WO2023040376A1 - 激光雷达 - Google Patents

激光雷达 Download PDF

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Publication number
WO2023040376A1
WO2023040376A1 PCT/CN2022/098404 CN2022098404W WO2023040376A1 WO 2023040376 A1 WO2023040376 A1 WO 2023040376A1 CN 2022098404 W CN2022098404 W CN 2022098404W WO 2023040376 A1 WO2023040376 A1 WO 2023040376A1
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WIPO (PCT)
Prior art keywords
array
focal length
light
laser
lens group
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PCT/CN2022/098404
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English (en)
French (fr)
Inventor
陈杰
向少卿
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上海禾赛科技有限公司
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Publication of WO2023040376A1 publication Critical patent/WO2023040376A1/zh

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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
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements

Definitions

  • the present application relates to the technical field of optical ranging, in particular to laser radar.
  • Lidar is a detection device that calculates the distance of an object by emitting a laser and detecting the echo signal reflected after the laser reaches the surface of the object. Therefore, the lidar needs to include two parts: the light emitting (TransmitterX) element and the light detecting (Receiver X) element, which can be called the light emitting module and the light detecting module.
  • the laser radar includes an optical system, which is distributed in the light emission module and the light detection module.
  • the light emission module includes a main lens group for collimating the emission signal of the laser, etc.
  • the light detection module includes a lens for converging the echo signal to the detector receiving lens etc.
  • FOV field of view
  • the longitudinal dimension of the light-emitting surface of the light-emitting module (or the photosensitive surface of the light-detecting module) is positively related to the emitting and/or receiving lens (group) is negatively correlated with the equivalent focal length.
  • the longitudinal dimension of the light-emitting surface (or light-sensitive surface) is positively related to the height of the whole laser radar.
  • the height dimension of lidar products is an important parameter that is concerned by customers.
  • the focal length of the transmitting module and/or detection module has to be reduced, such as replacing the one with a shorter focal length.
  • Optical devices, etc. will not only reduce the duty cycle of the light-emitting surface but also limit the vertical resolution of the longitudinal direction.
  • the present application provides a light detection device and a detection method to solve the above-mentioned problems caused by the mutual restriction between the focal length and the height of the laser radar, and can improve the radar without increasing the height of the radar. ranging capability.
  • the first aspect of this application provides a laser radar, including:
  • the light emitting module is arranged on the focal plane of the first optical component, including: a laser array, arranged in a linear array or an area array, suitable for sending out a transmitting signal, and the transmitting signal is transmitted along the transmitting optical path;
  • the first optical component is arranged in the emitting optical path, and forms an equivalent focal length greater than the first preset value, so as to increase the power density in the field of view of the point cloud, thereby improving the ranging capability of the radar; wherein, the The first preset value is the focal length of the main lens group unit;
  • the optical detection module includes: an optical detector array arranged in a line array or an area array, adapted to detect the reflected echo signal after the transmitted signal encounters an obstacle from the receiving optical path.
  • the first optical assembly includes: a main lens group unit, adapted to collimate the transmitted signal;
  • a first diverging unit configured between the laser array and the main lens group unit, adapted to diverge the transmitted signal collimated by the main lens group unit, so that the first optical assembly has The equivalent focal length of the set value.
  • the equivalent focal length of the first optical component is M times the focal length of the main lens unit, M>1, so that the area of the light emitting surface of each laser is increased by M2 times.
  • the first diverging unit includes: a concave lens array, wherein each concave lens corresponds to one emission channel.
  • the embodiment of the present invention also provides another laser radar, including:
  • the optical transmitting module includes: a laser array, arranged in a linear array or an area array, suitable for transmitting a transmitting signal, and the transmitting signal is transmitted along the transmitting optical path;
  • the light detection module is arranged on the focal plane of the second optical component, including: a light detector array, arranged in a linear array or an area array, suitable for detecting the reflected echo after the transmitted signal encounters an obstacle from the receiving optical path Signal;
  • the second optical component is arranged on the receiving optical path to form an equivalent focal length greater than the second preset value, so as to reduce the background light noise power in the field of view angle area of the point cloud, thereby improving the ranging capability of the radar; wherein , the second preset value is the focal length of the main lens group unit.
  • the second optical assembly includes: a receiving lens group unit adapted to converge received signals;
  • the second optical assembly also includes: a second diverging unit,
  • the second optical component has an equivalent focal length longer than a second preset value, and is suitable for diverging received signals converged by the receiving lens group unit.
  • the equivalent focal length of the second optical component is P times the focal length of the main lens unit, P>1, so that the area of the acceptance angle is reduced by P2 times.
  • the second diverging unit includes: a concave lens array, wherein each concave lens is arranged corresponding to a detector.
  • the lidar includes: a first optical component, arranged in the emitting optical path, forming an equivalent focal length greater than a first preset value, so as to increase the power in the area of the field of view of the point cloud Density, thereby improving the ranging capability of the radar; wherein, the first preset value is the focal length of the main lens group unit in the first optical assembly; the equivalent focal length of the first optical assembly and the second optical assembly is proportional relation.
  • the laser radar provided by the present application includes: a laser array arranged in a linear array or an area array, arranged on the focal plane of the first optical assembly, and the first optical assembly is arranged on the emitting optical path, forming a larger than The equivalent focal length of the focal length of the main lens group unit at the transmitting end; and/or, the photodetector array arranged in a linear array or an area array is arranged on the focal plane of the second optical assembly, and the second optical assembly is set On the receiving optical path, an equivalent focal length greater than the focal length of the main lens group unit at the receiving end is formed.
  • the power density within the field of view of the point cloud is increased by setting the first optical component at the light emitting end, and/or, the field of view of the point cloud is reduced by setting the second optical component at the receiving end.
  • the background light noise power in the angular area can improve the ranging capability of the radar.
  • FIG. 1A shows a schematic diagram of the relationship between the field of view and the focal length of the light emitting module of the light detection system in an example.
  • FIG. 1B shows a schematic diagram of the relationship between the field of view and the focal length of the light detection module of the light detection system in an example.
  • FIG. 1C shows a schematic diagram of the channel correspondence between the transmitter and the receiver of the horizontal scanning mechanical radar in an example.
  • Figure 2A shows a schematic diagram of the light-emitting surface of a laser in one example.
  • Figure 2B shows a simplified representation of Figure 2A.
  • FIG. 3 shows a schematic diagram illustrating the vertical resolution of the light emitting module in an example.
  • FIG. 4 shows a schematic diagram of a receiving and receiving optical circuit of a lidar in an embodiment of the present application.
  • FIG. 5A shows a schematic structural diagram of a light emitting module in an embodiment of the present application.
  • FIG. 5B shows a schematic structural diagram of a light emitting module in another embodiment of the present application.
  • FIG. 6 is a schematic diagram of a front view structure of an enlarged light-emitting surface formed at different focal lengths in the embodiment of the present application.
  • FIG. 7 shows a schematic structural diagram of a light detection module of a lidar in an embodiment of the present application.
  • FIG. 8 shows a schematic diagram of the principle of determining the value of M according to the specific structural parameters of the light emitting module in the embodiment of the present application.
  • FIG. 9 shows a front view structural diagram of the layout of the enlarged light-emitting surface and the matching concave lens array under different focal lengths in the embodiment of the present application.
  • FIG. 10A shows a schematic structural diagram of a laser radar with a paraxial optical path structure in an embodiment of the present application.
  • FIG. 10B shows a schematic structural diagram of a front view of a laser array and a photodetector array of a laser radar with a paraxial optical path structure in an embodiment of the present application.
  • FIG. 10C shows a schematic curve diagram of the simulation results of the ranging capability of the lidar in FIG. 10B .
  • FIG. 11A shows a schematic structural diagram of a laser radar with a coaxial optical path structure in an embodiment of the present application.
  • FIG. 11B shows a schematic structural diagram of a laser radar with a coaxial optical path structure in another embodiment of the present application.
  • FIG. 12A shows a schematic diagram of the optical path of the emitting end without a sleeve in the embodiment of the present application.
  • FIG. 12B shows a schematic diagram of the optical path of the emitting end of the sleeve in the embodiment of the present application.
  • FIG. 12C shows a schematic diagram of the optical path of the receiving end of the sleeve in the embodiment of the present application.
  • first, second, etc. are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, the first interface and the second interface are described. Furthermore, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms “comprising”, “comprising” indicate the presence of stated features, steps, operations, elements, components, items, species, and/or groups, but do not exclude one or more other features, steps, operations, The existence, occurrence or addition of an element, component, item, species, and/or group.
  • Lidar is a device that measures distance based on an optical detection system.
  • the application scenarios of lidar such as automatic driving
  • the size of lidar needs to be reduced as much as possible, especially the height of lidar, which is the parameter that customers are most concerned about. one.
  • the large field of view and low altitude which affects the performance of LiDAR.
  • the following is an example to illustrate the principle.
  • FIG. 1A and FIG. 1B are schematic diagrams showing the relationship between field of view and focal length in an optical detection system in an example.
  • FIG. 1A shows a schematic diagram of the relationship between the field of view and the focal length of the light emitting module in the light detection system.
  • FIG. 1B shows a schematic diagram of the relationship between the field of view and the focal length of the light detection module of the light detection system.
  • a is the height (or longitudinal dimension) of the light-emitting surface of a single laser 101A or the photosensitive surface of a single photodetector 101B
  • f is the focal length of the lenses 102A and 102B (both are schematically represented as f in the figure, but not Indicates that the focal lengths defining the two optical paths are the same, just to avoid confusion caused by too many numbers).
  • the field of view of a single laser/single detector satisfies equation (1).
  • the height of the single light-emitting surface 101A/single photosensitive surface 101B, or all the multiple lasers/detectors in the vertical direction all satisfy the formula (1), and the size of the field of view is positively correlated with the height of the lidar.
  • the size of the light-emitting surface of the light emitting module of the laser radar and the photosensitive surface of the detection module is positively related to the size of the laser radar.
  • the height dimension of the lidar is a parameter that is paid more attention to than the width and depth.
  • Various application scenarios usually require a suitable height to fit the limited installation space.
  • the size of the field of view FOV is positively correlated with the size of the light-emitting surface and the photosensitive surface, and negatively correlated with the equivalent focal length f of the optical components (such as the main lens group) in the light-emitting module and the light-detecting module. It can be seen that if you want to maintain a larger FOV, you must either increase a or decrease f, but increasing a may lead to an increase in the height of the lidar, so f is generally reduced to achieve the goal, but this will have an impact Problems with lidar performance.
  • the receiving and receiving light path can be different, and the focal plane layout of the receiving and receiving can also be different, but in the end, it is hoped that the emitted light will fall on a certain area on the target, and the reflected light in this area can just return to the detector, that is, the emission and reception can match , the sending and receiving channels can correspond. To avoid confusion, some terms are defined below.
  • Number of scan lines that is, the number of channels for laser transceivers, or the number of minimum addressable channels.
  • lasers and detectors are in a 1:1 configuration, and the number of scanning lines is equal to the number of lasers or detectors, and also equal to the number of transmitting channels or receiving channels.
  • the number of scanning lines is equal to the number of lasers or detectors, and also equal to the number of transmitting channels or receiving channels.
  • Divergence angle area refers to the angular area of the laser light-emitting area of a certain channel projected in the far field through the optical system.
  • Acceptance angular area refers to the angular area projected on the far field by the photosensitive surface of a certain channel detector through the optical system.
  • Point cloud field of view area refers to the overlapping part of the divergence angle and the receiving angle, which is the real range covered by the point cloud, and is the superposition of all target reflection echo signals within this range.
  • point cloud field angle area can be equal to the divergence angle area and smaller than the acceptance angle area, for example, it can be equal to the acceptance angle area and smaller than the divergence angle area, or it can be equal to the overlapping part of the two.
  • the field of view area of the point cloud is consistent with the area of the divergence angle and the acceptance angle.
  • the field of view FOV often includes the horizontal field of view HFOV, and the vertical field of view VFOV refers to the total angle range detected by all transceiver channels.
  • TX transmitter
  • TX transmitter
  • multiple lasers referring to the smallest addressable light-emitting unit
  • the right side is the receiving end (RX, receiver), and the receiving end is provided with multiple detectors (also refers to the smallest addressable unit).
  • FIG. 2A and FIG. 2B are schematic diagrams showing a light-emitting surface of a laser in an example.
  • the laser is exemplarily a Vertical Cavity Surface Emitting Laser 200 (Vertical Cavity Surface Emitting Laser, VCSEL).
  • FIG. 2A is a schematic top view of a more practical VCSEL, and FIG. 2B is an abstract and simplified schematic diagram based on FIG. 2A .
  • the light-emitting duty cycle refers to the ratio of the area covered by the light-emitting surface to the total area, which can be the ratio of the sum of the areas of each light-emitting point 201 in the figure to the dotted box 202 or the area of the entire VCSEL top surface.
  • the lighting duty cycle is limited by OA/PITCH.
  • OA is the area of one light-emitting point 201
  • PITCH is the vertical pitch of adjacent light-emitting points 201 (ie, the distance between the centers of adjacent light-emitting points, as indicated by the double-headed arrows in the figure). It can be seen that when the OA is larger or the pitch is smaller, the duty cycle is higher. It should be noted that this is just an example.
  • the type of laser is not limited.
  • the laser can be EEL (Edge Emitting Laser), VCSEL, or PCSEL (Photonic Crystal Surface Emitting Semiconductor Lasers). ).
  • the photodetector can be an APD, a single photon avalanche diode array SPAD(s), or a silicon photomultiplier tube SiPM.
  • the vertical angular resolution of the laser radar is based on the distance d and
  • the ratio d between the equivalent focal lengths f of the main lens group (here only shows a convex lens 303 as an equivalent situation in the embodiment, the actual main lens group may include multiple lens groups, which is not limited here) /f determines that it is positively correlated with d and negatively correlated with f.
  • the focal length has to be reduced as much as possible.
  • the duty cycle of the light-emitting surface of the laser is limited by the area of the light-emitting point/the pitch of the light-emitting point, resulting in a low duty cycle.
  • the vertical resolution is limited by d/f.
  • the laser radar is provided in the embodiment of the present application.
  • optical improvement a longer equivalent focal length is achieved with a relatively short physical size, thereby increasing the power density within the field of view of the point cloud, and or, The background light noise power in the field of view area of the point cloud is reduced, thereby improving the distance measurement capability of the radar.
  • FIG. 4 shows a schematic diagram of a receiving and receiving optical circuit of a lidar.
  • lidar can include:
  • the light emitting module that is, the laser array arranged in a linear array or an area array, is arranged corresponding to the first optical component, for example, it can be arranged on the focal plane of the first optical component, and is suitable for sending out a transmitting signal, and the transmitting signal is transmitted along the transmitting optical path .
  • the first optical component may have an equivalent focal length greater than a first preset value.
  • the photodetection module that is, the photodetector array arranged in a linear array or an area array, is arranged corresponding to the second optical component, for example, it can be arranged on the focal plane of the second optical component, and is suitable for detecting the emitted signal after it reaches the object. reflected echo signal.
  • the second optical component may have an equivalent focal length greater than a second preset value. Therefore, by setting the optical components of the laser radar transmitting end and/or receiving end, the focal length of the receiving/transmitting side can be extended, and the power within the field of view area of the point cloud can be increased while keeping the height of the radar machine unchanged. Density, and/or, reduce the background light noise power within the field of view area of the point cloud, greatly improving the ranging capability of the radar.
  • FIG. 5A shows a schematic structural diagram of a light emitting module in an embodiment of the present application.
  • the light emitting module includes: a laser array 501 and a first optical component.
  • the laser array 501 includes a plurality of lasers 511 .
  • the plurality of lasers 511 may be arranged in a line array or an area array.
  • Each laser 511 is configured to output a transmission signal, ie to emit laser light.
  • the laser 511 may be realized by, for example, a vertical cavity surface emitting laser (VSCEL), or an edge emitting laser (EEL).
  • VSCEL vertical cavity surface emitting laser
  • EEL edge emitting laser
  • the first optical component is arranged on the emitting light path and configured with an equivalent focal length longer than a first preset value.
  • the first optical assembly includes: a main lens group unit, specifically, the original main lens group used to collimate the transmitted signal in the light transmitting module, as shown in the example in Figure 5A is shown as an equivalent convex lens 502; and the first diverging unit is used to diverge the transmitted signal, and the first diverging unit is exemplarily presented as a concave lens array 503 in FIG. 5A.
  • each concave lens 531 in the concave lens array 503 corresponds to a laser 511 (single addressable and controllable unit that can be turned on) and is set to elongate (relative to the focal length formed by only the emitting light path of the main lens group)
  • the focal length of the emitting light path thereby realizing the improvement of the light-emitting surface of the laser 511 corresponding to the single pixel (relative to the size of the laser in the scheme of setting the laser on the focal plane A of the main lens group unit, but actually in the present application with
  • the laser is only set at the focal plane B, not A), and at the point cloud level, it is to increase the power density in the field of view of the point cloud, which is used to form the point cloud.
  • the pixel refers to a pixel point or point cloud in the point cloud image corresponding to the lidar, for example, the light-emitting surface of each laser/photosensitive surface of each photodetector may correspond to a pixel point, and then the transceiver unit Together they form a channel, which then also corresponds to the harness mentioned above.
  • the pitch between two adjacent concave lenses 531 in the concave lens array 503 may be the same as the center-to-center distance between adjacent lasers 511 .
  • the main lens group unit is exemplarily represented by a convex lens 502 in the figure, but in fact the convex lens 502 is only a representation of the main lens group unit, and the main lens group unit can be a
  • the main lens group which can include a plurality of lenses (such as shown in Figure 4), so it is not limited to the simplified representation of the convex lens 502 in the figure; in addition, the equivalent lens of the main lens group unit may also be other forms of convex lenses, For example, plano-convex lenses, etc., are not limited here.
  • the main lens group unit may have a first focal length, represented in the figure as the distance f" from the main plane C of the convex lens 502 to its double focal point (the corresponding focal plane is A).
  • the concave lens array 503 is arranged between the laser array 501 and the main lens group unit, and each concave lens 531 in the concave lens array 503 corresponds to one laser 511 .
  • the concave lens array 503 is adapted to diverge the transmitted signal and then converge it through the main lens group unit, so as to form an equivalent focal length of the first optical component that is longer than a first preset value.
  • f is the equivalent focal length of 2 lenses (being convex lens 502+concave lens array 503) combination in the figure
  • L is physical entity size.
  • positive and negative lens groups i.e.
  • the combined main plane will move forward, as shown in the figure, the left end point of f is moved forward to the left compared with the left end point of f", that is, it is located at Compared with the main plane C of the main lens unit, the main plane D at the left end of f moves forward to the left, and the entire focal plane will move back, for example, from A to B.
  • the position of the main plane D can be determined according to the reverse extension of the converging light, whose reverse extension can be seen as the dotted lines E1 and E2 in FIG. 5A . This is also an advantage of this optical path: L ⁇ f, a relatively short physical size L is used to achieve a longer equivalent focal length f.
  • the distance between the first diffusion unit and the main plane of the main lens group unit may be smaller than f".
  • a corresponds to an equivalent increase, that is, the light-emitting surface of each pixel will be equivalently increased.
  • the luminous energy of a single pixel (corresponding to a point in the point cloud image in the lidar) can be increased, and the power density in the area of the field of view of the corresponding point cloud can be increased (that is, the more luminous points 201 are included in the same area).
  • the long-distance ability is also increased proportionally, for example, the long-distance measurement ability can be increased from 200m to 300m.
  • the viewing angle of the laser array may be compressed.
  • FIG. 5B shows a schematic structural diagram of a light emitting module in another embodiment of the present application.
  • a laser array 501 and a first optical assembly of another embodiment are shown in FIG. 5B.
  • the first optical assembly includes a main lens unit and a micro lens unit 503 .
  • the convex lens 502 is still used to equivalently represent the main lens group unit.
  • the main lens group unit may have a first focal length, which is represented as the distance f" from its main plane C to its double focal point (the corresponding focal plane is A).
  • the microlens group unit 504 includes a microlens array 505 in addition to the concave lens array 503 .
  • the microlens array 551 is disposed between the laser array 501 and the concave lens array 503 .
  • each laser 511 such as VCSEL
  • a plurality of micro-lenses 551 (specifically micro-convex lenses) in the micro-lens array 551, each micro-lens is set corresponding to one light-emitting point , so that the emitted light from the light-emitting point is converged and transmitted to the corresponding concave lens 531 .
  • the divergence angle of each light-emitting point can be compressed, and the divergence angle of the emitted signal output by the laser 511 and the laser array 501 can be further suppressed, thereby preventing the light rays F1 and F2 in FIG. 5A from deviating from the concave lens.
  • the array 503 exits.
  • the focal length is extended by the equivalent focal length combined by three lenses (ie, convex lens 502 + concave lens 530 in concave lens array 503 + microlens 551 in microlens array 505 ).
  • f " is the main lens group (in Fig. 5 B, the main lens group unit is replaced with 1 convex lens, but generally can be a main lens group, and in Fig.
  • f is the equivalent focal length of 3 lenses (being the microlens 551 in convex lens 502+concave lens array 503+microlens 530+microlens array 505) combination among the figure
  • L is Physical entity size.
  • the main plane after the combination of the positive and negative lens groups (that is, the concave lens 530 in the convex lens 502+concave lens array 503) will move forward, as shown in the figure, the left end point of f is compared to f "
  • the left end point has moved forward to the left, that is, the main plane D of the left end point of f has moved forward to the left compared with the main plane C of the main lens group unit, and the entire focal plane will move back, for example, from A moves to B.
  • the position of the main plane is determined according to the reverse extension line of the convergent light, and the reverse extension line can be seen as the dotted lines S1 and S2 in FIG. 5B .
  • the FOV remains the same, and the focal length f increases, a correspondingly increases, that is, the light-emitting surface is increased.
  • the luminous energy of a single pixel can be increased, the power density in the corresponding point cloud field of view area can be increased, and the distance measurement capability can also be proportionally improved.
  • the pitch between two adjacent microlenses in the microlens array 504 is the same as the pitch of the light emitting points. It should be noted that the 3 concave lenses corresponding to the 3 lasers 511 and the 3 microlenses corresponding to each laser 511 shown in the figure are schematic numbers and not limiting their specific implementation.
  • the light exit surface B of the laser array 501 (including the light exit surface of each laser) is located on the focal plane of the equivalent lens of the first optical assembly, so as to be between the principal plane D of the equivalent lens Keep the distance at the equivalent focal length f.
  • FIG. 6 it is a schematic front view structure diagram of an enlarged light-emitting surface formed under different focal lengths in the embodiment of the present application.
  • M is less than but approximately 1 (that is, the light-emitting surface is not enlarged, or the optical path without a concave lens, such as the optical path that only includes the main lens group unit), M is less than but approximately 2, and M is less than However, it is similar to the comparison of the size of the light-emitting surface in the 4 cases; the equivalent magnification of the light-emitting area of the 8 light-emitting surfaces 11, 12, 13, 14, 21, 22, 23 and 24 in the three cases is shown. It can be understood in conjunction with FIG. 5A or FIG. 5B and FIG.
  • each laser is correspondingly provided with one of the micro-concave lenses Y in a concave lens array. For visual illustration, only a light-emitting surface 21 is selected on the right side of FIG.
  • the lasers are also provided with corresponding concave lenses, which are only omitted here.
  • the diameter of the concave lens is larger than the diameter of the light-emitting surface to fully cover the light-emitting surface so as to receive more light from the transmitted signal, but at the same time, the height of the lidar must also be considered to limit the diameter of the concave lens to an appropriate size.
  • the light-emitting surfaces of the nearest adjacent lasers are relatively close (such as light-emitting surface 11 and light-emitting surface 13), but when the emission angle area a2" equivalent to the far field will be a2 /M, there will be no problem of overlapping and being unable to be identified as two light-emitting surfaces.
  • the equivalent focal length of the first optical component is M times the focal length of the main lens group unit
  • the laser is set at the second The focal plane of an optical assembly
  • the whole area of each laser is if it is M2 times of the area of the laser that is arranged on the focal plane of the main lens group unit. If under the constant situation of the duty ratio of the laser, then every The area of the light-emitting surface of each laser will increase by M2 times relative to the area of the light-emitting surface if it is arranged on the focal plane of the main lens group.
  • the height dimension can be maintained by adjusting the layout of the light emitting surface at different focal length magnifications M.
  • h2 is slightly larger than h1
  • h1 is slightly larger than h0
  • their gap can be ignored in actual situations, that is to say, the lidar is
  • the lidar is There can be almost no change in the height dimension, but the light-emitting surface of each laser has been magnified by M 2 times.
  • the power density in the field of view of the point cloud can be increased by M 2 times, so that the laser radar The telemetry capability has been improved.
  • similar optical components can be used on one side of the light detection module to expand the focal length.
  • the area of the receiving angle can be reduced, thereby reducing the background light noise power in the area of the field of view of the point cloud, thereby improving The range finding capability of the radar.
  • the photodetection module includes a photodetector array 701 including a plurality of photodetectors 711 arranged in an array.
  • the light detector 711 is configured to detect that the transmitted signal reaches an object and is reflected to achieve detection.
  • a "channel" is formed between one or more photodetectors 711 and one or more lasers, for example, a channel is formed between a photodetector and a laser, and the echo signal of the emission signal of the laser is included in the same channel.
  • each channel corresponds to the detection of a certain viewing angle or a certain viewing angle range (receiving angle area).
  • each of the photodetectors 711 can be realized by, for example, SiPM (Silicon Photo Multiplier, silicon photomultiplier tube) or SPAD(s) (Single Photon Avalanche Diode, single photon avalanche diode).
  • the photodetection module may further include a second optical component disposed corresponding to the photodetector array 701 .
  • the second optical assembly specifically includes a second converging unit and a second diverging unit.
  • the second converging unit can be the original lens or lens group for converging the echo signals, which can be equivalently shown as the leftmost convex lens 702 in the figure, for converging the echo signals to the light
  • the detector array 701 transmits.
  • the second diverging unit can be implemented as a concave lens array 703, wherein each concave lens 731 is set corresponding to a photodetector 711; The distance between the centers of adjacent photodetectors 711 is equal.
  • the focal length of the convex lens 702 is f2 ", which is schematically shown as the length between the main plane G of the convex lens 702 and the focal plane H thereof.
  • the distance between the main plane G of the convex lens 702 and the concave lens array 703 It can be within the focal length f2" of the equivalent lens.
  • the principal plane of the formed equivalent lens is I, which is shifted to the left compared to G.
  • the principle is the same as that of the previous illustrations 5A and 5B, the position of the I plane can be determined by the reverse extension lines K1 and K2 in the figure, which is intuitive and clear, and the figures are abbreviated ("")
  • the simple representation of the method should be understood by referring to the previous diagram.
  • the focal length f2 extended from the focal length f2" of the convex lens 702 is formed, and the distance from I to the focal plane J is formed.
  • the photosensitive surface of the photodetector array 701 can be located at the focal point at the right end of f2. On the plane J to obtain the focus of the echo signal.
  • the physical length from G to J is L2, and it can be seen that f2 exceeds the physical distance limit of L2.
  • the receiving end of the lidar Unlike the focal length extension of the optical transmitter module (ie, the TX end), for the receiving end of the lidar, it is necessary to ensure that as many real detection signals (echo signals reflected after the transmitted signal encounters obstacles) are received as possible. Under the premise, it is necessary to reduce the received background light intensity as much as possible to improve the signal-to-noise ratio.
  • the following formula gives the background light P B on the receiving side:
  • pb is the background radiation density
  • BW is the half maximum width of the filter (nm)
  • ⁇ is the reflectivity of the target
  • tr is the optical efficiency of the receiving lens barrel
  • A is the effective aperture (m)
  • Sr is the effective area of the detector
  • f is the focal length.
  • the focal length of the light detection module that is, the RX end
  • the background light noise power in the field of view of the point cloud can be reduced, the signal-to-noise ratio can be improved, and the entire lidar
  • the ranging capability is improved, and the height of the lidar can be maintained.
  • the equivalent focal length of the second optical component is P times the focal length of the main lens group unit at the receiving end, P>1, then the area of the receiving angle can be reduced by P 2 times.
  • the transmitter and receiver use different letters and symbols, such as M and P respectively to represent the focal length magnification of the elongated optical component, just to illustrate that the transceiver side can use different magnifications, but it is understandable that , the transceiver side can also be set to the same magnification.
  • a control module (not shown) is also included in the laser radar to control the light transmitting module to emit the transmitting signal, and to control the light detecting module to detect the data of the echo signal, and can Calculations are performed on the data to obtain detection results.
  • the laser radar can increase the focal length by M times while maintaining the total height of the focal plane, so that the overall size of the laser radar has almost no change.
  • the size of the light-emitting surface corresponding to a single pixel can be increased, thereby increasing the power density; for the receiving module RX, the area of the receiving angle can be reduced, thereby reducing the area of the field of view of the point cloud.
  • the noise power of the background light in turn, it is beneficial to improve the ranging capability; and the increase of f reduces the d/f, which means that the angular difference between adjacent lasers in the vertical direction is reduced, thereby improving the vertical angular resolution.
  • a microlens array is arranged in front of the laser array to converge the transmitted signals, which is also beneficial to further improve the utilization efficiency of the emitted light.
  • FIG. 8 and FIG. 9 for discussing a reasonable value of M.
  • f is the focal length of the convex lens 802 equivalent to the main lens group unit
  • f is the focal length of the first optical component
  • L is the physical dimension.
  • ⁇ y is the laser height (y direction) located on the focal plane of the extended back focal length, that is, the height of the light-emitting surface corresponding to this position
  • ⁇ y" is the equivalent height of the light-emitting surface corresponding to the focal plane of the convex lens 802.
  • the cone angle ⁇ (laser divergence angle ⁇ *OA/PITCH) be as small as possible
  • the F value aperture value f is the focal length, and D is the diameter of the aperture
  • main lens cone angle ⁇
  • divergence angle of laser 801 ⁇
  • ⁇ is related to the light quality of the laser 801 itself on the one hand, and the compression effect of the microlens array on the other hand.
  • an upper bound on M can also be derived.
  • the focal length f the same area of the light-emitting surface (it can be understood as a constant)
  • the lasers in the laser array are arranged in multiple columns (N columns) staggered.
  • the number N of staggered columns should be limited. N may affect the width of the radar product. Although the width direction is not as important as the height direction, it cannot be unrestricted. If there are N columns of lasers arranged in a staggered manner, considering that all the light emitted by each laser can pass through the concave lenses set in one-to-one correspondence (for example, it is covered by concave lenses in Figure 9), the height of the light-emitting surface needs to be slightly smaller than that of adjacent concave lenses the pitch. It should be noted that the specific size referred to by the height of light emission is related to the shape of the laser. If the laser is circular, the height refers to the diameter of the entire laser; if the laser is rectangular, the height refers to the width or length of the laser.
  • FIG. 9 shows an enlarged schematic view of the light emitting surface in another embodiment of the present application.
  • the figure also exemplarily shows the concave lens provided corresponding to each laser, such as the ring Z surrounding the light-emitting surface 11 in the figure.
  • the constraint condition that the concave lens must completely cover the light-emitting surface can be set.
  • the height of the light-emitting surface before magnification is y0
  • the height of the light-emitting surface after approximately 2 times of magnification is y1
  • the height of the light-emitting surface after approximately 4 times of magnification is y2
  • the pitch of the concave lens, such as y2 needs to be smaller than the height of Z (Z is a circle, and the height is its diameter).
  • the edges of the light-emitting surface (11-24) with approximately 2 times and 4 times the magnification of the light-emitting surface in Figure 9 are schematically drawn as dotted lines, while the edges of the concave lens are schematically drawn is drawn as a solid line, and the edge of the dotted line corresponding to each light-emitting surface falls into the solid line ring of the corresponding concave lens.
  • Concave lens pitch focal length of main lens group unit * vertical angular resolution * N
  • the concave lens pitch is the distance between the centers of adjacent light-emitting surfaces, in the illustration, the interval b is the unit of measurement, and the interval b It is equal to the focal length of the main lens group unit * the vertical angular resolution, and the concave lens pitch is equal to N times the interval b.
  • the pitch of the concave lenses is 2b; when the light-emitting surface is magnified four times, the pitch of the concave lenses is 4b.
  • M*y0 ⁇ b*N can be obtained by substituting y0, f" and d/f according to M* height of light-emitting surface before magnification ⁇ focal length of main lens unit*vertical angular resolution*N; If the adjacent light-emitting surfaces are adjacent to each other almost without intervals, y0 ⁇ b. Therefore, M (magnification) ⁇ N (number of staggered columns) can be obtained. In other words, the entire optical path cannot be enlarged without limit, and the laser can be The number of arranged columns N is the upper limit of the magnification M, that is, M ⁇ N.
  • the receiving end is also similar. If the detector array is set as Q columns of detectors arranged in a staggered manner, and the equivalent focal length of the second optical component is P times the focal length of the main lens group unit, then Q>P, where I won't repeat them here.
  • FIG. 10A shows a schematic structural diagram of a laser radar with a paraxial optical path structure in an embodiment of the present application.
  • FIG. 10B shows a front view layout structure diagram of a laser array and a light detection component of a laser radar with a paraxial optical path structure in an embodiment of the present application.
  • FIG. 10C shows a schematic diagram of the curve of the ranging simulation result of the lidar in FIG. 10B .
  • this example shows a laser radar 100 with a paraxial optical path structure, that is, there is no overlapping section between the transmitting optical path of the transmitting signal and the detecting optical path of the echo signal.
  • the laser radar 100 may be a mechanical laser radar 100 , that is, it includes a rotating mechanism.
  • the number of lines of the lidar 100 can be more than 32 lines, such as 32 lines, 64 lines, 128 lines, 256 lines, etc., wherein 128 lines, if the laser 1011 and the photodetector 1041 form a 1-to-1 channel, it means There are 128 lasers 1011 and 128 photodetectors 1041 in one-to-one correspondence to form 128 channels. Multiple lasers 1011 may be arranged in multiple columns.
  • the laser array includes a laser array 1001, and the emission signal light output by each laser 1011 (which can be first processed by the microlens array) passes through each concave lens 1022 of the first optical assembly 1002 and the main lens group unit 1021 in sequence. (equivalent to a convex lens) processing, and then emit the laser radar 100 , irradiate the obstacle P and reflect to form an echo signal.
  • the echo signal enters the laser radar 100 , and is converged to the light detection module 1003 through the receiving lens group unit 1051 (equivalent to a convex lens) and each concave lens 1052 of the optional second optical assembly 1005 in turn.
  • the light detection component in the light detection module 1003 may include a light detector array 1004, wherein the light detector 1041 of a channel corresponding to the echo signal can detect the echo signal.
  • the first optical assembly 1002 and the second optical assembly 1005 respectively form an extended equivalent focal length, such as M times the focal length of the original lens group, so that the distance measuring capability of the laser radar 100 is improved, so that it can detect farther obstacle P.
  • M may be a magnification of 1.5 times or more.
  • the laser radar 100 based on the paraxial optical path structure of FIG. 10A can adopt, for example, the layout structure of the laser array 1001B and the photodetector array 1004B shown in FIG. 10B .
  • two columns of lasers 1011B are arranged non-aligned
  • two columns of photodetectors 1041B are arranged non-aligned.
  • the ranging simulation is performed based on the laser radar 100 with the paraxial optical path structure based on FIG. 10A and FIG. 10B , and the simulation result is shown in FIG. 10C .
  • the horizontal axis represents the farthest distance that can be measured (corresponding to the distance measuring capability of the lidar 100 ), and the vertical axis represents the detection probability. It can be seen that in the case of a detection probability of 90%, the measurable furthest distance reaches about 90 meters, but when the solution of the embodiment of the present application is not adopted, the measurable furthest distance of the same type of lidar is only about 45 meters about. Therefore, through the solution of extending the focal length in the embodiment of the present application to improve the telemetry distance, the telemetry capability can actually be improved by more than 2 times.
  • the solution of the present application can also be applied to laser radars with coaxial optical path structures.
  • Coaxial means that there is the same optical path section between the emission optical path and the detection optical path .
  • FIG. 11A shows a schematic structural diagram of a laser radar with a coaxial optical path structure in an embodiment of the present application.
  • the lidar includes:
  • the light splitting unit 1103 arranged in the overlapping optical path section is adapted to receive the transmission signal from the first optical path section connected to the laser array (laser array 1101 in this example) and deflect or direct it to the overlapping optical path section, and is suitable for The echo signal is received from the overlapping optical path section and is directly irradiated or deflected to the second optical path section connected to the photodetector array 1102; wherein, the main lens group unit 1104 in the first optical assembly (as in the previous embodiment The central main lens group) and the first diverging unit 1105 (such as the concave lens array in the foregoing embodiment) are respectively arranged in the overlapping optical path section and the first optical path section.
  • the light splitting unit 1103 may be realized by, for example, a mirror or a polarizing unit (such as a polarizer, a polarizing prism, etc.).
  • the emission signal output by the laser array can first be diverged by the first diverging unit 1105 arranged in the first optical path section, and then enter the light splitting unit 1103, so as to be redirected by the light splitting unit 1103 (for example, turning, such as reflection, etc.)
  • the overlapping optical path section that is, the optical path section shared by the emitted optical path and the detection optical path
  • it is transmitted to the left through the overlapping optical path section to the main lens group unit 1104, and then emerges after converging, as shown in the emitting optical path indicated by the black solid arrow in the figure.
  • the lidar also includes a scanning unit 1106 (such as a galvanometer, a rotating mirror), to select the transmission signal of the channel to be detected to exit the lidar, through the main lens group unit 1104 (exemplarily shown in the figure) A convex lens is shown) cooperate with the first diverging unit 1105 to obtain the relatively extended equivalent focal length of the light emitting module; and, select the echo signal of the channel to be detected to turn into the overlapping optical path section, and go right to the spectroscopic unit 1103 is transmitted, redirected (for example, direct) by the light splitting unit 1103 to the second optical path section connected to the optical detection component (laser array 1102 in this example), and transmitted to the laser array 1102 along the second optical path section, as shown in gray in the figure The receiving light path indicated by the arrow.
  • the scanning unit 1106 may include one or more resonant single-axis micro-electromechanical system (MEMS) vibrating mirrors to perform two-dimensional rotation to select the transmission signal and echo signal of the desired detection
  • only a convex lens 1107 may be provided in the second optical path section for converging echo signals, and no concave lens may be provided.
  • EEL edge-emitting laser
  • the difference from the embodiment in FIG. 11A is that in the laser array 1101B of the laser array, the lasers can be implemented by VCSELs instead of the EEL in the embodiment in FIG. 11A to further improve the ranging capability.
  • the microlens array 1109 can be set correspondingly (a convex lens can also be added in the first optical path section) to compress the divergence angle of the VCSEL, leaving the periphery of the light exit aperture for the detection optical path. See Fig.
  • the divergence angle of the laser is compressed and transmitted along the middle part of the coaxial optical path (indicated by a thin solid arrow), while the echo signal is transmitted in the peripheral area relative to the middle part (indicated by a thick solid arrow) .
  • FIG. 12A and FIG. 12B are used to illustrate the effect of encapsulating the optical path section between each laser and the corresponding concave lens in the sleeve in the embodiment of the present application.
  • the inner wall of the sleeve is made of absorbing material to absorb light.
  • the optical path diagram shown in FIG. 12A takes the emission optical path as an example.
  • the emission signal of the light-emitting point near the edge of the laser 1201 (such as C ) may avoid the concave lens (concave lens 1202) and enter the main lens group unit (such as the main lens group, not drawn in this figure), this part of the transmitted signal that does not pass through the first diverging unit will produce defocus, and pass through the main lens group
  • the echo signal formed after the unit sends out with a large divergence angle will be received by the photodetectors of other channels, thus forming crosstalk. Therefore, this part of the potential stray light can be absorbed by the absorbing material.
  • the optical path section between the laser 1201 and the corresponding concave lens 1202 is encapsulated by the sleeve 1203, so that the transmitted signal that originally avoids the concave lens 1202 is reflected and limited to pass through the concave lens 1202 and then to the main The lens group unit, then this part of the transmitted signal will not be out of focus, so that the light emitting area with the same or similar size as the concave lens can be realized.
  • VCSEL because the light-emitting area is increased, the corresponding peak power is also increased.
  • FIG. 12C it is used to illustrate the effect of the optical path section between the concave lenses 1302 corresponding to the echo signal in the embodiment of the present application after being packaged in the sleeve 1303 to each detector 1301.
  • the optical path is similar to the emission At the end, it also absorbs the potential stray light, thereby improving the signal-to-noise ratio, and the details will not be repeated here.
  • the laser radar provided by the present application includes: a laser array arranged in a linear array or an area array, arranged on the focal plane of the first optical assembly, and the first optical assembly is arranged on the emitting optical path, forming a larger than The equivalent focal length of the focal length of the main lens group unit at the transmitting end; and/or, the photodetector array arranged in a linear array or an area array is arranged on the focal plane of the second optical assembly, and the second optical assembly is set On the receiving optical path, an equivalent focal length greater than the focal length of the main lens group unit at the receiving end is formed.
  • the power density within the field of view of the point cloud is increased by setting the first optical component at the light emitting end, and/or, the field of view of the point cloud is reduced by setting the second optical component at the receiving end.
  • the background light noise power in the angular area can improve the ranging capability of the radar.

Abstract

一种激光雷达，包括：以线阵或者面阵排布的激光器阵列（501），设置于第一光学组件（502,503）的焦平面，以及第一光学组件（502,503），设于发射光路，形成有大于发射端的主透镜组单元（502）的焦距的等效焦距；和/或，以线阵或者面阵排布的光探测器阵列（701），设置于第二光学组件（702,703）的焦平面，以及第二光学组件（702,703），设于接收光路，形成有大于接收端的主透镜组单元（702）的焦距的等效焦距。通过光发射端的第一光学组件（502,503）的设置，来提高点云视场角面积内的功率密度，和/或，通过接收端的第二光学组件（702,703）的设置，来降低点云视场角面积内的背景光噪声功率，进而均可提高雷达的测距能力。

Description

激光雷达
相关申请交叉引用
本专利申请要求于2021年09月15日提交的、申请号为202111079553.7、发明名称为“激光雷达”的中国专利申请的优先权，上述申请的全文以引用的方式并入本文中。
技术领域
本申请涉及光学测距技术领域，尤其涉及激光雷达。
背景技术
激光雷达是通过发射激光，并探测激光到达物体表面后反射的回波信号来计算物体距离的探测设备。因此，激光雷达需包括光发射(TransmitterX)元件和光探测(Receiver X)元件两个部分，可被称为光发射模块和光探测模块。
激光雷达中包含光学系统，分布在光发射模块和光探测模块，比如光发射模块包括用于准直激光器的发射信号的主透镜组等，光探测模块包括用于将回波信号汇聚向探测器的接收透镜等。对于光发射模块(或光探测模块)而言，其视场角(FOV)与光发射模块的发光面(或光探测模块的感光面)的纵向尺寸正相关，而与发射和/或接收透镜(组)的等效焦距负相关。其中，所述发光面(或感光面)的纵向尺寸是正相关于激光雷达整机的高度。
激光雷达产品的高度尺寸是被客户关注的重要参数。为了使激光雷达整机能在覆盖较大视场角(比如105°)的情况下，仍保持在合适的高度，则不得不缩小发射模块和/或探测模块的焦距，比如更换焦距更短的光学器件等，如此不仅会造成发光面的占空比降低且会使得纵向的垂直分辨率受限。
发明内容
鉴于以上所述现有技术的缺点，本申请提供光探测装置及探测方法，解决上述 激光雷达因焦距和高度之间相互制约所导致的问题，可以在不增加雷达高度的前提下，提高雷达的测距能力。
为实现上述目标及其他相关目标，本申请第一方面提供一种激光雷达，包括：
光发射模块，设置于第一光学组件的焦平面，包括：激光器阵列，以线阵或者面阵排布，适于发出发射信号，所述发射信号沿发射光路传输；
第一光学组件，设于所述发射光路，形成有大于第一预设值的等效焦距，以提高点云视场角面积内的功率密度，进而提高雷达的测距能力；其中，所述第一预设值为主透镜组单元的焦距；
光探测模块，包括：光探测器阵列，以线阵或者面阵排布，适于从接收光路探测所述发射信号遇到障碍物后被反射的回波信号。
在本发明一实施例中，所述第一光学组件包括：主透镜组单元，适于准直发射信号；
还包括：第一发散单元，配置在激光器阵列和主透镜组单元之间，适于发散经所述主透镜组单元准直后的发射信号，以使得所述第一光学组件具有长于第一预设值的等效焦距。
在本发明一实施例中，所述第一光学组件的等效焦距为主透镜组单元的焦距的M倍，M>1，以使每个激光器的发光面的面积提高M2倍。
在本发明一实施例中，所述第一发散单元包括：凹透镜阵列，其中每个凹透镜对应于一个发射通道。
本发明实施例还提供了另一种激光雷达，包括：
光发射模块，包括：激光器阵列，以线阵或者面阵排布，适于发出发射信号，所述发射信号沿发射光路传输；
光探测模块，设置于第二光学组件的焦平面，包括：光探测器阵列，以线阵或者面阵排布，适于从接收光路探测所述发射信号遇到障碍物后被反射的回波信号；
以及所述第二光学组件，设于接收光路，形成有大于第二预设值的等效焦距，以降低点云视场角面积内的背景光噪声功率，进而提高雷达的测距能力；其中，所述第二预设值为主透镜组单元的焦距。
在本发明一实施例中，所述第二光学组件包括：接收透镜组单元，适于汇聚接收信号；
所述第二光学组件还包括：第二发散单元，
配置在光探测器阵列和接收透镜组单元之间，以使得所述第二光学组件具有长于第二预设值的等效焦距，适于发散经所述接收透镜组单元汇聚后的接收信号。
在本发明一实施例中，所述第二光学组件的等效焦距为主透镜组单元的焦距的P倍，P>1，以使接收角面积缩小P2倍。
在本发明一实施例中，所述第二发散单元包括：凹透镜阵列，其中每个凹透镜对应于一个探测器设置。
在本发明一实施例中，所述激光雷达包括：第一光学组件，设于所述发射光路，形成有大于第一预设值的等效焦距，以提高点云视场角面积内的功率密度，进而提高雷达的测距能力；其中，所述第一预设值为第一光学组件中主透镜组单元的焦距；所述第一光学组件和第二光学组件的等效焦距成一定比例关系。
综上所述，本申请提供激光雷达包括：以线阵或者面阵排布的激光器阵列，设置于第一光学组件的焦平面，以及第一光学组件，设于所述发射光路，形成有大于发射端的主透镜组单元的焦距的等效焦距；和/或，以线阵或者面阵排布的光探测器阵列，设置于第二光学组件的焦平面，以及所述第二光学组件，设于接收光路，形成有大于接收端的主透镜组单元的焦距的等效焦距。本申请实施例中，通过光发射端的第一光学组件的设置，来提高点云视场角面积内的功率密度，和/或，通过接收端的第二光学组件的设置，来降低点云视场角面积内的背景光噪声功率，进而均可提高雷达的测距能力。
附图说明
图1A展示一示例中光探测系统的光发射模块的视场和焦距的关系示意图。
图1B展示一示例中光探测系统的光探测模块的视场和焦距的关系示意图。
图1C展示一示例中水平扫描式机械雷达的发射端和接收端的通道对应关系示意图。
图2A展示一示例中一个激光器的发光面的示意图。
图2B展示图2A的简化表示示意图。
图3展示一示例中用于说明光发射模块的垂直分辨率的原理示意图。
图4展示本申请一实施例中激光雷达的收发光路的示意图。
图5A展示本申请一实施例中光发射模块的结构示意图。
图5B展示本申请又一实施例中光发射模块的结构示意图。
图6展示为本申请实施例中不同焦距下形成放大的发光面的正视结构示意图。
图7展示本申请实施例中激光雷达的光探测模块的结构示意图。
图8展示本申请实施例中根据光发射模块的具体结构参数确定M取值的原理示意图。
图9展示本申请实施例中不同焦距下形成放大的发光面的布局及配合的凹透镜阵列的正视结构示意图。
图10A展示本申请一种实施例中旁轴光路结构的激光雷达的结构示意图。
图10B展示本申请一种实施例中旁轴光路结构的激光雷达的激光器阵列和光探测器阵列的正视的结构示意图。
图10C展示图10B中激光雷达的测距能力仿真结果的曲线示意图。
图11A展示本申请一种实施例中同轴光路结构的激光雷达的结构示意图。
图11B展示本申请又一种实施例中同轴光路结构的激光雷达的结构示意图。
图12A展示本申请实施例中未设置套筒的发射端的光路示意图。
图12B展示本申请实施例中设置套筒的发射端的光路示意图。
图12C展示本申请实施例中设置套筒的接收端的光路示意图。
具体实施方式
以下通过特定的具体实例说明本申请的实施方式，本领域技术人员可由本说明书所揭露的内容轻易地了解本申请的其他优点与功效。本申请还可以通过另外不同的具体实施方式加以实施或应用系统，本说明书中的各项细节也可以基于不同观点与应用系统，在没有背离本申请的精神下进行各种修饰或改变。需说明的是，在不 冲突的情况下，本申请中的实施例及实施例中的特征可以相互组合。
下面以附图为参考，针对本申请的实施例进行详细说明，以便本申请所属技术领域的技术人员能够容易地实施。本申请可以以多种不同形态体现，并不限定于此处说明的实施例。
为了明确说明本申请，省略与说明无关的器件，对于通篇说明书中相同或类似的构成要素，赋予了相同的参照符号。
在通篇说明书中，当说某器件与另一器件“连接”时，这不仅包括“直接连接”的情形，也包括在其中间把其它元件置于其间而“间接连接”的情形。另外，当说某种器件“包括”某种构成要素时，只要没有特别相反的记载，则并非将其它构成要素排除在外，而是意味着可以还包括其它构成要素。
当说某器件在另一器件“之上”时，这可以是直接在另一器件之上，但也可以在其之间伴随着其它器件。当对照地说某器件“直接"在另一器件“之上”时，其之间不伴随其它器件。
虽然在一些实例中术语第一、第二等在本文中用来描述各种元件，但是这些元件不应当被这些术语限制。这些术语仅用来将一个元件与另一个元件进行区分。例如，第一接口及第二接口等描述。再者，如同在本文中所使用的，单数形式“一”、“一个”和“该”旨在也包括复数形式，除非上下文中有相反的指示。应当进一步理解，术语“包含”、“包括"表明存在所述的特征、步骤、操作、元件、组件、项目、种类、和/或组，但不排除一个或多个其他特征、步骤、操作、元件、组件、项目、种类、和/或组的存在、出现或添加。此处使用的术语“或”和“和/或”被解释为包括性的，或意味着任一个或任何组合。因此，“A、B或C”或者“A、B和/或C"意味着“以下任一个：A；B；C；A和B；A和C；B和C；A、B和C”。仅当元件、功能、步骤或操作的组合在某些方式下内在地互相排斥时，才会出现该定义的例外。
此处使用的专业术语只用于言及特定实施例，并非意在限定本申请。此处使用的单数形态，只要语句未明确表示出与之相反的意义，那么还包括复数形态。在说明书中使用的“包括"的意义是把特定特性、区域、整数、步骤、作业、要素及/或 成份具体化，并非排除其它特性、区域、整数、步骤、作业、要素及/或成份的存在或附加。
表示“下"、“上"等相对空间的术语可以为了更容易地说明在附图中图示的一器件相对于另一器件的关系而使用。这种术语是指，不仅是在附图中所指的意义，还包括使用中的装置的其它意义或作业。例如，如果翻转附图中的装置，曾说明为在其它器件“下"的某器件则说明为在其它器件“上"。因此，所谓“下"的示例性术语，全部包括上与下方。装置可以旋转90°或其它角度，代表相对空间的术语也据此来解释。
虽然未不同地定义，但包括此处使用的技术术语及科学术语，所有术语均具有与本申请所属技术领域的技术人员一般理解的意义相同的意义。普通使用的字典中定义的术语追加解释为具有与相关技术文献和当前提示的内容相符的意义，只要未进行定义，不得过度解释为理想的或非常公式性的意义。
激光雷达是一种基于光学探测系统进行测距的设备。目前激光雷达的应用场景(比如自动驾驶)等存在高精度、大视场的需求，同时实际场景中又需要激光雷达尽可能地尺寸减小，尤其是激光雷达的高度，是客户最为关注的参数之一。但是，大视场和低高度之间存在矛盾，从而影响激光雷达的性能。以下通过举例来说明原理。
请参阅图1A和图1B，展示为一示例中光探测系统中视场和焦距关系的示意图。图1A展示光探测系统中光发射模块的视场和焦距关系的示意图。图1B展示光探测系统的光探测模块的视场和焦距的关系示意图。
根据图1A或图1B中示意的视场FOV所对应的三角形，可以计算得到：
Figure PCTCN2022098404-appb-000001
其中，a为单个激光器101A的发光面或单个光探测器101B的感光面的高度(或称纵向尺寸)，f为透镜102A、102B的焦距(图中示意性地都表示为f，但并不表示限定两个光路的焦距相同，只是为了避免太多编号造成混乱)。对于激光雷达来说，单个激光器/单个探测器的视场满足公式(1)。同时，在理想情况下(纵向上多个激光器/探测器可以无缝隙地相接时)，则无论是单个发光面101A/单个感光面 101B，还是纵向上所有的多个激光器/探测器的高度，均满足公式(1)，视场大小均与激光雷达的高度正相关。
故而，从式(1)可推知，激光雷达的光发射模块的发光面以及探测模块的感光面的尺寸与激光雷达的尺寸正相关。尤其是激光雷达的高度尺寸，相较于宽度和深度来讲，是更被着重关注的参数，各种应用场景中通常都需要合适的高度以适配有限的安装空间。
并且，由式(1)可知，视场FOV大小与发光面、感光面的尺寸正相关，与光发射模块、光探测模块中的光学部件(如主透镜组)的等效焦距f负相关。可见，如果要维持较大的FOV，要么增加a或者要么减小f，但是增加a，可能会导致激光雷达的高度增加，故一般会减小f以达到目的，但是这样一来，会造成影响激光雷达性能的问题。
另外，对于雷达系统而言，发射与接收有一定的对应关系。收发光路可以不一样，收发的焦平面布局也可能不一样，但最终都希望发出去的光落在目标上某个区域，这个区域反射光能正好回到探测器上，即发射和接收能够匹配，收发通道能够对应起来。为避免混淆，以下先定义一些术语。
扫描线数：也就是激光收发的通道数，或者说是最小可寻址通道的数目。一般激光器和探测器是1：1配置，扫描线数即等于激光器或者探测器的个数，也等于发射通道或者接收通道的个数。同时，也存在多个探测器共享一个激光器的情况，或者反之，或者甚至可能有交错的情况，此时就要具体分辨最小可寻址的通道的数目。
发散角面积：是指某个通道的激光器发光区域经过光学系统投射在远场的角面积。
接收角面积：是指某个通道的探测器光敏面经过光学系统投射在远场的角面积。
点云视场角面积：是指发散角和接收角的重叠部分，这个是点云所覆盖的真正范围，并且是这个范围内所有目标反射回波信号的叠加。在不同的光路设计中，点云视场角面积与发散角面积及接收角面积呈现出不同的相对关系。点云视场角面积比如可以等于发散角面积且小于接收角面积，比如可以等于接收角面积且小于发散 角面积，或者比如可以等于二者重叠的部分。最理想的情况下，点云视场角面积与发散角和接收角面积均一致。
视场FOV，往往包含了水平视场HFOV，垂直视场VFOV，是指所有收发通道探测的总角度范围。
参考图1C，左边是发射端(TX，transmitter)，发射端设置有多个激光器(是指最小可寻址的发光单元)。
右边是接收端(RX，receiver)，接收端设置有多个探测器(同样也是指最小可寻址单元)。
中间是点云视场角，每个点的水平位置表示水平角，水平角θ随着雷达转子转动而偏移，垂直位置表示俯仰角γ＝β。
再有，见图2A和图2B所示，展示为一示例中一个激光器的发光面的示意图。所述激光器示例性地为垂直腔面发射激光器200(Vertical Cavity Surface Emitting Laser，VCSEL)。图2A为较为实际的VCSEL的顶视示意图，图2B为基于图2A进行抽象简化的示意图。发光占空比指的是发光面覆盖的面积占总面积的比例，可以是图示中各个发光点201的面积之和与虚线方框202或整个VCSEL顶面面积等之比。总而言之，发光占空比受限于OA/PITCH。其中，OA为其中1个发光点201的面积，PITCH为相邻发光点201在纵向上的节距(即相邻发光点的中心之间的间距，如图中双向箭头所标示)。可见，当OA越大或者节距越小，占空比越高。需要说明的是，此处只是示例，在本申请中，并不对激光器的类型做任何限定，比如激光器可以为EEL(Edge Emitting Laser)，可以为VCSEL，也可以为PCSEL(Photonic Crystal Surface Emitting Semiconductor Lasers)。类似的，在本申请中，也并不对探测器的类型做任何限定，比如所述光探测器可以为APD，可以为单光子雪崩二极管阵列SPAD(s)，也可以为硅光电倍增管SiPM。
进一步的，如图3所示，当光发射模块采用例如激光器阵列作为激光器阵列，激光雷达的垂直角度分辨率是根据纵向排列(或称列向)的相邻激光器301、302的中心间距d与主透镜组(此处只是示出一个凸透镜303作为实施例中的一种等效情况，实际主透镜组可能包括多个透镜组，此处不做限定)的等效焦距f之间的比 值d/f所确定，即与d正相关而与f负相关。
基于上述可知，现有的激光雷达的光路系统仍存在改进的空间。一方面，为了覆盖较大视场(比如105°)，且为了维持高度不增加，则不得不尽量缩小焦距。另一方面，激光器的发光面占空比受限于发光点面积/发光点节距，导致占空比低。再一方面，垂直分辨率受限于d/f。
鉴于上述，本申请实施例中提供激光雷达，通过光学改进方式，实现以相对短的物理尺寸实现了更长的等效焦距，进而提高了点云视场角面积内的功率密度，和或，降低了点云视场角面积内的背景光噪声功率，从而可以提高雷达的测远能力。
图4示出了一种激光雷达的收发光路的示意图。激光雷达具体可以包括：
光发射模块，即以线阵或者面阵排布的激光器阵列，与第一光学组件对应设置，例如可设置于第一光学组件的焦平面，适于发出发射信号，发射信号沿着发射光路传输。所述第一光学组件可以形成有大于第一预设值的等效焦距。
光探测模块，即以线阵或者面阵排布的光探测器阵列，与第二光学组件对应设置，例如可设置于第二光学组件的焦平面，适于探测所述发射信号达到物体后而反射的回波信号。所述第二光学组件，可以形成有大于第二预设值的等效焦距。从而，通过设置激光雷达发射端和/或接收端的光学组件的设置，实现收/发侧拉长的焦距，在保持雷达整机高度不变的情况，可以提高点云视场角面积内的功率密度，和/或，降低点云视场角面积内的背景光噪声功率，大大提高雷达的测距能力。
下面分别从发射TX端及接收RX端各自单侧进行更加详细的介绍。
如图5A所示，展示本申请一种实施例中光发射模块的结构示意图。
所述光发射模块包括：激光器阵列501以及第一光学组件。
所述激光器阵列501包括多个激光器511。所述多个激光器511可以按线阵或面阵形式排布。每个激光器511配置成输出发射信号，也即发出激光。示例性的，所述激光器511可以例如为垂直腔面发射激光器(VSCEL)实现，或者边缘发射激光器(EEL)实现。
所述第一光学组件，设于所述发射光路上，配置有长度大于第一预设值的等效焦距。具体来讲，如图5A示例所展示的，所述第一光学组件包括：主透镜组单元， 具体可以是光发射模块中原有的用于准直发射信号的主透镜组，在图5A中示例性地以等效的凸透镜502展示；以及第一发散单元，用于对发射信号进行发散，在图5A中第一发散单元示例性地呈现为凹透镜阵列503。其中，凹透镜阵列503中的每个凹透镜531对应于一个激光器511(单个可寻址及可控制是否开启的单元)设置，以拉长(相对于只有主透镜组的发射光路形成的焦距而言)发射光路的焦距，从而实现该单个像素对应的激光器511的发光面的提升(相对于将激光器设置于主透镜组单元的焦平面A的方案中激光器的尺寸而言，但实际在本申请的具有更长焦距的方案中，激光器只设置于焦平面B处，而非A处)，在点云层面的话，则是提高点云视场角面积内的功率密度，即用来形成点云中的其中一个点的发射端能量更大。其中，所述像素指的是对应激光雷达所成点云图中的一个像素点或者点云，例如每个激光器的发光面/每个光探测器的感光面可对应于一个像素点，进而收发单元共同构成一个通道，然后也对应于上文提及的线束。凹透镜阵列503中相邻的两个凹透镜531彼此之间的节距可与相邻激光器511间的中心间距相同。
需说明的是，所述主透镜组单元在图示中示例性地用凸透镜502来表示，实际上该凸透镜502也只是主透镜组单元的一种表示，主透镜组单元可以是光发射模块中的主透镜组，其中可包含多个透镜(例如图4所示)，故非以图示凸透镜502的简化表示为限制；另外，主透镜组单元的等效透镜也可能是其它形式的凸透镜，比如平凸透镜等，此处不做限定。所述主透镜组单元可以具有第一焦距，图中表示为从凸透镜502的主平面C至其一倍焦点(对应的焦平面为A)之间的距离f"。
在一些实施例中，所述凹透镜阵列503配置在激光器阵列501和主透镜组单元之间，凹透镜阵列503中的每个凹透镜531对应于一个激光器511设置。
所述凹透镜阵列503适于发散所述发射信号后经所述主透镜组单元汇聚，从而形成所述第一光学组件的长于第一预设值的等效焦距。具体示例而言，f"是主透镜组(即图5A的主透镜组单元，以1个凸透镜代替性地表示，但一般会是一个主透镜组，在图5A中，主透镜组单元＝主透镜组＝正透镜＝凸透镜＝最左边的透镜)的焦距，f是图中2个透镜(即凸透镜502+凹透镜阵列503)组合的等效焦距，L是物理实体尺寸。其中，正负透镜组(即凸透镜502+凹透镜阵列503)组合后的主平面 会前移，如图中所展示的，f的左侧端点相比于f"的左侧端点发生了向左的前移，也就是位于f左侧端点的主平面D相比于主透镜组单元的主平面C发生了向左的前移，整个的焦平面会后移，比如从A后移到B。在计算焦距时，可根据会聚光线的反向延长线，来确定主平面D位置，其反向延长线可见图5A中的虚线E1、E2。这也是本光路的一个优点：L＜f，实现用相对短的物理尺寸L实现了更长的等效焦距f。
根据上述可以理解的是，对于光发射模块(即TX端)而言，在激光雷达原有的主透镜组(即图中的主透镜组单元/凸透镜502)的光路基础上，本申请实施例中增加一个凹透镜阵列503与其组合来拉长焦距，即将焦距从主透镜组的焦距f"拉长到了2个透镜(即凸透镜502+凹透镜阵列503中的凹透镜530)组合的等效焦距f，令M为焦距放大倍数，M＝f/f"。可选的，第一扩散单元相距于主透镜组单元的主平面间距可以小于f"。
根据式(1)，当FOV不变，焦距f等效增大，则a对应等效增大，即会使得每个像素的发光面获得等效增大。进而，单像素(对应激光雷达中点云图中的一个点)的发光能量可以提高，相应的点云视场角面积内的功率密度提高(即相同面积中包含的发光点201越多)，测远的能力也等比例提高，比如测远能力可以从200m提高到300m等。
需说明的是，对于如VSCEL激光器，其视角较大，可能会导致发射的光线F1、F2会偏出凹透镜530，这部分未经过凹透镜530的光线会产生脱焦，经过主透镜组单元以较大发散角送出之后很有可能形成的回波信号会被其它通道的光探测器所接收，从而形成串扰；或者，偏离出主透镜组单元而形成信号损失。为此，在一些实施例中，可以对激光器阵列的视角进行压缩。
如图5B所示，展示本申请又一种实施例中光发射模块的结构示意图。
图5B中展示有激光器阵列501以及另一种实施例的第一光学组件。
在本实施例中，第一光学组件包括主透镜组单元和微透镜组单元503。
需说明的是，图5B中仍然用凸透镜502来等效表示所述主透镜组单元。所述主透镜组单元可以具有第一焦距，图中表示为从其主平面C至其一倍焦点(对应的 焦平面为A)之间的距离f"。
在本实施例中，所述微透镜组单元504除了包括所述凹透镜阵列503，还包括微透镜阵列505。在图5B中，所述微透镜阵列551设置在激光器阵列501和凹透镜阵列503之间。其中，由于每个激光器511(如VCSEL)的发光面具有多个发光点，则所述微透镜阵列551中多个微透镜551(具体为微凸透镜)，每个微透镜对应于一个发光点设置，以将发光点的出光进行汇聚后向对应的凹透镜531传输。也就是说，通过微透镜阵列551，可以压缩每个发光点发光的发散角，也就进而压制激光器511、激光器阵列501输出发射信号的发散角，从而避免图5A中F1、F2光线偏离于凹透镜阵列503出射的情况。
具体说明本实施例中的原理。不同于图5A实施例，图5B实施例中是由3个透镜(即凸透镜502+凹透镜阵列503中的凹透镜530+微透镜阵列505中的微透镜551)组合的等效焦距达成焦距延长。图5B中f"是主透镜组(图5B中主透镜组单元以1个凸透镜代替性地表示，但一般会是一个主透镜组，在图5B中，主透镜组单元＝主透镜组＝正透镜＝凸透镜＝最左边的透镜)的焦距，f是图中3个透镜(即凸透镜502+凹透镜阵列503中的凹透镜530+微透镜阵列505中的微透镜551)组合的等效焦距，L是物理实体尺寸。其中，正负透镜组(即凸透镜502+凹透镜阵列503中的凹透镜530)组合后的主平面会前移，如图中所展示的，f的左侧端点相比于f"的左侧端点发生了向左的前移，也就是f左侧端点的主平面D相比于主透镜组单元的主平面C发生了向左的前移，整个的焦平面会后移，比如从A后移到B。在计算焦距时，根据会聚光线的反向延长线，来确定主平面位置，反向延长线可见图5B中的虚线S1、S2。这也是本光路的一个优点：L＜f，实现用相对短的物理实体尺寸L实现了更长的焦距f。
对于TX端，在原有的主透镜组单元(即主透镜组)的光路基础上，本申请实施例中使用一个凹透镜阵列503来拉长焦距，并通过微透镜阵列505来压缩限制激光器501的发散角，将焦距从主透镜组单元的焦距f"拉长到了等效焦距f，令M为焦距放大倍数,M＝f/f"。根据式(1)，FOV不变，焦距f增大则a对应增大，即发光面获得增大。进而，单像素(对应激光雷达中点云图中的一个点)的发光能量可 以提高，相应的点云视场角面积内的功率密度提高，测远的能力也等比例提高。
示例性地，微透镜阵列504中相邻的两个微透镜彼此之间的节距和发光点的节距相同。需说明的是，图中所展示的与3个激光器511一一对应的3个凹透镜，以及与每个激光器511对应的3个微透镜，皆为示意性的数量，而非限制其具体实施。
在图5A和图5B示例中，激光器阵列501的出光表面B(包含每个激光器的出光表面)位于第一光学组件的等效透镜的焦平面上，以与等效透镜的主平面D之间保持间距为等效焦距f。
为了更直观看到发光面的增大，可以参考图6所示。
在图6中，展示为本申请实施例中不同焦距下形成放大的发光面的正视结构示意图。图6中从左至右依次展示M小于但近似于1(即发光面未放大，或者未采用凹透镜的光路，比如仅包括主透镜组单元的光路)、M小于但近似于2、及M小于但近似于4情况下的发光面的大小对比；其中展示8个发光面11、12、13、14、21、22、23及24在三种情况下的发光面积的等效放大情况。可以结合图5A或图5B及图6进行理解，图5A、图5B中侧视视角中纵向排列的3个激光器可以是位于1列的，比如对应图6中M小于但近似于2所对应的一列发光面11、12及13。每个激光器对应设置一个凹透镜阵列中的其中一个微凹透镜Y，为直观示意，仅在图6中右侧选择一个发光面21绘制一个凹透镜，呈现为环绕发光面21外的圆圈，但实际其它的激光器也都对应设置有凹透镜，此处只是省略了。需说明的是，凹透镜的直径大于发光面直径以能全面覆盖发光面，以能较多地接收到发射信号的光线，但同时也要考虑激光雷达的高度而限制凹透镜的直径处于合适尺寸。
根据图6可知，随M的变化，根据三种情况下的单个发光面直径从a0→a1→a2得到M倍的放大，发光面面积从a0→a1→a2得到M 2倍的放大。每个激光器对应的发光面变大后，该激光器的照远能力增加，在点云层面，可提高点云视场角面积内的功率密度，进而使得激光雷达的测远能力提高。另外，虽然在M小于但近似于4的情况中，最邻近的激光器的发光面较为接近(如发光面11和发光面13)，但当等效到远场的发射角面积a2"会是a2/M，不会存在重叠而无法被辨认为两个发光面的问题。需要说明的是，当第一光学组件的等效焦距为主透镜组单元的焦距的M倍，如 果把激光器设置在第一光学组件的焦平面，则每个激光器的整个面积，为如果是设置在主透镜组单元焦平面上的激光器的面积的M 2倍。如果激光器的占空比不变的情况下，则每个激光器的发光面的面积，相对若设置于主透镜组焦平面上的发光面的面积将提高M 2倍。
另外可选的，如图6可见，可以通过调节不同焦距放大倍数M下的发光面的布局，可以维持高度尺寸。例如，从图6中3种情况下的高度h0、h1、h2比较来看，h2略大于h1，h1略大于h0，而它们的差距在实际情况中可以忽略，也即是说，激光雷达在高度尺寸上可以几乎没有变化，然而每个激光器的发光面却得到了M 2倍放大，在点云层面，可提高点云视场角面积内的功率密度达M 2倍，而使激光雷达的测远能力得到了提高。
在另外的示例中，光探测模块一侧可以通过类似的光学组件来扩大焦距。对探测端而言，拉长焦距的同时，在保持接收器件的面积不变的情况下，可缩小接收角面积，进而可以降低点云视场角面积内的背景光噪声功率，从而也可以提高雷达的测远能力。
如图7所示，展示本申请实施例中激光雷达的光探测模块的结构示意图。所述光探测模块包括光探测器阵列701，包含阵列排布的多个光探测器711。光探测器711配置成探测所述发射信号达到物体而反射以实现探测。其中，一或多个光探测器711与一或多个激光器之间形成“通道"，比如一个光探测器和一个激光器之间形成一个通道，激光器的发射信号的回波信号被属于同一通道的光探测器711所接收，每个通道对应于某视场角度或者某视场角度范围(接收角面积)的探测。在具体实例中，每个所述光探测器711可以由例如SiPM(Silicon Photo Multiplier，硅光电倍增管)或者SPAD(s)(Single Photon Avalanche Diode，单光子雪崩二极管)所实现。
示例性地，所述光探测模块还可以包括对应光探测器阵列701设置的第二光学组件。所述第二光学组件具体包括第二汇聚单元和第二发散单元。在图6中，第二汇聚单元可以是原有的用于汇聚回波信号的透镜或透镜组，可以等效地展示为图中最左侧的凸透镜702，以用于汇聚回波信号向光探测器阵列701传输。第二发散单 元可以实现为凹透镜阵列703，其中每个凹透镜731分别对应于一个光探测器711设置；相应的，纵向相邻的凹透镜731之间的节距可与光探测器阵列701中一列中的相邻光探测器711中心的间距相等。
凸透镜702的焦距为f2"，如图中示意地展示为从凸透镜702的主平面G至其焦平面H之间的长度。示例性地，所述凸透镜702的主平面G和凹透镜阵列703的间距可在所述等效透镜的焦距f2"以内。
通过凸透镜702+凹透镜阵列703的组合，形成的等效透镜的主平面为I，相比于G发生了向左的前移。可以理解的是，与之前图示5A、图5B原理相同，I平面的位置可由图中的反向延长线K1和K2所确定，为直观清晰，图示中以简略(“...”)的方式简单表示，应当可以参考之前图示来加以理解。
从而，如图中所示，形成相比于凸透镜702的焦距f2"延长的焦距f2，从I到焦平面J的距离，可选的，光探测器阵列701的感光表面可以位于f2右端的焦平面J上，以获得回波信号的聚焦。G到J的物理长度为L2，可见f2超出了L2的物理距离限制。
与光发射模块(即TX端)的焦距延长不同，对于激光雷达的接收端而言，在确保尽可能多的接收真正的探测信号(发射信号遇到障碍物后被反射的回波信号)的前提下，需要尽可能地降低接收到的背景光强，以提高信噪比，下面公式给出了接收侧的背景光P B：
Figure PCTCN2022098404-appb-000002
其中，pb为背景辐射密度；BW为滤光片半高宽(nm)；ρ为目标的反射率；tr为接收镜筒的光学效率；A为有效孔径(m)，Sr为探测器有效面积，f为焦距。
根据上述公式可以看到，通过将所述光探测模块(即RX端)的焦距获得延长，可以降低点云视场角面积内的背景光噪声功率，提高信噪比，进而也使得整个激光雷达的测距能力提升，且又能维持激光雷达的高度尺寸。另外，若第二光学组件的等效焦距为接收端主透镜组单元的焦距的P倍，P>1，则可以使接收角面积缩小P 2倍。需要说明的是，发射端和接收端的采用不同的字母符号，比如分别采用M和P来表征 光学组件拉长的焦距放大倍数，只是为了说明收发侧可以采用不同的放大倍数，但是可以理解的是，收发侧也是可以设置为相同的放大倍数。文中有些处只做了比如对M的探讨，P也是类似，在申请中并未做二次赘述。
除了光发射模块和光探测模块，通常在激光雷达中还包括控制模块(未图示)，以用于控制光发射模块发射所述发射信号，以及控制光探测模块探测回波信号的数据，并可以对数据进行计算以得到探测结果。
根据上述实施例或实施例的结合，可解决之前所阐述的多种问题。一方面，通过使光发射模块和光探测模块的光路获得更大的焦距，实现令激光雷达在提升焦距M倍的同时，保持焦平面的总高度，使得激光雷达的整机尺寸几乎没有变化。另一方面，对发射模块TX，可以提升单像素点对应的发光面的尺寸，从而可以提高功率密度；对于接收模块RX而言，可以降低接收角面积，进而降低点云视场角面积内的背景光噪声功率；进而均利于提高测距能力；且f增大使d/f减小，意味着相邻激光器在垂直方向的角度差减小，从而提高了垂直角度分辨率。再一方面，图5B中激光器阵列前设置微透镜阵列以汇聚发射信号，也利于进一步提高出射光的利用效率。
在一些实施例中，可以参考图8和图9，以用于探讨M的合理取值。
与之前图5A和图5B相似，在图8中，f"是主透镜组单元等效的凸透镜802的焦距，f是第一光学组件的焦距，L是物理尺寸。通过凸透镜802和凹透镜803的组合，实现的等效焦距为f，f＝M*f"。需要说明的是，图8中示意性地绘制了1个激光器801的其中1个发光点的发射信号被微透镜804压缩后，又被对应的凹透镜803扩散后的光路，并未绘制该激光器801的所有发光点，也未绘制出其它激光器和对应的其它凹透镜(代表凹透镜)，但它们实际上是可以存在的。
根据图示中所示意的标记，M的计算公式如下式(2)所示：
M＝f/f"＝Δy/Δy"≈a/β              (2)
其中，Δy是位于经延长后焦距的焦平面上的激光器高度(y方向)即该位置对应的发光面高度，Δy"是在凸透镜802对应焦平面等效的发光面高度。为了尽可能提高放大倍数M，需要锥角β＝(激光器发散角θ*OA/PITCH)尽可能小，并设计 F值(光圈值
Figure PCTCN2022098404-appb-000003
f为焦距，D为光圈直径)较小，即光圈比较大的主镜头(即主透镜组)。参考图8，主镜头锥角＝α；激光器801的发散角＝θ；β由一方面与激光器801本身的出光质量相关，另一方面与微透镜阵列的压缩效果有关。
另外，还可以推导M的上限。在放大焦距f后，同样面积的发光面(可理解为a不变)，发散角等比缩小了(公发散角θ＝2×arctan(a/2f))，角度分辨率提高了，所以允许激光器阵列中的各激光器呈多列(N列)交错排布。
交错排布的列数N应有所限制，N可能影响雷达产品的宽度，虽然宽度方向并不如高度方向重要，但也不能不加以限制。假如有N列激光器交错排布，考虑到要每个激光器发出的所有的光都能通过一一对应设置的凹透镜(例如图9中被凹透镜覆盖)，则需要发光面的高度略小于相邻凹透镜的节距。需要说明的是，发光的高度所指的具体尺寸与激光器的形状有关，如果激光器是圆形，则高度是指整个激光器的直径；如果激光器是长方形，则高度是指激光器的宽度或者长度。
参考图9，展示本申请又一实施例中发光面放大的示意图。
图9中从左至右分别展示M小于但近似于1，N＝1；M小于但近似于2，N＝2；M小于但近似于4，N＝4三种情况下的8个发光面示意图。也即是说，最左侧对应M小于但近似于1，N＝1，呈现为8个发光面11～24不放大，并按一列排布；中间对应M小于但近似于2，N＝2，呈现为8个发光面均得到接近4倍放大，并按2列排布；最右侧对应M小于但近似于4，N＝4，呈现为8个发光面均得到接近16倍放大，且按4列排布。
图中还示例性地展示了对应每个激光器设置的凹透镜，例如图中环绕在发光面11外的环形Z。为避免激光器的发射信号避开凹透镜，可设置凹透镜需完整地覆盖发光面的约束条件。若设放大前的发光面高度为y0，放大近似于2倍后的发光面高度为y1，放大近似于4倍后的发光面高度为y2，为了使凹透镜皆能覆盖发光面，纵向的相邻凹透镜的节距例如y2需小于Z的高度(Z是圆形则高度就是其直径长度)。
在以上实施例所描述的限制下，可以得到下式：
放大后的发光面高度＝M*放大前发光面高度＜凹透镜节距＝主透镜组单元(等效凸透镜)焦距*垂直角分辨率*N；
关于：放大后的发光面高度<凹透镜节距；直观可见，图9中发光面放大近似2倍和4倍的发光面(11～24)的边缘示意性地绘制为虚线，而凹透镜的边缘示意性地绘制为实线，每个发光面所对应的虚线边缘均落入对应的凹透镜的实线环中。图中示意性地标示了放大近似4倍时候的发光面11落入凹透镜Z中。
关于：放大后的发光面高度＝M*放大前发光面高度；参考图9，如果发光面放大2倍，放大后的发光面高度为y1；如果发光面放大4倍，放大后的发光面高度为y2；放大前像素高度为y0，y2＝2*y1＝4*y0。
关于：凹透镜节距＝主透镜组单元焦距*垂直角分辨率*N，参考图9，凹透镜节距为相邻发光面中心之间的间距，图示中以间隔b为尺寸衡量单位，间隔b等于主透镜组单元焦距*垂直角分辨率，凹透镜节距即等于N倍的间隔b。如图9中所示，发光面放大两倍时，凹透镜节距为2b；发光面放大四倍时，凹透镜节距为4b。
可以根据M*放大前发光面高度<主透镜组单元焦距*垂直角分辨率*N，代入y0、f"、d/f，得到M*y0<b*N；如果不考虑工艺的限制，可以使相邻发光面几乎无间隔地邻设的话，y0≈b。因此，可以得到M(放大倍数)<N(交错排布的列数)，换言之，整个光路也不能无限制的放大，激光器可排列的列数N是放大倍数M的上限，即M<N。
如图6和图9，可以看到，M＝N＝1，M＝N＝2，M＝N＝4的三种情况下，在M<N的限制下，使得发光面排布后在高度方向的增加极小，相比于整个激光雷达尺寸而言可以忽略，即h0≈h1≈h2，从而实现在通过延长发射模块的焦距来提升激光雷达的测远能力的同时，又不会有高度方向的增加。
需要说明的是，接收端也是类似，若探测器阵列设置为交错排布的Q列探测器，第二光学组件的等效焦距为主透镜组单元的焦距的P倍，则Q>P，此处不再赘述。
以下通过多种激光雷达的实施例来说明上述方案的应用及功效。
如图10A所示，展示本申请一种实施例中旁轴光路结构的激光雷达的结构示意图。图10B展示本申请一种实施例中旁轴光路结构的激光雷达的激光器阵列和光探测部件正视的布局结构示意图。图10C展示图10B中激光雷达的测距仿真结果的曲线示意图。
如图10A所示，本示例中展示的是旁轴光路结构的激光雷达100，即发射信号的发射光路和回波信号的探测光路之间没有重叠段。在可能的具体实例中，所述激光雷达100可以是机械式激光雷达100，即包含旋转机构。所述激光雷达100的线数可以是32线以上，例如32线、64线、128线、256线等，其中128线，如果激光器1011和光探测器1041是1对1形成通道的话，也就表示有128个激光器1011和128个光探测器1041一一对应形成128个通道。多个激光器1011可以按多列排布。
在光发射模块1000中，激光器阵列包括激光器阵列1001，其中的各个激光器1011输出的发射信号光(可先经微透镜阵列处理)依次经第一光学组件1002的各个凹透镜1022和主透镜组单元1021(等效为凸透镜)处理，之后再出射激光雷达100，照射到障碍物P后反射形成回波信号。回波信号进入激光雷达100，依次经可选的第二光学组件1005的接收透镜组单元1051(等效为凸透镜)和各凹透镜1052收束至射向光探测模块1003。光探测模块1003中的光探测部件可以包括光探测器阵列1004，其中与回波信号相应通道的光探测器1041可探测到该回波信号。
其中，所述第一光学组件1002和第二光学组件1005分别形成延长的等效焦距，比如是原透镜组焦距的M倍，使得激光雷达100的测远能力提升，以能探测到更远的障碍物P。可选的，M可以是1.5倍以上的放大倍数。
基于图10A的旁轴光路结构的激光雷达100，可以采用例如图10B所展示的激光器阵列1001B和光探测器阵列1004B的布局结构。其中，两列激光器1011B非对齐地排布，两列光探测器1041B非对齐地排布。
基于采用基于图10A和图10B的旁轴光路结构的激光雷达100进行测距仿真，仿真结果如图10C所示。在图10C中，横轴为可测的最远距离(对应激光雷达100的测远能力)，纵轴为探测概率。可以看到，在90％的探测概率情况下，可测最远距离达到大约90米左右，而未采用本申请实施例的方案时，同类型的激光雷达的可测最远距离大约只有45米左右。故而，通过本申请实施例中的延长焦距以提升测远距离的方案，实际提升测远能力可达2倍以上。
除了应用在旁轴光路结构的激光雷达，在一些实施例中，本申请的方案还可以 应用在同轴光路结构的激光雷达，同轴指的是发射光路和探测光路之间存在相同的光路段。
如图11A所示，展示本申请一种实施例中同轴光路结构的激光雷达的结构示意图。
所述激光雷达包括：
设于重叠光路段的分光单元1103，适于从连通激光器阵列(本示例中为激光器阵列1101)的第一光路段中接收发射信号并经偏折或直射至所述重叠光路段，且适于从所述重叠光路段中接收回波信号并经直射或偏折至连通光探测器阵列1102的第二光路段；其中，所述第一光学组件中的主透镜组单元1104(如前述实施例中主透镜组)和第一发散单元1105(如前述实施例中凹透镜阵列)分别设于所述重叠光路段和第一光路段。
示例性地，所述分光单元1103可以是例如反光镜或偏振单元(如偏振片、偏振棱镜等)实现。图示示例中，激光器阵列输出的发射信号可以先经设置在第一光路段中的第一发散单元1105进行发散后进入分光单元1103，以由分光单元1103重定向(例如转折，如反射等)到重叠光路段(即被发射光路和探测光路共用的光路段)，经重叠光路段向左传输至主透镜组单元1104，经汇聚后出射，如图中黑色实线箭头所指示的发射光路。
进一步的，所述激光雷达还包括扫描单元1106(比如振镜、转镜)，以选择所需探测的通道的发射信号出射于激光雷达，通过所述主透镜组单元1104(图中示例性地展示了一个凸透镜)和第一发散单元1105配合以得到光发射模块的相对延长的等效焦距；以及，选择所需探测的通道的回波信号转折进入所述重叠光路段，向右往分光单元1103传输，经分光单元1103重定向(例如直射)至连通光探测部件(本示例中为激光器阵列1102)的第二光路段中，并沿第二光路段传输至激光器阵列1102，如图中灰色箭头所指示的接收光路。可能的，所述扫描单元1106可以包括一个或多个谐振单轴微机电系统(MEMS)振镜，以进行二维转动来选择所需探测通道的发射信号、回波信号进行传输。
在图示的可选示例中，在第二光路段中可以仅设置凸透镜1107以用于汇聚回 波信号，而不设置凹透镜。
通过配置光探测模块(RX端)和光发射模块(TX端)的焦距之间成一定比例关系，例如光探测模块的等效焦距数倍于(比如K＝3.5倍)第一光学组件的等效焦距；且可选的，激光器阵列的激光器阵列1101中，激光器可以使用边缘发射激光器(EEL)，以利用其发光面积小，亮度高的特性来照亮整个接收视场；光探测部件的光探测器阵列1102中，光探测器可以采用SiPM实现，光探测器阵列1102的尺寸也可以是数倍(比如K)于激光器阵列1101。从而，获得超长的探测焦距使得激光雷达的测距能力大幅度提升，例如从200米提升至300米等。
再如图11B所示，与图11A实施例的差别在于，激光器阵列的激光器阵列1101B中，激光器可以由VCSEL实现，以代替图11A实施例中的EEL，以进一步提高测距能力。相应的，本示例中可以对应设置微透镜阵列1109(还可以在第一光路段中另外增加凸透镜等)以压缩VCSEL的发散角，留出出光孔径的外围给探测光路。见图11B中，激光器的发散角被压缩而沿同轴光路的中间部分传输(以细实线箭头表示)，而回波信号在相对该中间部分的外围区域传输(以粗实线箭头表示)。
再请参考图12A和图12B所示，用于说明本申请实施例中将每个激光器至对应的凹透镜之间的光路段封装于套筒中的功效。其中，所述套筒内壁为吸收材质，以吸收光。
如图12A所展示的光路图，以发射光路为例。在不使用套筒的情况下，虽然也能实现对发光面的放大，但需要保持主透镜组焦距*垂直角分辨率的大小，否则激光器1201上靠近边缘部分的发光点的发射信号(比如C)可能会避开凹透镜(凹透镜1202)而进入主透镜组单元(如主透镜组，此图示中未绘制)，这部分未经过第一发散单元的发射信号会产生脱焦，经过主透镜组单元以较大发散角送出之后很有可能形成的回波信号会被其它通道的光探测器所接收，从而形成串扰。因此，可以通过吸收材质吸收这部分潜在的杂光。
如图11B所展示的光路图，通过套筒1203来封装激光器1201至对应的凹透镜1202之间的光路段，就可以使原本避开凹透镜1202的发射信号被反射而限制必须经过凹透镜1202然后到主透镜组单元，那么这一部分发射信号就不会产生脱焦， 如此即可实现和凹透镜尺寸相同或相近的发光面积。这对于VCSEL来说，因为发光面积提高了，相应的峰值功率也提高了。
相类似地，如图12C所示，用于说明本申请实施例中回波信号对应的凹透镜1302之间的光路段封装于套筒1303中后至每个探测器1301的功效，光路类似于发射端，也是吸收掉潜在的杂光，进而提高信噪比，具体此处不再赘述。
综上所述，本申请提供激光雷达包括：以线阵或者面阵排布的激光器阵列，设置于第一光学组件的焦平面，以及第一光学组件，设于所述发射光路，形成有大于发射端的主透镜组单元的焦距的等效焦距；和/或，以线阵或者面阵排布的光探测器阵列，设置于第二光学组件的焦平面，以及所述第二光学组件，设于接收光路，形成有大于接收端的主透镜组单元的焦距的等效焦距。本申请实施例中，通过光发射端的第一光学组件的设置，来提高点云视场角面积内的功率密度，和/或，通过接收端的第二光学组件的设置，来降低点云视场角面积内的背景光噪声功率，进而均可提高雷达的测距能力。
上述实施例仅例示性说明本申请的原理及其功效，而非用于限制本申请。任何熟悉此技术的人士皆可在不违背本申请的精神及范畴下，对上述实施例进行修饰或改变。因此，举凡所属技术领域中具有通常知识者在未脱离本申请所揭示的精神与技术思想下所完成的一切等效修饰或改变，仍应由本申请的权利要求所涵盖。

Claims (17)

  1. 一种激光雷达，其特征在于，包括：
    光发射模块，设置于第一光学组件的焦平面，包括：激光器阵列，以线阵或者面阵排布，适于发出发射信号，所述发射信号沿发射光路传输；
    第一光学组件，设于所述发射光路，形成有大于第一预设值的等效焦距，以提高点云视场角面积内的功率密度，进而提高雷达的测距能力；其中，所述第一预设值为主透镜组单元的焦距；
    光探测模块，包括：光探测器阵列，以线阵或者面阵排布，适于从接收光路探测所述发射信号遇到障碍物后被反射的回波信号。
  2. 根据权利要求1所述的激光雷达，其特征在于，所述第一光学组件包括：主透镜组单元，适于准直发射信号；
    还包括：第一发散单元，配置在激光器阵列和主透镜组单元之间，适于发散经所述主透镜组单元准直后的发射信号，以使得所述第一光学组件具有长于第一预设值的等效焦距。
  3. 根据权利要求2所述的激光雷达，其特征在于，所述第一光学组件的等效焦距为主透镜组单元的焦距的M倍，M>1，以使每个激光器的发光面的面积提高M 2倍。
  4. 根据权利要求2所述的激光雷达，其特征在于，所述第一发散单元包括：凹透镜阵列，其中每个凹透镜对应于一个发射通道。
  5. 根据权利要求4所述的激光雷达，其特征在于，所述凹透镜阵列中相邻凹透镜之间的竖直节距不小于所述激光器的发光面的高度。
  6. 根据权利要求1所述的激光雷达，其特征在于，所述激光器阵列包括交错排布的N列激光器，所述第一光学组件的等效焦距为主透镜组单元的焦距的M倍，N>M。
  7. 根据权利要求4所述的激光雷达，其特征在于，每个所述激光器至对应的凹透镜之间的至少部分光路段被封装于套筒中，所述套筒内壁为吸收材质。
  8. 根据权利要求1或4所述的激光雷达，其特征在于，所述第一光学组件还包括： 微透镜阵列，其中的每个微透镜对应于激光器的一个发光点设置。
  9. 根据权利要求1所述的激光雷达，其特征在于，所述激光雷达为具有转动机构的机械式激光雷达或MEMS激光雷达。
  10. 根据权利要求1所述的激光雷达，其特征在于，所述激光器阵列包括多个激光器，所述激光器为垂直腔面发射激光器或边缘发射激光器或光子晶体结构表面发射半导体激光器；和/或，所述光探测器为单光子雪崩二极管或硅光电倍增管。
  11. 一种激光雷达，其特征在于，包括：
    光发射模块，包括：激光器阵列，以线阵或者面阵排布，适于发出发射信号，所述发射信号沿发射光路传输；
    光探测模块，设置于第二光学组件的焦平面，包括：光探测器阵列，以线阵或者面阵排布，适于从接收光路探测所述发射信号遇到障碍物后被反射的回波信号；
    以及所述第二光学组件，设于接收光路，形成有大于第二预设值的等效焦距，以降低点云视场角面积内的背景光噪声功率，进而提高雷达的测距能力；其中，所述第二预设值为主透镜组单元的焦距。
  12. 根据权利要求11所述的激光雷达，其特征在于，所述第二光学组件包括：接收透镜组单元，适于汇聚接收信号；
    所述第二光学组件还包括：第二发散单元，配置在光探测器阵列和接收透镜组单元之间，以使得所述第二光学组件具有长于第二预设值的等效焦距，适于发散经所述接收透镜组单元汇聚后的接收信号。
  13. 根据权利要求11所述的激光雷达，其特征在于，所述第二光学组件的等效焦距为主透镜组单元的焦距的P倍，P>1，以使接收角面积缩小P 2倍。
  14. 根据权利要求12所述的激光雷达，其特征在于，所述第二发散单元包括：凹透镜阵列，其中每个凹透镜对应于一个探测器设置。
  15. 根据权利要求14所述的激光雷达，其特征在于，所述凹透镜阵列中相邻凹透镜之间的竖直节距大于每个探测器的接收面的高度。
  16. 根据权利要求11所述的激光雷达，其特征在于，所述探测器阵列包括交错排布的Q列探测器，所述第二光学组件的等效焦距为主透镜组单元的焦距的P倍，Q>P。
  17. 根据权利要求11所述的激光雷达，其特征在于，包括：第一光学组件，设于所述发射光路，形成有大于第一预设值的等效焦距，以提高点云视场角面积内的功率密度，进而提高雷达的测距能力；其中，所述第一预设值为第一光学组件中主透镜组单元的焦距；所述第一光学组件和第二光学组件的等效焦距成一定比例关系。
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