A rotating mirror laser radar

Abstract

The application discloses a rotating mirror type laser radar, comprising: a transmitter for emitting a first direction of the emitted light signal; a multi-faceted rotating mirror comprising at least two mirrors for deflecting the first direction of the emitted light signal by variable speed rotation and moving along a second direction to form a scanning field of view comprising at least two different angular resolution beams in a target area comprising a target object; wherein each mirror comprises an effective deflection area, and the size of the effective deflection area of each mirror is determined by the scanning range of the scanning field of view; and a collector for collecting the light beams reflected back by the target area to obtain point cloud data of the target object. The laser radar can flexibly set a specific area and meet the specific resolution scanning requirements of the specific area.

Description

Technical Field

[0001] This application relates to the field of optical detection technology, and in particular to a rotating mirror lidar. Background Technology

[0002] LiDAR is an optical detection system that typically includes a transmitter, a receiver, and a control and processor. Its working principle is as follows: the transmitter emits a light signal towards the target object; the light signal is reflected by the target object, forming an echo signal that is received by the receiver. After the receiver receives the echo signal, the control and processor combine the emitted light signal and the echo signal to perform signal processing and obtain the target object's characteristic information, such as distance, azimuth, altitude, velocity, attitude, and shape. As one of its most widespread applications, LiDAR can be combined with Time-of-Flight (TOF) technology. By calculating the time difference or phase difference between the emitted light signal and the received echo signal, the distance between the target object and the LiDAR unit can be calculated, resulting in point cloud data containing the target object's distance value.

[0003] In related technologies, lidar based on Time-of-Flight (TOF) technology mainly includes two categories: scanning lidar and all-solid-state lidar. Scanning lidar can be further divided into mechanical and non-mechanical lidar based on the scanning method. Mechanical lidar achieves a 360° wide field of view optical detection by placing the transmitter, collector, and control and processor on a rotating base; while non-mechanical lidar achieves a wide field of view scanning by setting up optical deflection elements such as multi-faceted rotating mirrors, galvanometers, and reflectors to deflect the optical path of the emitted light signal.

[0004] When scanning lidar uses multi-faceted rotating mirrors for optical detection, under the condition that the acquisition frame rate, single-line ranging time, rotation speed and number of rotating mirrors are fixed, the scanning field of view formed after the emitted light signal is deflected by the multi-faceted rotating mirror is a uniform angular resolution field of view. In other words, the collector receives the echo signal reflected back by the target object and obtains a point cloud with uniform density after control and processor processing. It is difficult to meet the detection requirements of smaller angular resolution or higher point cloud density in a specific area.

[0005] Therefore, there is an urgent need to improve the aforementioned scanning lidar. Summary of the Invention

[0006] This application provides a rotating mirror lidar, which aims to solve some of the problems mentioned in the background art.

[0007] To address the aforementioned technical problems, this application provides a rotating mirror lidar, comprising a transmitter for emitting a light signal in a first direction; a multi-faceted rotating mirror, including at least two reflectors, for deflecting the emitted light signal in the first direction by variable-speed rotation and moving it along a second direction to form a scanning field of view including at least two different angular resolution beams in a target area including a target object; wherein each reflector includes an effective deflection area, the size of which is determined by the scanning range of the scanning field of view; and a collector for collecting the beam reflected back from the target area to obtain point cloud data of the target object.

[0008] Compared with the prior art, the beneficial effects of this application are as follows: This application designs the effective deflection area of ​​the reflector in the multi-faceted rotating mirror according to the scanning range of the scanning field of view of the lidar. The transmitter emits a light signal in the first direction to the multi-faceted rotating mirror. The emitted light signal is deflected by the variable speed movement of the multi-faceted rotating mirror to form a scanning field of view in the second direction that includes at least two different angular resolution beams, thereby improving the angular resolution of the lidar. It can also flexibly set specific areas and meet the high-resolution scanning requirements of specific areas. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of the system principle of a lidar according to this application;

[0011] Figure 2 This is a schematic diagram of the structure of a lidar according to this application;

[0012] Figure 3 This is a schematic diagram of the structure of the light source in the transmitter provided in this application;

[0013] Figure 4 This is a schematic diagram of the pixel array structure in the collector provided in this application;

[0014] Figure 5 A schematic diagram illustrating the principle of light reflection provided in this application;

[0015] Figure 6 This is a schematic diagram of the rotational angular velocity of a multi-faceted rotating mirror according to this application;

[0016] Figure 7This is a schematic diagram of a scanning field of view provided in this application;

[0017] Figure 8 A schematic diagram of the rotational angular velocity of another multi-faceted rotating mirror provided in this application;

[0018] Figure 9 This is a schematic diagram of yet another scanning field of view provided in this application;

[0019] Figure 10 A schematic diagram of the rotational angular velocity of another multi-faceted rotating mirror provided in this application;

[0020] Figure 11 This is a schematic diagram of another scanning field of view provided in this application. Detailed Implementation

[0021] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many other different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0022] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0023] It should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the purpose of facilitating the description of this application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise expressly specified. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0025] It should also be noted that in the embodiments of this application, the same reference numerals are used to represent the same component or part. For the same part in the embodiments of this application, the reference numerals may only be used to mark one part or component as an example. It should be understood that the reference numerals are also applicable to other identical parts or components.

[0026] Figure 1 This is a schematic diagram of the system principle of a lidar. A lidar 10 typically includes a transmitter 11, a collector 12, and a control and processor 13 connected to the transmitter 11 and the collector 12. The transmitter 11 emits a pulse beam 30 with a fixed time interval (pulse period) towards the target object 20. At least a portion of the pulse beam 30 is reflected by the target object 20 to form a reflected beam 40, which is then incident on the collector 12. The collector 12 collects photons from the reflected beam 40 and outputs corresponding photon signals. The control and processor 13 synchronizes the trigger signals of the transmitter 11 and the collector 12 to calculate the flight time of the photons in the beam from emission to reception. Based on the flight time, the distance between the target object 20 and the lidar 10 is calculated, resulting in point cloud data containing the target object's distance value.

[0027] Specifically, the transmitter 11 typically includes one or more light sources 111, emitting optical elements 112, and a driver 113, etc., and each light source 111 is used to emit a pulsed beam 30 with a fixed time interval (pulse period) toward the target object 20. In practical applications, the light source 111 can be a VCSEL array light source chip formed by generating multiple VCSEL (Vertical-Cavity Surface-Emitting Laser, VCSEL) light sources on a single semiconductor substrate, and it can emit a pulsed beam 30 toward the target object 20 at a certain frequency (pulse period) under the control of the driver 113. The pulsed beam 30 is projected onto the target object 20 through the emitting optical elements 112 to form a corresponding illumination spot, and the frequency needs to be set according to the measurement distance. In some examples, the emitting optical element 112 may be one or more of the following forms: lens (a lens group consisting of multiple monolithic lenses), diffractive optical element (DOE), diffuser, metasurface optical element, microlens array (MLA), Powell prism, mask, mirror, MEMS (Micro-Electro-Mechanical System) galvanometer.

[0028] Specifically, the collector 12 typically includes a receiving optical element 122 and a pixel array 121 composed of multiple pixels. In practical applications, the receiving optical element 122 images the reflected light beam 40 reflected by the target object 20 onto the pixel array 121. At least one pixel in the pixel array 121 collects photons from the reflected light beam 40 reflected by the target object and outputs a corresponding photon signal to the control and processor 13 (the situation where a pixel in the pixel array 121 collects photons is considered a photon detection event, at which time a corresponding photon signal is output). For example, the pixel array 121 can be at least one of a single-photon device for collecting photons, such as a SPAD (Single Photon Avalanche Diode) or a SiPM (Silicon Photomultiplier). Preferably, the pixel array 121 is composed of multiple SPADs, which can respond to the incident single photon and output a signal indicating the arrival time of the received photon at each SPAD. In addition, the collector 12 generally includes a readout circuit (not shown) connected to the pixel array 121. The readout circuit is adapted to the pixels in the pixel array 121 to receive the photons in the reflected beam 40 collected by the pixels to generate a corresponding photon signal, and then outputs a signal indicating the corresponding flight time of the pulse beam 30 to and from the target object 20.

[0029] The readout circuit includes a Time Data Conversion (TDC) circuit, which records the flight time of photons from emission to acquisition and generates a time signal (e.g., a timecode). In some embodiments, the readout circuit also includes a histogram circuit, into which the time signal is input to locate the corresponding storage unit (time bin) and increment the photon count value in that time bin by 1. After multiple pulse beams 30 (pulse sequences) are repeatedly emitted towards the target object 20, the time signals from the multiple detections are input to the corresponding time bins of the histogram circuit and stored so that the histogram circuit generates a histogram containing the flight time corresponding to each pulse.

[0030] The controller and processor 13 receives and processes the histogram output by the acquisition unit 12. Typically, filtering is performed first to reduce the impact of noise. Then, echo extraction and centroid position calculation are performed on the filtered histogram. Finally, the flight time of the pulse to and from the target object 20 is determined based on the time corresponding to the centroid position (the time corresponding to the centroid position is the flight time of the pulse to and from the target point).

[0031] In some embodiments, when the lidar system is a rotating mirror lidar, it typically includes a multi-faceted rotating mirror electrically connected to the control and processor. This mirror is used to change the position of the laser signal transmission to the target area including the target object and to move it along one direction to achieve scanning of the target area. In this lidar system, the transmitting and receiving optical paths overlap, and it is generally referred to as a coaxial system. Figure 2 The image shown is a coaxial lidar system provided in this application. Figure 2 As shown, the coaxial lidar system includes a light source 21, a pixel array 22, a first reflective element 23, a multi-faceted rotating mirror 24, an emitting optical element 25, and a first receiving optical element 26. The light source 21 emits a pulsed light beam to the emitting optical element 25, which collimates the beam before it propagates to the first reflective element 23. The first reflective element 23 reflects the beam collimated by the emitting optical element 25 to the multi-faceted rotating mirror 24, which deflects the beam towards the target object for scanning. When the beam emitted by the light source 21 reaches the target area, it is reflected. The first receiving optical element 26 receives the reflected beam and focuses it onto the pixel array 22 located on the image plane. The pixel array 22 generates a histogram based on the acquired beam to obtain the point cloud data of the target object.

[0032] Furthermore, reflective elements can be placed in the transmitting and receiving optical paths, and beam folding is typically used to miniaturize the lidar. In one embodiment, such as... Figure 2 As shown, a second reflective element 27 is disposed between the transmitting optical element 25 and the first reflective element 23, and a third reflective element 28 is disposed between the multifaceted rotating mirror 24 and the first receiving optical element 26. This allows the beam emitted by the transmitter to be collimated by the transmitting optical element 25, and after two reflections by the second reflective element 27 and the first reflective element 23, it is transmitted to the multifaceted rotating mirror 24 to scan the target object. The beam emitted by the light source 21 is reflected after reaching the target object. The reflected beam enters the lidar along the same path as the lidar's transmission optical path and is deflected by the multifaceted rotating mirror 24 to the third reflective element 28. The third reflective element 28 reflects the beam back to the first receiving optical element 26 for focusing and imaging on the pixel array 22. Additionally, a second receiving optical element 29 can be disposed between the multifaceted rotating mirror 24 and the third reflective element 28 to collimate the beam deflected by the multifaceted rotating mirror to the third reflective element 28, ensuring that the beam entering the first receiving optical element 26 is a parallel beam.

[0033] It should be noted that by setting reflective elements in the transmitting and receiving optical paths, this application can not only fold the optical path and reduce the size of the lidar, but also increase the distance between the transmitter and the collector, thereby avoiding interference between the beam emitted by the transmitter and the beam received by the collector.

[0034] In practical applications, after the lidar starts working, the transmitter is configured to emit a linear beam of light at a fixed frequency towards a multi-faceted rotating mirror. The beam extends along a first direction, such as the vertical direction, and the vertical field of view of the linear beam corresponds to the vertical field of view of the lidar's scanning field of view. The beam emitted by the transmitter propagates sequentially to different areas of the multi-faceted rotating mirror, causing deflection and changing the position of the linear beam projected onto the target area. This results in the linear beam continuously shifting along a second direction, that is, continuously shifting along a direction perpendicular to the first direction, forming a scanning field of view, thereby completing the two-dimensional detection of the target area. For ease of description, the embodiments of this application will be described below using the first direction as the vertical direction as an example, while the second direction is the horizontal direction.

[0035] To further miniaturize the lidar and improve the angular resolution of the emitted beam in the first direction, this application designs the arrangement of the light source in the transmitter and the pixel array in the collector of the lidar, such as... Figure 3 and Figure 4 As shown. Figure 3 As shown, the light source 21 includes an emitting circuit board 211 and a plurality of emitting chips 212 arranged on the emitting circuit board 211. Each emitting chip includes at least one light-emitting unit 213 extending along a first direction 101. The light-emitting unit 213 includes a plurality of light-emitting elements 2131 arranged sequentially. The plurality of emitting chips are staggered along the first direction 101 so that the emission fields of adjacent emitting chips are spliced ​​along the first direction. Each emitting chip 212 is used to emit light signals to the target area, thereby improving the angular resolution of the beam emitted by the transmitter in the first direction. Figure 4 As shown, the pixel array 22 includes a data acquisition circuit board 221 and a plurality of data acquisition chips 222 arranged on the data acquisition circuit board 221. Each data acquisition chip includes a readout circuit and at least one photosensitive area extending along a first direction 101. The plurality of data acquisition chips are staggered along the first direction 101 so that the data acquisition fields of adjacent data acquisition chips are spliced ​​along the first direction. Each data acquisition chip 222 is used to receive the echo signal reflected from the target area, and the plurality of data acquisition chips 222 correspond one-to-one with the plurality of transmitting chips 212.

[0036] The emitting chip 212 is a VCSEL chip, which includes at least one light-emitting unit 313. The light-emitting unit 213 includes a plurality of light-emitting elements 2131 arranged in sequence. The acquisition chip is a SPAD chip, which includes a photosensitive area 224 and a circuit area 223. The photosensitive area 224 is formed by at least one photosensitive unit 225, which includes a plurality of photosensitive elements arranged in sequence for detecting reflected echo signals. The readout circuit connected to each photosensitive element forms the circuit area 213.

[0037] In the embodiments of this application, SPAD chips can be manufactured from silicon wafers using known CMOS manufacturing processes to form a stacked structure. However, since the size of the circuit region 224 is larger than that of the photosensitive region 223, if the acquisition chips 222 are arranged sequentially on the circuit board along the vertical direction (first direction), the receiving field of view of two adjacent acquisition chips will be discontinuous in the first direction, i.e., the detection field of view of the lidar will be discontinuous. Therefore, this application proposes to arrange multiple SPAD chips in a staggered manner in the vertical direction, so that the photosensitive regions in adjacent acquisition chips are continuous along the vertical direction, i.e., the photosensitive regions in adjacent acquisition chips are spliced ​​together in the vertical direction without overlapping. Correspondingly, multiple emitting chips 312 are also configured to be staggered along the vertical direction, and the emitting regions corresponding to the emitting units in the multiple emitting chips are also spliced ​​together in the vertical direction without overlapping. Multiple transmitting chips 212 correspond to multiple acquiring chips 222, which means that the echo signal of the light signal emitted by each transmitting chip 212 after being reflected by the target area is received by the corresponding acquiring chip 222. The purpose of setting multiple transmitting chips 212 and multiple acquiring chips 222 to be staggered in the vertical direction is to ensure the continuity of the field of view in the vertical direction when the lidar detects the target area.

[0038] It is understood that the splicing without overlap mentioned in this application refers to an idealized situation that covers the entire field of view and minimizes signal interference, but it is not the only limitation. For example, deviations during the manufacturing process, the influence of temperature during product use, or slight overlap or separation should all be included within the scope of this application.

[0039] In one embodiment, among the multiple acquisition chips 222 arranged on the pixel array 22, the photosensitive areas 224 in two adjacent acquisition chips are located at different positions on the acquisition chip and are configured symmetrically along the vertical direction. Because the acquisition chips have a relatively large size due to the presence of circuitry, while the emitting chips have a compact structure and a small size, and the light-emitting units within the emitting chips are only arranged corresponding to the photosensitive areas, this arrangement allows for a compact arrangement of the emitting chips, reducing the overall size of the transmitter.

[0040] However, when the overall size of the lidar transmitter is minimized, meaning that the angular resolution of the scanning field of view cannot be improved by designing the transmitter, how to achieve flexible deployment of lidar in specific areas and meet the high-resolution scanning requirements of those areas through other means is a problem that urgently needs to be solved. To address this, this application provides a variable-speed rotating mirror lidar by designing a multi-faceted rotating mirror to solve the aforementioned technical problems.

[0041] In one embodiment, each reflector in the multi-faceted rotating mirror provided in this application includes an effective deflection area or an effective deflection area and an ineffective deflection area. The size of the effective deflection area is determined by the preset scanning range of the scanning field of view of the lidar, and the size of the ineffective deflection area is determined by the scanning field of view of the lidar and the size of the effective deflection area.

[0042] Specifically, this application uses a four-sided rotating mirror as an example of a multi-faceted rotating mirror in a lidar system, and describes the preset scanning field of view in the second direction as 120° after being deflected by the multi-faceted rotating mirror. Figure 5 According to the law of light reflection, when the multifaceted rotating mirror rotates by an angle of 'a', the linear beam emitted by the transmitter in the first direction will generate a scanning field of view of angle 2a in the second direction. Therefore, when the preset scanning field of view in the second direction is 120°, the multifaceted rotating mirror only needs to rotate by 60° to obtain a scanning field of view that meets the preset range.

[0043] Assuming the multifaceted rotating mirror has N reflective surfaces, and the beam emitted by the transmitter is perpendicular to the rotation axis of the multifaceted rotating mirror, and the maximum rotation angle of each reflector during operation is γ, then γ = 360° / N. That is, when the multifaceted rotating mirror is a four-sided rotating mirror, the maximum rotation angle of each reflector is 90°. Specifically, if the lidar needs to achieve a 120° scanning field of view within a single frame measurement cycle, then each reflector in the multifaceted rotating mirror needs to rotate 60° during the rotation process. Since the maximum rotation angle of each reflector in the multifaceted rotating mirror is 90°, the effective rotation angle of each reflector during rotation is 60°, and the ineffective rotation angle is 30°. For a single mirror, when the multifaceted rotating mirror rotates 60° along its axis, the transmitter emits a light signal in the first direction to the current mirror of the multifaceted rotating mirror. This light signal is deflected by the current mirror to form a 120° scanning field of view in the second direction. The area in the mirror used to deflect the emitted light signal at this time is called the effective deflection area. After the multifaceted rotating mirror rotates 60° along its axis, the transmitter stops working and does not emit any light signal. Since the maximum rotation angle of the mirror is 90°, that is, the remaining non-effective rotation angle is 30° (maximum rotation angle of the mirror - effective rotation angle). Therefore, when the multifaceted rotating mirror continues to rotate 30° along its axis without interruption, there is an area in the mirror that is not used to deflect the emitted light signal during this rotation process. This area is called the non-effective deflection area. This area is only used to transition the current mirror in the multifaceted rotating mirror to the next mirror in the multifaceted rotating mirror to open a new round of scanning field of view.

[0044] It should be noted that the above explanation only uses the example of a four-sided rotating mirror in a lidar achieving a 120° scanning field of view within a single frame measurement cycle to illustrate the area of ​​the effective deflection region and the ineffective deflection region of the reflector. When the range of the lidar's scanning field of view is different, the area of ​​the effective deflection region and the ineffective deflection region of the reflector in the multi-sided rotating mirror will be different. For example, if the four-sided rotating mirror in the lidar needs to achieve a 180° scanning field of view within a single frame measurement cycle, then the effective rotation angle of each reflector in the four-sided rotating mirror is 90°. In this case, the entire area of ​​the reflector is the effective deflection region, and the area of ​​the ineffective deflection region is 0. This area can be defined according to the scanning field of view required by the lidar, and this application does not impose any restrictions on it.

[0045] After determining the effective and ineffective deflection areas of each mirror in the multi-faceted rotating mirror, when the controller and processor control the multi-faceted rotating mirror to rotate at a constant speed within a single measurement frame period, the emitted light signal in the first direction emitted by the transmitter is deflected by the multi-faceted rotating mirror and forms a scanning field of view with uniform angular resolution in the second direction in the target area. The point cloud density of the target area obtained by the acquisition device acquiring the light beam reflected back from the target area and processing it by the controller and processor is uniform.

[0046] To achieve high-precision detection of target objects in the target area, this application, without changing the frame rate, transmits a light signal in a first direction to a multi-faceted rotating mirror. By controlling the multi-faceted rotating mirror to rotate at a variable speed, the transmitted light signal is deflected and moved along a second direction to form a scanning field of view in the target area that includes at least two different angular resolution beams. The target object in the target area is scanned using the beam with the higher angular resolution of the two different angular resolutions to obtain high-precision point cloud data including the distance value of the target object, thereby completing the high-precision detection of the target object.

[0047] Specifically, ensuring that the acquisition frame rate of the lidar remains constant, i.e., the measurement period T for a single frame of point cloud is constant, a scanning field of view within a preset range needs to be formed by the single-sided reflector of the multi-faceted rotating mirror within the single-frame measurement period T to complete a single scan of the target area. Based on this, the effective deflection area of ​​a single reflector in the multi-faceted rotating mirror can be divided into multiple sub-regions according to the application scenario of the lidar. By controlling the rotation angular velocity of the multi-faceted rotating mirror, the rotation angular velocity of each sub-region can be indirectly controlled. Thus, when the transmitter emits a transmitted light signal in the first direction to each sub-region in the effective deflection area of ​​the multi-faceted rotating mirror, the rotation angular velocity of the multi-faceted rotating mirror is changed so that when the light beam propagates sequentially to different sub-regions in the effective deflection area of ​​the reflector, it is deflected in the second direction by different sub-regions to form a scanning field of view that meets the preset range and includes at least two different angular resolution beams, thereby realizing the flexible configuration of specific areas and specific scanning resolutions for specific areas.

[0048] To better illustrate how the variable-speed rotation of a multifaceted rotating mirror creates scanning fields of view with different angular resolutions, this application uses a case where the multifaceted rotating mirror rotates at a constant speed as a comparison. Figure 6 As shown. For a single mirror in a multi-faceted rotating mirror system, it includes an effective deflection area and an ineffective deflection area. Given a fixed frame rate, single-line ranging time, and number of rotating mirror surfaces in the lidar system, and considering the lidar's scanning field of view, if the multi-faceted rotating mirror rotates at a fixed angular velocity ω0, Figure 6 S1-S3, as shown, correspond to different sub-regions of the effective deflection area of ​​the mirror, while S4 corresponds to the ineffective deflection area of ​​the mirror.

[0049] During the effective deflection region of the reflector, it needs to scan the target object and background area within the target region. Generally, the target object is placed in the center of the target region, and the background area is located on either side. Based on this, the beam deflected by sub-regions S1 and S3 of the effective deflection region completes the scanning of the background area, while the beam deflected by region S2 completes the scanning of the target object. The non-effective deflection region S4 of the reflector is used to transition from the current reflector to the next reflector in the multi-faceted rotating mirror system. Taking a four-faceted rotating mirror as an example, the emitted light signal from the transmitter, after being deflected by sub-regions S1-S3 of the effective deflection region of a certain reflector in the uniformly rotating multi-faceted rotating mirror, forms a uniform horizontal angular resolution scanning field of view in the target region, such as... Figure 7 As shown. When the emitted light signal from the transmitter is deflected by the multi-faceted rotating mirror to form a uniform horizontal angular resolution scanning field of view, the point cloud data containing the target object distance value obtained by the collector after acquiring the photon signal reflected back from the target area and processing it through control and processor is also uniform, as is... Figure 7 As shown.

[0050] In one embodiment, when the transmitter continuously emits pulsed light beams in a first direction at a fixed frequency f, and the multifaceted rotating mirror rotates at an angular velocity ω0, the angular resolution formed by the continuously emitted light beams at intervals t = 1 / f is ω0t, and the scanning range of the scanning field of view formed in the second direction within a single measurement frame period T after the emitted light signal is deflected by the multifaceted rotating mirror is ω0T. Therefore, the angular resolution of the scanning field of view is related to the rotational angular velocity of the multifaceted rotating mirror.

[0051] In order to achieve high-precision detection of the target object and acquire the dense point cloud of the target object area within the same measurement frame period, the transmitter beam needs to form a scanning field of view with smaller angular resolution in the target object area. Since the angular resolution of the scanning field of view is related to the rotation angular velocity of the multi-faceted rotating mirror, this application changes the angular resolution of the scanning field of view by changing the rotation angular velocity of the multi-faceted rotating mirror.

[0052] like Figure 8 As shown, when the emitted light signal from the transmitter in the first direction propagates to sub-regions S1-S3 of the effective deflection area of ​​the reflector, the rotational angular velocity of the multifaceted rotating mirror first decreases and then increases to perform variable-speed rotation, thereby adjusting the angular resolution of the scanning field of view of the target object's location. This results in a scanning field of view with at least two different angular resolution beams in the second direction, as shown in the diagram. Figure 9 The point cloud data shown is divided into dense point clouds corresponding to the area where the target object is located and sparse point clouds corresponding to the background area, so as to obtain high-precision detection results of the target object through dense point cloud data.

[0053] In one embodiment, assuming the lidar's scanning field of view is a symmetrical field of view with low angular resolution in the middle and high angular resolution at both ends, then during the variable-speed rotation of the multi-faceted rotating mirror in a single measurement cycle T, the rotational angular velocities of the effective deflection sub-regions S1 and S3 of the reflector change symmetrically, and the rotational angular velocity of the effective deflection sub-region S2 of the reflector also changes symmetrically during the rotation process, such as... Figure 8 As shown. During the effective deflection region of the multi-faceted rotating mirror, it rotates with at least two different angular accelerations. Thus, when the beam emitted by the transmitter in the first direction propagates sequentially to different sub-regions within the effective deflection region of the mirror, the deflection through these sub-regions with different angular accelerations can, in the second direction, form a scanning field of view that satisfies a preset range and includes at least two different angular resolution beams, such as... Figure 9 As shown.

[0054] Specifically, when the emitted light signal from the transmitter in the first direction first propagates to the sub-region S1 of the effective deflection area of ​​the reflector, the rotational angular velocity of the multifaceted mirror decreases with a first angular acceleration within time period T1 to obtain a scanning field of view with a larger angular resolution, thereby completing a sparse scan of an edge region in the target area. When the multifaceted mirror rotates to the sub-region S2 of the effective deflection area of ​​the reflector, the emitted light signal from the transmitter in the first direction propagates to the sub-region S2 of the effective deflection area of ​​the reflector. Assuming that a fine scan of the area where the target object is located in the target area needs to be completed through the sub-region S2 of the effective deflection area of ​​the reflector within time period T2, the rotational angular velocity of the multifaceted mirror first decreases and then increases with a second angular acceleration based on the reduced rotational angular velocity to obtain a scanning field of view with a smaller angular resolution. This allows for the acquisition of denser point cloud data, enabling high-precision detection of the target object. After a time interval T2, the emitted beam propagates to sub-region S3 of the effective deflection area of ​​the reflector. The rotational angular velocity of the multifaceted rotating mirror increases with a first angular acceleration during the time interval T3 to complete a sparse scan of another edge region of the target area, so that the beam deflected by the multifaceted rotating mirror forms a symmetrical scanning field of view in the second direction, including at least two angular resolutions.

[0055] It should be noted that the first angular acceleration in this application refers to the angular acceleration used during the scanning of the edge region by utilizing sub-regions S1 and S3 within the effective deflection area of ​​the mirror, and the second angular acceleration refers to the angular acceleration used during the scanning of the target object's region by utilizing sub-region S2 within the effective deflection area of ​​the mirror. In other words, the first and second angular accelerations can include one or more acceleration values. In other words, during the scanning of the target region by utilizing each sub-region of the effective deflection area of ​​the mirror, the angular acceleration used can be a constant or variable value, as long as the rotational angular velocity when scanning the target object's region using the multi-faceted rotating mirror is less than the rotational angular velocity when scanning the edge region.

[0056] Furthermore, after the multifaceted rotating mirror has rotated for a period of time (T1+T2+T3), the transmitter stops working. At this time, the current reflector of the multifaceted rotating mirror transitions to the next reflector through the ineffective deflection region (S4) to perform a new round of scanning. Since the single-frame measurement period T of the lidar is constant, that is, during the period when any mirror in the multi-faceted rotating mirror is used to acquire a single-frame point cloud, the sum of the rotation time of the effective deflection area and the rotation time of the ineffective deflection area of ​​any mirror in the multi-faceted rotating mirror must be equal to the single-frame measurement period of the lidar. Therefore, during the process of the current mirror of the multi-faceted rotating mirror transitioning to the next mirror through the ineffective deflection area S4, its rotation time T4 must satisfy T-(T1+T2+T3). Furthermore, since the ineffective rotation angle corresponding to the ineffective deflection area of ​​the mirror of the multi-faceted rotating mirror is determined by the maximum rotation angle and the effective rotation angle of the mirror, that is, when the number of faces of the multi-faceted rotating mirror and the scanning range of the scanning field of view are determined, the ineffective rotation angle of the mirror is a constant value. At this time, the multi-faceted rotating mirror needs to complete the rotation of the ineffective rotation angle within the rotation time T4.

[0057] With a fixed ineffective rotation angle of the reflector, the shorter the rotation time T4, the greater the rotational angular velocity of the multi-faceted mirror, thus ensuring that the single-frame measurement period T of the lidar remains constant. Furthermore, since the ineffective deflection region S4 is used to transition from the current reflector to the next reflector for a new round of scanning, meaning the final rotational angular velocity of the current reflector's ineffective deflection region S4 is the same as the initial velocity of the next reflector's effective deflection region S1, and the rotation of the multi-faceted mirror forms a closed loop, the initial rotational angular velocity of each reflector is equal to its final rotational angular velocity. Therefore, during the rotation time T4 of the ineffective deflection region, the rotational angular velocity of the multi-faceted mirror first increases and then decreases, as shown below. Figure 8 As shown, this is done so that the ineffective rotation angle transition to the next reflector is completed within time period T4, while ensuring that the end rotation angular velocity of each reflector is equal to the initial rotation angular velocity.

[0058] Furthermore, if a high-resolution scan of the background areas on both sides of the target object is also required, the rotational angular velocity of the multi-faceted rotating mirror can be further reduced, such as... Figure 10 As shown, the rotational angular velocity of its multifaceted rotating mirror is relative to... Figure 8 The rotational angular velocity shown has decreased, and the corresponding point clouds of the edge region and the target object region are as follows: Figure 11 As shown, it is relative to Figure 9 The point cloud density shown will be higher.

[0059] It should be noted that the above design of the multi-faceted rotating mirror is based on a symmetrical scanning field of view with a small angular resolution in the middle area and a large angular resolution in the two side areas. In practical applications, the multi-faceted rotating mirror can be designed according to the actual required angular resolution and scanning range of each area of ​​the scanning field of view. This application does not impose any restrictions on this.

[0060] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A rotating mirror laser radar characterized by comprising: include: A transmitter used to transmit optical signals in the first direction; A multi-faceted rotating mirror includes at least two mirrors for deflecting an emitted light signal in a first direction and moving it in a second direction by rotating at a variable speed to form a scanning field of view including at least two different angular resolution beams in a target area including a target object; wherein each mirror includes an effective deflection area, the size of which is determined by the scanning range of the scanning field of view. The collector is used to collect photons in the light beam reflected back from the target area and output the corresponding photon signal to obtain the point cloud data of the target object.

2. The lidar of claim 1, wherein, include: Each of the reflectors also includes a non-effective deflection region, the size of which is determined by the scanning range of the scanning field of view and the size of the effective deflection region.

3. The lidar as described in claim 1, characterized in that, include: The lidar also includes a control and processor electrically connected to the transmitter, the multi-faceted rotating mirror, and the collector. The control and processor is used to control the transmitter, the multi-faceted rotating mirror, and the collector, and is also used to calculate the flight time of the beam based on the photon signal, so as to obtain point cloud data containing the distance value of the target object based on the flight time.

4. The lidar of claim 3, wherein, The effective deflection region includes multiple sub-regions. The controller and processor control the rotational angular velocity of the multifaceted rotating mirror to indirectly control the rotational angular velocity of each sub-region. When the transmitter emits a light signal in the first direction to each sub-region in the effective deflection region of the multifaceted rotating mirror, the beam propagates sequentially to different sub-regions in the effective deflection region of the reflector by changing the rotational angular velocity of the multifaceted rotating mirror. Through the deflection of different sub-regions, a scanning field of view is formed in the second direction that satisfies a preset range and includes at least two different angular resolution beams.

5. The lidar of claim 1, wherein, include: When the transmitter emits a light signal in the first direction and it propagates to the effective deflection area of ​​the reflector, the rotational angular velocity of the multifaceted rotating mirror rotates at a variable speed, first decreasing and then increasing, thereby adjusting the angular resolution of the scanning field of view of the area where the target object is located, and forming a scanning field of view with at least two different angular resolution beams in the second direction.

6. The lidar of claim 1, wherein, include: The multifaceted rotating mirror rotates at least two different angular accelerations during the effective deflection region of the rotating mirror. When the light beam emitted by the transmitter in the first direction propagates sequentially to different sub-regions in the effective deflection region of the mirror, the deflection of the sub-regions with different angular accelerations can form a scanning field of view in the second direction that satisfies a preset range and includes at least two different angular resolution light beams.

7. The lidar of claim 1, wherein, include: The initial rotational angular velocity of each mirror in the multifaceted rotating mirror is equal to its final rotational angular velocity.

8. The lidar of claim 2, wherein, include: The sum of the rotation time of the effective deflection region and the rotation time of the non-effective deflection region of any mirror in the multi-faceted rotating mirror is equal to the single-frame measurement cycle of the lidar.

9. The lidar of any one of claims 1-8, wherein, include: The transmitter includes a light source, which includes a transmitting circuit board and a plurality of transmitting chips arranged in a staggered manner along the first direction on the transmitting circuit board. Each transmitting chip includes at least one light-emitting unit extending along the first direction for transmitting the transmitted light signal.

10. The lidar of any one of claims 1-8, wherein, include: The data acquisition device includes a pixel array, which includes a data acquisition circuit board and multiple data acquisition chips arranged on the data acquisition circuit board. The multiple data acquisition chips are staggered along the first direction so that the data acquisition fields of adjacent data acquisition chips are stitched together along the first direction. Each data acquisition chip is used to receive the echo signal reflected from the target area.

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