System and method for light detection and ranging

Abstract

A light detection and ranging system is provided for improving imaging accuracy and measurement range. The light detection and ranging system may include: a light source configured to emit a multi-pulse sequence into a three-dimensional environment, wherein the multi-pulse sequence includes multiple light pulses having temporal characteristics; a photodetector configured to detect light pulses returning from the three-dimensional environment and generate an output signal representing the light energy associated with a subset of the light pulses; and one or more processors electrically coupled to the light source and the photodetector, and the one or more processors being configured to: generate temporal characteristics based on one or more real-time conditions; and determine one or more parameters for selecting a subset of the light pulses.

Description

[0001] Cross-referencing

[0002] This application relates to International PCT Application No. PCT / CN2018 / 119721, filed on July 12, 2018, which claims the benefit of Chinese Application No. 201711303228.8, filed on December 8, 2017, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Lidar (Light Detection and Ranging) technology can be used to acquire three-dimensional information about the environment by measuring the distance to an object. A Lidar system can include at least a light source configured to emit light pulses and a detector configured to receive returning light pulses. The returning light pulse, or beam, can be called an echo beam. The distance can be obtained based on the time interval between the emitted light pulse and the detection of the returning light pulse (i.e., time of flight). The light pulse can be generated by a laser emitter and then focused by a lens or lens array. The returning light pulse can be received by a detector located near the laser emitter. The returning light pulse can be scattered light from the surface of an object.

[0004] The aforementioned light pulses can be used to detect obstacles within the field of view. In some cases, the dynamic range of the detector, the signal-to-noise ratio of the detected signal, or the contrast may be limited by stray light. Stray light in a Lidar system can be caused by various sources. For example, transmitted light may contaminate or interfere with the detector's reception of returned light pulses. This contamination or interference can make it difficult to identify near-field echoes. For instance, a small portion of the emitted pulses (stray light) may be directly received by detectors such as avalanche photodiodes (APDs) within the Lidar system, causing the detection circuit of a high-sensitivity APD to enter the nonlinear saturation region. When the detection circuit saturates, the amplification factor of the stray light waveform tail will be greater than the amplification factor of its top pulse, causing the stray light pulse width in the detection circuit to increase. This may cause the laser pulse echo signal reflected from near-field obstacles to be submerged in the trailing waveform tail of the stray light, making it impossible to determine the location information of near-field obstacles and creating a measurement blind zone. Invention Overview

[0006] There is a need for a LiDAR system for 3D measurement with improved optical ranging accuracy and efficiency. More specifically, there is a need for methods and systems capable of measuring near-field obstacles and reducing blind spots caused by stray light within the LiDAR.

[0007] The Lidar system proposed in this application meets the above requirements by utilizing a laser pulse sequence corresponding to the temporal profile. This laser pulse sequence enables the receiver or receiving device of the Lidar system to have a higher dynamic range. The receiver may include a detector with a high dynamic range, enabling the Lidar system to image with high imaging resolution and a wide measurement range. For example, the receiver may include a pulse detection circuit configured to convert optical signals into electrical signals. The pulse detection circuit may be configured to generate a sensor output signal by changing the received photon energy that has been converted into at least one electrical signal. Alternatively, when the electrical signal corresponds to a single optical pulse, the pulse detection circuit may generate a sensor output signal by accumulating different combinations of electrical signals used to generate the sensor output signal. In some cases, the pulse detection circuit may generate a sensor output signal representing the optical energy associated with a selected subset of returned optical pulses. The photon energy can be changed by varying the number / count of returned optical pulses accumulated for generating the output signal and / or by changing the selection of the subset of returned optical pulses, thereby allowing selection of the corresponding total optical energy.

[0008] In some cases, a detector or photodetector can be configured to accumulate a selected subset of returned modulated pulses received in the activated region of the photodetector to generate a sensor output signal. The sensor output signal can determine the intensity of a pixel in a 3D image. The intensity or value of a pixel can be proportional to the light energy of the subset of light pulses accumulated by the photodetector or its pulse detection circuitry. In some cases, the intensity or peak power of the output signal (e.g., a voltage signal) can be dynamically adjusted on a pixel-by-pixel basis. In other cases, the intensity or peak power of the output signal can be adjusted individually for the activated region of the detector or for the entire detector.

[0009] On the one hand, this disclosure allows the detector to accumulate selected optical pulses to provide a high dynamic range detector. Preset timing characteristics also help suppress crosstalk between channels and improve the measurement accuracy of near-field obstacles. In some cases, this method can be used to generate a dual-pulse sequence. This method generates a dual-pulse sequence by emitting a first laser pulse at a first time and a second laser pulse at a second time, wherein the peak power of the first laser pulse is lower than the peak power of the second laser pulse, and the time interval between the second time and the first time is greater than T, where T is the duration between the time of laser pulse emission and the time of receiving the laser pulse echo signal reflected from the near-field obstacle.

[0010] In some cases, a portion of the emitted laser pulse propagating through the imaging optics in a LiDAR system may cause stray light to enter adjacent channels or be directly received by detectors within the LiDAR system, such as avalanche photodiodes (APDs), resulting in inaccurate readout of the reflected light. As mentioned above, when the detection circuit becomes saturated due to stray light from the emitted laser pulse, the laser pulse echo signal received by the detector in the saturated state may be obscured by the trailing waveform of the stray light. For example, the detector circuit may enter the nonlinear saturation region due to stray light. When the detection circuit is saturated, the amplification factor of the stray light waveform tail is greater than the amplification factor of its top pulse, increasing the pulse width of the stray light pulse in the detection circuit. This means that the laser pulse echo signal received by the detector in the saturated state may be obscured by the trailing waveform of the stray light.

[0011] Stray light-induced signal contamination can be critical in near-field measurements. For example, when an echo signal returns from the near field with a short corresponding time delay (i.e., short distance or near field) (e.g., an echo signal reflected by a near-field obstacle), such an echo signal may be received within the time window when the detector is saturated, making it impossible to accurately determine the position information of the near-field obstacle, thus creating a measurement blind zone.

[0012] In conventional LiDAR systems, the near field may correspond to the measurement blind zone caused by stray light contamination, which may prevent the near-field echo signal from being properly resolved. As used herein, the term "near field" generally refers to the space at a relatively short distance from the LiDAR system. For example, the near-field distance can range from approximately 5 to 50 meters. In some cases, the measurement blind zone caused by stray light contamination may depend on the sensitivity of the LiDAR system's detector / sensor and / or the reflectivity of the object. For example, the time window for detector saturation may be based on the moment / intensity of stray light and the detector's sensitivity. In conventional LiDAR systems, the measurement blind zone caused by stray light contamination may correspond to the near-field distance (e.g., between 5 and 50 meters) at which the echo signal reflected by an object located in the near field might be received within the time window of detector saturation. Similarly, the term "far field" (e.g., greater than 50 meters) as used herein can generally refer to a range of distances greater than the corresponding near-field distance.

[0013] On the other hand, a light detection and ranging system is provided for improving imaging accuracy and measurement range. The light detection and ranging system may include: a light source configured to emit a multi-pulse sequence into a three-dimensional environment, wherein the multi-pulse sequence includes multiple light pulses having temporal characteristics; a photodetector configured to detect light pulses returning from the three-dimensional environment and generate an output signal representing the light energy associated with a subset of the light pulses; and one or more processors electrically coupled to the light source and the photodetector, wherein the one or more processors are configured to: generate temporal characteristics based on one or more real-time conditions; and determine one or more parameters for selecting a subset of the light pulses.

[0014] In some embodiments, one or more processors are further configured to calculate distances based on the time of flight associated with a subset of light pulses, and the time of flight is determined by matching the detected light pulse sequence with temporal characteristics. In some cases, one or more parameters used to select a subset of light pulses are determined based on the distance between the LiDAR system and an object in a three-dimensional environment.

[0015] In some embodiments, the timing characteristics include one or more of the following: amplitude of each pulse in the plurality of pulses, duration of each pulse in the plurality of pulses, time interval between the plurality of pulses, and number of the plurality of pulses. In some embodiments, the one or more parameters for selecting a subset of optical pulses are determined at least in part based on the timing characteristics. In some embodiments, the one or more parameters include the number of optical pulses in the subset or a parameter representing a combination of non-immediately adjacent optical pulses.

[0016] In some embodiments, the one or more real-time conditions are obtained based on detected light pulses. In some embodiments, the one or more real-time conditions include the detection of an object within a predetermined distance threshold. In some embodiments, the one or more processors are further configured to generate a 3D image based on the output signal.

[0017] In a related but independent aspect of the invention, a method for imaging using a light detection and ranging system is provided. The method may include: generating temporal characteristics based on one or more real-time conditions; transmitting a multi-pulse sequence into a three-dimensional environment, wherein the multi-pulse sequence comprises a plurality of pulses having the temporal characteristics; detecting light pulses from the three-dimensional environment; and generating an output signal representing the light energy associated with a subset of the light pulses.

[0018] In some embodiments, the method further includes determining one or more parameters for selecting a subset of optical pulses. In some cases, the one or more parameters for selecting a subset of optical pulses are determined based on the distance between the LiDAR system and an object located in a three-dimensional environment. In some cases, the one or more parameters for selecting a subset of optical pulses are determined at least in part based on temporal characteristics. In some cases, the one or more parameters include the number of optical pulses in the subset or parameters representing combinations of non-immediately adjacent optical pulses.

[0019] In some embodiments, the method further includes calculating the distance based on the time of flight associated with the detected light pulses. In some cases, determining the time of flight includes determining that the sequence of detected light pulses matches temporal characteristics.

[0020] In some embodiments, the timing characteristics include one or more of the following: amplitude of each of the plurality of pulses, duration of each of the plurality of pulses, time interval between the plurality of pulses, and number of the plurality of pulses.

[0021] In some embodiments, the one or more real-time conditions are obtained based on detected light pulses. In some embodiments, the one or more real-time conditions include the detection of an object within a predetermined distance threshold.

[0022] In some embodiments, the method further includes generating a 3D image based on the output signal. In some cases, the output signal corresponds to the intensity value of a pixel in the 3D image.

[0023] Other aspects and advantages of this disclosure will immediately become apparent to those skilled in the art from the following detailed description. This disclosure only shows and describes exemplary embodiments, and only illustrates the best mode contemplated for carrying out this disclosure. It should be understood that other different embodiments of this disclosure may be possible, and its various details may be modified in a variety of obvious ways, all without departing from this disclosure. Therefore, the drawings and description are to be considered illustrative in nature and not restrictive.

[0024] By incorporating via reference

[0025] All publications, patents and patent applications mentioned in this specification are incorporated herein by reference to the same extent that each individual publication, patent or patent application is specifically and individually indicated as being incorporated by reference. Attached Figure Description

[0026] The features of the invention are particularly set forth in the appended claims. A detailed understanding of the features and advantages of the invention will be obtained by referring to the following detailed description. These descriptions establish several illustrative embodiments utilizing the principles of the invention, along with a detailed description of the accompanying drawings, which include:

[0027] Figure 1 An example of a detection signal contaminated by stray light is shown.

[0028] Figure 2 A method for transmitting a double-pulse sequence according to some embodiments of the present invention is shown.

[0029] Figure 3 Examples of multi-pulse sequences according to some embodiments of the present invention are shown.

[0030] Figure 4 Examples of detection signals generated by an avalanche photodiode (APD) according to some embodiments of the present invention are shown.

[0031] Figure 5 The illustration shows an exemplary method for obtaining obstacle information according to some embodiments of the present invention.

[0032] Figures 5A-5D It illustrates various measurement scenarios that enable accurate distance measurements.

[0033] Figure 6 The illustration depicts a method for processing detection signals to obtain obstacle information according to some embodiments of the present invention.

[0034] Figure 7 A schematic diagram of a laser pulse emitting device according to some embodiments of the present invention is shown.

[0035] Figure 8 A schematic diagram of an exemplary laser pulse emitting device according to some embodiments of the present invention is shown.

[0036] Figure 9 An example of a laser pulse emitting device according to some embodiments of the present invention is illustrated schematically.

[0037] Figure 10 An example is shown where a selected subset of pulses is accumulated in a returned multi-pulse sequence to generate a sensor output signal.

[0038] Figure 11 An example of a multi-pulse sequence with varying peak power is shown.

[0039] Figure 12 A configurable multi-pulse sequence adapted to eye safety requirements is shown.

[0040] Figure 13 A block diagram of a Lidar system according to some embodiments of the present invention is shown schematically. Invention Details

[0042] While preferred embodiments of the invention have been shown and described herein, it will be apparent to those skilled in the art that these embodiments are provided by way of example only. Many variations, modifications, and substitutions will now occur to those skilled in the art without departing from the invention. It will be understood that various alternatives may be made to the embodiments described herein when practicing the invention.

[0043] LiDAR is a ranging sensor characterized by its long detection range, high resolution, and low susceptibility to environmental interference. LiDAR has been widely used in fields such as intelligent robots, drones, and autonomous driving. The working principle of LiDAR is to estimate distance based on the round-trip time (e.g., flight time or delay time) between the electromagnetic wave and the target.

[0044] As used herein, the term "multipulse sequence" generally refers to a sequence of pulses or signals. Unless the context otherwise requires, the terms "measurement signal" and "measurement pulse" generally refer to optical pulses emitted from the transmitter of a LiDAR system. The term "echo beam" generally refers to a returning signal or pulse. Delay time can refer to the time interval between the departure of the optical pulse sequence from the transmitter and the reception of the reflected optical pulse sequence at the receiver. The delay time can then be used to calculate distance measurements. The delay time may also be referred to as time of flight, and this term is used interchangeably throughout the specification.

[0045] A light pulse sequence can comprise multiple pulses emitted within a short duration, allowing it to be used to obtain distance measurement points. For example, LiDAR can be used for three-dimensional (3D) imaging or obstacle detection. In this case, the distance measurement associated with the light pulse sequence can be considered as a single pixel, and the continuously emitted and captured set of pixels can be presented as an image or analyzed for other reasons (e.g., obstacle detection). Light pulse sequences can be generated and emitted for durations not exceeding 10 ns, 20 ns, 30 ns, 40 ns, 50 ns, 60 ns, 70 ns, 80 ns, 90 ns, 100 ns, 200 ns, 300 ns, 400 ns, 500 ns, 600 ns, 700 ns, 800 ns, 900 ns, 1 μs, 2 μs, 3 μs, 4 μs, 5 μs, or longer. In some cases, the time interval between adjacent sequences can correspond to the temporal resolution of 3D imaging. The time interval between sequences can be constant or variable. In some embodiments, a sequence of light pulses is emitted from a light source guided or rotated by a rotor or scanner of the Lidar system. The duration of this sequence can be short enough that multiple pulses are emitted in substantially the same direction in the 3D environment, or multiple pulses can be used to measure the distance from the Lidar system to a specific location in the 3D environment.

[0046] In some cases, a multi-pulse sequence can be emitted to a single point in a 3D environment, and subsequent multi-pulse sequences can be emitted to different points in the 3D environment. In some cases, all pixels (e.g., distance measurements) are obtained using a multi-pulse sequence. In other cases, a selected subset of pixels is obtained using a multi-pulse sequence, and the remaining pixels can be obtained using an uncoded signal (e.g., a single light pulse). For example, in 3D imaging, a selected subset of pixels can be obtained using a coded signal, so that each pixel can be generated based on a multi-pulse sequence, and another subset of pixels can be obtained using an uncoded signal, so that each pixel can be generated using a single light pulse. In some cases, selected portions of multiple pulses returned in the sequence can be used to obtain pixel values ​​(e.g., intensity) and / or to calculate distance.

[0047] In some embodiments, multi-pulse sequences including optical pulses can be used to improve the dynamic range of the detector, the signal-to-noise ratio (SNR) of the detected signal, or the contrast, which would otherwise be limited by stray light. Stray light in a LiDAR system can be caused by a variety of sources. For example, transmitted light can contaminate or interfere with the detector's reception of the returned beam. This contamination or interference can cause near-field echoes to be difficult to identify. For example, during laser pulse emission, a small fraction of the emitted pulses may be directly received by a detector such as an avalanche photodiode (APD), causing the detection circuit of a high-sensitivity APD to enter the nonlinear saturation region. When the detection circuit saturates, the amplification factor of the stray light waveform tail is greater than that of its top pulse, increasing the pulse width of the stray light pulse in the detection circuit. This causes the laser pulse echo signal reflected from near-field obstacles to be submerged in the trailing waveform tail of the stray light. The location of the near-field obstacle cannot be determined, resulting in a measurement blind zone. The detector may be referred to as a photodetector, optical receiver, optical sensor, photodetector, photosensitive detector, or optical detector, and these terms are used interchangeably throughout this specification. Unless otherwise specified, in this application, the terms "optical pulse subset," "returning pulse subset," "returning optical pulse subset," and "subset" can all refer to the returning optical pulse subset and can all represent the same meaning.

[0048] Figure 1 An example of the detected return signal being contaminated by stray light is shown. As mentioned above, when part of the emitted laser pulse is directly absorbed by the APD, the detection circuit may saturate, thereby obscuring the laser pulse echo signal reflected by near-field obstacles and creating a measurement blind zone.

[0049] like Figure 1 As shown, when a laser pulse is emitted from the transmitter of a LiDAR system, a portion of the emitted laser pulse may be scattered or deflected within the LiDAR system and directly received by the detector. For example... Figure 1As shown, the detector's detection circuit has a saturation value; detection signals exceeding this saturation value will be truncated to it. The detection (voltage) signal generated by the APD can include a flat voltage segment 11, the value of which corresponds to the saturation of the detection circuit. This flat segment 11 is caused by the APD directly absorbing stray light. Figure 1 The detected signals also include laser pulse echo signals 12 caused by laser pulses reflected from near-field obstacles. Because stray light directly absorbed by the APD causes saturation of the detection circuit, the flat voltage segment 11 equals the voltage saturation value, which may be greater than the laser pulse echo signal 12 reflected from near-field obstacles. Figure 1 As shown, echo signal 12 is detected at the edge of the detection signal. Due to the small peaks and valleys of echo signal 12, it is still possible to detect it. In some cases, echo signal 12 appears in segment 11, causing echo signal 12 to be completely obscured and making it impossible to obtain distance information of near-field obstacles. In this case, a measurement blind zone is created. The saturation voltage signal caused by stray light has a duration Ta, which can be considered as the duration of the measurement blind zone. Within the duration Ta of the measurement blind zone, the detector cannot accurately detect the reflected laser pulse echo signal, and therefore cannot obtain distance information of obstacles.

[0050] Traditional LiDAR systems may employ two technical solutions to address the aforementioned issues: i. using a narrower transmit pulse width to reduce the measurement blind zone; ii. replacing the original fixed-gain amplifier with a fast-adjustable gain amplifier after the avalanche photodiode (APD). This can appropriately reduce the gain saturation effect of stray light and reduce the measurement blind zone by using a small gain for strong reflected light and a large gain for weak reflected light. Existing solutions have drawbacks. For example, reducing the transmit pulse width increases the detection bandwidth. However, this introduces more RF noise, significantly increasing the cost of the transmitter and detector units. The adjustable-gain amplifier solution merely optimizes the amplifier circuit after the APD in the detection circuit, improving the dynamic range without changing the internal gain of the APD. Therefore, in most cases, due to the high gain of the APD, the stray light signal is already saturated within the APD, and the subsequent amplifier circuit cannot address the saturation effect of the APD itself and the resulting blind zone problem.

[0051] In some embodiments of this application, a multi-pulse sequence comprising multiple optical pulses of different amplitudes can be used to eliminate measurement blind zones. In some cases, the multi-pulse sequence may include a first laser pulse with low peak power emitted at a first moment and a second laser pulse with high peak power emitted at a second moment. The multi-pulse sequence may be emitted in substantially the same direction in 3D space or emitted to a single point. Because the peak power of the first laser pulse is relatively low, stray light will not cause voltage saturation in the detection circuit, thus enabling the detection of the first laser pulse echo signal reflected by near-field obstacles. Using optical pulses of different amplitudes can effectively solve the problem of measurement blind zones for near-field obstacles caused by stray light inside the LiDAR, while using a second laser pulse with higher peak power maintains the detection of far-field obstacles.

[0052] Alternatively or otherwise, the multiple optical pulses in a multipulse sequence may have the same amplitude. This disclosure provides a method for transmitting a multipulse sequence with a preset temporal profile. This advantageously allows the detector to generate a configurable sensor output signal by accumulating selected return optical pulses, thereby providing a high dynamic range detector. The preset temporal profile also helps to suppress crosstalk between channels and improve the measurement accuracy of near-field obstacles. In some cases, the multipulse sequence may be a dual-pulse sequence. A method for generating a multipulse sequence may include: transmitting a first laser pulse at a first time; transmitting a second laser pulse at a second time, wherein the peak power of the first laser pulse is lower than the peak power of the second laser pulse, and the time interval between the second time and the first time is greater than T, where T is the duration between the time of laser pulse transmission and the time of receiving the laser pulse echo signal reflected by a near-field obstacle.

[0053] Figure 2 A method for transmitting a double-pulse sequence according to some embodiments of the present invention is illustrated. The double-pulse sequence can extend the measurement range to the near field at low cost. The double-pulse sequence may include laser pulses with different peak powers, and a single double-pulse sequence may correspond to a point in space. The double-pulse sequence can be used to generate distance measurements. The method of transmitting the laser pulse may include: transmitting a first laser pulse at a first time in step S201; and transmitting a second laser pulse at a second time in step S202. In some cases, the peak power of the first laser pulse is lower than the peak power of the second laser pulse. In some cases, the time interval between the second time and the first time is greater than T, where T is the duration between the time of transmitting the laser pulse and the time of receiving the laser pulse echo signal reflected by a near-field obstacle.

[0054] In traditional LiDAR systems, the emitted laser pulses are directly absorbed by the APD, causing the detection circuit to saturate and thus obscuring the laser pulse echo signals reflected from near-field obstacles, creating a measurement blind zone. The proposed dual-pulse emission method, which emits a weak first laser pulse at the first moment for near-field obstacle measurement and a strong second laser pulse at the second moment for far-field obstacle measurement, effectively avoids this measurement blind zone.

[0055] In some cases, since a weak first laser pulse can be used to measure near-field obstacles, the time interval between the second and first moments can be greater than the time interval T to improve the accuracy of near-field obstacle measurements. The time interval T can be the delay time corresponding to the measurement of the near-field obstacle, i.e., the duration between the moment the laser pulse is emitted and the moment the echo signal of the same laser pulse reflected by the near-field obstacle is received. The time interval T can be a preset value corresponding to distance measurements that may be contaminated by stray light. For example, a value of T can be chosen such that the return signal of the first laser pulse can be detected without being obscured by stray light from the second laser pulse. The value of T can be determined based on the characteristics of the stray light of the second laser pulse and / or the typical range of TOF. For example, T can be in the range of 10 ns to 500 ns.

[0056] According to one embodiment of the Lidar system described in this application, due to the low power of the first laser pulse, the direct absorption of stray light caused by the first laser pulse by the APD will not cause APD saturation. Subsequently, the pulse signal reflected by obstacles in 3D space can be effectively separated or distinguished from noise, thereby eliminating the measurement blind zone. Using light pulses of different amplitudes can effectively solve the measurement blind zone problem of near-field obstacles caused by stray light inside the Lidar, while using a second laser pulse with higher peak power maintains the detection of far-field obstacles.

[0057] Figure 3 Examples of multi-pulse sequences according to some embodiments of the present invention are shown. The laser pulses can be a dual-pulse sequence comprising two pulses with different peak powers. For example... Figure 3As shown, at time T1, a first laser pulse 31 with a first peak power P1 can be emitted, and at time T2, a second laser pulse 32 with a second peak power P2 can be emitted. In some cases, P2 can be greater than P1, for example, at least ten times, 20 times, 50 times, 100 times, 200 times, 500 times, or more than P1. The time interval between T2 and T1 is T. The pulse width can be any commonly used range, such as 1 ns - 1000 ns. P1 can be any value for which stray light will not cause saturation of the photodetector, while P2 can be any value for which stray light may cause saturation of the photodetector. For example, P1 can have a value no greater than 20 W, 10 W, 1 W, 0.1 W, or less. The value of P1 can be determined based on empirical data. For example, P1 can be determined during the calibration or pre-operation phase, which generates a certain range of peak powers, and the peak power that causes APD saturation can be determined. Then, P1 can be selected to be a value no greater than the peak power that causes APD saturation. For example, because P1 is low, the corresponding stray light will not cause APD saturation, thus effectively separating the echo signal reflected by the near-field obstacle from the first laser pulse 31 from the detected stray light signal. The peak power of the second laser pulse 32 can be selected so that long-distance measurement can be achieved through the high peak power of the second laser pulse. For example, the peak power of the second laser pulse can be selected to be sufficient for distance measurement in the far field. The echo signal corresponding to the far field can be distinguished from the waveform trailing of the stray light (i.e., not annihilated) because the echo signal can be received after the detector's saturation period (e.g., due to a larger TOF), and / or the amplitude of the echo signal is greater than the waveform trailing of the stray light. This can advantageously enable the detection of far-field obstacles without interference from stray light.

[0058] Can launch such as Figure 3 The diagram shows a dual-pulse sequence, and the returning pulses can be received by a detector (e.g., an avalanche photodiode). The detector can output a probe voltage signal, which can be further processed to calculate distance or obtain obstacle information over a wide range. Figure 4 An example of a detection signal generated by an avalanche photodiode (APD) is shown. The detection signal can be represented as... Figure 3 The returned pulses corresponding to the dual-pulse sequence shown. The probe signal can be a voltage signal generated by the APD. For example... Figure 4The detection signals shown may include: a first voltage signal 41 caused by stray light corresponding to the emitted first laser pulse 31; an echo signal 42 of the laser pulse 31 reflected by an obstacle in the near field; a second voltage signal 43 caused by stray light corresponding to the absorption of the emitted second laser pulse 32 by the APD, resulting in saturation of the detection circuit; and an echo signal 44 of the second laser pulse 32 reflected by the (same) obstacle in the near field. The time delay of the first laser pulse 31 being reflected by the near-field obstacle is denoted as X1, the emission time interval between the second laser pulse 32 and the first laser pulse 31 is denoted as T, and the duration of the voltage signal 43 corresponding to the time window during which the returned lower peak power echo signal may be contaminated / annihilated is denoted as Ta. As described elsewhere in this document, in some cases, this time window may correspond to the measurement blind zone in a conventional Lidar system. It should be noted that the measurement blind zone may refer to the saturation time window of the detector, during which near-field measurements may be contaminated by stray light. Unless the context otherwise requires, the duration Ta may refer to the measurement blind zone of a conventional Lidar system throughout this specification. In some cases, the time interval T is greater than Ta, i.e., T>Ta, such that the return signal of the first laser pulse 31 is not saturated by stray light from the second laser pulse, while the time delay of the second laser pulse 32 being reflected by a near-field obstacle is T+X1. Note that this example is for illustrative purposes only, and the detection signals may have different configurations. For example, due to various characteristics of the Lidar system (e.g., detector sensitivity, optics in the system, etc.), the peak power of the echo signal 41 may be greater than or may not be greater than that of the echo signal 42.

[0059] Figure 5 Exemplary processes for acquiring obstacle information according to some embodiments of the present invention are illustrated. In some cases, the process of acquiring obstacle information may include the following operations: calculating and acquiring distance information of near-field obstacles based on the echo signal of a first laser pulse (operation S501); calculating and acquiring distance information of far-field obstacles based on the echo signal of a second laser pulse (operation S502).

[0060] Because the first laser pulse has low power, even if the corresponding stray light is directly absorbed by the APD system, the stray light will not cause APD saturation, and the distance information of near-field obstacles can be calculated and obtained. At the same time, because the second laser pulse signal has high power and a sufficiently long delay time corresponding to the far-field obstacle, it is sufficient to separate the actual return signal (such as the detection signal 44) from the corresponding stray light signal (such as the detection signal 43), and the distance information of the far-field obstacle can be calculated and obtained based on the echo signal of the second laser pulse.

[0061] The following Figure 5A-D shows the emitted laser pulses and the returned signals of each laser pulse detected when the laser pulse is pointed at an object moving from a near-field position to a far-field position. In each figure, a double-pulse sequence is emitted and pointed at the object. In each figure, two emitted pulses (p1' and p2') are shown, along with two returned signals (p1 and p2) corresponding to each pulse reflected by the object. The double-pulse sequence consists of an earlier emitted low-power pulse p1' and a later emitted high-power pulse p2'. As a result, stray light from the second high-power laser pulse will cause detector saturation and may overlay / annihilate the returned signals, depending on the relationship between the measured TOF and the double-pulse emission interval, which will be discussed in the following sections of the specification. Figure 5A This represents the first instance, where the object is located near the LiDAR and the detector saturation time caused by the second laser pulse partially covers the return signal of the second pulse. Figure 5B This represents the second instance, where the object is further away from the LiDAR, and the detector saturation time caused by the second laser pulse does not cover the return signal of any emitted pulse. Figure 5C This represents the third instance, where the object moves further away from the LiDAR, and the detector's saturation time caused by the second laser pulse annihilates the return signal of the first pulse. Figure 5D The fourth example illustrates a scenario where the object is located very far from the LiDAR, and the detector saturation caused by the second laser pulse does not overwrite any returned signal. The dual-pulse sequence and corresponding measurement method can advantageously extend the measurement distance range and adapt to various scenarios.

[0062] Figure 5A The illustration shows a scenario where a probe signal returns from a near-field object. In the example shown, the probe signal could be a voltage signal generated by an avalanche photodiode (APD). The probe signal could include, for example, a voltage signal generated by an avalanche photodiode (APD). Figure 3 The return pulse corresponding to the double-pulse sequence shown. For example... Figure 5 The detection signal shown can be basically similar to Figure 4The signals shown are as follows. For example, the detection signals may include: a first voltage signal 51 caused by stray light corresponding to the emitted first laser pulse (e.g., small laser pulse 31); an echo signal 52 of the laser pulse (e.g., small laser pulse 31) reflected by an obstacle in the near field; a second voltage signal 53 caused by stray light corresponding to the emitted second laser pulse (e.g., large laser pulse 32) causing saturation of the detection circuit; and an echo signal 54 of the second laser pulse (e.g., large laser pulse 32) reflected by the same obstacle in the near field. The time delay (i.e., TOF) of the first laser pulse 51 reflected by the near-field obstacle is denoted as X, and in some cases, it can be measured as the time delay between peaks p1' and p1, which correspond to the first voltage signal 51 and the second voltage signal 52, respectively. It should be noted that the emission time of the laser pulse can be the time corresponding to the peak power of the stray light, the control signal that triggers the laser pulse, etc. The difference in emission time using different signals can be a constant value, and the delay time can be measured using any signal (as emission time) based on Lidar system settings or calibration. The voltage signals corresponding to the stray light (e.g., voltage signals 51 and 53) can be known in advance. For example, such signals (e.g., timing, waveform, etc.) can be based on optical system characteristics and the emitted light pulses (e.g., amplitude), rather than on the detection distance. The emission time interval between the second laser pulse 32 and the first laser pulse 31 is denoted as T. delay This can be a known value, such as obtained from the signal that triggers the laser pulse. The duration of the voltage signal 53, corresponding to the time length of the measurement blind zone, is denoted by Ta and can be obtained by processing the probe signal. In the near-field scenario illustrated, the echo signal 52 of the first laser pulse is not obscured by the saturation caused by the second laser pulse and also has a signal-to-noise ratio greater than a predetermined threshold. In this case, the time delay X, i.e., the flight time corresponding to the first laser pulse, can be used to measure the distance.

[0063] In the second scenario, the double-pulse sequence can be reflected by obstacles located at a greater distance than in the first scenario. Figure 5B A second scenario is illustrated, in which the echo signal 52 of the second laser pulse is not obscured by saturation caused by stray light from the second laser pulse. In the illustrated example, the signal-to-noise ratio (SNR) of the echo signal 54 of the second laser pulse is greater than that of the first echo signal 51. In this case, the second laser pulse signal and the corresponding echo signal can be used to generate a distance measurement. For example, this can be achieved by measuring the time interval T between the first voltage signal 51 (e.g., the peak value p1' of the probe signal 51) and the last probe signal, i.e., the second echo signal 54 (e.g., the peak value p2 of the probe signal 54). delay +X, then subtract the known T between the first and second laser pulses. delayThe time of flight X can be calculated using a different method. Alternatively, other suitable methods can be used to obtain the time of flight based on the second laser pulse and the corresponding echo signal. For example, the time of flight X can be calculated based on the time interval between the peak p2' of the stray light-induced voltage signal 53 and the peak p2 of the second echo signal 54. In some cases, the delay time X of the first and second laser pulses can be calculated, and the average of the two can be used as the final output. Alternatively or otherwise, the SNR can be calculated for the two echo signals, and the delay time X can be obtained using the signal with the better SNR.

[0064] In the third scenario, the double-pulse sequence can be reflected by obstacles located at a greater distance than in the first or second scenario. Figure 5C A third scenario is illustrated, in which the echo signal 52 of the second laser pulse is saturated by the stray light 53 of the second laser pulse. In this case, the second laser pulse signal and the corresponding echo signal can be used to generate a distance measurement. For example, this can be achieved by measuring the time interval T between the first voltage signal 51 (e.g., the peak value p1' of the voltage signal 51) and the last detection signal 54 (e.g., the peak value p2 of the detection signal 54). delay +X, then subtract the known T between the first and second laser pulses. delay The flight time X can be calculated using the second laser pulse and the corresponding echo signal. Alternatively, other suitable methods can be used to obtain the flight time based on the second laser pulse and the corresponding echo signal. For example, the flight time X can be calculated based on the time interval between the peak value p2' of the stray light-induced voltage signal 53 and the peak value p2 of the second echo signal 54.

[0065] In the fourth scenario, the double-pulse sequence can be reflected by obstacles located in the far field. Figure 5D A fourth scenario is shown, in which neither echo signals 52 nor 54 are obscured by saturation caused by stray light. In this case, due to the far-field range, the signal-to-noise ratio (SNR) of the echo signal 54 of the second laser pulse can be greater than that of the first echo signal 51. The second laser pulse signal and the corresponding echo signal can be used to generate a distance measurement. For example, the distance measurement can be generated by measuring the time interval T between the first voltage signal 51 (e.g., the peak value p1' of the probe signal 51) and the last probe signal 54 (e.g., the peak value p2 of the echo signal 54). delay +X, then subtract the known T between the first and second laser pulses. delay The flight time X can be calculated using a different method. Alternatively, other suitable methods can be used to obtain the flight time based on the second laser pulse and the corresponding echo signal. For example, the flight time X can be calculated based on the time interval between the peak value p2' of the stray light-induced voltage signal 53 and the peak value p2 of the second echo signal 54.

[0066] As mentioned above, dual-pulse sequences can be advantageously used for near-field and far-field distance measurements. Figure 6 An exemplary method for processing detection signals to obtain obstacle information over an extended distance range, according to some embodiments of the present invention, is illustrated. As described above, the voltage signals (e.g., voltage signals 51 and 53) caused by stray light can be known in advance. For example, the detection signals corresponding to stray light (e.g., timing, waveform, etc.) can be based on optical system characteristics and emitted light pulses (e.g., amplitude, trigger time, etc.) and can remain unchanged regardless of the detection distance. For example, the timing and / or waveform of the stray light signal can be known during system setup or calibration. Based on such information, echo signals can be analyzed for stray light signals (e.g., voltage signals 51 and 53), and the correct distance can be calculated. For example, the signal processing algorithm can include detecting the presence of one or both voltage signals (e.g., echo signals) relative to the voltage signals corresponding to the stray light, and determining a qualified echo signal or corresponding delay time based on different presence scenarios. Various different presence scenarios can be associated with... Figures 5A-5D The same as those discussed in [the text]. For example, various existence scenarios can include situations where there are two stray light signals (e.g., [the text is incomplete]). Figure 5A There is a clear detection signal between signals 51 and 53 in the signal (e.g., Figure 5A Signal 52 in the middle), and there is no clear detection signal after the second stray light signal; two stray light signals (e.g. Figure 5B There is a clear detection signal (e.g., between signals 51 and 53) in the signal(s). Figure 5B The signal 52 in the middle), and there is a clear detection signal (e.g., after the second stray light signal) after the second stray light signal. Figure 5B Signal 54); two stray light signals (e.g., Figure 5C There is no probe signal between signals 51 and 53 in the signal spectrum, and there is a clear probe signal after the second stray light signal (e.g., Figure 5C Signal 54), two stray light signals (e.g. Figure 5C There is no probe signal between signals 51 and 53 in the above, and there are two clear probe signals (e.g., after the second stray light signal) after the second stray light signal. Figure 5C Signal 54 in the middle.

[0067] An example method for processing the probe signal according to the aforementioned scenario may include: determining the number of clear and non-overlapping waveforms following the signal corresponding to the stray light caused by the second light pulse (operation S601). If the number is two, the method may continue. Figure 5DThe process described in [the document] is used to calculate the distance (operation S602). If the quantity is one, the method can continue to determine whether a waveform exists between the two stray light signals, and if no waveform exists between the two stray light signals, then [the method can] use [the appropriate method]. Figure 5C The process described in the text is used to calculate the distance; otherwise, the following can be used: Figure 5B The process described in [the document] is used to calculate the distance (operation S602). In operation S601, if no waveform is detected after the second stray light signal, the method can continue to determine whether there is a clear and non-overlapping waveform between the two stray light signals (operation S603). If it exists, then [the method can be used]. Figure 5A The process described in the document is used to calculate the distance (operation S604), otherwise the process can be terminated (operation S605) and the corresponding detection signal is not used to output a valid distance measurement value.

[0068] Although Figure 6 Methods according to some embodiments are illustrated, and those skilled in the art will recognize that many adaptations are possible for various embodiments. For example, operations can be performed in any order. Some operations can be excluded, some operations can be performed simultaneously in a single step, some operations can be repeated, and some operations can include sub-steps of other operations. For example, instead of detecting a clear and non-overlapping waveform after a second stray light signal in a first operation, it can be determined that a clear and non-overlapping waveform exists between two stray light signals. The method can also be modified according to other aspects of this disclosure provided herein.

[0069] The presence of a clear and non-overlapping waveform can be detected using any suitable method described elsewhere in this document. For example, operation S601 can determine the presence of a clear signal after the second stray light signal. This can be achieved by detecting after T2 (as in, for example, in...). Figure 5A or Figure 5B The operation is performed when one or more waveforms (e.g., SNR greater than a predetermined threshold) exist at the time corresponding to the detection signal of the stray light caused by the second pulse (e.g., pulse width greater than a predetermined threshold). As described above, by checking the SNR, pulse width, or other parameters of the detected waveforms, the waveforms can be determined to be clear and non-overlapping. When it is determined that two clear and non-overlapping waveforms exist, the method can continue to be used. Figure 5D The process described in the document calculates the distance (operation S602).

[0070] As described above, if a clear signal is detected or no clear signal is detected after the second stray light signal, the method can continue to determine whether a clear signal exists between the two stray light signals. This can be achieved by detecting T1 (e.g., with, for example...). Figure 5A or Figure 5B The time corresponding to the detection signal of stray light caused by the first pulse of 51 (e.g., the time of T1) and T2 (and, for example, the time of T2) Figure 5A or Figure 5B The detection signal of stray light caused by the second pulse (e.g., at the time corresponding to the detection signal) exists between waveforms (e.g., SNR greater than a predetermined threshold) to perform the operation. Similarly, the SNR, pulse width, or other parameters of the detected waveform can be processed to determine whether the waveform is clear and non-overlapping.

[0071] In some cases, during operation S602, the distance information of the far-field obstacle can be calculated and obtained based on the reflection delay of the second pulse waveform. In other cases, since the time delay of the second pulse waveform is distance-dependent, the distance information of the far-field obstacle can be calculated and obtained based on the time delay of the second pulse waveform. In some cases, since the second laser pulse 32 is delayed by a time interval T relative to the first laser pulse 31, the time delay can be calculated based on T+X2 to obtain the distance information of the obstacle, where X2 is the duration between the moment the second laser pulse 32 is emitted and the moment the echo signal of the second laser pulse 32 reflected from the far-field obstacle is received.

[0072] In operation S603, the process can continue to determine whether a clear and non-overlapping waveform exists between the first voltage signal 41 caused by stray light and the second voltage signal 43 caused by stray light. When a clear and non-overlapping waveform is determined, the method can continue to operation S604; otherwise, operation S605 can be executed to terminate the detection iteration. In some cases, when there is no clear and overlapping waveform after the second voltage signal 43 caused by stray light within the Lidar system, it indicates that there are no obstacles in the far field, and further analysis can be performed to determine whether there are obstacles in the near field. When there is a clear and non-overlapping pulse waveform between the first voltage signal 41 caused by stray light and the second voltage signal 43 caused by stray light, it indicates that there are obstacles in the near field. The pulse waveform is the first pulse waveform, which is the echo signal of the first laser pulse 31 reflected by the near-field obstacle.

[0073] In operation S604, the distance information of near-field obstacles can be calculated and obtained based on the time delay of the first pulse waveform. In some cases, the time delay can be calculated based on X1 to obtain the distance information of near-field obstacles, where X1 is the duration between the moment the first laser pulse 31 is emitted and the moment the echo signal of the first laser pulse 31 reflected by the near-field obstacle is received.

[0074] In certain situations, when there is no clear and overlapping second pulse waveform after the second voltage signal 43 caused by stray light inside the Lidar system, and there is no clear and non-overlapping first pulse waveform between the first voltage signal 41 caused by stray light and the second voltage signal 43 caused by stray light, the detection ends (operation S605), and the conclusion is that there are no obstacles in the far field and near field.

[0075] Figure 7 A functional diagram of a laser pulse emitting device 70 according to some embodiments of the present invention is shown schematically. The laser pulse emitting device may also be referred to as an emitting device or an emitting module; these terms are used interchangeably throughout the specification. Figure 7 As shown, the laser pulse emitting device 70 may include a waveform generator 71 and a laser 72 coupled thereto. In some embodiments, the waveform generator 71 may be adapted to output a first driving current to the laser 72 at a first moment and a second driving current to the laser 72 at a second moment, wherein the current value of the second driving current may be greater than the current value of the first driving current. In some cases, the time interval between the second moment and the first moment may be greater than T, where T is the duration between the moment the laser pulse is emitted and the moment the laser pulse echo signal reflected from a near-field obstacle is received.

[0076] Laser 72 can be configured to generate and emit a first laser pulse at a first moment based on a first drive current input to waveform generator 71; and to generate and emit a second laser pulse at a second moment based on a second drive current input to waveform generator 71. In some cases, the laser can be a semiconductor laser or other types of lasers.

[0077] Figure 8 A schematic diagram of an exemplary laser pulse emitting device 80 according to some embodiments of the present invention is shown. Figure 8 As shown, the laser pulse emitting device 80 may include a laser 81, and a first branch 82 and a second branch 83 coupled to the laser 81. In some cases, the first branch 82 may include a first branch optical fiber 821 and a first attenuator 822 coupled to each other. The second branch 83 may include a second branch optical fiber 831 and a second attenuator 832 coupled to each other. In some cases, the attenuation value of the second attenuator 832 may be less than the attenuation value of the first attenuator 822. In some cases, the delay introduced by the second branch optical fiber 831 may be greater than the delay introduced by the first branch optical fiber 821, the delay time interval being denoted by T, where T is the duration between the moment the laser pulse is emitted and the moment the laser pulse echo signal reflected by a near-field obstacle is received. The laser 81 may be a semiconductor laser or any other suitable type of laser.

[0078] Figure 9 An example of a laser pulse emitting device 90 according to some embodiments of the present invention is illustrated schematically. Figure 9As shown, the laser pulse emitting device 90 may include a first emitting unit 91 and a second emitting unit 92. In some embodiments, the first emitting unit 91 may be configured to emit a first laser pulse at a first moment. The second emitting unit 92 may be configured to emit a second laser pulse at a second moment. In some cases, the peak power of the first laser pulse may be lower than the peak power of the second laser pulse. In some cases, the time interval between the second moment and the first moment may be greater than T, where T is the duration between the moment the laser pulse is emitted and the moment the laser pulse echo signal reflected from a near-field obstacle is received.

[0079] As described above, the multi-pulse sequence emitted by the transmitting device can be reflected by obstacles in the three-dimensional environment and returned to the detector. In some cases, the delay time interval or time of flight associated with the detected light pulse sequence can be the average of the time of flight associated with each detected light pulse.

[0080] In some cases, the receiver module of a LiDAR system may include one or more avalanche photodiodes (APDs) or one or more single-photon avalanche photodiodes (SPADs). In other cases, the receiver module may include a photodetector, such as one or more PN photodiodes (e.g., a photodiode structure formed from p-type and n-type semiconductors) or one or more PIN photodiodes (e.g., a photodiode structure formed from an undoped intrinsic semiconductor region located between p-type and n-type regions). The photodetector may be a single photodetector capable of detecting photons, such as an avalanche photodiode, SPAD, RCP (resonant cavity photodiode), etc., or multiple photodetectors, such as a SPAD array, that work together to act as a single photodetector, typically having a higher dynamic range, lower dark count rate, or other beneficial characteristics than a single, larger photon detection region. Each photodetector may be an activated region capable of sensing photons (i.e., light). In some cases, the performance of the receiver module, such as the dynamic range of the detector, the signal-to-noise ratio of the detected signal, or the contrast, may be limited by stray light.

[0081] The LiDAR system disclosed herein can provide a detector with improved dynamic range, signal-to-noise ratio, and accuracy, adaptable to measurements over an extended range. In some cases, high dynamic range can be achieved by using pulses with low peak power for near-field measurements and pulses with high peak power for far-field measurements. Alternatively or additionally, high dynamic range can be achieved by acquiring fewer pulses from shorter distances, thereby reducing the overall intensity level of the detection signal for near-field scenes and avoiding high-intensity reflections from very close objects.

[0082] In some cases, the echo pulse detection circuit can be configured to convert the received photon energy into multiple parallel electrical signals, combine multiple subsets of parallel electrical signals, and output the combined electrical signal as the sensor output. Alternatively, when the electrical signal corresponds to a single optical pulse, the pulse detection circuit can generate a sensor output signal by accumulating different combinations of electrical signals. In some cases, the pulse detection circuit can generate a sensor output signal representing the optical energy associated with a selected subset of the returned optical pulses. The photon energy can be configured or adjusted by changing the number / count of returned optical pulses accumulated to generate the output signal, and / or by changing the selection of the subset of returned optical pulses so that the corresponding total optical energy can be selected.

[0083] In some cases, the measured or emitted light pulses can be modulated using preset timing characteristics. The Lidar system according to embodiments of this application may include a photoelectric sensor. A photoelectric sensor having a pixel array for generating a 3D image can be configured to accumulate a selected number of modulated pulses received in the activated region of the photoelectric sensor to generate a sensor output signal. The sensor output signal can determine the intensity of a pixel in the 3D image, and the intensity can be determined by the amount of light energy or light pulses accumulated during a time window. The intensity or amplitude of the output signal can be dynamically adjusted pixel-by-pixel. In some cases, the intensity or amplitude of the output signal can be adjusted individually for the activated region of the detector. The receiving module of the Lidar system may include a processing unit configured to read the sensor output signal generated by the accumulated pulses from the return pulse portion and generate an image and / or related image data based on the sensor output signal.

[0084] Figure 10 An example is shown of accumulating a selected subset of returned pulses from a returned multi-pulse sequence 1020 to generate a sensor output signal 1030. The multi-pulse sequence 1011 may include multiple pulses. The multi-pulse sequence 1011 may be laser pulses emitted from a transmitting device of a LiDAR system. The multi-pulse sequence may be emitted to a point in 3D space or along substantially the same direction. The multi-pulse sequence, or at least a portion thereof, may be used to generate a measurement signal. In some cases, the multi-pulse sequence may be a coded sequence of pulses modulated according to preset timing characteristics. Figure 11Another example of a multipulse sequence 1100 with different peak powers is shown. A multipulse sequence can include any number of pulses. For example, at least one, two, three, four, five, six, seven, eight, nine, ten, or more pulses can be generated and produce a multipulse sequence within a short time period Ti2. The duration of Ti2 can, for example, not exceed 10 ns, 20 ns, 30 ns, 40 ns, 50 ns, 60 ns, 70 ns, 80 ns, 90 ns, 100 ns, 200 ns, 300 ns, 400 ns, 500 ns, 600 ns, 700 ns, 800 ns, 900 ns, or longer. The duration Ti2 of different multipulse sequences may be the same or different. In some cases, the duration Ti2 of adjacent multipulse sequences may be different. The number of pulses in adjacent multipulse sequences may be the same or different.

[0085] exist Figure 11 In a multi-pulse sequence, the time interval Ti1 between any two adjacent pulses can be constant or variable. The time interval can, for example, be no more than 1 ns, 5 ns, 10 ns, 20 ns, 30 ns, 40 ns, 50 ns, 60 ns, 70 ns, 80 ns, 90 ns, 100 ns, 200 ns, or longer. The time interval Ti1 within the multi-pulse sequence can vary according to timing characteristics. For example, the time interval between the first and second pulses can differ from the time interval between the second and third pulses.

[0086] Within the multi-pulse sequence 1011, multiple pulses can have different amplitudes (e.g., Am n, Am n+1) 1100 or constant amplitudes. In some cases, the amplitude or intensity of the pulses can typically be at a lower level so that the accumulation of a selected subset of return pulses does not oversaturate the detector.

[0087] In some cases, a subset of return pulses can be selected based on one or more parameters. These parameters determine the amplitude or intensity of the sensor output signal. These parameters can be generated by a computing unit of a controller, such as that of a LiDAR system. In some cases, these parameters can be generated based on the temporal characteristics of a multi-pulse sequence and one or more real-time conditions. As mentioned above, the temporal characteristics of the sequence can be defined by the number of pulses, time intervals (e.g., Ti1), sequence duration (e.g., Ti2), pulse amplitude, or combinations thereof within the sequence. The one or more real-time conditions can include the estimated measurement range, objects detected in the near field, etc. In some cases, the number of pulses accumulated for generating the signal or the selection of pulses can be determined based on the detection range. For example, for measurements of long-distance objects (e.g., objects in the far field), a larger number of pulses can be accumulated because echoes reflected from the far field tend to be weak, while for measurements of short-distance objects (e.g., objects in the near field) or scenarios with higher reflectivity, a smaller number of pulses can be accumulated because echoes from the near field or highly reflective surfaces tend to be strong. This can benefit the improvement of the SNR of the sensor output signal regardless of the measurement distance range.

[0088] The one or more parameters may include, for example, parameters representing a selected subset of pulses. For instance, the one or more parameters may include the number of pulses accumulated to generate the sensor output signal or parameters representing a selected combination of pulses to generate the sensor output signal. The one or more parameters may include any other factors that can determine the total optical energy of the selected subset of pulses (e.g., the time window for receiving the returned optical pulses). For example, when multiple pulses in a multi-pulse sequence have constant amplitudes, the optical energy converted into a sensor output signal can be determined by the number of pulses. For example, as... Figure 10 As shown, the number / count of returned light pulses 1020 can be selected and accumulated to generate a sensor output signal. The number / count of light pulses selected from individual multi-sequences 1021, 1023 can be controlled individually, allowing the sensor output signal 1030 to have adjustable amplitude / intensity 1031, 1033. In some cases, when multiple pulses in a multi-pulse sequence have different amplitudes, the light energy converted into a sensor output signal can be determined by selecting a combination of pulses from the returned light pulses. For example, as... Figure 11As shown, the amplitudes of the light pulses in sequence 1100 can have a predetermined relationship, for example, the amplitude of a successive light pulse is twice that of the previous light pulse (e.g., Am n+1 / Am n=2). In this case, by selecting different combinations of light pulses, multiple values ​​of accumulated light energy can be generated. The subset of light pulses selected to generate the sensor output signal can be, or may not be, a sequence of adjacent light pulses. For example, non-adjacent light pulses can be selected to generate the sensor output signal.

[0089] The timing characteristics can be predetermined and may not change over time, thereby allowing for the adjustment of detection range and / or measurement accuracy by varying the light energy used to generate the output signal. Alternatively or otherwise, the emitted light pulses can be dynamically adjusted based on one or more real-time conditions. In some cases, the timing characteristics can be dynamically adjusted based on one or more real-time conditions. The methods and systems for providing dynamic timing characteristics are identical to those described in U.S. Patent No. 10,466,342, filed October 30, 2018, the entire contents of which are incorporated herein by reference.

[0090] The parameters used to determine the subset of returned signals for generating the sensor output may be preset. Alternatively or otherwise, the parameters may be dynamically determined based on the one or more real-time conditions, such as estimated / target measurement range (e.g., near-field obstacle detection or imaging, far-field obstacle detection or imaging), temporal variations in the transmitted signal, eye safety limitations, and various other factors.

[0091] In some cases, to meet eye safety regulations, the emitting device of a Lidar system can be configured to adjust the instantaneous laser pulse energy to control the maximum energy over a specific time period. Figure 12 Configurable multi-pulse sequences that adaptively meet eye safety requirements are shown. For example, such as... Figure 12 As shown, a multi-sequence 1200, 1210 can be generated, comprising at least one light pulse 1211 with low peak power and a light pulse 1213 with higher peak power. The two light pulses 1211, 1213 can be separated by a time interval greater than a predetermined time threshold (e.g., 10 ns), such that when an object is detected within a distance corresponding to the time threshold (e.g., 1.5 m), the second light pulse 1213 with a higher amplitude may not be emitted.

[0092] Figure 13A block diagram of a Lidar system 1300 according to some embodiments of the present invention is shown schematically. The Lidar system 1300 may include a high dynamic range receiving module 1330 and a transmitting module 1320 capable of generating multi-pulse sequences with preset timing characteristics. The delay time can refer to the time interval between the departure of the optical pulse sequence from the transmitter and the reception of the reflected optical pulse sequence at the receiver. The delay time can be used to calculate distance measurements. The delay time can also be referred to as time of flight.

[0093] As described above, a light pulse sequence can include multiple pulses emitted within a short duration, allowing the light pulse sequence to be used to obtain distance measurement points. For example, the provided Lidar system 1300 can be used for three-dimensional (3D) imaging or obstacle detection. In these cases, the distance measurement associated with the light pulse sequence can be considered as a pixel, and the set of pixels can be presented as an image or analyzed for other reasons (e.g., obstacle detection). In some cases, the time interval between adjacent sequences can correspond to the temporal resolution of 3D imaging. The duration of the sequence can be short enough that multiple pulses are emitted in substantially the same direction. In some cases, selected portions of the return signals corresponding to multiple pulses in the sequence can be used to calculate the distance from the Lidar system to a specific location in the 3D environment. For example, a dual-pulse sequence including pulses with different peak powers can be used for measurements of different measurement ranges. Methods for generating and processing dual-pulse sequences have been well described above (e.g., Figures 2-6 In some cases, a selected portion of the returned signal corresponding to multiple pulses can be accumulated to generate the detector output (e.g., a measurable output voltage pulse) and generate pixel values. In other cases, the portion of the returned signal can be selected based on the estimated or target measurement range, noise level (e.g., caused by stray light), or timing characteristics of the emitted light pulses, thereby avoiding detector saturation or measurement in dead zones and improving measurement accuracy.

[0094] In some embodiments, one or more optical pulse sequences can be generated based on timing characteristics. For example... Figure 13As shown, the LiDAR system 1300 may include a transmitting module 1320, a receiving module 1330, and a control unit 1310. The control unit 1310 includes a timing characteristic generator 1311 and a signal analysis module 1313. The transmitting module 1320 can communicate with the timing characteristic generator 1311. The transmitting module 1320 can be configured to transmit light pulses that conform to the timing characteristics generated by the timing characteristic generator 1311. The receiving module 1330 may include a detector and various other optical components configured to detect or collect returned light pulses or signals. The detected signals can be processed by the signal analysis module 1313 to correlate the detected signal sequence with a multi-pulse sequence of the transmitted light pulses and output a 3D point cloud image. In some cases, the signal analysis module 1313 may include a filter to identify timing characteristics in the returned signal that match the timing characteristics of the transmitted signal sequence, thereby correlating the sequence of the returned signal with the sequence of transmitted light pulses. In some cases, the signal analysis module 1313 can also obtain one or more real-time conditions to determine timing characteristics and / or one or more parameters for adjusting the sensor output signal.

[0095] In some cases, the timing characteristic generator 1311 can be configured to generate timing characteristics for emitting light pulses based on real-time conditions. In some cases, for eye safety purposes, when an object is detected within a threshold distance, a light pulse with a high peak power may not be emitted (or the amplitude of the light pulse may be reduced) until no object is detected within the threshold range. In some cases, such detection can be performed by the signal analysis module 1313. In some cases, the signal analysis module 1313 can notify the timing characteristic generator 1311 when an object is detected within the threshold distance of the Lidar system.

[0096] Timing characteristics can be transmitted to the transmitting module 1320 to generate a pulse sequence. The transmitting module 1320 may include one or more light sources. The one or more light sources may be configured to generate a laser beam or light pulses. In some embodiments, the wavelength of the laser beam may be between 895 nm and 915 nm (e.g., 905 nm). This wavelength range can correspond to invisible and penetrating infrared light, which can improve the detection range of the LiDAR and prevent interference with the environment. Depending on the specific application, the wavelength of the laser beam may be in any other range. In some cases, the light source may include at least a laser diode and driving circuitry. In some embodiments, the light source or driving circuitry may include multiple charging units controlled to emit a pulse sequence within a short time period or at short time intervals between consecutive pulses. The light pulse sequence can be emitted according to the timing characteristics received from the timing characteristic generator. In some embodiments, the light pulses generated by the transmitting module may be directed to one or more optical elements, such as lenses or lens assemblies (e.g., one or more spherical lenses, cylindrical lenses, or aspherical lenses) for collimating or focusing the beam. One or more lenses or one or more mirrors of the transmitting device of the LiDAR system may be used to expand, focus, or collimate the output beam. In some cases, the launch module may include a reference Figures 7 to 9 The device described is the same laser pulse emitting device. The emitting module 1320 can employ any suitable technology, such as a MEMS scanner, a vertical-cavity surface-emitting laser (VCSEL), a multi-line rotating LiDAR, etc., which may or may not require movement of the light source.

[0097] The light source may include a laser diode. The light source may include any suitable type of laser, such as a Fabry-Perot laser diode, a quantum well laser, a distributed Bragg reflector (DBR) laser, a distributed feedback (DFB) laser, a fiber laser module, or a vertical cavity surface-emitting laser (VCSEL).

[0098] The receiving module 1330 may include one or more detectors configured to receive echo beams or return signals. In some cases, the detector may correspond to a laser and may be configured to receive light originating from the corresponding laser source. The detector may be a photoreceiver, a light receiver, a light sensor, a photodetector, or a light detector. In some cases, the receiving module may include one or more avalanche photodiodes (APDs) or one or more single-photon avalanche diodes (SPADs). In some cases, the receiving module may include a photosensor, such as one or more PN photodiodes (e.g., a photodiode structure formed from p-type and n-type semiconductors) or one or more PIN photodiodes (e.g., a photodiode structure formed from undoped intrinsic semiconductor regions located between p-type and n-type regions). The photosensor may be a single photodetector capable of detecting photons, such as an avalanche photodiode, SPAD, RCP (resonant cavity photodiode), etc., or multiple photodetectors, such as a SPAD array, that cooperate to act as a single photosensor, typically having a higher dynamic range, lower dark count rate, or other beneficial characteristics than a single, larger photon detection area. Each photodetector may be a sensitive surface capable of sensing photons, such as light.

[0099] In some cases, the received optical signal can be converted into an electrical signal and further processed by embedded circuitry or a computing unit to generate an output signal with improved signal-to-noise ratio, signal contrast, and adaptability to a wide range of measurement distances. The output signal can then be processed by the signal analysis module 1313 to generate an image (i.e., a "3D point cloud").

[0100] Embedded circuitry or computing units can be pulse detection circuits configured to convert optical signals into electrical signals. The pulse detection circuit can be configured to generate a sensor output signal by varying the energy of received photons converted into at least one electrical signal. Alternatively, when the electrical signal corresponds to a single optical pulse, the pulse detection circuit can adjust the sensor output signal by accumulating different combinations of electrical signals to generate a given sensor output signal. In some cases, the pulse detection circuit can generate a sensor output signal representing the optical energy associated with a selected subset of returned optical pulses. The amount of photon energy can be varied by changing the number / count of returned optical pulses accumulated to generate the output signal and / or by changing the selection of the subset of returned optical pulses, thereby selecting the corresponding total optical energy. In some cases, the number / count of optical pulses selected from individual multi-sequences can be controlled individually, allowing the sensor output signal to have adjustable amplitude / intensity on a pixel-by-pixel basis.

[0101] In some embodiments, the receiving module 1330 may include embedded circuitry or a processor to generate an output signal representing the light energy associated with a subset of returned light pulses. The amount of light energy can be dynamically adjusted to avoid sensor saturation and / or to enable measurements over a wide range of distances. The embedded circuitry or processor may be configured to accumulate the output from a photodetector corresponding to a single pixel associated with a selected subset of light pulses. The photodetector corresponding to a single pixel may be a single photodetector capable of detecting photons, such as an avalanche photodiode, SPAD, RCP, etc., or multiple photodetectors, such as a SPAD array. In some cases, the embedded circuitry or processor may accumulate an electrical signal (e.g., a probe voltage) corresponding to a selected portion of the returned echo beam and generate a sensor output. The embedded circuitry or processor may be a field-programmable gate array (FPGA), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or any other suitable computing device.

[0102] In some cases, embedded circuitry or a processor can select a subset of the received light pulses based on one or more parameters. As described elsewhere herein, the one or more parameters determining the selection of the subset of returned signals for generating the sensor output can be preset. Alternatively or in addition, the one or more parameters can be dynamically determined based on real-time conditions, such as target / estimated measurement range (e.g., near-field obstacle detection or imaging, far-field obstacle detection or imaging), temporal variations in the emitted signal, and / or eye safety limitations.

[0103] In some cases, the one or more parameters can be determined by the control unit 1310. For example, the control unit 1310 can generate one or more parameters to adjust the amplitude or intensity of the sensor output signal based on the timing characteristics of the multi-pulse sequence and / or previous distance measurements generated by the signal analysis module 1313. As described above, the timing characteristics of the sequence can be defined by the number of pulses, the time interval, the duration of the sequence, the amplitude of the pulses, or combinations thereof in the sequence. In some cases, one or more parameters can be generated based on the timing characteristics of the multi-pulse sequence and one or more real-time conditions extracted from the detection and measurement generated by the signal analysis module 1313. The one or more real-time conditions may include the estimated measurement range, objects detected in the near field, etc. In some cases, the number of pulses accumulated for generating the signal or the selection of pulses can be determined based on the detection distance. For example, a larger number of pulses can be accumulated for long-distance measurements, and a smaller number of pulses can be accumulated for short-distance or higher reflectivity scenes. In another example, when an object is detected in the near field, fewer light pulses or light pulses with lower peak power can be selected to output the sensor signal.

[0104] The one or more parameters may include, for example, parameters representing a selected subset of pulses. For instance, the one or more parameters may include a pulse count accumulated for generating the sensor output signal, or a parameter representing a selected combination of pulses for generating the sensor output signal. The one or more parameters may include any other factors that may represent the total optical energy of the selected subset of pulses (e.g., the time window for receiving the returned optical pulses). The control unit 1310 may send the one or more parameters to the receiving module 1330 to generate the sensor output signal.

[0105] Signal analysis module 1313 can receive sensor output signals from receiving module and generate images. In some cases, signal analysis module 1313 can be configured to correlate the returned signal with a sequence of measured signals and calculate distance based on the time delay between the correlated signals. In some embodiments, the time of flight associated with a multi-pulse sequence can be used to calculate the distance. In some cases, the average of the time of flight associated with each pulse within the sequence can be used to determine the time of flight associated with the multi-pulse sequence. Signal analysis module 1313 can calculate distance based on the time of flight associated with a subset of optical pulses and can determine the time of flight by determining a match between the detected optical pulse sequence and temporal characteristics.

[0106] It is important to note that the provided methods and apparatus can be applied to any type of Lidar system. For example, the Lidar system can be a multi-line rotating Lidar system, which generates multiple lines by multiplexing the same or a set of lenses with multiple laser sources arranged at different heights on the focal plane of the lenses. In another example, the Lidar system can be a multi-beam flash Lidar system or a non-rotating Lidar system (e.g., MEMS scanning Lidar, optical phased array Lidar, etc.).

[0107] The described functions, methods, or one or more components, such as a timing characteristic generator or a signal analysis module, can be implemented using software, hardware, firmware, or a combination thereof. In some embodiments, components such as a timing characteristic generator, receiving module, transmitting module, and signal analysis module may include one or more processors and at least one memory for storing program instructions. The processor may be located internally to the Lidar system. Alternatively, the processor may be external to the Lidar system but communicate with it. The processor may be a single or multiple microprocessors, a field-programmable gate array (FPGA), or a digital signal processor (DSP) capable of executing a specific instruction set. Computer-readable instructions may be stored on a tangible, non-transitory computer-readable medium, such as a floppy disk, hard disk, CD-ROM (optical disc read-only memory), MO (magneto-optical), DVD-ROM (digital universal disk read-only memory), DVD RAM (digital universal disk random access memory), or semiconductor memory. The timing characteristic generator may be a separate device or system that communicates with the Lidar system. Alternatively, the timing characteristic generator may be a component of the Lidar system. The methods disclosed herein, such as dual-pulse measurement methods and / or high dynamic range output signal generation processes, can be implemented in hardware components or a combination of hardware and software, such as ASICs, dedicated computers, or general-purpose computers.

[0108] As used herein, A and / or B includes one or more of A or B, and combinations thereof, such as A and B. It should be understood that although the terms “first,” “second,” “third,” etc., are used herein to describe various elements, components, regions, and / or portions, these elements, components, regions, and / or portions should not be limited by these terms. These terms are used only to distinguish one element, component, region, or portion from another. Therefore, without departing from the teachings of the invention, the first element, component, region, or portion discussed herein may be referred to as the second element, component, region, or portion.

[0109] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that, when used in this specification, the terms “comprising” and / or “including” or “including” and / or “comprising” designate the stated features, regions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and / or groups thereof.

[0110] Throughout this specification, references to "some embodiments" or "one embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment. Therefore, the phrases "some embodiments" or "one embodiment" appearing in various places in this specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0111] Whenever the terms "at least," "greater than," or "greater than or equal to" precede the first value in a series of two or more values, the terms "at least," "greater than," or "greater than or equal to" apply to each value in the series. For example, greater than or equal to 1, 2, or 3 is equivalent to greater than or equal to 1, greater than or equal to 2, or greater than or equal to 3.

[0112] While preferred embodiments of the invention have been shown and described herein, these embodiments will be apparent to those skilled in the art if provided by way of example only. Many variations, modifications, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in the practice of the invention. Many different combinations of the embodiments described herein are possible, and such combinations are considered part of this disclosure. Furthermore, all features discussed in connection with any embodiment herein can be readily applied to other embodiments herein. This disclosure is intended by the following claims to define the scope of the invention, as well as the methods and structures covered within the scope of these claims and their equivalents.

Claims

1. A light detection and ranging system, comprising: The light source is configured to emit a sequence of laser pulses according to timing characteristics; A photodetector is configured to detect return pulses reflected by an object in a three-dimensional environment from the laser pulse sequence and generate an output signal representing the light energy associated with a subset of the return pulses. The photodetector is configured to accumulate the subset of return pulses to form the output signal. as well as One or more processors are electrically coupled to the light source and the photodetector, wherein the one or more processors are configured to: Determine one or more parameters for selecting the subset of returned pulses; the one or more parameters include the number of optical pulses in the subset of returned pulses, a parameter representing a combination of immediately adjacent optical pulses, and / or a parameter representing a combination of non-immediately adjacent optical pulses; Selecting the subset of returned pulses based on one or more parameters includes: determining the number of pulses accumulated to generate the output signal or selecting pulses based on the detection range; The photodetector includes a SPAD array, and the photodetector is configured to accumulate a subset of returned pulses to form the output signal, including: A selected number of modulation pulses received in the activated region of the SPAD array are accumulated to generate the output signal; The output signal is generated by accumulating a combination of selected adjacent optical pulses received in the activated region of the SPAD array; and / or The output signal is generated by accumulating a combination of selected non-adjacent optical pulses received in the activated region of the SPAD array.

2. The optical detection and ranging system according to claim 1, wherein, The one or more processors are further configured to calculate distance based on the time of flight associated with the subset of returned pulses, wherein the time of flight is determined by determining that the detected sequence of light pulses matches the timing characteristics, the timing characteristics including one or more of the following: amplitude of each pulse in a plurality of pulses, duration of each pulse in a plurality of pulses, time interval between the plurality of pulses, and number of the plurality of pulses.

3. The optical detection and ranging system according to claim 2, wherein, The one or more parameters used to select the subset of returned pulses are determined based on the distance between the optical detection and ranging system and the object located in the three-dimensional environment.

4. The optical detection and ranging system according to claim 1, wherein, The one or more parameters used to select the subset of returned pulses are determined at least in part based on the timing characteristics.

5. The optical detection and ranging system according to claim 1, wherein, The one or more processors are configured to generate the timing characteristics based on one or more real-time conditions, which are obtained based on detected light pulses.

6. The optical detection and ranging system according to claim 5, wherein, The one or more real-time conditions include detecting an object within a predetermined distance threshold.

7. The optical detection and ranging system according to claim 1, wherein, The one or more processors are also configured to generate 3D images based on the output signal.

8. A method for imaging using a light detection and ranging system, comprising: A laser pulse sequence is emitted into a three-dimensional environment, wherein the laser pulse sequence comprises multiple pulses having temporal characteristics; Detect the return pulse from the three-dimensional environment; as well as An output signal is generated to represent the light energy associated with a subset of the returned pulses; Generating the output signal includes: accumulating a subset of return pulses to form the output signal; The method further includes: determining one or more parameters for selecting the subset of returned pulses; the one or more parameters including the number of optical pulses in the subset of returned pulses, a parameter representing a combination of adjacent optical pulses, and / or a parameter representing a combination of non-adjacent optical pulses; selecting the subset of returned pulses based on the one or more parameters, including: determining the number of pulses accumulated for generating the output signal or the selection of pulses based on the detection range; The accumulation of a subset of return pulses to form the output signal includes: A selected number of modulation pulses received in the activated region of the SPAD array of the photodetector are accumulated to generate the output signal; The output signal is generated by accumulating a combination of selected adjacent optical pulses received in the activated region of the SPAD array; and / or The output signal is generated by accumulating a combination of selected non-adjacent optical pulses received in the activated region of the SPAD array.

9. The method according to claim 8, wherein, The one or more parameters used to select the subset of returned pulses are determined based on the distance between the optical detection and ranging system and the object located in the three-dimensional environment.

10. The method according to claim 8, wherein, The one or more parameters used to select the subset of returned pulses are determined at least in part based on the timing characteristics, which include one or more of the following: amplitude of each pulse in the plurality of pulses, duration of each pulse in the plurality of pulses, time interval between the plurality of pulses, and number of the plurality of pulses.

11. The method of claim 8, further comprising calculating the distance based on the time of flight associated with the detected light pulse.

12. The method of claim 11, further comprising determining the flight time by determining that the detected optical pulse sequence matches the timing characteristics.

13. The method of claim 8, further comprising generating the timing characteristics based on one or more real-time conditions, wherein, The one or more real-time conditions are obtained based on the detected light pulses.

14. The method according to claim 13, wherein, The one or more real-time conditions include detecting an object within a predetermined distance threshold.

15. The method of claim 8, further comprising generating a 3D image based on the output signal.

16. The method according to claim 15, wherein, The output signal corresponds to an intensity value of a pixel in the 3D image.

Images