Light reflector

Abstract

To provide a light reflector with a stable swinging range.SOLUTION: A light reflector is provided, comprising: a support body; a swinging body 26 supported by the support body in a manner that allows the swinging body to swing about a swing axis, the swinging body having a first surface 26A including a reflective area and a second surface 26B on a side opposite the first surface; and first and second protrusions 31, 32, each being provided on at least either of the first surface and the second surface of the swinging body to be spaced apart and facing each other across the swing axis.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a light reflector that reflects light.

Background Art

[0002] Conventionally, a scanning device that performs optical scanning of an object to obtain information regarding the distance, shape, etc. to the object has been known. The scanning device has, for example, a movable mirror that emits scanning light toward the object while deflecting it in a direction-variable manner. For example, Patent Document 1 discloses an optical device including a plate-shaped movable part and a reflective film formed on the movable part.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The scanning device has a scanning area corresponding to the movable range of the movable mirror. For example, when a rotary mirror is used as the light deflection element, the scanning area is an area corresponding to the maximum rotation angle of the mirror. However, during the period when the mirror is rotating at the maximum rotation angle or an angular position near it, the rotational stability may decrease. Examples of the case where the rotational stability decreases include, for example, the case where the maximum rotation angle of the mirror varies for each rotation cycle.

[0005] In this case, the emission direction of the light corresponding to the maximum rotation angle of the mirror may be different from the designed direction, and as a result, light may not be emitted at the designed position or coordinates within the scanning area. In this case, the scanning area may shrink or expand unstably, or the outer edge shape thereof may deform unstably.

[0006] In this case, for example, scanning information obtained from a portion of an unstable scanning area may be information that cannot be treated as valid scanning information. Also, there may be a case where it is inevitable to set an area smaller than the area corresponding to the entire range of the light emitted from the mirror as the valid scanning area.

[0007] The present invention has been made in view of the above points, and one of its objectives is to provide a light reflector having a stable rotation range.

Means for Solving the Problems

[0008] The invention according to claim 1 includes a support, a rotating body supported by the support so as to rotate around a rotation axis, having a first surface including a light-reflective area and a second surface opposite to the first surface, and first and second protrusions each provided on at least one of the first surface and the second surface of the rotating body, spaced apart from each other and facing each other across the rotation axis.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 5

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Figure 10

Figure 11

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail.

Embodiment

[0011] FIG. 1 is a schematic layout diagram of a scanning device 10 according to Example 1. In this embodiment, the scanning device 10 is a scanning type distance measuring device that performs optical scanning of a predetermined region (hereinafter referred to as a scanning region) R0 and measures the distance to an object OB existing within the scanning region R0. The configuration of the scanning device 10 will be described with reference to FIG. 1. Note that FIG. 1 schematically shows the scanning region R0 and the object OB.

[0012] The scanning device 10 has a light source 11 that generates and emits, for example, pulsed light as primary light L1. In this embodiment, the light source 11 generates laser light having a peak wavelength in the infrared region as the primary light L1 and emits this intermittently.

[0013] The scanning device 10 has a rotating element 12 that rotates around rotation axes (second and first rotation axes) AX and AY orthogonal to each other and reflects the primary light L1 emitted from the light source 11 toward the scanning region R0. In this embodiment, the rotating element 12 functions as a deflecting element that deflects the emitted light L1 in a direction-variable manner. The rotating element 12 emits the reflected emitted light L1 as secondary light L2. The secondary light L2 becomes scanning light for scanning the scanning region R0.

[0014] In this embodiment, the rotating element 12 is a rotating mirror having one light reflecting surface 12S that rotates around the rotation axes AX and AY. Further, the light reflecting surface 12S of the rotating element 12 has reflectivity at least with respect to the primary light L1.

[0015] Further, the rotating element 12 is configured such that the light reflecting surface 12S rotates periodically. Therefore, the emission direction of the secondary light L2 emitted from the rotating element 12 changes periodically. The region irradiated with the secondary light L2 within the change period of the emission direction of the secondary light L2 becomes the scanning region R0.

[0016] For example, the scanning region R0 is a virtual three-dimensional space where the secondary light L2 is emitted. In FIG. 1, the outer edge of the scanning region R0 is schematically shown by a broken line. For example, the scanning region R0 can be defined as a conical space having a height direction range along the height direction D1 corresponding to the axial direction of the rotation axis AY, a width direction range along the width direction D2 corresponding to the axial direction of the rotation axis AX, and a depth direction range along the depth direction corresponding to the axial direction of the optical axis of the scanning light L2 reflected by the light reflecting surface 12S when not rotating.

[0017] For example, the normal vector of the light reflecting surface 12S of the rotating element 12 changes periodically according to the rotation of the rotating element 12. Further, in the present embodiment, the light source 11 emits the primary light L1 toward the rotating element 12 so that the primary light L1 is incident on the light reflecting surface 12S of the rotating element 12 during rotation.

[0018] Therefore, for example, the height direction range of the scanning region R0 corresponds to the change range of the component in the axial direction of the rotation axis AY in the axial direction of the optical axis of the primary light L1 and the axial direction of the optical axis of the secondary light L2 determined by the normal vector of the light reflecting surface 12S of the rotating element 12 at the time of incidence of the primary light L1. Further, the width direction range of the scanning region R0 corresponds to the change range of the component in the axial direction of the rotation axis AX in the axial direction of the secondary light L2. Further, the depth direction range of the scanning region R0 corresponds to the range of the distance within which the secondary light L2 can maintain a predetermined intensity (intensity detectable by the scanning device 10).

[0019] Also, when a virtual plane separated from the rotating element 12 by a predetermined distance within the scanning region R0 is defined as the scanning plane R1, the scanning plane R1 can be defined as a two-dimensional region extending along the height direction D1 and the width direction D2. The secondary light L2 is emitted toward the scanning region R0 so as to scan this scanning plane R1.

[0020] Also, as shown in FIG. 1, when an object OB (i.e., an object or substance having reflectivity or scatterability with respect to the secondary light L2) exists in the scanning region R0, the secondary light L2 is reflected or scattered by the object OB. A part of the secondary light L2 reflected by the object OB travels as the tertiary light L3 in substantially the same optical path as the secondary light L2 in the direction opposite to the secondary light L2 and returns to the rotation element 12.

[0021] The scanning device 10 includes a separation element 13 provided on the optical path of the primary light L1 for separating the primary light L1 and the tertiary light L3, and a light receiving element 14 for receiving the separated tertiary light L3. The separation element 13 is, for example, a beam splitter that reflects the primary light L1 and transmits the tertiary light L3.

[0022] In this embodiment, the light receiving element 14 receives the tertiary light L3 that is projected through the rotation element 12, reflected by the object OB, and passes through the rotation element 12. Further, the light receiving element 14 has at least one detection element that detects the tertiary light L3 and generates an electrical signal indicating the detection result of the tertiary light L3, for example, the intensity value of the tertiary light L3. The scanning device 10 generates the electrical signal generated by the light receiving element 14 as the scanning result of the scanning region R0.

[0023] Although not shown, the scanning device 10 may have, for example, an optical system provided on the optical path of the primary light L1 between the light source 11 and the rotation element 12 for shaping the primary light L1. Further, the scanning device 10 may have an optical system provided on the optical path of the tertiary light L3 between the separation element 13 and the light receiving element 14 for condensing the tertiary light L3. These optical systems include, for example, at least one lens and may include a filter.

[0024] The scanning device 10 includes a control unit 15 that drives and controls the light source 11, the rotation element 12, and the light receiving element 14. The control unit 15 includes a light source control unit 15A that drives and controls the light source 11, a rotation element control unit 15B that drives and controls the rotation element 12, and a light receiving element control unit 15C that drives and controls the light receiving element 14.

[0025] Further, the control unit 15 has a distance measuring unit 15D that measures the distance to the object OB based on the light reception result of the third-order light L3 by the light receiving element 14. In the present embodiment, the distance measuring unit 15D detects a pulse indicating the third-order light L3 from the electrical signal generated by the light receiving element 14. Further, the distance measuring unit 15D measures the distance to the object OB (or a surface area of a part thereof) by the time-of-flight method based on the time difference between the emission timing of the second-order light L2 and the light reception timing of the third-order light L3. Further, the distance measuring unit 15D generates data (distance measurement data) indicating the measured distance information.

[0026] Further, in the present embodiment, the distance measuring unit 15D divides the scanning region R0 (scanning surface R1) into a plurality of distance measuring points (scanning points), and generates an image (distance measurement image) of the scanning region R0 showing the distance measurement results (distance values) of each of the plurality of distance measuring points as pixels. In the present embodiment, the distance measuring unit 15D associates information indicating the displacement between the distance measuring point and the light reflecting surface 12S of the rotating element 12, and generates image data showing a two-dimensional map or a three-dimensional map of the scanning region R0.

[0027] Further, the distance measuring unit 15D sets, for example, the change period of the emission direction of the second-order light L2 as the scanning period that is the period for scanning the scanning region R0, and generates one distance measurement image for each scanning period. Note that the distance measuring unit 15D may be connected to a display unit (not shown) that displays the distance measurement image, and may be configured to transmit the distance measurement image to the display unit.

[0028] FIG. 2 is a schematic perspective view of the rotating element 12. In the present embodiment, the rotating element 12 is a MEMS (Micro Electro Mechanical System) mirror configured such that the light reflecting surface 12S rotates around the rotation axes AX and AY.

[0029] First, in the present embodiment, the rotating element 12 has a base 21 and an annular fixed frame 22 fixed to the base 21. The fixed frame 22 has a rectangular plate-like outer shape, and is supported by the base 21 at the outer peripheral portion of one plate surface thereof.

[0030] The rotation element 12 has a first support portion 23 composed of first and second torsion bars 23A and 23B that are each provided on the inner peripheral portion of the fixed frame 22 and extend along the x-direction so as to face each other in the first direction (hereinafter referred to as the x-direction). In the present embodiment, each of the first and second torsion bars 23A and 23B has elasticity.

[0031] The rotation element 12 is supported by the first support portion 23 at its outer peripheral portion and has an annular rotation frame 24 that rotates around a first rotation axis (an axis corresponding to the rotation axis AX, hereinafter referred to as the rotation axis AX) having the x-direction as the axial direction.

[0032] In the present embodiment, the rotation frame 24 is elastically supported at the end portions of the first and second torsion bars 23A and 23B on the side opposite to the fixed frame 22. Also, in the present embodiment, the rotation frame 24 has an overall rectangular annular shape and has a frame-shaped inner peripheral frame portion 24A at its inner peripheral portion. In the present embodiment, the inner peripheral frame portion 24A has a portion overlapping with the portion forming the outer peripheral portion of the rotation frame 24.

[0033] The rotation element 12 has a second support portion 25 composed of third and fourth torsion bars 25A and 25B that are each provided on the inner peripheral portion of the movable frame 24 and extend along the y-direction so as to face each other in the second direction (hereinafter referred to as the y-direction) perpendicular to the x-direction. In the present embodiment, each of the third and fourth torsion bars 25A and 25B has elasticity.

[0034] The rotation element 12 is supported by the second support portion 25 at its outer peripheral portion and has a disk-shaped rotation plate 26 that rotates around a second rotation axis (an axis corresponding to the rotation axis AY, hereinafter referred to as the rotation axis AY) having the y-direction as the axial direction. Also, the rotation element 12 has a light reflection film 27 that is provided concentrically with the rotation plate 26 on one plate surface of the rotation plate 26 and has light reflectivity with respect to the primary light L1. In the present embodiment, the light reflection film 27 constitutes the light reflection surface 12S in the rotation element 12.

[0035] Further, the rotating element 12 has a drive source 28 that generates a rotational force for rotating the rotating frame 24 and the rotating plate 26. In the present embodiment, the drive source 28 includes a first permanent magnet 28A provided on the base 21 and arranged so as to sandwich the fixed frame 22 in the y direction, and a first coil 28B formed on the outer peripheral portion of the movable frame 24 and wired so as to surround the rotating plate 26 on the outer peripheral portion and be disposed inside the first permanent magnet 28A. The first permanent magnet 28A and the second coil 28B generate a rotational force for rotating the rotating frame 24 and the rotating plate 26 around the rotation axis AX.

[0036] Also, in the present embodiment, the drive source 28 includes a second permanent magnet 28C provided between the rotating plate 26 and the base 21 on the base 21, and a second coil 28D wired so as to surround the rotating plate 26 on the inner peripheral portion 24A of the rotating frame 24. The second permanent magnet 28C and the second coil 28D generate a rotational force for rotating the rotating plate 26 around the rotation axis AY.

[0037] Further, in the present embodiment, the rotating frame 24 has two openings 24B provided so as to sandwich the rotating plate 26 in the x direction. Also, the drive source 28 has two magnetic bodies 28E that extend in the z direction so as to be inserted into the openings 24B of the rotating frame 24 on the base 21 and are arranged so as to sandwich the second permanent magnet 28C and the second coil 28D in the x direction.

[0038] Also, the rotation element control unit 15B in the control unit 15 is connected to the first and second coils 28B and 28D, and applies a voltage to the first and second coils 28B and 28D as a drive signal.

[0039] By applying voltage to the first and second coils 28B and 28D, a rotational force for the rotating frame 24 and the rotating plate 26 is generated based on the magnetic fields generated by the first and second permanent magnets 28A and 28C and the current flowing through the first and second coils 28B and 28D. For example, based on the current flowing through the first coil 28B and the magnetic field in the y direction generated between the first permanent magnet 28A, a rotational force around the rotation axis AX with respect to the rotating frame 24 is generated.

[0040] Also, in the present embodiment, based on the current flowing through the second coil 28D and the magnetic field generated between the second permanent magnet 28C and the magnetic body 28E, a rotational force around the rotation axis AY with respect to the rotating frame 24 is generated, and accordingly the rotating plate 26 rotates around the rotation axis AY.

[0041] In this way, the rotation element control unit 15B functions as a drive circuit that rotates the rotating plate 26 (and the light reflecting surface 12S) around the rotation axes AX and AY by driving the drive source 28.

[0042] In the present embodiment, the rotation element control unit 15B applies voltage to the first and second coils 28B and 28D so that the rotating plate 24 rotates in a non-resonant mode around the rotation axis AX and rotates while resonating around the rotation axis AY.

[0043] Specifically, for example, the rotation element control unit 15B applies a voltage whose voltage value periodically changes at a frequency different from the frequency for resonating the rotating frame 24 and the rotating plate 26 to the first coil 28B, for example, a sawtooth wave-shaped voltage whose voltage value changes at a frequency lower than the resonance frequency. On the other hand, the rotation element control unit 15B applies a voltage whose voltage value periodically changes at a frequency corresponding to the resonance frequency of the rotating frame 24 and the rotating plate 26 to the second coil 28D, for example, a sine wave-shaped voltage.

[0044] In the following description, the direction perpendicular to the x - direction and the y - direction may be referred to as the z - direction. For example, the z - direction corresponds to the normal direction of the rotating plate 26 or the light - reflecting surface 12S when not rotating. The primary light L1 is incident on the light - reflecting surface 12S along a direction having a component in the z - direction, for example.

[0045] FIG. 3 and FIG. 4 are plan views of the vicinity of the rotating plate 26 in the rotating element 12. FIG. 3 is a plan view showing the plate surface (hereinafter, may be referred to as the first surface or the front surface) 26A of the rotating plate 26 on which the light - reflecting film 27 is provided. FIG. 4 is a plan view showing the plate surface (hereinafter, may be referred to as the second surface or the back surface) 26B on the opposite side of the plate surface 26A of the rotating plate 26.

[0046] Also, FIG. 5 is a cross - sectional view taken along the line 5 - 5 of FIG. 3 and is a cross - sectional view of the rotating plate 26 along the rotation axis AX. The configuration of the vicinity of the rotating plate 26 in the rotating element 12 will be described with reference to FIGS. 3 to 5.

[0047] First, as shown in FIGS. 3 and 5, in this embodiment, the rotating element 12 has a surface protrusion group 30 composed of first and second surface protrusions (first and second protrusions) 31 and 32 that each protrude in the z - direction (the direction perpendicular to the surface of the light - reflecting film 27) at the outer edge of the surface of the light - reflecting film 27.

[0048] In this embodiment, each of the first and second surface protrusions 31 and 32 is composed of one protrusion formed continuously in a curved shape along the outer edge of the light - reflecting film 27. Also, the first and second surface protrusions 31 and 32 are arranged apart from each other with the rotation axis AY interposed therebetween. Further, each of the first and second surface protrusions 31 and 32 has a shape symmetric with respect to the rotation axis AX. Also, the first and second surface protrusions 31 and 32 are arranged at symmetric positions with respect to the rotation axis AY.

[0049] Also, as shown in FIGS. 4 and 5, in this embodiment, the rotating element 12 has a back surface protrusion group 40 composed of first, second, and third back surface protrusions (third, fourth, and fifth protrusions) 41, 42, and 43 that each protrude in the z direction (a direction perpendicular to the back surface 26B of the rotating plate 26) from the back surface 26B of the rotating plate 26.

[0050] In this embodiment, the first and second back surface protrusions 41 and 42 are respectively provided at positions facing the first and second surface protrusions 31 and 32 with the rotating plate 26 interposed therebetween. Also, the third back surface protrusion 43 is provided in a region 26BB of the back surface 26B of the rotating plate 26 that faces the light reflecting film 27.

[0051] The first and second back surface protrusions 41 and 42 are each formed so as to extend in a curved shape, similar to each of the first and second surface protrusions 31 and 32. Also, the first and second back surface protrusions 41 and 42 are spaced apart from each other with the rotation axis AY interposed therebetween. Also, each of the first and second back surface protrusions 41 and 42 has a shape that is symmetric with respect to the rotation axis AX. Also, the first and second back surface protrusions 41 and 42 are arranged at symmetric positions with respect to the rotation axis AY.

[0052] Also, in this embodiment, the third back surface protrusion 43 has a shape that is symmetric with respect to each of the rotation axes AX and AY. Also, in this embodiment, the third back surface protrusion 43 is formed in a mesh shape or a lattice shape on the back surface 26B of the rotating plate 26.

[0053] Also, as shown in FIG. 5, the surface protrusion group 30 is smaller and thinner than the back surface protrusion group 40. More specifically, for example, the width W1 of the first surface protrusion 31 is narrower than the width W2 of the first back surface protrusion 41. Also, the height H1 of the first surface protrusion 31 is lower than the height H2 of the first back surface protrusion 41.

[0054] For example, the rotating plate 26 is integrally formed together with the fixed frame 22, the first support portion 23, the rotating frame 24, and the second support portion 25. These can be formed by processing a semiconductor substrate such as a silicon substrate, for example.

[0055] Also, the back surface protrusion group 40 can be formed by processing a semiconductor substrate different from the semiconductor substrate for forming the rotating plate 26 and bonding the processed substrate to the back surface 26B of the rotating plate 26. That is, in the present embodiment, the first, second, and third back surface protrusion portions 41, 42, and 43 are integrally formed.

[0056] On the other hand, the front surface protrusion group 30 is formed of the same material as and by the same process as the first and second coils 28B and 28D of the drive source 28, for example. For example, the front surface protrusion group 30 is made of copper plating.

[0057] Therefore, for example, the width W1 and height H1 of the front surface protrusion group 30 (for example, the first front surface protrusion portion 31) are less than or equal to half of the width W2 and height H2 of the back surface protrusion group 40 (for example, the first back surface protrusion portion 41). Also, in the present embodiment, the width W1 and height H1 of the front surface protrusion group 30 are smaller than the thickness T1 of the rotating plate 26.

[0058] For example, the width W1 and height H1 of the first front surface protrusion portion 31 are each about 20 μm. On the other hand, the width W2 and height H2 of the first back surface protrusion portion 41 are about 40 μm and 140 μm, respectively. Also, the thickness T1 of the rotating plate 26 is about 40 μm.

[0059] FIG. 6 is a diagram showing a schematic configuration of a system for measuring the emission range of the secondary light L2. In the present embodiment, a screen SC having a small hole is prepared, the light source 11 is arranged so that the primary light L1 passes through this hole, and the rotating element 12 is arranged on the side opposite to the light source 11 of the screen SC.

[0060] Then, after driving the rotating element 12 to periodically rotate the rotating plate 26, the light source 11 was driven to emit the primary light L1. Then, the angular range (hereinafter referred to as the stable rotation angle) SA around the rotation axis AY where the secondary light L2 on the screen SC is stably emitted was measured. Specifically, the rotation angle of the rotating plate 26 was gradually increased, and the rotation angle of the rotating plate 26 at which the variation in the irradiation width of the secondary light irradiated on the screen SC in the x direction becomes equal to or less than a predetermined value was defined as the stable rotation angle SA.

[0061] FIG. 7 is a diagram showing the measurement results. FIG. 7 is a diagram showing the stable rotation angle SA in the scanning device 10 according to the present embodiment including the rotating element 12 and the scanning device 100 according to a comparative example including a rotating element 101 having the same configuration as the rotating element 12 except that the surface protrusion group 30 is not provided on the rotating plate 26. Further, FIG. 7 shows the measurement results of the change in the stable rotation angle SA when the ambient temperature around the rotating elements 12 and 101 is changed.

[0062] First, as shown in FIG. 7, it can be seen that at all ambient temperatures, the stable rotation angle SA of the rotating element 12 is greater than the stable rotation angle SA of the rotating element 101. This is presumably because the provision of the surface protrusion group 30 stabilizes the gas flow in the atmosphere near the rotating plate 26 when the rotating plate 26 rotates.

[0063] More specifically, every time the rotating plate 26 rotates, it displaces the gas around it. And the faster the rotation speed of the rotating plate 26, the more easily the gas flow (airflow) displaced by the rotating plate 26 is disturbed. This is presumably due to the generation of turbulent flow in the airflow.

[0064] In particular, the rotating plate 26 rotates faster as its maximum rotation angle increases. Therefore, the larger the rotation angle of the rotating plate 26, the greater the disturbance of the airflow near the rotating plate 26. Therefore, the inventor of the present application considered that the stable rotation angle SA of the rotation angle could be increased by stabilizing the gas flow around the rotating plate 26.

[0065] For example, in the present embodiment, the surface protrusion group 30 is disposed opposite to each other with the rotation axis AX interposed therebetween and has a shape symmetric with respect to the rotation axis AX. As a result, the gas pushed away by the rotating plate 26 during rotation is likely to move stably in the y direction (the direction along the rotation axis AY). Further, since the surface protrusion group 30 also has a shape symmetric with respect to the rotation axis AY, the control effect of this air flow is high.

[0066] The inventor of the present application believes that, at least at the time of filing the present application, the stable rotation angle SA of the rotating plate 26 could be increased by the surface protrusion group 30 based on such a principle.

[0067] In addition, when the ambient temperature decreases, the viscosity of the gas decreases, so the air flow is likely to be disturbed. Therefore, the lower the ambient temperature, the smaller the stable rotation angle SA. Even in this case, as shown in FIG. 7, it can be seen that the effect of stabilizing the air flow by the surface protrusion group 30 exists at any ambient temperature. Although not shown in FIG. 7, based on the above-described principle, it is presumed that the stable rotation angle SA also increases at other ambient temperatures.

[0068] Similarly, when the atmospheric pressure increases, the gas is likely to be disturbed in the same manner as when the ambient temperature decreases. Even in this case, it is considered that the effect of the surface protrusion group 30 can be obtained. Therefore, it is considered that the stable rotation angle SA increases even when used in various environments. Therefore, the scanning device 10 capable of stably emitting the secondary light L2 over a wide range can be configured by the rotation element 12.

[0069] In the present embodiment, the rotating plate 26 is driven to rotate while resonating around the rotation axis AY. In this case, the rotating plate 26 rotates at a high speed, and the air flow is greatly disturbed. Therefore, when the rotating plate 26 is resonated, the effect of suppressing the disturbance of the air flow by the surface protrusion group 30 is great.

[0070] Also, in this embodiment, a back surface protrusion group 40 is provided on the back surface 26B of the rotating plate 26. Among these back surface protrusion groups 40, the first and second back surface protrusion parts 41 and 42 are considered to have the effect of suppressing the turbulence of the air flow, similar to the front surface protrusion group 30. Further, the third back surface protrusion part 43 has the effect of suppressing the deformation (for example, wavy deformation) of the rotating plate 26 during rotation. Therefore, by providing the back surface protrusion group 40, the more stable rotation angle SA becomes larger, and the deformation of the light reflection film 27 is suppressed, so that the emission direction of the secondary light L2 is stabilized.

[0071] Note that the configuration of the front surface protrusion group 30 is not limited to the above-described case. For example, each of the first and second front surface protrusion parts 31 and 32 may be formed intermittently. FIG. 8 is a plan view showing the front surface 26A of the rotating plate 26 of the rotating element 12A in the scanning device 10A according to the first modification of this embodiment.

[0072] As shown in FIG. 8, the rotating element 12A of the scanning device 10A has the same configuration as the rotating element 12, except that it has a front surface protrusion group 30A composed of the first and second front surface protrusion parts 31A and 32A formed intermittently.

[0073] In this modification, the first front surface protrusion part 31A has a plurality of protrusions P11 and P12 that are opposed to and spaced apart from each other with the rotation axis AX interposed therebetween. Similarly, the second front surface protrusion part 32A has a plurality of protrusions P21 and P22 that are opposed to and spaced apart from each other with the rotation axis AX interposed therebetween.

[0074] Similar to the front surface protrusion group 30, the first and second front surface protrusion parts 31A and 32A may have a plurality of protrusions P11, P12, P21, and P22. Even in this case, the effect of stabilizing the air flow can be obtained.

[0075] In consideration of effectively stabilizing the air flow, it is preferable that protrusions are provided at portions where the displacement amount is the largest and the displacement speed is the largest during the rotation of the rotating plate 26, such as the surface protrusion group 30, for example, at portions on the rotation axis AX, at portions farthest from the rotation axis AY, or at the outer edge portion of the surface 26A of the rotating plate 26. That is, for example, as shown in FIG. 3, it is preferable that the first and second surface protrusions 31 and 32 are formed in a region on the rotation axis AX of the rotating plate 26.

[0076] Also, in the example shown in FIG. 8, each of the protrusions P11, P12, P21, and P22 in each of the first and second surface protrusion portions 31A and 32A is continuously formed linearly. However, each of the first and second surface protrusion portions 31A and 32A may include a plurality of columnar protrusions.

[0077] Also, the surface protrusion group 30 only needs to be provided on the surface 26A of the rotating plate 26. FIG. 9 is a plan view showing the surface 26A of the rotating plate 26 of the rotating element 12B in the scanning device 10B according to Modification 2 of the present embodiment.

[0078] As shown in FIG. 9, the rotating element 12B of the scanning device 10B has the same configuration as the rotating element 12, except that it has a surface protrusion group 30B composed of the first and second surface protrusion portions 31B and 32B formed outside the light reflection film 27.

[0079] In this modification, each of the first and second surface protrusion portions 31B and 32B is formed in a curve along the outer edge of the light reflection film 27 on the surface 26A of the rotating plate 26. Even in this case, the effect of stabilizing the air flow can be obtained.

[0080] In consideration of securely fixing the surface protrusion group 30B onto the rotating plate 26, it is preferable that the surface protrusion group 30B is formed on the light reflection film 27 as shown in this embodiment. This is because when forming the surface protrusion group 30 by metal plating as in this embodiment, by forming it on the light reflection metal as the light reflection film with high affinity to the metal, even minute protrusions like the surface protrusion group 30 can be sufficiently fixed to the rotating plate 26.

[0081] Also, the protrusion for obtaining the effect of stabilizing the air flow may be provided on the back surface 26B of the rotating plate 26. FIG. 10 is a cross-sectional view of the rotating plate 26 of the rotating element 12C in the scanning device 10C according to Modification 3 of this embodiment.

[0082] As shown in FIG. 10, the rotating element 12C of the scanning device 10C has the same configuration as the rotating element 12 except that no protrusion is provided on the front surface 26A of the rotating plate 26 and except for the configuration of the back surface protrusion group 40A.

[0083] In this modification, the back surface protrusion group 40A has first and second back surface protrusions 41A and 42A having the same configuration as the first and second surface protrusions 31 and 32 in the surface protrusion group 30. That is, each of the first and second back surface protrusions 41A and 42A is provided on the back surface 26B of the rotating plate 26, faces each other across the rotation axis AY, and is spaced apart from each other. Also, each of the first and second back surface protrusions 41A and 42A is made of, for example, the same material as the surface protrusion group 30, such as copper plating.

[0084] By providing the back surface protrusion group 40A on the back surface 26B of the rotating plate 26 as in this modification, it is also possible to suppress the disturbance of the air flow during rotation. That is, for the rotating element 12, for example, it is sufficient if the surface protrusion group 30 (the first and second surface protrusions 31 and 32) or the back surface protrusion group 40A (the first and second back surface protrusions 41A and 42A) is provided.

[0085] Further, when the rotating plate 26 has the property of reflecting part or all of the primary light L1, it is not necessary to provide the light reflecting film 27. FIG. 11 is a cross-sectional view of the rotating plate 26 of the rotating element 12D in the scanning device 10D according to Modification Example 4 of the present embodiment.

[0086] As shown in FIG. 11, the rotating element 12D of the scanning device 10D has the same configuration as the rotating element 12, except that the light reflecting film 27 is not provided and the surface 26A (plate surface) of the rotating plate 26 functions as the light reflecting surface 12S.

[0087] In this case, the light source 11 and the rotating element 12D may be configured and arranged such that the primary light L1 is incident on the surface 26A of the rotating plate 26. Further, the surface protrusion group 30 may be provided on the surface 26A of the rotating plate 26. That is, the rotating plate 26 may have at least the surface 26A including a light-reflective region and the back surface 26B opposite to the surface 26A.

[0088] In the present embodiment, the case where the rotating plate 26 is configured to rotate around the rotation axes AX and AY has been described. However, the configuration of the rotating plate 26 is not limited to this. The rotating plate 26 may be configured to rotate at least around the rotation axis AY. In this case, for example, the rotating frame 24 may be fixed to the base 21 or the fixed frame 22 and may function as a support for rotatably supporting the rotating plate 26.

[0089] Further, the rotating plate 26 is not limited to having a disc shape. The rotating plate 26 may have, for example, a rectangular plate or a polygonal plate shape. Also, the rotating plate 26 does not have to have a plate shape. The rotating plate 26 only needs to have at least the light reflecting surface 12S and can have various shapes.

[0090] Therefore, for example, when the rotating element 12 is configured to rotate only around the rotation axis AY, it may be configured as a light reflector having at least a rotating frame 24 as a support and a rotating plate 26 as a rotating body supported by the support and rotating around the rotation axis AY. And at least one of the front surface 26A and the back surface 26B of the rotating plate 26 as the rotating body may be provided with protrusions. Further, in this case, when the rotating plate 26 as the rotating body is configured to rotate while resonating around the rotation axis AY, the effect of providing the protrusions is great.

[0091] Also, when rotating the rotating plate 26 only around the rotation axis AY, for example, each of the first and second surface protrusions 31 and 32 may be formed on a straight line passing through at least one of the centers of the front surface 26A and the back surface 26B of the rotating plate 26 and perpendicular to the rotation axis AY. Further, for example, each of the first and second surface protrusions 31 and 32 may have a shape symmetric with respect to a straight line passing through at least one of the centers of the front surface 26A and the back surface 26B of the rotating plate 26 and perpendicular to the rotation axis AY.

[0092] In addition, in this embodiment, the case where the surface protrusion group 30 is formed on a curve has been described. However, the surface protrusion group 30 is not limited to being formed on a curve. For example, the surface protrusion group 30 may be formed in such a manner as to function like fins that control the flow of gas pushed away by the rotating plate 26. As a preferable arrangement example, for example, each of the first and second surface protrusions 31 and 32 may have at least one protrusion continuously formed along at least one of the outer edges of the front surface 26A and the back surface 26B of the rotating plate 26.

[0093] In addition, in this embodiment, the case where the rotating element 12 is mounted as a deflection element that deflects the primary light L1 in a direction-variable manner and emits it as the secondary light L2 toward the scanning region R0 in the scanning device 10 has been described. However, the rotating element 12 can be mounted on a device other than the scanning device 10. That is, the rotating element 12 can function as a light reflector that deflects light in a direction-variable manner for uses other than scanning.

[0094] Thus, in this embodiment, the light reflector includes a support (e.g., the rotating frame 24), a rotating body (e.g., the rotating plate 26) that is supported by the support so as to rotate around the rotation axis AY and has a first surface (e.g., the surface 26A) including a light-reflective region and a second surface (e.g., the back surface 26B) opposite to the first surface, and first and second protrusions (e.g., the first and second surface protrusions 31 and 32, or the first and second back surface protrusions 41A and 42A) that are respectively provided on at least one of the first surface and the second surface of the rotating body, are spaced apart from each other with the rotation axis AY interposed therebetween, and are arranged opposite to each other. Therefore, a light reflector having a stable rotation range can be provided.

Explanation of Reference Numerals

[0095] 12, 12A, 12B, 12C, 12D Rotating elements 30, 30A, 30B Surface protrusion groups 40, 40A Back surface protrusion groups

Claims

[Claim 1] A support; a rotating body supported by the support so as to rotate about a rotation axis, the rotating body having a first surface including a light-reflective area and a second surface opposite to the first surface; a first protrusion and a second protrusion, each of which is provided on at least one of the first surface and the second surface of the rotating body, and which are arranged opposite each other and spaced apart across the rotating axis.

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