CN112068150A

CN112068150A - Laser radar and ranging method

Info

Publication number: CN112068150A
Application number: CN202010885895.7A
Authority: CN
Inventors: 朱雪洲; 闫凯民; 刘海华; 向少卿
Original assignee: Hesai Technology Co Ltd
Current assignee: Hesai Technology Co Ltd
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2020-12-11
Anticipated expiration: 2040-08-28
Also published as: CN117741679A; CN112068150B

Abstract

The invention relates to a lidar comprising: a transmitting unit including a plurality of lasers and a driving circuit configured to drive the lasers to emit a detection laser beam for detecting a target object, wherein the transmitting unit further includes a blind-fill unit configured such that the target object in a short range of the laser radar can receive the detection laser beam and a reflected echo can be received by the detector; a receiving unit including a plurality of detectors configured to receive echoes of the detection laser beams reflected by the target object and convert the echoes into electrical signals; and a processing unit coupled to the receiving unit and configured to receive the electrical signal to calculate the distance and/or reflectivity of the target object.

Description

Laser radar and ranging method

Technical Field

The present disclosure relates to the field of photoelectric detection, and more particularly, to a laser radar and a method for ranging using the same.

Background

Laser radar is a range finding sensor commonly used, has characteristics such as detection range is far away, resolution ratio is high, receive environmental disturbance little, and the wide application is in fields such as intelligent robot, unmanned aerial vehicle, unmanned driving. The principle of operation of lidar is to estimate the magnitude of the distance using the time of flight (TOF) taken by the probe laser beam to and from the lidar and the target.

Traditional mechanical radar, the transmission light passes through the inflection of 2 speculum, through the emergence of transmission lens group, incides on external object and is reflected, and the echo passes through the receiving lens group, is received by the detector after the inflection of 2 speculums, later through subsequent digital signal processing, through calculating time of flight TOF, reachs the distance information of external object and radar.

In addition, the conventional lidar is a separate transmitting and receiving optical system, in order to test a long-distance target, the laser emission beam and the field of view of the detector are aligned at a long distance (e.g. 200m), as shown in fig. 1A, in a certain distance range close to the lidar, the laser emission beam and the field of view of the detector are completely non-overlapped, so that in this distance range, the detector of the lidar cannot receive the signal light reflected by the target obstacle, or the received signal light is very 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 emitting optical path and the signal receiving optical path are not completely overlapped, and with reference to fig. 1A, the transmitting lens and the receiving lens are horizontally translated.

Regarding the generation of the close range blind zone, there can be 2 explanations:

the first explanation: referring to fig. 1A, the near-distance blind area is an area where the emitted laser beam does not overlap at all with the reception field of view at a near distance. 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 from the targets in this area, and thus there is no cloud of points from the obstacles that generated this area.

The second explanation: referring to fig. 1B, if there is a target in the near-distance blind area, 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 shown schematically in FIG. 1B. 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 traditional laser radar has a large close-range blind area (for example, more than 5m), and a target object in the blind area (0-5m) can not be detected by the laser radar, so that potential safety hazards are caused to products using the laser radar.

In addition, in the conventional radar, the laser at the transmitting end and the driving circuit of the laser are arranged on different circuit boards and even on different components, the wiring connected with each other is long, and the signal loss is high. The detector at the receiving end and the analog front-end circuit required by the detector are also arranged on different circuit boards and even arranged on different components, and similar loss problems exist, and for a high-precision distance measurement system such as a laser radar, the lost signals are also very important.

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 problems of the prior art, the present invention provides a laser radar including: a transmitting unit including a plurality of lasers and a driving circuit configured to drive the lasers to emit a detection laser beam for detecting a target object, wherein the transmitting unit further includes a blind-fill unit configured such that the target object in a short range of the laser radar can receive the detection laser beam and a reflected echo can be received by the detector; a receiving unit including a plurality of detectors configured to receive echoes of the detection laser beams reflected by the target object and convert the echoes into electrical signals; and a processing unit coupled to the receiving unit and configured to receive the electrical signal to calculate the distance and/or reflectivity of the target object.

The invention also provides a laser ranging method, which comprises the following steps:

emitting a detection laser beam by an emission unit including a plurality of lasers and a driving circuit;

changing the direction of the detection laser beam through a blind complementing unit so that a target object in a short distance range can receive the detection laser beam and the reflected echo can be received by a detector;

receiving echoes from the target object by a plurality of detectors, converting the echoes into electrical signals,

reading the electrical signal output by the detector through an analog front end component; and

and calculating the distance and/or the reflectivity of the target object according to the electric signal.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure. In the drawings:

FIGS. 1A and 1B are schematic diagrams illustrating possible causes of near blind zones;

FIG. 1C illustrates a lidar in accordance with one embodiment of the present invention;

FIG. 1D illustrates an application scenario of a lidar in accordance with one embodiment of the present invention;

FIG. 2 shows a laser and a driving circuit in a conventional laser radar;

FIG. 3A shows a transmitting unit according to an embodiment of the invention;

FIG. 3B shows a detection unit of an embodiment of the invention;

FIG. 4A shows a top view of a lidar in accordance with one embodiment of the present invention;

FIG. 4B shows the internal structure of the lidar according to the embodiment of FIG. 4A;

FIG. 4C shows a top view of the lidar according to the embodiment of FIG. 4A;

FIG. 4D shows a schematic diagram of the optical path of the lidar according to the embodiment of FIG. 4A;

FIG. 4E shows a blind area comparison schematic using the embodiment of FIG. 4A and a prior art lidar;

FIG. 4F is a schematic diagram showing the relationship between parameters of the optical path of the laser radar according to the embodiment in FIG. 4A;

fig. 5 shows a blind complementing unit according to another embodiment of the invention;

FIG. 6 illustrates a blind-fill light source according to one embodiment of the present invention;

FIG. 7 illustrates a lidar in accordance with one embodiment of the present invention;

FIG. 8 shows a schematic view of an upper and lower deck;

FIG. 9 shows a schematic view of the upper deck from the top;

FIG. 10 shows a bottom view of the opto-mechanical rotor;

FIG. 11 shows a perspective view of the opto-mechanical rotor;

FIGS. 12, 12A and 13 show the transmitting lens group and the receiving lens group secured to the lidar by the resilient tab assembly;

fig. 14 shows a mounting diagram of a PCB circuit board with a laser and a driving circuit mounted in a transmitting unit of the laser radar;

fig. 15A and 15B are schematic views showing mounting of a PCB circuit board with a detector and an analog front-end circuit mounted in a receiving unit of a laser radar;

fig. 16A and 16B are schematic diagrams illustrating the back surface of a PCB circuit board at the transmitting end and the back surface of a PCB circuit board at the receiving end of the lidar, respectively;

FIG. 17 illustrates a ranging method according to an embodiment of the present invention; and

fig. 18 shows a ranging method according to another 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.

Fig. 1C shows a lidar 100 according to an embodiment of the present invention, which may be used in various fields, such as unmanned driving, V2X, sweeping robots, logistics carts, etc., and fig. 1D shows an application scenario of the lidar according to an embodiment of the present invention, which is described in detail below with reference to the accompanying drawings.

As shown in fig. 1C, laser radar 100 includes a transmitting unit 110, a receiving unit 120, and a processing unit 130. Wherein the transmitting unit 110 comprises a plurality of lasers 111 and a driving circuit 112 (as shown in fig. 3A). The driving circuit is used for driving the laser to emit a detection laser beam L1 to detect the target object. The laser may be an edge emitting laser (eel), a vertical cavity surface emitting laser (vcsel), or even a mixture of eel and vcsel. In a specific light emitting mode, the lasers can emit light (crosstalk is reduced) one by one according to a certain sequence, part of the lasers can emit light simultaneously, and all the lasers can emit light simultaneously. The laser device needs to establish high voltage when working, and can control the on-off of laser device through switch circuit, and drive circuit can be used for establishing the required high voltage of its normal work and on-off control for the laser device to control the luminous time and the time length of laser device, with the demand of cooperation realization laser radar product detection distance to and the index of considering human eye safety. The present invention does not relate to a specific structure of the driving circuit, and thus the structure of the driving circuit is not described excessively.

The receiving unit 120 includes one or more detectors 121 configured to receive the echo L1' of the detection laser beam L1 reflected by the target object and convert it into an electrical signal, and an analog front-end component 122 (shown in fig. 3B), which is coupled to the detectors 121 and adapted to read and amplify the electrical signal output by the detectors 122.

According to one embodiment of the invention, the detector may comprise an avalanche diode, APD. The signal output by the avalanche diode APD is an analog signal, which is typically weak, so the analog front end component 122 may include an analog-to-digital converter ADC and an optional signal amplification circuit for converting the analog signal output by the avalanche diode APD into a digital signal and amplifying the digital signal for subsequent digital signal processing. According to one embodiment of the invention, the detector may also include a plurality of Single Photon Avalanche Diodes (SPADs), each of which may be responsive to incident photons. For a single photon avalanche diode, the output signal is a digital signal, and correspondingly, the analog front end component 122 may include a time-to-digital converter TDC. In the present invention, the detector may also include other types of photodiodes or detectors (such as SiPM), and the analog front-end component may correspond to a specific detector, and read and amplify the signal output by the detector.

The processing unit 130 is coupled to the receiving unit 120, and optionally to the transmitting unit 110, and is configured to receive the electrical signal to calculate the distance and/or reflectivity of the target object. The processing unit 130 may calculate the distance to the target object according to the flight time of the detection pulse, and may calculate the reflectivity of the target object according to the intensity of the echo, which is not described herein again.

Fig. 2 shows a laser and a driving circuit arrangement in a conventional laser radar, which is considered by the inventor of the present application, and as shown in fig. 2, a plurality of lasers (and a circuit board) are arranged on a laser holder, and a driving circuit is arranged on a transmitting circuit holder. The laser device support and the emitting circuit support are separated from each other, and the laser device and the driving circuit are electrically connected through the flexible flat cable, so that the laser device is driven to emit light. In the arrangement mode shown in fig. 2, the laser at the emitting end and the driving circuit of the laser are arranged on different circuit boards, and the wiring between the laser at the emitting end and the driving circuit of the laser is long, so that the signal loss is high. Similar problems exist for the detector at the receiving end and the analog front-end circuitry required for the detector.

As shown in fig. 3A and 3B, the laser 111 and the driving circuit 112 are disposed on the same PCB, and the detector 121 and the analog front-end component 122 are disposed on the same PCB, which is a direct comparison with the prior art scheme of fig. 2, it can be seen that the scheme of the present application greatly avoids the problem of long routing, and for the laser radar product with high performance requirement, even a weak SNR improvement can contribute to the overall radar detection effect, which is a high improvement. In addition, through reducing the line length of walking, can optimize or alleviate laser radar's electric crosstalk, be favorable to improving the range finding precision of target object.

In addition, after the chip scheme is adopted, the number of plug connectors required in a board-level circuit of the existing laser radar can be reduced, and the assembly is also more convenient.

Fig. 3A shows a transmitting unit 10 according to an embodiment of the present invention, in which the driving circuit 112 is integrated with the laser 111 on the same PCB circuit board. As shown in fig. 3A, the driving circuit 112 is integrated in the form of a chip, and a plurality of lasers 111 are disposed on the same PCB circuit board together with the driving circuit 112 corresponding thereto. According to an embodiment of the present invention, the driving circuit 112 and the laser 111 may be in a one-to-one correspondence relationship. Alternatively, the driving circuit 112 is in a one-to-many relationship with the laser 111. For example, as shown in fig. 3A, the driving circuit 112 may be a multi-channel chip, such as 4 lasers 111 may be connected and driven. For a 32-line lidar, 4 chips of drive circuit 112 may be used. In addition, preferably, the GaN switches and capacitors needed for operation of the laser 111 may also be provided on the same PCB circuit board. The GaN switch is preferably a dual-channel GaN switch, i.e., one GaN switch is connected to 2 lasers. Of course, single channel GaN switches may also be used. These are all within the scope of the present invention. In addition, the PCB circuit board provided with the laser 111 and the driving circuit 112 is preferably connected to the upper chamber plate of the lidar by a flexible disk line.

In addition, in the embodiment of the invention, all the lasers of the laser radar and the corresponding driving circuits can be arranged on one PCB. Alternatively, for the high-beam laser radar, such as 64-line or 128-line laser radar, all the lasers and the driving circuit can be arranged on one PCB, and meanwhile, the laser can be arranged on a plurality of PCBs in consideration of the performance indexes of simpler assembly, electrical isolation requirements and radar vertical resolution, but each laser and the driving circuit corresponding to the laser are ensured to be arranged on the same PCB, so that the problem of overlong routing can be avoided. Of course, for the high beam lidar, as the package size of the laser is continuously reduced, it is also feasible to arrange the laser and the driving circuit on the same circuit board, and the invention is also within the protection scope.

The chip of the driving circuit 112 may be configured according to the requirements of the lidar operation. Taking 16-line laser radar as an example, when the rotation speed of the laser radar is 10HZ, for example, the 16-line laser is driven to sequentially emit light at intervals of 0.1 °. In the process of driving the laser, rapid charging and discharging are needed, and a plurality of parasitic capacitances exist in the board level circuit in the prior art to influence the work and the speed of the circuit.

Fig. 3B shows a detection unit 120 of an embodiment of the present invention, in which a detector 121 is integrated with an analog front-end component 122 on the same PCB circuit board. As shown in fig. 3B, the analog front-end components 122 are integrated in the form of a chip, and a plurality of probes 121 and the corresponding analog front-end components 122 are disposed on the same PCB circuit board. Preferably, the analog front-end component 122 is a multi-channel chip, such as a 16-channel chip as shown in fig. 3B, and each chip can be connected to 16 detectors 121 to read and amplify the electrical signals output by the detectors 121. For a 32-line lidar, two chips of analog front end components 122 may be provided. The detector 121 may be an avalanche diode, an SiPM, or a SPADs. As shown in fig. 3B, the analog front end module is preferably connected to the upper bulkhead of the lidar via a floppy disk line.

In addition, in the embodiment of the present invention, all the detectors 121 of the lidar, together with the corresponding analog front-end components 122, may be disposed on a PCB circuit board. Alternatively, the detectors may be disposed on multiple circuit boards, but each detector and the analog front end component 122 corresponding to the detector are ensured to be disposed on the same PCB, which can avoid the problem of too long routing. And will not be described in detail herein.

After the detection laser beam emitted by the laser radar is subjected to diffuse reflection of a target object, part of echo returns to the laser radar, is received by a detector of the laser radar and is converted into an electric signal. When the distance between the target object and the laser radar exceeds a certain distance range (for example, within more than or equal to 5 meters), the transmitting view field and the receiving view field are at least partially overlapped, so that the echo reflected by the target object can be converged on a detector by a receiving lens group of the laser radar, and further the obstacle information can be generated on a point cloud image of the laser radar. When the target object is close to the lidar (for example, within 5 meters), the transmitting field of view and the receiving field of view do not overlap completely, so that from the perspective of the lidar, any information of the target object cannot be presented in the point cloud image, that is, the lidar cannot detect the target object, and for possible reasons of the generation of the close-range blind area, please refer to related descriptions in fig. 1A and 1B, which are not described herein again. For the existing laser radar of the paraxial light path system, a certain detection blind area is usually provided, a target object in the detection blind area cannot be detected by the laser radar, and the range of the detection blind area is also an important index for measuring the performance of the laser radar.

The inventor of the application conceives that the blind area of the radar can be greatly reduced by additionally arranging the blind supplementing unit at the transmitting end of the laser radar. Specifically, the blind complementing unit may be disposed downstream of the optical path of the laser, the detection beam emitted by the laser may be received by a target object in a short distance range after being processed by the blind complementing unit, and an echo reflected by the target object in the short distance range may be received by the detector and further processed by the subsequent signal processing unit, and finally information of the obstacle is presented in a cloud point image obtained by scanning with the laser radar. In other words, the blind complementing unit can deflect a part of the emitted light to the receiving field of view of the detector at a specific angle, so that the light beam emitted by the blind complementing unit starts to overlap the receiving field of view of the detector in a region close to the radar, thereby reducing the near-distance blind area. This application is through adopting mend blind unit, greatly reduced the blind area scope of radar, eliminated the blind area completely even, greatly promoted the performance of radar. To facilitate a better understanding and implementation of the present application by those skilled in the art, various embodiments of blind complementing units are described in detail below with reference to specific fig. 4A-4E. In a specific implementation, the short-distance range may be 0 to 3m, or 0.1m to 2m, or 0.3m to 2.5m, and those skilled in the art may adapt to information such as a detection distance requirement of the laser radar, a size of the radar, and a parameter of a lens group of the radar when actually implementing the present application. The relationship between the deflection angle of the blind complementing unit and the reduction of the near-distance blind area range is shown with reference to fig. 4F. In fig. 4F, the light beam deflection angle is θ (θ is an angle between the light beam deflected by the blind complementing unit and the received light beam), the distance from the position where the radar exits to the center of the receiving lens is D, the diameter of the receiving lens is D, the near-distance signal enhancement region is L farthest from the vertex of the receiving lens and L' nearest to the vertex of the receiving lens, and as shown in fig. 4F, the following relationship is satisfied between them:

L′＝L-D/tan θ

therefore, parameters such as the installation position and the deflection angle of the blind compensation unit are determined according to the minimum distance L' to be enhanced by the relational expression.

Fig. 4A shows a top view of lidar 100 according to one embodiment of the invention. As shown in fig. 4A, the transmitting unit 110 of the laser radar 100 includes a laser 111, a first reflecting mirror 113 (may also be referred to as a first reflecting portion), and a transmitting lens group 115. Wherein the laser 111 emits a detection laser beam, the detection laser beam irradiates the first reflector 113, is reflected toward the emission lens group 115, and passes through a mask of the laser radar 100 after being modulated (e.g., collimated) by the emission lens group 115 and exits into the surrounding environment. The transmitting unit 110 further comprises a second mirror 114 (second reflecting part) serving as a blind-fill unit, the first mirror 113 and the second mirror 114 being arranged relatively non-parallel, i.e. the first mirror 113 and the second mirror form an angle different from zero. The second mirror 114 deflects the detection laser beam more toward the receiving optical axis of the receiving unit than the first mirror 113, so that at least a part of the target object in the dead zone can receive the detection laser beam and the reflected echo can be received by the detector.

In fig. 4A, during the operation of the laser radar, the detection laser beam emitted from the laser 111 is not strictly collimated light, but is divergent light with a relatively large divergence angle, so that some light reaches the second reflecting mirror 114, and since the light can irradiate a target object at a short distance, although the intensity of the light is relatively weak, the echo intensity is enough to be received by the detector because the distance to the target object is small, and the electrical signal output by the detector can be used for subsequent signal processing and calculation.

The first mirror 113 and the second mirror 114 may be disposed adjacently, and disposed non-parallel in the optical path downstream of the laser 111, to receive the detection laser beam emitted from the laser 111. The emission lens group 115 is disposed downstream of the optical paths of the first reflector 113 and the second reflector 114, and the detection laser beam is reflected by the first reflector and the second reflector, directly enters the emission lens group 115, and is modulated by the emission lens group 115 and then exits. According to an embodiment of the invention, both the first mirror 113 and the second mirror 114 may be integrally formed, i.e. belong to different parts of the same mirror (at an angle to each other). Alternatively, the first reflector 113 and the second reflector 114 may be separate reflectors, and fixed on the reflector holder by glue or mechanical fastener, for example, and the specific manufacturing and installation manner of the first reflector 113 and the second reflector 114 are not limited in this application.

The first mirror 113 may be used as a primary mirror (mainly for detecting other obstacles in non-blind areas), and the second mirror 114 may be used for blind-fill, preferably making an angle with the reflecting surface of the first mirror 113 greater than 180 °, less than 360 °, preferably 190 degrees, for example, to enhance the near blind-fill function. It can be understood that the included angle formed by the reflecting surfaces of the first reflecting mirror 113 and the second reflecting mirror 114 is related to the size of the optical-mechanical rotor of the whole laser radar, and the included angle is set in consideration of both blind compensation and deflection of the light beam reflected by the blind compensation reflecting mirror to exit out of the radar. In addition, since the detection laser beam is reflected by the first reflecting mirror and the second reflecting mirror and then directly enters the emission lens group 115, the space of the laser radar can be fully utilized by the design of the once-returning light path, and the focal length of the radar is enlarged in a limited space. In this embodiment, the width of the first reflector 113 may be greater than that of the second reflector 114, and the second reflector may reflect a part of light from the light source to a target object closer to the laser radar, so as to achieve the effect of blind-spot compensation.

To further facilitate the effect of adding the blind-fill unit, fig. 4D shows the schematic diagram of the optical path of the lidar with the second reflecting mirror 114 added, and fig. 4E shows the schematic diagram of the blind area improvement of the lidar with the second reflecting mirror 114 added. Referring to fig. 4D and 4E, most of the laser light emitted from the laser 111 is incident on the first reflecting mirror 113, reflected by the first reflecting mirror 113, and then emitted to the outside of the laser radar through the reflecting lens group 115 to form a detection laser beam L1; a small portion of the laser light (e.g., a portion of the light that may be an off-edge with a large divergence angle) emitted from the laser 111 is incident on the second reflecting mirror 114, reflected by the second reflecting mirror 114, and then emitted to the outside of the laser radar through the reflecting lens group 115, so as to form a blind-supplementary laser beam L2. The blind-fill laser beam L2 is closer to the reception optical axis of the reception lens group 125 than the detection laser beam L1 (see fig. 4A). It will be appreciated that the blind-fill unit functions to split a portion of the emitted laser beam from the emitted beam and redirect it (which may also include a change in the divergence angle of the emitted beam) from a position very close to the radar 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. Referring to fig. 4E, after the blind compensating reflector is adopted, the blind area is greatly reduced, and can be even reduced to 0.

With continued reference to fig. 4A, the receiving unit 120 may further include a receiving lens group 125, and a filter 123 and a mirror 124 disposed in the optical path upstream of the detector 121. The detector 121 is disposed on the focal plane of the receiving lens group 125. Wherein the mirror 124 and the filter 123 are sequentially disposed between the receiving lens group 125 and the detector 121. The echo from the object is converged by the receiving lens group 125, then changed in direction by the reflecting mirror 124, passes through the filter 123, is incident on the detector 121, and is converted into an electric signal by the detector 121. By providing the filter 123 on the surface of the detector 121, adapted to filter the probe echo incident to the detector, and selecting a predetermined wavelength range of the probe echo incident to the detector, the influence of noise light can be reduced. Meanwhile, the problem of blue shift of wavelengths of different light beam incidence angles is considered, and the bandwidth of the optical filter can be properly increased on the premise of balancing the signal-to-noise ratio.

Fig. 4B shows an internal structure of the laser radar according to the embodiment of fig. 4A, and fig. 4C shows a top view of the laser radar. As shown in fig. 4B and 4C, the emission unit 110 includes two mirrors, a first mirror 113 and a second mirror 114, which are disposed non-parallel. In addition, the width of the first reflector 113 is greater than that of the second reflector 114, the first reflector 113 is used for normal laser radar detection, and the second reflector 114 is used for near-distance blind repairing, namely, part of detection laser beams emitted by the light source 111 are reflected to an obstacle close to the laser radar, so that the blind repairing effect is achieved.

In addition, according to an embodiment of the present invention, as shown in fig. 4C, the receiving unit 120 of the lidar further includes a light barrier 126, and the light barrier 126 is located between the reflector 124 and the detector 121, and is used for blocking part of the echo reflected from the reflector 124, so that ghost lines in the lidar point cloud can be reduced.

Fig. 5 shows a blind-fill unit according to another embodiment of the invention. As shown in fig. 5, the blind complementing unit includes a first blind complementing reflector 116 and a second blind complementing reflector 117 located outside the transmitting lens group 115, where the first blind complementing reflector 116 and the second blind complementing reflector 117 may be disposed in parallel or disposed in non-parallel, as long as the detection light beam that is refracted by the first blind complementing reflector 116 and the second blind complementing reflector 117 may be closer to the receiving optical axis than the light beam that is not refracted, so that the detection light beam may be received by an obstacle within a preset threshold range (e.g. less than or equal to 5m), and the echo reflected by the obstacle may be received by a detector, so that the information of the obstacle may finally appear in the point cloud of the radar. The first blind complementing mirror 116 receives the detection laser beam emitted from the emitting lens group 115 and reflects it toward the second blind complementing mirror 117, which reflects the detection laser beam and emits it to the outside, forming a blind complementing laser beam L2, wherein the blind complementing laser beam L2 is further close to the optical axis of the receiving lens group 125 with respect to the detection laser beam emitted from the emitting lens group, thereby enhancing the blind complementing effect.

Fig. 4A-4D, and fig. 5 show two embodiments of a blind-fill unit, respectively. It is easy to conceive for those skilled in the art that the two embodiments can be combined together to further deflect the detection laser beam toward the receiving optical axis of the receiving lens group 125 to further enhance the blind-compensating effect.

In addition, as shown in fig. 6, in order to enhance the blind-complementing effect, the blind-complementing unit may include blind-complementing light sources (for example, 3 to 8, the specific number is selected as required, and the application is exemplified by 3) which are disposed at a position deviated from the focal plane of the emission lens group.

As shown in fig. 6, the lasers 111 and the detectors 121 are generally in one-to-one correspondence, and the lasers 111 are disposed on the focal plane of the emission lens group 115, so that the laser beams emitted by the lasers 111 can be reflected and collimated, and then emitted from the laser radar as parallel light, and when the laser beams irradiate a target object at a maximum detection distance (e.g., 200m) and the echoes return to the laser radar, the laser beams are received by the detectors 121 corresponding to the lasers 111. In order to reduce the blind area, a blind-fill light source 111' is added to the present embodiment, which is disposed to be deviated from the focal plane position of the transmitting lens group 115. Therefore, after the laser emitted from the blind-fill light source 111' is reflected by the target, the spot formed by the echo on the photodetector is relatively large (as circled by the dotted line shown in fig. 6), and can cover a plurality of detectors 121 (four detectors 121 are shown in fig. 6). When the target is far away, the light energy on the detector 121 is very low and may not be sensed by the detector 121, or will be filtered out as noise, and only the echo reflected by the target at a close distance is enough to be received by the photodetector, so it can be used to make up for the close distance.

Preferably, the laser comprises an edge-emitting laser, the detector comprises an Avalanche Photodiode (APD), and the edge-emitting lasers preferably emit light not simultaneously but sequentially in a certain order, so that crosstalk between detection channels can be reduced, and the signal-to-noise ratio can be improved. The probing laser pulses emitted by the laser may be encoded with double pulses, for example by the time interval and/or amplitude of the double pulses, to reduce cross-talk. The luminous intensity of the laser may be fixed, i.e. emitted at the same power per detection. Alternatively, the luminous intensity of the laser may be dynamically adjusted, for example, according to the intensity of the ambient light of the lidar. For example, when the ambient light intensity of the laser radar is higher than a threshold value, the luminous intensity or power of the laser is increased; when the ambient light intensity is below the threshold, the light emission intensity or power of the laser is reduced. In addition, the light emitting intensity of the laser can be adjusted according to the target object reflectivity detected by the previous channel. For example, when the reflectivity of the target is high, the light emission intensity or power of the laser can be reduced appropriately; when the target reflectance is low, the light emission intensity or power of the laser can be appropriately provided.

Fig. 7 shows a lidar according to an embodiment of the invention, as shown in fig. 7, the lidar further includes an upper chamber plate 101, a lower chamber plate 102, and a rotating shaft 103, wherein the rotating shaft 103 is located between the upper chamber plate 101 and the lower chamber plate 102. The rotor of the optical machine, which is composed of the emitting unit 110 and the receiving unit 120, is fixed on the upper chamber plate and is driven to rotate by the motor through the rotating shaft. In the embodiment of fig. 7, the optical machine rotor and the upper bin plate 101 are fixed together and are driven to rotate together by the rotating shaft 103, the rotating frequency is, for example, 10Hz or 20Hz, detection is performed every preset angle (for example, 0.1 degree or 0.2 degree) during the rotation process, the laser of the transmitting unit 110 performs round-robin transmission to complete transmission of one cycle, and meanwhile, the receiving unit 120 receives an echo and performs corresponding signal processing to complete detection.

In addition, in the embodiment of fig. 7, the rotating shaft 103 does not penetrate through the entire height of the lidar, but only occupies a small portion of the height of the lidar, so that the space above the upper chamber plate can be fully used for the optomechanical rotor of the lidar, and the arrangement and utilization of the space are facilitated. In addition, due to the adoption of the scheme of a non-penetrating shaft, the rotating shaft and the bearing are enlarged, and the service life and the reliability of the shaft system can be enhanced. To drive the shaft, the lidar may further include a motor (not shown), which may be disposed on the lower deck 102. The motor terminal can be integrated into a flexible disk wire first, avoiding the need for soldering.

Fig. 8 shows a schematic view of the upper and

lower deck plates

101 and 102, and fig. 9 shows a schematic view of the upper deck plate 101 as viewed from the top. As shown in fig. 8, lidar 100 also includes a communication upper board 104 and a communication lower board, wherein the communication lower board is integrated with the lower bulkhead 102. A two-way wireless communication link may be established between the upper communication board 104 and the lower communication board. The description will be made taking a bidirectional communication link as an example. Detection signals formed after target object detection is carried out on an optical machine rotor of the laser radar can be transmitted from the upper communication plate 104 to the lower communication plate through a downlink communication link, and then transmitted to the lower bin plate, and after operations such as adding a coordinate system and the like of the lower bin plate, point clouds of the laser radar are generated; if it is desired to control the illumination of certain lasers or to adjust the intensity of illumination of certain lasers or to gate certain detectors, corresponding control signals to be sent to the opto-mechanical rotor may be transmitted from the lower communication board to the upper communication board 104 via the upstream communication link. The communication upper plate is arranged to be emptied on the rotating shaft, and is supported above the upper chamber plate through a plurality of base plates, so that the communication upper plate is spaced from the rotating shaft by a certain distance. Communicating with the upper plate 104 and coupled to the upper plenum plate 101. As shown in fig. 9, the communication upper plate 104 is, for example, long.

Fig. 10 shows a bottom view of the optomechanical rotor, and fig. 11 shows a perspective view of the optomechanical rotor after being flipped over. As shown in fig. 10 and 11, a cavity 1011 corresponding to the communication upper board 104 is disposed at the bottom of the optical mechanical rotor for accommodating the communication upper board 104. In this manner, communication upper plate 104 is embedded in the opto-mechanical rotor, and therefore communication upper plate 104 does not substantially increase the overall height of the lidar, helping to keep the height of the lidar at a small level, thereby matching the needs of individual customers.

When the detector comprises an avalanche photodiode APD, said receiving unit may further comprise an amplifying circuit coupled with said avalanche photodiode to amplify said electrical signal and an analog-to-digital converter ADC coupled with said amplifying circuit and analog-to-digital converting the amplified electrical signal. Additionally or alternatively, the detector comprises a SiPM or a single photon avalanche diode SPAD, and the receiving unit further comprises a time-to-digital converter coupled to the detector.

In the existing laser radar, the transmitting lens group and the receiving lens group are usually fixed by glue. The operation process of fixing with glue is more tedious, for example, the selection of the glue, the curing temperature of the glue, the required time for curing, the stress caused by curing, the temperature-resistant condition after curing and the like are involved. According to an embodiment of the present invention, instead of fixing the transmitting lens set and the receiving lens set by using glue, the transmitting lens set and the receiving lens set may be fixed on the laser radar through the elastic piece assembly and the optical-mechanical rotor. As shown in fig. 12, 12A and 13, the transmitting lens group 115 and the receiving lens group 125 are preferably fixed to the lidar by the resilient member 107, thereby achieving a more reliable connection. The resilient assembly 107 may be disposed on a frame or housing of the lidar, and the resilient assembly 107 compresses the transmitting lens group 115 and the receiving lens group 125 in place by the resilience of the resilient assembly or by using screw fasteners. After glue is replaced by the elastic sheet assembly, the reliability of the laser radar can be greatly improved.

Fig. 14 shows a schematic diagram of a PCB circuit board in which a laser and a driving circuit are mounted in the transmitting unit 110 of the laser radar. When fixing the PCB, it is preferable to fix the PCB by using a pressing plate and a screw instead of glue.

Fig. 15A and 15B show a mounting schematic diagram of a PCB circuit board in which the probe 121 and the analog front-end circuit 122 are mounted in the receiving unit 120 of the laser radar. When mounting the PCB, it is preferable to use a screw method. This circuit board of the receiving unit 120 is shown in fig. 15A, as shown, with, for example, four through holes therein. The receiving unit 120 also includes a mounting member (shown in fig. 15B) that also has through holes therein, for example, at locations corresponding to the through holes in the PCB circuit board. And the screws penetrate through the through holes on the mounting part and the through holes on the circuit board so as to fix the circuit board. In addition, when the circuit board is mounted, a certain margin is required in the left-right direction, the up-down direction, and the direction perpendicular to the paper surface in the drawing for the convenience of mounting. For example, the through hole of the circuit board and the through hole of the mounting member have a diameter larger than the diameter of the screw, so that the circuit board, that is, the position of the probe 121, can be adjusted in the left-right direction and the up-down direction in the drawing. This is particularly advantageous in lidar calibration, as it is often necessary to fine tune the position of the detector 121 so that it can receive the echo generated by the detection laser beam from the corresponding laser. In the direction perpendicular to the paper in fig. 15A and 15B, the positioning may be performed by adding a spacer to the bottom of the PCB circuit board.

Fig. 16A and 16B show the way of electrical connection of the circuit board of the transmitting unit and the circuit board of the receiving unit. As shown in fig. 16A, the transmitting unit has a connecting wire, one end of which is connected to the circuit board of the transmitting unit, and the other end of which has a connector that can be connected to the upper chamber plate 101 of the laser radar (as shown in fig. 7 and 8). Similarly, as shown in fig. 16B, the receiving unit has a connecting wire, one end of which is connected to the circuit board of the receiving unit, and the other end of which has a connector that can be connected to the upper deck 101 of the laser radar (as shown in fig. 7 and 8). Preferably, the connection lines of the receiving unit are all hard board lines or soft board lines, and a mixed mode of the hard board lines and the soft board lines is avoided. The hybrid board line is very expensive and therefore can be cost effective in large quantities.

As shown in fig. 17, the present invention also relates to a ranging method 200, comprising the following steps.

In step S201, a detection laser beam is emitted through an emission unit including a plurality of lasers and a driving circuit to detect an object, wherein the driving circuit is integrated in a chip, and the plurality of lasers and the driving circuit are disposed on the same PCB.

In step S202, echoes from the target object are received by a plurality of probes, and the echoes are converted into electric signals.

In step S203, the electrical signals output by the detectors are read by an analog front end component, wherein the analog front end component is integrated on a chip, and the plurality of detectors and the corresponding analog front end components are disposed on the same PCB.

In step S204, the distance and/or reflectivity of the target object is calculated according to the electrical signal.

According to an embodiment of the present invention, the laser ranging method 200 further includes:

the detection laser beam is incident on a target object in a short-distance range through a blind-repairing unit arranged on the downstream of the optical path of the laser;

receiving, by the probe, echoes from objects within the close range.

According to one embodiment of the invention, the driving circuit is adapted to drive the plurality of lasers to sequentially emit light in a round trip manner;

the analog front end component is suitable for amplifying electric signals output by different detectors according to the detection requirements of the radar.

For example, the driver chip of the laser is a 4-channel driver chip, and correspondingly drives 4 lasers in sequence. The chip of each analog front-end circuit is a 16-channel chip, and is continuously switched among 16 channels, so that the electric signal output by each detector is sequentially read and amplified.

As shown in fig. 18, the present invention also relates to a ranging method 300, comprising the following steps.

In step S301: emitting a detection laser beam by an emission unit including a plurality of lasers and a driving circuit;

in step S302: changing the direction of the detection laser beam through a blind complementing unit so that a target object in a short distance range can receive the detection laser beam and the reflected echo can be received by a detector;

in step S303: receiving echoes from the target object through a plurality of detectors, and converting the echoes into electric signals;

in step S304: reading the electrical signal output by the detector through an analog front end component; and

in step S305: and calculating the distance and/or the reflectivity of the target object according to the electric signal.

According to one embodiment of the invention, the driving circuit is integrated on a chip, and a plurality of lasers and the driving circuits corresponding to the plurality of lasers are arranged on the same PCB; the analog front end component is integrated on a chip, and the plurality of detectors and the analog front end components corresponding to the plurality of detectors are arranged on the same PCB.

According to one embodiment of the invention, the driving circuit is adapted to drive the plurality of lasers to sequentially emit light in a round trip;

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 transmitting unit including a plurality of lasers and a driving circuit configured to drive the lasers to emit a detection laser beam for detecting a target object, wherein the transmitting unit further includes a blind-fill unit configured such that the target object in a short range of the laser radar can receive the detection laser beam and a reflected echo can be received by the detector;

a receiving unit including a plurality of detectors configured to receive echoes of the detection laser beams reflected by the target object and convert the echoes into electrical signals; and

a processing unit coupled to the receiving unit and configured to receive the electrical signal to calculate the distance and/or reflectivity of the target object.

2. The lidar of claim 1, wherein the driving circuit is integrated on a chip, and a plurality of lasers and the driving circuits corresponding to the plurality of lasers are disposed on a same PCB;

the receiving unit further comprises an analog front end component, the analog front end component is coupled with the detectors and is suitable for reading the electric signals output by the detectors, the analog front end component is integrated on a chip, and the plurality of detectors and the analog front end components corresponding to the plurality of detectors are arranged on the same PCB.

3. The lidar of claim 1, wherein the transmitting unit comprises a first reflective portion and the blind compensating unit comprises a second reflective portion, the first and second reflective portions being disposed relatively non-parallel.

4. The lidar of claim 3, wherein the second reflecting portion deflects the detection laser beam more toward an optical axis direction of the receiving unit than the first reflecting portion.

5. The lidar of claim 4, wherein the first and second reflective portions are separate mirrors; alternatively, the first and second reflective portions are different portions of the same mirror.

6. The lidar of any of claims 3-5, wherein an angle formed by the reflective surfaces of the first and second mirrors is greater than 180 ° and less than 360 °.

7. The lidar of any one of claims 1-5, wherein the transmitting unit comprises a first reflecting portion and a transmitting lens group, the blind complementing unit comprises a first blind complementing mirror and a second blind complementing mirror;

the first blind-filling reflector is suitable for receiving the detection laser beam from the transmitting lens group and then reflecting the detection laser beam to the second blind-filling reflector;

the second blind-complementing reflector is suitable for emitting the detection laser beam to the outside from the laser radar after being reflected again; wherein the detection laser beam emitted to the outside is closer to the optical axis of the receiving unit than the detection laser beam emitted from the emission lens group.

8. The lidar of claim 2, wherein the transmitting unit further comprises a transmitting lens group, the blind complementing unit comprising a blind complementing light source;

the emission lens group is arranged on the downstream of the optical path of the laser;

and the blind-complementing light source is arranged at a position deviating from the focal plane of the emission lens group.

9. The lidar of any of claims 1-8, further comprising an upper tray, a lower tray, and a shaft between the upper tray and the lower tray;

and the optical machine rotor formed by the transmitting unit and the receiving unit is fixed on the upper bin plate and is driven to rotate by a motor through the rotating shaft.

10. The lidar of claim 9, further comprising a communication upper plate and a communication lower plate between which a bidirectional wireless communication link can be established, wherein the communication lower plate is integrated with the lower bulkhead;

the communication upper plate is arranged on the rotating shaft and is coupled with the upper cabin plate;

the bottom of ray apparatus rotor is provided with the chamber that holds that the board matches on the communication is used for holding the communication upper plate.

11. The lidar of any of claims 1-10, wherein the receiving unit further comprises a filter arranged in the optical path upstream of the detector, adapted to select a predetermined wavelength range of the detection echo to be incident on the detector.

12. The lidar as claimed in any of claims 1-10, wherein the detector comprises an avalanche photodiode;

the processing unit further includes an amplification circuit coupled to the avalanche photodiode to amplify the electrical signal and an analog-to-digital converter coupled to the amplification circuit and analog-to-digital converting the amplified electrical signal.

13. The lidar of any of claims 1-10, wherein the detector comprises SiPM or spad(s), the processing unit further comprising a time-to-digital converter coupled with the detector.

14. The lidar of any of claims 1-10, wherein the laser comprises an edge-emitting laser or a vertical-cavity surface-emitting laser.

15. The lidar of any of claims 1-10, further comprising a receive lens group, the detector disposed on a focal plane of the receive lens group, the receive lens group configured to focus the echo onto the detector.

16. The lidar of claim 15, wherein the transmit lens group and the receive lens group are secured to the optomechanical rotor by a spring assembly.

17. A laser ranging method, comprising:

18. The laser ranging method of claim 17, wherein the driving circuit is integrated on a chip, and a plurality of lasers and the driving circuits corresponding to the plurality of lasers are disposed on the same PCB; the analog front end component is integrated on a chip, and the plurality of detectors and the analog front end components corresponding to the plurality of detectors are arranged on the same PCB.

19. The laser ranging method according to claim 17 or 18, wherein the driving circuit is adapted to drive the plurality of lasers to emit light in sequence;