Optical reflection element and light deflector

Abstract

An optical reflection element (100) comprises: a flat plate-shaped movable part (103) that rotates about a rotation axis (R0); a reflection surface (M1a) that is disposed on an upper surface (103a) of the movable part (103) in order to be scanned with light; and at least one rib (131) that is disposed on a lower surface (103b) of the movable part (103) in order to suppress deflection of the movable part (103). In a radiation region of the lower surface (103b) that is irradiated with monitor light (L1) in order to detect the operation of the movable part (103), the rib (131) continues with no step at least in a direction parallel to the upper surface (103a) and approximately perpendicular to the rotation axis (R0).

Description

Optical reflective element and optical deflector

[0001] The present invention relates to an optical reflecting element and an optical deflector including the same.

[0002] Conventionally, optical deflectors that rotate a mirror are known. This type of optical deflector 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 deflector. In this case, a configuration for monitoring the scanning position of the light, i.e., the rotation position of the mirror, can be further provided.

[0003] In the configuration described in Patent Document 1 below, a position sensitive detector (PSD) is used to monitor the rotational position of a mirror. Specifically, monitoring light is irradiated onto the rear surface of the mirror, and the reflected light is received by the PSD. As the mirror rotates, the position at which the reflected light is received moves. A detection signal corresponding to the position at which the reflected light is received is output from the PSD. The rotational position of the mirror is detected by the detection signal from the PSD.

[0004] Japanese Patent Application Laid-Open No. 2004-144926

[0005] In the optical deflector described above, the movable part having the reflective surface is repeatedly rotated at a relatively high speed. Therefore, the movable part is bent during the rotation, which causes warping of the reflective surface. The warping of the reflective surface reduces the scanning accuracy of the light.

[0006] Such deflection of the movable part can be suppressed by providing ribs on the underside of the movable part. However, this configuration can cause the ribs to diffract the monitor light irradiated onto the underside of the movable part. Unwanted light generated by the diffraction generates noise in the output of the position sensitive detector (PSD). This noise reduces the detection accuracy of the rotational position of the movable part.

[0007] In view of these problems, the present invention aims to provide an optical reflecting element and an optical deflector that can accurately detect the rotational position of a movable part having a reflective surface using monitor light while reinforcing the movable part with ribs.

[0008] A first aspect of the present invention relates to an optical reflecting element. The optical reflecting element according to this aspect includes a flat movable part that rotates about a rotation axis, a reflective surface disposed on the upper surface of the movable part for scanning light, and at least one rib disposed on the lower surface of the movable part for suppressing deflection of the movable part. In an illumination area on the lower surface where monitor light is irradiated to detect the operation of the movable part, the rib is continuous without steps at least in a direction parallel to the upper surface and substantially perpendicular to the rotation axis.

[0009] According to the optical reflecting element of this aspect, the monitor light reflected by the lower surface of the movable part is not diffracted at least in a direction parallel to the upper surface of the movable part and substantially perpendicular to the rotation axis. Therefore, on the light-receiving surface of the position detecting element that receives this reflected light, the diffracted light of the reflected light is not aligned in the scanning direction of the reflected light accompanying the rotation of the movable part. Therefore, the rotational position of the movable part can be accurately detected from the output of the position detecting element while suppressing the deflection of the movable part by providing a rib.

[0010] A second aspect of the present invention relates to an optical deflector, comprising the optical reflecting element according to the first aspect, a light source that emits the monitor light, and a position detecting element that receives the monitor light reflected by the lower surface and detects the receiving position of the monitor light on the light receiving surface.

[0011] According to the optical deflector of this aspect, the same effects as those of the first aspect can be achieved.

[0012] As described above, the present invention provides an optical reflecting element and an optical deflector that can accurately detect the rotational position of a movable part having a reflective surface using monitor light while reinforcing the movable part with ribs.

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

[0014] FIG. 1 is a 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 plan view showing the configuration of an optical deflector according to an embodiment. FIG. 4 is a cross-sectional view showing the configuration of an optical deflector according to an embodiment. FIG. 5(a) is a diagram schematically showing a rib arrangement method according to Comparative Example 1. FIG. 5(b) is a diagram showing a beam spot of monitor light on the light receiving surface of a PSD when ribs are arranged using the arrangement method of Comparative Example 1. FIG. 6(a) is a diagram schematically showing a rib arrangement method according to Comparative Example 2. FIG. 6(b) is a diagram showing a beam spot of monitor light on the light receiving surface of a PSD when ribs are arranged using the arrangement method of Comparative Example 2. FIG. 7(a) is a diagram schematically showing a rib arrangement method according to an embodiment. FIG. 7(b) is a diagram showing a beam spot of monitor light on the light receiving surface of a PSD when ribs are arranged using the arrangement method of the embodiment. FIG. 8 is a diagram explaining the allowable range of the direction in which ribs are connected without steps according to an embodiment. Fig. 9(a) is a diagram schematically showing a rib arrangement method according to Modification Example 1. Fig. 9(b) is a diagram schematically showing a rib arrangement method according to Modification Example 2. Fig. 10(a) is a diagram schematically showing a rib arrangement method according to Modification Example 3. Fig. 10(b) is a diagram schematically showing a rib arrangement method according to Modification Example 4.

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

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] For convenience, each figure is labeled with X, Y, and Z axes that are orthogonal to one another. The Z axis direction is the up-down direction of optical reflecting element 100, and the X axis direction and the Y axis direction are the long side direction and the short side direction, respectively, of optical reflecting element 100. The positive direction of the Z axis is the up direction of optical reflecting element 100.

[0018] 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 along a plane parallel to the XZ plane at the position of the rotation axis R0 in FIG. 1.

[0019] 1, in this embodiment, the optical reflecting element 100 is configured by a meandering MEMS mirror. However, the optical reflecting element 100 is not limited to the meandering MEMS mirror, and may have other configurations as long as the movable part 103 can be rotated about the rotation axis R0.

[0020] The optical reflecting element 100 includes a support portion 101 , a pair of drive portions 102 , and a movable portion 103 .

[0021] 2, the support part 101, the pair of drive parts 102, and the movable part 103 share 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 configured 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 substrates 121 and 122. The rigidity of the support part 101 is increased by having two silicon substrates 121 and 122.

[0022] As shown in FIG. 1, the support portion 101 is a frame-shaped member having a rectangular outline in a plan view.

[0023] 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.

[0024] The four piezoelectric actuators 111 are respectively disposed on the upper surface of four regions 110a of the substrate 110, which extend in a direction perpendicular to the rotation axis R0 (the Y-axis direction). Each piezoelectric actuator 111 is configured by sandwiching a piezoelectric body of a certain thickness between an upper electrode and a lower electrode.

[0025] The piezoelectric body is made of, for example, PZT (lead zirconate titanate). The upper electrode and the lower electrode are made of, for example, platinum. When a voltage (drive signal) is applied between the upper electrode and the lower electrode, 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.

[0026] The movable part 103 is supported by a pair of drive parts 102. The movable part 103 is a part of the silicon substrate 121 described above. In a plan view, the movable part 103 has a circular shape. However, the shape of the movable part 103 in a plan view may be another shape, such as a square.

[0027] 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 an upper surface 103a and a lower surface 103b parallel to the XY plane. A mirror M1 is formed on the upper surface 103a of the movable part 103. As a result, a reflective surface M1a is disposed on the upper surface 103a of the movable part 103. If the reflectivity of the upper surface 103a of the movable part 103 is high, the mirror M1 may be omitted and the upper surface 103a of the movable part 103 may be used as the reflective surface.

[0028] 2, a plurality of ribs 131 are formed on the lower surface 103b of the movable part 103. The plurality of ribs 131 are made of silicon, similar to the silicon substrate 122. Each rib 131 extends linearly in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0, i.e., in the Y-axis direction. Each rib 131 has a wall shape with a substantially constant width and height.

[0029] A structure in which silicon substrates 121 and 122 of a fixed thickness are stacked is used to manufacture optical reflecting element 100. The outline of this structure in a plan view is the same as the outline of optical reflecting element 100 in Fig. 1. Furthermore, a layer structure of piezoelectric actuator 111 is uniformly stacked on the upper surface of this structure.

[0030] 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 region corresponding to the support portion 101 and the plurality of ribs 131 is left unremoved. As a result, the plurality of ribs 131 are formed on the lower surface 103b of the movable portion 103. Furthermore, the thickness of the support portion 101 is ensured.

[0031] Next, the layer structure of piezoelectric actuator 111 is removed by etching from the top surface of this layer structure, leaving only the region of piezoelectric actuator 111. Next, mirror M1 is vapor-deposited in the region of mirror M1. Furthermore, silicon substrates 121 and 122 are removed by etching in regions other than support portion 101, pair of drive portions 102, and movable portion 103. This completes the manufacture of optical reflecting element 100 having the shape shown in Figures 1 and 2.

[0032] In the configuration of Figure 1, when drive voltages of the same phase are applied to 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 deforms the piezoelectric bodies in the piezoelectric actuators 111, and the even-numbered substrates 110 (regions 110a) deform so as to bend. In this way, the deformation of each substrate 110 causes the movable part 103 to rotate about the rotation axis R0.

[0033] Fig. 3 is a plan view showing the configuration of the optical deflector 10. Fig. 4 is a cross-sectional view of the optical deflector 10 taken along a plane parallel to the YZ plane at position AA in Fig. 3. In Fig. 4, the optical axis of the monitor light L1 emitted from the light source 301 is indicated by a dashed line.

[0034] As shown in Figures 3 and 4, optical reflecting element 100 is mounted in frame member 200. Frame member 200 has a rectangular shape that is long in the X-axis direction in plan view, and has a rectangular recess 201 into which optical reflecting element 100 fits. Frame member 200 has a constant thickness, and recess 201 has a constant depth. Recess 201 has a rectangular opening 202 formed therein that surrounds drive unit 102 and movable unit 103 of optical reflecting element 100 in plan view. Optical reflecting element 100 is mounted in recess 201 with an adhesive or the like.

[0035] 4, a light source 301 for emitting monitor light L1 and a position sensitive detector (PSD) 302 for receiving monitor light L1 are disposed below the frame member 200. The light source 301 and the PSD 302 are supported by a support member (not shown). The support member is fixed to the lower surface of the frame member 200.

[0036] The light source 301 includes a semiconductor laser, a collimator lens, and an aperture. Laser light emitted from the semiconductor laser is collimated by the collimator lens and further adjusted into a circular beam by the aperture. In this manner, monitor light L1 is generated. The light source 301 is disposed so that the monitor light L1 is incident obliquely on the lower surface 103b of the movable part 103. The optical axis of the monitor light L1 is perpendicular to the rotation axis R0. Therefore, the optical axis of the monitor light L1 after being reflected by the lower surface 103b of the movable part 103 is also perpendicular to the rotation axis R0.

[0037] The PSD 302 receives the monitor light L1 reflected by the lower surface 103b of the movable part 103. The PSD 302 is tilted so that the reflected light of the monitor light L1 is incident on the light-receiving surface 302a approximately perpendicularly when the movable part 103 is in the neutral position (the position shown in FIG. 4). As the movable part 103 rotates about the rotation axis R0, the beam spot of the monitor light L1 moves on the light-receiving surface 302a of the PSD 302. The PSD 302 outputs a detection signal corresponding to the position of the beam spot. From this detection signal, a detection circuit (not shown) detects the rotation position of the movable part 103.

[0038] When the optical deflector 10 is used in an image display device such as a head-up display, the movable part 103 is repeatedly rotated at a relatively high speed. Therefore, the movable part 103 is bent during the rotation, which causes warping of the reflecting surface M1a. The warping of the reflecting surface M1a reduces the scanning accuracy of the light incident on the reflecting surface M1a.

[0039] Such deflection of the movable part 103 can be suppressed by providing the ribs 131 on the lower surface 103b of the movable part 103, as described above. However, in this case, when the monitor light L1 irradiated onto the lower surface of the movable part 103 falls on the ribs 131, the monitor light L1 is diffracted by the ribs 131. Depending on how the ribs 131 are provided, the diffracted light by the ribs 131 may cause noise in the output of the PSD 302. This noise reduces the detection accuracy of the rotational position of the movable part 103.

[0040] Therefore, in this embodiment, a method for arranging the ribs 131 is devised. The method for arranging the ribs 131 will be described below in comparison with a comparative example.

[0041] Fig. 5A is a diagram schematically illustrating a method for arranging the ribs 131 according to Comparative Example 1. Fig. 5A shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0042] As shown in Fig. 5A, in Comparative Example 1, two ribs 131 extending in a direction parallel to the rotation axis R0 (X-axis direction) and two ribs 131 extending in a direction perpendicular to the rotation axis R0 (Y-axis direction) are arranged to intersect with each other. Monitor light L1 emitted from the light source 301 in Fig. 4 is irradiated onto an irradiation area A1. For convenience, the irradiation area A1 is shown as a perfect circle in Fig. 5A, but the actual irradiation area A1 has a shape elongated in the Y-axis direction.

[0043] Here, the irradiation area A1 is defined as a range where the intensity of the monitor light L1 is substantially generated on the lower surface 103b of the movable part 103 when the rib 131 is not formed. For example, the irradiation area A1 is 1 / e of the peak intensity of the monitor light L1. ２ The intensity range above can be defined as (e is Napier's number).

[0044] Furthermore, the illumination area A1 is the range of the lower surface 103b of the movable part 103 that is illuminated with the monitor light L1 when the movable part 103 rotates within its rotation range during normal operation. When the movable part 103 rotates from the neutral position about the rotation axis R0, the range of the lower surface 103b of the movable part 103 that is illuminated with the monitor light L1 can change in a direction perpendicular to the rotation axis R0 from the illumination range of the monitor light L1 when the movable part 103 is in the neutral position. The illumination area A1 is the range that includes this change in the illumination range of the monitor light L1 on the lower surface 103b when the movable part 103 is in the neutral position.

[0045] FIG. 5B is a diagram showing the beam spot of the monitor light L1 on the light receiving surface 302a of the PSD 302 when the ribs 131 are arranged according to the arrangement method of Comparative Example 1.

[0046] Figure 5(b) shows the results of a simulation of the beam spot. For convenience, Figure 5(b) shows only the range of the light-receiving surface 302a of the PSD 302 onto which the monitor light L1 is incident when the movable part 103 is in the neutral position. As the movable part 103 rotates, the beam spot of the monitor light L1 moves in the scanning direction D1. The PSD 302 is a one-dimensional PSD that can detect the position of the beam spot in the scanning direction D1.

[0047] When the monitor light L1 is reflected by the lower surface 103b of the movable part 103, it is diffracted by the four ribs 131 in a direction perpendicular to the direction in which each rib 131 extends. This generates multiple orders of diffracted light in each direction, and beam spots due to these diffracted lights are generated on the light receiving surface 302a of the PSD 302.

[0048] 5B, beam spot B0 is a beam spot of monitor light L1 (zeroth-order light) that is incident on the light-receiving surface 302a without being diffracted by the four ribs 131. Multiple beam spots B1 above and below beam spot B0 are beam spots of multiple orders of diffracted light generated when monitor light L1 is diffracted by ribs 131 extending parallel to the rotation axis R0. Multiple beam spots B2 on the left and right of beam spot B0 are beam spots of multiple orders of diffracted light generated when monitor light L1 is diffracted by ribs 131 extending perpendicular to the rotation axis R0. In comparative example 1, these beam spots B0, B1, and B2 move in the scanning direction D1 in response to the rotation of the movable part 103.

[0049] Fig. 6A is a diagram schematically illustrating a method for arranging the ribs 131 according to Comparative Example 2. Fig. 6A shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0050] As shown in FIG. 6A, in Comparative Example 2, the monitor light L1 is arranged on three ribs 131 extending in a direction parallel to the rotation axis R0 (X-axis direction). In Comparative Example 2, the monitor light L1 emitted from the light source 301 in FIG. 4 is also irradiated onto the irradiation area A1. For convenience, the irradiation area A1 is shown as a perfect circle in FIG. 6A, but the actual irradiation area A1 has a shape elongated in the Y-axis direction. The definition of the irradiation area A1 is the same as in Comparative Example 1.

[0051] FIG. 6B is a diagram showing the beam spot of the monitor light L1 on the light receiving surface 302a of the PSD 302 when the ribs 131 are arranged according to the arrangement method of the second comparative example.

[0052] 6B shows the results of a simulation of the beam spot. For convenience, as with FIG. 5B, FIG. 6B shows only the range of the light-receiving surface 302a onto which the monitor light L1 is incident when the movable part 103 is in the neutral position. As the movable part 103 rotates, the beam spot of the monitor light L1 moves in the scanning direction D1.

[0053] When the monitor light L1 is reflected by the lower surface 103b of the movable part 103, it is diffracted by the three ribs 131 in a direction perpendicular to the direction in which each rib 131 extends. This generates multiple orders of diffracted light in this direction, and beam spots due to these diffracted lights are generated on the light receiving surface 302a of the PSD 302.

[0054] 6B, beam spot B0 is a beam spot of monitor light L1 (zeroth-order light) that is incident on the light-receiving surface 302a without being diffracted by the three ribs 131. Multiple beam spots B1 above and below beam spot B0 are beam spots of multiple orders of diffracted light that are generated when monitor light L1 is diffracted by the ribs 131 extending parallel to the rotation axis R0. In comparative example 2, these beam spots B0 and B1 move in the scanning direction D1 in response to the rotation of the movable part 103.

[0055] 5B and 6B, the rotational position of the movable part 103 corresponds to the position of the beam spot B0 (beam spot of zero-order light) on the light receiving surface 302a. Therefore, it is desirable that the PSD 302 accurately output a detection signal corresponding to the position of this beam spot B0.

[0056] However, in Comparative Examples 1 and 2, an unwanted beam spot B1 is generated in the scanning direction D1 relative to this beam spot B0 due to diffracted light. As a result, the PSD 302 outputs a detection signal in which signal components based on the unwanted beam spot B1 are superimposed on the signal components of the original beam spot B0. Because the unwanted beam spot B1 is generated over a wide range in the scanning direction D1, the signal components based on the unwanted beam spot B1 can become significant noise compared to the signal components of the original beam spot B0. As a result, the accuracy of the detection signal from the PSD 302 decreases.

[0057] 7A is a diagram schematically illustrating a method for arranging the ribs 131 according to the embodiment, in which a plan view of the movable part 103 is shown as viewed from the bottom side (Z-axis negative side).

[0058] As shown in Fig. 7A, in this embodiment, three ribs 131 are arranged extending in a direction perpendicular to the rotation axis R0 (Y-axis direction). Each rib 131 is connected without steps in an irradiation area A1 on the lower surface 103b of the movable part 103, which is irradiated with the monitor light L1, in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0 (Y-axis direction in Fig. 7A). Each rib 131 extends without steps in this direction to the outside of the irradiation area A1, reaching the outer edge of the movable part 103.

[0059] In this embodiment, the monitor light L1 emitted from the light source 301 in Fig. 4 is irradiated onto the irradiation area A1. For convenience, the irradiation area A1 is shown as a perfect circle in Fig. 7A as well, but the actual irradiation area A1 has a shape that is elongated in the Y-axis direction. The definition of the irradiation area A1 is the same as in Comparative Example 1.

[0060] FIG. 7B is a diagram showing the beam spot of the monitor light L1 on the light receiving surface 302a of the PSD 302 when the ribs 131 are arranged by the arrangement method of the embodiment.

[0061] 7B shows the results of a simulation of the beam spot. For convenience, as with FIG. 5B, FIG. 7B shows only the range of the light-receiving surface 302a onto which the monitor light L1 is incident when the movable part 103 is in the neutral position. As the movable part 103 rotates, the beam spot of the monitor light L1 moves in the scanning direction D1.

[0062] When the monitor light L1 is reflected by the lower surface 103b of the movable part 103, it is diffracted by the three ribs 131 in a direction perpendicular to the direction in which each rib 131 extends. This generates multiple orders of diffracted light in this direction, and beam spots due to these diffracted lights are generated on the light receiving surface 302a of the PSD 302.

[0063] 7B, beam spot B0 is a beam spot of monitor light L1 (zeroth-order light) that is incident on the light-receiving surface 302a without being diffracted by the three ribs 131. Multiple beam spots B2 on the left and right of beam spot B0 are beam spots of multiple orders of diffracted light that are generated when monitor light L1 is diffracted by the ribs 131 that extend perpendicular to the rotation axis R0. In comparative example 2, these beam spots B0 and B2 move in the scanning direction D1 in response to the rotation of the movable part 103.

[0064] Compared to the comparative examples 1 and 2, in the embodiment, no unnecessary beam spots B1 due to diffracted light are generated in the scanning direction D1 relative to the beam spot B0. Therefore, noise due to the unnecessary beam spots B1 is not superimposed on the detection signal output from the PSD 302. On the other hand, in the embodiment, beam spots B2 due to diffracted light are generated in a direction perpendicular to the scanning direction D1 relative to the beam spot B0. However, these beam spots B2 are located at approximately the same position as the beam spot B0 in the scanning direction D1. Therefore, these beam spots B1 do not substantially contribute to noise in the detection signal corresponding to the position of the beam spot B0. Therefore, according to the arrangement method of the ribs 131 in the embodiment, a highly accurate detection signal can be obtained from the PSD 302.

[0065] <Effects of the embodiment> According to the above embodiment, the following effects are achieved.

[0066] As shown in Figures 2, 4 and 7(a), in the irradiation area A1 of the lower surface 103b where the monitor light L1 is irradiated to detect the operation of the movable part 103, ribs 131 are continuously arranged without steps in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0.

[0067] As a result, the monitor light L1 reflected by the lower surface 103b of the movable part 103 is not diffracted at least in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0. Therefore, as shown in Figure 7B, on the light-receiving surface 302a of the PSD 302 (position-sensitive element), the diffracted light of the monitor light L1 (beam spot B1 in Figure 5B or 6B) is not aligned with the scanning direction D1 of the monitor light L1 that accompanies the rotation of the movable part 103. Therefore, while providing the rib 131 to suppress bending of the movable part 103, the rotation position of the movable part 103 can be detected with high accuracy from the output of the PSD 302, as described above.

[0068] The direction in which the ribs 131 are connected without any steps does not have to be strictly parallel to the upper surface 103a and perpendicular to the rotation axis R0, and may be slightly deviated from this direction. In other words, the direction in which the ribs 131 are connected without any steps may be any direction that is parallel to the upper surface 103a and approximately perpendicular to the rotation axis R0.

[0069] FIG. 8 is a diagram illustrating the allowable range of the direction in which the ribs 131 are connected without any steps.

[0070] The left side of Fig. 8 shows the light receiving surface 302a of the PSD 302 and the beam spot B0 moving on the light receiving surface 302a. The light receiving surface 302a is a rectangle that is elongated in the scanning direction D1 of the beam spot B0. The long sides of the rectangle are parallel to the scanning direction D1. As the movable part 103 rotates, the beam spot B0 moves in the scanning direction D1 at the middle position of the width W0 of the light receiving surface 302a.

[0071] The right side of FIG. 8 shows an enlarged view of the portion enclosed by the dashed dotted line shown on the left side of FIG.

[0072] When the beam spot B2 based on the diffracted light is included in the light receiving surface 302a together with the beam spot B0, the intensity of the beam spot B0 is several times higher than the intensity of the beam spot B2 based on the diffracted light. Therefore, as shown on the right side of FIG. 8, the diameter d0 of the beam spot B0 (for example, 1 / e of the peak intensity) ２When the center of the beam spot B2 of the diffracted light is included within the range of the diameter in the scanning direction D1 of the above range, the signal component due to the beam spot B2 of the diffracted light does not substantially become noise in the detection signal corresponding to the position of the beam spot B0.

[0073] Therefore, the direction in which the ribs 131 are connected without any steps (the direction in which the ribs 131 extend in the above embodiment) is angled at an angle ±α (α=tan －１ When the angle α is within the range of d0 / W0, a detection signal corresponding to the position of the beam spot B0 can be detected with high accuracy. Therefore, the range of this angle ±α is the allowable range of deviation, and is defined as a direction parallel to the upper surface 103a and approximately perpendicular to the rotation axis R0. The direction in which the ribs 131 are connected without any steps is defined as being parallel to the upper surface 103a and approximately perpendicular to the rotation axis R0. When the diameter d0 is 0.1 mm and the width W0 is 1 mm, the angle α is approximately 5°, and the allowable angle range ±α is approximately ±5°.

[0074] In the configurations of FIGS. 2, 4 and 7A, the height of the ribs 131 in the irradiation area A1 is constant in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0.

[0075] This makes it possible to reliably suppress diffraction in a direction parallel to the upper surface 103a of the movable portion 103 and perpendicular to the rotation axis R0.

[0076] As shown in FIGS. 2, 4 and 7A, the rib 131 in the irradiation area A1 has a wall shape that extends linearly in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0.

[0077] According to this configuration, the monitor light L1 irradiated onto the irradiation area A1 is guided and reflected by an area of ​​the lower surface 103b of the movable part 103 that does not have the ribs 131. Therefore, by receiving this reflected light with the PSD 302, the rotational position of the movable part 103 can be detected with high accuracy.

[0078] As shown in FIGS. 2, 4 and 7A, a plurality of linearly extending ribs 131 are arranged side by side in a direction parallel to the rotation axis R0.

[0079] According to this configuration, the plurality of ribs 131 can effectively suppress the deflection of the movable portion 103 .

[0080] As shown in FIGS. 2, 4 and 7A, the rib 131 extends without steps to the outside of the irradiation area A1 in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0.

[0081] With this configuration, even if the monitor light L1 is irradiated in a position shifted in the Y-axis direction from the intended irradiation area A1 due to an assembly error or the like, the monitor light does not diffract in a direction parallel to the upper surface 103 a of the movable part 103 and perpendicular to the rotation axis R0. Therefore, the robustness of the position detection of the optical reflecting element 100 can be improved, and the rotation position of the movable part 103 can be stably detected.

[0082] As shown in FIGS. 2, 4 and 7A, the portion of the rib 131 extending outside the irradiation area A1 extends linearly in a direction parallel to the upper surface 103a and perpendicular to the rotation axis R0.

[0083] With this configuration, the portion of the rib 131 extending outside the irradiation area A1 does not produce diffraction in a direction parallel to the upper surface 103 a of the movable part 103 and perpendicular to the rotation axis R0. Therefore, even if the monitor light L1 is emitted in a direction shifted in the Y-axis direction from the original irradiation area A1 due to an assembly error or the like, the rotation position of the movable part 103 can be stably detected.

[0084] As shown in Figures 3 and 4, the optical deflector 10 includes an optical reflecting element 100, a light source 301 that emits monitor light, and a PSD 302 (position detecting device) that receives the monitor light L1 reflected by the lower surface 103b and detects the receiving position of the monitor light L1 on the light receiving surface 302a.

[0085] According to this configuration, since the optical reflecting element 100 having the above configuration is provided, the rotational position of the movable part 103 can be detected with high accuracy from the output of the PSD 302 while the deflection of the movable part 103 is suppressed by providing the rib 131 .

[0086] <Modification 1> Fig. 9(a) is a diagram schematically showing a method of arranging the ribs 131 according to Modification 1. Fig. 9(a) shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0087] 9A, in the first modification, a rib 131 that extends without steps across the entire irradiation area A1 is disposed on the lower surface 103b of the movable part 103. In a plan view, the rib 131 is slightly wider than the irradiation area A1.

[0088] The lower surface (surface on the negative side of the Z axis) of the rib 131 is a flat surface with a constant height. Therefore, in the irradiation area A1 of the lower surface 103b of the movable part 103, which is irradiated with the monitor light L1, the rib 131 is continuous without steps in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0 (the Y-axis direction in FIG. 9A). Here, the rib 131 is also continuous without steps in a direction parallel to the upper surface 103a of the movable part 103 and parallel to the rotation axis R0 (the X-axis direction in FIG. 9A).

[0089] In this configuration, the lower surface of the rib 131 forms the lower surface of the movable part 103 onto which the monitor light L1 is irradiated, and an irradiation area A1 is defined on the lower surface of the rib 131. The PSD 302 receives the monitor light L1 reflected by the lower surface of the rib 131. In this configuration, no diffraction occurs in the monitor light L1 reflected by the lower surface of the rib 131, so only a beam spot B0 is generated on the light-receiving surface 302a of the PSD 302. Because there is no diffraction, the intensity of the beam spot B0 is higher than in the configuration of the embodiment. Therefore, the detection signal of the PSD 302 has a high signal-to-noise ratio and is less susceptible to noise due to stray light, etc.

[0090] Effect of Modification Example 1 As in the above embodiment, in Modification Example 1, in the irradiation area A1 irradiated with the monitor light L1, the ribs 131 are continuously arranged without any steps in a direction parallel to at least the upper surface 103a of the movable part 103 and substantially perpendicular to the rotation axis R0. Therefore, the monitor light L1 reflected by the lower surface of the movable part 103 (here, the lower surface of the ribs 131 corresponds to the lower surface of the movable part 103) is not diffracted at least in this direction. Therefore, on the light-receiving surface 302a of the PSD 302 (position-sensitive element) that receives this reflected light, the diffracted light of the monitor light L1 is not aligned in the scanning direction of the monitor light L1 that accompanies the rotation of the movable part 103. Therefore, the provision of the ribs 131 suppresses bending of the movable part 103, and the rotational position of the movable part 103 can be accurately detected from the output of the PSD 302.

[0091] As shown in FIG. 9A, the rib 131 is arranged on the lower surface 103b of the movable part 103 so as to extend across the entire irradiation area A1 without any steps.

[0092] As a result, the monitor light L1 irradiated onto the irradiation area A1 is reflected by the stepless lower surface of the rib 131. By receiving this reflected light with the PSD 302, the rotational position of the movable part 103 can be detected with high accuracy. Furthermore, because the rib 131 is disposed over a wide range near the center of the movable part 103 corresponding to the irradiation area A1, deflection of the movable part 103 (warping of the reflecting surface M1a) can be suppressed over a wide range near the center of the upper surface 103a of the movable part 103. Therefore, the light incident on the reflecting surface M1a can be scanned stably and accurately by the rotation of the movable part 103.

[0093] 9A, in a plan view, the rib 131 is slightly wider than the irradiation area A1. That is, the rib 131 extends without steps to the outside of the irradiation area A1 in a direction parallel to the upper surface 103a of the movable part 103 and substantially perpendicular to the rotation axis R0.

[0094] As a result, even if the monitor light L1 is irradiated in a direction shifted in the Y-axis direction from the intended irradiation area A1 due to an assembly error or the like, the monitor light L1 is not diffracted in a direction parallel to the upper surface 103 a of the movable part 103 and substantially perpendicular to the rotation axis R0. This increases the robustness of the position detection of the PSD 302, enabling stable detection of the rotation position of the movable part 103.

[0095] In this case, since the rib 131 extends in the X-axis direction relative to the illumination area A1, no diffracted light is generated even if the monitor light L1 is irradiated in a position shifted in the X-axis direction from the original illumination area A1, thereby enabling more stable detection of the rotational position of the movable part 103.

[0096] <Modification 2> Fig. 9(b) is a diagram schematically showing a method of arranging the ribs 131 according to Modification 2. Fig. 9(b) shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0097] 9B, in the second modification, the rib 131 extends without steps to the outside of the irradiation area A1 in a direction parallel to the upper surface of the movable part 103 and perpendicular to the rotation axis R0 (here, the Y-axis direction). In a plan view, the width of the rib 131 in the X-axis direction is slightly narrower than that of the irradiation area A1.

[0098] The lower surface (surface on the negative side of the Z axis) of the rib 131 is a flat surface with a constant height. Therefore, in the irradiation area A1 of the lower surface 103b of the movable part 103, which is irradiated with the monitor light L1, the rib 131 is continuous without steps in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0 (the Y-axis direction in FIG. 9A). Here, the rib 131 is also continuous without steps in a direction parallel to the upper surface 103a of the movable part 103 and parallel to the rotation axis R0 (the X-axis direction in FIG. 9A).

[0099] In this configuration, the lower surface of the rib 131 mainly constitutes the lower surface of the movable part 103 onto which the monitor light L1 is irradiated, and the irradiation area A1 is mainly defined on the lower surface of the rib 131. The PSD 302 receives the monitor light L1 reflected by the lower surface of the rib 131 and the lower surface 103b of the movable part 103 included in the irradiation area A1.

[0100] In this configuration, the monitor light L1 is diffracted by the edge of the rib 131 in the X-axis direction. However, the diffraction direction is the X-axis direction, not a direction parallel to the upper surface 103a of the movable portion 103 and perpendicular to the rotation axis R0 (the Y-axis direction in FIG. 9B). Therefore, the beam spot B1 (see FIGS. 5B and 6B) as in Comparative Examples 1 and 2 above is not generated. Furthermore, because the edge of the rib 131 is covered by the vicinity of the outer periphery of the monitor light L1, the intensity of the diffracted light generated by this edge is several times smaller than the intensity of the monitor light L1 reflected by the rib 131. Therefore, the intensity of the beam spot B0 formed by the monitor light L1 reflected by the rib 131 is higher than in the configuration of the embodiment. Therefore, the detection signal of the PSD 302 is less susceptible to noise due to stray light, etc.

[0101] Effect of Modification Example 2 As in the above embodiment, in Modification Example 2, in the irradiation area A1 irradiated with the monitor light L1, the ribs 131 are arranged without any steps in a direction parallel to at least the upper surface 103a of the movable part 103 and substantially perpendicular to the rotation axis R0. Therefore, the monitor light L1 reflected by the lower surface of the movable part 103 (here, the lower surface of the ribs 131 mainly corresponds to the lower surface of the movable part 103) is not diffracted in at least this direction. Furthermore, although the monitor light L1 is diffracted by the edges of the ribs 131 in the X-axis direction, the diffraction direction is the X-axis direction. Therefore, on the light-receiving surface 302a of the PSD 302 (position-sensitive detector) that receives this reflected light, the diffracted light of the monitor light L1 is not aligned in the scanning direction of the monitor light L1 accompanying the rotation of the movable part 103. Therefore, the provision of the ribs 131 suppresses bending of the movable part 103, and the rotational position of the movable part 103 can be accurately detected from the output of the PSD 302.

[0102] As shown in FIG. 9B, the rib 131 extends without steps to the outside of the irradiation area A1 in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0.

[0103] As a result, even if the monitor light L1 is irradiated in a direction shifted in the Y-axis direction from the intended irradiation area A1 due to an assembly error or the like, the monitor light L1 is not diffracted in a direction parallel to the upper surface 103 a of the movable part 103 and substantially perpendicular to the rotation axis R0. This increases the robustness of the position detection of the PSD 302, enabling stable detection of the rotation position of the movable part 103.

[0104] As shown in FIG. 9B, the portion of the rib 131 extending outside the irradiation area A1 extends linearly in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0.

[0105] As a result, the portion of the rib 131 extending outside the irradiation area A1 does not produce diffraction in a direction parallel to the upper surface 103 a of the movable part 103 and perpendicular to the rotation axis R0. Therefore, even if the monitor light L1 is irradiated in a direction shifted in the Y-axis direction from the original irradiation area A1 due to an assembly error or the like, the rotation position of the movable part 103 can be stably detected.

[0106] <Modification 3> Fig. 10(a) is a diagram schematically showing a method of arranging ribs according to Modification 3. Fig. 10(a) shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0107] As shown in FIG. 10( a), in Modification Example 3, two ribs 131a and 131b are arranged. The rib 131a extends smoothly across the entire irradiation area A1. The rib 131a has the same configuration as the rib 131 in FIG. 9( a) according to Modification Example 1. The rib 131b extends at a constant height to the outer periphery of the movable part 103 in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0 (the Y-axis direction in FIG. 10( a)). Therefore, the rib 131b is continuous in this direction without any steps. The heights of the ribs 131a and 131b are equal to each other.

[0108] <Effects of Modification Example 3> According to the configuration of Modification Example 3, the rib 131a has the same configuration as the rib 131 according to Modification Example 1 shown in FIG. 9(a), and therefore the same effects as those of Modification Example 1 can be achieved.

[0109] Furthermore, since the ribs 131b are disposed at the ends of the movable part 103 in the positive and negative directions of the Y axis, which are prone to bending due to rotation, bending of these parts can be suppressed, thereby enabling stable scanning of the light incident on the reflecting surface M1a.

[0110] The rib 131b extends without a step from the rib 131a to the outside of the irradiation area A1 in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0.

[0111] As a result, even if the monitor light L1 is irradiated in a direction shifted in the Y-axis direction from the intended irradiation area A1 due to an assembly error or the like, the monitor light L1 is not diffracted in a direction parallel to the upper surface 103 a of the movable part 103 and perpendicular to the rotation axis R0. This increases the robustness of the position detection of the PSD 302, enabling stable detection of the rotation position of the movable part 103.

[0112] The rib 131b extending to the outside of the irradiation area A1 extends linearly in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0.

[0113] As a result, the ribs 131b extending outside the irradiation area A1 do not produce diffraction in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0. Therefore, even if the monitor light L1 is emitted in a position shifted from the intended irradiation area A1 due to an assembly error or the like, the rotation position of the movable part 103 can be stably detected.

[0114] <Modification 4> Fig. 10(b) is a diagram schematically illustrating a method of arranging ribs according to Modification 4. Fig. 10(b) shows a plan view of the movable part 103 as viewed from the bottom side (Z-axis negative side).

[0115] Compared to the configuration in Fig. 10(a), the configuration in Fig. 10(b) has an annular rib 131c that surrounds the rib 131a. The rib 131c is arranged in an annular shape along the outer periphery of the movable part 103. The height of the rib 131c is constant over the entire circumference. The inner rib 131a and the outer rib 131b are connected by the rib 131b. The configuration of the rib 131b is the same as the rib 131b in Fig. 10(b). The heights of the ribs 131a, 131b, and 131c are equal to each other.

[0116] <Effects of Modification 4> According to the configuration of Modification 4, the same effects as those of Modification 3 are achieved.

[0117] The optical reflecting element 100 also has a rib 131a (first rib) that extends without steps across the entire area including the irradiation area A1, and a ring-shaped rib 131c (second rib) that surrounds the rib 131a (first rib).

[0118] As a result, the rotational position of the movable part 103 can be detected by the monitor light L1 reflected by the lower surface of the rib 131a (first rib) which has no step. Furthermore, since the rib 131a (first rib) is arranged over a wide area near the center of the movable part 103, deflection of the movable part 103 (warping of the reflecting surface M1a) can be suppressed over a wide area near the center of the upper surface 103a of the movable part 103. Furthermore, the annular rib 131c (second rib) surrounding the rib 131a (first rib) can reinforce the outer periphery of the movable part 103. This further suppresses deflection of the movable part 103 (warping of the reflecting surface M1a) near the outer periphery of the movable part 103.

[0119] Optical reflecting element 100 also includes rib 131b (third rib) that connects rib 131a (first rib) and rib 131c (second rib) in a direction parallel to upper surface 103a of movable portion 103 and perpendicular to rotation axis R0.

[0120] According to this configuration, the rib 131a (first rib) and the rib 131c (second rib) are connected and integrated by the rib 131b (third rib), thereby increasing the strength of the entire movable part 103. Therefore, warping of the reflecting surface M1a can be more reliably suppressed. Furthermore, because the rib 131b (third rib) extends in a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0, even if the monitor light L1 is irradiated in a direction shifted from the intended irradiation area A1 due to an assembly error or the like and falls on the rib 131b (third rib), the monitor light L1 is not diffracted in this direction. Therefore, the rotation position of the movable part 103 can be stably detected.

[0121] The heights of the rib 131a (first rib), the rib 131c (second rib), and the rib 131b (third rib) are constant and equal to each other.

[0122] This allows the rib 131a (first rib), the rib 131c (second rib), and the rib 131b (third rib) to be smoothly formed by the same process.

[0123] In the configurations of Modifications 1 to 4, the area where the ribs 131 are arranged is wider than in the embodiment of Fig. 7A, so the movable part 103 is heavier than in the embodiment. Therefore, from the viewpoint of making the movable part 103 lighter and improving the drive response, the configuration of the above embodiment is preferable.

[0124] Furthermore, the rib 131 of modified example 2 and the rib 131b of modified examples 3 and 4 may extend in a direction slightly inclined from a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0 (a direction within an angle range of ±α centered on a direction parallel to the upper surface 103a of the movable part 103 and perpendicular to the rotation axis R0), as described with reference to Figure 8, similar to the rib 131 of Figure 7(a) relating to the embodiment.

[0125] Furthermore, the rib 131b may be omitted from the configuration of the fourth modified example shown in FIG. 10(b).

[0126] <Other Modifications> The ribs 131, 131 a in the irradiation area A1 do not have to be connected at the same height in a direction parallel to the upper surface 103 a of the movable part 103 and substantially perpendicular to the rotation axis R0, and may vary in height as long as diffraction does not occur in this direction. For example, the ribs 131, 131 a may gradually decrease in height from one end to the other in this direction, or may be connected in a curved shape from one end to the other in this direction.

[0127] 9(a) and 10(a) and 10(b) (Modifications 1, 3, and 4), the ribs 131 and 131a are arranged in an area slightly wider than the irradiation area A1 in plan view, but the ribs 131 and 131a may be arranged in an area the same size as the irradiation area A1 in plan view. Furthermore, the shape of the ribs 131 and 131a in Modifications 1, 3, and 4 may be a circle, an ellipse, a square, a rectangle, a track shape, or the like in plan view.

[0128] In the configuration of FIG. 9B (modification example 2), the width of the rib 131 in the X-axis direction may be the same as the width of the irradiation area A1 in the X-axis direction.

[0129] 7A, the ribs 131 extend to the outside of the irradiation area A1 at the same height, but there may be a step in the area of ​​the ribs 131 outside the irradiation area A1. In this case, it is preferable that the step be positioned so that the monitor light L1 is not incident on the ribs 131 if, due to an assembly error or the like, the monitor light L1 is irradiated in a position that is shifted in the Y-axis direction from the original irradiation area A1. This also applies to the configurations of Modifications 1 to 4.

[0130] In the above embodiment, a semiconductor laser is used as the light source of the light source 301, but the present invention is not limited to this, and for example, a light emitting diode may be used as the light source.

[0131] Furthermore, the devices to which the optical reflecting element 100 and the optical deflector 10 are applied are not limited to head-up displays, and the optical reflecting element and optical deflector of the present invention can be used in various devices that require a configuration to scan light by rotating the reflecting surface M1a.

[0132] The embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical idea defined in the claims.

[0133] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0134] (Technology 1) An optical reflecting element comprising: a flat movable part that rotates about a rotation axis; a reflective surface arranged on the upper surface of the movable part for scanning light; and at least one rib arranged on the lower surface of the movable part for suppressing deflection of the movable part, wherein the ribs are arranged without steps in an irradiation area on the lower surface where monitor light is irradiated to detect operation of the movable part, at least in a direction parallel to the upper surface and approximately perpendicular to the rotation axis.

[0135] According to this technology, the monitor light reflected by the lower surface of the movable part is not diffracted in at least a direction parallel to the upper surface of the movable part and substantially perpendicular to the rotation axis. Therefore, on the light-receiving surface of the position-sensitive detector that receives this reflected light, the diffracted light of the reflected light is not aligned in the scanning direction of the reflected light that accompanies the rotation of the movable part. Therefore, the rotational position of the movable part can be accurately detected from the output of the position-sensitive detector while suppressing the deflection of the movable part by providing a rib.

[0136] (Technology 2) The optical reflecting element according to Technology 1, wherein the height of the ribs in the irradiation area is constant in the direction parallel to the upper surface and substantially perpendicular to the rotation axis.

[0137] According to this technique, diffraction in a direction parallel to the upper surface of the movable portion and substantially perpendicular to the rotation axis can be reliably suppressed.

[0138] (Technology 3) In the optical reflecting element described in Technology 1 or 2, the rib in the irradiation area has a wall shape that extends linearly in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

[0139] According to this technology, the monitor light irradiated onto the illumination area is guided to and reflected by the rib-free area on the underside of the movable part, and by receiving this reflected light with a position detection element, the rotational position of the movable part can be detected with high accuracy.

[0140] (Technology 4) The optical reflecting element according to Technology 3, wherein the plurality of linearly extending ribs are arranged side by side in a direction parallel to the rotation axis.

[0141] According to this technique, the deflection of the movable part can be effectively suppressed by the multiple ribs.

[0142] (Technology 5) The optical reflecting element according to Technology 1 or 2, characterized in that the rib extending without steps across the entire irradiation area is disposed on the lower surface.

[0143] According to this technology, the monitor light irradiated onto the irradiation area is reflected by the stepless underside of the rib. Therefore, by receiving this reflected light with a position detection element, the rotational position of the movable part can be detected with high accuracy. Furthermore, since the rib is disposed over a wide area near the center of the movable part corresponding to the irradiation area, deflection of the movable part (warping of the reflective surface) can be suppressed over a wide area near the center of the upper surface of the movable part. Therefore, the light incident on the reflective surface on the upper surface of the movable part can be scanned stably and accurately by rotating the movable part.

[0144] (Technology 6) An optical reflecting element according to any one of technologies 1 to 5, characterized in that the rib extends without steps to the outside of the irradiation area in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

[0145] According to this technology, even if the monitor light is irradiated in a region that is shifted from the intended irradiation region due to an assembly error or the like, the monitor light is not diffracted in a direction parallel to the upper surface of the movable part and substantially perpendicular to the rotation axis, thereby improving the robustness of position detection of the optical reflecting element and enabling stable detection of the rotation position of the movable part.

[0146] (Technology 7) In the optical reflecting element described in Technology 6, the portion of the rib extending outside the irradiation area extends linearly in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

[0147] According to this technology, the rib extending outside the illumination area does not cause diffraction in a direction parallel to the upper surface of the movable part and substantially perpendicular to the rotation axis, so that the rotation position of the movable part can be reliably detected even if the monitor light is irradiated in a direction shifted from the intended illumination area due to assembly errors or the like.

[0148] (Technology 8) An optical reflecting element according to Technology 1 or 2, characterized in that the at least one rib comprises a first rib that extends without steps across the entire area including the irradiation area, and a ring-shaped second rib that surrounds the first rib.

[0149] This technology allows the rotational position of the movable part to be detected by the monitor light reflected by the step-free underside of the first rib. Furthermore, because the first rib is disposed over a wide area near the center of the movable part, deflection of the movable part (warping of the reflective surface) can be suppressed over a wide area near the center of the upper surface of the movable part. Furthermore, the annular second rib surrounding the first rib reinforces the area near the outer periphery of the movable part. This further suppresses deflection of the movable part (warping of the reflective surface) near the outer periphery of the movable part.

[0150] (Technology 9) The optical reflecting element described in Technology 8, further comprising a third rib as the at least one rib, the third rib connecting the first rib and the second rib in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

[0151] According to this technology, the first and second ribs are connected and integrated by the third rib, thereby increasing the strength of the entire movable part. This more reliably suppresses warping of the reflective surface. Furthermore, because the third rib extends parallel to the top surface of the movable part and approximately perpendicular to the rotation axis, even if the monitor light is irradiated in a direction that deviates from the intended irradiation area and falls on the third rib due to assembly errors or the like, the monitor light is not diffracted in this direction. Therefore, the rotation position of the movable part can be reliably detected.

[0152] (Technology 10) The optical reflecting element according to Technology 9, wherein the heights of the first rib, the second rib, and the third rib are constant and equal to each other.

[0153] According to this technique, the first rib, the second rib, and the third rib can be smoothly formed by the same process.

[0154] (Technology 11) An optical deflector comprising: an optical reflecting element according to any one of technologies 1 to 10; a light source that emits the monitor light; and a position detection element that receives the monitor light reflected by the lower surface and detects the reception position of the monitor light on the light receiving surface.

[0155] According to this technique, similar to the techniques 1 to 10, the rib is provided to suppress the deflection of the movable part, and the rotational position of the movable part can be detected with high accuracy from the output of the position detection element.

[0156] REFERENCE SIGNS LIST 10 Optical deflector 100 Optical reflecting element 103 Movable part 103a Upper surface 103b Lower surface 131 Rib 131a Rib (first rib) 131b Rib (third rib) 131c Rib (second rib) A1 Irradiation area L1 Monitor light M1a Reflection surface

Claims

1. An optical reflecting element comprising: a flat movable part that rotates about a rotation axis; a reflective surface arranged on an upper surface of the movable part for scanning light; and at least one rib arranged on a lower surface of the movable part for suppressing deflection of the movable part, wherein in an illumination area of ​​the lower surface where monitor light is irradiated to detect the operation of the movable part, the ribs are connected without steps at least in a direction parallel to the upper surface and approximately perpendicular to the rotation axis.

2. An optical reflecting element as described in claim 1, characterized in that the height of the ribs within the irradiation area is constant in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

3. An optical reflecting element as described in claim 1, characterized in that the rib in the irradiation area has a wall shape extending linearly in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

4. An optical reflecting element according to claim 3, characterized in that the plurality of linearly extending ribs are arranged side by side in a direction parallel to the rotation axis.

5. An optical reflecting element according to claim 1, characterized in that the rib, which extends across the entire irradiation area without any steps, is disposed on the lower surface.

6. An optical reflecting element as described in claim 1, characterized in that the rib extends without steps to the outside of the irradiation area in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

7. An optical reflecting element as described in claim 6, characterized in that the portion of the rib extending outside the irradiation area extends linearly in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

8. An optical reflecting element as described in claim 1, characterized in that the at least one rib comprises a first rib that extends without steps over the entire area including the irradiation area, and a ring-shaped second rib that surrounds the first rib.

9. An optical reflecting element as described in claim 8, further comprising, as the at least one rib, a third rib connecting the first rib and the second rib in the direction parallel to the upper surface and approximately perpendicular to the rotation axis.

10. An optical reflecting element according to claim 9, wherein the heights of the first rib, the second rib and the third rib are constant and equal to each other.

11. An optical deflector comprising: an optical reflecting element according to any one of claims 1 to 10; a light source which emits the monitor light; and a position detection element which receives the monitor light reflected by the lower surface and detects the receiving position of the monitor light on the light receiving surface.

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