WO2025115667A1 - Optical reflection element - Google Patents

Abstract

This optical reflection element (100) comprises: a movable part (103) having a flat plate-shape that rotates about a rotation axis (R0); a reflection surface (M1a) that is disposed on an upper surface (103a) of the movable part (103); and at least one rib (131a, 131b) that is disposed on a lower surface (103b) of the movable part (103). The reflection surface (M1a) is irradiated with light (L1) that decreases in intensity with increasing distance from a central axis (C0). The rib (131a) in a specific region of the lower surface (103b) corresponding to the vicinity of the center of a region irradiated with the light (L1) in the reflection surface (M1a) has a substantially curved shape in plan view.

Description

Optical Reflective Elements

The present invention relates to an optical reflecting element for scanning light.

Conventionally, optical reflecting elements that rotate a reflecting surface to scan light are known. This type of optical reflecting element can be used, for example, in image display devices such as head-up displays. For example, a MEMS (Micro Electro Mechanical Systems) mirror is used as the optical reflecting element. Such optical reflecting elements are provided with a structure for suppressing bending of the reflecting surface.

The following Patent Document 1 describes an optical scanning device in which intersecting linear ribs are formed on the underside of a plate-like movable part that rotates together with the reflective surface. With this configuration, the rigidity of the movable part is increased by the ribs, so that deflection of the movable part and the reflective surface on the upper surface of the movable part can be suppressed.

Patent No. 7121258

However, the inventors' investigations revealed that in the above configuration, the ribs formed on the underside of the movable part cause diffraction of the light reflected by the reflecting surface. As a result, the light reflected by the reflecting surface contains not only the original reflected light, but also unwanted diffracted light that becomes noise in the optical scanning.

In view of these problems, the present invention aims to provide an optical reflecting element that can suppress the effects of diffracted light caused by the ribs while reinforcing a movable part having a reflecting surface with ribs.

The optical reflecting element according to the first aspect of the present invention comprises a flat movable part that rotates about a rotation axis, a reflecting surface disposed on the upper surface of the movable part, and at least one rib disposed on the lower surface of the movable part. The reflecting surface is irradiated with light whose intensity decreases with increasing distance from the central axis. The rib in a specific area of the lower surface corresponding to the vicinity of the center of the light irradiated area on the reflecting surface has a substantially curved shape in a planar view.

In the optical reflecting element according to this embodiment, ribs are disposed on the underside of the movable part, so that the movable part is reinforced by the ribs. This makes it possible to prevent bending of the movable part and the reflecting surface disposed on its upper surface. Furthermore, a rib having a substantially curved shape is disposed in a specific area on the underside of the movable part. Therefore, diffracted light caused by changes in the shape of the reflecting surface due to this rib is dispersed, making it difficult for peaks to occur in the diffracted light. This makes it possible to effectively prevent diffracted light from the light near the center, where the intensity is high, from affecting the light scanning.

The optical reflecting element according to the second aspect of the present invention comprises a flat movable part that rotates about a rotation axis, a reflecting surface arranged on the upper surface of the movable part, and at least one rib arranged on the lower surface of the movable part. The reflecting surface is irradiated with light having a plurality of peak intensities near the central axis and decreasing in intensity with increasing distance from the position of each of the peak intensities. The rib in a specific area of the lower surface corresponding to the vicinity of the center of the light irradiated area on the reflecting surface has a substantially curved shape in a planar view.

In the optical reflecting element according to this embodiment, ribs are disposed on the underside of the movable part, so that the movable part is reinforced by the ribs. This makes it possible to prevent bending of the movable part and the reflecting surface disposed on its upper surface. Furthermore, a rib having a substantially curved shape is disposed in a specific area on the underside of the movable part. Therefore, diffracted light caused by changes in the shape of the reflecting surface due to this rib is dispersed, making it difficult for peaks to occur in the diffracted light. This makes it possible to effectively prevent diffracted light from the light near the center, where the intensity is high, from affecting the light scanning.

The optical reflecting element according to the third aspect of the present invention comprises a flat movable part that rotates about a rotation axis, a reflecting surface arranged on the upper surface of the movable part, a first rib arranged on the lower surface of the movable part and surrounding the center of the lower surface, and a second rib arranged on the lower surface outside the first rib and extending substantially parallel to the rotation axis. The first rib has a substantially curved shape in a plan view, and no other ribs are provided inside the first rib.

In the optical reflecting element according to this embodiment, the first rib and the second rib are disposed on the lower surface of the movable part, and the movable part is reinforced by these ribs. This makes it possible to suppress the occurrence of bending in the movable part and the reflective surface disposed on its upper surface. In addition, since the second rib is disposed substantially parallel to the rotation axis, the second rib can suppress the moment of inertia of the movable part rotating about the rotation axis from increasing. This allows the movable part to rotate smoothly. In addition, only the first rib, which is substantially curved, is disposed in the area surrounding the center of the lower surface of the movable part. Therefore, the shape change of the reflective surface due to the first rib also becomes a shape that substantially surrounds the center with a curve. Therefore, diffraction does not occur inside the shape change of the reflective surface, and the diffracted light generated by this shape change is dispersed and is less likely to produce a peak. This makes it possible to effectively suppress the effect of diffraction by the first rib on the light near the center where the intensity of the irradiated light is high.

As described above, the present invention provides an optical reflecting element that can suppress the effects of diffracted light caused by the ribs while reinforcing a movable part having a reflecting surface with the ribs.

The effects and significance of the present invention will become clearer from the description of the embodiment shown below. However, the embodiment shown below is merely an example of how the present invention may be put into practice, and the present invention is in no way limited to the embodiment described below.

FIG. 1 is a plan view showing the configuration of an optical reflecting element according to an embodiment. FIG. 2 is a cross-sectional view showing the configuration of an optical reflecting element according to an embodiment. FIG. 3 is a diagram illustrating a schematic structure of the lower surface 103b of the movable portion according to the embodiment. FIG. 4 is a plan view showing the configuration of an optical deflector according to an embodiment. FIG. 5 is a diagram showing a configuration of an optical scanning device 20 according to an embodiment. FIG. 6 is a diagram illustrating a schematic view of a light irradiation area on a reflecting surface and a light intensity distribution in the irradiation area according to the embodiment. Fig. 7A is a diagram showing a schematic configuration of a rib according to Comparative Example 1. Fig. 7B is a diagram showing a simulation result according to Comparative Example 1. Fig. 8(a) is a diagram showing a schematic configuration of a rib according to Example 1. Fig. 8(b) is a diagram showing a simulation result according to Example 1. Fig. 9(a) is a diagram showing a schematic diagram of a rib configuration according to Comparative Example 2. Fig. 9(b) is a diagram showing a simulation result according to Comparative Example 2. Fig. 9(c) is a diagram showing a schematic diagram of a rib configuration according to Comparative Example 3. Fig. 9(d) is a diagram showing a simulation result according to Comparative Example 3. Fig. 10(a) is a diagram showing a schematic configuration of a rib according to Example 2. Fig. 10(b) is a diagram showing a simulation result according to Example 2. Fig. 10(c) is a diagram showing a schematic configuration of a rib according to Example 3. Fig. 10(d) is a diagram showing a simulation result according to Example 3. FIG. 11 is a diagram showing a schematic arrangement of ribs according to the first modified example. Fig. 12A is a diagram for explaining a simulation method according to Modification Example 1. Fig. 12B is a diagram for explaining a method for acquiring parameter values indicating the intensity of diffracted light in a simulation according to Modification Example 1. FIG. 13 is a graph showing a simulation result according to the first modification. 14A and 14B are diagrams illustrating another method of arranging ribs according to the first modified example. 15(a) and 15(b) are diagrams each showing a schematic diagram of a rib arrangement method according to a second modification and a third modification, respectively. FIG. 16 is a diagram illustrating a schematic view of a light irradiation area on a reflecting surface and a light intensity distribution in the irradiation area according to the second modification. 17(a) and 17(b) are diagrams each showing a schematic diagram of a rib arrangement method according to a fourth and fifth modified examples, respectively. 18(a) and 18(b) are diagrams each showing a schematic diagram of a rib arrangement method according to Modification Example 6 and Modification Example 7. In FIG. 19(a) and 19(b) are diagrams each showing a schematic diagram of a rib arrangement method according to Modification Example 8 and Modification Example 9. In FIG. Fig. 20A is an enlarged cross-sectional view of the movable portion and its surroundings according to the embodiment, and Fig. 20B is an enlarged cross-sectional view of the movable portion and its surroundings according to a tenth modified example. FIG. 21 is a diagram illustrating a schematic view of an irradiated area of a reflecting surface and a light intensity distribution in the irradiated area according to the eleventh modification. 22A to 22C are diagrams showing simulation results of beam spots generated on the detection surface by the configurations of comparative examples 1 to 3, respectively, in accordance with Modification Example 11. 23A to 23C are diagrams showing simulation results of beam spots generated on the detection surface by the configurations of Examples 1 to 3, respectively, in Modification Example 11. FIG. 24 is a graph showing a simulation result according to the eleventh modification. Fig. 25(a) is a diagram showing a specific region and a method of arranging ribs according to Modification Example 1. Fig. 25(b) is a diagram showing a region where curved ribs are arranged and a method of arranging the ribs according to a reference example.

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

The following describes an embodiment of the present invention with reference to the drawings.

For convenience, each figure is labeled with mutually orthogonal X, Y, and Z axes. The Z-axis direction is the up-down direction of the optical reflecting element 100, and the X-axis and Y-axis directions are the long-side and short-side directions of the optical reflecting element 100, respectively. The positive Z-axis direction is the upward direction of the optical reflecting element 100.

FIG. 1 is a plan view showing the configuration of the optical reflecting element 100, and FIG. 2 is a cross-sectional view of the optical reflecting element 100 when the optical reflecting element 100 is cut at the position of the rotation axis R0 in FIG. 1 along a plane parallel to the X-Z plane.

As shown in FIG. 1, in this embodiment, the optical reflecting element 100 is configured as a meandering MEMS mirror. However, the optical reflecting element 100 is not limited to a meandering MEMS mirror, and may have other configurations as long as the movable part 103 rotates about the rotation axis R0.

The optical reflecting element 100 includes a support portion 101, a pair of drive portions 102, and a movable portion 103.

As shown in FIG. 2, the support part 101, the pair of drive parts 102, and the movable part 103 have a common silicon substrate 121 made of silicon. The support part 101, the pair of drive parts 102, and the movable part 103 are connected by the silicon substrate 121. The support part 101 is constructed by laminating a silicon substrate 122 made of silicon on the lower surface of the silicon substrate 121. A silicon oxide film is interposed between the silicon substrate 121 and the silicon substrate 122. The rigidity of the support part 101 is increased by having two silicon substrates 121, 122.

As shown in FIG. 1, the support portion 101 is a frame-shaped member that has a rectangular outline in a plan view.

The driving unit 102 includes a substrate 110 and four piezoelectric actuators 111 formed on the upper surface of the substrate 110. The substrate 110 has a meandering shape that snakes in a direction perpendicular to the rotation axis R0. The thickness of the substrate 110 is constant. The substrate 110 is a part of the silicon substrate 121 described above.

The four piezoelectric actuators 111 are arranged on the upper surface of the four regions 110a of the substrate 110, which extend in a direction perpendicular to the rotation axis R0 (the Y-axis direction). The piezoelectric actuators 111 are configured by sandwiching a piezoelectric body of a certain thickness between an upper electrode and a lower electrode.

The piezoelectric body is made of, for example, PZT (lead zirconate titanate). The upper and lower electrodes are made of, for example, platinum. When a voltage (drive signal) is applied between the upper and lower electrodes, the piezoelectric actuator 111 (piezoelectric body) expands and contracts. This causes the substrate 110 to bend, generating a drive force for driving the movable part 103.

The movable part 103 is supported by a pair of drive parts 102. The movable part 103 is part of the silicon substrate 121 described above. In a plan view, the movable part 103 is circular. The shape of the movable part 103 in a plan view may be another shape, such as a square.

The thickness of the movable part 103 is the same as the thickness of the silicon substrate 121 in FIG. 2. The movable part 103 has a flat plate shape with the upper surface 103a and the lower surface 103b parallel to the XY plane. A mirror M1 is formed on the upper surface 103a of the movable part 103. Here, the mirror M1 is formed on the entire upper surface 103a of the movable part 103.

Mirror M1 is formed by laminating an optical reflective film made of platinum, silver, or an alloy thereof onto upper surface 103a. Mirror M1 may be formed of an optical multilayer film made of these materials. Alternatively, mirror M1 may be formed of a dielectric material. By forming mirror M1, a reflective surface M1a is disposed on upper surface 103a of movable part 103. If upper surface 103a of movable part 103 has a high reflectivity, mirror M1 may be omitted and upper surface 103a of movable part 103 may be used as the reflective surface.

As described below, the reflecting surface M1a is irradiated with light whose intensity decreases with increasing distance from the central axis C0 (see Figures 5 and 6). In other words, the intensity of this light has a Gaussian distribution. In this embodiment, the intensity of the light irradiated to the reflecting surface M1a has a similar Gaussian distribution all around the central axis C0. Such a light intensity distribution can be achieved, for example, by using a vertical cavity surface emitting laser (VCSEL) as the light source.

As shown in FIG. 2, ribs 131a and 131b are formed on the lower surface 103b of the movable part 103. The ribs 131a and 131b are made of silicon, similar to the silicon substrate 122. Each of the ribs 131a and 131b is arranged in a circular ring shape. Each of the ribs 131a and 131b has a wall shape with a substantially constant width and height.

Figure 3 is a diagram showing a schematic structure of the lower surface 103b of the movable part 103.

As shown in FIG. 3, two ribs 131a, 131b having a circular shape in a planar view are arranged on the lower surface 103b of the movable part 103. The ribs 131a, 131b are arranged concentrically with the center C1 of the lower surface 103b of the movable part 103. The rib 131a is included in a specific area CA1 set near the center of the lower surface 103b. The other ribs 131b are arranged along the outer periphery of the lower surface 103b. In other words, the outer diameter D11 of the rib 131a is smaller than the diameter of the specific area CA1, and the outer diameter D12 of the other ribs 131b is equal to the diameter of the movable part 103. The width and height of the ribs 131a, 131b are the same.

The specific area CA1 where the rib 131a is arranged is an area corresponding to the vicinity of the center of the light irradiation area on the reflection surface M1a. In this embodiment, since the light irradiation area is circular, the specific area CA1 is also circular. The center of the specific area CA1 coincides with the center C1 of the lower surface 103b. The specific area CA1 may have the same size as the area where the intensity of the light irradiated to the reflection surface M1a is half or more of the peak intensity. Alternatively, the specific area CA1 may have a size equal to or larger than the size of the area where the intensity of the light irradiated to the reflection surface M1a is half or more of the peak intensity, and the specific area CA1 may have a size equal to or smaller than the size of the area where the intensity of the light irradiated to the reflection surface M1a is 1/e ² (e is Napier's constant) of the peak intensity or more.

To manufacture the optical reflecting element 100, a structure in which silicon substrates 121, 122 of a fixed thickness are stacked is used. The outline of this structure in a plan view is the same as the outline of the optical reflecting element 100 in FIG. 1. In addition, a layered structure of piezoelectric actuators 111 is uniformly stacked on the upper surface of this structure.

The silicon substrate 122 on the lower surface side is removed by etching this structure. At this time, as shown in FIG. 2, the silicon substrate 122 in the areas corresponding to the support portion 101 and the ribs 131a, 131b is left behind without being removed. As a result, the ribs 131a, 131b are formed on the lower surface 103b of the movable portion 103. In addition, the thickness of the support portion 101 is ensured by the silicon substrate 122 remaining on the support portion 101.

Then, the layer structure of the piezoelectric actuator 111 is removed by etching from the top surface of this layer structure, leaving only the region of the piezoelectric actuator 111. Next, the mirror M1 is vapor-deposited in the region of the mirror M1. Furthermore, the silicon substrates 121 and 122 are removed by etching in the regions other than the support portion 101, the pair of drive portions 102, and the movable portion 103. This completes the manufacture of the optical reflecting element 100 having the shape shown in Figures 1 and 2.

In the configuration of FIG. 1, when a drive voltage of the same phase is applied to the odd-numbered piezoelectric actuators 111 from the movable part 103 side, the piezoelectric bodies of these piezoelectric actuators 111 deform, and the odd-numbered substrates 110 (regions 110a) vibrate so as to bend. At this time, a drive voltage of the opposite phase to the drive voltage applied to the odd-numbered piezoelectric actuators 111 is applied to the even-numbered piezoelectric actuators 111 from the movable part 103 side. This causes the piezoelectric bodies in the piezoelectric actuators 111 to deform, and the even-numbered substrates 110 (regions 110a) to bend. In this way, the deformation of each substrate 110 causes the movable part 103 to rotate about the rotation axis R0.

FIG. 4 is a plan view showing the configuration of the optical deflector 10. FIG. 5 is a diagram showing the configuration of the optical scanning device 20. FIG. 5 shows a cross-sectional view of the optical deflector 10 of FIG. 4 cut by a plane parallel to the YZ plane at the A-A position. FIG. 5 shows a cross-sectional view of the optical deflector 10 when the movable part 103 is in a neutral position (a position when in a non-operating state). FIG. 5 also shows the outer edge of the light L1 with a dashed line, and the central axis C0 of the light L1 (the optical axis of the optical system 300) with a dashed line.

As shown in Figures 3 and 4, the optical reflecting element 100 is mounted on a frame member 200. The frame member 200 has a rectangular shape that is long in the X-axis direction in a plan view, and has a rectangular recess 201 into which the optical reflecting element 100 fits. The frame member 200 has a constant thickness, and the recess 201 has a constant depth. The recess 201 has a rectangular opening 202 that surrounds the drive unit 102 and movable unit 103 of the optical reflecting element 100 in a plan view. The optical reflecting element 100 is mounted in the recess 201 with an adhesive or the like.

As shown in FIG. 5, an optical system 300 for irradiating light L1 onto the reflecting surface M1a is disposed above the frame member 200. The optical system 300 includes a light source 301, a collimator lens 302, a polarizing beam splitter 303 (hereinafter referred to as "PBS 303"), and a quarter-wave plate 304.

Light source 301 is the above-mentioned vertical cavity surface emitting laser light source (VCSEL), and emits laser light (light L1) of a predetermined wavelength in the positive direction of the Y axis. Light source 301 is arranged so that it is S-polarized with respect to PBS 303. Light source 301 emits light L1 at the same radiation angle over the entire circumference. Therefore, the cross-sectional shape of light L1 emitted from light source 301 is circular.

The collimator lens 302 collimates the light L1 emitted from the light source 301 and makes it incident on the PBS 303. The PBS 303 has a cubic shape and has a polarization separation film 303a inside. Since the light L1 is incident on the polarization separation film 303a as S-polarized light, it is reflected by the polarization separation film 303a in the negative direction of the Z axis. The quarter-wave plate 304 converts the light L1 incident from the PBS 303 side into circularly polarized light. The light L1 transmitted through the quarter-wave plate 304 is incident on the reflecting surface M1a of the optical reflecting element 100.

Light L1 reflected in the positive direction of the Z axis by reflecting surface M1a passes through quarter-wave plate 304 again, where it is converted to a polarization direction that becomes P-polarized with respect to polarization separation film 303a. As a result, light L1 passes through polarization separation film 303a and is emitted from PBS 303 in the positive direction of the Z axis. As movable part 103 and mirror M1 rotate about rotation axis R0 from the neutral position shown in FIG. 5, the direction of light L1 emitted from PBS 303 rotates in the Y axis direction. As a result, light L1 is scanned in the Y axis direction in a specified target area.

FIG. 6 is a diagram showing a schematic diagram of an irradiation area E1 of light L1 on the reflecting surface M1a and the light intensity distribution in the irradiation area E1.

Figure 6 shows the irradiation area E1 when the movable part 103 is in the neutral position. In the example of Figure 6, the diameter D0 of the irradiation area E1 of the light L1 is set to be slightly smaller than the diameter of the reflecting surface M1a. The central axis C0 of the light L1 (the center of the irradiation area E1) coincides with the center of the reflecting surface M1a. As shown in Figure 5, the central axis C0 of the light L1 when it enters the reflecting surface M1a is parallel to the Z axis.

The upper side of Figure 6 shows the intensity distribution of light L1 in a direction parallel to the rotation axis R0 (X-axis direction), and the right side of Figure 6 shows the intensity distribution of light L1 in a direction perpendicular to the rotation axis R0 (Y-axis direction). As shown in these figures, the intensity distribution of light L1 has a similar Gaussian distribution in both the direction parallel to the rotation axis R0 (X-axis direction) and the direction perpendicular to the rotation axis R0 (Y-axis direction). The intensity distribution of light L1 in other directions is also similar to the intensity distribution shown in Figure 6. In other words, the intensity distribution of light L1 in the irradiation area E1 has a similar Gaussian distribution over the entire circumference.

As shown in Fig. 6, the region E1a where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than 1/ ^e2 of the peak intensity P is a circular region having its center at the center of the irradiation region E1 and the reflecting surface M1a. Also, the region E1b where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than half the peak intensity P is a circular region having its center at the center of the irradiation region E1 and the reflecting surface M1a. As described above, the specific region CA1 shown in Fig. 3 may have the same size as the region E1b shown in Fig. 6, or may have a size equal to or greater than the size of the region E1b and equal to or less than the size of the region E1a.

Incidentally, the movable part 103 may bend (dynamic bend) due to the inertial force generated during rotation. Furthermore, as described above, when the mirror M1 is formed on the upper surface 103a of the movable part 103, the difference between the residual stress of the mirror M1 and the residual stress of the movable part 103 may cause bending (static bending) in the mirror M1 and the movable part 103. These bendings can be suppressed by forming ribs on the lower surface 103b of the movable part 103 to increase the strength (rigidity) of the movable part 103.

However, on the other hand, when ribs are formed on the lower surface 103b of the movable part 103, the formation of the ribs affects the flatness of the upper surface of the movable part 103, causing diffraction of the light L1 reflected by the reflecting surface M1a. As a result, the light L1 reflected by the reflecting surface M1a contains not only the original reflected light that is not diffracted, but also unnecessary diffracted light that becomes noise in the optical scanning.

The inventors have discovered a relationship between the configuration of the ribs formed on the lower surface 103b of the movable part 103 and the diffracted light that occurs in the light L1 reflected by the reflecting surface M1a. According to this finding, by configuring the ribs 131a, 131b as described above, the movable part 103 can be reinforced and the influence of the diffracted light on the scanning of the light L1 can be effectively suppressed. Below, the above relationship discovered by the inventors is explained, and a preferred configuration of the ribs formed on the lower surface 103b of the movable part 103 is explained.

FIG. 7(a) is a diagram showing a schematic diagram of the configuration of the rib 132 in Comparative Example 1.

In the comparative example, four intersecting ribs 132 are arranged on the lower surface 103b of the movable part 103. The four ribs 132 extend linearly. Two ribs 132 extend parallel to the X-axis, and the remaining two ribs 132 extend in the Y-axis direction. The ribs 132 adjacent to each other in the X-axis direction are arranged symmetrically about the X-axis on the lower surface 103b, and the ribs 132 adjacent to each other in the Y-axis direction are arranged symmetrically about the Y-axis on the lower surface 103b. The distance between adjacent ribs 132 in the X-axis direction is the same as the distance between adjacent ribs 132 in the Y-axis direction.

The inventors performed a simulation to determine the diffracted light that occurs in the light L1 reflected by the reflecting surface M1a when the rib 132 is configured as in Comparative Example 1.

In this simulation, it was assumed that a change in shape along the four ribs 132 occurred on the reflecting surface M1a. The irradiation area E1 of the light L1 was the entire reflecting surface M1a. The intensity distribution of the light L1 was set to a Gaussian distribution, as in FIG. 6. The reflecting surface M1a was set to a neutral position, as in FIG. 5. It was also assumed that the light L1 reflected by the reflecting surface M1a was focused on the detection surface by an ideal lens. The height and width of the change in shape that occurred on the reflecting surface M1a based on the ribs 132 (hereinafter referred to as the derived ribs) were set to 100 nm and 50 μm, respectively. The diameter of the reflecting surface M1a was set to 1.4 mm, and the spacing between adjacent ribs 132 (spacing between derived ribs) was set to 0.4 mm.

Figure 7(b) shows the simulation results for Comparative Example 1 under the above conditions.

FIG. 7(b) shows the beam spot of light L1 on the detection surface. As shown in FIG. 7(b), in the configuration of the rib 132 in Comparative Example 1, multiple beam spots B0, B1, and B2 were generated.

Beam spot B0 is a beam spot of light L1 (zeroth order light) focused on the detection surface substantially without being subjected to diffraction by the derived ribs of the reflecting surface M1a based on the four ribs 132. The multiple beam spots B1 above and below beam spot B0 are beam spots of multiple orders of diffracted light generated when light L1 is diffracted by the derived ribs of the reflecting surface M1a based on the ribs 132 extending parallel to the rotation axis R0. The multiple beam spots B2 on the left and right of beam spot B0 are beam spots of multiple orders of diffracted light generated when light L1 is diffracted by the derived ribs of the reflecting surface M1a based on the ribs 132 extending perpendicular to the rotation axis R0.

In Comparative Example 1, these beam spots B0, B1, and B2 move in the Y-axis direction in response to the rotation of the movable part 103. Because the intensity of the beam spots B1 and B2 based on the diffracted light is relatively high, these beam spots B1 and B2 become noise in the scanning of the original beam spot B0.

FIG. 8(a) is a diagram showing a schematic configuration of the rib 132 according to the first embodiment.

In Example 1, only the inner rib 131a is arranged on the lower surface 103b of the movable part 103. In other words, the outer rib 131b is omitted from the configuration in FIG. 3. The diameter of the rib 131a is 0.5 mm. The other simulation conditions are the same as those in Comparative Example 1.

Figure 8(b) shows the simulation results for Example 1 under the above conditions.

Similar to FIG. 7(b), FIG. 8(b) shows the beam spot of light L1 on the detection surface. As shown in FIG. 8(b), in the configuration of rib 131a according to Example 1, only beam spot B0 was generated. In other words, in the derived rib generated on reflecting surface M1a based on rib 131a according to Example 1, the distribution of beam spots based on diffracted light was hardly generated on the detection surface, and beam spot B0 of light L1 (zeroth order light) that was condensed substantially without being subjected to the diffraction effect of this derived rib was generated on the detection surface.

When the rib 131a has a curved shape as in Example 1, the derived rib generated on the reflecting surface M1a also has a curved shape. In this case, the diffracted light generated by this derived rib is dispersed according to the curved shape, so that beam spots B1 and B2 based on the diffracted light do not substantially occur on the detection surface as shown in FIG. 8(b). In this way, the configuration of the rib 131a in Example 1 makes it possible to effectively suppress the influence of the diffracted light based on the rib 131a.

The inventors further examined how diffracted light occurs for various rib configurations.

FIG. 9(a) is a diagram showing a schematic diagram of the configuration of rib 133 in Comparative Example 2, and FIG. 9(b) is a diagram showing the simulation results of the beam spot generated on the detection surface when rib 133 in Comparative Example 2 is arranged.

As shown in FIG. 9(a), in Comparative Example 2, only one rib 133 extending linearly along one diameter of the movable part 103 is arranged on the underside 103b of the movable part 103. In this case, the derived rib generated on the reflecting surface M1a by this rib 133 also extends linearly along the same diameter. The height and width of the rib 133 in the simulation are the same as those in Comparative Example 1. The other simulation conditions are also the same as those in Comparative Example 1.

As shown in FIG. 9(b), in the configuration of Comparative Example 2, beam images B4 based on diffracted light were generated to the left and right of beam spot B0. In this case, too, the intensity of beam image B4 is relatively high, so beam image B4 becomes noise in the scanning of the original beam spot B0.

FIG. 9(c) is a diagram showing a schematic diagram of the configuration of rib 134 in Comparative Example 3, and FIG. 9(d) is a diagram showing the simulation results of the beam spot generated on the detection surface when rib 134 in Comparative Example 3 is arranged.

As shown in FIG. 9(c), in Comparative Example 3, four ribs 134 extending linearly along the four diameters of the movable part 103 are arranged on the lower surface 103b of the movable part 103. The four diameters are evenly arranged in the circumferential direction of the lower surface 103b. In this case, the derived ribs generated on the reflecting surface M1a by these ribs 133 also extend linearly along the same diameters. The height and width of the ribs 134 in the simulation are the same as those in Comparative Example 1. The other simulation conditions are also the same as those in Comparative Example 1.

As shown in FIG. 9(d), in the configuration of Comparative Example 3, a beam image B5 based on diffracted light was generated radially from beam spot B0. In this case, too, the intensity of beam image B5 is relatively high, so beam image B5 becomes noise in the scanning of the original beam spot B0.

FIG. 10(a) is a diagram showing a schematic diagram of the configuration of rib 131a1 according to Example 2, and FIG. 10(b) is a diagram showing the results of a simulation of the beam spot generated on the detection surface when rib 131a1 according to Example 2 is arranged.

As shown in FIG. 10(a), in the second embodiment, the shape of the rib 131a1 is an ellipse. The center of the ellipse coincides with the center of the lower surface 103b. The derived rib generated on the reflecting surface M1a by the rib 131a1 also has a similar elliptical shape.

In the simulation of Example 2, the long diameter D21 of the rib 131a1 (derived rib) was set to the same as the diameter of the rib 131a in Example 1. The short diameter D22 of the rib 131a1 (derived rib) was set to 0.25 mm. The other simulation conditions were the same as those in Comparative Example 1.

As shown in FIG. 10(b), in the configuration of Example 2, almost no image based on diffracted light was generated around beam spot B0, and essentially only beam spot B0 was generated. With the configuration of rib 131a1 in Example 2, the effect of diffracted light based on rib 131a1 could be effectively suppressed, as in Example 1.

FIG. 10(c) is a diagram showing a schematic configuration of the rib 131a2 according to the third embodiment, and FIG. 10(d) is a diagram showing the results of a simulation of the beam spot that appears on the detection surface when the rib 131a2 according to the third embodiment is arranged.

As shown in FIG. 10(c), in the third embodiment, the ribs 131a2 are arranged along a curved amplitude waveform. The center of the area surrounding the amplitude waveform coincides with the center of the lower surface 103. The derived ribs generated on the reflecting surface M1a by the ribs 131a2 also have a shape that follows the same amplitude waveform.

In the simulation of Example 2, the width D31 of the rib 131a2 (derived rib) was set to 0.7 mm, and the amplitude D32 of the rib 131a2 (derived rib) was set to 0.25 mm. The other simulation conditions were the same as those of Comparative Example 1.

As shown in FIG. 10(d), in the configuration of Example 3, almost no image based on diffracted light was generated around beam spot B0, and essentially only beam spot B0 was generated. With the configuration of rib 131a2 in Example 3, the influence of diffracted light based on rib 131a2 could be effectively suppressed, as in Example 1.

From the above simulation results, it can be said that it is preferable to arrange only ribs that are curved in plan view on the lower surface 103b of the movable part 103. This makes it possible to suppress the generation of high-intensity beam images based on diffracted light, and to suppress the effect of diffracted light on the scanning of light L1.

In particular, it is preferable to arrange only ribs that are curved in plan view in a specific area CA1 of the lower surface 103b that corresponds to the vicinity of the center of the reflecting surface M1a where the intensity of the irradiated light L1 is high. This makes it possible to prevent the generation of high-intensity diffracted light and to prevent the diffracted light from affecting the scanning of the light L1.

Incidentally, the region outside the specific region CA1 corresponds to the region at the base of the Gaussian distribution shown in Figure 6, and therefore the intensity of the light L1 irradiated to the reflecting surface M1a is low. For this reason, even if a linear rib is placed in this outer region, the intensity of the diffracted light diffracted by the derived rib based on this rib is significantly lower than the intensity of the original light L1 (zeroth-order diffracted light). Therefore, the effect of this diffracted light on the scanning of light L1 is significantly reduced.

From this perspective, linear ribs may be arranged in a planar view in the area outside the specific area CA1. This reinforces the outer area and further suppresses deflection of the movable part 103 and the reflecting surface M1a. However, if it is desired to more thoroughly suppress the effect of diffracted light on the scanning of the light L1, it is preferable not to arrange linear ribs in the area outside the specific area CA1.

When the movable part 103 tilts from the neutral position, the irradiation area E1 deforms from a perfect circle in the tilting direction, and accordingly, the area near the center of the irradiation area E1, where the light intensity is high, also deforms from a perfect circle. However, usually, due to this deformation, the portion that protrudes from the area near the center (perfect circle) at the neutral position is small compared to the entire area (perfect circle), and the intensity of the protruding portion is considerably lower than the peak intensity. Therefore, as described above, if the area of the lower surface 103b corresponding to the area near the center (perfect circle) at the neutral position is set as specific area CA1, and only curved ribs are arranged within this specific area CA1, the effect of diffracted light due to the ribs can be appropriately suppressed even if the movable part 103 rotates and the reflecting surface M1a tilts from the neutral position during actual operation.

However, a specific area CA1 may be set on the lower surface 103b corresponding to the area obtained by combining the range in which the area near the center of the irradiation area E1 may deviate from a perfect circle during actual operation with the range of this perfect circle, and essentially only curved ribs may be placed in this specific area CA1. This also applies to the cases in which the intensity distribution of the irradiation area E1 is not uniform, as shown in Modifications 2 and 3 below.

Effects of the embodiment
According to the above embodiment, the following effects are achieved.

1 and 2, the optical reflecting element 100 includes a flat movable part 103 that rotates about a rotation axis R0, a reflecting surface M1a disposed on the upper surface 103a of the movable part 103, and at least one rib 131a, 131b disposed on the lower surface 103b of the movable part 103. As shown in FIG. 6, light L1, the intensity of which decreases with distance from the central axis C0, is irradiated onto the reflecting surface M1a. The central axis C0 of the light L1 substantially coincides with the center of the reflecting surface M1a. As shown in FIG. 3, FIG. 8(a), FIG. 10(a) and FIG. 10(c), the ribs 131a, 131a1, 131a2 in a specific area CA1 of the lower surface 103b corresponding to the vicinity of the center of the irradiation area E1 of the light L1 on the reflecting surface M1a have a curved shape in a plan view.

With this configuration, ribs 131a, 131b, 131a1, and 131a2 are arranged on the lower surface 103b of the movable part 103, so that the movable part 103 is reinforced by these ribs. This makes it possible to suppress the occurrence of bending (dynamic bending, static bending) in the movable part 103 and the reflecting surface M1a arranged on its upper surface 103a. In addition, curved ribs 131a, 131a1, and 131a2 are arranged in a specific area CA1 on the lower surface of the movable part 103. Therefore, the diffracted light generated by the shape change (derived ribs) of the reflecting surface M1a based on these ribs is dispersed, and as shown in Figures 8(b), 10(b), and 10(d), peaks are unlikely to occur in the diffracted light. This effectively suppresses the diffracted light of the light L1 near the center, which has a high intensity, from affecting the light scanning.

As shown in Figures 3, 8(a) and 10(a), the ribs 131a, 131a1 in the specific area CA1 are arranged in a ring shape in a plan view.

With this configuration, the strength of the movable part 103 near the center can be stably increased by the ribs 131a and 131a1. Therefore, deflection near the center of the reflecting surface M1a, where the intensity of the irradiated light is high, can be effectively suppressed.

As shown in Figures 3 and 8(a), the ribs 131a in the specific area CA1 are arranged along a perfect circle.

With this configuration, as shown in FIG. 6, when the intensity distribution (Gaussian distribution) of the light L1 is uniform over the entire circumference, it is possible to stably increase the intensity of the area of the movable part 103 where the intensity of the irradiated light is high, and it is possible to effectively suppress the bending of the reflecting surface M1a in this area.

As shown in FIG. 10(a), the ribs 131a1 in the specific area CA1 are arranged along an ellipse.

With this configuration, the strength of the movable part 103 near the center can be stably increased by the rib 131a1. Therefore, deflection near the center of the reflecting surface M1a, where the intensity of the irradiated light is high, can be effectively suppressed.

As shown in FIG. 10(c), the ribs 131a2 in the specific area CA1 are arranged along a curved amplitude waveform.

With this configuration, curved ribs can be placed in the area of the movable part 103 where the intensity of the irradiated light is high. This increases the strength of the area of the movable part where the intensity of the irradiated light is high, and suppresses the deflection of the reflective surface in this area.

As shown in FIG. 3, another rib 131b is disposed outside the specific area CA1.

With this configuration, the other ribs 131b can increase the strength of the movable part 103 on the outside from near the center. This makes it possible to expand the range in which deflection of the reflecting surface M1a can be suppressed.

As shown in FIG. 3, the other ribs 131b are arranged in a ring shape in a plan view.

With this configuration, the other ribs 131b can increase the strength of the movable part 103 near its outer periphery. This can suppress the deflection of the reflecting surface M1a near the outer periphery of the movable part 103.

As described with reference to FIG. 6, the specific area CA1 may have substantially the same size as the area E1b where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than half the peak intensity.

This makes it possible to suppress the effect of diffraction by the rib 131a on at least the light L1 that is irradiated to the reflecting surface M1a and that is within an intensity range equal to or greater than half the peak intensity. This makes it possible to effectively suppress the effect of diffracted light on the scanning of the light.

Alternatively, as described with reference to Figure 6, the specific area CA1 may have a size that is substantially greater than the size of area E1b where the intensity of light L1 irradiated to the reflecting surface M1a is equal to or greater than half the peak intensity, and less than the size of area E1a where the intensity of light L1 irradiated to the reflecting surface M1a is equal to or greater than 1/ ^e2 (e is Napier's constant) of the peak intensity.

This makes it possible to suppress the effect of diffraction by the ribs on the light L1 that is included in the high intensity range. This makes it possible to more effectively suppress the effect of diffracted light on the light scanning.

As shown in FIG. 2, a mirror M1 (optical reflection film) is formed on the upper surface 103a of the movable part 103 to form a reflection surface M1a.

As a result, the reflectance of the reflecting surface M1a can be increased and the surface roughness can be suppressed compared to when the upper surface 103a of the movable part 103 is used as a reflecting surface as is. Therefore, scanning of the light L1 can be performed with high precision.

<Modification 1>
Fig. 11 is a diagram showing a schematic diagram of a method for arranging ribs according to Modification Example 1. Fig. 11 shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

As shown in FIG. 11, in modified example 1, two ribs 131c are added compared to the embodiment in FIG. 3. The two ribs 131c are arranged along the rotation axis R0 and connect the ribs 131a and 131b. The width and height of the rib 131c are the same as those of the ribs 131a and 131b. The outer diameter of the inner rib 131a is approximately the same as the diameter of the specific area CA1.

In the configuration of FIG. 11, the two ribs 131c suppress the deflection (particularly static deflection) of the area of the movable part 103 between the ribs 131a and 131b. On the other hand, in this configuration, the irradiation area E1 of the light L1 on the reflecting surface M1a includes a derived rib corresponding to the rib 131c, so that this derived rib can cause a peak in the diffracted light.

The inventors conducted a simulation to verify the relationship between the diameter of rib 131a and the length of rib 131c and the intensity of diffracted light.

In this verification, as shown in FIG. 12(a), the outer rib 131b was omitted and the outer diameter D of the inner rib 131a was changed. As the outer diameter D increased, the length of the rib 131c was decreased. As in the simulation in the above embodiment, the light L1 was irradiated onto the entire reflecting surface M1a. The height and width of the ribs 131a and 131c were set in the same way as in the simulation in the above embodiment. The rest of the simulation was the same as in the simulation in the above embodiment.

In this simulation, as shown in FIG. 12(b), a reference line L0 was set on the detection surface that passed through the center of the beam spot and was parallel to the diffraction direction, and the intensity of the diffracted light distributed on the reference line L0 was obtained. More specifically, in a range W1 other than the range W0 of the beam spot B0 that is not affected by diffraction, a value corresponding to the sum of the intensities of the diffracted light distributed on the reference line L0 was obtained as a parameter value indicating the intensity of the diffracted light. As this parameter value, the total value obtained by integrating, for the range W1, the ratio of the intensity of the diffracted light at each position on the reference line L0 to the peak value of the intensity of the light L1 reflected by the reflecting surface M1a when no ribs are provided on the lower surface 103b of the movable part 103 was obtained. The range W1 was set to the range in which diffracted light is substantially generated.

Figure 13 is a graph showing the simulation results.

In the graph of FIG. 13, the horizontal axis is the diameter of the region between the two ribs 131c, which corresponds to the outer diameter D in FIG. 12. The vertical axis is the parameter value indicating the intensity of the diffracted light described with reference to FIG. 12(b).

D1 indicated in the graph is the diameter of the region (corresponding to region E1b in FIG. 6) where the intensity of light L1 irradiated on the reflecting surface M1a is half the peak intensity, D2 is the diameter of the region (corresponding to region E1a in FIG. 6) where the intensity of light L1 irradiated on the reflecting surface M1a is 1/ ^e2 or more of the peak intensity, and D3 is half the diameter of the irradiation region E1 of light L1 on the reflecting surface M1a.

Referring to FIG. 13, the parameter value indicating the intensity of the diffracted light decreases as the diameter (outer diameter D) of the region between ribs 131c increases, and after this diameter (outer diameter D) reaches diameter D1 of region E1b, the tendency for the parameter value to decrease becomes gentler. Furthermore, after this diameter (outer diameter D) reaches diameter D2 of region E1a, the tendency for the parameter value to decrease becomes even gentler, and after this diameter (outer diameter D) reaches diameter D3b, the parameter value indicating the intensity of the diffracted light remains near zero.

For this reason, it is preferable that the two straight ribs 131c are not arranged in a range of diameters smaller than the diameter D1 of the region (region E1b in Figure 6) where the intensity of the light L1 irradiated to the reflecting surface M1a is half the peak intensity or more, and it is even more preferable that the two straight ribs 131c are not arranged in a range of diameters smaller than the diameter D2 of the region (region E1a in Figure 6) where the intensity of the light L1 irradiated to the reflecting surface M1a is 1/ ^e2 or more of the peak intensity.

Therefore, it is preferable that the specific area CA1 where the curved rib is arranged has substantially the same size as the area (area E1b in FIG. 6) where the intensity of the light L1 irradiated to the reflecting surface M1a is half the peak intensity or more. Alternatively, it is preferable that the specific area CA1 where the curved rib is arranged has a size substantially equal to or larger than the area (area E1b in FIG. 6) where the intensity of the light L1 irradiated to the reflecting surface M1a is half the peak intensity or more, and is smaller than the area where the intensity of the light L1 irradiated to the reflecting surface M1a is 1/ ^e2 or more of the peak intensity. As a result, even if other ribs extending linearly are arranged outside this area CA1, the influence of the diffracted light generated by the other ribs can be significantly reduced. Therefore, the influence of the diffracted light on the scanning of the light L1 can be effectively suppressed.

<Effects of Modification Example 1>
As shown in FIG. 11, the other ribs 131c extend radially from the center of the lower surface 103b.

With this configuration, the other ribs 131c can increase the strength of the movable part 103 up to near the outer periphery, and the range in which deflection of the reflecting surface M1a can be suppressed can be expanded up to near the outer periphery.

As shown in FIG. 11, the direction in which the other rib 131c extends is parallel to the rotation axis R0.

This configuration makes it possible to prevent the moment of inertia of the movable part 103 rotating about the rotation axis R0 from increasing due to the rib 131c. This allows the movable part 103 to rotate smoothly.

As shown in FIG. 11, the other ribs 131c are arranged along a straight line.

This configuration allows the other ribs 131c to be formed smoothly. In addition, the increase in the moment of inertia caused by the other ribs 131c can be kept to a minimum.

In the configuration of FIG. 11, the other ribs 131c are parallel to the rotation axis R0 in a plan view, but as shown in FIGS. 14(a) and (b), the other ribs 131c may be slightly tilted (for example, about 5°) with respect to the rotation axis R0 in a plan view. In other words, the other ribs 131c only need to be substantially parallel to the rotation axis R0 in a plan view. This also effectively prevents the moment of inertia of the movable part 103 rotating about the rotation axis R0 from increasing beyond the ribs 131c.

<Modifications 2 and 3>
15(a) and 15(b) are diagrams each showing a schematic diagram of a rib arrangement according to Modification Example 2 and Modification Example 3. Fig. 15(a) and (b) show plan views of the movable part 103 as viewed from the bottom side (Z-axis negative side).

In modified examples 2 and 3, the irradiation area E1 when the movable part 103 is in the neutral position is changed to an ellipse. Therefore, the specific area CA1 is also elliptical in shape, and the rib 131a arranged within the area CA1 is also elliptical in shape. The other configurations are the same as modified example 1.

FIG. 16 is a schematic diagram showing the irradiation area E1 of the light L1 on the reflecting surface M1a and the light intensity distribution in the irradiation area E1 in the second modified example.

As in FIG. 6, FIG. 16 shows the irradiation area E1 when the movable part 103 is in the neutral position. The minor axis of the ellipse that defines the irradiation area E1 is parallel to the rotation axis R0, and the major axis of the ellipse is perpendicular to the rotation axis R0. For example, the major axis is equal to the diameter of FIG. 6.

Such an illumination area E1 occurs, for example, when the light source 301 in FIG. 5 is an edge-emitting laser diode. The major axis of the ellipse corresponds to the fast axis of the laser diode, and the minor axis of the ellipse corresponds to the slow axis of the laser diode.

In this case, similarly to the first modification, the specific area CA1 in which the curved rib is arranged should have substantially the same size as the area E1b in which the intensity of the light L1 irradiated to the reflecting surface M1a is half the peak intensity or more. Alternatively, it is preferable that the specific area CA1 in which the curved rib is arranged should have a size substantially equal to or larger than the area E1b in which the intensity of the light L1 irradiated to the reflecting surface M1a is half the peak intensity or more, and be smaller than the area in which the intensity of the light L1 irradiated to the reflecting surface M1a is 1/ ^e2 or more of the peak intensity. This makes it possible to significantly reduce the influence of the diffracted light caused by the other rib 131c even if another rib 131c extending linearly is arranged outside this area CA1. Therefore, the influence of the diffracted light on the scanning of the light L1 can be effectively suppressed.

When the long axis of the irradiation area E1 is perpendicular to the rotation axis R0 as shown in FIG. 16, the rib 131a arranged in the specific area CA1 can be set to, for example, an elliptical shape as shown in FIG. 15(a). This allows the rib 131a to be smoothly arranged in the elliptical irradiation area E1. When the long axis of the irradiation area E1 is parallel to the rotation axis R0, the rib 131a arranged in the specific area CA1 can be set to, for example, an elliptical shape as shown in FIG. 15(b). This allows the rib 131a to be smoothly arranged in the elliptical irradiation area E1.

In these cases, it is preferable that the specific area CA1 has substantially the same size as the area E1b where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than half the peak intensity. Alternatively, it is preferable that the specific area CA1 where the curved rib is arranged has a size substantially equal to or greater than the size of the area E1b where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than half the peak intensity, and less than the size of the area where the intensity of the light L1 irradiated to the reflecting surface M1a is equal to or greater than 1/ ^e2 of the peak intensity.

As a result, even if another rib 131c extending linearly is disposed outside this area CA1, the effect of the diffracted light caused by this other rib 131c can be significantly reduced. Therefore, the effect of the diffracted light on the scanning of the light L1 can be effectively suppressed.

Note that when the irradiation area E1 is an ellipse as in FIG. 16, the specific area CA1 does not necessarily have to be an ellipse. For example, the specific area CA1 may be a circle whose diameter is the major axis of area E1b, or a circle whose diameter is the major axis of area E1a. Alternatively, the specific area CA1 may be a circle whose diameter is the minor axis of area E1a, or a circle whose diameter is the length between the major axis of area E1a and the major axis of area E1b.

<Effects of Modification Example 2>
As shown in FIGS. 15(a) and 15(b), the ribs 131a in the specific area CA1 are arranged along an ellipse.

As shown in Figure 16, when the intensity distribution (Gaussian distribution) of light L1 is uneven in two orthogonal directions, the area near the center of the movable part where the intensity of the irradiated light is high will have an elliptical shape. Therefore, by arranging ribs on the lower surface 103b along this ellipse, it is possible to stably increase the strength of the area of the movable part 103 where the intensity of the irradiated light is high, while effectively suppressing the deflection of the reflecting surface M1a in this area.

<Modifications 4 to 7>
Figures 17(a) and 17(b) are diagrams that typically show rib arrangement methods according to Modifications 4 and 5, respectively. Figures 18(a) and 18(b) are diagrams that typically show rib arrangement methods according to Modifications 6 and 7, respectively. Figures 17(a), (b) and 18(a), (b) show plan views of the movable part 103 as viewed from the bottom side (Z-axis negative side).

When linear ribs 131c are arranged outside specific area CA1 as in modification example 1 above, the shape of the curved ribs arranged in specific area CA1 is not limited to a circle or an ellipse, and may be, for example, a shape as shown in modification example 4 of FIG. 17(a), or a wave shape as shown in modifications examples 6 and 7 of FIG. 18(a) and (b). In these cases as well, by setting the diameter of specific area CA1 to be close to diameter D1 in FIG. 13 or in the range of diameters D1 to D2, the influence of diffracted light due to linear ribs 131c can be effectively suppressed, as in the verification results of FIG. 13.

Furthermore, the ribs arranged in the specific area CA1 do not necessarily have to be continuously connected; for example, as shown in FIG. 17(b), they may be arranged along a circular shape with some parts interrupted. Similarly, when the shape of the ribs arranged in the specific area CA1 is another shape such as an ellipse or a wave shape, the ribs may also be partially interrupted. This also allows the strength of the specific area CA1 to be increased by these ribs.

<Modifications 8 and 9>
19(a) and 19(b) are diagrams each showing a schematic diagram of a rib arrangement according to Modification Example 8 and Modification Example 9. Fig. 19(a) and (b) show plan views of the movable part 103 as viewed from the bottom side (Z-axis negative side).

The other ribs 131c arranged outside the specific area CA1 do not necessarily have to be arranged along a straight line. For example, as shown in modification example 8 of FIG. 19(a), the other ribs 131c may be arranged along a curved amplitude waveform.

With this configuration, the diffracted light caused by the change in shape of the reflecting surface M1a due to the other ribs 131c is dispersed by the curved shape, making it difficult for peaks to occur in the diffracted light due to the other ribs 131c. This makes it possible to further suppress the effects of the diffracted light due to the other ribs.

In this case, too, it is preferable that the direction in which the other ribs 131c extend is substantially parallel to the rotation axis R0, as shown in FIG. 19(a). This makes it possible to prevent the moment of inertia of the movable part 103 rotating about the rotation axis R0 from increasing compared to the other ribs 131c. This allows the movable part 103 to rotate smoothly.

Furthermore, the ribs arranged in the specific region CA1 need only have a substantially curved shape, and the ribs arranged in the region CA1 may include a slight straight line portion. For example, as shown in modification example 9 of FIG. 19(b), the rib 131a arranged in the specific region CA1 may include a slight straight line portion P1. When the straight line portion included in the region CA1 is extremely small in this way, the diffracted light caused by this can be substantially ignored. Therefore, with this configuration, as with the above embodiment and each modification example, the effect of diffracted light on the scanning of light L1 can be effectively suppressed.

<Modification 10>
In the above embodiment, as shown in FIG. 20(a), the height of the ribs 131a, 131b is constant in the width direction of the ribs (the Y-axis direction in FIG. 20(a)). However, the height of the ribs 131a, 131b is not limited to this and may vary in the width direction of the ribs.

For example, as shown in modification example 10 in FIG. 20(b), the height of ribs 131a, 131b may vary in the width direction of the ribs so that the lower surfaces of ribs 131a, 131b are curved in the width direction of the ribs.

By varying the height of the ribs 131a and 131b in the width direction in this way, the shape (derived rib) created on the reflecting surface M1a by the ribs 131a and 131b can be made to vary in the height direction, making diffraction less likely to occur due to this shape (derived rib). This makes it possible to suppress the effect of diffracted light by the ribs 131a and 131b on the scanning of the light L1.

This configuration may be similarly applied to ribs 131a1, 131a2, and other ribs 131c. In addition, this configuration may be applied only to linear ribs that are likely to cause diffraction, or this configuration may be applied only to ribs located in specific area CA1 that corresponds to the area where high-intensity light is irradiated.

<Modification 11>
In the above embodiment, as shown in Fig. 6, light whose intensity decreases with increasing distance from the central axis C0 is irradiated onto the reflecting surface M1a. That is, the intensity distribution of this light is a Gaussian distribution having only one peak near the central axis C0. In contrast, in the eleventh modification, light whose intensity has multiple peak intensities near the central axis C0 and decreases with increasing distance from each peak intensity position is irradiated onto the reflecting surface M1a.

FIG. 21 is a schematic diagram showing the irradiation area E1 of the light L1 on the reflecting surface M1a and the light intensity distribution in the irradiation area E1 in Modification Example 11.

As in FIG. 6, FIG. 21 shows the irradiation area E1 when the movable part 103 is in the neutral position. In the example of FIG. 21, the diameter D0 of the irradiation area E1 of the light L1 is set to be slightly smaller than the diameter of the reflecting surface M1a. The central axis C0 of the light L1 (the center of the irradiation area E1) coincides with the center of the reflecting surface M1a.

The upper side of Figure 21 shows the intensity distribution of light L1 in a direction parallel to the rotation axis R0 (X-axis direction), and the right side of Figure 21 shows the intensity distribution of light L1 in a direction perpendicular to the rotation axis R0 (Y-axis direction).

As shown in the intensity distribution on the right, the intensity distribution of light L1 has two peak intensities near the central axis C0. Here, the positions of these peak intensities are aligned in a direction perpendicular to the rotation axis R0 (Y-axis direction). As shown in the intensity distribution on the top, the intensity distribution of light L1 has a Gaussian distribution in a direction parallel to the rotation axis R0 (X-axis direction). The intensity of light L1 decreases as it moves away from each peak intensity position. Light L1 with such an intensity distribution is emitted, for example, from a multi-mode laser light source.

In this case, the region E1a where the intensity of the light L1 irradiated to the reflecting surface M1a is 1/ ^e2 or more of the peak intensity P has a shape of two overlapping circles each having a center at the position of the two peak intensities, and the region E1b where the intensity of the light L1 is half the value of the peak intensity P or more also has a shape of two overlapping circles each having a center at the position of the two peak intensities. The above-mentioned specific region CA1 may have substantially the same size as the region E1b, or may have a size substantially equal to or larger than the size of the region E1b and smaller than the size of the region E1a. The specific region CA1 may be a circular or elliptical region inscribed with the region E1a or the region E1b in a plan view.

Figures 22(a) to (c) show simulation results of the beam spots generated on the detection surface by the configurations of comparative examples 1 to 3 in modification example 11.

The upper parts of Figures 22(a) to (c) show schematic diagrams of the arrangement of ribs 132, 133, and 134 in Comparative Examples 1 to 3. The lower parts of Figures 22(a) to (c) show simulation results of the beam spots that are generated on the detection surface when the configurations of Comparative Examples 1 to 3 are used.

The simulation conditions are the same as those of Comparative Examples 1 to 3 in Figures 7(a), (b) and Figures 9(a) to (d), except that the intensity distribution of light L1 irradiated to the reflecting surface M1a is the intensity distribution in Figure 21.

As can be seen by looking at the simulation results in the lower rows of Figures 22(a) to (c), with the rib arrangements of Comparative Examples 1 to 3, even when light L1 having the intensity distribution in Figure 21 is irradiated onto reflecting surface M1a, in addition to the original beam spot B0, beam spots B1 and B2 and beam images B4 and B5 based on diffracted light are generated.

Figures 23(a) to (c) show simulation results of the beam spots generated on the detection surface by the configurations of Examples 1 to 3 in Modification Example 11.

The upper parts of Figures 23(a) to (c) show schematic diagrams of the arrangement of ribs 131a, 131a1, and 131a2 in Examples 1 to 3. The lower parts of Figures 23(a) to (c) show simulation results of the beam spots that are generated on the detection surface when the configurations of Examples 1 to 3 are used.

The simulation conditions are the same as those of Examples 1 to 3 in Figures 8(a), (b) and 10(a) to (d), except that the intensity distribution of light L1 irradiated to the reflecting surface M1a is the intensity distribution in Figure 21.

As can be seen by looking at the simulation results in the lower part of Figures 23(a) to (c), the rib arrangements of Examples 1 to 3 were able to effectively prevent the generation of unwanted beam images due to diffracted light other than the original beam spot B0, even when light L1 having the intensity distribution of Figure 21 was irradiated onto the reflecting surface M1a.

FIG. 24 is a graph showing the results of a simulation performed under the same conditions as in FIG. 13 to determine the intensity of diffracted light that occurs when light L1 having the intensity distribution in FIG. 21 is irradiated onto reflecting surface M1.

The simulation conditions are the same as those in FIG. 13, except that the intensity distribution of the irradiated light L1 is the intensity distribution in FIG. 21. The vertical and horizontal axes in FIG. 24 are also the same as those in FIG. 13.

Unlike the case of FIG. 13, in the simulation results of FIG. 24, in the range in which the outer diameter D of the inner rib 131a in FIG. 12(a) reaches diameter D1', the diffracted light intensity decreases as the outer diameter D increases, and in the range in which the outer diameter D is from diameter D1' to diameter D2', the diffracted light intensity increases slightly as the outer diameter D increases. Then, when the outer diameter D becomes larger than diameter D2', the diffracted light intensity decreases as the outer diameter D increases.

Here, diameter D1' corresponds to the width of the constricted portion of region E1a that is equal to or greater than 1/ ^e2 of the peak intensity P in the intensity distribution of Fig. 21, i.e., the width of region E1a in the X-axis direction at the position of rotation axis R0. Therefore, when the outer diameter D of the inner rib 131a becomes equal to or greater than diameter D1', the two outer ribs 131c in Fig. 12(a) no longer overlap region E1a, and the effects of diffraction by these ribs 131c are suppressed.

However, on the other hand, when the outer diameter D of the inner rib 131a becomes equal to or larger than diameter D1', the inner rib 131a falls on the peak of the intensity distribution of light L1, and the intensity of the diffracted light based on the inner rib 131a increases. Therefore, in the range where the outer diameter D of the inner rib 131a is between diameter D1' and diameter D2', the intensity of the diffracted light increases slightly as the outer diameter D increases. Then, when the outer diameter D of the inner rib 131a exceeds diameter D2', the peak of the intensity distribution of light L1 is included inside the inner rib 131a. Therefore, in the range where the outer diameter D of the inner rib 131a exceeds diameter D2', the intensity of the diffracted light decreases as the outer diameter D increases.

Therefore, when the intensity distribution of light L1 has multiple peaks as in modification example 11, it is preferable to set the area where the inner rib 131a is placed, i.e., the area of specific area CA1, to a size that includes all of the peaks. In this case, specific area CA1 may be circular or elliptical. For example, when the peaks are lined up in one direction as in FIG. 21, specific area CA1 may be in the shape of an ellipse with its major axis aligned in the direction in which the peaks are lined up. Alternatively, specific area CA1 may have a shape similar or nearly similar to area E1a. By setting specific area CA1 in this manner, the effects of diffracted light can be effectively suppressed.

<Reference example>
In the above-described modified example 1, the light L1, whose intensity decreases with increasing distance from the central axis, is irradiated onto the reflecting surface M1a, and the specific area CA1 is set as shown in Fig. 25(a). The center C1 of the lower surface 103b and the center C2 of the irradiation area E1 are substantially coincident with each other in a plan view.

In contrast, in the reference example, as shown in FIG. 25(b), light with a uniform intensity distribution is irradiated onto the reflecting surface M1a. In this case, the area of the region CB1 in which the curved rib 131a is arranged may be set so that the area of the region CB1 is larger than the area of the lower surface 103b outside the region CB1. Alternatively, when the movable part 103 is in the neutral position, the area of the region CB1 may be set so that the area of the region CB1 is larger than the area of the region corresponding to the irradiation region E1 outside the region CB1.

As a result, the proportion of the amount of light contained in the area of reflecting surface M1a corresponding to area CB1 out of the total amount of light irradiated to reflecting surface M1a can be increased, and the proportion of the amount of light that does not undergo diffraction can be increased. Therefore, the effect of diffracted light on the scanning of the light can be suppressed.

In addition, when the intensity distribution of the irradiated light is uniform, even if the center C1 of the lower surface 103b and the center C2 of the irradiation area E1 are misaligned in a planar view, as shown in Figure 25 (b), the ratio of the amount of light that does not undergo diffraction to the total amount of light irradiated to the reflecting surface M1a remains the same as when the centers C1 and C2 are coincident. Therefore, by setting the area CB1 as described above, the effect of diffracted light on the light scanning can be similarly suppressed even when the centers C1 and C2 are misaligned.

<Other changes>
In the above embodiment, the optical system 300 in Fig. 5 is exemplified as an optical system that irradiates the reflecting surface M1a with light, but the configuration of the optical system is not limited to this. For example, the PBS 303 and the ¼ wavelength plate 304 may be omitted from the optical system 300 in Fig. 5. In this case, when the movable part 103 is in the neutral position, the light L1 is irradiated obliquely onto the reflecting surface M1a so that the central axis C0 is inclined by a predetermined angle with respect to the normal line of the reflecting surface M1a.

When the optical system is configured in this way, the irradiation area E1 of the reflecting surface M1a is not a perfect circle, but a curved ring shape that is long in the direction in which the central axis C0 is tilted. In this case, as in the above, it is preferable that the area CA1 near the center has a size substantially the same as the area in this irradiation area E1 where the light intensity is half or more of the peak intensity, or has a size substantially equal to or larger than the area where the light intensity irradiated to the reflecting surface is half or more of the peak intensity and smaller than the area where the light intensity irradiated to the reflecting surface is 1/ ^e2 (e is Napier's constant) of the peak intensity.

In addition, in the above modification examples 1 to 9, the direction in which the other ribs 131c extend is substantially parallel to the rotation axis R0, but the direction in which the other ribs 131c extend may be non-parallel to the rotation axis R0.

In addition, in the above embodiment and modified example, the central axis C0 of the light L1 substantially coincides with the center of the reflecting surface M1a (the center of the upper surface 103a of the movable part 103), but the central axis C0 of the light L1 may be offset from the center of the reflecting surface M1a (the center of the upper surface 103a of the movable part 103). For example, even if the central axis C0 of the light L1 is slightly offset from the center of the reflecting surface M1a (the center of the upper surface 103a of the movable part 103) in a direction parallel to the rotation axis R0, the scanning of the light L1 itself can be performed in the same way.

In addition, in the above embodiment and modified example, the height and width of the ribs arranged within the specific area CA1 are the same as the height and width of the ribs arranged outside this area CA1, but one or both of the heights and widths of these ribs may be different from each other.

In the above embodiment, a laser light source is used as the light source 301, but this is not limiting, and for example, a light emitting diode may be used as the light source 301.

In addition, the device to which the optical reflecting element 100 and the optical deflector 10 are applied is not particularly limited, and may be any device that requires a configuration for scanning light by rotating the reflecting surface M1a.

The embodiments of the present invention may be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims.

(Additional Note)
The above description of the embodiments discloses the following techniques.

(Technology 1)
A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
At least one rib disposed on a lower surface of the movable part,
A light beam having an intensity decreasing with distance from the central axis is irradiated onto the reflecting surface,
The rib in a specific region of the lower surface corresponding to the vicinity of the center of the light irradiation region on the reflecting surface has a substantially curved shape in a plan view.
An optical reflecting element characterized by:

With this technology, ribs are placed on the underside of the movable part, reinforcing the movable part with the ribs. This makes it possible to prevent bending of the movable part and the reflective surface placed on its upper surface. Furthermore, ribs that are substantially curved are placed in specific areas on the underside of the movable part. As a result, diffracted light caused by changes in the shape of the reflective surface due to these ribs is dispersed, making it less likely that peaks will occur in the diffracted light. This makes it possible to effectively prevent the effect of diffraction by the ribs on light near the center, where the intensity of the irradiated light is high.

(Technology 2)
In the optical reflecting element described in Technology 1,
The ribs in the specific region are arranged in a ring shape in a plan view.
An optical reflecting element characterized by:

This technology allows the strength of the moving part near the center to be stably increased by the ribs. This effectively reduces deflection near the center of the reflective surface, where the intensity of the irradiated light is high.

(Technology 3)
In the optical reflecting element described in Technology 2,
The ribs in the specific region are arranged along a perfect circle.
An optical reflecting element characterized by:

With this technology, when the light intensity distribution (Gaussian distribution) is uniform around the entire circumference, it is possible to stably increase the strength of the area of the moving part where the intensity of the irradiated light is high, and effectively suppress the deflection of the reflective surface in this area.

(Technology 4)
In the optical reflecting element described in Technology 2,
The ribs in the specific region are arranged along an ellipse.
An optical reflecting element characterized by:

With this technology, when the light intensity distribution (Gaussian distribution) is uneven in two orthogonal directions, the specific area of the movable part where the intensity of the irradiated light is high will have an elliptical shape. Therefore, by arranging ribs on the underside along this ellipse, it is possible to stably increase the strength of the area of the movable part where the intensity of the irradiated light is high, while effectively suppressing the deflection of the reflective surface in this area.

(Technology 5)
In the optical reflecting element according to any one of the first to fourth aspects,
The ribs in the specific region are arranged along a curved amplitude waveform.
An optical reflecting element characterized by:

This technology allows curved ribs to be placed in areas of the moving part where the intensity of the irradiated light is high. This increases the strength of the areas of the moving part where the intensity of the irradiated light is high, and suppresses deflection of the reflective surface in these areas.

(Technology 6)
In the optical reflecting element according to any one of the first to fifth aspects,
The other ribs are arranged outside the specific region.
An optical reflecting element characterized by:

With this technology, the strength of the movable parts on the outside can be increased by using other ribs, which makes it possible to expand the range in which deflection of the reflective surface can be suppressed.

(Technology 7)
In the optical reflecting element according to the sixth aspect of the present invention,
The other rib extends radially from the center of the lower surface.
An optical reflecting element characterized by:

With this technology, the strength of the moving part can be increased up to the outer periphery by using other ribs, and the range in which deflection of the reflective surface can be suppressed can be expanded up to the outer periphery.

(Technology 8)
In the optical reflecting element according to the seventh aspect of the present invention,
The direction in which the other rib extends is substantially parallel to the pivot axis.
An optical reflecting element characterized by:

This technology makes it possible to prevent the moment of inertia of the movable part rotating about the rotation axis from increasing due to other ribs. This allows the movable part to rotate smoothly.

(Technology 9)
In the optical reflecting element according to the seventh or eighth aspect of the present invention,
The other ribs are arranged along a straight line.
An optical reflecting element characterized by:

This technology allows the other ribs to be formed smoothly. Also, if the other ribs are parallel to the rotation axis, the increase in the moment of inertia caused by the other ribs can be kept to a minimum.

(Technology 10)
In the optical reflecting element according to the seventh or eighth aspect of the present invention,
The other ribs are arranged along a curved amplitude waveform.
An optical reflecting element characterized by:

With this technology, the diffracted light caused by changes in the shape of the reflective surface due to other ribs is dispersed, making it less likely that peaks will occur in the diffracted light due to other ribs. This makes it possible to suppress the effects of diffracted light due to other ribs.

(Technology 11)
In the optical reflecting element according to the sixth aspect of the present invention,
The other rib is arranged in an annular shape in a plan view.
An optical reflecting element characterized by:

With this technology, the strength of the movable part near its outer periphery can be increased by using other ribs. This makes it possible to suppress deflection of the reflective surface near the outer periphery of the movable part.

(Technology 12)
In the optical reflecting element according to any one of the techniques 1 to 11,
The specific region has a size substantially the same as that of a region where the intensity of the light irradiated on the reflecting surface is equal to or greater than half of the peak intensity.
An optical reflecting element characterized by:

This technology can suppress the effect of diffraction by the ribs on light irradiated onto the reflecting surface that is within an intensity range of at least half the peak intensity. This effectively suppresses the effect of diffracted light on the scanning light.

(Technology 13)
In the optical reflecting element according to any one of the first to eleventh aspects of the present invention,
The specific area has a size that is substantially equal to or larger than the size of an area where the intensity of the light irradiated onto the reflecting surface is equal to or larger than half the peak intensity, and is equal to or smaller than the size of an area where the intensity of the light irradiated onto the reflecting surface is equal to or larger than 1/ ^e2 (e is Napier's constant) of the peak intensity.
An optical reflecting element characterized by:

This technology can suppress the effect of diffraction by the ribs on light that is irradiated onto the reflecting surface and falls within a high-intensity range. This makes it possible to more effectively suppress the effect of diffracted light on the scanning light.

(Technology 14)
In the optical reflecting element according to any one of the first to third aspects of the present invention,
The height of the rib varies continuously in the width direction of the rib.
An optical reflecting element characterized by:

With this technology, by varying the height of the ribs in the width direction, the shape created by the ribs on the reflective surface can be varied in the height direction, making diffraction less likely to occur. This makes it possible to suppress the effect of diffracted light on the scanning light.

(Technology 15)
In the optical reflecting element according to any one of the first to fourth aspects,
The reflecting surface is disposed by forming an optical reflecting film on an upper surface of the movable portion.
An optical reflecting element characterized by:

This technology makes it possible to increase the reflectivity of the reflective surface and suppress surface roughness compared to when the upper surface of the movable part is used as the reflective surface itself. This allows for highly accurate light scanning.

(Technology 16)
A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
At least one rib disposed on a lower surface of the movable part,
The reflecting surface is irradiated with light having a plurality of peak intensities near a central axis, the intensity of which decreases with distance from each of the peak intensities;
The rib in a specific region of the lower surface corresponding to the vicinity of the center of the light irradiation region on the reflecting surface has a substantially curved shape in a plan view.
An optical reflecting element characterized by:

With this technology, ribs are placed on the underside of the movable part, reinforcing the movable part with the ribs. This makes it possible to prevent bending of the movable part and the reflective surface placed on its upper surface. Furthermore, ribs that are substantially curved are placed in specific areas on the underside of the movable part. As a result, diffracted light caused by changes in the shape of the reflective surface due to these ribs is dispersed, making it less likely that peaks will occur in the diffracted light. This makes it possible to effectively prevent the effect of diffraction by the ribs on light near the center, where the intensity of the irradiated light is high.

(Technology 17)
A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
A first rib is disposed on a lower surface of the movable portion and surrounds a center of the lower surface;
a second rib disposed on the lower surface outside the first rib and extending substantially parallel to the pivot axis;
The first rib has a substantially curved shape in a plan view,
No other ribs are provided on the inside of the first rib.
An optical reflecting element characterized by:

According to this technology, the first rib and the second rib are arranged on the lower surface of the movable part, and the movable part is reinforced by these ribs. This makes it possible to suppress the occurrence of bending in the movable part and the reflective surface arranged on its upper surface. In addition, since the second rib is arranged substantially parallel to the rotation axis, the second rib can suppress the moment of inertia of the movable part rotating about the rotation axis from increasing. This allows the movable part to rotate smoothly. Furthermore, in the area surrounding the center of the lower surface of the movable part, substantially only the first rib, which has a curved shape, is arranged. Therefore, the shape change of the reflective surface due to the first rib also becomes a shape that substantially surrounds the center with a curve. Therefore, diffraction does not occur inside the shape change of the reflective surface, and the diffracted light generated by this shape change is dispersed and is less likely to produce a peak. This makes it possible to effectively suppress the effect of diffraction by the first rib on the light near the center where the intensity of the irradiated light is high.

100 Optical reflecting element 103 Movable part 103a Upper surface 103b Lower surface 131a, 131b, 131c, 131a1, 131a2 Rib CA1 Specific area E1 Irradiation area E1a Area (area with an intensity of 1/ ^e2 or more of the peak intensity)
E1b region (region with intensity equal to or greater than half the peak intensity)
L1 light M1a reflective surface

Claims (17)

A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
At least one rib disposed on a lower surface of the movable part,
A light beam having an intensity decreasing with distance from the central axis is irradiated onto the reflecting surface,
The rib in a specific region of the lower surface corresponding to the vicinity of the center of the light irradiation region on the reflecting surface has a substantially curved shape in a plan view.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The ribs in the specific region are arranged in a ring shape in a plan view.
An optical reflecting element characterized by:
3. The optical reflecting element according to claim 2,
The ribs in the specific region are arranged along a perfect circle.
An optical reflecting element characterized by:
3. The optical reflecting element according to claim 2,
The ribs in the specific region are arranged along an ellipse.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The ribs in the specific region are arranged along a curved amplitude waveform.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The other ribs are arranged outside the specific region.
An optical reflecting element characterized by:
7. The optical reflecting element according to claim 6,
The other rib extends radially from the center of the lower surface.
An optical reflecting element characterized by:
8. The optical reflecting element according to claim 7,
The direction in which the other rib extends is substantially parallel to the pivot axis.
An optical reflecting element characterized by:
8. The optical reflecting element according to claim 7,
The other ribs are arranged along a straight line.
An optical reflecting element characterized by:
8. The optical reflecting element according to claim 7,
The other ribs are arranged along a curved amplitude waveform.
An optical reflecting element characterized by:
7. The optical reflecting element according to claim 6,
The other rib is arranged in an annular shape in a plan view.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The specific region has a size substantially the same as that of a region where the intensity of the light irradiated on the reflecting surface is equal to or greater than half of the peak intensity.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The specific area has a size that is substantially equal to or larger than the size of an area where the intensity of the light irradiated onto the reflecting surface is equal to or larger than half the peak intensity, and is equal to or smaller than the size of an area where the intensity of the light irradiated onto the reflecting surface is equal to or larger than 1/ ^e2 (e is Napier's constant) of the peak intensity.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The height of the rib varies continuously in the width direction of the rib.
An optical reflecting element characterized by:
2. The optical reflecting element according to claim 1,
The reflecting surface is disposed by forming an optical reflecting film on an upper surface of the movable portion.
An optical reflecting element characterized by:
A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
At least one rib disposed on a lower surface of the movable part,
The reflecting surface is irradiated with light having a plurality of peak intensities near a central axis, the intensity of which decreases with distance from each of the peak intensities;
The rib in a specific region of the lower surface corresponding to the vicinity of the center of the light irradiation region on the reflecting surface has a substantially curved shape in a plan view.
An optical reflecting element characterized by:
A flat plate-shaped movable part that rotates about a rotation axis;
A reflecting surface disposed on an upper surface of the movable portion;
A first rib is disposed on a lower surface of the movable portion and surrounds a center of the lower surface;
a second rib disposed on the lower surface outside the first rib and extending substantially parallel to the pivot axis;
The first rib has a substantially curved shape in a plan view,
No other ribs are provided on the inside of the first rib.
An optical reflecting element characterized by:

Images