Scanner control for lidar systems

Abstract

A scanner for a lidar system and a method for controlling the scanner are provided. The method includes: generating a drive signal including a first component of a first frequency and a second component of a second frequency; sending the drive signal to a scanner configured to perform a first periodic motion at a first frequency around a first axis and a second periodic motion at a second frequency around a second axis; changing the driving signal to change the movement speed of the scanner, and changing the resolution of the selected area; wherein the selected region comprises the region of interest, and the step of changing the resolution in the selected region comprises the substeps of improving the resolution in the selected region; and / or, the selected area comprises an edge area of the field of view of the lidar, and changing the resolution in the selected area comprises reducing the resolution in the selected area.

Description

Background Technology

[0001] This application is a divisional application of patent application 2019800957023, filed on May 6, 2019, entitled "Scanner Control for a LiDAR System". LiDAR (light detection and ranging) technology can be used to acquire three-dimensional information about the environment by measuring the distance to an object. A LiDAR system may include at least one light source configured to emit light pulses and at least one detector configured to receive returning light pulses. The returning light pulse or beam may be referred to as an echo beam. The distance can be obtained based on the elapsed time (i.e., time of flight) between the emission of the light pulse and the detection of the returning light pulse. The light pulse may be generated by a laser emitter and then shaped (collimated or focused) by a lens or lens assembly. The returning light pulse may be received by a detector located near the laser emitter. The returning light pulse may be scattered light from the surface of an object.

[0002] In some cases, multiple light pulses or sequences of light pulses can be emitted into the environment for large-area scanning. In other cases, lidar systems can utilize scanners to guide one or more beams in one or more directions according to a scanning pattern. It is important to provide lidar systems with improved scanner control to increase the efficiency of sampling the environment or providing adaptive scanning patterns. Summary of the Invention

[0003] There is a need for improved lidar systems for 3D measurement. Lidar systems with fine-grained, controllable scanning patterns are also required. In some cases, lidar systems may utilize a scanner to guide one or more beams in one or more directions, which may require the scanner's movement to be controlled by an improved control system. In some cases, to achieve the desired scanning pattern, the scanner's movement can be controlled at a fine-grained level. The provided lidar system can meet the above needs by providing an improved scanner configured to guide light pulses according to a configurable scanning pattern. In some cases, to achieve the desired scanning pattern, the systems or methods of this disclosure provide mechanisms for controlling the scanner, thereby improving the efficiency of sampling the environment and allowing automatic adaptation to various real-time conditions. In particular, the scanning pattern / path and / or measurement resolution can be adapted to real-time conditions (e.g., environmental conditions). The provided lidar system is capable of dynamically adjusting the resolution of sampling points emitted into a selected region in 3D space, as well as the x and / or y resolution of pixels in the selected region of a 3D point cloud image. The provided methods and apparatus can be used in conjunction with light source control, thereby emitting a beam into space according to the movement of the scanner. By integrating control of the scanner and light source, the pixel (point) distribution or resolution in selected areas of an image frame can be dynamically controlled in both the x and y directions. Furthermore, the provided mechanism allows for the stabilization of LiDAR images or point cloud images across image frames.

[0004] In one aspect of the invention, a method for controlling a scanner in a lidar system is provided. The method may include: generating a trigger signal from a position sensor of the scanner; generating a single drive signal comprising a first component of a first frequency and a second component of a second frequency, wherein the first component and the second component are superimposed with a fixed phase relationship via the trigger signal; sending the single drive signal to the scanner, wherein the scanner has a resonant response at the first frequency; and actuating the scanner to perform a first periodic motion around a first axis at the first frequency and a second periodic motion around a second axis at the second frequency.

[0005] In some embodiments, the scanner includes a single multi-axis mirror. In some embodiments, a first periodic motion is performed about the first axis at a first resonant frequency of the scanner. In some embodiments, a second periodic motion is performed about the second axis at a second resonant frequency of the scanner. In some embodiments, the second component includes a ramp waveform. In some cases, the second component includes a low-frequency waveform component and a high-frequency waveform component. In some examples, the frequency of the high-frequency waveform component is twice the first frequency of the first component, and the high-frequency waveform component and the low-frequency waveform component are synchronized with the aid of a trigger signal. Alternatively, the high-frequency waveform component has a variable amplitude, and the high-frequency waveform component and the low-frequency waveform component are combined with a predetermined phase relationship. In some cases, the high-frequency waveform component is generated in response to real-time conditions. Such real-time conditions may include target detection.

[0006] In some embodiments, the trigger signal is generated at the beginning or end of a sweeping cycle of the first cycle motion. In some embodiments, a second component is generated in response to receiving the trigger signal. In some embodiments, the position sensor is an optical position sensor or a position-sensitive detector.

[0007] In some embodiments, the scanner guides a sequence of optical pulses along a scan pattern that approximates a raster scan pattern. In some cases, the method may further include dynamically adjusting the scan pattern along a second axis based on real-time conditions. For example, adjusting the scan pattern along the second axis includes altering the second-cycle motion by superimposing a high-frequency waveform component onto a single drive signal. In this case, the amplitude or frequency of the high-frequency waveform component is determined based on real-time conditions. In some cases, the method may further include dynamically adjusting the scan pattern along a first axis based on real-time conditions. For example, adjusting the scan pattern along the first axis includes changing the time interval of the emitted optical pulse sequence.

[0008] Another aspect of this disclosure provides a scanner for a lidar system. The scanner may include: a scanner actuated to perform a first-cycle motion about a first axis at a first frequency and a second-cycle motion about a second axis at a second frequency; a position sensor configured to generate a trigger signal; and a controller configured to generate a single drive signal to actuate the scanner, wherein the single drive signal includes a first component of a first frequency and a second component of a second frequency, further wherein the first component and the second component are superimposed with a fixed phase relationship with the aid of the trigger signal.

[0009] In some embodiments, the scanner includes a single multi-axis mirror. In some cases, the single multi-axis mirror includes a scanning plate suspended on a gimbal by one or more torque arms. For example, the one or more torque arms are H-shaped.

[0010] In some embodiments, a first periodic motion is performed around the first axis at a first resonant frequency of the scanner. In some embodiments, a second periodic motion is performed around the second axis at a second resonant frequency of the scanner. In some embodiments, the second component includes a ramp waveform. In some cases, the second component includes a low-frequency waveform component and a high-frequency waveform component. For example, the frequency of the high-frequency waveform component is twice the first frequency of the first component; in some cases, the high-frequency waveform component and the low-frequency waveform component are synchronized by means of a trigger signal. In some cases, the high-frequency waveform component has a variable amplitude. For example, the high-frequency waveform component is generated by combining the high-frequency waveform component and the low-frequency waveform component with a fixed phase relationship or in response to real-time conditions. For example, real-time conditions may include the detection of a target.

[0011] In some embodiments, the position sensor is an optical position sensor or a position-sensitive detector. In some embodiments, the position sensor is used to detect the movement of the scanner. In some embodiments, a trigger signal is generated at the beginning or end of a sweep cycle of the first cycle motion. In some embodiments, a controller is configured to generate the second component in response to receiving the trigger signal. In some embodiments, the scanner guides a sequence of optical pulses along a scan pattern approximating a grating scan pattern. In some cases, the scan pattern is dynamically adjusted along a second axis direction based on real-time conditions. In some cases, the scan pattern is adjusted by superimposing a high-frequency waveform component onto the single drive signal to change the second cycle motion. For example, the amplitude or frequency of the high-frequency waveform component is determined based on real-time conditions. In one example, the real-time conditions include the detection of a target.

[0012] In some embodiments, the position sensor is an optical position sensor or a position-sensitive detector. In some embodiments, the position sensor is used to detect movement of the scanner. In some embodiments, a trigger signal is generated at the beginning or end of a sweep cycle of the first cycle of motion. In some embodiments, the controller is configured to generate a second component in response to receiving the trigger signal.

[0013] In some embodiments, the scanner guides a sequence of optical pulses along a scan pattern that approximates a grating scan pattern. In some cases, the scan pattern is dynamically adjusted along a second axis based on real-time conditions. In some cases, the scan pattern is adjusted by superimposing a high-frequency waveform component onto a single drive signal to change the second-cycle motion. In some cases, the amplitude or frequency of the high-frequency waveform component is determined based on real-time conditions. In some cases, the scan pattern is dynamically adjusted along a first axis based on real-time conditions. In some cases, the scan pattern is adjusted by changing the time interval of the emitted optical pulse sequence.

[0014] Other aspects and advantages of this disclosure will become readily apparent to those skilled in the art from the following detailed description, wherein exemplary embodiments of the disclosure are shown and described only by way of illustrating the best pattern intended for performance. It should be understood that other different embodiments of the disclosure may be possible, and its various details may be modified in a variety of obvious ways without departing from the disclosure. Therefore, the drawings and description are to be considered illustrative in nature and not restrictive.

[0015] By incorporating references

[0016] All publications, patents and patent applications mentioned in this specification are incorporated herein by reference as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. Attached Figure Description

[0017] The novel features of the invention are specifically set forth in the appended claims. The features and advantages of the invention will be better understood with reference to the following detailed description and accompanying drawings, which set forth illustrative embodiments in which the principles of the invention are utilized, wherein:

[0018] Figure 1 An example of a lidar system according to some embodiments of the present invention is illustrated schematically.

[0019] Figure 2 Examples of distorted scan patterns and raster scan patterns are shown.

[0020] Figure 3 An example of a multi-axis scanning mirror according to some embodiments of the present invention is illustrated schematically.

[0021] Figure 4 An example of a multi-axis scanning mirror according to some embodiments of the present invention is illustrated schematically.

[0022] Figure 5 An example component of a scanning mirror according to an embodiment of the present invention is shown.

[0023] Figure 6 An example of a sensor configured to provide signals for synchronizing or combining drive signal components or individual waveforms is shown.

[0024] Figure 7 Examples of waveforms for driving a scanning mirror according to some embodiments of the present invention are shown.

[0025] Figure 8 Examples of waveforms for driving a scanning mirror with grating shrinkage correction according to some embodiments of the present invention are shown.

[0026] Figure 9 Another example of a composite drive signal illustrated by individual waveforms is shown according to some embodiments of the present invention.

[0027] Figure 10 An example of a change in the drive signal corresponding to a slow scanning motion according to some embodiments of the invention is illustrated.

[0028] Figure 11 An example of a scan pattern with a configurable pixel distribution is shown.

[0029] Figure 12 An example illustrating the dynamic configuration of pixel / measurement point distribution and / or density in response to real-time conditions is shown.

[0030] Figure 13 A block diagram of a control system for a scanner according to some embodiments of the present invention is shown schematically. Invention Details

[0031] While preferred embodiments of the invention have been shown and described herein, these embodiments will be apparent to those skilled in the art if provided by way of example only. Many variations, modifications, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of this invention.

[0032] A lidar system can also be called a laser ranging system, lidar system, LIDAR system, or laser detection and ranging (LADAR or ladar) system. Lidar is a ranging sensor characterized by its long detection range, high resolution, and low susceptibility to environmental interference. Lidar has been widely used in intelligent robots, drones, autonomous driving, and other fields. The working principle of lidar is to estimate distance based on the round-trip time (e.g., time of flight) of the electromagnetic waves between the source and the target.

[0033] In some cases, a lidar system may include a transmitting device that emits laser pulses into the environment to scan space. A sequence of laser pulses may be emitted according to a scanning pattern. The scanning pattern (which may be referred to as an optical scanning pattern, optical scanning path, or scanning path) refers to the pattern or path along which the laser beam or laser beam spot is guided. Multiple laser beam spots may be uniformly distributed or non-uniformly distributed along this scanning pattern. The scanning pattern can be controlled by various factors, such as the movement of the scanner or the arrangement of multiple light sources.

[0034] In some embodiments, the scanner may include one or more scanning mirrors configured to rotate, oscillate, tilt, pivot, or move at an angle about one or more axes. In some cases, the scanner may be a two-dimensional (2D) scanner. The scanner may use a single scanning mirror driven to rotate about two scanning axes. In some cases, the scanning mirror may be driven to perform a fast scan along one axis and a slow scan along another axis. The two axes may be orthogonal to each other. Traditionally, a fast scan sweeps horizontally back and forth in the field of view (FOV), while a slow scan sweeps vertically back and forth in the field of view. Fast scans operate at a relatively high scan rate, while slow scans operate at a scan rate equal to the video frame rate. In some cases, fast scans operate resonantly, while slow scans provide a basic zigzag pattern, progressively scanning down the frame over a (large) portion of the frame time and then returning to the top of the frame to restart or scanning back from bottom to top in a continuous manner. In other cases, interlaced zigzag scans, triangular wave scans, sine scans, and other waveforms may be used to drive one or both axes. A full sweep along the fast axis can be in any range, such as ±60°, ±50°, ±40°, ±30°, ±20°, ±10°, or any value in between. A full sweep along the slow axis can be in any range, such as ±60°, ±50°, ±40°, ±30°, ±20°, ±10°, or any value in between.

[0035] A single scanning mirror can be controlled to follow a scanning path that substantially covers the field of view (FOV). For example, the scanning path may result in the pixels of a point cloud substantially covering the FOV. Pixels can be distributed across the entire FOV according to the scanning pattern. In some cases, by controlling the movement of the scanning mirror, pixels can have a specific non-uniform distribution (e.g., pixels can have a higher density in one or more selected areas of the FOV). Alternatively or otherwise, by controlling the movement of the scanning mirror, pixels can be uniformly distributed along the scanning pattern.

[0036] In some cases, a pixel or measurement point may correspond to a light pulse. Alternatively, one pixel or measurement point may correspond to multiple light pulses. A pixel or measurement point can be a distance measurement point. In some cases, a distance measurement point can be generated using a single light pulse. In some cases, a measurement point can be obtained by emitting a sequence of coded light pulses emitted over a short duration, making the light pulse sequence usable for deriving the distance measurement point. For example, lidar can be used for three-dimensional (3D) imaging (e.g., 3D point clouds) or obstacle detection. In this case, the distance measurement associated with the light pulse sequence can be considered as a pixel, and the continuously emitted and captured set of pixels (i.e., a “point cloud”) can be rendered as an image or analyzed for other reasons (e.g., obstacle detection). A sequence of light pulses can be generated and emitted over durations of, for example, at least 10 ns, 20 ns, 30 ns, 40 ns, 50 ns, 60 ns, 70 ns, 80 ns, 90 ns, 100 ns, 200 ns, 300 ns, 400 ns, 500 ns, 600 ns, 700 ns, 800 ns, 900 ns, 1 μs, 2 μs, 3 μs, 4 μs, 5 μs, 50 μs, 100 μs, 200 μs, 300 μs, 400 μs, 500 μs, or longer. In some cases, the time interval between consecutive sequences can correspond to the temporal resolution of 3D imaging. The temporal resolution of the point cloud image also affects the pixel resolution in the horizontal or fast scanning direction. The time interval between sequences can be constant or variable.

[0037] It should be noted that the fast scan direction does not need to be aligned with the horizontal direction (it rotates about the vertical scan axis), and the slow scan direction does not need to be aligned with the vertical direction (it rotates about the horizontal scan axis). The fast scan direction and / or the slow scan direction can be any orientation relative to the ground reference frame.

[0038] As used herein, unless the context otherwise requires, the terms "optical pulse sequence," "pulse sequence," "signal sequence," etc., are used interchangeably throughout the specification. Unless the context otherwise requires, the terms "measurement signal," "measurement pulse," "signal light," "output beam," etc., may refer to optical pulses emitted from the transmitting device of the lidar system. The terms "echo beam," "return signal," "return pulse," etc., may refer to optical pulses received by the detector of the lidar system and are used interchangeably throughout the specification unless the context otherwise requires.

[0039] The output beam or signal beam can then be directed into space for measurement. For example, the output beam can have an average power of approximately 1mW, 10mW, 100mW, 1W, 10W, or any other suitable average power. As another example, the output beam can include pulses with pulse energies of approximately 0.1μJ, 1μJ, 10μJ, 100μJ, 1mJ, or any other suitable pulse energies. As another example, the output beam can include pulses with peak powers of approximately 10W, 100W, 1kW, 2kW, 5kW, 10kW, or any other suitable peak power. A light pulse with a duration of 400ps and a pulse energy of 1μJ has a peak power of approximately 2.5kW. If the pulse repetition frequency is 500kHz, the average power of an output beam with a 1μJ pulse is approximately 0.5W. In some cases, the wavelength of the output beam can be in the range of 900nm to 1600nm or in any other suitable range. In some cases, the wavelength of the output beam can be in the range of 1530nm to 1570nm to provide eye-safe laser light.

[0040] Figure 1 An example of a lidar system 100 is illustrated schematically. In some embodiments, the lidar system 100 may include a transmitting module 110, a receiving module, a scanner 120, and multiple optical components, such as lens assemblies 161, 165, and a mirror 163.

[0041] The emitting module 110 may include at least one light source configured to generate a laser beam or light pulse. Depending on the specific application, the wavelength of the laser beam may be in any suitable range. In some cases, the light source may include an eye-safe laser. An eye-safe laser can refer to a laser whose emission wavelength, average power, peak power, peak intensity, pulse energy, beam size, beam divergence, or exposure time results in little or no risk of harm to the human eye from the light emitted from the laser. For example, the light source may be classified as a Class 1 laser product (as defined by the International Electrotechnical Commission (IEC) standard 60825-1) or a Class I laser product (as defined by Section 1040.10 of Article 21 of the U.S. Federal Regulations (CFR), which are safe under all normal operating conditions. In some embodiments, the light source may include an eye-safe laser (e.g., a Class 1 or Class I laser) configured to operate at any suitable wavelength between approximately 1400 nm and approximately 2100 nm. In some cases, the light source may include an eye-safe laser operating at a wavelength between approximately 1400 nm and approximately 1600 nm. In some cases, the light source may include an eye-safe laser with an operating wavelength between approximately 1530 nm and approximately 1560 nm.

[0042] The light source may include a laser diode. The light source may include any suitable type of laser, such as a Fabry-Perot laser diode, a quantum well laser, a distributed Bragg reflector (DBR) laser, a distributed feedback (DFB) laser, or a vertical-cavity surface-emitting laser (VCSEL). In some cases, the light source may include a fiber laser module. In one example, the fiber laser module may include a current-modulated laser diode with a peak wavelength of approximately 1550 nm, followed by a single-stage or multi-stage erbium-doped fiber amplifier (EDFA). The fiber laser module may include a seed laser, a pump laser, an optical amplifier (e.g., a gain fiber or fiber amplifier), and other components.

[0043] The output beam or signal light may be directed to one or more optical elements (e.g., reflectors) and / or through a lens assembly 161 (e.g., a collimating lens, collimating lens assembly) for collimating or focusing the beam 111. The lidar system 100 may include any suitable optical components, such as one or more lenses, mirrors, filters (e.g., bandpass or interference filters), beam splitters, polarizers, polarization beam splitters, waveplates (e.g., half-wave or quarter-wave plates), diffractive or holographic elements, or telescopes, to extend, focus, or collimate the output beam 111 to a desired beam diameter or divergence.

[0044] Similarly, the returned beam 131 can pass through one or more optical components 165, such that the returned beam can be guided and focused onto the active region of the detector of the detection module 130. The one or more optical components may include, for example, one or more mirrors (e.g., plane mirrors, concave mirrors, convex mirrors, parabolic mirrors) or lens / lens assemblies for guiding the returned beam to the detector.

[0045] The lidar system 100 may include a mirror 163 configured to allow signal light 111 to pass through the mirror while directing return light 131 to the detector. In some cases, the mirror 163 may include an aperture, slot, or orifice through which the signal light 111 passes. In some cases, the mirror 163 may be configured such that at least a portion of the signal light 111 (e.g., at least 90%, 80%, 70%, 60%, etc.) passes through the mirror and at least a portion of the return beam 131 (e.g., at least 90%, 80%, 70%, 60%, etc.) is reflected by the mirror 163. In some cases, the mirror 163 may provide that the signal light 111 and the return beam 131 are substantially coaxial, such that the two beams propagate along substantially the same optical path but in opposite directions. For example, the mirror 163 may include an aperture, slot, or orifice through which the signal light 111 passes and a reflective surface that reflects at least a portion of the return beam 131 toward an active region of the detector 130.

[0046] The detection module 130 may include one or more detectors configured to receive the echo beam 160. The detector may be a photoreceiver, optical receiver, optical sensor, photodetector, or optical detector. In some cases, the detection module may include one or more avalanche photodiodes (APDs) or one or more single-photon avalanche photodiodes (SPADs). In some cases, the receiving module may include one or more PN photodiodes (e.g., a photodiode structure formed from p-type and n-type semiconductors) or one or more PIN photodiodes (e.g., a photodiode structure formed from an undoped intrinsic semiconductor region located between the p-type and n-type regions).

[0047] The returned beam can be guided to the active region of the detector. The active region can have any suitable size or diameter, such as approximately 25 μm, 50 μm, 80 μm, 100 μm, 200 μm, 500 μm, 1 mm, 2 mm, or 5 mm in diameter. In some cases, the mirror 163 can have a substantially flat reflective surface or the reflective surface can be curved (e.g., the mirror can be an off-axis parabolic mirror configured to focus the input beam 131 onto the active region of the receiver). The reflective surface of the mirror 163 can include a reflective metallic coating (e.g., gold, silver, or aluminum) or a reflective dielectric coating, and the reflective surface can have any suitable reflectivity R at the operating wavelength of the light source (e.g., R is greater than or equal to 70%, 80%, 90%, 95%, 98%, or 99%).

[0048] In some embodiments, the lidar system 100 may include an optical receiver 165 (e.g., a focusing lens, a focusing lens assembly) and one or more optical elements (e.g., a reflector) 163, which allow reflected light from external objects to pass through the light receiver and then be received by the detection module 130. The received optical signal may be converted into an electrical signal and processed by the controller 140.

[0049] The lidar system 100 may include a scanner 120 to guide an output beam 111 in one or more directions. The scanner 120 may be configured to scan the output beam 111 within an angular range. In some cases, the scanner 120 may be configured to scan the output beam 111 within an angular range of 5 degrees, 20 degrees, 30 degrees, 60 degrees, or any other suitable angular range. As an example, the scanning mirror may be configured to periodically oscillate or rotate within a 15-degree range, resulting in the output beam 111 scanning within a 30-degree range (e.g., a Θ-degree rotation of the scanning mirror results in a 2Θ-degree angular scan of the output beam). In some embodiments, the field of observation (FOR) of the lidar system 100 may refer to the area, region, or angular range within which the lidar system may be configured to scan or capture range information. As an example, a lidar system with an output beam 111 having a 30-degree scanning range may be referred to as having a 30-degree angular field of observation. As another example, a lidar system 100 with a scanning mirror that rotates within a 30-degree range can generate an output beam 111 that scans within a 60-degree range (e.g., 60-degree FOR). In certain embodiments, the lidar system 100 may have a FOR of approximately 10°, 20°, 40°, 60°, 120°, or any other suitable FOR. In some cases, the FOR may be referred to as the full scan area.

[0050] In some embodiments, scanner 120 may include one or more scanning mirrors configured to rotate, oscillate, tilt, pivot, or move angularly about one or more axes. In some cases, planar scanning mirror 125 may be attached to a scanner actuator or mechanism that actuates the mirror portion to scan within a specific angular range. In some cases, scanner 120 may include a resonant scanning mirror or galvanometer 125. In some cases, the scanner may be a two-dimensional (2D) scanner. The scanner may use a single scanning mirror driven to rotate about two scanning axes. In some cases, the scanning mirror may be driven to perform a fast scan along one axis and a slow scan along another axis. The two axes may be orthogonal to each other. Scanning mirror 125 may be designed such that the single scanning mirror has a resonant response at one or more frequencies of the drive signal to produce the desired periodic motion. For example, the resonant frequency and amplification factor of the scanning mirror may be selected independently on each of the two axes by distributing its mass differently about each axis and by designing support structures (e.g., support arms or torsion arms with different torsional stiffness on each axis). Details regarding the design of the scanning mirror and drive signals will be described later.

[0051] The scanner can be actuated by any suitable actuator or mechanism, such as a galvanometer scanner, piezoelectric actuator, polygon scanner, rotating prism scanner, voice coil motor, electric motor (e.g., DC motor, brushless DC motor, synchronous motor or stepper motor), or microelectromechanical system (MEMS) device, etc.

[0052] A resonant scanner (which may be referred to as a resonant actuator) may comprise a spring-like mechanism driven by the actuator to generate periodic oscillations at a substantially fixed frequency. The periodic oscillation frequency associated with the fast scan axis may be the same as the resonant frequency around the fast scan axis. The periodic oscillation frequency of the scanning mirror rotating about the slow scan axis may be either the resonant frequency or a detuned frequency component around the slow scan axis. The oscillation frequency around the fast scan axis may be approximately 1 kHz. The fast scan oscillation frequency may be any value below or above 1 kHz. The slow scan oscillation frequency may be any value in the range of approximately 10 Hz to 100 Hz. The slow scan oscillation frequency may be any value below or above 100 Hz. In some cases, the fast scan oscillation frequency and the slow scan oscillation frequency may have a predetermined relationship. For example, the fast scan oscillation frequency can be at least about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90 or 100 times the slow scan oscillation frequency.

[0053] Scanner 120 may include scanning mirror 125, which may have any suitable geometry or size, such that the scanning mirror can oscillate at a resonant frequency about one or more axes in response to a drive signal. In some cases, the scanning mirror may include a scanning plate with a diameter or width between approximately 3 mm and 15 mm. In some cases, the scanning mirror may also receive a return beam 131 and guide the return beam to mirror section 163.

[0054] A scanning mirror can be rotated using any suitable actuation mechanism, such as electromagnetic actuation. In an example, the scanning mirror can be actuated by a voice coil motor (which may be referred to as a voice coil actuator), which may include a magnet and a coil. When current is supplied to the coil, a translational force is applied to the magnet, which causes the scanning mirror attached to the magnet to move or rotate. A galvanometer scanner (which may be referred to as a galvanometer actuator) may include a galvanometer-based scanning motor with a magnet and a coil. When current is supplied to the coil, a rotational force is applied to the magnet, which causes the mirror attached to the galvanometer scanner to rotate. The current supplied to the coil can be controlled to dynamically change the position of the galvanometer.

[0055] In some embodiments, scanner 120 may include scanner control unit 121, which can control the scanning mirror to guide the output beam 111 in a desired direction or along a desired scanning pattern. Scanner control unit 121 may generate a drive signal to actuate scanning mirror 125. The drive signal actuating the scanning mirror may include one or more components having different frequencies or one or more individual waveforms. In some cases, the drive signal may be a single drive signal comprising multiple frequency components (e.g., multiplexed frequencies), such that at least one of the frequency components is modulated at a resonant frequency for fast scanning, and at least one of the frequency components is used for slow scanning. The frequency of slow scanning may or may not be a resonant frequency around the slow scanning axis. The signal component used for slow scanning may be a superimposed waveform comprising different frequency components. Alternatively, separate drive signals corresponding to two scanning axes may be provided to the scanning mirror. Details regarding the drive signals and waveform (frequency) components will be described later.

[0056] In some cases, the scanner 120 may also include one or more sensors 123 configured to detect the angular position and / or angular motion of the scanning mirror. A position signal 150 may be transmitted to the scanner control unit 121 to control the scanner's drive signals. In some embodiments, the position signal 150 may be used to synchronize oscillations on two axes, thereby stabilizing the point cloud image frame by frame. For example, by means of the position signal, the zero-velocity position of the horizontal oscillation cycle is synchronized with the start or end of the vertical oscillation cycle, making the pixel (point) coordinates substantially the same across different frames.

[0057] Any suitable sensor can be used to detect the motion or angular position of the scanning mirror. For example, piezoresistive sensors, photodetectors, optical position sensors (OPS), position-sensitive detectors (PSDs), or other sensors can be used to sense motion or position. In some cases, a PSD can be used to measure the angular position of the scanning mirror. Angular position can be measured with an angular resolution of no more than 0.01 degrees, 0.05 degrees, 0.1 degrees, or less than or greater than 0.1 degrees.

[0058] In an optional embodiment, the sensor signal generated by position signal 150 or position sensor 123 can also be used by transmitter module 110 to coordinate the movement of light pulses and scanning mirror. This can advantageously allow adjustment of the distribution or resolution of pixels (measurement points) in the selected area in both fast and slow scanning directions.

[0059] In the case of using a two-dimensional resonant scanner, the scanning speed of the resonant scanner varies continuously in both the horizontal and vertical directions. Like a pendulum, the scanner accelerates towards the center and then decelerates towards the sweep endpoint. It then reverses the cycle. This can result in non-linear horizontal lines (i.e., fast scan lines) and / or undesirable pixel distribution in the scan pattern. Figure 2 Examples of a scan pattern 201 subjected to raster pinch distortion and a raster scan pattern 203 with the distortion corrected are shown. The scan pattern 201 without raster pinch correction is "pinched" at the outer edge of the field of view in the horizontal direction. That is, during successive forward and reverse sweeps of the light pulses, the pixel spacing near the edge of the scan pattern is uneven. This uneven spacing causes pixel overlap or gaps between adjacent rows of pixels. The distribution of the horizontal rows is also uneven in the vertical direction, resulting in sparse pixels towards the center of the field of view and denser pixels towards the top and bottom of the field of view.

[0060] The provided scanner or lidar system can offer improved scanner control so that measurement points along the scan pattern can be stabilized across image frames, utilizing built-in raster shrinkage correction features, allowing the scan pattern to be better approximated as a raster pattern, and / or the distribution (resolution) of pixels along the slow scan direction (i.e., the fast scan cycle along the slow scan direction) can be configured and controlled substantially in real time. As described later herein, the scan path followed by the light pulses responding to the vertical scan of the ramp (taking a single waveform including a low-frequency component and twice the high-frequency component of the fast scan as an example) can approximate a raster scan pattern.

[0061] In some embodiments of the invention, a single scanning mirror can be used to perform oscillating motion about two or more axes. The scanning mirror can be a resonant mirror, its geometry, mass distribution, and structure designed such that the scanning mirror can oscillate at a resonant frequency about one or more axes in response to a drive signal. These two axes can correspond to a fast scanning axis and a slow scanning axis.

[0062] Figure 3 An example of a multi-axis scanning mirror 300 according to some embodiments of the present invention is illustrated schematically. The scanning mirror 300 can be actuated to rotate about a fast scanning axis 301 and a slow scanning axis 303. In the illustrated example, movement about the fast scanning axis 301 can produce a horizontal scanning cycle, and movement about the slow scanning axis 303 can result in a periodic vertical scan.

[0063] In some embodiments, the scanning mirror 300 may include a scanning plate 317. The scanning plate 317 may include a mirror portion formed thereon or attached thereto. The scanning plate 317 may have a diameter or width between approximately 3 mm and 15 mm. The scanning plate 317 may have any shape element, such as circular, elliptical, rectangular, square, and various other shapes. The movement of the scanning plate 317 may be controlled by a system to guide incident light pulses in a desired direction, such as following a scanning pattern.

[0064] The scanning mirror 300 can be coupled to an actuator or mounting structure via a torque arm 315. For example, the torque arm 315 can be mechanically connected to a fixed substrate or mounting structure to receive drive signals. The torque arm 315 can be coupled to a gimbal 316. The gimbal 316 can be of any shape, such as circular, rectangular, elliptical, etc.

[0065] For a given drive frequency, the amplitude of motion of the gimbal 316 (and other structures suspended thereon) can be proportional (though not necessarily linearly proportional) to the voltage of the drive signal and the mechanical amplification factor of the rotating mass at the drive frequency. For drive frequency components at or near the resonant frequency of the gimbal (and suspended structures), the rotational motion about the slow axis 303 can be amplified. For detuned drive frequency components, the rotational amplitude of the gimbal decreases and reverses over certain frequency ranges. In some cases, the frequency of the drive signal can be chosen to be outside the resonant frequency of the slow axis to avoid frequency drift during operation. Alternatively, the resonant frequency drive component can be used to drive an oscillating response around the slow scan axis.

[0066] The inner universal joint 318 can be suspended from the universal joint 316 via a torque arm 311, allowing the inner universal joint ring and the components carried thereon to rotate relative to the universal joint 316 about the fast scan axis 301. The combined mass and mass distribution of the components including the scan plate 317 and the inner universal joint 318, as well as the stiffness of the torque arm 311, determine the resonant frequency and amplification factor for the rotation of the scan plate 317 about the fast scan axis 301. Any suitable resonant frequency and amplification factor of the fast scan axis or both axes can be selected by changing the mass distribution of the components and the stiffness of the mass and / or the torque arm. The oscillation frequency about the fast scan axis can be the resonant frequency, which can be approximately 1 kHz. The fast scan oscillation frequency can be any value below or above 1 kHz. The slow scan oscillation frequency can be any value in the range of approximately 10 Hz to 100 Hz. The slow scan oscillation frequency can be any value below 10 Hz or above 100 Hz. In some cases, the fast scan oscillation frequency and the slow scan oscillation frequency can have a predetermined relationship. For example, the fast scan oscillation frequency can be at least about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90 or 100 times the slow scan oscillation frequency.

[0067] In some embodiments, the scan plate 317 can be coupled to the inner gimbal 318 via a torque arm 313. The torque arm can be coupled to two opposite sides of the scan plate 317. It can be seen that the scan plate 317 is suspended from the inner gimbal 318 via the torque arm 313, allowing the scan plate 317 to rotate relative to the inner gimbal 318 about the slow scan axis 303. The introduction of the torque arm 313 and the inner gimbal 318 allows the scan plate 317 to have an auxiliary mode at twice the resonant frequency of the fast scan axis, thereby correcting raster shrinkage distortion. For example, to correct raster shrinkage distortion, the drive signal can be a single composite drive signal comprising a superposition of a low-frequency (e.g., the resonant frequency of the slow scan axis) vertical drive waveform and a vertical drive sawtooth waveform at twice the resonant frequency of the fast scan axis, with the inner gimbal 318 oscillating at the resonant frequency in mode 2 due to the torque arm and the inner gimbal.

[0068] The scanning mirror 300 may include or be actuated by an actuator (e.g., a coil). The actuator may be driven to generate rotational movement of the gimbal 316, inner gimbal 318, and suspended scanning plate 317 about axes 301, 303. In some cases, combined coils may be included to drive movement of the scanning mirror about two axes. Alternatively or otherwise, separate coils may be driven to generate rotational movement of the scanning plate 317 about a fast scanning axis, and rotational movement of the assembly including the gimbal, inner gimbal, and scanning plate about a slow scanning axis, respectively. When the coils receive a signal that is periodically driven at a rate corresponding to the resonant frequency of the scanning plate 317 about the fast scanning axis (or any frequency that produces a suitable response), the rotational amplitude of the scanning plate about the fast scanning axis can be amplified due to a mechanical amplification factor. Similarly, when the coil receives a signal that is periodically driven at a rate corresponding to the resonant frequency of the components including the scan plate, torque arm, inner universal joint, and gimbal, the components can oscillate around the slow scan axis with enhanced amplitude due to the mechanical amplification factor, thereby achieving a larger angular range with relatively little input energy. Alternatively, the oscillation frequency associated with the slow scan axis may not be at or near the resonant frequency to avoid frequency drift during operation.

[0069] Figure 4 Another example of a multi-axis scanning mirror 400 according to some embodiments of the present invention is illustrated schematically. Similar to the description of... Figure 3 The described scanning mirror 400 can be actuated to rotate about a fast scan axis 401 and a slow scan axis 403. In the illustrated example, periodic motion about the fast scan axis 401 produces a horizontal scan cycle, and periodic motion about the slow scan axis 403 produces a periodic vertical scan. The scanning mirror 400 can have different structures to provide a high-frequency response around the slow scan axis, thereby allowing for a compact overall design of the scanning mirror or an increased effective / active area of ​​the scanning plate.

[0070] Scanning mirror 400 can be used with Figure 3 A similar manner to that described herein is coupled to an actuator or mounting structure via a torque arm 415. For example, the torque arm 415 may be mechanically connected to a fixed substrate or mounting structure to receive a drive signal. The torque arm 415 may be coupled to a gimbal 416, which serves as a support structure for the scanning plate. The gimbal 416 may be of any shape, such as circular, rectangular, elliptical, square, etc.

[0071] For a given drive frequency, the amplitude of motion of the gimbal 416 (and other structures suspended thereon) can be proportional (though not necessarily linearly proportional) to the voltage of the drive signal and the mechanical amplification factor of the rotating mass at the drive frequency. For drive frequency components at or near the resonant frequency of the gimbal (and suspension structures), the rotational motion about the slow axis 403 can be amplified. For detuned drive frequency components, the amplitude of rotation of the gimbal decreases and reverses over certain frequency ranges. In some cases, the frequency of the drive signal can be chosen as a de-harmonic frequency of the slow scan axis to avoid frequency drift during operation. Alternatively, the resonant frequency can be used to drive motion about the slow scan axis to achieve a wider angular range. For example, the combined mass and mass distribution of the assembly including the scan plate 417, any components disposed between the scan plate and the torque arm 415, and the stiffness of the torque arm 415 can determine the resonant frequency and amplification factor for the rotation of the scan plate 417 about the slow scan axis 403.

[0072] The scanning plate 417 can be suspended on the gimbal 416 via a first pair of torque arms 413a, 413b and a second pair of torque arms 411a, 411b, allowing the scanning plate 417 to rotate relative to the gimbal 416 about the fast scanning axis 401 and the slow scanning axis 403. In the illustrated example, the scanning plate 417 can be coupled to the gimbal 416 via an H-shaped structure disposed on opposite sides of the scanning plate 417. Similar to... Figure 3 The example shown, by introducing torque arms 413a and 413b, allows the scan plate 417 to have an auxiliary mode with twice the resonant frequency of the fast scan axis, thereby correcting for grating shrinkage distortion. As shown in the side view 420, a vibrational response around the resonant frequency of the slow scan axis in mode 2 can be achieved. By replacing the inner gimbal and torque arms with H-shaped torque arms, a compact design or a scan plate with increased effective area can be provided at a minimal cost to the overall size of the scan mirror.

[0073] The combined mass and mass distribution of the components including the scan plate 417, torque arms 413a, 413b, and the stiffness of the torque arms 411a, 411b determine the resonant frequency and amplification factor for the rotation of the scan plate 417 around the fast scan axis 401. Any suitable resonant frequency and amplification factor for the fast scan axis, or both axes, can be selected by changing the mass distribution and mass of the components. The oscillation frequency around the fast scan axis can be the resonant frequency, which in some cases can be approximately 1 kHz. The fast scan oscillation frequency can be any value below or above 1 kHz. The slow scan oscillation frequency can be any value in the range of approximately 10 Hz to 100 Hz. The slow scan oscillation frequency can be any value below 10 Hz or above 100 Hz. In some cases, the fast scan oscillation frequency and the slow scan oscillation frequency can have a predetermined relationship. For example, the fast scan oscillation frequency can be at least about 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90 or 100 times the slow scan oscillation frequency.

[0074] The scanning mirror 400 may include or be actuated by an actuator (e.g., a coil). The actuator may be driven to produce rotational motion of the gimbal 416, the H-shaped torsion structure, and the suspended scan plate 417 about axes 401, 403. In some cases, combined coils may be used to drive motion about two axes. Alternatively or otherwise, separate coils may be driven to produce rotational motion of the scan plate 417 about a fast scanning axis, and rotational motion of the assembly including the gimbal, the H-shaped torsion structure, and the scan plate about a slow scanning axis, respectively. When the coils receive a signal that is periodically driven at a rate corresponding to the resonant frequency of the scan plate 417 about the fast scanning axis (or any frequency that produces a suitable response), the rotational amplitude of the scan plate about the fast scanning axis can be amplified due to a mechanical amplification factor. Similarly, when the coil receives a signal that is periodically driven at a rate corresponding to the resonant frequency of an assembly including the scan plate, torque arm, gimbal, and any components carried thereon, the assembly can oscillate around the slow scan axis with enhanced amplitude due to the mechanical amplification factor, thereby achieving an increased angular range with relatively little input energy. Alternatively, the oscillation frequency associated with the slow scan axis may not be at or near the resonant frequency to avoid frequency drift during operation.

[0075] Figure 5An example assembly of a scanning mirror according to an embodiment of the present invention is shown. Scanning mirror 500 may be the same scanning mirror described above. For example, scanning mirror 500 may include a scanning plate 505 coupled to a gimbal 501 via a torque arm 503. The scanning mirror may be attached to or secured to a substrate or mounting unit via a torque arm as described elsewhere herein. In some cases, the scanning mirror, actuator (not shown), and mounting structure may be enclosed in housings 507, 508. The housing may have at least one surface 507 with an opening or hole, allowing light pulses to be incident on the scanning mirror 500 and directed in one or more directions.

[0076] As described above, to correct raster shrinkage distortion and / or stabilize image frames, the drive signals for the slow and fast scan axes can be synchronized such that there is a substantially fixed phase difference between their oscillations. In some cases, the oscillation frequency of the fast scan can be n times the oscillation frequency of the slow scan, where n can be an integer, such as 2, 3, 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 25, 40, 45, 50, 60, 70, 80, 90, 100, or more. In some cases, the oscillating motions about the two axes can be synchronized, and the phase difference can be zero.

[0077] In some embodiments, the sensor (e.g., Figure 1 Synchronization is achieved with the help of a position sensor (123) in the scanner. The sensor can be a position sensor used to control the movement of the scanning mirror. The position signal generated by the position sensor can be used by the scanner control unit to generate drive signals for the scanner. For example, the scanning motion of the scanning plate can be detected by the position sensor and used to synchronize or combine multiple components of the drive signal. A position signal can be generated when the scanning plate reaches the end of a sweep (e.g., the start or end). In some cases, a position signal can be generated and used to trigger a cycle of vertical scanning when the scanning plate reaches the start or end of a horizontal sweep, thereby synchronizing the oscillating motion along the two scanning axes. The position signal can be generated at the beginning or end of a horizontal (i.e., fast scan) sweep cycle. In some embodiments, the position signal can be generated by a position sensor (123) in the scanner control unit to generate drive signals for the scanner. Figure 1 The same position sensor described herein (e.g., sensor 123) generates the position signal. Alternatively, the position signal may be generated by any other sensor capable of detecting the angular position of the scanner.

[0078] Figure 6An example of a sensor 610 configured to provide a signal for synchronizing or combining drive signal components or individual waveforms is shown. For example, the sensor signal can be used as a trigger signal to synchronize periodic slow scanning motion with periodic fast scanning motion. As described above, sensor 610 can be used to detect the angular position and / or angular motion of scanning mirror 620. Scanning mirror 620 can be configured to rotate, tilt, pivot, or move angularly about one or more axes. Scanning mirror 620 can be the same as the scanning plate described elsewhere herein. Any suitable sensor (e.g., a position-sensitive detector) can be used to detect the motion or angular position of the mirror. For example, piezoresistive, photodetector, optical position sensor (OPS), or other sensors can be used to sense motion or angular position. In some embodiments, the position sensor can be a position-sensitive detector (PSD).

[0079] In some cases, the transmitting module can also use position signals to control the light source. For example, the position signal can be used by the transmitting module to coordinate the movement of light pulses and scanning mirrors. This provides the advantage of providing trigger signals that can be used by both the light source controller and the scanner controller without introducing additional components into the lidar system.

[0080] In the illustrated example, the position sensor 610 may be located on one side 621 of the scanning mirror, opposite to the side 623 where the output beam 111 is incident on the scanning mirror 620. The position sensor 610 may be an optical position sensor, which may not be in direct contact with the scanning mirror 620. In the illustrated example, the position sensor 610 may include a light source 612 configured to generate measurement light. The measurement light may be incident on this side 621 of the scanning mirror 620, guided back to the position sensor 610, and captured by the detector component 618. The measurement light may be pulsed or continuous. In some cases, the side 621 of the scanning mirror facing the position sensor 610 may have a reflective surface, allowing the measurement light to be guided back to the position sensor.

[0081] The light source 612 and detector component 618 can be arranged at an angle such that the measurement light emitted by the light source can be captured by the active region of the detector component 618. In some cases, support elements 615, 616, and 617 can be used to position the light source and detector component at a predetermined angle relative to each other and / or relative to the scanning mirror 620. The light source 612 and / or detector component 618 can be permanently fixed to such support elements or detachably coupled to such support elements.

[0082] The light source 612 can be any suitable light source used to generate the measurement light. For example, the light source can include lasers such as solid-state lasers, gas lasers, liquid lasers, semiconductor lasers, fiber lasers, etc. The detector component 618 can be a position-sensitive detector that can measure the position of the light spot one-dimensionally or two-dimensionally on the sensor surface. Based on the position of the light spot, the angle of the scanning mirror can be calculated. Angular position can be measured with an angular resolution of no more than 0.01 degrees, 0.05 degrees, 0.1 degrees, or less than or greater than 0.1 degrees.

[0083] In some cases, the position sensor 610 may include other components, such as a filter 614 or a connection plate 619, to enhance the measurement signal or provide electrical connection and various other functions.

[0084] As mentioned above, fast scans can operate at relatively high scan rates, while slow scans can operate at a scan rate equal to the video frame rate. In some applications, fast scans operate resonantly, while slow scans provide a basic sawtooth pattern, progressively scanning down the frame over a (large) portion of the frame time, then flying back to the top of the frame to restart, or scanning back from bottom to top in a continuous manner. In other applications, interlaced sawtooth scans, triangular wave scans, sine scans, and other waveforms can be used to drive one or two axes. The drive signal can be a composite signal comprising multiple components or individual waveforms.

[0085] One or more components of the drive signal can be synchronized by a clock signal or combined with a fixed phase relationship using a clock signal. Figure 7 An example waveform for driving the scanning mirror is shown. As shown in Example 700, the drive signals for generating rotational motion about the fast scan axis and the slow scan axis can be synchronized by a clock signal 720. The clock signal 720 can have the same frequency as the fast scan as described above, or be a predetermined multiple n (n = 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.) of the fast scan frequency. The clock signal can be a pulse signal, a digital signal, a continuous signal, or any other form. As shown in Example 700, the slow scan waveform 701 can begin in response to the clock signal 720 generated when the fast scan sweep reaches the start / end.

[0086] In some cases, the drive signals used to actuate according to many embodiments of the invention may involve combinations of waveforms. For example, waveform 703 is a high-frequency signal / component for driving a first oscillating motion about a first axis at a corresponding high resonant frequency. In this case, waveform 703 may be a drive frequency component for fast scanning. Waveform 701 is a low-frequency signal for driving a second oscillating motion about a second axis at a corresponding low (resonant) frequency. In this case, waveform 701 may be a drive frequency component for slow scanning. The slow scanning waveform 701 and the fast scanning waveform 703 may be a composite frequency component of the drive signal provided to the scanning mirror.

[0087] In some cases, the pixel distribution (vertical resolution) along the vertical direction or the slow scan direction can be controlled by changing the drive signal used for the slow scan motion. As shown in Example 710, the waveform 710 used to drive the oscillating motion about the slow scan axis can be a composite signal 711 including a low-frequency component 713 and a high-frequency component 715. These two components can be combined with a predetermined phase relationship so that the superimposed signal 711 can drive the scan plate to rotate at an increasing / decreasing speed within a selected time interval (within the vertical scan cycle), thereby decreasing / increasing the pixel density in the selected area. With the aid of a clock signal 720, these two components can be synchronized or combined with a fixed phase relationship.

[0088] Figure 8 An example of waveform 801 for driving a scanning mirror with grating shrinkage correction is shown. The waveform used to actuate the slow scanning motion can be a ramp waveform. The path followed by the scanning beam or a series of light pulses in response to the ramp vertical scan can approximate a grating pattern. The waveform used to drive the oscillating motion about the slow scanning axis can be a composite signal 801 comprising a low-frequency component 803 and a high-frequency component 805. The low-frequency component 803 can be a resonant signal superimposed with a deflection frequency signal, for example, as an approximate sawtooth waveform 805. The low-frequency component 803 may or may not be at or near the resonant frequency around the slow scanning axis. In some cases, the low-frequency component may be at the resonant frequency to achieve a wider range of deflection angles. Alternatively, the low-frequency component may be a deflection frequency to avoid frequency drift during operation. The high-frequency component 805 can approximate a sawtooth wave and can be twice the resonant frequency of the fast scanning axis. The high-frequency component 805 can be used to drive the scan plate to rotate at twice the resonant frequency of the fast scan, and the phase is synchronized by a clock signal. By combining high-frequency components, which are twice the speed of the scanning motion, with low-frequency components and synchronizing them with the help of a clock signal, the scanning mirror can deflect light pulses along essentially parallel paths, including scanning directions from left to right and from right to left, effectively eliminating grating shrinkage distortion.

[0089] Figure 9Another example of a composite drive signal 901, illustrated by individual waveforms 903 and 905, is shown. As shown in the example, the waveform used to drive oscillating motion about a slow scan axis can be a composite signal 901, which includes a low-frequency component 903 and a high-frequency component 905. These two components can be combined with a predetermined phase relationship so that the superimposed signal 901 can drive the scan plate to move at an increasing / decreasing speed within a selected time interval (within the vertical sweep), thereby decreasing / increasing the pixel density in the selected area. In some cases, the high-frequency component may have a varying amplitude, allowing the waveform / amplitude of the combined signal to be adjusted at a fine-grained control level. It should be noted that the high-frequency component 905 can have any arbitrary waveform, as long as the synthesized composite signal 901 can have a desired waveform for slowing down or accelerating the speed in the vertical direction.

[0090] Figure 10 An example illustrating the alteration of a drive signal corresponding to a slow scan motion is shown. In response to the drive signal (e.g., Figure 9 The drive signal 901 adjusts the pixel distribution / density along the vertical direction shown in the scan pattern 1001, thereby increasing the vertical resolution in the central region 1005. This also means that denser measurement pulses are emitted into the central region 1005 of the field of view. This advantageously allows for improved efficiency in sampling the environment.

[0091] It should be noted that the driving signals described above can be combined in any suitable manner to produce the desired effect. For example, by combining the signal components described above, raster shrinkage correction and pixel distribution variation can be performed simultaneously. Figure 11 An example of a scan pattern with a configurable measurement point distribution or pixel resolution is shown. The scan pattern 1101 can be dynamically adjusted by generating a drive signal to the scan mirror. The drive signal may include multiple signal components, wherein a first component has a resonant frequency for fast scanning to generate motion around a fast scan axis, a second component has a (resonant) frequency for slow scanning to generate motion around a slow scan axis, a third component has a frequency twice that of the fast scan to generate high-frequency movement around the slow scan axis (to correct raster shrinkage distortion), and a fourth component has a frequency and / or waveform for changing the speed of the slow scan motion (to adjust the pixel density of a selected area in the vertical direction).

[0092] Multiple components can be combined with a fixed phase difference or synchronized with the aid of a position signal as described elsewhere herein. For example, a first component with a fast scanning resonant frequency can be synchronized with a second component to actuate low-frequency movements of a slow scan with zero phase difference (i.e., the horizontal sweep reaches its start / end position when the vertical scan is at its start / end position). This can also be achieved by selecting resonant frequencies and / or oscillation frequencies for oscillating movements in both directions such that one frequency is a predetermined multiple of the other. Similarly, the first component can also be synchronized with a third component at a frequency twice that of the first component to correct for grating shrinkage distortion. The fourth and second components can have controllable or configurable phase or amplitude relationships, allowing for dynamic control of the slow scanning movement of the scanning mirror based on real-time conditions.

[0093] In some cases, the pixel distribution along the horizontal direction or the fast scanning direction can also be adjusted. This can be achieved by controlling the light source to generate light pulses at desired time intervals. For example, when using a fiber laser, the variable time interval can be achieved by controlling the time interval of the seed light pulses.

[0094] In some cases, a non-uniform pixel (dot) distribution may be preferred so that a dense spot of light can be emitted onto a selected area in a controlled manner. For example, the spot may preferably be denser in the middle of an online scan, or denser in areas where a target object has been detected and detail is required. This advantageously provides adjustable resolution over the selected area, thereby improving the sampling and computational efficiency of lidar imaging. As an example, the pixel distribution and / or scan pattern can be dynamically adjusted in response to the detection of a potential target. The scan pattern or pixel distribution can be dynamically determined based on one or more real-time conditions, including environmental conditions or conditions of the lidar system.

[0095] Figure 12 An example of dynamically configuring the distribution and density of pixels / measurement points in response to real-time conditions is illustrated. In some cases, during the first operating setting 1201, a target of interest 1205 may be identified, and more information may be needed for further identification. In response to identifying the target's position in the field of view, the provided system may adopt a second operating setting 1203 and adjust the drive signals generated for the scanning mirror and the light source accordingly. The second operating setting may result in a higher density of pixels or measurement points allocated to the region of interest.

[0096] In some cases, the scanning pattern or pixel distribution can be dynamically changed to improve the energy efficiency of the lidar system. For example, when the lidar system is detected in a less complex environment (e.g., rural areas), a scanning pattern or resolution with fewer pixels distributed toward the edge of the field of view can be selected. This can be achieved by changing the drive signal or altering one or more components of the drive signal used to actuate the slow scanning motion and / or adjusting the control signal of the light source.

[0097] Figure 13 A block diagram schematically illustrates a control system 1300 for a scanner according to some embodiments of the present invention. The control system 1300 can be coupled with... Figure 1 The scanner control unit described herein is the same. Scan mirror 1301 can be controlled by control system 1300. The scan mirror can be the same as that described elsewhere herein. For example, the scan mirror can include a single multi-axis scan mirror. In some embodiments, scan mirror 1303 can be actuated to rotate about a fast scan axis and a slow scan axis.

[0098] Slow-scan motion can be detected by a position sensor. In some cases, slow-scan motion can be analyzed by signal analyzer 1305. In some cases, slow-scan motion can be a ramp vertical scan at twice the resonant frequency of the fast-scan axis. The various waveforms (characteristics of oscillating motion) associated with slow-scan motion can be extracted by the signal analyzer and fed to controller 1307 for further adjustment or generation of control signals to the slow-scan control unit.

[0099] In some cases, controller 1307 can communicate with a main controller or an external control entity. For example, controller 1307 can receive instructions from the main controller to adjust the drive signal to change the slow scanning motion of the scanning mirror. For example, when a target is detected, controller 1307 can receive instructions containing information about the target's position (coordinates). In response to this instruction, controller 1307 can generate instructions to slow scanning waveform generator 1311 to generate waveforms or component waveforms of the drive signal used to change the vertical / slow scanning motion of the scanning mirror. For example, high-frequency components with varying amplitudes or separate high-frequency waveforms can be generated and added to the signal components used to drive the slow scanning motion, thereby reducing the speed of movement at the target position. With the assistance of a clock signal generated by clock 1309, the variable high-frequency waveform can be combined with other components.

[0100] The individual waveform associated with the slow scan motion can then be sent to the slow scan control unit 1313 to generate a control signal. A drive signal component for actuating the slow scan motion can be generated and combined with a drive signal component for actuating the fast scan motion.

[0101] The rapid scanning motion of the scanning mirror 1301 can be monitored and detected by the position sensor as described above. The rapid scanning motion can be used to generate a clock signal for synchronizing the slow and rapid scanning motions, as described elsewhere herein. In some embodiments, the clock signal can be generated by clock 1309 and provided to the slow scanning waveform generator 1311 to trigger a control signal for the slow scanning motion. The clock signal can also be used to synchronize or combine various signal components of a composite drive signal for the various purposes described above.

[0102] The rapid scanning motion can be fed as feedback information to the rapid scanning control unit 1303 to generate a control signal. The rapid scanning control unit 1303 can dynamically adjust the control signal or generate a drive signal to actuate the rapid scanning motion based on the feedback information.

[0103] In some cases, a combined drive signal, including outputs from the fast scan control unit 1303 and the slow scan control unit 1313, can be sent to the drive circuit of the scanning mirror.

[0104] Control units, functions, algorithms, operations, circuits, or methods can be implemented using software, hardware, firmware, or a combination thereof. In some embodiments, the control unit may include one or more processors and at least one memory for storing program instructions. The processor may be a component of the lidar system. Alternatively, the processor may be external to the lidar system but in communication with it. The processor may be a single or multiple microprocessors, field-programmable gate arrays (FPGAs), or digital signal processors (DSPs) capable of executing a specific set of instructions. Computer-readable instructions may be stored on a tangible, non-transitory computer-readable medium, such as a floppy disk, hard disk, CD-ROM (optical disc read-only memory), MO (magneto-optical), DVD-ROM (digital universal disk read-only memory), DVD RAM (digital universal disk random access memory), or semiconductor memory. The control unit may be a separate device or system in communication with the lidar system. Alternatively, the control unit may be a component of the lidar system. Methods disclosed herein, such as generating variable vertical scan motion in response to real-time conditions, may be implemented in hardware components or a combination of hardware and software, such as ASICs, special-purpose computers, or general-purpose computers.

[0105] The provided laser control or stabilization methods and mechanisms can be used in conjunction with various lidar systems or for a wide range of applications. For example, when a denser spot is needed in a given area, the vertical scanning motion can be altered. In this case, the methods and mechanisms described above can also provide stability and grating shrinkage correction for the scanner.

[0106] A lidar system equipped with the aforementioned scanner control mechanism can be mounted on a moving object to sense the environment around the moving object. Alternatively, the lidar system can be mounted on a stationary object.

[0107] The movable object of the present invention can be configured to move in any suitable environment, such as in the air (e.g., a fixed-wing aircraft, a rotorcraft, or an aircraft without either fixed wings or rotors), in water (e.g., a boat or submarine), on the ground (e.g., a motor vehicle, such as a car, truck, bus, van, motorcycle, bicycle; a movable structure or frame, such as a stick, fishing rod; or a train), underground (e.g., a subway), in space (e.g., a space shuttle, satellite, or probe), or any combination of these environments. The movable object can be a vehicle, such as the vehicle described elsewhere herein. In some embodiments, the movable object can be carried by a living body or launched from a living body, such as a person or animal.

[0108] In some cases, a movable object can be an autonomous vehicle, which may be referred to as an autonomous car, driverless car, self-driving car, robotic car, or driverless car. In other cases, an autonomous vehicle can refer to a vehicle configured to sense its environment and navigate or drive with little or no human input. For example, an autonomous vehicle may be configured to drive to any suitable location and control or perform all safety-critical functions (e.g., driving, steering, braking, parking) throughout the journey without requiring constant driver control. As another example, an autonomous vehicle may allow the driver to safely divert their attention from driving tasks in a specific environment (e.g., on a highway), or an autonomous vehicle may provide control of the vehicle in all but a few environments, requiring little or no driver input or attention.

[0109] In some cases, lidar systems can be integrated into vehicles as part of autonomous driving systems. For example, a lidar system can provide information about the surrounding environment to the autonomous vehicle's driving system. In one example, a lidar system can provide the vehicle with a 360-degree horizontal field of view. The autonomous vehicle driving system may include one or more computing systems that receive information about the surrounding environment from the lidar system, analyze the received information, and provide control signals to the vehicle's driving system (e.g., steering wheel, accelerator, brake, or turning signals).

[0110] As used herein, A and / or B includes one or more of A or B, and combinations thereof, such as A and B. It should be understood that although the terms “first,” “second,” “third,” etc., are used herein to describe various elements, components, regions, and / or portions, these elements, components, regions, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, or portion from another. Therefore, without departing from the teachings of the invention, the first element, component, region, or portion discussed herein may be referred to as the second element, component, region, or portion.

[0111] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that, when used in this specification, the terms “comprising” and / or “including” or “comprises” and / or “including” designate the stated features, regions, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0112] Throughout this specification, references to "some embodiments" or "one embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Therefore, the phrases "some embodiments" or "one embodiment" appearing in various places in this specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0113] While preferred embodiments of the invention have been shown and described herein, these embodiments will be apparent to those skilled in the art if provided by way of example only. Many variations, modifications, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. Many different combinations of the embodiments described herein are possible, and such combinations are considered part of this disclosure. Furthermore, all features discussed in connection with any embodiment herein can be readily applied to other embodiments herein. The following claims are intended to define the scope of the invention and are thereby covered by the methods and structures within the scope of these claims and their equivalents.

Claims

1. A method for controlling a scanner in a lidar system, comprising: Generate a drive signal that includes a first component of a first frequency and a second component of a second frequency; The drive signal is sent to the scanner, which is configured to move in a first cycle around a first axis at a first frequency and in a second cycle around a second axis at a second frequency; as well as The drive signal is changed to change the movement speed of the scanner, thereby changing the resolution of the selected area; Wherein, the selected area includes a region of interest, and changing the resolution in the selected area includes: increasing the resolution in the selected area; and / or, the selected area includes the edge region of the field of view of the lidar, and changing the resolution in the selected area includes: decreasing the resolution in the selected area.

2. The method as described in claim 1, characterized in that, The scanner has a resonant response at a first frequency; The method of changing the drive signal to change the movement speed of the scanner includes: The second component is changed to change the movement speed of the scanner in the second cycle.

3. The method as described in claim 1, characterized in that, The method further includes: The scanner's position sensor generates a position signal; The method of changing the drive signal to change the movement speed of the scanner includes: The drive signal is changed according to the position signal to change the movement speed of the scanner.

4. The method as described in claim 1, characterized in that, The method of changing the drive signal to change the movement speed of the scanner includes: The drive signal is changed according to real-time conditions to change the movement speed of the scanner.

5. The method as described in claim 4, characterized in that, The real-time conditions include the detection of a target.

6. The method as described in claim 1, characterized in that, The method further includes: The time interval of the light pulse sequence emitted by the lidar system is changed to alter the resolution of the selected area.

7. A scanning device for a lidar system, comprising: A control system configured to generate a drive signal, wherein the drive signal includes a first component and a second component, the first component including a first frequency and the second component including a second frequency; A scanning mirror includes a first axis and a second axis; the scanning mirror receives the drive signal and is configured to perform a first cycle motion around the first axis at a first frequency and a second cycle motion around the second axis at a second frequency. The control system is configured to change the drive signal to change the movement speed of the scanning mirror and change the resolution in the selected area; Wherein, the selected area includes a region of interest, and changing the resolution in the selected area includes: increasing the resolution in the selected area; and / or, the selected area includes the edge region of the field of view of the lidar, and changing the resolution in the selected area includes: decreasing the resolution in the selected area.

8. The scanning device as claimed in claim 7, characterized in that, The scanning mirror has a resonant response at a first frequency; The control system includes a controller configured to change the second component to change the movement speed of the second cycle of the scanning mirror.

9. The scanning apparatus as described in claim 7 or 8, characterized in that, The control system includes a fast scan control unit; The fast scan control unit is configured to change the first component to change the movement speed of the scanning mirror in the first cycle.

10. The scanning device as claimed in claim 9, characterized in that, It also includes a position sensor; the control system also includes a signal analyzer; The position sensor is configured to generate a position signal; The signal analyzer is configured to receive the position signal and output a control signal; Wherein, the controller changes the second component according to the control signal; and / or, the fast scan control unit changes the first component according to the control signal.

11. The scanning apparatus as claimed in claim 10, characterized in that, The position sensor includes at least one of the following: Optical position sensor; or, Position-sensitive detector.

12. The scanning device as claimed in claim 9, characterized in that, The control system also includes a clock; The clock is configured to generate a clock signal used to synchronize the first periodic motion and the second periodic motion.

13. A lidar system, comprising: The transmitting module is configured to generate a laser beam; Detection module; The scanning apparatus as described in any one of claims 7-12 is configured to receive the laser beam and scan it outwards into the external environment, and to receive the echo of the laser beam after it has been reflected by an object and reflect it back to the detection module.

14. The lidar system as described in claim 13, characterized in that, The transmitting module emits multiple laser beams; The transmitting module is also configured to change the time interval between the plurality of laser beams to change the resolution of the selected area.

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