Dynamic laser power control for LiDAR systems

Abstract

Embodiments of the present invention provide an optical sensing system, a method of controlling a transmit power level in an optical sensing system, and a control device for controlling a transmit power level in an optical sensing system. An exemplary optical sensing system includes a transmitter configured to transmit a light beam from a plurality of vertical detection angles to scan an object. The optical sensing system also includes a controller configured to dynamically vary a transmit power level of the light beam transmitted at the respective vertical detection angles. The optical sensing system also includes a receiver configured to detect the light beam returned by the object.

Description

[0001] Cross-references

[0002] This application claims priority to U.S. Patent Application No. 16 / 920,650, filed July 3, 2020, the entire contents of which are expressly incorporated herein by reference. Technical Field

[0003] This disclosure relates to laser power control for optical detection and ranging (LiDAR) systems, and more specifically, to dynamic laser power control to compensate for variations in detection distance at different vertical detection angles in a LiDAR system. Background Technology

[0004] Optical sensing systems, such as LiDAR systems, have been widely used in advanced navigation technologies, such as assisting autonomous driving or generating high-resolution maps. For example, a typical LiDAR system measures the distance to a target by illuminating it with a pulsed laser beam and using sensors, such as detectors or detector arrays, to measure the reflected pulses. Differences in the laser's return time, wavelength, and / or phase can be used to construct a digital three-dimensional (3D) representation of the target. Because it uses a narrow laser beam as the incident light, it can map physical features with very high resolution, making LiDAR systems particularly suitable for sensing applications such as autonomous driving and high-resolution mapping.

[0005] LiDAR systems typically emit pulsed laser beams that are pointed in multiple directions to cover the field of view (FOV). For example, the vertical detection angle of a LiDAR system (called the view angle when the scanning laser beam is pointed downwards) varies as objects in vertical space are scanned. The required detection distance also varies with the vertical detection angle. For instance, when the view angle is small, meaning the scanning laser beam emitted by the LiDAR is almost horizontal, the distance to the object is relatively long. On the other hand, as the view angle increases, the distance towards the ground decreases.

[0006] Traditional LiDAR systems use a constant laser emission power for different vertical detection angles. This leads to several problems. First, the laser beam reflected by objects at shorter distances (e.g., close to the ground) may carry high power, causing saturation at the receiver and impairing scanning accuracy. The increased operating temperature due to high power reduces the system's thermal performance. Furthermore, high-power laser beams can pose an eye safety hazard to pedestrians near the LiDAR scanning area. Using a constant power at different vertical angles also compromises the overall system power efficiency.

[0007] Embodiments of the present invention improve the performance of optical sensing systems (e.g., LiDAR systems) by implementing dynamic laser power control to compensate for changes in the detection distance of the sensing system at different vertical detection angles. Summary of the Invention

[0008] Embodiments of the present invention provide an optical sensing system. An exemplary optical sensing system includes a transmitter configured to emit light beams from multiple vertical detection angles to scan an object. The optical sensing system further includes a controller configured to dynamically change the emission power level of the light beams emitted at each vertical detection angle. The optical sensing system also includes a receiver configured to detect the light beams reflected back from the object.

[0009] Embodiments of the present invention also provide a method for controlling the transmission power level in an optical sensing system. The method includes scanning an object by emitting light beams from multiple vertical detection angles via a transmitter. The method further includes dynamically changing the transmission power level of the light beams emitted at each vertical detection angle via a controller. The method also includes detecting the light beams reflected back from the object via a receiver.

[0010] Embodiments of the present invention also provide a control device for controlling the emission power level in an optical sensing system. The control device includes a drive circuit configured to drive an emitter to emit a light beam at dynamically varying emission power levels. The light beam is emitted at multiple vertical detection angles. The control device further includes a controller configured to control the drive circuit to dynamically change the emission power level of the light beam emitted at each vertical detection angle.

[0011] It should be understood that, as required, the above general description and the following detailed description are merely exemplary and explanatory descriptions, and not restrictive descriptions of the invention. Attached Figure Description

[0012] Figure 1 A schematic diagram of an exemplary vehicle equipped with a LiDAR system according to some embodiments of the present disclosure is shown;

[0013] Figure 2 A block diagram of an exemplary LiDAR system according to some embodiments of the present disclosure is shown;

[0014] Figure 3 A schematic diagram of an exemplary controller for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure is shown;

[0015] Figure 4 The vertical detection angle and corresponding detection distance used during LiDAR scanning according to some embodiments of the present disclosure are shown;

[0016] Figure 5 An exemplary emitter drive circuit for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure is shown;

[0017] Figure 6 A flowchart is shown of an exemplary method for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail with reference to examples thereof, which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to denote the same or similar parts.

[0019] Embodiments of this disclosure provide systems and methods for dynamically controlling the emission power level in an optical sensing system (e.g., a LiDAR system). For example, the optical sensing system may include an emitter configured to emit a light beam (e.g., a laser beam) at multiple vertical detection angles to scan an object. Smaller vertical detection angles result in longer detection distances; larger vertical detection angles result in shorter detection distances. In some embodiments, the optical sensing system includes a controller configured to dynamically change the emission power level of the light beam emitted at each vertical detection angle. For example, the emission power level may be adjusted based on the detection distance at different vertical detection angles, since shorter detection distances ensure less laser power is used. In some embodiments, the emission power level may be proportional to the square of the detection distance. In some embodiments, the emission power level may also be proportional to the ratio of the reflectivity of the ground to the reflectivity of the object. As another example, the controller may determine a threshold angle based on the height of the optical sensing system above the ground and a threshold detection distance of the optical sensing system. Then, when the vertical detection angle is greater than the threshold angle, the controller reduces the emission power level.

[0020] In some embodiments, the transmitter may further include an emitter configured to emit a light beam and a drive circuit (e.g., a FET control drive circuit or a capacitor discharge drive circuit) configured to drive the emitter to emit the light beam at dynamically varying power levels. For example, a controller is configured to provide a voltage command signal to the drive circuit, and the drive circuit is configured to provide a varying drive current to the emitter in response to the voltage command signal. In some embodiments, the controller is configured to change the amplitude or pulse width of the voltage command signal such that the varying drive current is proportional to the desired power level. The emitted light beam is reflected back from the scanned object and received by a receiver of an optical sensing system.

[0021] By dynamically and adaptively varying the transmit power level, embodiments of the present invention improve the performance of the optical sensing system. For example, system power consumption can be more effectively distributed across different vertical viewing angles. This not only saves the overall system power but also improves eye safety in areas close to the ground. Furthermore, reducing output power also benefits the system's thermal and laser efficiency. The improved optical sensing system has broad application prospects. For instance, it can be used in advanced navigation technologies, such as assisted autonomous driving or high-definition map generation, where the optical sensing system can be mounted on a vehicle.

[0022] For example, Figure 1 A schematic diagram of an exemplary vehicle 100 equipped with an optical sensing system (e.g., a LiDAR system) 102 (hereinafter also referred to as LiDAR system 102) according to some embodiments of the present disclosure is shown. Consistent with some embodiments, vehicle 100 may include a survey vehicle configured to acquire data for constructing high-definition maps or 3-D building and city models. Vehicle 100 may also be an autonomous vehicle.

[0023] like Figure 1 As shown, vehicle 100 may be equipped with a LiDAR system 102 mounted on vehicle body 104 via mounting structure 108. Mounting structure 108 may be an electromechanical device mounted on or otherwise connected to the vehicle body 104 of vehicle 100. In some embodiments, mounting structure 108 may use screws, adhesives, or other mounting mechanisms. Vehicle 100 may additionally equip sensor 110 inside or outside vehicle body 104 using any suitable mounting mechanism. Sensor 110 may include sensors for a navigation unit, such as a Global Positioning System (GPS) receiver and one or more Inertial Measurement Unit (IMU) sensors. It is contemplated that the manner in which LiDAR system 102 or sensor 110 may be mounted on vehicle 100 is not limited to... Figure 1 The examples shown are limitations and can be modified depending on the type of LiDAR system 102 and sensor 110 and / or vehicle 100 to achieve the desired 3D sensing performance.

[0024] Consistent with some embodiments, the LiDAR system 102 and sensor 110 can be configured to capture data as the vehicle 100 moves along a trajectory. For example, the transmitter of the LiDAR system 102 can be configured to scan the surrounding environment. The LiDAR system 102 measures the distance to a target by illuminating it with a pulsed laser beam and measuring the reflected / scattered pulses with a receiver. The laser beam used for the LiDAR system 102 can be ultraviolet, visible, or near-infrared. In some embodiments of this disclosure, the LiDAR system 102 can capture a point cloud that includes depth information of objects in the surrounding environment. As the vehicle 100 moves along the trajectory, the LiDAR system 102 can continuously capture data. Each set of scene data captured within a certain time range is called a data frame.

[0025] In some embodiments, the LiDAR system 102 can be installed at a certain height above the ground (e.g., Figure 1 As shown in h0), this allows the use of laser beams emitted at different vertical detection angles to scan an object within a certain height range. For example, Figure 1 The field of view (FOV) is shown, which consists of the range of vertical detection angles covering an object 112 at a height of h1 above the ground. The vertical detection angle is relative to the horizontally upward laser beam (e.g., Figure 1 The angle α shown can be called the upward angle, which is the vertical detection angle relative to the horizontally downward laser beam (e.g., Figure 1 The angle θ shown can be called the top-down angle.

[0026] In some embodiments, the vertical detection angle of the LiDAR system 102 can be adjusted via the mounting structure 108 and / or the scanner within the LiDAR system 102. In some embodiments, the vertical detection angle may also be affected by the attitude of the vehicle 100, for example, whether the vehicle 100 is traveling uphill or downhill. When the viewing angle θ is greater than a certain value, the laser beam emitted by the LiDAR system 102 may collide with the target group, resulting in a detection distance that is less than the maximum detection distance. In this case, due to the shorter transmission distance of the laser beam, its attenuation is less, and the remaining power in the returned laser beam is higher. According to this disclosure, the LiDAR system 102 is configured to dynamically and adaptively adjust the emission power level of its laser beam emitted during scanning to compensate for the shorter detection distance at larger vertical detection angles θ.

[0027] Figure 2A block diagram of an exemplary LiDAR system 102 according to an embodiment of the present disclosure is shown. The LiDAR system 102 may include a transmitter 202, a receiver 204, and a controller 206. The transmitter 202 may emit a light beam (e.g., a laser beam) in multiple directions. The transmitter 202 may include one or more laser sources (including a laser emitter 208 and driving circuitry 218) and a scanner 210. Figure 2 As shown, transmitter 202 can continuously emit pulsed laser beams in different directions within a scanned field of view (e.g., an angular range).

[0028] The laser emitter 208 can be configured to provide a laser beam 207 (also referred to as a "natural laser beam") to the scanner 210. In some embodiments of the invention, the laser emitter 208 can generate a pulsed laser beam in the ultraviolet, visible, or near-infrared wavelength range. In some embodiments of this disclosure, the laser emitter 208 may include a pulsed laser diode (PLD), a vertical-cavity surface-emitting laser (VCSEL), a fiber laser, etc. For example, the PLD may be a semiconductor device similar to a light-emitting diode (LED), wherein the laser beam is generated at the junction of the diode. In some embodiments of the invention, the PLD includes a PIN diode, wherein the active region is located in the intrinsic (I) region, and charge carriers (electrons and holes) are pumped into the active region from the N-region and the P-region, respectively. Depending on the semiconductor material, the wavelength of the incident laser beam 207 provided by the PLD may be less than 1100 nm, for example, between 405 nm, 445 nm and 465 nm, between 510 nm and 525 nm, 532 nm, 635 nm, between 650 nm and 660 nm, 670 nm, 760 nm, 785 nm, 808 nm, 848 nm, or 905 nm. It should be understood that any suitable laser source can be used as the laser source to emit the laser beam 207.

[0029] The driving circuit 218 provides power to the laser emitter 208 to turn it on, thereby driving the laser emitter. Consistent with embodiments of this disclosure, the driving circuit 218 can be controlled to adjust the emission power level of the laser emitter 208. For example, the drive current of the driving circuit 218 can be varied to cause the laser emitter 208 to emit laser beams at different emission power levels. In some embodiments, the varying drive current provided by the driving circuit 218 is proportional to the dynamically varying emission power level. The driving circuit 218 can be implemented using any suitable circuit topology to achieve the desired functionality. For example, in some embodiments, the driving circuit 218 may be a FET control driving circuit or a capacitor discharge driving circuit.

[0030] Scanner 210 can be configured to emit a laser beam 209 toward object 212 within a vertical detection angle range (together forming the field of view (FOV) of emitter 202, such as...). Figure 1 (As shown). The vertical detection angle can be an upward angle (pointing up from the horizontal) or a downward angle (pointing down from the horizontal). In some embodiments, the scanner 210 may also include optical components (e.g., lenses, mirrors) to collimate the pulsed laser into a narrow laser beam to increase the scanning resolution and the range of the scanned object 212.

[0031] In some embodiments, the object 212 may be made of a variety of materials, including, for example, nonmetallic objects, rocks, rainwater, compounds, aerosols, clouds, or even single molecules. The wavelength of the laser beam 209 may vary based on the composition of the object 212. In some embodiments, at each point in time during scanning, the scanner 210 may emit the laser beam 209 toward the object 212 in a direction within the scanning angle range by rotating a deflector (e.g., a micromachining mirror assembly).

[0032] In some embodiments, receiver 204 can be configured to detect a laser beam 211 returning from object 212. The returning laser beam 211 may be in a different direction from laser beam 209. Receiver 204 can collect the laser beam returning from object 212 and output an electrical signal reflecting the intensity of the returning laser beam. Upon contact, the laser beam can be reflected / scattered by object 212 through backscattering (e.g., Rayleigh scattering, Mie scattering, Raman scattering, and fluorescence). Figure 2 As shown, receiver 204 may include lens 214 and detector 216. Lens 214 may be configured to collect light from various directions within the receiver's field of view (FOV) and converge the beam to focus it on detector 216. At various points in time during the scan, lens 214 may collect the returning laser beam 211. The returning laser beam 211 may return from object 212 and has the same wavelength as laser beam 209.

[0033] Detector 216 may be configured to detect a returning laser beam 211 that returns from object 212 and is converged by lens 214. In some embodiments, detector 216 may convert the laser beam converged by lens 214 (e.g., the returning laser beam 211) into an electrical signal 213 (e.g., a current or voltage signal). The electrical signal 213 may be generated when photons are absorbed by a photodiode contained in detector 216. In some embodiments, detector 216 may include a PIN detector, an avalanche photodiode (APD) detector, a single-photon avalanche diode (SPAD) detector, a silicon photomultiplier (SiPM) detector, etc.

[0034] The electrical signal 213 can be transmitted to a data processing unit, such as the signal processor 220 of the LiDAR system 102, for processing and analysis. For example, the signal processor 220 can determine the distance between the object 212 and the LiDAR system 102 based on the data from the electrical signal 213 and the laser beam 209. In some embodiments, the signal processor 220 may be part of the controller 206.

[0035] Controller 206 can be configured to control transmitter 202 and / or receiver 204 to perform detection / sensing operations. In some embodiments, controller 206 can dynamically determine an appropriate emission power level for laser emitter 208 based on the vertical detection angle of LiDAR system 102 and control drive circuit 218 to adjust the emission power of laser emitter 208 to an appropriate level. For example, controller 206 can determine the detection distance at various vertical detection angles and calculate the desired emission power level based on the detection distance. In some embodiments, the emission power level can be proportional to the square of the detection distance. In some further embodiments, the emission power level can also be proportional to the ratio of the reflectivity of the ground to the reflectivity of object 212. For example, controller 206 can determine the reflectivity of object 212 based on the returned laser beam received by receiver 204. In another example, controller 206 can determine a threshold angle based on the upward angle of LiDAR system 102 located above the ground and a threshold detection distance of LiDAR system 102. When the vertical detection angle is greater than the threshold angle, controller 206 can reduce the emission power level.

[0036] In some embodiments, the controller 206 may control the drive circuit 218 to dynamically change the emission power level of the laser emitter 208 at various vertical detection angles. For example, the controller 206 may provide a voltage command signal to the drive circuit 218 so that the drive circuit provides a varying drive current to the laser emitter 208 in response to the voltage command signal provided by the controller 206.

[0037] For example, Figure 3 The figure illustrates a schematic diagram of an exemplary controller 206 for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure. Figure 3As shown, controller 206 may include communication interface 302, processor 304, memory 306, and storage 308. In some embodiments, controller 206 may have different modules in a single device, such as integrated circuit (IC) chips (e.g., implemented as application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs), or stand-alone devices with dedicated functions. In some embodiments, one or more components of controller 206 may be located in the cloud, or alternatively in a single location (e.g., inside a mobile device) or distributed locations. Components of controller 206 may be in an integrated device or distributed in different locations but communicate with each other via a network (not shown in the figures). According to this disclosure, controller 206 may be configured to dynamically control the emission power level of a laser beam emitted by laser emitter 208 based on different vertical detection angles of the emitted laser beam. In some embodiments, controller 206 may also perform various other control functions of other components of LiDAR system 102.

[0038] Communication interface 302 can be connected via communication cable, wireless local area network (WLAN), wide area network (WAN), wireless network (such as radio waves), cellular network and / or local or short-range wireless network (such as Bluetooth). TM The communication interface 302 can transmit and receive signals to components of transmitter 202 (such as driver circuitry 218 and scanner 210) and receiver 204 via other communication methods. In some embodiments, the communication interface 302 may include an Integrated Services Digital Network (ISDN) card, a cable modem, a satellite modem, or a modem to provide a data communication connection. As another example, the communication interface 302 may include a Local Area Network (LAN) card to provide a data communication connection to a compatible LAN. A wireless link can also be implemented via the communication interface 302. In this implementation, the communication interface 302 can transmit and receive electrical, electromagnetic, or optical signals in analog or digital form.

[0039] According to some embodiments, the communication interface 302 can receive electrical signals from the returned laser beam from the receiver 204. The communication interface 302 can provide control signals to the drive circuitry to dynamically adjust the emission power level of the emitted laser beam. The communication interface 302 can also receive acquired signals from various other components of the LiDAR system 102 and provide control signals thereto.

[0040] Processor 304 may include any suitable type of general-purpose or special-purpose microprocessor, digital signal processor, or microcontroller. Processor 304 may be configured as a separate processor module specifically for LiDAR transmit power control, for example, dynamically determining an appropriate transmit power level for the emitted laser beam based on different vertical detection angles of the emitted laser beam and generating control signals to control the drive circuit 218 to achieve that transmit power level. Alternatively, processor 304 may be configured as a shared processor module for performing other functions of LiDAR control.

[0041] Memory 306 and memory 308 may include any suitable type of mass storage provided to store any type of information that processor 304 may need to operate. Memory 306 and memory 308 may include volatile or non-volatile, magnetic, semiconductor, magnetic tape, optical, removable, non-removable, or other types of storage devices or tangible (i.e., non-transitory) computer-readable media, including but not limited to ROM, flash memory, dynamic RAM, and static RAM. Memory 306 and / or memory 308 may be configured to store one or more computer programs that can be executed by processor 304 to perform the functions disclosed herein. For example, memory 306 and / or memory 308 may be configured to store a program for dynamic LiDAR power control that can be executed by processor 304. In some embodiments, memory 306 and / or memory 308 may also store intermediate data, such as threshold vertical detection angles, detection distances corresponding to different vertical detection angles, reflectivity of the scanned object, expected emission power levels for each vertical detection angle, etc.

[0042] like Figure 3 As shown, processor 304 may include multiple modules, such as a detection distance determination unit 342, a power level determination unit 344, and an instruction signal generation unit 346. These modules may be hardware units of processor 304 (e.g., part of an integrated circuit), designed to be used in conjunction with other components or software units implemented by processor 304 by executing at least a portion of a program. This program may be stored on a computer-readable medium and, when executed by processor 204, may perform one or more functions. Although Figure 3 Units 342-346, all within a single processor 304, are shown, but it is conceivable that these units could be distributed among different processors, either close to or far from each other.

[0043] In some embodiments, the detection distance determination unit 342 can calculate the detection distance within the transmitter's field of view (FOV) corresponding to various vertical detection angles. For example, Figure 4 The vertical detection angle and corresponding detection distance used during LiDAR scanning according to an embodiment of the present invention are shown. Figure 4As shown, the LiDAR system 102 can be located at a height of [missing information - likely a specific height or height] above the ground. For example, the LiDAR system 102 can be mounted on a vehicle 100, thus allowing it to be raised above the ground. The LiDAR system 102 may have the largest detection range. (Also known as the threshold detection distance), corresponding to the horizontal distance between object 112 and LiDAR system 102. The maximum output power of laser emitter 208 at the maximum detection distance is... .

[0044] In some embodiments, the detection distance can be calculated as a function of the vertical detection angle (e.g., Figure 4 The vertical detection angle (θ) is shown. For example, the vertical detection angle can be determined based on the vertical scanning angle of scanner 210, the tilt angle of LiDAR system 102 (e.g., via mounting structure 108), and the upward angle if the vehicle with LiDAR system 102 is traveling on a slope (e.g., uphill or downhill). In some embodiments, the vertical scanning angle of scanner 210 can be stored in controller 206 or obtained from another controller that controls the laser beam scanning. If the vertical scanning angle is not zero, the vertical detection angle is obtained by subtracting the tilt angle and / or the upward angle from the vertical scanning angle. For example, if the vertical scanning angle is 40°, the LiDAR system 102 is tilted upward by 10°, and the vehicle 100 is traveling downhill at a slope of 15° (i.e., upward angle -15°), then the vertical detection angle is determined to be 40° - 10° - (-15°) = 45°.

[0045] In some embodiments, for vertical detection angles within two ranges, the detection distance can be calculated in different ways: the first range is [0, ... ],in It is the threshold angle, and the second range is [ [90°]. In some embodiments, the threshold angle It can be determined according to equation (1):

[0046] (1)

[0047] in, The height of the LiDAR system 102 above the ground plane. This represents the maximum detection distance.

[0048] When the vertical detection angle (e.g.) Figure 4 The top-down angle θ shown is less than (i.e., within the first range) the detection distance remains When the downward viewing angle θ is greater than (i.e., within the second range) detection distance The detection distance decreases. In some embodiments, the detection distance can be determined using equation (2):

[0049] (2)

[0050] Based on the determined detection distance, the power level determination unit 344 can calculate the appropriate emission power level output by the laser emitter 208. In some embodiments, for distances less than the maximum detection distance... Detection distance (That is, for angles greater than the threshold) The vertical detection angle θ), and the power level determination unit 344 can determine the transmit power level from the maximum available output power level. Reduced to a smaller but sufficient level. In some embodiments, the transmit power level may be proportional to the square of the corresponding detection distance. In some embodiments, the transmit power level is proportional to the ratio of the second reflectivity of the ground to the first reflectivity of the target object. For example, the power level determination unit 344 may calculate the transmit power level at the top-down viewing angle θ according to equation (3). ):

[0051] (3)

[0052] in, This represents the maximum available output power level. The reflectivity of the target object. The reflectivity of the ground plane, The detection distance is the angle of view θ. The maximum detection distance is specified. In some embodiments, the reflectivity of the ground plane can be preset and pre-programmed into the controller 206. In some embodiments, the reflectivity of the target object (e.g., object 112) can be dynamically determined based on the returned laser beam signal received in real time by the receiver 204.

[0053] Once the emission power level is determined, the command signal generation unit 346 can generate a command signal to control the drive circuit 218, driving the laser emitter 208 to emit a laser beam at the determined emission power level. In some embodiments, a voltage command signal can be generated and provided to the drive circuit 218. In response to the voltage command signal, the drive circuit 218 can provide a varying drive current to the laser emitter 208. In some embodiments, the varying drive current can be proportional to the emission power level through the laser emitter 208. Therefore, the emission power level can be controlled by adjusting the voltage command signal generated by the command signal generation unit 346.

[0054] Figure 5An exemplary emitter drive circuit for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure is illustrated. In some embodiments, the drive circuit 218 uses a semiconductor switch (e.g., gallium nitride (GaN) power FETs) that controls a voltage command signal V applied to the controller 206. command The instruction has a gate response (e.g., drive current i) LASER The driving circuit can be connected in series with the laser emitter 208 to make the driving current i LASER A laser beam is emitted by flowing through a laser diode. The emission power level of the laser emitter 208 is generally proportional to the product of the amplitude and pulse width of the drive current provided by the drive circuit 218. Therefore, the emission power level can be adjusted by applying appropriate control signals. For example, based on the desired emission power level, the command signal generation unit 346 can change one or more control signals applied to one or more components of the drive circuit 218 to change the amplitude or pulse width of the drive current. In some embodiments, the pulse width of the driver current can be controlled by a voltage command signal generated by the command signal generation unit 346. In some other embodiments, the amplitude of the drive current can be controlled by controlling the power supply voltage of the drive circuit 218.

[0055] Figure 5 The capacitor discharge drive circuit 510 and FET control drive circuit 520 are shown as examples of drive circuit 218. It is conceivable that drive circuit 218 can employ other suitable circuit topologies. In some embodiments, capacitor discharge drive circuit 510 uses a small Cbus, so Vbus varies with the capacitor charging and discharging time. As a result, the circuit is shown in the figure below, and the FET gate response includes a pulse width ratio V... command Narrow pulse drive current i LASER In contrast, the FET control drive circuit 520 uses a large Cbus, so Vbus is almost constant. As a result, the drive current i in the gate response shown in the figure below... LASER The pulse width is almost the same as V command The pulse widths are consistent. In some embodiments, the capacitor discharge drive circuit 510 may be preferred due to its faster switching and ability to accept stray inductance.

[0056] Figure 6 A flowchart of an exemplary method 600 for adjusting the laser power of a LiDAR system according to some embodiments of the present disclosure is shown. In some embodiments, method 600 may be performed by various components of the LiDAR system 102, such as transmitter 202, receiver 204, and controller 206. In some embodiments, method 600 may include steps S602-620. It should be understood that some steps may be optional. Furthermore, some steps may be performed simultaneously or in combination with... Figure 6 The different execution sequences shown are illustrated.

[0057] In step S602, controller 206 may determine the vertical detection angle of the current scan angle. In some embodiments, controller 206 may receive the current scan angle used by transmitter 202. In some embodiments, controller 206 may be the same controller that determines scan parameters and thus stores said parameters in its memory / storage. Therefore, controller 206 can retrieve the scan angle from its own memory / storage. Otherwise, controller 206 may receive it from an external source. In some embodiments, if the vehicle is traveling on a slope, detection distance determination unit 342 may first determine the current vertical detection angle based on the scan angle and the upward angle adjusted by the tilt angle of LiDAR system 102.

[0058] In step S604, the controller 206 can calculate the detection distance corresponding to the current vertical detection angle. For example, when the vertical detection angle θ is less than a threshold angle... During calculation, according to equation (1), the detection distance determination unit 342 can determine the detection distance to maintain the maximum detection distance. When the angle θ is greater than At that time, the detection distance determination unit 342 can utilize height The detection distance is determined by the trigonometric functions of angle θ, as shown in equation (2).

[0059] In step S606, the controller 206 can determine the transmission power level of the current scanning angle based on the detection distance determined in step S604. In some embodiments, for distances less than the maximum detection distance... Detection distance The power level determination unit 344 can determine the transmit power level from the maximum available output power level. The power level is reduced to a smaller but sufficient level. In some embodiments, the transmit power level may be proportional to the square of the corresponding detection distance. In some embodiments, the transmit power level is proportional to the ratio of the second reflectivity of the ground to the first reflectivity of the target object. For example, the power level determination unit 344 may calculate the transmit power level according to equation (3).

[0060] In step S608, controller 206 may generate control signals to be applied to one or more components of drive circuit 218 corresponding to the emission power level determined in step S606. In some embodiments, command signal generation unit 346 may generate control signals to cause drive circuit 218 to increase drive current to laser emitter 208, so that laser emitter 208 emits a laser beam at a determined emission power level. Since the emission power level is generally proportional to the product of the amplitude of drive current and pulse width, the control signal generated by command signal generation unit 346 may change the amplitude of drive current or pulse width. For example, command signal generation unit 346 may control the supply voltage (Vbus) of capacitor discharge drive circuit 510 or FET control drive circuit 520, which is proportional to the amplitude of drive current. As another example, command signal generation unit 346 may adjust the pulse width of voltage command signal of FET control drive circuit 520 to control the pulse width of drive current. When generating control signals, command signal generation unit 346 may take into account the specific circuit topology and corresponding circuit gate response implemented by drive circuit 218.

[0061] In step S610, controller 206 may provide a control signal to the emitter driving circuit (e.g., driving circuit 218). The control signal will regulate the driving current generated in the driver circuit. When the driving current is provided to drive the laser emitter 208, it causes the laser emitter 208 to emit a laser beam. By regulating the driving current, the control signal controls the emission power level. In step S612, laser emitter 208 emits a beam at the emission power level determined in step S606.

[0062] In step S614, receiver 204 can detect the light beam reflected from the target object. For example, receiver 204 can detect the laser beam 211 reflected from object 212. Receiver 204 can acquire the laser beam reflected from object 212 and output an electrical signal reflecting the intensity of the reflected laser beam. In step S616, controller 206 can determine the reflectivity of the target object based on the intensity of the reflected laser beam. In step S606, the reflectivity of the object can be used to determine the emission power level. For example, the emission power level can be proportional to the ratio of the reflectivity of the ground to the reflectivity of the target object.

[0063] In step S618, the controller 206 can determine whether all scanning angles of the scanner 210 have been covered. If not (S618: NO), method 600 continues to step S620, determines and adjusts the transmit power level for the next scanning angle, for example, repeating steps S602-S618. Method 600 ends after the scanner 210 has passed all scanning angles (S618: YES).

[0064] While this disclosure uses a LiDAR system as an example, the disclosed embodiments are applicable to other types of optical sensing systems that use receivers to receive light signals, not limited to laser beams. For example, the embodiments can be readily adapted to optical imaging systems or radar detection systems that use electromagnetic waves to scan objects. Different emitters and driving circuits than those disclosed above can be used. For example, the emitter can be any other light emitter suitable for emitting light signals used by the respective optical sensing systems, and the driving circuit can be any driver suitable for driving the corresponding emitter.

[0065] Another aspect of this disclosure relates to a non-transitory computer-readable medium that stores instructions, which, when executed, cause one or more processors to perform the methods described above. The computer-readable medium may include volatile or non-volatile, magnetic, semiconductor-based, magnetic tape-based, optical, removable, non-removable, or other types of computer-readable media or computer-readable storage devices. For example, as disclosed, a computer-readable medium may be a storage device or storage module storing computer instructions. In some embodiments, the computer-readable medium may be a disk or flash drive storing computer instructions.

[0066] Various modifications and variations can be made to the disclosed system and related methods by those skilled in the art. Other embodiments will be clearly apparent to those skilled in the art in light of the specifications and practices of the disclosed system and related methods.

[0067] This specification and examples are to be considered exemplary only, and their true scope is indicated by the claims and their equivalents.

Claims

1. An optical sensing system, comprising: The transmitter is configured to emit beams from multiple vertical detection angles to scan an object; The controller, configured to dynamically change the emission power level of the beam emitted at each of the vertical detection angles, includes: Determine the detection distance of the light beam corresponding to each of the vertical detection angles; wherein, when the vertical detection angle is less than a threshold angle, the threshold detection distance of the optical sensing system is determined as the detection distance corresponding to the vertical detection angle; when the vertical detection angle is greater than the threshold angle, the detection distance is determined based on the vertical detection angle and the height of the optical sensing system above the ground plane; and For each of the stated vertical detection angles, the transmit power level is determined based on the ratio of the detection distance corresponding to the vertical detection angle to the threshold detection distance; and The receiver is configured to detect the beam of light reflected back by the object.

2. The optical sensing system according to claim 1, characterized in that, The optical sensing system includes a light detection and ranging system.

3. The optical sensing system according to claim 1, characterized in that, The transmitter further includes an emitter configured to emit a beam and a drive circuit configured to drive the emitter to emit the beam at dynamically varying power levels.

4. The optical sensing system according to claim 3, characterized in that, The controller is configured to provide at least one control signal to the drive circuit, and the drive circuit is configured to provide a varying drive current to the transmitter in response to the at least one control signal, wherein the varying drive current is proportional to the dynamically varying transmission power level.

5. The optical sensing system according to claim 4, characterized in that, The at least one control signal is used to change at least one of the amplitude or pulse width of the drive current.

6. The optical sensing system according to claim 3, characterized in that, The driving circuit includes a FET control driving circuit or a capacitor discharge driving circuit.

7. The optical sensing system according to claim 1, characterized in that, In order to dynamically change the emission power level of the beam, the controller is further configured to: When the vertical detection angle is greater than the threshold angle, the transmission power level is reduced.

8. The optical sensing system according to claim 1, characterized in that, The transmission power level is proportional to the square of the ratio of the detection distance to the threshold detection distance.

9. The optical sensing system according to claim 1, characterized in that, The controller is further configured to determine a first reflectivity of the object based on the beam received by the receiver, wherein the emission power level is proportional to the ratio of a second reflectivity of the ground to the first reflectivity.

10. A method for controlling the transmit power level in an optical sensing system, comprising: The transmitter emits beams at multiple vertical detection angles to scan objects; Dynamically changing the emission power level of the beam at each of the vertical detection angles via a controller includes: Determine the detection distance of the light beam corresponding to each of the vertical detection angles; wherein, when the vertical detection angle is less than a threshold angle, the threshold detection distance of the optical sensing system is determined as the detection distance corresponding to the vertical detection angle; when the vertical detection angle is greater than the threshold angle, the detection distance is determined based on the vertical detection angle and the height of the optical sensing system above the ground plane; and For each of the stated vertical detection angles, the transmit power level is determined based on the ratio of the detection distance corresponding to the vertical detection angle to the threshold detection distance; and The beam of light returned by the object is detected by a receiver.

11. The method of claim 10, further comprising: When the vertical detection angle is greater than the threshold angle, the transmission power level is reduced.

12. The method according to claim 10, characterized in that, The transmitter further includes an emitter configured to emit the light beam and a drive circuit configured to drive the emitter; The method further includes: providing at least one control signal to the driving circuit to cause the driving circuit to provide a varying driving current to the transmitter in response to the at least one control signal, wherein the varying driving current is proportional to a dynamically varying transmission power level.

13. The method according to claim 10, characterized in that, The transmission power level is proportional to the square of the ratio of the detection distance to the threshold detection distance.

14. A control device for controlling the transmit power level in an optical sensing system, comprising: A driving circuit is configured to drive the emitter of the optical sensing system to emit a light beam, wherein the light beam is emitted at multiple perpendicular detection angles; and The controller, configured to control the drive circuit to dynamically change the emission power level of the beam emitted at each of the vertical detection angles, includes: Determine the detection distance of the light beam corresponding to each of the vertical detection angles; wherein, when the vertical detection angle is less than a threshold angle, the threshold detection distance of the optical sensing system is determined as the detection distance corresponding to the vertical detection angle; when the vertical detection angle is greater than the threshold angle, the detection distance is determined based on the vertical detection angle and the height of the optical sensing system above the ground plane; and For each of the vertical detection angles, the transmission power level is determined based on the ratio of the detection distance corresponding to the vertical detection angle to the threshold detection distance.

15. The control device according to claim 14, characterized in that, The controller is further configured to provide at least one control signal to the drive circuit, and the drive circuit is configured to provide a varying drive current to the transmitter in response to a voltage command signal, wherein the varying drive current is proportional to the dynamically varying transmission power level.

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