CN113640819A

CN113640819A - Laser radar

Info

Publication number: CN113640819A
Application number: CN202111079553.7A
Authority: CN
Inventors: 陈杰; 向少卿
Original assignee: Hesai Technology Co Ltd
Current assignee: Hesai Technology Co Ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2021-11-12
Also published as: WO2023040376A1

Abstract

The application provides a laser radar includes: the laser array is arranged in a linear array or an area array, is arranged on a focal plane of the first optical assembly, and the first optical assembly is arranged on the emission light path and forms an equivalent focal length which is larger than the focal length of the main lens group unit at the emission end; and/or the optical detector array arranged in a linear array or an area array is arranged on a focal plane of the second optical assembly, and the second optical assembly is arranged on the receiving light path and forms an equivalent focal length which is larger than the focal length of the main lens group unit of the receiving end. In the embodiment of the application, the power density in the point cloud field of view area is improved through the arrangement of the first optical assembly of the light emitting end, and/or the background light noise power in the point cloud field of view area is reduced through the arrangement of the second optical assembly of the receiving end, so that the distance measuring capability of the radar can be improved.

Description

Laser radar

Technical Field

The application relates to the technical field of optical ranging, in particular to a laser radar.

Background

The lidar is a detection device that calculates an object distance by emitting laser light and detecting an echo signal reflected after the laser light reaches the surface of the object. Therefore, the lidar includes two parts, namely a Transmitter X element and a Receiver X element, which may be referred to as an optical Transmitter module and an optical detector module.

The laser radar comprises an optical system distributed on a light emitting module and a light detecting module, wherein the light emitting module comprises a main lens group and the like used for collimating a transmitting signal of a laser, and the light detecting module comprises a receiving lens and the like used for converging an echo signal to a detector. For a light emitting module (or light detecting module), its field of view (FOV) is positively correlated to the longitudinal dimension of the light emitting face of the light emitting module (or the light sensing face of the light detecting module) and negatively correlated to the equivalent focal length of the emitting and/or receiving lens (group). Wherein, the longitudinal dimension of the light emitting surface (or the light sensitive surface) is positively correlated with the height of the whole laser radar.

The height dimension of the lidar product is an important parameter that is of interest to customers. In order to maintain the laser radar device at a suitable height while covering a large field angle (e.g., 105 °), the focal length of the transmitting module and/or the detecting module has to be reduced, for example, optical devices with shorter focal length are replaced, which not only reduces the duty cycle of the light emitting surface, but also limits the vertical resolution in the longitudinal direction.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present application provides an optical detection apparatus and an optical detection method, which solve the above problems caused by the mutual restriction between the focal length and the height of the laser radar, and can improve the ranging capability of the radar without increasing the height of the radar.

To achieve the above and other related objects, a first aspect of the present application provides a lidar including:

the optical transmission module is arranged on the focal plane of the first optical assembly and comprises: the laser array is arranged in a linear array or an area array and is suitable for sending a transmitting signal, and the transmitting signal is transmitted along a transmitting optical path;

the first optical component is arranged on the emission light path and forms an equivalent focal length larger than a first preset value so as to improve the power density in the area of the field angle of the point cloud and further improve the distance measuring capability of the radar; wherein the first preset value is the focal length of the main lens group unit;

a light detection module comprising: and the optical detector array is arranged in a linear array or an area array and is suitable for detecting the reflected echo signals after the transmitting signals encounter obstacles from the receiving optical path.

In an embodiment of the present invention, the first optical component includes: a primary lens group unit adapted to collimate the emission signal;

further comprising: the first divergence unit is arranged between the laser array and the main lens group unit and is suitable for diverging the emission signal collimated by the main lens group unit so that the first optical assembly has an equivalent focal length longer than a first preset value.

In an embodiment of the invention, the equivalent focal length of the first optical component is M times of the focal length of the main lens group unit, and M >1, so that the area of the light emitting surface of each laser is increased by M2 times.

In an embodiment of the present invention, the first diverging unit includes: an array of concave lenses, wherein each concave lens corresponds to one emission channel.

An embodiment of the present invention further provides another laser radar, including:

a light emitting module comprising: the laser array is arranged in a linear array or an area array and is suitable for sending a transmitting signal, and the transmitting signal is transmitted along a transmitting optical path;

the optical detection module is arranged on the focal plane of the second optical assembly and comprises: the optical detector array is arranged in a linear array or an area array and is suitable for detecting an echo signal reflected after the transmitting signal meets an obstacle from a receiving optical path;

the second optical assembly is arranged on the receiving light path and forms an equivalent focal length larger than a second preset value so as to reduce the background light noise power in the point cloud field angle area and further improve the distance measuring capability of the radar; and the second preset value is the focal length of the main lens group unit.

In an embodiment of the present invention, the second optical component includes: a receiving lens group unit adapted to converge a receiving signal;

the second optical assembly further comprises: a second diverging section for the second beam of radiation,

and the second optical assembly is arranged between the light detector array and the receiving lens assembly unit, so that the second optical assembly has an equivalent focal length longer than a second preset value and is suitable for diverging the received signals converged by the receiving lens assembly unit.

In an embodiment of the invention, the equivalent focal length of the second optical element is P times the focal length of the main lens group unit, and P >1, so as to reduce the receiving angle area by P2 times.

In an embodiment of the present invention, the second diverging unit includes: an array of concave lenses, wherein each concave lens corresponds to a detector arrangement.

In an embodiment of the present invention, the laser radar includes: the first optical component is arranged on the emission light path and forms an equivalent focal length larger than a first preset value so as to improve the power density in the area of the field angle of the point cloud and further improve the distance measuring capability of the radar; the first preset value is the focal length of a main lens group unit in the first optical assembly; the equivalent focal lengths of the first optical assembly and the second optical assembly are in a proportional relationship.

In summary, the present application provides a lidar comprising: the laser array is arranged in a linear array or an area array, is arranged on a focal plane of the first optical assembly, and the first optical assembly is arranged on the emission light path and forms an equivalent focal length which is larger than the focal length of the main lens group unit at the emission end; and/or the optical detector array arranged in a linear array or an area array is arranged on a focal plane of the second optical assembly, and the second optical assembly is arranged on the receiving light path and forms an equivalent focal length which is larger than the focal length of the main lens group unit of the receiving end. In the embodiment of the application, the power density in the point cloud field of view area is improved through the arrangement of the first optical assembly of the light emitting end, and/or the background light noise power in the point cloud field of view area is reduced through the arrangement of the second optical assembly of the receiving end, so that the distance measuring capability of the radar can be improved.

Drawings

FIG. 1A shows a schematic view of the field of view and focal length of the optical transmit module of an exemplary light detection system.

FIG. 1B shows a schematic view of the field of view and focal length of the light detection modules of the light detection system in one example.

Fig. 1C shows a schematic diagram of a channel correspondence relationship between a transmitting end and a receiving end of a horizontal scanning mechanical radar in an example.

FIG. 2A shows a schematic diagram of the light emitting face of one laser in one example.

FIG. 2B shows a simplified representation schematic of FIG. 2A.

Fig. 3 shows a schematic diagram illustrating the vertical resolution of an optical transmit module in one example.

Fig. 4 shows a schematic diagram of a transmitting and receiving optical path of a lidar in an embodiment of the present application.

Fig. 5A shows a schematic structural diagram of a light emitting module in an embodiment of the present application.

Fig. 5B shows a schematic structural diagram of a light emitting module in another embodiment of the present application.

Fig. 6 is a schematic front view showing an enlarged light emitting surface formed at different focal lengths according to an embodiment of the present disclosure.

Fig. 7 shows a schematic structural diagram of a light detection module of a laser radar in an embodiment of the present application.

Fig. 8 shows a schematic diagram of the principle of determining the value of M according to the specific structural parameters of the optical transmission module in the embodiment of the present application.

Fig. 9 shows a schematic front view structure diagram of a layout for forming an enlarged light emitting surface and a matched concave lens array at different focal lengths in the embodiment of the present application.

Fig. 10A shows a schematic structural diagram of a lidar with a paraxial optical path structure according to an embodiment of the present application.

Fig. 10B shows a front view schematic diagram of a laser array and a photodetector array of a laser radar with a paraxial optical path structure according to an embodiment of the present application.

FIG. 10C shows a graphical representation of the results of the ranging capability simulation of the lidar of FIG. 10B.

Fig. 11A shows a schematic structural diagram of a lidar with a coaxial optical path structure according to an embodiment of the present application.

Fig. 11B shows a schematic structural diagram of a lidar with a coaxial optical path structure according to another embodiment of the present application.

Fig. 12A shows a schematic optical path diagram of the emission end without the sleeve in the embodiment of the present application.

Fig. 12B shows a schematic diagram of the optical path of the emission end of the setting sleeve in the embodiment of the present application.

Fig. 12C shows a schematic view of the optical path of the receiving end of the positioning sleeve according to the embodiment of the present application.

Detailed Description

The following description of the embodiments of the present application is provided by way of specific examples, and other advantages and effects of the present application will be readily apparent to those skilled in the art from the disclosure herein. The present application is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present application. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.

Embodiments of the present application will be described in detail below with reference to the accompanying drawings so that those skilled in the art to which the present application pertains can easily carry out the present application. The present application may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly explain the present application, components that are not related to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

Throughout the specification, when a device is referred to as being "connected" to another device, this includes not only the case of being "directly connected" but also the case of being "indirectly connected" with another element interposed therebetween. In addition, when a device "includes" a certain component, unless otherwise stated, the device does not exclude other components, but may include other components.

When a device is said to be "on" another device, this may be directly on the other device, but may also be accompanied by other devices in between. When a device is said to be "directly on" another device, there are no other devices in between.

Although the terms first, second, etc. may be used herein to describe various elements in some instances, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, the first interface and the second interface, etc. are described. Also, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, steps, operations, elements, components, items, species, and/or groups, but do not preclude the presence, or addition of one or more other features, steps, operations, elements, components, species, and/or groups thereof. The terms "or" and/or "as used herein are to be construed as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a; b; c; a and B; a and C; b and C; A. b and C ". An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" include plural forms as long as the words do not expressly indicate a contrary meaning. The term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components.

Terms representing relative spatial terms such as "lower", "upper", and the like may be used to more readily describe one element's relationship to another element as illustrated in the figures. Such terms are intended to include not only the meanings indicated in the drawings, but also other meanings or operations of the device in use. For example, if the device in the figures is turned over, elements described as "below" other elements would then be oriented "above" the other elements. Thus, the exemplary terms "under" and "beneath" all include above and below. The device may be rotated 90 or other angles and the terminology representing relative space is also to be interpreted accordingly.

Although not defined differently, including technical and scientific terms used herein, all terms have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Terms defined in commonly used dictionaries are to be additionally interpreted as having meanings consistent with those of related art documents and the contents of the present prompts, and must not be excessively interpreted as having ideal or very formulaic meanings unless defined.

Lidar is a device that is based on an optical detection system for ranging. At present, the application scenes (such as automatic driving) of the laser radar and the like have the requirements of high precision and large field of view, and meanwhile, the size of the laser radar is required to be reduced as much as possible in the actual scenes, particularly the height of the laser radar is one of the most concerned parameters of customers. However, there is a conflict between a large field of view and a low altitude, thereby affecting the performance of the lidar. The principle is illustrated below by way of example.

Referring to fig. 1A and 1B, a schematic view of the relationship between the field of view and the focal length in an exemplary light detection system is shown. FIG. 1A shows a schematic view of the field of view and focal length relationship of a light emitting module in a light detection system. Fig. 1B shows a view of the relationship between the field of view and the focal length of the light detection module of the light detection system.

From the triangles corresponding to the FOV of the field of view illustrated in fig. 1A or 1B, it can be calculated:

where a is the height (or longitudinal dimension) of the light emitting surface of the single laser 101A or the light sensing surface of the single photodetector 101B, and f is the focal length of the

lenses

102A and 102B (both are schematically indicated as f in the figure, but it is not indicated that the focal lengths defining the two optical paths are the same, just to avoid confusion due to too many numbers). For lidar, the field of view of a single laser/single detector satisfies equation (1). Meanwhile, in an ideal situation (when multiple lasers/detectors can be connected in a gapless manner in the longitudinal direction), the heights of a single light-emitting surface 101A/a single light-sensitive surface 101B and all the multiple lasers/detectors in the longitudinal direction satisfy formula (1), and the size of the field of view is positively correlated with the height of the laser radar.

Therefore, as can be understood from the equation (1), the sizes of the light emitting surface of the light emitting module and the light sensing surface of the detection module of the laser radar are positively correlated with the size of the laser radar. Especially the height dimension of the lidar is a parameter of more importance than the width and depth, and a suitable height is usually required in various application scenarios to fit the limited installation space.

As can be seen from the equation (1), the FOV of the field of view positively correlates with the dimensions of the light emitting surface and the light sensing surface, and negatively correlates with the equivalent focal length f of the optical components (e.g., the main lens group) in the light emitting module and the light detecting module. It can be seen that if a larger FOV is to be maintained, either increasing a or decreasing f, but increasing a may result in an increase in the height of the lidar, so f is typically decreased for this purpose, but in so doing, can cause problems affecting the performance of the lidar.

In addition, for a radar system, transmission and reception have a certain correspondence. The light paths of the transceiver and the focal plane layout of the transceiver may be different, but it is desired that the emitted light finally falls on a certain area on the target, the reflected light of the area can return to the detector, that is, the emission and the reception can be matched, and the transceiver channels can be corresponded. To avoid confusion, certain terms are defined below.

Number of scanning lines: i.e. the number of channels over which the laser is transmitted and received, or the minimum number of addressable channels. Typical lasers and detectors are 1: 1 configuration, the number of scanning lines is equal to the number of lasers or detectors and also equal to the number of transmitting channels or receiving channels. At the same time, there are also situations where multiple detectors share a laser, or vice versa, or even where there may be staggering, where the number of minimally addressable channels is to be specifically resolved.

Divergence angle area: refers to the angular area of the laser light emitting area of a certain channel projected in the far field through the optical system.

Area of reception angle: refers to the angular area of the detector photosurface of a certain channel projected in the far field through the optical system.

Point cloud field angle area: it is the overlapping part of the divergence angle and the receiving angle, which is the real range covered by the point cloud and the superposition of all the target reflected echo signals in the range. In different light path designs, the area of the field angle of the point cloud presents different relative relationships with the area of the divergence angle and the area of the receiving angle. The point cloud field angle area may be equal to the divergence angle area and smaller than the reception angle area, may be equal to the reception angle area and smaller than the divergence angle area, or may be equal to a portion where both overlap. In the most ideal case, the field angle area of the point cloud is consistent with both the divergence angle and the acceptance angle area.

The field of view FOV, which often includes the horizontal field of view HFOV and the vertical field of view VFOV, refers to the total angular range detected by all the transmit-receive channels.

Referring to fig. 1C, a transmitting end (TX) provided with a plurality of lasers (referring to a minimum addressable light emitting unit) is on the left.

On the right is the receiving end (RX) with multiple probes (also referred to as minimum addressable units).

The middle is a point cloud field angle, the horizontal position of each point represents a horizontal angle, the horizontal angle theta deviates along with the rotation of the radar rotor, and the vertical position represents a pitch angle gamma which is equal to beta.

Further, fig. 2A and 2B are schematic views showing the light emitting surface of one laser in one example. The Laser is illustratively a Vertical Cavity Surface Emitting Laser 200 (VCSEL). Fig. 2A is a schematic top view of a more practical VCSEL, and fig. 2B is a schematic diagram of abstraction simplification based on fig. 2A. The light emission duty ratio refers to the ratio of the area covered by the light emission surface to the total area, and may be the ratio of the sum of the areas of the respective light emission points 201 to the area of the dotted square 202 or the entire VCSEL top surface in the drawing, or the like. In summary, the emission duty cycle is limited to OA/PITCH. Where OA is the area of 1 light-emitting point 201, and PITCH is the PITCH of adjacent light-emitting points 201 in the longitudinal direction (i.e., the distance between the centers of adjacent light-emitting points, as indicated by the double-headed arrow in the figure). It can be seen that the duty cycle is higher when the OA is larger or the pitch is smaller. It should be noted that this is only an example, and in the present application, the type of the laser is not limited at all, for example, the laser may be an eel (edge Emitting laser), a VCSEL (VCSEL), or a pcsel (photonic Crystal Emitting Semiconductor laser). Similarly, the type of the detector is not limited in this application, for example, the photodetector may be an APD, a single photon avalanche diode array spad(s), or a silicon photomultiplier SiPM.

Further, as shown in fig. 3, when the light emitting module uses, for example, a laser array as the laser array, the vertical angular resolution of the lidar is determined according to the ratio d/f between the center-to-center distance d of the

adjacent lasers

301 and 302 arranged in the longitudinal direction (or column direction) and the equivalent focal length f of the main lens group (here, only one convex lens 303 is shown as an equivalent in the embodiment, the actual main lens group may include a plurality of lens groups, which is not limited herein), that is, d is positively correlated and f is negatively correlated.

Based on the above, there is still room for improvement in the existing optical path system of the laser radar. On the one hand, to cover a larger field of view (say 105 °), and to maintain a height that is not increased, the focal length has to be minimized. On the other hand, the light emitting surface duty ratio of the laser is limited by the light emitting point area/light emitting point pitch, resulting in a low duty ratio. In yet another aspect, the vertical resolution is limited by d/f.

In view of the above, the laser radar provided in the embodiment of the present application realizes that a longer equivalent focal length is realized with a relatively short physical size through an optical improvement manner, so as to improve power density in a point cloud field angle area, and/or reduce background light noise power in the point cloud field angle area, thereby improving a distance measurement capability of the radar.

Fig. 4 shows a schematic diagram of the transmit-receive optical path of a lidar. The laser radar may specifically include:

the light emitting module, i.e. the laser array arranged in a linear array or an area array, is disposed corresponding to the first optical component, for example, may be disposed on a focal plane of the first optical component, and is adapted to emit a transmitting signal, and the transmitting signal is transmitted along a transmitting optical path. The first optical assembly may be formed with an equivalent focal length greater than a first preset value.

The optical detection module, that is, the optical detector array arranged in a linear array or an area array, is disposed corresponding to the second optical component, for example, may be disposed on a focal plane of the second optical component, and is adapted to detect an echo signal reflected by the transmitted signal after reaching the object. The second optical assembly may be formed with an equivalent focal length greater than a second preset value. Therefore, by arranging the optical assembly of the laser radar transmitting end and/or the receiving end, the lengthened focal length of the receiving/transmitting side is realized, the power density in the point cloud field angle area can be improved under the condition that the height of the whole radar is kept unchanged, and/or the background light noise power in the point cloud field angle area is reduced, and the distance measuring capability of the radar is greatly improved.

More detailed description will be given below from each single side of the transmitting TX end and the receiving RX end, respectively.

Fig. 5A is a schematic structural diagram of an optical transmitter module according to an embodiment of the present disclosure.

The light emitting module includes: a laser array 501 and a first optical assembly.

The laser array 501 includes a plurality of lasers 511. The plurality of lasers 511 may be arranged in a linear array or an area array. Each laser 511 is configured to output a transmit signal, i.e., emit laser light. Illustratively, the laser 511 may be implemented, for example, as a vertical cavity surface emitting laser (VSCEL) or an Edge Emitting Laser (EEL).

The first optical assembly is arranged on the emission light path and is provided with an equivalent focal length with the length larger than a first preset value. Specifically, as illustrated by way of example in fig. 5A, the first optical assembly comprises: a primary lens group unit, which may be specifically a primary lens group originally in the optical transmission module for collimating the transmission signal, is exemplarily illustrated in fig. 5A as an equivalent convex lens 502; and a first diverging unit for diverging the transmission signal, which is exemplarily represented as a concave lens array 503 in fig. 5A. Each concave lens 531 in the concave lens array 503 is arranged corresponding to one laser 511 (individually addressable and controllable on/off unit) to elongate (relative to the focal length formed by the emission optical path of only the main lens group) the focal length of the emission optical path, so as to raise the light emitting surface of the laser 511 corresponding to the individual pixel (relative to the size of the laser in the solution of arranging the laser at the focal plane a of the main lens group unit, but actually in the solution of the present application with longer focal length, the laser is arranged only at the focal plane B, not at a), and at the point cloud level, the power density in the field angle area of the point cloud is raised, that is, the energy of the emission end used to form one of the points in the point cloud is greater. The pixel refers to a pixel point or a point cloud in a cloud map of points formed by the corresponding laser radar, for example, the light emitting surface of each laser/the light sensing surface of each photodetector may correspond to a pixel point, and the transceiver units together form a channel, and then correspond to the above-mentioned wiring harness. The pitch between adjacent two concave lenses 531 in the concave lens array 503 may be the same as the center-to-center distance between adjacent lasers 511.

It should be noted that the main lens group unit is exemplarily represented by a convex lens 502 in the drawing, in fact, the convex lens 502 is also only a representation of the main lens group unit, and the main lens group unit may be a main lens group in the light emitting module, which may include a plurality of lenses (for example, as shown in fig. 4), so the simplified representation of the convex lens 502 in the drawing is not a limitation; in addition, the equivalent lens of the main lens group unit may also be other types of convex lens, such as a plano-convex lens, and the like, which is not limited herein. The main lens group unit may have a first focal length, represented in the figure as the distance f "from the main plane C of the convex lens 502 to its focal point of one time (the corresponding focal plane is a).

In some embodiments, the concave lens array 503 is disposed between the laser array 501 and the main lens group unit, and each concave lens 531 in the concave lens array 503 is disposed corresponding to one laser 511.

The concave lens array 503 is adapted to diverge the emission signal and then converge the emission signal through the main lens group unit, so as to form an equivalent focal length of the first optical component, which is longer than a first preset value. Specifically, f "is the main lens group (i.e., the main lens group unit in fig. 5A, which is represented by 1 convex lens instead, but is generally a main lens group, in fig. 5A, the main lens group unit is the focal length of the main lens group (positive lens and convex lens and leftmost lens), f is the equivalent focal length of the combination of 2 lenses in the figure (i.e., convex lens 502+ concave lens array 503), and L is the physical size. In which, the main plane of the positive and negative lens groups (i.e. convex lens 502+ concave lens array 503) moves forward, as shown in the figure, the left end point of f moves forward to the left compared to the left end point of f ″, that is, the main plane D at the left end point of f moves forward to the left compared to the main plane C of the main lens group unit, and the whole focal plane moves backward, for example, from a to B. In calculating the focal length, the main plane D position can be determined from the reverse extensions of the converging light, which can be seen in dashed lines E1, E2 in fig. 5A. This is also an advantage of the present optical path: l < f, a longer equivalent focal length f is achieved with a relatively short physical dimension L.

As can be understood from the above description, for the optical transmitting module (i.e. TX end), on the basis of the optical path of the original main lens group (i.e. main lens group unit/convex lens 502 in the figure) of the lidar, in the embodiment of the present application, one concave lens array 503 is added and combined with it to lengthen the focal length, i.e. the focal length is lengthened from the focal length f "of the main lens group to the equivalent focal length f of the combination of 2 lenses (i.e. convex lens 502+ concave lens 530 in concave lens array 503), where M is the focal length magnification, and M is f/f". Alternatively, the first diffusing unit may be spaced apart from the main plane of the main lens group unit by less than f ".

According to the equation (1), when the FOV is not changed and the focal length f is equivalently increased, a is equivalently increased, that is, the light emitting surface of each pixel is equivalently increased. Furthermore, the luminous energy of a single pixel (corresponding to one point in the point cloud image in the laser radar) can be increased, the power density in the corresponding point cloud field angle area is increased (namely, the more luminous points 201 are included in the same area), and the distance measurement capability is also increased in equal proportion, for example, the distance measurement capability can be increased from 200m to 300 m.

It should be noted that, for example, for a VSCEL laser, the large viewing angle may cause the emitted light rays F1 and F2 to deviate from the concave lens 530, the part of the light rays that do not pass through the concave lens 530 may be defocused, and the echo signal that is likely to be formed after being sent out through the main lens group unit with a large divergence angle may be received by the optical detector of another channel, thereby forming crosstalk; alternatively, the signal is deviated from the main lens group unit to cause a signal loss. To this end, in some embodiments, the viewing angle of the laser array may be compressed.

Fig. 5B is a schematic structural diagram of a light emitting module according to another embodiment of the present application.

Shown in fig. 5B is a laser array 501 and a first optical component of another embodiment.

In the present embodiment, the first optical assembly includes a main lens group unit and a micro lens group unit 503.

It should be noted that the main lens group unit is still equivalently represented by a convex lens 502 in fig. 5B. The main lens group unit may have a first focal length, represented in the figure as the distance f "from its main plane C to its focal point (the corresponding focal plane is a).

In this embodiment, the microlens assembly unit 504 includes a microlens array 505 in addition to the concave lens array 503. In fig. 5B, the microlens array 551 is disposed between the laser array 501 and the concave lens array 503. Since the light emitting surface of each laser 511 (such as VCSEL) has a plurality of light emitting points, each microlens 551 (specifically, a micro convex lens) in the microlens array 551 is disposed corresponding to one light emitting point, so as to converge the light emitted from the light emitting point and transmit the converged light to the corresponding concave lens 531. That is, the divergence angle of the light emitted from each light-emitting point can be compressed by the microlens array 551, and thus the divergence angles of the emission signals output by the

lasers

511 and 501 can be suppressed, thereby avoiding the case where the light rays F1 and F2 are emitted from the concave lens array 503 in fig. 5A.

The principle in this embodiment is explained in detail. Unlike the embodiment of fig. 5A, the embodiment of fig. 5B is to achieve the focal length extension by the equivalent focal length of the combination of 3 lenses (i.e. convex lens 502+ concave lens 530 in concave lens array 503 + micro lens 551 in micro lens array 505). In fig. 5B, f "is the focal length of the main lens group (in fig. 5B, the main lens group unit is represented by 1 convex lens instead, but it would be a main lens group, in fig. 5B, the main lens group unit is the focal length of the main lens group (positive lens) and the convex lens (left-most lens), f is the equivalent focal length of the combination of 3 lenses in the figure (i.e., convex lens 502+ concave lens 530 in concave lens array 503 + micro lens 551 in micro lens array 505), and L is the physical size. In which the combined principal plane of the positive and negative lens groups (i.e. convex lens 502+ concave lens 530 in concave lens array 503) moves forward, as shown in the figure, the left end point of f moves forward to the left compared with the left end point of f ″, i.e. the principal plane D of the left end point of f moves forward to the left compared with the principal plane C of the main lens group unit, and the whole focal plane moves backward, e.g. from a to B. In calculating the focal length, the main plane position is determined from the reverse extensions of the converging light, which can be seen as the dashed lines S1, S2 in fig. 5B. This is also an advantage of the present optical path: l < f, a longer focal length f is achieved with a relatively short physical entity size L.

For the TX end, based on the optical path of the original main lens group unit (i.e. the main lens group), in the embodiment of the present application, a concave lens array 503 is used to elongate the focal length, and the divergence angle of the laser 501 is limited by the micro lens array 505, so as to elongate the focal length from the focal length f "of the main lens group unit to the equivalent focal length f, where M is the focal length magnification, and M is f/f". According to equation (1), the FOV is unchanged, and a increases correspondingly with an increase in the focal length f, i.e., the light-emitting surface increases. Furthermore, the luminous energy of a single pixel (corresponding to one point in a point cloud image in the laser radar) can be improved, the power density in the corresponding point cloud field angle area is improved, and the distance measuring capability is also improved in an equal proportion.

Illustratively, the pitch between two adjacent microlenses in the microlens array 504 is the same as the pitch of the light emitting points. It should be noted that the 3 concave lenses corresponding to the 3 lasers 511 and the 3 micro lenses corresponding to each laser 511 are shown in the figures as a number that is illustrative and not limiting.

In the example of fig. 5A and 5B, the light exit surface B of the laser array 501 (including the light exit surface of each laser) is located at the focal plane of the equivalent lens of the first optical assembly to maintain a separation distance f from the principal plane D of the equivalent lens.

To more intuitively see the increase in the light emitting surface, reference may be made to fig. 6.

In fig. 6, an elevational structure schematic diagram of an enlarged light emitting surface formed at different focal lengths in the embodiment of the present application is shown. The size contrast of the light emitting surface when M is smaller than but approximately 1 (i.e. the light emitting surface is not enlarged, or the light path without the concave lens, such as the light path including only the main lens group unit), M is smaller than but approximately 2, and M is smaller than but approximately 4 is shown in sequence from left to right in fig. 6; the equivalent enlargement of the light-emitting area of the 8 light-emitting

areas

11, 12, 13, 14, 21, 22, 23 and 24 is shown in three cases. As will be understood in conjunction with fig. 5A or fig. 5B and fig. 6, the 3 lasers arranged longitudinally in the side view of fig. 5A and 5B may be located in 1 row, for example, a row of light emitting

surfaces

11, 12 and 13 corresponding to M in fig. 6 being smaller than but approximately 2. Each laser is correspondingly provided with one of the micro-concave lenses Y in the concave lens array, for visual illustration, only one light emitting surface 21 is selected on the right side in fig. 6 to draw one concave lens, which appears as a circle surrounding the light emitting surface 21, but actually, other lasers are also correspondingly provided with concave lenses, and only the concave lenses are omitted here. It should be noted that the diameter of the concave lens is larger than that of the light-emitting surface so as to cover the light-emitting surface completely, so as to receive more light of the emitted signal, but at the same time, the diameter of the concave lens is limited to a proper size in consideration of the height of the lidar.

As can be seen from FIG. 6, the variation in M gives M times of enlargement from a0 → a1 → a2 for the individual luminous surface diameter in three cases, and M from a0 → a1 → a2 for the luminous surface area²Magnification of the magnification. After the light emitting surface corresponding to each laser is enlarged, the illumination capacity of the laser is increased, and the point cloud layer surface can improve the point cloud view fieldThe power density in the angular area further improves the distance measurement capability of the laser radar. In addition, although in the case where M is smaller but is close to 4, the light emitting surfaces of the nearest neighboring lasers are closer (such as the light emitting surface 11 and the light emitting surface 13), when the emission angle area a2 ″ equivalent to the far field would be a2/M, there is no problem of overlapping so as not to be recognized as two light emitting surfaces. It should be noted that when the equivalent focal length of the first optical component is M times the focal length of the main lens group unit, if the laser is disposed at the focal plane of the first optical component, the entire area of each laser is M times the area of the laser if it is disposed at the focal plane of the main lens group unit²And (4) doubling. If the duty ratio of the laser is not changed, the area of the light emitting surface of each laser is increased by M relative to the area of the light emitting surface if the light emitting surface is arranged on the focal plane of the main lens group²And (4) doubling.

Alternatively, as can be seen from fig. 6, the height dimension can be maintained by adjusting the layout of the light emitting surface at different focal length magnifications M. For example, from the comparison of the heights h0, h1 and h2 in the case of 3 in fig. 6, h2 is slightly larger than h1 and h1 is slightly larger than h0, and the differences are negligible in practical cases, that is, the laser radar may have almost no change in height dimension, while the light emitting surface of each laser obtains M²The power density in the field angle area of the point cloud can be improved to M by multiplying the power density on the surface of the point cloud layer²And the distance measurement capability of the laser radar is improved.

In other examples, the optical detection module side may be extended in focal length by similar optical components. For the detection end, the area of a receiving angle can be reduced while the focal length is lengthened and the area of a receiving device is kept unchanged, so that the background light noise power in the area of the field angle of the point cloud can be reduced, and the distance measuring capability of the radar can be improved.

Fig. 7 is a schematic structural diagram of a light detection module of a lidar in an embodiment of the present application. The light detection module includes a light detector array 701 including a plurality of light detectors 711 arranged in an array. The light detector 711 is configured to detect the emission signal reaching the object to be reflected to enable detection. In which one or more photo detectors 711 and one or more lasers form a "channel", for example, one photo detector and one laser form a channel, and the echo signal of the emission signal of the laser is received by the photo detectors 711 belonging to the same channel, and each channel corresponds to the detection of a certain field angle or a certain field angle range (receiving angle area). In a specific example, each of the photodetectors 711 may be implemented by, for example, SiPM (Silicon Photo Multiplier ) or spad (Single Photon Avalanche Diode).

Illustratively, the light detection module may further include a second optical assembly disposed corresponding to the light detector array 701. The second optical assembly specifically includes a second converging unit and a second diverging unit. In fig. 6, the second focusing unit may be an original lens or a lens group for focusing the echo signal, and may be equivalently illustrated as a left-most convex lens 702 in the figure, for focusing the echo signal to be transmitted to the optical detector array 701. The second diverging unit may be implemented as a concave lens array 703, wherein each concave lens 731 is disposed corresponding to one photo detector 711, respectively; accordingly, the pitch between longitudinally adjacent concave lenses 731 can be the same as the pitch between the centers of adjacent photodetectors 711 in a column of the photodetector array 701.

The focal length of the convex lens 702 is f2", shown schematically as the length from the principal plane G of the convex lens 702 to its focal plane H. Illustratively, the separation between the principal plane G of the convex lens 702 and the concave lens array 703 may be within the focal length f2 ″ of the equivalent lens.

By the combination of the convex lens 702+ the concave lens array 703, the principal plane of the equivalent lens formed is I, which is shifted forward to the left compared to G. It will be appreciated that the position of the I-plane is determined by the reverse extensions K1 and K2 of the figures, which are schematically illustrated in simplified form (". said.") for visual clarity, as in the principle of the previous figures 5A, 5B, and should be understood with reference to the previous figures.

Thus, as shown in the figure, forming a focal length f2 that is extended compared to the focal length f2 ″ of the convex lens 702, the distance from I to the focal plane J, the photosensitive surface of the photodetector array 701 may be alternatively located on the focal plane J at the right end of f2 to obtain focusing of the echo signal. The physical length of G to J is L2, and it can be seen that f2 exceeds the physical distance limit of L2.

Unlike the extension of the focal length of the optical transmission module (i.e., TX end), for the receiving end of the lidar, on the premise of ensuring that as much as possible of the true detection signal (the echo signal reflected after the transmission signal meets an obstacle) is received, the received background light intensity needs to be reduced as much as possible to improve the signal-to-noise ratio, and the following formula gives the background light P at the receiving end_B：

Wherein pb is background radiation density; BW is the filter half-height width (nm); rho is the reflectivity of the target; tr is the optical efficiency of the receiving barrel; a is the effective aperture (m), Sr is the effective area of the detector, and f is the focal length.

According to the formula, the focal length of the optical detection module (namely, the RX end) is prolonged, so that the background light noise power in the area of the field angle of the point cloud can be reduced, the signal to noise ratio is improved, the ranging capability of the whole laser radar is improved, and the height and the size of the laser radar can be maintained. In addition, if the equivalent focal length of the second optical assembly is P times of the focal length of the receiving end main lens group unit, P>1, the receiving angle area can be reduced by P²And (4) doubling. It should be noted that different letter symbols are used for the transmitting end and the receiving end, such as M and P to represent the focal length magnification of the optical assembly elongation, respectively, only for illustrating that the transmitting side and the receiving side may use different magnification, but it is understood that the transmitting side and the receiving side may be set to the same magnification. Some parts are discussed with reference to M, and P is similar, and will not be described again in the application.

In addition to the optical transmitting module and the optical detecting module, a control module (not shown) is also typically included in the laser radar for controlling the optical transmitting module to transmit the transmitting signal and controlling the optical detecting module to detect data of the echo signal, and the data may be calculated to obtain a detection result.

According to the above embodiments or combinations of embodiments, various problems as previously explained can be solved. On the one hand, the light paths of the light emitting module and the light detection module obtain larger focal length, so that the total height of a focal plane is kept while the focal length of the laser radar is increased by M times, and the size of the whole laser radar is almost unchanged. On the other hand, for the emission module TX, the size of the light-emitting surface corresponding to the single pixel point can be increased, so that the power density can be increased; for the receiving module RX, the receiving angle area can be reduced, and then the background light noise power in the point cloud field angle area is reduced; thereby being beneficial to improving the distance measuring capability; and increasing f decreases d/f, meaning that the angular difference in the vertical direction between adjacent lasers decreases, thereby improving vertical angular resolution. On the other hand, in fig. 5B, the microlens array is disposed in front of the laser array to converge the emission signal, which is also beneficial to further improving the utilization efficiency of the emergent light.

In some embodiments, reference may be made to fig. 8 and 9 for a discussion of the reasonable values of M.

Similar to the previous fig. 5A and 5B, in fig. 8, f "is the focal length of the convex lens 802 equivalent to the main lens group unit, f is the focal length of the first optical component, and L is the physical size. By the combination of the convex lens 802 and the concave lens 803, the equivalent focal length is achieved as f, f ═ M × f ". It should be noted that fig. 8 schematically depicts an optical path of an emission signal of 1 light-emitting point of 1 laser 801 compressed by the micro lens 804 and diffused by the corresponding concave lens 803, and does not depict all light-emitting points of the laser 801, nor depicts other lasers and corresponding other concave lenses (representing concave lenses), but they may exist in practice.

According to the notation illustrated in the figure, the formula for M is shown in the following equation (2):

M＝f/f"＝Δy/Δy"≈a/β (2)

where Δ y is the laser light at the focal plane of the extended back focal lengthThe device height (y direction) is the light emitting surface height corresponding to this position, and Δ y "is the light emitting surface height equivalent to the focal plane at the convex lens 802. In order to increase the magnification M as much as possible, it is necessary to design the cone angle β (laser divergence angle θ OA/PITCH) to be as small as possible, and to design the F value (aperture value)

f is focal length, D is aperture diameter), i.e., the main lens (i.e., main lens group) with a larger aperture. Referring to fig. 8, the main lens cone angle ═ α; the divergence angle of the laser 801 is θ; the β is related to the light output quality of the laser 801 itself on the one hand and the compression effect of the microlens array on the other hand.

In addition, the upper limit of M may also be derived. After the focal length f is enlarged, the light emitting surface with the same area (it can be understood that a is unchanged), the divergence angle is reduced in an equal ratio (the common divergence angle theta is 2 × arctan (a/2f)), and the angular resolution is improved, so that the lasers in the laser array are allowed to be arranged in a staggered mode in multiple rows (N rows).

The number of columns N in the staggered arrangement should be limited, and N may affect the width of the radar product, although the width direction is not as important as the height direction, but is not limited. If N rows of lasers are staggered, it is desirable that the height of the light-emitting surface be slightly less than the pitch of the adjacent concave lenses, considering that all the light to be emitted by each laser can pass through the concave lenses arranged in one-to-one correspondence (e.g., covered by concave lenses in fig. 9). It should be noted that the specific size of the emitting height is related to the shape of the laser, and if the laser is circular, the height refers to the diameter of the whole laser; if the laser is rectangular, height refers to the width or length of the laser.

Referring to fig. 9, a schematic diagram of a light emitting surface in a further embodiment of the present application is shown.

From left to right in fig. 9, M is less than but approximately 1, N is 1; m is less than but approximately 2, N ═ 2; m is smaller than but approximately 4, and N is 8 luminous surfaces in the three cases of 4. That is, the left-most side corresponds to M smaller than but similar to 1, N is 1, and 8 light-emitting surfaces 11-24 are not enlarged and are arranged in a row; the middle corresponds to M smaller than but similar to 2, N is 2, 8 luminous surfaces are amplified by 4 times and are arranged in 2 rows; the rightmost side corresponds to M being less than but approximately 4, N being 4, presenting that 8 light emitting faces are each magnified approximately 16 times and arranged in 4 columns.

The figure also shows exemplarily a concave lens provided for each laser, for example, a ring Z in the figure around the light emitting surface 11. In order to prevent the emission signal of the laser from avoiding the concave lens, a constraint condition that the concave lens needs to completely cover the light emitting surface can be set. If the height of the light emitting surface before enlargement is y0, the height of the light emitting surface after enlargement by approximately 2 times is y1, and the height of the light emitting surface after enlargement by approximately 4 times is y2, the pitch of the vertically adjacent concave lenses, for example, y2 is smaller than the height of Z (the height is the diameter length if Z is circular) in order to allow the concave lenses to cover the light emitting surface.

Under the limitations described in the above examples, the following formula can be obtained:

the enlarged light emitting surface height (M) is the enlarged front light emitting surface height < the concave lens pitch (the focal length of the main lens group unit (equivalent convex lens)) is the vertical angular resolution (N);

with regard to: the height of the enlarged luminous surface is less than the pitch of the concave lens; it is intuitive that the edges of the light emitting surfaces (11-24) in fig. 9, which light emitting surfaces are enlarged approximately 2 and 4 times, are schematically drawn as dotted lines, and the edges of the concave lenses are schematically drawn as solid lines, and the dotted line edge corresponding to each light emitting surface falls in the solid line ring of the corresponding concave lens. The figure schematically indicates that the light emitting surface 11 falls into the concave lens Z at approximately 4 times magnification.

With regard to: amplifying the height of the front light emitting surface (M); referring to FIG. 9, if the light emitting surface is magnified by a factor of 2, the magnified light emitting surface height is y 1; if the luminous surface is amplified by 4 times, the height of the amplified luminous surface is y 2; the pixel height before enlargement is y0, y2 ═ 2 ═ y1 ═ 4 × -y 0.

With regard to: referring to fig. 9, the concave lens pitch is the distance between the centers of the adjacent light emitting surfaces, and is measured by the space b, which is equal to the focal length of the main lens group unit and the vertical angular resolution, and the concave lens pitch is equal to N times the space b. As shown in fig. 9, when the light emitting surface is enlarged twice, the concave lens pitch is 2 b; the concave lens pitch is 4b when the light emitting surface is enlarged four times.

Substituting y0, f', d/f according to M × enlarged front light emitting surface height < main lens group unit focal length × vertical angular resolution × N to obtain M × y0< b × N; y0 ≈ b if adjacent light emitting surfaces can be arranged with almost no space, regardless of process limitations. Therefore, M (magnification) < N (number of columns in staggered arrangement) can be obtained, in other words, the entire optical path cannot be enlarged without limitation, and the number N of columns in which the laser can be arranged is the upper limit of the magnification M, i.e., M < N.

As shown in fig. 6 and fig. 9, it can be seen that, in three cases where M is 1, N is 2, and M is 4, under the limitation of M < N, the increase in the height direction after the light emitting surfaces are arranged is very small, and can be ignored compared with the size of the whole laser radar, that is, h0 is approximately equal to h1 is approximately equal to h2, so that the increase in the height direction is not caused while the distance measurement capability of the laser radar is improved by extending the focal length of the transmitting module.

It should be noted that, the receiving end is also similar, if the detector array is set as Q rows of detectors arranged in a staggered manner, and the equivalent focal length of the second optical assembly is P times the focal length of the main lens assembly unit, Q > P, which is not described herein again.

The application and efficacy of the above solution are illustrated by various laser radar embodiments.

Fig. 10A is a schematic structural diagram of a lidar showing a paraxial optical path structure according to an embodiment of the present application. Fig. 10B shows a schematic front view layout structure of a laser array and a light detection component of a laser radar with a paraxial optical path structure according to an embodiment of the present application. FIG. 10C shows a graphical representation of the ranging simulation results for the lidar of FIG. 10B.

As shown in fig. 10A, the laser radar 100 of the paraxial optical path structure, i.e., the transmission optical path of the transmission signal and the detection optical path of the echo signal have no overlapping section therebetween, is illustrated in this example. In a possible embodiment, the lidar 100 may be a mechanical lidar 100, i.e. comprising a rotary mechanism. The line number of the laser radar 100 may be 32 or more, for example, 32 lines, 64 lines, 128 lines, 256 lines, etc., where 128 lines, if the laser 1011 and the light detector 1041 form channels in a 1-to-1 manner, that means that 128 lasers 1011 and 128 light detectors 1041 form 128 channels in a one-to-one correspondence. The plurality of lasers 1011 may be arranged in a plurality of columns.

In the optical transmission module 1000, the laser array includes a laser array 1001, wherein the emitted signal light (which may be processed by a micro lens array) output by each laser 1011 is processed by each concave lens 1022 and the main lens assembly unit 1021 (which is equivalently a convex lens) of the first optical assembly 1002 sequentially, and then exits the laser radar 100, and irradiates an obstacle P and then is reflected to form an echo signal. The echo signal enters the laser radar 100, and is sequentially received by a receiving lens group unit 1051 (equivalently, a convex lens) and each concave lens 1052 of the optional second optical assembly 1005 to be emitted to the light detection module 1003. The photo detection components in the photo detection module 1003 may include a photo detector array 1004, wherein the photo detectors 1041 of the channels corresponding to the echo signals may detect the echo signals.

The first optical assembly 1002 and the second optical assembly 1005 respectively form an extended equivalent focal length, for example, M times of the focal length of the original lens group, so that the distance measurement capability of the laser radar 100 is improved, and a farther obstacle P can be detected. Alternatively, M may be an amplification factor of 1.5 or more.

The laser radar 100 based on the paraxial optical path structure of fig. 10A may employ a layout structure of the laser array 1001B and the photodetector array 1004B illustrated in fig. 10B, for example. Two rows of lasers 1011B are arranged in a non-aligned manner, and two rows of photodetectors 1041B are arranged in a non-aligned manner.

The simulation result is shown in fig. 10C based on the distance measurement simulation performed by the laser radar 100 using the paraxial optical path structure based on fig. 10A and 10B. In fig. 10C, the horizontal axis represents the measurable farthest distance (corresponding to the distance measurement capability of laser radar 100), and the vertical axis represents the detection probability. It can be seen that the maximum measurable distance reaches about 90 meters at a detection probability of 90%, whereas the maximum measurable distance of the same type of lidar is only about 45 meters without the solution of the embodiments of the present application. Therefore, the scheme of extending the focal length to improve the distance measurement in the embodiment of the application can actually improve the distance measurement capability by more than 2 times.

In addition to being applied to a lidar in a paraxial optical path structure, in some embodiments, the solution of the present application may also be applied to a lidar in a coaxial optical path structure, where coaxial means that the same optical path segment exists between the transmit optical path and the probe optical path.

Fig. 11A is a schematic structural diagram of a lidar with a coaxial optical path structure according to an embodiment of the present disclosure.

The laser radar includes:

a splitting unit 1103 arranged in the overlapping optical path section, adapted to receive a transmit signal from a first optical path section of a connected laser array (in this example, the laser array 1101) and to deflect or direct the transmit signal to the overlapping optical path section, and adapted to receive a return signal from the overlapping optical path section and to direct or deflect the return signal to a second optical path section of the connected photodetector array 1102; wherein the main lens group unit 1104 (as the main lens group in the previous embodiment) and the first dispersing unit 1105 (as the concave lens array in the previous embodiment) in the first optical assembly are respectively provided in the overlapping optical path section and the first optical path section.

Illustratively, the light splitting unit 1103 may be implemented by, for example, a reflective mirror or a polarizing unit (e.g., a polarizing plate, a polarizing prism, etc.). In the illustrated example, the emission signal output by the laser array may first be diverged by the first divergence unit 1105 disposed in the first optical path segment, and then enter the optical splitting unit 1103, so as to be redirected (e.g., turned, such as reflected, etc.) by the optical splitting unit 1103 to an overlapping optical path segment (i.e., an optical path segment shared by the emission optical path and the detection optical path), and then transmitted to the left through the overlapping optical path segment to the main lens group unit 1104, and then converged and emitted, as the emission optical path indicated by a black solid arrow in the figure.

Further, the lidar further comprises a scanning unit 1106 (such as a galvanometer or a rotating mirror) for selecting a transmission signal of a channel to be detected to be emitted to the lidar, and the main lens group unit 1104 (a convex lens is exemplarily shown in the figure) and the first scattering unit 1105 cooperate to obtain a relatively extended equivalent focal length of the optical transmission module; and selecting the echo signal of the channel to be detected to turn into the overlapped optical path segment, transmitting to the right to the optical splitting unit 1103, redirecting (e.g. directing) to the second optical path segment connected to the optical detection component (in this example, the laser array 1102) through the optical splitting unit 1103, and transmitting to the laser array 1102 along the second optical path segment, as indicated by the gray arrow in the figure. Possibly, the scanning unit 1106 may include one or more resonant single-axis micro-electro-mechanical systems (MEMS) galvanometers for two-dimensional rotation to select the transmit signal and the echo signal of the desired detection channel for transmission.

In the illustrated alternative example, only the convex lens 1107 for converging the echo signal may be provided in the second optical path section without providing the concave lens.

By configuring a proportional relationship between the focal lengths of the optical detection module (RX end) and the optical transmission module (TX end), for example, the equivalent focal length of the optical detection module is several times (for example, K is 3.5 times) that of the first optical assembly; and optionally, in the laser array 1101 of the laser array, the laser may use an Edge Emitting Laser (EEL) to illuminate the whole receiving field of view by using its characteristics of small light emitting area and high brightness; in the photo detector array 1102 of the photo detection component, the photo detectors may be implemented by SiPM, and the size of the photo detector array 1102 may also be several times (for example, K) larger than that of the laser array 1101. Therefore, the super-long detection focal length is obtained, so that the ranging capability of the laser radar is greatly improved, for example, the ranging capability is improved from 200 meters to 300 meters.

As shown in fig. 11B, the difference from the embodiment of fig. 11A is that in the laser array 1101B of the laser array, the lasers may be implemented by VCSELs, instead of EELs in the embodiment of fig. 11A, to further improve the ranging capability. Accordingly, in this example, the microlens array 1109 may be correspondingly disposed (a convex lens may be additionally added in the first optical path section, etc.) to compress the divergence angle of the VCSEL, leaving the periphery of the optical aperture to give the detection optical path. In fig. 11B, the divergence angle of the laser is compressed to travel along the middle portion of the coaxial optical path (indicated by the thin solid line arrow), and the echo signal travels in the peripheral region with respect to the middle portion (indicated by the thick solid line arrow).

Reference is also made to fig. 12A and 12B for explaining the efficacy of encapsulating the optical path segment between each laser and the corresponding concave lens in the sleeve in the embodiment of the present application. The inner wall of the sleeve is made of an absorbing material so as to absorb light.

As shown in the light path diagram of fig. 12A, the emission light path is taken as an example. In the case of not using a sleeve, although the light emitting surface can be enlarged, it is necessary to maintain the focal length of the main lens group at the vertical resolution, otherwise, an emission signal (e.g., C) of a light emitting point on the laser 1201 near the edge portion may escape from the concave lens (concave lens 1202) and enter a main lens group unit (e.g., a main lens group, which is not shown in the figure), the emission signal that does not pass through the first diverging unit may be defocused, and an echo signal that is likely to be formed after being sent out through the main lens group unit at a large divergence angle may be received by a photodetector of another channel, thereby forming crosstalk. Thus, this portion of the potentially stray light may be absorbed by the absorbing material.

As shown in the optical path diagram of fig. 11B, the sleeve 1203 encapsulates the optical path segment between the laser 1201 and the corresponding concave lens 1202, so that the emitted signal originally avoiding the concave lens 1202 is reflected to limit the emitted signal to pass through the concave lens 1202 and then reach the main lens group unit, and the emitted signal does not generate defocusing, thereby achieving a light emitting area with the same or similar size as the concave lens. This is true for VCSELs, since the light emitting area is increased, and the corresponding peak power is also increased.

Similarly, as shown in fig. 12C, the effect of the optical path segment between the concave lenses 1302 corresponding to the echo signal in the embodiment of the present application after being packaged in the sleeve 1303 and reaching each detector 1301 is described, the optical path segment is similar to the emitting end, and also absorbs the potential parasitic light, so as to improve the signal-to-noise ratio, which is not described herein again.

The above embodiments are merely illustrative of the principles and utilities of the present application and are not intended to limit the application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of the present application.

Claims

1. A lidar, comprising:

2. The lidar of claim 1, wherein the first optical assembly comprises: a primary lens group unit adapted to collimate the emission signal;

3. Lidar according to claim 2, wherein the first optical assembly has an equivalent focal length M times the focal length of the main lens group unit, M>1, so as to increase the area of the light emitting surface of each laser by M²And (4) doubling.

4. The lidar of claim 2, wherein the first scattering unit comprises: an array of concave lenses, wherein each concave lens corresponds to one emission channel.

5. The lidar of claim 4, wherein a vertical pitch between adjacent concave lenses in the array of concave lenses is no less than a height of a light emitting face of the laser.

6. The lidar of claim 1, wherein the laser array comprises N columns of staggered lasers, the first optical assembly has an equivalent focal length M times the focal length of the main lensed unit, and N > M.

7. The lidar of claim 4, wherein at least a portion of the optical path between each laser and the corresponding concave lens is enclosed in a sleeve, and an inner wall of the sleeve is made of an absorbing material.

8. The lidar of claim 1 or 4, wherein the first optical assembly further comprises: and a micro lens array, wherein each micro lens is arranged corresponding to one light-emitting point of the laser.

9. Lidar according to claim 1, wherein the lidar is a mechanical lidar or a MEMS lidar having a rotational mechanism.

10. The lidar of claim 1, wherein the laser array comprises a plurality of lasers, the lasers being vertical cavity surface emitting lasers or edge emitting lasers or photonic crystal structure surface emitting semiconductor lasers; and/or the light detector is a single photon avalanche diode or a silicon photomultiplier.

11. A lidar, comprising:

12. The lidar of claim 11, wherein the second optical assembly comprises: a receiving lens group unit adapted to converge a receiving signal;

the second optical assembly further comprises: and the second diverging unit is arranged between the optical detector array and the receiving lens group unit, so that the second optical assembly has an equivalent focal length longer than a second preset value and is suitable for diverging the received signals converged by the receiving lens group unit.

13. Lidar according to claim 11, wherein the equivalent focal length of the second optical assembly is P times the focal length of the main lens set unit, P>1, to reduce the acceptance angle area by P²And (4) doubling.

14. The lidar of claim 12, wherein the second diverging unit comprises: an array of concave lenses, wherein each concave lens corresponds to a detector arrangement.

15. The lidar of claim 14, wherein a vertical pitch between adjacent concave lenses in the array of concave lenses is greater than a height of a receiving face of each detector.

16. The lidar of claim 11, wherein the detector array comprises a staggered arrangement of Q columns of detectors, the second optical assembly has an equivalent focal length P times the focal length of the main lensed unit, Q > P.

17. Lidar according to claim 11, comprising: the first optical component is arranged on the emission light path and forms an equivalent focal length larger than a first preset value so as to improve the power density in the area of the field angle of the point cloud and further improve the distance measuring capability of the radar; the first preset value is the focal length of a main lens group unit in the first optical assembly; the equivalent focal lengths of the first optical assembly and the second optical assembly are in a proportional relationship.