CN113552578A - Laser radar and method for detecting target object by using same - Google Patents
Laser radar and method for detecting target object by using same Download PDFInfo
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- CN113552578A CN113552578A CN202010260771.XA CN202010260771A CN113552578A CN 113552578 A CN113552578 A CN 113552578A CN 202010260771 A CN202010260771 A CN 202010260771A CN 113552578 A CN113552578 A CN 113552578A
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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
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
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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
- G01S7/4811—Constructional features, e.g. arrangements of optical elements common to transmitter and receiver
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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
- G01S7/4817—Constructional features, e.g. arrangements of optical elements relating to scanning
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Abstract
The present invention provides a laser radar, including: a laser emission unit including an array of a plurality of lasers configured to emit a detection laser beam; an echo detection unit comprising an array of a plurality of detectors configured to receive echoes of the detection laser beam after reflection by a target object; and the multi-surface rotating mirror can rotate around the rotating shaft of the multi-surface rotating mirror, and is provided with a plurality of reflecting surfaces parallel to the rotating shaft, wherein the multi-surface rotating mirror is positioned at the downstream of the optical path of the laser emission unit and positioned at the upstream of the optical path of the echo detection unit, one of the reflecting surfaces can receive the detection laser beam and reflect the detection laser beam to the outside of the laser radar, and the other reflecting surface can receive the echo and face the echo to the echo detection unit for reflection.
Description
Technical Field
The present disclosure relates to the field of photoelectric technologies, and in particular, to a laser radar based on a polygon mirror for transmitting and receiving light from different surfaces and a method for detecting a target object using the laser radar.
Background
The laser radar is a radar system for detecting characteristic quantities such as position, speed and the like of a target by emitting laser beams, and is an advanced detection mode combining a laser technology and a photoelectric detection technology. Laser radar is widely applied to the fields of automatic driving, traffic communication, unmanned aerial vehicles, intelligent robots, resource exploration and the like due to the advantages of high resolution, good concealment, strong active interference resistance, good low-altitude detection performance, small volume, light weight and the like.
Lidar is generally composed of a transmitting system, a receiving system, information processing and the like, wherein the transmitting system generally includes various forms of lasers and transmitting optical systems, and the receiving system generally includes various forms of photodetectors and receiving optical systems.
How to optimize the mechanical and optical path structure of the laser radar, thereby improving the receiving and transmitting efficiency, improving the range finding and enabling the laser radar to be more miniaturized, and is a problem which needs to be continuously solved by technical personnel in the related field.
The statements in this background section merely represent techniques known to the public and are not, of course, representative of the prior art.
Disclosure of Invention
The invention provides a laser radar and a method for detecting a target object by using the laser radar.
According to one aspect of the invention, a lidar comprises:
a laser emission unit including an array of a plurality of lasers, wherein the array of lasers is non-uniformly distributed and configured to emit a detection laser beam;
an echo detection unit comprising an array of a plurality of detectors configured to receive echoes of the detection laser beam after reflection by a target object; and
the multi-surface rotating mirror can rotate around the rotating shaft of the multi-surface rotating mirror and is provided with a plurality of reflecting surfaces parallel to the rotating shaft, wherein the multi-surface rotating mirror is positioned on the downstream of the optical path of the laser emission unit and on the upstream of the optical path of the echo detection unit, one of the reflecting surfaces can receive the detection laser beam and reflect the detection laser beam to the outside of the laser radar, and the other reflecting surface can receive the echo and face the echo to the echo detection unit for reflection.
According to another aspect of the invention, the density of the laser array is relatively higher at a middle position along the longitudinal direction of the laser radar and the density of the lasers is relatively lower at two side positions, and the polygon mirror includes one of a double-sided mirror, a regular three-sided mirror, a square-shaped mirror, or a regular pentagon-shaped mirror, and the polygon mirror is configured to rotate unidirectionally around its rotation axis.
According to another aspect of the invention, the array of lasers and the array of detectors are disposed at substantially the same longitudinal position relative to the axis of rotation of the polygon.
According to another aspect of the present invention, the polygon mirror further comprises a driving mechanism substantially located in a space surrounded by the first and second reflecting surfaces.
According to another aspect of the invention, the array of lasers includes a plurality of rows of lasers along the axis of rotation, each row including at least one laser; the array of the plurality of detectors includes a plurality of rows of detectors along the axis of rotation, each row including at least one detector.
According to another aspect of the present invention, an angle between a detection laser beam incident to the polygon mirror and an echo reflected by the polygon mirror upon reception is twice an external angle of the polygon mirror.
According to another aspect of the invention, the lidar further comprises:
the transmitting swing mirror and the transmitting lens are sequentially arranged between the array of the lasers and the multi-surface rotating mirror, wherein the detection laser beams are incident on the transmitting swing mirror, reflected to the transmitting lens and incident on the multi-surface rotating mirror after being shaped by the transmitting lens;
the receiving lens and the receiving swing mirror are sequentially arranged between the multi-surface rotating mirror and the array of the detector, wherein the multi-surface rotating mirror reflects the echo to the receiving lens, the echo is incident on the receiving swing mirror after being shaped by the receiving lens, and then the echo is reflected to the array of the detector.
According to another aspect of the invention, the array of lasers comprises a plurality of columns of lasers distributed along a second direction perpendicular to the direction of the rotation axis, each column comprising at least one laser, wherein the lasers of different columns are mutually staggered along the direction of the rotation axis.
According to another aspect of the present invention, the polygon mirror is configured such that a direction of a detection laser beam finally emitted from the laser radar and a direction of an echo received by the laser radar are substantially parallel.
According to another aspect of the invention, the array of lasers is driven to emit light in a column-out, spaced-within-a-column emission.
The invention also relates to a method for object detection using a lidar as described above.
According to the laser radar system for realizing two-dimensional scanning by the vertical array transceiving unit and the horizontal multi-surface rotating mirror, the angle of field is determined by the position of the array and the optical lens group in the vertical direction, and the vertical linear array or the 1.5-dimensional array is horizontally scanned by the reciprocating swing mirror in the horizontal direction. Embodiments of the present invention enable a highly compact lidar. Compared with the laser radar in a coaxial multi-surface rotating mirror mode, the scheme provided by the embodiment of the invention has higher transceiving efficiency, thereby being beneficial to expanding the absolute measuring range. Compared with the laser radar of the paraxial polygon mirror with upper and lower layers, the laser radar is higher in height due to the upper and lower layers, and the laser radar can be effectively reduced in height and can be more conveniently installed on a vehicle.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure. In the drawings:
FIG. 1 shows a schematic diagram of a lidar in accordance with one embodiment of the invention;
2-4 show schematic views of a lidar according to a preferred embodiment of the invention with a polygon mirror of different shape;
FIGS. 5A and 5B show a polygon mirror according to a preferred embodiment of the present invention, in which a driving mechanism is provided inside;
FIGS. 6 and 7 illustrate the arrangement of laser arrays according to a preferred embodiment of the present invention;
FIG. 8 shows a schematic diagram of the timing of light emission from a laser array; and
fig. 9A and 9B are schematic diagrams showing changes in the transmitting aperture and the receiving aperture of the lidar during rotation.
Detailed Description
In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection, either mechanically, electrically, or in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly above and obliquely above the second feature, or simply meaning that the first feature is at a lesser level than the second feature.
The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Fig. 1 shows a lidar 10 according to an embodiment of the invention, described in detail below with reference to fig. 1. As shown in fig. 1, the laser radar 10 includes a laser emitting unit 11, an echo detecting unit 12, and a polygon mirror 13. Wherein the laser emitting unit 11 includes an array of a plurality of lasers 111, for example, arranged in a direction perpendicular to the paper surface in fig. 1. The laser 111 is mounted on the circuit board and is configured to emit a detection laser beam L1 for detecting the target object. The array of lasers 111 may be an array of lasers formed from a single laser or a line or area array laser, including edge emitting or vertical cavity surface emitting lasers. The probe laser beam L1 is diffusely reflected on the target object, and a partially reflected echo L2 is returned to the laser radar 10. The echo detection unit 12 includes an array of a plurality of detectors 121, for example, arranged along a direction perpendicular to the paper surface in fig. 1, and configured to receive the echo of the detection laser beam reflected by the target object. The detector 141, including but not limited to a photodiode, SiPM, SPAD, etc., may convert the echo L2 into an electrical signal that may reflect the intensity of the echo L2. The processing device of the laser radar can calculate the distance to the target object according to the time difference between the emission time of the detection laser beam and the receiving time of the echo, that is, the time of flight tof (time of flight).
According to a preferred embodiment of the invention, the laser arrangement is arranged in an array of lasers, which are non-uniformly distributed, for example in the longitudinal direction of the lidar, with a higher density of lasers at the middle position of the array relative to the positions on both sides, and with a relatively lower density of lasers at the positions on both sides. By the mode, the detection accuracy of the laser radar in the visual field approximately corresponding to the parallel direction of the eyes of the driver can be effectively improved, the parallel visual field of the eyes of the driver is the most critical part in the visual field of the laser radar, or the important visual field of the forward radar, and therefore the improvement of the detection accuracy of the visual field at the middle position has important significance on the laser radar.
The polygon mirror 13 is rotatable about its rotational axis 135, preferably in one direction, as indicated by arrow R in fig. 1. The polygon mirror 13 has a plurality of reflecting surfaces parallel to the rotation axis 135. In fig. 1, a case is shown where the polygon mirror 13 is a square-section mirror in which four sides of a square form four reflecting surfaces, 131, 132, 133 and 134, respectively. The polygon mirror 13 is located downstream of the optical path of the laser emitting unit 11 and upstream of the optical path of the echo detecting unit 12, one of the reflecting surfaces may receive the detection laser beam L1 and reflect the detection laser beam to the outside of the laser radar for detecting a target object, and the other reflecting surface may receive the echo L2 and reflect the echo toward the echo detecting unit 12. As shown in fig. 1, at the present position, the probe laser beam L1 is incident on the reflection surface 131 and reflected outside the laser radar, and the echo L2 is incident on the reflection surface 132 and then reflected toward the echo detection unit 12. As the polygon mirror 13 rotates about its rotation axis 135, different ones of the plurality of reflection surfaces thereof are used to reflect the detection laser beam and reflect the radar echo, respectively. And preferably the same reflecting surface is not used for both reflecting the probe laser beam and reflecting the radar echo.
An embodiment of a square turning mirror is shown in fig. 1, the present invention is not limited thereto, and the polygon mirror 13 may be any one of a double-sided mirror, a regular triangular turning mirror, a regular pentagonal turning mirror, or a regular polygon with a larger number of sides (greater than 5), and the polygon mirror 13 is configured to rotate in one direction around its rotation axis. An embodiment of a double-sided turning mirror is shown in fig. 2. As shown in fig. 2, the polygon mirror 13 is a double-sided mirror, and includes two opposite reflecting surfaces 131 and 132. And in order to meet the requirement of optical path arrangement in the laser radar 10, a first turning mirror 136 and a second turning mirror 137 may be further included, wherein the first turning mirror 136 is configured to change the direction of the detection laser beam L1 reflected by the polygon mirror 13, and the second turning mirror 136 is configured to change the direction of the echo L2 received by the laser radar so as to make the echo L2 incident on the reflecting surface 132 of the polygon mirror 13. The first and second folding mirrors 136 and 137 are generally fixed so as to reflect incident light in a fixed direction. Of course, the first folding mirror 136 and the second folding mirror 137 may be configured to vibrate or rotate, and may further improve the resolution of the point cloud by cooperating with the polygon mirror 13. By providing the first turning mirror 136 and the second turning mirror 137, the structure of the laser radar 10 can be made more compact. A schematic view of a regular pentagonal turning mirror is shown in fig. 5. As shown in the figure, the mirrors formed by two adjacent sides of the regular pentagon turning mirror 13 are used for reflecting the detection laser beam L1 and the echo L2, respectively.
Fig. 4 shows a preferred embodiment according to the invention, wherein the polygon mirror 13 is a regular triangular mirror with reflecting surfaces 131, 132 and 133. In addition, the laser radar 10 further includes a transmitting swing mirror 14, a transmitting lens 15, a receiving lens 16, and a receiving swing mirror 17. The emission swing mirror 14 and the emission lens 15 are sequentially disposed between the array of the lasers 11 and the polygon mirror 13, wherein the detection laser beam L1 is incident on the emission swing mirror 14, reflected to the emission lens 15, and then incident on the polygon mirror after being shaped by the emission lens 15. The detection beam emitted by the laser 111 generally has a certain divergence angle, and can be shaped into a parallel beam by the emission lens 15 and emitted for detecting the target object. The receiving lens 17 and the receiving swing mirror 17 are sequentially disposed between the polygon mirror 13 and the array of the detector 121, wherein the polygon mirror 13 reflects the echo to the receiving lens 16, and the echo is shaped by the receiving lens 16, incident on the receiving swing mirror 17, and then reflected to the array of the detector 121. The laser 111 is typically arranged in the focal plane of the transmit lens 15 and the detector 121 is typically arranged in the focal plane of the receive lens 16. In addition, those skilled in the art will appreciate that the two commonly emitted or received light beams illustrated in fig. 4 refer only to divergence (gradually changing from a point to a large spot) or convergence (gradually narrowing from a spot to a point) of the light beams and do not refer to the horizontal scanning range.
The transmit pendulum 14 and receive pendulum 17 are particularly preferred in some embodiments. The inventors found that as the number of mirror surfaces of the polygon mirror increases, the field of view FOV that can be actually used gradually decreases, but by means of the tilting mirror encryption or the like, the vertical beam and the angular resolution that can be achieved gradually increase.
According to a preferred embodiment of the present invention, the array of lasers 111 and the array of detectors 121 of the lidar 10 are one-dimensional linear arrays or 1.5-dimensional linear arrays along the vertical direction (i.e. the direction of the rotation axis 135 of the polygon mirror 13 in the figure), and the light emitting direction of each laser in the linear arrays corresponds to an angle in the vertical plane, so as to realize scanning in the vertical direction; and in the horizontal direction, scanning is realized by unidirectional rotation of the polygon mirror 13, thereby realizing two-dimensional scanning in the vertical direction and the horizontal direction. In the present invention, a 1.5-dimensional linear array refers to an array in which the length of one dimension of the linear array is much greater than the length of the other dimension, for example, greater than or equal to 10 times the length of the other dimension. For example, an array of lasers, such as 64 x 2 or 40 x 2, may be considered a 1.5 dimensional linear array within the meaning of the present invention.
Fig. 5A and 5B show a preferred embodiment of the present invention, and as shown, the regular triangular polygon mirror 13 further includes a driving mechanism 138 located inside thereof, and the driving mechanism 138 is, for example, a rotating motor, and includes a bearing 140, and the bearing 140 is matched with the rotating shaft 135 of the polygon mirror 13, so as to rotate around the rotating shaft 135 of the polygon mirror 13, and rotate the plurality of reflecting surfaces on the outer periphery of the polygon mirror 13. The drive mechanism 138 is located substantially within the space enclosed by the reflective surface to help further reduce the height of the lidar without the upper and lower ends extending beyond the axial extent of the reflective surface. In addition, as shown in fig. 5A, the polygon mirror 13 further includes a code disc 139, and the code disc 139 is disposed at the bottom of the polygon mirror 13 and is used for measuring and coding the rotation movement of the polygon mirror 13, so that the control system of the laser radar 10 can know the current position and angle of the polygon mirror 13.
According to the above embodiment, the height of the polygon mirror 10 substantially restricts the overall height of the lidar, while still enabling a very flat lidar system while maintaining a large aperture, which is substantially the height of the lidar, which may be on the order of several centimeters. The lidar may be classified into various types according to its function, including a lidar for automatic driving, a lidar for a sweeping robot, and a lidar for an automatic guided vehicle. In addition, the lidar may be mounted at different locations. Taking the example of a vehicle-mounted lidar, it may be mounted on the roof of a vehicle as the primary radar, on the front of the vehicle (e.g., integrated into the vehicle lights) as the forward radar, or on the side of the vehicle as the side radar. By implementing a flattened lidar, the lidar can be conveniently integrated at various locations of the vehicle, such as within the vehicle lamp or within the vehicle body, reducing changes and effects on the appearance of the vehicle.
According to a preferred embodiment of the present invention, the angle between the detection laser beam L1 incident on the polygon mirror 13 and the echo L2 reflected by the polygon mirror upon reception is twice the outer angle of the polygon mirror 13, or may be described as the angle between the light emitting direction of the laser 111 and the detection direction of the detector 121 is twice the outer angle of the polygon mirror 13. As shown in fig. 1, in the case of the square turning mirror 13, an angle between the detection laser beam L1 incident on the turning mirror 13 and the echo L2 reflected by the turning mirror at the time of reception is 180 degrees, and each external angle of the turning mirror 13 is 90 degrees, which are in a double relationship. In the present invention, the outer angle of the polygon mirror is an angle that has a complementary relationship with the inner angle of the polygon mirror. For the regular pentagon shaped turning mirror 13 of fig. 3, the angle between the detection laser beam L1 incident on the turning mirror 13 and the echo L2 reflected by the turning mirror at the time of reception is 144 degrees, and the external angle of the turning mirror 13 is 72 degrees, which are in a double relationship. For the regular triangular turning mirror 13 of fig. 4, an angle between the detection laser beam L1 incident on the turning mirror 13 and the echo L2 reflected by the turning mirror at the time of reception is 240 degrees, and each external angle of the turning mirror 13 is 120 degrees, which are in a double relationship. Through the above angular relationship, it is helpful to make the direction of the probe beam finally emitted by the laser radar and the direction of the echo received by the radar substantially parallel, including remaining parallel during the oscillation. In addition, the emission and the reception of the laser radar can be aligned, that is, the echo of the detection laser beam emitted by the laser reflected by the target object can be incident into the corresponding detector 121 after being reflected by the polygon mirror. When the light beam is a diffused or converged light beam, the direction of the light beam refers to the direction in which the center of the light beam is located. The same is true for the echo. In the case of the double-sided mirror, as shown in fig. 2, the probe laser beam L1 incident on the polygon mirror 13 may be in the same direction as the echo L2 reflected by the other reflecting surface upon reception.
Fig. 6 shows an arrangement of lasers 111 according to a preferred embodiment of the present invention, wherein the array of lasers 111 comprises a plurality of rows of lasers distributed along a second direction perpendicular to the direction of the rotation axis, shown as two rows, each row comprising at least one laser, wherein the lasers of different rows are mutually staggered along the direction of the rotation axis. Through arranging the encryption in the dislocation in the vertical direction, can reduce the vertical direction height of arranging, promote vertical direction resolution ratio. In addition, although not shown in fig. 6, those skilled in the art will readily appreciate that the two sets of lasers in fig. 6 are preferably offset from each other in a direction perpendicular to the plane of the drawing to facilitate the placement of the lasers.
Alternatively, as shown in fig. 7, the array of lasers 111 may be configured in a single row along the direction of the rotation axis, encrypted by the transmitting oscillating mirror 14 shown in fig. 4. Assuming that the transmitting oscillating mirror 14 has three positions at which the detection laser beam can be reflected, the detection laser beam emitted by the same laser will be encrypted into three beams, as shown in "surface 1", "surface 2", and "surface 3" in fig. 7. In addition, according to an embodiment of the present invention, in the encryption process by the swing mirror, the swing mirror swings vertically by a fixed small angle every time the polygon mirror 13 switches to a reflecting surface; thus reducing the number of channels required for the vertical transmit and receive arrays or achieving a super-resolution effect when the same number of channels is used.
Further, according to a preferred embodiment of the present invention, the arrays of the plurality of lasers 111 and the arrays of the plurality of detectors 121 are disposed at substantially the same longitudinal position with respect to the rotation axis 135 of the polygon mirror 13, thereby contributing to a very flat lidar. Still taking fig. 6 and 7 as an example, in the direction of the rotation axis 135 along the multi-facet rotation axis 13, the array of lasers 111 and the array of detectors 121 are corresponding in axial position, without exceeding the axial range of the plurality of reflection surfaces, so that the height of the lidar can be significantly reduced.
The invention also relates to a method for object detection using a lidar 10 as described above.
Fig. 8 shows a lighting strategy according to a preferred embodiment of the invention: light is emitted according to the columns, and the light is emitted at intervals in the single column. The arrangement of the laser array is schematically shown in fig. 8, for example divided into four columns of 9 lasers each. When the detection light beam is emitted, the mode of emitting light according to the column light and emitting light at intervals in a single column is adopted. Specifically, part of the lasers in the first row of lasers are driven to emit light, after the first row of lasers emit light, the second row of lasers are driven to emit light, and therefore the lasers in the third row and the fourth row are driven to emit light. Wherein for the first column of lasers it is preferred to avoid that adjacent lasers emit light simultaneously, thereby ensuring eye safety. For this purpose, light emission may be performed at certain intervals, for example, first, a plurality of lasers in the a-sequence are driven to emit light (positions 1, 4, 7), after the light emission of the lasers is completed and the detection and reception of the corresponding channel are completed, a plurality of lasers in the B-sequence are driven to emit light (positions 2, 5, 8), and finally, lasers in the C-sequence are driven to emit light (positions 3, 6, 9). The time interval between adjacent column sequences is related to the number of polygon mirrors and the horizontal resolution of the system. This scanning mode is particularly effective for increasing the eye safety threshold, and on the other hand, the minimum transverse extraction time interval Δ t, even at very high transverse angular resolutions2Will still be much longer than the light emission time interval deltat1(ii) a Then, within a given eye-safe computation window (e.g., within a typical 5 mrad field of view), the eye-safe of the lidar is limited to adjacent light-exiting units within a single column. In the process of switching the scanning sequence from i to ii, the physical distance between two front and back light-emitting lasers can be increased by staggered light emission, so that the safety threshold of human eyes is further effectively improved; wherein in the same column, the light-emitting interval of the nearest adjacent unit is pulled to the maximumThen, for example, the A sequence emits light first, then the C sequence, and finally the B sequence in the figure. In addition, as will be readily understood by those skilled in the art, the simultaneous emission of a plurality of lasers in the a sequence in the present invention does not mean that a plurality of lasers in the a sequence are driven to emit light at the same time in a strict sense, and may be separated by a slight time difference as long as the time difference is much smaller than the time difference between adjacent columns, for example, 10% or less, or 1% or less of the time difference between adjacent columns. In this case, it can be considered that a plurality of lasers of the a sequence emit light simultaneously.
One of the salient features of the embodiments of the present invention is that the transceiving has energy complementary characteristics. As shown in fig. 9A and 9B. A regular triangular polygon mirror is illustrated in fig. 9A and 9B, in which a solid line of triangle a indicates the polygon mirror in the initial centered position, triangle a' indicates the case where the polygon mirror is rotated toward the transmitting end, and triangle a "indicates the case where the polygon mirror is rotated toward the receiving end.
As shown in fig. 9A and 9B, when the polygon mirror is initially centered, the transmitting aperture and the receiving aperture correspond exactly to the width of the reflecting surface of the polygon mirror. When the polygonal mirror rotates towards the emitting end, as shown by a triangle A', the effective emergent light energy is increased, but the effective receiving caliber is reduced; on the contrary, when the polygon mirror rotates toward the receiving end, as indicated by the triangle a ″, the effective outgoing light energy decreases, but the effective receiving aperture increases. The significant advantages of this approach are primarily the fact that a polygon mirror with a smaller reflective surface can be used to achieve a larger horizontal field of view, the size and inertia of the moving parts of the polygon mirror with a smaller reflective surface is smaller, the system size is reduced and the reliability of the system is improved, but still a longer range can be guaranteed.
The above describes a laser radar system with a vertical array transceiver unit and a horizontal polygon mirror for two-dimensional scanning, wherein the vertical direction determines the field angle through the position of the array and the optical lens group, and the horizontal direction horizontally scans the vertical linear array or the 1.5-dimensional array through the reciprocating oscillating mirror. Embodiments of the present invention enable a highly compact lidar. Compared with the laser radar in a coaxial multi-surface rotating mirror mode, the scheme provided by the embodiment of the invention has higher transceiving efficiency, thereby being beneficial to expanding the absolute measuring range. Compared with the laser radar of the paraxial polygon mirror with upper and lower layers, the laser radar is higher in height due to the upper and lower layers, and the laser radar can be effectively reduced in height and can be better installed on a vehicle. In addition, because the transmitting optical system and the receiving optical system are physically separated in the upper-lower layered mode, a relatively considerable short-distance blind area inevitably exists, and transmitting and receiving light spots of the different-surface transceiving scheme theoretically overlap, so that a part of energy can be received by the receiving end optical system inevitably even if the distance is very short, and the short-distance blind area of the different-surface transceiving scheme is smaller than that of the upper-lower layered scheme.
In addition, in the embodiment of the invention, the transceiving of the laser can be close to the theoretical transceiving efficiency limit, thereby being beneficial to remote measurement. In addition, the reflecting aperture of the low-speed rotating multi-surface rotating mirror can be very large, and the measuring range can be very far. The radar structure is very efficient and beneficial in both system transceiving efficiency and human eye safety, so that the laser emergent light energy can be reduced, the system power consumption can be reduced, or the reliability of a transmitting unit can be provided, and the radar structure is beneficial to human eye safety, or a longer measuring range can be obtained under the condition of using energy equivalent to that of other similar systems.
In the embodiment of the invention, the channel number can be realized through the array in the vertical direction, the whole array realizes two-dimensional scanning through the rotary scanning of the horizontal multi-surface rotating mirror, but the adjacent surfaces of the multi-surface rotating mirror are used for transmitting and receiving, thereby realizing the separation of receiving and transmitting. In the embodiment of the invention, the vertical field of view of the laser radar can reach dozens of degrees (depending on the length, the focal length and the like of the array in the vertical direction), and the horizontal field of view can be from a few degrees, dozens of degrees to more than one hundred degrees. The radar beam is ensured by the number of detector channels in the vertical direction, and the laser array at the transmitting end can be independent light sources corresponding to the number of detectors one by one or segmented line light sources for simultaneously illuminating a plurality of units.
In addition, the frequency of horizontal scanning may be matched with the frame frequency of the laser radar, for example, the radar frame frequency is 10 hz, the rotation frequency of the polygon mirror is 10/N hz when one set of transceiving reflective surfaces of the polygon mirror is a frame, and the rotation frequency of the polygon mirror is equal to 10 hz if N reflective surfaces of the polygon mirror are combined into a frame.
In addition, the height of the system of the invention is finally basically determined by the height of the reflector (the whole motor can be embedded in the reflector module), so that the scheme can realize a laser radar system with very compact and flat height, thereby meeting the requirement of large-scale mass production passenger vehicles. When the polygon mirror transmits and receives light in different planes, the effective optical apertures of transmitting and receiving are unequal when the polygon mirror rotates by using larger optical apertures of transmitting and receiving, so that the transmission and reception in different planes can have complementary characteristics of energy: when the effective emergent energy of the transmitting end is reduced, the effective receiving caliber of the receiving end is increased, thereby making up the range loss caused by the reduction of the transmitting energy, and vice versa, so that the actual external circle radius of the multi-surface rotating mirror can be smaller, the reduction of the volume is facilitated, and the reliability is improved
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A lidar comprising:
the laser emission unit comprises a plurality of laser arrays, wherein the laser arrays are non-uniformly distributed and are configured to emit detection laser beams for detecting a target object;
an echo detection unit comprising an array of a plurality of detectors configured to receive echoes of the detection laser beam after reflection by a target object; and
the multi-surface rotating mirror can rotate around the rotating shaft of the multi-surface rotating mirror and is provided with a plurality of reflecting surfaces parallel to the rotating shaft, wherein the multi-surface rotating mirror is positioned on the downstream of the optical path of the laser emission unit and on the upstream of the optical path of the echo detection unit, one of the reflecting surfaces can receive the detection laser beam and reflect the detection laser beam to the outside of the laser radar, and the other reflecting surface can receive the echo and face the echo to the echo detection unit for reflection.
2. The lidar of claim 1, wherein the array of lasers has a relatively higher arrangement density of lasers at a middle position along a longitudinal direction of the lidar and a relatively lower arrangement density of lasers at two side positions, and the polygon mirror comprises one of a double-sided mirror, a regular triple-sided mirror, a square-shaped mirror, a regular pentagon-shaped mirror, or a regular polygon having a number of sides greater than 5, and the polygon mirror is configured to rotate unidirectionally about its rotational axis.
3. The lidar according to claim 1 or 2, wherein the array of the plurality of lasers and the array of the plurality of detectors are arranged at substantially the same axial position with respect to the rotational axis of the polygon.
4. The lidar according to claim 1 or 2, wherein the polygon mirror further comprises a drive mechanism located substantially within a space enclosed by the one and the other reflective surface.
5. The lidar according to claim 1 or 2, wherein the polygon mirror is a regular polygon mirror, and an angle between a detection laser beam incident to the polygon mirror and an echo reflected by the polygon mirror is twice an outer angle of the polygon mirror.
6. The lidar according to claim 1 or 2, further comprising:
the transmitting swing mirror and the transmitting lens are sequentially arranged between the array of the lasers and the multi-surface rotating mirror, wherein the detection laser beams are incident on the transmitting swing mirror, reflected to the transmitting lens and incident on the multi-surface rotating mirror after being shaped by the transmitting lens;
receive lens and receipt swing mirror, set gradually the polygon mirror with between the array of detector, wherein the polygon mirror will the echo reflection incides receive lens, the warp incide after receive lens assembles on the receipt swing mirror, then reflected to the array of detector.
7. The lidar according to claim 1 or 2, wherein the array of lasers comprises a plurality of columns of lasers distributed along a second direction perpendicular to the direction of the rotation axis, each column comprising at least one laser, wherein the lasers of different columns are mutually staggered along the direction of the rotation axis.
8. The lidar according to claim 1 or 2, wherein the polygon is configured such that a direction of a detection laser beam finally emitted by the lidar and a direction of an echo received by the lidar are substantially parallel.
9. The lidar of claim 7, wherein the array of lasers is driven to emit light in a column-out, spaced-within-single-column manner.
10. Method for object detection using a lidar according to any of claims 1-9.
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| CN202010260771.XA CN113552578A (en) | 2020-04-03 | 2020-04-03 | Laser radar and method for detecting target object by using same |
| PCT/CN2021/082801 WO2021197170A1 (en) | 2020-04-03 | 2021-03-24 | Lidar and method for detecting target object by using lidar |
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