CN110873868A - Laser radar system based on MEMS scanning mirror - Google Patents
Laser radar system based on MEMS scanning mirror Download PDFInfo
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- CN110873868A CN110873868A CN201811011435.0A CN201811011435A CN110873868A CN 110873868 A CN110873868 A CN 110873868A CN 201811011435 A CN201811011435 A CN 201811011435A CN 110873868 A CN110873868 A CN 110873868A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
Abstract
The present disclosure relates to a lidar system based on a MEMS scanning mirror. The system comprises: the laser emitting device is used for emitting laser beams; the MEMS scanning mirror is used for reflecting the laser beam to form a scanning laser beam and realizing the scanning of the laser beam in a first direction; the optical rotating mirror is used for reflecting the scanning laser beam to form a reflected laser beam and realizing the beam scanning in the second direction; the optical rotating mirror is also used for reflecting the received target echo to form a reflected echo; the laser receiving device is used for receiving the reflected echo; the scanning control device is used for controlling the laser emitting device and/or the MEMS scanning mirror, so that the laser beam incident to the MEMS scanning mirror in each swing period has a plurality of incident angles, and the incident angles of the laser beam in adjacent swing periods are different. The system has the advantages of high light energy utilization rate of laser beams, large detection distance and high detection precision, and improves the fine degree and the resolution of detection in a time-sharing multiplexing mode.
Description
Technical Field
The present disclosure relates to the field of laser radar technology, and more particularly, to a laser radar system based on a MEMS scanning mirror.
Background
The laser radar technology is a radar system that detects characteristic quantities such as a position and a velocity of a target object by emitting a laser beam. The laser radar technology calculates a feature quantity of a target object based on a Time of flight (TOF). The laser radar technology is widely applied to the fields of automatic driving, surface topography mapping, military reconnaissance, atmospheric exploration, robot vision and the like. In the related art, the resolution of detection by the lidar system cannot meet the use requirement due to the limitation of the number of array units of the sensor for receiving the target echo in the lidar system.
Disclosure of Invention
In view of this, the present disclosure proposes a lidar system based on a MEMS scanning mirror.
According to an aspect of the present disclosure, there is provided a MEMS scanning mirror based lidar system, the system comprising:
a laser emitting device for emitting a laser beam;
the MEMS scanning mirror is used for reflecting the laser beam to form a scanning laser beam, the MEMS scanning mirror can swing within a preset deflection angle range to realize beam scanning in a first direction, and the emergent direction of the scanning laser beam is related to the deflection angle of the MEMS scanning mirror;
the optical rotating mirror is used for reflecting the scanning laser beam to form a reflected laser beam, and the optical rotating mirror rotates or swings around a rotating shaft of the optical rotating mirror to realize the light beam scanning in the second direction;
the optical rotating mirror is also used for reflecting the received target echo to form a reflected echo, and the target echo is an echo generated after the reflected laser beam is subjected to diffuse reflection on a target object;
the laser receiving device is used for receiving the reflection echo;
scanning control means for controlling the timing of the laser beam emission by the laser emission means and/or controlling the deflection angle of the MEMS scanning mirror in the oscillation period so that the laser beam incident on the MEMS scanning mirror in each oscillation period has a plurality of incident angles and the incident angles of the laser beam in adjacent oscillation periods are different,
the rotating shaft of the optical rotating mirror is perpendicular to the rotating shaft of the MEMS scanning mirror, and the first direction is perpendicular to the second direction.
For the above system, in one possible implementation manner, the scan control device includes:
the first control module is used for controlling the deflection angle of the MEMS scanning mirror in the swing period according to a plurality of preset time for the laser emitting device to emit the laser beam in the swing period and a plurality of preset incidence angles in the swing period.
For the above system, in one possible implementation manner, the scan control device includes:
and the second control module is used for controlling the time of the laser emitting device for emitting the laser beam in the swing period according to the preset deflection angle of the MEMS scanning mirror in the swing period and a plurality of preset incidence angles in the swing period.
For the above system, in one possible implementation manner, the scan control device includes:
a third control module, configured to control a time for the laser emitting device to emit the laser beam in the swing period according to the obtained feedback control signal and a plurality of preset incident angles in the swing period,
wherein the feedback control signal comprises a deflection angle of the MEMS scanning mirror.
For the above system, in a possible implementation manner, the system further includes:
a rotating mirror control device for controlling the rotation or swing of the optical rotating mirror according to the obtained feedback control signal,
wherein the feedback control signal comprises a deflection angle of the MEMS scanning mirror.
For the system, in one possible implementation mode, the laser receiving device comprises an optical receiving element and a linear array APD detector,
the optical receiving element is positioned on an optical path between the optical rotating mirror and the linear array APD detector and converges the received reflection echo to the linear array APD detector;
and the linear array APD detector is used for receiving the converged reflection echo.
For the above system, in a possible implementation manner, the system further includes:
and the collimating device is positioned on a light path between the laser emitting device and the MEMS scanning mirror and is used for compressing the divergence angle of the laser beam so as to collimate the laser beam.
For the above system, in a possible implementation manner, the MEMS scanning mirror is a single-axis MEMS scanning mirror, the maximum deflection angle of the MEMS scanning mirror is ± 10 ° to ± 30 °, and the scanning frequency is 1kHz to 1000 kHz.
For the above system, in one possible implementation, the optical turning mirror includes any one of:
a single-sided coated reflector, a double-sided coated reflector and a multi-sided coated polygonal prism reflector.
For the above system, in a possible implementation manner, the system further includes:
and the analysis device is used for comparing and analyzing the reflected echo and the laser beam received by the laser receiving device and determining the information related to the target object according to the analysis result.
The laser radar system based on the MEMS scanning mirror provided by the embodiment of the disclosure comprises: a laser emitting device for emitting a laser beam; the MEMS scanning mirror is used for reflecting the laser beam to form a scanning laser beam, the MEMS scanning mirror can swing within a preset deflection angle range to realize beam scanning in a first direction, and the emergent direction of the scanning laser beam is related to the deflection angle of the MEMS scanning mirror; the optical rotating mirror is used for reflecting the scanning laser beam to form a reflected laser beam, and the optical rotating mirror rotates or swings around a rotating shaft of the optical rotating mirror to realize the scanning of the light beam in the second direction; the optical rotating mirror is also used for reflecting the received target echo to form a reflected echo, and the target echo is an echo generated after the reflected laser beam is subjected to diffuse reflection on a target object; the laser receiving device is used for receiving the reflected echo; and the scanning control device is used for controlling the time of the laser emitting device for emitting the laser beam and/or controlling the deflection angle of the MEMS scanning mirror in the swinging period, so that the laser beam incident to the MEMS scanning mirror in each swinging period has a plurality of incident angles, and the incident angles of the laser beam in the adjacent swinging periods are different. The rotating shaft of the optical rotating mirror is vertical to the rotating shaft of the MEMS scanning mirror, and the first direction is vertical to the second direction. The system has the advantages of high light energy utilization rate of laser beams, large detection distance and high detection precision, and greatly improves the fine degree and the resolution of detection in a time-sharing multiplexing mode.
Other features and aspects of the present disclosure will become apparent from the following detailed description of exemplary embodiments, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features, and aspects of the disclosure and, together with the description, serve to explain the principles of the disclosure.
Fig. 1 shows a schematic structural diagram of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure.
FIG. 2 shows a schematic structural diagram of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure.
Fig. 3a, 3b and 3c are schematic diagrams illustrating application scenarios of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure.
Detailed Description
Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.
Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present disclosure. It will be understood by those skilled in the art that the present disclosure may be practiced without some of these specific details. In some instances, methods, means, elements and circuits that are well known to those skilled in the art have not been described in detail so as not to obscure the present disclosure.
Fig. 1 shows a schematic structural diagram of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure. As shown in fig. 1, the system includes a laser emitting device 11, a MEMS scanning mirror 12, an optical turning mirror 13, a laser receiving device 14, and a scanning control device 15.
The laser emitting device 11 is for emitting a laser beam. The MEMS scanning mirror 12 is used for reflecting the laser beam to form a scanning laser beam, and the MEMS scanning mirror 12 can swing within a preset deflection angle range to realize beam scanning in the first direction. The exit direction of the scanning laser beam is related to the deflection angle of the MEMS scanning mirror 12. The optical turning mirror 13 is used to reflect the scanning laser beam to form a reflected laser beam. The optical rotating mirror 13 rotates or swings around the rotating shaft of the optical rotating mirror 13, and the light beam scanning in the second direction is realized. The optical turning mirror 13 is further configured to reflect the received target echo to form a reflected echo, where the target echo is an echo obtained by diffusely reflecting the reflected laser beam on the target object. The laser receiving device 14 is used for receiving the reflected echo. The scanning control device 15 is used for controlling the time of the laser emitting device 11 emitting the laser beam and/or controlling the deflection angle of the MEMS scanning mirror 12 in the swing period, so that the laser beam incident to the MEMS scanning mirror 12 in each swing period has a plurality of incident angles, and the incident angles of the laser beam in adjacent swing periods are different. The rotation axis of the optical rotating mirror 13 is perpendicular to the rotation axis of the MEMS scanning mirror 12, and the first direction is perpendicular to the second direction. The first direction may be horizontal, vertical, or the like.
In this embodiment, the MEMS scanning mirror may be disposed on an exit light path of the laser beam emitted by the laser emitting device, and the optical turning mirror may be disposed on a light path of the scanning laser beam reflected by the MEMS scanning mirror. Therefore, the scanning laser beam reflected by the MEMS scanning mirror can be directly irradiated on the optical rotating mirror, and the reflected laser beam can be formed after the reflection of the optical rotating mirror.
In the present embodiment, the laser emitting device may be a fiber laser, a semiconductor laser, or the like capable of emitting a laser beam. The MEMS scanning mirror (also called MEMS Micro mirror) is an optical MEMS device manufactured by a Micro-Electro-Mechanical System (MEMS) manufacturing process and integrating a Micro mirror with a MEMS driver.
In the present embodiment, the number and incidence angles of the plurality of incidence angles of the laser beam incident to the MEMS scanning mirror in each oscillation period, and the number of adjacent oscillation periods may be set according to the requirements of the detection resolution and the detection angle range. For example, three adjacent wobbling periods may be provided as needed, and the laser beam may have three incident angles in each wobbling period. Three incident angles of the laser beam may be set to θ 1, θ 2, and θ 3, respectively, in the first wobbling period; setting three incident angles of the laser beam as theta 1 ', theta 2 ' and theta 3 ' respectively in a second swing period; in the third wobbling period, three incident angles of the laser beam are set to θ 1 ", θ 2", and θ 3 ", respectively. Therefore, time-sharing multiplexing of the laser receiving device on receiving time is realized, the laser receiving device can receive the reflection echoes of the scanning laser beams corresponding to different emission angles in different swing periods, the detection line number of the system is improved, and the detection resolution is further improved. The larger the number of adjacent wobble periods, the higher the detection resolution and the higher the fineness; the greater the number of laser beams incident on the MEMS scanning mirror per oscillation period, the higher the detection resolution and fineness.
In the present embodiment, the MEMS scanning mirror reflects the laser beam capable of scanning "one point" into the scanning laser beam capable of scanning "one line" by the reflection action of the MEMS scanning mirror and the optical turning mirror, and the beam scanning in the first direction is realized. The optical rotating mirror reflects the scanning laser beam capable of scanning one line into a reflected laser beam capable of scanning one surface, so that the beam scanning in the second direction is realized, and a scanning light field (or a detection view field) is formed through the reflection action of the MEMS scanning mirror and the optical rotating mirror, so that the three-dimensional scanning is realized. The detection angle of the formed scanning light field is large, and the detection range of the system is expanded. And because the incident angles of the laser beams in the adjacent swing periods are different, the number of lines of the obtained scanning light field is large, and the detection resolution and the detection fineness are high.
FIG. 2 shows a schematic structural diagram of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure. In one possible implementation, as shown in fig. 2, the scan control device 15 may include a first control module 151. The first control module 151 is configured to control a deflection angle of the MEMS scanning mirror 12 in the swing period according to a plurality of preset times during which the laser emitting device 11 emits the laser beam in the swing period and a plurality of preset incident angles in the swing period.
In this implementation, the plurality of preset incident angles in the wobble period may be set according to detection requirements such as the resolution of detection. For example, the preset incident angles of a certain wobble period may be set to θ 1, θ 2, and θ 3 as required. The first control module may determine a plurality of preset times according to a frequency or a time interval at which the laser emitting device emits the laser beam. For example, if the period of oscillation of the MEMS scanning mirror is 1 × 10-3s, emission time interval of laser beam is 1 × 10-4s, the determined plurality of preset times may be 3 × 10 th of the wobble period-4s、4×10-4s、8×10-4And s. Then, the first control module may emit the laser beam according to a plurality of preset times (3 × 10 th time within the wobbling period) during which the laser emitting device emits the laser beam during the wobbling period-4s、4×10-4s、8×10-4s) and a plurality of preset incidence angles (theta 1, theta 2 and theta 3) in the swing period, and controlling the deflection angle of the MEMS scanning mirror in the swing period so that when the laser beam emitted by the laser emitting device reaches the MEMS scanning mirror at each preset time, the incidence angle is one of the preset incidence angles. The manner in which the first control module controls the deflection angle of the MEMS scanning mirror during the oscillation period can include adjusting the oscillation frequency of the MEMS scanning mirrorRate (or period of oscillation), adjusting the maximum deflection angle of the MEMS scanning mirror, etc.
In one possible implementation, as shown in fig. 2, the scan control apparatus 15 may include a second control module 152. The second control module 152 is configured to control the time of the laser emitting device 11 emitting the laser beam in the swing period according to the preset deflection angle of the MEMS scanning mirror 12 in the swing period and a plurality of preset incident angles in the swing period.
In this implementation manner, the second control module may determine a plurality of time points at which the laser emitting device needs to emit the laser beam in the swing period according to a preset deflection angle of the MEMS scanning mirror in the swing period and a plurality of preset incident angles in the swing period, so as to control the laser emitting device to emit the laser beam at the corresponding time point, so that the incident angle of the laser beam reaching the MEMS scanning mirror in the swing period is one of the plurality of preset incident angles. The second control module can determine the preset deflection angle of the MEMS scanning mirror in the swing period according to the preset maximum deflection angle, the preset swing frequency and other information related to the swing of the MEMS scanning mirror in the swing period.
In one possible implementation, as shown in fig. 2, the scan control device 15 may include a third control module 153. The third control module 153 is configured to control the time for the laser emitting device 11 to emit the laser beam in the swing period according to the obtained feedback control signal and the plurality of preset incident angles in the swing period. The feedback control signal may include, among other things, the deflection angle of the MEMS scanning mirror 12.
In this implementation, the third control module may determine a plurality of time points at which the laser emitting device emits the laser beam in the swing period according to the deflection angle of the MEMS scanning mirror included in the feedback control signal and a plurality of preset incident angles in the swing period, so as to control the laser emitting device to emit the laser beam at the corresponding time points, so that the incident angle of the laser beam reaching the MEMS scanning mirror in the swing period is one of the plurality of preset incident angles. The feedback control signal may be from the MEMS scanning mirror or detected by a third control module.
In one possible implementation, as shown in fig. 2, the system may further include a turning mirror control device 16. The turning mirror control device 16 is used for controlling the rotation or swing of the optical turning mirror according to the acquired feedback control signal. Wherein the feedback control signal may comprise a deflection angle of the MEMS scanning mirror.
In this implementation, the turning mirror control device may control rotation or oscillation of the optical turning mirror according to a deflection angle of the MEMS scanning mirror, so that the reflected laser beam reflected by the optical turning mirror can be perpendicular to the scanning laser beam, thereby realizing scanning in two directions perpendicular to each other within a certain angle range and with a certain resolution, and the target echo can be received by the optical turning mirror, which can be reflected to the laser receiving device by the optical turning mirror. The turning mirror control device can control the speed, angle, direction and the like of the rotation of the optical turning mirror, or the swing angle, speed and the like of the swing. By the method, the utilization rate of the laser beam can be improved, the obtained target echo has high energy and low signal-to-noise ratio, and the detection distance of the laser radar system is favorably increased.
In one possible implementation, the optical turning mirror 13 may include any one of the following: a single-sided coated reflector, a double-sided coated reflector and a multi-sided coated polygonal prism reflector.
In this implementation, the optical rotating mirror may be a mirror with at least one surface coated with a film, and the film coated on the mirror may be a thin film of metallic silver or aluminum. The combination of the optical rotating mirror and the MEMS scanning mirror can expand the scanning range to a three-dimensional space. In the process of realizing the three-dimensional scanning of the system, the existence of the optical rotating mirror enables the system to acquire effective information within a longer scanning time (also called detection time, the scanning time refers to the time of actually scanning the system in unit time) and/or a larger angle range, and the measurement efficiency of the laser radar system is greatly improved. The larger the number of the coated surfaces and the larger the size of the optical rotating mirror, the more scanning laser beams can be reflected by the optical rotating mirror, the larger the detection angle of the system is, and the longer the detection time is.
For example, taking the optical rotating mirror as a reflecting mirror with two coated surfaces as an example, because the two coated mirror surfaces can reflect the scanning laser beam, in a swing period, the two coated mirror surfaces can scan the target object when respectively rotating to be opposite to the laser emitting device, and compared with the optical rotating mirror with one coated mirror surface, the detection time is longer, the detection angle is larger, and the measurement efficiency of the laser radar system can be improved.
In one possible implementation, as shown in fig. 2, the laser receiving device 14 may include an optical receiving element 141 and a linear APD detector 142. The optical receiving element 141 is located on the optical path between the optical turning mirror 13 and the linear array APD detector 142, and converges the received reflected echo. The linear array APD detector 142 is used to receive the converged reflected echoes.
In one possible implementation, the optical receiving element 141 may include a converging lens. The condensing lens may be a lens having a condensing function such as a convex lens.
In this implementation manner, the aperture, the focal length, and the like of the converging lens may be set according to information such as the size of the effective area of the linear array APD detector, the incident angle of the reflected echo, and the like, so that the reflected echo can be received by the linear array APD detector after being converged by the converging lens.
In this implementation, the linear APD detector may include a plurality of array units, each array unit being capable of receiving reflected echoes over a particular range of fields of view, i.e., each array unit being capable of receiving reflected echoes over a particular range of incident angles. Then, the emission angle of the reflected laser beam corresponding to the reflected echo received by each array unit needs to be in a specific emission angle range, that is, the incident angle of the laser beam corresponding to the reflected echo that can be received by each array unit entering the MEMS scanning mirror needs to be in a specific incident angle range. The number of the reflected laser beams emitted by the system in the swing period of each MEMS scanning mirror can be set according to the number of array units in the linear array APD detector. For example, the number of reflected laser beams emitted by the system during each oscillation period of the MEMS scanning mirror may be set to the number of array cells included in the linear array APD detector. Therefore, the energy of the laser beam emitted by the laser emitting device can be more effectively utilized, multi-channel parallel measurement is realized, and the detection efficiency of the laser radar system is improved.
In this implementation, the larger the number of array units included in the linear APD detector, the larger the field of view of each array unit (i.e., the larger the specific range of incident angles of reflected echoes that can be received), the larger the detection field of view of the system.
In one possible implementation, the MEMS scanning mirror 12 can be a single axis MEMS scanning mirror, the maximum deflection angle of the MEMS scanning mirror 12 can be + -10 deg. -30 deg., and the oscillation frequency can be 1 kHz-1000 kHz.
In this implementation, the maximum deflection angle, the oscillation frequency, etc. of the MEMS scanning mirror can be set according to the desired detection range, detection speed. The larger the maximum deflection angle is, the larger the detection range is; the higher the wobble frequency, the faster the detection speed.
In one possible implementation, as shown in fig. 2, the system may further comprise a collimating means 17. The collimating means 17 is located on the optical path between the laser emitting means 11 and the MEMS scanning mirror 12 for compressing the divergence angle of the laser beam to collimate the laser beam.
In this implementation, the collimating means may be a plano-convex lens, a lens group, or the like capable of collimating the laser beam. By collimating the laser beam, the energy of the laser beam can be effectively utilized, providing detection accuracy.
In a possible implementation, the diameter of the collimated laser beam emitted from the collimating means 17 may be 0.1mm to 10 mm.
In this implementation, the diameter of the collimated laser beam may be set according to the mirror surface size, the detection range, and the like of the MEMS scanning mirror, and an appropriate collimating device may be selected according to the determined diameter.
In one possible implementation, as shown in fig. 2, the system may further include an analysis device 18. The analysis device 18 is used for comparing and analyzing the reflected echo and the laser beam received by the laser receiving device 14, and determining the information related to the target object according to the analysis result.
In this implementation, the determined information related to the target object may include information such as a relative position of the target object and the system, a distance between the target object and the system, and a direction in which the target object is located, which is not limited by the present disclosure.
The laser radar system based on the MEMS scanning mirror provided by the embodiment of the disclosure has the advantages of high light energy utilization rate of laser beams, low signal-to-noise ratio and high energy of target echoes, can greatly improve the detection distance and the detection precision of the laser radar system while realizing three-dimensional scanning, and greatly improves the fine degree and the resolution of detection in a time-sharing multiplexing mode.
It should be noted that, although the above embodiments are described as examples of the laser radar system based on the MEMS scanning mirror, those skilled in the art will understand that the disclosure should not be limited thereto. In fact, the user can flexibly set each part according to personal preference and/or actual application scene as long as the technical scheme of the disclosure is met.
Application example
An application example according to the embodiment of the present disclosure is given below in conjunction with "scanning a target object with a laser radar system based on a MEMS scanning mirror" as an exemplary application scenario to facilitate understanding of the working principle and process of the laser radar system based on the MEMS scanning mirror. It is to be understood by those skilled in the art that the following application examples are for the purpose of facilitating understanding of the embodiments of the present disclosure only and are not to be construed as limiting the embodiments of the present disclosure.
Fig. 3a, 3b and 3c are schematic diagrams illustrating application scenarios of a laser radar system based on a MEMS scanning mirror according to an embodiment of the present disclosure, taking a linear array APD detector including N array units as an example, the incident angle ranges of laser beams corresponding to the N array units are sequentially that the incident angle range corresponding to the 1 st array unit is [ α 1, α 1 '], the incident angle range corresponding to the 2 nd array unit is [ α 2, α 2' ], … …, the incident angle range corresponding to the nth array unit is [ α N, α N '], that is, the reflected echo that can be received by the 1 st array unit corresponds to a laser beam having an incident angle range of [ α 1, α 1' ].
M different wobble periods may be set, where the number of reflected laser beams emitted by the system in each wobble period is N. And the incident angles of the N x m laser beams emitted by the system in the m different swing periods to enter the MEMS scanning mirror are different from each other. In m swing periods, target echoes received by the optical rotating mirror and subjected to diffuse reflection of the reflected laser beam on a target object have Nxm beams, and the linear array APD detector can receive the Nxm beams of reflected echoes reflected by the optical rotating mirror.
In fig. 3a, 3b, the laser spot formed by the reflected echo on the field of view of the array unit characterizes its corresponding received reflected echo. For convenience of explanation, laser spots formed on the radiation array APD detector by N × m reflected echoes are numbered as 1, 2, 3, …, N × m, and are replaced by numbers in the figure.
As shown in fig. 3a, taking m as 1 as an example, in each oscillation period, each array unit can receive one reflected echo, and the linear APD detector can receive N reflected echoes corresponding to different transmission times. The 1 st array unit receives the 1 st laser spot, the 2 nd array unit receives the 2 nd laser spot, …, and the Nth array unit receives the N laser spot.
As shown in fig. 3b, taking m as a positive integer greater than 1 as an example, in each oscillation period, the laser emitting device emits N laser beams, and the linear array APD detector receives N laser spots. After m swing periods, the linear array APD detector receives N multiplied by m laser spots. Table 1 below shows the number of laser spots received by each array element for m different wobble periods.
TABLE 1 numbering of laser spots received by each array unit of linear array APD detector
| 1 |
2 nd array unit | Ith array unit | The |
||
| 1 st period of oscillation | 1 | m+1 | (i-1)×m+1 | (N-1)×m+1 | |
| 2 nd period of |
2 | m+2 | (i-1)×m+2 | (N-1)×m+2 | |
| J th wobble period | j | m+j | (i-1)×m+j | (N-1)×m+j | |
| M-th period of | m | 2m | i×m | N×m |
The incidence angle of the laser beam emitted by the laser emitting device corresponding to the laser spot with the number of 1, 2, …, m received by the 1 st array unit to the MEMS scanning mirror is in the range of [ α 1, α 1 ' ], the incidence angle of the laser beam emitted by the laser emitting device corresponding to the laser spot with the number of m +1, m +2, …, 2m received by the 2 nd array unit to the MEMS scanning mirror is in the range of [ α 2, α 2 ' ], … …, and the incidence angle of the laser beam emitted by the laser emitting device corresponding to the laser spot with the number of (N-1) × m +1, (N-1) × m +2, …, N × m received by the nth array unit to the MEMS scanning mirror is in the range of [ α N, α N ' ].
Thus, in m wobble periods, as shown in fig. 3c, the linear array APD detector can sequentially receive N × m laser spots. The receiving time of each laser spot is S1、Sm+1、…、S(N-1)×m+1；S2、Sm+2、…、S(N-1)×m+2；…；Sm、S2m、…、SN×m. The laser beam has high light energy utilization rate, low signal-to-noise ratio of target echo and high energy, can greatly improve the detection distance and the detection precision of a laser radar system while realizing three-dimensional scanning, and improves the fine degree and the resolution of detection in a time-sharing multiplexing mode.
Having described embodiments of the present disclosure, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terms used herein were chosen in order to best explain the principles of the embodiments, the practical application, or technical improvements to the techniques in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.
Claims (10)
1. A lidar system based on a MEMS scanning mirror, the system comprising:
a laser emitting device for emitting a laser beam;
the MEMS scanning mirror is used for reflecting the laser beam to form a scanning laser beam, the MEMS scanning mirror can swing within a preset deflection angle range to realize beam scanning in a first direction, and the emergent direction of the scanning laser beam is related to the deflection angle of the MEMS scanning mirror;
the optical rotating mirror is used for reflecting the scanning laser beam to form a reflected laser beam, and the optical rotating mirror rotates or swings around a rotating shaft of the optical rotating mirror to realize the light beam scanning in the second direction;
the optical rotating mirror is also used for reflecting the received target echo to form a reflected echo, and the target echo is an echo generated after the reflected laser beam is subjected to diffuse reflection on a target object;
the laser receiving device is used for receiving the reflection echo;
scanning control means for controlling the timing of the laser beam emission by the laser emission means and/or controlling the deflection angle of the MEMS scanning mirror in the oscillation period so that the laser beam incident on the MEMS scanning mirror in each oscillation period has a plurality of incident angles and the incident angles of the laser beam in adjacent oscillation periods are different,
the rotating shaft of the optical rotating mirror is perpendicular to the rotating shaft of the MEMS scanning mirror, and the first direction is perpendicular to the second direction.
2. The system of claim 1, wherein the scan control means comprises:
the first control module is used for controlling the deflection angle of the MEMS scanning mirror in the swing period according to a plurality of preset time for the laser emitting device to emit the laser beam in the swing period and a plurality of preset incidence angles in the swing period.
3. The system of claim 1, wherein the scan control means comprises:
and the second control module is used for controlling the time of the laser emitting device for emitting the laser beam in the swing period according to the preset deflection angle of the MEMS scanning mirror in the swing period and a plurality of preset incidence angles in the swing period.
4. The system of claim 1, wherein the scan control means comprises:
a third control module, configured to control a time for the laser emitting device to emit the laser beam in the swing period according to the obtained feedback control signal and a plurality of preset incident angles in the swing period,
wherein the feedback control signal comprises a deflection angle of the MEMS scanning mirror.
5. The system of claim 1, further comprising:
a rotating mirror control device for controlling the rotation or swing of the optical rotating mirror according to the obtained feedback control signal,
wherein the feedback control signal comprises a deflection angle of the MEMS scanning mirror.
6. The system of claim 1, wherein the laser receiving device comprises an optical receiving element and a linear array APD detector,
the optical receiving element is positioned on an optical path between the optical rotating mirror and the linear array APD detector and converges the received reflection echo to the linear array APD detector;
and the linear array APD detector is used for receiving the converged reflection echo.
7. The system of claim 1, further comprising:
and the collimating device is positioned on a light path between the laser emitting device and the MEMS scanning mirror and is used for compressing the divergence angle of the laser beam so as to collimate the laser beam.
8. The system of claim 1, wherein the MEMS scanning mirror is a single axis MEMS scanning mirror having a maximum deflection angle of ± 10 ° to ± 30 ° and a scanning frequency of 1kHz to 1000 kHz.
9. The system of claim 1, wherein the optical turning mirror comprises any one of:
a single-sided coated reflector, a double-sided coated reflector and a multi-sided coated polygonal prism reflector.
10. The system of claim 1, further comprising:
and the analysis device is used for comparing and analyzing the reflected echo and the laser beam received by the laser receiving device and determining the information related to the target object according to the analysis result.
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| CN201811011435.0A CN110873868A (en) | 2018-08-31 | 2018-08-31 | Laser radar system based on MEMS scanning mirror |
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