CN112099023B - Multi-line laser radar - Google Patents
Multi-line laser radar Download PDFInfo
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- CN112099023B CN112099023B CN202010968174.2A CN202010968174A CN112099023B CN 112099023 B CN112099023 B CN 112099023B CN 202010968174 A CN202010968174 A CN 202010968174A CN 112099023 B CN112099023 B CN 112099023B
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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
- G01S7/4814—Constructional features, e.g. arrangements of optical elements of transmitters alone
- G01S7/4815—Constructional features, e.g. arrangements of optical elements of transmitters alone using multiple transmitters
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- 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
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Abstract
The application belongs to the technical field of laser radars, and particularly relates to a multi-line laser radar which comprises a first transmitting module, a second transmitting module, a first receiving module, a second receiving module and a reflecting mirror module; according to the multi-line laser radar provided by the application, the two transmitting modules are arranged to respectively transmit laser beams from two opposite directions, the laser beams are reflected by the reflector module in a rotating way to form a scanning range, and the laser beams are received by the two corresponding transmitting modules after being reflected by the target, so that the detection of the target is realized; the multi-line laser radar is formed with symmetrical scanning tracks, so that a wider horizontal field angle is maintained, the horizontal scanning angle and vertical spatial resolution of a target are improved, and the spatial detection is more effectively realized.
Description
Technical Field
The application belongs to the technical field of laser radars, and particularly relates to a multi-line laser radar.
Background
The multi-line scanning scheme that the incident light is combined with the rotating mirror with multiple faces and different pitching angles and vertical to the rotating shaft is widely applied due to the factors of large scanning angle of view, high scanning speed, high resolution, mature technology and the like, and the 4-line SCALA laser radar of the Germany IBEO company adopts the scanning scheme to realize 145-degree detection field of view and becomes a first-money vehicle-scale laser radar product.
Along with the development of technology, velodyne company provides Velodyne 64 line laser radar with smaller volume and higher unit energy density, and the Velodyne 64 line laser radar is widely applied to vehicle navigation by virtue of good performance. Since most of laser beam pitch angles of the Velodyne 64 line laser radar are downward, the Velodyne 64 line laser radar is usually installed at a higher position, such as the top of an automobile, about 1.6m, and the detection track of the Velodyne 64 line laser radar in the front 140 DEG range can be calculated to be a hyperbolic track through a space scanning equation. In a short distance, the Velodyne 64 line laser radar has a good detection effect on a person in front of the vehicle, but the larger the off-center azimuth angle is, the lower the spatial resolution is, and as the off-center azimuth angle of the target is larger, the fewer the laser lines of the target are detected, and the problems of small horizontal scanning angle and low vertical spatial resolution of the target exist.
Disclosure of Invention
In view of the above, the embodiment of the application provides a multi-line laser radar to solve the problems of small horizontal scanning angle and low vertical spatial resolution of the existing multi-line radar to a target.
A first aspect of an embodiment of the present application provides a multi-line lidar comprising: the device comprises a first transmitting module, a second transmitting module, a first receiving module, a second receiving module and a reflecting mirror module;
the first emission module is positioned at the first side of the reflector module and is used for emitting a first laser beam from a first direction to the reflector module;
the second emission module is positioned at the second side of the reflector module and is used for emitting a second laser beam from a second direction to the reflector module; wherein the first side of the mirror module and the second side of the mirror module are opposite sides, and the first direction and the second direction are opposite directions;
the first receiving module is positioned at the first side of the first reflecting mirror module and is used for receiving the first laser beam reflected by the target;
the second receiving module is positioned at the second side of the second reflecting mirror module and is used for receiving the second laser beam reflected by the target;
the reflector module rotates around the axis at a preset rotation speed and is used for reflecting a first laser beam emitted by the first emitting module from a first direction so that the first laser beam covers a first preset range, and reflecting a second laser beam emitted by the second emitting module from a second direction so that the second laser beam covers a second preset range.
Optionally, the mirror module includes a mirror composed of N mirror surfaces;
the N reflecting mirror surfaces form the side surfaces of a N prism, and N is more than or equal to 3;
when the N reflecting mirror surfaces rotate around the axis at a preset rotation speed, two reflecting mirror surfaces in the N reflecting mirror surfaces respectively reflect a first laser beam emitted by the first emitting module from a first direction and a second laser beam emitted by the second emitting module from a second direction.
Optionally, the first emission module and the second emission module are symmetrically arranged at two sides of the reflecting mirror; the position of the first transmitting module, the position of the second transmitting module, the emergent angle corresponding to the first laser beam after being rotationally reflected by one reflecting mirror surface, the emergent angle corresponding to the second laser beam after being rotationally reflected by one reflecting mirror surface and the reflecting mirror surface meet a first preset relation;
establishing a coordinate system by taking the first plane as a plane and taking the intersection point of the axle center and the first plane as an origin; wherein the first plane is a plane in which the first laser beam and the second laser beam are located;
the first preset relationship includes:
in the method, in the process of the application,for the corresponding emergent angle range of the first laser beam after being rotationally reflected by a reflecting mirror face, +.>The second laser beam is rotated and reflected by a reflecting mirror surface to correspond to the emergent angle range,x 0 is the abscissa of the first transmit module; defining c as a line segment formed by projection of a reflecting mirror surface on a first plane, defining a as a line segment formed by connecting one end point of c with an origin, b as a line segment formed by connecting the other end point of c with the origin, and r a Length of line segment a, r b Length of line segment b, +.>The included angle between the line segment a and the line segment b, and the included angle between the line segment a and the line segment c.
Optionally, n=8, and each mirror surface is the same, and 8 mirror surfaces form a side surface of the regular eight prism; the first direction and the second direction are opposite directions;
the positions of the first transmitting module, the second transmitting module and the size of the reflecting mirror surface satisfy the following conditions:
wherein x is 0 Y is the abscissa, y, of the first transmitting module 0 Is the ordinate, x 'of the first emission module' 0 Is the abscissa, y 'of the second transmitting module' 0 And l is the bottom side length of the regular eight prism, which is the ordinate of the second transmitting module.
Optionally, the first laser beam and the second laser beam are flat top beams.
Optionally, the ratio of the diameter of the first laser beam to the bottom side length of the regular eight prism is a first preset value;
the ratio of the diameter of the second laser beam to the bottom side length of the regular eight-prism is a second preset value;
the first preset value is determined according to the position of the first transmitting module, the corresponding emergent angle range of the first laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the first laser beam after being reflected by the reflecting mirror surface;
and the second preset value is determined according to the position of the second transmitting module, the corresponding emergent angle range of the second laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the second laser beam after being reflected by the reflecting mirror surface.
Optionally, the laser radar further includes: a first lens arranged in front of the first receiving module and a second lens arranged in front of the second receiving module;
the first lens is used for converging the first laser beam reflected by the target to the first receiving module;
the second lens is used for converging the second laser beam reflected by the target to the second receiving module.
Optionally, the projection of the first lens and the second lens on the receiving surface covers the projection of the reflecting mirror module on the receiving surface.
Optionally, the laser radar further includes: a first lens arranged in front of the first receiving module and a second lens arranged in front of the second receiving module;
the first lens is used for converging the first laser beam reflected by the target to the first receiving module;
the second lens is used for converging the second laser beam reflected by the target to the second receiving module;
the first lens and the second lens are square, and the projection of the first lens on the receiving surface is the same as the projection of the largest area of the reflecting mirror surface on the receiving surface when the first laser beam or the second laser beam is reflected;
the abscissa of the center of the first lens and the abscissa of the center of the second lens satisfy:
wherein x is r Is the abscissa of the center of the first lens or the center of the second lensAnd the abscissa, i is the bottom side length of the regular eight-prism.
Optionally, the N reflecting mirror surfaces and the first plane form N inclination angles respectively, so as to satisfy scanning in a third direction; the first plane is a plane where the first laser beam and the second laser beam are located, and the third direction is a direction perpendicular to the first plane.
The multi-line laser radar provided by the embodiment of the application comprises a first transmitting module, a second transmitting module, a first receiving module, a second receiving module and a reflecting mirror module; the first transmitting module and the second transmitting module are respectively arranged at two opposite sides of the reflecting mirror module, so that laser beams are transmitted to the reflecting mirror module from two opposite directions; correspondingly, the first receiving module and the second receiving module which are oppositely arranged at two sides of the reflecting mirror module are used for receiving the laser beam reflected by the target; the reflector module is arranged to rotate around the axis at a preset rotation speed, and the first laser beam of the first transmitting module and the second laser beam transmitted by the second transmitting module are reflected to form a first preset range and a second preset range which are used as detection ranges respectively. By arranging the two transmitting modules and the two receiving modules, the problem that the horizontal view angle is reduced due to the fact that the scanning track of the single transmitting module is asymmetric and deflection occurs when the scanning angle is increased can be avoided. The two emission modules are arranged to emit laser beams from two opposite directions to detect respectively, so that symmetrical scanning tracks are formed, a wider horizontal view angle is maintained, the horizontal scanning angle and vertical spatial resolution of a target are improved, and spatial detection is more effectively realized.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a multi-line lidar according to an embodiment of the present application;
FIG. 2 is a schematic diagram of space vector analysis of a rotating mirror scanning optical path provided by an embodiment of the present application;
fig. 3 is a schematic diagram of a scan trajectory at x=10m for different mirror pitch angles provided by an embodiment of the present application;
FIG. 4 is a schematic view of any one of the facets and the light source position and the horizontal scan angle of a polygon mirror provided by an embodiment of the present application;
fig. 5 is a schematic three-dimensional structure of a multi-line lidar according to an embodiment of the present application;
fig. 6 is a schematic top view of a multi-line lidar according to an embodiment of the present application;
fig. 7 is a schematic diagram of a front view structure of a multi-line lidar according to an embodiment of the present application;
FIG. 8 is a schematic diagram of an integration region provided by an embodiment of the present application;
FIG. 9 is a schematic diagram of the relationship between the exit angle and the relative intensity according to the embodiment of the present application;
FIG. 10 is a schematic diagram of a relationship between a scan angle and a maximum detection distance according to an embodiment of the present application;
FIG. 11 is a schematic diagram of a comparison of scanning detection of a multi-line lidar and a Velodyne 64 line lidar at 10m according to an embodiment of the present application;
FIG. 12 is a schematic diagram of a contrast of scanning detection of a multi-line lidar and a Velodyne 64 line lidar at 50m according to an embodiment of the present application;
fig. 13 is a schematic diagram of a scanning detection contrast of a multi-line lidar and a Velodyne 64 line lidar at 100m according to an embodiment of the present application.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth such as the particular system architecture, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.
The term "comprising" in the description of the application and the claims and in the above figures, as well as any other variants, means "including but not limited to", intended to cover a non-exclusive inclusion. For example, a process, method, or system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed but may optionally include additional steps or elements not listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," and "third," etc. are used for distinguishing between different objects and not for describing a particular sequential order.
In order to illustrate the technical scheme of the application, the following description is made by specific examples.
Fig. 1 is a schematic structural diagram of a multi-line laser radar provided in an embodiment of the application, and referring to fig. 1, the multi-line laser radar includes: a first transmitting module 101, a second transmitting module 102, a first receiving module 103, a second receiving module 104 and a mirror module 105.
The first emitting module 101 is located at a first side of the mirror module 105 and is used for emitting a first laser beam from a first direction to the mirror module 105.
A second emission module 102, located at a second side of the mirror module 105, for emitting a second laser beam from a second direction to the mirror module 105; wherein the first side of the mirror module 105 and the second side of the mirror module 105 are opposite sides, and the first direction and the second direction are opposite directions.
The first receiving module 103 is located at a first side of the first mirror module 105 and is used for receiving the first laser beam reflected back by the target.
A second receiving module 104, located on a second side of the second mirror module 105, is configured to receive the second laser beam reflected back by the target.
The mirror module 105 rotates around the axis at a preset rotation speed, and is configured to reflect the first laser beam emitted by the first emitting module 101 from the first direction such that the first laser beam covers a first preset range, and reflect the second laser beam emitted by the second emitting module 102 from the second direction such that the second laser beam covers a second preset range.
In the embodiment of the application, the reflection track formed by the incident light beam reflected by any plane mirror can be described by vector optics theory. The axis of the mirror, i.e. the rotation axis, can be coincident with the z-axis of the cartesian coordinate system, at x=x, as can be seen in fig. 2 L The right-hand rectangular coordinate system of the detection surface is arranged at the plane. ω is the rotation angle of the mirror about the rotation axis, and is located to the left of the detection plane perpendicular to the yoz plane when the mirror is in its initial position ω=0° (i.e., y<0) The unit normal vector of the reflector isRay slave position vector r 0 ＝(x 0 ,y 0 ,z 0 ) Point A is incident, the incident ray unit vector is +.>Point r 1 ＝(x 1 ,y 1 ,z 1 ) Is the intersection point of the incident light ray and the mirror surface, and the unit vector of the reflected light ray is +.>Let the distance of the mirror from the origin of coordinates be d +.>According to the vector transformation relation and the coordinate equation of the incident light, the intersection point of the incident light and the mirror surface can be obtained to meet the following relation:
according to the law of optical reflection, the unit vector of incident light isThe unit normal vector of the mirror is +.>And reflected ray unit vector +.>The following relationship is satisfied:
after the light is reflected by the mirror surface, the light is reflected by the mirror surface and then is reflected by the mirror surface at x=x L The trajectory equation of the detection surface at the plane is r= (x) L Y, z) satisfies the following relationship:
assuming that the inclination angle of the reflecting mirror is delta, namely the included angle between the normal vector of the reflecting mirror and the yoz plane is delta, the unit normal vector of the reflecting mirror isIn the case where light is incident from the left side perpendicularly to the rotation axis,the method can obtain:
in the trajectory equation r= (x) L Y, z), there are:
as can be seen from the above-described scanning trajectories, the scanning trajectories are asymmetrically distributed and are related to the mirror angle ω, and gradually decrease as the rotation angle ω increases. If a 140-degree scanning angle of the x-axis is assumed to be, -70 degrees, the rotation angle omega of the corresponding reflector around the rotation axis is from 10-80 degrees, the distance d=8 mm between the reflector and the origin of coordinates is assumed, and the incident light spot position x is determined 0 ＝5mm，y 0 ＝-10mm，z 0 The mirror tilt angles δ= -1 °,0 °,1 °,2 ° at x=10m are calculated for each of =2mm, and the scanning trajectories of the four-wire lidar are shown in fig. 3. As can be seen from fig. 3, the longitudinal spatial resolution of the scanning probe is asymmetrically distributed, and the resolution is higher as the rotation angle ω is larger. For pedestrians of 1.8m height, the radar is mounted at a height of 0.4m for the right angular range, i.e. y>0, can detect four lines, and for the left angular range, y<0, as the angle becomes larger gradually to the left, the scanning beam is deflected gradually upward and downward, from the initial detection of 4 lines, gradually becomes 3 lines and 2 lines, and finally becomes 1 line.
Therefore, in the embodiment of the application, the scanning track y of each transmitting module is taken through the two transmitting modules>A part of 0, i.e. a first preset range of the first transmitting module and a second preset range of the second transmitting module, can be avoided from occurring in y<The deflection problem of the scanning beam at 0 avoids the problem that the scanning beam is too high to scan the sky at a distance or too low to scan the ground so as to effectively utilize the detection beam of the multi-line laser radar, thereby maintaining a wider horizontal field angle, improving the vertical spatial resolution of target scanning, and assuming that the inclination angles of two adjacent reflecting surfaces are delta respectively 1 And delta 2 The corresponding vertical spatial resolution is
Since omega is greater thanAngle of (2)The range, as can be seen from the above equation, does not appear to be left (y) in the multi-line scan trace of FIG. 3<0) As ω becomes smaller and the longitudinal spacing becomes larger, the vertical spatial resolution becomes smaller, but the right scanning trajectory is larger than +.>The range of the multi-line scanning beam gradually becomes smaller along with the gradual increase of omega, and the longitudinal interval gradually becomes approximately parallel, so that the vertical spatial resolution is uniform, and the utilization rate of the multi-line scanning beam on target detection is improved.
In some embodiments, the mirror module includes a mirror comprised of N mirror faces; the N reflecting mirror surfaces form the side surfaces of a N prism, and N is more than or equal to 3; when the N reflecting mirror surfaces rotate around the axis at a preset rotation speed, two reflecting mirror surfaces in the N reflecting mirror surfaces respectively reflect a first laser beam emitted by the first emitting module from a first direction and a second laser beam emitted by the second emitting module from a second direction.
In some embodiments, the first and second emission modules are symmetrically disposed on two sides of the reflector; the position of the first transmitting module, the position of the second transmitting module, the emergent angle corresponding to the first laser beam after being rotationally reflected by one reflecting mirror surface, the emergent angle corresponding to the second laser beam after being rotationally reflected by one reflecting mirror surface and the reflecting mirror surface meet a first preset relation; establishing a coordinate system by taking the first plane as a plane and taking the intersection point of the axle center and the first plane as an origin; wherein the first plane is a plane in which the first laser beam and the second laser beam are located;
the first preset relationship includes:
in the method, in the process of the application,passing the first laser beam through a counterThe corresponding emergent angle range after the reflection of the reflecting mirror surface is rotated, < >>The second laser beam is rotated and reflected by a reflecting mirror surface to correspond to the emergent angle range,x 0 is the abscissa of the first transmit module; defining c as a line segment formed by projection of a reflecting mirror surface on a first plane, defining a as a line segment formed by connecting one end point of c with an origin, b as a line segment formed by connecting the other end point of c with the origin, and r a Length of line segment a, r b Length of line segment b, +.>The included angle between the line segment a and the line segment b, and the included angle between the line segment a and the line segment c.
In the embodiment of the application, after the arrangement mode of the double-emission module is determined, the positions of the emission modules, the preset scanning ranges, the positions of the reflector modules, the shape and the size of the reflector modules are discussed. Reference may be made to fig. 4, fig. 4 being a schematic illustration of any one of the facets and the light source position versus horizontal scan angle in a polygon mirror. In this embodiment, the emitting module generates a laser beam, that is, the position of the emitting module is the light source position, and the horizontal portion in the addition of the first preset range and the second preset range is the horizontal scanning angle. Referring to fig. 4, for the case of tilt angle δ=0°, the projection of the mirror surface on the xoy plane, i.e. the first plane, forms a line segment c with a length r c The method comprises the steps of carrying out a first treatment on the surface of the a is a line segment formed by connecting one end point of c with an origin, and the length of the line segment is r shown in the figure a B is a line segment formed by connecting the other end point of c with the origin, and the length of the line segment is r shown in the figure b ，The included angle between the line segment a and the line segment b, and the included angle between the line segment a and the line segment c. The reflecting mirror surface rotates around the origin, the rotation angle is omega, and two light sources are arrangedThe coordinates of the source points a and a' (corresponding to the first and second emission modules) on the xoy plane are (x) 0 ，y 0 )，(x 0 ’，y 0 '), incident from left and right sides respectively, the incident vectors are [0,1,0 respectively]And [0, -1,0]The emergent angle range corresponding to the rotation reflection of the reflecting mirror surface is +.> Constraint according to scan size arrangement:
order theFrom the trigonometric relationship, it is possible to:
further, according to the law of reflection, the following first preset relationship can be obtained:
the meaning of each parameter in the formula can be referred to above, and is not described herein. Based on the above relation, the range of the emergent angle corresponding to the rotation reflection of the reflecting mirror surface is presetAfter that, the unique solutions α, β, σ and +.>Based on the four amounts, it is possible to determine that the prism constituted by the plurality of reflecting mirror surfaces that realize the above-described emission angle range is a few prisms, that is, the number of N can be determined based on the emission angle range.
In some embodiments, n=8, and each mirror surface is identical, 8 mirror surfaces forming the sides of a regular eight prism; the first direction and the second direction are opposite directions; the positions of the first transmitting module, the second transmitting module and the size of the reflecting mirror surface satisfy the following conditions:
wherein x is 0 Y is the abscissa, y, of the first transmitting module 0 Is the ordinate, x 'of the first emission module' 0 Is the abscissa, y 'of the second transmitting module' 0 And l is the bottom side length of the regular eight prism, which is the ordinate of the second transmitting module.
In the embodiment of the present application, the three-dimensional structure of the multi-line lidar provided in the embodiment of the present application is shown in fig. 5, fig. 6 is a top view of the multi-line lidar, and fig. 7 is a front view of the multi-line lidar. N=8, i.e. the mirror module comprises an octahedral reflecting prism, the sides of which are the respective mirror surfaces, for each mirror surfaceBased on the first preset relationship, the following can be obtainedThat is, based on the 8 reflecting mirror surfaces in the present embodiment and forming the side surfaces of the regular eight prism, it can be determined that the absolute values of the abscissas of the first and second transmitting modules are equal, the directions of the laser beams emitted by the first and second transmitting modules are opposite, and the size of each reflecting mirror surface specifically meets the second presetRelationship:
the meaning of each parameter in the formula can be referred to above, and is not described herein. The arrangement mode provided by the embodiment of the application can realize large-angle scanning detection of two symmetrically arranged emission modules, wherein the horizontal scanning angle which can be met by one emission module is-90-0 degrees, and the horizontal scanning angle which can be met by the other emission module is 0-90 degrees.
In some embodiments, the first laser beam and the second laser beam are flat top beams.
In the embodiment of the application, the actual laser beam has a certain width, and is analyzed by using a flat-top beam, namely, a laser beam with a circular cross section.
In some embodiments, the ratio of the diameter of the first laser beam to the bottom side length of the regular eight prism is a first preset value; the ratio of the diameter of the second laser beam to the bottom side length of the regular eight-prism is a second preset value; the first preset value is determined according to the position of the first transmitting module, the corresponding emergent angle range of the first laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the first laser beam after being reflected by the reflecting mirror surface; and the second preset value is determined according to the position of the second transmitting module, the corresponding emergent angle range of the second laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the second laser beam after being reflected by the reflecting mirror surface.
In the embodiment of the application, the positions and the sizes of the modules of the multi-line laser radar can be determined according to the first preset relation, the absolute value of the abscissa of the first transmitting module or the second transmitting module is in direct proportion to the side length l of the reflecting mirror surface, and the smaller the abscissa is, the smaller the side length l of the reflecting mirror surface is, and the smaller the whole size is. In practice, however, the laser beam has a certain width, and therefore it is necessary to analyze the laser beam width, the emission module, the scanning angle and the mirror surface sizeAnd the structure design of the multi-line laser radar is more reasonable by combining the radar receiving caliber. Assume that the left laser beam is at position a (x 0 ，y 0 ，z 0 ) P of incident, laser beam exit power 0 The laser beam has a circular cross section, a width (diameter) w, and a laser beam energy density distribution function g (x, z), and the following are:
ignoring beam transmission transformation and diffraction effects, and obtaining any emergent angle of the octahedral reflecting prism according to a first preset relationThe relative intensity distribution of (2) is:
wherein D is a function ofStraight line x=x 0 -w/2 and straight line x=x 0 An integration region of +w/2, wherein +.> As shown in fig. 8.
For laser beams with uniformly distributed intensity, i.e. flat-top beamsSetting the width of the first laser beam to be the same as the width of the second laser beam, wherein the first preset value is the same as the second preset value, and simulating the relation between the emergent angle and the relative intensity by integrating the laser beam and the emergent angle and simulating the relation between the emergent angle and the relative intensity by Zemax respectivelyThe results obtained were consistent. When the ratio of the diameter of the laser beam to the side length of the bottom surface of the regular eight-prism is a different first preset value, as shown in fig. 9, the relationship between the emergent angle and the relative intensity is that the radar is symmetrically arranged on the left and right sides of the dual-emission module, and only the characteristics of one side of the laser beam need to be analyzed. In FIG. 9, the first preset values are 1/16, 1/10 and 1/8, respectively. It can be seen that the smaller the width of the laser beam, the more concentrated the relative intensity thereof is within the preset angle range, because the abscissa of each point of the laser beam corresponds to different outgoing angles, and the abscissa x of the center of the emitting module 0 The larger the laser beam width is, the larger the overlapping range of different emission angles is, and the more the relative intensity is dispersed in the preset angle range.
Therefore, under the same condition, the smaller the laser beam width is, the smaller the corresponding side length of the reflecting mirror is, the smaller the abscissa of the transmitting module is, and the smaller the whole machine volume is, the more compact the structure is. In practice, the laser beam width cannot be too small, and in the case of the emission lens having the same numerical aperture, the smaller the light source width is, the smaller the focal length is, so that the beam divergence angle becomes larger, and in the case of the same focal length, the smaller the lens emergent caliber is, so that the laser beam width is reduced, and the emission power is also reduced. By comprehensively considering the relation between the overall performance of the radar system and the design constraint, the ratio of the width of the laser beam to the side length of the reflecting mirror surface can be 1/10 in the embodiment, and the scanning system parameters of the multi-line laser radar with the arrangement of the octahedral reflecting prism and the double-emission module can be obtained.
In some embodiments, the lidar further comprises: a first lens arranged in front of the first receiving module and a second lens arranged in front of the second receiving module; the first lens is used for converging the first laser beam reflected by the target to the first receiving module; the second lens is used for converging the second laser beam reflected by the target to the second receiving module.
In the embodiment of the application, the radar receiving system has great influence on the radar ranging performance, and the echo receiving power is proportional to the projection area of the reflecting mirror surface on the receiving plane. The first lens and the second lens are arranged in front of the corresponding receiving modules, so that the received echo receiving power can be increased.
In one embodiment, in order to increase the received echo receive power as much as possible, the projection of the first lens and the second lens on the receiving surface should cover the projection of the mirror module on the receiving surface.
In one embodiment, in order to maximize the received echo power without receiving unnecessary stray light, the projection of the first lens and the second lens on the receiving surface should be the same as the projection of the mirror module on the receiving surface.
In a specific embodiment, for the case where the mirror module is an octahedral reflecting prism, the exit angleAbove zero, the projection center abscissa of the reflecting mirror surface on the receiving plane is +.> Projection width isThe first lens and the second lens are square, and the projection of the first lens on the receiving surface is the same as the projection of the largest area of the reflecting mirror surface on the receiving surface when the first laser beam or the second laser beam is reflected; the width of the first lens and the second lens is +.>The abscissa of the center of the first lens and the abscissa of the center of the second lens satisfy:
wherein x is r Is the abscissa of the center of the first lens or the second lensThe abscissa of the center of the mirror, l, is the bottom side length of the regular octagon, corresponding to the projection receiving area
In some embodiments, the detection distance corresponding to any scanning angle is set by a lidar equation based on the dimensional parameter of the mirror module.
In the embodiment of the application, according to the relation between the luminous relative power and the effective receiving area and the scanning angle, the maximum detection distance corresponding to each scanning angle is different. For example, taking the above-mentioned reflector module including an octahedral reflecting prism as an example, if the detection distance in the 140 ° scanning range right in front of the radar is guaranteed to be above 100m, the detection distance of the lateral 70 ° scanning angle needs to be 100m, and according to the conditions and constraint relation to be satisfied by the system parameters, for the diffuse reflection surface target with 10% reflectivity, the method is based on the laser radar equation:
presetting P m ＝10nW、P 0 ＝25W、ρ＝10％、η r ＝0.9、η e ＝0.85、θ＝70°、/>And L m The bottom side length of the octahedral reflecting prism l=5.86 cm can be obtained by=100 m; wherein P is m At minimum detectable power, P 0 For the light source emission power, ρ is the target reflectivity, A r For the effective receiving area of the echo signal, +.>Relative intensity distribution of exit angles, eta r To receive the lens efficiency, eta e For emission lens efficiency, θ isIncluded angle between beam normal and target surface normal, L m Is the maximum detection distance; namely, the length of the bottom surface side of the octahedral reflecting prism is more than 5.86cm, and the distance detection requirement can be met. FIG. 10 is a graph of the corresponding scan angle versus the maximum detection distance for an octagon side length l=4.86 cm, 5.86cm, 6.68cm, 7.86cm, as it can be seen from the calculation that the bottom side length l of an octahedral reflecting prism is proportional to the maximum detection distance of the radar for the same exit angle, due to the minimum detectable power P m For a fixed system, L m The ratio to a is constant, and the bottom side length l square of the octahedral reflecting prism is proportional to the receiving area, so that the echo power is also proportional to the receiving area.
In some embodiments, the N reflecting mirror surfaces and the first plane form N inclination angles, respectively, for satisfying the scanning in the third direction; the first plane is a plane where the first laser beam and the second laser beam are located, and the third direction is a direction perpendicular to the first plane.
In the embodiment of the application, each reflecting mirror surface and the first plane can be provided with an inclination angle so as to meet the scanning of the view field range in the vertical direction right in front of the radar. Taking the example of a mirror module comprising an octahedral reflecting prism, if the radar is to be satisfied directly in front of (i.e.) Field of view range ψ in the vertical direction i Is-1.5 degrees, -1.0 degrees, -0.5 degrees, -0.0 degrees, +0.5 degrees, +1.0 degrees, +1.5 degrees, +2.0 degrees according to an angle resolution calculation formula
The inclination delta of each reflecting mirror surface can be obtained i Set to-1.06 °, -0.71 °, -0.35 °,0 °, 0.35 °, 0.71 °, 1.06 ° and 1.41 °; in delta i Represents the i-th inclination angle, i=1, …,8, ψ i Indicating the i-th field of view range in the vertical direction directly in front of the radar.
Compared with Velodyne 64-line laser radar, the multi-line laser radar provided by the embodiment of the application has better detection performance. The field of view of the Velodyne 64 line laser radar in the vertical direction is-24.9 degrees to +2.0 degrees, the Velodyne 64 line laser radar is usually arranged at a higher position, such as the top of an automobile, for better detection effect because most of laser beam pitch angles are downward detected, about 1.6m, the detection track of the Velodyne 64 line laser radar in the front 140 degrees range can be calculated according to a space scanning equation, and the multi-line laser radar provided by the embodiment of the application is calculated to be 0.5m because most of laser beam pitch angles with fewer lines are upward and are usually arranged at a lower position. Fig. 11-13 show comparison of detection effects at 10m, 50m and 100m for a person about 1.8m in height at the front, sides and edges of the field of view. The detection distance of 10m near is calculated by a vector optical method and Zemax non-sequence simulation respectively, the calculation results of the vector optical method and the Zemax non-sequence simulation are identical, and the result shows that the Velodyne 64 line laser radar has a good detection effect on a person in front of the alignment, and as the azimuth angle of the target away from the center is larger, the laser line number of the detected target is smaller, and only 4 laser beams detect the target at the edge, because the scanning track is a hyperbolic track at the detection surface, and the spatial resolution is lower as the azimuth angle is larger from the center, the scanning line of the multi-line laser radar provided by the embodiment of the application is approximately parallel, so that the target can be detected by 8 laser beams no matter in the center azimuth or the edge azimuth. With the increase of the detection distance, the difference between the two is obvious, and at a distance of 50m far away, the Velodyne 64 line laser radar can detect 3 lines on the target right in front, and only 1 line at the edge, while the multi-line laser radar provided by the embodiment of the application can detect 5 lines on the target right in front, and the target can still detect 6 lines at the side and the edge. When the detection distance is increased to 100m, the Velodyne 64 line laser radar can only detect 1 line in different directions on the target, 2 lines can be detected right in front of the target by the multi-line laser radar provided by the embodiment of the application, and 3 lines can still be detected on the side and the edge of the target. Therefore, the multi-line laser radar provided by the embodiment of the application has the advantage of high spatial resolution in the aspect of long-distance lateral edge scanning detection.
It will be clearly understood by those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of each functional unit and module is illustrated, and in practical application, the above-mentioned functional allocation may be performed by different functional units and modules according to needs, i.e. the internal structure of the multi-line lidar setting device is divided into different functional units or modules, so as to perform all or part of the above-mentioned functions. Each functional unit and module in the embodiment may exist alone physically, or two or more units may be integrated into one unit. In addition, the specific names of the functional units and modules are only for distinguishing from each other, and are not used for limiting the protection scope of the present application.
The above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.
Claims (9)
1. A multi-line lidar comprising: the device comprises a first transmitting module, a second transmitting module, a first receiving module, a second receiving module and a reflecting mirror module;
the first emission module is positioned at the first side of the reflector module and is used for emitting a first laser beam from a first direction to the reflector module;
the second emission module is positioned at the second side of the reflector module and is used for emitting a second laser beam from a second direction to the reflector module; wherein the first side of the mirror module and the second side of the mirror module are opposite sides, and the first direction and the second direction are opposite directions;
the first receiving module is positioned at the first side of the reflecting mirror module and is used for receiving the first laser beam reflected by the target;
the second receiving module is positioned at the second side of the reflecting mirror module and is used for receiving the second laser beam reflected by the target;
the reflecting mirror module rotates around the axis at a preset rotation speed and is used for reflecting a first laser beam emitted by the first emitting module from a first direction so that the first laser beam covers a first preset range and reflecting a second laser beam emitted by the second emitting module from a second direction so that the second laser beam covers a second preset range;
wherein the reflector module comprises a reflector consisting of N reflector surfaces; the first emission module and the second emission module are symmetrically arranged on two sides of the reflecting mirror; the position of the first transmitting module, the position of the second transmitting module, the emergent angle corresponding to the first laser beam after being rotationally reflected by one reflecting mirror surface, the emergent angle corresponding to the second laser beam after being rotationally reflected by one reflecting mirror surface and the reflecting mirror surface meet a first preset relation;
establishing a coordinate system by taking the first plane as a plane and taking the intersection point of the axle center and the first plane as an origin; wherein the first plane is a plane in which the first laser beam and the second laser beam are located;
the first preset relationship includes:
in the method, in the process of the application,the first laser beam is rotated and reflected by a reflecting mirror surface to correspond to the emergent angle range,is rotated by a reflecting mirror surface for the second laser beamThe corresponding emergent angle range after reflection is turned,x 0 is the abscissa of the first transmit module; defining c as a line segment formed by projection of a reflecting mirror surface on a first plane, defining a as a line segment formed by connecting one end point of c with an origin, b as a line segment formed by connecting the other end point of c with the origin, and r a Length of line segment a, r b Length of line segment b, +.>The included angle between the line segment a and the line segment b, and the included angle between the line segment a and the line segment c.
2. The multi-line lidar of claim 1, wherein the N mirror facets form sides of an N prism, N being ≡3;
when the N reflecting mirror surfaces rotate around the axis at a preset rotation speed, two reflecting mirror surfaces in the N reflecting mirror surfaces respectively reflect a first laser beam emitted by the first emitting module from a first direction and a second laser beam emitted by the second emitting module from a second direction.
3. The multi-line lidar of claim 2, wherein N = 8 and each mirror is identical, the 8 mirrors forming sides of a regular octagon; the first direction and the second direction are opposite directions;
the positions of the first transmitting module, the second transmitting module and the size of the reflecting mirror surface satisfy the following conditions:
wherein x is 0 Is saidThe abscissa, y, of the first emission module 0 X is the ordinate of the first transmitting module ′ 0 Y is the abscissa of the second transmitting module 0 ′ And l is the bottom side length of the regular eight prism, which is the ordinate of the second transmitting module.
4. The multi-line lidar of claim 3, wherein the first laser beam and the second laser beam are flat top beams.
5. The multi-line lidar of claim 4, wherein a ratio of a diameter of the first laser beam to a bottom side length of the regular octagon is a first preset value;
the ratio of the diameter of the second laser beam to the bottom side length of the regular eight-prism is a second preset value;
the first preset value is determined according to the position of the first transmitting module, the corresponding emergent angle range of the first laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the first laser beam after being reflected by the reflecting mirror surface;
and the second preset value is determined according to the position of the second transmitting module, the corresponding emergent angle range of the second laser beam after being rotationally reflected by a reflecting mirror surface and the relative intensity of the second laser beam after being reflected by the reflecting mirror surface.
6. The multi-line lidar of any of claims 1-5, wherein the lidar further comprises: a first lens arranged in front of the first receiving module and a second lens arranged in front of the second receiving module;
the first lens is used for converging the first laser beam reflected by the target to the first receiving module;
the second lens is used for converging the second laser beam reflected by the target to the second receiving module.
7. The multi-line lidar of claim 6, wherein the projection of the first lens and the second lens onto the receiving surface covers the projection of the mirror module onto the receiving surface.
8. The multi-line lidar of claim 3, wherein the lidar further comprises: a first lens arranged in front of the first receiving module and a second lens arranged in front of the second receiving module;
the first lens is used for converging the first laser beam reflected by the target to the first receiving module;
the second lens is used for converging the second laser beam reflected by the target to the second receiving module;
the first lens and the second lens are square, and the projection of the first lens on the receiving surface is the same as the projection of the largest area of the reflecting mirror surface on the receiving surface when the first laser beam or the second laser beam is reflected;
the abscissa of the center of the first lens and the abscissa of the center of the second lens satisfy:
wherein x is r The abscissa of the center of the first lens or the abscissa of the center of the second lens is l, and the bottom side length of the regular eight prism is l.
9. The multi-line lidar of claim 2, wherein the N mirror facets and the first plane each form N tilt angles for satisfying a scan in a third direction; the first plane is a plane where the first laser beam and the second laser beam are located, and the third direction is a direction perpendicular to the first plane.
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| CN112986956B (en) * | 2021-02-04 | 2024-02-13 | 广州市慧建科技有限公司 | Laser radar light wave receiving and transmitting control method and laser radar |
| CN115825987A (en) * | 2021-09-17 | 2023-03-21 | 华为技术有限公司 | Laser radar, detection device and vehicle |
| CN114935743B (en) * | 2022-04-18 | 2023-06-23 | 深圳阜时科技有限公司 | Emission module, photoelectric detection device and electronic equipment |
| CN114858097B (en) * | 2022-05-27 | 2023-08-01 | 森思泰克河北科技有限公司 | Laser radar rotating mirror included angle measuring method and measuring device |
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