CN112965045A

CN112965045A - Compact solid-state laser radar with large field angle

Info

Publication number: CN112965045A
Application number: CN202110225903.XA
Authority: CN
Inventors: 谢峰; 储政勇; 王俊; 王润; 鲍诚诚
Original assignee: ACADEMY OF PUBLIC SECURITY TECHNOLOGY HEFEI; CETC 38 Research Institute
Current assignee: ACADEMY OF PUBLIC SECURITY TECHNOLOGY HEFEI; CETC 38 Research Institute
Priority date: 2021-03-01
Filing date: 2021-03-01
Publication date: 2021-06-15

Abstract

The application relates to a compact solid-state laser radar with a large field angle, wherein the laser radar expands the vertical field angle of the laser radar by one time in a laser beam splitting mode under the conditions of not increasing the size and increasing devices, and the market range of the laser radar is greatly expanded. The laser radar system comprises a transmitting unit, a light splitting unit, a polarization unit, a triggering unit, a reflecting unit, a focusing unit, a projecting unit and a detecting unit. The emitting unit is used for emitting 2N beams of collimated emergent laser, wherein N is more than or equal to 1; the light splitting unit is used for splitting the 2N laser beams into 4N parallel isocandela light beams; the polarization unit is used for changing the polarization state of the light beam emitted by the polarization unit; and the trigger unit is used for detecting a laser trigger signal. The invention can realize the expansion of the field angle of the solid-state laser radar and provides the laser radar with low cost, compact structure and large field angle.

Description

Compact solid-state laser radar with large field angle

Technical Field

The invention relates to the technical field of laser radars, in particular to a compact solid-state laser radar with a large field angle.

Background

With the continuous development of automatic driving technology in recent years, the laser radar has been developed greatly as a core component of an automatic driving system, the measuring range of the laser radar can reach hundreds of meters, the measuring precision can reach millimeter level, and the laser radar has the advantages of high response speed, strong anti-interference capability and the like. Therefore, the laser radar also has wide application prospect in other fields such as unmanned aerial vehicles, security protection, topographic mapping and the like.

However, the hybrid solid-state lidar based on the two-dimensional galvanometer scanning technology has a limited scanning field of view, and is difficult to combine a large scanning field of view with a high scanning frequency. The reason is that the deflection angle of the two-dimensional galvanometer is contradictory to the working frequency of the two-dimensional galvanometer, and the requirement on the processing technology of the galvanometer is extremely high and the manufacturing cost is difficult to control when the two-dimensional galvanometer is required to simultaneously obtain a large-range deflection angle and a high working frequency.

Disclosure of Invention

The invention provides a design scheme of a compact solid-state laser radar with a large field angle to avoid the defects of the existing two-dimensional galvanometer scanning technology.

In order to achieve the purpose, the invention adopts the technical scheme that:

a compact solid-state laser radar with a large field angle expands the vertical field angle of the solid-state laser radar in a laser beam splitting mode. The solid-state laser radar system comprises a transmitting unit, a light splitting unit, a polarization unit, a triggering unit, a reflection unit, a focusing unit, a projection unit and a detection unit.

The number of the emission units is 2N, the emission units are distributed on one side of an incidence surface of the polarization unit, and the emission units are distributed along the polarization unit in a bilateral symmetry mode by taking the polarization unit as a center.

Furthermore, the number of the light splitting units is 2N, each light splitting unit comprises a light splitting element and a reflecting element, and 2N incident beams of the emitting unit are split into 4N parallel isocandela beams; and the 4N light beams are distributed along the polarization unit in an up-and-down symmetrical manner.

Furthermore, the polarization unit is composed of a polarization beam splitter and a polarization state conversion element, and the polarization state conversion element is parallel to the exit surface of the polarization beam splitter transmitting the light beam.

Furthermore, the number of the trigger units is 4N, the trigger units are parallel to one side of the reflection light emergent surface of the polarization unit, the positions of the trigger units correspond to the 4N laser beams one by one, the trigger units corresponding to the two groups of trigger units of the non-identical emission unit are in bilateral symmetry, and the trigger units corresponding to the two groups of light beams generated by the light splitting unit are in longitudinal symmetry.

Further, the reflection unit includes a first reflection unit, a second reflection unit, and a third emission unit. The first reflection unit is provided with a reflection element and two reflection surfaces, the included angle between the two reflection surfaces is 90 degrees, the included angle between the two reflection surfaces is 45 degrees, the included edge line between the two reflection surfaces is parallel to the central line of the polarization unit, the transmission light beams symmetrically arranged along the central line of the polarization unit are respectively turned by 90 degrees, and meanwhile, the echo light beams of the second reflection unit are turned by 90 degrees to the polarization unit; the second reflection unit is provided with two reflection elements, the reflection surfaces of the second reflection unit and the first reflection unit are respectively parallel, the second reflection unit is arranged in bilateral symmetry relative to the first reflection unit, emergent light of the first reflection unit is turned by 90 degrees and is incident to the third reflection unit in parallel with light beams of the emergent unit, and meanwhile, echo light beams of the third reflection unit are turned to the first reflection unit; the third reflecting unit is provided with two reflecting elements and reflects the incident light beams of the second reflecting unit to the focusing unit; recording that the horizontal field angle of the laser radar is 4 alpha, and the vertical field angle is 4 beta, then, the included angle between the reflecting surface of the third reflecting unit and the reflecting surface of the projecting unit in the horizontal direction is alpha, and the included angle in the vertical direction is 2 beta; the included angle between the reflected light of the third reflection unit and the reflected light of the second reflection unit in the horizontal direction is 2 alpha, and the included angle between the reflected light of the third reflection unit and the reflected light of the second reflection unit in the vertical direction is 4 beta.

Furthermore, the two focusing units are distributed along the polarization unit in bilateral symmetry, the focusing unit focuses the two parallel light beams obtained by the light splitting unit on the center of the projection unit, the included angle of the focusing light beams is recorded as gamma, the distance between the two parallel light beams split by the light splitting unit is d, the focal length of the focusing unit is f, d/gamma, the focusing unit is parallel to the third reflection unit, and the reflection surface of the projection unit is located on the focal plane of the focusing unit.

Furthermore, the projection unit is composed of a two-dimensional galvanometer, an included angle between the two-dimensional galvanometer and a vertical plane is 2 beta, so that the field angle of the laser radar in the vertical direction is symmetrical up and down, and the center of the projection unit is located at the focus of the focusing unit.

Furthermore, the number of the detection units is 4N, the detection units are composed of focusing elements and sensing elements, are parallel to the emergent surface of the reflected light beam of the polarization unit, are bilaterally symmetrical relative to the polarization unit with the trigger unit, and are vertical to the position of the laser echo light beam; the focusing element focuses the echo reflection signal of which the polarization state is changed after the first reflection unit is incident to the polarization unit on the surface of the sensing element, the sensing element is positioned at the focus of the focusing element and used for detecting the echo beam signal, and the detection distance is measured through the trigger signal generated by the detection unit.

Compared with the prior art, the invention has the beneficial effects that:

1. expanding the emergent light beam by using a light splitting unit and a focusing unit, and expanding the vertical field angle of the laser radar by one time under the condition of using a small deflection angle galvanometer;

2. the polarization unit based on the polarization light splitting element and the polarization state conversion element is used, so that the influence of parasitic reflected light on measurement is effectively avoided;

3. based on a common light path measurement principle, only one polarization unit is used, measurement of a trigger signal and a detection signal is achieved, and the size of the laser radar is effectively reduced.

Drawings

FIG. 1 is a schematic diagram of a large field angle compact solid state lidar of the present invention;

FIG. 2 is a schematic diagram of a large-field-angle compact solid-state lidar light splitting unit shown in the invention;

FIG. 3 is a schematic diagram of a large field angle compact solid state lidar horizontal field angle shown in the present invention;

fig. 4 is a schematic diagram of a vertical field angle of a large-field angle compact solid-state lidar according to the present invention.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that, the technical solution provided in the embodiments of the present application is described in detail with two transmitting units as a basis, and in specific implementation, the number of the transmitting units may be modified according to a required actual angle of view to implement different horizontal angles of view. Thus, modifications may occur to those skilled in the art within the scope of the claims and the described embodiments do not represent the only embodiments of the invention.

The embodiment of the lidar technical solution of the present invention is shown in fig. 1, and includes transmitting

units

201a and 201b,

beam splitting elements

202a and 202b, reflecting

elements

203a and 203b, polarization beam splitting element 204, polarization state conversion element 205, triggering unit 206, first reflecting unit 207, second reflecting

units

208a and 208b, third reflecting

units

209a and 209b, focusing

units

210a and 210b, projecting unit 211, and detecting unit 212.

Fig. 2 is a schematic diagram of a large-field-angle compact solid-state lidar beam splitting unit shown in the present invention, taking an outgoing light beam L201a of a transmitting unit 201a as an example, a light beam L201a enters a beam splitting element 202a and is split into two light beams, a transmitted light beam L202a1 and a reflected light beam L202a2 are perpendicular to each other, and the light intensity is equal to half of that of an incoming light beam L201 a. The angle between the reflection surface of the reflection element 203a and the exit surface of the reflected light beam from the beam splitter 202a is 45 degrees, the reflected light beam L202a2 enters the reflection element 203a from the beam splitter 202a and is turned by 90 degrees by the reflection element 203a to the light beam L203a, the light beam L203a and the light beam L202a1 have the same light intensity and are parallel to each other, and the vertical distance L between the two emitted light beams and the exit surface of the reflected light beam L202a2 from the beam splitter 202a_uAnd L_dAre equal in size. Use of a light-splitting unitThe beam splitting element 202a and the reflecting element 203a obtain two parallel isocandela beams, so that the problem of adjustment in the method for expanding beams by adding a transmitting unit is solved.

Fig. 3 is a schematic diagram of a large-field-angle compact solid-state lidar horizontal field angle shown in the present invention, which takes outgoing light beams L203a and L203b of reflecting

elements

203a and 203b in a beam splitting unit as an example, and analyzes the lidar horizontal field angle and an echo light beam detection path. Light beams L203a and L203b are respectively incident into the polarization beam splitter 204, the polarization beam splitter splits an incident light beam into P light and S light, the P light is emitted perpendicular to a polarization beam splitter surface M2 and then enters the polarization state conversion element 205, the P light is subjected to phase delay 1/4 wavelength to obtain emergent light beams Q205a and Q205b, the S light is emitted perpendicular to a polarization beam splitter surface M3, and the emergent light beams S206a and S206b are incident perpendicular to the surface of the trigger element 206 to generate trigger signals, so that the trigger time of the laser is marked. The light beams Q205a, Q205b are respectively bent by 90 ° by the first reflection unit 207 to obtain the bent light beams Q207a, Q207b, the bent light beams Q207a, Q207b are bent by 90 ° by the

second reflection units

208a, 208b to obtain the bent light beams Q208a, Q208b, the bent light beams Q208a, Q208b are left-right symmetric along the polarization beam splitting unit, the bent light beams Q208a, Q208b are reflected by the

third reflection units

209a, 209b, the reflected light beams Q209a, Q209b pass through the focusing unit 210 and then enter the center of the projection unit 211. Recording the horizontal vibration angle ± α of the MEMS micro-galvanometer adopted by the projection unit, in the XOY plane, the included angle between the reflection surface corresponding to the

third reflection unit

209a, 209b and the vertical direction is α, the included angle between the bent light beams Q208a, Q208b and the normal of the third reflection unit is α, the included angle between the two light beams bent by the

third reflection unit

209a, 209b is 2 α, and the included angle between the outgoing light beams Q211a, Q211b after being reflected by the projection unit 211 is 4 α.

Fig. 4 is a schematic diagram of a vertical field angle of a large-field angle compact solid-state lidar according to the present invention, taking two light beams split by the transmitting unit 201a as an example, the light beams are turned to the third reflecting unit 209a by the polarizing unit and the reflecting unit, the light beams Q208a, Q208a1 are parallel to each other, the distance between the two light beams is d, the light beams enter the third reflecting unit 209a, are turned to Q209a, Q209a1 by the third reflecting unit, the two turned light beams enter the focusing unit 210a, are converged by the focusing element into the light beams Q210a, Q201a1, the two light beams are converged at the center of the projecting unit 211, and are reflected by the projecting unit into the outgoing light beams Q211a, Q211a 1. The vertical vibration angle ± β of the MEMS micro-resonator adopted by the projection unit is recorded, the included angle between the third reflection unit 209a and the vertical Z axis is 2 β, the included angle between the light beams Q208a, Q208a1 and the normal of the third reflection unit is 2 β, the turning angle by the third reflection unit 209a is 4 β, the focusing unit 210a is perpendicular to the light beams Q209a, Q209a1, and the included angle between the light beams Q208a, Q208a1 and the vertical Z axis is 4 β, the focusing unit converges two parallel incident light beams with the distance d at the focal plane by 2 β, the focal length of the corresponding focusing unit is f ═ d ÷ 2 β, the focused light beams Q210a, Q210a1 project the laser radar by the projection unit 211 at the vertical field angle of 4 β, and the included angle between the projection unit and the vertical direction is 2 β, so as to realize the vertical symmetric ± 2 β vertical field angle.

The detection light path of the laser radar is shown by a dotted line in fig. 3, an outgoing light beam is reflected by a detected object, then an echo light beam returned according to the original path is refracted and reflected by the projection unit 211 and the three reflection units, and then enters the polarization state conversion element 206, the polarization state conversion element 206 delays the polarization state of the light beam by 1/4 wavelength, the polarization state of the corresponding echo light beam is changed into S light, the S light beam is totally reflected by the polarization beam splitter element 205, the light beams S212a and S212b are emitted in a direction perpendicular to the plane M1, and the corresponding echo light beam is converged on the sensing element on the focal plane by the focusing element in the detection unit 212, so that the detection time signal is measured. 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 a flight time method, and the laser radar ranging function is realized.

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

Claims

1. The utility model provides a solid-state lidar of compact of big field angle, includes transmitting element, beam splitting unit, polarization unit, trigger element, reflection element, focus unit, projection unit and detecting element, its characterized in that: the vertical field angle of the solid-state laser radar is expanded by means of laser beam splitting.

2. A large field angle compact solid state lidar according to claim 1, wherein: the number of the emission units is 2N, the emission units are distributed on one side of the incidence surface of the polarization unit, the number of the light splitting units is 2N, each light splitting unit is composed of a light splitting element and a reflecting element, and 2N parallel incident light beams of the emission units are divided into 4N parallel isocandela light beams.

3. A large field angle compact solid state lidar according to claim 1, wherein: the polarization unit consists of a polarization beam splitting element and a polarization state conversion element so as to prevent the returned laser beam from entering the transmitting unit and reduce interference; the polarization state conversion element is parallel to the emergent surface of the transmitted light beam of the polarization beam splitting element.

4. A large field angle compact solid state lidar according to claim 1, wherein: the reflection unit includes a first reflection unit, a second reflection unit, and a third emission unit.

The first reflection unit is provided with a reflection element, the reflection element is provided with two reflection surfaces, the included angle between the two reflection surfaces is 90 degrees, the included angle between the two reflection surfaces is 45 degrees, the included angle between the two reflection surfaces and the polarization unit is 45 degrees, the included edge line of the two reflection surfaces is parallel to the central line of the polarization unit, the transmission light beams symmetrically arranged along the central line of the polarization unit are respectively turned by 90 degrees, and the echo light beams of the second reflection unit are turned by 90 degrees to the polarization unit;

the second reflection unit is provided with two reflection elements, the reflection surfaces of the reflection elements are respectively parallel to the reflection surface of the first reflection unit, the reflection elements are symmetrically arranged left and right relative to the first reflection unit, emergent light of the first reflection unit is turned by 90 degrees, light beams are parallel to light beams of the emergent unit and are incident to the third reflection unit from the second reflection unit, and meanwhile, echo light beams of the third reflection unit are turned to the first reflection unit;

the third reflecting unit is provided with two reflecting elements and reflects the incident beam of the second reflecting unit to the focusing unit;

the horizontal angle of view of the laser radar is 4 alpha, the vertical angle of view of the laser radar is 4 beta, an included angle between the reflecting surface of the third reflecting unit and the reflecting surface of the projecting unit in the horizontal direction is alpha, and an included angle between the reflecting surface of the third reflecting unit and the reflecting surface of the projecting unit in the vertical direction is 2 beta;

the included angle between the reflected light of the third reflection unit and the reflected light of the second reflection unit in the horizontal direction is 2 alpha, and the included angle between the reflected light of the third reflection unit and the reflected light of the second reflection unit in the vertical direction is 4 beta.

5. A large field angle compact solid state lidar according to claim 1, wherein: the two focusing units are distributed along the polarization unit in a bilateral symmetry mode, the focusing units focus the two parallel light beams obtained by the light splitting unit on the center of the projection unit, the included angle of the focusing light beams is recorded as gamma, the distance between the two parallel light beams obtained by the same emitting unit is recorded as d, the focal length of the focusing unit can be calculated as f-d/gamma, the focusing units are parallel to the third reflecting unit, and the reflecting surface of the projection unit is located on the focal plane of the focusing unit.

6. A large field angle compact solid state lidar according to claim 1, wherein: the projection unit is composed of a two-dimensional galvanometer, the included angle between the two-dimensional galvanometer and a vertical plane is 2 beta, so that the field angle of the laser radar in the vertical direction is vertically symmetrical, and the center of the projection unit is located at the focus of the focusing unit.