A multi-line laser radar device

Abstract

The application relates to a multi-line laser radar device, belonging to the laser radar field, which comprises a measuring unit and a micro mirror; the micro mirror comprises a driving module, a measuring angle module and a mirror body; the driving module comprises a driving circuit and a coil connected with the driving circuit; the mirror body is arranged in the coil and connected with the coil; the coil is used for driving the reflecting surface of the mirror body to rotate; the measuring angle module is connected with the mirror body; the measuring angle module is used for measuring the rotating direction and rotating angle of the reflecting surface of the mirror body; the measuring unit is used for emitting laser to the reflecting surface of the mirror body; a measured object is arranged on the reflection light path of the reflecting surface; the measuring unit is also used for receiving the diffuse reflection laser of the measured object reflected by the reflecting surface and generating an image according to the diffuse reflection laser. The application can realize the functions of strong impact vibration resistance and low power consumption.

Description

Technical Field

[0001] This invention relates to the field of lidar, and in particular to a multi-line lidar device. Background Technology

[0002] In recent years, with the development of autonomous driving technology, the requirements for the perception of the surrounding environment by multi-line LiDAR have become increasingly stringent. Existing mechanical LiDAR on the market uses a motor to drive a rotating mirror to scan the laser beam. This approach suffers from drawbacks such as large rotational inertia, poor resistance to shock and vibration, and high power consumption. MEMS LiDAR, on the other hand, uses MEMS scanning mirrors to scan the laser beam. However, this approach has limitations such as small scanning mirror area, short lifespan, high manufacturing difficulty, and significant temperature-dependent angle measurements. Summary of the Invention

[0003] The purpose of this invention is to provide a multi-line lidar device that achieves strong resistance to shock and vibration, high reliability, low power consumption, and minimal impact from ambient temperature.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] A multi-line lidar device includes: a measurement unit and a micromirror; the micromirror includes a driving module, a measurement angle module, and a mirror body; the driving module includes a driving circuit and a coil connected to the driving circuit.

[0006] The mirror body is disposed inside the coil and connected to the coil; the coil is used to drive the reflective surface of the mirror body to rotate; the angle measurement module is connected to the mirror body; the angle measurement module is used to measure the rotation direction and rotation angle of the reflective surface of the mirror body.

[0007] The measuring unit is used to emit laser light onto the reflective surface of the mirror body; the object to be measured is placed in the reflected light path of the reflective surface; the measuring unit is also used to receive the diffuse reflected laser light of the object to be measured reflected by the reflective surface and generate an image based on the diffuse reflected laser light.

[0008] Optionally, the mirror body includes a magnet S pole, a magnet N pole, a reflecting mirror, a rotating shaft, and a frame;

[0009] The coil is wound around the outside of the frame; the rotating shaft is fixed inside the frame; the reflecting mirror passes through the rotating shaft and is disposed inside the frame; the S pole and N pole of the magnet are symmetrically disposed on the reflecting mirror; the S pole and N pole of the magnet are symmetrical about the rotating shaft.

[0010] Optionally, the angle measurement module includes a continuous laser emitting module, a continuous laser receiving module, a scale, and a signal processing module;

[0011] The continuous laser emitted by the continuous laser emission module illuminates the center of the back surface of the reflective mirror; the back surface of the reflective mirror reflects the continuous laser onto the scale; the continuous laser receiving module receives the continuous laser reflected by the scale; the continuous laser receiving module is connected to the signal processing module; the continuous laser receiving module converts the received continuous laser into an electrical signal; the signal processing module receives the electrical signal converted by the continuous laser receiving module and determines the rotation angle and rotation direction of the reflective mirror based on the intensity change of the electrical signal.

[0012] Optionally, the measurement unit includes a laser array emitting module, a laser array receiving module, and an image processing module;

[0013] The laser array emitting module emits a laser beam onto the front surface of the reflector; the front surface of the reflector reflects the laser beam onto the object under test; the laser array receiving module receives the diffusely reflected laser beam from the object under test; and the image processing module generates an image based on the diffusely reflected laser beam.

[0014] Optionally, the multi-line lidar device includes a reflector; the reflector is a reflector with a through hole in the center of the mirror surface; the through hole is used to allow laser light to pass through; the reflector is positioned in the optical path on the front side of the reflector surface; the reflector is used to reflect diffusely reflected laser light from the front side of the reflector surface.

[0015] Optionally, the multi-line lidar device further includes a lens; the lens is disposed between the reflector and the laser array receiving module; the laser array receiving module is disposed at the focal point of the lens; the lens is used to converge the diffuse laser reflected by the reflector.

[0016] Optionally, both the S pole and the N pole of the magnet are permanent magnets.

[0017] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0018] This invention includes a measurement unit and a micromirror; the micromirror includes a driving module, a measuring angle module, and a mirror body; the driving module includes a driving circuit and a coil connected to the driving circuit; the mirror body is disposed within the coil and connected to the coil; the coil is used to drive the reflective surface of the mirror body to rotate; the measuring angle module is connected to the mirror body; the measuring angle module is used to measure the rotation direction and rotation angle of the reflective surface of the mirror body; the measurement unit is used to emit laser light onto the reflective surface of the mirror body; the object under test is placed in the reflected light path of the reflective surface; the measurement unit is also used to receive the diffuse reflected laser light from the object under test reflected by the reflective surface and generate an image based on the diffuse reflected laser light. This invention drives the mirror body by controlling the magnitude and direction of the current in the coil, realizing the reciprocating oscillation of the scanning mirror, reducing the rotational inertia of the rotating components, which not only adjusts the size of the detection field of view but also improves the system's shock resistance and reduces the system's power consumption. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a block diagram of the multi-line lidar device provided by the present invention;

[0021] Figure 2 Optical path diagram of the multi-line lidar device provided by the present invention;

[0022] Figure 3 A flowchart of a single measurement operation for a multi-line lidar device provided by the present invention;

[0023] Figure 4 This is a schematic diagram of the micromirror structure provided by the present invention;

[0024] Figure 5 This is a schematic diagram of the scale provided by the present invention.

[0025] Symbol explanation:

[0026] 1-Multi-line lidar device, 2-Measurement unit, 3-Micro mirror, 4-Laser array emitting module, 5-Laser array receiving module, 6-Image processing module, 7-Drive module, 8-Measurement angle module, 9-Mirror body, 10-Drive circuit, 11-Coil, 12-Continuous laser emitting module, 13-Continuous laser receiving module, 14-Scale, 15-Signal processing module, 16-Magnet N pole, 17-Magnet S pole, 18-Reflecting mirror, 19-Rotating shaft, 20-Mirror frame, 21-Lens, 22-Reflecting mirror, 23-Object under test. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The purpose of this invention is to provide a multi-line lidar device that achieves strong resistance to shock and vibration and low power consumption.

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] like Figure 1 As shown, the present invention provides a multi-line lidar device 1, comprising: a measurement unit 2 and a micromirror 3; the micromirror 3 includes a drive module 7, a measurement angle module 8, and a mirror body 9; the drive module 7 includes a drive circuit 10 and a coil 11 connected to the drive circuit 10. The micromirror 3 is driven electromagnetically. The drive circuit 10 generates a force that repels or attracts the permanent magnet on the reflective mirror 18 by changing the magnitude and direction of the current through the coil 11, thereby driving the reflective mirror 18 to rotate around an axis. Simultaneously, the rotation direction and angle of the reflective mirror 18 are measured. The distance traveled by the reflected light on the scale 14 is determined by the pulse signal generated by the continuous laser receiving module 13, based on the light reflected from the reflective mirror 18 during rotation. Then, the rotation angle of the reflective mirror 18 is calculated in the signal processing module 15 using the direction and distance. The detection field of view can be changed by adjusting the current of the coil 11 as needed.

[0031] The mirror body 9 is disposed inside the coil 11 and is connected to the coil 11; the coil 11 is used to drive the reflective surface 18 of the mirror body 9 to rotate; the measuring angle module 8 is connected to the mirror body 9; the measuring angle module 8 is used to measure the rotation direction and rotation angle of the reflective surface 18 of the mirror body 9.

[0032] like Figure 2 As shown, the measurement unit 2 is used to emit laser light onto the reflective mirror 18 of the mirror body 9; the object under test 23 is placed in the reflected light path of the reflective mirror 18; the measurement unit 2 is also used to receive the diffuse reflected laser light of the object under test 23 reflected by the reflective mirror 18 and generate an image based on the diffuse reflected laser light.

[0033] The mirror body 9 includes a magnet S pole 17, a magnet N pole 16, a reflective mirror 18, a rotating shaft 19, and a frame 20. The coil 11 is wound around the outside of the frame 20. The rotating shaft 19 is fixed inside the frame 20. The reflective mirror 18 passes through the rotating shaft 19 and is disposed inside the frame 20. The magnet S pole 17 and the magnet N pole 16 are symmetrically arranged on the reflective mirror 18, with the rotating shaft 19 as the axis of symmetry. The frame 20 is made of a magnetic material. Both the magnet S pole 17 and the magnet N pole 16 are permanent magnets.

[0034] The N pole 16 and S pole 17 of the magnet are fixed on both sides of the rotation axis 19 of the reflector 18, respectively. The distances to the rotation axis 19 from the reflector 18 are equidistant. The reflector 18 is fixedly connected to the frame 20 via the rotation axis 19, and the reflector 18 can rotate around the rotation axis 19. The frame 20 is fixedly connected to the lidar body. The frame 20 is made of magnetic material and, together with the coil 11, forms an electromagnet. When current flows through the coil 11, a repulsive or attractive force is generated, driving the reflector 18 to rotate around the rotation axis 19. Different directions of current through the coil 11 result in different directions of rotation of the reflector 18, and different magnitudes of current through the coil 11 result in different angles of rotation of the reflector 18.

[0035] The reflector 18 is rotated by magnetic control. A permanent magnet is mounted on the reflector 18 and fixed to the structural housing by a shaft. The drive circuit 10 generates a force that repels or attracts the permanent magnet on the reflector 18 by changing the magnetic field strength of the coil 11, thereby driving the reflector 18 to rotate around the shaft. The electromagnet is realized with the help of structural components, which not only realizes the function of an electromagnet but also facilitates heat dissipation.

[0036] The angle measurement module 8 includes a continuous laser emitting module 12, a continuous laser receiving module 13, a scale 14, and a signal processing module 15. The continuous laser emitted by the continuous laser emitting module 12 illuminates the center of the back surface of the reflective mirror 18. The back surface of the reflective mirror 18 reflects the continuous laser onto the scale 14. The continuous laser receiving module 13 receives the continuous laser reflected by the scale 14. The continuous laser receiving module 13 is connected to the signal processing module 15. The continuous laser receiving module 13 converts the received continuous laser into an electrical signal. The signal processing module 15 receives the electrical signal converted by the continuous laser receiving module 13 and determines the rotation angle and rotation direction of the reflective mirror 18 based on the intensity changes of the electrical signal.

[0037] The scale 14 is made by depositing a high-reflectivity coating on a low-reflectivity material, and then etching scale lines. When the laser passes through the etched scale lines, it appears as dark stripes with low reflectivity; when it passes through the coating, it appears as bright stripes with high reflectivity. The reflected light is processed by the continuous laser receiving module 13 and converted into a pulse signal. The signal processing module 15 can calculate the rotation angle of the reflecting mirror 18 by counting the high pulses. The scale 14 is composed of black stripes, which are thicker in the middle and gradually taper towards both ends. The width of adjacent stripes in the scale 14 is different, gradually decreasing from the center of the scale 14 to both sides, and symmetrically arranged with the center of the scale 14 as the axis of symmetry. The signal processing module used in this invention is an embedded system based on FPGA or ARM.

[0038] Angle calculation method: Different scale positions represent different angle positions. When counting to a certain scale, the different angle positions can be calculated by looking up a table.

[0039] Since different positions of the stripes correspond to different scanning angles, by reading and recording the number of pulse stripes, the position of the pulse stripes can be determined, and then the angle of the reflector can be calculated.

[0040] like Figure 5 As shown, the scale 14 used in the multi-line lidar device 1 provided by the present invention consists of multiple bright stripes and multiple dark stripes. The stripe width is calculated based on the distance between the scale 14 and the reflecting mirror 18 and the speed of light, ensuring that the laser takes the same amount of time to pass through each stripe when the reflecting mirror 18 rotates.

[0041] The measurement unit 2 includes a laser array emitting module 4, a laser array receiving module 5, and an image processing module 6. The laser array emitting module 4 emits a laser beam onto the front surface of the reflecting mirror 18; the front surface of the reflecting mirror reflects the laser beam onto the object under test 23; the laser array receiving module 5 receives the diffusely reflected laser beam from the object under test 23; and the image processing module 6 generates an image based on the diffusely reflected laser beam. The laser array emitting module 4 uses a single-pulse-line laser emitter, and the laser array receiving module 5 uses a receiving array composed of multiple receivers.

[0042] like Figure 2 As shown, the multi-line lidar device 1 further includes a reflector 22 and a lens 21. The reflector 22 is disposed on the reflected light path of the front surface of the reflector surface 18. The reflector 22 is used to reflect the diffuse laser light reflected from the front surface of the reflector surface 18. The lens 21 is disposed between the reflector 22 and the laser array receiving module 5. The laser array receiving module 5 is disposed at the focal point of the lens 21. The lens 21 is used to converge the diffuse laser light reflected by the reflector 22. The reflector 22 is a reflector with a through hole in the center of the mirror surface; the through hole is used to allow the laser light to pass through.

[0043] The laser emitted by the laser array emitting module 4 shines through the through hole in the center of the reflector 22 onto the reflector surface 18 of the micromirror 3. After being reflected by the reflector surface 18 of the micromirror 3, the laser shines onto the object under test 23. After being reflected by the object under test 23, the laser shines back onto the reflector surface 18. After being reflected by the reflector surface 18, the laser is focused by the lens 21 onto the laser array receiving module 5. The laser array receiving module 5 converts the received light signal into an electrical signal and inputs it to the image processing module 6 to calculate the target distance.

[0044] The method for calculating the target distance is the time-of-flight method: distance = time of flight × speed of light. The image processing module includes a time interval measurement module that can measure the time difference between the transmitted pulse and the received pulse. This time difference × the speed of light gives the target distance. After calculating the distance from the signal detected by the array detector, an array distance image can be obtained. This method is well-known in the industry.

[0045] The laser array emitting module 4 and lens 21 have parallel normal directions. The reflecting mirror 18 is located in the optical path of the laser array emitting module 4 and lens 21. The detector is located at the focal point of lens 21. The image processing module 6 is connected to the detector via a wire. Coil 11 is wound on the frame 20, and the normal direction of the plane of coil 11 is parallel to the normal direction of the reflecting mirror 18. The driving circuit 10 is connected to coil 11 via a wire.

[0046] like Figure 2 and Figure 4As shown, during operation, the continuous laser emitting module 12 emits a continuous laser beam onto the reflecting mirror 18, which then reflects it onto the scale 14. As the reflecting mirror 18 rotates, the reflected laser beam travels along the scale 14. The continuous laser receiving module 13 detects the step signal of the reflected light from the scale 14 increasing in intensity. The signal processing module 15 calculates the rotation angle of the rotating mirror based on the step signal. Thus, the linear laser emitter emits a beam of light that passes through the reflecting mirror 22 to the mirror body 9 and then to the object under test 23. The light hitting the object under test 23 undergoes diffuse reflection, then returns to the rotating mirror and then to the reflecting mirror 22. After being focused by the lens 21, it reaches the laser array receiving module 5, completing one scan. The laser receiving module is connected to the signal processing module 15 via a wire. The continuous laser emitting module 12 of this invention is a continuous laser generator, and the continuous laser receiving module 13 detects the continuous laser signal and converts it into an electrical signal.

[0047] like Figure 3 As shown, the flowchart of a single measurement operation of the multi-line lidar device 1 provided by the present invention is as follows: During measurement, a continuous laser is first emitted, and then the coil 11 is driven to control the rotation of the reflector. Depending on whether the detection field of view needs to be modified, the current of the coil 11 is adjusted to change the detection field of view. The continuous laser emitting module 12 in the micromirror 3 emits a continuous laser to the reflector surface 18, which is then reflected onto the scale 14. The continuous laser receiver then detects the step signal of the reflected light from the scale 14 from weak to strong, thereby triggering the emitting module in the measurement unit 2 to emit an array of laser pulses. The line laser hits the micromirror 3 and is reflected onto the object 23 being measured, where it begins to be reflected and received. The received laser is reflected by the reflector surface 18 to the receiving module, and then the image processing module 6 synthesizes a series of point cloud pixels of the measured environment. This process is repeated until a 3D image of the surrounding environment is finally synthesized. When detecting a close-range target, the scanning angle is increased, and the detection field of view is increased; when detecting a distant target, the scanning angle is decreased, and the detection field of view is decreased.

[0048] Compared with traditional motor scanning and MEMS scanning methods, this invention has advantages such as strong resistance to shock and vibration, unaffected by ambient temperature, long lifespan, low power consumption, and adjustable detection field of view.

[0049] To address the material fatigue problem of silicon-based MEMS scanning mirrors, this invention employs a metal-based shaft-based method to achieve high-speed oscillation of the scanning mirror.

[0050] To address the issues of insufficient shock and vibration resistance and high power consumption in traditional motor scanning solutions, this solution controls the magnitude and direction of the current in coil 11 to drive a miniature scanning mirror, thereby achieving reciprocating oscillation of the scanning mirror. This reduces the rotational inertia of the rotating components, improving the system's shock resistance and reducing its power consumption.

[0051] To address the issue of temperature affecting the angle measurement of MEMS scanning mirrors, this invention designs a scanning mirror angle measurement scheme based on reflection space scale information. This scheme has the advantage that the angle measurement accuracy is not affected by ambient temperature.

[0052] This invention offers advantages such as low cost, high precision, high reliability, adjustable detection field of view, and insensitivity to ambient temperature. In summary, this invention features a novel and reasonable design, low cost, high precision, and high reliability. It possesses strong versatility and practicality, facilitating widespread adoption.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0054] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the device and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A multi-line lidar device, characterized in that, include: A measuring unit and a micromirror; the micromirror includes a driving module, a measuring angle module, and a mirror body; the driving module includes a driving circuit and a coil connected to the driving circuit; The mirror body is disposed inside the coil, and the mirror body is connected to the coil; the coil is used to drive the reflective surface of the mirror body to rotate; the angle measurement module is used to measure the rotation direction and rotation angle of the reflective surface of the mirror body. The measuring unit is used to emit laser light onto the reflective surface of the mirror body; the object to be measured is placed in the reflected light path of the reflective surface; the measuring unit is also used to receive the diffuse reflected laser light of the object to be measured reflected by the reflective surface and generate an image based on the diffuse reflected laser light; The mirror body includes a magnet S pole, a magnet N pole, a reflecting mirror surface, a rotating shaft, and a mirror frame; The coil is wound around the outside of the frame; the rotating shaft is fixed inside the frame; the reflecting mirror passes through the rotating shaft and is disposed inside the frame; the S pole and N pole of the magnet are symmetrically disposed on the reflecting mirror; the S pole and N pole of the magnet are symmetrical about the rotating shaft.

2. The multi-line lidar device according to claim 1, characterized in that, The angle measurement module includes a continuous laser emission module, a continuous laser receiving module, a scale, and a signal processing module; The continuous laser emitted by the continuous laser emission module illuminates the center of the back surface of the reflective mirror; the back surface of the reflective mirror reflects the continuous laser onto the scale; the continuous laser receiving module receives the continuous laser reflected by the scale; the continuous laser receiving module is connected to the signal processing module; the continuous laser receiving module converts the received continuous laser into an electrical signal; the signal processing module receives the electrical signal converted by the continuous laser receiving module and determines the rotation angle and rotation direction of the reflective mirror based on the intensity change of the electrical signal.

3. The multi-line lidar device according to claim 1, characterized in that, The measurement unit includes a laser array emitting module, a laser array receiving module, and an image processing module; The laser array emitting module emits a laser beam onto the front surface of the reflector; the front surface of the reflector reflects the laser beam onto the object under test; the laser array receiving module receives the diffusely reflected laser beam from the object under test; and the image processing module generates an image based on the diffusely reflected laser beam.

4. The multi-line lidar device according to claim 3, characterized in that, It also includes a reflector; the reflector is a reflector with a through hole in the center of the mirror surface; the through hole is used to allow laser light to pass through; the reflector is disposed in the optical path on the front side of the reflector surface; the reflector is used to reflect diffusely reflected laser light from the front side of the reflector surface.

5. The multi-line lidar device according to claim 4, characterized in that, It also includes a lens; the lens is disposed between the reflector and the laser array receiving module; the laser array receiving module is disposed at the focal point of the lens; the lens is used to converge the diffuse laser reflected by the reflector.

6. The multi-line lidar device according to claim 1, characterized in that, Both the S pole and the N pole of the magnet are permanent magnets.

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