Alternating power level scanning for a time-of-flight lidar system

Abstract

This document describes techniques and systems for alternating power level scanning of a ToF lidar system. The described lidar system transmits an initial signal having a first power level in a power level alternating pattern. The initial signal is associated with an initial pixel in a series of pixels. The lidar system then transmits a subsequent signal having a second power level associated with a subsequent pixel in the series of pixels. The transmission of the initial signal and the subsequent signal in the power level alternating pattern limits the total power level emitted by the lidar system during a time interval to comply with safety regulations. The power level alternating pattern also allows the lidar system to switch between a long detection range and a short detection range for consecutive pixels.

Description

Background Art

[0001] Automotive time-of-flight (ToF) lidar systems use laser signals to determine the speed and distance of stationary and moving objects (such as other vehicles, pedestrians, and obstacles). The lidar system compares the emitted transmit signal with the reflected return signal to make these measurements. For many applications, it is desirable to provide long-range detection capabilities. In particular, for time-of-flight lidar systems, providing long-range detection capabilities with high frame rates may require optical power output that exceeds safety regulations for certain exposure times. Summary of the Invention

[0002] This document describes techniques and systems for alternating power level scanning in ToF LiDAR systems.

[0003] For example, this document describes a transmitter of a ToF lidar system that maintains a power level alternating pattern that includes a first power level and a second power level. During an initial frame of a continuous frame, the transmitter emits an initial signal in a continuous signal having a first power level from the power level alternating pattern. The initial signal is emitted during a first interval and associated with an initial pixel in a continuous pixel. The transmitter then emits a subsequent signal in the continuous signal that is emitted during a second interval and associated with a subsequent pixel in the continuous pixel. The second signal has a second power level from the power level alternating pattern. Emitting the continuous signal in the power level alternating pattern effectively limits the total power level emitted by the lidar system during a third interval. The third interval includes at least a portion of the first interval and at least a portion of the second interval.

[0004] This document also describes methods performed by the systems summarized above and other methods set forth herein, as well as apparatus for performing these methods.

[0005] This summary introduces a simplified concept for power level scanning for an alternating ToF lidar system, which is further described in the detailed description and accompanying drawings. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The details of one or more aspects of alternating power level scanning for a ToF lidar system are described in this document with reference to the following figures. The same numbers are generally used throughout the figures to reference similar features and components:

[0007] Figure 1An example environment is shown in which a ToF lidar system with alternating power level scanning can be implemented;

[0008] Figure 2 An example implementation of a ToF lidar system as part of a vehicle is shown;

[0009] Figure 3-1 An example operation of a ToF lidar system with alternating power level scanning is shown;

[0010] Figure 3-2 shows the pixels scanned by the ToF lidar system during one frame;

[0011] Figure 4 An example transmitter of the described ToF lidar system is illustrated;

[0012] Figure 5 shows an example transmit signal with alternating power levels emitted by a ToF lidar system; and

[0013] Figure 6 An example method of alternating power level scanning performed by a ToF lidar system is shown. DETAILED DESCRIPTION

[0014] Overview

[0015] Automotive lidar systems are an important sensing technology that several vehicle-based systems rely on to obtain critical information about their surroundings. A lidar system has a field of view, which represents a volume of space within which it searches for nearby objects. The field of view consists of a large number of pixels (e.g., one million pixels). The time it takes for a lidar system to scan each pixel in the field of view (e.g., collect information about all pixels) is one frame. By scanning each pixel in a sequence of frames, a ToF lidar system can determine the range and reflectivity information of nearby objects.

[0016] A ToF lidar system scans each pixel by emitting a laser signal and detecting its reflection. Depending on the application, the lidar system may be subject to safety regulations regarding the amount of optical power that can be emitted within a specific time interval. For example, a lidar system in an automotive application can be regulated to maintain its optical power below a certain threshold (e.g., 1 mW) for a given period of time (e.g., 4 microseconds). A ToF lidar system can typically scan each pixel in 1-3 microseconds. Therefore, regulatory restrictions on optical power in automotive applications may limit the optical power of the laser signal emitted for two or more consecutive pixels. Such regulatory restrictions avoid damaging the vision of nearby individuals. Because the detection range is generally proportional to the optical power of the emitted signal, complying with safety regulations may limit the detection range of the lidar system. Maintaining a long detection range while complying with safety regulations regarding optical power limits may increase the hardware cost or complexity of the lidar system.

[0017] Some lidar systems use a uniform laser signal to scan each pixel to maintain the optical power limit for consecutive pixels within the prescribed regulatory limits. For example, if the regulatory period includes two consecutive pixels, the lidar system transmits a laser signal that does not exceed half the regulatory limit for each pixel. For each pixel in the field of view, the detection range of these lidar systems is reduced.

[0018] Other lidar systems scan each pixel with a low optical power signal and then scan the pixels within the region of interest with a higher optical power. The low power signal complies with safety regulations by limiting the power of each pixel. These systems increase the detection range of the region of interest by emitting a high power signal. Such lidar systems may have a reduced frame rate because the region of interest must be scanned twice per frame: once with a low power signal and once with a high power signal. The optical power of the high power signal of two consecutive pixels within the region of interest of a particular frame is still limited by safety regulations. As a result, the scan rate within the region of interest of the high power signal may also be reduced to comply with safety regulations. In addition, the beam steering (steer) control of these lidar systems may be more complex.

[0019] There are other lidar systems that scan each pixel in the field of view with high optical power for the initial frame in a series of frames, and then scan with low optical power for subsequent frames in the series of frames. Although each pixel is scanned with a signal with a long detection range, the power of the high-power frame must be low enough so that consecutive pixels do not exceed regulatory limits. Otherwise, the optical power or detection range of the lidar system must be reduced to avoid exceeding safety regulatory limits within the allocated time period. In addition, additional sensor hardware may be required to process the return signals from the low-power frame and the high-power frame.

[0020] Compared to those lidar systems, this document describes techniques and systems that comply with safety regulations regarding optical power while maintaining a long detection range and without reducing scan rate. For example, during an initial frame in a series of frames, the described lidar system includes a transmitter configured to transmit an initial signal having a first power level from a power level alternating pattern. The initial signal is transmitted during a first interval associated with the initial pixel in the series of pixels. The transmitter is further configured to transmit a subsequent signal having a second power level from the power level alternating pattern. The subsequent signal is transmitted during a second interval associated with a subsequent pixel in the series of pulses. By transmitting the series of pulses in the power level alternating pattern, the lidar system limits the total power level of the series of pixels. Compliance with safety regulations regarding power limits can be achieved without requiring additional hardware, reducing the lidar system's detection range, or reducing its scan rate or frame rate. Consequently, the ToF lidar system can provide lidar data to vehicle systems (e.g., collision avoidance systems) for objects in the surrounding environment at greater distances without exceeding safety regulations. The power level alternating mode also allows the ToF lidar system to switch between long and short detection ranges for consecutive pixels without the need for additional hardware or photodetectors with increased dynamic range.

[0021] This is just one example of how the described techniques and systems might perform scanning using alternating power levels in a ToF LiDAR system. This document describes other examples and implementations.

[0022] Operating Environment

[0023] Figure 1An example environment 100 is shown in which techniques using a ToF lidar system 102 with alternating power level scanning and an apparatus including the ToF lidar system 102 with alternating power level scanning can be implemented. The ToF lidar system 102 may be referred to simply as "lidar system 102." In the depicted environment 100, the lidar system 102 is mounted to or integrated within a vehicle 104. The lidar system 102 is capable of detecting one or more objects 108-1 and 108-2 in the vicinity of the vehicle 104. Although shown as a car, the vehicle 104 may represent other types of motor vehicles (e.g., motorcycles, buses, tractors, semi-trailers, or construction equipment), non-motor vehicles (e.g., bicycles), rail vehicles (e.g., trains or trams), watercraft (e.g., boats or ships), aircraft (e.g., airplanes or helicopters), or spacecraft (e.g., satellites). In some cases, the vehicle 104 may tow or include a trailer or other attachment. Generally, manufacturers can mount lidar system 102 to any mobile platform, including mobile machinery or robotic equipment.

[0024] In the depicted implementation, the lidar system 102 is mounted on the side of a vehicle 104 and provides a field of view 106 that illuminates objects 108-1 and 108-2. The lidar system 102 divides the field of view 106 into pixels (e.g., Figure 3-2 106 ). LiDAR system 102 can project field of view 106 from any exterior surface of vehicle 104. For example, a vehicle manufacturer can integrate lidar system 102 into a bumper, side-view mirror, headlight, taillight, or any other interior or exterior location where the distance or classification of object 108 needs to be detected. In some cases, vehicle 104 includes multiple lidar systems 102, such as a first lidar system 102 and a second lidar system 102 that together provide a larger field of view 106. In general, a vehicle manufacturer can design the position of one or more lidar systems 102 to provide a specific field of view 106 that includes an area of ​​interest in which object 108 may be present. Example fields of view 106 include a 360-degree field of view, one or more 180-degree fields of view, one or more 90-degree fields of view, and the like, which can overlap or be combined into a field of view 106 of a specific size.

[0025] Objects 108-1 and 108-2 are composed of one or more materials that reflect lidar signals. Depending on the application, objects 108-1 and 108-2 can represent targets of interest. In some cases, object 108-1 is a moving object 110, including another vehicle 110-1, a semi-trailer 110-2, a person 110-3, an animal 110-4, a bicycle 110-5, or a motorcycle 110-6. In other cases, object 108-2 represents a stationary object 112, including a traffic cone 112-1, a concrete barrier 112-2, a guardrail 112-3, a fence 112-4, a tree 112-5, or a parked vehicle 112-6. Stationary objects 112 can be continuous (e.g., concrete barrier 112-2, guardrail 112-3) or discontinuous (e.g., traffic cone 112-1) along a portion of the road.

[0026] Lidar system 102 represents a time-of-flight lidar system that transmits and receives lidar signals for each pixel of field of view 106. Lidar system 102 measures the distance to objects 108-1 and 108-2 based on the time it takes for the signals to travel from lidar system 102 to objects 108-1 and 108-2 and back to lidar system 102.

[0027] like Figure 1 As depicted, lidar system 102 emits transmit signals 114-1 and 114-2 within field of view 106. Lidar system 102 maintains an alternating power level pattern that includes a first power level and a second power level. For example, lidar system 102 emits transmit signal 114-1 at the first power level toward object 108-1. Lidar system 102 then emits transmit signal 114-2 at the second power level toward object 108-2. The first power level is lower than the second power level, as indicated by the pulse amplitudes of transmit signal 114-1 and transmit signal 114-2. The alternating power level pattern effectively limits the total power level emitted by the lidar system during consecutive pixels.

[0028] LiDAR system 102 may also measure the reflective properties of objects 108-1 and 108-2 based on the energy of the received signals. Information related to the energy may be used to classify objects 108-1 and 108-2. As an example, LiDAR system 102 may determine whether object 108-2 is a parked vehicle 112-6, a lane marking, a road surface, or a person 110-3. The energy information also enables LiDAR system 102 to determine the characteristics of objects 108-1 and 108-2, including the material composition of objects 108-1 and 108-2. Figure 2LiDAR system 102 and vehicle 104 are further described.

[0029] Figure 2 LiDAR system 102 is shown as part of vehicle 104. Vehicle 104 also includes at least one vehicle-based system 202, which relies on data from LiDAR system 102, including a driver assistance system 204 and an autonomous driving system 206. Typically, vehicle-based systems 202 use the LiDAR data provided by LiDAR system 102 to perform functions. For example, driver assistance system 204 provides blind spot monitoring and generates an alert indicating a potential collision with an object 108 detected by LiDAR system 102. In this case, the LiDAR data from LiDAR system 102 indicates when it is safe or unsafe to change lanes. Autonomous driving system 206 can move vehicle 104 to a specific location on the road while avoiding a collision with object 108 detected by LiDAR system 102. The LiDAR data provided by LiDAR system 102 can provide information about the distance and reflectivity of object 108, enabling autonomous driving system 206 to perform emergency braking, execute a lane change, or adjust the speed of vehicle 104.

[0030] The lidar system 102 includes a communication interface 208 to transmit lidar data to the vehicle-based system 202 or another component of the vehicle 104. For example, when individual components of the lidar system 102 are integrated into the vehicle 104, the communication interface 208 can transmit data via the communication bus of the vehicle 104. Generally speaking, the lidar data provided by the communication interface 208 is in a format that can be used by the vehicle-based system 202. In some implementations, the communication interface 208 can send information to the lidar system 102, including the speed of the vehicle 104 or whether the turn signal is on or off. The lidar system 102 uses this information to configure itself appropriately. For example, the lidar system 102 can adjust its frame rate or scanning speed based on the speed of the vehicle 104. Alternatively, the lidar system 102 can dynamically adjust the field of view 106 based on whether the right turn signal is on or the left turn signal is on.

[0031] The lidar system 102 also includes a transmitter 210 for transmitting lidar signals and a receiver 212 for receiving reflected versions of these lidar signals. The transmitter 210 includes components for emitting lidar signals (whether optical or other components, which may include laser drivers and laser diodes) and related components for directing the lidar signals. The receiver 212 includes one or more photodetector arrays (collectively referred to as photodetectors) to detect reflected lidar signals. The transmitter 210 and receiver 212 can be incorporated together on the same integrated circuit (e.g., a transceiver integrated circuit) or separately incorporated on different integrated circuits.

[0032] The lidar system 102 includes a power control module 214 for controlling the power level of the lidar signal emitted by the transmitter 210. The power control module 214 can be implemented using hardware, software, firmware, or a combination thereof. In some implementations, the power control module 214 is incorporated into the transmitter 210 and implemented on the same integrated circuit. In other implementations, the power control module 214 can be separate from the transmitter 210 and implemented on a different integrated circuit (or multiple integrated circuits), and in some implementations, at least a portion of the power control module 214 can be implemented by the processor 218. The power control module 214 can control components of the transmitter 214 to maintain an alternating pattern of power levels in the emitted lidar signal. About Figure 4 Maintenance of the power level alternating pattern is discussed in more detail.

[0033] The lidar system 102 also includes one or more processors 218 and a computer readable storage medium (CRM) 216. The processor 218 may be implemented as a microprocessor or a system on a chip. The processor 218 executes instructions stored in the CRM 216. As an example, the processor 218 may determine ( Figure 1 The processor 218 may also be used to determine the position of the object 108 relative to the lidar system 102 (e.g., determine the slant range, azimuth, and elevation to the object 108), determine the material composition of the object 108, or classify the object 108. As another example, the processor 218 may provide instructions to the power control module 214 to control the characteristics of the power level alternation pattern (e.g., the first power level, the second power level, the number of alternating power levels). The processor 218 also generates lidar data for the vehicle-based system 202.

[0034] Figure 3-1 An example operation of the lidar system 102 with alternating power level sweeps is shown. Figure 3-1In environment 300, objects 108-11 and 108-21 (collectively, objects 108) are located at a particular distance and angle from lidar system 102. To detect object 108, lidar system 102 emits a transmit signal 302 for each of pixels 306.

[0035] For reference, Figure 3-2 Pixels 306 of the field of view 106 are shown as being scanned by the lidar system 102 during a frame (not shown). The field of view 106 includes pixels 306-11, 306-21, 306-31, 306-X1, 306-12, 306-22, 306-32, 306-X2, 306-XY, 306-3Y, 306-2Y, 306-1Y, and all other pixels scanned during the frame. Pixels 306 are shown arranged in a grid that is X pixels wide by Y pixels high and are scanned individually in the order indicated by the arrows, one row (or column) at a time, although other orders for scanning pixels 306 are possible.

[0036] Return Reference Figure 3-1 , transmit signal 302 includes a single pulse 308. In other implementations, transmit signal 302 may include multiple pulses, such as pulses 308-1 through 308-N in a pulse train, where N represents a positive integer. Lidar system 102 may customize the number of pulses 308 and the transmission characteristics of pulses 308 (e.g., pulse width, time interval between each pulse 308, energy level) for each transmit signal in transmit signal 302 to achieve a specific scanning speed, detection range, or distance resolution.

[0037] LiDAR system 102 sequentially scans pixels 306 within field of view 106. One frame (not shown) represents the time it takes to scan all individual pixels 306 within field of view 106.

[0038] In the depicted example, the lidar system 102 emits transmit signals 302-11 and 302-21 for pixels 306-11 and 306-21, respectively. Transmit signals 302-11 and 302-21 are collectively referred to as transmit signals 302. Transmit signal 302-11 has a first power level greater than a second power level of transmit signal 302-21. The first power level is greater than the second power level, which is Figure 3-1This is depicted in FIG. 1 by the pulse amplitude of transmit signal 302-11 being greater than the pulse amplitude of transmit signal 302-21. The power level alternating pattern effectively configures lidar system 102 to alternate between long-range detection capability and short-range detection capability. In this example, the first power level is associated with long-range detection capability, and transmit signal 302-11 is capable of detecting object 108-11. In contrast, transmit signal 302-21 having a second power level may not be as capable of detecting object 108-11 as transmit signal 302-11. Transmit signal 302-21 is capable of detecting object 108-21, which is closer to lidar system 102 than object 108-11.

[0039] Object 108-11 reflects at least a portion of transmit signal 302-11. The reflected portion represents return signal 304-11. Lidar system 102 receives return signal 304-11 and processes return signal 304-11 to extract lidar data related to object 108-1 for vehicle-based system 202. As depicted, the amplitude of return signal 304-11 is less than the amplitude of transmit signal 302-11 due to losses incurred during propagation and reflection.

[0040] Similarly, object 108-21 reflects at least a portion of transmit signal 302-21. Return signals 304-11 and 304-21 are collectively referred to as return signal 304. Lidar system 102 receives return signal 304-21 and processes return signal 304-21 to extract lidar data related to object 108-21 for vehicle-based system 202.

[0041] At the lidar system 102, the return signals 304-11 and 304-21 represent delayed versions of the transmit signals 302-11 and 302-21, respectively. The amount of delay is proportional to the range (e.g., distance) from the objects 108-11 and 108-21 to the lidar system 102. For example, the delay represents the time it takes for the transmit signal 302-11 to propagate from the lidar system 102 to the object 108-11 and for the return signal 304-11 to travel back to the lidar system 102. Figure 4 The transmission of transmit signal 302 by lidar system 102 is described in more detail.

[0042] Figure 4An example transmitter 210 of the lidar system 102 is shown. In the depicted configuration, the transmitter 210 includes a laser driver 402, a laser diode 404, a focusing lens 406, a beam splitter 408, and a beam steering component 410. In some implementations, the focusing lens 406 and the beam splitter 408 can be omitted from the transmitter 210. Although not explicitly shown, the transmitter 210 can include other components, including a power control module 214.

[0043] Power control module 214 provides control signal 428 to laser driver 402. Control signal 428 may direct the operation of laser driver 402 to maintain an alternating pattern of power levels emitted by lidar system 102. Power control module 214 may generate control signal 428 based on instructions received from processor 218 or instructions stored in CRM 216.

[0044] The laser driver 402 drives the laser diode 404 by providing a current in the driver signal 420. Based on the control signal 428, the laser driver 402 can change the current level of the driver signal 420, the pulse width of the driver signal 420, or a combination thereof to adjust the power level of the transmit signal 302 and maintain the power level alternating pattern. In some implementations, the laser driver 402 can drive the laser diode 404 by providing a voltage signal as the driver signal 420.

[0045] The laser diode 404 generates a laser beam 422. The laser diode 404 converts the electrical energy in the driver signal 420 into light, which is emitted as the laser beam 422. The driver signal 420 controls the power level of the laser beam 422 output by the laser diode 404.

[0046] The focusing lens 406 forms a focused beam 424. In some implementations, the laser beam 422 can diverge rapidly after leaving the laser diode 404. The focusing lens 406 can focus or collimate the laser beam 422 into a focused beam 424. The focused beam 424 can be wide or narrow. The beam splitter 408 can split the focused beam 424 into two, including the split beam 426 and another beam (not shown). The other beam can be an input to the processor 218 to help determine the characteristics of the object 108.

[0047] Beam steering components 410 may include mechanical and / or electromechanical components to shape or steer split beams 426 into transmit signals 302. Using beam steering components 410, transmitter 210 may steer and shape transmit signals 302 through various optical beamforming techniques.

[0048] Beam steering component 410 may include mechanical components. In this case, beam steering component 410 includes advanced optics and a rotating assembly to produce a wide (e.g., three hundred and sixty degree) field of view. Alternatively, lidar system 102 may be a solid-state lidar system, such as a microelectromechanical system (MEMS)-based lidar system, a flash memory-based lidar system, or an optical phased array lidar system. When configured as a solid-state lidar system, beam steering component 410 does not include rotating mechanical components and may therefore be less expensive than a mechanically scanning lidar system.

[0049] LiDAR system 102 may include multiple solid-state LiDAR modules, with each module positioned at a different location on vehicle 104. For example, the modules may be on the front, rear, or sides of vehicle 104 and, when combined, create a single point cloud. In such an arrangement, LiDAR system 102 has a field of view 106 similar to the field of view 106 of a mechanically scanning LiDAR system.

[0050] During operation, the laser driver 402 outputs a driver signal 420 to the laser diode 404. As described above, the laser driver 402 can vary the current or pulse width of the driver signal 420 to adjust the power level of the laser beam 422 output by the laser diode 404. The focusing lens 406 can collimate the laser beam 422 to produce a focused beam 424. The beam splitter 408 can split the laser beam 422 or the focused beam 424 into two, including a split beam 426. The beam control component 410 emits the transmit signal 302 based on the laser beam 422, the focused beam 424, or the split beam 426.

[0051] Figure 5 An example transmit signal 302 having alternating power levels emitted by the lidar system 102 is shown. The transmitter 210 of the lidar system 102 emits transmit signals 302-11, 302-21, 302-31, and 302-41 for pixels 306-11, 306-21, 306-31, and 306-41, respectively. In the depicted example, the transmit signal 302 includes a single pulse 308. During each of the frames 508, the power level of the transmit signal 302 alternates from a high power level to a low power level for consecutive pixels 306. Figure 5, the power level of the transmit signal 302 is indicated by the amplitude of the pulse 308 in graphs 502, 504, and 506 and the length of the line in graphs 512, 514, and 516. The order of the power level alternating pattern is switched for consecutive frames 508. For example, the power level of the transmit signal 302-11 of the pixel 306-11 is high for the initial frame (e.g., frame 508-1) in the consecutive frames and low for the subsequent frames (e.g., frame 508-2). A high power level is associated with a long detection range, and a low power level is associated with a short detection range.

[0052] For frames 508-1 and 508-3, the power levels of transmit signals 302-11 and 302-31 are greater than the power levels of transmit signals 302-21 and 302-41. In other words, transmit signals 302-11 and 302-31 are at a high power level while transmit signals 302-21 and 302-41 are at a low power level. In the depicted example, the power of transmit signals 302-11 and 302-31 is approximately twice the power of transmit signals 302-21 and 302-41. In other implementations, the high power level may be approximately three, four, or five times the low power level. In yet other implementations, the high and low power levels may be fractions of regulatory limits (e.g., 75% and 25% of the limits, respectively), with the high power level being greater than the low power level.

[0053] For frame 508-2, the power levels of transmit signals 302-21 and 302-41 are greater than the power levels of transmit signals 302-11 and 302-31. In other words, transmit signals 302-11 and 302-31 are at low power levels while transmit signals 302-21 and 302-41 are at high power levels.

[0054] In other implementations, the power level alternation pattern can alternate between three or more power levels for consecutive pixels. For example, the power levels of transmit signals 302-11 and 302-41 of frame 508-1 are at a first power level. The power level of transmit signal 302-21 is at a second power level, and the power level of transmit signal 302-31 is at a third power level. For frame 508-2, transmit signals 302-11 and 302-41 are at the third power level, transmit signal 302-21 is at the first power level, and transmit signal 302-31 is at the second power level. For frame 508-3, transmit signals 302-11 and 302-41 are at the second power level, transmit signal 302-21 is at the third power level, and transmit signal 302-31 is at the first power level.

[0055] Example Method

[0056] Figure 6An example method 600 of alternating power level scanning performed by the lidar system 102 is depicted. The method 600 is shown as multiple sets of operations (or actions) being performed, but is not necessarily limited to the order or combination of operations shown herein. In addition, any one or more of the operations may be repeated, combined, or reorganized to provide other methods. In the following discussion, reference may be made to each of the methods. Figure 1 and Figure 3-1 Environments 100 and 300, and Figures 1 to 5 While the entities detailed in the foregoing are referenced herein, these are merely examples. The techniques are not limited to performance by one entity or multiple entities.

[0057] At 602, during an initial frame in a continuous frame, an initial signal in a continuous signal is transmitted. The initial signal has a first power level in a power level alternating pattern and is transmitted during a first interval. The first interval is associated with an initial pixel in a continuous pixel. For example, during frame 508-1, the transmitter 210 of the lidar system 102 on the vehicle 104 transmits the transmit signal 302-11, as shown in FIG. Figure 5 As shown, the transmit signal 302-11 has a first power level in the power level alternating pattern. The transmit signal 302-11 is transmitted during a first time interval associated with the pixel 306-11.

[0058] At 604, a subsequent signal in the continuous signal is transmitted having a second power level in the power level alternating pattern. The subsequent signal is transmitted during a second interval, the second interval being associated with a subsequent pixel in the continuous pixel. Transmitting the continuous signal in the power level alternating pattern effectively limits the total power during a third interval, the third interval including at least a portion of the first interval and at least a portion of the second interval. For example, transmitter 210 transmits transmit signal 302-21, as Figure 5 As shown, transmit signal 302-21 has a second power level in the power level alternating pattern. Transmit signal 302-21 is transmitted during a second time interval associated with pixel 306-21. Transmitting consecutive transmit signals 302-11 and 302-21 in the power level alternating pattern effectively limits the total power level during a third interval, which includes at least a portion of the first interval and at least a portion of the second interval. Power control module 214 can control laser driver 402 of transmitter 210 to maintain the power level alternating pattern.

[0059] At 606, during a subsequent frame of the continuous frame, an initial signal having a second power level is transmitted. The initial signal is transmitted during the first interval. For example, during frame 508-2, the transmitter 210 transmits the transmit signal 302-11, such as Figure 5 The transmit signal 302-11 has a second power level and is transmitted during the first interval.

[0060] At 608, a subsequent signal having the first power level is transmitted. The subsequent signal is transmitted during the second interval. For example, the transmitter 210 transmits the transmit signal 302-21, such as Figure 5 The transmit signal 302-21 has a first power level and is transmitted during the second interval.

[0061] Example

[0062] In the following sections, examples are provided.

[0063] Example 1: A method comprising: maintaining a power level alternating pattern by a time-of-flight lidar system, the power level alternating pattern comprising a first power level and a second power level; and during an initial frame in a continuous frame: transmitting, using the lidar system, an initial signal in a continuous signal during a first interval, the initial signal having a first power level from the power level alternating pattern and associated with the initial pixel in the continuous pixel; and transmitting, during a second interval, a subsequent signal in the continuous signal, the subsequent signal having a second power level from the power level alternating pattern and associated with a subsequent pixel in the continuous pixel, wherein transmitting the continuous signal in the power level alternating pattern effectively limits the total power level emitted by the lidar system during a third interval, the third interval comprising at least a portion of the first interval and at least a portion of the second interval.

[0064] Example 2: The method of Example 1, further comprising: during a subsequent frame in the continuous frame: transmitting an initial signal during a first interval, the initial signal having a second power level; and transmitting a subsequent signal during a second interval, the subsequent signal having the first power level.

[0065] Example 3: The method of Example 1, wherein: the first power level is associated with a first detection range; and the second power level is associated with a second detection range, and the power level alternating pattern further effectively configures the lidar system to alternate between detecting objects within the first detection range and detecting objects within the second detection range.

[0066] Example 4: The method of Example 3, wherein: the first power level is less than the second power level; and the first detection range is less than the second detection range.

[0067] Example 5: The method of Example 1, wherein the power control module provides a control signal to a laser driver of the lidar system to maintain a power level alternating pattern.

[0068] Example 6: The method of Example 5, wherein: the first power level is associated with at least one of a first current level or a first pulse width of the laser driver; and the second power level is associated with at least one of a second current level or a second pulse width of the laser driver, wherein the second current level is different from the first current level and the first pulse width is different from the second pulse width.

[0069] Example 7: The method of Example 1, wherein the total power level during the third time interval is less than a safety regulation limit for the lidar system.

[0070] Example 8: The method of Example 7, wherein the first power level is approximately seventy-five percent of a safety regulatory limit and the second power level is approximately twenty-five percent of a safety regulatory limit.

[0071] Example 9: The method of Example 1, wherein the first power level is at least twice the second power level.

[0072] Example 10: The method of Example 1, wherein the initial signal and the subsequent signal each comprise a pulse.

[0073] Example 11: A transmitter of a time-of-flight lidar system, the transmitter being configured to: maintain a power level alternating pattern, the power level alternating pattern comprising a first power level and a second power level; and during an initial frame in a continuous frame: transmit an initial signal in a continuous signal during a first interval, the initial signal having the first power level from the power level alternating pattern and associated with the initial pixel in the continuous pixel; and transmit a subsequent signal in the continuous signal during a second interval, the subsequent signal having the second power level from the power level alternating pattern and associated with the subsequent pixel in the continuous pixel, wherein transmitting the continuous signal in the power level alternating pattern effectively limits the total power level emitted by the lidar system during a third interval, the third interval comprising at least a portion of the first interval and at least a portion of the second interval.

[0074] Example 12: The transmitter of Example 11, wherein the transmitter is further configured to: during a subsequent frame in the continuous frame: transmit an initial signal during a first interval, the initial signal having a second power level; and transmit a subsequent signal during a second interval, the subsequent signal having the first power level.

[0075] Example 13: The transmitter of Example 11, wherein: the first power level is associated with a first detection range; and the second power level is associated with a second detection range, and the power level alternating pattern further effectively configures the lidar system to alternate between detecting objects within the first detection range and detecting objects within the second detection range.

[0076] Example 14: The transmitter of Example 13, wherein: the first power level is less than the second power level; and the first detection range is less than the second detection range.

[0077] Example 15: The transmitter of Example 11, wherein the transmitter is further configured to: provide a control signal from a power control module to a laser driver of the transmitter to maintain a power level alternating pattern; wherein the first power level is associated with at least one of a first current level or a first pulse width of the laser driver; and the second power level is associated with at least one of a second current level or a second pulse width of the laser driver, wherein the second current level is different from the first current level and the first pulse width is different from the second pulse width.

[0078] Example 16: The transmitter of Example 11, wherein the total power level during the third time interval is less than a safety regulation limit for the lidar system.

[0079] Example 17: The transmitter of Example 16, wherein the first power level is approximately seventy-five percent of a safety regulation limit and the second power level is approximately twenty-five percent of a safety regulation limit.

[0080] Example 18: The transmitter of Example 11, wherein the first power level is at least twice the second power level.

[0081] Example 19: The transmitter of Example 11, wherein the lidar system is a lidar system for an automobile.

[0082] Example 20: A transmitter of a time-of-flight lidar system, the transmitter being configured to: during a first frame in a succession of frames: transmit a first signal in a succession of signals during a first interval, the first signal having a first power level in a power level alternating pattern and associated with a first pixel in a succession of pixels; transmit a second signal in the succession of signals during a second interval, the second signal having a second power level in a power level alternating pattern and associated with a second pixel in a succession of pixels; and transmit a third signal in the succession of signals during a third interval, the third signal having a third power level in the power level alternating pattern and associated with a third pixel in a succession of pixels; during a second frame in the succession of frames: transmit the first signal in the first interval, the first signal having the second power level and associated with the first pixel; during the During the second interval, a second signal is emitted, the second signal has a third power level and is associated with the second pixel; and during the third interval, a third signal is emitted, the third signal has the first power level and is associated with the third pixel; and during the third frame in the consecutive frames: during the first interval, the first signal is emitted, the first signal has the third power level and is associated with the first pixel; during the second interval, the second signal is emitted, the second signal has the first power level and is associated with the second pixel; and during the third interval, the third signal is emitted, the third signal has the second power level and is associated with the third pixel, and the emission of consecutive signals in an alternating power level pattern effectively limits the total power level emitted by the lidar during a fourth interval, the fourth interval including at least a portion of the first interval, the second interval, and at least a portion of the third interval.

[0083] in conclusion

[0084] Although various embodiments of the present disclosure have been described in the foregoing description and shown in the accompanying drawings, it should be understood that the present disclosure is not limited thereto but may be implemented in various ways within the scope of the following claims. It will be apparent from the foregoing description that various modifications may be made without departing from the spirit and scope of the present disclosure as defined by the following claims.

Claims

1. A method for a time-of-flight lidar system, comprising: maintaining, by the time-of-flight lidar system, a power level alternating pattern, the power level alternating pattern comprising a first power level and a second power level; as well as During the initial frame in the sequence: transmitting, using the lidar system during a first interval, an initial signal in a continuous signal, the initial signal having the first power level from the alternating pattern of power levels and associated with an initial pixel in a continuous pixel; and transmitting, during a second interval, a subsequent signal in the succession of signals, the subsequent signal having the second power level from the power level alternating pattern and associated with a subsequent pixel in the succession of pixels, Transmitting the continuous signal in the alternating pattern of power levels is effective to limit the total power level emitted by the lidar system during a third interval, the third interval including at least a portion of the first interval and at least a portion of the second interval; and During a subsequent frame in the succession of frames: transmitting the initial signal during the first interval, the initial signal having the second power level and associated with the initial pixel; and The subsequent signal is transmitted during the second interval, the subsequent signal having the first power level and associated with the subsequent pixel.

2. The method for a time-of-flight lidar system according to claim 1, wherein: The first power level is associated with a first detection range; and The second power level is associated with a second detection range, and the power level alternating pattern further effectively configures the lidar system to alternate between detecting objects within the first detection range and detecting objects within the second detection range.

3. The method for a time-of-flight lidar system according to claim 2, wherein: The first power level is less than the second power level; and The first detection range is smaller than the second detection range.

4. The method for a time-of-flight lidar system according to claim 1, wherein: A power control module provides a control signal to a laser driver of the lidar system to maintain the power level alternating pattern.

5. The method for a time-of-flight lidar system according to claim 4, wherein: The first power level is associated with at least one of a first current level or a first pulse width of the laser driver; and The second power level is associated with at least one of a second current level or a second pulse width of the laser driver, wherein the second current level is different from the first current level and the first pulse width is different from the second pulse width.

6. The method for a time-of-flight lidar system according to claim 1, wherein: The total power level during the third interval is less than a safety regulation limit for the lidar system.

7. The method for a time-of-flight lidar system according to claim 6, wherein: The first power level is seventy-five percent of the safety regulation limit, and the second power level is twenty-five percent of the safety regulation limit.

8. The method for a time-of-flight lidar system according to claim 1, wherein: The first power level is at least twice the second power level.

9. The method for a time-of-flight lidar system according to claim 1, wherein: The initial signal and the subsequent signal each include a pulse.

10. A transmitter for a time-of-flight lidar system, the transmitter being configured to: maintaining a power level alternating pattern, the power level alternating pattern comprising a first power level and a second power level; and During the initial frame in the sequence: transmitting, during a first interval, an initial signal in a continuous signal, the initial signal having the first power level from the power level alternating pattern and associated with an initial pixel in a continuous pixel; and transmitting, during a second interval, a subsequent signal in the succession of signals, the subsequent signal having the second power level from the power level alternating pattern and associated with a subsequent pixel in the succession of pixels, Transmitting the continuous signal in the alternating pattern of power levels is effective to limit the total power level emitted by the lidar system during a third interval, the third interval including at least a portion of the first interval and at least a portion of the second interval; and During a subsequent frame in the succession of frames: transmitting the initial signal during the first interval, the initial signal having the second power level and associated with the initial pixel; and The subsequent signal is transmitted during the second interval, the subsequent signal having the first power level and associated with the subsequent pixel.

11. The transmitter according to claim 10, wherein: The first power level is associated with a first detection range; and The second power level is associated with a second detection range, and the power level alternating pattern further effectively configures the lidar system to alternate between detecting objects within the first detection range and detecting objects within the second detection range.

12. The transmitter according to claim 11, wherein: The first power level is less than the second power level; and The first detection range is smaller than the second detection range.

13. The transmitter according to claim 10, wherein The transmitter is further configured to: A power control module provides a control signal to the laser driver of the transmitter to maintain the power level alternating mode; wherein The first power level is associated with at least one of a first current level or a first pulse width of the laser driver; and The second power level is associated with at least one of a second current level or a second pulse width of the laser driver, wherein the second current level is different from the first current level and the first pulse width is different from the second pulse width.

14. The transmitter according to claim 10, wherein The total power level during the third interval is less than a safety regulation limit for the lidar system.

15. The transmitter according to claim 14, wherein The first power level is seventy-five percent of the safety regulation limit, and the second power level is twenty-five percent of the safety regulation limit.

16. The transmitter according to claim 10, wherein The first power level is at least twice the second power level.

17. The transmitter according to claim 10, wherein The lidar system is a lidar system for an automobile.

18. A transmitter for a time-of-flight lidar system, the transmitter being configured to: During the first frame in a sequence of frames: transmitting, during a first interval, a first signal in the continuous signal, the first signal having a first power level in the power level alternating pattern and associated with a first pixel in the continuous pixel; transmitting, during a second interval, a second signal in the continuous signal, the second signal having a second power level in the power level alternating pattern and associated with a second pixel in the continuous pixel; and transmitting, during a third interval, a third signal in the continuous series of signals, the third signal having a third power level in the power level alternating pattern and associated with a third pixel in the continuous series of pixels; During a second frame in the series of frames: transmitting the first signal during the first interval, the first signal having the second power level and associated with the first pixel; transmitting the second signal during the second interval, the second signal having the third power level and associated with the second pixel; and transmitting the third signal during the third interval, the third signal having the first power level and associated with the third pixel; and During a third frame in the series of frames: transmitting the first signal during the first interval, the first signal having the third power level and associated with the first pixel; transmitting the second signal during the second interval, the second signal having the first power level and associated with the second pixel; and transmitting the third signal during the third interval, the third signal having the second power level and associated with the third pixel; Transmitting the continuous signal in the alternating pattern of power levels effectively limits the total power level emitted by the lidar system during a fourth interval, the fourth interval including at least a portion of the first interval, the second interval, and at least a portion of the third interval.

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