2D Scanning High-Precision LiDAR Using a Combination of a Rotating Concave Mirror and a Beam Steering Device

Abstract

The present disclosure relates to a 2D scanning high-precision LiDAR using a combination of a rotating concave mirror and a beam steering device. The system includes a first light source configured to provide a first light pulse. The system further includes one or more beam steering devices optically coupled to the first light source. Each beam steering device includes a rotatable concave reflector and a beam steering device disposed at least partially within the rotatable concave reflector. When the beam steering device and the rotatable concave reflector move relative to each other, the combination of the two: turns one or more first light pulses both vertically and horizontally to illuminate an object within the field of view; obtains one or more first return light pulses, which are generated based on the turned first light pulses that illuminate the object within the field of view; and redirects one or more first return light pulses.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of December 20, 2017, an application number of 2017800032023, and an invention title of "2D Scanning High-Precision LiDAR Using a Combination of a Rotating Concave Mirror and a Beam Steering Device". Technical Field

[0002] The present disclosure generally relates to light detection and ranging (LiDAR), and more particularly to a system for scanning successive light pulses to illuminate an object in a field of view and coaxially collecting scattered light from each light pulse for ranging the object in the field of view. Background Art

[0003] To reduce the size of LiDAR systems, efforts have been made to implement on-chip microelectromechanical systems (MEMS) to steer light pulses to illuminate an object in a field of view. Such on-chip solutions reduce the size of LiDAR systems. However, these on-chip MEMS designs typically produce an optical aperture cross-section of a few millimeters (less than 5) or less, which makes it difficult to distinguish between light pulses reflected by an object located at a relatively long distance (e.g., 100 meters) and background noise signals. It has been found that a larger optical aperture cross-section improves the signal-to-noise ratio of light. However, due to their system configuration, typical LiDAR systems may be bulky and expensive. These systems may not be easily integrated with a vehicle and / or may be prohibitively expensive to integrate with a vehicle. Accordingly, there is a desire for a high-precision LiDAR system with reduced size and cost. Some of the challenges faced by high-precision LiDAR systems are to reduce the size of the LiDAR system while increasing the cross-section collecting optical aperture. Summary of the Invention

[0004] A brief summary of one or more examples is presented below to provide a basic understanding of the present disclosure. The summary of the invention is not an extensive overview of all contemplated examples, nor is it intended to identify key or critical elements of all examples or to delineate the scope of any or all examples. Its purpose is to present some concepts of one or more examples in a simplified form as a prelude to the more detailed description presented below.

[0005] According to some embodiments, a light detection and ranging (LiDAR) scanning system is provided. The system includes a first light source configured to provide one or more first light pulses. The system further includes one or more beam steering devices optically coupled to the first light source. Each beam steering device includes a rotatable concave reflector and a beam steering device, and the rotatable concave reflector and the beam steering device are arranged in such a position that the light pulse guided by the rotatable concave reflector or the beam steering device can be further guided to different directions by the beam steering device or the rotatable concave reflector. When the beam steering device and the rotatable concave reflector move relative to each other, the combination of the two steers one or more first light pulses in both the vertical and horizontal directions to illuminate an object within the field of view; one or more first return light pulses are obtained, the one or more first return light pulses are generated based on the steered first light pulses that illuminate the object within the field of view, and the one or more first return light pulses are redirected to one or more return light detectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] To better understand the various described aspects, the following description should be referred to in conjunction with the accompanying drawings, in which like reference numerals refer to corresponding parts in all the drawings.

[0007] Figure 1A A plurality of coaxial LiDAR systems attached to a vehicle are shown.

[0008] Figure 1B An exemplary beam steering device having a polyhedron located within a concave reflector is shown.

[0009] Figure 1C An exemplary beam steering device having a swinging mirror in place of the concave reflector is shown.

[0010] Figure 2A A binocular LiDAR system is shown.

[0011] Figure 2B A coaxial LiDAR system having a converging lens is shown.

[0012] Figure 2C A coaxial LiDAR system having a converging mirror is shown.

[0013] Figure 3 A dual coaxial LiDAR system is shown.

[0014] Figure 4A An exemplary beam steering device is shown that directs emitted light in a direction between the positive x-axis and the positive z-axis and collects scattered light from that direction.

[0015] Figure 4BAn exemplary beam steering device is shown that directs the emitted light to a direction between the negative x-axis and the positive z-axis and collects the scattered light from that direction.

[0016] Figure 5 An exemplary beam steering device is shown that directs the emitted light to a direction more towards the edge of the positive horizontal range of the field of view and collects the scattered light from that direction.

[0017] Figure 6A and Figure 6B An interleaved frame diagram showing the angular distribution of a dual coaxial LiDAR system in the horizontal and vertical directions is shown.

[0018] Figure 7 A heat map corresponding to the width of the collection aperture in the x-z plane along y = 0 in the horizontal and vertical directions of a dual coaxial LiDAR system is shown.

[0019] Figure 8 An exemplary process for LiDAR scan detection is shown.

[0020] Figures 9A to 9D Different views of another embodiment of a beam steering device according to an example of the present disclosure are shown.

[0021] Figures 10A to 10B Various exemplary configurations for generating a collimated illumination laser beam according to an example of the present disclosure are shown.

[0022] Figure 11 An exemplary configuration of a beam steering device for increasing the receiving aperture and for collecting return light pulses from different facets is shown according to an example of the present disclosure.

[0023] Figures 12A to 12C An exemplary configuration of a receiving optical system according to an example of the present disclosure is shown.

[0024] Figures 13A to 13B An exemplary detector element for light collection using a photosensitive device according to an example of the present disclosure is shown.

[0025] Figures 14A to 14B An exemplary configuration for combining light pulses from different facets using a combination of free space optics or fiber bundles and / or power combiners according to an example of the present disclosure is shown.

[0026] Figures 15A to 15E Various configurations of the facets of an exemplary polyhedron having curved and flat surfaces according to an example of the present disclosure are shown.

[0027] Figure 16An exemplary configuration of a LiDAR system for determining the time of flight of an optical pulse according to an example of the present disclosure is shown.

[0028] Figure 17 A reference pulse and a received return optical pulse according to an example of the present disclosure are shown.

[0029] Figure 18 Another embodiment of a beam steering device with a wobbling mirror according to an example of the present disclosure is shown.

[0030] Figure 19 An exemplary flowchart of a method for determining the time of flight of one or more laser pulses according to an example of the present disclosure is shown. Detailed Description

[0031] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0032] Examples of LiDAR scanning systems will now be presented with reference to various elements of the devices and methods. These devices and methods will be described and illustrated in the following detailed description and the drawings by means of various blocks, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements can be implemented using electronic hardware, computer software, or any combination thereof. Whether these elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0033] The present disclosure describes a 2D scanning high-precision LiDAR system using a combination of a rotatable concave reflector and a beam steering device. The LiDAR system includes a beam steering device having a polyhedral reflector located within a concave reflector aligned about a central axis. The concave reflector is configured to rotate about the central axis. The polyhedron is configured to rotate about a pivot along a direction at an angle (e.g., 90 degrees) to the central axis. The respective instantaneous positions of the concave reflector and the polyhedron steer light pulses to illuminate an object in the field of view while collecting scattered light scattered from the light pulses on the object. Each emitted light pulse is substantially coaxial or parallel with the collected scattered light from the corresponding light pulse. The LiDAR system includes a microcontroller for calculating the distance to the object based on the time difference between each emitted light pulse and the light collected from the scattering of the corresponding light pulse on the object. The present disclosure also describes interleaved sub-frames for achieving higher resolution frames. The technique includes sampling range points of one or more objects in successive horizontal and vertical directions to form one or more sub-frames. The vertical and / or horizontal positions of the sample points of the successively captured sub-frames are slightly offset, providing an interleaved higher density of sampling points when combined. The higher the sampling point density, the higher the resolution of the LiDAR system.

[0034] Although the examples of the present disclosure are described for integration in vehicles, other applications may also be considered. For example, a centralized laser delivery system and multiple LiDAR systems may be provided in or integrated with a robot, installed at multiple locations in a building for security monitoring purposes, or installed at traffic intersections or certain road locations for traffic monitoring, etc.

[0035] Figure 1A Multiple LiDAR scanning systems 300A to 300F attached to a vehicle 150 are shown. The LiDAR scanning systems 300A to 300F may be 2D scanning LiDAR systems. Each of the LiDAR scanning systems 300A to 300F detects and calculates the range of objects corresponding to positions at and around the vehicle 150 within the field of view. As an example, the LiDAR scanning system 300A disposed at the front of the vehicle 150 illuminates an adjacent vehicle 150' (and / or other objects) with light pulses that are collected substantially coaxial or parallel with each respective light pulse. The range (e.g., distance) to the adjacent vehicle 150' is determined based on the time difference at which each light pulse is emitted and scattered light from the corresponding light pulse is detected.

[0036] As Figure 1AIn the illustrated example, multiple LiDAR scanning systems 300A - 300F are distributed around vehicle 150 to cover the field of view between each individual coaxial LiDAR system. For example, the field of view can be configured such that LiDAR scanning system 300F can detect centerline 154 on one side of vehicle 150, and LiDAR scanning system 300C can detect lane divider 152 on the other side of vehicle 150. In some cases, the field of view of one or more of the multiple LiDAR scanning systems 300A - 300F can overlap. For example, the field of view of LiDAR scanning system 300B can overlap with the field of view of LiDAR scanning system 300A. The overlap of the field of view can provide a higher sampling density. Similarly, the field of view of LiDAR scanning system 300A can overlap with the field of view of LiDAR scanning system 300F. Each LiDAR scanning system 300A - 300F can include a beam steering device that can steer light pulses vertically and horizontally to emit into the field of view to scan objects. The steering of the light pulses enables continuous point sampling from one or more objects within the field of view.

[0037] It should be understood that Figure 1A the LiDAR scanning systems 300A - 300F depicted in can be relatively small in size. That is, each respective LiDAR scanning system (e.g., systems 300A - 300F) can occupy a space of, for example, no more than 1 cubic foot or 1 / 4 cubic foot.

[0038] Figure 1B An exemplary beam steering device 100 is shown having a beam steering device (e.g., polyhedron 102) disposed within concave reflector 112. As Figure 1B depicted, in some embodiments, concave reflector 112 is coaxially aligned (e.g., substantially concentric) with first axis 106. Concave reflector 112 can include one or more reflective surfaces (e.g., planar mirrors) located on the concave side around aperture 118. Aperture 118 of concave reflector 112 is coaxially aligned (e.g., substantially concentric) with first axis 106. In Figure 1B the depicted example, the mirrors are angled inward to form a hexagonal bowl of concave reflector 112. In Figure 1BIn the depicted example, the hexagonal aperture 118 of the concave reflector 112 can have a width of one inch on opposite sides of the aperture 118 (e.g., hexagonal), and the reflective surface (e.g., mirror) of the concave reflector 112 can be at a 45° angle to the hexagonal aperture 118 with a length of 2.45 inches (along the angled mirror). In some embodiments, the reflective surface (e.g., mirror) of the concave reflector 112 ranges between 0.2 inches and 4 inches. In some embodiments, the reflective surface of the concave reflector 112 can be curved. In some examples, the curved surface protrudes outward (e.g., convex), which can be used to increase the field of view of the beam steering device 100. In some examples, the curved surface protrudes inward (e.g., concave).

[0039] As Figure 1B depicted, the polyhedron 102 can be disposed within the concave reflector 112. The polyhedron 102 includes a pivot 120 coaxially aligned (e.g., substantially concentric) with a second axis 104 that is perpendicular to the first axis 106. The polyhedron 102 also includes at least one reflective surface (e.g., mirror) disposed at a facet of the polyhedron 102 to redirect light between the aperture 118 of the concave reflector 112 and at least one reflective surface (e.g., mirror) of the concave reflector 112. For example, a light pulse emitted through the aperture 118 toward the reflective surface of the polyhedron 102 can be redirected or steered toward the reflective surface of the concave reflector 112, and the light pulse can be further redirected or steered into the field of view. In Figure 1B the depicted example, the polyhedron 102 is a cube having six facets. In some examples, two opposite facets having the pivot 120 do not have a reflective surface (e.g., mirror), while the remaining four facets have outwardly directed reflective surfaces (e.g., mirror). In Figure 1B the depicted example, the cube has an edge length of approximately 1.22 inches.

[0040] It should be understood that the polyhedron 102 may have six non-fully orthogonal facets. For example, in some embodiments, the polyhedron 102 may have asymmetric facets that can offset and / or change the vertical and horizontal scan directions between sub-frames and the interleaved grating pattern. In some examples, the polyhedron 102 is a rhombohedron. It should also be understood that the polyhedron 102 may have fewer than six facets. For example, in some embodiments, the polyhedron 102 is a pentahedron. In such an embodiment, the polyhedron 102 may be a triangular prism, where the pivot is located at two opposite triangular facets and one or more reflective surfaces (e.g., mirrors) are located at the rectangular facets. It should also be understood that the polyhedron 102 may have more than six facets. For example, the polyhedron 102 may be a hexahedron, heptahedron, octahedron, etc. In some embodiments, the facets of the polyhedron 102 are curved. In some examples, the curved facets protrude outward (e.g., convex), which can be used to increase the field of view of the beam steering device 100. In some examples, the curved facets protrude inward (e.g., concave), which can reduce the field of view and form the profile of the outgoing laser beam.

[0041] In some embodiments, the beam steering device 100 includes one or more motors (not shown) operatively coupled to the concave reflector 112 and the polyhedron 102. In this example, the one or more motors may be configured to rotate the concave reflector 112 about the first axis 106 in a counterclockwise direction (when viewed along the -z direction) at a first rotational speed 116, as Figure 1B depicted. The one or more motors may also be configured to rotate the polyhedron 102 about the pivot 120, which rotates about the second axis 104 in a counterclockwise direction (when viewed along the +y direction) at a second rotational speed 114. In some embodiments, the rotation controller is configured to control the first rotational speed 116 of the concave reflector 112 and the second rotational speed 114 of the polyhedron 102. In some cases, the rotation controller is electrically coupled to the one or more motors to independently control the first rotational speed 116 of the concave reflector 112 and the second rotational speed 114 of the polyhedron 102. In some embodiments, the first rotational speed 116 of the concave reflector 112 is different from the second rotational speed 114 of the polyhedron 102. For example, the second rotational speed 114 of the polyhedron 102 may be faster than the first rotational speed 116 of the concave reflector 112. In Figure 1B the depicted example, the second rotational speed 114 of the polyhedron 102 may be set to 500 revolutions per second (rps), while the first rotational speed 116 of the concave reflector 112 may be set to 10 rps. In some embodiments, the second rotational speed 114 of the polyhedron 102 may be slower than the first rotational speed 116 of the concave reflector 112.

[0042] In some embodiments, for each sampling point in the scan enabled by the beam steering device 100, the instantaneous position of the rotating polyhedron 102 relative to the rotating concave reflector 112 is such that the beam steering device 100 can direct or steer an optical pulse to an object and collect a return optical pulse from the object along a substantially similar optical path. Refer to Figure 1B , the instantaneous position of the rotating polyhedron 102 can be measured relative to the positive z-axis. The angle of the polyhedron 102 is positive when measured from the counterclockwise direction (as viewed along the y-axis). The instantaneous position of the rotating concave reflector 112 can be measured relative to the negative y-axis. The angle of the concave reflector 112 is positive when measured from the clockwise direction (as viewed along the z-axis).

[0043] It should be understood that other mechanisms that provide the same effect as the rotating concave reflector 112 and / or the rotating polyhedron 102 can be applied. For example, as Figure 1C depicted, the concave reflector 112 can be replaced by a swing mirror 112A that swings along the axis 129. In this way, the rotation of the polyhedron 102 coupled to the swing mirror 112A can provide a similar steering mechanism that is used to scan successive optical pulses to illuminate an object in the field of view and to collect return light from each optical pulse coaxial or parallel to the illuminating optical pulse to range the object in the field of view. In another example, the polyhedron 102 can be driven by an actuator that swings the polyhedron back and forth along an axis. In some examples, the swing mirror 112A can swing about a first axis, and the polyhedron 102 can be disposed adjacent to the swing mirror 112A, as Figure 1C shown. The polyhedron 102 can include a pivot coaxially aligned with a second axis. The second axis can be disposed at an angle (e.g., 90 degrees or 75 degrees) to the first axis. At least one mirror can be disposed on the facets of the polyhedron 102 for reflecting an optical pulse between the aperture and the concave reflector 112. One or more motors or actuators are operably coupled to the swing mirror 112A and the polyhedron 102. One or more motors or actuators can be configured to rotate (as shown at 128A) or swing (as shown at 128B) the swing mirror 112A about the first axis at a first frequency and to rotate (as shown at 125A) or swing (as shown at 125B) the rotatable polyhedron about the second axis at a second frequency.

[0044] In Figure 1BIn the example depicted, the light pulse 307A obtained from the light source is directed through the aperture 118 towards the polyhedron 102, which produces a redirected light pulse 307B by redirecting or reflecting the light pulse 307A. The light pulse 307B is directed towards the mirror on the concave reflector 112. The concave reflector 112 then produces a steered light pulse 312A by redirecting or reflecting the steered light pulse 307B. The steered light pulse 312A is directed towards the field of view to illuminate an object within the field of view. The steered light pulse 312A illuminates the object, which scatters the light pulse in one or more directions. Some of the scattered light pulses return to the beam steering device 100 as the first return light pulse 207A. As Figure 1B shown, in some examples, the first return light pulse 207A may return to the beam steering device 100 (coaxially) along an optical path that is substantially similar to the steered light pulse 312A. Each of the first return light pulses 207A may be redirected or reflected by the concave reflector 112 to produce a redirected return light pulse 209. The redirected return light pulse 209 is directed towards the polyhedron 102, which then redirects and reflects the light pulse to produce a redirected return light pulse 214A. The redirected return light pulse 214A is directed back through the aperture 118 to the light detector.

[0045] Figure 2A A binocular LiDAR system 200 is shown. In some examples, the binocular LiDAR system 200 emits light pulses generated from a light source along an illumination optical path 210C through a first aperture 210A to an object within the field of view. The emitted light pulses reach the object and are scattered and dispersed in one or more directions. Some of the scattered light pulses return to the light detector through a second aperture 210B along a detection optical path 210D. The geometry of the binocular LiDAR system 200 determines the detection range, which is determined by Figure 2A the overlapping region between the depicted exemplary illumination optical path 210C and the detection optical path 210D. Thus, scattered light pulses in certain regions along the optical path of the binocular LiDAR system 200 may not return through the second aperture 210B. In some embodiments, the illumination optical path 210C and the detection optical path 210D are substantially parallel (e.g., with a small angle). Thus, the detection range can be wide. For example, as Figure 2A depicted, the detection range may not have a boundary on the right side. The advantage of the binocular LiDAR system is that the illumination optics and the detection optics are physically separated within the LiDAR scanning system, thereby making it easier to avoid optical interference in the detection module due to light scattering in the illumination optics.

[0046] Figure 2BShows a coaxial LiDAR scanning system 250 with a converging lens 224. In some embodiments, the coaxial LiDAR scanning system 250 includes a light source 220, a mirror 222, a converging lens 224, a mask 226 with a hole, a light detector 230, and a beam steering device 100. As Figure 2B depicted, an incident light pulse 212A generated from the light source 220 is directed to the mirror 222, which redirects or reflects the incident light pulse 212A to produce a redirected light pulse 212B. The redirected light pulse 212B is directed along the optical axis 211 to the beam steering device 100. Then, the beam steering device 100 can steer the redirected light pulse 212B as described above to produce a steered light pulse 212C for illuminating an object in the FOV, where Figure 2B the direction of 212C only shows the time point when the steering direction is parallel to the direction of 212B. At other time points, the direction of 212C can be in other directions in the FOV. In Figure 2B the depicted example, the mirror 222 can be a nearly 100% mirror disposed at the optical axis 211, which is along the optical paths of both the redirected light pulse 212B and the redirected return light pulse 214. It should be understood that the mirror 222 should be small enough so as not to block or interfere with the redirected return light pulse 214.

[0047] In Figure 2B the example, the beam steering device 100 can be the coaxial beam steering device 100 from Figure 1B . In some examples, the beam steering device 100 can be a dual coaxial device that implements two substantially parallel light pulses directed at one or more objects in the field of view. The beam steering device 100 can be configured to steer the redirected light pulse 212B in the vertical and horizontal directions to produce a steered light pulse 212C, while collecting the return light pulse 212D along substantially the same optical path as the steered light pulse 212C. The beam steering device 100 redirects the return light pulse 212D to produce a redirected return light pulse 214 in the opposite direction of 212B. In this way, the optical path of the return light pulse 212D to the redirected return light pulse 214 overlaps with the illumination optical path of the redirected light pulse 212B to steer the light pulse 212C, thereby increasing the effective detection range.

[0048] Referring to Figure 2B , the converging lens 224 of the coaxial LiDAR scanning system 250 is configured to collect the redirected return light pulse 214 along the optical axis 211 and guide the redirected return light pulse 214 through the hole of the mask 226 to the light detector 230. The converging lens 224 can be made of any transparent material (such as high refractive index glass, plastic, etc.). AsFigure 2B As depicted, the converging lens 224 can be substantially concentric with the optical axis 211. It should be understood that in some embodiments, the converging lens 224 is arranged such that it is not concentric with the optical axis 210.

[0049] As Figure 2B depicted, in some examples, the light detector 230 is arranged to be substantially concentric with the optical axis 211. The light detector 230 can be a photodiode, an avalanche photodiode, etc. In some embodiments, as Figure 2B depicted in the enlarged view of the light detector 230 shown, the light detector 230 can include a reflective surface 231 (e.g., a mirror) facing the opposite side of the light incident surface 232. The reflective surface 231 can redirect (e.g., reflect) the light back to the absorption region of the light detector 230, thereby improving the detection efficiency and sensitivity. In some embodiments, the mask 226 can be part of the light detector 230. Generally speaking, the mask 226 filters the redirected return light pulses 214 that are inclined at an angle relative to the optical path (e.g., the optical path along the optical axis 211) near the light detector 230, such that only the light pulses that are substantially parallel to the optical axis 211 can reach the light detector 230.

[0050] In Figure 2B the example depicted, the light source 220 can be a laser light source. In some examples, the laser generated by the light source 220 can have a wavelength in the visible spectrum. In some examples, the laser can have a wavelength in the infrared spectrum. In some examples, the laser can have a wavelength in the ultraviolet spectrum.

[0051] Figure 2C Shown is a coaxial LiDAR scanning system 250' having a converging mirror 221. In some embodiments, the coaxial LiDAR scanning system 250' includes a light source 220, a converging mirror 221, a mask 226 having a hole, a light detector 230, and a beam steering device 100. As Figure 2CAs depicted, an incident light pulse 212A generated from a light source 220 is guided along an optical axis 211 through an aperture of a focusing mirror 221 to a beam steering device 100. The beam steering device 100 steers (e.g., redirects and reflects) the incident light pulse 212A to generate a steered light pulse 212C to illuminate an object. The object may scatter the steered light pulse 212C. A portion of the scattered light pulse returns to the beam steering device 100 as a returned light pulse 212D. The returned light pulse 212D is guided along a path that is substantially similar or parallel to the path of the steered light pulse 212C. Then, the beam steering device 100 may guide the returned light pulse 212D to generate a redirected returned light pulse 214 that is directed toward the focusing mirror 221 in a direction coaxial with the optical axis 211, and the focusing mirror redirects (e.g., reflects) the redirected returned light pulse 214 through an aperture of a mask 226 toward a light detector 230.

[0052] In some embodiments, as described above, the focusing mirror 221 of the coaxial LiDAR scanning system 250 is configured to collect the redirected returned light pulse 214 along the optical axis 211 and redirect the redirected returned light pulse 214 through an aperture of the mask 226 to the light detector 230. In Figure 2C the depicted example, the focusing mirror 221 may be a nearly 100% reflecting mirror disposed at or near the optical axis 211, which is along the optical paths of both the steered light pulse 212C and the redirected returned light pulse 214. The focusing mirror 221 focuses the redirected returned light pulse 214 onto the light detector 230. It should be understood that in some embodiments, the focusing mirror 221 may be arranged such that it is not concentric with the optical axis 211. The focusing mirror 221 may be made of any substrate (e.g., glass, plastic, metal, etc.) having a mirror finish layer. In some examples, an anti-oxidation layer is applied to the mirror finish layer to hermetically isolate the reflective layer from air. This prevents oxygen and other corrosive agents (e.g., corrosive gases or corrosive liquids) from darkening the reflective portion of the surface of the focusing mirror 221.

[0053] In Figure 2C the depicted example, the beam steering device 100 may be Figure 1B a coaxial beam steering device 100. In some embodiments, the beam steering device 100 may be a dual coaxial device that implements two substantially parallel light pulses directed at one or more objects in a field of view. The beam steering device 100 may be configured to guide the incident light pulse 212A in a vertical direction and a horizontal direction to generate a steered light pulse 212C while collecting the returned light pulse 212D along substantially the same optical path as the steered light pulse 212C. For example, as Figure 2CAs shown, the optical path of the return optical pulse 212D can be substantially parallel to at least a portion of the optical path of the steered optical pulse 212C. In this way, the optical path of the return optical pulse 212D overlaps with the optical path of the steered optical pulse 212C.

[0054] As Figure 2C depicted, in some embodiments, the photodetector 230 is arranged to be substantially concentric with the reflected optical axis 211'. In some embodiments, the reflected optical axis 211' extends from the center of the aperture of the converging lens 221 (e.g., the center of the aperture of the converging lens 221) through the focal point of the converging lens 221. The reflected optical axis 211' can form an angle with the optical axis 211, and the optical axis 211 is substantially parallel to the optical path of the steered optical pulse 212C and the redirected return optical pulse 214. The photodetector 230 can be a photodiode, an avalanche photodiode, etc. In some embodiments, similar to Figure 2B the photodetector shown, the photodetector 230 can include a reflective surface (e.g., a mirror) facing the opposite side of the light incident surface. This reflective surface can redirect (e.g., reflect) the light back to the absorption region of the photodetector 230, thereby improving the detection efficiency and sensitivity. In some embodiments, the mask 226 can be a part of the photodetector 230.

[0055] In Figure 2C the depicted example, the light source 220 can be a laser light source. In some examples, the laser generated by the light source 220 can have a wavelength in the visible spectrum. In some examples, the laser can have a wavelength in the infrared spectrum. In some examples, the laser can have a wavelength in the ultraviolet spectrum.

[0056] Figure 3 illustrates a dual coaxial LiDAR scanning system 300. As Figure 3 depicted, the dual coaxial LiDAR scanning system 300 can include a light source 220, a mirror 222, a partially reflective mirror 322, a first converging lens 224A, a second converging lens 224B, a first mask 226A having an aperture, a second mask 226B having an aperture, a first photodetector 230A, a second photodetector 230B, and a dual beam steering device 100'. As Figure 3 depicted, the incident optical pulse 212A generated from the light source 220 is directed to the partially reflective mirror 322, which reflects a first portion of the incident optical pulse 212A to generate a redirected optical pulse 212B. The polyhedron 102 generates a redirected optical pulse 212C based on the redirected optical pulse 212B, which in turn is redirected by the concave reflector 112 to generate a steered optical pulse 312A. The steered optical pulse 312A can be directed through the aperture 118 of the beam steering device 100' to an object in the FOV. In Figure 3In the depicted example, the partial mirror 322 is a 50% mirror disposed along the first optical axis 311A. The partial mirror 322 can be configured to reflect, for example, 50% of the incident light along the first optical axis 311A. In some embodiments, the partial mirror 322 can be configured to reflect more than 50% of the incident light along the first optical axis 311A. In some embodiments, the partial mirror 322 can be configured to reflect less than 50% of the incident light along the first optical axis 311A. It should be understood that the partial mirror 322 should be small enough so as not to block a large portion of the first return light pulse 207A.

[0057] As Figure 3 depicted, another portion of the incident light pulse 212A passes through the partial mirror 322 and becomes the second portion of the incident light pulse 212A. The second portion of the incident light pulse 212A can be redirected to the mirror 222, which redirects the second portion of the incident light pulse 212A to produce a redirected light pulse 213B. The polygon 102 produces a redirected light pulse 213C based on the redirected light pulse 213B, which in turn is redirected by the concave reflector 112 to produce a steered light pulse 312B. The steered light pulse 312B can be directed along the second optical axis 311B through the aperture 118 of the beam steering device 100. In Figure 3 the depicted example, the mirror 222 can be a nearly 100% mirror disposed at the second optical axis 311B. It should be understood that the mirror 222 should be small enough so as not to block a large portion of the return light pulse 207B. It should also be understood that although Figure 3 two portions of the incident light pulse 212A are shown as being generated from the light source 220, two separate and independent light sources can be used to separately generate these two portions of the incident light pulse 212A.

[0058] Figure 3 The dual-beam steering device 100’ shown can be Figure 1BThe coaxial beam steering device 100 depicted. The difference in this example is that the beam steering device 100' is configured to direct two light pulse beams (e.g., a first steering light pulse 312A and a second steering light pulse 312B) to illuminate one or more objects in the field of view. For example, the beam steering device 100' can be configured to direct the first steering light pulse 312A and the second steering light pulse 312B in the vertical and horizontal directions while collecting the first return light pulse 207A and the second return light pulse 207B. The first return light pulse 207A and the second return light pulse 207B can have optical paths that are substantially the same as or parallel to the optical paths of the first steering light pulse 312A and the second steering light pulse 312B, respectively. Thus, the optical paths of the first return light pulse 207A and the second return light pulse 207B overlap with the optical paths of the first steering light pulse 312A and the second steering light pulse 312B, respectively. In some embodiments, the dual coaxial LiDAR scanning system 300 can also include a power controller (not shown) configured to dynamically control the power of the light source 220. The control of the power of the light source 220 can be based on the cross-sectional area of the aperture associated with the return light pulses 207A-B. Controlling the power of the light source 220 can compensate for aperture variations within the field of view.

[0059] In Figure 3 In the example depicted, the dual beam steering device 100' can generally be asymmetric in the x-z plane. Thus, the optical component geometry for generating the first steering light pulse 312A can be asymmetric with respect to the optical component geometry for generating the second steering light pulse 312B at any given point in time. Similarly, the optical component geometry for directing the first return light pulse 207A can be asymmetric with respect to the optical component geometry for directing the second return light pulse 207B at any given point in time. Accordingly, the optical path of the first steering light pulse 312A can be scanned over a different range and pattern than the second steering light pulse 312B.

[0060] Reference Figure 3, similar to those described above, the first return light pulse 207A and the second return light pulse 207B can be guided by the dual-beam steering device 100' through the aperture 118 towards the first converging lens 224A and the second converging lens 224B. Similar to those described above, the first return light pulse 207A and the second return light pulse 207B can be redirected by the polyhedron 102 and the concave reflector 112 to generate a first redirected return light pulse 214A and a second redirected return light pulse 214B, respectively. In some embodiments, the first converging lens 224A of the coaxial LiDAR scanning system 300 is configured to collect the first redirected return light pulse 214A along the first optical axis 311A and guide the first redirected return light pulse 214A through the aperture of the first mask 226A to the first photodetector 230A. Similarly, the second converging lens 224B of the coaxial LiDAR scanning system 300 is configured to collect the second redirected return light pulse 214B along the second optical axis 311B and guide the second redirected return light pulse 214B through the aperture of the second mask 226B to the second photodetector 230B. Both the first converging lens 224A and the second converging lens 224B can be made of any transparent material (such as high refractive index glass, plastic, etc.). In Figure 3 the illustrated example, the first converging lens 224A is not concentric with the first optical axis 311A, and the second converging lens 224B is not concentric with the second optical axis 311B. It should be understood that in some embodiments, one or both of the first converging lens 224A and the second converging lens 224B can be concentric with the first optical axis 311A and the second optical axis 311B, respectively.

[0061] As Figure 3As depicted, in some examples, the first light detector 230A may be disposed at or near the focal region of the first focusing lens 224A. Similarly, the second light detector 230B may be disposed at or near the focal region of the second focusing lens 224B. Accordingly, the first redirected return light pulse 214A may be focused on the first light detector 230A, and the second redirected return light pulse 214B may be focused on the second light detector 230B. One or both of the first light detector 230A and the second light detector 230B may be a photodiode, an avalanche photodiode, or the like. In some embodiments, similar to the light detector 230 described above, one or both of the first light detector 230A and the second light detector 230B may include a reflective surface (e.g., a mirror) facing the opposite side of the light incident surface. The light incident surface may redirect (e.g., reflect) light back to the absorption region of the first light detector 230A or the second light detector 230B, respectively. Thus, the efficiency and sensitivity of the first light detector 230A and the second light detector 230B can be improved. In some embodiments, the first mask 226A may be part of the first light detector 230A. In some embodiments, the second mask 226B may be part of the second light detector 230B.

[0062] In Figure 3 the depicted example, the light source 220 may be a laser light source. In some examples, the laser generated by the light source 220 may have a wavelength in the visible spectrum. In some examples, the laser may have a wavelength in the infrared spectrum. In some examples, the laser may have a wavelength in the ultraviolet spectrum.

[0063] As Figure 3 shown, in some examples, the dual coaxial LiDAR scanning system 300 includes a microprocessor 306, a light source 220, a first light detector 230A, a second light detector 230B, and one or more motors 302, and the microprocessor is electrically coupled to a computer-readable medium / memory 304. The microprocessor in the dual coaxial LiDAR scanning system 300 may execute software. The software may include, for example, instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, processes, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0064] In some embodiments, the microprocessor 306 may be configured to determine the distance to one or more objects in the field of view. As Figure 3As depicted, the microprocessor 306 includes a timer / clock module 308 and a calculator 310, which are configured to calculate the distance to one or more objects based on the time difference between the transmitted steering light pulse 312A and the first return light pulse 207A of each corresponding light pulse detected.

[0065] The timer / clock module 308 is configured to timestamp each light pulse transmitted or received. A timestamp is an encoded date and time. Examples of timestamps include "month-day-year@hour:minute:second", "month-day-year@hour:minute:second", "year-day-month@hour:minute:second", "1234567890 (Unix time)", etc. In some embodiments, the transmitted steering light pulse triggers the timer / clock module 308 to timestamp the steering light pulse. The timer / clock module 308 can also pair the steering light pulse with the corresponding return light pulse and determine the time difference based on the timestamp.

[0066] The calculator 310 is configured to calculate the distance to one or more objects based on the time difference. In some examples, the calculator 310 can multiply the time difference by the speed of light and divide by 2 (assuming a symmetric light path) to determine the distance to the object. For example, if the time difference is 0.8 microseconds, the calculator 310 calculates the distance to the object as approximately 120 meters away (e.g., (0.8 * 10 -6 ) * (2.9979 * 10 8 ) / 2). After calculating the distance, the calculator 310 can store the value in a computer-readable medium / memory 304.

[0067] The computer-readable medium / memory 304 is electrically coupled to the microprocessor 306 and can store identifiers associated with the steering light pulses transmitted into the field of view, identifiers associated with the return light pulses, timestamps, determined distances, and so on. In some examples, an identifier that uniquely identifies a particular pulse can be assigned to each pulse (e.g., the steering light pulse transmitted into the field of view and / or the return light pulse). Identifying the pulses enables determination of the time difference between the corresponding transmitted light pulse and the return light pulse.

[0068] In some embodiments, the microprocessor 306 may optionally include a rotation controller 312. The rotation controller 312 is configured to control the first rotation speed of the concave reflector 112 and the second rotation speed of the polyhedron 102. The rotation controller 312 is electrically coupled to one or more motors 302, and the motors are operably coupled to the concave reflector 112 and the polyhedron 102. In some examples, the rotation controller 312 can change the first rotation speed of the concave reflector 112 and the second rotation speed of the polyhedron 102 by changing the drive current flowing to one or more motors 302.

[0069] In some embodiments, the rotation controller 312 is configured to superimpose a random perturbation on the control parameters to cause the first rotation speed of the concave reflector 112 and / or the second rotation speed of the polyhedron 102 to increase proportionally with the random perturbation. The random perturbation to the first rotation speed of the concave reflector 112 and / or the second rotation speed of the polyhedron 102 causes a random distribution of the horizontal scan angle and the vertical scan angle associated with the light pulses emitted from the beam steering device 100' when the light pulses are substantially periodic (e.g., equally spaced). This facilitates more random coverage of the sub-frame. In some examples, the rotation controller 312 may set the first rotation speed of the concave reflector 112 to 10 rps and the second rotation speed of the polyhedron 102 to 500 rps. The rotation controller 312 may additionally add a perturbation of ±1 rps to one or both of the first rotation speed of the concave reflector 112 and the second rotation speed of the polyhedron 102. In some cases, the perturbations may be the same, while in other cases, the perturbations may be different.

[0070] One or more motors are operably coupled to the concave reflector 112 and the polyhedron 102. In some examples, a first motor may rotate the concave reflector 112 while a second motor may rotate the polyhedron 102. In some examples, a single motor coupled to one or more gears may rotate the concave reflector 112 and rotate the polyhedron 102. In Figure 3 the depicted example, one or more motors 302 may be configured to rotate the concave reflector 112 about a first axis 106 at a first rotation speed and rotate the polyhedron 102 about a second axis 104 at a second rotation speed. In some embodiments, the first rotation speed and the second rotation speed are controlled independently of each other.

[0071] Figure 3 It is shown that the first steering light pulse 312A and the second steering light pulse 312B are guided along the positive z-axis direction. The positions of the polyhedron 102 and the concave reflector 112 for generating the first steering light pulse 312A and the second steering light pulse 312B guided along the positive z-axis direction are as Figure 3 depicted, and these positions may be defined as nominal positions. When the polyhedron 102 and the concave reflector 112 are rotated at a specific angle, the beam steering device 100 can direct the steering light pulses to any desired direction in the field of view and collect the return light pulses from any desired direction in the field of view. Figure 4A An exemplary beam steering device 100 is shown that directs the steering light pulses to a direction between the positive x-axis and the positive z-axis and collects the return light pulses from that direction. In some examples, as Figure 4AAs depicted, the instantaneous position of the rotating polyhedron 102 is at +15° relative to the nominal position, while the instantaneous position of the rotating concave reflector 112 is at the nominal position. As Figure 4A As depicted, the optical pulse 307A is directed through the aperture 118 of the beam steering device 100 and then redirected (e.g., reflected) by the polyhedron 102 to produce a redirected optical pulse 307B. This redirection can occur at or near point 402 and can direct the redirected optical pulse 307B towards the concave reflector 112. The redirected optical pulse 307B is further redirected (e.g., reflected) by the reflective surface (e.g., mirror) of the concave reflector 112 to produce a first steered optical pulse 312A. This redirection can occur at or near point 404 and can direct the first steered optical pulse 312A towards one or more objects in the field of view in a direction between the positive x-axis and the positive z-axis. The first steered optical pulse 312A illuminates the object, and the first return optical pulse 207A returns along an optical path that is substantially coaxial or parallel to the first steered optical pulse 312A. In Figure 4A the example depicted, the first return optical pulse 207A overlaps with the first steered optical pulse 312A. For example, the first steered optical pulse 312A illuminates the object at an angle of approximately 30° relative to the horizontal direction (e.g., a 30° angle between the positive z-axis and the direction of the emitted optical pulse 312A), and the exemplary beam steering device 100 collects the first return optical pulse 207A at an angle of approximately 30° relative to the horizontal direction. Similar to those described above, the first return optical pulse 207A can be redirected by the polyhedron 102 and the concave reflector 112 to produce a redirected return optical pulse 214A.

[0072] Figure 4B An exemplary beam steering device 100 is shown that directs steered optical pulses to the field of view and collects return optical pulses from a direction between the negative x-axis and the positive z-axis. In some examples, as Figure 4B depicted, the instantaneous position of the rotating polyhedron 102 is at -5° (or 355°) relative to the nominal position, while the instantaneous position of the rotating concave reflector 112 is at the nominal position. As Figure 4BAs depicted, the optical pulse 307A is directed through the aperture 118 of the beam steering device 100 and then redirected (e.g., reflected) by the polyhedron 102 to produce a redirected optical pulse 307B. This redirection can occur at or near point 402 and can direct the redirected optical pulse 307B towards the concave reflector 112. The redirected optical pulse 307B is further redirected (e.g., reflected) by the reflective surface (e.g., mirror) of the concave reflector 112 to produce a first steered optical pulse 312A. This redirection can occur at or near point 404 and can direct the first steered optical pulse 312A towards one or more objects in the field of view in a direction between the negative x-axis and the positive z-axis. The first steered optical pulse 312A illuminates the object, and the first returned optical pulse 207A returns along an optical path that is substantially coaxial or parallel with the first steered optical pulse 312A. In Figure 4B the example depicted, the first returned optical pulse 207A overlaps with the first steered optical pulse 312A, where the first steered optical pulse 312A illuminates the object at an angle of approximately -10° towards the horizontal direction (e.g., a -10° angle between the positive z-axis and the direction of the first steered optical pulse 312A), and the exemplary beam steering device 100 collects the first returned optical pulse 207A at an angle of approximately -10° towards the horizontal direction. Similar to those described above, the first returned optical pulse 207A can be redirected by the polyhedron 102 and the concave reflector to produce a redirected returned optical pulse 214A.

[0073] In some embodiments, the beam steering device 100 can be configured to emit optical pulses in a direction more towards the edge of the field of view and collect returned optical pulses from that direction. Figure 5 An exemplary beam steering device 100 is shown that directs a steered optical pulse to a direction more towards the edge of the positive horizontal extent of the field of view and collects returned light from that direction. As Figure 5 shown, the instantaneous position of the rotating polyhedron 102 is at 15° relative to the nominal position, while the instantaneous position of the rotating concave reflector 112 is at 30° relative to the nominal position. As Figure 5As depicted, the optical pulse 307A is directed through the aperture 118 of the beam steering device 100 and then redirected (e.g., reflected) by the polyhedron 102 to produce a redirected optical pulse 307B at or near the point 402. This redirection can direct the redirected optical pulse 307B towards the concave reflector 112. The redirected optical pulse 307B is further redirected (e.g., reflected) by the reflective surface (e.g., mirror) of the concave reflector 112 to produce a first steered optical pulse 312A at or near the point 404. This redirection can direct the steered optical pulse 312A towards one or more objects in a direction more towards the edge of the field of view. The first steered optical pulse 312A illuminates the object, and the first returned optical pulse 207A returns along an optical path that is substantially coaxial or parallel to the first steered optical pulse 312A. In Figure 5 the depicted example, the first returned optical pulse 207A overlaps with the first steered optical pulse 312A. For example, the first steered optical pulse 312A illuminates the object at an angle of approximately 40° towards the positive x direction (e.g., a 40° angle between the positive z axis and the projection of the steered optical pulse 312A on the X-Z plane) and at an angle of approximately -7° towards the y direction (e.g., a 7° angle in the negative y direction between the z axis and the projection of the steered optical pulse 312A on the Y-Z plane), and the exemplary beam steering device 100 collects the first returned optical pulse 207A at an angle of approximately 40° towards the positive x direction and at an angle of approximately -7° towards the y direction. Similar to those described above, the first returned optical pulse 207A can be redirected by the polyhedron 102 and the concave reflector 112 to produce a redirected returned optical pulse 214A.

[0074] In some embodiments, to further extend the scanning range, a concave lens or a cylindrical lens can be disposed in the optical path of the steered optical pulse 312A and / or the second steered optical pulse 312B when the steered optical pulse 312A and / or the second steered optical pulse 312B are being emitted from the beam steering device 100. This configuration can further extend the horizontal scanning range and / or the vertical scanning range. In some examples, including a convex lens can also widen the optical angle, but this may reduce the resolution.

[0075] Figure 6A and Figure 6B shows an interleaved frame diagram of the angular distributions in the horizontal and vertical directions of the dual coaxial LiDAR scanning system 300( Figure 3 ). Figures 6A to 6BShows the results of an analog test in which the dual coaxial LiDAR scanning system 300 is configured to collect data in about 50 milliseconds. These figures show the combination of three consecutive sub-frames that form a frame, which corresponds to about 20 frames per second (fps). To form the first sub-frame 604, the dual coaxial LiDAR scanning system 300 continuously samples one or more objects at periodic intervals across the field of view in both the horizontal and vertical directions. In doing so, a laser beam (such as the beam spot at or near point 404, as shown in Figures 4A to 4B and Figure 5 ) redirected (e.g., reflected) by the reflective surface (e.g., a mirror) of the concave reflector 112 (such as shown in Figure 4A , Figure 4B , or Figure 5 ) moves across the mirror at one of the facets of the polyhedron 102 such that the beam spot moves from one edge of the mirror to the other edge of the mirror. To form the second sub-frame 606, the dual coaxial LiDAR scanning system 300 continuously samples one or more objects at periodic intervals across the field of view, except that the scans in the horizontal and vertical directions are slightly offset relative to the scans used to generate the first sub-frame 604. Due to this scan offset, the beam moves across the mirror at one of the facets of the polyhedron 102 such that the beam spot moves from one edge of the mirror to the other edge of the mirror. To form the third sub-frame 608, the dual coaxial LiDAR scanning system 300 continuously samples one or more objects at periodic intervals across the field of view, except that the scans in the horizontal and vertical directions are slightly offset relative to the scans used to generate the first sub-frame 604 and the scans used to generate the second sub-frame 606. The first sub-frame 604, the second sub-frame 606, and the third sub-frame 608 are interleaved to form a single frame with a higher sample density, where the higher sample density corresponds to a higher resolution. The single frame also represents motion correction for both the movement of the LiDAR scanning system and the movement of the detected objects.

[0076] As Figure 6A depicted, the rasterized points from the frame generated by the steering light pulse 312A form a pattern that covers a range of approximately -10° to 40° in the x-direction and -30° to 30° in the y-direction. Similarly, the rasterized points from the frame generated by the steering light pulse 312B form a pattern that covers a range of approximately -40° to 10° in the x-direction and -30° to 30° in the y-direction. Within the range of the dual coaxial LiDAR scanning system 300, there is an overlap region 602 between the first steering light pulse 312A and the second steering light pulse 312B. This overlap provides denser data sampling at the center of the field of view (e.g., generally between -10° and 10° in the x-direction and -30° to 30° in the y-direction). Therefore, the resolution in the overlap region 602 is higher.​​​​​​​​​​

[0077] Figure 6A and Figure 6B The shape of the rasterized frame pattern depicted in is based on the geometry of the dual-beam steering device 100' (e.g., the geometry of the polyhedron 102 and the concave reflector 112). Multiple factors blocking the optical path may contribute to the overall rasterized frame pattern as depicted in Figure 6A and Figure 6B For example, referring to Figures 4A to 4B 、 Figure 5 and Figures 6A to 6B , in some cases, the first steering light pulse 312A may miss the concave reflector 112 at a specific angle, which determines the end of the scanning range of the dual-beam steering device 100'. These may correspond to the horizontal peripheral range. Generally, in some embodiments, the scanning range of the dual-beam steering device 100' can direct the first steering light pulse 312A between approximately -10° and 40° in the x direction and between approximately -30° and 30° in the y direction. Similarly, the scanning range of the dual-beam steering device 100' can direct the second steering light pulse 312B between approximately -40° and 10° in the x direction and -30° to 30° in the y direction.

[0078] Figure 6B Shows an enlarged portion of the frame diagram of the angular distribution in the horizontal and vertical directions of the dual coaxial LiDAR scanning system 300. Figure 6B Thus, it more clearly shows the combination of three consecutive sub-frames (e.g., the first sub-frame 604, the second sub-frame 606, and the third sub-frame 608). As described above, if perturbations are added to the rotational speed of the polyhedron 102 and / or the rotational speed of the concave reflector 112, the angular distribution in the horizontal and vertical directions may be random.

[0079] In some examples, Figure 6A and Figure 6B The sub-frames and / or frames depicted in can be mapped to a three-dimensional space to form a "point cloud". For example, Figure 6A and Figure 6B Depict the two-dimensional positions of light scattering on an object. In some examples, the calculator 310 of the microprocessor 306 (shown in Figure 3 ) can provide a third dimension (e.g., the distance at the corresponding horizontal and vertical angles). Thus, the shape of the object around the LiDAR scanning system 300 can be reconstructed (e.g., by analyzing the "point cloud" using data analysis algorithms).

[0080] In some examples, an object located within the field of view may move or shift during the scan used to form a frame or sub-frame. For example, in some cases, the time span of the light pulses within a frame may be quite short (e.g., less than 1 millisecond), which means that the object (including both the dual coaxial LiDAR scanning system 300A and the object in the field of view) does not move significantly. In such cases, the sampled points in the point cloud of the frame are collected substantially simultaneously. However, in some cases, this time span may be relatively long (e.g., 20 milliseconds to 50 milliseconds), which is sufficient for one or more objects to move a measurable distance. For example, an object moving at approximately 65 miles per hour can move approximately 2 feet in 20 milliseconds. Thus, the position of each point in the point cloud of the frame can be compensated for by the movement of the LiDAR itself and the speed at which the moving object in the field of view is detected.

[0081] To accommodate such movement of the object, the dual coaxial LiDAR scanning system 300 can determine the sampling rate from one or more sub-frames, determine the relative speed of one or more objects, and compensate for the foregoing sampling rate and relative speed when forming the point cloud of three-dimensional points based on compensated aggregated distances. It should be understood that the data collected over any arbitrary time interval can be aggregated to form a frame of the point cloud. Thus, the density of the point cloud may be greater or less than the density described above.

[0082] Figure 7 A heat map showing the collection aperture area corresponding to a dual coaxial LiDAR system with certain system parameter values, where FIGS. 1, Figure 3 , Figure 4A , Figure 4B and Figure 5 The collection cross-sectional areas of the first redirected return light pulse 214A and the second redirected return light pulse 214B depicted are shown in Figure 7 and overlap at the center of the field of view. Thus, the area of the collection aperture varies with the angles of the polyhedron 102 and the concave reflector 112. For example, Figure 4A the cross-sectional area of the first redirected return light pulse 214A depicted is less than Figure 4B the cross-sectional area of the first redirected return light pulse 214A depicted. Thus, the intensity of the collected light corresponding to the configuration of the polyhedron 102 and the concave reflector 112 with the angles depicted in Figure 4A is less than the light intensity depicted in Figure 4B for the same intensity of the first steering light pulse 312A, the same reflectivity, and the same distance to the object in the field of view.

[0083] In Figure 7In the example depicted, the central region of the heat map corresponds to approximately -10° to 10° in the x-direction and -30° to 30° in the y-direction, and this region has high collection holes. This region forms an hourglass shape by overlapping double optical paths in substantially the same region. The regions corresponding to between approximately -35° to -30° in the x-direction and between approximately -5° to 5° in the y-direction, and between approximately 30° to 35° in the x-direction and between approximately -5° to 5° in the y-direction have low collection holes, which result from the tilt angle at the concave reflector 112.

[0084] In some embodiments, the power of the incident light pulse 212 from the light source 220 (shown in Figure 2B , Figure 2C and Figure 3 ) can vary based on the collection holes. Changing the power of the incident light pulse 212 can compensate for variations in the collection hole sizes of the first redirected return light pulse 214A and the second redirected return light pulse 214B in the vertical and horizontal directions in the field of view.

[0085] Figure 8 An exemplary method 800 for LiDAR scanning detection according to the present disclosure is shown. The method 800 can be executed by a system provided or included in a vehicle, such as the various systems depicted in Figures 1A to 1B , Figures 2A to 2C , Figure 3 , Figures 4A to 4B and Figure 5 , and the systems depicted in Figures 9A to 9D , Figures 10A to 10B and Figure 11 [[ID=2Y]]as will be described in detail below. As Figure 8 shown, at block 802, a first light source of the LiDAR scanning system can provide one or more first light pulses. In the examples described herein, the first light source can be a laser light source. It should be understood that the first light source can be an incandescent lamp, a fluorescent lamp, etc. Additionally, the first light source can have one or more wavelengths in the visible spectrum, one or more wavelengths in the infrared spectrum, or one or more wavelengths in the ultraviolet spectrum.

[0086] At block 804, a beam steering device of the LiDAR scanning system can steer the first light pulse to irradiate an object along an optical path. The beam steering device can be a coaxial beam steering device 100 configured to emit a single beam of light pulse (e.g., the light pulse 312A depicted in Figure 1B ), or a coaxial beam steering device configured to emit a double beam of light pulse (e.g., as depicted in Figure 3Dual coaxial beam steering device 100' for the depicted optical pulses 312A and 312B). During continuous scanning, rotation of the beam steering device (such as polygon 102) and the concave reflector (such as concave reflector 112) can cause the reflecting facets of the beam steering device and the concave reflector located in the optical path of the optical pulse to change over time. The rotational positions of the beam steering device and the concave reflector can be used to calculate the angle by which the beam steering device causes the optical pulse to be steered. It should be understood that for some embodiments, the rotational positions of the beam steering device and the concave reflector can trigger the light source to emit an optical pulse.

[0087] At block 806, in some examples, a beam steering device (such as beam steering device 100 or dual beam steering device 100') can collect and redirect a returned optical pulse (such as a first returned optical pulse 207A generated based on the first steered optical pulse 312A that illuminates an object). The collected returned optical pulse can be coaxially aligned or parallel with the optical path. The returned optical pulse can be redirected by the concave reflector and the beam steering device towards the receiving optical system. When using a beam steering device, in some examples, the steered optical pulse and the returned optical pulse can be coaxially aligned. Additionally, the beam steering device can emit a steered optical pulse while collecting the returned optical pulse in parallel or substantially simultaneously. For example, the time at which the emitted steered optical pulse travels to illuminate an object and returns along the same optical path is more or less instantaneous with respect to the positions of the beam steering device (such as polygon 102) and the concave reflector. For example, for an object approximately 150 meters away, the flight time of the optical pulse is approximately 1 microsecond. This corresponds to the polygon 102 (rotating at 500 rps, for example) rotating approximately 0.18°.

[0088] At block 808, a receiving optical system including an optical focusing device can further direct (such as converge or focus) the redirected returned optical pulse onto a light detector (such as, Figure 3 the first light detector 230A depicted). In some examples, the optical focusing device can be a converging lens 224 ( Figure 2B ) or a converging mirror 221 ( Figure 2C ).

[0089] At block 810, the microcontroller / processor can calculate (such as determine) the distance from the LiDAR scanning system to the object based on the time difference between the emitted steered optical pulse and the detected corresponding returned optical pulse. The flight time of the optical pulse along the optical path is proportional to the distance that the optical pulse travels to illuminate the object. Generally, the flight time for the optical pulse to illuminate the object is approximately half of the time required to detect the optical pulse.

[0090] At optional block 812, the microcontroller may generate one or more sub-frames (e.g., first sub-frame 604, second sub-frame 606, third sub-frame 608, Figure 6A and Figure 6B ) based on aggregated values of distances to one or more objects across successive or consecutive horizontal scans and vertical scans. For example, a coaxial LiDAR scanning system or a dual-coaxial LiDAR system (e.g., system 300) may continuously sample the same one or more objects in the field of view at periodic intervals in both the horizontal and vertical directions. The sampled (e.g., scanned) field of view may be aggregated according to a first sub-pattern similar to the first sub-frame 604 (as Figure 6A and Figure 6B annotated). The dual-coaxial LiDAR system may continuously sample the same one or more objects in the same field of view at periodic intervals again, except that the horizontal and vertical directions are slightly offset relative to the first sub-frame 604. The sampled (e.g., scanned) field of view may be aggregated according to a second sub-pattern similar to the Figure 6A and Figure 6B of the second sub-frame 606. The dual-coaxial LiDAR system may continuously sample the same one or more objects in the same field of view or a partially same field of view at periodic intervals again, except that the horizontal and vertical directions are slightly offset relative to the first sub-frame 604 and the second sub-frame 606. The sampled (e.g., scanned) field of view may be aggregated according to a third sub-pattern similar to the Figure 6A and Figure 6B of the third sub-frame 608.

[0091] At optional block 814, the microcontroller may interleave one or more sub-frames to form a frame with a higher resolution. For example, as Figure 6A and Figure 6B depicted, the LiDAR system may interleave the first sub-frame 604, the second sub-frame 606, and the third sub-frame 608 to form one frame with a higher sample density. A higher sample (non-overlapping sample points) density corresponds to a higher resolution. It should be understood that many sample points in the overlapping region 602 ( Figure 6A ) of the dual-coaxial LiDAR system (e.g., system 300) may have a higher density. Thus, the resolution is higher in the overlapping region 602 shown in Figure 6A .

[0092] As ​ , ​ , ​ and ​ depicted, the beam steering devices 100 and 100’ include a polyhedron 102 having six facets. As explained, the polyhedron may have any number of facets (e.g., more than six or less than six). ​Shows different views of another exemplary embodiment of a beam steering device 900. The beam steering device 900 may have a polyhedron with more than six facets. The beam steering device 900 may be used to perform one or more steps of methods 800 and / or 1900 (e.g., steering light pulses in ​ the boxes 1904 and 1910 shown). ​ Shows a perspective view of the beam steering device 900; ​ Shows a side view of the beam steering device 900 along the positive y-axis direction; ​ Shows a rear view of the beam steering device 900 along the positive z-axis direction; and ​ Shows a side view of the beam steering device 900 along the positive x-axis direction. Referring to ​ , the polyhedron 910 may include a plurality (e.g., 18) of side facets parallel to the y-axis of the polyhedron 910. In some embodiments, the polyhedron 910 may be centered about the y-axis and rotated about or along the y-axis. That is, the y-axis may be the axis of rotation of the polyhedron 910. In some embodiments, each of the plurality of side facets may be polished and may operate in a manner similar to a reflective surface (e.g., a mirror surface) for emitting and collecting laser light.

[0093] Referring to ​ , the beam steering device 900 may further include a concave reflector 920. The concave reflector 920 may include a plurality (e.g., four) of flat or curved reflective surfaces (e.g., mirrors). In some embodiments, each of the flat or curved mirrors of the concave reflector 920 may have a polygonal shape (e.g., a trapezoidal shape) or any other desired shape. In some embodiments, each of the flat or curved mirrors may have corners and / or bottom edges that are cut or trimmed such that incident laser light can pass through the concave reflector 920. For example, the cut corners and / or bottom edges in the concave reflector 920 are shown in ​ . In some embodiments, similar to the concave reflector 112 shown in ​ , the concave reflector 920 may rotate about or along the z-axis, and the rotation speed is independent of the rotation speed of the polyhedron 910. Referring to ​ , at the instantaneous positions of the rotating polyhedron 910 and the rotating concave reflector 920, a collimated beam of one or more light pulses 930 may be directed towards the facet 940 of the polyhedron 910 at an angle 935 (e.g., the angle between this collimated beam of one or more light pulses 930 and the negative z-direction) in the x-z plane.

[0094] ​Shows an embodiment of an arrangement for generating a collimated illumination laser beam including one or more optical pulses. As ​ shown, the light source 1010 can direct one or more optical pulses towards the optical lens 1020. In some embodiments, the optical lens 1020 and the light source 1010 can be configured to have a predetermined distance such that an illumination laser beam (e.g., a Gaussian beam) can be formed with a predetermined beam divergence angle. The illumination laser beam can be directed to a facet of the polyhedron 910. The light source 1010 can be a fiber laser, a semiconductor laser, or other types of laser light sources. Alternatively, other collimating optics (such as aspherical lenses, compound lenses, reflective spheres, reflective paraboloids, etc.) can be used to generate a collimated laser beam. In some embodiments, the concave reflector 920 can be configured to have geometric structure parameter values such that the illumination laser beam can be blocked or partially blocked by one or more reflective surfaces (e.g., mirrors) of the concave reflector 920 at a certain rotation angle. As described above, in the concave reflector 920, a part of the bottom edge of one or more trapezoidal mirrors (e.g., the cut section 1030) can be cut off or exposed to allow the laser beam from the light source to pass through, as ​ shown.

[0095] ​ Shows another embodiment of an arrangement for generating a collimated illumination laser beam including optical pulses. In this arrangement, one or more optical pulses can be generated by a light source ( ​ not shown in the figure) such as a fiber laser, a semiconductor laser, or other types of laser light sources. One or more optical pulses can be transmitted by the optical fiber 1042 and directed by the mirror 1040 towards a facet of the polyhedron 910. ​ The optical transmission arrangement shown enables the optics (such as optical fibers, mirrors) to be placed inside the concave reflector 920, thus eliminating or reducing the need to cut the edges of the concave reflector 920 (e.g., removing the cut section 1030 as ​ shown or reducing the size of the cut section 1030).

[0096] Referring to ​ and ​ , in some embodiments, the relative position and / or angle of the transmitted laser beam (e.g., the laser beam transmitted by the optical fiber 1042 and the mirror 1040) with respect to the rotation axis of the reflective surface (e.g., the polygonal mirror) of the polyhedron 910 can be configured in such a way that the effective LiDAR scan range (e.g., the horizontal scan coverage angle and the vertical scan coverage angle) reaches a desired coverage value. In one example, the position and / or angle of the laser beam reaching one of the facets of the polygonal mirror of the polyhedron 910 is configured such that the angle 965 (in ​shown) is about 59° from the vertical direction (e.g., ​ the negative z-direction in ) to obtain a horizontal field of view of about 100° and a vertical field of view of 25°.

[0097] In some embodiments of the optical transmission configuration, the laser beam reaching the side facets of the polyhedron 910 may have different Gaussian beam parameters, such as beam waist width and beam divergence angle, in the y-axis direction and in the direction within the x-z plane. By using one or more aspherical lenses or cylindrical lenses between the laser light source and a side facet of the polyhedron 910, different Gaussian beam parameters can be obtained. In some embodiments, it is desirable and beneficial to configure the lenses or other components of the LiDAR system such that the beam waist width at the position where the laser beam reaches the side facet of the polyhedron 910 is very narrow. In a typical embodiment, a divergence angle of about 0.06° can be used to obtain a beam waist width of 0.45 mm. A narrow or small laser beam waist width (e.g., 0.2 mm) can reduce the proportion or percentage of the polyhedron rotation positions at which a portion of the beam reaches two side facets simultaneously (e.g., the laser beam spot reaches two facets sharing a common edge) relative to all the polyhedron rotation positions at which the beam arrives. Since the beam reaching two side facets simultaneously may make it difficult to analyze the signal, such a beam may be undesirable.

[0098] When the beam waist width of a Gaussian beam is narrow in one direction, its beam divergence angle may become large in that direction, which may be undesirable for some embodiments. For example, for a Gaussian beam with a waist width of 0.2 mm, the divergence angle may be about 0.14°. To reduce the beam divergence angle, in some examples, the polyhedron 910 may have curved facets with curved surfaces. In some embodiments, the curved surfaces can be used for the side facets of the polyhedron 910, as ​ shown.

[0099] ​ shows a plurality of facets 1510A-C of an exemplary polyhedron 910 with curved surfaces. In ​ it, the solid lines show three of the side facets of the polyhedron 910 in the case of using flat surfaces. The dashed lines show the curved surfaces that can modify the Gaussian beam to reduce the beam divergence angle. Although ​ the curved surfaces are shown as convex surfaces, those skilled in the art can understand that concave surfaces can also be used for some embodiments. In another embodiment, the curved surfaces can also be used for the reflective surface (e.g., a mirror) of the concave reflector 920 ( ​ and ​ shown) to modify the Gaussian beam.

[0100] In some embodiments, the portion of the polyhedron that reflects the illuminating laser beam can be configured to have a set of parameters (flat or curved surfaces, diameter, number of facets), while the remaining portion of the polyhedron that collects the returned light can be configured to have a different set of parameters. ​ A top view of one such embodiment is shown, where the portion of the polyhedron 910 that reflects the illuminating laser beam or emits the laser beam has a curved surface (e.g., facets 1520A-C) and a larger diameter, while the remaining portion of the polyhedron that collects the returned light has a flat surface with a smaller diameter (e.g., facets 1522A-C). These two portions of the polyhedron 910 can have the same number (e.g., eighteen) of facets. ​ A side view of this embodiment of the polyhedron 910 is shown, which includes facets 1520A-N having a curved surface for reflecting the illuminating laser beam or emitting the laser beam, and includes facets 1522A-N having a flat surface for collecting the returned light.

[0101] ​ A top view of another embodiment of the polyhedron 910 is shown. As ​ shown, the portion of the polyhedron that reflects the illuminating laser beam can have a first number (e.g., eighteen) of facets (e.g., facets 1540A-D) that have a curved surface and a larger diameter; while the portion that collects the returned light can have a second number (e.g., six) of facets (e.g., facets 1542A-B) that have a flat surface and a smaller diameter. ​ A side view of this embodiment of the polyhedron 910 is shown, which includes facets 1540A-N having a curved surface for reflecting the illuminating laser beam or emitting the laser beam, and includes facets 1542A-M having a flat surface for collecting the returned light.

[0102] Returning to ​ and ​ , as described above, a collimated beam of one or more light pulses 930 can be directed at an angle 935 in the x-z plane towards a facet 940 of the polyhedron 910. The angle 935 can be configured such that the angle between the direction of the light pulse 930 of the illuminating laser beam and the direction of the returned light incident on the returned light detector 960 is 2N times the span angle of one side of the polyhedron 910. The span angle is the angle between two radii extending from the center of the polyhedron 910 to two adjacent edges of a facet. Thus, for a polyhedron with 18 facets, the span angle is 20° (i.e., 360° / 18 = 20°). In ​ the exemplary embodiment, for a polyhedron with 18 facets and a span angle of 20°, the value of "N" can be 1, and the value of the angle 935 can be 40°. As ​As shown, one or more redirected light pulses 942 generated (e.g., reflected) from the facet 940 are directed to the mirror 945 of the concave reflector 920, then reflected by the mirror 945, and then redirected as steering light pulses 948 to the field of view.

[0103] Reference ​ , after one or more steering light pulses 948 reach an object in the field of view, they can be reflected or scattered in multiple directions, and a portion of the return light pulses 950 can be reflected back to the mirror 945 and collected by the mirror. When the object is relatively far from the LiDAR system (e.g., more than 1 meter), the return light pulses 950 can be approximately collimated beams and in a direction that is substantially parallel but opposite to the original direction of the steering light pulses 948. The return light pulses 950 can be redirected by the mirror 945 and then propagate in the opposite direction from the redirected light pulses 942 towards the polyhedron 910.

[0104] ​ An exemplary configuration of a beam steering device 1100 for effectively increasing the acceptance aperture and for collecting return light pulses from different facets is shown. Reference ​ and ​ , ​ One or more of the return light pulses 950 shown (e.g., light pulses collected by the LiDAR system from light pulses scattered or reflected by an object in the field of view) can correspond to ​ the return light pulses 1110 shown. The return light pulses 1110 can, for example, reach the reflective surface (e.g., mirror 1130) of the concave reflector 920. After being first reflected by the mirror 1130 of the concave reflector 920, the return light pulses 1110 can be redirected towards the polyhedron 910. In some embodiments, one or more of the return light pulses 1110 can be scattered and can extend sufficiently in a direction perpendicular to the beam propagation. Thus, most or the entire surface of the mirror 1130 can receive one or more of the return light pulses 1110 (except for the portion that is blocked by the shadow of the polyhedron 910 and is within that shadow). Thus, one or more of the return light pulses 1110 can be reflected by the mirror 1130 to produce pulses that direct light to multiple portions of different facets of the polyhedron 910. For example, as ​ shown, a portion of the return light pulses 1120 propagating towards the polyhedron 910 can reach the facet 1140 (e.g., ​The same facet 940) as shown and can be reflected / redirected by the facet 1140 into the optical pulse 1150; another part of the return optical pulse 1122 propagating towards the polyhedron 910 can reach a different facet 1142 and can be reflected / redirected by the facet 1142 into the optical pulse 1152; yet another part of the return optical pulse 1124 propagating towards the polyhedron 910 can reach a different facet 1144 and can be reflected / redirected by the facet 1144 into the optical pulse 1154.

[0105] Reference ​ , in some embodiments, the light beams reflected / redirected by different facets of the polyhedron 910 can be collected by different receiving optical systems (e.g., systems 1160, 1162, and 1164). For example, the first receiving optical system 1160 can be disposed in the path of the optical pulse 1150; the second receiving optical system 1162 can be disposed in the path of the optical pulse 1152, and so on.

[0106] ​ An exemplary configuration of the receiving optical system is shown. Reference ​ , ​ and ​ , the receiving optical system can include a refractive optical lens 1210 ( ​ as shown in ​ ); or a compound optical lens 1220 that includes a plurality of optical elements ( ​ as shown in ​ The refractive optical lens shown can be a spherical or aspherical lens, or a combination of both. ​ Any of the receiving optical systems shown, regardless of whether the pulses of the incident light may have slightly tilted and divergent angles, can focus the substantially parallel incident light onto the detector element 1240. Although ​ lists three exemplary embodiments, it can be understood that other configurations of the receiving optical system can be used to achieve the same purpose.

[0107] ​ The detector element 1240 shown can include a photosensitive device capable of detecting an optical signal and converting the optical signal into an electrical signal. ​ An exemplary embodiment of the detector element 1240 that directly collects light using the photosensitive device 1320 is shown. As ​As shown, the optical pulse can propagate through the optional window 1310 and reach the photosensitive device 1320, which converts the optical signal into an electrical signal. The electrical signal can be further processed by circuit elements on the circuit board 1330 and can be converted into digital data for further processing. In some examples, the photosensitive device 1320 can include a refractive index matching material disposed on the surface of the photosensitive device 1320. For example, the photosensitive device 1320 can include an indium gallium arsenide material, the refractive index of which does not match that of air. Therefore, a refractive index matching material is disposed on the surface of the photosensitive device 1320 to mitigate or eliminate such mismatch.

[0108] ​ Another exemplary embodiment of the detector element 1240 for collecting light using the optical fiber 1350 is shown. As ​ shown, the optical pulse received by the photosensitive device 1370 can first be focused by the optical device 1340 onto one end of the optical fiber 1350. The optical fiber 1350 can be a multimode fiber, a single-mode fiber, or a double-clad fiber, in which the light entering the inner cladding of the fiber is slowly absorbed into the small core. In one embodiment, the optical pulse exiting from the other end of the optical fiber 1350 can be converged by the optical device 1360 onto the photosensitive device 1370, which can convert the optical signal into an electrical signal. The optical device 1360 for converging the optical signal from the optical fiber 1350 can be an optical lens, a spherical or aspherical mirror, or directly coupled to the photosensitive device 1370 with an optional refractive index matching material disposed on the surface of the device 1370 to improve the amount of light received by the photosensitive device 1370. The electrical signal can be further processed by circuit elements on the circuit board 1380. In this embodiment, the electronic device (such as the circuit board 1380) and / or the photosensitive device 1370 can be disposed away ​ from the beam steering device 1100 shown (e.g., at a distance greater than 0.1 meter, greater than 1 meter, or even greater than 5 meters from the beam steering device), which can reduce the size of the beam steering device 1100. For example, the beam steering device 1100 can be configured to have a smaller physical size except for the light-exiting end of the optical fiber 1350.

[0109] Returning to the reference ​, in another embodiment, the receiving optical system 1160 may be disposed in the path of the optical pulse 1150. In another embodiment, the receiving optical system 1164 may be disposed in the path of the optical pulse 1154. In yet another embodiment, two or more receiving optical systems (e.g., both 1160 and 162, or all of 1160, 1162, and 1164) may coexist in the LiDAR system. In one embodiment, each of these receiving optical systems may be independent of each other, and each receiving optical system has its own photosensitive device. In another embodiment, some or all of these receiving optical systems may share a photosensitive device.

[0110] ​ An exemplary configuration for combining redirected return optical pulses from different facets using a combination of free space optics or fiber bundles and / or power combiners is shown. As ​ shown, in some embodiments, one photosensitive device (e.g., device 1420) may be shared among multiple receiving optical systems. In such embodiments, optical pulses of light beams from different directions may be redirected by multiple mirrors and focusing optics (e.g., optics 1410, 1412, and 1414) to the same photosensitive device 1420. For example, the optical pulse 1150 may be focused by the focusing optics 1410 and then become a pulse of focused light 1450 and reach the photosensitive device 1420. Similarly, the pulse of the optical pulse 1152 may be redirected and focused by the optics 1412 and then become a pulse of focused light beam 1452 and reach the photosensitive device 1420. The pulse of the optical pulse 1154 may be redirected and focused by the optics 1414 and then become a focused light beam 1454 and reach the photosensitive device 1420.

[0111] ​ Another embodiment in which one photosensitive device 1440 is shared among multiple receiving optical systems is shown. In this embodiment, the pulses of each beam of light from each different direction may be focused by an optical converging device ( ​ not shown in the figure). Subsequently, each of the focused light beams may be coupled into the receiving ends of each of the three fiber optic channels 1430, 1432, and 1434, respectively. These three fiber optic channels may be combined together using, for example, a three - to - one optical combinational device (e.g., a reverse fan - out fiber bundle) to form one optical channel. Subsequently, the optical pulse emitted from the transmitting end of the combined optical channel may be directed to a shared photosensitive device 1440. In some embodiments, instead of using an optical combinational device, the optical pulse emitted from the transmitting end of a fiber bundle (e.g., a bundle of three fibers) may be directly focused onto a shared photosensitive device.

[0112] ​Another embodiment of a beam steering device 1800 with a swinging mirror is shown. As ​ shown, the beam steering device 1800 does not include the polyhedron 910 (shown in ​ ), but instead includes a single-faceted or multi-faceted swinging mirror 1810. For a multi-faceted mirror, the angle formed by adjacent facets can be similar to the angle formed by adjacent facets of the polyhedron 910 (e.g., 20°) as shown in ​ . The mirror 1810 can swing along an axis 1820 parallel to the y-axis or back and forth along the y-axis, such that pulses of light beams incident on one or more facets of the mirror 1810 can be steered in different directions in the x-z plane. It should be understood that similar to the embodiments described for the polyhedron in ​ , the portion of the swinging mirror 1810 that reflects the incident light pulses can be curved, and / or can have a different size from the portion of the swinging mirror 1810 that collects the returned light pulses.

[0113] Returning to reference ​ , in some embodiments, in order to accurately determine the time of flight of a pulse (e.g., the time it takes for a pulse emitted from a LiDAR system to be scattered / reflected by an object in the field of view and received by the detector of the LiDAR system), it is necessary to determine the time when the pulse is emitted from the LiDAR system. ​ A beam steering device 1610, a light source 1620, and a photosensitive device 1630 are shown. The beam steering device 1610 can be similar or identical to the beam steering device 100 shown in ​ , ​ , ​ or ​ ; and the light source 1620 can be similar or identical to the light source 220 shown in ​ and the light sources 1010 shown in ​ , ​ or ​ ; and the photosensitive device 1630 can be similar or identical to those shown in ​ and ​ and ​ , ​ and ​ . As described above, the photosensitive device can include a photodetection module for detecting and converting the received optical signal.

[0114] Referring to ​, in one embodiment, the light source 1620 generates one or more light pulses based on an electrical trigger signal that can be provided by an external signal source or an internally generated signal source. In some embodiments, the time elapsed between generating the electrical trigger signal and emitting one or more light pulses from the light source 1620 can be considered constant from pulse to pulse (e.g., negligible variation) and / or can be calibrated. The electrical trigger signal can be transmitted via an electrical connection (e.g., a cable) 1640 to the photosensitive device 1630 and then used to determine the reference time of the light pulse.

[0115] In some embodiments, an optical fiber 1650 can be used to direct a portion of the one or more light pulses emitted from the light source 1620. A beam splitter can be used to split the light pulse and obtain a portion of the light pulse as a reference signal. The portion can be any percentage of the total light pulse, such as 10%, 1%, 0.1%, or 0.0001%, or any desired percentage. The portion of the light pulse can be directed by the optical fiber 1650 to the photosensitive device 1630 and then used to determine the reference time of the light pulse emitted from the light source 1620.

[0116] In some embodiments, the reference pulse generation device 1660 can be provided together with the beam steering device 1610 to obtain a portion of the light pulse as a reference signal and redirect the portion to the photosensitive device 1630 after the light pulse is emitted from the light source 1620. The portion can be any percentage of the total light pulse, such as 10%, 1%, 0.1%, or 0.0001%, or any desired percentage. Those skilled in the art will understand that ​ the reference pulse generation device 1660 shown in is illustrative only; and any optics that can obtain a portion of one or more light pulses as a reference signal and redirect them to the photosensitive device 1630 can be used. For example, the reference pulse generation device 1660 can be a partially reflective device that reflects a portion of the light pulse to the photosensitive device.

[0117] In the foregoing embodiments discussed with respect to ​ the reference signal (e.g., the reference light pulse) can be detected by the photosensitive device 1630. The reference ​ , this reference signal is shown as the reference pulse 1710. ​A return light pulse 1720 is also shown. The return light pulse (e.g., a pulse reflected / scattered by an object in the field of view and received by the photosensitive device 1630) is shown as pulse 1720. Pulse 1720 may have a different intensity and pulse width from the reference pulse 1710. In some embodiments, pulses 1710 and 1720 may have a similar shape profile. In one embodiment, the reference pulse 1710 can be used as a template to match the received return pulse 1720 to accurately determine the time difference (or TOF) between the return pulse and the reference pulse. Based on the TOF, the distance of the object in the field of view can be determined.

[0118] ​ An exemplary flowchart of a method for determining the time of flight of one or more light pulses for generating a 3D image using a LiDAR scanning system (e.g., various systems depicted in ​ , ​ , ​ , ​ , ​ , ​ , ​ and ​ is shown. Referring to ​ , at block 1902, one or more light pulses (e.g., short laser pulses having a pulse width of about 0.01 nanoseconds to 5 nanoseconds or light pulses having a pulse width of 5 nanoseconds to 30 nanoseconds or longer) can be generated from a light source of the LiDAR scanning system. At block 1904, a beam steering device can steer or scan one or more light pulses in the field of view in both the horizontal and vertical directions. At block 1906, one or more light pulses or a portion thereof irradiate or reach an object and are scattered and reflected in one or more directions. In some embodiments, a portion of the scattered or reflected light pulse can return to the LiDAR scanning system and reach the collection aperture of the detector of the LiDAR scanning system.

[0119] At block 1910, one or more returned light pulses can be steered or redirected in a direction that is substantially opposite to the steering direction of the light pulses emitted from the LiDAR scanning system and substantially parallel to the direction of the light pulses emitted from the LiDAR scanning system. At block 1912, the one or more redirected returned light pulses can be focused onto a photodetector of the receiving optical system. At block 1914, the photodetector converts the photons of the redirected returned light pulses arriving at the photodetector into one or more electrical signals. At block 1916, an amplifier circuit or device can be used to amplify the one or more output electrical signals generated by the photodetector by a predetermined factor. At block 1920, the amplified one or more electrical signals can be sampled and converted into digital values at a predetermined sampling rate. In some embodiments, the digitized signal data can be collected over a period of time corresponding to the desired maximum TOF of the farthest object in the field of view. At block 1922, the digitized signal data can be analyzed to determine the TOF of the one or more returned light pulses and to determine the distance from the LiDAR scanning system to the point of reflection or scattering of the object.

[0120] It should be understood that the specific order or hierarchy of the blocks in the disclosed methods and / or flowcharts is illustrative of exemplary methods. Based on design preferences, it should be understood that the specific order or hierarchy of the blocks in the methods and / or flowcharts can be rearranged. Additionally, some blocks can be combined or omitted. The appended method claims present the elements of the various blocks in an exemplary order, but are not meant to be limited to the specific order or hierarchy presented.

[0121] The foregoing description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein but are to be accorded the full scope consistent with the language of the claims, where the use of the element in the singular is not intended to mean "one and only one" but rather "one or more" unless specifically stated otherwise. The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any aspect described herein as "exemplary" is not necessarily to be construed as preferred or more advantageous than other aspects. Unless specifically stated otherwise, the term "some" means one or more. Combinations such as "at least one of A, B, or C," "one or more of A, B, or C," "at least one of A, B, and C," "one or more of A, B, and C," and "any combination of A, B, C, or their any combination" include any combination of A, B, and / or C and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as "at least one of A, B, or C," "one or more of A, B, or C," "at least one of A, B, and C," "one or more of A, B, and C," and "any combination of A, B, C, or their any combination" can be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combination can include one or more members or multiple members of A, B, or C. All structural and functional equivalents of the elements of the various aspects described throughout this disclosure that are known or later will be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be covered by the claims. Further, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words "module," "mechanism," "element," "device," etc. may not be substitutes for the word "unit." Thus, under 35 U.S.C. § 112(f), no claim element needs to be construed as a means-plus-function element unless the phrase "means for" is used to expressly recite the element.

Claims

1. A light detection and ranging LiDAR system, comprising: One or more light sources configured to provide a plurality of light beams; A beam steering device optically coupled to the one or more light sources to receive the plurality of light beams, the beam steering device including a reflector and a rotatable polyhedron having a plurality of facets, Wherein the rotatable polyhedron is configured, when rotating, to: Receive the plurality of light beams at one or more of the plurality of facets of the rotatable polyhedron, and Redirect the light beams through the one or more of the plurality of facets for scanning a field of view; and Wherein the combination of the reflector and the rotatable polyhedron is configured, when moving relative to each other, to: Vertically and horizontally scan the light beams to illuminate an object within the field of view, wherein the plurality of light beams from the one or more light sources are redirected through one or more of the plurality of facets, and the redirected plurality of light beams exit from the reflector, and Receive return light generated based on the illumination of the object within the field of view through the reflector, and Direct the return light to a photosensitive device through one or more of the plurality of facets.

2. The LiDAR system according to claim 1, wherein the reflector is a swing mirror.

3. The LiDAR system according to claim 2, wherein the rotatable polyhedron is operable to rotate about a first axis, and the swing mirror is operable to swing about a second axis, wherein the combination of the rotatable polyhedron and the swing mirror uses the light beams to coaxially illuminate the object and receive the return light when moving based on their respective axes.

4. The LiDAR system according to claim 2, wherein the swing mirror is a single-facet mirror or a multi-facet mirror.

5. The LiDAR system according to any one of claims 1-4, wherein the beam steering device is a dual coaxial device configured to direct two parallel light beams to the field of view.

6. The LiDAR system according to any one of claims 1-4, wherein the rotatable polyhedron receives the light beams at two different facets of the plurality of facets.

7. The LiDAR system according to any one of claims 1-4, wherein the light beams are provided to the beam steering device by at least one of the one or more light sources through an optical fiber.

8. The LiDAR system according to any one of claims 1-4, wherein the rotatable polyhedron includes flat facets or curved facets.

9. The LiDAR system according to any one of claims 1-4, wherein the rotatable polyhedron includes a pentahedron, a hexahedron, a heptahedron, or an octahedron.

10. The LiDAR system according to any one of claims 1-4, wherein the angle between any two adjacent facets of the plurality of facets is not a 90-degree angle.

11. The LiDAR system according to any one of claims 1-4, wherein the plurality of light beams includes a first light beam and a second light beam, and wherein the beam steering device scans the first light beam within a first range in the field of view and scans the second light beam within a second range in the field of view, the first range overlapping the second range.

12. The LiDAR system according to any one of claims 1-4, further comprising a controller configured to: control the reflector to move at a first speed; and control the rotatable polyhedron to rotate at a second speed, the second speed being different from the first speed.

13. The LiDAR system according to claim 12, wherein the controller is further configured to superimpose random perturbations on the control parameters such that at least one of the first speed and the second speed has random perturbations.

14. The LiDAR system according to any one of claims 1-4, further comprising one or more optical elements, wherein the returned light includes light pulses of light beams having different directions, and the light beams are guided to the photosensitive device through the one or more optical elements.

15. The LiDAR system according to any one of claims 1-4, further comprising a plurality of optical fibers configured to guide the returned light to the photosensitive device.

16. The LiDAR system according to any one of claims 1-4, further comprising one or more converging optical elements configured to focus the returned light onto the photosensitive device.

17. The LiDAR system according to claim 16, wherein at least one of the one or more converging optical elements includes an aperture through which the light beam is guided from at least one of the one or more light sources to the beam steering device.

18. A light detection and ranging LiDAR system, comprising: one or more light sources configured to generate a plurality of light beams; a beam scanner configured to scan a field of view of the LiDAR system using the plurality of light beams, the beam scanner including a planar mirror and a rotatable polygon mirror including a plurality of reflective surfaces, wherein the rotatable polygon mirror is configured, when rotating, to: receive the light beam at one or more of the plurality of reflective surfaces of the rotatable polygon mirror, and guide the light beam to the planar mirror through the one or more of the plurality of reflective surfaces, wherein the planar mirror is pivotable to redirect the light beam to the field of view; and wherein the beam scanner is optically coupled to the one or more light sources and is positioned to: vertically and horizontally scan the light beam to illuminate an object within the field of view of the LiDAR system, wherein the plurality of light beams from the one or more light sources are redirected via one or more of the plurality of reflective surfaces, and the redirected plurality of light beams exit from the planar mirror, and Receiving, via the planar mirror, the return light formed based on the illumination of the object within the field of view, and Directing the return light to the detector via one or more of the plurality of reflective surfaces.

19. The LiDAR system according to claim 18, further comprising a plurality of optical elements configured to direct the light beam to two adjacent reflective surfaces of the rotatable polygon mirror.

20. The LiDAR system according to claim 19, wherein the plurality of optical elements includes any one of an optical fiber cable, a lens, and a mirror.

21. The LiDAR system according to any one of claims 18 - 20, wherein the rotatable polygon mirror is operative to rotate about a polygon mirror axis that extends into the block through two opposite non-reflective surfaces of the block of the polygon mirror.

22. The LiDAR system according to any one of claims 18 - 20, wherein: The light beam includes a first light beam and a second light beam, The light beam scanner scans the first light beam and the second light beam to respectively define a first field of view and a second field of view, The first field of view and the second field of view combinatorially define the field of view of the LiDAR system, and The first field of view and the second field of view partially overlap to define an overlapping region within the field of view of the LiDAR system.

23. The LiDAR system according to any one of claims 18 - 20, wherein: The light beam includes a first light beam and a second light beam, and The light beam scanner scans each of the first light beam and the second light beam to define a corresponding partial field of view that is 60 degrees wide in one direction.

24. The LiDAR system according to any one of claims 18 - 20, further comprising a mirror configured to direct the return light to the detector, the mirror having an aperture through which the light beam is directed from the one or more light sources to the light beam scanner.

25. The LiDAR system according to any one of claims 18 - 20, wherein the light beam includes a first light beam and a second light beam, and the first light beam and the second light beam are incident on different reflective surfaces of the plurality of reflective surfaces.

26. The LiDAR system according to any one of claims 18 - 20, further comprising a microcontroller configured to construct a point cloud using the data received by the detector.

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