JP2023160407A - Lidar device, and lighting fixture for vehicle - Google Patents

Abstract

To provide a lidar device that can recognize a remote obstacle with high accuracy.SOLUTION: A lidar device 1 comprises: a laser source 3 that emits a laser beam; an optical deflector 10 that reflects a laser beam La on a mirror part 12 to perform scanning in the horizontal direction and the vertical direction; and a control unit 40 that controls rotation of the mirror part 12. The control unit 40 performs scanning in the horizontal direction with a laser beam Lb by using a resonance mode of the mirror part 12, and performs scanning in the vertical direction with the laser beam Lb by using a non-resonance mode. In the scanning in the vertical direction with the laser beam Lb, the control unit 40 controls to decrease a scan speed on the lower side of a boundary scan line compared to that on the upper side.SELECTED DRAWING: Figure 2

Description

The present invention relates to a LiDAR device mounted on a vehicle or the like, and a vehicle lamp incorporating the LiDAR device.

BACKGROUND ART Conventionally, systems are known in which a vehicle is equipped with an object recognition device such as a LiDAR (Light Detection and Ranging) device, and the vehicle recognizes vehicles and obstacles around the vehicle while driving and notifies the driver.

For example, the driving support system of Patent Document 1 includes a radar device, a vehicle control section, a communication section, and an external device. A radar device is a laser radar that detects each distance measurement point of an object by intermittently irradiating laser light, which is an electromagnetic wave, to a predetermined area in any direction around the vehicle and receiving each reflected light. It is.

The radar control section causes the laser beam from the optical unit to scan within a predetermined area using the scanning drive section. Then, while changing the range in which the laser beam is irradiated in the horizontal direction from the upper left corner to the upper right corner of this region, the laser beam is intermittently irradiated at equal intervals and at equal angles. When the laser beam reaches the upper right corner, the range to which the laser beam is irradiated is changed, and the laser beam is irradiated again to scan (Patent Document 1/Paragraphs 0018 and 0019, FIG. 2).

Patent No. 6938846

However, when the laser beams are scanned at equal intervals and at equal angles as in Patent Document 1, the distance between the laser beams increases as the distance from the vehicle increases. As a result, there has been a problem in that the accuracy of recognizing distant obstacles is reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a LiDAR device that can recognize distant obstacles with high accuracy.

In order to achieve the above object, the LiDAR device of the present invention includes:
a light source that emits a laser beam, an optical deflector that has a mirror section that rotates about each axis orthogonal to each other, and that scans the laser beam in the horizontal and vertical directions by reflecting the laser beam on the mirror section; A control unit that controls light emission and rotation of the mirror unit,
The control unit scans the laser beam in the horizontal direction using a resonance mode of the mirror unit, scans the laser beam in the vertical direction using a non-resonance mode, and scans the laser beam in the vertical direction using a non-resonance mode. Scanning is performed with respect to a boundary scanning line existing below the center position in the vertical direction such that the scanning speed is slower below the boundary scanning line than above the boundary scanning line.

The LiDAR device of the present invention can scan in two directions, a horizontal direction and a vertical direction, by reflecting a laser beam on a mirror portion of an optical deflector. The control unit that controls the mirror unit uses a resonant mode for horizontal scanning and a non-resonant mode for vertical scanning, so vertical scanning is slower than horizontal scanning. Become.

The control unit further controls the scanning speed in the vertical direction so that the scanning speed below the boundary scanning line (on the road surface side) is slower than that above the boundary scanning line. Thereby, the LiDAR device can recognize obstacles and the like that are present from the front direction to the road surface with high accuracy.

In the LiDAR device of the present invention, it is preferable that, when scanning the laser beam in the vertical direction, the control unit scans so that the interval between horizontal scanning lines becomes gradually narrower as it approaches the boundary scanning line.

This LiDAR device scans a predetermined irradiation area by scanning the laser beam in the horizontal direction and advancing it in the vertical direction. Here, when scanning the laser beam in the vertical direction, the control unit scans so that the interval between the horizontal scanning lines becomes gradually narrower as it approaches the boundary scanning line. As a result, the number of measurement points in the front direction near the boundary scanning line increases, so that object recognition accuracy can be improved.

Further, in the LiDAR device of the present invention, the control unit may be configured such that when scanning the laser beam in the vertical direction, the interval between horizontal scanning lines is the narrowest between the boundary scanning line and the vertical center position. It is preferable to scan.

The control unit scans so that the interval between the horizontal scanning lines becomes the narrowest between the boundary scanning line and the center position in the vertical scanning direction above the boundary scanning line. By increasing the density of measurement points in a region where the most obstacles exist, it is possible to improve the recognition accuracy of the region.

Further, when the LiDAR device of the present invention is disposed at a position less than half the height of the vehicle, it is preferable that the boundary scanning line is maintained at a position above the road surface.

Even when the LiDAR device of the present invention is installed at a position less than half the height of the vehicle, the boundary scanning line is maintained at a position above the road surface. Therefore, the LiDAR device can maintain recognition near the boundary scanning line (in the front direction of the vehicle) with high accuracy, and can therefore detect obstacles in the distance compared to conventional devices.

Another invention is a vehicle lamp incorporating the above LiDAR device. According to this configuration, the LiDAR device can be installed by effectively utilizing the empty space of the vehicle lamp, and obstacles etc. around the vehicle can be detected.

1 is a schematic diagram of a LiDAR device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating the internal structure of a LiDAR device. FIG. 2 is a diagram illustrating the flow of internal signals of a LiDAR device. FIG. 2 is a diagram showing a scanning pattern (side view) of laser light emitted from the LiDAR device. 5 is a diagram illustrating an irradiation area (front view) generated by a laser beam of the LiDAR device in FIG. 4. FIG. FIG. 7 is a diagram showing a scanning pattern (side view) of laser light emitted from the LiDAR device of the second embodiment. 7 is a diagram illustrating an irradiation area (front view) generated by a laser beam of the LiDAR device of FIG. 6. FIG.

Preferred embodiments of the present invention will be described below, but these may be modified and combined as appropriate. In the following description and accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

[First embodiment]
FIG. 1 is a schematic diagram of a LiDAR device 1 according to a first embodiment of the present invention.

The LiDAR device 1 is mounted in front of the vehicle V, and can detect other vehicles, obstacles, pedestrians, bicycles, etc. around the vehicle V using laser light. In this embodiment, the LiDAR device 1 is built into the tip of the hood of the vehicle V between the headlights 2L and 2R. Note that the LiDAR device 1 may be disposed at the bumper or grill of the vehicle V.

The LiDAR device 1 emits laser light (wavelength: approximately 900 nm) from a light source. Furthermore, the LiDAR device 1 receives laser light that has been reflected and bounced back from an object (for example, a pedestrian P) around the vehicle V, and measures the distance between the vehicle V and the object (active method). To measure the distance to the object, a time-of-flight (TOF) method is used, in which the transmitted laser light (pulse wave) is reflected after reaching the object and measures how many seconds it takes to be received. .

FIG. 2 shows the internal structure of the LiDAR device 1 described above. The LiDAR device 1 includes an optical deflector 10, a laser light source 20, a light receiving element 30, and a control device 40.

The optical deflector 10 is manufactured using a semiconductor process or MEMS (Micro Electro Mechanical System) technology. The optical deflector 10 reflects incident light from a certain direction with a mirror section 12 that rotates about mutually orthogonal axes, and outputs the reflected light as scanning light.

Inside the movable frame 13 of the optical deflector 10, a mirror section 12, a circular piezoelectric actuator 14, torsion bars 15a and 15b, which are horizontal driving beams, and the like are arranged. Further, the laser light source 20 (the "light source" of the present invention) emits laser light La (solid line). The laser beam La is reflected by the mirror section 12, and the laser beam Lb scans a predetermined irradiation area.

The control device 40 (the "control unit" of the present invention) transmits control signals to the movable frame 13 and the laser light source 20 via wiring (not shown). This control signal drives the circular piezoelectric actuator 14 of the movable frame 13. When the torsion bars 15a and 15b coupled to the circular piezoelectric actuator 14 are twisted on the axis extending in the Y-axis direction, the mirror portion 12 rotates around the Y-axis. Further, in the laser light source 20, the on/off and brightness of the laser light La are controlled by control signals from the control device 40.

The movable frame 13 is coupled to meander-type piezoelectric actuators 16a and 16b, respectively, at its lower end side. The control device 40 transmits control signals to the meandering piezoelectric actuators 16a and 16b via wiring (not shown). As a result, the mirror section 12 rotates around the X axis. As a result, when the optical deflector 10 reflects the laser beam La at the mirror section 12, the optical deflector 10 emits the laser beam La in front of the optical deflector 10 and scans it in two directions, the X-axis direction and the Y-axis direction. I can do it.

The laser beam Lb reflected by the mirror section 12 hits a surrounding obstacle 50 and is reflected. The reflected light Ra (broken line) enters the mirror portion 12 of the optical deflector 10 and is reflected again. Further, the reflected light Rb is detected by a light receiving element 30 composed of a photodiode. Information on the reflected light Rb is transmitted to the control device 40, and ranging information that is the distance from the LiDAR device 1 to the obstacle 50 is generated.

FIG. 3 shows the internal signal flow of the LiDAR device 1.

As illustrated, the control device 40 transmits a light emission control signal to the laser light source 20. Further, the control device 40 transmits a rotation angle control signal in two axial directions of the mirror section 12 to the optical deflector 10.

Since the laser beam Lb is reflected by the obstacle 50, the reflected light Rb enters the light receiving element 30. The light receiving element 30 transmits optical information based on the reflected light Rb to the control device 40. The control device 40 outputs measurement results (distance information) based on the received optical signal. This measurement can provide the driver of the vehicle V with the distance from the LiDAR device 1 to the obstacle 50, the three-dimensional shape of the obstacle 50, and the like.

FIG. 4 shows a scanning pattern (side view) of the laser beam Lb emitted from the LiDAR device 1 of the vehicle V.

As illustrated, the LiDAR device 1 (laser light emitting unit) is disposed in front of the vehicle V at a position (height h) that is less than half the vehicle height. If a LiDAR device (conventional product) with uniform horizontal scanning line spacing is installed at a position less than half the vehicle height, recognition of the front side of the vehicle will be poor, so it is necessary to install it as high as possible in the vehicle height. there were. In this regard, the LiDAR device 1 according to the present invention can recognize obstacles over a wide range from the road surface in front of the vehicle V to the front direction (details will be described later).

In FIG. 4, "dmin" is the shortest distance that the laser beam Lb reaches the road surface, that is, the shortest observable distance. Moreover, "dmax" is the longest distance that the laser beam Lb reaches the road surface. The laser beam La emitted from the laser beam emitting section of the LiDAR device 1 in a substantially horizontal direction coincides with the central axis C of the LiDAR device 1 .

FIG. 5 shows an irradiation area R (front view) generated by the laser beam Lb of the LiDAR device 1.

The LiDAR device 1 moves the laser beam Lb vertically downward while scanning horizontally from the upper left end to the upper right end of the irradiation area R. The horizontal scanning lines in the irradiation area R are referred to as a first horizontal scanning line SL1, a second horizontal scanning line SL2, . . . , an n-th horizontal scanning line SLn from above. Note that FIG. 5 is a diagram for explaining the concept, and the actual interval between horizontal scanning lines is narrower than the interval shown.

In the area above the central axis C of the irradiation area R, horizontal scanning lines exist at approximately equal intervals. Further, below the central axis C, there is a j-th horizontal scanning line SLj that is a boundary scanning line. The j-th horizontal scanning line SLj is a horizontal scanning line by the laser beam Lb that reaches far from the road surface. A k-th horizontal scanning line SLk (corresponding to "dmax") exists below the j-th horizontal scanning line SLj. At a height near the k-th horizontal scanning line SLk, the interval between the horizontal scanning lines is the narrowest.

Furthermore, the lowest horizontal scanning line of the irradiation area R is the n-th horizontal scanning line SLn (corresponding to "dmin"), and the range from the k-th horizontal scanning line SLk to the n-th horizontal scanning line SLn corresponds to the road surface area. do. The control device 40 controls scanning so that the interval between the horizontal scanning lines gradually narrows as the scanning progresses from the n-th horizontal scanning line SLn to the k-th horizontal scanning line SLk.

When there is an obstacle, reflected light Ra (point cloud) detected by the light receiving element 30 approaches from the n-th horizontal scanning line SLn to the j-th horizontal scanning line SLj (boundary scanning line) above it. As the number increases, the density increases. Even if the LiDAR device 1 (laser light emitting unit) is disposed in front of the vehicle V and at a position less than half the vehicle height, many measurement points can be taken near the j-th horizontal scanning line SLj. , it is possible to improve the recognition accuracy of obstacles that exist from the road surface to the front direction.

In addition, when an obstacle is located far away, the density of the horizontal scanning lines irradiated onto the road surface was conventionally almost uniform, so the distance between the horizontal scanning lines becomes wider as the distance increases, and the road surface position (higher There was a possibility that information on

In this regard, in the present invention, the density of horizontal scanning lines is increased as the distance from the road surface increases. Therefore, the horizontal scanning lines irradiated onto the road surface can be arranged at approximately equal intervals even in a far distance. The road surface position (height) can be accurately recognized, and the height of the road surface where the obstacle is located can be calculated based on the height of the obstacle obtained from the horizontal scanning line illuminated above the boundary scanning line. By subtracting it, the exact height of the obstacle can be calculated. This makes it possible to further improve recognition accuracy.

The horizontal scanning of the laser beam Lb is performed by driving the circular piezoelectric actuator 14 (torsion bars 15a, 15b) of the optical deflector 10. Since the horizontal optical scanning utilizes the resonance mode (resonant frequency) of the torsion bars 15a and 15b, it is faster than the vertical optical scanning.

On the other hand, vertical scanning of the laser beam Lb is performed by driving the meandering piezoelectric actuators 16a and 16b of the optical deflector 10. Vertical optical scanning uses the non-resonant mode (frequency other than the resonant frequency) of the meandering piezoelectric actuators 16a and 16b, so the scanning speed is 1/1000 to 1/100 of the horizontal optical scanning speed. That's about it.

Since the scanning speed of the laser beam Lb in the vertical direction is relatively low, the scanning speed can be further controlled. In scanning below the j-th horizontal scanning line SLj (boundary scanning line) of the irradiation area R, the control device 40 first generates a light emission control signal so that the light emission pulse output from the laser light source 20 is constant.

Further, the control device 40 generates a rotation angle control signal (voltage waveform) such that the mirror unit 12 gradually becomes slower as it approaches the k-th horizontal scanning line SLk from the n-th horizontal scanning line SLn. Thereby, the number of horizontal scanning lines can be increased as it approaches the k-th horizontal scanning line SLk (furthermore, the j-th horizontal scanning line SLj).

Furthermore, in this LiDAR device 1, the number of horizontal scanning lines immediately in front of the vehicle V (road surface) is relatively small, and the measurement point of the shortest distance dmin is located closer to the vehicle V than in the past. Therefore, the recognition range of obstacles in front of the vehicle V can be expanded.

Note that when the number of measurement points in the road surface area of the irradiation area R is "num(>1)", the longest distance "interval_max" between the measurement points of the LiDAR device 1 is given by the following equation (1).
interval_max=(dmax - dmin)/num-1...(1)

For example, when num=36 (pieces), dmax=40 (m), and dmin=5 (m), interval_max=1 (m). Since this value is approximately 1/6 of the distance between measurement points of conventional LiDAR devices, it can be said that object recognition accuracy has been improved.

The control device 40 can also improve the object recognition accuracy by a control method different from the above method. For example, the control device 40 controls the scanning speed of the mirror section 12 to be constant. Then, the control device 40 may perform control such that the number of light emission pulses output from the laser light source 20 increases as the horizontal scanning line SLn approaches the k-th horizontal scanning line SLk (furthermore, the j-th horizontal scanning line SLj). .

[Second embodiment]
Next, an object detection system and LiDAR device according to a second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

FIG. 6 shows a scanning pattern (side view) of the laser beam Lb emitted from the LiDAR device 60 of the vehicle V.

As illustrated, the LiDAR device 60 is disposed in front of the vehicle V at a position (height h) that is less than half the vehicle height. Laser light La irradiated from the LiDAR device 60 in a substantially horizontal direction coincides with the central axis C of the LiDAR device 60.

FIG. 7 shows an irradiation area S (front view) generated by the laser beam Lb of the LiDAR device 60.

The area above the j-th horizontal scanning line SLj (boundary scanning line) of the irradiation area S corresponds to the area in front of the vehicle V, and includes an obstacle dense area including the central axis C and an obstacle sparse area above it. It is divided into. The obstacle sparsely populated area is an area where there are almost no obstacles, so the number of horizontal scanning lines may be small.

On the other hand, the obstacle dense area is set such that the interval between the horizontal scanning lines gradually narrows as it progresses from the first horizontal scanning line SL1 to the j-th horizontal scanning line SLj (boundary scanning line), and the control device 40 Control scanning as follows.

For example, the obstacle dense area may be set such that the height of the obstacle is within the height range of the vehicle from the road surface, and obstacles within the height range can be recognized with high accuracy. Alternatively, the area within a predetermined angle (for example, ±1° to ±15°) in the vertical direction with respect to the central axis C, starting from the LiDAR device 60, may be defined as the obstacle dense area.

As a result, the reflected light Ra (point cloud) detected by the light receiving element 30 when there is an obstacle is transmitted from the first horizontal scanning line SL1 to the j-th horizontal line below the first horizontal scanning line SL1. The closer to the scanning line SLj (boundary scanning line), the larger the number of lines, and the higher the density.

Further, the area below the j-th horizontal scanning line SLj (boundary scanning line) corresponds to a road surface area. When there is an obstacle, the reflected light Ra detected by the light receiving element 30 increases as it approaches from the n-th horizontal scanning line SLn to the j-th horizontal scanning line SLj (boundary scanning line) above it, and becomes denser. Become.

In the vertical scanning of the laser beam Lb in the obstacle-dense area and the road surface area, the control device 40 first generates a light emission control signal so that the light emission pulse output from the laser light source 20 is constant.

Further, the control device 40 generates a rotation angle control signal such that the mirror unit 12 gradually becomes slower as it approaches the k-th horizontal scanning line SLk corresponding to the longest distance on the road surface. Thereby, the number of horizontal scanning lines can be increased as the k-th horizontal scanning line SLk (furthermore, horizontal scanning line SLj) is approached.

The reflected light Ra detected by the light receiving element 30 when there is an obstacle is at its maximum in a relatively wide range near the central axis C. Therefore, the recognition accuracy of distant objects can be improved over a wider range centering on the front direction of the vehicle V.

The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit thereof. The LiDAR devices 1 and 60 can also be built into the headlights 2L and 2R of the vehicle V (see FIG. 1; the "vehicle lamp" of the present invention). Thereby, obstacles around the vehicle V can be detected by effectively utilizing the space of the vehicle lamp.

1, 60... LiDAR device, 2L, 2R... headlight, 10... optical deflector, 12... mirror section, 13... movable frame, 14... circular piezoelectric actuator, 15a, 15b... torsion bar, 16a, 16b... meander type Piezoelectric actuator, 20... Laser light source, 30... Light receiving element, 40... Control device, 50... Obstacle, P... Pedestrian, R, S... Irradiation area, V... Vehicle.

Claims (5)

a light source that emits laser light;
an optical deflector that has a mirror section that rotates about each axis orthogonal to each other, and that scans the laser beam in the horizontal and vertical directions by reflecting the laser beam on the mirror section;
a control unit that controls the light emission of the light source and the rotation of the mirror unit,
The control unit includes:
Scanning the laser beam in the horizontal direction using a resonant mode of the mirror portion, and scanning the laser beam in the vertical direction using a non-resonant mode;
LiDAR characterized in that the vertical scanning of the laser beam is performed with respect to a boundary scanning line existing below the vertical center position such that the scanning speed on the lower side is slower than on the upper side. Device. The LiDAR device according to claim 1, wherein when the control unit scans the laser beam in the vertical direction, it scans so that the interval between horizontal scanning lines becomes gradually narrower as it approaches the boundary scanning line. 3. The control unit scans the laser beam in a vertical direction such that an interval between horizontal scanning lines is the narrowest between the boundary scanning line and the vertical center position. LiDAR device. The LiDAR device according to claim 1 or 2, wherein the boundary scanning line is maintained at a position above a road surface when disposed at a position less than half the height of a vehicle. A vehicular lamp incorporating the LiDAR device according to claim 1 or 2.