Optical reflection element and light deflector

Abstract

An optical reflection element (1) comprises: a movable portion (30) provided with a reflection surface (31); a beam portion (50) extending along a rotation axis (R10) and connected to the movable portion (30); a drive portion (20) that rotates the movable portion (30) about the rotation axis (R10) via the beam portion (50); a connection portion (60) having one end connected to a fixed portion (10) and the other end connected to the beam portion (50); and a mass addition portion (70) that adds mass to the connection portion (60). The connection portion (60) is divided into a first region (61) on the fixed portion (10) side and a second region (62) on the movable portion (30) side, the first region (61) has higher bending rigidity than the second region (62), and the mass addition portion (70) adds mass to the first region (61).

Description

Optical reflective element and optical deflector

[0001] The present invention relates to an optical reflecting element having a movable portion on which a reflecting surface is formed, and an optical deflector.

[0002] An optical reflecting element having a movable part on which a reflective surface is formed is known. In this type of optical reflecting element, for example, the reflective surface is disposed on a movable part that rotates about a rotation axis, and a beam incident on the reflective surface is scanned as the movable part rotates. Patent Document 1 listed below describes an optical reflecting element having a so-called meander-type drive part.

[0003] JP 2010-122480 A

[0004] In the optical reflecting element described above, a plurality of different resonance frequencies may occur, such as a resonance frequency at which the movable part resonates in the rotation direction, and a resonance frequency at which the movable part resonates in a direction perpendicular to the reflective surface, etc. Such resonance in the perpendicular direction can cause instability in the rotational movement of the movable part.

[0005] Furthermore, in the optical reflecting element described above, when an external impact is applied, the moving part with a large mass is displaced significantly. Although such displacement of the moving part can be suppressed by a stopper or the like, the stopper must be spaced a certain distance from the moving part so as not to impede the original rotation of the moving part. Therefore, if the optical reflecting element includes a portion that is difficult to bend and a fragile portion, there is a risk that the fragile portion will be displaced excessively before the moving part abuts against the stopper, and this portion will be damaged.

[0006] In view of such problems, the present invention aims to provide an optical reflecting element and an optical deflector that can stabilize the rotational movement of the movable part while suppressing damage when an external impact is applied.

[0007] A first aspect of the present invention relates to an optical reflecting element, the optical reflecting element according to this aspect includes a movable part provided with a reflective surface, a beam part extending along a rotation axis and connected to the movable part, a drive part that rotates the movable part about the rotation axis via the beam part, a connection part having one end connected to a fixed part and the other end connected to the beam part or a portion of the movable part near a connection position of the beam part, and a mass addition part that adds mass to the connection part, the connection part being divided into a first region on the fixed part side and a second region on the movable part side, the first region having higher bending rigidity than the second region, and the mass addition part adding mass to the first region.

[0008] According to the optical reflecting element of this aspect, by adjusting the bending rigidity of the connection portion as described above, the resonant frequency corresponding to the rotational movement of the movable portion can be separated from the other resonant frequency closest to it, thereby stabilizing the rotational movement of the movable portion. Furthermore, when an external impact is applied to the optical reflecting element, a large inertial force is generated in the mass-adding portion as well as the movable portion, which has a large mass. Therefore, the first region, which has high rigidity and is difficult to bend, is significantly deformed by the inertial force of the mass-adding portion, allowing the movable portion to abut against the stopper before the second region, which has low bending rigidity, is excessively displaced and damaged. This prevents damage to the connection portion.

[0009] A second aspect of the present invention relates to an optical deflector, comprising the optical reflecting element according to the first aspect and a stopper for preventing the movable portion from being excessively displaced.

[0010] The optical deflector according to this aspect has the same effects as those of the first aspect. Furthermore, even if an external impact is applied to the optical deflector, the stopper can prevent the movable portion from being excessively displaced.

[0011] As described above, the present invention can provide an optical reflecting element and an optical deflector that can stabilize the rotational movement of the movable part while suppressing damage when an external impact is applied.

[0012] 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.

[0013] FIG. 1 is a top view schematically showing the configuration of an optical reflecting element according to an embodiment. FIG. 2 is a bottom view schematically showing the configuration of an optical reflecting element according to an embodiment. FIG. 3 is a cross-sectional view of an optical deflector according to an embodiment, taken along a plane parallel to the X-Z plane at position C1-C2 in FIG. 1 . FIG. 4 is a cross-sectional view of an optical deflector according to an embodiment, taken along a plane parallel to the Y-Z plane at position C3-C4 in FIG. 1 . FIG. 5 is a top view schematically showing the configuration of an optical reflecting element according to Comparative Example 1. FIGS. 6( a) and 6(b) are diagrams showing resonance modes occurring in the optical reflecting element according to Comparative Example 1. FIG. 7(a) is a diagram showing simulation results of stress distribution occurring in the connection portion when the movable portion rotates the largest in R mode in the configuration of Comparative Example 1. FIG. 7(b) is a diagram showing simulation results of stress distribution occurring in the connection portion when the movable portion displaces the largest in P mode in the configuration of Comparative Example 1. FIG. 8 is a graph showing simulation results of stress distribution occurring at two connecting portions aligned in a direction perpendicular to the rotation axis according to Comparative Example 1. FIG. 9 is a top view schematically showing the configuration of an optical reflecting element according to Comparative Example 2. FIG. 10 is a simulation result showing the relationship between the distribution of bending rigidity of the connecting portions and the resonance frequencies of the R mode and P mode according to Comparative Example 2. FIGS. 11(a) and 11(b) are diagrams schematically showing the vertical positional relationship between a fixed portion near the connecting portion, the connecting portion, the movable portion, and a stopper located above the movable portion according to Comparative Example 2 and the embodiment, respectively. FIG. 12 is a diagram for explaining simulation conditions for verifying the embodiment. FIGS. 13(a) and 13(b) are graphs showing simulation results for verifying the embodiment. FIGS. 14(a) and 14(b) are bottom views schematically showing the configuration of a mass adding portion according to Modification Example 1. 15(a) and 15(b) are bottom views schematically showing the configuration of the mass adding portion according to Modification Example 1. FIGS. 16(a) and 16(b) are bottom views schematically showing the configuration of the connecting portion according to Modification Example 2. FIGS. 17(a) and 17(b) are bottom views schematically showing the configuration of the connecting portion according to Modification Example 2. FIG. 18(a) is a bottom view schematically showing the configuration of the connecting portion according to Modification Example 2.Fig. 18(b) is a top view schematically showing the configuration of the mass adding portion according to Modification Example 3. Figs. 19(a) and 19(b) are a top view and a bottom view, respectively, schematically showing the configuration of the connecting portion according to Modification Example 4. Fig. 20(a) is a cross-sectional view of the optical deflector according to Modification Example 5, taken along a plane parallel to the YZ plane at the position C3-C4 in Fig. 1. Fig. 20(b) is a cross-sectional view of the optical deflector according to Modification Example 5, taken along a plane parallel to the YZ plane at the position C3-C4 in Fig. 1.

[0014] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with mutually orthogonal X, Y, and Z axes. The positive Z axis is the vertically upward direction, which corresponds to the thickness direction (height direction) of the optical reflecting element 1. The X axis is parallel to the rotation axis R10 of the optical reflecting element 1.

[0016] The following embodiments describe an optical reflecting element that scans a beam incident on a reflecting surface by rotating the reflecting surface. This optical reflecting element is mounted, for example, on an image display device that displays a predetermined image by scanning a beam. However, the device in which the optical reflecting element is mounted is not limited to this. For example, an optical reflecting element having the following configuration may be mounted on an object detection device that detects the presence or absence of an object in the projection direction of a beam and the distance to the object.

[0017] Fig. 1 is a top view schematically showing the configuration of an optical reflecting element 1 according to an embodiment. Fig. 2 is a bottom view schematically showing the configuration of an optical reflecting element 1 according to an embodiment.

[0018] For convenience, in Figures 1 and 2, the exposed portions of the base layer 101 and the active layer 103 in Figures 3 and 4 are hatched in the same manner as the base layer 101 and the active layer 103 in Figures 3 and 4. In Figure 1, the piezoelectric body 22 and the reflecting surface 31 are also hatched in a manner different from the hatching of the base layer 101 and the active layer 103, respectively.

[0019] The optical reflecting element 1 includes a fixed portion 10, a pair of drive portions 20, a movable portion 30, a pair of linking portions 40, a pair of beam portions 50, and four connection portions 60. The optical reflecting element 1 has a shape that is symmetrical about a center C10 in a plan view.

[0020] The fixed unit 10 has a rectangular frame shape with an opening 11 in plan view. The fixed unit 10 supports the movable unit 30 via a pair of drive units 20, a pair of connecting units 40, and a pair of beam units 50. The pair of drive units 20 are arranged to sandwich the movable unit 30 in the X-axis direction. The drive units 20 have a meandering shape in the Y-axis direction in plan view. That is, in one drive unit 20, four rectangular piezoelectric cantilevers 21 whose long sides are parallel to the Y-axis in plan view are arranged side by side in the X-axis direction. Two adjacent piezoelectric cantilevers 21 are connected at their ends on the positive side of the Y-axis or the negative side of the Y-axis so that one drive unit 20 has a meandering shape in plan view.

[0021] Each piezoelectric cantilever 21 includes a piezoelectric body 22 that is rectangular in plan view. The piezoelectric body 22 has a structure in which a piezoelectric body layer is sandwiched between a lower electrode layer and an upper electrode layer. The lower electrode layer is made of, for example, platinum (Pt). The piezoelectric body layer is made of, for example, PZT (lead zirconate titanate: Pb(Zr,Ti)O ３ The upper electrode layer is made of, for example, gold (Au). However, the materials constituting the lower electrode layer, the piezoelectric layer, and the upper electrode layer are not limited to these.

[0022] One end of the driving unit 20 is connected to the fixed unit 10, and the other end of the driving unit 20 is connected to the connecting unit 40. The movable unit 30 is circular in a plan view. The upper surface of the movable unit 30 forms a reflective surface 31. The reflective surface 31 may be formed by mirror-finishing the upper surface of the movable unit 30, or a reflective film may be formed on the upper surface of the movable unit 30 to form the reflective surface 31.

[0023] In a plan view, the pair of connecting portions 40 extend parallel to the Y axis from the ends of the drive portion 20 and are connected to the ends of the pair of beam portions 50. In a plan view, the pair of beam portions 50 extend along the rotation axis R10 from the ends of the pair of connecting portions 40 and are connected to the movable portion 30. The four connecting portions 60 extend parallel to the Y axis from the inner surface of the fixed portion 10 and are connected to the beam portions 50. In a plan view, the four connecting portions 60 are arranged symmetrically with respect to the rotation axis R10 and with respect to a line L10 that passes through the center C10 of the movable portion 30 and is perpendicular to the rotation axis R10.

[0024] The connection portion 60 is divided into a first region 61 on the fixed portion 10 side and a second region 62 on the movable portion 30 side. The first region 61 has a rectangular shape with a constant width in the X-axis direction in a plan view, while the second region 62 has a narrower width than the first region 61 and a meandering shape that snakes in the Y-axis direction in a plan view. This creates a distribution of bending rigidity in the connection portion 60. In other words, because the width of the second region 62 is narrower than the width of the first region 61, the bending rigidity of the second region 62 is smaller than the bending rigidity of the first region 61.

[0025] The mass adding portion 70 is provided in the first region 61. The mass adding portion 70 adds mass to the first region 61 on the movable portion 30 side of a dividing line that passes through the center of gravity of the first region 61 and divides the first region 61 in the direction in which the connecting portion 60 extends (the Y-axis direction). The arrangement position of the mass adding portion 70 will be described later in the verification of the embodiment.

[0026] The mass adding portion 70 protrudes from the first region 61 in the width direction (X-axis direction) of the first region 61. The mass adding portion 70 includes a first portion 71 that overlaps with the connection portion 60 in a plan view, and a second portion 72 that protrudes from the first region 61 in the width direction (X-axis direction) of the first region 61. The second portion 72 is longer than the first portion 71 in the direction in which the connection portion 60 extends (Y-axis direction).

[0027] The fixed portion 10, the pair of drive portions 20, the movable portion 30, the pair of linking portions 40, the pair of beam portions 50, the four connection portions 60, and the four mass adding portions 70 are connected by a common active layer 103 (see FIGS. 3 and 4). Specifically, the active layer 103 is made of silicon (Si) and the active layer 103 is made of silicon dioxide (SiO ２An SOI wafer in which an intermediate oxide film 102 (see Figures 3 and 4) made of silicon (SiO2) and a base layer 101 (see Figures 3 and 4) made of silicon (Si) are stacked in this order from above is subjected to an etching process to form the outline of the optical reflecting element 1 in a planar view.

[0028] Furthermore, the base layer 101 and the intermediate oxide film 102 are removed from this SOI wafer by etching. At this time, the base layer 101 and the intermediate oxide film 102 remain in the fixed portion 10 to ensure the desired thickness. The base layer 101 and the intermediate oxide film 102 remain in the drive portion 20 so that ribs are formed at the positive and negative ends of the Y-axis. The base layer 101 and the intermediate oxide film 102 are also left on the outer periphery of the movable portion 30 so that ribs are formed. The base layer 101 and the intermediate oxide film 102 are also left in the coupling portion 40, the beam portion 50, and the mass adding portion 70. The base layer 101 and the intermediate oxide film 102 are not left in the connection portion 60 except at positions overlapping with the mass adding portion 70.

[0029] A piezoelectric body 22 is disposed in the region of the driving section 20 on the active layer 103. The piezoelectric body 22 is formed by disposing an upper electrode layer and a lower electrode layer above and below the piezoelectric body layer. In addition, a plurality of terminal sections (not shown) disposed on the fixed section 10 and a plurality of wiring sections (not shown) for connecting each terminal section to a corresponding piezoelectric body 22 are disposed on the upper surface of the active layer 103.

[0030] An upper cover 210 and a lower cover 220 (described later) are placed on the optical reflecting element 1 shown in FIGS. 1 and 2, thereby completing the optical deflector 2 (see FIGS. 3 and 4).

[0031] A drive voltage is applied to each piezoelectric element 22 from a drive circuit (not shown) via multiple terminals and multiple wiring portions. For the four piezoelectric elements 22 on the positive side of the X axis with respect to the center C10, a first drive voltage is applied to the odd-numbered piezoelectric elements 22 from the center C10, and a second drive voltage, which is opposite in phase to the first drive voltage, is applied to the even-numbered piezoelectric elements 22 from the center C10. For the four piezoelectric elements 22 on the negative side of the X axis with respect to the center C10, a second drive voltage is applied to the odd-numbered piezoelectric elements 22 from the center C10, and the first drive voltage is applied to the even-numbered piezoelectric elements 22 from the center C10. As a result, the piezoelectric elements 22 to which the first drive voltage is applied and the piezoelectric elements 22 to which the second drive voltage is applied deform in opposite directions, causing the movable part 30 to rotate about the rotation axis R10.

[0032] The optical reflecting element 1 configured as described above has a plurality of resonant frequencies that are different from one another. In general, the optical reflecting element 1 is configured so that the movable part 30 rotates repeatedly at a low-order resonant frequency. For example, when the movable part 30 is rotated repeatedly at 60 Hz, the optical reflecting element 1 is configured so that the low-order resonant frequency generated in the movable part 30 is around 60 Hz. This allows the movable part 30 to rotate repeatedly efficiently. In this case, a 60 Hz sinusoidal driving voltage can be applied to each piezoelectric element 22.

[0033] Fig. 3 is a cross-sectional view of the optical deflector 2 taken along a plane parallel to the XZ plane at the position C1-C2 shown in Fig. 1. Fig. 4 is a cross-sectional view of the optical deflector 2 taken along a plane parallel to the YZ plane at the position C3-C4 shown in Fig. 1.

[0034] The upper cover 210 is made of a light-transmitting material such as glass or resin, and the lower cover 220 is made of a material such as resin. In a plan view, the outer contours of the upper cover 210 and the lower cover 220 approximately match the outer contour of the fixed part 10. A recess 211 is formed in the center of the lower side of the upper cover 210, and the lower surface of the outer periphery of the upper cover 210 is placed on the upper surface of the outer periphery of the fixed part 10. A recess 221 is formed in the center of the upper side of the lower cover 220, and the upper surface of the outer periphery of the lower cover 220 is placed on the lower surface of the outer periphery of the fixed part 10. The space between the upper cover 210 and the lower cover 220 is an enclosed space, which prevents dust from entering this enclosed space.

[0035] The upper and lower surfaces near the center of the top cover 210 are parallel to the XY plane. When the optical deflector 2 is used, light is incident on the optical deflector 2 in an oblique direction from the positive side of the Z axis. The light incident on the optical deflector 2 passes through the top cover 210 and proceeds to the reflective surface 31, is reflected by the reflective surface 31, and then passes through the top cover 210 again and proceeds from the optical deflector 2 to the target area. This allows the light to scan the target area.

[0036] Furthermore, the areas of the upper cover 210 and the lower cover 220 that face the movable part 30 respectively constitute stoppers 81, 82 for suppressing excessive displacement of the movable part 30. That is, the stopper 81 is the part of the upper cover 210 that faces the movable part 30, and the stopper 82 is the part of the lower cover 220 that faces the movable part 30.

[0037] Note that stopper 81 is not limited to being configured as a part of top lid 210, but may be provided integrally with top lid 210 and made of the same material as top lid 210 or a material having optical transparency different from top lid 210. Similarly, stopper 82 is not limited to being configured as a part of bottom lid 220, but may be provided integrally with bottom lid 220 and made of the same material as bottom lid 220 or a different material.

[0038] For example, when an external impact is applied to the optical deflector 2 in the Z-axis direction, an inertial force in the Z-axis direction is generated in the movable part 30, causing the movable part 30 to move in the Z-axis direction within the optical deflector 2. In this case, the rib (base layer 101) on the upper or lower surface of the movable part 30 abuts against the stopper 81 or stopper 82, thereby preventing the movable part 30 from being excessively displaced in the Z-axis direction. The prevention of excessive displacement of the movable part 30 will be described later with reference to FIGS. 11(a) and 11(b).

[0039] The reason why optical reflecting element 1 is provided with connecting portion 60 as described above will now be described with reference to FIGS.

[0040] FIG. 5 is a top view schematically showing the configuration of an optical reflecting element 3 according to a first comparative example.

[0041] 1 , the optical reflecting element 3 of Comparative Example 1 has a connecting portion 60 that has a rectangular shape with a constant width in the X-axis direction in a plan view. The connecting portion 60 of Comparative Example 1 is composed of only the active layer 103.

[0042] In Comparative Example 1, the movable part 30 is supported by the fixed part 10 by the four connection parts 60, so that it is possible to suppress translational movement of the movable part 30 in the vertical direction (the direction perpendicular to the reflecting surface 31 when the movable part 30 is in the neutral position) during rotation. Furthermore, because the four connection parts 60 are arranged symmetrically as described above, the forces in the horizontal direction (the direction parallel to the reflecting surface 31 when the movable part 30 is in the neutral position) that are generated in the four connection parts 60 during rotation of the movable part 30 cancel each other out. Therefore, it is possible to suppress translational movement of the movable part 30 in the horizontal direction during rotation.

[0043] 6(a) and (b) are diagrams showing resonance modes occurring in the optical reflecting element 3 of Comparative Example 1. Fig. 6(a) shows a resonance mode (R mode) for causing the movable part 30 to perform a target rotational movement, and Fig. 6(b) shows another resonance mode (P mode) whose resonance frequency is closest to the resonance frequency of the R mode. The P mode is a resonance mode in which the movable part 30 resonates in a direction perpendicular to the reflecting surface 31. The resonance of the P mode is one order lower than the R mode.

[0044] 6(a) and 6(b) show the simulation results of the displacement distribution when the movable part 30 is displaced the most in each resonance mode, expressed in color. For convenience, FIGS. 6(a) and 6(b) are shown in gray scale, but in the actual simulation results, the displacement distribution is expressed using the color scale shown at the bottom of FIGS. 6(a) and 6(b). The color scale has the minimum value at the left end and the maximum value at the right end. The color scale is also blue at the left end, green in the middle, and red at the right end.

[0045] In this case, when a drive voltage for performing a target rotational movement in R mode is applied to each piezoelectric element 22, the target rotational movement and vertical resonant movement in P mode may occur in the movable part 30. In this case, if the resonant frequency of P mode and the resonant frequency of R mode are close to each other, the P mode movement will be excited simultaneously when the R mode movement is excited, and the P mode resonant movement will have a significant effect on the target rotational movement.

[0046] This problem can be suppressed by including a notch filter in the drive circuit to suppress the P-mode resonance. However, if the R-mode resonance frequency and the P-mode resonance frequency are close to each other, it is difficult to suppress only the P-mode resonance with a notch filter. For this reason, it is preferable that these two resonance frequencies are as far apart as possible.

[0047] In this case, it is preferable to separate the P-mode resonance frequency from the R-mode resonance frequency while maintaining the R-mode resonance frequency, which is the target resonance mode, as much as possible. From this perspective, the inventors have focused on the fact that the stress distribution and magnitude generated in each connection portion 60 differ between the R-mode and the P-mode.

[0048] 7A is a diagram showing the simulation results of the stress distribution occurring in the connection part 60 when the movable part 30 rotates the most in R mode in the configuration of Comparative Example 1. Fig. 7B is a diagram showing the simulation results of the stress distribution occurring in the connection part 60 when the movable part 30 displaces the most in P mode in the configuration of Comparative Example 1.

[0049] For convenience, the stress distribution is shown in grayscale in Figures 7(a) and (b), but the actual simulation results show the magnitude of stress in colors that change from blue to red. The color scale colors are set in the same way as in Figures 6(a) and (b). In Figures 7(a) and (b), the connection part 60, which is colored red and has the maximum stress, is circled with a dashed line.

[0050] FIG. 8 is a graph showing the simulation results of the stress distribution occurring in two connecting portions 60 aligned in the Y-axis direction according to Comparative Example 1.

[0051] Figure 8 shows the distribution of surface stress in two connection parts 60 when optical reflecting element 3 of Comparative Example 1 is cut along the C3-C4 cross section shown in Figure 5. Here, the stress distribution is shown when movable part 30 resonates in R mode and P mode in a configuration in which a pair of drive parts 20 and a pair of linking parts 40 are omitted from the configuration of Figure 5. The stress distribution in the remaining two connection parts 60 is also the same as in Figure 8.

[0052] The positive range of the horizontal axis shows the stress distribution of the connection part 60 on the positive side of the Y-axis, and the negative range of the horizontal axis shows the stress distribution of the connection part 60 on the negative side of the Y-axis. The values ​​on the horizontal axis in FIG. 8 represent the distance from the base of each connection part 60 on the rotation axis R10 side. In the negative range of the horizontal axis, the larger the value in the negative direction, the further away from the rotation axis R10. In other words, −1000 on the horizontal axis indicates a position 1000 μm in the negative Y-axis direction from the base of the connection part 60 on the negative side of the Y-axis, on the side of the movable part 30. The vertical axis in FIG. 8 is normalized with the maximum stress in each of the R mode and P mode being 100%.

[0053] 7( a), (b) and 8, in the R mode, the stress in the connection part 60 is higher at the end on the movable part 30 side, whereas in the P mode, the stress in the connection part 60 is higher not only at the end on the movable part 30 side but also at the end on the fixed part 10 side. Therefore, if the bending rigidity of the connection part is increased in the region of the connection part 60 on the fixed part 10 side where the stress is higher in the P mode than in the R mode, it is possible to change the resonance frequency in the P mode while maintaining the resonance frequency in the R mode.

[0054] For example, if the bending rigidity of the connecting portion 60 is distributed so that it is smaller (softer) on the rotation axis R10 side and larger (harder) on the fixed portion 10 side, this distribution will be more consistent with the P-mode stress distribution than with the R-mode stress distribution. That is, the areas with high stress and areas with high bending rigidity are closer in the P-mode than in the R-mode. Therefore, by setting the bending rigidity distribution of the connecting portion 60 in this manner, the resonant frequency of the P-mode, in which a high stress distribution occurs at the end on the fixed portion 10 side, can be changed more significantly than the resonant frequency of the R-mode, in which a high stress distribution does not occur at the end on the fixed portion 10 side. This allows the resonant frequency of the P-mode to be separated from the resonant frequency of the R-mode while suppressing fluctuations in the resonant frequency of the R-mode.

[0055] From this viewpoint, the optical reflecting element 4 of Comparative Example 2 shown in FIG. 9 is constructed.

[0056] FIG. 9 is a top view schematically showing the configuration of an optical reflecting element 4 according to a second comparative example.

[0057] In Comparative Example 2, the connection portion 60 is divided into a first region 61 and a second region 62, and the distribution of the bending rigidity of the connection portion 60 is set so that the bending rigidity of the first region 61 is higher than the bending rigidity of the second region 62. More specifically, the first region 61 is rectangular in plan view, and the second region 62 has a meandering shape that snakes in the X-axis direction. This makes it possible to separate the P-mode resonance frequency from the R-mode resonance frequency while maintaining the R-mode resonance frequency, compared to a case in which the connection portion 60 does not have a bending rigidity distribution as in Comparative Example 1 of Figure 5.

[0058] FIG. 10 shows the results of a simulation showing the relationship between the distribution of bending rigidity of the connection portion 60 and the resonance frequencies of the R mode and the P mode in the second comparative example.

[0059] In this simulation, the distribution of bending rigidity of the connection portion 60 was changed by changing the number of meander-shaped folds constituting the second region 62. Here, each time the number of meander-shaped folds of the second region 62 increases by one, the length of the second region 62 in the Y-axis direction increases by a predetermined pitch, and the length of the first region 61 in the Y-axis direction decreases in response to the increase in the length of the second region 62. Similarly, each time the number of meander-shaped folds of the second region 62 decreases by one, the length of the second region 62 in the Y-axis direction decreases by a predetermined pitch, and the length of the first region 61 in the Y-axis direction increases in response to the decrease in the length of the second region 62. In other words, the overall length of the connection portion 60 does not change even if the number of meander-shaped folds of the second region 62 increases or decreases. An increase in the number of folds means that the second region 62 is widened in the Y-axis direction, and a decrease in the number of folds means that the second region 62 is shortened in the Y-axis direction.

[0060] In this way, the rate of change in the resonance frequencies of the R mode and the P mode was obtained while changing the number of times the meandering shape of the second region 62 was folded to change the distribution of bending rigidity of the connection portion 60. Here, the rate of change was obtained as the ratio (percentage) of the resonance frequencies of the R mode and the P mode obtained by each number of folding times to the resonance frequencies of the R mode and the P mode when a connection portion 60 with a predetermined number of folding times was used.

[0061] 10, the horizontal axis of the graph represents the increase or decrease in the number of folds (number of springs) for each configuration relative to a predetermined number of folds (number of springs) for the meandering shape, and the vertical axis of the graph represents the resonant frequencies of the R mode and P mode normalized to 100% when the increase or decrease in the number of folds (number of springs) is 0.

[0062] 10 , although the P-mode resonance frequency fluctuates relatively greatly depending on the increase or decrease in the number of folds (number of springs) of the meandering shape of the second region 62, the R-mode resonance frequency does not fluctuate as much. From this, it was confirmed that by adjusting the ratio of the second region 62 (soft range) with low bending rigidity on the rotation axis R10 side to the first region 61 (hard range) with high bending rigidity on the fixed portion 10 side in the connecting portion 60, the P-mode resonance frequency can be changed significantly relative to the R-mode resonance frequency, and as a result, the difference between these resonance frequencies can be effectively widened.

[0063] However, when the bending rigidity distribution is set in the connection portion 60 so that the first region 61 and the second region 62 have different bending rigidities, as in Comparative Example 2 in Fig. 9 , there is a risk that the fragile second region 62 will be damaged if an external impact is applied to the optical deflector including the optical reflecting element 4. Therefore, in this embodiment, a mass adding portion 70 is provided in the first region 61. The effect of the mass adding portion 70 will be described below with reference to Figs. 11(a) and 11(b).

[0064] Figures 11(a) and (b) are schematic diagrams showing the vertical (Z-axis) positional relationship between the fixed portion 10 near the connection portion 60, the connection portion 60, the movable portion 30, and a stopper 81 (part of the upper cover 210) located above the movable portion 30.

[0065] 11A and 11B show the positional relationships of the components when the upper surface of the movable component 30 reaches the stopper 81, according to Comparative Example 2 and the embodiment, respectively. For convenience, the second region 62 is illustrated as a straight line rather than a meandering shape, and the components are illustrated as being aligned in the horizontal direction.

[0066] In both Comparative Example 2 and the embodiment, when an external impact is applied to the optical deflector and the upper surface of the movable portion 30 reaches the stopper 81, the movable portion 30 moves upward by a distance H1. In Comparative Example 2, as shown in FIG. 11A , the height-direction deformation amounts of the first region 61 and the second region 62 are H21 and H22, respectively. Because the first region 61 has significantly higher rigidity than the second region 62, the deformation amount H22 of the second region 62 is greater than the deformation amount H21 of the first region 61. If the deformation amount H22 exceeds a level at which the second region 62 may be damaged, the second region 62 may be damaged.

[0067] In contrast, in the embodiment, because the mass adding portion 70 is provided in the first region 61, a relatively large inertial force is also generated in the mass adding portion 70 when an external impact is applied to the optical deflector 2. For this reason, in the embodiment, as shown in FIG. 11B , the deformation amount H31 of the first region 61 is larger than the deformation amount H21 of the first region 61 of Comparative Example 2. As a result, the deformation amount H32 of the second region 62 in the embodiment is smaller than the deformation amount H22 of the second region 62 of Comparative Example 2. Therefore, the deformation amount H32 is less likely to exceed a level of deformation that could cause damage to the second region 62, and damage to the second region 62 can be suppressed.

[0068] <Verification> The inventor verified the relationship between the position of the mass adding portion 70 and the rate of change of the movement distance H1 of the movable portion 30 and the rate of change of the deformation amount H32 of the second region 62 by simulation.

[0069] FIG. 12 is a diagram for explaining the conditions of this simulation.

[0070] The width W1 of the connecting portion 60 was set to 285 μm, and the length L1 of the first region 61 and the length L2 of the second region 62 were set to 850 μm and 380 μm, respectively. The width W2 of the region where the mass adding portion 70 is installed in the first region 61 in the Y-axis direction was set to 50 μm. For convenience, FIG. 12 shows only the portion of the mass adding portion 70 that overlaps with the first region 61 in a plan view. The movable portion 30 was square, and the length L3 of one side of the movable portion 30 was set to 1300 μm. The distance L11 from the fixed portion 10 to the installation region of the mass adding portion 70 was varied to 0 μm, 200 μm, 400 μm, 600 μm, and 800 μm. However, when the distance L11 was set to 0 μm, the mass adding portion 70 was omitted. In this simulation, the stoppers 81 and 82, the drive portion 20, and the connecting portion 40 were omitted.

[0071] In this way, a static acceleration of 5000 G was applied to the optical deflector 2 while changing the distance L11, and the rate of change in the movement distance of the movable part 30 and the rate of change in the deformation amount of the second region 62 were calculated at the timing when the displacement amount of the movable part 30 reached a maximum. Here, the movement distance of the movable part 30 and the deformation amount of the second region 62 when the mass adding portion 70 was not provided in the first region 61 and the length L1 of the first region 61 was 800 μm were used as comparison objects, and the ratio (percentage) of the calculated movement distance of the movable part 30 to the movement distance of the movable part 30 for comparison and the ratio (percentage) of the calculated deformation amount of the second region 62 to the deformation amount of the second region 62 for comparison were calculated as the rate of change, respectively.

[0072] 13(a) and 13(b) are graphs showing the results of this simulation.

[0073] The horizontal axes of the graphs in Figures 13(a) and (b) represent the distance L11 in Figure 12. The vertical axes of the graphs in Figures 13(a) and (b) represent the rate of change in the movement distance of the movable portion 30 and the rate of change in the deformation amount of the second region 62, respectively. In Figures 13(a) and (b), the plots where the distance L11 is 0 μm correspond to a configuration in which the mass adding portion 70 is not provided. In Figure 13(a), the rate of change (100%) when the mass adding portion 70 is not provided and the distance L1 is 800 μm is shown by a white circle.

[0074] 13A, as the distance L11 increases, i.e., as the installation position of the mass adding unit 70 moves farther away from the fixed unit 10, the rate of change of the movement distance of the movable unit 30 generally increases. However, as also shown in FIG. 13A, when the distance L11 is between 0 μm and 400 μm, the rate of change of the movement distance of the movable unit 30 is equal to or less than the rate of change (approximately 105.5%) when the distance L11 is 0 μm. Therefore, in this simulation, it can be seen that by setting the distance L11 to 400 μm or more, in other words, by arranging the mass adding unit 70 closer to the movable unit 30 than the dividing line that passes through the center of gravity of the first region 61 and divides the first region 61 in the direction in which the connection unit 60 extends (the Y-axis direction), the amount of displacement of the movable unit 30 can be effectively increased.

[0075] On the other hand, referring to FIG. 13B, the rate of change in the deformation amount of the second region 62 remains almost unchanged regardless of the magnitude of the distance L11.

[0076] 13A and 13B, it was confirmed that the movement distance of the movable part 30 can be increased while suppressing the amount of deformation of the second region 62 by changing the distance L11 between the mass adding part 70 and the fixed part 10. Therefore, from these results, it can be seen that when an external impact is applied to the optical deflector 2, the amount of displacement of the second region 62 can be suppressed to a level below that which may cause damage, and the movable part 30 can be brought into contact with the stoppers 81, 82.

[0077] The reason why the rate of change of the movement distance of the movable part 30 becomes lower than the rate of change when the mass addition part 70 is not provided when the mass addition part 70 is positioned closer to the fixed part 10 is thought to be that the installation area of ​​the mass addition part 70, which has a width W2 in the Y-axis direction, becomes closer to the fixed part 10, making the first region 61 less likely to bend. Therefore, it is preferable to install the mass addition part 70 away from the fixed part 10 so that the rate of change of the movement distance of the movable part 30 exceeds the rate of change when the mass addition part 70 is not provided. However, the appropriate distance from the fixed part 10 to which the mass addition part 70 should be placed varies depending on the configuration of each part of the optical reflecting element 1. However, regardless of the configuration of the optical reflecting element 1, it is expected that the amount of displacement of the movable part 30 can be increased to some extent by placing the mass addition part 70 on the movable part 30 side of the first region 61.

[0078] <Effects of the embodiment> According to the above embodiment, the following effects are achieved.

[0079] 1 and 2, the optical reflecting element 1 includes a movable section 30 provided with a reflecting surface 31, a beam section 50 extending along a rotation axis R10 and connected to the movable section 30, a drive section 20 that rotates the movable section 30 about the rotation axis R10 via the beam section 50, a connection section 60 having one end connected to the fixed section 10 and the other end connected to the beam section 50, and a mass addition section 70 that adds mass to the connection section 60. The connection section 60 is divided into a first region 61 on the fixed section 10 side and a second region 62 on the movable section 30 side, the first region 61 having higher bending rigidity than the second region 62, and the mass addition section 70 adds mass to the first region 61.

[0080] According to this configuration, by adjusting the bending rigidity of the connection portion 60 as described above, the resonant frequency corresponding to the rotational movement of the movable portion 30 can be separated from the closest resonant frequency, as shown in the simulation results of Comparative Example 2 in FIG. 10 , thereby stabilizing the rotational movement of the movable portion 30. Furthermore, when an external impact is applied to the optical reflecting element 1, a large inertial force is generated in the mass-adding portion 70 as well as the movable portion 30, which has a large mass. Therefore, as shown in FIG. 11B , the first region 61, which has high rigidity and is difficult to bend, is significantly deformed by the inertial force of the mass-adding portion 70, allowing the movable portion 30 to abut against the stoppers 81 and 82 before the second region 62, which has a lower bending rigidity, is excessively displaced and damaged. This prevents damage to the connection portion 60.

[0081] As shown in Figures 1 and 2, the mass adding portion 70 adds mass to the first region 61 on the movable portion 30 side of the dividing line that passes through the center of gravity of the first region 61 and divides the first region 61 in the direction in which the connection portion 60 extends (the Y-axis direction).

[0082] 13A, this configuration effectively increases the displacement of the movable part 30 due to the inertial force generated in the mass adding part 70. This allows the movable part 30 to come into contact with the stoppers 81 and 82 more quickly, thereby more reliably preventing damage to the connection part 60.

[0083] As shown in FIGS. 1 and 2, the mass adding portion 70 protrudes from the first region 61 in the width direction (X-axis direction) of the first region 61 .

[0084] If the installation area of ​​the mass adding portion 70 relative to the first region 61 increases, the first region 61 becomes less likely to bend. In contrast, with the above configuration, the installation area of ​​the mass adding portion 70 relative to the first region 61 is reduced, while the mass of the mass adding portion 70 can be effectively increased by the second portion 72 protruding from the connection portion 60. Therefore, when an external impact is applied, the inertial force of the mass adding portion 70 can effectively deform the first region 61, thereby effectively preventing damage to the connection portion 60.

[0085] 1 and 2 , the mass adding portion 70 includes a first portion 71 that overlaps with the first region 61 in a plan view, and a second portion 72 that protrudes from the first region 61 in the width direction (X-axis direction) of the first region 61. The second portion 72 is longer than the first portion 71 in the direction in which the connecting portion 60 extends (Y-axis direction).

[0086] According to this configuration, by lengthening the second portion 72 in the direction in which the connecting portion 60 extends, the mass of the mass adding portion 70 can be increased while reducing the installation area of ​​the mass portion relative to the connecting portion 60.

[0087] As shown in FIG. 4, the mass adding portion 70 is formed integrally with the connecting portion 60 on the lower surface of the connecting portion 60 (the lower surface of the active layer 103 ).

[0088] According to this configuration, the mass adding portion 70 can be easily disposed relative to the connecting portion 60, and the accuracy of processing and positioning the mass adding portion 70 can be improved.

[0089] The mass adding portion 70 includes silicon (Si).

[0090] As shown in FIG. 4, the mass adding portion 70 and the fixed portion 10 are both composed of a base layer 101 (silicon) and an intermediate oxide film 102 (silicon dioxide), and therefore, by etching the SOI wafer from the underside, the mass adding portion 70 and the fixed portion 10 can be formed in the same process.

[0091] As shown in Figures 1 and 2, a pair of beam portions 50 are arranged parallel to the rotation axis R10, sandwiching the movable portion 30 therebetween, a pair of drive portions 20 are arranged parallel to the rotation axis R10, sandwiching the movable portion 30 therebetween, and four connection portions 60 are arranged symmetrically about the rotation axis R10 in a plan view and about a straight line L10 that passes through the center C10 of the movable portion 30 and is perpendicular to the rotation axis R10.

[0092] According to this configuration, the movable part 30 is supported on the fixed part 10 by the four connection parts 60, so that it is possible to suppress translational movement of the movable part 30 in the vertical direction (the direction perpendicular to the reflecting surface 31 when the movable part 30 is in the neutral position) during rotation. Furthermore, because the four connection parts 60 are arranged symmetrically as described above, forces in the horizontal direction (the direction parallel to the reflecting surface 31 when the movable part 30 is in the neutral position) that are generated in the four connection parts 60 during rotation of the movable part 30 cancel each other out. Therefore, it is possible to suppress translational movement of the movable part 30 in the horizontal direction during rotation.

[0093] As shown in FIGS. 1 and 2, the mass adding portions 70 disposed on the four connecting portions 60 are disposed symmetrically with respect to the center C10 of the movable portion 30.

[0094] According to this configuration, the four mass adding parts 70 are arranged in a well-balanced manner with respect to the center C10 of the movable part 30, so that the movable part 30 can be rotated stably.

[0095] As shown in FIGS. 1 and 2, the optical reflecting element 1 includes a fixed portion 10 that supports a pair of driving portions 20 and four connecting portions 60 .

[0096] According to this configuration, each part of the optical reflecting element 1 is stably supported by the fixing part 10, so that the optical reflecting element 1 can be positioned with high precision by placing the fixing part 10 on the installation surface.

[0097] As shown in FIGS. 1 and 2, the pair of driving units 20 is configured by connecting a plurality of piezoelectric cantilevers 21 in a meandering shape.

[0098] According to this configuration, by connecting a plurality of piezoelectric cantilevers 21 in a meandering manner, the movable part 30 can be driven at a large rotation angle.

[0099] As shown in FIG. 3, the optical deflector 2 includes the optical reflecting element 1 and stoppers 81 and 82 for preventing the movable portion 30 from being excessively displaced.

[0100] According to this configuration, even if an external impact is applied to the optical deflector 2, the stoppers 81 and 82 can prevent the movable part 30 from being excessively displaced.

[0101] The stopper 81 is made of a transparent member that allows light incident on the reflecting surface 31 and light reflected by the reflecting surface 31 to pass through.

[0102] According to this configuration, a transparent member that is normally provided in the optical deflector 2 can be used as the stopper 81, so that it is possible to omit providing a separate material for forming the stopper 81.

[0103] <Modification 1> The shape of the mass adding portion 70 is not limited to that of the above embodiment. In Modification 1 shown in Figures 14(a) to 15(b) below, the layered structure of the mass adding portion 70 is the same as that of the above embodiment, but the shape and number of the mass adding portions 70 in plan view are different.

[0104] For example, as shown in Fig. 14(a), the length of the second portion 72 in the Y-axis direction may be the same as the length of the first portion 71 in the Y-axis direction. Furthermore, as shown in Figs. 14(b) and 15(a), the second portion 72 may be omitted. In this case, the length of the first portion 71 in the X-axis direction may be the same as the length of the first region 61 in the X-axis direction, as shown in Fig. 14(b), or may be shorter than the length of the first region 61 in the X-axis direction, as shown in Fig. 15(a). Furthermore, as shown in Fig. 15(b), multiple mass adding portions 70 may be arranged with a predetermined gap between them in the Y-axis direction.

[0105] <Modification 2> The shape of the connection portion 60 is not limited to that of the above embodiment, as long as the first region 61 has a higher bending rigidity than the second region 62. In Modification 2 shown in Figures 16(a) to 18(a) below, the layered structure of the connection portion 60 (first region 61 and second region 62) is the same as in the above embodiment, but the shape of the connection portion 60 in plan view is different.

[0106] For example, in the above embodiment, the second region 62 has a meandering shape that snakes in the Y-axis direction. However, as shown in FIG. 16( a), the second region 62 may have a meandering shape that snakes in the X-axis direction. Also, as shown in FIG. 16( b), the width of the second region 62 in the X-axis direction may be constant and narrower than the width of the first region 61 in the X-axis direction. Also, as shown in FIG. 17( a), the width of the end of the first region 61 on the second region 62 side may become narrower as it approaches the second region 62. Also, as shown in FIG. 17( b), the overall width of the first region 61 may become narrower as it approaches the second region 62. Also, the end of the connection portion 60 on the movable portion 30 side may be connected to the movable portion 30 near the connection position of the beam portion 50. In this case, for example, as shown in FIG. 18( a), the end of the second region 62 on the movable portion 30 side may be connected to the movable portion 30.

[0107] <Modification 3> Although the mass adding unit 70 is configured by the base layer 101 and intermediate oxide film 102 provided on the lower surface side (negative side of the Z axis) of the first region 61, the present invention is not limited to this. For example, as shown in FIG. 18( b), the mass adding unit 70 may be configured by a piezoelectric body 73 provided on the upper surface side (positive side of the Z axis) of the first region 61. The piezoelectric body 73 is configured similarly to the piezoelectric body 22 of the drive unit 20 shown in FIG. 1, but no wiring is connected to the piezoelectric body 73. In this case as well, mass can be added to the first region 61.

[0108] In FIG. 18B, a mass addition portion made up of a base layer 101 and an intermediate oxide film 102 may be further disposed on the lower surface side of the first region 61, as in the embodiment.

[0109] Furthermore, a member other than the piezoelectric body 73 may be disposed on the upper surface of the first region 61 as the mass adding portion 70. Furthermore, in the above embodiment, a member other than the base layer 101 and the intermediate oxide film 102 may be disposed on the lower surface of the first region 61 as the mass adding portion 70. The other member disposed as the mass adding portion 70 is, for example, a metal material with a high specific gravity (such as tungsten or gold). When a metal material is used as the other member, the other member is formed as the mass adding portion 70 by, for example, sputtering.

[0110] <Modification 4> Although the first region 61 has a shape extending in the Y-axis direction, it may also have a shape extending in another direction parallel to the XY plane. For example, as shown in Figures 19(a) and 19(b), the first region 61 may have a T-shape.

[0111] The first region 61 in this modified example is composed of a portion 61a extending in the Y-axis direction and a portion 61b extending in the X-axis direction. The portion 61a is connected to the second region 62 on the movable portion 30 side, and the end of the portion 61a on the fixed portion 10 side is separated from the fixed portion 10. The portion 61b extends in the positive direction and the negative direction of the X-axis at the end of the portion 61a on the fixed portion 10 side. Both ends of the portion 61b are connected to a pair of protrusions 12 protruding from the fixed portion 10 toward the movable portion 30 side. The mass adding portion 70 is provided near the center of the portion 61b.

[0112] In this modified example, the mass adding portion 70 is separated from the protrusion 12 of the fixed portion 10, so when an external impact is applied to the optical deflector 2, the portion 61b between the mass adding portion 70 and the protrusion 12 is deflected by the inertial force generated in the mass adding portion 70. This makes it possible to bring the movable portion 30 into contact with the stoppers 81, 82 before the second region 62 is excessively displaced and damaged, as in the above embodiment.

[0113] <Modification 5> In the above embodiment, it is also assumed that after the movable portion 30 abuts against the stopper 81 or 82, the first region 61 may be further deformed by the inertial force of the mass adding portion 70. If such further deformation of the first region 61 becomes a problem, stoppers 91, 92 may be provided to suppress excessive displacement of the mass adding portion 70.

[0114] FIG. 20A is a cross-sectional view of the optical deflector 2 according to this modification, taken along a plane parallel to the YZ plane at the position C3-C4 shown in FIG.

[0115] 1 , in this modified example, a stopper 91 is arranged in the recess 211 of the upper lid 210 at a position on the positive side of the mass adding portion 70 in the Z axis, and a stopper 92 is arranged in the recess 221 of the lower lid 220 at a position on the negative side of the mass adding portion 70 in the Z axis. The stoppers 91 and 92 are formed integrally with the upper lid 210 and the lower lid 220, respectively.

[0116] Stopper 91 is made of the same material as stopper 81 (see FIG. 3), and stopper 92 is made of the same material as stopper 82 (see FIG. 3). This allows stoppers 81 and 91 to be formed using the same process for molding top cover 210, thereby enabling smooth formation of stoppers 81 and 91. Similarly, stoppers 82 and 92 can be formed using the same process for molding bottom cover 220, thereby enabling smooth formation of stoppers 82 and 92.

[0117] 20(b), the stopper 91 may be made of a material different from that of the stopper 81 and the upper cover 210, and the stopper 92 may be made of a material different from that of the stopper 82 and the lower cover 220. In this case, the stoppers 91 and 92 may be made of a material that is not optically transparent.

[0118] 20A and 20B, the optical deflector 2 further includes stoppers 81 and 82 (other stoppers) for preventing excessive displacement of the mass adding portion 70. With this configuration, when an external impact is applied to the optical deflector 2, it is possible to prevent damage to the first region 61 due to excessive displacement of the first region 61.

[0119] <Other Modifications> In the above embodiment, the stoppers 81, 82 are provided above and below the movable portion 30 in a range corresponding to the movable portion 30, but they may be provided in a range wider than the range corresponding to the movable portion 30. Furthermore, in the above modification 5, the stoppers 91, 92 are provided above and below the mass adding portion 70 in a range corresponding to the mass adding portion 70, but they may be provided in a range wider than the range corresponding to the mass adding portion 70.

[0120] In the above embodiment, the surfaces of the stoppers 81 and 82 facing the movable part 30 are parallel to the X-Y plane, but this is not limited thereto and may be, for example, a surface including a plurality of protrusions. Similarly, in the above fifth modified example, the surfaces of the stoppers 91 and 92 facing the first region 61 and the mass adding part 70 are parallel to the X-Y plane, but this is not limited thereto and may be, for example, a surface including a plurality of protrusions.

[0121] In the above embodiment, the stoppers 81, 82 are provided above and below the movable portion 30, but it is also possible to provide only one of the stoppers 81, 82. In the above-described fifth modification, the stoppers 91, 92 are provided above and below the mass adding portion 70, but it is also possible to provide only one of the stoppers 91, 92.

[0122] In the above embodiment, the stoppers 81 and 82 may protrude relative to the recesses 211 and 221, respectively, similar to the stoppers 91 and 92. The distance between the stoppers 81 and 82 and the movable part 30 is set according to the range within which it is desired to restrict the vertical movement of the movable part 30 without interfering with the normal rotational movement of the movable part 30. In the above-described fifth modified example, the stoppers 91 and 92 may be formed by a part of the upper cover 210 and the lower cover 220, respectively, similar to the stoppers 81 and 82. The distance between the stoppers 91 and 92 and the mass adding part 70 is set according to the range within which it is desired to restrict the vertical movement of the mass adding part 70.

[0123] In the above embodiment and modified example, the bending rigidity of the first region 61 and the second region 62 is made different by making the shapes of the first region 61 and the second region 62 different in a plan view, but the method for making the bending rigidity of the first region 61 and the second region 62 different is not limited to this. For example, the bending rigidity may be made different by making the thickness of the first region 61 and the second region 62 different. Alternatively, the bending rigidity may be made different by stacking another material on the upper surface of the first region 61.

[0124] In the above embodiment, the fixed portion 10 supports the four connection portions 60 and the pair of drive portions 20, but this is not limiting and the fixed portions supporting these portions may be different. For example, the fixed portion supporting the four connection portions 60 and the fixed portion supporting the pair of drive portions 20 may be different from each other. Furthermore, the optical reflecting element 1 does not necessarily have to include the fixed portion 10. In this case, the four connection portions 60 and the pair of drive portions 20 are supported by fixed portions provided on the optical deflector 2, for example.

[0125] In the above embodiment and modified examples, some of the four connecting portions 60 may be omitted. For example, two of the four connecting portions 60 on the positive side of the X-axis or the negative side of the X-axis may be omitted. However, as described in Comparative Examples 1 and 2, providing four connecting portions 60 can further suppress translational motion and more accurately adjust the resonance frequencies of the R mode and the P mode.

[0126] In the above embodiment, a structure consisting of one drive unit 20, one coupling unit 40, and one beam unit 50 is arranged on both the X-axis positive side and the X-axis negative side of the movable unit 30 so as to sandwich the movable unit 30 in a plan view, but such a structure may be arranged on only one of the X-axis positive side and the X-axis negative side of the movable unit 30. In this case, two connection units 60 are arranged corresponding to one beam unit 50.

[0127] In the above embodiment, the drive unit 20 has a meandering type configuration, but the drive unit 20 may have a configuration of another type.

[0128] 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.

[0129] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0130] (Technology 1) An optical reflecting element comprising: a movable part provided with a reflective surface; a beam part extending along a rotation axis and connected to the movable part; a drive part that rotates the movable part about the rotation axis via the beam part; a connection part having one end connected to a fixed part and the other end connected to the beam part or near a connection position of the beam part on the movable part; and a mass adding part that adds mass to the connection part, wherein the connection part is divided into a first region on the fixed part side and a second region on the movable part side, the first region having a higher bending rigidity than the second region, and the mass adding part adding mass to the first region.

[0131] According to this technology, by adjusting the bending rigidity of the connection portion as described above, the resonant frequency corresponding to the rotational movement of the movable portion can be separated from the other resonant frequency closest to it, thereby stabilizing the rotational movement of the movable portion. Furthermore, when an external impact is applied to the optical reflecting element, a large inertial force is generated in the mass-adding portion as well as the movable portion, which has a large mass. Therefore, the first region, which has high rigidity and is difficult to bend, is significantly deformed by the inertial force of the mass-adding portion, allowing the movable portion to abut against the stopper before the second region, which has low bending rigidity, is excessively displaced and damaged. This prevents damage to the connection portion.

[0132] (Technology 2) In the optical reflecting element described in Technology 1, the mass adding portion adds mass to the first region on the movable portion side of a dividing line that passes through the center of gravity of the first region and divides the first region in the direction in which the connecting portion extends.

[0133] According to this technology, the displacement of the movable part can be effectively increased by the inertial force generated in the mass-addition part. As a result, the movable part comes into contact with the stopper more quickly, and damage to the connection part can be more reliably prevented.

[0134] (Technology 3) The optical reflecting element according to Technology 1 or 2, wherein the mass adding portion protrudes from the first region in a width direction of the first region.

[0135] If the installation area of ​​the mass addition portion relative to the first region is increased, the first region becomes less likely to bend. In contrast, with the above technology, the installation area of ​​the mass addition portion relative to the first region can be reduced while the mass of the mass addition portion can be effectively increased by the portion protruding from the connection portion. Therefore, when an external impact is applied, the inertial force of the mass addition portion can effectively deform the first region, thereby effectively preventing damage to the connection portion.

[0136] (Technology 4) An optical reflecting element described in any one of technologies 1 to 3, characterized in that the mass-adding portion comprises a first portion that overlaps with the first region in a planar view and a second portion that protrudes from the first region in a width direction of the first region, and the second portion is longer than the first portion in a direction in which the connecting portion extends.

[0137] According to this technique, by lengthening the second portion in the direction in which the connecting portion extends, it is possible to increase the mass of the mass adding portion while suppressing the installation area of ​​the mass portion relative to the connecting portion.

[0138] (Technology 5) The optical reflecting element according to any one of Technologies 1 to 4, wherein the mass adding portion is formed integrally with the connecting portion on a lower surface of the connecting portion.

[0139] According to this technique, the mass adding portion can be easily disposed relative to the connecting portion, and the accuracy of processing and positioning the mass adding portion can be improved.

[0140] (Technology 6) The optical reflecting element according to any one of Technologies 1 to 5, wherein the mass adding portion contains silicon (Si).

[0141] (Technology 7) An optical reflecting element described in any one of technologies 1 to 6, characterized in that: the beam portions are arranged in pairs parallel to the rotation axis so as to sandwich the movable portion; the drive portions are arranged in pairs parallel to the rotation axis so as to sandwich the movable portion; and four connection portions are arranged symmetrically about the rotation axis in a planar view and symmetrically about a line that passes through the center of the movable portion and is perpendicular to the rotation axis.

[0142] According to this technology, the movable part is supported by the fixed part by four connecting parts, so that vertical translational movement (a direction perpendicular to the reflecting surface when the movable part is in the neutral position) of the movable part during rotation can be suppressed. Furthermore, because the four connecting parts are arranged symmetrically as described above, horizontal forces (a direction parallel to the reflecting surface when the movable part is in the neutral position) generated at the four connecting parts during rotation of the movable part cancel each other out. Therefore, horizontal translational movement of the movable part during rotation can be suppressed.

[0143] (Technology 8) In the optical reflecting element described in Technology 7, the mass adding portions respectively disposed at the four connecting portions are disposed symmetrically with respect to the center of the movable portion.

[0144] According to this technique, the four mass adding parts are arranged in a well-balanced manner with respect to the center of the movable part, so that the movable part can be rotated stably.

[0145] (Technology 9) The optical reflecting element according to Technology 7 or 8, further comprising the fixing portion supporting the pair of driving portions and the four connecting portions.

[0146] According to this technique, each part of the optical reflecting element is stably supported by the fixing parts, so that the optical reflecting element can be positioned with high precision by placing the fixing parts on the installation surface.

[0147] (Technology 10) The optical reflecting element according to any one of Techniques 7 to 9, wherein the pair of driving sections is configured by connecting a plurality of piezoelectric cantilevers in a meandering shape.

[0148] According to this technology, by connecting a plurality of piezoelectric cantilevers in a meandering manner, the movable part can be driven at a large rotation angle.

[0149] (Technology 11) An optical deflector comprising: the optical reflecting element according to any one of technologies 1 to 10; and a stopper for preventing the movable portion from being excessively displaced.

[0150] This technique provides the same effects as the first aspect, and also allows the stopper to prevent excessive displacement of the movable portion even when an external impact is applied to the optical deflector.

[0151] (Technology 12) In the optical deflector described in Technology 11, the stopper is made of a transparent member that allows light incident on the reflecting surface and light reflected by the reflecting surface to pass through.

[0152] According to this technique, a transparent member that is normally provided in an optical deflector can be used as the stopper, so that it is possible to omit providing a separate material for forming the stopper.

[0153] (Technology 13) The optical deflector according to Technology 11 or 12, further comprising another stopper for preventing the mass adding portion from being excessively displaced.

[0154] According to this technique, when an external impact is applied to the optical deflector, it is possible to prevent the first region from being damaged due to excessive displacement of the first region.

[0155] (Technology 14) In the optical deflector according to Technology 13, the stopper and the other stopper are made of the same material.

[0156] According to this technique, the stopper and the other stopper can be formed in the same process, and therefore the stopper and the other stopper can be formed smoothly.

[0157] REFERENCE SIGNS LIST 1 Optical reflecting element 2 Optical deflector 10 Fixed portion 20 Drive portion 21 Piezoelectric cantilever 30 Movable portion 31 Reflecting surface 50 Beam portion 60 Connection portion 61 First region 62 Second region 70 Mass adding portion 71 First portion 72 Second portion 81, 82 Stoppers 91, 92 Stoppers (other stoppers) C10 Center L10 Straight line R10 Rotation axis

Claims

1. An optical reflecting element comprising: a movable part provided with a reflective surface; a beam part extending along a rotation axis and connected to said movable part; a drive part that rotates said movable part about said rotation axis via said beam part; a connection part having one end connected to a fixed part and the other end connected to said beam part or near the connection position of said beam part on said movable part; and a mass adding part that adds mass to said connection part, wherein said connection part is divided into a first region on the fixed part side and a second region on the movable part side, said first region having higher bending rigidity than said second region, and said mass adding part adding mass to said first region.

2. An optical reflecting element according to claim 1, characterized in that the mass adding portion adds mass to the first region on the movable portion side of a dividing line that passes through the center of gravity of the first region and divides the first region in the direction in which the connecting portion extends.

3. An optical reflecting element according to claim 1, characterized in that the mass adding portion protrudes from the first region in the width direction of the first region.

4. An optical reflecting element as described in claim 3, wherein the mass-adding portion comprises a first portion that overlaps with the first region in a plan view and a second portion that protrudes from the first region in the width direction of the first region, and the second portion is longer than the first portion in the direction in which the connecting portion extends.

5. An optical reflecting element according to claim 1, wherein the mass adding portion is formed integrally with the connecting portion on the lower surface of the connecting portion.

6. An optical reflecting element according to claim 5, wherein the mass adding portion contains silicon (Si).

7. An optical reflecting element as described in claim 1, characterized in that: the beam portions are arranged in pairs parallel to the rotation axis so as to sandwich the movable portion; the drive portions are arranged in pairs parallel to the rotation axis so as to sandwich the movable portion; and four connection portions are arranged symmetrically about the rotation axis in a plan view and about a line that passes through the center of the movable portion and is perpendicular to the rotation axis.

8. An optical reflecting element according to claim 7, characterized in that the mass adding portions disposed at the four connecting portions are disposed symmetrically with respect to the center of the movable portion.

9. An optical reflecting element according to claim 7, characterized in that it comprises the fixed portion that supports the pair of drive portions and the four connection portions.

10. An optical reflecting element according to claim 7, wherein the pair of driving sections are constructed by connecting a plurality of piezoelectric cantilevers in a meandering pattern.

11. An optical deflector comprising: an optical reflecting element according to any one of claims 1 to 10; and a stopper for preventing the movable part from being excessively displaced.

12. An optical deflector according to claim 11, characterized in that the stopper is made of a transparent member that allows light incident on the reflecting surface and light reflected by the reflecting surface to pass through.

13. An optical deflector according to claim 11, further comprising another stopper for preventing the mass adding portion from being excessively displaced.

14. An optical deflector according to claim 13, wherein the stopper and the other stopper are made of the same material.

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