Light emitting device and distance measuring device

Abstract

To provide a light emitting device having a turning element having a turning type light reflector and capable of emitting light in a desired direction over a wide range, and a distance measuring device including the light emitting device.SOLUTION: The optical device includes a light source for emitting light, and a turning element having a turning body which turns around a first turning axis and has at least one light reflecting surface for reflecting light, wherein the turning element is provided with a reflection type diffraction grating for diffracting light so that diffracted light of a specific order becomes a main component in any one of the light reflecting surfaces.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a light emitting device that emits light and a distance measuring device that performs optical distance measurement. [Background technology]

[0002] Distance measuring devices that measure the distance to an object by emitting light toward the object and detecting the light reflected by the object have been known. Optical scanning distance measuring devices are also known that perform optical scanning of the object to obtain information about the shape and orientation of the object in addition to the distance to the object. For example, Patent Document 1 discloses a scanning optical system that includes a mirror unit with a first mirror surface and a second mirror surface tilted with respect to a rotation axis, and a light projection system including at least one light source that emits a light beam toward the first mirror surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 056545 Summary of the Invention [Problem to be solved by the invention]

[0004] A scanning distance measuring device, for example, has a light emitting unit that emits pulsed light toward a scanning area. The distance measuring device defines each irradiated area of ​​the pulsed light as seen from the light emitting unit as a distance measuring point, and receives light from each of the distance measuring points to obtain scanning information within the scanning area. For example, Patent Document 1 discloses an optical system in which light is incident from multiple positions onto a rotating mirror having multiple light reflecting surfaces inclined with respect to the rotation axis. This allows the pulsed light emission area to be expanded along the axial direction of the rotation axis, enabling scanning over a wide area.

[0005] Other examples of methods for scanning a wide area include a method of directing pulsed light onto a rotating mirror having multiple light-reflecting surfaces with different inclination angles relative to the rotation axis, and a method of directing pulsed light onto a mirror that rotates back and forth around at least one rotation axis.

[0006] In either case, in order to efficiently scan the scan area and obtain scan information that is easy to handle, it is preferable to maintain the elevation and depression angles of the scan trajectory as constant as possible within the scan area.

[0007] However, with a rotating mirror, the direction of the normal vector of the mirror's light-reflecting surface changes relative to the optical axis of the pulsed light entering from the light-emitting unit during operation, causing the elevation and depression angles of the scanning trajectory of the light reflected by the light-reflecting surface to change. This tendency becomes more pronounced as the mirror's swing angle increases. In other words, it has been difficult to widen the scanning area while maintaining a constant elevation and depression angle of the scanning trajectory.

[0008] The present invention has been made in consideration of the above-mentioned points, and one of its objects is to provide a light-emitting device that has a rotating element with a rotating light reflector and is capable of emitting light in a desired direction over a wide range, and a distance measuring device that includes the light-emitting device. [Means for solving the problem]

[0009] The invention described in claim 1 is a light emitting device comprising: a light source that emits light; and a rotating element having a rotating body that rotates around a first rotation axis and has multiple side surfaces with light-reflecting surfaces that reflect the light, wherein the rotating body has a reflective diffraction grating on one of the multiple light-reflecting surfaces that diffracts the light so that a specific order of diffraction light becomes the main component, wherein the diffraction grating includes a first diffraction grating provided on a first one of the multiple reflecting surfaces of the rotating body, and a second diffraction grating provided on a second one of the multiple reflecting surfaces of the rotating body that is different from the first reflecting surface, wherein the first diffraction grating is a blazed diffraction grating having a wave vector in a first direction in the axial direction of the first rotation axis, and the second diffraction grating is a blazed diffraction grating having a wave vector in a second direction opposite to the first direction in the axial direction of the first rotation axis.

[0010] Invention 1 is a distance measuring device characterized by having the above-mentioned light emitting device, a light receiving element that receives light that is projected through a rotating element, reflected by an object, and passes through the rotating element, and a distance measuring unit that measures the distance to the object based on the result of reception of light that has passed through the rotating element by the light receiving element.

[0011] Invention 2 is a light-emitting device comprising: a light source that emits light; a rotating element having a rotating body that rotates around a rotation axis and has a pyramidal, truncated pyramidal, or prismatic shape with the axial direction of the rotation axis as its height direction; and a reflective diffraction grating provided on at least one of a plurality of side surfaces of the rotating body, wherein at least one of the plurality of side surfaces of the rotating body and the other side surfaces reflect the light emitted from the light source in directions that form different angles with a plane perpendicular to the rotation axis. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating an overall configuration of a distance measuring device according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a rotary element of the distance measuring device according to the first embodiment. [Figure 3]FIG. 2 is a side view of a rotary element of the distance measuring device according to the first embodiment. [Figure 4] 4A and 4B are diagrams illustrating a reflection pattern of light at a rotary element of the distance measuring device according to the first embodiment. [Figure 5A] FIG. 10 is a side view of a rotary element of a distance measuring device according to a comparative example. [Figure 5B] 4 is a diagram showing elevation and depression angles of the distance measuring device according to the first embodiment and a conventional distance measuring device using a mirror surface. FIG. [Figure 6] FIG. 2 is a diagram showing a scanning area of ​​the distance measuring device according to the first embodiment. [Figure 7] 3 is a diagram illustrating an example of the arrangement of light sources in the distance measuring device according to the first embodiment. FIG. [Figure 8] FIG. 10 is a diagram illustrating the overall configuration of a distance measuring device according to a second embodiment. [Figure 9] FIG. 10 is a perspective view of a rotary element of a distance measuring device according to a second embodiment. [Figure 10] FIG. 10 is a side view of a rotary element of a distance measuring device according to a second embodiment. [Figure 11] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a second embodiment. [Figure 12] FIG. 10 is a side view of a rotary element of a distance measuring device according to a second embodiment. [Figure 13] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a second embodiment. [Figure 14] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a second embodiment. [Figure 15] FIG. 10 is a diagram showing a scanning area of ​​a distance measuring device according to a second embodiment. [Figure 16] FIG. 10 is a diagram illustrating the overall configuration of a distance measuring device according to a third embodiment. [Figure 17] FIG. 11 is a perspective view of a rotary element of a distance measuring device according to a third embodiment. [Figure 18A] FIG. 11 is a side view of a rotary element of a distance measuring device according to a third embodiment. [Figure 18B] FIG. 11 is a side view of a rotary element of a distance measuring device according to a third embodiment. [Figure 19A] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a third embodiment. [Figure 19B] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a third embodiment. [Figure 19C] 10A and 10B are diagrams illustrating a reflection pattern of light at a rotary element of a distance measuring device according to a third embodiment. [Figure 20] FIG. 10 is a diagram showing a scanning area of ​​a distance measuring device according to a third embodiment. [Figure 21] FIG. 10 is a diagram illustrating an example of the arrangement of light sources in a distance measuring device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Examples of the present invention will be described in detail below. [Example]

[0014] FIG. 1 is a schematic layout diagram of a distance measuring device 10 according to a first embodiment. In this embodiment, the distance measuring device 10 is a scanning type distance measuring device that performs optical scanning of a predetermined area (hereinafter referred to as a scanning area) R0 and measures the distance to an object OB present within the scanning area R0. The configuration of the distance measuring device 10 will be described with reference to FIG. 1. Note that FIG. 1 schematically shows the scanning area R0 and the object OB.

[0015] The distance measuring device 10 has a light source 11 that generates and emits, for example, pulsed light as the emitted light L1. In this embodiment, the light source 11 generates laser light having a peak wavelength in the infrared region as the emitted light L1 and emits it intermittently.

[0016] The distance measuring 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 emitted light L1 emitted from the light source 11 toward the scanning region 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 scanning light L2.

[0017] 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. The light reflecting surface 12S of the rotating element 12 is reflective to at least the emitted light L1.

[0018] The rotating element 12 is configured so that the light reflecting surface 12S rotates periodically. Therefore, the emission direction of the scanning light L2 emitted from the rotating element 12 changes periodically. The area irradiated with the scanning light L2 within the period of change in the emission direction of the scanning light L2 is the scanning area R0. The scanning area R0 is a virtual three-dimensional space into which the scanning light L2 is emitted. In FIG. 1, the outer edge of the scanning area R0 is schematically indicated by a dashed line.

[0019] For example, the scanning area R0 can be defined as a cone-shaped space having a height range along a height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along a width direction D2 corresponding to the rotation axis AX, and a depth range along a 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.

[0020] For example, the normal vector of light reflecting surface 12S of rotating element 12 changes periodically in response to the rotation of rotating element 12. In this embodiment, light source 11 emits output light L1 toward rotating element 12 so that output light L1 is incident on light reflecting surface 12S of rotating element 12.

[0021] Therefore, for example, the height direction range of the scanning region R0 corresponds to the range of change of the axial component of the rotation axis AY in the axial direction of the optical axis of the scanning light L2, which is determined by the axial direction of the optical axis of the output light L1 and the normal vector of the light reflecting surface 12S of the rotating element 12 at the time of incidence of the output light L1. The width direction range of the scanning region R0 corresponds to the range of change of the axial component of the rotation axis AX in the axial direction of the scanning light L2. The depth direction range of the scanning region R0 corresponds to the range of distances within which the scanning light L2 can maintain a predetermined intensity (intensity detectable by the distance measuring device 10).

[0022] Furthermore, when a virtual plane within the scanning region R0 that is a predetermined distance away from the rotating element 12 is defined as a scanning plane R1, the scanning plane R1 can be defined as a two-dimensional region that spreads along a height direction D1 and a width direction D2. The scanning light L2 is emitted toward the scanning region R0 so as to scan this scanning plane R1.

[0023] 1, if an object OB (i.e., an object or substance that is reflective or scattering to the scanning light L2) is present in the scanning region R0, the scanning light L2 is reflected or scattered by the object OB. A portion of the scanning light L2 reflected by the object OB travels as reflected light L3 along substantially the same optical path as the scanning light L2 in the opposite direction to the scanning light L2, and returns to the rotating element 12.

[0024] The distance measuring device 10 includes a separation element 13 provided on the optical path of the emitted light L1 to separate the emitted light L1 from the reflected light L3, and a light receiving element 14 to receive the separated reflected light L3. The separation element 13 is, for example, a beam splitter that reflects the emitted light L1 and transmits the reflected light L3.

[0025] In this embodiment, the light receiving element 14 receives reflected light L3, which is light that is projected via the rotating element 12, reflected by the object OB, and then passes through the rotating element 12. The light receiving element 14 also has at least one detection element that detects the reflected light L3 and generates an electrical signal that indicates the detection result of the reflected light L3, for example, the intensity value of the reflected light L3. The distance measuring device 10 generates the electrical signal generated by the light receiving element 14 as the scanning result of the scanning area R0.

[0026] Although not shown, the distance measuring device 10 may have an optical system that is provided on the optical path of the emitted light L1 between the light source 11 and the rotating element 12 and that shapes the emitted light L1. The distance measuring device 10 may also have an optical system that is provided on the optical path of the reflected light L3 between the separating element 13 and the light receiving element 14 and that collects the reflected light L3. These optical systems may include, for example, at least one lens and may also include a filter.

[0027] The distance measuring 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 has 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.

[0028] The control unit 15 also has a distance measurement unit 15D that measures the distance to the object OB based on the result of reception of the reflected light L3 by the light receiving element 14. In this embodiment, the distance measurement unit 15D detects pulses indicating the reflected light L3 from the electrical signal generated by the light receiving element 14. The distance measurement unit 15D also measures the distance to the object OB (or a partial surface area thereof) using a time-of-flight method based on the time difference between the emission timing of the scanning light L2 and the reception timing of the reflected light L3. The distance measurement unit 15D also generates data (distance measurement data) indicating the measured distance information.

[0029] 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 (distance measuring image) of the scanning area R0 that indicates the distance measuring results (distance values) of each of the plurality of distance measuring points as pixels. In this embodiment, the distance measuring unit 15D associates the distance measuring points with information indicating the displacement of the light reflecting surface 12S of the rotating element 12, and generates image data that indicates a two-dimensional map or a three-dimensional map of the scanning area R0.

[0030] The distance measuring unit 15D generates one distance measuring image for each scanning period, which is the period during which the scanning area R0 is scanned, by changing the emission direction of the scanning light L2. The distance measuring unit 15D may be connected to a display unit (not shown) that displays the distance measuring image, and may be configured to transmit the distance measuring image to the display unit.

[0031] 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 so that a light reflecting surface 12S rotates around rotation axes AX and AY.

[0032] First, in this embodiment, the rotating element 12 has a support 12A and a rotating body 12B that is supported by the support 12A and rotates around rotation axes AX and AY. For example, the support 12A is an annular frame body.

[0033] Furthermore, for example, the rotating body 12B has a rotating frame 12BA that is supported by the support body 12A so as to be rotatable around a rotation axis AX on the inner periphery of the support body 12A. For example, the rotating frame 12BA is supported by the support body 12A by a pair of torsion bars that extend along the rotation axis AX and have elasticity in the circumferential direction of the rotation axis AX. The rotating frame 12BA is, for example, an annular frame body provided inside the support body 12A.

[0034] The rotating body 12B has a rotating plate 12BB supported by the rotating frame 12BA inside the rotating frame 12BA so as to be rotatable around the rotation axis AY. For example, the rotating plate 12BB is supported by the rotating frame 12BA by a pair of torsion bars that extend along the rotation axis AY and have elasticity in the circumferential direction of the rotation axis AY. The rotating plate 12BB is, for example, a disk-shaped plate provided inside the rotating frame 12BA.

[0035] The rotating frame 12BA rotates about the rotation axis AX as a result of the torsion bar between the support body 12A and the rotating frame 12BA twisting, and the rotating plate 12BB rotates about the rotation axis AY as a result of the torsion bar between the rotating frame 12BA and the rotating plate 12BB twisting.

[0036] In this way, the rotating plate 12BB rotates around the rotation axes AX and AY. In other words, the rotating body 12B is a movable body that is supported by the support body 12A and has the rotating plate 12BB that is rotatable around the rotation axes AX and AY.

[0037] Furthermore, the rotating plate 12BB is reflective to the emitted light L1. The surface of the rotating plate 12BB functions as the light reflecting surface 12S of the rotating body 12B. The surface of the rotating plate 12BB may be provided with a metal reflective film, a dielectric multilayer film, or the like. These films can be designed to maintain high reflectivity against changes in the angle of incidence of the emitted light L1 and fluctuations in wavelength. This stabilizes the light reflectivity characteristics (reflectivity, etc.) of the rotating plate 12BB.

[0038] The surface of the rotating plate 12BB may be provided with a wavelength-selective reflective film that selectively reflects the emitted light L1. In this case, the surface of the rotating plate 12BB functions as a reflective band-pass filter. This prevents unwanted wavelengths of light other than the emitted light L1, such as ambient light, from being mixed with the reflected light L3 and entering the light receiving element 14.

[0039] Furthermore, for example, the rotating element 12 has a driving force generating unit (not shown) that is provided on the support body 12A and the rotating body 12B, is connected to the control unit 15, and generates a force (driving force) to rotate the rotating body 12B. For example, the driving force generating unit generates a piezoelectric force or an electromagnetic force as the driving force in response to a driving signal supplied from the control unit 15.

[0040] Next, the distance measuring device 10 has a reflective diffraction grating 20 provided on the light reflecting surface 12S of the rotating body 12B in the rotating element 12. That is, in this embodiment, the light reflecting surface 12S of the rotating body 12B functions as a diffractive reflecting surface that diffracts and reflects the emitted light L1.

[0041] In this embodiment, the diffraction grating 20 has a plurality of grating grooves 21 arranged along the light-reflecting surface 12S. Furthermore, in this embodiment, each of the grating grooves 21 of the diffraction grating 20 extends on the light-reflecting surface 12S of the rotating body 12B in a direction perpendicular to the axial direction of a first rotation axis AY, which is one of the rotation axes AX and AY. Furthermore, these plurality of grating grooves 21 are arranged along the axial direction of the one rotation axis, the rotation axis AY.

[0042] 3 is a schematic side view of the rotating body 12B when the rotating plate 12BB is viewed along the axial direction of the rotation axis AX. The configuration of the diffraction grating 20 will be described with reference to FIG. 3. In this embodiment, the diffraction grating 20 has a wave vector in one direction DY1 in the axial direction of the rotation axis AY, and a blaze angle of θ b is a blazed diffraction grating.

[0043] More specifically, the diffraction grating 20 has a grating surface DP1 (a surface defined by the tops of the grating grooves 21, i.e., a diffraction grating surface) parallel to the light reflecting surface 12S of the rotating body 12B, and an angle (blaze angle) θ b and a blazed surface 21A inclined by θ and arranged at a pitch (the distance between adjacent grating grooves 21) d.

[0044] 4 is a diagram schematically illustrating the incident direction of the emitted light L1 and the emission direction of the scanning light L2 relative to the rotating body 12B (rotating plate 12BB) of the rotating element 12. The incident mode of the emitted light L1 relative to the light reflecting surface 12S and the emission mode of the scanning light L2 will be described with reference to FIG.

[0045] 4, for ease of understanding, an example will be described in which the outgoing light L1 is incident on the light reflecting surface 12S when not rotated, with the optical axis tilted by an angle (incident angle) θ1 in the direction DY1 from the normal to the light reflecting surface 12S. In this embodiment, the outgoing light L1 is incident on the grating surface DP1 at an incident angle θ1 (=2θ b ), is diffracted and reflected by the blazed diffraction grating, and is emitted as scanning light L2 in the normal direction of the grating surface DP1.

[0046] More specifically, a blazed diffraction grating is a diffraction grating configured to maximize the diffraction efficiency of a predetermined diffraction order and wavelength and minimize the diffraction efficiency of other diffraction orders and wavelengths. Therefore, the light diffracted by a blazed diffraction grating is light that is mainly composed of diffracted light of a specific order. In this embodiment, the emission direction of the diffracted light of the order that is the main component is determined by the blaze angle θ b, is determined by the pitch d of the grating grooves 21, the wavelength of the emitted light L1, and the incident angle θ1 of the emitted light L1.

[0047] That is, the blaze angle θ of the blazed diffraction grating is adjusted according to the wavelength of the output light L1. b By setting the pitch d of the grating grooves 21, the outgoing light L1 incident on the grating surface DP1 of the blazed diffraction grating at an incident angle θ1 can be reflected at a desired angle as scanning light L2.

[0048] In other words, the scanning light L2 is emitted at an angle in the axial direction of the rotation axis AY that is different from the angle at which the emitted light L1 is specularly reflected by the light reflecting surface 12S. Furthermore, the component of the emission direction of the scanning light L2 along the axial direction of the rotation axis AY remains almost unchanged even when the light reflecting surface 12S rotates around the rotation axis AY.

[0049] 5A and 5B, the emission direction of scanning light L2 when a diffraction grating 20 is provided and when it is not provided will be described. Fig. 5A is a schematic side view of a rotating element 101 of a distance measuring device 100 according to a comparative example. Fig. 5B is a diagram showing changes in the emission angle of scanning light L2 emitted from each of rotating element 12 (this embodiment) and rotating element 101 (comparative example).

[0050] 5A, distance measuring device 100 according to the comparative example has the same configuration as distance measuring device 100, except that it has rotating element 101. Rotating element 101 has the same configuration as rotating element 12, except that it has rotating body 101B having mirror surface 101S, which is a light reflecting surface without a diffraction grating.

[0051] FIG. 5B is a diagram showing the change in the emission angle (the elevation angle of the optical axis of the scanning light L2) in the height direction D1 and the change in the emission angle (the left-right angle of the optical axis of the scanning light L2) in the width direction D2 of the scanning light L2 emitted from the light reflecting surface 12S of the rotating body 12B and the mirror surface 101S of the rotating body 101B, when the normal to the light reflecting surface 12S of the rotating body 12B when not rotating is used as the reference (0 degrees).

[0052] 5A, mirror surface 101S of rotating body 101B rotates around a rotation axis inclined by θ1 / 2 with respect to rotation axis AY. That is, rotation axis AYH of rotating body 101B is inclined by θ1 / 2 with respect to rotation axis AY of rotating body 12B.

[0053] Also in the distance measuring device 100, the light source 11 is arranged so that the emitted light L1 is incident on the mirror surface 101S along a direction inclined at an angle θ1 with respect to a plane (shown by a broken line) perpendicular to the rotation axis AY.

[0054] 5B, the elevation and depression angles of scanning light L2 emitted from rotating element 101 of distance measuring device 100 change suddenly when the normal to mirror surface 101S rotates from a non-rotating position until it exceeds 20° to the left and right. On the other hand, the elevation and depression angles of scanning light L2 emitted from rotating element 12 of distance measuring device 10 do not change even when light reflecting surface 12S rotates.

[0055] Fig. 6 is a diagram schematically showing the irradiated position of the scanning light L2 on the scanning surface R1. In Fig. 6, the scanning trajectory of the scanning light L2 on the scanning surface R1 is shown by a dashed line. In this embodiment, the distance measuring device 10 sequentially emits the scanning light L2 on the scanning surface R1 while deflecting it along the width direction D2, and performs this multiple times along the height direction D1.

[0056] More specifically, in this embodiment, for example, the control unit 15 rotates the light reflecting surface 12S of the rotating body 12B at high speed in the width direction D2 corresponding to the axial direction of the rotation axis AX, and at low speed in the height direction D1 corresponding to the axial direction of the rotation axis AY. The scanning light L2 emitted from the rotating body 12B is deflected at high speed in the width direction D2 and at low speed in the height direction D1.

[0057] In other words, the distance measuring device 10 performs raster scanning on the scanning area R0 to obtain a plurality of scanning lines along the height direction D1 that are aligned along the width direction D2 corresponding to the direction perpendicular to the rotation axis AY of the rotating body 12B of the rotating element 12. The distance measuring device 10 also operates to perform this raster scanning periodically.

[0058] In this case, since the diffraction grating 20 is provided on the light reflecting surface 12S as in the case of the rotating body 12B, the component of the scanning light L2 in the height direction D1 hardly changes while the rotating body 12B rotates (goes back and forth) once along the width direction D2 (i.e., the resonance direction). Therefore, even at the end of the scanning region R0, for example, the elevation / depression angle of the scanning trajectory of the scanning light L2 hardly changes. This stabilizes the component of the height direction D1 in the emission direction of the scanning light L2 over a wide range.

[0059] In this manner, in this embodiment, the rotating element 12, which has a blazed diffraction grating as the diffraction grating 20 on the light reflecting surface 12S of the rotating body 12B, is rotated, and the emitted light L1 is reflected by this rotating element 12, thereby emitting the scanning light L2 toward the scanning area R0.

[0060] Therefore, for example, changes in the elevation and depression angles of the scanning trajectory of the scanning light L2 (pulsed light) on the scanning region R0 are suppressed, making it possible to efficiently scan a wide range of the scanning region R0 and obtain scanning results and distance measurement results that are easy to handle.

[0061] Furthermore, by combining the rotating element 12 and the diffraction grating 20, the emission direction of the scanning light L2 is stabilized, even when the emission light L1 is incident from various directions, which significantly improves the degree of freedom in arranging other optical elements such as the light source 11.

[0062] Fig. 7 is a diagram schematically illustrating an example of the arrangement of the light source 11 and the rotating element 12. As shown in Fig. 7, the light source 11 can be configured and arranged, for example, to emit light L1 incident on the light reflecting surface 12S of the rotating element 12 along a direction intersecting with a plane PL1 perpendicular to the rotation axis AY.

[0063] As a result, the output light L1 is incident on the rotating element 12 with an optical axis along a direction having an axial component of the rotation axis AY. In this case, as shown in Figure 7, the solid angle of the light reflecting surface 12S of the rotating element 12 as seen from the point of the object OB during rotation is maximized.

[0064] Specifically, the light-reflecting surface 12S of the rotating element 12 needs to be positioned so that both the emitted light L1 and the reflected light L3 are incident on the surface over a wide rotation range. Furthermore, the reflected light L3 is typically light scattered by the object OB and has a very weak intensity. Therefore, when receiving the reflected light L3 via the rotating element 12 as in this embodiment, it is preferable that the light-reflecting surface 12S have a larger solid angle as viewed from the object OB in order to improve the light-receiving accuracy of the light-receiving element 14.

[0065] If the diffraction grating 20 were not provided, it would be difficult to arrange the rotating body 12B so that the light reflecting surface 12S faces the front with respect to the emitted light L1, and also difficult to arrange so that the light reflecting surface 12S faces the front with respect to the scanning region R0. Therefore, if the diffraction grating 20 is not provided, the light reflecting surface 12S of the rotating body 12B must be arranged so that its normal direction always forms an angle with respect to the optical axis of the emitted light L1 and also forms an angle with respect to the optical axis of the reflected light L3 (scanning light L2) during rotation.

[0066] In contrast to this, in this embodiment, by providing a diffraction grating 20 and adjusting its diffraction conditions, it is possible to emit scanning light L along the normal direction of the light reflecting surface 12S, even if the emitted light L1 is incident with an optical axis tilted from the normal to the light reflecting surface 12S.

[0067] Therefore, the position of the rotating body 12B can be adjusted so that the solid angle of the light reflecting surface 12S as seen from the object OB is increased, for example, so that the rotating body 12B faces the scanning area R0. This makes it possible to prevent a decrease in the amount of reflected light L3 incident on the light receiving element 14. This improves the accuracy of receiving the reflected light L3, as well as the scanning accuracy and distance measurement accuracy.

[0068] In this embodiment, the diffraction grating 20 is a blazed diffraction grating having a wave vector in the axial direction of the rotation axis AY, but the configuration of the diffraction grating 20 is not limited to this.

[0069] For example, the diffraction grating 20 may be any diffraction grating that diffracts the output light L1 so that a specific diffracted light becomes the main component. Also, for example, the diffraction grating 20 may have a plurality of grating grooves 21 that each extend along a direction perpendicular to the axial direction of one rotation axis (rotation axis AX or AY) and are arranged along the axial direction of the one rotation axis.

[0070] In this embodiment, the rotating body 12B has the light reflecting surface 12S that rotates around two rotation axes, AX and AY. However, the rotating body 12B may be configured to rotate around only one rotation axis, for example, only the rotation axis AY. Even in this case, the scanning light L2 can be stably emitted in the desired direction.

[0071] Thus, the distance measuring device 10 includes, for example, a light source 11 that emits light (emitted light L1), a rotating element 12 that has a rotating body 12B that rotates around at least one rotation axis (e.g., rotation axes AX and AY) and has a light-reflecting surface 12S that reflects the light, with a diffraction grating 20 provided on light-reflecting surface 12S that diffracts the light so that a specific order of diffraction light becomes a main component, a light-receiving element 14 that receives light (reflected light L3) that is projected through the rotating element 12, reflected by the object OB, and passes through the rotating element 12, and a distance measuring unit 15D that measures the distance to the object OB based on the light-receiving element 14 receiving the light that has passed through the rotating element 12. Therefore, it is possible to provide a distance measuring device 10 that has a rotating light-reflecting body and is capable of performing high-quality distance measurement by emitting light in a desired direction over a wide range. [Example]

[0072] 8 is a schematic layout diagram of a distance measuring device 30 according to Example 2. The distance measuring device 30 includes a light source 31, a rotating element 32, a separating element 33, and a light receiving element 34. The distance measuring device 30 also includes a control unit 35 that controls the light source 31, the rotating element 32, and the light receiving element 34.

[0073] The light source 31, the separation element 33, the light receiving element 34, and the control unit 35 have the same configurations as the light source 11, the separation element 13, the light receiving element 14, and the control unit 15 of the distance measuring device 10, respectively. On the other hand, in this embodiment, the distance measuring device 30 has a plurality of side surfaces 32S, each of which functions as a light reflecting surface, and a rotating element 32 that rotates around a rotation axis AY.

[0074] Specifically, the distance measuring device 10 of the first embodiment has been described as including a rotating mirror that rotates around mutually perpendicular rotation axes AX and AY and has one light reflecting surface 12S as the rotating element 12. On the other hand, the rotating element 32 of the distance measuring device 30 of the present embodiment is a rotating mirror that rotates around one rotation axis AY and has a light reflecting surface provided on each of multiple side surfaces 32S.

[0075] In this embodiment, the rotating element 32 is a polygon mirror having a truncated pyramidal shape (a polygonal truncated pyramidal shape) with a plurality of side surfaces 32S each inclined with respect to the rotation axis AY. Each of the side surfaces 32S of the rotating element 32 is reflective to the emitted light L1 and is disposed on the optical axis of the emitted light L1.

[0076] The emission direction of the scanning light L2 emitted from the rotating element 32 changes periodically. The area irradiated with the scanning light L2 within one change period of the emission direction of the scanning light L2 (within one rotation period of the rotating element 12A) is the scanning area R0. The scanning area R0 is a virtual three-dimensional space into which the scanning light L2 is emitted. In FIG. 8, the outer edge of the scanning area R0 is schematically indicated by a dashed line.

[0077] For example, in this embodiment, the scanning region R0 can be defined as a cone-shaped space having a height range along a height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along a width direction D2 corresponding to the direction perpendicular to the rotation axis AY, and a depth range along a depth direction corresponding to the axial direction of the optical axis of the scanning light L2.

[0078] For example, the normal vector of the side surface 32S of the rotating element 32 changes periodically in response to the rotation of the rotating element 32. In this embodiment, the light source 31 emits the output light L1 toward the rotating element 32 so that the output light L1 is incident on one of the side surfaces 32S of the rotating element 32.

[0079] Therefore, for example, in this embodiment, the height direction range of the scanning region R0 corresponds to the range of change of the axial component of the rotation axis AY in the axial direction of the optical axis of the scanning light L2, which is determined by the axial direction of the optical axis of the output light L1 and the normal vector of the side surface 32S of the rotating element 32 on which the output light L1 is incident. Furthermore, the width direction range of the scanning region R0 corresponds to the range of change of the component of the scanning light L2 in the axial direction perpendicular to the rotation axis AY. Furthermore, the depth direction range of the scanning region R0 corresponds to the range of distances within which the scanning light L2 can maintain a predetermined intensity (intensity detectable by the distance measuring device 30).

[0080] Furthermore, when a virtual plane within the scanning region R0 that is a predetermined distance away from the rotating element 32 is defined as a scanning plane R1, the scanning plane R1 can be defined as a two-dimensional region that extends along a height direction D1 and a width direction D2. The scanning light L2 is emitted toward the scanning region R0 so as to scan this scanning plane R1.

[0081] 9 is a perspective view of the rotating element 32. In this embodiment, the rotating element 32 includes a support 32A and a rotating body 32B supported by the support 32A so as to be rotatable about a rotation axis AY. That is, in this embodiment, the rotating element 32 is a polygon mirror having the rotating body 32B.

[0082] In this embodiment, the rotating body 32B of the rotating element 32 has a regular truncated polygonal pyramid shape with the height direction being the axial direction of the rotation axis AY. In this embodiment, the rotating body 32B has a regular truncated triangular pyramid shape with three side surfaces 32SA, 32SB, and 32SC as the side surface 32S. Hereinafter, the side surface 32S of the rotating body 32B may be referred to as the first side surface, and similarly, the side surfaces 32SB and 32SC may be referred to as the second and third side surfaces, respectively.

[0083] In this embodiment, each of the side surfaces 32SA, 32SB, and 32SC of the rotating body 32B is part of a plane inclined with respect to the axial direction of the rotation axis AY. Furthermore, the side surfaces 32SA, 32SB, and 32SC of the rotating body 32B are arranged to surround the rotation axis AY at positions spaced apart from the rotation axis AY when viewed in the axial direction of the rotation axis AY.

[0084] In this specification, the expression "rotating body 32B has a truncated pyramid shape" means, for example, that rotating body 32B has a portion with an outer shape that forms the side surface of a pyramid or a truncated pyramid. For example, rotating body 32B may have a portion with a shape other than the truncated pyramid shape. Furthermore, rotating body 32B may have irregularities or through holes on the side surface 32S, top surface, or bottom surface.

[0085] For example, the rotating body 32B of the rotating element 32 has a truncated pyramidal main body and a protrusion that protrudes from the bottom surface of the main body along the axial direction of the rotation axis AY. The protrusion is rotatably coupled to the support 32A at its end. For example, the protrusion is part of a shaft that passes through the bottom and top surfaces of the main body.

[0086] Furthermore, for example, the rotating element 32 has a driving force generating unit (not shown) that is provided in the support body 32A, connected to the control unit 35, and generates a force (driving force) that rotates the rotating body 32B. For example, the driving force generating unit is a motor that rotates in response to a driving signal supplied from the control unit 35. Furthermore, for example, the driving force generated by the driving force transmitting unit is transmitted to the rotating body 32B by a transmitting unit (not shown) such as a bearing.

[0087] Next, the distance measuring device 30 has a reflective diffraction grating 40 provided on at least one of the side surfaces 32S of the rotating body 32B of the rotating element 32. In this embodiment, the diffraction grating 40 has first and second reflective diffraction gratings 41 and 42 provided on the first and second side surfaces 32SA and 32SB, respectively. The first and second diffraction gratings 41 and 42 have a plurality of grating grooves 41A and 42A arranged along the first and second side surfaces 32SA and 32SB, respectively.

[0088] In this embodiment, the first diffraction grating 41 has a plurality of grating grooves 41A that extend in a direction perpendicular to the rotation axis AY on the first side surface 32SA of the rotating body 32B and are arranged in the axial direction of the rotation axis AY. The second diffraction grating 42 has a plurality of grating grooves 42A that extend in a direction perpendicular to the axial direction of the rotation axis AY on the second side surface 32SB of the rotating body 32B and are arranged in the axial direction of the rotation axis AY.

[0089] In this embodiment, the third side surface 32SC of the rotating body 32B is not provided with a diffraction grating 40. In this embodiment, the third side surface 32SC is a side surface portion of the rotating body 32B that has specular reflectivity with respect to the emitted light L1. That is, in this embodiment, the first and second side surfaces 32SA and 32SB function as diffracting and reflecting surfaces that diffract and reflect the emitted light L1, and the third side surface 32SC functions as a reflecting surface that reflects the emitted light L1.

[0090] Fig. 10 is a schematic side view of rotating body 32B when viewed in a direction perpendicular to rotation axis AY and parallel to first side surface 32SA of rotating body 32B. Fig. 10 shows only a portion of rotating body 32B. The configuration of diffraction grating 40 will be described using Fig. 10.

[0091] In this embodiment, the first diffraction grating 41 has a wave vector in the direction from the bottom surface to the top surface of the rotating body 32B along the first side surface 32SA, in the upward direction DY3 in the figure, and a blaze angle of θ b1The first diffraction grating 41 is a blazed diffraction grating having a grating surface 41SA (a surface defined by the tops of the grating grooves 41A, a first diffraction grating surface) parallel to the first side surface 32SA of the rotating body 32B, and an angle (first blaze angle) θ b1 10, the blazed surface 41SB is inclined by an angle θ b1 is the angle between the normal to the grating surface 41SA and the normal to the blazed surface 41SB.

[0092] 11 is a diagram schematically illustrating the incident direction of the output light L1 and the emission direction of the scanning light L2 relative to the first side surface 32SA of the rotating body 32B. The incident mode of the output light L1 relative to the first side surface 32SA and the emission mode of the scanning light L2 will be described with reference to FIG.

[0093] First, in this embodiment, the light source 31 is configured and arranged to emit light L1 onto the first to third side surfaces 32SA to 32SC along a direction intersecting a plane PL1 that is perpendicular to the rotation axis AY of the rotating body 32B. In this embodiment, the light source 31 is configured and arranged to emit light L1 onto the first to third side surfaces 32SA to 32SC with its optical axis inclined in a direction DY3 with respect to the plane PL1.

[0094] 11, while the rotating body 32B is rotating so that the output light L1 is incident on the first side surface 32SA, the output light (hereinafter referred to as the first output light) L11 is incident on the first diffraction grating 41. The first output light L11 is then diffracted and reflected by the first diffraction grating 41. The first output light L11 diffracted and reflected by the first diffraction grating 41 is emitted as scanning light (hereinafter referred to as the first scanning light) L21.

[0095] In this embodiment, the first diffraction grating 41 is a blazed diffraction grating, and more specifically, the blazed diffraction grating is configured to maximize the diffraction efficiency of a predetermined diffraction order and wavelength and minimize the diffraction efficiency of other diffraction orders and wavelengths. Therefore, the light diffracted by the blazed diffraction grating is light whose main component is diffracted light of a specific order.

[0096] In this embodiment, the direction of emission of the diffracted light of the order that is the main component is determined by the blaze angle θ b1 , the pitch d1 of the grating grooves 41A, the wavelength of the emitted light L1, and the incident angle θ of the emitted light L1. 11 That is, the blaze angle θ of the blazed diffraction grating is determined according to the wavelength of the output light L1. b1 By setting the pitch d1 of the grating grooves 41A, the incident angle θ 11 The first outgoing light L11 incident at the first scanning light L21 can be reflected at a desired angle as the first scanning light L21.

[0097] In this embodiment, the first outgoing light L11 is diffracted and reflected by the first diffraction grating 41, and as a result, the scanning light L21 is angled at an angle of θ 11 -2(θ b1 ) along an optical axis tilted in the opposite direction to the direction DY3.

[0098] In other words, the first scanning light L21 is emitted at an angle in the axial direction of the rotation axis AY that is different from the angle at which the first outgoing light L11 is specularly reflected by the first side surface 32SA. Furthermore, the component of the emission direction of the first scanning light L21 along the axial direction of the rotation axis AY remains almost unchanged even when the first side surface 32SA rotates around the rotation axis AY.

[0099] 12 is a schematic side view of the rotating body 32B when the rotating body 32B is viewed in a direction perpendicular to the rotation axis AY and parallel to the second side surface 32SB of the rotating body 32B. In this embodiment, a second diffraction grating 42 is provided on the second side surface 32SB. The direction from the bottom surface to the top surface of the rotating body 32B along the second diffraction grating 42 has a wave vector in the upward direction DY3 in the figure, and the blaze angle is θ b2 is a blazed diffraction grating.

[0100] The second diffraction grating 42 has a grating surface 42SA (a surface defined by the tops of the grating grooves 42A, a second diffraction grating surface) parallel to the second side surface 32SB of the rotating body 32B, and an angle (second blaze angle) θ b2 12, the blazed surface 42SB is inclined by an angle θ b2 is the angle between the normal to the grating surface 42SA and the normal to the blazed surface 42SB.

[0101] In this embodiment, the pitch d2 of the grating grooves 42A is equal to the pitch d1 of the grating grooves 41A, and the second blaze angle θ b2 is the first blaze angle, θ b1 That is, the inclination angle of blazed surface 42SB of second diffraction grating 42 relative to grating surface 42SA is smaller than the inclination angle of blazed surface 41SB of first diffraction grating 41 relative to grating surface 41SA.

[0102] FIG. 13 is a diagram schematically showing the incident direction of the emitted light (hereinafter referred to as second emitted light L12) and the emission direction of the scanning light (hereinafter referred to as second scanning light) L22 relative to the second side surface 32SB of the rotating body 32B.

[0103] 13, the second outgoing light L12 incident on the second side surface 32SB is incident on the second diffraction grating 42 and is diffracted. The second outgoing light L12 diffracted by the second diffraction grating 42 is emitted as the second scanning light L21.

[0104] In this embodiment, the second diffraction grating 42 has a wave vector in the direction DY3 and a blaze angle equal to the first blaze angle θ b1 Angle θ smaller than b2 Therefore, in this embodiment, as a result of the second outgoing light L12 being diffracted and reflected by the second diffraction grating 42, the scanning light L22 is angled at an angle of θ 11 -2(θ b2 ) toward the opposite side from the direction DY3. For example, as shown in Fig. 13, the second scanning beam L22 is emitted from the second diffraction grating 42 along an optical axis that is approximately parallel to a plane PL1 that is perpendicular to the rotation axis AY.

[0105] In other words, in this embodiment, as shown in Figures 10 and 12, the diffraction grating 40 includes a first diffraction grating 41 provided on a first side surface 32SA of the rotating body 32B, and a second diffraction grating 42 provided on a second side surface 32SB different from the first side surface 32SA.

[0106] The first and second diffraction gratings 41 and 42 each have a plurality of grating grooves 41A and 42A that extend in a direction perpendicular to the axial direction of the rotation axis AY and are arranged in the first and second side surfaces 32SA and 32SB along the axial direction of the rotation axis AY. In this embodiment, the first and second diffraction gratings 41 and 42 are blazed diffraction gratings having different characteristics.

[0107] FIG. 14 is a diagram schematically showing the incident direction of the emitted light (hereinafter referred to as third emitted light L13) and the emission direction of the scanning light (hereinafter referred to as third scanning light) L23 relative to the third side surface 32SC of the rotating body 32B.

[0108] In this embodiment, the diffraction grating 40 is not provided on the third side surface 32SC of the rotating body 32B. Therefore, the third output light L13 is specularly reflected by the third side surface 32SC. Therefore, the output direction of the third scanning light L23 is a direction that corresponds to the reflection condition of the third output light L13 at the third side surface 32SC. In other words, as a result of the third output light L13 being specularly reflected by the third side surface 32SC, the third scanning light L23 is angled θ with respect to the normal direction of the third side surface 32SC. 11 The light is emitted along an optical axis tilted in the opposite direction to the direction DY3.

[0109] In this way, the scanning light L2 is sequentially emitted while changing the component in the direction perpendicular to the rotation axis AY in accordance with the rotation of the rotating body 32B so that the component in the axial direction of the rotation axis AY differs between the first, second, and third side faces 32SA, 32SB, and 32SC of the rotating body 32B. In other words, the scanning light L2 is reflected in a plurality of directions that form different angles with the plane PL1 between the first, second, and third side faces 32SA, 32SB, and 32SC.

[0110] Fig. 15 is a diagram schematically showing the irradiated position of the scanning light L2 on the scanning surface R1. In Fig. 15, the scanning trajectory of the scanning light L2 on the scanning surface R1 is shown by a broken line. In this embodiment, the scanning light L2 is emitted to trace three trajectories TR1, TR2, and TR3 along the width direction D2 at different positions in the height direction D1.

[0111] In other words, the distance measuring device 30 performs raster scanning on the scanning area R0 to obtain multiple scanning lines along the height direction D1 along the width direction D2, which corresponds to the direction perpendicular to the rotation axis AY of the rotating body 32B of the rotating element 32. The distance measuring device 30 also operates to perform this raster scanning periodically. The portion of the scanning surface R1 that is almost completely irradiated with the scanning light L2 along the width direction D2A, for example, the central portion of the scanning surface R1, becomes the effective scanning area R11.

[0112] As described above, in this embodiment, a blazed diffraction grating is provided as a diffraction grating 40 on at least one side surface 32S of the rotating element 32 having a truncated pyramidal rotating body 32B, and the rotating element 32 is rotated, and the emitted light L1 is reflected by the rotating element 32, thereby emitting scanning light L2 toward the scanning region R0A.

[0113] Therefore, for example, by selecting whether or not to provide a diffraction grating 40 on each side surface 32S, or by changing the diffraction conditions (such as the tilt direction of the blaze surface and the pitch of the grating grooves) of the diffraction grating 40 provided on each side surface 32S, it is possible to perform optical scanning over a wide range using a polygon mirror with a simple shape. For example, even if the first and second diffraction gratings 41 and 42 have the same blaze angle and the same grating groove pitch, they can be considered to have different diffraction conditions as long as they have the same wave vectors in different directions. This eliminates the need to prepare multiple light sources or use a polygon mirror with a complex shape to expand the scanning area in the axial direction of the rotation axis AY, for example.

[0114] Furthermore, the rotating body 32B can be easily manufactured because it has a shape that is rotationally symmetrical about the rotation axis AY. Furthermore, the center of gravity of the rotating body 32B is located on the rotation axis AY, ensuring high rotational stability. Therefore, rattles are less likely to occur when the rotating body 32B rotates, and the resulting instability in the emission direction of the scanning light L2 is also suppressed. In other words, changes in the elevation and depression angles of the scanning trajectory of the scanning light L2 can be suppressed. Therefore, highly accurate and consistent scanning and distance measurement results can be obtained over a wide scanning area R0.

[0115] Furthermore, by combining the rotating element 32 and the diffraction grating 40, for example, even when the emitted light L1 is incident from various directions, the scanning light L2 can be emitted in a desired direction by adjusting the configuration of the diffraction grating 40. For example, even when the rotating body 32B has a truncated pyramidal shape in which the inclinations of the first to third side surfaces 32SA to 32SC relative to the rotation axis AY are different at least in part, and the diffraction grating 40 is disposed on one of the first to third side surfaces 32SA to 32SC, the scanning light L2 can be emitted in a desired direction. Therefore, the degree of freedom in arranging other optical elements such as the light source 31 is greatly improved.

[0116] In this embodiment, the third side surface 32SC of the rotating body 32B is not provided with a diffraction grating 40, but is provided with a reflective surface having specular reflectivity. However, the third side surface 32SC may also be provided with, for example, a blazed diffraction grating as the diffraction grating 40. That is, diffraction gratings 40 having different diffraction conditions from one another may be provided on all side surfaces 32SA to 32SC of the rotating body 32B.

[0117] Even in this case, by changing the diffraction conditions (such as the tilt direction of the blaze surface and the pitch of the grating grooves) of the diffraction grating 40 provided for each side surface 32S, the scanning light L2 reflected by each side surface 32S can be reflected at the desired angle.

[0118] Furthermore, when all of the scanning light L2 is generated by diffraction, even if the output light L1 is incident on the side surface 32S at a large incident angle, it is possible to suppress a change in the elevation / depression angle of the scanning trajectory of the scanning light L2 due to each of the side surfaces 32S. Therefore, it is possible to arrange the light source 31 and the light receiving element 34 so that the incident angle of the output light L1 on the side surface 32S is large, and it is possible to significantly reduce the size of the housing that houses the light source 31, the rotating element 32, and the light receiving element 34, particularly in the size in the optical axis direction of the scanning light L2.

[0119] In this embodiment, the diffraction grating 30 is a blazed diffraction grating in which the normal to the blazed surface is tilted in a direction (e.g., direction DY3) along the axial direction of the rotation axis AY on each side surface of the rotating body 32B. However, the configuration of the diffraction grating 40 is not limited to this. For example, the first and second diffraction gratings 41 and 42 may be any diffraction gratings that diffract the output light L1 so that a specific diffracted light component is the main component. Furthermore, for example, the first and second diffraction gratings 41 and 42 may each extend in a direction perpendicular to the axial direction of the rotation axis AY on each side surface 32S and have a plurality of grating grooves 41A and 42A arranged along the axial direction of the rotation axis AY on each side surface 32S.

[0120] In addition, in this embodiment, the case where the diffraction grating 40 has the first and second diffraction gratings 41 and 42 with different diffraction conditions has been described. However, it is sufficient that the diffraction grating 40 is provided on at least one side surface 32S. For example, the diffraction grating 40 may be composed of only the first diffraction grating 41 provided on only the first side surface 32SA. Furthermore, the first and second diffraction gratings 41 and 42 may have the same diffraction condition.

[0121] In this embodiment, the rotating body 32B has been described as having a truncated pyramidal shape. However, the rotating body 32B is not limited to having a truncated pyramidal shape, and may have a pyramidal shape with an apex.

[0122] In this embodiment, the rotating body 32B has a truncated pyramidal shape with three sides. However, the number of sides of the rotating body 32B is not limited to three, and the rotating body 32B may have three or more sides.

[0123] As described above, in this embodiment, the distance measuring device 10A includes, for example, a light source 31 that emits light (emitted light L1), a rotating element 32 that has a pyramidal or truncated pyramidal shape rotating about a rotation axis AY and having a height direction in the axial direction of the rotation axis AY, and on at least one of a plurality of side surfaces 32SA of the rotating body 32B is provided a reflective diffraction grating 40 that diffracts the light so that a specific order of diffraction light becomes a main component, a light receiving element 34 that receives light (reflected light L3) that is projected through the rotating element 32, reflected by the object OB, and passes through the rotating element 32, and a distance measuring unit 35D that measures the distance to the object OB based on the light receiving element 34 receiving the light that has passed through the rotating element 32. Therefore, it is possible to provide a distance measuring device 30 that has a simple configuration or a high degree of freedom in arrangement and is capable of performing high-quality distance measurement by emitting light in a desired direction over a wide range. [Example]

[0124] 16 is a schematic layout diagram of a distance measuring device 50 according to Example 3. The distance measuring device 50 includes a light source 51, a rotating element 52, a separating element 53, and a light receiving element 54. The distance measuring device 50 also includes a control unit 55 that controls the light source 51, the rotating element 52, and the light receiving element 54.

[0125] The light source 51, the separation element 53, the light receiving element 54, and the control unit 55 have the same configurations as the light source 31, the separation element 33, the light receiving element 34, and the control unit 35 of the distance measuring device 30. On the other hand, in this embodiment, the rotating element 52 of the distance measuring device 50 has a plurality of side surfaces 52S each functioning as a light reflecting surface, and is a prismatic rotating element 52 that rotates around a rotation axis AY.

[0126] More specifically, in the distance measuring device 30 of the second embodiment, the rotating element 32 is a polygon mirror having a truncated pyramid shape (a polygonal truncated pyramid shape). On the other hand, in the present embodiment, the rotating element 52 is a polygon mirror having a prismatic shape (a polygonal prismatic shape).

[0127] In this embodiment, the emission direction of the scanning light L2 emitted from the rotating element 52 changes periodically. The area irradiated with the scanning light L2 within one change period of the emission direction of the scanning light L2 is a scanning area R0. The scanning area R0 is a virtual three-dimensional space into which the scanning light L2 is emitted. In FIG. 16, the outer edge of the scanning area R0 is schematically indicated by a dashed line.

[0128] For example, the scanning region R0 can be defined as a cone-shaped space having a height range along a height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along a width direction D2 corresponding to the direction perpendicular to the rotation axis AY, and a depth range along a depth direction corresponding to the axial direction of the optical axis of the scanning light L2.

[0129] For example, the normal vector of the side surface 52S of the rotating element 52 changes periodically in response to the rotation of the rotating element 52. In this embodiment, the light source 51 emits the output light L1 toward the rotating element 52 so that the output light L1 is incident on one of the side surfaces 52S of the rotating element 52.

[0130] Therefore, for example, the height direction range of the scanning region R0 corresponds to the range of change of the axial component of the rotation axis AY in the axial direction of the optical axis of the scanning light L2, which is determined by the axial direction of the optical axis of the output light L1 and the normal vector of the side surface 52S of the rotating element 52 on which the output light L1 is incident. Furthermore, the width direction range of the scanning region R0 corresponds to the range of change of the component of the scanning light L2 in the axial direction perpendicular to the rotation axis AY. Furthermore, the depth direction range of the scanning region R0 corresponds to the range of distances within which the scanning light L2 can maintain a predetermined intensity (intensity detectable by the distance measuring device 50).

[0131] Furthermore, when a virtual plane within the scanning region R0 that is a predetermined distance away from the rotating element 52 is defined as a scanning plane R1, the scanning plane R1 can be defined as a two-dimensional region that extends along a height direction D1 and a width direction D2. The scanning light L2 is emitted toward the scanning region R0 so as to scan this scanning plane R1.

[0132] 17 is a perspective view of the rotating element 52. In this embodiment, the rotating element 52 includes a support 52A and a rotating body 52B supported by the support 52A so as to be rotatable around a rotation axis AY relative to the support 52A. That is, in this embodiment, the rotating element 52 is a polygon mirror having the rotating body 52B.

[0133] In this embodiment, the rotating body 52B of the rotating element 52 has a right-prism shape with its height direction aligned with the axial direction of the rotation axis AY. In this embodiment, the rotating body 52B has a regular triangular prism shape with three side surfaces 52SA, 52SB, and 52SC as the side surface 52S. Hereinafter, the side surface 52SA of the rotating body 52B may be referred to as the first side surface, and the side surfaces 52SB and 52SC may be referred to as the second and third side surfaces, respectively.

[0134] In this embodiment, each of the side surfaces 52SA, 52SB, and 52SC of the rotating body 52B is part of a plane parallel to the axial direction of the rotation axis AY. The side surfaces 52SA, 52SB, and 52SC of the rotating body 52B are arranged to surround the rotation axis AY at positions spaced apart from the rotation axis AY when viewed in the axial direction of the rotation axis AY.

[0135] In this specification, the expression "rotating body 52B has a prismatic shape" means, for example, that rotating body 52B has a portion with an outer shape that forms the side surface of a prismatic column. For example, rotating body 52B may have a portion with a shape other than the prismatic column shape. Furthermore, rotating body 52B may have irregularities or through holes on side surface 52S, the top surface, or the bottom surface.

[0136] For example, the rotating body 52B of the rotating element 52 has a prismatic main body and a protrusion that protrudes from the bottom surface of the main body along the axial direction of the rotation axis AY. The protrusion is rotatably coupled to the support 52A at its end. For example, the protrusion is part of a shaft that passes through the bottom and top surfaces of the main body.

[0137] Next, distance measuring device 50 has a reflective diffraction grating 60 provided on at least one of side surfaces 52S of rotating body 52B of rotating element 52. In this embodiment, diffraction grating 60 has first and second reflective diffraction gratings 61 and 62 provided on side surfaces 52SA and 52SB, respectively. First and second diffraction gratings 61 and 62 have a plurality of grating grooves 61A and 62A arranged along side surfaces 52SA and 52SB, respectively.

[0138] In this embodiment, the first diffraction grating 61 has a plurality of grating grooves 61A that extend in a direction perpendicular to the rotation axis AY on the side surface 52SA of the rotating body 52B and are arranged in the axial direction of the rotation axis AY. The second diffraction grating 62 has a plurality of grating grooves 62A that extend in a direction perpendicular to the extension direction of the rotation axis AY on the side surface 52SB of the rotating body 52B and are arranged in the axial direction of the rotation axis AY.

[0139] In this embodiment, the third side surface 52SC of the rotating body 52B is not provided with a diffraction grating 60. In this embodiment, the third side surface 52SC is parallel to the axial direction of the rotation axis AY and is a flat surface that is reflective to the output light L1. That is, in this embodiment, the first and second side surfaces 52SA and 52SB function as diffracting and reflecting surfaces that diffract and reflect the output light L1, and the third side surface 52SC functions as a reflecting surface that reflects the output light L1.

[0140] Fig. 18A is a schematic side view of the rotating body 52B when viewed in a direction perpendicular to the rotation axis AY and parallel to the first side surface 52SA of the rotating body 52B. Fig. 18B is a schematic side view of the rotating body 52B when viewed in a direction perpendicular to the rotation axis AY and parallel to the second side surface 52SB of the rotating body 52B. Figs. 18A and 18B show only a partial side surface of the rotating body 52B. The configuration of the diffraction grating 60 will be described using Figs. 18A and 18B.

[0141] In this embodiment, the first diffraction grating 61 is a blazed diffraction grating having a wave vector in a first direction DY4 in the axial direction of the rotation axis AY (the direction from the support 52A to the rotating body 52B in the axial direction of the rotation axis AY, that is, the upward direction in the figure).

[0142] The first diffraction grating 61 has a grating surface DP1 (a surface defined by the tops of the grating grooves 61A, the first diffraction grating surface) parallel to the side surface 52SA of the rotating body 52B, and an angle (first blaze angle) θ b3 18A, the angle between the normal to the grating surface DP1 and the normal to the blaze surface 61AS is θ b3 is.

[0143] In addition, the second diffraction grating 62 is a blazed diffraction grating having a wave vector in a second direction DY5 (a direction from the rotating body 52B toward the support body 52A in the axial direction of the rotation axis AY, downward in the figure) opposite to the first direction DY4 in the axial direction of the rotation axis AY.

[0144] The second diffraction grating 62 has a grating surface (a surface defined by the tops of the grating grooves 62A, a second diffraction grating surface) DP2 parallel to the side surface 52SB of the rotating body 52B, and an angle (second blaze angle) θ b4 18B, the angle between the normal to the grating surface DP2 and the normal to the blaze surface 62AS is θ b4 is.

[0145] In other words, in this embodiment, the diffraction grating 60 includes a first diffraction grating 61 provided on a first side surface 52SA of the rotating body 52B and a second diffraction grating 62 provided on a second side surface 52SB different from the first side surface 52SA. The first and second diffraction gratings 61 and 62 each extend in a direction perpendicular to the axial direction of the rotation axis AY and have a plurality of grating grooves 61A and 62A arranged along the axial direction of the rotation axis AY. In this embodiment, the first and second diffraction gratings 61 and 62 are blazed diffraction gratings having different characteristics from each other.

[0146] 19A, 19B, and 19C are diagrams schematically showing the incident direction of the emitted light L1 and the emission direction of the scanning light L2 with respect to the rotating body 52B of the rotating element 52. The incident mode of the emitted light L1 and the emission mode of the scanning light L2 will be described with reference to FIGS.

[0147] 19A to 19C, for clarity of explanation, the axial direction of the rotation axis AY is referred to as the y-direction. Also, in FIGS. 19A to 19C, an example will be described in which the output light L1 is incident on the rotating body 52B in a direction perpendicular to the y-direction, and the pitch d4 of the grating grooves 62A is equal to the pitch d3 of the grating grooves 61A. The axial direction of the optical axis of the output light L1 upon incidence on the rotating body 52B is referred to as the z-direction. The direction perpendicular to both the y-direction and the z-direction is referred to as the x-direction.

[0148] For example, in this embodiment, each of the side surfaces 52S of the rotating body 52B is a plane extending along the axial direction of the rotation axis AY. Therefore, the normal vector of each of the side surfaces 52S of the rotating body 52B does not have a y-direction component. Furthermore, the rotating body 52B rotates such that the x-direction and z-direction components of the normal vectors of each of the side surfaces 52S and the grating surfaces DP1 and DP2 of the first and second diffraction gratings 61 and 62 change periodically.

[0149] Figure 19A is a diagram schematically showing the state of the emitted light L1 (first emitted light L11) and the scanning light L2 (first scanning light L21) during the first period P1 in which the emitted light L1 is incident on the first side surface 52SA of the rotating body 52B.

[0150] In the first period P1, the first outgoing light L11 is diffracted and reflected by the first diffraction grating 61. Furthermore, the first outgoing light L11 diffracted and reflected by the first diffraction grating 61 is emitted as the scanning light L21.

[0151] In this embodiment, the first diffraction grating 61 is a blazed diffraction grating. A blazed diffraction grating is configured to maximize the diffraction efficiency of a predetermined diffraction order and wavelength and minimize the diffraction efficiency of other diffraction orders and wavelengths. Therefore, the light diffracted by a blazed diffraction grating is mainly composed of diffracted light of a specific order.

[0152] In this embodiment, the direction of emission of the diffracted light of the order that is the main component is determined by the blaze angle θ b3 , is determined by the pitch d3 of the grating grooves 61A, the wavelength of the emitted light L1, and the incident angle of the emitted light L1. That is, the blaze angle θ of the blazed diffraction grating is determined according to the wavelength of the emitted light L1. b3 By setting the pitch d3 of the grating grooves 61A, the first outgoing light L11 incident on the grating surface DP1 of the blazed diffraction grating can be reflected at a desired angle as the first scanning light L21.

[0153] In this embodiment, the output light L11 is incident on the first diffraction grating 21B from a direction perpendicular to the y direction, and the normal to the blazed surface 61AS of the first diffraction grating 61 is inclined from the first side surface 52SA to the first direction DY4 in the y direction at an angle θ b3 Therefore, in the y direction, the first scanning light L21 is diffracted and reflected by the first diffraction grating 61 in the first direction DY4.

[0154] Thus, during the first period P1, the first scanning light L21 is emitted in a y direction different from the direction in which the first outgoing light L11 is specularly reflected by the first side surface 52SA. In the example shown in FIG. 19A, the first outgoing light L11 does not have a y-direction component, but the first scanning light L21 has a y-direction component. Furthermore, the y-direction component of the first scanning light L21 hardly changes during the first period P1.

[0155] 19B is a diagram schematically illustrating the state of the output light L1 (second output light L12) and the scanning light L2 (second scanning light L22) during a second period P2 in which the output light L1 is incident on the second side surface 52SB of the rotating body 52B. During the second period P2B, the output light L1 is diffracted and reflected by the second diffraction grating 62.

[0156] In this embodiment, the second diffraction grating 62 is a blazed diffraction grating having different characteristics from the first diffraction grating 61, in that the normal to the blazed surface 62AS is tilted in a second direction DY5 opposite to the first direction DY4 in the y direction.

[0157] Therefore, in the y direction, the second outgoing light L12 is diffracted and reflected by the second diffraction grating 62 as scanning light L22 in a second direction DY5, i.e., a direction different from the first direction DY4. Moreover, the second scanning light L22 is emitted in a direction different from the first scanning light L21 in the y direction. Moreover, the y direction component of the second scanning light L22 hardly changes during the second period P2.

[0158] Figure 19C is a diagram schematically showing the state of the emitted light L1 (third emitted light L13) and the scanning light L2 (third scanning light L23) during the third period P3B in which the emitted light L1 is incident on the third side surface 52SC of the rotating body 52B.

[0159] In this embodiment, no diffraction grating is provided on the third side surface 52SC. Therefore, during the third period P3, the output light L1 is reflected by the third side surface 52SC. Therefore, the output direction of the third scanning light L23 corresponds to the reflection conditions of the third output light L13 at the third side surface 52SC in all of the x, y, and z directions. For example, in the example shown in FIG. 19C, both the third output light L13 and the third scanning light L23 have no y-direction component.

[0160] In this way, scanning light L2 is emitted while changing its x- and z-direction components in accordance with the rotation of rotating body 52B such that the y-direction component differs between first, second, and third side surfaces 52SA, 52SB, and 52SC of rotating body 12BB. In other words, if a plane passing through the incident position of emitted light L1 on rotating body 52B and perpendicular to rotation axis AY is defined as plane PL1, scanning light L2 is reflected in a plurality of directions that form different angles with plane PL1 between first, second, and third side surfaces 52SA, 52SB, and 52SC.

[0161] Fig. 20 is a diagram schematically showing the irradiated position of the scanning light L2 on the scanning surface R1. In Fig. 20, the scanning trajectory of the scanning light L2 on the scanning surface R1 is shown by a dashed line. In this embodiment, the scanning light L2 is sequentially emitted so as to trace trajectories TR1, TR2, and TR3 along the width direction D2 in the first period P1 (first side surface 52SA), the second period P2 (second side surface 52SB), and the third period P3 (third side surface 52SC), respectively.

[0162] In other words, the distance measuring device 50 performs raster scanning on the scanning area R0 to obtain a plurality of scanning lines along the height direction D1 that are aligned along the width direction D2 corresponding to the direction perpendicular to the rotation axis AY of the rotating body 52B of the rotating element 52. The distance measuring device 50 also operates to perform this raster scanning periodically.

[0163] As described above, in this embodiment, a blazed diffraction grating is provided as a diffraction grating 60 on at least one side surface 52S of the rotating element 52 having a prismatic rotating body 52B, and the rotating element 52 is rotated, and the emitted light L1 is reflected by the rotating element 52, thereby emitting scanning light L2 toward the scanning region R0.

[0164] Therefore, for example, by selecting whether or not to provide a diffraction grating 60 on each side surface 52S, or by changing the diffraction conditions (such as the tilt direction of the blaze surface and the pitch of the grating grooves) of the diffraction grating 60 provided on each side surface 52S, it is possible to perform optical scanning over a wide range using a simple prismatic polygon mirror. For example, even if the first and second diffraction gratings 61 and 62 have the same blaze angle and the same grating groove pitch, they can be considered to have different diffraction conditions if they have the same wave vectors in different directions. This eliminates the need to prepare multiple light sources or use a polygon mirror with a complex shape to expand the scanning area, for example, in the axial direction of the rotation axis AY.

[0165] For example, fluctuations in the elevation and depression angles of light when light is specularly reflected by a side surface inclined with respect to the rotation axis AY, and the resulting non-uniformity in the irradiation density of the scanning light L2 (pulsed light) on the scanning area R0 (the formation of areas with large and small intervals between the irradiation positions of adjacent scanning light L2) do not occur. Furthermore, because the rotating body 52B has a simple prismatic shape, it can be easily manufactured and can maintain high rotation accuracy, which prevents the emission direction of the scanning light L2 from becoming unstable. Therefore, highly accurate and consistent scanning and distance measurement results can be obtained over a wide range of the scanning area R0.

[0166] Furthermore, by combining the rotating element 52 and the diffraction grating 60, the emission direction of the scanning light L2 is stabilized, even when the emission light L1 is incident from various directions, which significantly improves the degree of freedom in arranging other optical elements such as the light source 51.

[0167] 21 is a diagram schematically illustrating an example of the arrangement of light source 51 and rotating element 52. As shown in Fig. 21, light source 51 can be configured and arranged, for example, to emit light L1 onto each side surface 52S of rotating element 52 along a direction intersecting with plane PL1 perpendicular to rotation axis AY. In other words, emitted light L1 may be configured to enter rotating element 52 from a direction having a component in the y direction.

[0168] Even in this case, the emission direction of the scanning light L2, for example, the y-direction component in the emission direction of the scanning light L2, is stabilized by the blaze condition of the diffraction grating 60. This makes it possible to reduce the size of the distance measuring device 50, for example, without sacrificing the scanning accuracy and distance measuring accuracy.

[0169] In this embodiment, the first and second diffraction gratings 61 and 62 are blazed diffraction gratings having a wave vector in the axial direction of the rotation axis AY (i.e., the y direction). However, the configuration of the first and second diffraction gratings 61 and 62 is not limited to this.

[0170] For example, the first and second diffraction gratings 61 and 62 may be any diffraction gratings that diffract the output light L1 so that a specific diffracted light is the main component. Also, for example, the first and second diffraction gratings 61 and 62 may each extend in a direction perpendicular to the axial direction of the rotation axis AY and have a plurality of grating grooves 61A and 62A arranged along the axial direction of the rotation axis AY.

[0171] Furthermore, even when the first and second diffraction gratings 61 and 62 are blazed diffraction gratings, the first and second diffraction gratings 61 and 62 are not limited to having wave vectors in different directions. For example, the first and second diffraction gratings 61 and 62 may have wave vectors in the same direction (for example, the first direction DY4) and have different blaze angles (angle θ b3 and θ b4Even in this case, the first and second scanning beams L21 and L22 are emitted from the first and second diffraction gratings 21B and 22B, respectively, toward different positions in the y direction, for example.

[0172] In this embodiment, the diffraction grating 60 has first and second diffraction gratings 61 and 62 that have different diffraction conditions. However, it is sufficient that the diffraction grating 60 is provided on at least one side surface 52S. For example, the diffraction grating 60 may be provided only on the first side surface 52SA. Furthermore, the first and second diffraction gratings 61 and 62 may have the same diffraction condition.

[0173] In this embodiment, the rotating body 52B has been described as having a triangular prism shape, but the number of side surfaces of the rotating body 52B is not limited to three, and the rotating body 52B may have three or more side surfaces.

[0174] Thus, the distance measuring device 50 includes, for example, a light source 51 that emits light (emitted light L1), a rotating element 52 that has a prismatic rotating body 52B that rotates about a rotation axis AY and has a height direction in the axial direction of the rotation axis AY, and has a reflective diffraction grating 60 that diffracts the light so that a specific order of diffraction light becomes a main component on at least one side surface (first and second side surfaces 52SA and 52SB) of a plurality of side surfaces 52S of the rotating body 52B, a light receiving element 54 that receives light (reflected light L3) that is projected through the rotating element 52, reflected by the object OB, and passes through the rotating element 52, and a distance measuring unit 55D that measures the distance to the object OB based on the light receiving element 54 receiving the light that has passed through the rotating element 52. Therefore, it is possible to provide a distance measuring device 50 that has a rotating light reflector and is capable of performing high-quality distance measurement by emitting light in a desired direction over a wide range.

[0175] In the above-described second and third embodiments, the side surface 32S of the rotating body 32B and the side surface 52S of the rotating body 52 each function as a light reflecting surface that reflects (and diffracts) the emitted light L1. However, the light reflecting surface may be any of the side surfaces 32S of the rotating body 32 or any of the side surfaces 52S of the rotating body 52.

[0176] In other words, when a rotating body rotates around a rotation axis AY (first rotation axis) like rotating bodies 32 and 52 and has a pyramidal, truncated pyramidal or prism shape with the axial direction of the rotation axis as the height direction, at least one light reflecting surface that reflects the emitted light L1 may be provided on at least one of the multiple side surfaces of the rotating body.

[0177] Furthermore, the scanning light L2 of the present invention can be used for purposes other than distance measurement, such as scanning purposes or simple lighting purposes. In this case, for example, the distance measuring device 10 does not need to have the light receiving element 14 and the distance measuring unit 15D. In this case, for example, the light source 11, the rotating element 12, and the diffraction grating 20 function as a light emitting device that emits the scanning light L2. Even in this case, stable scanning information and light distribution can be obtained because changes in the elevation and depression angles of the scanning light L2 are suppressed.

[0178] In other words, for example, a light emitting device according to the present invention includes a light source that emits light, and a rotating body (rotating body 12B, 32B, or 52B) that rotates around at least one rotation axis (first rotation axis) and has at least one light reflecting surface (light reflecting surface 12S, side surface 32S, or 52S) that reflects the light, and a rotating element (rotating element 12, 32, or 52) on which a reflective diffraction grating (diffraction grating 20, 40, or 60) that diffracts the light so that a specific order of diffraction light becomes the main component is provided on any of the at least one light reflecting surface (light reflecting surface 12S, side surface 32SA, 32SB, 52SA, or 52SB). This makes it possible to provide a light emitting device that can emit light in a desired direction over a wide range. [Explanation of symbols]

[0179] 10, 30, 50 range finder 11, 31, 51 light source 12, 32, 52 Rotating element 12B, 32B, 52B rotating body 20, 40, 60 diffraction grating

Claims

1. A light source that emits light; a rotating element including a rotating body that rotates around a first rotation axis and has a plurality of side surfaces provided with light-reflecting surfaces that reflect the light, the rotating body having a reflective diffraction grating that diffracts the light so that a specific order of diffraction light becomes a main component on one of the light-reflecting surfaces; the diffraction grating includes a first diffraction grating provided on a first reflecting surface of the plurality of reflecting surfaces of the rotating body, and a second diffraction grating provided on a second reflecting surface of the plurality of reflecting surfaces of the rotating body that is different from the first reflecting surface, the first diffraction grating is a blazed diffraction grating having a wave vector in a first direction in an axial direction of the first rotation axis, The light output device, wherein the second diffraction grating is a blazed diffraction grating having a wave vector in a second direction opposite to the first direction in the axial direction of the first rotation axis.

2. 2. The light output device according to claim 1, wherein the diffraction grating has a plurality of grating grooves, each extending along a direction perpendicular to the axial direction of the first rotation axis and arranged along the axial direction of the first rotation axis.

3. 3. The light emitting device according to claim 1, wherein the light source causes light to be incident on each of the at least one light reflecting surfaces of the rotating body along a direction intersecting a plane perpendicular to the first rotation axis.

4. The light output device according to any one of claims 1 to 3, characterized in that the rotating body rotates around the first rotation axis and has a pyramidal shape, a truncated pyramidal shape, or a prism shape with the axial direction of the first rotation axis as the height direction.

5. A light emitting device according to any one of claims 1 to 4; a light receiving element that receives light that is projected through the rotating element, reflected by an object, and passed through the rotating element; a distance measuring unit that measures the distance to the object based on the result of reception of light by the light receiving element that has passed through the rotating element.

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