a plan view showing the configuration of a vibration module (optical deflector) according to Modification 3 of Embodiment 1. Fig. 18 is a perspective view showing the configuration of a drive element according to Embodiment 2.Fig. 19(a) is a diagram showing the configuration of a drive element used in a simulation for resonantly driving a movable part according to embodiment 2. Fig. 19(b) is a diagram showing simulation results according to embodiment 2. Fig. 20 is a plan view showing the configuration of a vibration module (optical deflector) according to embodiment 2. Fig. 21 is a plan view showing the configuration of a vibration module (optical deflector) according to embodiment 3.

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

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with X, Y, and Z axes that are orthogonal to each other. The Y axis direction is parallel to the rotation axis of the drive element, and the Z axis direction is the thickness direction of the drive element.

[0017] First Embodiment FIG. 1 is a perspective view showing the configuration of a driving element 1, and FIG. 2 is a perspective view of the driving element 1 as viewed from the bottom side (Z-axis negative side).

[0018] The driving element 1 includes a movable portion 11, two driving portions 12, two torsion portions 13, two connecting portions 14, and a fixed portion 15. The driving element 1 has a rectangular outline in a plan view. The driving element 1 has a shape that is symmetrical in the Y-axis direction and in the X-axis direction about the center of the movable portion 11.

[0019] The movable portion 11 is supported by the fixed portion 15 via two torsion portions 13 and two connecting portions 14 so as to be rotatable about a rotation axis R0. The rotation axis R0 extends parallel to the length direction (Y axis direction) of the drive element 1 at the midpoint in the width direction (X axis direction) of the drive element 1. A reflective surface 11a is formed on the upper surface (the surface on the positive side of the Z axis) of the movable portion 11. The reflective surface 11a is formed by laminating a highly reflective material (e.g., metals or metal compounds such as gold, silver, copper, or aluminum, or silicon dioxide or titanium dioxide) on the upper surface of the movable portion 11. The reflective surface 11a may be formed of a dielectric multilayer film. Alternatively, the reflective surface 11a may be formed by the upper surface of the movable portion 11. In this case, the reflective surface may be formed by mirror-finishing the upper surface of the movable portion 11.

[0020] The two torsion sections 13 have a beam-like shape extending along the rotation axis R0 and are arranged to sandwich the movable section 11 in the Y-axis direction. One end of the torsion section 13 on the Y-axis positive side is connected to the side surface of the movable section 11 on the Y-axis positive side, and the other end is connected to the connecting section 14 on the Y-axis positive side. One end of the torsion section 13 on the Y-axis negative side is connected to the side surface of the movable section 11 on the Y-axis negative side, and the other end is connected to the connecting section 14 on the Y-axis negative side.

[0021] The two connecting portions 14 have a plate-like shape extending along the rotation axis R0. The connecting portions 14 connect the drive portion 12 and the torsion portion 13 to the fixed portion 15.

[0022] The two driving units 12 each include a piezoelectric element 12b as a driving source and rotate the movable unit 11 about a rotation axis R0. Each of the two driving units 12 is formed by a tuning fork vibrator. That is, the two driving units 12 are formed by arranging the two tuning fork vibrators in opposite directions along the rotation axis R0.

[0023] Each drive unit 12 includes a pair of arm units 12a extending in an L-shape from the connecting unit 14. A piezoelectric element 12b for driving the movable unit 11 is disposed on the upper surface of the portion of each arm unit 12a extending in the Y-axis direction. In addition, a piezoelectric element 12c for detecting the vibration state of the arm unit 12a is disposed near the base of each arm unit 12a.

[0024] The piezoelectric bodies 12b and 12c have a laminated structure in which an upper electrode layer and a lower electrode layer are respectively arranged above and below a piezoelectric thin film of a predetermined thickness. The piezoelectric thin film is made of a piezoelectric material with a high piezoelectric constant, such as lead zirconate titanate (PZT). The material of the piezoelectric thin film is not limited to PZT, and piezoelectric materials with other compositions may also be used. The upper electrode layer and the lower electrode layer are made of a material with low electrical resistance and high heat resistance, such as platinum (Pt) or gold (Au). The piezoelectric bodies 12b and 12c are formed on the upper surface of the arm portion 12a by a method such as sputtering.

[0025] The fixed portion 15 has a rectangular frame shape in a plan view. The outer periphery of the fixed portion 15 forms the outer periphery of the drive element 1. The fixed portion 15 supports the movable portion 11, the drive portion 12, and the torsion portion 13 via two connecting portions 14. The fixed portion 15 is fixed to the support substrate 2 (see FIG. 3 ), as described below.

[0026] Four terminals 16 are arranged on the upper surface of the fixed portion 15. Each terminal 16 is connected to the corresponding piezoelectric element 12b, 12c via two wirings 16b. Similar to the piezoelectric elements 12b, 12c, the wirings 16b have a laminated structure in which an upper electrode layer and a lower electrode layer are arranged above and below a piezoelectric thin film. The upper surface of each terminal 16 is provided with two electrode pads 16a connected to the upper electrode layer of the corresponding piezoelectric element 12b, 12c, and one electrode pad 16a connected to the lower electrode layer of the corresponding piezoelectric element 12b, 12c for connecting the lower electrode layer to ground. Each electrode pad 16a is exposed upward. An insulating protective film is arranged on the upper surface of the terminal 16 in the region other than the electrode pads 16a, the upper surface of the wirings 16b, and the upper surfaces of the piezoelectric elements 12b, 12c.

[0027] The driving element 1 is formed by removing the material layer 1b by etching or the like from an integral structure consisting of a substrate 1a of a predetermined thickness and a material layer 1b so as to leave a region corresponding to the fixed portion 15. This increases the mechanical strength of the fixed portion 15.

[0028] The material of the material layer 1b may be different from that of the base material 1a, or may be the same as that of the base material 1a. The driving element 1 may also be configured by laminating the material layer 1b on the lower surface of a base material 1a having a predetermined thickness. In this case, the material layer 1b is laminated only in the region corresponding to the fixed portion 15.

[0029] The substrate 1a has the same contour as the drive element 1 in a plan view and a constant thickness. A reflecting surface 11a, piezoelectric elements 12b and 12c, terminal portion 16, electrode pads 16a, and wiring 16b are arranged in corresponding regions on the top surface of the substrate 1a. The substrate 1a is also removed by etching or the like so as to leave the movable portion 11, drive portion 12, torsion portion 13, and connecting portion 14, thereby forming the movable portion 11, drive portion 12, torsion portion 13, and connecting portion 14 on the substrate 1a. The area of ​​the substrate 1a other than the movable portion 11, drive portion 12, torsion portion 13, and connecting portion 14 forms an opening 15a that penetrates vertically.

[0030] The substrate 1a is integrally formed from, for example, silicon (Si). However, the material constituting the substrate 1a is not limited to silicon (Si) and may be other materials. The material constituting the substrate 1a is preferably a material with high mechanical strength and Young's modulus. The same applies to the material of the material layer 1b.

[0031] When the drive element 1 is driven, an AC voltage is applied to the four piezoelectric bodies 12b to resonantly drive the movable part 11 at the natural frequency (resonance frequency) of the drive element 1. As a result, each of the four piezoelectric bodies 12b deforms due to the inverse piezoelectric effect. At this time, the AC voltage applied to two piezoelectric bodies 12b aligned in the Y-axis direction is set to the same phase, and the AC voltage applied to two piezoelectric bodies 12b aligned in the X-axis direction is set to the opposite phase. As a result, the deformation direction (amplitude direction) of the two piezoelectric bodies 12b on the positive side of the X-axis is opposite to the deformation direction (amplitude direction) of the piezoelectric body 12b on the negative side of the X-axis. In this way, the deformation of the four piezoelectric bodies 12b deforms the arm portion 12a, and the movable part 11 is resonantly driven around the rotation axis R0 at a predetermined resonant frequency via the two torsion portions 13.

[0032] The four piezoelectric elements 12c for vibration detection generate electric currents due to the piezoelectric effect in response to the deformation of the corresponding arms 12a. Therefore, the vibration state of the arms 12a can be monitored from these electric currents. An external drive circuit connected to the support substrate 2 (described later) uses these electric currents to control the AC voltages applied to the piezoelectric elements 12b so that the amplitude, frequency, and phase of each arm 12a converge to their respective target values. This causes the movable element 11 and the reflecting surface 11a to rotate at the target resonant frequency and deflection angle.

[0033] Fig. 3 is a perspective view showing the configuration of the support substrate 2. Fig. 3 is a perspective view of the support substrate 2 when viewed from the bottom surface side (Z-axis negative side).

[0034] The support substrate 2 has a frame shape with a rectangular outline in a plan view. An opening 2a is formed in the support substrate 2, penetrating the support substrate 2 in the Z-axis direction. The opening 2a has a rectangular shape in a plan view. Four screw holes 2b are formed in the corners of the support substrate 2, penetrating the support substrate 2 in the Z-axis direction. The support substrate 2 is made of a material with a high elastic modulus, such as a glass epoxy substrate, a paper phenol substrate, a ceramic substrate, or a glass substrate.

[0035] Four terminals 21 are arranged on the lower surface (negative surface of the Z-axis) of the support substrate 2. Each terminal 21 has three electrode pads 21a exposed downward (in the negative Z-axis direction). The electrode pads 21a are made of a metal with high electrical conductivity, such as copper (Cu) or gold (Au). Each electrode pad 21a in the two terminals 21 is connected to a connection terminal 22 installed on the side of the support substrate 2 via a wiring pattern (not shown) arranged on the surface of the support substrate 2. In this case, the wiring pattern is also made of a metal with high electrical conductivity, such as copper (Cu) or gold (Au). An insulating protective film is arranged on the lower surface (negative surface of the Z-axis) of the area other than the electrode pads 21a in the terminals 21 and on the lower surface (negative surface of the Z-axis) of the wiring pattern connecting each electrode pad 21a to the connection terminal 22. For convenience, FIG. 3 shows a state in which a flexible printed circuit board (FPC) is connected to the connection terminal 22.

[0036] The twelve electrode pads 21a provided on the support substrate 2 are positioned so as to overlap with the twelve electrode pads 16a (see Figure 1) provided on the drive element 1 when the support substrate 2 and the drive element 1 are fixed together.

[0037] The electrode pads 21a and 16a arranged at positions where they overlap each other are equal in size, and the centers of the electrode pads 21a and 16a arranged at positions where they overlap each other are aligned. However, the electrode pads 21a and 16a arranged at positions where they overlap each other may be different in size, and the centers of the electrode pads 21a and 16a arranged at positions where they overlap each other may not be aligned.

[0038] FIG. 4 is a perspective view showing the assembly of the vibration module 3. As shown in FIG.

[0039] The upper surface (the surface on the positive side of the Z axis) of the fixing portion 15 of the driving element 1 is fixed to the lower surface (the surface on the negative side of the Z axis) of the support substrate 2 with an adhesive 23, which will be described later. The adhesive 23 is disposed near the opposing electrode pads 21 a and 16 a. At this time, the fixing portion 15 is fixed to the lower surface of the support substrate 2 so that the center of the driving element 1 and the center of the support substrate 2 coincide in a plan view. When the support substrate 2 supports the driving element 1, a vibration module 3 consisting of the driving element 1 and the support substrate 2 is completed.

[0040] By fixing the driving element 1 to the support substrate 2, each electrode pad 21a provided on the support substrate 2 is electrically connected to a corresponding electrode pad 16a provided on the driving element 1. In this way, the electrode pad 16a of the driving element 1 is connected to a connection terminal 22 (see FIG. 3) via the electrode pad 21a on the support substrate 2, and is connected to an external driving circuit via a flexible substrate FPC (see FIG. 3) connected to the connection terminal 22.

[0041] In this embodiment, a reflecting surface 11a is formed on the upper surface of the movable part 11. Therefore, the vibration module 3 constitutes an optical deflector 3a that deflects light incident on the reflecting surface 11a in response to the driving of the movable part 11.

[0042] FIG. 5 is a perspective view showing an example of mounting the vibration module 3 (optical deflector 3a).

[0043] The vibration module 3 (optical deflector 3a) is mounted on the target device by being fixed to a housing 4 as shown in Fig. 5. Assembly in this case will be described below.

[0044] The housing 4 is a plate-like member with a rectangular outline in a plan view. Four holes 41 are formed in the housing 4, which respectively face the four screw holes 2b of the support substrate 2 when the support substrate 2 and the housing 4 are stacked together. The upper ends of four bolts 42 are fixed to the four screw holes 2b of the fixing portion 15, and the lower ends of the four bolts 42 are fixed to the four holes 41 of the housing 4 by nuts 43. In this way, the vibration module 3 (optical deflector 3a) is installed in the housing 4 with a predetermined gap between it and the top surface of the housing 4.

[0045] FIG. 6 is a cross-sectional view of the vibration module 3 (optical deflector 3a) installed in the housing 4, taken along the YZ plane passing through the rotation axis R0, as viewed in the negative direction of the X axis.

[0046] Incident light incident on the vibration module 3 (optical deflector 3a) from above (positive side of the Z axis) is irradiated onto the reflective surface 11a of the movable part 11 through the opening 2a of the support substrate 2. The incident light is reflected by the reflective surface 11a in a direction according to the rotation angle of the movable part 11. The incident light reflected by the reflective surface 11a is irradiated as reflected light onto a scanning region located above the vibration module 3 (optical deflector 3a) through the opening 2a.

[0047] FIG. 7 is a perspective view showing an example of a usage form of the vibration module 3 (optical deflector 3a) of FIG.

[0048] In the example of Fig. 7, the vibration module 3 (optical deflector 3a) is used in a head-mounted display. Examples of head-mounted displays include AR glasses, AR goggles, VR glasses, and VR goggles. The head-mounted display in Fig. 7 is AR glasses. However, the usage form in Fig. 7 is just one example, and the vibration module 3 (optical deflector) can also be used in an in-vehicle head-up display, etc.

[0049] The AR glasses 5 include a frame 51, a pair of image generating units 52, and a pair of mirrors 53. The AR glasses 5 are worn on the user's head, similar to ordinary eyeglasses.

[0050] The frame 51 holds a pair of image generating units 52 and a pair of mirrors 53. The frame 51 has a front portion 51a and a pair of support portions 51b. The pair of support portions 51b extend rearward from the right and left ends of the front portion 51a. When the frame 51 is worn by a user, the front portion 51a is positioned in front of the user's pair of eyes E1. The frame 51 is made of a transparent material. The frame 51 may also be made of an opaque material.

[0051] The pair of image generation units 52 are arranged symmetrically in the width direction of the AR glasses 5. The image generation units 52 generate an image in the eye E1 of a user wearing the AR glasses 5 on the head.

[0052] The mirror 53 has a concave reflective surface and is installed on the inner surface of the front surface 51a of the frame 51. The mirror 53 almost totally reflects the light projected from the corresponding projection unit 52a and guides it to the user's eye E1.

[0053] The image generating unit 52 includes a projection unit 52a and a detection unit 52b.

[0054] The projection unit 52a is installed on the inner surface of the support unit 51b. The projection unit 52a projects light modulated by a video signal onto the corresponding mirror 53. The light from the projection unit 52a reflected by the mirror 53 is irradiated onto the fovea centralis, which is located at the center of the retina in the eye E1. This allows the user to visually grasp the frame image generated by the image generation unit 52. The pair of detection units 52b are installed on the inner surface of the front surface 51a, between the pair of mirrors 53. The detection units 52b are used to detect the user's line of sight.

[0055] The projection unit 52a scans the light modulated by the video signal horizontally and vertically across the retina of the eye E1. This projects a frame image onto the retina. At this time, the projection unit 52a changes the scanning range of the light so that the frame image is positioned at a position corresponding to the line of sight detected by the detection unit 52b. Horizontal scanning is several times faster than vertical scanning.

[0056] The vibration module 3 (optical deflector 3a) in Fig. 5 is used for horizontal scanning of light modulated by a video signal. On the other hand, vertical scanning is performed at a low speed, so a low-speed optical deflector is used for this scanning. For example, an optical deflector 3a (vibration module 3) (see Fig. 21) using a meander-type drive element is used for vertical scanning.

[0057] For example, three light sources emitting red, green, and blue light, respectively, are used as light sources. The emission intensity of each light source is modulated by a video signal. The light from these light sources is collimated by a collimator lens and then combined by two dichroic mirrors. The combined light is incident on the reflecting surface 11a of the vibration module 3 (optical deflector 3a) shown in Figure 5. The movable part 11 is resonantly driven, causing the light to repeatedly scan in the horizontal direction. The light reflected by the reflecting surface 11a is scanned in the vertical direction by the subsequent optical deflector 3a (vibration module 3) (see Figure 21). In this way, a frame image is projected onto the retina in the eye E1.

[0058] In the driving element 1 having the above configuration, the four piezoelectric bodies 12b are driven so that the movable part 11 rotates repeatedly at a natural resonant frequency, as described above. However, the driving amount (static displacement) of the piezoelectric bodies 12b when a constant voltage is applied changes depending on the temperature. Therefore, even if the same driving voltage (AC voltage) is applied to the piezoelectric bodies 12b, the rotation amount of the movable part 11 during resonant driving changes depending on the temperature.

[0059] FIG. 8 is a graph showing the results of measuring the static displacement of the piezoelectric body 12b at each temperature.

[0060] Here, a MEMS mirror for static displacement measurement, formed using a piezoelectric element with the same configuration as the piezoelectric element 12b, was driven at a low speed (static displacement) to measure the total optical angle of the movable part. The drive signal was a 60 Hz sine wave (AC voltage). The MEMS mirror was placed in a thermostatic chamber with a window, and laser light was incident on the mirror through the window, scanning the detection surface with the laser light. The rotation angle (total optical angle) of the movable part was measured from the scanning length at this time.

[0061] By this measurement method, the temperature in the thermostatic chamber was changed, and the optical angle at each temperature was measured as the static displacement of the piezoelectric element 12b. The temperature in the thermostatic chamber was increased from room temperature to 85°C and then decreased to around room temperature.

[0062] In Fig. 8, the solid line shows the measurement results of the static displacement amount when the temperature in the thermostatic chamber was increased from room temperature to 85°C, and the dashed line shows the measurement results when the temperature in the thermostatic chamber was decreased from 85°C to near room temperature. The black circles indicate the measurement points. The solid line connects the measurement results of adjacent measurement points when the temperature was increased, and the dashed line connects the measurement results of adjacent measurement points when the temperature was decreased.

[0063] As shown in Figure 8, the static displacement of the piezoelectric body 12b increased as the temperature increased and decreased as the temperature decreased. Furthermore, the static displacement changed in a similar manner when the temperature increased and decreased. This confirmed that the amount of static displacement was approximately the same when the temperature increased and decreased, as long as the environmental temperature of the piezoelectric body 12b was the same.

[0064] Due to such characteristics of the piezoelectric body 12b, the deflection angle (amplitude in the rotation direction) of the movable part 11 and the reflecting surface 11a when they are resonantly driven changes depending on the environmental temperature of the drive element 1. That is, even if the movable part 11 is resonated with the same AC voltage, the deflection angle of the movable part 11 and the reflecting surface 11a increases as the environmental temperature rises. For this reason, the vibration module 3 is required to have a robust configuration in which the deflection angle of the movable part 11 and the reflecting surface 11a is less likely to change even when the environmental temperature changes.

[0065] Therefore, in this embodiment, the method of fixing the driving element 1 to the support substrate 2 is improved so as to suppress the influence of static displacement caused by temperature changes.

[0066] Generally, the output of the vibration module 3, i.e., the deflection angle of the movable part 11 during resonant driving, is determined by the value obtained by multiplying the static displacement by the Q value of the vibration module 3. Therefore, when the static displacement increases with increasing temperature as described above, fluctuations in the output of the vibration module 3 due to temperature changes can be suppressed by decreasing the Q value of the vibration module 3 with increasing temperature. Preferably, by changing the Q value so that the value obtained by multiplying the static displacement and the Q value remains constant even when the temperature of the vibration module 3 changes, the effects of changes in static displacement due to temperature changes can be substantially eliminated.

[0067] In this embodiment, the Q value of the vibration module 3 is reduced in response to an increase in temperature by the characteristics of the adhesive that bonds the fixing portion 15 of the driving element 1 to the support substrate 2 and the method of arranging the adhesive.

[0068] That is, in the past, adhesive was applied uniformly to the entire upper surface of fixed portion 15, and fixed portion 15 was fixed to the lower surface of support substrate 2. In contrast, in this embodiment, the upper surface of fixed portion 15 is fixed to the lower surface of support substrate 2 with adhesive in multiple discrete portions. Here, the multiple portions to which adhesive is applied include portions corresponding to antinodes of vibration generated in fixed portion 15 when movable portion 11 is resonantly driven. In addition, an adhesive whose elastic modulus decreases with increasing temperature is used as the adhesive.

[0069] In this way, if the portions corresponding to the antinodes of vibration generated in the fixed part 15 when the movable part 11 is resonantly driven are fixed with an adhesive whose elastic modulus decreases with increasing temperature, the adhesive in the antinode portions will soften with increasing temperature, increasing the vibration of the antinode portions. This causes a loss of vibration energy and reduces the Q value of the vibration module 3. In this way, the Q value of the vibration module 3 can be reduced with increasing temperature, and as a result, the effects of static displacement due to temperature changes can be suppressed as described above.

[0070] Here, the decrease in the adhesive's elastic modulus with increasing temperature only needs to occur within the temperature range expected in the environment in which the vibration module 3 is used. For example, adhesives whose main components are epoxy resin, silicone resin, acrylic resin, and urethane resin can be used as such adhesives. Preferably, adhesives whose main components are silicone resin, urethane resin, and modified silicone resin, such as silicone-modified epoxy resin, which have a small elastic modulus after curing and a large temperature change in elastic modulus, are used. The elastic modulus may also be adjusted by mixing a filler into the resin. An adhesive having properties that can further suppress the effects of the static displacement described above should be selected.

[0071] The thickness of the adhesive should be set so that the bonded vibration antinode can vibrate appropriately at each temperature. In the area of ​​the upper surface of the fixed portion 15 that is not fixed with adhesive, a gap corresponding to the thickness of the adhesive is generated.

[0072] FIG. 9 is a diagram showing the results of a simulation of vibrations in the Z-axis direction that occur in the fixed part 15 when the movable part 11 is resonantly driven.

[0073] For convenience, only the configuration of the fixing portion 15 is shown in FIG. 9. In FIG. 9, the closer to black the color, the greater the vibration, and the closer to white the color, the smaller the vibration. In FIG. 9, vibration is greater in the portions P11 to P13 and P21 to P23 circled by dashed lines. In other words, these portions P11 to P13 and P21 to P23 correspond to the antinodes of vibration. Therefore, by discretely fixing these portions P11 to P13 and P21 to P23 to the support substrate 2 with the adhesive described above, the Q value of the vibration module 3 can be reduced as the temperature rises.

[0074] On the other hand, if the entire lower surface of the fixing portion 15 is uniformly fixed to the support substrate 2 with an adhesive, as in the past, the vibration of the antinode portion is limited by the adhesion of the portions other than the antinode portion, making it difficult for the antinode portion to vibrate smoothly. Therefore, even if the temperature of the vibration module 3 rises, the vibration of the antinode portion is unlikely to change significantly, and energy loss due to the vibration of the antinode portion is unlikely to occur. For this reason, it is difficult to reduce the Q value of the vibration module 3 as the temperature rises.

[0075] In contrast, in this embodiment, as described above, the portions P11 to P13 and P21 to P23 corresponding to the vibration antinodes are discretely fixed to the underside of the support substrate 2 with the adhesive, so that the vibration of the vibration antinodes can be increased as the temperature rises. Therefore, the Q value of the vibration module 3 can be effectively reduced as the temperature rises, and as a result, the effects of static displacement can be effectively suppressed.

[0076] 9 do not necessarily have to be fixed to the support substrate 2 with the adhesive. For example, the middle portions P13 and P23 may not be applied with adhesive, and only the portions P11, P12, P21, and P22 near the four corners may be fixed to the support substrate 2 with adhesive.

[0077] However, it is preferable that the parts that form a pair symmetrical about the rotation axis R0 (parts P11 and P21, parts P12 and P22, and parts P13 and P23) are either both fixed or neither fixed. In other words, if only one part of a pair is fixed with an adhesive, the support of the drive element 1 relative to the support substrate 2 will be unbalanced across the rotation axis R0, which may cause unstable resonant driving of the movable part 11. Therefore, in order to stably resonantly drive the movable part 11, it is preferable that the parts that form a pair symmetrical about the rotation axis R0 are either both fixed to the support substrate 2 or neither fixed to the support substrate 2.

[0078] FIG. 10 is a plan view showing the configuration of the vibration module 3 (optical deflector 3a).

[0079] 10, for convenience, the support substrate 2 is shown in a transparent state, and the outer periphery of the support substrate 2 and the outline of the opening 2a are shown by thick dotted lines. Also, for convenience, the positions of portions P11, P12, P21, and P22 are shown by dashed-line enclosures, and the adhesive 23 is shown by halftone dots surrounded by a dotted line.

[0080] In this fixing method, adhesive 23 is applied to portions P11, P12, P21, and P22 of the six antinode portions P11 to P13 and P21 to P23 shown in Fig. 9, and the drive element 1 is fixed to the lower surface (the surface on the negative side of the Z axis) of the support substrate 2. That is, as shown in Fig. 10, adhesive 23 is placed at the four corners of the fixing portion 15 of the drive element 1 corresponding to portions P11, P12, P21, and P22, and then the drive element 1 is placed on the lower surface of the support substrate 2. As a result, as shown in Fig. 10, the electrode pad 21a on the support substrate 2 side and the electrode pad 16a on the drive element 1 side are connected to overlap in the Z axis direction, and the vibration module 3 (optical deflector 3a) is configured.

[0081] It should be noted that instead of disposing the adhesive 23 on the fixing portion 15 side, the adhesive 23 may be disposed on the support substrate 2 side for fixing.

[0082] FIG. 11 is a cross-sectional view taken along the line C1-C2 of FIG. 10 when viewed in the negative direction of the X axis.

[0083] As described above, the adhesive 23 is an adhesive whose elastic modulus decreases with increasing temperature, and includes an adhesive material and a conductive filler dispersed in the adhesive material. The adhesive material of the adhesive 23 can be a material such as the resin described above, and the conductive filler of the adhesive 23 can be a conductive metal material. The adhesive 23 is, for example, an anisotropic conductive paste (ACP) or an anisotropic conductive film (ACF). In the portion P11 corresponding to the antinode, the adhesive 23 is disposed within the range of the portion P11. Similarly, in the portions P12, P21, and P22 corresponding to the antinodes, the adhesive 23 is disposed within the range of each portion. The conductive filler contained in the adhesive 23 electrically connects two electrode pads disposed opposite each other in the Z-axis direction while electrically disconnecting adjacent electrode pads disposed parallel to the X-Y plane.

[0084] The thickness of the adhesive 23 is set to, for example, 1 μm or more, preferably 5 μm or more, and more preferably 20 μm or more, in order to increase the vibration of the antinode portion.

[0085] Figures 12(a) and (b) are diagrams showing a verification example in which the vibration in the Z-axis direction occurring in the fixed portion 15 is measured when the drive element 1 fixed using the fixing method of Figures 10 and 11 is actually driven in resonance.

[0086] In this verification, for convenience, the support substrate on which the driving element 1 is mounted is changed from support substrate 2 to support substrate 6. Furthermore, it is assumed that the bottom surface of the driving element 1 is mounted on support substrate 6, and the adhesive that bonds the driving element 1 to the support substrate 6 is an adhesive that does not contain a conductive filler. However, whether the surface of the driving element 1 that is mounted on the support substrate is the top or bottom does not have much of an effect on the verification results, and whether or not the adhesive contains a conductive filler does not have much of an effect on the temperature characteristics of the adhesive. Therefore, it is expected that the same verification results as below will be obtained even when the top surface of the driving element 1 is mounted on the support substrate and the adhesive contains a conductive filler, as described above.

[0087] As shown in Figure 12(a), in this verification, the lower surface (negative surface of the Z axis) of the driving element 1 was placed on the upper surface of the support substrate 6 (positive surface of the recess 6a along the Z axis). The recess 6a has a rectangular shape in a plan view and is slightly larger than the outline of the driving element 1. The depth of the recess 6a is constant and equal to the thickness of the driving element 1. Between the lower surface (negative surface of the Z axis) of the fixed portion 15 of the driving element 1 and the bottom surface of the recess 6a, adhesive was applied to portions P11, P12, P21, and P22 corresponding to the vibration antinodes of the fixed portion 15, and the lower surface of the fixed portion 15 was fixed to the recess 6a. In this configuration, the driving element 1 was resonantly driven at around 55 kHz. The AC voltage applied to the piezoelectric body 12b was set to approximately 5 V. The vibration of the driving element 1 was measured at six positions A to F in Figure 12(a) under room temperature. The thickness of the adhesive was set to approximately 1 μm.

[0088] FIG. 12B is a graph showing the measurement results.

[0089] In Figure 12(b), the horizontal axis represents the phase of one vibration cycle, and the vertical axis represents the displacement of each part in the Z-axis direction. As shown in Figure 12(b), vibrations of approximately 60 nm to 80 nm were measured at positions A, C, D, and F, which are close to the antinodes of the vibration. In contrast, almost no vibration occurred at positions B and E, which correspond to the nodes of the vibration.

[0090] In order to appropriately reduce the Q value of the vibration module 3 during resonant driving, it is necessary to appropriately vibrate the vibration antinode of the fixed part 15 fixed with adhesive in the temperature range expected in the usage environment of the vibration module 3. The measurement results in Figure 12(b) show that in a room temperature environment, the Q value of the vibration module 3 can be appropriately reduced by vibrating the vibration antinode of the fixed part 15 fixed with adhesive with a vibration displacement (amplitude) of about 60 nm to 80 nm.

[0091] For example, if the expected temperature range in the usage environment is 0°C to 50°C, the elastic modulus of the adhesive is smaller at around 50°C than at room temperature, so the vibration at the antinode of the vibration of the fixed part 15 fixed with adhesive will be larger than in the case of Fig. 12(b). Conversely, the elastic modulus of the adhesive is larger at around 0°C than at room temperature, so the vibration at the antinode of the vibration of the fixed part 15 fixed with adhesive will be smaller than in the case of Fig. 12(b).

[0092] 7 is mounted on the vibration module 3 (optical deflector), in order to obtain a larger swing angle, the voltage applied to the piezoelectric body 12b is increased to about 10 V. In this case, if the temperature range expected in the usage environment is 0° C. or higher and 50° C. or lower, the vibration displacement (amplitude) of the vibration antinode of the fixed part 15 fixed with adhesive will be about 50 nm even when the environmental temperature is 0° C.

[0093] 10 and 11, if the antinode of vibration of the fixed portion 15 fixed with the adhesive 23 is 50 nm or more in this temperature range during resonant driving, it can be said that the antinode can be vibrated appropriately and the Q value of the vibration module 3 can be reduced appropriately. This makes it possible to properly suppress the influence of static displacement of the piezoelectric body 12b during resonant driving.

[0094] The thickness of the adhesive 23 must be set to a thickness necessary to properly generate vibrations that may occur at the antinodes of vibration of the adhesively fixed fixed part 15. For example, the thickness of the adhesive 23 should be set to about 100 times or more the maximum vibration displacement (maximum amplitude) that occurs at the antinodes of vibration of the adhesively fixed fixed part 15 in the expected temperature range.

[0095] FIG. 13A is a graph that schematically shows the ideal relationship between the change in static displacement of the vibration module 3 due to a change in temperature and the change in the Q value of the vibration module 3 due to a change in temperature.

[0096] 13(a), ideally, the Q value of the vibration module 3 should change so that the value obtained by multiplying the static displacement and the Q value at each temperature is approximately constant over the entire temperature range. This allows the output characteristics of the vibration module 3 to be maintained approximately constant regardless of temperature changes. As a result, as shown in FIG. 13(b), the deflection angle of the movable part 11 and the reflecting surface 11a during resonant driving can be maintained approximately constant regardless of temperature changes.

[0097] In other words, the type (temperature characteristics) of the adhesive 23 and the thickness of the adhesive 23 can be adjusted so that such a change in the Q value is obtained in relation to the change in static displacement accompanying a change in temperature. This allows the effect of static displacement accompanying a change in temperature on the resonant driving of the movable part 11 to be offset by the change in the Q value caused by the adhesive 23 in response to the temperature of the vibration module 3. As a result, the deflection angle of the movable part 11 and the reflecting surface 11a during resonant driving can be kept approximately constant regardless of temperature changes.

[0098] In addition, in embodiment 1, the connection of the electrode pads 21a, 16a and the fixing of the support substrate 2 and the fixing portion 15 are not limited to being performed using adhesive 23, but may also be performed using solder 24 and adhesive 25, for example, as shown in Figure 114.

[0099] In the example shown in FIG. 14 , the adhesive 25 is, for example, an underfill material. The adhesive 25 may be, for example, the same adhesive material as the adhesive 23 described above. When the fixing portion 15 is fixed to the support substrate 2, solder 24 is applied to the electrode pad 21 a or the electrode pad 16 a, and the upper surface of the fixing portion 15 is placed on the lower surface of the support substrate 2. This electrically connects the two corresponding electrode pads 21 a and 16 a via the solder 24. Thereafter, the adhesive 25 is injected through the gap between the support substrate 2 and the fixing portion 15 so as to fit within the ranges of portions P11, P12, P21, and P22, thereby fixing the lower surface of the support substrate 2 and the upper surface of the fixing portion 15 to each other. In this case, too, the thickness of the adhesive 25 is set to, for example, 1 μm or more, preferably 5 μm or more, and more preferably 20 μm or more, in order to increase the vibration of the antinode portion.

[0100] 14, when solder 24 and adhesive 25 are used, if the area to which the adhesive 25 is applied is large and the amount is large, the adhesive 25 can adjust the Q value of the vibration module 3 in the same manner as described above in accordance with temperature changes. Therefore, in the case of the fixing shown in Fig. 14, by adjusting the adhesive 25 arranged around the solder 24 so as to obtain the change in Q value shown in Fig. 13(a), the deflection angle can be kept approximately constant regardless of temperature changes, as shown in Fig. 13(b).

[0101] <Effects of First Embodiment> According to the first embodiment, the following effects are achieved.

[0102] As shown in FIG. 4 , the vibration module 3 includes a driving element 1 and a support substrate 2 that supports the driving element 1. As shown in FIG. 1 , the driving element 1 includes a movable portion 11, a driving portion 12 that rotates the movable portion 11 about a rotation axis R0, a fixed portion 15 that supports the movable portion 11 and the driving portion 12 and is fixed to the support substrate 2, and a plurality of electrode pads 16 a (first electrode pads) that are installed on the upper surface of the fixed portion 15 and connected to the piezoelectric elements 12 b and 12 c of the driving portion 12 by wiring 16 b (wiring pattern). As shown in FIG. 4 , a plurality of electrode pads 21 a (second electrode pads) are arranged on the lower surface of the support substrate 2 at positions that respectively face the plurality of electrode pads 16 a (first electrode pads). As shown in FIG. 10 , the upper surface of the fixed portion 15 is fixed to the lower surface of the support substrate 2 at a plurality of discrete portions P11, P12, P21, and P22 by adhesives 23 and 25 whose elastic modulus decreases with increasing temperature. 9, the plurality of portions P11, P12, P21, and P22 include portions corresponding to antinodes of vibration generated in the fixed portion 15 when the movable portion 11 is resonantly driven. The pair of electrode pad 16a (first electrode pad) and electrode pad 21a (second electrode pad) are connected to each other at the plurality of portions P11, P12, P21, and P22.

[0103] With this configuration, the elastic modulus of the adhesives 23 and 25 decreases with increasing temperature, making the portion of the fixed portion 15 fixed with the adhesives 23 and 25 corresponding to the vibration antinode more likely to vibrate with increasing temperature. Therefore, with increasing temperature, the loss of vibration energy at the vibration antinode increases, reducing the Q value of the vibration module 3. As a result, the increase in static displacement and the decrease in Q value with increasing temperature act in opposite directions, thereby suppressing changes in the output of the vibration module 3 with temperature changes. This suppresses changes in the deflection angle of the movable portion 11 due to temperature changes. Furthermore, because the paired electrode pads 16 a and 21 a are connected to each other, the support substrate 2 and the fixed portion 15 can be electrically connected without using additional wiring means such as wire bonding. This allows the overall configuration of the vibration module 3 to be miniaturized.

[0104] As shown in Figure 10, the multiple parts P11, P12, P21, and P22 of the fixed part 15, which are discretely fixed to the support substrate 2 with adhesives 23 and 25, are all parts that correspond to the antinodes of vibration that occur in the fixed part 15 during resonant driving.

[0105] With this configuration, the vibration antinode portions fixed with the adhesives 23 and 25 can vibrate smoothly without being restricted by other fixed portions. Therefore, vibration energy can be smoothly dissipated in the vibration antinode portions fixed with the adhesives 23 and 25, and the Q value of the vibration module 3 can be appropriately reduced with temperature changes. Therefore, the effect of static displacement caused by temperature changes on resonant drive can be appropriately suppressed.

[0106] As shown in Figure 10, the multiple parts of the fixed part 15 fixed by adhesives 23 and 25 include parts P11, P12, P21, and P22 corresponding to an even number of vibration antinodes, and these parts P11, P12, P21, and P22 corresponding to the even number of vibration antinodes form symmetric pairs (part P11 and part P21, part P12 and part P22) with respect to the rotation axis R0.

[0107] According to this configuration, the driving element 1 is supported in a well-balanced manner in the direction perpendicular to the rotation axis R0 relative to the support substrate 2. Therefore, the movable portion 11 can be resonantly driven stably.

[0108] As shown in Figure 10, the fixed portion 15 has a rectangular (oblong) frame shape in a planar view, and the multiple parts fixed with adhesives 23 and 25 include parts P11, P12, P21, and P22 corresponding to the antinodes of vibration near the four corners of this frame shape.

[0109] According to this configuration, the fixing portion 15 can be stably supported by the support substrate 2 by fixing the vicinity of the four corners of the rectangle.

[0110] The vibration displacement at the vibration antinode portion fixed by the adhesives 23 and 25 during resonant driving is preferably set to 50 nm or more in a predetermined temperature range (0° C. or more and 50° C. or less).

[0111] 12(b), at a predetermined temperature within this temperature range, this configuration allows vibrations according to the elastic modulus of the adhesives 23 and 25 to be generated at the antinode of vibration of the fixed part 15. Therefore, the Q value of the vibration module 3 can be appropriately changed in accordance with temperature changes, and changes in the deflection angle of the movable part 11 due to temperature changes can be appropriately suppressed.

[0112] Here, the above-mentioned predetermined temperature range can be set to 0°C or higher and 50°C or lower.

[0113] With this configuration, for example, the Q value of the vibration module 3 can be appropriately changed in accordance with temperature changes within the temperature range expected in the everyday use environment of the AR glasses 5, etc., and changes in the deflection angle of the movable part 11 due to temperature changes can be appropriately suppressed. Therefore, the vibration module 3 can be made to perform operations suited to the everyday use environment.

[0114] As shown in FIG. 11, the adhesive 23 is formed by mixing conductive filler into a resin material, and the pair of electrode pad 16 a (first electrode pad) and electrode pad 21 a (second electrode pad) are electrically connected to each other by the adhesive 23.

[0115] This configuration allows the electrode pads 16a, 21a to be electrically connected and the Q value to be adjusted without using a separate member such as solder 24. Furthermore, as shown in FIG. 14 , when connecting the electrode pads 16a, 21a using solder 24, it is necessary to place the solder 24, overlap the lower surface of the support substrate 2 with the upper surface of the fixing portion 15, and then inject adhesive 25 into the gap between the support substrate 2 and the fixing portion 15. However, when using adhesive 23, the bonding process can be completed simply by placing the adhesive 23 at a predetermined position on the lower surface of the support substrate 2 or the upper surface of the fixing portion 15, and then overlapping the support substrate 2 with the fixing portion 15. Therefore, using adhesive 23 makes it easy to place the adhesive 23 at the desired position and simplifies the bonding process.

[0116] As shown in FIG. 14, solder 24 and adhesive 25 may be provided in portions P11, P12, P21, and P22 where a pair of electrode pads 16a (first electrode pad) and electrode pads 21a (second electrode pad) are arranged, electrically connecting these electrode pads to each other.

[0117] According to this configuration, the electrode pads 16a and 21a can be reliably electrically connected, and the Q value can be adjusted by the adhesive 25.

[0118] 10 , among the multiple portions of the fixed portion 15 fixed with the adhesives 23 and 25, a pair of electrode pad 16 a (first electrode pad) and electrode pad 21 a (second electrode pad) is arranged at portions P11, P12, P21, and P22 that are the shortest distance to the drive unit 12. That is, in Modification 1 of Embodiment 1 described later with reference to FIG. 15 , the electrode pads 21 a and 16 a are arranged at portions P13 and P23 that are the longest distance to the drive unit 12, but in Embodiment 1, the electrode pads 21 a and 16 a are not arranged at portions P13 and P23 shown in FIG.

[0119] According to the configuration shown in FIG. 10, the wiring pattern (wiring 16b and terminal portion 16) connecting the driving portion 12 and the electrode pad 16a can be made short, so that the driving portion 12 can be driven efficiently.

[0120] As shown in FIG. 1, the driving unit 12 is a tuning fork type vibrator.

[0121] According to this configuration, the movable part 11 can be smoothly and repeatedly rotated (resonantly driven) about the rotation axis R0.

[0122] As shown in FIG. 1, two tuning fork vibrators (drive units 12) are arranged in opposite directions along a rotation axis R0.

[0123] According to this configuration, the movable part 11 can be driven stably with a larger torque.

[0124] As shown in FIG. 4, the optical deflector 3 a includes a vibration module 3 and a reflecting surface 11 a disposed on a movable part 11 .

[0125] Since the optical deflector 3a includes the vibration module 3, this configuration can suppress changes in the deflection angle of the movable part 11 and the reflecting surface 11a due to temperature changes, so that the light incident on the reflecting surface 11a can be stably deflected and scanned at a predetermined deflection angle.

[0126] <First Modification of First Embodiment> In the first embodiment, the electrode pads 21 a, 16 a and the adhesive 23 are arranged on the portions P11, P12, P21, and P22 among the portions corresponding to the antinodes of vibration generated in the fixed portion 15 during resonant driving. However, this is not limiting, and the electrode pads 21 a, 16 a and the adhesive 23 may be arranged on all the portions P11, P12, P13, P21, P22, and P23 corresponding to the antinodes.

[0127] FIG. 15 is a plan view showing the configuration of the vibration module 3 (optical deflector 3a) according to the first modification of the first embodiment.

[0128] In this modified example, compared to the first embodiment shown in Fig. 10, the inner ends (on the movable portion 11 side) of the terminal portions 21, 16 extend to near the center position in the Y-axis direction of the fixed portion 15. Two terminal portions 21, 16 adjacent to each other in the Y-axis direction are arranged side by side with a predetermined gap in the Y-axis direction. The inner electrode pad 21a of the terminal portion 21 is disposed near the inner end of the terminal portion 21, and the inner electrode pad 16a of the terminal portion 16 is disposed near the inner end of the terminal portion 16. The inner electrode pad 16a of the terminal portion 16 is connected to the lower electrode layers of the piezoelectric bodies 12b, 12c and is used to connect these lower electrode layers to ground.

[0129] As a result, two electrode pads 21a and two electrode pads 16a are positioned at the portions P11 to P13 and P21 to P23 corresponding to the antinodes, respectively. Then, adhesive 23 is applied to the portions P11 to P13 and P21 to P23, respectively, to fix the support substrate 2 and the fixing portion 15. Note that in this modified example, solder 24 and adhesive 25 may be applied instead of the adhesive 23.

[0130] According to this modification, the number of connection points between the support substrate 2 and the fixing portion 15 is increased compared to the first embodiment, so that the strength of the fixation between the support substrate 2 and the driving element 1 can be increased.

[0131] <Modification 2 of Embodiment 1> In the first embodiment and Modification 1 of Embodiment 1, the electrode pads 21 a, 16 a are disposed only at portions corresponding to the antinodes of vibration generated in the fixed portion 15 during resonant driving, and the adhesive 23 is disposed only at the positions of the electrode pads 21 a, 16 a. However, the present invention is not limited to this, and the adhesive may be disposed in portions other than the portions P11 to P13 and P21 to P23 corresponding to the antinodes of vibration.

[0132] FIG. 16 is a plan view showing the configuration of a vibration module 3 (optical deflector 3a) according to a second modification of the first embodiment.

[0133] In this modified example, adhesive 23 is placed at vibration node portions P31 and P32, as compared to Modification 1 of Embodiment 1 shown in Fig. 15. In this modified example, adhesive 23 is placed at portions P11 to P13, P21 to P23, P31, and P32, respectively, and the support substrate 2 and the fixing portion 15 are fixed together.

[0134] In this modified example, solder 24 and adhesive 25 may be disposed in portions P11 to P13 and P21 to P23 instead of adhesive 23. Furthermore, in portions P31 and P32, only adhesive 23 that does not contain conductive filler may be disposed in place of adhesive 23, or an adhesive that does not have the property of decreasing elastic modulus with increasing temperature may be disposed.

[0135] In this modification, the bonding strength between the support substrate 2 and the drive element 1 can be increased compared to Modification 1 of Embodiment 1. However, because the node portions P31 and P32 near the portions P11, P12, P21, and P22 bonded with the adhesive 23 are also bonded, the vibration of the vibration antinode portions P11, P12, P21, and P22 is likely to be restricted by the bonding of the node portions P31 and P32. Therefore, in order to more stably vibrate the antinode portions in response to temperature changes and appropriately control the Q value of the vibration module 3, it is preferable to discretely bond only the vibration antinode portions of the fixing portion 15 to the support substrate 2, as in Embodiment 1 and Modification 1 of Embodiment 1.

[0136] <Modification 3 of Embodiment 1> In the first embodiment, two tuning-fork vibrators (drive units 12) are arranged in opposite directions along the rotation axis R0 in a plan view, but as shown in FIG. 17 , only one may be arranged along the rotation axis R0.

[0137] FIG. 17 is a plan view showing the configuration of a vibration module 3 (optical deflector 3a) according to a third modification of the first embodiment.

[0138] 10, in this modified example, a set of the drive unit 12 and the connecting unit 14 is arranged on only one side of the movable unit 11 along the rotation axis R0. In this case, as in the first embodiment, the electrode pads 21a and 16a are arranged at the vibration antinode portions P11 and P21, and the adhesive 23 is arranged at the portions P21 and P22. Note that in this modified example, solder 24 and adhesive 25 may be arranged at the portions P11 and P21 instead of the adhesive 23.

[0139] According to this modified example, compared to the first embodiment, the configuration on the negative side of the Y axis of the movable part 11 is omitted, so that the support substrate 2 and the vibration module 3 (optical deflector 3a) can be made smaller in the Y axis direction.

[0140] Second Embodiment In the first embodiment, the fixing portion 15 is configured in a frame shape, but in the second embodiment, the fixing portion 15 is configured by two first portions 17a and one second portion 17b.

[0141] FIG. 18 is a perspective view showing the configuration of a driving element 1 according to the second embodiment.

[0142] In the second embodiment, compared to the first embodiment shown in FIG. 1 , the fixing portion 15 includes a first portion 17a that supports the connecting portion 14 on the positive side of the Y axis from the outside, a first portion 17a that supports the connecting portion 14 on the negative side of the Y axis from the outside, and a second portion 17b (lower cover) that connects the lower surfaces of the two first portions 17a (lower surfaces of the material layer 1b). The second portion 17b may be made of, for example, silicon (Si). The second portion 17b may be processed and molded together with the driving element 1 from a single SOI wafer, or the second portion 17b molded separately from the driving element 1 may be bonded to the lower surfaces of the two first portions 17a.

[0143] FIG. 19(a) is a diagram showing the configuration of the driving element 1 used in a simulation for resonantly driving the movable part 11, and FIG. 19(b) is a diagram showing the simulation results.

[0144] For convenience, FIG. 19( a) illustrates the driving element 1 without the second portion 17b of the fixed portion 15, while FIG. 19( b) illustrates the two first portions 17a of the fixed portion 15 and the second portion 17b of the fixed portion 15 indicated by dashed lines. In FIG. 19( b), the closer to black the color, the greater the vibration, and the closer to white the color, the smaller the vibration. In FIG. 19( b), the vibration is greater at portions P11, P12, P21, and P22 enclosed by dashed lines. That is, these portions P11, P12, P21, and P22 correspond to the antinodes of the vibration. Therefore, by discretely adhering these portions P11, P12, P21, and P22 to the support substrate 2 with the adhesive described in embodiment 1, the Q value of the vibration module 3 can be reduced with increasing temperature.

[0145] 19B, all of the four antinode portions P11, P12, P21, and P22 shown in FIG. 19B do not have to be fixed to the support substrate 2 with the adhesive. However, it is preferable that the portions that form pairs symmetrical with respect to the rotation axis R0 (portion P11 and portion P21, and portion P12 and portion P22) are set so that both are fixed or neither are fixed.

[0146] FIG. 20 is a plan view showing the configuration of the vibration module 3 (optical deflector 3a) according to the second embodiment.

[0147] In the second embodiment, as in the first embodiment, the electrode pads 21a, 16a and the adhesive 23 are arranged in the antinode portions P11, P12, P21, and P22, and the support substrate 2 and the fixing portion 15 are fixed to each other in these antinode portions. Note that in the second embodiment, the solder 24 and the adhesive 25 may be arranged in place of the adhesive 23 in the antinode portions P11, P12, P21, and P22.

[0148] <Effects of Second Embodiment> According to the second embodiment, the following effects are achieved.

[0149] 20 , the driving element 1 includes driving units 12 on both sides of the movable unit 11 along the rotation axis R0 in a plan view. The fixed unit 15 includes two first portions 17a that respectively support the two driving units 12, and a second portion 17b that connects the lower ends of the two first portions 17a. The fixed unit 15 includes multiple portions P11, P12, P21, and P22 that are discretely fixed to the support substrate 2 with adhesives 23 and 25, and include portions that correspond to vibration antinodes near both ends of the two first portions 17a that are distant from the rotation axis R0.

[0150] According to this configuration, the two first portions 17 a are fixed near both ends, so that the fixed portion 15 can be stably supported by the support substrate 2 .

[0151] <Embodiment 3> In the first and second embodiments, the driving unit 12 is a tuning fork type vibrator, but the driving unit 12 may be a vibrator of another type that is resonantly driven. In embodiment 3, the driving unit 12 is a meander type vibrator that is resonantly driven.

[0152] FIG. 21 is a plan view showing the configuration of a vibration module 3 (optical deflector 3a) according to the third embodiment.

[0153] In the third embodiment, compared to the first embodiment shown in Fig. 10, the pair of torsion units 13 is omitted, and the pair of drive units 12 are meandering vibrators. The drive units 12 include four rectangular arm units 12a connected to each other, and two piezoelectric bodies 12b and two piezoelectric bodies 12c installed on the four arm units 12a. The inner end of the drive unit 12 is connected to the movable unit 11, and the outer end of the drive unit 12 is connected to the fixed unit 15 via a connecting unit 14. In the third embodiment, too, each terminal unit 16 is connected to the corresponding piezoelectric body 12b, 12c via a wiring pattern (not shown).

[0154] In the third embodiment, vibration antinodes occur at portions P11 to P13 and P21 to P23 similar to those in the first embodiment shown in Fig. 9, and similar to the first embodiment shown in Fig. 10, terminal portions 21, 16, electrode pads 21a, 16a, and adhesive 23 are arranged at portions P11, P12, P21, and P22, and the support substrate 2 and the fixing portion 15 are fixed to each other. Note that in the third embodiment, solder 24 and adhesive 25 may be arranged at portions P11, P12, P21, and P22 instead of adhesive 23.

[0155] <Other Modifications> The configuration examples of the present invention are not limited to the above-described embodiment and modifications, and various modifications are possible.

[0156] In the above embodiment and modified example, the electrode pads 21a, 16a are arranged together with adhesive placed in the portion corresponding to the belly, but this is not limited to this, and only adhesive may be placed in the portion corresponding to the belly.

[0157] In the above-described second and third embodiments, as in the second modification of the first embodiment, adhesive may be placed in areas other than those corresponding to the belly, for example, adhesive may be placed in areas corresponding to the joints.

[0158] In the third embodiment, similarly to the first modification of the first embodiment, the electrode pads 21a, 16a and adhesive may be disposed on the portions P13, P23 corresponding to the abdomens.

[0159] In the above embodiment and modified example, the electrode pads 21a, 16a and adhesive are placed only in the areas corresponding to the antinodes of vibration, but this is not limiting and they may be placed in areas other than those corresponding to the antinodes of vibration.

[0160] In the above embodiment and modified examples, the shapes of the terminals 16, 21 are not limited to those of the above embodiment and modified examples, as long as adjacent terminals 16 and adjacent terminals 21 do not overlap each other. Furthermore, the positions of the three electrode pads 16a in the terminal 16 connected to the upper electrode layer of the piezoelectric body 12b, the upper electrode layer of the piezoelectric body 12c, and the lower electrode layers of the piezoelectric bodies 12b and 12c, respectively, may be interchanged. Furthermore, the position of the wiring 16b connecting the terminal 16 and the piezoelectric bodies 12b and 12c is not limited to those of the above embodiment and modified examples. However, it is preferable that the wiring 16b be arranged so as to connect the mutually connected terminals 16 and the piezoelectric bodies 12b and 12c via the shortest route.

[0161] In the above embodiment and modified examples, the support substrate 2 is preferably made of a material whose elastic modulus decreases with increasing temperature. This allows the Q value of the vibration module 3 to be more effectively reduced with increasing temperature. Examples of such materials include a glass epoxy substrate and a ceramic substrate.

[0162] In the above embodiment and modified examples, the shape of the movable part 11 is circular, but the shape of the movable part 11 may be other shapes such as square. The shape of the driving element 1 in a plan view and the dimensions of each part of the driving element 1 can also be changed as appropriate.

[0163] Furthermore, the driving element 1 may be used as an element other than an optical deflector. When the driving element 1 is used as an element other than an optical deflector, the movable part 11 does not need to have the reflecting surface 11 a, and may have another member other than the reflecting surface 11 a.

[0164] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims.

[0165] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0166] a plurality of first electrode pads provided on an upper surface of the fixed part and connected to the driving part by a wiring pattern; a plurality of second electrode pads arranged on a lower surface of the support substrate at positions facing the plurality of first electrode pads, respectively; the upper surface of the fixed part is fixed to the lower surface of the support substrate at a plurality of mutually separated portions by an adhesive whose elastic modulus decreases with increasing temperature, the plurality of portions including portions corresponding to antinodes of vibration generated in the fixed part when the movable part is resonantly driven; and

[0167] According to this technology, the elastic modulus of the adhesive decreases with increasing temperature, making the portion of the fixed portion fixed with the adhesive corresponding to the antinode of vibration more likely to vibrate with increasing temperature. Therefore, as the temperature increases, the loss of vibration energy at the antinode increases, reducing the Q value of the vibration module. As a result, the increase in static displacement and the decrease in Q value with increasing temperature act in opposite directions, thereby suppressing changes in the output of the vibration module with temperature changes. This suppresses changes in the deflection angle of the movable portion due to temperature changes. Furthermore, because the first electrode pad and the second electrode pad are connected to each other, the support substrate and the fixed portion can be electrically connected without using a separate wiring method such as wire bonding. This allows the overall configuration of the vibration module to be miniaturized.

[0168] (Technology 2) The vibration module according to Technology 1, wherein the plurality of portions are all portions corresponding to antinodes of the vibration.

[0169] According to this technology, the vibration antinodes fixed with adhesive can vibrate smoothly without being restricted by other fixed parts. This allows vibration energy to be smoothly dissipated in the vibration antinodes fixed with adhesive, and the Q value of the vibration module can be appropriately reduced with temperature changes. Therefore, the effect of static displacement due to temperature changes on resonant drive can be appropriately suppressed.

[0170] (Technology 3) A vibration module according to Technology 1 or 2, characterized in that the plurality of portions include portions corresponding to an even number of antinodes of the vibration, and the portions corresponding to the even number of antinodes of the vibration form pairs symmetrical with respect to the rotation axis.

[0171] According to this technique, the drive element is supported on the support substrate in a well-balanced manner in the direction perpendicular to the rotation axis, thereby enabling the movable part to be resonantly driven in a stable manner.

[0172] (Technology 4) A vibration module described in any one of technologies 1 to 3, characterized in that the fixing portion has a rectangular frame shape in a planar view, and the multiple portions include portions corresponding to antinodes of the vibration near the four corners of the frame shape.

[0173] According to this technique, the fixing portion can be stably supported on the support substrate by fastening the vicinity of the four corners of the rectangle.

[0174] (Technology 5) A vibration module described in any one of technologies 1 to 3, characterized in that the drive element has the drive units on both sides of the movable unit along the rotation axis in a planar view, the fixed unit has two first parts that support the two drive units respectively and a second part that connects the lower ends of the two first parts, and the multiple parts include parts that correspond to antinodes of the vibration near both ends of the two first parts that are away from the rotation axis.

[0175] According to this technique, the two first portions are fixed near their ends, so that the fixed portion can be stably supported on the support substrate.

[0176] (Technology 6) A vibration module according to any one of technologies 1 to 5, characterized in that the vibration displacement of the antinode portion fixed with the adhesive during resonant driving is 50 nm or more in a predetermined temperature range.

[0177] This technology allows vibrations corresponding to the elastic modulus of the adhesive to be generated at the antinode of the vibration of the fixed part at a predetermined temperature within the temperature range, thereby allowing the Q value of the vibration module to be appropriately changed in accordance with temperature changes, and appropriately suppressing changes in the deflection angle of the movable part due to temperature changes.

[0178] (Technology 7) The vibration module according to Technology 6, wherein the temperature range is 0°C or more and 50°C or less.

[0179] This technology allows the Q value of the vibration module to be appropriately changed in accordance with temperature changes within the expected temperature range of everyday use environments, such as AR glasses, and appropriately suppresses changes in the deflection angle of the moving part due to temperature changes, thereby enabling the vibration module to perform operations suited to everyday use environments.

[0180] (Technology 8) A vibration module described in any one of technologies 1 to 7, characterized in that the adhesive is formed by mixing a conductive filler into a resin material, and the first electrode pad and the second electrode pad that make up the pair are electrically connected to each other by the adhesive.

[0181] According to this technique, the first electrode pad and the second electrode pad can be electrically connected without using a separate member such as solder, and the Q value can be adjusted.

[0182] (Technology 9) A vibration module described in any one of technologies 1 to 8, characterized in that the portion where the pair of first electrode pad and second electrode pad is arranged is provided with solder that electrically connects these electrode pads to each other and the adhesive.

[0183] According to this technique, the Q value can be adjusted by the adhesive while the first electrode pad and the second electrode pad are reliably electrically connected.

[0184] (Technology 10) A vibration module described in any one of technologies 1 to 9, characterized in that the first electrode pad and the second electrode pad that make up the pair are arranged in the part of the plurality of parts that has the shortest distance to the driving unit.

[0185] According to this technique, the wiring pattern connecting the drive unit and the first electrode pad can be shortened, so that the drive unit can be driven efficiently.

[0186] (Technology 11) The vibration module according to any one of techniques 1 to 10, wherein the driving unit is a tuning fork vibrator.

[0187] According to this technique, the movable part can be smoothly and repeatedly rotated (resonantly driven) about the rotation axis.

[0188] (Technology 12) The vibration module according to Technology 11, wherein the two tuning-fork vibrators are arranged in opposite directions along the rotation axis.

[0189] This technique allows the moving part to be driven stably with a larger torque.

[0190] (Technology 13) An optical deflector comprising: the vibration module according to any one of technologies 1 to 12; and a reflecting surface disposed on the movable part.

[0191] Since this technology includes the vibration module, it is possible to suppress changes in the deflection angle of the movable part and the reflecting surface due to temperature changes, thereby enabling the light incident on the reflecting surface to be stably deflected and scanned at a predetermined deflection angle.

[0192] REFERENCE SIGNS LIST 1 Drive element 2 Support substrate 3 Vibration module 3a Optical deflector 11 Movable portion 11a Reflecting surface 12 Drive portion (tuning fork vibrator) 12b, 12c Piezoelectric body 15 Fixed portion 16a Electrode pad (first electrode pad) 16b Wiring (wiring pattern) 17a First portion 17b Second portion 21a Electrode pad (second electrode pad) 23 Adhesive 24 Solder 25 Adhesive P11 to P13, P22 to P23 Portions (portions corresponding to vibration loops) R0 Rotation axis

Claims

1. A vibration module comprising a driving element and a support substrate for supporting the driving element, wherein the driving element includes a movable part, a driving part for rotating the movable part about a rotation axis, a fixing part for supporting the movable part and the driving part and fixed to the support substrate, and a plurality of first electrode pads installed on an upper surface of the fixing part and connected to the driving part by wiring patterns; a plurality of second electrode pads are arranged on a lower surface of the support substrate at positions respectively facing the plurality of first electrode pads; the upper surface of the fixing part is fixed to the lower surface of the support substrate by an adhesive whose elastic modulus decreases as the temperature rises in a plurality of discrete portions; the plurality of portions include portions corresponding to antinodes of vibration generated in the fixing part during resonant driving of the movable part; and the first electrode pads and the second electrode pads that form a pair are connected to each other in any of the plurality of portions.

2. The vibration module according to claim 1, wherein all of the plurality of portions are portions corresponding to the antinodes of the vibration.

3. The vibration module according to claim 1, wherein the plurality of portions include portions corresponding to an even number of the antinodes of the vibration, and the portions corresponding to the even number of antinodes of the vibration form a pair symmetric about the rotation axis.

4. The vibration module according to claim 1, wherein the fixing part has a rectangular frame shape in plan view, and the plurality of portions include portions corresponding to the antinodes of the vibration near the four corners of the frame shape.

5. The vibration module according to claim 1, wherein in plan view, the driving element includes the driving parts on both sides of the movable part along the rotation axis, the fixing part includes two first parts respectively supporting the two driving parts and a second part connecting lower ends of the two first parts, and the plurality of portions include portions corresponding to the antinodes of the vibration near both ends of the two first parts away from the rotation axis.

6. The vibration module according to claim 1, wherein a vibration displacement during resonant driving of the portion of the antinode fixed by the adhesive is 50 nm or more in a predetermined temperature range.

7. The vibration module according to claim 6, wherein the temperature range is from 0°C to 50°C, inclusive.

8. The vibration module according to claim 1, wherein the adhesive is composed of a resin material mixed with conductive fillers, and the first electrode pad and the second electrode pad that form the set are electrically connected to each other by the adhesive.

9. The vibration module according to claim 1, wherein the portion where the first electrode pad and the second electrode pad that form the set are arranged is provided with solder for electrically connecting these electrode pads to each other and the adhesive.

10. The vibration module according to claim 1, wherein the first electrode pad and the second electrode pad that form the set are arranged in the portion of the plurality of portions that has the shortest distance to the drive portion.

11. The vibration module according to claim 1, wherein the drive portion is a tuning fork type vibrator.

12. The vibration module according to claim 11, wherein two of the tuning fork type vibrators are arranged in opposite directions along the rotation axis.

13. An optical deflector comprising the vibration module according to any one of claims 1 to 12 and a reflecting surface arranged on the movable portion.

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