Optical reflection element

Abstract

An optical reflection element (1) comprises: a movable part (30) provided with a reflection surface (31); a pair of drive parts (20); a fixed part (10) that supports the pair of drive parts (20); a pair of beam parts (50) that extend along a rotation axis (R10) and are connected to the movable part (30); a pair of coupling parts (40) that couple the pair of beam parts (50) and the pair of drive parts (20); and four connection parts (60) that each have one end connected to the fixed part (10) and the other end connected to the pair of beam parts (50) or the vicinity of the connection position of each of the pair of beam parts (50) in the movable part (30). In plan view, the four connection parts (60) are arranged symmetrically with respect to the rotation axis (R10) and symmetrically with respect to a straight line (L10) that passes through the center (C10) of the movable part (30) and is perpendicular to the rotation axis (R10).

Description

Optical Reflective Elements

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

[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.

[0003] The following Patent Document 1 describes a mirror drive device that rotates a mirror section (movable section) about a rotation axis. The mirror section is fixed to a fixed section near the rotation axis via a vertical movement suppression structure. The mirror section is also connected to a piezoelectric actuator at an end opposite the vertical movement suppression structure. When the piezoelectric actuator is driven, the mirror section rotates about the rotation axis. At this time, vertical translational movement of the mirror section is suppressed by the vertical movement suppression structure.

[0004] JP 2013-057819 A

[0005] In the mirror drive device with the above configuration, the vertical movement suppression structure deforms when the mirror part (movable part) rotates, and the return force is applied to the mirror part. As a result, when the mirror part (movable part) rotates, it receives a horizontal force directed toward the fixed end of the movement suppression structure, causing a deviation in the rotation axis depending on the deflection angle.

[0006] Furthermore, the optical reflecting element may have a plurality of different resonance frequencies, 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. Resonance in the perpendicular direction can cause instability in the rotational movement of the movable part.

[0007] This problem can be reduced by including a notch filter in the drive circuit that can suppress the vertical resonance. However, if the resonant frequency for rotation and the vertical resonance frequency are close to each other, it is difficult to suppress only the vertical resonance frequency with a notch filter. For this reason, it is preferable that these two resonance frequencies are as far apart as possible.

[0008] In view of such problems, the present invention aims to provide an optical reflecting element that can effectively separate the resonant frequency for rotational operation from the closest resonant frequency and that can operate the movable part stably.

[0009] 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 having a reflective surface, a pair of drive parts arranged parallel to a rotation axis so as to sandwich the movable part and rotate the movable part about the rotation axis, a fixed part supporting the pair of drive parts, a pair of beam parts extending along the rotation axis and connected to the movable part, a pair of connectors connecting the pair of beam parts to the pair of drive parts, and four connectors having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection positions of the pair of beam parts on the movable part. In a plan view, the four connectors are arranged symmetrically about the rotation axis and symmetrically about a line passing through the center of the movable part and perpendicular to the rotation axis.

[0010] According to the optical reflecting element of this aspect, the movable part is supported by the fixed part by four connecting parts, which prevents the movable part from translating in the vertical direction (the direction perpendicular to the reflecting surface when the movable part is in the neutral position) during rotation. Furthermore, because the four connecting parts are symmetrically arranged as described above, horizontal forces (the 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 motion of the movable part during rotation can be prevented. Furthermore, because the four connecting parts are connected to a pair of beam parts or positions near the rotation axis of the movable part, adjusting the bending rigidity of the four connecting parts can effectively separate the resonant frequency corresponding to the rotation of the movable part from the closest resonant frequency. Therefore, according to the optical reflecting element of this aspect, the resonant frequency of the rotational motion can be effectively separated from the closest resonant frequency, and the movable part can be operated stably.

[0011] A second aspect of the present invention relates to an optical reflecting element. The optical reflecting element according to this aspect includes a movable part having a reflective surface, a pair of drive parts arranged parallel to a rotation axis so as to sandwich the movable part and rotate the movable part about the rotation axis, a fixed part supporting the pair of drive parts, a pair of beam parts extending along the rotation axis and connected to the movable part, a pair of link parts connecting the pair of beam parts to the pair of drive parts, and at least two connection parts having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection position of the pair of beam parts on the movable part. In a plan view, the at least two connection parts are arranged symmetrically about the rotation axis.

[0012] According to the optical reflecting element of this aspect, the translational motion of the movable part during rotation can be suppressed by at least two connecting parts, and by adjusting the bending rigidity of each connecting part, the resonance frequency corresponding to the rotation of the movable part can be separated from another resonance frequency closest to it.

[0013] As described above, according to the present invention, an optical reflecting element can be provided that can effectively separate the resonant frequency for rotational operation from the resonant frequency closest to it, and that can operate the movable part stably.

[0014] 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.

[0015] FIG. 1 is a top view schematically showing the configuration of an optical reflecting element according to the first embodiment. FIG. 2 is a bottom view schematically showing the configuration of the optical reflecting element according to the first embodiment. FIG. 3 is a cross-sectional view of the optical reflecting element according to the first embodiment, cut along a plane parallel to the YZ plane at the position A-A' in FIG. 1. FIGS. 4(a) and 4(b) are diagrams showing resonance modes occurring in the optical reflecting element according to the first embodiment. FIGS. 5(a) and 5(b) are diagrams for explaining simulation conditions according to the first embodiment. FIG. 6 is a graph showing simulation results according to the first embodiment. FIG. 7 is a top view schematically showing the configuration of an optical reflecting element according to the second embodiment. FIG. 8(a) is a diagram showing simulation results of stress distribution occurring in the connection part when the movable part rotates the most in R mode in the configuration of FIG. 1. FIG. 8(b) is a diagram showing simulation results of stress distribution occurring in the connection part when the movable part displaces the most in P mode in the configuration of FIG. 1. FIG. 9 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 the second embodiment. FIGS. 10(a) and 10(b) are diagrams for explaining simulation conditions according to the second embodiment. FIG. 11 is a graph showing simulation results according to the second embodiment. FIG. 12 is a top view schematically showing the configuration of an optical reflecting element according to the third embodiment. FIG. 13 is a top view schematically showing the configuration of an optical reflecting element according to the fourth embodiment. FIGS. 14(a) to 14(f) are top views schematically showing the configuration of connecting portions according to a modified example. FIGS. 15(a) to 15(f) are top views schematically showing the configuration of connecting portions according to a modified example. FIG. 16 is a top view schematically showing the configuration of an optical reflecting element according to another modified example. FIG. 17 is a bottom view schematically showing the configuration of an optical reflecting element according to another modified example.

[0016] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0017] 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.

[0018] 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.

[0019] <Embodiment 1> Fig. 1 is a top view schematically showing the configuration of an optical reflecting element 1 according to embodiment 1. Fig. 2 is a bottom view schematically showing the configuration of the optical reflecting element 1 according to embodiment 1. Fig. 3 is a cross-sectional view of the optical reflecting element 1 according to embodiment 1, taken along a plane parallel to the YZ plane at the position AA' in Fig. 1.

[0020] For convenience, in Figures 1 and 2, the exposed portions of the base layer 101 and the active layer 103 in Figure 3 are hatched in the same manner as the base layer 101 and the active layer 103 in Figure 3. In Figure 1, the piezoelectric body 22 and the reflecting surface 31 are hatched in a manner different from the hatching of the base layer 101 and the active layer 103, respectively.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] In a plan view, the pair of connecting portions 40 extend parallel to the Y axis from the ends of the drive unit 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 from the ends of the pair of connecting portions 40 along the rotation axis R10 and are connected to the movable unit 30. The four connecting portions 60 extend parallel to the Y axis from the inner surface of the fixed unit 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 unit 30 and is perpendicular to the rotation axis R10. In this embodiment, the width of each connecting portion 60 in the X axis direction is constant in a plan view.

[0026] The fixed section 10, the pair of drive sections 20, the movable section 30, the pair of linking sections 40, the pair of beam sections 50 and the four connection sections 60 are connected by a common active layer 103 (see FIG. 3).

[0027] Specifically, an etching process is performed on a substrate on which active layer 103 made of silicon (Si), intermediate oxide film 102, and base layer 101 made of silicon are stacked in this order from above, to form the outline of optical reflecting element 1 in a plan view. Furthermore, base layer 101 and intermediate oxide film 102 are removed from this substrate by etching.

[0028] At this time, the base layer 101 and intermediate oxide film 102 remain in the fixed portion 10 to ensure the required thickness. The base layer 101 and 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 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 intermediate oxide film 102 are also left in the coupling portion 40 and the beam portion 50. As shown in FIG. 3 , the base layer 101 and intermediate oxide film 102 are not left in the connection portion 60, and the connection portion 60 is composed only of the active layer 103.

[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] 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.

[0031] 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.

[0032] In this case, a sine wave driving voltage of 60 Hz can be applied to each piezoelectric element 22 .

[0033] 4A and 4B are diagrams showing resonance modes occurring in optical reflecting element 1. FIG.

[0034] 4A shows a resonance mode (R mode) for causing the movable part 30 to perform a target rotational movement, and FIG. 4B 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 that of the R mode.

[0035] 4(a) and 4(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. 4(a) and 4(b) are shown in gray scale, but in the actual simulation results, the displacement distribution is expressed using a color scale shown at the bottom of the figure. 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 center, and red at the right end.

[0036] In this case, when a drive voltage for performing a target rotational movement in R mode is applied to each piezoelectric element 22, vertical resonant movement in P mode may occur in the movable portion 30 along with the target rotational movement. In an optical reflecting element 1 having a drive portion 20 with a meandering structure, the resonant frequencies of P mode and R mode tend to be close to each other, so that when R mode movement is excited, P mode movement may be excited simultaneously. For this reason, P mode resonant movement has a significant effect on the target rotational movement.

[0037] 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.

[0038] Therefore, in this embodiment, the bending rigidity of connecting portion 60 is adjusted so that the R-mode resonance frequency and the P-mode resonance frequency are relatively far apart. Specifically, the bending rigidity of connecting portion 60 is adjusted by adjusting the width of connecting portion 60 in the X-axis direction. Changing the bending rigidity of connecting portion 60 changes the resonance frequency of optical reflecting element 1, and also changes the resonance frequencies of R-mode and P-mode.

[0039] 8(a) and 8(b), the stress distribution and magnitude generated in each connection portion 60 differ between the R mode and the P mode. Therefore, when the bending rigidity of the connection portion 60 is changed, this change has a greater effect on the stress distribution of one of the resonance modes, resulting in a difference in the range of change in the resonance frequency of each resonance mode. This difference in the range of change can be used to adjust the difference between the R mode resonance frequency and the P mode resonance frequency. In other words, by adjusting the bending rigidity of the connection portion 60, the difference between the R mode resonance frequency and the P mode resonance frequency can be widened.

[0040] <Verification 1> The inventors conducted a simulation to examine the relationship between the change in bending rigidity of the connection portion 60 and the difference between the resonance frequency of the R mode and the resonance frequency of the P mode.

[0041] 5(a) and 5(b) are diagrams for explaining the conditions of this simulation.

[0042] Referring to Fig. 5(a), the width W1 and length L1 of each connecting portion 60 were set to 140 µm and 1060 µm, respectively. Referring to Fig. 5(b), the width W2 of the beam portion 50 in the Y-axis direction was set to 40 µm. The distance L2 between the inner surface of the fixed portion 10 and the outer surface of the beam portion 50 was 1060 µm, the same as the length L1 of the connecting portion 60.

[0043] Under these conditions, the width W1 of the connecting portion 60 was gradually reduced from 140 μm to change the bending rigidity of the connecting portion 60. Then, the change in the difference between the R-mode resonance frequency and the P-mode resonance frequency due to the change in width W1 (change in bending rigidity) was calculated. In the simulation, the difference between the R-mode resonance frequency and the P-mode resonance frequency when the connecting portion 60 was omitted was also calculated.

[0044] FIG. 6 is a graph showing the results of this simulation.

[0045] The horizontal axis of the graph is shown as a ratio, with 100% being when the width W1 is 140 μm. The value on the horizontal axis when the four connecting portions 60 are omitted is 0%. The vertical axis of the graph shows the value obtained by subtracting the P-mode resonance frequency from the R-mode resonance frequency.

[0046] 6, the difference between the R-mode resonance frequency and the P-mode resonance frequency increased as the width W1 of each connecting portion 60 was reduced from 140 μm. At around 20% which is the processing limit width of the connecting portion 60, the difference between the R-mode resonance frequency and the P-mode resonance frequency was about 175 Hz, which was about 70 Hz larger than the difference when no connecting portion 60 was provided. This confirmed that by providing four connecting portions 60 and adjusting their bending rigidity (width W1), it was possible to widen the difference between the R-mode resonance frequency and the P-mode resonance frequency.

[0047] <Effects of First Embodiment> According to the first embodiment, the following effects are achieved.

[0048] As shown in FIG. 1, in a plan view, the four connection parts 60 are arranged symmetrically about the rotation axis R10 and about a line L10 that passes through the center C10 of the movable part 30 and is perpendicular to the rotation axis R10.

[0049] According to this configuration, the movable part 30 is supported by the fixed part 10 by the four connection parts 60, so that 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) can be suppressed during rotation. Furthermore, because the four connection parts 60 are arranged symmetrically as described above, horizontal forces (the direction parallel to the reflecting surface 31 when the movable part 30 is in the neutral position) generated at the four connection parts 60 during rotation of the movable part 30 cancel each other out. Therefore, translational movement of the movable part 30 in the horizontal direction can be suppressed during rotation. Furthermore, because the four connection parts 60 are connected to a pair of beam parts 50, the bending rigidity of the four connection parts 60 can be adjusted to effectively separate the R-mode resonance frequency of the movable part 30 from the closest P-mode resonance frequency.

[0050] Therefore, according to the optical reflecting element 1 of this embodiment, the resonant frequency of the R mode corresponding to the rotational movement can be effectively separated from the resonant frequency of the P mode closest thereto, and the movable part 30 can be operated stably.

[0051] As shown in FIGS. 1 and 3, the movable section 30, the pair of drive sections 20, the fixed section 10, the pair of beam sections 50, the pair of linking sections 40 and the four connection sections 60 are connected by a common active layer 103.

[0052] According to this configuration, the movable portion 30, the pair of driving portions 20, the fixed portion 10, the pair of beam portions 50, the pair of connecting portions 40 and the four connecting portions 60 can be formed integrally, thereby simplifying the manufacturing process of the optical reflecting element 1.

[0053] 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.

[0054] 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.

[0055] In the first embodiment, the width of the connection portion 60 is constant, and the bending stiffness of the connection portion 60 is uniform. In contrast, in the second embodiment, the width of the connection portion 60 is varied, thereby providing the connection portion 60 with a bending stiffness distribution.

[0056] FIG. 7 is a top view schematically showing the configuration of an optical reflecting element 1 according to the second embodiment.

[0057] 1 , in the configuration of FIG. 7 , a meander-shaped stiffness adjustment portion 61 that folds back at least once is disposed in each connection portion 60, thereby imparting a bending stiffness distribution to each connection portion 60. The stiffness adjustment portion 61 is narrower than the other portions of the connection portion 60. Therefore, the bending stiffness of the stiffness adjustment portion 61 is smaller than the other portions of the connection portion 60. By changing the number of folds in the meander shape, the length of the stiffness adjustment portion 61 in the Y-axis direction changes, and the bending stiffness distribution of the connection portion 60 changes.

[0058] In embodiment 2, the distribution of bending rigidity of each connection part 60 is adjusted so that the distribution of bending rigidity of the connection part 60 is more consistent with either the stress distribution that occurs in each connection part 60 when the movable part 30 operates in R mode or the stress distribution that occurs in each connection part 60 when the movable part 30 operates in P mode.

[0059] 8A 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 the R mode in the configuration of FIG. 1 of the first embodiment. FIG. 8B 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 the P mode in the configuration of FIG. 1 of the first embodiment.

[0060] For convenience, the stress distribution is shown in grayscale in Figures 8(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 4(a) and (b). In Figures 8(a) and (b), the connection part 60, which is colored red and has the maximum stress, is circled with a dashed line.

[0061] FIG. 9 is a graph showing the results of a simulation of the stress distribution occurring in two connecting portions 60 arranged in the Y-axis direction.

[0062] Figure 9 shows the distribution of surface stresses in the two connection parts 60 at the A-A' cutting position in Figure 1. This shows the stress distribution when the movable part 30 resonates in the R mode and the P mode in a configuration in which the pair of drive parts 20 and the pair of linking parts 40 are omitted from the configuration in Figure 1. The stress distributions in the remaining two connection parts 60 are the same as those in Figure 9.

[0063] 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. 9 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. 9 is normalized with the maximum stress in each of the R mode and P mode being 100%.

[0064] 8(a), (b), and 9, in the R mode, the stress in the connection part 60 is increased at the end on the movable part 30 side, whereas in the P mode, the stress in the connection part 60 is increased not only at the end on the movable part 30 side but also at the end on the fixed part 10 side. Therefore, by dividing each connection part 60 into two parts by a line parallel to the rotation axis R10 and making the bending rigidity of each part different from each other, it is possible to make the fluctuation range of the resonance frequency in each mode different from the case where no stress distribution is applied to the connection part 60.

[0065] For example, if the bending rigidity of the connecting portion 60 is distributed so that it is small (soft) on the rotation axis R10 side and large (hard) on the fixed portion 10 side, this distribution will be more consistent with the stress distribution of the P mode than with the stress distribution of the R mode. 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 resonance 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 resonance frequency of the R mode, in which a high stress distribution does not occur at the end on the fixed portion 10 side.

[0066] 7 , the meandering-shaped stiffness adjusting portion 61 is disposed on the rotation axis R10 side, and the bending stiffness distribution is set in the connecting portion 60 so that the bending stiffness on the rotation axis R10 side is smaller than that on the fixed portion 10 side. This makes it possible to effectively widen the difference between the resonance frequency of the R mode and the resonance frequency of the P mode compared to when no stress distribution is applied to the connecting portion 60.

[0067] <Verification 2> To further explore the above viewpoint, the inventors conducted a simulation to examine the relationship between the distribution of bending rigidity of the connection portion 60 and the resonance frequencies of the R mode and P mode. In this simulation, the distribution of bending rigidity of the connection portion 60 was changed by changing the number of folds of the meandering shape that constitutes the rigidity adjustment portion 61.

[0068] 10(a) and 10(b) are diagrams for explaining the conditions of this simulation.

[0069] 10A, the width W11 of each connection portion 60 was set to 140 μm, and the lengths L11 and L12 were set to 512.5 μm and 547.5 μm, respectively. The pitch P11 of one meandering fold was set to 100 μm, and the width W12 of the meandering shape was set to 140 μm, the same as the width W11.

[0070] 10(b), the width W2 of the beam portion 50 in the Y-axis direction was set to 40 μm, as in the case of FIG. 5(b). The distance L2 between the inner surface of the fixed portion 10 and the outer surface of the beam portion 50 was set to 1060 μm, as in the case of FIG. 5(b). The distance L2 is the sum of the lengths L11 and L12 in FIG. 10(a).

[0071] Under these conditions, the number of meandering folds in the stiffness adjusting portion 61 of the connecting portion 60 was increased or decreased from the number of folds in FIG. 10( a ) to change the distribution of bending stiffness of the connecting portion 60 .

[0072] Here, each time the number of turns in the meandering shape increases by one, the length L12 increases by the pitch P11 and the length L11 decreases by the pitch P11. Similarly, each time the number of turns in the meandering shape decreases by one, the length L12 decreases by the pitch P11 and the length L11 increases by the pitch P11. In other words, even if the number of turns in the meandering shape increases or decreases, the overall length of the connection portion 60 (the sum of the lengths L11 and L12) does not change. An increase in the number of turns means that portions with pitch P11 are added in series in the Y-axis direction, widening the rigidity adjustment portion 61 in the Y-axis direction, and a decrease in the number of turns means that portions with pitch P11 are deleted, shortening the rigidity adjustment portion 61 in the Y-axis direction.

[0073] 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 folds in the meandering shape 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 folds to the resonance frequencies of the R mode and the P mode when the connection portion 60 with the number of folds shown in Figure 10(a) was used.

[0074] FIG. 11 is a graph showing the results of this simulation.

[0075] The horizontal axis of the graph represents the increase or decrease in the number of turns (number of springs) relative to the number of turns (shown as the number of springs) of the meandering shape in FIG. 10( a). +1 on the horizontal axis indicates that the number of turns has increased by one relative to the number of turns in FIG. 10( a), and −1 on the horizontal axis indicates that the number of turns has decreased by one relative to the number of turns in FIG. 10( a). Because the number of turns can be decreased by only four from the number of turns in FIG. 10( a), the minimum value of the horizontal axis range plotted on the graph is −4.

[0076] The vertical axis of the graph is normalized to 100% as the resonance frequencies of the R mode and P mode when the connection part 60 in Fig. 10(a) is used, i.e., the resonance frequencies of the R mode and P mode when the increase / decrease in the number of folds (number of springs) is 0. At the position on the horizontal axis where the number of springs is 0, only the plot of the open circle corresponding to the resonance frequency of the P mode is displayed, but behind this plot, the filled circle corresponding to the resonance frequency of the R mode is hidden.

[0077] 11, although the P-mode resonance frequency fluctuates relatively greatly depending on the number of folds (number of springs) of the meandering shape, the R-mode resonance frequency does not fluctuate as much. From this, it was confirmed that by adjusting the ratio of the range of low bending rigidity (soft range) on the rotation axis R10 side to the range of high bending rigidity (hard range) on the fixed part 10 side in the connecting part 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.

[0078] <Effects of Second Embodiment> According to the configuration of the second embodiment, in addition to the effects of the first embodiment, the following effects are further achieved.

[0079] 7, a stiffness adjustment portion 61 is disposed in each connection portion 60. This provides a bending stiffness distribution to each connection portion 60 so that the bending stiffnesses of the two portions obtained by dividing the connection portion 60 in two along a dividing line parallel to the rotation axis R10 are different from each other.

[0080] With this configuration, the distribution of bending rigidity imparted to the connection portion 60 is more likely to match either the stress distribution generated in the connection portion 60 by the R mode or the stress distribution generated in the connection portion 60 by the P mode. Therefore, compared to a case in which the connection portion 60 does not have a bending rigidity distribution, it is possible to change one resonance frequency more greatly than the other. Therefore, it is possible to smoothly separate the resonance frequency in the R mode from the resonance frequency in the P mode that is closest to it.

[0081] More specifically, by arranging a meander-shaped stiffness adjustment part 61, of the two parts obtained by dividing the connection part 60 in two along a dividing line parallel to the rotation axis R10, the bending stiffness of the part on the fixed part 10 side is higher than the bending stiffness of the part on the movable part 30 side.

[0082] With this configuration, the distribution of bending stiffness imparted to the connection portion 60 is more consistent with the stress distribution generated in the connection portion 60 by the P mode than with the stress distribution generated in the connection portion 60 by the R mode. Therefore, the resonance frequency in the P mode can be changed more significantly than in the R mode, compared to when the connection portion 60 does not have a bending stiffness distribution. Therefore, the resonance frequency in the R mode and the resonance frequency in the P mode can be smoothly separated from each other.

[0083] As shown in FIG. 7, by varying the width of each connecting portion 60 in plan view, a distribution of bending rigidity is imparted to each connecting portion 60.

[0084] According to this configuration, it is possible to impart a distribution of bending rigidity to the connection portion 60 by a simple method such as adjusting the width of the connection portion 60 .

[0085] As shown in FIG. 7, when viewed from above, each connection portion 60 has a meandering shape that is folded back at least once, thereby imparting a distribution of bending rigidity to each connection portion.

[0086] According to this configuration, as described above, the meandering shape makes it possible to adjust the distribution of bending rigidity of the connection portion.

[0087] Third Embodiment FIG. 12 is a top view schematically showing the configuration of an optical reflecting element 1 according to a third embodiment.

[0088] In the third embodiment, a piezoelectric body 71 is disposed on the upper surface of each connecting portion 60. The piezoelectric body 71 has the same layer structure as the piezoelectric body 22. The shape and size of each piezoelectric body 71 are the same. Each piezoelectric body 71 is used to drive the movable portion 30 together with the piezoelectric body 22 of the driving portion 20. Wiring portions (not shown) for connecting each piezoelectric body 71 to a corresponding terminal portion (not shown) are further disposed on the upper surface of the active layer 103.

[0089] The above-mentioned first drive voltage is applied to the two piezoelectric bodies 71 on the positive side of the Y axis with respect to the center C10, and the above-mentioned second drive voltage is applied to the two piezoelectric bodies 71 on the negative side of the Y axis with respect to the center C10. As a result, the drive force for rotating the movable part 30 is increased by these four piezoelectric bodies 71, and the movable part 30 can be rotated more efficiently.

[0090] The shape and size of the piezoelectric body 71 are not limited to the example shown in Fig. 12. In the example of Fig. 12, the width of the connection portion 60 is constant as in the first embodiment, but the width of the connection portion 60 may vary as in the second embodiment. In this case, the piezoelectric body 71 may be disposed in a region of the connection portion 60 other than the stiffness adjustment portion 61 in which the meandering shape is formed, for example.

[0091] <Effects of Third Embodiment> According to the configuration of the third embodiment, in addition to the effects of the first and second embodiments, the following effects are further achieved.

[0092] As shown in FIG. 12, piezoelectric bodies 71 (other driving parts) for driving the movable part 30 are disposed on the four connecting parts 60, respectively.

[0093] According to this configuration, the driving efficiency of the movable part 30 can be improved.

[0094] Fourth Embodiment FIG. 13 is a top view schematically showing the configuration of an optical reflecting element 1 according to a fourth embodiment.

[0095] In the fourth embodiment, a monitoring piezoelectric element 72 is further disposed on the upper surface of each connecting portion 60. The piezoelectric element 72 has the same layer structure as the piezoelectric element 22. A monitor signal (current) corresponding to the deformation of the connecting portion 60 is output from the piezoelectric element 72. Wiring portions (not shown) for connecting each piezoelectric element 72 to a corresponding terminal portion (not shown) are further disposed on the upper surface of the active layer 103. The drive circuit uses the monitor signal output from the terminal portion to adjust the drive voltage so that the movable portion 30 performs a predetermined rotational movement.

[0096] The shape and size of the piezoelectric body 72 are not limited to the example shown in Fig. 13. In the example of Fig. 13, the width of the connection portion 60 is constant as in the first embodiment, but the width of the connection portion 60 may vary as in the second embodiment. In this case, the piezoelectric bodies 71 and 72 may be disposed in an area of ​​the connection portion 60 other than the stiffness adjustment portion 61 in which the meandering shape is formed, for example.

[0097] Furthermore, not all four piezoelectric bodies 72 need to be used for monitoring. From the viewpoint of monitoring the operation of the movable part 30, it is sufficient that a piezoelectric body 72 is disposed in at least one of the four connection parts 60. However, if the piezoelectric body 72 is omitted from any of the four connection parts 60, the symmetry and rigidity balance of the part consisting of the movable part 30, the pair of beam parts 50, and the four connection parts 60 will be lost. For this reason, even if any of the piezoelectric bodies 72 is not used for monitoring, it is preferable that this piezoelectric body 72 is not omitted, and that the piezoelectric body 72 is disposed in all of the four connection parts 60.

[0098] <Effects of Fourth Embodiment> According to the configuration of the fourth embodiment, in addition to the effects of the first to third embodiments, the following effects are further achieved.

[0099] A piezoelectric element 72 (monitor portion) that outputs a signal according to the operation of the movable portion is disposed on at least one of the four connection portions 60 .

[0100] According to this configuration, the operation of the movable part 30 can be monitored by a signal from the piezoelectric body 72 (monitor part). Furthermore, by using the area of ​​the connection part 60 for arranging the monitor part, it is not necessary to arrange the piezoelectric body 72 (monitor part) in the drive part 20. Therefore, the arrangement area of ​​the piezoelectric body 22 (drive source) in the drive part 20 can be expanded.

[0101] <Modifications> The configuration of the connection portion 60 is not limited to the configurations shown in the first to fourth embodiments.

[0102] 14(a) to 15(f) are top views schematically showing the configuration of the connection portion 60 according to the modified example. In these figures, only the areas near the movable portion 30 and the four connection portions 60 are shown.

[0103] For example, as shown in Fig. 14(a), a stiffness adjusting section 62 may be provided that changes the width of the connecting section 60 in stages, thereby giving the connecting section 60 a distribution of bending stiffness. Alternatively, as shown in Fig. 14(b) and (c), stiffness adjusting sections 63 and 64 may be provided in which the width of the connecting section 60 gradually decreases as it approaches the beam section 50, thereby giving the connecting section 60 a distribution of bending stiffness.

[0104] 14(d), a stiffness adjustment section 64 with a gradually decreasing width and a meander-shaped stiffness adjustment section 65 may be provided in the connecting section 60, thereby imparting a distribution of bending stiffness to the connecting section 60. The number of folds of the meander-shaped structure arranged in the stiffness adjustment section 61 is not limited to the number of folds shown in the second embodiment, but may be a meander-shaped structure with one or two folds, as shown in FIGS.

[0105] 15( a) and 15(b), a stiffness adjustment portion 64 with a gradually reduced width and two meander-shaped stiffness adjustment portions 66 may be provided in one connection portion 60, thereby imparting a distribution of bending stiffness to the connection portion 60. Furthermore, as shown in FIG. 15(c), two sets of a stiffness adjustment portion 64 with a gradually reduced width and a meander-shaped stiffness adjustment portion 66 may be disposed between the fixed portion 10 and one beam portion 50.

[0106] Furthermore, as shown in Figure 15(d), the rigidity adjustment portion 67 may be configured so that the meandering direction of the meandering shape is perpendicular to the extension direction of the beam portion 50 (the direction along the rotation axis R10), and as shown in Figure 15(e), the connection portion 60 may consist solely of a meandering shape.

[0107] 15(f), the meandering-shaped stiffness adjustment portion 68 may be connected not to the beam portion 50 but to the side surface of the movable portion 30 near the connection position of the beam portion 50 (at a position near the pivot axis). In the other configurations shown in FIGS. 14(a) to 15(f), the end of the connection portion 60 on the movable portion 30 side may also be connected to the side surface of the movable portion 30 near the connection position of the beam portion 50 (at a position near the pivot axis). These configurations are substantially equivalent to the configurations in which the connection portion 60 is connected to the beam portion 50 as in the first and second embodiments, because the connection portion 60 is connected to the movable portion 30 near the connection position of the beam portion 50. Therefore, these configurations can also achieve the same effects as the first and second embodiments.

[0108] In the modified examples of Figures 14(a) to 15(f), as described above, it is preferable to impart a bending stiffness distribution to the connection portion 60 so that the bending stiffness distribution of the connection portion 60 is more consistent with either the stress distribution of the connection portion 60 in R mode or P mode.

[0109] <Other Modifications> In the second embodiment and the modifications described above, the width of the connection portion 60 is changed in plan view to impart a distribution of bending rigidity to the connection portion 60, but the method of imparting a distribution of bending rigidity to the connection portion 60 is not limited to this. For example, the thickness of the connection portion 60 may be changed to impart a distribution of bending rigidity to the connection portion 60. Alternatively, when another material is layered on the upper surface of the connection portion 60, the area over which the material is layered and / or the thickness of the material may be changed to impart a distribution of bending rigidity to the connection portion 60.

[0110] In the above embodiment, the driving unit 20 has a meandering type configuration, but the driving unit 20 may have another type of configuration. For example, the driving unit 20 may be configured with a tuning-fork-shaped active layer 103, and a pair of arms of this active layer 103 may each have a piezoelectric element disposed thereon as a driving source.

[0111] In addition, in the configuration of Figure 13, the piezoelectric body 71 (another driving section) and the piezoelectric body 72 (monitor section) are arranged in the connection section 60, but only the piezoelectric body 72 (monitor section) may be arranged in the connection section 60.

[0112] Furthermore, the layer structure constituting the substrate of optical reflecting element 1 is not limited to the layer structure shown in FIG. 3, and for example, other layers may be added to this layer structure.

[0113] Furthermore, the movable section 30, the pair of drive sections 20, the fixed section 10, the pair of linking sections 40, the pair of beam sections 50, and the four connection sections 60 may be connected in another layer together with the active layer 103. Alternatively, the movable section 30, the pair of drive sections 20, the fixed section 10, the pair of linking sections 40, the pair of beam sections 50, and the four connection sections 60 do not have to be connected in a common layer, and for example, the active layer 103 in the linking section 40 may be removed from the configuration of the above embodiment.

[0114] Furthermore, in the above embodiments 1 to 4, the other resonance frequency closest to the resonance frequency corresponding to the target rotational movement of the movable part 30 was the resonance frequency due to the P mode, but if the other resonance frequency closest to the resonance frequency corresponding to the target rotational movement is a resonance frequency due to a resonance movement other than the P mode, the bending rigidity or the distribution of bending rigidity of the connection part 60 may be adjusted so that the target resonance frequency and the other resonance frequency are separated from each other.

[0115] Furthermore, the dimensions of each part shown in the above simulations are merely examples, and the dimensions of each part can be changed as appropriate.

[0116] Furthermore, in the above-described first to fourth embodiments, the four connection parts 60 are arranged symmetrically with respect to the rotation axis R10 and with respect to the line L10 that passes through the center C10 of the movable part 30 and is perpendicular to the rotation axis R10, but at least two connection parts 60 may be arranged symmetrically with respect to the rotation axis R10. This makes it possible to prevent horizontal translational movement of the movable part 30 when the movable part 30 rotates.

[0117] 16 and 17, two connecting parts 60 may be arranged symmetrically with respect to the rotation axis R10. In this case, a pair of driving parts 20 are connected to the fixed part 10 in a direction parallel to the X-axis, and the upper surface of the movable part 30 itself serves as the reflective surface 31.

[0118] In this configuration, as in the above-described first and second embodiments, the R-mode resonance frequency and the P-mode resonance frequency can be effectively separated by adjusting the distribution of bending rigidity of the two connection portions 60. The method of adjusting the bending rigidity distribution can be the same as that of the above-described second embodiment and the modified examples shown in FIGS. 14 and 15. Also in this configuration, as in the above-described third and fourth embodiments, a driving piezoelectric element and a monitoring piezoelectric element may be disposed in the two connection portions 60.

[0119] In this configuration, two connection parts 60 are arranged on only one side of the movable part 30, which results in unbalanced support of the movable part 30 in the X-axis direction. Therefore, in order to stably support the movable part 30 and further stabilize the rotational movement, it is preferable to arrange two connection parts 60 on the positive side of the X-axis of the movable part 30 as well, and it is even more preferable to arrange multiple connection parts 60 symmetrically about the rotation axis R10 and symmetrically about a line L10 that passes through the center C10 of the movable part 30 and is perpendicular to the rotation axis R10.

[0120] 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.

[0121] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0122] (Technology 1) An optical reflecting element comprising: a movable part provided with a reflective surface; a pair of drive parts arranged parallel to a rotation axis to sandwich the movable part and rotate the movable part about the rotation axis; a fixed part supporting the pair of drive parts; a pair of beam parts extending along the rotation axis and connected to the movable part; a pair of connection parts connecting the pair of beam parts and the pair of drive parts; and four connection parts having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection position of the pair of beam parts on the movable part, wherein in a planar view, the four connection parts are arranged symmetrically about the rotation axis and symmetrically about a straight line that passes through the center of the movable part and is perpendicular to the rotation axis.

[0123] According to this technology, the movable part is supported by the fixed part by four connection parts, which can suppress vertical translational motion of the movable part (a direction perpendicular to the reflecting surface when the movable part is in the neutral position) during rotation. Furthermore, because the four connection parts are symmetrically arranged 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 connection parts during rotation of the movable part cancel each other out. Therefore, horizontal translational motion of the movable part during rotation can be suppressed. Furthermore, because the four connection parts are connected to a pair of beam parts or to positions near the rotation axis of the movable part, adjusting the bending rigidity of the four connection parts can effectively separate the resonant frequency corresponding to the rotational motion of the movable part from the closest resonant frequency. Therefore, according to this technology, the resonant frequency of the rotational motion can be effectively separated from the closest resonant frequency, and the movable part can be operated stably.

[0124] (Technology 2) The optical reflecting element described in Technology 1, characterized in that a distribution of bending rigidity is imparted to each of the connection portions so that the bending rigidities of the two portions obtained by dividing the connection portion into two by a straight line parallel to the rotation axis are different from each other.

[0125] According to this technology, the distribution of bending stiffness imparted to the connection part is more likely to match either the stress distribution of the connection part due to the rotational movement or the stress distribution of the connection part due to the resonant movement of another resonant frequency. Therefore, compared to when the connection part does not have a distribution of bending stiffness, one resonant frequency can be changed more significantly than the other. Therefore, the resonant frequency of the movable part corresponding to the rotational movement can be smoothly separated from the other resonant frequency closest to it.

[0126] (Technology 3) The optical reflecting element according to Technology 2, wherein the bending rigidity of the portion on the fixed portion side of the two portions is higher than the bending rigidity of the portion on the movable portion side.

[0127] According to this technology, when the resonance due to the other resonant frequency is a vertical resonance in which the movable part resonates in a direction perpendicular to the reflecting surface, the distribution of bending stiffness imparted to the connection part is more consistent with the stress distribution of the connection part due to the vertical resonance than with the stress distribution of the connection part due to the pivoting motion. Therefore, the resonance frequency due to the pivoting motion can be changed more significantly than the resonance frequency due to the vertical resonance compared to when the connection part does not have a bending stiffness distribution. Therefore, the resonance frequency due to the pivoting motion and the resonance frequency due to the vertical resonance can be smoothly separated.

[0128] (Technology 4) The optical reflecting element according to Technology 2 or 3, characterized in that the distribution of bending rigidity is imparted to each of the connection portions by changing the width of each of the connection portions in plan view.

[0129] According to this technique, it is possible to impart a distribution of bending rigidity to the connection portion by a simple method such as adjusting the width of the connection portion.

[0130] (Technology 5) An optical reflecting element according to any one of technologies 2 to 4, characterized in that, in plan view, each of the connection parts has a meandering shape that folds back at least once, thereby imparting the distribution of bending rigidity to each of the connection parts.

[0131] According to this technique, the distribution of bending rigidity of the connection portion can be adjusted by the meandering shape.

[0132] (Technology 6) In the optical reflecting element described in any one of Technologies 1 to 5, the movable portion, the pair of drive portions, the fixed portion, the pair of beam portions, the pair of connecting portions and the four connecting portions are connected by a common layer.

[0133] According to this technique, the movable portion, the pair of drive portions, the fixed portion, the pair of beam portions, the pair of linking portions and the four connecting portions can be integrally formed, which simplifies the manufacturing process of the optical reflecting element.

[0134] (Technology 7) The optical reflecting element according to any one of Technologies 1 to 6, characterized in that other driving parts for driving the movable parts are respectively disposed at the four connecting parts.

[0135] This technique can improve the driving efficiency of the moving part.

[0136] (Technology 8) An optical reflecting element according to any one of technologies 1 to 7, characterized in that a monitor unit that outputs a signal according to the operation of the movable unit is disposed in at least one of the four connection parts.

[0137] This technology allows the operation of the moving part to be monitored by signals from the monitor unit. Furthermore, by using the area of ​​the connection part for arranging the monitor unit, it is not necessary to place the monitor unit on the drive unit. This allows for a wider area for arranging the drive source on the drive unit.

[0138] (Technology 9) The optical reflecting element according to any one of Technologies 1 to 8, wherein the pair of driving sections are configured by connecting a plurality of piezoelectric cantilevers in a meandering shape.

[0139] 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.

[0140] (Technology 10) An optical reflecting element comprising: a movable part provided with a reflective surface; a pair of drive parts arranged parallel to a rotation axis to sandwich the movable part and rotate the movable part about the rotation axis; a fixed part supporting the pair of drive parts; a pair of beam parts extending along the rotation axis and connected to the movable part; a pair of connection parts connecting the pair of beam parts and the pair of drive parts; and at least two connection parts having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection position of the pair of beam parts on the movable part, wherein in a planar view, the at least two connection parts are arranged symmetrically about the rotation axis.

[0141] According to this technology, the translational motion of the movable part during rotation can be suppressed by at least two connecting parts, and by adjusting the bending stiffness of each connecting part, the resonance frequency corresponding to the rotation of the movable part can be separated from the closest resonance frequency.

[0142] REFERENCE SIGNS LIST 1 Optical reflecting element 10 Fixed portion 20 Driving portion 21 Piezoelectric cantilever 22 Piezoelectric body 30 Movable portion 31 Reflecting surface 40 Linking portion 50 Beam portion 60 Connection portion 103 Active layer (common layer) 71 Piezoelectric body (other driving portion) 72 Monitor portion R10 Rotation axis

Claims

1. An optical reflecting element comprising: a movable part provided with a reflective surface; a pair of drive parts arranged parallel to a rotation axis to sandwich the movable part and rotate the movable part about the rotation axis; a fixed part supporting the pair of drive parts; a pair of beam parts extending along the rotation axis and connected to the movable part; a pair of link parts connecting the pair of beam parts and the pair of drive parts; and four connection parts each having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection position of the pair of beam parts on the movable part, wherein in a plan view, the four connection parts are arranged symmetrically about the rotation axis and symmetrically about a line that passes through the center of the movable part and is perpendicular to the rotation axis.

2. An optical reflecting element according to claim 1, wherein a distribution of bending rigidity is imparted to each of the connecting portions so that the bending rigidity of the two portions obtained by dividing the connecting portion into two by a straight line parallel to the rotation axis differs from each other.

3. An optical reflecting element according to claim 2, wherein, of the two portions, the portion on the fixed portion side has a higher bending rigidity than the portion on the movable portion side.

4. An optical reflecting element according to claim 2, characterized in that the distribution of bending rigidity is imparted to each of the connecting portions by changing the width of each of the connecting portions in plan view.

5. An optical reflecting element according to claim 2, wherein, in plan view, each of the connection parts has a meandering shape that folds back at least once, thereby imparting the distribution of bending rigidity to each of the connection parts.

6. An optical reflecting element according to claim 1, characterized in that the movable portion, the pair of drive portions, the fixed portion, the pair of beam portions, the pair of linking portions and the four connecting portions are connected by a common layer.

7. An optical reflecting element according to claim 1, characterized in that other driving parts for driving the movable part are respectively disposed at the four connecting parts.

8. An optical reflecting element according to claim 1, characterized in that a monitor section is disposed in at least one of the four connecting sections, for outputting a signal according to the operation of the movable section.

9. An optical reflecting element according to claim 1, wherein the pair of drive sections are configured by a plurality of piezoelectric cantilevers connected in a meandering pattern.

10. An optical reflecting element comprising: a movable part provided with a reflective surface; a pair of drive parts arranged parallel to a rotation axis to sandwich the movable part and rotate the movable part about the rotation axis; a fixed part supporting the pair of drive parts; a pair of beam parts extending along the rotation axis and connected to the movable part; a pair of connecting parts connecting the pair of beam parts and the pair of drive parts; and at least two connecting parts having one end connected to the fixed part and the other end connected to the pair of beam parts or near the connection position of the pair of beam parts on the movable part, wherein in a plan view, the at least two connecting parts are arranged symmetrically about the rotation axis.

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