CN111896934A - MEMS laser radar receiving system and method - Google Patents

MEMS laser radar receiving system and method Download PDF

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Publication number
CN111896934A
CN111896934A CN202010743816.9A CN202010743816A CN111896934A CN 111896934 A CN111896934 A CN 111896934A CN 202010743816 A CN202010743816 A CN 202010743816A CN 111896934 A CN111896934 A CN 111896934A
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mems
mirror
mirror group
vibrating
semi
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CN111896934B (en
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郑文会
魏凌志
范乔丹
张燕妮
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Zhisensor Technologies Co ltd
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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
    • 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
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • 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
    • G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

The invention belongs to the field of laser radars, and particularly relates to an MEMS laser radar receiving system and method. The problem of inconsistent range finding ability of radar in different angles in the traditional receiving system is solved. The MEMS vibration mirror comprises a light beam convergence unit, a laser receiving unit, a first MEMS vibration mirror group and a second MEMS vibration mirror group, wherein the surfaces of the vibration mirrors form a certain included angle; when all the MEMS vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group work normally, the MEMS vibrating mirrors vibrate synchronously in the same direction, and the vibration frequencies are kept consistent; enabling the projections of the vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group on a plane vertical to the direction of echo light to be in a complementary relation, and splicing to form an effective receiving surface; and light beams returned by the detected target are synchronously reflected to the light beam converging unit through the first MEMS vibrating mirror group and the second MEMS vibrating mirror group and then are focused to the laser receiving unit. The invention can reduce the echo energy difference received by the MEMS laser radar at different scanning angles and ensure the consistency of the ranging capability of the MEMS laser radar at different scanning angles.

Description

MEMS laser radar receiving system and method
Technical Field
The invention belongs to the field of laser radars, and particularly relates to an MEMS laser radar receiving system and method.
Background
The laser scanning radar emits the emitted light beam in a scanning mode to form a scanning area, and then receives the returned light beam through a receiving system of the laser radar, so that the characteristic information of the detected target, such as profile, speed, position, distance and the like, can be obtained. The laser scanning method includes single line scanning and multi-line scanning. The MEMS laser radar realizes laser scanning by taking an MEMS galvanometer as a scanning structure, and the MEMS galvanometer has one-dimensional scanning, two-dimensional scanning and other modes. The MEMS galvanometer system has the advantages of small volume, low power consumption, low cost and the like, so the MEMS galvanometer system has great application potential in the field of laser radars.
As shown in fig. 1, in the conventional MEMS lidar, the receiving system includes a MEMS galvanometer 01, a receiving lens group 02 and a photodetector 03; and a MEMS galvanometer is used for receiving the returned laser beam, and the effective receiving area is equal to the projection area of the galvanometer surface on a plane vertical to the direction of the echo light. When the galvanometer works at different angles, the included angle between the surface of the galvanometer and the echo light is changed, the smaller the included angle is, the smaller the projection area of the surface of the galvanometer on a plane vertical to the direction of the echo light is, the larger the included angle is, and the larger the projection area of the surface of the galvanometer on the plane vertical to the direction of the echo light is. Therefore, effective energy received by the vibrating mirror at the same distance and different angles is inconsistent, the corresponding distance measuring capability of the MEMS laser radar at different angles is inconsistent, and the practicability is reduced.
Disclosure of Invention
The invention aims to provide an MEMS laser radar receiving system to solve the problem that the distance measuring capabilities of radars at different angles in the traditional receiving system are inconsistent.
The conception of the invention is as follows: because the effective receiving area S of the laser radar determines the ranging capability of the laser radar, the effective receiving area is related to the scanning angle of the galvanometer, and the scanning angle of the galvanometer is changed in the scanning process, so that the corresponding ranging capability of the laser radar is different at different scanning angles. Therefore, by increasing the effective receiving area S of the laser radar, the ranging capability of the radar can be improved. The effective receiving area S can be increased by using a method of synchronously vibrating a plurality of MEMS vibrating mirrors, the receiving surfaces of all the vibrating mirrors are parallel planes at any time, and the total receiving area of the N MEMS vibrating mirrors is N x S. However, although the overall range-finding capability of the laser radar is improved in this way, the problem that the range-finding capabilities of the scanning angles are inconsistent still exists. Therefore, the invention considers that the number of the galvanometers is increased, and the specific position, the scanning angle and the frequency of each galvanometer are adjusted, so that the galvanometers at different positions are in a complementary relation with the projection on the plane vertical to the echo direction in the same time, and a larger effective receiving surface is formed; the echo energy difference of the laser radar received at different scanning angles is reduced, and the consistency of the ranging capability of the laser radar at different scanning angles is ensured.
The technical scheme of the invention is to provide an MEMS laser radar receiving system, which comprises a light beam convergence unit and a laser receiving unit; it is characterized in that: the MEMS vibration mirror group comprises a first MEMS vibration mirror group and a second MEMS vibration mirror group, wherein the surfaces of the vibration mirrors form a certain included angle; each MEMS vibrating mirror group comprises at least one MEMS vibrating mirror; if two or more MEMS galvanometers are included, the galvanometer surfaces of the MEMS galvanometers are positioned on the same plane;
when all the MEMS vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group work normally, the MEMS vibrating mirrors vibrate synchronously in the same direction, and the vibration frequencies are kept consistent; enabling the projections of the vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group on a plane vertical to the direction of echo light to be in a complementary relation, and splicing to form an effective receiving surface;
and light beams returned by the detected target are synchronously reflected to the light beam converging unit through the first MEMS vibrating mirror group and the second MEMS vibrating mirror group and then are focused to the laser receiving unit.
Further, in order to obtain higher echo energy, an included angle between the surface of the first MEMS galvanometer group galvanometer and the surface of the second MEMS galvanometer group galvanometer is larger than or equal to 90 degrees and smaller than 180 degrees.
Furthermore, in order to simplify the optical path alignment and reduce the system blind area, the receiving system also comprises a reflecting mirror and a semi-transparent and semi-reflective mirror;
the semi-transparent semi-reflecting mirror is parallel to and coaxial with the first MEMS vibrating mirror group and is positioned in a reflection light path of the first MEMS vibrating mirror group;
the reflecting mirror is parallel to and coaxial with the second MEMS vibrating mirror group and is positioned in a reflecting light path of the second MEMS vibrating mirror group;
the semi-transparent semi-reflecting mirror is positioned in a reflecting light path of the reflecting mirror, and the center of the semi-transparent semi-reflecting mirror and the center of the reflecting mirror are positioned on the same straight line;
the beam converging unit and the laser receiving unit are positioned in an emergent light path of the semi-transparent semi-reflecting mirror;
one path of light beams returned by the detected target sequentially passes through the first MEMS vibration mirror group and the semi-transparent semi-reflective mirror, the other path of light beams sequentially passes through the second MEMS vibration mirror group, the reflecting mirror and the semi-transparent semi-reflective mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being combined through the semi-transparent semi-reflective mirror.
Further, in order to better realize the system function, the light beam converging unit is a lens or a lens group;
the laser receiving unit is an Avalanche Photodiode (APD) photodetector.
The reflection and transmission ratio of the semi-transparent semi-reflecting mirror is 1: 1.
Further, the MEMS galvanometer may be a one-dimensional MEMS galvanometer or a two-dimensional MEMS galvanometer.
Furthermore, the receiving system can also be an anisometric receiving system, and comprises a first reflecting mirror and a second reflecting mirror;
the first reflector is parallel to the first MEMS vibrating mirror group and is positioned in a reflection light path of the first MEMS vibrating mirror group; the second reflector is parallel to the second MEMS vibrating mirror group and is positioned in a reflection light path of the second MEMS vibrating mirror group;
one path of light beam returned by the measured target sequentially passes through the first MEMS vibration mirror group and the first reflecting mirror, the other path of light beam sequentially passes through the second MEMS vibration mirror group and the second reflecting mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being reflected and combined by the first reflecting mirror and the second reflecting mirror.
Further, in order to obtain higher echo energy, an included angle between the surface of the first MEMS galvanometer group galvanometer and the surface of the second MEMS galvanometer group galvanometer is larger than or equal to 90 degrees and smaller than 180 degrees.
Further, the light beam converging unit is a lens or a lens group;
the laser receiving unit is an Avalanche Photodiode (APD) photodetector.
Further, the MEMS galvanometer is a one-dimensional MEMS galvanometer or a two-dimensional MEMS galvanometer.
The invention also provides a receiving method based on the MEMS laser radar receiving system, which is characterized by comprising the following steps:
the method comprises the following steps of firstly, controlling a first MEMS vibration mirror group and a second MEMS vibration mirror group to synchronously vibrate in the same direction at the same frequency;
and step two, beams returned by the detected target are synchronously reflected to the beam converging unit through the first MEMS vibrating mirror group and the second MEMS vibrating mirror group and then are focused to the laser receiving unit.
Further, the second step is specifically: one path of light beams returned by the detected target sequentially passes through the first MEMS vibration mirror group and the semi-transparent semi-reflective mirror, the other path of light beams sequentially passes through the second MEMS vibration mirror group, the reflecting mirror and the semi-transparent semi-reflective mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being combined through the semi-transparent semi-reflective mirror;
or one path of light beam returned by the detected target sequentially passes through the first MEMS vibration mirror group and the first reflecting mirror, the other path of light beam sequentially passes through the second MEMS vibration mirror group and the second reflecting mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being reflected and combined by the first reflecting mirror and the second reflecting mirror.
The invention has the beneficial effects that:
1. the invention adopts at least two MEMS galvanometers to receive the light beam returned by the measured object, and when all the MEMS galvanometers work normally, the vibrating directions of the galvanometers should vibrate synchronously in the same direction and the vibrating frequencies are kept consistent. The projections of the vibrating mirrors on a plane perpendicular to the direction of the echo light are in a complementary relationship, so that a larger receiving surface can be always maintained. Therefore, the echo energy difference of the MEMS laser radar received at different scanning angles can be reduced, and the consistency of the ranging capability of the MEMS laser radar at different scanning angles is ensured.
2. According to the invention, the receiving area of a single vibration mirror group is increased by increasing the number of the vibration mirrors in each vibration mirror group, so that a large receiving energy can be kept for APD, and the overall distance measuring capability of the radar is improved.
Drawings
FIG. 1 is a schematic diagram of a conventional MEMS lidar receiving system;
in the figure: 01-MEMS galvanometer, 02-receiving lens group, 03-photoelectric detector;
FIG. 2 is a schematic diagram of the optical path of a transmitting-receiving coaxial MEMS lidar system (galvanometer stationary) according to one embodiment of the invention;
in the figure: 1-a first MEMS galvanometer, 2-a second MEMS galvanometer, 3-a semi-transparent semi-reflecting mirror, 4-a reflecting mirror, 5-a receiving lens group, 6-a photoelectric detector and 7-a laser emission unit;
FIG. 3 is a schematic diagram of the optical path of a transmitting-receiving coaxial MEMS lidar system (galvanometer deflection) according to a first embodiment of the invention;
in the figure: 1-a first MEMS galvanometer, 2-a second MEMS galvanometer, 3-a semi-transparent semi-reflecting mirror, 4-a reflecting mirror, 5-a receiving lens group, 6-a photoelectric detector and 7-a laser emission unit;
FIG. 4 is a simulation diagram of the energy received by the first MEMS galvanometer in accordance with the first embodiment of the present invention;
FIG. 5 is a simulation diagram of the energy received by the second MEMS galvanometer in accordance with the first embodiment of the present invention;
FIG. 6 is a simulation diagram of the total received energy of the first MEMS galvanometer and the second MEMS galvanometer in the first embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a MEMS resonator assembly according to a second embodiment of the present invention;
in the figure: 1-a first MEMS vibrating mirror group, 2-a second MEMS vibrating mirror group, 11-an MEMS vibrating mirror I, 12-an MEMS vibrating mirror II, 13-an MEMS vibrating mirror N;
FIG. 8 is a diagram of an off-axis MEMS lidar receiving system according to a third embodiment of the present invention;
in the figure: 1-a first MEMS galvanometer, 2-a second MEMS galvanometer, 3-a first reflector, 4-a second reflector, 5-a receiving lens group and 6-a photoelectric detector.
FIG. 9 is a diagram of a MEMS lidar receiving system according to a fourth embodiment of the present invention;
in the figure: 1-a first MEMS galvanometer, 2-a second MEMS galvanometer, 3-a first reflector, 4-a second reflector, 5-a receiving lens group and 6-a photoelectric detector.
Detailed Description
The invention adopts at least two MEMS galvanometers with surfaces forming a certain included angle to receive light beams returned by a measured target, and when all the MEMS galvanometers work normally, the vibrating direction should be synchronous vibration towards the same direction, the vibrating frequency is kept consistent, and a larger receiving surface can be always kept. Therefore, the echo energy difference of the MEMS laser radar received at different scanning angles can be reduced, and the consistency of the ranging capability of the MEMS laser radar at different scanning angles is ensured.
The invention is further described with reference to the following figures and specific embodiments.
Example one
The MEMS lidar receiving system and the transmitting system of the present embodiment are coaxial, and fig. 2 is a schematic diagram of the transmitting and receiving coaxial MEMS lidar system (with the vibrating mirror stationary). As can be seen from the figure, the system comprises a laser emitting unit 7, a half mirror 3, a first MEMS galvanometer 1, a second MEMS galvanometer 2, a reflecting mirror 4, a receiving lens group 5 and a photoelectric detector 6.
When the first MEMS galvanometer 1 and the second MEMS galvanometer 2 are at initial positions (static), the centers of the semi-transparent semi-reflective mirror 3 and the reflector 4 are on the same straight line and are positioned in an emergent light path of the reflector 4 to reflect a reflected light beam of the reflector 4; the semi-transparent semi-reflective mirror 3 is parallel to and coaxial with the first MEMS galvanometer 1, is positioned in a reflection light path of the first MEMS galvanometer 1, and transmits a reflection light beam of the first MEMS galvanometer 1; the photodetector 6 is positioned in the emergent light path of the half-mirror 3. The reflecting mirror 4 and the second MEMS galvanometer are parallel and coaxial with each other and are positioned in a reflecting light path of the second MEMS galvanometer 2. In the embodiment, the included angle between the surfaces of the first MEMS galvanometer 1 and the second MEMS galvanometer 2 is 90 degrees, and the reflector 4 and the semi-transparent and semi-reflective mirror 3 are vertical to each other; in other embodiments, the included angle between the surfaces of the first MEMS galvanometer 1 and the second MEMS galvanometer 2 may be set to any angle according to actual needs, and the included angle between the reflective mirror 4 and the half mirror 3 is equal to the included angle between the surfaces of the first MEMS galvanometer 1 and the second MEMS galvanometer 2.
The laser emission unit 7 emits high-energy near-parallel light beams, one path of the near-parallel light beams sequentially passes through the semi-transparent semi-reflecting mirror 3 and the first MEMS oscillating mirror 1, the other path of the near-parallel light beams sequentially passes through the semi-transparent semi-reflecting mirror 3, the reflecting mirror 4 and the second MEMS oscillating mirror 2 and is emitted to a target object, one path of reflected light beams reflected by the target object sequentially passes through the first MEMS oscillating mirror 1 and the semi-transparent semi-reflecting mirror 3, and the other path of the reflected light beams sequentially passes through the second MEMS oscillating mirror 2, the reflecting mirror 4 and the semi-transparent semi-reflecting mirror 3 and finally reaches the.
Fig. 3 is a schematic diagram of optical paths when the first MEMS galvanometer 1 and the second MEMS galvanometer 2 both deflect at a certain angle when the system operates. As can be seen from the figure, compared with fig. 2, in the figure, both MEMS mirrors are deflected by the same angle in the clockwise direction, the projection of the first MEMS mirror 1 on the plane perpendicular to the direction of the echo light is reduced, and the projection of the second MEMS mirror 2 on the plane perpendicular to the direction of the echo light is increased, which are complementary, so that the system can always maintain a larger effective receiving surface.
In order to better realize the function of the system, the reflection and transmission ratio of the half mirror 3 shown in the figure is preferably 1:1, and the photodetector 6 in the system is an Avalanche Photodiode (APD).
In a traditional MEMS lidar receiving system, laser actively emits a laser signal and transmits the laser signal to a target, which is reflected by the target and then transmitted back to the lidar, and this process can be expressed by a lidar transmission equation:
Figure BDA0002607649630000061
in the formula: psThe power of an echo signal received by the laser radar; piIs the peak power of the laser pulse emitted by the lidar; s is the effective receiving area of the laser radar; r is the distance between the target and the laser radar; etasysIs a laser radar system parameter; etaatmIs a letterInfluence factors of the signal in the atmospheric transmission process; the effective receiving area S of the lidar determines the echo signal power of the lidar. According to the formula, when the test is carried out in the same environment, the echo energy of the laser radar is only related to the effective receiving area S of the laser radar and the distance R between the target and the laser radar, and other influence factors can be regarded as a fixed value, so that the radar transmission equation can be simplified as follows:
Figure BDA0002607649630000071
and because of the relation of the vibration angle of the MEMS galvanometer, the actual effective receiving area of the laser radar receiving system is the projection area of the galvanometer surface on a plane vertical to the direction of incident light, A is the galvanometer surface area, and theta is the included angle between the galvanometer surface and the incident light. Thus:
Figure BDA0002607649630000072
taking the example that the included angle between the first MEMS galvanometer and the second MEMS galvanometer is 90 °, that is, when the galvanometers are stationary, the included angle between the incident light and the surface of the two MEMS galvanometers is 45 °. The distance R between the target and the radar is a fixed value, and when theta is more than 30 degrees and less than 60 degrees, the received energy of the first MEMS galvanometer is simulated to obtain a graph 4 (assuming that the echo power of the single galvanometer is 1 when receiving at 45 degrees). It can be seen that when the MEMS galvanometer surface area and the target distance from the radar are fixed, the received echo energy is not the same and is very different in different directions according to the incident angle of the light.
The included angle between the surface of the second MEMS galvanometer and the incident light is 90-theta. The second MEMS galvanometer echo energy formula can be written as:
Figure BDA0002607649630000073
the above equation is simulated to obtain fig. 5 (assuming that the unit of the single-mirror echo power is 1 at 45 ° reception). It can be seen that, with the first MEMS galvanometer, the received echo energy is different according to the incident angle of the light, and the echo power curves of the first MEMS galvanometer and the second MEMS galvanometer are substantially mirror images under the same deflection angle.
The first MEMS galvanometer and the second MEMS galvanometer are simultaneously received, and the integral echo energy is Ps+Ps' simulation results in fig. 6 (assuming that the single-mirror echo power is unit 1 at 45 ° reception). Fig. 6 illustrates that, when the position of the measurement target of the MEMS lidar is unchanged from the radar, the difference between the echo energies at different angles of the radar is not large within the measurement angle range of the radar, and it can be seen from comparing fig. 4, fig. 5 and fig. 6 that the dual-mirror receiving system can effectively reduce the problem of the difference between the echo energies at different angles and at the same distance in the MEMS lidar receiving system. Meanwhile, the optical system belongs to a coaxial optical system, and compared with an anisometric optical system, the optical path contrast is simpler and the system blind area is smaller.
Example two
The difference between the present embodiment and the first embodiment is that, in the first embodiment, the first MEMS galvanometer is replaced by a first MEMS galvanometer group 1, the second MEMS galvanometer is replaced by a second MEMS galvanometer group 2, the first MEMS galvanometer group 1 and the second MEMS galvanometer group 2 both include N MEMS galvanometers, and mirror surfaces of the N MEMS galvanometers are arranged in the same plane and have centers on the same straight line. Wherein N is a positive integer greater than 1. Fig. 7 is a front view of the MEMS oscillator group.
And correspondingly, parameters and sizes of other optical devices are changed in a matching manner, so that the MEMS laser radar system is composed of a laser emission unit, a semi-transparent semi-reflective mirror, a first MEMS vibration mirror group, a second MEMS vibration mirror group, a reflecting mirror, a receiving lens group and a photoelectric detector.
When the first MEMS vibration mirror group and the second MEMS vibration mirror group are in initial positions (static), the centers of the semi-transparent semi-reflective mirror and the reflector are in the same straight line and positioned in an emergent light path of the reflector, and a reflected light beam of the reflector is reflected; the semi-transparent semi-reflecting mirror is parallel to and coaxial with the first MEMS vibrating mirror, is positioned in a reflection light path of the first MEMS vibrating mirror and transmits a reflection light beam of the first MEMS vibrating mirror; the photoelectric detector is arranged in an emergent light path of the half-transmitting and half-reflecting mirror. The reflecting mirror and the second MEMS galvanometer are parallel and coaxial with each other and are positioned in a reflecting light path of the second MEMS galvanometer.
In order to better realize the function of the system, the reflection and transmission ratio of the half-mirror is 1:1, and the photodetector in the system is Avalanche Photodiode (APD).
The system compares with the system in the first embodiment to conclude that the echo power of the lidar should be N (P)s+Ps') for the whole system, the problem of the echo energy difference of the same distance and different angles in the MEMS laser radar receiving system can be effectively reduced, and meanwhile, the whole ranging capability of the laser radar can be improved.
EXAMPLE III
As shown in fig. 8, the system of this embodiment is a receiving system of an iso-axial lidar, and the system includes a first MEMS galvanometer 1, a second MEMS galvanometer 2, a first mirror 3, a second mirror 4, a receiving lens group 5 (the receiving lens group includes 1 or more than 1 lens), and a photodetector 6. The first reflector 3 is parallel to the first MEMS galvanometer 1 and is located in the reflective optical path of the first MEMS galvanometer 1, and the second reflector 4 is parallel to the second MEMS galvanometer 2 and is located in the reflective optical path of the second MEMS galvanometer 2. The first MEMS galvanometer 1 and the second MEMS galvanometer 2 are arranged at a certain included angle, the first reflector 3 and the second reflector 4 are also arranged at the same included angle, the schematic diagram is given by the fact that the surfaces of the two MEMS galvanometers form an included angle of 90 degrees, and the included angle of the two MEMS galvanometers is set according to actual use conditions in actual use. The MEMS galvanometer includes, but is not limited to, a one-dimensional MEMS galvanometer and a two-dimensional MEMS galvanometer, the first MEMS galvanometer may also be a first MEMS galvanometer group, the second MEMS galvanometer may also be a second MEMS galvanometer group, and the photodetector 6 includes, but is not limited to, an Avalanche Photodiode (APD).
After a reflected light beam reflected by a target enters a system, one light beam sequentially passes through a first MEMS vibrating mirror 1 and a first reflecting mirror 3, the other light beam sequentially passes through a second MEMS vibrating mirror 2 and a second reflecting mirror 4, two light beams enter a receiving lens group 5 through the reflected light beams of the two reflecting mirrors, and are focused on an APD after being collimated and converged, the two vibrating mirrors work simultaneously, so that the echo energy of the whole system receiving the same distance and different angles keeps a small difference, and the system also meets the formulas (1), (2), (3) and (4) in the first embodiment, so that the problem of large difference of distance measuring capability of different angles in an MEMS laser radar receiving system can be effectively solved. The optical system is a receiving scheme of the off-axis optical system, and meanwhile, a semi-transparent semi-reflecting mirror is not used in the scheme, so that light received by the two vibrating mirrors can be focused on an APD (avalanche photo diode), double receiving efficiency can be realized, echo energy received by the radar system is improved, and the distance measuring capability is improved.
Example four
Different from the third embodiment, in the present embodiment, the included angle between the surfaces of the first MEMS galvanometer 1 and the second MEMS galvanometer 2 is 120 °, and the included angle between the first reflecting mirror 2 and the second reflecting mirror 4 is also 120 ° as shown in fig. 9.
The first reflector 3 is parallel to the first MEMS galvanometer 1, and the second reflector 4 is parallel to the second MEMS galvanometer 2. When the galvanometer is static, the included angles between the incident light and the surfaces of the two galvanometers are both 60 degrees, if the vibrating angle of the galvanometer is +/-15 degrees, namely theta is more than 45 degrees and less than 75 degrees,
Figure BDA0002607649630000091
Figure BDA0002607649630000092
the first MEMS galvanometer 1 and the second MEMS galvanometer 2 receive simultaneously, and the integral echo energy is Ps+Ps'. From the formula, it can be seen that when the included angle between the two MEMS galvanometers is 120 degrees, P is compared with the included angle of 90 degreess+Ps' the calculation result is larger, namely the echo energy received by the radar system is higher, and the distance measuring capability is stronger. When a system is actually built according to the content of the invention, the setting of the included angle between the two galvanometers needs to comprehensively consider the conditions of light paths, structures and the like to select an optimal scheme.
Finally, it should be noted that: the above-mentioned embodiments are merely illustrative of specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or make equivalent substitutions for some technical features within the technical scope of the present disclosure; the modifications, changes or substitutions do not cause the essence of the corresponding technical solutions to depart from the concept and scope of the technical solutions of the embodiments of the present invention, and all should be covered within the protection scope of the present invention.

Claims (12)

1. An MEMS laser radar receiving system comprises a light beam convergence unit and a laser receiving unit; the method is characterized in that: the MEMS vibration mirror group comprises a first MEMS vibration mirror group and a second MEMS vibration mirror group, wherein the surfaces of the vibration mirrors form a certain included angle; each MEMS vibrating mirror group comprises at least one MEMS vibrating mirror; if two or more MEMS galvanometers are included, the galvanometer surfaces of the MEMS galvanometers are positioned on the same plane;
when all the MEMS vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group work normally, the MEMS vibrating mirrors vibrate synchronously in the same direction, and the vibration frequencies are kept consistent; enabling the projections of the vibrating mirrors in the first MEMS vibrating mirror group and the second MEMS vibrating mirror group on a plane vertical to the direction of echo light to be in a complementary relation, and splicing to form an effective receiving surface;
and light beams returned by the detected target are synchronously reflected to the light beam converging unit through the first MEMS vibrating mirror group and the second MEMS vibrating mirror group and then are focused to the laser receiving unit.
2. The MEMS lidar receiving system of claim 1, wherein:
the included angle between the surface of the vibrating mirror of the first MEMS vibrating mirror group and the surface of the vibrating mirror of the second MEMS vibrating mirror group is larger than or equal to 90 degrees and smaller than 180 degrees.
3. The MEMS lidar receiving system of claim 2, wherein: the device also comprises a reflector and a semi-transparent semi-reflecting mirror;
the semi-transparent semi-reflecting mirror is parallel to and coaxial with the first MEMS vibrating mirror group and is positioned in a reflection light path of the first MEMS vibrating mirror group;
the reflecting mirror is parallel to and coaxial with the second MEMS vibrating mirror group and is positioned in a reflecting light path of the second MEMS vibrating mirror group;
the semi-transparent semi-reflecting mirror is positioned in a reflecting light path of the reflecting mirror, and the center of the semi-transparent semi-reflecting mirror and the center of the reflecting mirror are positioned on the same straight line;
the beam converging unit and the laser receiving unit are positioned in an emergent light path of the semi-transparent semi-reflecting mirror;
one path of light beams returned by the detected target sequentially passes through the first MEMS vibration mirror group and the semi-transparent semi-reflective mirror, the other path of light beams sequentially passes through the second MEMS vibration mirror group, the reflecting mirror and the semi-transparent semi-reflective mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being combined through the semi-transparent semi-reflective mirror.
4. The MEMS lidar receiving system of claim 3, wherein: the light beam converging unit is a lens or a lens group;
the laser receiving unit is an Avalanche Photodiode (APD) photodetector.
5. The MEMS lidar receiving system of claim 4, wherein: the reflection and transmission ratio of the semi-transparent semi-reflecting mirror is 1: 1.
6. The MEMS lidar receiving system of claim 5, wherein: the MEMS galvanometer is a one-dimensional MEMS galvanometer or a two-dimensional MEMS galvanometer.
7. The MEMS lidar receiving system of claim 1, wherein: the device also comprises a first reflecting mirror and a second reflecting mirror;
the first reflector is parallel to the first MEMS vibrating mirror group and is positioned in a reflection light path of the first MEMS vibrating mirror group; the second reflector is parallel to the second MEMS vibrating mirror group and is positioned in a reflection light path of the second MEMS vibrating mirror group;
one path of light beam returned by the measured target sequentially passes through the first MEMS vibration mirror group and the first reflecting mirror, the other path of light beam sequentially passes through the second MEMS vibration mirror group and the second reflecting mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being reflected and combined by the first reflecting mirror and the second reflecting mirror.
8. The MEMS lidar receiving system of claim 7, wherein:
the included angle between the surface of the vibrating mirror of the first MEMS vibrating mirror group and the surface of the vibrating mirror of the second MEMS vibrating mirror group is larger than or equal to 90 degrees and smaller than 180 degrees.
9. The MEMS lidar receiving system of claim 8, wherein: the light beam converging unit is a lens or a lens group;
the laser receiving unit is an Avalanche Photodiode (APD) photodetector.
10. The MEMS lidar receiving system of claim 9, wherein: the MEMS galvanometer is a one-dimensional MEMS galvanometer or a two-dimensional MEMS galvanometer.
11. A receiving method of the MEMS lidar receiving system according to claim 1, comprising the steps of:
the method comprises the following steps of firstly, controlling a first MEMS vibration mirror group and a second MEMS vibration mirror group to synchronously vibrate in the same direction at the same frequency;
and step two, beams returned by the detected target are synchronously reflected to the beam converging unit through the first MEMS vibrating mirror group and the second MEMS vibrating mirror group and then are focused to the laser receiving unit.
12. The receiving method according to claim 11, wherein the second step is specifically: one path of light beams returned by the detected target sequentially passes through the first MEMS vibration mirror group and the semi-transparent semi-reflective mirror, the other path of light beams sequentially passes through the second MEMS vibration mirror group, the reflecting mirror and the semi-transparent semi-reflective mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being combined through the semi-transparent semi-reflective mirror;
or the like, or, alternatively,
one path of light beam returned by the measured target sequentially passes through the first MEMS vibration mirror group and the first reflecting mirror, the other path of light beam sequentially passes through the second MEMS vibration mirror group and the second reflecting mirror, and the two paths of light beams are focused to the laser receiving unit through the light beam converging unit after being reflected and combined by the first reflecting mirror and the second reflecting mirror.
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