Laser radar and method for detecting with the same

Abstract

The present invention relates to a laser radar comprising a laser configured to emit a laser beam, an emission lens arranged downstream of the optical path of the laser and configured to shape the laser beam and to emit a probe beam, the emission lens having an aperture stop region, a receiving lens configured to receive the probe beam after reflection outside the laser radar, and a compensating mirror arranged in the aperture stop region of the emission lens and configured to receive at least a portion of the laser beam and / or of the probe beam and to deflect it towards the receiving lens.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic technology, and in particular to a lidar and a method for detection using the lidar. Background Technology

[0002] LiDAR consists of a laser emitting system and a detection and receiving system. The emitted laser beam is reflected after encountering a target and received by the detection system. By measuring the round-trip time of the laser beam, the distance to the corresponding target point can be measured (e.g., using time-of-flight methods). After scanning and detecting the entire target area, three-dimensional imaging can ultimately be achieved. LiDAR has important applications in autonomous driving systems, requiring it to possess characteristics such as high imaging frame rate, high resolution, long-range ranging capability, small size, high reliability, and low cost.

[0003] Currently, most lidar systems have separate transmitting and receiving systems (unlike cases where the transmitting and receiving systems share a single lens). To test distant targets, the laser beam is aligned with the detector's field of view at a distance (e.g., 200m). Figure 1 As shown, within a certain distance range close to the lidar, the laser beam emitted does not overlap with the detector's field of view at all. Therefore, within this distance range, the lidar detector cannot receive the signal light reflected from the target, or the received signal light is extremely weak. This is the near-range blind zone.

[0004] The reason for near-range blind spots or weak near-range LiDAR signals is the non-common optical path structure with separate transmit and receive optical paths. That is, the laser emission optical path and the signal receiving optical path are not completely overlapped in a common optical path structure. (Refer to...) Figure 1 There is a horizontal translation between the transmitting lens and the receiving lens. The applicant identified two possible reasons.

[0005] First reason: Reference Figure 1 The near-range blind zone is the area where the emitted laser beam does not overlap with the receiving field of view at close range. This means that the lidar detector "cannot see" the emitted laser beam in this area; that is, the detector cannot receive the signal light reflected back from the target in this area.

[0006] The second reason: (refer to) Figure 2 If there is a target within the near-range blind zone, the image point formed by the signal light reflected from the near-range target through the receiving lens is not on the focal plane of the receiving lens, but behind it. Furthermore, because the near-range target is above the optical axis of the receiving lens, its image point must be below the optical axis of the receiving lens. Considering these two factors, the relative position of the focal point of the reflected light from the near-range target to the detector is as follows: Figure 2As shown. Within the near-range blind zone of the lidar, the lidar detector cannot receive the target's reflected signal at all.

[0007] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0008] In view of at least one deficiency of the prior art, the present invention provides a lidar comprising:

[0009] A laser, configured to emit a laser beam;

[0010] An emitting lens is disposed downstream of the optical path of the laser and configured to shape the laser beam and emit a probe beam. The emitting lens has an aperture stop region.

[0011] A receiving lens, configured to receive the probe beam reflected off the lidar surface; and

[0012] A compensating mirror, disposed in the aperture stop region of the transmitting lens, is configured to receive at least a portion of the laser beam and / or the probe beam and deflect it toward the receiving lens.

[0013] According to one aspect of the invention, the aperture stop region is located on the side of the emitting lens closer to the laser, or on the side farther from the laser, or in the middle of the emitting lens.

[0014] According to one aspect of the invention, the compensation mirror comprises one or more of an optical wedge, a microprism, a diffractive optical element, or a combination thereof with a spherical lens or a cylindrical lens, which is fixed in the aperture stop region by an adhesive or a bracket.

[0015] According to one aspect of the invention, the compensation mirror is located in the aperture stop region near the receiving lens.

[0016] According to one aspect of the invention, wherein the transmitting lens and the receiving lens are juxtaposed along a horizontal direction, and the positions of the compensating mirror satisfy the following relationship:

[0017]

[0018] L′=LD / tanθ1

[0019] Where θ1 is the beam deflection angle, the angle between the beam deflected by the compensating mirror and the beam received by the receiving lens.

[0020] d is the distance from the installation position of the compensating mirror to the center of the receiving lens.

[0021] D is the diameter of the receiving lens.

[0022] The range between L and L′ is the region of near-field signal enhancement. The distance between the intersection of the beam deflected by the compensating mirror and the receiving beam and the vertex of the receiving lens is L at its farthest point and L′ at its closest point.

[0023] According to one aspect of the invention, the angle between the beam deflected by the compensating mirror and the main field of view of the lidar is smaller than the angle between the ghost line field of view and the main field of view.

[0024] The lidar further includes a receiving end reflector structure and a detector located sequentially downstream of the optical path of the receiving lens, and a ghost line elimination device located between the receiving end reflector structure and the detector to block the light beam that would cause ghost lines in the point cloud of the lidar from entering the detector.

[0025] According to one aspect of the invention, the ghost line elimination device includes an aperture, and the aperture and the detector satisfy the following relationship:

[0026]

[0027] Where D is the diameter of the receiving lens, f is the focal length of the receiving lens, h is the distance from the aperture to the detector, and d1 is the width of the aperture.

[0028] According to one aspect of the invention, the aperture is a strip-shaped or circular aperture, and the aperture is made of any of the following materials: metal, glass that can absorb or reflect light, or ceramic.

[0029] According to one aspect of the invention, the ghost line elimination device includes a light-blocking sheet.

[0030] According to one aspect of the invention, the ghost line elimination device is configured to block light beams that have not been reflected once by the reflector structure.

[0031] According to one aspect of the invention, the receiving end reflector structure includes a first reflector and a second reflector arranged opposite to each other, the detector includes a photodiode, and the ghost line elimination device is configured to block beams other than those beams reflected once by the first reflector and the second reflector, respectively.

[0032] The present invention also provides a method for detection using the lidar described above, comprising:

[0033] A laser beam is emitted through the laser;

[0034] The laser beam is shaped by the emitting lens to produce a detection beam.

[0035] The compensation mirror deflects at least a portion of the laser beam and / or the probe beam toward the receiving lens.

[0036] The receiving lens receives the beam of light reflected by external obstacles of the lidar from the detection beam.

[0037] The solution proposed in this invention can reduce the near-range blind zone of a split-transmitter lidar and / or enhance the signal strength for near-range detection. Attached Figure Description

[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0039] Figure 1 and Figure 2 A schematic diagram illustrating the possible causes of near-field blind spots is shown.

[0040] Figure 3 A schematic diagram of a lidar according to an embodiment of the present invention is shown;

[0041] Figure 4 A schematic diagram is shown showing multiple laser beams emitted from the laser on the focal plane of the emitting lens passing through an aperture stop;

[0042] Figure 5 A schematic diagram of ghost lines in a lidar point cloud according to an embodiment of the present disclosure is shown;

[0043] Figure 6 A schematic diagram showing a ghost line caused by a transmitter according to an embodiment of the present disclosure is shown;

[0044] Figure 7 A schematic diagram showing a ghost line caused by a receiver according to an embodiment of the present disclosure is shown;

[0045] Figure 8A A schematic diagram of a receiving system for suppressing ghost lines with an aperture according to an embodiment of the present disclosure is shown;

[0046] Figure 8B A schematic diagram of the parameters of the aperture and the detector is shown;

[0047] Figure 9 A schematic diagram of a strip aperture according to an embodiment of the present disclosure is shown;

[0048] Figure 10 A schematic diagram of a circular aperture according to an embodiment of the present disclosure is shown;

[0049] Figure 11A schematic diagram of a receiving system for suppressing ghost lines with a light-blocking sheet according to an embodiment of the present disclosure is shown;

[0050] Figure 12 A schematic diagram of a light-blocking sheet according to an embodiment of the present disclosure is shown;

[0051] Figure 13 A method for suppressing ghost lines in a point cloud of a lidar system according to an embodiment of the present disclosure is shown.

[0052] Figure 14 A schematic diagram of a lidar according to a preferred embodiment of the present invention is shown;

[0053] Figure 15 A schematic diagram of a lidar according to a preferred embodiment of the present invention is shown;

[0054] Figure 16 A schematic diagram of a lidar according to a preferred embodiment of the present invention is shown;

[0055] Figure 17 A schematic diagram of a lidar according to a preferred embodiment of the present invention is shown; and

[0056] Figure 18 A method for detection using lidar according to an embodiment of the present invention is shown. Detailed Implementation

[0057] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0058] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0059] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0060] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0061] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0062] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0063] First aspect

[0064] Figure 3 A schematic diagram of a lidar 100 according to an embodiment of the present invention is shown below. Figure 3 Detailed description. For example... Figure 3As shown, the lidar 100 includes a laser 101, a emitting lens 102, a receiving lens 103, and a detector 105. The laser 101, for example, is a side-emitting laser (EEL) or a vertical-cavity surface-emitting laser (VCSEL), configured to emit a laser beam. The laser beam is incident on the emitting lens 102 downstream of the optical path. The emitting lens 102 is configured to shape the laser beam and emit a probe beam; the emitting lens 102 has an aperture stop region. The probe beam is incident on an object OB outside the lidar 100, causing diffuse reflection. Part of the reflected beam returns to the receiving lens 103 and is focused onto the detector 105. The detector 105 is, for example, a photodiode, such as an avalanche photodiode (APD), or a single-photon detector (such as a SiPM or SPAD). After receiving the reflected beam, the detector 105 generates an electrical signal that is related to the intensity or number of photons of the beam. The subsequent circuit amplifies and filters the electrical signal to obtain one or more data signals of parameters such as distance, angle, and reflectivity of the obstacle, thereby forming point cloud data of the lidar for subsequent processing. This will not be elaborated here.

[0065] Furthermore, according to embodiments of the present invention, in Figure 3 In order to reduce the blind zone of the lidar 100, a compensation mirror 104 is provided in the aperture stop region of the emitting lens 102. The aperture stop region is an inherent parameter of the emitting lens (or lens group). The compensation mirror 104 is configured to receive at least a portion of the laser beam emitted by the laser 101 and / or the probe beam emitted from the emitting lens 102, and deflect it toward the receiving lens 103. Figure 3 As shown, the receiving lens 103 is, for example, juxtaposed with the transmitting lens 102 in the horizontal direction, and the compensating mirror 104 deflects the probe beam toward one side of the receiving lens 103 in a certain direction.

[0066] Those skilled in the art will readily understand that the emitting lens 102 may comprise a single lens or a lens group consisting of multiple lenses, both of which fall under the category of emitting lenses as referred to in this invention. When the emitting lens 102 is a single lens, its aperture stop region can be located on either side of the emitting lens 102 according to the optical design, such as... Figure 3The emitting lens 102 can be located on either the left or right side, i.e., the side closer to or farther from the laser 101. If the emitting lens 102 is a lens group composed of multiple lenses, its aperture stop region can be located on either side of the lens group, or in the middle of the emitting lens, i.e., between two lenses, depending on the optical design. When the compensating mirror 104 is located closer to the laser 101, it receives and deflects the laser beam emitted by the laser 101, which is then shaped by the emitting lens and emitted as a probe beam. When the compensating mirror 104 is located farther from the laser 101, it receives and deflects the probe beam. When the compensating mirror 104 is located in the middle of the emitting lens, it receives and deflects a partially shaped laser beam. All of these are within the scope of this invention.

[0067] According to a preferred embodiment of the present invention, the compensation mirror 104 includes one or more of an optical wedge, a microprism, and a diffractive optical element, or combinations thereof with a spherical lens or a cylindrical lens, as long as it enables at least a portion of the laser beam emitted from the laser 101 and / or the probe beam emitted from the emitting lens 102 to be deflected toward the receiving lens 103. The compensation mirror 104 can be fixed in the aperture stop region by means of adhesive, bracket, etc.

[0068] exist Figure 3 In this embodiment, by providing a compensation mirror 104 in the transmission system, a portion of the emitted beam (e.g., a beam emitted by a laser, or a detection beam emitted by a transmitting lens) is deflected at a specific angle toward the receiving field of view of the detector. Therefore, the beam emitted through the compensation mirror 104 is positioned very close to the lidar. Figure 3 Point A) in the image begins to overlap with the detector's receiving field of view, thereby reducing the near-range blind zone. Figure 3 As shown, the new blind zone is significantly smaller than the original blind zone.

[0069] In the above technical solution, a compensation mirror 104 is provided in the aperture stop region of the transmitting system. The aperture stop region is an inherent parameter of the transmitting lens (or lens group), and can be located on one side of the transmitting lens (group) or in the middle of the transmitting lens group, depending on the system optical design. Figure 4 The illustration shows a configuration where multiple lasers (at different heights) are positioned on the focal plane of the emitting lens (group) 102, emitting laser beams. Three lasers, 101-1, 101-2, and 101-3, are schematically shown. In the aperture stop region of the emitting lens, the beams of the multiple lasers overlap, thus requiring only a single compensation mirror 104 to achieve proportional compensation for the multiple laser beams. Figure 4 It is the aperture stop region (e.g.) Figure 4The diagram (shown by the dashed circle) shows the laser beams emitted from multiple lasers overlapping in the aperture stop region. The compensating mirror 104 separates a portion of the detection beam, altering its direction (and potentially its divergence angle), so that it begins to overlap with the detector's field of view from a position very close to the lidar. This allows the detector to receive the signal light reflected from nearby targets, thus reducing the lidar's near-range blind zone.

[0070] According to a preferred embodiment of the present invention, the compensation mirror 104 is located in the aperture stop region near the receiving lens. Figure 3 For example, in a top view of the lidar 100, the transmitting lens 102 and the receiving lens 103 are arranged side by side in the horizontal direction and have approximately the same vertical height.

[0071] Second aspect

[0072] This application claims priority to PCT International Application PCT / CN2019 / 103724, the contents of which are incorporated herein by reference in their entirety.

[0073] For lidar with a folded mirror structure (where two or more mirrors between the lidar receiving lens and detector form a mirror structure to fold the optical path), a smaller structural size can be obtained with the same lens focal length. This is the architecture of a multi-line mechanical lidar in one embodiment of the present invention. When the lidar with the folded mirror structure scans a high-reflectivity plate (high-reflectivity obstacle, such as a road sign) at close range, such as... Figure 5 As shown, ghost lines appear in the obtained LiDAR point cloud, meaning that some point clouds that do not actually exist appear on the left and right sides of the high-reflectivity plate. During autonomous driving, when the LiDAR scans a road sign with high reflectivity, it will identify the ghost lines generated by the sign in the LiDAR point cloud as obstacles, causing the vehicle to stop automatically.

[0074] Through extensive research and experimentation, the applicant discovered that ghost lines can be generated in lidar with folded reflector structures due to a variety of reasons. Figure 6 The diagram illustrates the ghost line phenomenon caused by the transmitter. At the lidar transmitter, because the transmittance of the coating on the transmitting lens 22 is not 100%, the laser emitted by the laser 23 undergoes multiple reflections at each glass-air interface of the transmitting lens 22 and the photomask 21 before exiting. The final illumination of the near-range target is a very large spot. Although the energy of the spot is very low except for the very center, it is still possible to detect it when the reflectivity of the target is high.

[0075] Figure 7 A schematic diagram illustrating ghost lines caused by factors at the receiver is shown. At the lidar receiver, in the optical path of the folded reflectors, besides the main field of view where the beam is reflected once on each reflector, there are also fields of view where the beam is not reflected on any reflector and fields of view where the total number of reflections on any reflector exceeds the number of reflectors. When the lidar scans, the detector at the receiver receives beams that are not reflected on any reflector and / or whose total number of reflections on any reflector exceeds the number of reflectors, thus generating ghost lines. Figure 7 As shown, the field of view of the lidar includes: a main field of view (FOV B) and ghost line fields of view (FOV A and FOV C). The main field of view (FOV B) is the field of view where the beam is reflected once on the first reflector 311 and once on the second reflector 312. The ghost line field of view (FOV A) is the field of view where the beam is not reflected on the first reflector 311 and once on the second reflector 312. The ghost line field of view (FOV C) is the field of view where the beam is reflected more than twice in total on the first reflector 311 and once on the second reflector 312.

[0076] Assuming the lidar scans counterclockwise, when the main field of view (FOV) B is still outside the high-reflectivity plate, the ghost line field of view (FOV) A can already see the high-reflectivity plate. Because the high-reflectivity plate is relatively close, it is illuminated by a large spot of light from the transmitter. Therefore, the detector 32 receives the light beam through the optical path of the ghost line field of view (FOV) A, generating a ghost line on the right side of the high-reflectivity plate. As the lidar continues scanning, when the main field of view (FOV) B moves away from the high-reflectivity plate and the ghost line field of view (FOV) C is still on the high-reflectivity plate, the detector 32 can still receive the reflected light beam from the high-reflectivity plate through the optical path of the ghost line field of view (FOV) C, thus generating a ghost line on the left side of the high-reflectivity plate. Alternatively, when the lidar scans clockwise, the ghost line field of view (FOV C) sees the high-reflectivity plate before the main field of view (FOV B). When the main field of view (FOV B) leaves the high-reflectivity plate, the ghost line field of view (FOV A) is still on the high-reflectivity plate. The ghost line fields of view (FOV A) and (FOV C) result in ghost lines on the right and left sides of the high-reflectivity plate, respectively. The detector 32 is, for example, a photodiode, such as an avalanche photodiode (APD), or a single-photon detector (such as a SiPM or Spad).

[0077] To reduce or suppress the aforementioned ghost line problem, this disclosure provides a receiving system for lidar, comprising: a receiving lens, a reflector structure, a detector, and a ghost line elimination device. The reflector structure is disposed downstream of the optical path of the receiving lens, the detector is disposed downstream of the optical path of the reflector structure, and the ghost line elimination device is disposed between the reflector structure and the detector. An external light beam enters the reflector structure through the receiving lens, undergoes reflection by multiple reflectors within the reflector structure to change its propagation direction, and then passes through the ghost line elimination device. Part or all of the light beam that would cause ghost lines in the lidar point cloud is blocked by the ghost line elimination device, and finally, the remaining light beam reaches the detector.

[0078] The lidar field of view of embodiments of this disclosure includes a main field of view and a ghost line field of view. The main field of view is the field of view where the beam is reflected once on each mirror, and the ghost line field of view is the field of view where the beam is not reflected on any mirror and / or the total number of reflections on mirrors exceeds the number of mirrors. Because there is a gap between the ghost line field of view and the main field of view at a specific position on the optical path, an aperture stop and / or a light-blocking device can be used as a ghost line elimination device to block the optical path of the ghost line field of view, thereby suppressing the generation of ghost lines in the lidar point cloud by near-range high reflectivity plates.

[0079] The following is combined with Figures 8A-10 An embodiment of this disclosure will be described in detail.

[0080] Figure 8A A schematic diagram of a receiving system 40 applicable to lidar according to an embodiment of the present disclosure is shown. Figure 8A As shown, the receiving system 40 for use with lidar includes: a receiving lens 41, a reflector structure, an aperture 44, and a detector 43. The reflector structure includes a first reflector 421 and a second reflector 422. The receiving lens 41 receives external light beams, such as the beam reflected back from an external obstacle by the output laser beam of the lidar. The first reflector 421 and the second reflector 422 are disposed downstream of the optical path of the receiving lens 41, facing each other. The light beam received by the receiving lens is incident on the reflector structure, and the propagation direction of the light beam is changed by the reflection of the first reflector 421 and the second reflector 422. The detector 43 is disposed downstream of the optical path of the reflector structure. It receives the light beam from the reflector structure and generates an electrical signal. The electrical signal undergoes further signal processing, such as filtering, amplification, AD conversion, and digital signal processing, to form point cloud data for the lidar. An aperture 44 is positioned between the reflector structure and the detector 43, allowing light from the main field of view to pass through and be incident on the detector 43, while simultaneously restricting the passage of some light beams. For example, it can partially or completely block light beams that would cause ghost lines in the point cloud of the lidar, preventing these ghost-line-causing beams from incident on the detector. Figure 8A As shown, the beam corresponding to the main field of view (FOV) B is deflected after passing through the receiving lens 41, then incident on the first reflecting mirror 421 and reflected by it. It is then reflected by the second reflecting mirror 422, and finally, the beam reflected by the second reflecting mirror 422 passes through the aperture 44 and illuminates the detector 43, generating an electrical signal. The beam corresponding to the ghost line field of view (FOVA), after passing through the receiving lens 41, does not incident on the first reflecting mirror 421 or the second reflecting mirror 422, but directly illuminates the aperture 44, where it is blocked or absorbed, preventing it from illuminating the detector 43 and causing ghost lines in the point cloud of the lidar. The beam corresponding to the ghost line field of view (FOV C) passes through the receiving lens 41 and is incident on the first reflecting mirror 421. It is reflected by the first reflecting mirror 421 to the second reflecting mirror 422, and then reflected by the second reflecting mirror 422 back to 421. Subsequently, it is reflected once by the first reflecting mirror 421 and once by the second reflecting mirror 422, and finally incident on the aperture 44. It is blocked or absorbed by the aperture 44 to prevent it from illuminating the detector 43 and generating ghost lines in the lidar point cloud.

[0081] Therefore, by setting an aperture 44 between the reflector structure and the detector 43 as a ghost line elimination device, it is possible to at least partially block the light rays that would cause ghost lines in the point cloud of the lidar from entering the detector 43.

[0082] Furthermore, this is readily understood by those skilled in the art. Figure 8A In this embodiment, the number of reflectors is two, which is only illustrative. More reflectors may be included, such as three or four. This disclosure does not impose any limitation on the number of reflectors.

[0083] According to a preferred embodiment of this disclosure, when the distance between the aperture 44 and the detector 43 satisfies a certain relationship, the beams of the ghost line field of view FOV A and FOV C can be better blocked.

[0084] Specifically, assuming the diameter of the receiving lens 41 is D, its focal length is f, the distance from the aperture 44 to the detector 43 (e.g., a single APD, or an APD linear array or area array) is h, and the horizontal width of the aperture 44 is d1 (e.g., ... Figure 8B As shown), when the horizontal width d1 of the aperture 44 and the distance h from the aperture 44 to the detector 43 satisfy the following relationship, the beams of the ghost line field of view FOV A and FOV C can be better blocked:

[0085]

[0086] like Figure 8AAs shown, when the lidar scans counterclockwise or clockwise, the beams of the ghost line fields of view FOVA and FOV C are blocked by the aperture 44 and cannot reach the detector 43. However, the beam of the main field of view FOV B can reach the detector 43 through the aperture of the aperture 44. This achieves the suppression or even elimination of ghost lines generated by the near-range high reflectivity plate in the lidar point cloud, avoids false identification by the lidar, and improves detection accuracy.

[0087] As described above, the mirror structure may include multiple mirrors, and the ghost line elimination device, such as aperture 44, is configured to block light beams that have not been reflected once by the mirror structure. In this invention, a light beam reflected once by the mirror structure refers to a light beam reflected once by each mirror in the mirror structure (such as...). Figure 8A The field of view (FOV B) in the context of the mirror structure; a beam that has not been reflected once by the mirror structure refers to a beam that has not been reflected by at least one of the mirrors (such as...). Figure 8A The beam corresponding to the FOV A of the ghost line, or reflected more than twice by at least one of the mirrors (such as...). Figure 8A The beam corresponding to the field of view (FOV C) of the ghost line.

[0088] According to one embodiment of the receiving system disclosed herein, the material used to make the aperture may be metal, glass that can absorb or reflect light, or ceramic.

[0089] According to a receiving system based on an embodiment of the present disclosure, the aperture includes: a strip-shaped aperture or a circular aperture. Figure 9 A schematic diagram of an embodiment of the strip-shaped aperture of this disclosure is shown. Figure 10 A schematic diagram of an embodiment of the circular aperture of this disclosure is shown. Alternatively, the aperture of the aperture can also be square or elliptical; this disclosure does not impose any limitation on the shape of the aperture.

[0090] Figure 9 A schematic diagram of a strip aperture according to an embodiment of the present disclosure is shown, as follows: Figure 9 As shown, the aperture 52 has a strip-shaped aperture 51 with a horizontal width of d1. The aperture 52 is mounted on a bracket 53, for example, the aperture 52 can be attached to the bracket 53, which is positioned in front of a circuit board 55. The detectors 54 can be arranged in a linear array or a surface array on the circuit board 55. The distance from the aperture 52 to the detector 54 is h. d1 and h satisfy the constraints described above. For example, once we determine the horizontal width of the aperture aperture as d1, we can determine the distance h from the aperture 52 to the detector 54 by taking the equality sign of the above constraints. The number of linear arrays (columns) of the detectors 54 corresponds to the number of strip-shaped apertures in the aperture 52. Figure 9As shown, six rows of detectors 54 are arranged on the circuit board 55. Correspondingly, six strip-shaped holes 51 are arranged on the aperture 52 (the width of the strip-shaped hole 51 is d1, the center-to-center distance between adjacent holes 51 is set with reference to the center-to-center distance between adjacent detectors 54 on the circuit board 55, and the length of the strip-shaped hole is also set with reference to the length of the detectors 54 on the circuit board 55). This can block the beams from the ghost line field of view of all APD arrays. Of course, the number of strip-shaped holes can also be adjusted as needed to block the beams from the ghost line field of view of part of the APD array.

[0091] When the detector 54 rotates and scans around the lidar axis, the beams of the ghost field of view (FOV A) and FOV C are blocked by the left and right sides of the strip-shaped aperture 51 of the aperture 52, restricting the passage of the beams of the ghost field of view (FOV A) and FOV C. However, the beam of the main field of view (FOV B) can pass through the strip-shaped aperture 51 of the aperture 52 and reach the detector 54.

[0092] Figure 10 A schematic diagram of a circular aperture according to an embodiment of the present disclosure is shown, as follows: Figure 10 As shown, the aperture 62 has a circular aperture 61 with a horizontal width of d1 (i.e., the diameter of the aperture is d1). The aperture 62 is mounted on a bracket 63. For example, the aperture 62 can be attached to the bracket 63, which is positioned in front of the circuit board 65, in front of the detector 64 on the circuit board 65. The detector 64 can be, but is not limited to, a photodiode, such as an APD. The distance from the aperture 62 to the detector 64 is h. d1 and h satisfy the constraints described above. For example, once we determine the horizontal width of the aperture aperture as d1 (i.e., the diameter of the aperture), we can determine the distance h from the aperture 62 to the detector 64 by taking the equality of the above constraints. Each detector 64 corresponds to one circular aperture 61 of the aperture 62. The number of linear arrays (columns) of the detector 64 corresponds to the number of columns of the circular aperture 61 of the aperture 62, such as... Figure 10 As shown, three rows of detectors 64 are arranged on the circuit board 65, and correspondingly, three rows of circular holes 61 are arranged on the aperture 62 to block the beams from the ghost line field of view of all APD arrays. Of course, the number of circular holes can be adjusted as needed to block the beams from the ghost line field of view of part of the APD array.

[0093] When the detector 64 rotates and scans around the lidar axis, the beams of the ghost field of view (FOV A) and FOV C are blocked by the circular aperture 61 of the aperture 62, restricting the passage of the beams of the ghost field of view (FOV A) and FOV C. However, the beam of the main field of view (FOV B) can pass through the circular aperture 61 of the aperture 62 and reach the detector 64.

[0094] The following is combined with Figure 11 , Figure 12 Another embodiment of this disclosure will be described in detail below.

[0095] Figure 11 A schematic diagram of a receiving system 70 applicable to lidar according to an embodiment of the present disclosure is shown. Figure 11 As shown, a receiving system 70 for use with a lidar includes: a receiving lens 71, a reflector structure, a light-blocking plate 74, and a detector 73. The reflector structure includes a first reflector 721 and a second reflector 722. The receiving lens 71 receives an external light beam. The first reflector 721 and the second reflector 722, positioned opposite each other downstream of the optical path of the receiving lens 71, receive the light beam and change its propagation direction through reflection. The light-blocking plate 74, positioned downstream of the optical paths of the first reflector 721 and the second reflector 722, blocks part or all of the light beam that would cause ghost lines in the point cloud of the lidar. Finally, the detector 73, positioned downstream of the optical path of the light-blocking plate 74, receives the light beam that is not blocked by the light-blocking plate 74. The detector 73 can rotate around the lidar's axis. Alternatively, the number of reflectors can be three or four; this disclosure does not impose any limitation on the number of reflectors.

[0096] The light-blocking plates 74 can be disposed on the left and right sides of the detector 73, and can be directly disposed on the circuit board. When the detector 73 rotates and scans around the laser radar axis, the beams of the ghost field of view (FOV A) and FOV C are blocked by the light-blocking plates 74 on the left and right sides of the detector 73, limiting the beams of the ghost field of view (FOV A) and FOV C from reaching the detector 73. However, the beam of the main field of view (FOV B) is not blocked by the light-blocking plates 74 and can reach the detector 73.

[0097] The detectors 73 can be arranged in a linear array or a planar array on the circuit board. In the case of multiple detector arrays, some light-blocking plates can be reused as needed to reduce the number of light-blocking plates used, and at the same time, the effect of suppressing ghost lines generated by near-range high reflectivity plates in the lidar point cloud can be achieved. The number of light-blocking plates disclosed herein can be multiple, such as two, three, or four. This disclosure does not impose any limitation on the number of light-blocking plates.

[0098] Figure 12 A schematic diagram of a light-blocking sheet according to an embodiment of the present disclosure is shown. a is a front view, b is a right view, as shown. Figure 12As shown in Figure a, detector arrays 81, 82, and 83 are mounted on circuit board 87, and light-blocking plates 84, 85, and 86 are also mounted on circuit board 87. Preferably, the light-blocking plates 84, 85, and 86 are vertically mounted on circuit board 87. Detector arrays 81 and 82 share light-blocking plate 85, and detector arrays 82 and 83 share light-blocking plate 86. By reducing the number of light-blocking plates used, the effect of suppressing ghost lines generated by near-range high-reflectivity plates in the lidar point cloud can be achieved.

[0099] According to a preferred embodiment of this disclosure, the focal length of the receiving lens of the receiving system is set to 69mm, the angle between the first reflecting mirror and the horizontal direction is 45 degrees, and the angle between the second reflecting mirror and the horizontal direction is 51 degrees. Figure 12 As shown in Figure a, from left to right, the horizontal distances from the center of each column of APDs to the light-blocking plate are 2.45mm, 1.95mm, and 1.25mm, respectively. When the heights of the light-blocking plates are 4mm, 4mm, and 3.2mm, respectively, a good effect of confining the ghost line field of view can be achieved.

[0100] In the above embodiments, the lidar system includes an aperture or a light-blocking plate as a ghost line elimination device. According to a receiving system of one embodiment of this disclosure, the ghost line elimination device can also use both an aperture and a light-blocking plate simultaneously to suppress ghost lines generated in the lidar point cloud by a near-range high-reflectivity plate.

[0101] This disclosure also provides a lidar system, including a transmitting system and a receiving system as described above. The transmitting system emits a laser beam to detect a target, and the receiving system receives the echo of the laser beam reflected off the target. When the target being detected is a near-range, high-reflectivity obstacle, the receiving system can suppress the ghost lines generated by the high-reflectivity obstacle in the lidar point cloud, avoiding false identification by the lidar and improving detection accuracy. Furthermore, since the ghost line elimination device does not obstruct the main field-of-view beam, its impact on the lidar's range finding capability is minimized.

[0102] Figure 13 A method 100 for suppressing ghost lines in a point cloud of a lidar system, according to one embodiment of the present disclosure, is shown. Figure 13 As shown, the specific steps include the following:

[0103] Step S101: Receive the light beam from the outside of the lidar through the receiving lens;

[0104] Step S102: The beam of light from the receiving lens is received through the reflector structure, and the propagation direction of the beam is changed by reflection;

[0105] Step S103: Block the beam of light from the mirror structure that would cause ghost lines in the point cloud of the lidar;

[0106] Step S104: Receive the unobstructed light beam from the mirror structure via the detector.

[0107] According to one embodiment of this disclosure, the step of blocking the light beam from the mirror structure that would cause ghost lines in the point cloud of the lidar includes: blocking the light beam that would cause ghost lines in the point cloud of the lidar by means of an aperture and / or a light-blocking plate.

[0108] The lidar receiving system disclosed herein solves the problem of lidar misidentification caused by ghost lines generated in the lidar point cloud by near-range high-reflectivity obstacles through the use of ghost line elimination devices, such as specific apertures and / or light-blocking sheets. In autonomous driving applications, when the lidar of this disclosure scans near-range high-reflectivity road signs, it can avoid the road signs generating ghost lines in the lidar point cloud, thereby improving detection accuracy.

[0109] Third aspect

[0110] The technical solution of adding a compensation mirror in the first aspect of the present invention can be combined with the solution of eliminating ghost lines in the second aspect of the present invention.

[0111] Figure 14 A schematic diagram of a lidar 100 according to a preferred embodiment of the present invention is shown. Figure 14 As shown, in addition to the laser 101, emitting lens 102, receiving lens 103, compensating mirror 104, and detector 105, the lidar 100 also includes a receiving-end reflector structure. The receiving-end reflector structure includes two or more reflectors; two reflectors 107-1 and 107-2 are schematically shown in the figure. Those skilled in the art will readily understand that the receiving-end reflector structure may also include a greater number of reflectors. The receiving-end reflector structure is positioned downstream of the optical path of the receiving lens 103, located between the receiving lens 103 and the detector 105, for receiving the echo beam converged by the receiving lens 103 and reflecting it through the reflectors so that it is incident on the detector 105. Furthermore, the lidar 100 also includes a ghost line elimination device, as described in the second aspect of the invention, located between the receiving-end reflector structure and the detector, to block beams that would cause ghost lines in the lidar's point cloud from incident on the detector. Figure 14 The ghost line elimination device shown is an aperture stop 108. The aperture stop 108 can block the light beams L1 and L3 of the ghost line fields of view A and FOV C from incident on the detector 105, but will not or will not significantly prevent the light beam L2 of the main field of view B from incident on the detector 105.

[0112] According to a preferred embodiment of the present invention, the aperture and the detector satisfy the following relationship:

[0113]

[0114] Where D is the diameter of the receiving lens, f is the focal length of the receiving lens, h is the distance from the aperture to the detector, and d1 is the width of the aperture, as shown in the reference. Figure 8B The descriptions will not be repeated here.

[0115] As described in the second aspect of the invention, the aperture 108 is, for example, a strip-shaped aperture or a circular aperture, and the aperture is made of any of the following materials: metal, glass that can absorb or reflect light, or ceramic.

[0116] Alternatively, as described in the second aspect of the invention, the ghost line elimination device includes a light-blocking plate. Further details are omitted here. Preferably, the ghost line elimination device is configured to block light beams that have not undergone a single reflection from the receiving end reflector structure. For example, for Figure 14 In the case where the receiver reflector structure shown includes a first reflector 107-1 and a second reflector 107-2 arranged facing each other, the ghost line elimination device is configured to block beams other than those beams that have been reflected once by the first reflector and the second reflector, respectively.

[0117] Other preferred options include, for example Figure 14 As shown, the angle θ1 between the beam deflected by the compensation mirror 104 and the main field of view of the lidar is smaller than the angles θ2 and θ3 between the ghost line field of view and the main field of view.

[0118] The compensation mirror in this invention deflects a small portion of the light beam. The angle θ1 between the deflected beam and the detector's main field of view is smaller than the angles θ2 and θ3 between the ghost line field of view and the main field of view of the mechanical radar with a double-mirror folded optical path. Figure 14 As shown (line L2 represents the beam in the detector's main field of view (FOV) B, and lines L1 and L3 represent the beams in the ghost field of view (FOV) A and FOV C), this design, when applied to a lidar system that eliminates ghost lines through an aperture scheme, will not introduce new ghost lines. However, if the angle θ1 between the beam deflected by the compensating mirror 104 and the lidar's main field of view is greater than the angle θ2 or θ3 between the original ghost line field of view and the main field of view, new ghost lines will be introduced on both sides of the deflected beam. Installing a compensating mirror in a lidar receiving system typically introduces new ghost lines.

[0119] Additionally, the lidar 100 also includes a transmitter reflector structure. The transmitter reflector structure includes at least one reflector, such as... Figure 14As shown in the figure, two reflectors 106-1 and 106-2 are schematically illustrated. Those skilled in the art will readily understand that the emitting reflector structure may also include more or fewer reflectors. The emitting reflector structure is disposed between the laser 101 and the emitting lens 102, and is used to receive the laser beam emitted from the laser 101, reflect it, and direct it onto the emitting lens 102 for shaping before emission.

[0120] Figure 15 An embodiment of the present invention is shown, in which the components of the lidar system mainly include: a laser, a transmitting lens, a compensating mirror, a receiving lens, a folded receiving end reflector structure, a detector (such as an APD), and the compensating mirror is located, for example, at the center of the transmitting lens (within the aperture stop region).

[0121] Figure 16 Another embodiment of the invention is shown, which is... Figure 15 The difference lies in the addition of an aperture to block ghost lines in the lidar structure. The compensating mirror can be an optical wedge, microprism, diffraction element, or a combination of these with a spherical or cylindrical lens, capable of deflecting a small portion of the emitted beam at a specific angle. Furthermore, the compensating mirror can be fixed to the emitting lens by adhesive bonding or by a bracket.

[0122] According to a preferred embodiment of the present invention, the transmitting lens and the receiving lens are arranged side by side along the horizontal direction, and the relationship between the deflection angle of the compensating mirror and the reduction of the near-field blind zone range is as follows: Figure 17 As shown.

[0123] Figure 17 The beam deflection angle is θ1 (θ1 is the angle between the beam deflected by the compensating mirror and the receiving beam [i.e., the main field-of-view beam L2]), the distance from the compensating mirror to the center of the receiving lens is d, the diameter of the receiving lens is D, and the region of near-field signal enhancement is L at its farthest point from the vertex of the receiving lens and L′ at its closest point, as shown in the figure. Then, the following relationship is satisfied between them:

[0124]

[0125] L'=LD / tanθ1

[0126] Therefore, the installation position and deflection angle of the compensating mirror can be determined using the above relationship, based on the required minimum distance L′.

[0127] In this invention, the ghost line field of view can also be blocked by a light-blocking sheet. The specific details have been clearly explained in the previous patent on the ghost line field of view, and will not be repeated here.

[0128] The present invention also relates to a method 200 for detection using the lidar 100 described above, such as... Figure 18 As shown, it includes:

[0129] Step S201: Emit a laser beam through the laser;

[0130] Step S202: The laser beam is shaped by the emitting lens to emit a detection beam;

[0131] Step S203: Deflect at least a portion of the laser beam and / or the probe beam toward the receiving lens through the compensation mirror;

[0132] Step S204: Receive the beam of light reflected by the external obstacle of the lidar through the receiving lens.

[0133] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0134] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lidar, comprising: Multiple lasers are configured to emit multiple laser beams, each having a different field of view orientation. An emitting lens is disposed downstream of the laser's optical path and configured to shape the laser beam before emitting a probe beam. The emitting lens has an aperture stop region. The plurality of lasers are disposed at different heights on the focal plane of the emitting lens, and the multiple laser beams emitted by the plurality of lasers are emitted through the same emitting lens. A receiving lens, configured to receive the probe beam after it has been reflected outside the lidar; and A compensating mirror, disposed in the aperture stop region of the emitting lens, is configured to receive at least a portion of the laser beam and / or the probe beam, and deflect it toward the receiving lens. The transmitting lens and the compensating mirror are located on one side of the receiving lens; The angle between the beam deflected by the compensation mirror and the main field of view of the lidar is smaller than the angle between the ghost line field of view and the main field of view. The lidar further includes a receiving end reflector structure and a detector located sequentially downstream of the optical path of the receiving lens, and a ghost line elimination device located between the receiving end reflector structure and the detector to block the light beam that would cause ghost lines in the point cloud of the lidar from entering the detector.

2. The lidar according to claim 1, wherein the aperture stop region is located on the side of the emitting lens closer to the laser, or on the side farther from the laser, or in the middle of the emitting lens.

3. The lidar according to claim 1 or 2, wherein the compensation mirror comprises one or more of an optical wedge, a microprism, a diffractive optical element, or a combination thereof with a spherical lens or a cylindrical lens, which is fixed in the aperture stop region by an adhesive or a bracket.

4. The lidar according to any one of claims 1-2, wherein the compensation mirror is located in the aperture stop region near the receiving lens.

5. The lidar according to claim 4, wherein the transmitting lens and the receiving lens are juxtaposed along the horizontal direction, and the position of the compensation mirror satisfies the following relationship: ， ， in θ 1 represents the beam deflection angle, the angle between the beam deflected by the compensating mirror and the beam received by the receiving lens. d is the distance from the installation position of the compensating mirror to the center of the receiving lens. D is the diameter of the receiving lens. The range between L and L′ is the region of near-field signal enhancement. The distance between the intersection of the beam deflected by the compensating mirror and the receiving beam and the vertex of the receiving lens is L at its farthest point and L′ at its closest point.

6. The lidar according to claim 1 or 2, wherein the ghost line elimination device includes an aperture, and the aperture and the detector satisfy the following relationship: ， in, D is the diameter of the receiving lens, f is the focal length of the receiving lens, h is the distance from the aperture to the detector, and d1 is the width of the aperture.

7. The lidar according to claim 6, wherein the aperture is a strip-shaped aperture or a circular aperture, and the aperture is made of any one of the following materials: metal, glass that can absorb or reflect light, or ceramic.

8. The lidar according to claim 1 or 2, wherein the ghost line elimination device includes a light-blocking plate.

9. The lidar of claim 8, wherein the ghost line elimination device is configured to block beams that have not been reflected once by the mirror structure.

10. The lidar of claim 8, wherein the receiver reflector structure includes a first reflector and a second reflector facing each other, the detector includes a photodiode, and the ghost line elimination device is configured to block beams other than those beams reflected once by the first reflector and the second reflector, respectively.

11. A method for detection using a lidar as described in any one of claims 1-10, comprising: A laser beam is emitted through the laser; The laser beam is shaped by the emitting lens to produce a detection beam. The compensation mirror deflects at least a portion of the laser beam and / or the probe beam toward the receiving lens. The receiving lens receives the beam of light reflected by external obstacles of the lidar from the detection beam.

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