CN111090082A

CN111090082A - Laser radar and method for detecting using the same

Info

Publication number: CN111090082A
Application number: CN201911137252.8A
Authority: CN
Inventors: 杨金涛; 向少卿
Original assignee: Hesai Photonics Technology Co Ltd
Current assignee: Hesai Photonics Technology Co Ltd
Priority date: 2019-08-30
Filing date: 2019-11-19
Publication date: 2020-05-01

Abstract

The invention relates to a lidar comprising: a laser configured to emit a laser beam; the emitting lens is arranged on the downstream of the optical path of the laser and is configured to emit a detection beam after shaping the laser beam, and the emitting lens is provided with an aperture diaphragm area; a receiving lens configured to receive a beam of the probe beam after being reflected outside the laser radar; and a compensation mirror disposed in an aperture stop region of the transmit lens and configured to receive and deflect at least a portion of the laser beam and/or the probe beam toward the receive lens.

Description

Laser radar and method for detecting using the same

Technical Field

The invention relates to the technical field of photoelectricity, in particular to a laser radar and a detection method using the laser radar.

Background

The laser radar comprises a laser transmitting system and a detecting and receiving system, wherein the transmitted laser is reflected after encountering a target and is received by the detecting system, the distance of a corresponding target point can be measured by measuring the round-trip time of the laser (such as a time flight method), and after the whole target area is scanned and detected, three-dimensional imaging can be finally realized. The laser radar has important application in an unmanned system, and the laser radar is required to have the characteristics of high imaging frame frequency, high resolution, long-distance measuring capability, small volume, high reliability, low cost and the like.

At present, most of the laser radar transmitting systems and receiving systems are separated (different from the case that the transmitting system and the receiving system share a set of lenses), in order to test a target at a long distance, the laser emission beam is aligned with the field of view of the detector at a long distance (such as 200m), as shown in fig. 1, in a certain distance range close to the laser radar, the laser emission beam and the field of view of the detector are completely non-overlapped, so that in the certain distance range, the detector of the laser radar cannot receive signal light reflected on the target, or the received signal light is extremely weak, which is a short-distance blind area.

The reason why the short-distance blind area or the short-distance signal of the laser radar is weak is that the receiving and transmitting are separated and are not in a common optical path structure, that is, the laser transmitting optical path and the signal receiving optical path are not completely overlapped, and referring to fig. 1, the transmitting lens and the receiving lens are horizontally translated. Applicants have found that there are two possible reasons.

The first reason is: referring to fig. 1, the near-distance blind area is an area where the emitted laser beam does not overlap at a near distance with the reception field of view at all. This means that the detector of the lidar "cannot see" the transmitted laser beam in this area, i.e. the detector does not receive signal light reflected back from the target in this area.

The second reason is that: referring to fig. 2, a target is located in the near-distance blind area, and an image point formed by the signal light reflected from the near-distance target through the receiving lens is not on the focal plane of the receiving lens but behind the focal plane. In addition, since the close-distance target is above the optical axis of the receiving lens, its image point formed by the receiving lens is necessarily below the optical axis of the receiving lens. Combining these two considerations, the relative position of the focus of the near target reflected light and the detector is illustrated in FIG. 2. Within the close-range blind area range of the laser radar, the laser radar detector can not completely receive the reflected signal of the target.

The statements in the background section are merely prior art as they are known to the inventors and do not, of course, represent prior art in the field.

Disclosure of Invention

In view of at least one of the drawbacks of the prior art, the present invention provides a lidar comprising:

a laser configured to emit a laser beam;

the emitting lens is arranged on the downstream of the optical path of the laser and is configured to emit a detection beam after shaping the laser beam, and the emitting lens is provided with an aperture diaphragm area;

a receiving lens configured to receive a beam of the probe beam after being reflected outside the laser radar; and

a compensation mirror disposed in an aperture stop region of the transmit lens and configured to receive and deflect at least a portion of the laser beam and/or the probe beam toward the receive lens.

According to an aspect of the invention, the aperture stop area is located on a side of the emission lens close to the laser, or a side remote from the laser, or in the middle of the emission lens.

According to an aspect of the invention, wherein the compensation mirror comprises one or more of wedges, microprisms, diffractive optical elements, or a combination thereof with spherical or cylindrical lenses, respectively, which are fixed in the aperture stop area by means of an adhesive or a holder.

According to an aspect of the invention, wherein the compensation mirror is located in the aperture stop area at a position close to the receiving lens.

According to an aspect of the present invention, wherein the transmitting lens is juxtaposed with the receiving lens in a horizontal direction, a position of the compensation mirror satisfies the following relationship:

L′＝L-D/tanθ₁

wherein theta is₁The angle of the light beam deflection angle is the included angle between the light beam deflected by the compensating mirror and the light 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 distance signal enhancement, and the distance between the intersection of the beam deflected by the compensation mirror and the received beam and the vertex of the receiving lens is L at the farthest distance and L' at the nearest distance.

According to an aspect of the invention, wherein an angle between the compensated mirror-deflected beam and a main field of view of the lidar is smaller than an angle between a ghost field of view and the main field of view,

the laser radar also comprises a receiving end reflecting mirror structure and a detector which are sequentially positioned on the downstream of the light path of the receiving lens, and a ghost line eliminating device positioned between the receiving end reflecting mirror structure and the detector so as to prevent light beams which can cause ghost lines in the point cloud of the laser radar from being incident to the detector.

According to an aspect of the present invention, wherein the ghost elimination apparatus includes an aperture, the aperture and the detector satisfy the following relationship:

wherein D is the diameter of the receiving lens, f is the focal length of the receiving lens, h is the distance from the diaphragm to the detector, and D1 is the width of the diaphragm.

According to an aspect of the present invention, wherein the diaphragm is in a shape of a strip hole or a circular hole, the diaphragm is made of any one of the following materials: metal, glass that absorbs or reflects light, or ceramic.

According to an aspect of the present invention, wherein the ghost elimination device includes a light-shielding sheet.

According to an aspect of the invention, wherein the ghost eliminating means is configured to block the light beam not reflected once by the mirror structure.

According to an aspect of the present invention, wherein the receiving end reflecting mirror structure includes a first reflecting mirror and a second reflecting mirror disposed to face each other, the detector includes a photodiode, and the ghost wire eliminating device is configured to block light beams other than the light beams reflected once by the first reflecting mirror and the second reflecting mirror, respectively.

The invention also provides a method for detecting by using the laser radar, which comprises the following steps:

emitting a laser beam by the laser;

shaping the laser beam through the transmitting lens and emitting a detection beam;

deflecting, by the compensation mirror, at least a portion of the laser beam and/or the detection beam towards the receive lens;

and receiving the light beam of the probe light beam reflected by the external obstacle of the laser radar through the receiving lens.

By the scheme of the embodiment of the invention, the short-distance blind area range of the transmitting and receiving split laser radar can be reduced, and/or the signal intensity of short-distance detection can be enhanced.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 and 2 show schematic views of possible causes of the generation of a close-range blind area;

FIG. 3 shows a schematic diagram of a lidar in accordance with one embodiment of the invention;

FIG. 4 shows a schematic diagram of multiple laser exit beams through an aperture stop at the focal plane of a transmit lens;

FIG. 5 shows a schematic diagram of ghost lines in a lidar point cloud according to one embodiment of the present disclosure;

FIG. 6 shows a schematic diagram of a transmitting end causing ghost lines, according to one embodiment of the present disclosure;

FIG. 7 illustrates a schematic diagram of a receiving end causing ghost lines according to one embodiment of the present disclosure;

FIG. 8A shows a schematic diagram of a reception system with a stop suppressing ghost lines, according to one embodiment of the present disclosure;

FIG. 8B shows a parametric schematic of the diaphragm and detector;

FIG. 9 shows a schematic view of a strip aperture diaphragm according to an embodiment of the present disclosure;

FIG. 10 shows a schematic view of a circular aperture-shaped diaphragm according to an embodiment of the present disclosure;

FIG. 11 illustrates a schematic view of a receiver system for ghost line suppression by a light barrier according to one embodiment of the present disclosure;

FIG. 12 shows a schematic view of a light barrier sheet according to one embodiment of the present disclosure;

FIG. 13 illustrates a method of suppressing ghost lines in a point cloud of a lidar according to one embodiment of the present disclosure;

FIG. 14 shows a schematic diagram of a lidar in accordance with a preferred embodiment of the present invention;

FIG. 15 shows a schematic diagram of a lidar in accordance with a preferred embodiment of the present invention;

FIG. 16 shows a schematic diagram of a lidar in accordance with a preferred embodiment of the present invention;

FIG. 17 shows a schematic diagram of a lidar in accordance with a preferred embodiment of the present invention; and

FIG. 18 illustrates a method of detection using lidar in accordance with one embodiment of the present invention.

Detailed Description

In the following, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like, indicate orientations and positional relationships based on those shown in the drawings, and are used only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be considered as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection, either mechanically, electrically, or in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly above and obliquely above the second feature, or simply meaning that the first feature is at a lesser level than the second feature.

The following disclosure provides many different embodiments or examples for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art may recognize applications of other processes and/or uses of other materials.

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

First aspect

Fig. 3 shows a schematic diagram of a lidar 100 according to an embodiment of the invention. As described in detail below in conjunction with fig. 3. As shown in fig. 3, the laser radar 100 includes a laser 101, a transmitting lens 102, a receiving lens 103, and a detector 105. The laser 101 is, for example, an Edge Emitting Laser (EEL) or a Vertical Cavity Surface Emitting Laser (VCSEL), and is configured to emit a laser beam, which is incident on an emission lens 102 downstream of the optical path. The emission lens 102 is configured to shape the laser beam and emit a detection beam, and the emission lens 102 has an aperture stop region. The probe beam is incident on an object OB outside the laser radar 100, and is diffusely reflected, and part of the reflected beam is returned to the receiving lens 103, and is converged onto the detector 105 through the receiving lens 103. The detector 105 is, for example, a photodiode, such as an Avalanche Photodiode (APD), or a single photon detector (e.g., SiPM, Spad). After receiving the reflected beam, the detector 105 generates an electrical signal having a certain relationship with the intensity of the beam or the number of photons, and amplifies and filters the electrical signal through a subsequent circuit, so that one or more data signals of parameters such as the distance, angle, reflectivity and the like of an obstacle can be obtained, and point cloud data of the laser radar is formed for subsequent processing and is not described herein any more.

In addition, according to an embodiment of the present invention, in fig. 3, in order to reduce the blind area of the laser radar 100, a compensation mirror 104 is provided in the aperture stop area of the transmitting lens 102. The aperture stop area is a parameter inherent to 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 exiting the transmit lens 102 and to deflect it towards said receive lens 103. As shown in fig. 3, in which the receiving lens 103 is juxtaposed in a horizontal direction with the transmitting lens 102, for example, the compensating mirror 104 deflects the probe beam in a certain direction toward the side of the receiving lens 103.

As will be readily understood by those skilled in the art, the emission lens 102 may comprise a single lens, or may be a lens group consisting of a plurality of lenses, all of which are referred to as emission lenses in the present invention. In the case where the emission lens 102 is a single lens, the aperture stop area thereof may be located on either side of the emission lens 102, such as the left or right side of the emission lens 102 in fig. 3, i.e., the side closer to the laser 101 or the side farther from the laser 101, depending on the optical design; in the case where the emission lens 102 is a lens group composed of a plurality of lenses, its aperture stop area may be located on either side of the lens group, or may be located in the middle of the emission lens, i.e., between two of the lenses, depending on the optical design. Under the condition that the compensating mirror 104 is positioned at one side close to the laser 101, the compensating mirror receives and deflects the laser beam emitted by the laser 101, and then the laser beam is shaped by the emitting lens to emit a detection beam; under the condition that the compensating mirror 104 is positioned at the side far away from the laser 101, the compensating mirror receives the detection light beam and deflects the detection light beam; it is within the scope of the present invention for the compensator 104 to receive and deflect the partially shaped laser beam with the compensator in the middle of the emitter lens.

According to a preferred embodiment of the present invention, the compensation mirror 104 comprises one or more of a wedge, a micro prism, a diffractive optical element, or a combination thereof with a spherical lens or a cylindrical lens, respectively, as long as it is capable of deflecting at least a portion of the laser beam emitted by the laser 101 and/or the probe beam emitted from the emission lens 102 towards the receiving lens 103. The compensator 104 may be fixed in the aperture stop area by an adhesive, a bracket, or the like.

In the embodiment of fig. 3, by providing the compensating mirror 104 in the transmitting system, a part of the transmitted light beam (for example, the light beam emitted by the laser or the probe light beam emitted by the transmitting lens) is deflected at a specific angle toward the receiving field of view of the detector, so that the light beam transmitted by the compensating mirror 104 starts to overlap with the receiving field of view of the detector at a position (point a in fig. 3) close to the lidar, thereby reducing the near-range blind area, as shown in fig. 3, the range of the new blind area is significantly smaller than the original blind area.

In the above technical solution, the compensation mirror 104 is disposed in the aperture stop area of the emission system. The aperture stop area is a parameter inherent to the emitting lens (or group of lenses) and may be located on either side of the emitting lens (or group of lenses) or in the middle of the emitting lens group depending on the optical design of the system. Fig. 4 shows a case where a plurality of lasers (at different heights) are arranged on the focal plane of the emitting lens (group) 102 to emit laser light, in which three lasers 101-1, 101-2, and 101-3 are schematically shown. In the aperture stop area of the transmitting lens, the light spots of the plurality of lasers are overlapped, so that the equal proportion compensation of the plurality of laser beams can be realized by using only one compensating mirror 104. Fig. 4 is a schematic diagram in which an aperture stop region (indicated by a dashed circle in fig. 4) where spots of outgoing light beams of a plurality of lasers coincide is located on the side of the emission lens group (on the downstream side of the optical path). The compensator 104 functions to redirect a portion of the probe beam (which may also include a change in divergence angle) away from the probe beam, from a position very close to the lidar, to overlap the field of view of the detector. Therefore, the detector can receive the signal light reflected by the close-range target, and the purpose of reducing the close-range blind area of the laser radar is achieved.

According to a preferred embodiment of the invention, the compensation mirror 104 is located in the aperture stop area close to the receiving lens. Fig. 3 is a plan view of, for example, laser radar 100, and transmission lens 102 and reception lens 103 are arranged side by side in the horizontal direction, and have substantially the same vertical height.

Second aspect of the invention

This application claims priority to PCT international application PCT/CN2019/103724, the contents of which are incorporated herein by reference in their entirety.

For a laser radar with a folding reflector structure (more than two reflectors of a laser radar receiving lens and a detector form a reflector structure to fold a light path), a smaller structural size can be obtained under the condition of the same lens focal length, and the structure is the structure of the multi-line mechanical laser radar in one embodiment of the invention. When the lidar with the folding mirror structure scans a high reflection plate (high-reflectivity obstacle, such as a guideboard) at a short distance, ghost lines may appear in the obtained lidar point cloud as shown in fig. 5, that is, some points clouds that do not exist actually may appear on the left and right sides of the high reflection plate. In the unmanned driving process, when the laser radar scans the high-reflectivity guideboard, ghost lines generated in the laser radar point cloud are identified as obstacles, and automatic parking is caused.

Through a great deal of research and experiments, the applicant finds that the laser radar with the folding reflector structure can cause ghost lines due to various reasons. Fig. 6 is a diagram illustrating a ghost phenomenon caused by the reason of the transmitting end. At the laser radar transmitting end, because the transmittance of the coating film of the transmitting lens 22 is not 100%, the laser emitted by the laser 23 forms multiple reflections at each glass-air interface of the transmitting lens 22 and the mask 21 and then is emitted, and finally, a very large light spot is used for illuminating a short-distance target.

Fig. 7 shows a schematic diagram of the receiver-side cause ghost lines. At the receiving end of the laser radar, in the light path of the folding reflector, besides the main view field that the light beam is reflected once on the reflector, the view field that the light beam is not reflected on the reflector and the view field that the total number of times of reflection on the reflector exceeds the number of reflectors exist. When the laser radar scans, the detector at the receiving end receives the light beams which are not reflected on the reflecting mirror and/or are reflected on the reflecting mirror for a total number of times exceeding the number of the reflecting mirror, thereby generating ghost lines. As shown in fig. 7, the field of view of the lidar includes: a main field of view FOV B and ghost fields of view FOV a, FOV C. The main field of view FOV B is a field of view in which the light beam is reflected once on the first mirror 311 and the second mirror 312, the ghost field of view FOV a is a field of view in which the light beam is not reflected on the first mirror 311 and the second mirror 312, and the ghost field of view FOV C is a field of view in which the light beam is reflected more than twice in total on the first mirror 311 and the second mirror 312.

Assuming that the lidar scans counterclockwise, when the main field of view FOV B is still outside the high reflection plate, the ghost line field of view FOV a can already see the high reflection plate, and since the high reflection plate is closer to the high reflection plate and the high reflection plate is illuminated by a spot with a large emission end, the detector 32 receives the light beam through the optical path of the ghost line field of view FOV a, and ghost lines on the right side of the high reflection plate are generated; the lidar continues to scan, and when the main field of view FOV B leaves the high-reflection plate and the ghost field of view FOVC remains on the high-reflection plate, the detector 32 may still receive the reflected beam of the high-reflection plate through the optical path of the ghost field of view FOV C, thus creating a ghost line to the left of the high-reflection plate. Alternatively, the ghost field FOV a, FOV C, when the lidar scans clockwise sees the high-reflection plate before the main field FOV B, which when leaving the high-reflection plate still is on the high-reflection plate, the ghost field FOV a, FOV C, respectively, leading to ghost lines on the right and left side of the high-reflection plate, wherein the detector 32 is for example a photodiode, such as an Avalanche Photodiode (APD), or a single photon detector (e.g. SiPM, Spad).

In order to reduce or suppress the ghost line problem described above, the present disclosure provides a receiving system usable for a laser radar, including: receiving lens, reflector structure, detector, ghost line eliminating device. The reflector structure is arranged on the downstream of the optical path of the receiving lens, the detector is arranged on the downstream of the optical path of the reflector structure, and the ghost line eliminating device is arranged between the reflector structure and the detector. External light beams enter the reflector structure through the receiving lens, the propagation direction of the external light beams is changed in the reflector structure through reflection of the plurality of reflectors, the external light beams pass through the ghost line eliminating device, part or all of the ghost line light beams in the point cloud of the laser radar are blocked by the ghost line eliminating device, and finally the residual light beams reach the detector.

The lidar field of view of embodiments of the present disclosure includes: the main field of view is the field of view in which the beam is reflected once on each mirror, and the ghost field of view is the field of view in which the beam is not reflected on the mirrors and/or the total number of reflections on the mirrors exceeds the number of mirrors. Because the ghost line field of view and the main field of view are in clearance at a specific position on the optical path, the ghost line can be restrained from being generated in the laser radar point cloud by using a diaphragm and/or a light blocking sheet device as the ghost line eliminating device for blocking the optical path of the ghost line field of view.

One embodiment of the present disclosure is described in detail below in conjunction with fig. 8A-10.

FIG. 8A shows a schematic diagram of a receiving system 40 that may be used for lidar in accordance with one embodiment of the present disclosure. As shown in fig. 8A, a receiving system 40 usable for a lidar includes: a receiving lens 41, a mirror structure comprising a first mirror 421 and a second mirror 422, an aperture 44, a detector 43. The receiving lens 41 may receive an external light beam, such as a light beam of an outgoing laser beam of a laser radar reflected back through an external obstacle. The first mirror 421 and the second mirror 422 are disposed downstream of the receiving lens 41 in the optical path, and are disposed to face each other, and the light beam received by the receiving lens is incident on the mirror structure, and the traveling direction of the light beam is changed by reflection of the first mirror 421 and the second mirror 422. A detector 43 is arranged in the optical path downstream of the mirror structure for receiving the light beam from the mirror structure and generating an electrical signal which is subjected to further signal processing, such as filtering, amplification, AD conversion, digital signal processing, etc., to form point cloud data of the lidar. An aperture 44 is provided between the mirror structure and the detector 43 to allow light of the main field of view to pass through and be incident on the detector 43 while limiting the passage of part of the light beam, for example to partially or completely block those light beams which would cause ghost lines in the point cloud of the lidar, preventing these light beams which would cause ghost lines from being incident on the detector. As shown in fig. 8A, the light beam corresponding to the main field of view FOV B is deflected after passing through the receiving lens 41, and then enters the first reflecting mirror 421 and is reflected by the first reflecting mirror 421, and then is reflected by the second reflecting mirror 422, and finally the light beam reflected by the second reflecting mirror 422 may pass through the diaphragm 44 and irradiate on the detector 43 to generate an electrical signal. After passing through the receiving lens 41, the light beam corresponding to the ghost view field FOV a does not enter the first reflecting mirror 421 or the second reflecting mirror 422, but directly irradiates the diaphragm 44, and is blocked or absorbed by the diaphragm 44, so as to avoid generating ghost lines in the point cloud of the laser radar due to the fact that the light beam irradiates the detector 43. After passing through the receiving lens 41, the light beam corresponding to the ghost view field FOV C is incident on the first reflecting mirror 421, reflected by the first reflecting mirror 421 to the second reflecting mirror 422, then reflected by the second reflecting mirror 422 to the second reflecting mirror 421, then reflected by the first reflecting mirror 421 and the second reflecting mirror 422 respectively once, finally incident on the diaphragm 44, and blocked or absorbed by the diaphragm 44, so as to prevent the light beam from irradiating on the detector 43 to generate ghost lines in the lidar point cloud.

Thus, by providing the diaphragm 44 between the mirror structure and the detector 43 as ghost eliminating means, light rays which would cause ghost lines in the point cloud of the lidar can be at least partially blocked from entering the detector 43.

In addition, as those skilled in the art will readily understand, the number of the mirrors in the embodiment of fig. 8A is two, which is only illustrative, and a larger number of mirrors may be included, for example, the number of the mirrors may also be three or four, and the present disclosure does not set any limit to the number of the mirrors.

According to a preferred embodiment of the present disclosure, when the distance between the diaphragm 44 and the detector 43 satisfies a certain relationship, the light beams shielding the ghost line fields of view FOV a and FOV C can be better achieved.

Specifically, assuming that the diameter of the receiving lens 41 is D, the focal length thereof is f, the distance from the diaphragm 44 to the detector 43 (e.g. a single APD, or an APD linear array or an area array) is h, and the horizontal width of the aperture of the diaphragm 44 is D1 (as shown in fig. 8B), when the horizontal width D1 of the aperture of the diaphragm 44 and the distance h from the diaphragm 44 to the detector 43 satisfy the following relation, the light beams blocking the ghost line fields of view FOV a and FOV C can be better achieved:

as shown in fig. 8A, when the laser radar scans counterclockwise or clockwise, the light beams of the ghost view FOV and FOV C are blocked by the diaphragm 44 and cannot reach the detector 43, but the light beam of the main view field FOV B can reach the detector 43 through the hole of the diaphragm 44, so that the ghost lines generated in the laser radar point cloud by the close-distance high reflective plate are suppressed or even eliminated, the misrecognition of the laser radar is avoided, and the detection accuracy is improved.

As described above, the mirror structure may include a plurality of mirrors, and the ghost eliminating means, such as the diaphragm 44, is configured to block the light beam that is not reflected once by the mirror structure. In the present invention, the light beam reflected once by the mirror structure refers to a light beam reflected once by each mirror in the mirror structure (such as the field of view FOV B in fig. 8A); a light beam that is not reflected once by the mirror structure means that the light beam is not reflected by at least one of the mirrors (such as the light beam corresponding to the ghost view FOV a in fig. 8A), or is reflected twice or more by at least one of the mirrors (such as the light beam corresponding to the ghost view FOV C in fig. 8A).

According to the receiving system of one embodiment of the present disclosure, the material of which the diaphragm is made may be metal, glass that can absorb or reflect light, or ceramic.

According to an embodiment of the present disclosure, the diaphragm includes: a strip-shaped hole or a circular-shaped hole, fig. 9 shows a schematic view of an embodiment of the strip-shaped hole diaphragm of the present disclosure, and fig. 10 shows a schematic view of an embodiment of the circular-shaped hole diaphragm of the present disclosure. Or alternatively, the shape of the aperture of the diaphragm may also be square or oval, and the present disclosure does not make any limitation on the shape of the aperture of the diaphragm.

Fig. 9 shows a schematic diagram of a strip-shaped aperture stop according to an embodiment of the present disclosure, as shown in fig. 9, an aperture of the aperture stop 52 is a strip-shaped aperture 51, a horizontal width of the aperture is d1, the aperture stop 52 is disposed on a support 53, for example, the aperture stop 52 may be attached to the support 53, the support 53 is disposed in front of a circuit board 55, the detector 54 may be arranged in a linear array or an area array on the circuit board 55, and a distance h from the aperture stop 52 to the detector 54 is provided. d1 and h satisfy the above restriction relationship, for example, when we determine that the horizontal width of the aperture of the diaphragm is d1, the distance h from the diaphragm 52 to the detector 54 can be determined by taking the equal sign of the above restriction relationship. The number of linear arrays (columns) of the detector 54 corresponds to the number of strip-shaped holes of the diaphragm 52. As shown in fig. 9, 6 rows of detectors 54 are disposed on the circuit board 55, and correspondingly, 6 strip-shaped holes 51 are disposed on the aperture 52 (the width of the strip-shaped hole 51 is d1, the center-to-center distance between adjacent shaped holes 51 is set with reference to the center-to-center distance between the linear arrays of 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 linear arrays of detectors 54 on the circuit board 55), i.e., light beams from ghost view fields of all APD arrays can be blocked. Of course, the number of the strip-shaped holes can be adjusted according to the requirement, and the light beams from the ghost line field of view of part of the APD array can be shielded.

When the detector 54 rotates and scans around the laser radar rotating shaft, the light beams of the ghost view fields FOV a and FOV C are blocked by the left and right sides of the strip-shaped hole 51 of the diaphragm 52, the light beams of the ghost view fields FOV a and FOV C are limited to pass through, but the light beam of the main view field FOV B can pass through the strip-shaped hole 51 of the diaphragm 52 and reach the detector 54.

Fig. 10 shows a schematic diagram of a circular aperture diaphragm according to an embodiment of the present disclosure, as shown in fig. 10, the aperture of the diaphragm 62 is a circular aperture 61, the horizontal width of the aperture is d1 (i.e. the diameter of the aperture is d1), the diaphragm 62 is disposed on a bracket 63, for example, the diaphragm 62 can be attached to the bracket 63, the bracket 63 is disposed in front of the circuit board 65 and in front of a detector 64 on the circuit board 65, wherein the detector 64 can be, but is not limited to, a photodiode, such as an APD. The distance h from the diaphragm 62 to the detector 64. d1 and h satisfy the constraint relationship, for example, when we determine that the horizontal width of the aperture of the diaphragm is d1 (i.e., the diameter of the aperture), the distance h from the diaphragm 52 to the detector 54 can be determined by taking the equal sign of the constraint relationship. Each detector 64 corresponds to a circular aperture 61 of said diaphragm 62. The number of linear arrays (columns) of the detectors 64 corresponds to the number of columns of the circular holes 61 of the diaphragm 62, as shown in fig. 10, 3 columns of the detectors 64 are arranged on the circuit board 65, and correspondingly, 3 columns of the circular holes 61 are arranged on the diaphragm 62, so that light beams from ghost line fields of view of all the APD arrays can be blocked. Of course, the number of circular apertures can be adjusted as desired to block portions of the APD array from the ghost field of view.

When the detector 64 is scanned around the rotation axis of the laser radar, the light beams of the ghost view fields FOV a and FOV C are blocked by the periphery of the circular-shaped hole 61 of the diaphragm 62, and the light beams of the ghost view fields FOV a and FOV C are restricted from passing through, but the light beam of the main view field FOV B can pass through the circular-shaped hole 61 of the diaphragm 62 and reach the detector 64.

Another embodiment of the present disclosure is described in detail below with reference to fig. 11 and 12.

FIG. 11 shows a schematic diagram of a receiving system 70 that may be used for lidar in accordance with one embodiment of the present disclosure. As shown in fig. 11, a receiving system 70 usable for a laser radar includes: a receiving lens 71, a reflector structure including a first reflector 721 and a second reflector 722, a light-blocking sheet 74, and a detector 73. The receiving lens 71 may receive an external light beam, the first and

second mirrors

721 and 722 disposed opposite to the optical path downstream of the receiving lens 71 may receive the light beam and change the propagation direction of the light beam by reflection, the light barrier 74 disposed downstream of the optical path of the first and

second mirrors

721 and 722 may block a part or all of the light beam that may cause ghost lines in the point cloud of the laser radar, and finally the detector 73 disposed downstream of the optical path of the light barrier 74 receives the light beam that is not blocked by the light barrier 74. The detector 73 is rotatable about the lidar axis. Alternatively, the number of the reflecting mirrors may also be three or four, and the present disclosure does not set any limit to the number of the reflecting mirrors.

The light-shielding sheets 74 may be disposed on the left and right sides of the detector 73, and may be directly disposed on a circuit board. When the detector 73 is scanned around the rotation axis of the laser radar, the light beams of the ghost view field FOV a and FOV C are blocked by the light blocking sheets 74 on the left and right sides of the detector 73, so that the light beams of the ghost view field FOV a and FOV C are restricted from reaching the detector 73, but the light beams of the main view field FOV B are not blocked by the light blocking sheets 74 and can reach the detector 73.

The detectors 73 can be arranged on the circuit board to form a linear array or an area array, and for the case of a plurality of detector arrays, a part of light separation sheets can be multiplexed as required to reduce the number of the light separation sheets, and the effect of inhibiting the close-range high-reflection plate from generating ghost lines in the laser radar point cloud can be achieved at the same time. The number of the light-shielding sheets of the present disclosure may be plural, for example, two, three, or four, and the present disclosure does not set any limit to the number of the light-shielding sheets.

FIG. 12 shows a schematic view of a light barrier sheet according to one embodiment of the present disclosure. a is a front view, b is a right view, as shown in a in fig. 12, the

detector arrays

81, 82 and 83 are arranged on the circuit board 87, the light-shielding

sheets

84, 85 and 86 are also arranged on the circuit board 87, and preferably, the light-shielding

sheets

84, 85 and 86 are vertically arranged on the circuit board 87. The

detector arrays

81 and 82 share the light shielding sheet 85, and the

detector arrays

82 and 83 share the light shielding sheet 86. The effect of restraining the close-range high-reflection plate from generating ghost lines in the laser radar point cloud can be achieved while the using number of the light-blocking sheets is reduced.

According to a preferred embodiment of the present disclosure, when the focal length of the receiving lens of the receiving system is set to 69mm, the included angle between the first reflector and the horizontal direction is 45 degrees, and the included angle between the second reflector and the horizontal direction is 51 degrees, as shown in a in fig. 12, from left to right, the horizontal distances from the center of each column of APDs to the light shielding sheet are respectively 2.45mm, 1.95mm and 1.25mm, and from left to right, and the heights of the light shielding sheets are respectively 4mm, 4mm and 3.2mm, a good effect of restricting ghost line field of view can be obtained.

In the above embodiments, the system of the laser radar includes a diaphragm or a light-shielding sheet, respectively, as the ghost line elimination device. According to the receiving system of one embodiment of the present disclosure, the ghost elimination apparatus may further use a diaphragm and a light blocking sheet at the same time, so as to achieve the purpose of suppressing the ghost generated in the laser radar point cloud by the close-range high-reflection plate.

The present disclosure also provides a lidar comprising: a transmitting system and a receiving system as described above. The emitting system can emit laser beams for detecting targets, and the receiving system can receive echoes of the laser beams after the laser beams are reflected on the targets. When the detected target is a close-range high-reflectivity obstacle, the receiving system can inhibit the high-reflectivity obstacle from generating ghost lines in the laser radar point cloud, so that the false recognition of the laser radar is avoided, the detection accuracy is improved, and meanwhile, because the ghost line eliminating device does not shield the main view field beam, the influence on the distance measuring capability of the laser radar is minimized.

FIG. 13 illustrates a method 100 of suppressing ghost lines in a point cloud of a lidar according to one embodiment of the present disclosure. As shown in fig. 13, the method specifically includes the following steps:

step S101, receiving a light beam from the outside of the laser radar through a receiving lens;

step S102, receiving the light beam from the receiving lens through a reflector structure and changing the propagation direction of the light beam through reflection;

step S103, blocking light beams which come from the reflector structure and can cause ghost lines in the point cloud of the laser radar;

step S104, receiving the light beam which is not blocked and comes from the reflector structure through a detector.

According to one embodiment of the present disclosure, the step of blocking a beam from the mirror structure that would cause ghost lines in a point cloud of a lidar comprises: the light beams which would cause ghost lines in the point cloud of the lidar are blocked by the diaphragm and/or the light barrier.

The laser radar receiving system disclosed by the invention solves the problem of false identification of the laser radar caused by ghost lines generated in the laser radar point cloud by a short-distance high-reflectivity obstacle by using a ghost line eliminating device such as a specific diaphragm and/or a light isolating sheet. In unmanned application, when the laser radar scans the short-distance high-reflectivity guideboard, ghost lines generated by the guideboard in the point cloud of the laser radar can be avoided, and the detection accuracy is improved.

Third aspect of the invention

The solution of the first aspect of the invention for adding a compensation mirror can be combined with the solution of the second aspect of the invention for eliminating ghost lines.

Fig. 14 shows a schematic diagram of a lidar 100 according to a preferred embodiment of the invention. As shown in fig. 14, the laser radar 100 includes a receiving end mirror structure in addition to the laser 101, the transmitting lens 102, the receiving lens 103, the compensating mirror 104, and the detector 105. The receiving end mirror structure includes two or more mirrors, two mirrors 107-1 and 107-2 being schematically illustrated, and it will be readily understood by those skilled in the art that the receiving end mirror structure may include a greater number of mirrors. The receiving end mirror structure is arranged on the optical path downstream of the receiving lens 103, is positioned between the receiving lens 103 and the detector 105, and is used for receiving the echo light beam converged by the receiving lens 103, and is reflected by the mirror so as to be incident on the detector 105. In addition, the lidar 100 further comprises ghost eliminating means between the receiving end mirror structure and the detector as described in the second aspect of the invention to block light beams that would cause ghost lines in the point cloud of the lidar from being incident on the detector. The ghost elimination means shown in fig. 14 is a diaphragm 108. The diaphragm 108 is capable of blocking the incidence of the light beams L1 and L3 of the ghost fields FOV a and FOV C on said detector 105, but does not or substantially does not prevent the incidence of the light beam L2 of the main field FOV B on the detector 105.

According to a preferred embodiment of the invention, the diaphragm and the detector satisfy the following relationship:

where D is the diameter of the receiving lens, f is the focal length of the receiving lens, h is the distance from the diaphragm to the detector, and D1 is the width of the diaphragm, as described with reference to fig. 8B, which is not repeated herein.

As described in the second aspect of the present invention, the diaphragm 108 is, for example, a strip-shaped hole or a circular hole, and is made of any one of the following materials: metal, glass that absorbs or reflects light, or ceramic.

Or as described in the second aspect of the present invention, the ghost elimination device includes a light-shielding sheet. And will not be described in detail herein. Preferably, the ghost wire eliminating means is configured to block a light beam that is not reflected once by the receiving end mirror structure. For example, in the case where the receiving-end reflecting mirror structure shown in fig. 14 includes the first reflecting mirror 107-1 and the second reflecting mirror 107-2 disposed to face each other, the ghost-wire eliminating means is configured to block light beams other than those reflected once by the first reflecting mirror and the second reflecting mirror, respectively.

Further preferably, as shown in fig. 14, the angle θ between the deflected beam by the compensated mirror 104 and the main field of view of the lidar₁Less than the angle theta between the ghost view field and the main view field₂And theta₃。

The compensating mirror provided by the invention can deflect a small part of light beam, and the angle theta between the deflected light beam and the main view field of the detector₁Angle theta smaller than angle theta between ghost view and main view of mechanical radar with double-mirror folded optical path₂And theta₃As shown in fig. 14 (line L2 represents the beam of the main field of view FOV B of the detector, and lines L1 and L3 represent the beams of the ghost fields FOV a and FOV C), and therefore no new ghost lines are introduced for application above a lidar in which the ghost fields are eliminated by the diaphragm scheme. E.g. angle theta between the beam deflected by the compensator 104 and the main field of view of the lidar₁Greater than the angle theta between the original ghost line field of view and the main field of view₂Or theta₃New ghost lines are then introduced on both sides of the deflected beam. The provision of a compensating mirror in a lidar receiving system typically introduces new ghost lines.

In addition, lidar 100 also includes a transmitting end mirror configuration. The transmitting end mirror structure includes at least one mirror, as shown in FIG. 14, which schematically illustrates two mirrors 106-1 and 106-2, and those skilled in the art will readily appreciate that the transmitting end mirror structure may include a greater or lesser number of mirrors. The transmitting end reflector structure is arranged between the laser 101 and the transmitting lens 102, and is used for receiving the laser beam emitted by the laser 101, reflecting the laser beam to enable the laser beam to be incident on the transmitting lens 102, shaping the laser beam and then emitting the laser beam.

Fig. 15 shows an embodiment of the invention in which the components of the lidar system consist essentially of: a laser, an emission lens, a compensation mirror, a receiving lens, a folded receiving end mirror structure, a detector (e.g., APD), and the compensation mirror is located, for example, at the center of the emission lens (within the aperture stop area).

Fig. 16 shows another embodiment of the present invention, which differs from fig. 15 in that a stop is added to the lidar structure that blocks the ghost view field. The compensating mirror may be a wedge, a microprism, a diffractive element, or a combination of these with a spherical lens or a cylindrical lens, respectively, capable of deflecting a small portion of the emitted beam by a specific angle. In addition, the compensation mirror can be fixed to the emission lens by means of an adhesive or by means of a holder.

According to a preferred embodiment of the present invention, the transmitting lens and the receiving lens are juxtaposed in the horizontal direction, and the relationship between the deflection angle of the compensation mirror and the reduction of the near-distance blind area range is shown in fig. 17.

In FIG. 17, the beam deflection angle is θ₁(θ₁The angle between the beam deflected by the compensation mirror and the receiving beam (i.e. the main field beam L2) is D, the diameter of the receiving lens is D, the region of the close-distance signal enhancement is L at the farthest distance from the vertex of the receiving lens and L' at the nearest distance from the vertex of the receiving lens, and as shown in the figure, the following relationship is satisfied:

L'＝L-D/tanθ₁

therefore, parameters such as the installation position and the deflection angle of the compensation mirror can be determined according to the minimum distance L' needing to be enhanced through the relational expression.

In the invention, the ghost line view field can be shielded by adopting the light-shielding sheet, and the specific content is clearly described in the patent before the ghost line view field, and is not described again here.

The invention also relates to a method 200 for detection using a lidar 100 as described above, as shown in fig. 18, comprising:

step S201: emitting a laser beam by the laser;

step S202: shaping the laser beam through the transmitting lens and emitting a detection beam;

step S203: deflecting, by the compensation mirror, at least a portion of the laser beam and/or the detection beam towards the receive lens;

step S204: and receiving the light beam of the probe light beam reflected by the external obstacle of the laser radar through the receiving lens.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A lidar comprising:

a laser configured to emit a laser beam;

2. The lidar of claim 1, wherein the aperture stop region is located on a side of the transmit lens that is closer to the laser, or a side that is further from the laser, or a middle of the transmit lens.

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

4. The lidar according to any of claims 1-2, wherein the compensating mirror is located in the aperture stop area close to the receive lens.

5. The lidar of claim 4, wherein the transmit lens is juxtaposed with a receive lens along a horizontal direction, a position of the compensating mirror satisfying the following relationship:

L′＝L-D/tanθ₁

d is the diameter of the receiving lens,

6. The lidar according to any of claims 1-2, wherein an angle between the compensated mirror-deflected light beam and a lidar main field of view is smaller than an angle between a ghost line field of view and the main field of view,

7. The lidar of claim 6, wherein the ghost elimination apparatus comprises an optical stop, the optical stop and the detector satisfying the following relationship:

8. The lidar according to claim 7, wherein the diaphragm is in the shape of a strip hole or a round hole, the diaphragm being made of any one of the following materials: metal, glass that absorbs or reflects light, or ceramic.

9. The lidar of claim 6, wherein the ghost elimination device comprises a light barrier.

10. The lidar according to claim 7 or 9, wherein the ghost wire eliminating means is configured to obstruct a light beam not primarily reflected by the mirror structure.

11. The lidar according to claim 7 or 9, wherein the receiving end mirror structure comprises a first mirror and a second mirror arranged opposite to each other, the detector comprises a photodiode, and the ghost eliminating means is configured to block light beams other than those reflected once by the first mirror and the second mirror, respectively.

12. A method of detection using a lidar according to any of claims 1 to 11, comprising:

emitting a laser beam by the laser;