A compact solid-state lidar with a large field of view

Abstract

The present application relates to a compact solid-state laser radar with a large field of view. The laser radar doubles its vertical field of view by laser beam splitting without increasing the volume or the number of devices, thereby greatly improving the field of view of the laser radar. The laser radar system includes a transmitting unit, a spectroscopic unit, a polarization unit, a triggering unit, a reflecting unit, a focusing unit, a projection unit and a detection unit. Among them, the transmitting unit is used to emit 2N collimated laser beams, where N≥1; the spectroscopic unit is used to split the 2N laser beams into 4N parallel beams of equal intensity; the polarization unit is used to change the polarization state of the light beam emitted by the polarization unit; and the triggering unit is used to detect the laser trigger signal. The present invention can achieve the expansion of the field of view of the solid-state laser radar, and provide a laser radar with low cost, compact structure and large field of view.

Description

Technical Field

[0001] The present invention relates to the technical field of laser radars, and in particular to a compact solid-state laser radar with a large field of view. Background Art

[0002] In recent years, with the continuous development of autonomous driving technology, LiDAR, as the core component of the autonomous driving system, has made great progress. Its measurement range can reach hundreds of meters, and its measurement accuracy can reach millimeter level. It has many advantages such as fast response speed and strong anti-interference ability. Therefore, LiDAR also has broad application prospects in other fields such as drones, security, and terrain mapping.

[0003] However, the hybrid solid-state laser radar based on two-dimensional galvanometer scanning technology has a limited scanning field of view, and it is difficult to take into account both a large scanning field of view and a high scanning frequency. The reason is that there is a contradiction between the deflection angle of the two-dimensional galvanometer and its operating frequency. To obtain a large range of deflection angles and a high operating frequency at the same time, the galvanometer processing technology is extremely demanding and the production cost is difficult to control. Summary of the invention

[0004] The present invention aims to avoid the shortcomings of the above-mentioned existing two-dimensional galvanometer scanning technology and provide a compact solid-state laser radar design with a large field of view.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A compact solid-state laser radar with a large field of view expands the vertical field of view of the solid-state laser radar by laser beam splitting. The solid-state laser radar system includes a transmitting unit, a light splitting unit, a polarization unit, a triggering unit, a reflecting unit, a focusing unit, a projection unit and a detection unit.

[0007] The number of the emitting units is 2N, which are distributed on one side of the incident surface of the polarizing unit and are symmetrically distributed along the polarizing unit with the polarizing unit as the center.

[0008] Furthermore, the number of the splitting units is 2N, each splitting unit comprises a splitting element and a reflecting element, which splits the 2N incident light beams of the emitting unit into 4N parallel light beams of equal intensity; the 4N light beams, the laser beams generated by the same emitting unit, are symmetrically distributed up and down along the polarization unit.

[0009] Furthermore, the polarization unit is composed of a polarization beam splitter element and a polarization state conversion element, and the polarization state conversion element is parallel to the light beam exit plane of the polarization beam splitter element.

[0010] Furthermore, the number of the trigger units is 4N, which are parallel to the side of the reflected light output surface of the polarization unit, and their positions correspond one-to-one to the 4N laser beams. The two groups of trigger units corresponding to the non-identical emitting units are symmetrical on the left and right, and the trigger units corresponding to the two groups of light beams generated by the splitting unit are symmetrical on the top and bottom.

[0011] Furthermore, the reflection unit includes a first reflection unit, a second reflection unit and a third emission unit. The first reflection unit has a reflection element and two reflection surfaces. The two reflection surfaces are at an angle of 90° and 45° with the polarization unit. The edge line between the two reflection surfaces is parallel to the center line of the polarization unit. The transmitted light beams symmetrically along the center line of the polarization unit are turned 90° respectively, and the echo light beam of the second reflection unit is turned 90° to the polarization unit. The second reflection unit has two reflection elements. The reflection surfaces are parallel to the reflection surfaces of the first reflection unit respectively, and are placed symmetrically with respect to the first reflection unit. The emitted light of the first reflection unit is turned 90° to be parallel to the center line of the polarization unit. The light beam of the emission unit is incident on the third reflection unit in parallel, and at the same time, the echo light beam of the third reflection unit is turned to the first reflection unit; the third reflection unit has two reflection elements, which reflects the incident light beam of the second reflection unit to the focusing unit; the horizontal field of view angle of the laser radar is 4α, and the vertical field of view angle is 4β, then the horizontal angle between the reflection surface of the third reflection unit and the reflection surface of the projection unit is α, and the vertical angle is 2β; the horizontal angle between the reflected light of the third reflection unit and the reflected light of the second reflection unit is 2α, and the vertical angle is 4β.

[0012] Furthermore, there are two focusing units, which are symmetrically distributed along the polarization unit. The focusing unit focuses the two parallel light beams obtained by the splitting unit on the center of the projection unit. The angle of the focused light beams is γ. The spacing between the two parallel light beams divided by the splitting unit is d. The focal length of the focusing unit is f=d / γ. The focusing unit is parallel to the third reflecting unit, and the reflecting surface of the projection unit is located at the focal plane of the focusing unit.

[0013] Furthermore, the projection unit is composed of a two-dimensional galvanometer, and the two-dimensional galvanometer forms an angle 2β with the vertical plane, so that the vertical field of view of the laser radar is symmetrical up and down, and the center of the projection unit is located at the focus of the focusing unit.

[0014] Furthermore, the number of the detection units is 4N, which are composed of focusing elements and sensor elements. They are parallel to the exit surface of the reflected light beam of the polarization unit, symmetrical with the trigger unit relative to the polarization unit, and perpendicular to the position of the laser echo beam. The focusing element focuses the echo reflection signal whose polarization state is changed after the first reflection unit is incident on the polarization unit on the surface of the sensor element. The sensor element is located at the focus of the focusing element, and is used to detect the echo beam signal, and measure the detection distance through the trigger signal generated by the detection unit.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. Use a beam splitter unit and a focusing unit to expand the outgoing light beam, and under the condition of using a small deflection angle galvanometer, double the vertical field of view of the laser radar;

[0017] 2. Use a polarization unit based on polarization beam splitter and polarization state conversion element to effectively avoid the influence of parasitic reflected light on the measurement;

[0018] 3. Based on the common optical path measurement principle, only one polarization unit is used to measure the trigger signal and the detection signal, effectively reducing the size of the lidar. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a compact solid-state laser radar with a large field of view shown in the present invention;

[0020] Figure 2 It is a schematic diagram of a compact solid-state laser radar spectrometer unit with a large field of view shown in the present invention;

[0021] Figure 3 is a schematic diagram of the horizontal field of view of a compact solid-state laser radar with a large field of view shown in the present invention;

[0022] Figure 4 It is a schematic diagram of the vertical field of view of a compact solid-state laser radar with a large field of view shown in the present invention. DETAILED DESCRIPTION

[0023] In order to make the above-mentioned purposes, features and advantages of the present invention more intuitive and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. It should be noted that the technical solution provided in the embodiment of the present application is described in detail based on two transmitting units. During the specific implementation, the number of transmitting units can be modified according to the actual field of view required to achieve different horizontal field of view angles. Therefore, the technicians can make modifications within the scope of the claims during the specific implementation, and this embodiment does not represent the only implementation method of the present invention.

[0024] The specific implementation example of the laser radar technical solution of the present invention is as follows Figure 1 As shown, it includes transmitting units 201a, 201b, splitting elements 202a, 202b, reflecting elements 203a, 203b, a polarization splitting element 204, a polarization state conversion element 205, a triggering unit 206, a first reflecting unit 207, a second reflecting unit 208a, 208b, a third reflecting unit 209a, 209b, focusing units 210a, 210b, a projection unit 211 and a detection unit 212.

[0025] Figure 2 This is a schematic diagram of a compact solid-state laser radar spectrometer unit with a large field of view shown in the present invention. Taking the outgoing light beam L201a of the transmitting unit 201a as an example, the light beam L201a is incident on the spectrometer element 202a and is divided into two light beams. The transmitted light beam L202a1 and the reflected light beam L202a2 are perpendicular to each other and have equal light intensities, both of which are half of the incident light beam L201a. The reflection surface of the reflective element 203a and the reflected light beam exit surface of the spectrometer element 202a are at an angle of 45°. The reflected light beam L202a2 is incident on the reflective element 202a to the reflective element 203a, and is turned 90° to the light beam L203a through the reflective element 203a. The light beam L203a has the same light intensity as the light beam L202a1 and is parallel to each other. The two outgoing light beams are at a vertical distance L from the exit surface of the reflected light beam L202a2 of the spectrometer element 202a. u and L d The light splitting unit uses the light splitting element 202a and the reflecting element 203a to obtain two parallel light beams with equal light intensity, thus avoiding the adjustment problem existing in the method of achieving beam expansion by adding an emitting unit.

[0026] Figure 3This is a schematic diagram of the horizontal field of view of a compact solid-state laser radar with a large field of view shown in the present invention. Taking the outgoing light beams L203a and L203b of the reflective elements 203a and 203b in the light splitting unit as an example, the horizontal field of view of the laser radar and the detection path of the echo light beam are analyzed. The light beams L203a and L203b are respectively incident on the polarization beam splitting element 204, which splits the incident light beams into P light and S light. The P light is emitted perpendicularly to the polarization beam splitting element surface M2 and then enters the polarization-normal conversion element 205. After the phase of the P light is delayed by 1 / 4 wavelength, the outgoing light beams Q205a and Q205b are obtained. The S light is emitted perpendicularly to the polarization beam splitting element surface M3. The outgoing light beams S206a and S206b are incident perpendicularly to the surface of the trigger element 206, generating a trigger signal to mark the laser triggering moment. The light beams Q205a and Q205b are respectively turned 90° by the first reflecting unit 207 to obtain turned light beams Q207a and Q207b. The turned light beams Q207a and Q207b are turned 90° by the second reflecting units 208a and 208b to obtain turned light beams Q208a and Q208b. The turned light beams Q208a and Q208b are symmetrical along the polarization splitting unit. The turned light beams Q208a and Q208b are reflected by the third reflecting units 209a and 209b. The reflected light beams Q209a and Q209b are incident on the center of the projection unit 211 after passing through the focusing unit 210. Note that the horizontal vibration angle of the MEMS micro-vibration mirror used in the projection unit is ±α. In the XOY plane, the corresponding angle between the reflection surface of the third reflection unit 209a, 209b and the vertical direction is α, the angle between the turned light beams Q208a, Q208b and the normal of the third reflection unit is α, the angle between the two light beams after being turned by the third reflection units 209a, 209b is 2α, and the angle between the outgoing light beams Q211a, Q211b after reflection by the projection unit 211 is 4α.

[0027] Figure 4It is a schematic diagram of the vertical field of view of a compact solid-state laser radar with a large field of view shown in the present invention. Taking the two light beams divided by the transmitting unit 201a as an example, the light beams are turned to the third reflecting unit 209a through the polarization unit and the reflecting unit. The light beams Q208a and Q208a1 are parallel to each other, and the distance between the two light beams is d. They are incident on the third reflecting unit 209a, and are turned to Q209a and Q209a1 through the third reflecting unit. The two turned light beams are incident on the focusing unit 210a, and are converged into light beams Q210a and Q201a1 through the focusing element. The two light beams converge at the center of the projection unit 211, and are reflected by the projection unit to be output light beams Q211a and Q211a1. Note that the vertical vibration angle of the MEMS micro-vibration mirror used in the projection unit is ±β, the angle between the third reflection unit 209a and the vertical Z axis is 2β, the angle between the light beams Q208a, Q208a1 and the normal of the third reflection unit is 2β, the turning angle through the third reflection unit 209a is 4β, the focusing unit 210a is perpendicular to the light beams Q209a, Q209a1, and has an angle of 4β with the vertical Z axis. The focusing unit converges two parallel incident light beams with a spacing of d at a focal plane at 2β, and the corresponding focal length of the focusing unit is f=d÷2β. The focused light beams Q210a, Q210a1 are projected out of the laser radar at a vertical field of view angle of 4β through the projection unit 211, and the projection unit has an angle of 2β with the vertical direction to achieve a vertical field of view angle of ±2β that is symmetrical in the vertical direction.

[0028] The laser radar detection optical path is as follows Figure 3 As shown by the dotted line, the outgoing light beam is reflected by the detected object and then returns along the original path. After being refracted and reflected by the projection unit 211 and the three reflection units, it is incident on the polarization state conversion element 206. The polarization state conversion element 206 delays the polarization state of the light beam by 1 / 4 wavelength, and the corresponding polarization state of the echo light beam is changed to S light. After being totally reflected by the polarization beam splitter 205, the light beams S212a and S212b are emitted perpendicular to the surface M1. The corresponding echo light beams are converged to the sensor element on the focal plane by the focusing element in the detection unit 212, so as to realize the measurement of the detection time signal. According to the time signal interval received by the trigger unit 206 and the detection unit 212, the distance measurement of the detected object can be realized by the time of flight method, and the laser radar ranging function can be realized.

[0029] Although the embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A compact solid-state laser radar with a large field of view, comprising a transmitting unit, a light splitting unit, a polarization unit, a triggering unit, a reflecting unit, a focusing unit, a projection unit and a detection unit, characterized in that: The vertical field of view of solid-state laser radar is expanded by laser beam splitting; The number of transmitting units is 2 N , distributed on one side of the incident surface of the polarization unit, and the number of the light splitting units is 2 N Each light splitting unit is composed of a light splitting element and a reflecting element. N The parallel incident beam is divided into 4 N A parallel beam of equal intensity; The polarization unit is composed of a polarization beam splitter and a polarization state conversion element to prevent the return laser beam from entering the emission unit and reduce interference; the polarization state conversion element is parallel to the transmission light beam exit surface of the polarization beam splitter; The reflecting unit comprises a first reflecting unit, a second reflecting unit and a third reflecting unit; The first reflection unit has a reflection element, and the reflection element has two reflection surfaces, the two reflection surfaces have an angle of 90°, and an angle of 45° with the polarization unit, and the edge line between the two reflection surfaces is parallel to the center line of the polarization unit, and the transmission light beams symmetrically along the center line of the polarization unit are turned 90° respectively, and the echo light beam of the second reflection unit is turned 90° to the polarization unit at the same time; The second reflection unit has two reflection elements, the reflection surfaces of the reflection elements are parallel to the reflection surfaces of the first reflection unit, and are placed symmetrically with respect to the first reflection unit, so as to deflect the outgoing light of the first reflection unit by 90 degrees, so that the light beam is parallel to the light beam of the outgoing unit, and is incident on the third reflection unit from the second reflection unit, and at the same time deflect the return light beam of the third reflection unit to the first reflection unit; a third reflecting unit, having two reflecting elements, for reflecting the incident light beam of the second reflecting unit to the focusing unit; The horizontal field of view of the laser radar is , the vertical field of view is , then the horizontal angle between the reflection surface of the third reflection unit and the reflection surface of the projection unit is , the vertical angle is ; The horizontal angle between the light reflected by the third reflecting unit and the light reflected by the second reflecting unit , vertical angle ； There are two focusing units, which are symmetrically distributed along the polarization unit. The focusing unit focuses the two parallel light beams obtained by the light splitting unit at the center of the projection unit. The angle of the focused light beams is , the distance between the two parallel beams of light divided by the same transmitting unit is , the focal length of the focusing unit can be obtained as f = d / γ , the focusing unit is parallel to the third reflecting unit, and the reflecting surface of the projection unit is located at the focal plane of the focusing unit; The projection unit is composed of a two-dimensional galvanometer, and the angle between the two-dimensional galvanometer and the vertical plane is , so that the vertical field of view angle of the laser radar is symmetrical up and down, and the center of the projection unit is located at the focus of the focusing unit.

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