Optical reflection element

Abstract

An optical reflection element (1) comprises: a first support part (13) that extends along a rotation axis (R1); a second support part (16) that extends along the rotation axis (R1); a movable part (15) that has a reflection surface (15a) and is supported by the first support part (13) and the second support part (16); a drive part (12) that is connected to an end of the first support part (13) on the opposite side from the movable part (15) and applies driving force for rotating the movable part (15) to the movable part (15) via the first support part (13); a rigid fixed part (11) that comprises a base part (11a) supporting the drive part (12), and a pair of arm parts (11b) symmetrically disposed with respect to the rotation axis (R1) without sandwiching the second support part (16) therebetween; and a pair of flexible frame-shaped folded parts (17) that respectively connect an end of the second support part (16) on the opposite side from the movable part (15) and the pair of arm parts (11b).

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 repeatedly 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 an optical reflecting element in which a mirror portion (movable portion) is rotated by a tuning fork vibrator. In this configuration, the mirror portion is connected to the tuning fork vibrator by a beam-shaped support portion extending along the rotation axis. Since the support portion and tuning fork vibrator are disposed on only one side of the mirror portion, the optical reflecting element can be made compact. However, since only one side of the mirror portion is supported and rotated, deflection (dynamic deflection) occurs in the mirror portion when the mirror portion is rotated repeatedly. This dynamic deflection becomes more pronounced as the frequency of the repeated rotation increases.

[0004] Such dynamic deflection can be suppressed by symmetrically arranging a structure consisting of a support and a tuning fork vibrator on both sides of the movable part, but this configuration requires a support and a tuning fork vibrator on both sides of the movable part, which leads to an increase in the size of the optical reflecting element.

[0005] The following Patent Document 2 describes a mirror device configured to support a movable part from both sides while applying a driving force to the movable part from only one side. This mirror device includes a fixed part in the shape of a rectangular frame that surrounds the movable part in a plan view. Two beam-shaped support parts, each extending along a rotation axis, are connected to both sides of the movable part. One support part has one end connected to the movable part and the other end connected to a tuning-fork-shaped drive part. The drive part is connected to the fixed part. The other support part has one end connected to the movable part and the other end connected to the fixed part. With this configuration, the drive part is located only on one side of the movable part, allowing the device to be more compact than when drive parts are located on both sides of the movable part.

[0006] Patent No. 5,045,463 U.S. Patent Publication No. 2023 / 0408808

[0007] However, in the configuration described in Patent Document 2, although the movable part can be supported from both sides, the fixed part is also arranged around the movable part on the opposite side from the drive part, so the device cannot be made sufficiently small.

[0008] In view of the above problems, an object of the present invention is to provide an optical reflecting element that can stably drive a movable part while achieving a compact external size.

[0009] The optical reflecting element according to a main aspect of the present invention comprises a first support portion extending along a rotation axis and a second support portion extending along the rotation axis, a movable portion having a reflective surface and supported by the first support portion and the second support portion, a drive portion connected to an end portion of the first support portion opposite the movable portion and applying a drive force to the movable portion via the first support portion to rotate the movable portion, a base portion supporting the drive portion, a rigid fixed portion consisting of a pair of arms arranged symmetrically about the rotation axis and without sandwiching the second support portion, and a pair of flexible frame-shaped folded portions respectively connecting the end portion of the second support portion opposite the movable portion to the pair of arms.

[0010] According to the optical reflecting element of this aspect, the second support portion is connected to the fixed portion (the pair of arms) via a pair of folded portions. This allows the movable portion to be flexibly supported from both sides by the first support portion, the second support portion, and the pair of folded portions, even if the length of the second support portion is shortened. This suppresses dynamic deflection that occurs in the movable portion when the movable portion rotates. Furthermore, since the fixed portion does not extend around the movable portion on the side opposite the drive portion, and the pair of arms are limited in length so as not to sandwich the second support portion, the shape of the optical reflecting element in a direction parallel to the rotation axis can be made small. Furthermore, since the length of the second support portion can be shortened as described above, the shape of the optical reflecting element in a direction parallel to the rotation axis can be made even smaller. Therefore, the movable portion can be stably driven while miniaturizing the external shape of the optical reflecting element.

[0011] As described above, according to the present invention, it is possible to provide an optical reflecting element that can stably drive a movable part while achieving a compact outer shape.

[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 perspective view schematically illustrating the configuration of an optical reflecting element according to Embodiment 1. FIGS. 2(a) and 2(b) are a top view and a bottom view, respectively, schematically illustrating the configuration of the optical reflecting element according to Embodiment 1. FIG. 3 is a top view illustrating the configuration of an optical reflecting element used in Verification 1 of Embodiment 1. FIGS. 4(a) to 4(c) are graphs illustrating simulation results for Verification 1 of Embodiment 1. FIG. 5 is a top view illustrating the configuration of an optical reflecting element used in Verification 2 of Embodiment 1. FIGS. 6(a) and 6(b) are graphs illustrating simulation results for Verification 2 of Embodiment 1. FIGS. 7(a) to 7(c) are top views schematically illustrating other configuration examples (Configuration Examples 1 to 3) of an optical reflecting element according to Embodiment 1 when the shapes of a pair of folded portions are changed. FIGS. 8(a) and 8(b) are diagrams illustrating simulation results of stress distributions that occur when the dimensions of each part in Configuration Example 3 according to Embodiment 1 are finely adjusted. FIGS. 9(a) and 9(b) are top and bottom views, respectively, schematically illustrating the configuration of an optical reflecting element according to Embodiment 2. FIG. 10(a) is a diagram illustrating simulation conditions used in examining the effect of a pair of folded portions according to Embodiment 2. FIG. 10(b) is a bottom view illustrating the configuration of an optical reflecting element according to a comparative example used in the examination. FIG. 11 is a diagram illustrating simulation results in Verification 5 of Embodiment 2. FIGS. 12(a) to 12(c) are top views each schematically illustrating the configuration of an optical reflecting element according to Modification Example 1. FIGS. 13(a) to 13(c) are top views each schematically illustrating the configuration of an optical reflecting element according to Modification Example 2. FIG. 14(a) is a top view each schematically illustrating the configuration of an optical reflecting element according to Modification Example 3. FIG. 14(b) is a bottom view each schematically illustrating the configuration of an optical reflecting element according to Modification Example 4. Figures 15(a) and (b) are top views each schematically showing the configuration of an optical reflecting element according to Modification Example 5. Figures 16(a) and (b) are a plan view and a side view for explaining the effect of miniaturizing the optical reflecting element according to Embodiments 1 and 2. Figure 17 is a diagram showing the results of a simulation of the stress distribution (Mises stress distribution) when a movable part of the optical reflecting element according to Embodiment 3 is rotated.FIG. 18( a) is a top view schematically showing the configuration of an optical reflecting element according to embodiment 3, and FIG. 18( b) is a top view schematically showing the configuration of the optical reflecting element according to embodiment 1. FIG. 19( a) is a diagram showing the results of a simulation of the torsional stress generated in the detection piezoelectric element during rotation of the movable part in the configuration of embodiment 3. FIG. 19( b) is a diagram showing the results of a simulation of the torsional stress generated in the detection piezoelectric element during rotation of the movable part in the configuration of embodiment 1. FIG. 20 is a diagram showing the configuration of a circuit unit for driving the driving piezoelectric element using a monitor signal output from the detection piezoelectric element according to embodiment 3. FIG. 21 is a top view schematically showing the configuration of an optical reflecting element according to a modified example of embodiment 3. FIG. 22( a) is a diagram showing the results of a simulation of the distribution of torsional stress (distribution of stress in the torsional direction) generated in the optical reflecting element during rotation of the movable part according to a modified example of embodiment 3. FIG. 22( b) is a diagram showing the results of a simulation of the distribution of compressive (tensile) stress (distribution of stress in the compressive / tensile direction) generated in the optical reflecting element during the rotational movement of the movable part according to a modified example of embodiment 3. FIG. 23 is a top view schematically showing the configuration of an optical reflecting element according to embodiment 4. FIG. 24 is a diagram showing the configuration of a circuit unit for driving the driving piezoelectric element and the auxiliary driving piezoelectric element using a monitor signal output from the detection piezoelectric element according to embodiment 4. FIG. 25 is a top view schematically showing the configuration of an optical reflecting element according to a modified example of embodiment 4. FIG. 26 is a top view schematically showing the configuration of an optical reflecting element according to embodiment 5. FIG. 27 is a top view schematically showing the configuration of an optical reflecting element according to modified example 1 of embodiment 5. FIG. 28 is a top view schematically showing the configuration of an optical reflecting element according to modified example 2 of embodiment 5.

[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 direction of the Z axis is the vertically upward direction.

[0016] <Embodiment 1> Fig. 1 is a perspective view schematically showing the configuration of optical reflecting element 1. Fig. 2(a) and Fig. 2(b) are a top view and a bottom view, respectively, schematically showing the configuration of optical reflecting element 1. For convenience, piezoelectric bodies 12d and 12e are hatched in Fig. 2(a), and fixing portion 11 is hatched in Fig. 2(b).

[0017] The optical reflecting element 1 includes a fixed portion 11, a drive portion 12, a first support portion 13, a pair of frame portions 14a and 14b, a movable portion 15, a second support portion 16, and a pair of folded portions 17. The optical reflecting element 1 is configured to be symmetrical about a rotation axis R1 parallel to the Y axis. The upper and lower surfaces of the optical reflecting element 1 are substantially parallel to the X-Y plane, and the side surfaces of the optical reflecting element 1 are substantially perpendicular to the X-Y plane. However, a rib may be formed on the lower surface of the movable portion 15, and some of the side surfaces of the optical reflecting element 1 may have a predetermined inclination with respect to the Z axis.

[0018] As shown in FIG. 1, the optical reflecting element 1 includes a base layer 111 made of silicon (Si) and a silicon dioxide (SiO ２ The fixed portion 11 is formed by processing a single SOI wafer in which a box layer (oxide film) 112 made of silicon (SiO2) and an active layer 113 made of silicon (Si) are stacked. The base layer 111, box layer 112, and active layer 113 of the SOI wafer are all left in the region of the fixed portion 11. The fixed portion 11 has high rigidity because it includes the thick base layer 111.

[0019] In the regions of each part of the optical reflecting element 1 other than the fixed portion 11, the base layer 111 and the box layer 112 are removed from the SOI wafer by etching, leaving the active layer 113. That is, each part of the optical reflecting element 1 other than the fixed portion 11 includes the active layer 113 as a layer common to the fixed portion 11. Each part of the optical reflecting element 1 other than the fixed portion 11 does not include the base layer 111, and is composed of a relatively thin active layer 113. Therefore, each of these parts has flexibility that allows elastic deformation.

[0020] The fixed portion 11 includes a base portion 11a extending in the X-axis direction and a pair of arms 11b arranged symmetrically about the rotation axis R1 without sandwiching the second support portion 16. The pair of arms 11b protrude from both ends of the base portion 11a in the X-axis direction toward the movable portion 15. Here, the pair of arms 11b protrude from both ends of the base portion 11a in the positive Y-axis direction so as to be parallel to the rotation axis R1. Furthermore, here, the Y-axis positive side ends of the pair of arms 11b and the Y-axis positive side end of the first support portion 13 are positioned approximately in the same position in the Y-axis direction. Therefore, the pair of arms 11b are arranged so as not to sandwich the pair of frame portions 14a, 14b, the movable portion 15, the second support portion 16, or the pair of frames 14a, 14b.

[0021] The width of each arm 11b in the X-axis direction is constant. The thickness of the fixed portion 11 is also constant and is the same as the thickness of the SOI wafer described above. The lower surface of the fixed portion 11 is a mounting surface for mounting the optical reflecting element 1 on an object.

[0022] The pair of arms 11b extend from the base 11a by a distance equal to or greater than the distance from the base 11a to the center of gravity C0 of the optical reflecting element 1 in the direction parallel to the rotation axis R1. This makes it difficult for the optical reflecting element 1 to tip over in a direction in which the end of the optical reflecting element 1 on the positive side of the Y axis becomes lower when the optical reflecting element 1 is installed. This makes it possible to prevent damage to the second support portion 16 and the pair of folded portions 17 due to this tipping over.

[0023] The driving unit 12 is a tuning fork-type driving unit. The driving unit 12 includes a pair of vibrating units 12a, a connecting unit 12b, a plate-shaped unit 12c, a pair of driving piezoelectric elements 12d, and a pair of detecting piezoelectric elements 12e. The pair of vibrating units 12a are arranged symmetrically with respect to the rotation axis R1. Each vibrating unit 12a has a curved shape in which a portion parallel to the rotation axis R1 and a portion inclined relative to the rotation axis R1 are joined together. The width of the straight portions of the pair of vibrating units 12a is constant except for the tip portions.

[0024] The pair of vibrating parts 12a are connected to the connecting part 12b. The connecting part 12b extends along the rotation axis R1 and is connected to the plate-shaped part 12c. The plate-shaped part 12c is connected to the base part 11a of the fixed part 11. As described above, the pair of vibrating parts 12a, the connecting part 12b, and the plate-shaped part 12c are configured from the active layer 113 common to the fixed part 11. In this way, the driving part 12 is supported by the fixed part 11.

[0025] The pair of driving piezoelectric elements 12d are respectively disposed on the upper surfaces of the pair of vibrating parts 12a. Furthermore, the pair of detecting piezoelectric elements 12e are respectively disposed on the upper surfaces of the pair of vibrating parts 12a. The pair of driving piezoelectric elements 12d are disposed on the tip side of the pair of vibrating parts 12a, and the pair of detecting piezoelectric elements 12e are disposed on the base side of the pair of vibrating parts 12a.

[0026] The pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e have a layer structure consisting of a lower electrode layer, a piezoelectric body layer, and an upper electrode layer. The pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e are connected to electrodes (not shown) on the fixed part 11 via the pair of vibrating parts 12a, the connecting part 12b, and wiring on the fixed part 11. A cable (external wiring) leading to an external device is connected to the electrode on the fixed part 11 by, for example, wire bonding.

[0027] The first support portion 13 extends linearly along the rotation axis R1. Both ends of the first support portion 13 are connected to the connecting portion 12b of the drive portion 12 and the frame portion 14a on the negative side of the Y axis, respectively. The width of the base portion (end on the negative side of the Y axis) of the first support portion 13 increases toward the connecting portion 12b. The width of the tip portion (end on the positive side of the Y axis) of the first support portion 13 increases toward the frame portion 14a. The width of the first support portion 13 other than the tip portion and the base portion is constant. In a plan view, the outer surface of the connection portion between the first support portion 13 and the connecting portion 12b is curved, and the outer surface of the connection portion between the first support portion 13 and the frame portion 14a is also curved.

[0028] In a plan view, the pair of frame portions 14a, 14b surround the movable portion 15. Each of the pair of frame portions 14a, 14b has a curved shape in a plan view.

[0029] The frame portion 14a on the first support portion 13 side (Y-axis negative side) branches off from the end of the first support portion 13 on the Y-axis positive side symmetrically with respect to the rotation axis R1 (symmetrically with respect to the X-axis direction) and surrounds the outer periphery of the movable portion 15 on the first support portion 13 side (Y-axis negative side) symmetrically with respect to the rotation axis R1 (symmetrically with respect to the X-axis direction). Both ends of this frame portion 14a are connected to the movable portion 15 in a direction perpendicular to the rotation axis R1 (X-axis direction). More specifically, both ends of this frame portion 14a are connected to the outer periphery of the movable portion 15 near the position where a straight line passing through the center C1 of the movable portion 15 and perpendicular to the rotation axis R1 intersects with the outer periphery of the movable portion 15.

[0030] The frame portion 14b on the second support portion 16 side (negative side of the Y axis) branches off from the end of the second support portion 16 on the negative side of the Y axis symmetrically about the rotation axis R1 (symmetrically about the X axis) and surrounds the outer periphery of the movable portion 15 on the second support portion 16 side (positive side of the Y axis) symmetrically about the rotation axis R1 (symmetrically about the X axis). Both ends of this frame portion 14b are connected to the movable portion 15 in a direction perpendicular to the rotation axis R1 (X axis direction). More specifically, both ends of this frame portion 14b are connected to the outer periphery of the movable portion 15 near the position where a straight line passing through the center C1 of the movable portion 15 and perpendicular to the rotation axis R1 intersects with the outer periphery of the movable portion 15.

[0031] The movable portion 15 is disposed inside the pair of frame portions 14a, 14b and has a reflecting surface 15a on its upper surface (the surface on the positive side of the Z axis). The movable portion 15 is formed in a plate shape and has a circular outline in a plan view. The center C1 of the movable portion 15 is located at a position overlapping with the rotation axis R1 in a plan view.

[0032] As described above, the movable part 15 is made up of the active layer 113, and the upper surface of the active layer 113 usually has sufficient reflectivity due to the generation of an SOI wafer. Therefore, the upper surface of the movable part 15 (active layer 113) can also be used as the reflecting surface 15a. In this case, the upper surface of the movable part 15 (active layer 113) may be polished to increase the reflectivity of the reflecting surface 15a. Alternatively, an optical reflecting film may be formed on the upper surface of the movable part 15 and used as the reflecting surface 15a.

[0033] The second support portion 16 extends linearly along the rotation axis R1. Both ends of the second support portion 16 are connected to a pair of folded portions 17 and the frame portion 14b on the positive side of the Y axis, respectively. The width of the end of the second support portion 16 on the frame portion 14b side (the end on the negative side of the Y axis) increases toward the frame portion 14b. The width of the other end of the second support portion 16 (the end on the positive side of the Y axis) increases toward the joint position with the pair of folded portions 17. The width of the second support portion 16 other than these end portions is constant.

[0034] The pair of folded portions 17 connect the pair of arm portions 11b to the end (end in the positive Y-axis direction) of the second support portion 16 opposite the movable portion 15. The pair of folded portions 17 are arranged outside the frame portions 14a, 14b and the second support portion 16 in a plan view. As described above, the second support portion 16 has a structure in which the base layer 111 and the box layer 112 are removed from the SOI wafer and the active layer 113 remains, and therefore has flexibility that allows elastic deformation.

[0035] Each of the pair of folded portions 17 includes a pair of first adjustment portions 17a, a pair of second adjustment portions 17b, a pair of relay portions 17c, a pair of curved portions 17d, and a pair of connecting portions 17e. The pair of first adjustment portions 17a are disposed symmetrically with respect to the rotation axis R1 and extend in a direction away from the pair of arm portions 11b. Here, the pair of first adjustment portions 17a extend linearly substantially parallel to the rotation axis R1.

[0036] The pair of second adjustment units 17b are disposed closer to the rotation axis R1 than the pair of first adjustment units 17a, and farther from the pair of arms 11b than the pair of first adjustment units 17a. The pair of second adjustment units 17b are disposed symmetrically with respect to the rotation axis R1, and extend in a direction away from the pair of arms 11b. Here, the pair of second adjustment units 17b extend linearly substantially parallel to the rotation axis R1.

[0037] The pair of relay portions 17c respectively connect the pair of first adjustment portions 17a and the pair of second adjustment portions 17b. The pair of relay portions 17c has a portion that extends obliquely from the end of the pair of first adjustment portions 17a and a portion that extends in a curved shape from the end of the oblique portion and connects to the second support portion 16. As will be described later, the relay portions 17c become an inflection point for the deformation state of the pair of folded portions 17 when the movable portion 15 rotates repeatedly.

[0038] The pair of curved portions 17d connect the pair of second adjustment portions 17b and the second support portion 16. In a plan view, the pair of curved portions 17d have a semicircular shape. The pair of curved portions 17d smoothly branch out in the in-plane direction of the XY plane from the end of the second support portion 16 on the Y-axis positive side.

[0039] The pair of connecting portions 17e are disposed near the boundary between the pair of arm portions 11b and the pair of folded portions 17 and are connected to the pair of arm portions 11b. The pair of connecting portions 17e each increase in width toward the pair of arm portions 11b. Here, the position of the first adjustment portion 17a on the positive side of the X-axis is shifted toward the negative side of the X-axis from the midpoint of the width of the arm portion 11b on the positive side of the X-axis, so the widths of both side surfaces of the connecting portion 17e on the positive side of the X-axis are different from each other. The shape of both side surfaces of this connecting portion 17e is an inwardly concave arc shape in plan view. Similarly, the position of the first adjustment portion 17a on the negative side of the X-axis is shifted toward the positive side of the X-axis from the midpoint of the width of the arm portion 11b on the negative side of the X-axis, so the widths of both side surfaces of the connecting portion 17e on the negative side of the X-axis are also different from each other.

[0040] In the optical reflecting element 1 configured as described above, by applying a drive voltage of a predetermined frequency to the pair of driving piezoelectric bodies 12d, the movable part 15 and the reflecting surface 15a can be repeatedly rotated about the rotation axis R1. More specifically, by applying a drive voltage of a frequency corresponding to the resonant frequency of the movable part 15 to the pair of piezoelectric bodies 12d, the movable part 15 rotates repeatedly at the resonant frequency. At this time, the resonant motion of the movable part 15 is contributed to by the drive part 12, first support part 13, and frame part 14a on the negative side of the Y axis, as well as the frame part 14b and the pair of folded parts 17 on the positive side of the Y axis.

[0041] That is, application of a drive voltage causes the pair of piezoelectric bodies 12d to expand and contract, and in response, the pair of vibrating portions 12a to vibrate up and down. This vibration causes the first support portion 13 to twist around the rotation axis R1, which rotates the movable portion 15. At this time, in response to the rotation of the movable portion 15, the second support portion 16 twists, which in turn causes the pair of folded portions 17 to twist and vibrate. The reaction forces of this twisting and vibration (elastic restoring forces of each portion) are transmitted to the movable portion 15. In this way, the movable portion 15 resonates around the rotation axis R1 due to the drive force from the structure on the negative side of the Y axis (the drive portion 12, the first support portion 13, and the frame portion 14a) and the drive force from the structure on the positive side of the Y axis (the frame portion 14b, the second support portion 16, and the pair of folded portions 17).

[0042] Here, the resonance modes of the movable part 15 include an in-phase mode in which the pair of vibrating parts 12a vibrate in the same direction to vibrate the movable part 15, and an anti-phase mode in which the pair of vibrating parts 12a vibrate in opposite directions to vibrate the movable part 15. Generally, the resonance frequency of the anti-phase mode is higher than the resonance frequency of the in-phase mode, and the smaller the frequency difference between these two resonance modes, the more stably the movable part 15 can be resonated by one of the resonance modes.

[0043] When the pair of vibrating portions 12a vibrate during the rotational movement of the movable portion 15, the detection piezoelectric element 12e deforms in response to this vibration. This deformation generates a current from the piezoelectric element 12e. This current reflects the vibrational movement of the pair of vibrating portions 12a, i.e., the rotational movement of the movable portion 15. Therefore, this current can be used as a monitor signal for the rotational movement of the movable portion 15. The drive circuit of the optical reflecting element 1 adjusts the drive voltage in response to this monitor signal so that the movable portion 15 performs the desired rotational movement.

[0044] 1 and 2(a) and (b), by connecting second support portion 16 to a pair of arm portions 11b (fixed portion 11) via a pair of folded portions 17, movable portion 15 can be driven stably while miniaturizing the external shape of optical reflecting element 1. This effect will be explained below while showing simulation results.

[0045] <Verification 1> FIG. 3 is a top view showing the configuration of the optical reflecting element 1a used in verification 1. As shown in FIG.

[0046] In this optical reflecting element 1a, the folded portion 17 is omitted from the above-described optical reflecting element 1, and the end portion on the Y-axis positive side of the second support portion 16 is fixed. The other configurations of the optical reflecting element 1a are the same as those of the above-described optical reflecting element 1.

[0047] In the simulation of Verification 1, the distance D12 from the base of the first support portion 13 to the center C1 of the movable portion 15 was set to approximately 1600 μm. The radius of the movable portion 15 was set to approximately 500 μm. The width, thickness, length, etc. of each portion other than the distance D12 were adjusted so that the movable portion 15 would resonate at the target resonance frequency (assuming approximately 25,000 to 30,000 Hz in the in-phase mode).

[0048] Under these conditions, various parameters relating to the resonant operation when the movable part 15 is resonated at a target frequency by changing the distance D11 between the center C1 of the movable part 15 and the fixed end were determined by simulation.

[0049] 4A to 4C are graphs showing the simulation results of Verification 1.

[0050] In the simulation of FIG. 4( a), the difference in resonant frequency between the in-phase mode and the anti-phase mode was determined while varying the distance D11. In the simulation of FIG. 4( b), the drive voltage Vpp required to resonate the movable part 15 in the in-phase mode at a full angle of approximately 60° was determined while varying the distance D11. In the simulation of FIG. 4( c), the maximum amount of deflection (maximum displacement from a reference position without deflection) that occurs in the movable part 15 during resonant operation was determined while varying the distance D11. In FIGS. 4( a) to 4( c), the horizontal axis represents the distance D11, and the vertical axis represents the parameter values ​​determined in each simulation.

[0051] From the simulation results of FIGS. 4A to 4C, it can be seen that by changing the distance D11 and adjusting the softness of the second support portion 16, the movable portion 15 can be made to resonate stably.

[0052] For example, the verification results of FIG. 4( c ) show that by setting the distance D11 to approximately 2000 μm, the maximum deflection of the movable part 15 can be suppressed to less than 0.2 μm, thereby effectively suppressing the dynamic deflection of the movable part 15. Furthermore, the verification results of FIG. 4( a ) show that by setting the distance D11 to approximately 2000 μm, the difference in resonance frequency between the in-phase mode and the anti-phase mode can be suppressed, thereby enabling stable operation of the movable part 15. Furthermore, the verification results of FIG. 4( c ) show that by setting the distance D11 to approximately 2000 μm, the drive voltage Vpp required to resonate the movable part 15 at a full angle of approximately 60° can be suppressed, thereby improving the drive efficiency of the movable part 15.

[0053] However, these verification results show that in order for second support portion 16 to flexibly support movable portion 15, it is necessary to set distance D11 to approximately 2000 μm and ensure a certain degree of length for second support portion 16. In this case, distance D11 (2000 μm) is significantly longer than distance D12 (1600 μm) in FIG. 3, and the length obtained by adding distances D11 and D12 is approximately 3600 μm. Therefore, simply increasing the length of second support portion 16 in order to suppress dynamic distortion of movable portion 15 would significantly increase the external dimensions of optical reflecting element 1a.

[0054] <Verification 2> In contrast, in the configuration of the above embodiment, movable portion 15 is flexibly supported by paired folded portions 17 together with second support portion 16, and therefore dynamic deflection of movable portion 15 can be effectively suppressed while suppressing the length in the Y-axis direction of the portion of optical reflecting element 1 on the Y-axis positive side of movable portion 15. This effect will be further clarified by the following verification 2.

[0055] FIG. 5 is a top view showing the configuration of the optical reflecting element 1 used in the second test.

[0056] The optical reflecting element 1 used in Verification 2 was the same as the optical reflecting element 1 shown in Figure 1 and Figures 2(a) and (b) above. In Verification 2, the distance D22 from the end of the pair of curved portions 17d in the positive Y-axis direction to the center C1 of the movable portion 15 was set to approximately 1400 µm, and the radius of the movable portion 15 was set to approximately 500 µm. It was assumed that the movable portion 15 resonated at a resonance frequency (target frequency) similar to that in Verification 1 above. Under these conditions, the distance D21 between the center C1 of the movable portion 15 and the pair of arm portions 11b was changed to change the length of the first adjustment portion 17a, and the dynamic deflection generated in the movable portion 15 was obtained by simulation.

[0057] 6A and 6B are diagrams showing the simulation results of Verification 2, respectively.

[0058] Fig. 6(a) shows overhead views of the maximum dynamic deflection occurring in the movable part 15 when the distance D21 is 100 μm, 500 μm, 600 μm, 700 μm, and 1100 μm. Fig. 6(b) shows lateral views of each of the overhead views of Fig. 6(a) viewed from the side. In each of Figs. 6(a) and 6(b), the amount of deflection in the vertical direction relative to a reference position with no deflection is indicated by a shaded area. In each of Figs. 6(b), the maximum amount of deflection is indicated by a numerical value (positive in the upward direction, negative in the downward direction).

[0059] 6( a) and 6(b) , by setting the distance D21 to approximately 500 to 700 μm, the maximum amount of dynamic deflection occurring in the movable portion 15 can be significantly suppressed to less than 0.2 μm. Even when the distance D21 is set to approximately 100 μm or 1100 μm, the maximum amount of dynamic deflection occurring in the movable portion 15 can be suppressed to slightly more than 0.2 μm. The distance D22 in this case is approximately 1400 μm, as described above. From this, it was confirmed that in the configuration of this embodiment, by flexibly supporting the movable portion 15 with the pair of folded portions 17 together with the second support portion 16, the dynamic deflection of the movable portion 15 can be effectively suppressed while suppressing the length in the Y-axis direction of the portion of the optical reflecting element 1 on the Y-axis positive side of the movable portion 15.

[0060] In Verification 2, the distance D21 capable of effectively suppressing dynamic deflection was determined with the distance D22 fixed at 1,400 μm. However, this is an example of a simulation, and the distances D22 and D11 are not necessarily limited to the above lengths. Various lengths of the first adjustment portion 17 a and the second adjustment portion 17 b capable of effectively suppressing dynamic deflection of the movable portion 15 may exist other than those described above. That is, it is sufficient that the length of the first adjustment portion 17 a is adjusted to a length capable of effectively suppressing dynamic deflection of the movable portion 15 while adjusting the length of the second adjustment portion 17 b. Suppression of dynamic deflection of the movable portion 15 can be achieved by adjusting both the lengths of the first adjustment portion 17 a and the second adjustment portion 17 b within the range of the target length in the Y-axis direction of the optical reflecting element 1.

[0061] <Verification 3> Next, the inventors investigated the case where the shape of pair of folded portions 17 in optical reflecting element 1 was changed from the shapes shown in FIG. 1 and FIGS. 2(a) and (b).

[0062] 7(a) to 7(c) are top views that schematically show other configuration examples of optical reflecting element 1 when the shapes of pair of folded portions 17 are changed.

[0063] 7A (Configuration Example 1), the pair of second adjustment portions 17b, the pair of relay portions 17c, the pair of curved portions 17d, and the pair of connecting portions 17e are omitted, and the pair of first adjustment portions 17a are longer than the pair of folded-back portions 17 in FIG. 2A. The tips of the pair of first adjustment portions 17a are connected by a pair of curved portions 17f that are quarter-circular in plan view.

[0064] 7B (Configuration Example 2), the pair of second adjustment portions 17b, the pair of relay portions 17c, the pair of curved portions 17d, and the pair of connecting portions 17e are omitted, and the pair of first adjustment portions 17a are longer than the pair of folded portions 17 in FIG. 2A. The tips of the pair of first adjustment portions 17a are connected by a pair of curved portions 17g that are semicircular in plan view.

[0065] In the configuration of FIG. 7C (configuration example 3), the length of the pair of connecting portions 17e in the Y-axis direction is smaller than that of the pair of folded portions 17 in FIG. 2A.

[0066] For these configuration examples 1 to 3, the inventors also performed simulations to determine the maximum amount of dynamic distortion that occurs in the movable part 15 when the movable part 15 is resonated at a resonance frequency (target frequency) similar to that of Verifications 1 and 2 above.

[0067] In the simulation for Configuration Example 1 of FIG. 7( a), the distance D31 from the Y-axis most positive end of the pair of folded portions 17 to the center C1 of the movable portion 15 was set to 1484 μm. In the simulation for Configuration Example 2 of FIG. 7( b), this distance D31 was set to 1532 μm, and in the simulation for Configuration Example 3 of FIG. 7( c), this distance D31 was set to 1405 μm. In these simulations, the width of the pair of arms 11b in the X-axis direction was set smaller than the width of the pair of arms 11b in Verification 2 above. In Configuration Examples 1 to 3, the width of each portion was adjusted so that the movable portion 15 resonated at the same resonance frequency (common mode).

[0068] In the simulation of the configuration example 1 of Fig. 7(a), a simulation result of approximately 229 nm was obtained as the maximum amount of dynamic deflection occurring in the movable part 15. In the simulation of the configuration example 2 of Fig. 7(b), a simulation result of approximately 270 nm was obtained as the maximum amount of dynamic deflection occurring in the movable part 15. In the simulation of the configuration example 3 of Fig. 7(c), a simulation result of approximately 195 nm was obtained as the maximum amount of dynamic deflection occurring in the movable part 15.

[0069] From these simulation results, it was confirmed that even when the shape of the folded portion 17 is changed, the pair of folded portions 17, together with the second support portion 16, softly support the movable portion 15, thereby effectively suppressing the dynamic deflection of the movable portion 15 while suppressing the length in the Y-axis direction of the portion of the optical reflecting element 1 on the positive side of the Y-axis relative to the movable portion 15.

[0070] Next, the inventors conducted simulations to determine the stresses generated in vibrating portion 12a, piezoelectric body 12d, first support portion 13, and near the boundaries between arm portion 11b and folded portion 17, as well as the drive voltage Vpp required to resonate movable portion 15 at a target swing angle for optical reflecting element 1 of configuration examples 1 to 3. As a result, the following simulation results were obtained. The following table also shows the simulation results for the maximum amount of dynamic deflection described above.

[0071]

[0072] Referring to the above simulation results, in Configuration Example 3, stress in each part is generally alleviated and driving efficiency is maintained at a high level compared to Configuration Examples 1 and 2. Therefore, from the viewpoint of suppressing stress generated in each part due to the resonant operation of movable part 15 and suppressing damage to optical reflecting element 1, it can be said that it is preferable to arrange first adjustment part 17a and second adjustment part 17b in folded part 17, as in Configuration Example 3.

[0073] Considering the above simulation results, in configuration examples 1 and 2, second adjustment unit 17b and relay unit 17c are not provided, so the torsion of second support unit 16 caused by the resonant operation of movable unit 15 is propagated to first adjustment unit 17a, and this torsion acts on the boundary between arm unit 11b and folded-back unit 17. For this reason, in configuration examples 1 and 2, it is thought that a relatively large stress is generated near the boundary between arm unit 11b and folded-back unit 17, as in the above simulation results.

[0074] In contrast, in Configuration Example 3, because the second adjustment portion 17b and the relay portion 17c are provided, the torsion of the second support portion 16 caused by the resonant operation of the movable portion 15 propagates to the curved portion 17d and the second adjustment portion 17b, but is less likely to propagate to the first adjustment portion 17a due to the presence of the relay portion 17c. When the behavior of each portion during the resonant operation of the movable portion 15 in Configuration Example 3 was confirmed by simulation, it was found that although torsion occurred in the second adjustment portion 17b, the first adjustment portion 17a deformed substantially only in the vertical direction (Z-axis direction). In other words, the relay portion 17c was the inflection point between the torsion in the folded portion 17 and the deformation only in the vertical direction. Therefore, in Configuration Example 3, torsion does not substantially act on the boundary between the arm portion 11b and the folded portion 17. As a result, it is believed that in Configuration Example 3, the stress generated near the boundary between the arm portion 11b and the folded portion 17 is significantly alleviated compared to Configuration Examples 1 and 2, as shown in the above simulation results.

[0075] <Verification 4> In optical reflecting element 1, it is preferable to mitigate as much as possible the stress that occurs in each part during the resonant operation of movable part 15, from the viewpoint of preventing damage due to stress concentration.

[0076] For example, when forming piezoelectric body 12d by laminating a thin film on the upper surface of active layer 103 having a thickness of about 100 μm, the stress generated in piezoelectric body 12d is preferably suppressed to 500 MPa or less, and the stress generated in vibrating portion 12a and first support portion 13 is preferably suppressed to 900 MPa or less. Also, the stress generated near the boundary between arm portion 11b and folded portion 17 is preferably suppressed to 500 MPa or less. Furthermore, from the viewpoint of stable light scanning by reflecting surface 15a, the maximum amount of dynamic deflection of movable portion 15 during resonant operation of movable portion 15 is preferably suppressed to 200 nm or less.

[0077] Since the simulation results for Configuration Example 3 are close to these conditions, it can be assumed that these conditions can be realized by fine-tuning the dimensions of each part in Configuration Example 3. Therefore, the inventors studied how to adjust the dimensions of each part in Configuration Example 3 so that the stress in each part can approach the above conditions.

[0078] 8(a) and (b) are diagrams showing the results of a simulation of stress distribution that occurs when the dimensions of each part are finely adjusted in Configuration Example 3. For convenience, in FIGS. 8(a) and (b), the pair of arms 11b are shown separated from the base 11a.

[0079] Fig. 8(a) shows the stress distribution in optical reflecting element 1 before adjustment, and corresponds to the stress distribution occurring in optical reflecting element 1 of Configuration Example 3. As shown in Fig. 8(a) , in optical reflecting element 1 (Configuration Example 3) before adjustment, high stress is concentrated on the inside of the base of vibrating portion 12a, and high stress is also concentrated near the boundary between arm portion 11b and folded portion 17. Furthermore, in optical reflecting element 1 (Configuration Example 3) before adjustment, stress is high in first support portion 13 and second support portion 16, and stress is also high near the connection position of frame portion 14a with first support portion 13 and near the connection position of frame portion 14b with second support portion 16.

[0080] FIG. 8( b) shows the stress distribution in the optical reflecting element 1 after adjustment. In the optical reflecting element 1 after adjustment, the length L1 of the first adjustment portion 17a and the length L2 of the second adjustment portion 17b are each increased compared to the optical reflecting element 1 before adjustment shown in FIG. 8( a). Furthermore, the width W1 of the arm portion 11b is increased, and the length L3 of the connecting portion 17e is increased compared to before adjustment. The two arc-shaped side surfaces of the connecting portion 17e are adjusted so that the outer side is wider than the inner side. Furthermore, the curved shape near the boundary between the side surface of the first support portion 13 and the inner side surface of the vibrating portion 12a (shown by the dashed circle in FIG. 8( b)) has been adjusted to be more rounded (with a larger radius of curvature) compared to before adjustment.

[0081] 8(a) and 8(b), by adjusting the dimensions and shapes of each part as described above, in the adjusted optical reflecting element 1, the stress generated in each part during the resonant operation of movable part 15 was significantly alleviated. That is, the stress inside the base of vibrating part 12a was significantly alleviated, and the stress near the boundary between arm part 11b and folded part 17 was also significantly alleviated. In addition, the stress in first support part 13 and second support part 16 was also significantly alleviated, and the stress near the connection position of frame part 14a with first support part 13 and the stress near the connection position of frame part 14b with second support part 16 were also alleviated.

[0082] More specifically, in the optical reflecting element 1 after adjustment shown in FIG. 8( b), the maximum stress in the piezoelectric body 12d was suppressed to less than 450 MPa, compared to the above-mentioned condition of 500 MPa or less. The maximum stress generated in the vibrating portion 12a and the first support portion 13 was suppressed to approximately 600 MPa and approximately 800 MPa, respectively, compared to the above-mentioned condition of 900 MPa or less. Furthermore, the maximum stress generated near the boundary between the arm portion 11b and the folded portion 17 was suppressed to approximately less than 500 MPa, compared to the above-mentioned condition of 500 MPa or less. Furthermore, the maximum amount of dynamic deflection of the movable portion 15 during resonant operation of the movable portion 15 was suppressed to approximately 70 nm. The voltage value of the drive voltage Vpp required to rotate the movable portion 15 at the target swing angle was slightly above 10 V, slightly higher than before adjustment.

[0083] In this way, when the pair of folding sections 17 have first adjustment section 17a, second adjustment section 17b, and relay section 17c as in configuration example 3, adjusting the shape of each section while adjusting the lengths of first adjustment section 17a and second adjustment section 17b makes it possible to significantly alleviate the stress generated in each section of optical reflecting element 1 during resonant operation of movable section 15, and also significantly suppress the maximum amount of dynamic deflection in movable section 15. Therefore, it is possible to realize an optical reflecting element 1 that can stably scan high-quality light and has high reliability.

[0084] <Effects of First Embodiment> According to the first embodiment, the following effects are achieved.

[0085] As shown in Figures 1, 2(a) and (b), and 7(a) to (c), the optical reflecting element 1 comprises: a first support portion 13 extending along the rotation axis R1; a second support portion 16 extending along the rotation axis R1; a movable portion 15 having a reflective surface 15a and supported by the first support portion 13 and the second support portion 16; a drive portion 12 connected to the end of the first support portion 13 opposite the movable portion 15 and applying a drive force to the movable portion 15 via the first support portion 13 to rotate the movable portion 15; a base portion 11a supporting the drive portion 12; a rigid fixed portion 11 consisting of a pair of arms 11b arranged symmetrically about the rotation axis R1 and without sandwiching the second support portion 16; and a pair of flexible frame-shaped folded portions 17 connecting the end of the second support portion 16 opposite the movable portion 15 to the pair of arms 11b, respectively.

[0086] According to this configuration, the second support portion 16 is connected to the fixed portion 11 (the pair of arms 11b) via the pair of folded portions 17. As a result, even if the length of the second support portion 16 is shortened, the movable portion 15 can be flexibly supported from both sides by the first support portion 13, the second support portion 16, and the pair of folded portions 17. As a result, as shown in Verifications 2 and 3 above, dynamic deflection occurring in the movable portion 15 during rotation of the movable portion 15 can be suppressed. Furthermore, since the fixed portion 11 does not extend around the side of the movable portion 15 opposite the drive portion 12, and the pair of arms 11b are limited in length so as not to sandwich the second support portion 16, the shape of the optical reflecting element 1 in the direction parallel to the rotation axis R1 can be reduced. Furthermore, as described above, the length of the second support portion 16 can be shortened, so the shape of the optical reflecting element 1 in the direction parallel to the rotation axis R1 can be further reduced. Therefore, the movable portion 15 can be stably driven while achieving a compact external shape of the optical reflecting element 1.

[0087] As shown in FIG. 1, the thickness of the pair of folded portions 17 is smaller than the thickness of the pair of arm portions 11b.

[0088] According to this configuration, the pair of folded portions 17 can be made flexible by a simple method such as adjusting the thickness.

[0089] As shown in FIG. 1, the fixed portion 11 includes an active layer 113 and a base layer 111 that is thicker than the active layer 113, and the pair of folded portions 17 include the active layer 113 as a layer common to the fixed portion 11, but do not include the base layer 111.

[0090] According to this configuration, flexibility can be imparted to the pair of folded portions 17 through a simple process of removing at least the base layer 111 from a substrate having the base layer 111 and the active layer 113 .

[0091] As shown in Figures 1, 2(a), (b) and 7(a) to (c), the optical reflecting element 1 comprises a frame portion 14a (first frame portion) that surrounds the outer circumferential portion of the movable portion 15 on the first support portion 13 side symmetrically about the rotation axis R1 and has both ends connected to the movable portion 15, and a frame portion 14b (second frame portion) that surrounds the outer circumferential portion of the movable portion 15 on the second support portion 16 side symmetrically about the rotation axis R1 and has both ends connected to the movable portion 15, and the first support portion 13 is connected to the movable portion 15 via the frame portion 14a (first frame portion), and the second support portion 16 is connected to the movable portion 15 via the frame portion 14b (second frame portion).

[0092] According to this configuration, the movable part 15 is supported at a position away from the rotation axis R1, i.e., near a position where dynamic deflection is likely to occur during rotation, and a driving force for rotation is applied to the movable part 15. Therefore, dynamic deflection occurring in the movable part 15 can be effectively suppressed.

[0093] As shown in Verification 2 above and Figures 6(a) and (b), it is preferable that the pair of folded portions 17 be configured so that the deflection (dynamic deflection) that occurs in the movable portion 15 during resonant operation of the movable portion 15 at the target frequency is substantially 200 nm or less.

[0094] According to this configuration, by adjusting the dimensions and shape of the pair of folded portions 17, dynamic deflection of the movable portion 15 can be significantly suppressed.

[0095] As shown in Figures 1 and 2(a) and (b), the pair of folded portions 17 have a pair of first adjustment portions 17a arranged symmetrically about the rotation axis R1, a pair of second adjustment portions 17b arranged symmetrically about the rotation axis R1 at positions closer to the rotation axis R1 than the pair of first adjustment portions 17a and farther from the pair of arms 11b than the pair of first adjustment portions 17a, and a pair of relay portions 17c connecting the pair of first adjustment portions 17a and the pair of second adjustment portions 17b, respectively.

[0096] With this configuration, the intermediary of the relay portion 17c makes it difficult for the torsion generated in the second support portion 16 during the rotational movement of the movable portion 15 to propagate from the second adjustment portion 17b to the first adjustment portion 17a. Therefore, during the rotational movement of the movable portion 15, torsion occurs in the pair of second adjustment portions 17b, but substantially no torsion occurs in the pair of first adjustment portions 17a, and the pair of first adjustment portions 17a substantially only deform in the vertical direction. In other words, the relay portion 17c becomes an inflection point for the deformation state of the pair of folded portions 17 during the rotational movement of the movable portion 15. Under these effects, by adjusting the lengths of the first adjustment portions 17a and the second adjustment portions 17b, dynamic deflection of the movable portion 15 can be significantly suppressed, as shown in Test 2 above.

[0097] As shown in FIGS. 1 and 2(a) and (b), the pair of first adjustment portions 17a and the pair of second adjustment portions 17b extend substantially parallel to the rotation axis R1.

[0098] According to this configuration, as shown in the above-mentioned verification 2, by adjusting the lengths of the first adjustment portion 17a and the second adjustment portion 17b, the dynamic deflection of the movable portion 15 can be significantly suppressed.

[0099] As shown in Figures 1 and 2(a) and (b), the width of each of the pair of folded portions 17 is smaller than the width of each of the pair of arm portions 11b, and the pair of folded portions 17 each have a pair of connecting portions 17e whose width increases toward the pair of arm portions 11b, and the pair of connecting portions 17e are respectively connected to the pair of arm portions 11b.

[0100] This configuration can prevent stress from concentrating near the boundaries between the pair of folded-back portions 17 and the pair of arm portions 11 b when the movable portion 15 rotates, thereby preventing damage due to stress concentration near these boundaries when the movable portion 15 rotates.

[0101] As shown in Figures 1 and 2(a) and (b), the pair of arms 11b extend from the base 11a in a direction parallel to the rotation axis R1 by a distance greater than the distance from the base 11a to the center of gravity C0 of the optical reflecting element 1.

[0102] According to this configuration, as described above, the optical reflecting element 1 is less likely to tip over when the optical reflecting element 1 is installed. Therefore, damage to the second support portion 16 and the pair of folded portions 17 due to the tipping over can be suppressed.

[0103] In the first embodiment, the movable portion 15 is supported by the first support portion 13 and the second support portion 16 via the pair of frame portions 14 a, 14 b. In contrast, in the second embodiment, the pair of frame portions 14 a, 14 b are omitted, and the movable portion 15 is supported by the first support portion 13 and the second support portion 16.

[0104] 9(a) and 9(b) are respectively a top view and a bottom view schematically showing the configuration of optical reflecting element 1 according to embodiment 2. For convenience, piezoelectric bodies 12d and 12e are hatched in Fig. 9(a), and fixing portion 11 is hatched in Fig. 9(b).

[0105] 9(a) and 9(b), in the optical reflecting element 1 according to the second embodiment, compared to the optical reflecting element 1 according to the first embodiment shown in FIGS. 2(a) and 2(b), the pair of frame portions 14a and 14b are omitted, and the movable portion 15 is supported by the first support portion 13 and the second support portion 16. In other words, the first support portion 13 and the second support portion 16 are directly connected to the movable portion 15. The other configurations of the optical reflecting element 1 according to the second embodiment are the same as those of the optical reflecting element 1 according to the first embodiment.

[0106] <Verification 5> The inventors also conducted a simulation to examine the effect of the pair of folded portions 17 in the configuration of the second embodiment.

[0107] Fig. 10(a) is a diagram showing simulation conditions for examining the effect of a pair of folded portions 17. Fig. 10(b) is a bottom view showing the configuration of an optical reflecting element 1b according to a comparative example used in the examination.

[0108] 10A corresponds to the bottom view of FIG. 9B. In the simulation, the distance D42 from the ends of the pair of curved portions 17d in the positive Y-axis direction to the center of the movable portion 15 was set to approximately 1400 μm, and the radius of the movable portion 15 was set to approximately 500 μm.

[0109] Under these conditions, the length of first adjustment portion 17a was changed by changing distance D41 between center C1 of movable portion 15 and pair of arm portions 11b, and the dynamic deflection occurring in movable portion 15 during resonant operation of movable portion 15 was calculated by simulation. Furthermore, for optical reflecting element 1b of a comparative example in which second support portion 16 and pair of folded portions 17 are omitted from the configuration of Figure 10(a), the dynamic deflection occurring in movable portion 15 during resonant operation of movable portion 15 was determined by simulation.

[0110] FIG. 11 shows the simulation results of Verification 5.

[0111] 11 shows overhead views of the maximum dynamic deflection occurring in the movable part 15 when the distance D41 is 500 μm, 1000 μm, and 1500 μm, as well as overhead views of the maximum dynamic deflection occurring in the movable part 15 in a comparative example. In each view of FIG. 11, the amount of deflection is shown in shades of gray, with the center of the movable part 15 being a deviation of 0, and the maximum amount of deflection in the up and down directions is also indicated as a numerical value (upward is positive, downward is negative). The character "small" in each view indicates that the amount of deflection at that position is substantially 0.

[0112] 11 , it was confirmed that the configuration of the second embodiment significantly suppresses dynamic deflection compared to the configuration of the comparative example. Furthermore, in the configuration of the second embodiment according to this simulation, by setting the distance D41 to approximately 1000 μm, the maximum amount of dynamic deflection was effectively suppressed, and the symmetry of the dynamic deflection in the direction of the rotation axis R1 was improved. This confirms that the dynamic deflection of the movable part 15 can be effectively suppressed by adjusting the length of the pair of first adjustment parts 17 a to adjust the flexibility of the pair of folded parts 17.

[0113] Furthermore, because distance D42 is 1400 μm as described above, the length in the Y-axis direction of the portion on the Y-axis positive side of movable part 15 can be relatively small. Therefore, in the configuration of embodiment 2 as well, it was confirmed that by flexibly supporting movable part 15 with pair of folded parts 17 together with second support part 16, it is possible to effectively suppress dynamic deflection of movable part 15 while suppressing the length in the Y-axis direction of the portion of optical reflecting element 1 on the Y-axis positive side of movable part 15.

[0114] Note that the distances D41 and D42 shown in Verification 5 are examples of simulations, similar to the distances D21 and D22 in Verification 2 above, and in the configuration of Embodiment 2, the lengths of the first support portion 13 and the second support portion 16 that can suppress the dynamic deflection of the movable portion 15 can be various lengths other than those corresponding to the distances D41 and D42 shown in the simulation above.

[0115] Also in the second embodiment, the shape of the pair of folded portions 17 in plan view may be changed from the shape shown in Figures 9(a) and 9(b). For example, the pair of frame portions 14a and 14b may be omitted from the configuration examples 1 to 3 shown in Figures 7(a) to 7(c), and the movable portion 15 may be directly supported by the first support portion 13 and the second support portion 16. In these cases, the dimensions (length, thickness, width, etc.) and shape of each part of the pair of folded portions 17 may be adjusted so as to effectively suppress dynamic deflection of the movable portion 15 while suppressing the length in the Y-axis direction of the portion of the optical reflecting element 1 on the Y-axis positive side of the movable portion 15. Also in the configuration of the second embodiment, the dimensions (length, thickness, width, etc.) and shape of each part may be adjusted so as to mitigate stress in each part as much as possible.

[0116] According to the configuration of embodiment 2, it can be easily inferred from the above verifications 1 to 3 that it is possible to suppress dynamic deflection while suppressing the length in the Y-axis direction of the portion of the Y-axis positive side of the movable part 15, compared to the configuration in the comparative example of Figure 10 (b) in which the Y-axis positive side of the movable part 15 is connected to the fixed end via the second support part 16 (a configuration in which the pair of frame parts 14a, 14b are omitted from Figure 3 and the movable part 15 is directly supported by the first support part 13 and the second support part 16).

[0117] <Modification 1> The present invention is not limited to the above-described first and second embodiments, and the realization of the present invention can be appropriately modified from the above-described first and second embodiments.

[0118] For example, the pair of first adjustment portions 17a and the pair of second adjustment portions 17b do not necessarily have to extend parallel to the rotation axis R1, and one or both of them may be inclined with respect to the rotation axis R1.

[0119] For example, as shown in Fig. 12(a), the pair of second adjustment units 17b may be inclined so that the Y-axis negative side is closer to the rotation axis R1 than the Y-axis positive side, or as shown in Fig. 12(b), the pair of first adjustment units 17a may be inclined so that the Y-axis positive side is closer to the rotation axis R1 than the Y-axis negative side. Alternatively, as shown in Fig. 12(b), both the pair of first adjustment units 17a and the pair of second adjustment units 17b may be inclined with respect to the rotation axis R1.

[0120] The length of relay portion 17c and the like are changed depending on the inclination of pair of first adjustment portions 17a and / or pair of second adjustment portions 17b. In the configurations of Figures 12(a) to 12(c), the dimensions of each portion of pair of folded portions 17 may be adjusted so as to suppress dynamic deflection of movable portion 15 during resonant operation. The direction in which pair of first adjustment portions 17a and / or pair of second adjustment portions 17b are inclined relative to rotation axis R1 may be opposite to the direction shown in Figures 12(a) to 12(c).

[0121] The same modifications as those in the first modified example can be applied to the configuration of the second embodiment.

[0122] <Modification 2> The configuration of the pair of vibrating parts 12a is not limited to the configurations shown in the first and second embodiments, and can be modified as appropriate.

[0123] For example, as shown in Fig. 13(a), the pair of vibrating parts 12a may each have an L-shape that is bent almost vertically, or as shown in Fig. 13(b), the Y-axis positive side portions of the pair of vibrating parts 12a may be spaced further from the rotation axis R1 as they move in the Y-axis positive direction. Also, as shown in Fig. 13(c), the pair of arms 11b of the fixed part 11 may be inclined in accordance with the inclination of the pair of vibrating parts 12a. The pair of arms 11b do not necessarily need to extend parallel to the rotation axis R1, and may, for example, be inclined so that the Y-axis positive side is farther from the rotation axis R1 than the Y-axis negative side.

[0124] In the configuration of the second modification, the modifications of the first modification may also be applied.

[0125] The same modifications as those in the second modified example can be applied to the configuration of the second embodiment.

[0126] <Modification 3> The configuration of the pair of frame portions 14a, 14b is not limited to the configurations shown in the first and second embodiments, and can be modified as appropriate.

[0127] For example, as shown in Figure 14(a), a gap G may be provided between the pair of frame portions 14a, 14b, and the pair of frame portions 14a, 14b may be separated from each other. However, dynamic deflection of the movable portion 15 is likely to occur at the end of the movable portion 15 that is farthest from the rotation axis R1. Therefore, it is preferable that the connection positions of the pair of frame portions 14b to the movable portion 15 are as close as possible to a straight line that passes through the center C1 of the movable portion 15 and is perpendicular to the rotation axis R1. For this reason, it is preferable that the gap G is as small as possible, and it is most preferable that there is no gap G as in the first embodiment.

[0128] Modification Example 4 In the first and second embodiments, as shown in Fig. 2(b) and Fig. 9(b), the boundaries between the pair of folded portions 17 and the pair of arm portions 11b are parallel to the X-axis. However, these boundaries do not necessarily have to be parallel to the X-axis. For example, as shown in Fig. 14(b), these boundaries may be inclined with respect to the X-axis. Furthermore, these boundaries do not have to be straight in plan view. For example, they may be curves that are convex in the negative Y-axis direction. The shapes of these boundaries, in combination with the width of the pair of connecting portions 17e, can be adjusted to a shape that can effectively suppress stress generated at these boundaries during resonant operation.

[0129] The same modifications as those in the fourth modified example can also be applied to the configuration of the second embodiment.

[0130] <Modification 5> In the first and second embodiments, the first adjustment unit 17a and the connection unit 17e are disposed, but the connection unit 17e may be integrated into the first adjustment unit 17a.

[0131] 15(a), the ends of the pair of first adjustment parts 17a on the negative side in the Y-axis direction may be connected to the pair of arms 11b of the fixed part 11, and the width of the pair of first adjustment parts 17a in the X-axis direction may gradually decrease with increasing distance from the pair of arms 11b. In this case as well, the pair of first adjustment parts 17a extend substantially parallel to the rotation axis R1.

[0132] With this configuration, the force propagating from the end on the negative side of the Y-axis to the end on the positive side of the Y-axis in the pair of first adjustment parts 17a is more easily dispersed, thereby effectively suppressing the stress that occurs at the boundary between the pair of first adjustment parts 17a and the pair of arm parts 11b during resonant operation.

[0133] Also, as shown in Figure 15 (b), the width of the end of the pair of arms 11b on the positive side of the Y axis may be wider than that of the other arms 11b, and a first adjustment unit 17a with an integrated connection unit 17e may be connected to this end.

[0134] According to this configuration, the width of the boundary between the pair of first adjustment portions 17a and the pair of arm portions 11b is increased, so that the stress generated at this boundary during resonant operation can be suppressed more effectively.

[0135] <Effects of Miniaturization> According to the configurations of the above-described first and second embodiments and each modified example, the optical reflecting element 1 can be miniaturized in a direction parallel to the rotation axis R1, and in particular, the portion of the movable part 15 on the opposite side of the drive part 12 can be effectively miniaturized in a direction parallel to the rotation axis R1. Such miniaturization can effectively reduce the size of the entire optical system, for example, when combining with other optical reflecting elements to scan a beam around two axes.

[0136] 16(a) and 16(b), in the case of an optical system in which a beam B1 reflected by a reflecting surface 15a of an optical reflecting element 1 is reflected by a mirror 3 and directed to a reflecting surface 23a of another optical reflecting element 2, a pair of folding portions 17 of the optical reflecting element 1 can be arranged to overlap the frame-shaped fixing portion 21 of the other optical reflecting element 2. This allows the reflecting surfaces 15a and 23a to be closer to each other, making it possible to miniaturize the entire optical system in the Y-axis direction. Furthermore, because the reflecting surfaces 15a and 23a can be closer to each other, it is possible to reduce the distance H between the top surface of the optical reflecting element 1 and the mirror 3, making it possible to miniaturize the entire optical system in the Z-axis direction as well.

[0137] 16(a) and 16(b), a meander-type optical reflecting element is shown as the other optical reflecting element 2. This optical reflecting element 2 includes a frame-shaped fixed portion surrounding the periphery of a movable portion 23 and a pair of meander-type driving portions 22 arranged along a rotation axis R2. The movable portion 23 is rotated about the rotation axis R2 by the pair of driving portions 22. The two optical reflecting elements 1 and 2 are arranged so that their respective rotation axes R1 and R2 are orthogonal to each other in a plan view. The other optical reflecting element 2 is not limited to a meander-type optical reflecting element, and may be an optical reflecting element of another configuration.

[0138] Third Embodiment In a third embodiment, the arrangement of the pair of piezoelectric elements 12e (sensor portions) for detecting the rotation of the movable portion is changed compared to the configuration of the first embodiment.

[0139] FIG. 17 is a diagram showing the results of a simulation of stress distribution (Mises stress distribution) when movable portion 15 of optical reflecting element 1 is rotated according to the third embodiment.

[0140] For convenience, the color simulation results are shown in grayscale in Figure 17. The color scale at the bottom right of Figure 17 is blue at the left and red at the right, with green at the middle of the color scale.

[0141] Referring to the simulation results, the stress generated in the pair of folded portions 17 is approximately the same as the stress generated near the base of the pair of vibrating portions 12a, i.e., the region where the pair of detection piezoelectric bodies 12e are arranged in the above-described embodiment 1. In particular, the stress generated in the pair of first adjustment portions 17a and the pair of second adjustment portions 17b is approximately the same as or greater than the stress near the base of the pair of vibrating portions 12a. Therefore, by arranging the pair of piezoelectric bodies 12e (sensor units) in the pair of folded portions 17, a monitor signal corresponding to the rotational movement of the movable portion 15 can be obtained from these piezoelectric bodies 12e.

[0142] Figure 18(a) is a top view schematically showing the configuration of the optical reflecting element 1 according to embodiment 3, and Figure 18(b) is a top view schematically showing the configuration of the optical reflecting element 1 according to embodiment 1.

[0143] 18(a), in the third embodiment, a pair of piezoelectric elements 12e for detection are disposed on the upper surfaces of a pair of first adjustment units 17a, respectively. The configuration of the lower surface side of the optical reflecting element 1 according to the third embodiment is the same as that of the first embodiment.

[0144] The pair of piezoelectric bodies 12e are connected to a pair of terminals T2 arranged on the base 11a via a pair of wirings P2. The pair of driving piezoelectric bodies 12d arranged on the upper surfaces of the pair of vibrating parts 12a are connected to a pair of terminals T2 arranged on the base 11a via a pair of wirings P1. A pair of ground terminals T0 are arranged on the base 11a.

[0145] The pair of terminals T1 and the pair of terminals T2 have a layer structure consisting of a lower electrode layer, a piezoelectric layer, and an upper electrode layer, similar to the pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e. Furthermore, the wiring P1 and P2 connecting the pair of terminals T1 and the pair of terminals T2 to the pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e also have a layer structure consisting of a lower electrode layer, a piezoelectric layer, and an upper electrode layer, similar to the pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e. The pair of terminals T0 consists only of a lower electrode layer and is connected to the lower electrode layers of the pair of terminals T1 and the pair of terminals T2. That is, the lower electrode layer extends uniformly over the upper surface of the base 11a, and the protective film covering the upper surface of the optical reflecting element 1 is removed in the regions corresponding to the pair of terminals T0 to form the terminals T0. The protective film is also removed in the regions corresponding to the pair of terminals T1 and the pair of terminals T2.

[0146] The pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e, the terminals T0 to T1, and the wiring are formed, for example, by the following method.

[0147] First, a layer structure consisting of a lower electrode layer, a piezoelectric layer, and an upper electrode layer is uniformly formed on the upper surfaces of the fixed portion 11, the drive portion 12, and the pair of folded portions 17. Next, this layer structure is subjected to an etching process using a mask to remove unnecessary layer structure. In this process, the layer structure consisting of the lower electrode layer, the piezoelectric layer, and the upper electrode layer remains only in the areas of the pair of piezoelectric bodies 12d and 12e, the terminals T1 and T2, and the wiring P1 and P2. The lower electrode layer remains over almost the entire upper surface of the base portion 11a, while the upper electrode layer and the piezoelectric layer are removed in the areas of the base portion 11a other than the areas of the terminals T1 and T2 and the wiring P1 and P2. Here, in areas other than the piezoelectric bodies 12e and 12d and the terminals T0, T1, and T2, only the upper electrode layer may be removed, leaving the piezoelectric layer on the entire surface, similar to the lower electrode layer. After this process, a protective film is formed on the upper surface of the optical reflecting element 1 in areas other than the terminals T0 to T1. In this way, a pair of piezoelectric bodies 12d and a pair of piezoelectric bodies 12e, terminals T0 to T1, and wirings P1 and P2 are formed.

[0148] In the configuration of the first embodiment shown in FIG. 18(b), the pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12e, the terminals T0 to T1, and the wirings P1 and P2 are formed by the same process.

[0149] According to the configuration of embodiment 3 in Figure 18 (a), detection piezoelectric elements 12e are each placed on a pair of first adjustment parts 17a, which are areas where stress occurs when the movable part 15 rotates, i.e., areas that deform in response to rotation during rotation, and therefore the rotation of the movable part 15 can be monitored from the output of these piezoelectric elements 12e.

[0150] Furthermore, in the configuration of embodiment 3, the driving piezoelectric element 12d and the detecting piezoelectric element 12e are not adjacent to each other as in embodiment 1 shown in Figure 18 (b), so the arrangement area of ​​the driving piezoelectric element 12d can be expanded compared to the configuration of embodiment 1, and the driving efficiency of the movable part 15 can be improved.

[0151] 18(b), the driving piezoelectric element 12d and the detecting piezoelectric element 12e are adjacent to each other, and therefore, due to capacitive coupling between these piezoelectric elements, the driving signal applied to the driving piezoelectric element 12d adversely affects the monitor signal output from the detecting piezoelectric element 12e, reducing the S / N ratio of the monitor signal. In contrast, according to the configuration of embodiment 3, as shown in FIG. 18(a), the driving piezoelectric element 12d and the detecting piezoelectric element 12e can be arranged apart, making it less likely that the monitor signal will be degraded by capacitive coupling as in embodiment 1. Therefore, a better quality monitor signal can be obtained than in embodiment 1.

[0152] Furthermore, when the movable portion 15 rotates, torsional vibrations occur in the connecting portion 12b and the plate-like portion 12c (see FIG. 2B). In the configuration of the first embodiment, a detection piezoelectric element 12e is disposed near the location where such torsional vibrations occur, and wiring P2 connected to the piezoelectric element 12e passes through these locations. Therefore, in the configuration of the first embodiment, the piezoelectric element 12e and wiring P2 detect the torsional vibrations, and unwanted vibration components (harmonic components) based on the torsional vibrations may be superimposed on the monitor signal. In contrast, in the configuration of the third embodiment, as shown in FIG. 18A, the detection piezoelectric element 12e and wiring P2 are not disposed near the location where such torsional vibrations occur, so that unwanted vibration components based on the torsional vibrations are prevented from being superimposed on the monitor signal. Therefore, a better quality monitor signal can be obtained than in the first embodiment.

[0153] Fig. 19(a) is a diagram showing the results of a simulation of the torsional stress generated in the detection piezoelectric element 12e when the movable part 15 rotates in the configuration of embodiment 3. Fig. 19(b) is a diagram showing the results of a simulation of the torsional stress generated in the detection piezoelectric element 12e when the movable part 15 rotates in the configuration of embodiment 1.

[0154] For convenience, the color simulation results are shown in grayscale in Figures 19(a) and (b). The color scale in the lower right corner of Figures 19(a) and (b) ranges from blue at the left to red at the right. The middle of this color scale is green.

[0155] As shown in Figure 19(b), in the configuration of embodiment 1, a large change in stress occurs in the width direction of the piezoelectric element 12e (the longitudinal direction of the dashed frame). In the color scale at the bottom right of Figure 19(b), the range enclosed in brackets indicates the range of stress occurring in the longitudinal direction of the dashed frame. Therefore, in the configuration of embodiment 1, a relatively large twist occurs in the detection piezoelectric element 12e during the rotational movement of the movable part 15, and this twist causes unnecessary signal components to be superimposed on the monitor signal.

[0156] In contrast, in the configuration of embodiment 3, as shown in FIG. 19( a), almost no change in stress occurs in the width direction of the detection piezoelectric element 12e, and only a small change in stress occurs in the longitudinal direction of the piezoelectric element 12e. In the color scale at the bottom right of FIG. 19( a), the range enclosed in brackets indicates the range of stress occurring in the longitudinal direction of the piezoelectric element 12e. As such, in the configuration of embodiment 3, no significant twisting occurs in the detection piezoelectric element 12e during the rotational movement of the movable part 15. Therefore, it is possible to prevent unnecessary signal components from being superimposed on the monitor signal, and a high-quality monitor signal can be obtained.

[0157] FIG. 20 is a diagram showing the configuration of a circuit section for driving the driving piezoelectric element 12d using a monitor signal output from the detecting piezoelectric element 12e according to the third embodiment.

[0158] The pair of piezoelectric elements 12e for detection are connected to the control circuit 4a via the two terminals T2 in Fig. 18(a), and the pair of piezoelectric elements 12d for driving are connected to the drive circuit 4b via the two terminals T1 in Fig. 18(a). Terminal T0 is connected to the ground on the control circuit 4a and drive circuit 4b side. The control circuit 4a, drive circuit 4b, and optical reflecting element 1 constitute a drive device 4 that rotates the movable part 15.

[0159] The control circuit 4a performs I / V conversion and digital conversion on the monitor signals (currents) from the pair of piezoelectric bodies 12e (sensor units). The control circuit 4a adds the monitor signal based on one piezoelectric body 12e to a signal obtained by inverting the polarity of the monitor signal based on the other piezoelectric body 12e, and generates drive signals to be applied to the pair of piezoelectric bodies 12d so that the added monitor signal approaches an ideal waveform when the movable part 15 performs an appropriate rotational movement. Specifically, the control circuit 4a generates drive signals so that the amplitude, frequency, and phase of the added monitor signal become target amplitude, frequency, and phase.

[0160] The drive circuit 4b performs analog conversion and amplification of the drive signal to be applied to the pair of piezoelectric bodies 12d. The drive circuit 4b applies the processed drive signal (AC voltage) to one of the piezoelectric bodies 12d, and applies a drive signal with the polarity of the processed drive signal (AC voltage) reversed to the other piezoelectric body 12d. Through this feedback control, the movable part 15 is resonantly driven at the target deflection angle and frequency.

[0161] The above-described feedback control can also be performed on the optical reflecting element 1 having the configuration of the first embodiment shown in FIG. 18(b) using a configuration similar to that of FIG. 20. This causes the movable portion 15 to be resonantly driven at the target deflection angle and frequency. As described above, the configuration of the third embodiment provides a monitor signal of better quality than the configuration of the first embodiment. Therefore, by using the optical reflecting element 1 having the configuration of the third embodiment, feedback control of the movable portion 15 can be performed with greater precision.

[0162] <Effects of Third Embodiment> The configuration of the third embodiment can also achieve the same effects as those of the first embodiment.

[0163] In addition, in the configuration of embodiment 3, as shown in Figure 18 (a), the optical reflecting element 1 is provided with a pair of piezoelectric elements 12e (sensor parts) arranged on each of a pair of folded parts 17, for detecting the rotation of the movable part 15.

[0164] 17 , stress (distortion) occurs in the pair of folded portions 17 when the movable portion 15 rotates. For this reason, by arranging a pair of piezoelectric bodies 12 e (sensor portions) for detecting the rotation of the movable portion 15 in the pair of folded portions 17, a monitor signal corresponding to the rotation of the movable portion 15 can be obtained satisfactorily.

[0165] Furthermore, since the driving piezoelectric element 12d and the detecting piezoelectric element 12e are disposed apart from each other, the area in which the driving piezoelectric element 12d is disposed can be expanded, thereby improving the driving efficiency of the movable part 15. Furthermore, as described above, deterioration of the monitor signal due to capacitive coupling can be avoided, and a high-quality monitor signal can be obtained.

[0166] As shown in FIG. 18A, a pair of piezoelectric bodies 12e (sensor parts) are disposed on a pair of first adjustment parts 17a, respectively.

[0167] According to this configuration, as described above, it is possible to obtain a monitor signal having a high S / N ratio and in which unnecessary signal components due to torsional stress are suppressed.

[0168] As described above, the driving source of the driving unit 12 is the piezoelectric body 12d, and the pair of sensor units is the other piezoelectric body 12e.

[0169] This configuration allows the piezoelectric bodies 12d and 12e to be disposed in the same process, and also allows the other piezoelectric body 12e, which serves as a sensor, to smoothly output a monitor signal.

[0170] 18(a), the detection piezoelectric element 12e is disposed in the first adjustment portion 17a, but the detection piezoelectric element 12e may be disposed in another position in the folded portion 17. As shown in Fig. 17, stress is generated in the folded portion 17 when the movable portion 15 rotates, and therefore, even when the detection piezoelectric element 12e is disposed in a portion of the folded portion 17 other than the first adjustment portion 17a, a monitor signal corresponding to the rotational movement of the movable portion 15 can be obtained from the piezoelectric element 12e.

[0171] For example, as shown in Fig. 21 , the detection piezoelectric element 12e may be disposed in the second adjustment unit 17b. However, compared to the first adjustment unit 17a, the second adjustment unit 17b is more susceptible to torsional stress during the rotational movement of the movable unit 15. For this reason, when the detection piezoelectric element 12e is disposed in the second adjustment unit 17b as shown in Fig. 21 , unnecessary signal components due to the torsional stress are more likely to be superimposed on the monitor signal.

[0172] Fig. 22(a) is a diagram showing the results of a simulation of the distribution of torsional stress (distribution of stress in the torsional direction) occurring in optical reflecting element 1 during rotation of movable portion 15, according to a modified example of embodiment 3. Fig. 22(b) is a diagram showing the results of a simulation of the distribution of compressive (tensile) stress (distribution of stress in the compressive / tensile directions) occurring in optical reflecting element 1 during rotation of movable portion 15, according to a modified example of embodiment 3.

[0173] For convenience, the color simulation results are shown in grayscale in Figures 22(a) and (b). The color scale in the lower right corner of Figures 22(a) and (b) ranges from blue at the left to red at the right. The middle of this color scale is green.

[0174] Referring to the torsional stress distribution in Figure 22(a), the first adjustment unit 17a shows almost no change in stress, resulting in a nearly uniform stress distribution. In contrast, the second adjustment unit 17b shows almost no change in stress in the longitudinal direction, but does show a change in stress in the width direction. Therefore, it can be said that the torsional stress generated during the rotational movement of the movable unit 15 is greater in the second adjustment unit 17b than in the first adjustment unit 17a. Therefore, from the perspective of avoiding unnecessary signal components due to torsional stress, it can be said that it is preferable to place the detection piezoelectric element 12e in the first adjustment unit 17a, as in the configuration of the third embodiment described above.

[0175] Referring to the compressive / tensile stress distribution in Figure 22(b), stress changes in the longitudinal direction in both the first adjustment unit 17a and the second adjustment unit 17b. However, the change in longitudinal stress is significantly greater in the first adjustment unit 17a than in the second adjustment unit 17b. The monitor signal (current) output from the piezoelectric element 12e increases with increasing compression / expansion. Therefore, placing the piezoelectric element 12e in the first adjustment unit 17a rather than in the second adjustment unit 17b allows the piezoelectric element 12e to output a larger monitor signal during rotation of the movable part 15, thereby improving the S / N ratio of the monitor signal.

[0176] For these reasons, it is preferable to place the detection piezoelectric element 12e in the first adjustment unit 17a rather than the second adjustment unit 17b. This increases the S / N ratio of the monitor signal output from the piezoelectric element 12e and suppresses the superposition of unnecessary signal components due to torsional stress. It is most preferable to place the detection piezoelectric element 12e in the first adjustment unit 17a of the folded portion 17. However, a configuration in which the detection piezoelectric element 12e is placed in the second adjustment unit 17b allows the distance between the piezoelectric element 12e and the piezoelectric element 12d and the distance between the wiring P1 and the wiring P2 to be greater than in the first embodiment. As a result, capacitive coupling between the two elements can be suppressed, thereby increasing the S / N ratio of the monitor signal. Furthermore, the area of ​​the detection piezoelectric element 12d can be increased, thereby improving drive efficiency.

[0177] 7(a) to 7(c) and optical reflecting elements 1 configured as shown in FIGS. 12(a) to 15(b), similarly to the above, the location of detection piezoelectric element 12e may be changed to a predetermined portion of folded-back portion 17. In these cases, similarly to the above, it is preferable to place detection piezoelectric element 12e in a portion of folded-back portion 17 where torsional stress is small and compressive / tensile stress is large.

[0178] <Embodiment 4> In the above-mentioned embodiment 3, a pair of piezoelectric elements 12e (sensor units) for detection are arranged on each of the pair of folded portions 17, but in embodiment 4, a pair of piezoelectric elements (auxiliary driving units) that apply a driving force to the movable portion 15 via the second support portion 16 to rotate the movable portion 15 are arranged on each of the pair of folded portions 17.

[0179] 17 , stress is generated in each folded portion 17 when the movable portion 15 rotates. Therefore, by arranging a piezoelectric element (auxiliary driving portion) that applies an auxiliary driving force in each folded portion 17, the rotation of the movable portion 15 can be promoted, and the driving efficiency of the movable portion 15 can be improved.

[0180] FIG. 23 is a top view schematically showing the configuration of an optical reflecting element 1 according to the fourth embodiment.

[0181] Here, a pair of piezoelectric bodies 12f are arranged as auxiliary drive units in the pair of first adjustment units 17a. The pair of piezoelectric bodies 12f are arranged symmetrically about the rotation axis R1. The piezoelectric bodies 12f expand and contract in the longitudinal direction when a drive voltage is applied. On the other hand, as shown in FIG. 22(b), large compressive / tensile stresses are generated in the longitudinal direction in the first adjustment units 17a when the movable unit 15 rotates. Therefore, by arranging the piezoelectric bodies 12f in each first adjustment unit 17a, the rotation of the movable unit 15 can be effectively promoted by driving the piezoelectric bodies 12f.

[0182] Compared to the configuration of Fig. 18(b), a pair of terminals T3 are arranged on the base 11a, and these terminals T3 and the piezoelectric body 12f are connected by wiring P3. The piezoelectric body 12f, terminal T3, and wiring P3 can be arranged in the same process as the piezoelectric body 12e, terminal T2, and wiring P2 shown in Fig. 18(a). In the configuration of Fig. 23, a pair of piezoelectric bodies 12e for detection are arranged near the bases of the pair of vibrating parts 12a, as in the configuration of Fig. 18(b). The configuration of the underside of the optical reflecting element 1 is the same as in the first embodiment.

[0183] FIG. 24 is a diagram showing the configuration of a circuit section for driving the driving piezoelectric element 12d and the auxiliary driving piezoelectric element 12f using a monitor signal output from the detecting piezoelectric element 12e according to the fourth embodiment.

[0184] A pair of piezoelectric elements 12f for auxiliary driving is further connected to the drive circuit 4b via two terminals T3 in Fig. 23(a). The connection configuration of the control circuit 4a and the drive circuit 4b with respect to the other terminals is the same as in Fig. 20. The drive circuit 4b applies a drive signal generated from a monitor signal from the pair of piezoelectric elements 12e to the pair of piezoelectric elements 12f as well as the pair of piezoelectric elements 12d.

[0185] Here, drive signals of the same polarity are applied to piezoelectric bodies 12d and 12f on the positive side of the X axis in Fig. 23, and drive signals of opposite polarity to the drive signals applied to piezoelectric bodies 12d and 12f on the negative side of the X axis in Fig. 23 are applied to piezoelectric bodies 12d and 12f on the positive side of the X axis. The magnitude of the drive signal applied to piezoelectric body 12d may be different from the magnitude of the drive signal applied to piezoelectric body 12f. As a result, the pair of piezoelectric bodies 12d and the pair of piezoelectric bodies 12f are deformed, the pair of vibrating units 12a and the pair of first adjustment units 17a are vibrated, and the movable unit 15 is rotated repeatedly about rotation axis R1.

[0186] <Effects of Fourth Embodiment> The configuration of the fourth embodiment can also achieve the same effects as those of the first embodiment.

[0187] Furthermore, in the configuration of embodiment 4, as shown in Figure 23, the optical reflecting element 1 is provided with a pair of piezoelectric elements 12f (auxiliary driving units) that are respectively arranged on a pair of folded portions 17 and that apply a driving force to the movable portion 15 via the second support portion 16 to rotate the movable portion 15.

[0188] 17 , stress (distortion) occurs in the pair of folded portions 17 when the movable portion 15 rotates. For this reason, by arranging a pair of piezoelectric bodies 12 f (auxiliary driving units) at the pair of folded portions 17, which apply a driving force to the movable portion 15 via the second support portion 16 to rotate the movable portion 15, a driving force that promotes the rotating operation can be applied to the movable portion 15, and the driving efficiency of the movable portion 15 can be improved.

[0189] As shown in FIG. 23, a pair of piezoelectric bodies 12f (auxiliary driving units) are disposed on a pair of first adjustment units 17a, respectively.

[0190] According to this configuration, the piezoelectric element 12f (auxiliary drive unit) is disposed in the first adjustment unit 17a, which experiences large compressive / tensile stress (strain) in the longitudinal direction during rotation, thereby effectively promoting the rotation of the movable unit 15.

[0191] As described above, the driving source of the driving unit 12 is the piezoelectric element 12d, and the pair of auxiliary driving units is the other piezoelectric element 12f.

[0192] This configuration allows each piezoelectric element to be disposed in the same process, and also allows the other piezoelectric elements serving as auxiliary driving units to generate driving force smoothly and efficiently.

[0193] <Modification> The auxiliary driving piezoelectric element 12f may be arranged in a portion of the folded portion 17 other than the first adjustment portion 17a. For example, as shown in Fig. 25, a pair of auxiliary driving piezoelectric elements 12f may be arranged in a pair of second adjustment portions 17b, respectively. In this way, application of a drive signal to the pair of piezoelectric elements 12f can deform and vibrate the pair of second adjustment portions 17b, thereby promoting the rotational movement of the movable portion 15.

[0194] In addition, in the optical reflecting element 1 having the configuration shown in Figures 7(a) to (c) and the optical reflecting element 1 having the configuration shown in Figures 12(a) to 15(b), the auxiliary driving piezoelectric element 12f may be arranged in the folded portion 17, as described above.

[0195] Fifth Embodiment In a fifth embodiment, a pair of piezoelectric elements 12 e for detection and a pair of piezoelectric elements 12 f for auxiliary driving are disposed on a pair of folded portions 17 .

[0196] FIG. 26 is a top view schematically showing the configuration of an optical reflecting element 1 according to the fifth embodiment.

[0197] Here, a pair of piezoelectric elements 12e for detection are respectively arranged on a pair of first adjustment sections 17a, and a pair of piezoelectric elements 12f for auxiliary driving are respectively arranged on a pair of second adjustment sections 17b. The pair of piezoelectric elements 12e for detection are connected to a pair of terminals T2 via a pair of wiring P2. The pair of piezoelectric elements 12f for auxiliary driving are connected to a pair of terminals T3 via a pair of wiring P3. The pair of wiring P3 passes outside the pair of piezoelectric elements 12e and is connected to the pair of piezoelectric elements 12f. The configuration of the underside of the optical reflecting element 1 is the same as in the first embodiment above.

[0198] <Effects of embodiment 5> According to embodiment 5, similar to embodiment 3, a pair of piezoelectric elements 12e for detection are arranged in a pair of folded portions 17 (here, first adjustment portion 17a), so that a high-quality monitor signal can be obtained, and similar to embodiment 4, a pair of piezoelectric elements 12f for auxiliary driving are arranged in a pair of folded portions 17 (here, second adjustment portion 17b), so that the driving efficiency of the movable portion 15 can be improved.

[0199] Furthermore, as shown in Figure 26, by arranging a pair of piezoelectric elements 12e for detection on a pair of first adjustment units 17a, it is possible to obtain a monitor signal with a high S / N ratio and in which unnecessary signal components due to torsional stress are suppressed, as described in the above embodiment 3.

[0200] In the configuration of Fig. 26, the pair of piezoelectric elements 12e for detection and the pair of piezoelectric elements 12f for auxiliary driving are respectively arranged in a pair of first adjustment units 17a and a pair of second adjustment units 17b, so that these piezoelectric elements can be arranged apart, and therefore the area of ​​the piezoelectric pair 12f for auxiliary driving can be made larger and the total area of ​​the piezoelectric pair 12f for auxiliary driving and the driving piezoelectric element 12d can be made larger than in Modification Example 1 of Fig. 27. Therefore, the drive efficiency of the movable part 15 can be improved compared to Modification Example 1 of Fig. 27.

[0201] <Modification 1> The arrangement of the pair of piezoelectric bodies 12e and the pair of piezoelectric bodies 12f relative to the pair of folded portions 17 is not limited to the arrangement shown in FIG. 26, and other arrangement methods may be applied.

[0202] For example, as shown in Fig. 27, a detection piezoelectric element 12e and an auxiliary driving piezoelectric element 12f may be arranged side by side in the width direction on the first adjustment unit 17a. Alternatively, as shown in Fig. 28, an auxiliary driving piezoelectric element 12g may be arranged on the second adjustment unit 17b, and the piezoelectric element 12f and the piezoelectric element 12g may be connected by a wiring P4. Like the other wirings, the wiring P4 has the same layer structure as the piezoelectric elements. With this configuration, the additional auxiliary driving piezoelectric element 12g can further increase the drive efficiency of the movable part 15.

[0203] As described above, it is preferable that the detection piezoelectric element 12e be disposed in the first adjustment unit 17a. Therefore, even when the positions of the detection piezoelectric element 12e and the auxiliary driving piezoelectric elements 12f and 12g are changed as in these modified examples, it is preferable that the detection piezoelectric element 12e be disposed in the first adjustment unit 17a as much as possible.

[0204] <Other Modifications> In the above-described first to fifth embodiments, the movable part 15 has a circular shape in a plan view, but the movable part 15 may have another shape. For example, the shape of the movable part 15 may be an ellipse that is elongated in a direction parallel to the rotation axis R1, or may be a square or a rectangle in a plan view.

[0205] Furthermore, the layer structure constituting the optical reflecting element 1 is not limited to the layer structure shown in the above-described first to fifth embodiments, and other layer structures may be used. For example, a layer other than the active layer 113 (e.g., the box layer 112) may be further included as a layer common to the fixed portion 11 and the other portions, and the fixed portion 11 may further include other layers other than the base layer 111, the box layer 112, and the active layer 113. It is sufficient that the optical reflecting element 1 is configured so that at least the fixed portion 11 has rigidity, and the drive portion 12, the first support portion 13, the second support portion 16, and the pair of folded portions 17 have flexibility. The materials constituting each portion are not limited to those shown above, and may be other materials (e.g., metal, resin, etc.) different from those mentioned above.

[0206] In the above-described first to fifth embodiments, when all piezoelectric bodies are omitted, the thickness of each part other than the fixed part 11 is constant, but the thickness of each of these parts does not necessarily have to be constant. For example, a rib may be formed on the lower surface of the movable part 15 to increase the thickness of the movable part 15, or a layer made of the same material as the frames 14a, 14b or a different material may be laminated on the lower surfaces of the pair of frames 14a, 14b to increase the thickness of the pair of frames 14a, 14b.

[0207] Furthermore, the shape and contour of the pair of frame portions 14a, 14b are not limited to the shape shown in the first embodiment, and other shapes and contours may be used. In the first embodiment, the pair of frame portions 14a, 14b have a substantially curved shape except for the area where they are connected to the movable portion 15. However, the area outside this connection area may have both a linear and a curved shape, or may have only a linear shape. However, a curved shape of the pair of frame portions 14a, 14b makes it easier to disperse stress, and therefore, damage to the frame portions 14a, 14b due to stress generated in the frame portions 14a, 14b can be suppressed.

[0208] In the third embodiment and its modifications, the piezoelectric element 12e is used as a sensor that outputs a monitor signal corresponding to the rotation of the movable element 15. However, a detection means other than the piezoelectric element 12e may be used as the sensor. For example, a well-known strain resistance material having a piezo-resistive effect may be disposed instead of the piezoelectric element 12e. The strain sensors made of the strain resistance material may be disposed, for example, on the upper surfaces of the pair of first adjustment elements 17a, respectively.

[0209] In this case, the strain resistance material may be formed in a strip shape on the upper surfaces of the pair of first adjustment portions 17a, similar to the piezoelectric element 12e. Alternatively, the strain resistance material may be formed on the upper surfaces of the pair of first adjustment portions 17a in a pattern that moves back and forth a predetermined number of times in the longitudinal direction from the base portion on the negative side of the Y axis. Two terminals connected to each strain resistance material via wiring may be disposed on the optical reflecting element 1 instead of terminal T2. The control circuit 4a is connected to these two sets of terminals and, using well-known methods and processes, acquires monitor signals corresponding to changes in the resistance value of each strain resistance material, and generates drive signals so that the acquired monitor signals approach an ideal waveform.

[0210] In this way, by using a resistive strain sensor made of a strain-resistant material as the sensor section, it is possible to detect not only the rotational state of the movable section 15 but also the stationary state of the movable section 15, i.e., the state in which no strain is generated in the strain-resistant material.

[0211] 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.

[0212] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0213] (Technology 1) An optical reflecting element comprising: a first support portion extending along a rotation axis; a second support portion extending along the rotation axis; a movable portion having a reflective surface and supported by the first support portion and the second support portion; a drive portion connected to an end portion of the first support portion opposite the movable portion and applying a drive force to the movable portion via the first support portion to rotate the movable portion; a rigid fixed portion consisting of a base portion supporting the drive portion and a pair of arms arranged symmetrically about the rotation axis and without sandwiching the second support portion; and a pair of flexible frame-shaped folded portions connecting the end portion of the second support portion opposite the movable portion to the pair of arms, respectively.

[0214] According to this technology, the second support portion is connected to the fixed portion (the pair of arms) via a pair of folded portions. As a result, even if the length of the second support portion is shortened, the movable portion can be flexibly supported from both sides by the first support portion, the second support portion, and the pair of folded portions. This suppresses dynamic deflection that occurs in the movable portion when the movable portion rotates. Furthermore, since the fixed portion does not extend around the movable portion on the side opposite the drive portion, and the pair of arms are limited in length so as not to sandwich the second support portion, the shape of the optical reflecting element in a direction parallel to the rotation axis can be made small. Furthermore, since the length of the second support portion can be shortened as described above, the shape of the optical reflecting element in a direction parallel to the rotation axis can be made even smaller. Therefore, the movable portion can be stably driven while miniaturizing the external shape of the optical reflecting element.

[0215] (Technology 2) The optical reflecting element according to Technology 1, characterized in that the thickness of the pair of folded portions is smaller than the thickness of the pair of arm portions.

[0216] According to this technique, flexibility can be imparted to the pair of folded portions by a simple method such as adjusting the thickness.

[0217] (Technology 3) In the optical reflecting element described in Technology 2, the fixed portion includes the active layer and a base layer having a thickness greater than that of the active layer, and the pair of folded portions include the active layer as a layer common to the fixed portion, but do not include the base layer.

[0218] According to this technique, flexibility can be imparted to the pair of folded portions through a simple process of removing at least the base layer from a substrate having a base layer and an active layer.

[0219] (Technology 4) An optical reflecting element described in any one of technologies 1 to 3, comprising: a first frame portion that surrounds the outer periphery of the movable portion on the first support portion side symmetrically with respect to the rotation axis and has both ends connected to the movable portion; and a second frame portion that surrounds the outer periphery of the movable portion on the second support portion side symmetrically with respect to the rotation axis and has both ends connected to the movable portion, wherein the first support portion is connected to the movable portion via the first frame portion, and the second support portion is connected to the movable portion via the second frame portion.

[0220] According to this technology, the movable part is supported at a position away from the rotation axis, i.e., near a position where dynamic deflection is likely to occur during rotation, and a driving force for rotation is applied to the movable part, thereby effectively suppressing dynamic deflection occurring in the movable part.

[0221] (Technology 5) The optical reflecting element according to Technology 4, wherein the pair of folded portions are configured so that the deflection of the movable portion that occurs during resonant operation of the movable portion at a target frequency is substantially 200 nm or less.

[0222] According to this technique, by adjusting the dimensions and shape of the pair of folded portions, the dynamic deflection of the movable portion can be significantly suppressed.

[0223] (Technology 6) An optical reflecting element described in any one of Technologies 1 to 5, characterized in that the pair of folded portions have: a pair of first adjustment portions arranged symmetrically about the rotation axis; a pair of second adjustment portions arranged symmetrically about the rotation axis, closer to the rotation axis than the pair of first adjustment portions and at a position farther from the pair of arm portions than the pair of first adjustment portions; and a pair of relay portions respectively connecting the pair of first adjustment portions and the pair of second adjustment portions.

[0224] According to this technology, the intermediary of the relay portion makes it difficult for torsion generated in the second support portion during rotation of the movable portion to propagate from the second adjustment portion to the first adjustment portion. Therefore, during rotation of the movable portion, torsion occurs in the pair of second adjustment portions, but substantially no torsion occurs in the pair of first adjustment portions, and the pair of first adjustment portions substantially only deform in the vertical direction. In other words, the relay portion becomes an inflection point for the deformation state of the pair of folded portions during rotation of the movable portion. Under these effects, by adjusting the lengths of the first adjustment portion and the second adjustment portion, dynamic deflection of the movable portion can be significantly suppressed, as shown in Verification 2 of Embodiment 1.

[0225] (Technology 7) The optical reflecting element according to Technology 6, wherein the pair of first adjustment parts and the pair of second adjustment parts extend substantially parallel to the rotation axis.

[0226] According to this technique, as shown in Verification 2 of the first embodiment, the dynamic deflection of the movable part can be significantly suppressed by adjusting the lengths of the first adjustment part and the second adjustment part.

[0227] (Technology 8) An optical reflecting element described in any one of Technologies 1 to 7, characterized in that the width of each of the pair of folded portions is smaller than the width of each of the pair of arm portions, and each of the pair of folded portions has a pair of connecting portions whose width increases toward the pair of arm portions, and the pair of connecting portions are respectively connected to the pair of arm portions.

[0228] This technology can prevent stress from concentrating near the boundaries between the pair of folded-back portions and the pair of arm portions when the movable portion rotates, thereby preventing damage due to stress concentration near these boundaries when the movable portion rotates.

[0229] (Technology 9) An optical reflecting element according to any one of technologies 1 to 8, characterized in that the pair of arms extend from the base in a direction parallel to the rotation axis by a distance greater than the distance from the base to the center of gravity of the optical reflecting element.

[0230] According to this technique, the optical reflecting element is less likely to tip over when it is installed, and therefore damage to the second support portion and the pair of folded portions due to the optical reflecting element tipping over can be suppressed.

[0231] (Technology 10) The optical reflecting element described in any one of Technologies 1 to 9, further comprising a pair of sensor units arranged at the pair of folding portions, respectively, for detecting rotation of the movable portion, or a pair of auxiliary driving units for applying a driving force to the movable portion via the second support portion to rotate the movable portion.

[0232] Stress (distortion) occurs in the pair of folded portions when the movable portion rotates. Therefore, by disposing a pair of sensor units for detecting the rotation of the movable portion at the pair of folded portions, a monitor signal corresponding to the rotation of the movable portion can be obtained effectively. Alternatively, by disposing a pair of auxiliary drive units that apply a driving force to the movable portion via the second support unit to rotate the movable portion at the pair of folded portions, a driving force that promotes the rotation can be applied to the movable portion, thereby improving the drive efficiency of the movable portion.

[0233] (Technology 11) In the optical reflecting element described in Technology 10, the pair of folded portions have: a pair of first adjustment portions arranged symmetrically about the rotation axis; a pair of second adjustment portions arranged symmetrically about the rotation axis, closer to the rotation axis than the pair of first adjustment portions and at a position farther from the pair of arm portions than the pair of first adjustment portions; and a pair of relay portions respectively connecting the pair of first adjustment portions and the pair of second adjustment portions.

[0234] This technique can achieve the same effects as technique 6 above.

[0235] (Technology 12) The optical reflecting element according to Technology 11, wherein the pair of first adjustment parts and the pair of second adjustment parts extend substantially parallel to the rotation axis.

[0236] This technique can achieve the same effects as technique 7 above.

[0237] (Technology 13) The optical reflecting element according to Technology 11 or 12, characterized in that the pair of sensor units are respectively disposed on the pair of first adjustment units.

[0238] This technique makes it possible to obtain a monitor signal with a high S / N ratio and in which unnecessary signal components due to torsional stress are suppressed.

[0239] (Technology 14) The optical reflecting element according to any one of Techniques 11 to 13, wherein the pair of auxiliary driving units are respectively disposed in the pair of first adjusting units.

[0240] According to this technique, the auxiliary drive unit is disposed in the first adjustment unit, which is subject to large compressive / tensile stress (strain) in the longitudinal direction during rotation, and therefore the rotation of the movable unit can be effectively promoted.

[0241] (Technology 15) In the optical reflecting element described in any one of Technology 10 to Technology 14, the driving source of the driving unit is a piezoelectric body, and the pair of sensor units and the pair of auxiliary driving units are other piezoelectric bodies.

[0242] This technology allows each piezoelectric element to be placed in the same process. Also, the other piezoelectric element serving as the sensor unit can smoothly output a monitor signal, and the other piezoelectric element serving as the auxiliary drive unit can smoothly and efficiently generate a monitor signal.

[0243] (Technology 16) The optical reflecting element according to any one of Techniques 10 to 14, wherein the pair of sensor portions are resistance-type strain sensors made of a strain resistance material.

[0244] According to this technique, the rotational state of the movable part can be monitored from the change in the resistance value of the strain sensor, and further, the stationary state of the movable part, i.e., the state in which no strain is generated in the strain resistance material, can also be detected.

[0245] REFERENCE SIGNS LIST 1 Optical reflecting element 11 Fixed portion 11a Base portion 11b Arm portion 12 Drive portion 12d Piezoelectric body 12e Piezoelectric body (sensor portion) 12f, 12g Piezoelectric body (drive portion) 13 First support portion 14a, 14b Frame portion 15 Movable portion 15a Reflecting surface 16 Second support portion 17 Folded portion 17a First adjustment portion 17b Second adjustment portion 17c Relay portion 17e Connection portion 111 Base layer 112 Box layer 113 Active layer (common layer) C0 Center of gravity C1 Center R1 Rotation axis

Claims

1. An optical reflecting element comprising: a first support section extending along a rotation axis; a second support section extending along the rotation axis; a movable section having a reflective surface and supported by the first support section and the second support section; a drive section connected to an end of the first support section opposite the movable section and applying a drive force to the movable section via the first support section to rotate the movable section; a rigid fixed section consisting of a base section supporting the drive section and a pair of arms arranged symmetrically about the rotation axis and without sandwiching the second support section; and a pair of flexible frame-shaped folded sections connecting the end of the second support section opposite the movable section to the pair of arms, respectively.

2. An optical reflecting element according to claim 1, wherein the thickness of said pair of folded portions is smaller than the thickness of said pair of arm portions.

3. An optical reflecting element according to claim 2, wherein the fixed portion includes the active layer and a base layer that is thicker than the active layer, and the pair of folded portions include the active layer as a layer common to the fixed portion, but do not include the base layer.

4. An optical reflecting element as described in claim 1, comprising: a first frame portion that surrounds the outer periphery of the movable portion on the first support portion side symmetrically with respect to the rotation axis and has both ends connected to the movable portion; and a second frame portion that surrounds the outer periphery of the movable portion on the second support portion side symmetrically with respect to the rotation axis and has both ends connected to the movable portion, wherein the first support portion is connected to the movable portion via the first frame portion, and the second support portion is connected to the movable portion via the second frame portion.

5. An optical reflecting element according to claim 4, wherein the pair of folded portions are configured so that the deflection of the movable portion that occurs during resonant operation of the movable portion at the target frequency is substantially 200 nm or less.

6. An optical reflecting element as described in claim 1, characterized in that the pair of folded portions have: a pair of first adjustment portions arranged symmetrically about the rotation axis; a pair of second adjustment portions arranged symmetrically about the rotation axis, closer to the rotation axis than the pair of first adjustment portions and at a position farther from the pair of arm portions than the pair of first adjustment portions; and a pair of relay portions respectively connecting the pair of first adjustment portions and the pair of second adjustment portions.

7. An optical reflecting element according to claim 6, wherein the pair of first adjustment parts and the pair of second adjustment parts extend substantially parallel to the rotation axis.

8. An optical reflecting element according to claim 1, wherein the width of each of the pair of folded portions is smaller than the width of each of the pair of arm portions, and each of the pair of folded portions has a pair of connecting portions whose width increases toward the pair of arm portions, and the pair of connecting portions are connected to the pair of arm portions, respectively.

9. An optical reflecting element as described in claim 1, wherein the pair of arms extend from the base in a direction parallel to the rotation axis by a distance equal to or greater than the distance from the base to the center of gravity of the optical reflecting element.

10. An optical reflecting element as described in claim 1, further comprising a pair of sensor units arranged on each of the pair of folded portions for detecting the rotation of the movable portion, or a pair of auxiliary driving units for applying a driving force to the movable portion via the second support portion to rotate the movable portion.

11. An optical reflecting element as described in claim 10, characterized in that the pair of folded portions have: a pair of first adjustment portions arranged symmetrically about the rotation axis; a pair of second adjustment portions arranged symmetrically about the rotation axis, closer to the rotation axis than the pair of first adjustment portions and at a position farther from the pair of arm portions than the pair of first adjustment portions; and a pair of relay portions respectively connecting the pair of first adjustment portions and the pair of second adjustment portions.

12. An optical reflecting element according to claim 11, wherein the pair of first adjustment portions and the pair of second adjustment portions extend substantially parallel to the rotation axis.

13. An optical reflecting element according to claim 11, wherein the pair of sensor sections are respectively arranged on the pair of first adjustment sections.

14. An optical reflecting element according to claim 11, wherein the pair of auxiliary driving units are respectively disposed in the pair of first adjusting units.

15. An optical reflecting element according to claim 10, wherein the driving source of the driving unit is a piezoelectric body, and the pair of sensor units and the pair of auxiliary driving units are other piezoelectric bodies.

16. An optical reflecting element according to claim 10, wherein the pair of sensor sections are resistive strain sensors made of a strain resistance material.

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