Light emission device and distance measuring device

Abstract

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 are provided. [Solution] The optical element includes a light source that emits light, and a rotating body that rotates around a first rotation axis and has at least one light-reflecting surface that reflects the light, and a rotating element in which a reflective diffraction grating is provided on one of the at least one light-reflecting surfaces that diffracts the light so that a specific order of diffracted light becomes the main component.

Description

[Technical Field]

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

[0002] Conventionally, distance measuring devices are known that measure the distance to an object by emitting light toward the object and detecting the light reflected by the object. Furthermore, optical scanning distance measuring devices are known that perform optical scanning of an object and 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 having a mirror unit with a first mirror surface and a second mirror surface inclined 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 [Overview of the project] [Problems that the invention aims to solve]

[0004] A scanning distance measuring device has, for example, a light emission unit that emits pulsed light toward a scanning area. The distance measuring device uses each area illuminated by the pulsed light as seen from the light emission unit as a distance measuring point, and obtains scanning information within the scanning area by receiving light from each of these distance measuring points. 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 a rotation axis. This expands the pulsed light emission area along the axial direction of the rotation axis, enabling scanning over a wide area.

[0005] Furthermore, to perform wide-area scanning, other examples include irradiating a rotating mirror having multiple light-reflecting surfaces with different inclination angles relative to the rotation axis with pulsed light, or irradiating a mirror that reciprocates around at least one rotation axis with pulsed light.

[0006] In either case, considering the efficient scanning of the scanning area and the acquisition of scanning information that is advantageous for handling, it is preferable to maintain the elevation and depression angles of the scanning trajectory as constant as possible within the scanning area.

[0007] However, in the case of a rotating mirror, the direction of the normal vector of the mirror's light-reflecting surface changes with respect to the optical axis of the pulsed light incident from the light-emitting part during its operation, causing a change in the elevation angle of the scanning trajectory of the light reflected by the mirror. This tendency becomes more pronounced as the angle of the mirror's swing increases. In other words, it was difficult to widen the scanning area while maintaining a constant elevation angle of the scanning trajectory.

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

[0009] The invention according to claim 1 includes a light source that emits light, and a rotating body having a plurality of side surfaces that rotate around a first rotation axis and have a light reflection surface that reflects the light. Among the plurality of light reflection surfaces, a reflecting diffraction grating is provided on any one of the light reflection surfaces to diffract the light so that diffracted light of a specific order becomes the main component. The rotating element has the rotating body, and the diffraction grating includes a first diffraction grating provided on a first reflection surface among the plurality of reflection surfaces of the rotating body, and a second diffraction grating provided on a second reflection surface different from the first reflection surface among the plurality of reflection surfaces of the rotating body. 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. The light emitting device is characterized by this.

[0010] In addition, Invention 1 includes the above-described light emitting device, a light receiving element that receives light that is projected through the rotating element, reflected by an object, and then passes through the rotating element, and a distance measuring unit that measures the distance to the object based on the light receiving result of the light passing through the rotating element by the light receiving element. The distance measuring device is characterized by this.

[0011] In addition, Invention 2 includes a light source that emits light, a rotating element having a rotating body that rotates around a rotation axis and has a pyramid shape, a truncated pyramid shape, or a prism shape with the axial direction of the rotation axis as the height direction, and a reflecting diffraction grating provided on at least one of the plurality of side surfaces of the rotating body. Among the plurality of side surfaces of the rotating body, at least one side surface and another side surface reflect the light emitted from the light source in directions where the angles formed with a plane perpendicular to the rotation axis are different from each other. The light emitting device is characterized by this.

Brief Description of the Drawings

[0012] [Figure 1] It is a diagram showing the overall configuration of the distance measuring device according to Example 1. [Figure 2] It is a perspective view of the rotating element of the distance measuring device according to Example 1. [Figure 3]It is a side view of the rotating element of the distance measuring device according to Example 1. [Figure 4] It is a diagram showing the light reflection mode in the rotating element of the distance measuring device according to Example 1. [Figure 5A] It is a side view of the rotating element of the distance measuring device according to the comparative example. [Figure 5B] It is a diagram showing the elevation and depression angles of the distance measuring device according to Example 1 and the conventional distance measuring device using a mirror surface. [Figure 6] It is a diagram showing the scanning area of the distance measuring device according to Example 1. [Figure 7] It is a diagram showing an example of the arrangement of the light source of the distance measuring device according to Example 1. [Figure 8] It is a diagram showing the overall configuration of the distance measuring device according to Example 2. [Figure 9] It is a perspective view of the rotating element of the distance measuring device according to Example 2. [Figure 10] It is a side view of the rotating element of the distance measuring device according to Example 2. [Figure 11] It is a diagram showing the light reflection mode in the rotating element of the distance measuring device according to Example 2. [Figure 12] It is a side view of the rotating element of the distance measuring device according to Example 2. [Figure 13] It is a diagram showing the light reflection mode in the rotating element of the distance measuring device according to Example 2. [Figure 14] It is a diagram showing the light reflection mode in the rotating element of the distance measuring device according to Example 2. [Figure 15] It is a diagram showing the scanning area of the distance measuring device according to Example 2. [Figure 16] It is a diagram showing the overall configuration of the distance measuring device according to Example 3. [Figure 17] It is a perspective view of the rotating element of the distance measuring device according to Example 3. [Figure 18A] It is a side view of the rotating element of the distance measuring device according to Example 3. [Figure 18B] It is a side view of the rotating element of the distance measuring device according to Example 3. [Figure 19A] It is a diagram showing the light reflection mode in the rotating element of the distance measuring device according to Example 3. [Figure 19B] This figure shows the reflection pattern of light at the rotating element of the distance measuring device according to Example 3. [Figure 19C] This figure shows the reflection pattern of light at the rotating element of the distance measuring device according to Example 3. [Figure 20] This figure shows the scanning area of ​​the distance measuring device according to Example 3. [Figure 21] This figure shows an example of the arrangement of the light source of the distance measuring device according to Example 3. [Modes for carrying out the invention]

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

[0014] Figure 1 is a schematic arrangement diagram of the distance measuring device 10 according to Embodiment 1. 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 the scanning area) R0 and measures the distance to an object OB located within the scanning area R0. The configuration of the distance measuring device 10 will be explained using Figure 1. Figure 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 area R0. In this embodiment, the rotating element 12 functions as a deflection element that deflects the emitted light L1 in a variable direction. The rotating element 12 emits the reflected emitted light L1 as 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. Furthermore, 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 such that the light-reflecting surface 12S rotates periodically. Therefore, the direction of emission of the scanning light L2 emitted from the rotating element 12 changes periodically. The region illuminated by the scanning light L2 within the period of change in the direction of emission of the scanning light L2 becomes the scanning region R0. The scanning region R0 is a virtual three-dimensional space from which the scanning light L2 is emitted. In Figure 1, the outer edge of the scanning region R0 is schematically shown by a dashed line.

[0019] For example, the scanning region R0 can be defined as a conical space having a height range along the height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along the width direction D2 corresponding to the rotation axis AX, and a depth range along the depth direction corresponding to the axial direction of the optical axis of the scanning light L2 reflected by the non-rotating light reflecting surface 12S.

[0020] For example, the normal vector of the light-reflecting surface 12S of the rotating element 12 changes periodically in accordance with the rotation of the rotating element 12. In this embodiment, the light source 11 emits light L1 towards the rotating element 12 such that the emitted light L1 is incident on the light-reflecting surface 12S of the rotating element 12.

[0021] Therefore, for example, the height range of the scanning region R0 corresponds to the range of change in 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 emitted light L1 and the normal vector of the optical axis of the rotating element 12S when the emitted light L1 is incident on it. The width range of the scanning region R0 corresponds to the range of change in the axial component of the rotation axis AX in the axial direction of the scanning light L2. The depth range of the scanning region R0 corresponds to the range of distance over which the scanning light L2 can maintain a predetermined intensity (an intensity detectable by the distance measuring device 10).

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

[0023] Furthermore, as shown in Figure 1, if an object OB (i.e., an object or substance that is reflective or scatterable 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 almost 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 and 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 emitted via the rotating element 12, reflected by the object OB, and has passed through the rotating element 12. The light-receiving element 14 also has at least one detection element that detects the reflected light L3 and generates an electrical signal indicating 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 in the figures, the distance measuring device 10 may have an optical system provided in the optical path of the emitted light L1 between the light source 11 and the rotating element 12 to shape the emitted light L1. The distance measuring device 10 may also have an optical system provided in the optical path of the reflected light L3 between the separating element 13 and the light receiving element 14 to focus 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 includes a light source control unit 15A that drives and controls the light source 11, a rotating element control unit 15A 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] Furthermore, the control unit 15 has a distance measuring unit 15D that measures the distance to the target object OB based on the reception result of the reflected light L3 by the light receiving element 14. In this embodiment, the distance measuring unit 15D detects a pulse indicating the reflected light L3 from the electrical signal generated by the light receiving element 14. The distance measuring unit 15D also measures the distance to the target object OB (or a part of its surface area) using the time-of-flight method based on the time difference between the emission timing of the scanning light L2 and the reception timing of the reflected light L3. The distance measuring 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 of the scanning area R0 (distance measuring image) that shows the distance measurement result (distance value) of each of the plurality of distance measuring points as pixels. In this embodiment, the distance measuring unit 15D associates information indicating the distance measuring points with the displacement of the light reflection surface 12S of the rotating element 12 and generates image data showing a two-dimensional map or a three-dimensional map of the scanning area R0.

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

[0031] Figure 2 is a schematic perspective view of the rotating element 12. In this embodiment, the rotating element 12 is a MEMS (Micro Electro Mechanical System) mirror configured such that the light-reflecting surface 12S rotates around the rotation axes AX and AY.

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

[0033] Furthermore, for example, the rotating body 12B has a rotating frame 12BA supported by the support 12A so as to be rotatable around the rotation axis AX on the inner circumference of the support 12A. For example, the rotating frame 12BA is supported by the support 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 provided inside the support 12A.

[0034] Furthermore, the rotating body 12B has a rotating plate 12BB supported by the rotating frame 12BA so as to be rotatable around the rotation axis AY inside the rotating frame 12BA. 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 disc-shaped plate provided inside the rotating frame 12BA.

[0035] The rotating frame 12BA rotates around the pivot axis AX due to the twisting of the torsion bar between the support 12A and the rotating frame 12BA. Similarly, the rotating plate 12BB rotates around the pivot axis AY due to the twisting of the torsion bar between the rotating frame 12BA and the rotating plate 12BB.

[0036] Thus, the rotating plate 12BB rotates around the pivot axes AX and AY. In other words, the rotating body 12B is a movable body supported by the support 12A and having a rotating plate 12BB that is rotatable around the pivot 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 a light-reflecting surface 12S on the rotating body 12B. A metal reflective film or a dielectric multilayer film may be provided on the surface of the rotating plate 12BB. These films can be designed to maintain high reflectivity with respect to changes in the incident angle and wavelength of the emitted light L1. This stabilizes the light reflection characteristics (reflectivity, etc.) of the rotating plate 12BB.

[0038] Furthermore, 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 bandpass filter. This makes it possible to suppress unwanted wavelengths of light other than the emitted light L1, such as ambient light, from mixing with the reflected light L3 and entering the photodetector 14.

[0039] Furthermore, for example, the rotating element 12 is provided on the support body 12A and the rotating body 12B, connected to the control unit 15, and has a driving force generation unit (not shown) that generates a force (driving force) to rotate the rotating body 12B. For example, the driving force generation unit generates voltage power or electromagnetic force as the driving force based on 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 diffraction-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. In this embodiment, each of the grating grooves 21 of the diffraction grating 20 extends along a direction perpendicular to the axial direction of the first rotation axis AY, which is one of the rotation axes AX and AY, on the light-reflecting surface 12S of the rotating body 12B. Furthermore, these plurality of grating grooves 21 are arranged along the axial direction of the rotation axis AY, which is the single rotation axis.

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

[0043] More specifically, the diffraction grating 20 has a grating surface (a surface defined by the tops of the grating grooves 21, the diffraction grating surface) DP1 parallel to the light-reflecting surface 12S of the rotating body 12B, and an angle (blaze angle) θ from the grating surface DP1 toward direction DY1. b It has blaze surfaces 21A that are inclined by a certain amount and arranged at a pitch (distance between adjacent grid grooves 21) d.

[0044] Figure 4 schematically shows the incident direction of the emitted light L1 and the emitted direction of the scanning light L2 with respect to the rotating body 12B (rotating plate 12BB) of the rotating element 12. The incident mode of the emitted light L1 and the emitted mode of the scanning light L2 with respect to the light reflecting surface 12S will be explained using Figure 4.

[0045] In Figure 4, for ease of understanding, the example is shown where the emitted light L1 is incident on the non-rotating light-reflecting surface 12S at an angle (incidence angle) θ1 from the normal to the light-reflecting surface 12S in direction DY1. In this embodiment, the emitted light L1 is incident on the lattice surface DP1 at an incidence angle θ1 (=2θ). b The light is incident on the ) and diffracted and reflected by the blazed diffraction grating, and emitted as scanning light L2 in the direction normal to the grating plane DP1.

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

[0047] In other words, the blaze angle θ of the blazed diffraction grating depends on the wavelength of the emitted light L1. b By setting the pitch d of the grating grooves 21, the emitted light L1 incident on the grating surface DP1 of the blazed diffraction grating at an incident angle θ1 can be reflected as scanning light L2 at a desired angle.

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

[0049] The emission direction of the scanning light L2 with and without the diffraction grating 20 will be explained using Figures 5A and 5B. Figure 5A is a schematic side view of the rotating element 101 of the distance measuring device 100 according to the comparative example. Figure 5B is a diagram showing the change in the emission angle of the scanning light L2 emitted from the rotating element 12 (this embodiment) and the rotating element 101 (comparative example), respectively.

[0050] First, as shown in Figure 5A, the distance measuring device 100 according to the comparative example has the same configuration as the distance measuring device 100, except that it has a rotating element 101. Furthermore, the rotating element 101 has the same configuration as the rotating element 12, except that it has a rotating body 101B having a mirror surface 101S which is a light-reflecting surface that does not have a diffraction grating.

[0051] Figure 5B also shows the changes in the emission angle (elevation angle of the optical axis of the scanning light L2) in the height direction D1 and the emission angle (left-right angle of the optical axis of the scanning light L2) in the width direction D2 for the scanning light L2 emitted from the light reflective surface 12S of the rotating body 12B and the mirror surface 101S of the rotating body 101B, respectively, with the normal of the light reflective surface 12S of the rotating body 12B when it is not rotating being used as the reference (0 degrees).

[0052] As shown in Figure 5A, the mirror surface 101S of the rotating body 101B rotates around a rotation axis that is inclined by θ1 / 2 with respect to the rotation axis AY. In other words, the rotation axis AYH of the rotating body 101B is inclined by θ1 / 2 with respect to the rotation axis AY of the rotating body 12B.

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

[0054] As shown in Figure 5B, the elevation and depression angles of the scanning light L2 emitted from the rotating element 101 of the distance measuring device 100 change rapidly when the normal to the mirror surface 101S rotates to more than 20° to the left or right from a non-rotating state. On the other hand, the elevation and depression angles of the scanning light L2 emitted from the rotating element 12 of the distance measuring device 10 do not change even when the light reflecting surface 12S rotates.

[0055] Figure 6 schematically shows the irradiated positions of the scanning light L2 on the scanning surface R1. In Figure 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 along the width direction D2 on the scanning surface R1 while deflecting it, and repeats this multiple times along the height direction D1.

[0056] More specifically, for example in this embodiment, 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 this 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 a raster scan in which it obtains multiple scan lines along the height direction D1 in the scanning region R0, along the width direction D2 which corresponds to the direction perpendicular to the rotation axis AY of the rotating body 12B of the rotating element 12. Furthermore, the distance measuring device 10 operates in such a way that it performs this raster scan 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 (reciprocates) once along the width direction D2 (i.e., the resonance direction). Therefore, even at the edges of the scanning region R0, for example, the elevation angle of the scanning trajectory of the scanning light L2 hardly changes. As a result, the component of the scanning light L2 in the height direction D1 in the emission direction is stable over a wide range.

[0059] In this embodiment, a rotating element 12, which has a blazed 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 region R0.

[0060] Therefore, for example, changes in the elevation angle of the scanning trajectory of the scanning light L2 (pulsed light) on the scanning area R0 are suppressed. Consequently, it is possible to efficiently scan a wide area of ​​the scanning area R0 and obtain scanning and distance measurement results that are advantageous for handling.

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

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

[0063] As a result, the emitted light L1 is incident on the rotating element 12 along an optical axis that has a component in the axial direction 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 viewed from the point OB of the object during rotation is maximized.

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

[0065] Furthermore, if the diffraction grating 20 is not provided, it is difficult to position the rotating body 12B so that the light-reflecting surface 12S faces directly toward the emitted light L1, and it is also difficult to position it so that it faces directly toward the scanning area R0. Therefore, if the diffraction grating 20 is not provided, the light-reflecting surface 12S of the rotating body 12B must be positioned so that, during rotation, its normal direction always has an angle with respect to the optical axis of the emitted light L1 and also with respect to the optical axis of the reflected light L3 (scanning light L2).

[0066] In contrast, in this embodiment, by providing a diffraction grating 20 and adjusting its diffraction conditions, for example, even when the emitted light L1 is incident on an optical axis inclined from the normal to the light-reflecting surface 12S, scanning light L can be emitted along the direction of the normal to the light-reflecting surface 12S.

[0067] Therefore, the position of the rotating body 12B can be adjusted to, for example, face directly in front of the scanning area R0, in order to increase the solid angle of the light-reflecting surface 12S as seen from the object OB. Consequently, a decrease in the amount of reflected light L3 incident on the light-receiving element 14 can be suppressed. As a result, the accuracy of receiving the reflected light L3, and furthermore, the scanning accuracy and distance measurement accuracy are improved.

[0068] In this embodiment, the case where the diffraction grating 20 is a blazed diffraction grating having a wave vector in the axial direction of the rotation axis AY was described. However, 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 emitted light L1 such that a specific diffracted light is the main component. Alternatively, for example, the diffraction grating 20 may have a plurality of grating grooves 21, each extending in a direction perpendicular to the axial direction of one pivot axis (pivot axis AX or AY) and arranged along the axial direction of said pivot axis.

[0070] Furthermore, in this embodiment, the case in which the rotating body 12B has a light-reflecting surface 12S that rotates around two rotation axes, rotation axes AX and AY, has been described. However, the rotating body 12B may be configured to rotate around only one rotation axis, for example, only rotation axis AY. Even in this case, scanning light L2 can be emitted stably 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 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, and a diffraction grating 20 that diffracts the light so that diffracted light of a specific order becomes the main component, a light-receiving element 14 that receives the light (reflected light L3) that is projected through the rotating element 12, reflected by the object OB, and passed through the rotating element 12, and a distance measuring unit 15D that measures the distance to the object OB based on the light-receiving result of the light that has passed through the rotating element 12 by the light-receiving element 14.Therefore, a distance measuring device 10 can be provided that has a rotating element 12 with a rotating light reflector and can emit light in a desired direction over a wide range, thereby enabling high-quality distance measurement. [Examples]

[0072] Figure 8 is a schematic arrangement diagram of the distance measuring device 30 according to Embodiment 2. The distance measuring device 30 includes a light source 31, a rotating element 32, a separation 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, separation element 33, light receiving element 34, and control unit 35 have the same configuration as the light source 11, separation element 13, light receiving element 14, and 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 sides 32S, each of which functions as a light reflecting surface, and a rotating element 32 that rotates around a pivot axis AY.

[0074] Specifically, the distance measuring device 10 of Embodiment 1 was described in which the rotating element 12 is a rotating mirror that rotates around mutually orthogonal rotation axes AX and AY and has one light-reflecting surface 12S. On the other hand, the rotating element 32 of the distance measuring device 30 of this embodiment is a rotating mirror that rotates around one rotation axis AY and has a light-reflecting surface on each of its multiple side surfaces 32S.

[0075] In this embodiment, the rotating element 32 is a frustum-shaped (or polyphonic frustum-shaped) polygonal mirror having multiple 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 positioned on the optical axis of the emitted light L1.

[0076] The scanning light L2 emitted from the rotating element 32 changes its emission direction periodically. The region illuminated by the scanning light L2 within one period of change in the emission direction of the scanning light L2 (the period it takes for the rotating element 12A to complete one rotation) is called the scanning region R0. The scanning region R0 is a virtual three-dimensional space from which the scanning light L2 is emitted. In Figure 8, the outer edge of the scanning region R0 is schematically shown with a dashed line.

[0077] For example, in this embodiment, the scanning region R0 can be defined as a conical space having a height range along the height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along the width direction D2 corresponding to the direction perpendicular to the rotation axis AY, and a depth range along the 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 accordance with the rotation of the rotating element 32. In this embodiment, the light source 31 emits light L1 towards the rotating element 32 such that the emitted 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 range of the scanning region R0 corresponds to the range of change in 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 emitted light L1 and the normal vector of the side surface 32S of the rotating element 32 to which the emitted light L1 is incident. The width range of the scanning region R0 corresponds to the range of change in the component of the scanning light L2 in the axial direction perpendicular to the rotation axis AY. The depth range of the scanning region R0 corresponds to the range of distance over which the scanning light L2 can maintain a predetermined intensity (an intensity detectable by the distance measuring device 30).

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

[0081] Figure 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 around a rotation axis AY. That is, in this embodiment, the rotating element 32 is a polygon mirror having a rotating body 32B.

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

[0083] In this embodiment, each of the side surfaces 32SA, 32SB, and 32SC of the rotating body 32B is a 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 a position spaced apart from the rotation axis AY when viewed from a direction along the axial direction of the rotation axis AY.

[0084] In this specification, the rotational body 32B having a truncated pyramidal shape means, for example, that the rotational body 32B has an outer shape such as the side surface of a pyramid or truncated pyramidal base. For example, the rotational body 32B may have parts with other shapes besides the truncated pyramidal part. Furthermore, the rotational body 32B may have irregularities, through holes, etc., on its 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 projection that protrudes from the bottom surface of the main body along the axial direction of the rotation axis AY. The projection is rotatably connected to the support 32A at its end. For example, the projection is part of a shaft that penetrates between the bottom and top surfaces of the main body.

[0086] Furthermore, for example, the rotating element 32 is provided within the support body 32A, connected to the control unit 35, and has a drive force generation unit (not shown) that generates a force (driving force) to rotate the rotating body 32B. For example, this drive force generation unit is a motor that rotates in response to a drive signal supplied from the control unit 35. Furthermore, for example, the driving force generated by this drive force transmission unit is transmitted to the rotating body 32B by a transmission 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 side surface 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 each 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 on the first side surface 32SA of the rotating body 32B, each extending in a direction perpendicular to the rotation axis AY and arranged along the axial direction of the rotation axis AY. The second diffraction grating 42 has a plurality of grating grooves 42A on the second side surface 32SB of the rotating body 32B, each extending in a direction perpendicular to the axial direction of the rotation axis AY and arranged along the axial direction of the rotation axis AY.

[0089] Furthermore, in this embodiment, the diffraction grating 40 is not provided on the third side surface 32SC of the rotating body 32B. In this embodiment, the third side surface 32SC is a side 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 diffraction 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] Figure 10 is a schematic side view of the rotating body 32B, viewed along a direction perpendicular to the rotation axis AY and parallel to the first side surface 32SA of the rotating body 32B. Only a portion of the rotating body 32B is shown in Figure 10. The configuration of the diffraction grating 40 will be explained using Figure 10.

[0091] In this embodiment, the first diffraction grating 41 is oriented along the first side surface 32SA from the bottom surface to the top surface of the rotating body 32B, has a wave vector in the upward direction DY3 in the figure, and a blaze angle of θ b1This is a blazed diffraction grating. The first diffraction grating 41 has a grating plane (a plane defined by the top of the grating groove 41A, the first diffraction grating plane) 41SA parallel to the first side surface 32SA of the rotating body 32B, and an angle (first blaze angle) θ from the grating plane 41SA toward direction DY3. b1 It has a blaze surface (first blaze surface) 41SB that is inclined by a certain angle θ and arranged at a pitch (distance between adjacent grid grooves 41A) d1. As shown in Figure 10, b1 This is the angle formed by the normal to the grid surface 41SA and the normal to the blaze surface 41SB.

[0092] Figure 11 schematically shows the incident direction of the emitted light L1 and the emitted direction of the scanning light L2 with respect to the first side surface 32SA of the rotating body 32B. The incident mode of the emitted light L1 and the emitted mode of the scanning light L2 with respect to the first side surface 32SA will be explained using Figure 11.

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

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

[0095] Here, in this embodiment, the first diffraction grating 41 is a blazed diffraction grating. More specifically, the blazed diffraction grating is a diffraction grating configured to maximize the diffraction efficiency for a predetermined diffraction order and wavelength and minimize the diffraction efficiency for other diffraction orders and wavelengths. Therefore, the light diffracted by the blazed diffraction grating is light mainly composed of diffracted light of a specific order.

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

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

[0098] In other words, in the axial direction of the rotation axis AY, the first scanning light L21 is emitted in a direction different from the angle at which the first emitted light L12 is specularly reflected on the first side surface 32SA. Also, the component along the axial direction of the rotation axis AY in the emission direction of the first scanning light L21 hardly changes even when the first side surface 32SA rotates around the rotation axis AY.

[0099] Figure 12 is a schematic side view of the rotating body 32B, viewed along 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. Furthermore, along the second diffraction grating 42, in the direction from the bottom surface to the top surface of the rotating body 32B, the wave vector is in the upward direction DY3 in the figure, and the blaze angle is θ b2 This is a blazed diffraction grating.

[0100] The second diffraction grating 42 has a lattice plane (a plane defined by the top of the lattice groove 42A, the second diffraction grating plane) 42SA parallel to the second side surface 32SB of the rotating body 32B, and an angle (second blaze angle) θ from the lattice plane 42SA toward direction DY3. b2 It has a blaze surface (second blaze surface) 42SB that is inclined by a certain angle θ and arranged at a pitch (distance between adjacent grid grooves 42A) d2. As shown in Figure 12, b2 This is the angle formed by the normal to the grid surface 42SA and the normal to the blaze surface 42SB.

[0101] Furthermore, in this embodiment, the pitch d2 of the grid groove 42A is equal to the pitch d1 of the grid groove 41A, and the second blaze angle is angle θ. b2 This is the first blaze angle, which is angle θ. b1 It is smaller than that. In other words, the inclination angle of the blaze surface 42SB in the second diffraction grating 42 with respect to the grating surface 42SA is smaller than the inclination angle of the blaze surface 41SB in the first diffraction grating 41 with respect to the grating surface 41SA.

[0102] Figure 13 schematically shows the incident direction of the emitted light (hereinafter referred to as the second emitted light L12) and the emitted direction of the scanning light (hereinafter referred to as the second scanning light) L22 with respect to the second side surface 32SB of the rotating body 32B.

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

[0104] Furthermore, in this embodiment, the second diffraction grating 42 has a wave vector in direction DY3 and a blaze angle equal to the first blaze angle θ. b1 An angle smaller than θ b2 This is a blazed diffraction grating. Therefore, in this embodiment, as a result of the second emitted light L12 being diffracted and reflected by the second diffraction grating 42, the scanning light L22 is θ with respect to the normal direction of the grating plane 42SA. 11 -2(θ b2 The second scanning beam L22 is emitted along an optical axis that is tilted to the opposite side of direction DY3. For example, as shown in Figure 13, the second scanning beam L22 is emitted from the second diffraction grating 42 along an optical axis that is approximately parallel to the plane PL1 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 the first side surface 32SA of the rotating body 32B, and a second diffraction grating 42 provided on a second side surface 32SB that is different from the first side surface 32SA.

[0106] Furthermore, each of the first and second diffraction gratings 41 and 42 has 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 along the axial direction of the rotation axis AY within the first and second sides 32SA and 32SB. In this embodiment, the first and second diffraction gratings 41 and 42 are blazed diffraction gratings having different characteristics from each other.

[0107] Figure 14 schematically shows the incident direction of the emitted light (hereinafter referred to as the third emitted light L13) and the emitted direction of the scanning light (hereinafter referred to as the third scanning light) L23 with respect 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 emitted light L13 is specularly reflected by the third side surface 32SC. Consequently, the direction of emission of the third scanning light L23 corresponds to the reflection condition of the third emitted light L13 at the third side surface 32SC. That is, as a result of the specular reflection of the third emitted light L13 by the third side surface 32SC, the third scanning light L23 is θ with respect to the normal direction of the third side surface 32SC. 11 It is emitted along an optical axis that is tilted in the opposite direction to DY3.

[0109] Thus, the scanning light L2 is sequentially emitted while changing its component perpendicular to the rotation axis AY in accordance with the rotation of the rotating body 32B, such that the axial component of the rotation axis AY differs between the first, second, and third sides 32SA, 32SB, and 32SC of the rotating body 32B. In other words, the scanning light L2 is reflected between the first, second, and third sides 32SA, 32SB, and 32SC in multiple directions, each with a different angle with respect to the plane PL1.

[0110] Figure 15 schematically shows the irradiated position of the scanning light L2 on the scanning surface R1. In Figure 15, 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 emitted so as to trace three trajectories TR1, TR2, and TR3 along the width direction D2, with different positions in the height direction D1.

[0111] In other words, the distance measuring device 30 performs a raster scan on the scanning area R0 such that it obtains multiple scan lines 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, along the height direction D1. The distance measuring device 30 also operates in such a way that it performs the raster scan periodically. Furthermore, the portion of the scanning surface R1 where the scanning light L2 is irradiated almost completely 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 a rotating element 32 having a truncated pyramidal rotating body 32B, and the rotating element is rotated, and the emitted light L1 is reflected by this rotating element 32 to emit the scanning light L2 toward the scanning region R0A.

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

[0114] Furthermore, since the rotating body 32B has a shape that is rotationally symmetric with respect to the rotation axis AY, it can be easily manufactured. Also, since the center of gravity of the rotating body 32B is located on the rotation axis AY, high rotational stability can be ensured. Therefore, rattling of the rotating body 32B during rotation is less likely to occur, and the resulting instability of the emission direction of the scanning light L2 is also suppressed. In other words, changes in the elevation angle of the scanning trajectory of the scanning light L2 can be suppressed. Therefore, highly accurate and uniform 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, 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 if the rotating body 32B is made into a truncated pyramidal shape in which the inclination of the first to third sides 32SA to 32SC with respect to the rotation axis AY is different in at least some parts, and the diffraction grating 40 is placed on any one of the first to third sides 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] Furthermore, in this embodiment, the case in which a diffraction grating 40 is not provided on the third side surface 32SC of the rotating body 32B, and a reflective surface having specular reflectivity is provided instead, has been described. However, a blazed diffraction grating, for example, may also be provided as the diffraction grating 40 on the third side surface 32SC. That is, diffraction gratings 40 with different diffraction conditions for each side surface may be provided on all sides 32SA to 32SC of the rotating body 32B.

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

[0118] Furthermore, when all scanning light L2 is generated by diffraction, even if the emitted light L1 is incident on the side surface 32S at a large incident angle, the change in the elevation angle of the scanning trajectory of the scanning light L2 due to each side surface 32S can be suppressed. Therefore, it becomes possible to arrange the light source 31 and the photodetector 34 so that the incident angle of the emitted light L1 on the side surface 32S is large, and the size of the housing that accommodates the light source 31, the rotating element 32, and the photodetector 34 can be significantly reduced, especially in terms of the size in the optical axis direction of the scanning light L2.

[0119] In this embodiment, the case described uses a blazed diffraction grating in which the normal of the blaze surface is inclined in a direction along the axial direction of the rotation axis AY within each side surface of the rotating body 32B (for example, direction DY3). 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 diffraction gratings that diffract the emitted light L1 such that a specific diffracted light is the main component. Also, for example, the first and second diffraction gratings 41 and 42 may 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 within each side surface 32S and are arranged along the axial direction of the rotation axis AY within each side surface 32S.

[0120] Furthermore, in this embodiment, the case in which the diffraction grating 40 has first and second diffraction gratings 41 and 42 having different diffraction conditions has been described. However, the diffraction grating 40 only needs to be provided on at least one side surface 32S. For example, the diffraction grating 40 may consist only of a first diffraction grating 41 provided only on the first side surface 32SA. Also, the first and second diffraction gratings 41 and 42 may have the same diffraction conditions.

[0121] Furthermore, in this embodiment, the case in which the rotating body 32B has a truncated pyramidal shape has been described. However, the rotating body 32B is not limited to having a truncated pyramidal shape, and may have a pyramidal shape with a vertex.

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

[0123] Thus, in this embodiment, the distance measuring device 10A includes, for example, a light source 31 that emits light (emitted light L1), a rotating body 32B that rotates around a rotation axis AY and has a pyramidal or truncated pyramidal shape with the axial direction of the rotation axis AY as the height direction, and a reflective diffraction grating 40 that diffracts light so that diffracted light of a specific order becomes the main component on at least one of the multiple sides 32SA of the rotating body 32B, a light receiving element 34 that receives the light (reflected light L3) that is emitted through the rotating element 32, reflected by the object OB, and passed through the rotating element 32, and a distance measuring unit 35D that measures the distance to the object OB based on the light receiving result of the light received by the light receiving element 34 after passing 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 can perform high-quality distance measurement by emitting light in a desired direction over a wide range. [Examples]

[0124] Figure 16 is a schematic arrangement diagram of the distance measuring device 50 according to Embodiment 3. The distance measuring device 50 includes a light source 51, a rotating element 52, a separation 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, separation element 53, light receiving element 54, and control unit 55 have the same configuration as the light source 31, separation element 33, light receiving element 34, and control unit 35 of the distance measuring device 30, respectively. On the other hand, in this embodiment, the rotating element 52 of the distance measuring device 50 has a prismatic rotating element 52 which has multiple sides 52S, each of which functions as a light reflecting surface, and rotates around a rotation axis AY.

[0126] More specifically, in the distance measuring device 30 of Example 2, the case where the rotating element 32 is a polygon mirror having a truncated pyramidal shape (or polygonal truncated pyramidal shape) was described. On the other hand, in this embodiment, the rotating element 52 is a polygon mirror with a prismatic shape (or polygonal prismatic shape).

[0127] In this embodiment, the scanning light L2 emitted from the rotating element 52 changes its emission direction periodically. The region illuminated by the scanning light L2 within one period of change in the emission direction of the scanning light L2 becomes the scanning region R0. The scanning region R0 is a virtual three-dimensional space from which the scanning light L2 is emitted. In Figure 16, the outer edge of the scanning region R0 is schematically shown with a dashed line.

[0128] For example, the scanning region R0 can be defined as a conical space having a height range along the height direction D1 corresponding to the axial direction of the rotation axis AY, a width range along the width direction D2 corresponding to the direction perpendicular to the rotation axis AY, and a depth range along the 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 accordance with the rotation of the rotating element 52. In this embodiment, the light source 51 emits light L1 towards the rotating element 52 such that the emitted light L1 is incident on one of the side surfaces 52S of the rotating element 52.

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

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

[0132] Figure 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 a rotating body 52B.

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

[0134] In this embodiment, each of the side surfaces 52SA, 52SB, and 52SC of the rotating body 52B is a 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 a position spaced apart from the rotation axis AY when viewed from a direction along the axial direction of the rotation axis AY.

[0135] In this specification, the statement that the rotating body 52B has a prismatic shape means, for example, that the rotating body 52B has an outer shape such that it forms the side surface of a prismatic column. For example, the rotating body 52B may have parts with other shapes in addition to the prismatic part. Furthermore, the rotating body 52B may have irregularities, through holes, etc., on its side surface 52S, top surface, or bottom surface.

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

[0137] Next, the distance measuring device 50 has a reflective diffraction grating 60 provided on at least one side surface 52S of the rotating body 52B of the rotating element 52. In this embodiment, the diffraction grating 60 has first and second reflective diffraction gratings 61 and 62 provided on side surfaces 52SA and 52SB, respectively. The first and second diffraction gratings 61 and 62 each 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 on the side surface 52SA of the rotating body 52B, each extending in a direction perpendicular to the rotation axis AY and arranged along the axial direction of the rotation axis AY. The second diffraction grating 62 has a plurality of grating grooves 62A on the side surface 52SB of the rotating body 52B, each extending in a direction perpendicular to the extension direction of the rotation axis AY and arranged along the axial direction of the rotation axis AY.

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

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

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

[0142] Furthermore, the first diffraction grating 61 has a lattice plane (a plane defined by the top of the lattice groove 61A, the first diffraction grating plane) DP1 parallel to the side surface 52SA of the rotating body 52B, and an angle (first blaze angle) θ from the lattice plane DP1 toward the first direction DY4. b3 It has blaze surfaces (first blaze surfaces) 61AS that are inclined by a certain amount and arranged at a pitch (distance between adjacent grid grooves 61A) d3. As shown in Figure 18A, the angle between the normal of the grid surface DP1 and the normal of the blaze surface 61AS is angle θ b3 That is the case.

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

[0144] Furthermore, the second diffraction grating 62 has a lattice plane (a plane defined by the top of the lattice groove 62A, the second diffraction grating plane) DP2 parallel to the side surface 52SB of the rotating body 52B, and an angle (second blaze angle) θ from the lattice plane DP2 toward the second direction DY5. b4 It has a blaze surface (second blaze surface) 62AS that is inclined by a certain amount and arranged at a pitch (distance between adjacent grid grooves 62A) d4. As shown in Figure 18B, the angle between the normal of the grid surface DP2 and the normal of the blaze surface 62AS is angle θ b4 That is the case.

[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 that is different from the first side surface 52SA. Furthermore, each of the first and second diffraction gratings 61 and 62 has a plurality of grating grooves 61A and 62A that extend in a direction perpendicular to the axial direction of the rotation axis AY and are 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] Figures 19A, 19B, and 19C schematically show the incident direction of the emitted light L1 and the emitted 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 emitted mode of the scanning light L2 will be explained using Figures 19A to 19C.

[0147] In Figures 19A to 19C, for clarity of explanation, the axial direction of the rotation axis AY is referred to as the y-direction. Furthermore, in Figures 19A to 19C, the explanation uses the example where the emitted light L1 is incident on the rotating body 52B along a direction perpendicular to the y-direction, and the pitch d4 of the grating groove 62A is equal to the pitch d3 of the grating groove 61A. The axial direction of the optical axis of the emitted light L1 when it is incident 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 side surface 52S of the rotating body 52B does not have a component in the y direction. Furthermore, the rotating body 52B rotates such that the x and z components of the normal vectors of each of the side surfaces 52S and the grating planes DP1 and DP2 of the first and second diffraction gratings 61 and 62 change periodically.

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

[0150] During the first period P1, the first emitted light L11 is diffracted and reflected by the first diffraction grating 61. The first emitted light L11 that has been diffracted and reflected by the first diffraction grating 61 is emitted as 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 at a predetermined order and wavelength, and minimize the diffraction efficiency at other orders and wavelengths. Therefore, the light diffracted by the blazed diffraction grating is light whose main component is diffracted light of a specific order.

[0152] Furthermore, in this embodiment, the emission direction of the diffracted light of the principal order is the Blaze angle θ. b3 The blaze angle θ of the blazed diffraction grating is determined by the pitch d3 of the grating groove 61A, the wavelength of the emitted light L1, and the incident angle of the emitted light L1. In other words, 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 groove 61A, the first emitted 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 emitted light L11 is incident on the first diffraction grating 21B from a direction perpendicular to the y-direction, and the normal to the blaze surface 61AS of the first diffraction grating 61 is at an angle θ from the first side surface 52SA to the first direction DY4 in the y-direction. b3 It is tilted only by a certain angle. Therefore, in the y-direction, the first scanning light L21 is diffracted and reflected by the first diffraction grating 61 toward the first direction DY4.

[0154] Thus, during the first period P1, the first scanning light L21 is emitted in a direction different from the direction in which the first emitted light L11 is specularly reflected at the first side surface 52SA in the y-direction. In the example shown in Figure 19A, the first emitted light L11 has no component in the y-direction, but the first scanning light L21 has a component in the y-direction. Furthermore, the y-direction component of the first scanning light L21 hardly changes during the first period P1.

[0155] Next, Figure 19B schematically shows the characteristics of the emitted light L1 (second emitted light L12) and scanning light L2 (second scanning light L22) during a second period P2 in which the emitted light L1 is incident on the second side surface 52SB of the rotating body 52B. During the second period P2B, the emitted 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 with different characteristics from the first diffraction grating 61, in which the normal of the blaze surface 62AS is inclined in a second direction DY5, opposite to the first direction DY4 in the y direction.

[0157] Therefore, in the y-direction, the second emitted 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. Furthermore, the second scanning light L22 is emitted in a direction different from the first scanning light L21 in the y-direction. Also, the y-direction component of the second scanning light L22 hardly changes during the second period P2.

[0158] Figure 19C schematically shows the characteristics of the emitted light L1 (third emitted light L13) and scanning light L2 (third scanning light L23) during the third period P3B when 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 emitted light L1 is reflected by the third side surface 52SC. Consequently, the emission direction of the third scanning light L23 corresponds to the reflection conditions of the third emitted light L13 at the third side surface 52SC in the x, y, and z directions. For example, in the example shown in Figure 19C, neither the third emitted light L13 nor the third scanning light L23 has a component in the y direction.

[0160] Thus, the scanning light L2 is emitted while changing its x and z components in accordance with the rotation of the rotating body 52B, such that its y-component differs between the first, second, and third sides 52SA, 52SB, and 52SC of the rotating body 12BB. In other words, if we define plane PL1 as the plane that passes through the point of incidence of the emitted light L1 onto the rotating body 52B and is perpendicular to the rotation axis AY, then the scanning light L2 will be reflected between the first, second, and third sides 52SA, 52SB, and 52SC in multiple directions, each with a different angle with respect to plane PL1.

[0161] Figure 20 schematically shows the irradiated positions of the scanning light L2 on the scanning surface R1. In Figure 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 emitted sequentially to trace trajectories TR1, TR2, and TR3 along the width direction D2 during 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 a raster scan in which it obtains multiple scan lines along the height direction D1 in the scanning region R0, along the width direction D2 which corresponds to the direction perpendicular to the rotation axis AY of the rotating body 52B of the rotating element 52. Furthermore, the distance measuring device 50 operates in such a way that it performs this raster scan 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 a rotating element 52 having a prismatic rotating body 52B, and the rotating element 52 is rotated, and the emitted light L1 is reflected by this rotating element 52 to emit scanning light L2 toward the scanning region R0.

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

[0165] For example, when light is specularly reflected by a side surface inclined with respect to the rotation axis AY, fluctuations in the elevation angle of the light, and the resulting non-uniformity of the irradiation density of the scanning light L2 (pulsed light) onto the scanning area R0 (where areas with large and small spacings between adjacent scanning light L2 irradiation positions are formed) do not occur. Furthermore, because the rotating body 52B has a simple prismatic shape, it can be easily manufactured and maintain high rotational accuracy, thus suppressing instability in the emission direction of the scanning light L2. Therefore, highly accurate and uniform scanning and distance measurement results can be obtained over a wide scanning area R0.

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

[0167] Figure 21 is a schematic diagram showing an example of the arrangement of the light source 51 and the rotating element 52. As shown in Figure 21, the light source 51 can be configured and arranged so that, for example, emitted light L1 is incident on each of the side surfaces 52S of the rotating element 52 along a direction intersecting a plane PL1 perpendicular to the rotation axis AY. That is, the emitted light L1 may be configured to be incident on the rotating element 52 from a direction having a component in the y direction.

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

[0169] In this embodiment, the case described is that the first and second diffraction gratings 61 and 62 are blazed diffraction gratings having a wave vector in the axial direction (i.e., the y-direction) of the rotation axis AY. 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 diffraction gratings that diffract the emitted light L1 such that a specific diffracted light is the main component. Alternatively, for example, the first and second diffraction gratings 61 and 62 may each have a plurality of grating grooves 61A and 62A that extend in a direction perpendicular to the axial direction of the rotation axis AY and are 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 case is not limited to the case where the first and second diffraction gratings 61 and 62 have wave vectors in different directions from each other. For example, the first and second diffraction gratings 61 and 62 may have wave vectors in the same direction (e.g., the first direction DY4) and have different blazing angles (angle θ) from each other. b3 and θ b4It may also be a blazed diffraction grating (which is different from the above). In this case as well, for example in the y direction, the first and second scanning beams L21 and 22 will be emitted from the first and second diffraction gratings 21B and 22B toward different positions, respectively.

[0172] Furthermore, in this embodiment, the case in which the diffraction grating 60 has first and second diffraction gratings 61 and 62 having different diffraction conditions has been described. However, the diffraction grating 60 only needs to be provided on at least one side surface 52S. For example, the diffraction grating 60 may be provided only on the first side surface 52SA. Also, the first and second diffraction gratings 61 and 62 may have the same diffraction conditions.

[0173] Furthermore, in this embodiment, the case where the rotating body 52B has a triangular prism shape has been described. However, the number of sides of the rotating body 52B is not limited to three, and it may have three or more sides.

[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 rotates around a rotation axis AY and has a prismatic rotating body 52B with the axial direction of the rotation axis AY as the height direction, and a reflective diffraction grating 60 that diffracts light so that diffracted light of a specific order becomes the main component on at least one of the multiple sides 52S of the rotating body 52B (first and second sides 52SA and 52SB), a light receiving element 54 that receives the light (reflected light L3) that has been emitted through the rotating element 52, reflected by the object OB, and passed through the rotating element 52, and a distance measuring unit 55D that measures the distance to the object OB based on the light receiving result of the light received by the light receiving element 54 after passing through the rotating element 52.Therefore, it is possible to provide a distance measuring device 50 that has a rotating element 52 with a rotating light reflector and can perform high-quality distance measurement by emitting light in a desired direction over a wide range.

[0175] In the above-described embodiments 2 and 3, the cases in which the side surface 32S of the rotating body 32B and the side surface 52S of the rotating body 52 each function as light-reflecting surfaces that reflect (and diffract) the emitted light L1 were explained. However, the light-reflecting surface can 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, if a rotating body, such as the rotating bodies 32 and 52, rotates around a rotation axis AY (first rotation axis) and has a pyramidal shape, truncated pyramidal shape, or prism shape with the axial direction of the rotation axis as the height direction, then at least one light-reflecting surface that reflects the emitted light L1 is provided on at least one of the multiple sides of the rotating body.

[0177] Furthermore, the scanning light L2 in the present invention can be used for applications other than distance measurement, such as scanning applications or simple illumination applications. In this case, for example, the distance measuring device 10 does not need to have a light receiving element 14 and a 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, since changes in the elevation angle of the scanning light L2 are suppressed, stable scanning information and light distribution can be obtained.

[0178] In other words, for example, the light emission 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 or more light-reflecting surfaces (light-reflecting surface 12S, side surface 32S, or 52S) that reflect the light, and a reflective diffraction grating (diffraction grating 20, 40, or 60) that diffracts the light so that diffracted light of a specific order becomes the main component is provided on one of the at least one light-reflecting surfaces (light-reflecting surface 12S, side surface 32SA, 32SB, 52SA, or 52SB). This makes it possible to provide a light emission 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 elements 12B, 32B, 52B rotating body 20, 40, 60 diffraction gratings

Claims

1. A light source that emits light, A rotating body having a plurality of sides that rotate around a first pivot axis and have light-reflecting surfaces that reflect the light, wherein a reflective diffraction grating is provided on one of the plurality of light-reflecting surfaces that diffracts the light so that diffracted light of a specific order is the main component, comprising: The diffraction grating includes a first diffraction grating provided on a first reflective surface among the plurality of reflective surfaces of the rotating body, and a second diffraction grating provided on a second reflective surface different from the first reflective surface among the plurality of reflective surfaces of the rotating body. 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, The light emission device is characterized in that 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 pivot axis.

2. The light emission device according to claim 1, characterized in that the diffraction grating has a plurality of grating grooves, each extending in a direction perpendicular to the axial direction of the first pivot axis and arranged along the axial direction of the first pivot axis.

3. The light emission device according to claim 1 or 2, characterized in that the light source causes light to be incident on each of the at least one light-reflecting surfaces of the rotating body in a direction intersecting with a plane perpendicular to the first rotation axis.

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

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

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