LiDAR device and method for controlling the LiDAR device

Abstract

To provide a structure that enables improvement in resolving power using a light reception element equivalent to conventional ones.SOLUTION: A LiDAR device comprises: a rotary mirror; a light emission unit; and a light reception unit that receives light to convert it into an electric signal. Each of a plurality of reflection surfaces the rotary mirror has is configured to cause light emitted by the light emission unit to scan in a lateral direction within a ranging range accompanied by rotation of the rotary mirror, and direct the reflected light from the ranging range to the light reception unit. The light emission unit has: a first light emission unit that emits light to a direction where an upper side having the ranging range vertically divided into two is scanned; and a second light emission unit that emits light to a direction where a lower side having the ranging range vertically divided into two is scanned. The first light emission unit and the second light emission unit are provided in a position facing a reflection surface different in direction, The light reception unit has: a first light reception unit that is provided in a position receiving the light emitted by the first light emission unit and reflected by the ranging range via the rotary mirror; and a second light reception unit that is provided in a position receiving the light emitted by the second light emission unit and reflected by the ranging range via the rotary mirror.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Embodiments of the present invention relate to a LiDAR device and a method for controlling a LiDAR device. [Background technology]

[0002] A device known as a LIDAR (Light Detection and Ranging or Laser Imaging Detection and Ranging) device is known. This LiDAR device irradiates a measurement range with pulsed light (e.g., laser light) emitted from a light source, captures light (reflected light, scattered light) reflected (or scattered) by an object (target) within the measurement range, and calculates the distance to the target by measuring the time from light emission to reception (round-trip time of light).

[0003] LiDAR devices are used in various technologies, such as autonomous driving, to determine the position and shape of a target by scanning the surface of the target with light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-071725 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-117996 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-125109 Summary of the Invention [Problem to be solved by the invention]

[0005] A LiDAR device scans a target by reflecting light (e.g., laser light) on a mirror and changing the direction of the mirror. When the scanning direction is horizontal (approximately horizontal), the vertical (approximately vertical) resolution depends on the number of pixels stacked vertically on the light receiving element.

[0006] Therefore, when increasing the vertical resolution (approximately vertical direction) of a LiDAR device, possible methods include increasing the number of pixels in the light receiving element, reducing the pixel size, or using a polygon mirror with multiple mirror surfaces with different vertical tilt angles.

[0007] However, with the above-mentioned methods, it is difficult to avoid the increased costs of manufacturing new light-receiving elements and mirrors. Furthermore, if a polygon mirror is used as the mirror, the increased size reduces earthquake resistance and rigidity. Furthermore, increasing the number of pixels not only increases the size of the light-receiving elements, but also requires extending the focal length of the lens that focuses the image onto the light-receiving elements, which inevitably increases the size of the device. Furthermore, reducing the pixel size reduces the amount of light received by each pixel, which requires an imaging optical system (lens, etc.) that does not cause performance problems, resulting in increased costs.

[0008] One example of a problem to be solved by the present invention is to provide a structure in a LiDAR device that can improve resolution using a light receiving element equivalent to that of a conventional device. [Means for solving the problem]

[0009] A LiDAR device according to one embodiment includes a rotating mirror that rotates around a vertical axis, a light emitter that emits light toward the rotating mirror, and a light receiver that receives the light reflected by the rotating mirror and converts it into an electrical signal. The rotating mirror has a plurality of reflective surfaces that reflect light. As the rotating mirror rotates, each of the reflective surfaces scans the light emitted by the light emitter laterally across a distance measurement range and directs light reflected from the distance measurement range toward the light receiver. The light emitter includes a first light emitter that emits light in a direction that scans the upper half of the distance measurement range, which is vertically halved, and a second light emitter that emits light in a direction that scans the lower half of the distance measurement range, which is vertically halved. The first light emitter and the second light emitter are positioned opposite the reflective surfaces, which are oriented in different directions. The light receiving unit has a first light receiving unit located at a position where it receives light emitted by the first light emitting unit and reflected in the distance measurement range via the rotating mirror, and a second light receiving unit located at a position where it receives light emitted by the second light emitting unit and reflected in the distance measurement range via the rotating mirror. [Brief explanation of the drawings]

[0010] [Figure 1-1] FIG. 1-1 is a plan view illustrating scanning of a distance measurement target by a LiDAR device. [Figure 1-2] FIG. 1-2 is a side view illustrating scanning of a target to be measured by a LiDAR device. [Figure 2] FIG. 2 is a side view illustrating scanning by the LiDAR device according to the first embodiment. [Figure 3-1] FIG. 3-1 is a plan view illustrating the structure of the LiDAR device according to the first embodiment. [Figure 3-2] FIG. 3-2 is a front view illustrating the structure of the LiDAR device according to the first embodiment. [Figure 4] FIG. 4 is a block diagram illustrating an example of the electrical configuration of the LiDAR device according to the first embodiment. [Figure 5] FIG. 5 is a flowchart illustrating an example of the flow of processing performed by the control unit of the LiDAR device according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating a double-sided mirror of a LiDAR device according to the second embodiment. [Figure 7] FIG. 7 is a side view illustrating scanning by the LiDAR device according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing a modified example of the rotating mirror included in the LiDAR device according to the second embodiment. [Figure 9] FIG. 9 is a front view showing the structure of the LiDAR device according to the third embodiment. [Figure 10] FIG. 10 is a front view showing the structure of the LiDAR device according to the fourth embodiment. [Figure 11-1] FIG. 11-1 is a plan view illustrating the structure of the LiDAR device according to the fifth embodiment. [Figure 11-2] FIG. 11-2 is a front view illustrating the structure of the LiDAR device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A LiDAR device according to an embodiment will be described with reference to the drawings. Note that in this specification, components according to an embodiment and descriptions of the components may be described using multiple expressions. The components and their descriptions are merely examples and are not limited by the expressions in this specification. The components may also be identified by names different from those in this specification. Furthermore, the components may also be described using expressions different from those in this specification.

[0012] (First embodiment) FIG. 1-1 is a plan view illustrating scanning of a distance measurement target by the LiDAR device 100. FIG. 1-2 is a side view illustrating scanning of a distance measurement target by the LiDAR device 100. The LiDAR device 100 is mounted on, for example, an autonomous vehicle, and measures various objects such as roads, buildings, pedestrians, other vehicles, and obstacles. Note that "LIDAR" is an abbreviation for Light Detection and Ranging or Laser Imaging Detection and Ranging.

[0013] The LiDAR device 100 irradiates a distance measurement range 20 with light 30 emitted from a light source, detects the reception of light (reflected light, scattered light) reflected (or scattered) by an object (distance measurement target) 21 present in the distance measurement range 20, and calculates the distance to the distance measurement target by measuring the time from light emission to light reception (round trip time of light). Note that the distance measurement range 20 is the "field of view" of the LiDAR device 100.

[0014] The light 30 emitted by the LiDAR device 100 is linear in plan view (see FIG. 1-1) and diverges in the vertical direction (approximately vertical direction) in side view (see FIG. 1-2). The LiDAR device 100 moves the irradiated light as shown by arrow A in FIG. 1-1 to illuminate the rectangular distance measurement range 20 vertically while scanning it horizontally (approximately horizontally), thereby grasping the position and shape of the distance measurement target 21.

[0015] 2 is a side view illustrating scanning by the LiDAR device 101 according to the first embodiment. The LiDAR device 101 of this embodiment divides the ranging range 20 into two halves, an upper part and a lower part, and scans each of these halves individually rather than simultaneously. As a result, the LiDAR device 101 uses a light receiving element with the same number of pixels and pixel size as conventional devices, while achieving approximately double the vertical resolution of conventional devices.

[0016] The configuration of the LiDAR device 101 will be described next. Fig. 3-1 is a plan view showing the structure of the LiDAR device 101 according to the first embodiment. Fig. 3-2 is a front view showing the structure of the LiDAR device 101 according to the first embodiment. Note that the structure of the LiDAR device 101 is not limited to the examples shown in Figs. 3-1 and 3-2.

[0017] The LiDAR device 101 includes a light source 1, a collimator lens 2, a rotating table 3, a double-sided mirror 4, an imaging lens 5, and a line sensor 6, and further includes a light source 11, a collimator lens 12, an imaging lens 13, and a line sensor 14. The LiDAR device 101 may further include other components and devices.

[0018] The light sources 1 and 11 and the collimator lenses 2 and 12 are an example of a light-emitting unit that emits light toward the double-sided mirror 4. The light sources 1 and 11 are, for example, laser diodes (LDs) capable of pulse oscillation. The light source 1 emits light (e.g., laser light) 31 by oscillating under the control of a control unit 110 (described later) included in the LiDAR device 101. Similarly, the light source 11 emits light (e.g., laser light) 32 by oscillating under the control of the control unit 110 (described later). The light 31 and 32 are, for example, visible light. Note that the light 31 and 32 may be infrared light, ultraviolet light, or X-rays.

[0019] The collimator lens 2 collimates (converts into parallel light) the light 31 that is emitted from the light source 1 and that is incident on the collimator lens 2, and emits the light toward the double-sided mirror 4. In other words, the collimator lens 2 converts the light that passes through the collimator lens 2 into light whose focal point is located at infinity.

[0020] Similarly, the collimator lens 12 collimates the light 32 that is emitted from the light source 11 and enters the collimator lens 12, and emits the parallel light toward the double-sided mirror 4. In other words, the collimator lens 12 converts the light that passes through the collimator lens 12 into light whose focal point is located at infinity.

[0021] The double-sided mirror 4 and the rotary table 3 constitute an example of a rotary mirror that is driven to rotate around a vertical (e.g., substantially vertical) rotation axis. The rotary table 3 rotates the double-sided mirror 4 around the rotation axis that is substantially vertical. The rotation axis is an imaginary central axis of rotation of the reflective surface. The double-sided mirror 4 is, for example, rectangular and is mounted upright on the rotary table 3 with its longitudinal direction aligned substantially vertically. The double-sided mirror 4 is a mirror having substantially planar reflective surfaces on both sides that can reflect laser light. As the double-sided mirror 4 rotates, each reflective surface scans the light emitted from the light source 1, 11 in a lateral direction (e.g., substantially horizontal direction) within the distance measurement range 20, and directs the light reflected from the distance measurement range 20 toward the line sensors 6, 14.

[0022] 3-2, in this embodiment, the optical axis of the light source 1 and the rotational symmetry axis of the collimator lens 2 are tilted upward with respect to an imaginary plane perpendicular to the double-sided mirror 4 and the rotation axis of the turntable 3. As a result, the light source 1 and the collimator lens 2 constitute an example of a first light-emitting unit, and emit light 31 in a direction that scans the upper half of the distance measurement range 20, which is divided into upper and lower halves.

[0023] 3-2, the optical axis of light source 11 and the rotational symmetry axis of collimator lens 12 are tilted downward with respect to an imaginary plane perpendicular to the double-sided mirror 4 and the rotation axis of turntable 3. As a result, light source 11 and collimator lens 12 constitute an example of a second light-emitting unit, and emit light 32 in a direction that scans the lower half of distance measurement range 20, which is divided into upper and lower halves.

[0024] The first light-emitting unit including light source 1 and the second light-emitting unit including light source 11 are positioned so that they do not simultaneously illuminate the same reflective surface of double-sided mirror 4. In other words, the first light-emitting unit and the second light-emitting unit are positioned so that they face reflective surfaces facing different directions. The first light-emitting unit and the second light-emitting unit are a pair of light-emitting units that emit light from two different directions, and illuminate double-sided mirror 4 from two different directions. Double-sided mirror 4 is positioned so that it receives the light emitted by the pair of light-emitting units from two different directions.

[0025] Next, the imaging lens 5 and the line sensor 6 are an example of a light receiving unit that receives light reflected by the double-sided mirror 4 and converts it into an electrical signal, and constitute a first light receiving unit, which receives light 31 emitted by the first light emitting unit and reflected in the distance measurement range 20 via the double-sided mirror 4. Similarly, the imaging lens 13 and the line sensor 14 are an example of a light receiving unit that receives light reflected by the double-sided mirror 4 and converts it into an electrical signal, and constitute a second light receiving unit that receives light 32 emitted by the second light emitting unit and reflected in the distance measurement range 20 via the double-sided mirror 4.

[0026] Imaging lens 5 collects light 31 reflected by target 21 and incident via double-sided mirror 4, and forms an image on line sensor 6. Similarly, imaging lens 13 collects light 32 reflected by target 21 and incident via double-sided mirror 4, and forms an image on line sensor 14 (FIG. 2 shows a schematic diagram of image 22 formed on line sensor 14).

[0027] The line sensors 6 and 14 are an example of a light receiving element having a plurality of pixels arranged vertically, which detects received light for each pixel and generates and outputs an electrical signal in response to the received light. However, the arrangement of the light receiving elements is not limited to this example.

[0028] In the LiDAR device 101 configured as described above, the light emitted from the light source 1 has its light distribution shaped by the collimator lens 2, is reflected by the upper part of the rotating double-sided mirror 4, and scans the distance measurement range 20 in a substantially horizontal direction. The light reflected from the distance measurement target 21 is reflected by the lower part of the double-sided mirror 4 and is imaged on the line sensor 6 by the imaging lens 5.

[0029] Similarly, the light emitted from light source 11 has its light distribution shaped by collimator lens 12, is reflected by the upper part of double-sided mirror 4, and scans distance measurement range 20 in a substantially horizontal direction. The light reflected from distance measurement target 21 is reflected by the lower part of double-sided mirror 4 and forms an image on line sensor 14 by imaging lens 13.

[0030] 4 is a block diagram showing an example of the electrical configuration of the LiDAR device 101 according to the first embodiment. The LiDAR device 101 further includes a control unit 110 and a motor 18.

[0031] When the motor 18 is driven, it rotates the rotary table 3, which causes the double-sided mirror 4 to rotate around a rotation axis along the longitudinal direction (substantially vertical direction). This further causes the light beams 31 and 32 emitted from the light sources 1 and 11 to scan the distance measurement range 20 in the lateral direction (substantially horizontal direction).

[0032] The control unit 110 is a computer having a processor such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory, and a bus connecting these. The control unit 110 is electrically connected to the light sources 1 and 11, the line sensors 6 and 14, and the motor 18.

[0033] The processor of the control unit 110 functions as a drive control unit 111 and a post-processing unit 112 by executing a program read from the ROM or flash memory.

[0034] The post-processing unit 112 performs various processes based on the outputs of the line sensors 6 and 14. For example, the post-processing unit 112 reconstructs an image that reflects the frontal view of the target 21. The post-processing unit 112 also measures the distance to each part of the target 21. The post-processing unit 112 also grasps the shape of the target 21.

[0035] More specifically, the post-processing unit 112 calculates the shape of the target and the distance to the target from, for example, the difference between the time when the light sources 1, 11 emit the light 31, 32 and the time when the line sensors 6, 14 receive the light 31, 32 reflected from the target. Note that the control unit 110 is not limited to this example.

[0036] The drive control unit 111 is a functional unit that controls the light sources 1 and 11 and the motor 18. More specifically, the drive control unit 111 appropriately synchronizes the direction of the reflecting surface of the rotating double-sided mirror 4 with the light emission timing of the light sources 1 and 11.

[0037] To ensure eye safety, light sources 1 and 11 are designed to emit light only when the light they emit is incident on one of the reflective surfaces of double-sided mirror 4. Furthermore, distance measurement range 20 is set to the front of LiDAR device 101, and distance measurement is not performed on the rear side. Therefore, drive control unit 111 alternately drives light source 1 and light source 11 one at a time.

[0038] For example, let the measurable distance be L, the speed of light be c, the measurement interval (time) for each light source 1, 11 be 4L / c, and the measurement timing for each light source 1, 11 be shifted by 2L / c. In this case, if the distance L is 300 m, the round-trip time for the pulsed light emitted by light source 1 or light source 11 is 2 μs. Therefore, if light source 1 is driven at time 0 μs, light source 11 will be driven at time 2 μs.

[0039] Furthermore, if the time difference set to prevent interference between the light 31 emitted by the light source 1 and the light 32 emitted by the light source 11 is Δ, then the processing flow described below can be considered.

[0040] FIG. 5 is a flowchart showing an example of the flow of processing performed by the control unit 110 of the LiDAR device 101 according to the first embodiment.

[0041] For example, the control unit 110 first functions as the drive control unit 111 to drive the motor 18 to rotate the double-sided mirror 4 (step S1). Next, the control unit 110 functions as the drive control unit 111 to pulse the light source 1 at a predetermined timing (step S2), and obtains the output of the line sensor 6 as the post-processing unit 112 (step S3).

[0042] Next, control unit 110 continues the above process until the elapsed time since step S2 reaches Δ (No in step S4), and when the elapsed time since step S2 reaches Δ (Yes in step S4), switches the optical system to be driven. That is, control unit 110, as drive control unit 111, stops driving light source 1 and starts driving light source 11 (step S5). In step S5, light source 11, like light source 1, pulses at a predetermined timing. Next, control unit 110, as post-processing unit 112, obtains the output of line sensor 14 (step S6).

[0043] The control unit 110 as the post-processing unit 112 performs image generation, distance measurement, AI analysis, and the like using the outputs (electrical signals) obtained from the line sensors 6 and 14.

[0044] Next, the control unit 110 continues the above process until the elapsed time since step S5 reaches Δ (No in step S7), and when the elapsed time since step S5 reaches Δ (Yes in step S7), it determines whether distance measurement has ended (step S8). If the timing to end distance measurement has not yet arrived (No in step S8), the control unit 110 switches the optical system to be driven. In other words, the control unit 110 returns the process to step S2.

[0045] Furthermore, when distance measurement is to be terminated (Yes in step S8), the control unit 110, as the drive control unit 111, stops the oscillation of the light source 1 or light source 11 that is in operation (step S9), and then stops the motor 18 (step S10).

[0046] According to the LiDAR device 101 of this embodiment that operates as described above, it is possible to double the vertical resolution as shown in FIG. 2 while using light receiving elements (line sensors 6, 14) equivalent to those of the conventional device.

[0047] Furthermore, according to this embodiment, the light sources 1, 11 and the collimator lenses 2, 12 are tilted and installed symmetrically on both sides of the double-sided mirror 4, and each measures the upper half and the lower half of the field of view (ranging range 20) of the LiDAR device 101. With this configuration, the LiDAR device 101 is somewhat larger than conventional devices, but because it uses the same sensor as conventional devices, there is no need to improve the performance of the imaging lenses 5, 13, and it is possible to measure the same vertical field of view as conventional devices with twice the resolution at a lower cost than other means.

[0048] Note that, while distance measurement results similar to those of the LiDAR device 101 can be achieved by using two conventional LiDAR devices, the LiDAR device 101 is advantageous in that the two optical systems share a rotating mirror, which automatically matches the frame rate, making image processing relatively easy.

[0049] Next, other embodiments will be described. The following embodiments are modifications of the first embodiment, so the same reference numerals will be used for parts that have already been described in the first embodiment, and the description will be omitted. Only the parts that differ from the first embodiment will be described in detail.

[0050] (Second embodiment) Fig. 6 is a diagram showing a double-sided mirror 401 and a rotary table 3 of the LiDAR device according to the second embodiment. Fig. 7 is a side view illustrating scanning by the LiDAR device 102 according to the second embodiment.

[0051] In the LiDAR device 102, one reflecting surface 41 of the double-sided mirror 401 is inclined in the tilt direction with respect to the rotation axis Ax, and the other reflecting surface 42 is inclined in the opposite direction. In addition, the reflecting surfaces 41 and 42 and the direction of incidence of light onto the reflecting surfaces 41 and 42 are not perpendicular to each other but are inclined at an angle.

[0052] In the LiDAR device 102 configured as described above, light emitted by the light source 1 and incident on the double-sided mirror 4 in an obliquely upward direction becomes even more upward when reflected by the reflecting surface 41, and the upward direction is somewhat offset when reflected by the reflecting surface 42. Furthermore, light emitted by the light source 11 and incident on the double-sided mirror 4 in an obliquely downward direction becomes even more downward when reflected by the reflecting surface 42, and the downward direction is somewhat offset when reflected by the reflecting surface 41.

[0053] By setting the angles of the reflecting surfaces 41 and 42 based on the above-described mechanism, the LiDAR device 102 is capable of scanning with light 311, 312, 321, and 322 in four directions as shown in Fig. 7. In Fig. 7, scanning with light 311 emitted by light source 1 and reflected by reflecting surface 41 and scanning with light 312 emitted by light source 1 and reflected by reflecting surface 42 have been completed, and scanning with light 321 emitted by light source 11 and reflected by reflecting surface 41 is currently underway, after which scanning with light 322 emitted by light source 11 and reflected by reflecting surface 42 is performed.

[0054] According to such a LiDAR device 102, the vertical resolution can be increased by two times compared to when the double-sided mirror 4 is used, and therefore, vertical resolution four times that of the conventional device can be obtained.

[0055] (Variation) FIG. 8 is a diagram showing a modified example of the rotating mirror (comprising a double-sided mirror 4 and a rotating table 3) included in the LiDAR device 102 according to the second embodiment, where (a) is a plan view, (b) is a front view, and (c) is a side view. The rotating mirror may be a polygon mirror. The polygon mirror 402 shown in FIG. 8 is substantially rectangular prism-shaped and has four reflective surfaces 43, 44, 45, and 46. The reflective surfaces 43 and 46 are inclined obliquely upward with respect to the rotation axis Ax, and the reflective surfaces 44 and 45 are inclined obliquely downward with respect to the rotation axis Ax. The upward-facing reflective surface 43 and the reflective surface 46 have different degrees of inclination, and the downward-facing reflective surface 44 and the reflective surface 45 also have different degrees of inclination. In other words, the inclination states of the reflective surfaces 43 to 46 are different from each other.

[0056] With such a polygon mirror 402, the vertical resolution can be increased by two times compared to when a double-sided mirror 401 having two reflecting surfaces 41 and 42 is used, and therefore, vertical resolution eight times higher than conventional techniques can be obtained.

[0057] It is also possible to use a polygon mirror with even more facets, or even a polygon mirror with three facets. However, since polygon mirrors tend to become larger as the number of facets increases, there is a possibility that there will be a trade-off between vertical resolution and rigidity.

[0058] (Third embodiment) 9 is a front view showing the structure of a LiDAR device 103 according to the third embodiment. In this embodiment, the optical axes of the light sources 1 and 11 and the rotational symmetry axes of the collimator lenses 2 and 12 are not tilted but are substantially parallel to an imaginary plane perpendicular to the rotation axis of the double-sided mirror 4 and the turntable 3. Note that this "substantially parallel" does not necessarily mean perfect parallelism, but also includes the intention of allowing a slight deviation from perfect parallelism. In addition, the rotational symmetry axes of the collimator lenses 2 and 12 are offset by a predetermined distance from the optical axis of the light sources 1 and 11 in the direction along the rotation axis of the double-sided mirror 4.

[0059] According to this configuration, it is possible to achieve substantially the same effects as the LiDAR device 101 of the first embodiment.

[0060] (Fourth embodiment) 10 is a front view showing the structure of a LiDAR device 104 according to the fourth embodiment. The optical axes of the light sources 1 and 11 and the rotational symmetry axes of the collimator lenses 2 and 12 of this embodiment are not tilted but are substantially parallel to an imaginary plane perpendicular to the rotation axes of the double-sided mirror 4 and the rotary table 3. Furthermore, in the LiDAR device 104 of this embodiment, the optical axes of the light sources 1 and 11 and the rotational symmetry axes of the collimator lenses 2 and 12, which were deviated in the LiDAR device 103 of the third embodiment, are not deviated but are substantially aligned.

[0061] The LiDAR device 104 also includes a prism 7 in the optical path between the collimator lens 2 and the double-sided mirror 4, which corrects the direction of the optical axis of the light source 1 to point upward. The LiDAR device 104 also includes a prism 15 in the optical path between the collimator lens 12 and the double-sided mirror 4, which corrects the direction of the optical axis of the light source 11 to point downward.

[0062] The LiDAR device 104 also includes a prism 8 in the optical path between the double-sided mirror 4 and the imaging lens 5. The prism 8 corrects the direction of light incident downward from diagonally above to a slightly upward direction. As a result, the prism 8 causes the direction of light incident from diagonally above to approximately coincide with the axis of the imaging lens 5. Here, the direction of light corrected by the prism 8 in this embodiment is approximately horizontal. Note that this approximately horizontal is not limited to being completely horizontal, but also includes the intention of allowing for a slight deviation from completely horizontal.

[0063] The LiDAR device 104 includes a prism 16 in the optical path between the double-sided mirror 4 and the imaging lens 13. The prism 16 corrects the direction of light incident obliquely upward from below to be slightly downward. As a result, the prism 16 causes the direction of light incident obliquely from below to be approximately aligned with the axis of the imaging lens 13. Here, the direction of light corrected by the prism 16 in this embodiment is approximately horizontal.

[0064] This configuration can achieve the same effects as the LiDAR device 101 of the first embodiment. That is, in the LiDAR device 104 of this embodiment, instead of shifting the axes of the collimator lenses 2 and 12 in the above-described third embodiment, the optical axis is corrected by the prism 7 or 15 immediately before incidence on the double-sided mirror 4, and the optical axis is corrected by the prism 8 or 16 immediately after incidence on the double-sided mirror 4. Therefore, aberrations that may occur in the LiDAR device 103 of the third embodiment are less likely to occur in the LiDAR device 104 of this embodiment. Therefore, according to this embodiment, the optical elements can be arranged upright while maintaining illuminance and resolution.

[0065] (Fifth embodiment) Fig. 11-1 is a plan view showing the structure of a LiDAR device 105 according to the fifth embodiment. Fig. 11-2 is a front view showing the structure of the LiDAR device 105 according to the fifth embodiment. The LiDAR device 105 of this embodiment includes cylindrical lenses 9 and 17 in the optical path between the collimator lenses 2 and 12 and the double-sided mirror 4, instead of the prisms 7 and 15 in the LiDAR device 104 of the fourth embodiment.

[0066] The cylindrical lenses diverge incident light into a sheet shape. In this embodiment, the cylindrical lenses 9 and 17 diverge light vertically, that is, the cylindrical lenses 9 and 17 spread light vertically.

[0067] Furthermore, the cylindrical lenses 9 and 17 are arranged so that their main axes are offset by a predetermined distance from the optical axis of the incident light (optical axis of the light-emitting element) in a direction along the rotation axis of the double-sided mirror 4 and the turntable 3. As a result, the cylindrical lens 9 corrects the direction of the optical axis of the incident light upward, and the cylindrical lens 17 corrects the direction of the optical axis of the incident light downward.

[0068] By shifting the optical axes of the cylindrical lenses 9 and 17 in the vertical (approximately vertical) direction, the cylindrical lenses 9 and 17 can both shape and tilt the beam. In a horizontal scanning LiDAR device, it is necessary to keep the horizontal divergence angle of the illumination light small. Since shifting the axes of the cylindrical lenses 9 and 17 hardly increases horizontal aberration, there is little adverse optical effect, unlike the shifting of the axes of the collimator lenses 2 and 12 in the third embodiment.

[0069] Therefore, with this configuration, it is possible to achieve effects equal to or greater than those of the LiDAR device 101 of the first embodiment.

[0070] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0071] 100, 101, 102, 103, 104, 105...LiDAR device, 1, 11...light source, 2, 12...Collimator lens, 3...turntable, 4...double-sided mirror, 402...polygon mirror, 41-46...reflective surface, 5, 13...imaging lens, 6, 14...Line sensor, 7, 8, 15, 16... Prism, 9, 17... Cylindrical lens, 18...motor, 20... distance measurement range, 21... distance measurement target, 22... image, 30, 31, 311, 312, 32, 321, 322...light, 110: control section, 111: drive control section, 112: post-processing section.

Claims

1. A device comprising: a rotating mirror that is driven to rotate around a vertical rotation axis; a light emitting unit that emits light toward the rotating mirror; and a light receiving unit that receives light reflected by the rotating mirror and converts it into an electrical signal, the rotating mirror has a plurality of reflective surfaces that reflect light; Each of the reflecting surfaces causes the light emitted by the light emitting unit to scan the distance measurement range in a horizontal direction in accordance with the rotation of the rotating mirror, and directs the light reflected from the distance measurement range toward the light receiving unit. The light emitting unit a first light emitting unit that emits light in a direction that scans the upper half of the distance measurement range, which is obtained by dividing the distance measurement range into upper and lower halves; a second light emitting unit that emits light in a direction that scans the lower half of the distance measurement range, which is obtained by dividing the distance measurement range into upper and lower halves; and the first light-emitting unit and the second light-emitting unit are provided at positions facing the reflecting surfaces that face different directions, The light receiving unit a first light receiving unit provided at a position to receive light emitted by the first light emitting unit and reflected within the distance measurement range via the rotating mirror; a second light receiving unit provided at a position to receive light emitted by the second light emitting unit and reflected within the distance measurement range via the rotating mirror; have LiDAR device.

2. each of the first light-emitting unit and the second light-emitting unit includes at least a light-emitting element and a collimator lens; The optical axis of the light emitting element and the rotational symmetry axis of the collimator lens are tilted with respect to a virtual plane perpendicular to the rotation axis of the rotating mirror. The LiDAR device of claim 1 .

3. each of the first light-emitting unit and the second light-emitting unit includes at least a light-emitting element and a collimator lens; an optical axis of the light-emitting element and a rotational symmetry axis of the collimator lens are approximately parallel to a virtual plane perpendicular to a rotation axis of the rotating mirror, The rotational symmetry axis of the collimator lens is shifted by a predetermined distance in a direction along the rotation axis of the rotating mirror with respect to the optical axis of the light emitting element. The LiDAR device of claim 1 .

4. each of the first light-emitting unit and the second light-emitting unit includes at least a light-emitting element and a collimator lens; an optical axis of the light-emitting element and a rotational symmetry axis of the collimator lens are substantially coincident with each other and are substantially parallel to a virtual plane perpendicular to the rotation axis of the rotating mirror, a cylindrical lens is included in the optical path between the collimator lens and the rotating mirror, and the main axis of the cylindrical lens is shifted by a predetermined distance in a direction along the rotation axis of the rotating mirror with respect to the optical axis of the light emitting element; The LiDAR device of claim 1 .

5. each of the first light-emitting unit and the second light-emitting unit includes at least a light-emitting element and a collimator lens; an optical axis of the light-emitting element and a rotational symmetry axis of the collimator lens are substantially coincident with each other and are substantially parallel to a virtual plane perpendicular to the rotation axis of the rotating mirror, the first light-emitting unit includes a prism in an optical path between the collimator lens and the rotating mirror that corrects the direction of the optical axis upward, The second light emitting unit includes a prism in the optical path between the collimator lens and the rotating mirror, which corrects the direction of the optical axis downward. The LiDAR device of claim 1 .

6. the first light receiving unit includes at least an imaging lens, a light receiving element that converts an image formed by the imaging lens into an electrical signal, and a prism that is disposed in an optical path between the rotating mirror and the imaging lens and corrects the direction of an optical axis that is incident obliquely from above to be approximately horizontal; The second light receiving unit includes at least an imaging lens, a light receiving element that converts an image formed by the imaging lens into an electrical signal, and a prism that is disposed in the optical path between the rotating mirror and the imaging lens and corrects the direction of the optical axis of light that is incident obliquely from below to approximately horizontal. The LiDAR device according to any one of claims 3 to 5.

7. A control method for a LiDAR device, which controls light emission timing by pulse oscillation of a pair of light-emitting elements provided in the LiDAR device and rotation of a rotating mirror arranged between the pair of light-emitting elements, Driving a motor that rotates the rotating mirror; a step of driving one of the pair of light-emitting elements to emit light in a direction that scans the upper half of the distance measurement range divided into upper and lower halves; acquiring an output of one of a pair of line sensors provided corresponding to the pair of light-emitting elements; waiting for a predetermined time to elapse; a step of driving the other of the pair of light-emitting elements to emit light in a direction that scans the lower half of the distance measurement range, which is obtained by dividing the distance measurement range into upper and lower halves; acquiring an output of the other of the pair of line sensors provided corresponding to the pair of light-emitting elements; a step of terminating the driving of both of the light-emitting elements upon completion of distance measurement; terminating the driving of the motor; A method for controlling a LiDAR device, including:

8. The method further includes a step of positioning the other of the pair of light-emitting elements so that it faces a reflecting surface of the rotating mirror that is oriented in a different direction from that of one of the pair of light-emitting elements, and emitting light. The method for controlling a LiDAR device according to claim 7.

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