Light reflector

Abstract

To provide a light reflector with a stable range of rotation. [Solution] The device comprises a support, a rotating body 26 supported by the support so as to rotate around a pivot axis and having a first surface 26A including a light-reflecting region and a second surface 26B opposite to the first surface, and a first projection 31 and a second projection 32, each provided on at least one of the first surface and the second surface of the rotating body, and arranged apart from and opposite to each other with respect to the pivot axis.

Description

Technical Field

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

[0002] Conventionally, scanning devices that perform optical scanning of a target object to obtain information related to the distance, shape, and the like to the target object have been known. The scanning device includes, for example, a movable mirror that emits scanning light toward the target object while variably deflecting the direction of the light. For example, Patent Document 1 discloses an optical device including a plate-shaped movable portion and a reflective film formed on the movable portion. Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Patent No. 5146204 Summary of the Invention Problems to be Solved by the Invention

[0004] The scanning device has a scanning region corresponding to the movable range of the movable mirror. For example, when a rotary mirror is used as an optical deflecting element, the scanning region is a region corresponding to the maximum rotation angle of the mirror. However, during the period in which the mirror rotates at the maximum rotation angle or an angular position in the vicinity thereof, the rotation stability may decrease. An example of a case where the rotation stability decreases includes a case where the maximum rotation angle of the mirror fluctuates for each rotation cycle.

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

[0006] In this case, for example, scanning information obtained from an unstable scanning area may not be considered valid scanning information. Furthermore, it may be necessary to set a valid scanning area smaller than the entire range of light emitted from the mirror.

[0007] This invention has been made in view of the above-mentioned points, and one of its objectives is to provide a light reflector having a stable range of rotation. [Means for solving the problem]

[0008] The invention described in claim 1 is characterized by comprising: a support; a rotating body supported by the support so as to rotate around a pivot axis, having a first surface including a light-reflecting region 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, and arranged apart from and opposite to each other with respect to the pivot axis. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the overall configuration of the scanning device according to Example 1. [Figure 2] This is a perspective view of the rotating element according to Example 1. [Figure 3] This is a plan view of the rotating element according to Example 1. [Figure 4] This is a plan view of the rotating element according to Example 1. [Figure 5] This is a cross-sectional view of the rotating element according to Example 1. [Figure 6] This is a schematic diagram of a system for measuring the range of light emitted from a rotating element according to Example 1. [Figure 7] This figure shows the change in the rotation angle of the rotating element according to Example 1 in response to the ambient temperature. [Figure 8] This is a plan view of a rotating element according to a modified example 1 of Example 1. [Figure 9] This is a plan view of the rotating element according to a modified example 2 of Example 1. [Figure 10]This is a cross-sectional view of a rotating element according to a modified example 3 of Example 1. [Figure 11] This is a cross-sectional view of a rotating element according to a modified example 4 of Example 1. [Modes for carrying out the invention]

[0010] Examples of the present invention will be described in detail below. [Examples]

[0011] Figure 1 is a schematic arrangement diagram of the scanning device 10 according to Embodiment 1. In this embodiment, the scanning device 10 is a scanning-type distance measuring device that performs optical scanning of a predetermined area (hereinafter referred to as the scanning area) R0 and measures the distance to an object OB located within the scanning area R0. The configuration of the scanning device 10 will be explained using Figure 1. Figure 1 schematically shows the scanning area R0 and the object OB.

[0012] The scanning device 10 has a light source 11 that generates and emits, for example, pulsed light as the 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 it intermittently.

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

[0014] In this embodiment, the rotating element 12 is a rotating mirror having one light-reflecting surface 12S that rotates around rotation axes AX and AY. Furthermore, the light-reflecting surface 12S of the rotating element 12 is reflective to at least 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 periodically changes. A region irradiated with the secondary light L2 within a change period of the emission direction of the secondary light L2 is a scanning region R0.

[0016] For example, the scanning region R0 is a virtual three-dimensional space from which 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 may 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 periodically changes in accordance with 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 such 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 variation range of the component in the axial direction of the rotation axis AY within the axial direction of the optical axis of the secondary light L2, which is determined by the axial direction of the optical axis of the primary light L1 and the normal vector of the light reflecting surface 12S of the rotating element 12 when the primary light L1 is incident. Further, the width direction range of the scanning region R0 corresponds to the variation range of the component in the axial direction of the rotation axis AX within the axial direction of the secondary light L2. Further, the depth direction range of the scanning region R0 corresponds to a range of distances over which the secondary light L2 can maintain a predetermined intensity (an intensity detectable by the scanning device 10).

[0019] Further, when a virtual plane separated from the rotating element 12 by a predetermined distance within the scanning region R0 is defined as a scanning surface R1, the scanning surface 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 the scanning surface R1.

[0020] Furthermore, as shown in Figure 1, if an object OB (i.e., an object or substance that is reflective or scatterable to the secondary light L2) is present in the scanning region R0, the secondary light L2 is reflected or scattered by the object OB. A portion of the secondary light L2 reflected by the object OB travels as tertiary light L3 along almost the same optical path as the secondary light L2, but in the opposite direction, and returns to the rotating element 12.

[0021] The scanning device 10 includes a separation element 13 provided on the optical path of the primary light L1 to separate the primary light L1 and the tertiary light L3, and a light-receiving element 14 to receive 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 third-order light L3, which is emitted via the rotating element 12, reflected by the object OB, and has passed through the rotating element 12. The light-receiving element 14 also has at least one detection element that detects the third-order light L3 and generates an electrical signal indicating the detection result of the third-order light L3, for example, the intensity value of the third-order light L3. The scanning device 10 generates the electrical signal generated by the light-receiving element 14 as the scanning result of the scanning area R0.

[0023] Although not shown in the figures, the scanning device 10 may have an optical system provided on the optical path of the primary light L1 between the light source 11 and the rotating element 12 to shape the primary light L1. The scanning device 10 may also 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 to focus the tertiary light L3. These optical systems may include, for example, at least one lens and may also include a filter.

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

[0025] Furthermore, the control unit 15 has a distance measuring unit 15D that measures the distance to the target object OB based on the light receiving result of the third-order light L3 by the light receiving element 14. In this 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. The distance measuring unit 15D also measures the distance to the target object OB (or a part of its surface area) using the time-of-flight method based on the time difference between the emission timing of the second-order light L2 and the reception timing of the third-order light L3. The distance measuring unit 15D also generates data (distance measurement data) indicating the measured distance information.

[0026] In this embodiment, the distance measuring unit 15D divides the scanning area R0 (scanning surface R1) into a plurality of distance measuring points (scanning points) and generates an image of the scanning area R0 (distance measuring image) that shows the distance measurement result (distance value) of each of the plurality of distance measuring points as pixels. In this embodiment, the distance measuring unit 15D associates information indicating the distance measuring points with the displacement of the light reflection surface 12S of the rotating element 12 and generates image data showing a two-dimensional map or a three-dimensional map of the scanning area R0.

[0027] Furthermore, the distance measuring unit 15D sets the period of change in the emission direction of the secondary light L2 as the scanning period, which is the period of scanning the scanning area R0, and generates one distance measuring image for each scanning period. The distance measuring unit 15D may be connected to a display unit (not shown) that displays the distance measuring images, and may be configured to transmit the distance measuring images to the display unit.

[0028] Figure 2 is a schematic perspective view of the rotating element 12. In this 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 this embodiment, the rotating element 12 has a base 21 and an annular fixing frame 22 fixed to the base 21. The fixing frame 22 has a rectangular plate-like outer shape and is supported by the base 21 at the outer circumference of one of its plate surfaces.

[0030] The rotating element 12 has a first support portion 23 consisting of first and second torsion bars 23A and 23B, each provided on the inner circumference of the fixed frame 22 and extending along the x-direction so as to face each other in the first direction (hereinafter referred to as the x-direction). In this embodiment, each of the first and second torsion bars 23A and 23B is elastic.

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

[0032] In this embodiment, the rotating frame 24 is elastically supported at the ends of the first and second torsion bars 23A and 23B opposite to the fixed frame 22. In this embodiment, the rotating frame 24 has an overall rectangular annular shape and has a frame-shaped inner circumferential frame portion 24A on its inner circumference. In this embodiment, the inner circumferential frame portion 24A has a portion that overlaps with the portion that forms the outer circumference of the rotating frame 24.

[0033] The rotating element 12 has a second support portion 25 consisting of third and fourth torsion bars 25A and 25B, each provided on the inner circumference of the movable frame 24 and extending along the y-direction so as to face each other in a second direction perpendicular to the x-direction (hereinafter referred to as the y-direction). In this embodiment, each of the third and fourth torsion bars 25A and 25B is elastic.

[0034] The rotating element 12 is supported at its outer circumference by a second support portion 25 and has a disc-shaped rotating plate 26 that rotates around a second rotation axis (the axis corresponding to the rotation axis AY, hereinafter referred to as rotation axis AY) with the y direction as its axial direction. The rotating element 12 also has a light-reflecting film 27 that is provided concentrically with the rotating plate 26 on one of its surfaces and has light-reflecting properties for primary light L1. In this embodiment, the light-reflecting film 27 constitutes the light-reflecting surface 12S of the rotating element 12.

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

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

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

[0038] Furthermore, the rotating 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] When a voltage is applied to the first and second coils 28B and 28D, a rotational force is generated for the rotating frame 24 and the rotating plate 26 based on the magnetic fields generated by the first and second permanent magnets 28A and 28C and the currents flowing through the first and second coils 28B and 28D. For example, a rotational force is generated around the rotation axis AX relative to the rotating frame 24 based on the current flowing through the first coil 28B and the magnetic field in the y-direction generated between the first permanent magnets 28A.

[0040] Furthermore, in this embodiment, the current flowing through the second coil 28D and the magnetic field generated between the second permanent magnet 28C and the magnetic material 28E generate a rotational force around the rotation axis AY relative to the rotating frame 24, and the rotating plate 26 rotates around the rotation axis AY accordingly.

[0041] In this way, the rotating 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 this embodiment, the rotating element control unit 15B applies voltages to the first and second coils 28B and 28D such that the rotating plate 24 rotates non-resonantly around the rotating axis AX and resonantly around the rotating axis AY.

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

[0044] In the following, the direction perpendicular to the x and y directions 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 it is not rotating. The primary light L1 is incident on the light-reflecting surface 12S along a direction having, for example, a component in the z direction.

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

[0046] Furthermore, Figure 5 is a cross-sectional view along the line 5-5 in Figure 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 explained using Figures 3 to 5.

[0047] First, as shown in Figures 3 and 5, in this embodiment, the rotating element 12 has a group of surface protrusions 30 consisting of first and second surface protrusions (first and second protrusions) 31 and 32, each protruding in the z direction (a 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 consists of a single protrusion formed continuously in a curved shape along the outer edge of the light-reflecting film 27. The first and second surface protrusions 31 and 32 are spaced apart from each other with respect to the rotation axis AY. Furthermore, each of the first and second surface protrusions 31 and 32 has a symmetrical shape with respect to the rotation axis AX. In addition, the first and second surface protrusions 31 and 32 are positioned symmetrically with respect to the rotation axis AY.

[0049] Furthermore, as shown in Figures 4 and 5, in this embodiment, the rotating element 12 has a group of back surface protrusions 40 consisting of first, second and third back surface protrusions (third, fourth and fifth protrusions) 41, 42 and 43, each protruding in the z direction (a direction perpendicular to the back surface 26B of the rotating plate 26).

[0050] In this embodiment, the first and second back surface protrusions 41 and 42 are provided at positions opposite to the first and second front surface protrusions 31 and 32, respectively, with the rotating plate 26 in between. The third back surface protrusion 43 is provided in the region 26BB on the back surface 26B of the rotating plate 26, opposite to the light-reflecting film 27.

[0051] The first and second back surface protrusions 41 and 42 are formed to extend in a curved shape, similar to the first and second front surface protrusions 31 and 32, respectively. The first and second back surface protrusions 41 and 42 are spaced apart from each other with respect to the pivot axis AY. Furthermore, each of the first and second back surface protrusions 41 and 42 has a symmetrical shape with respect to the pivot axis AX. In addition, the first and second back surface protrusions 41 and 42 are positioned symmetrically with respect to the pivot axis AY.

[0052] Furthermore, in this embodiment, the third back surface projection 43 has a symmetrical shape with respect to each of the rotation axes AX and AY. Also, in this embodiment, the third back surface projection 43 is formed in a mesh or grid pattern on the back surface 26B of the rotation plate 26.

[0053] Furthermore, as shown in Figure 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 with the fixed frame 22, the first support portion 23, the rotating frame 24, and the second support portion 25. These can be formed, for example, by processing a semiconductor substrate such as a silicon substrate.

[0055] Furthermore, the group of back surface protrusions 40 can be formed by processing a semiconductor substrate separate from the semiconductor substrate used to form the rotating plate 26, and joining the processed substrate to the back surface 26B of the rotating plate 26. In other words, in this embodiment, the first, second, and third back surface protrusions 41, 42, and 43 are formed integrally.

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

[0057] Therefore, for example, the width W1 and height H1 of the surface protrusion group 30 (e.g., the first surface protrusion 31) are less than or equal to half the width W2 and height H2 of the back surface protrusion group 40 (e.g., the first back surface protrusion 41). Also, in this embodiment, the width W1 and height H1 of the 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 surface projection 31 are approximately 20 μm each. On the other hand, the width W2 and height H2 of the first back surface projection 41 are approximately 40 μm and 140 μm, respectively. Also, the thickness T1 of the rotating plate 26 is approximately 40 μm.

[0059] Figure 6 shows a schematic configuration of a system for measuring the emission range of secondary light L2. In this embodiment, a screen SC with a small hole was prepared, the light source 11 was positioned so that the primary light L1 passes through this hole, and a rotating element 12 was placed on the opposite side of the screen SC from the light source 11.

[0060] Then, the rotating element 12 was driven to periodically rotate the rotating plate 26, and the light source 11 was driven to emit the primary light L1. The angular range SA around the rotation axis AY at which the secondary light L2 is stably emitted on the screen SC (hereinafter referred to as the stable rotation angle) 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 in the x direction of the secondary light irradiated onto the screen SC was kept below a predetermined level was defined as the stable rotation angle SA.

[0061] Figure 7 shows the measurement results. Figure 7 shows the stable rotation angle SA for the scanning device 10 according to this embodiment, which includes the rotating element 12, and the scanning device 100 according to a comparative example, which includes a rotating element 101 having the same configuration as the rotating element 12 except that the rotating plate 26 does not have a group of surface protrusions 30. Figure 7 also shows the measurement results of the change in the stable rotation angle SA when the ambient temperature of the rotating elements 12 and 101 is changed.

[0062] First, as shown in Figure 7, it can be seen that at all ambient temperatures, the stable rotation angle SA of the rotating element 12 exceeds the stable rotation angle SA of the rotating element 101. This is thought to be due to the fact that 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, with each rotation of the rotating plate 26, it pushes aside the surrounding gas. The faster the rotation speed of the rotating plate 26, the more turbulent the flow of gas (airflow) pushed aside by the rotating plate 26 becomes. This is thought to be due to the generation of turbulence in the airflow.

[0064] In particular, the larger the maximum rotation angle of the rotating plate 26, the faster it rotates. Consequently, the larger the rotation angle of the rotating plate 26, the more turbulent the airflow near the rotating plate 26 becomes. Therefore, the inventors of the present invention considered that the stable rotation angle SA could be increased by stabilizing the airflow around the rotating plate 26.

[0065] For example, in this embodiment, the surface protrusions 30 are arranged opposite each other across the rotation axis AX and have a symmetrical shape with respect to the rotation axis AX. As a result, the gas pushed aside by the rotating plate 26 during rotation can move stably in the y direction (the direction along the rotation axis AY). Furthermore, because the surface protrusions 30 also have a symmetrical shape with respect to the rotation axis AY, the airflow control effect is high.

[0066] The inventors of this application believe that, at least at the time of filing, the surface protrusion group 30 was able to increase the stable rotation angle SA of the rotating plate 26 by this principle.

[0067] Furthermore, as the ambient temperature decreases, the viscosity of the gas decreases, making the airflow more turbulent. Therefore, the lower the ambient temperature, the smaller the stable rotation angle SA becomes. Even in this case, as shown in Figure 7, it can be seen that the surface protrusion group 30 has an effect of stabilizing the airflow at any ambient temperature. In addition, although not shown in Figure 7, it can be estimated that the stable rotation angle SA will also increase at other ambient temperatures based on the principle described above.

[0068] Similarly, when the atmospheric pressure increases, the gas becomes more turbulent, just as when the ambient temperature decreases. In this case as well, the effect of the surface protrusion group 30 is expected to be obtained. Therefore, it is expected that the stable rotation angle SA will increase even when used in various environments. Consequently, the rotating element 12 can be used to configure a scanning device 10 that can stably emit secondary light L2 over a wide range.

[0069] Furthermore, in this 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 high speed, causing significant turbulence in the airflow. Therefore, when the rotating plate 26 is made to resonate, the effect of suppressing airflow turbulence by the surface protrusion group 30 is significant.

[0070] Furthermore, in this embodiment, a group of back surface protrusions 40 is provided on the back surface 26B of the rotating plate 26. Of this group of back surface protrusions 40, the first and second back surface protrusions 41 and 42 are thought to have the effect of suppressing airflow turbulence, similar to the surface protrusion group 30. In addition, the third back surface protrusion 43 has the effect of suppressing deformation of the rotating plate 26 during rotation (for example, wavy deformation). Therefore, by providing the group of back surface protrusions 40, the stable rotation angle SA becomes larger, and the deformation of the light reflective film 27 is suppressed, thereby stabilizing the emission direction of secondary light L2.

[0071] Note that the configuration of the surface protrusion group 30 is not limited to the case described above. For example, the first and second surface protrusions 31 and 32 may be formed intermittently. Figure 8 is a plan view showing the surface 26A of the rotating plate 26 of the rotating element 12A in the scanning device 10A according to Modification 1 of this embodiment.

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

[0073] In this modified example, the first surface projection 31A has a plurality of projections P11 and P12 that are arranged opposite to each other and spaced apart with respect to the pivot axis AX. Similarly, the second surface projection 32A has a plurality of projections P21 and P22 that are arranged opposite to each other and spaced apart with respect to the pivot axis AX.

[0074] As with the surface protrusion group 30, the first and second surface protrusions 31A and 32A may have multiple protrusions P11, P12, P21 and P22. Even in this case, the effect of stabilizing the airflow can be obtained.

[0075] Furthermore, considering the effective stabilization of the airflow, it is preferable that protrusions, such as the surface protrusion group 30, are provided in the portion of the rotating plate 26 where the displacement amount and displacement velocity are greatest during rotation, for example, the portion on the rotation axis AX, the portion furthest from the rotation axis AY, or the outer edge portion of the surface 26A of the rotating plate 26. That is, for example, as shown in Figure 3, it is preferable that the first and second surface protrusions 31 and 32 are formed in the region on the rotation axis AX of the rotating plate 26.

[0076] Furthermore, in the example shown in Figure 8, the protrusions P11, P12, P21, and P22 on the first and second surface protrusions 31A and 32A are each formed in a continuous linear shape. However, each of the first and second surface protrusions 31A and 32A may include a plurality of columnar protrusions.

[0077] Furthermore, the surface protrusion group 30 only needs to be provided on the surface 26A of the rotating plate 26. Figure 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 a modified example 2 of this embodiment.

[0078] As shown in Figure 9, the rotating element 12B of the scanning device 10B has the same configuration as the rotating element 12, except that it has a group of surface protrusions 30B consisting of first and second surface protrusions 31B and 32B formed on the outside of the light-reflecting film 27.

[0079] In this modified example, the first and second surface protrusions 31B and 32B are each formed in a curved shape along the outer edge of the light-reflecting film 27 on the surface 26A of the rotating plate 26. Even in this case, the effect of stabilizing the airflow can be obtained.

[0080] Furthermore, considering the need to securely fix the surface protrusion group 30B onto the rotating plate 26, it is preferable that the surface protrusion group 30B be formed on the light-reflective film 27, as shown in this embodiment. This is because, when the surface protrusion group 30 is formed by metal plating as in this embodiment, forming it on a light-reflective metal, which has a high affinity for the metal, allows even minute protrusions like the surface protrusion group 30 to be sufficiently fixed to the rotating plate 26.

[0081] Furthermore, protrusions for stabilizing the airflow may be provided on the back surface 26B of the rotating plate 26. Figure 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 Figure 10, the rotating element 12C of the scanning device 10C has the same configuration as the rotating element 12, except that there are no protrusions on the surface 26A of the rotating plate 26, and the configuration of the back surface protrusion group 40A.

[0083] In this modified example, the back surface projection group 40A has first and second back surface projections 41A and 42A having the same configuration as the first and second surface projections 31 and 32 in the surface projection group 30. That is, each of the first and second back surface projections 41A and 42A is provided on the back surface 26B of the rotating plate 26, facing each other across the rotating axis AY and also spaced apart from each other. Furthermore, each of the first and second back surface projections 41A and 42A is made of the same material as the surface projection group 30, for example, copper plating.

[0084] As shown in this modified example, turbulence in the airflow during rotation can also be suppressed by providing a group of back surface protrusions 40A on the back surface 26B of the rotating plate 26. In other words, the rotating element 12 only needs to be provided with, for example, a group of surface protrusions 30 (first and second surface protrusions 31 and 32) or a group of back surface protrusions 40A (first and second back surface protrusions 41A and 42A).

[0085] Furthermore, if the rotating plate 26 has the characteristic of reflecting part or all of the primary light L1, it is not necessary to provide the light-reflecting film 27. Figure 11 is a cross-sectional view of the rotating plate 26 of the rotating element 12D in the scanning device 10D according to modification 4 of this embodiment.

[0086] As shown in Figure 11, the rotating element 12D of the scanning device 10D has the same configuration as the rotating element 12, except that it does not have a light-reflecting film 27 and has a rotating plate 26 whose surface 26A (plate surface) functions as a light-reflecting surface 12S.

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

[0088] Furthermore, in this embodiment, the case in which 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 only needs to be configured to rotate at least around the rotation axis AY. In this case, for example, the rotating frame 24 only needs to be fixed to the base 21 or the fixed frame 22 and should function as a support that rotatably supports the rotating plate 26.

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

[0090] Therefore, for example, if the rotating element 12 is configured to rotate only around the rotation axis AY, it is sufficient that it 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 that is supported by the support and rotates around the rotation axis AY. Furthermore, a projection should be provided on at least one of the front surface 26A and back surface 26B of the rotating plate 26 as the rotating body. In this case, the effect of providing a projection is greater if the rotating plate 26 as the rotating body is configured to rotate while resonating around the rotation axis AY.

[0091] Furthermore, when the rotating plate 26 is rotated 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 that passes through the center of at least one of the surface 26A and back surface 26B of the rotating plate 26 and is perpendicular to the rotation axis AY. Also, for example, each of the first and second surface protrusions 31 and 32 may have a symmetrical shape with respect to a straight line that passes through the center of at least one of the surface 26A and back surface 26B of the rotating plate 26 and is perpendicular to the rotation axis AY.

[0092] Furthermore, in this embodiment, the case in which 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 a manner that functions like fins that control the flow of gas pushed aside by the rotating plate 26. As a preferred arrangement example, each of the first and second surface protrusions 31 and 32 may have at least one protrusion that is continuously formed along at least one outer edge of the surface 26A and back surface 26B of the rotating plate 26.

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

[0094] Thus, in this embodiment, the light reflector comprises a support (e.g., a rotating frame 24), a rotating body (e.g., a rotating plate 26) supported by the support so as to rotate around a rotation axis AY, having a first surface (e.g., a front surface 26A) including a region having light reflectivity and a second surface (e.g., a back surface 26B) opposite to the first surface, and first and second protrusions (e.g., first and second front surface protrusions 31 and 32, or first and second back surface protrusions 41A and 42A) each provided on at least one of the first and second surfaces of the rotating body, and arranged to be separated from each other and facing each other across the rotation axis AY. Therefore, a light reflector with a stable range of rotation can be provided. [Explanation of Symbols]

[0095] 12, 12A, 12B, 12C, 12D Rotating elements 30, 30A, 30B surface protrusions 40, 40A Rear surface protrusion group

Claims

[Claim 1] Support and A rotating body supported by the support so as to rotate around a pivot axis, having a first surface including a light-reflecting region and a second surface opposite to the first surface, A light reflector characterized by having first and second projections, each provided on at least one of the first and second surfaces of the rotating body, and arranged apart from and opposite to each other with respect to the pivot axis.

Images