Time-of-Flight Based Distance Measurement System, Method and Computer Readable Storage Medium

Abstract

This application relates to the field of optical measurement technologies, and provides a distance measurement system and method based on time of flight. The distance measurement system based on time of flight includes: an optical transmitter, an optical receiver, and a processing circuit. The processing circuit is electrically connected to the optical transmitter and the optical receiver. By configuring the detection optical signal emitted by the light source of the optical transmitter, the repetition rate of the delay times of the detection optical signals emitted by two light sources within a preset distance range within the same detection period does not exceed a preset threshold, thereby ensuring that the delay times of the multiple detection optical signals emitted by the two light sources within a preset distance range within one detection frame are not completely the same, such that the false counts formed by the crosstalk between pixels during histogram counting are also randomly distributed and no crosstalk peak is formed in a fixed time bin, thereby converting the photon counts received due to the crosstalk between pixels into background noise, avoiding the influence of optical crosstalk between pixels, and further improving the accuracy of distance measurement.

Description

Technical Field

[0001] This application relates to the technical field of optical measurement, and particularly to a distance measurement system, method and computer-readable storage medium based on time of flight. Background Art

[0002] Light detection and ranging (LiDAR) emits and receives detection light to sense the distance of surrounding objects, and obtains a 3D point cloud image of the environment by combining the azimuth information of the transceiver detection light. The current mainstream LiDAR is based on time of flight (ToF) technology, and calculates the distance of an object by measuring the time of flight of the detection light from emission, reflection by the object, to final reception.

[0003] As the coverage rate of vehicle-mounted LiDAR gradually increases, the performance of LiDAR depth imaging becomes increasingly important. Imaging resolution is one of the more important performance parameters. A higher resolution means that the number of pixels used by the receiving end of the LiDAR to receive light increases, the size of the pixels decreases, and the pitch between the pixels also becomes narrower. The crosstalk problem between pixels will affect the quality of depth imaging. The optical crosstalk between pixels is caused by multiple refractions and reflections of the optical path through the receiving end, such as the lens, filter, or inner wall of the module, resulting in the pixel receiving target light from a field of view not corresponding to that pixel, causing the pixel to generate a false count. The false count generated by the crosstalk between pixels belongs to noise, which will significantly reduce the signal-to-noise ratio, thereby affecting the accuracy of distance measurement. And when the crosstalk between pixels is serious, the electrical signals generated by each pixel no longer have differences and cannot reflect the true distance information of the object in the corresponding field of view, and the clarity of depth imaging will decrease. Summary of the Invention

[0004] In view of this, embodiments of this application provide a distance measurement system and method based on time of flight to solve the problem that optical crosstalk is likely to occur between pixels of existing LiDAR.

[0005] In a first aspect, embodiments of this application provide a distance measurement system based on time of flight, including:

[0006] An optical transmitter, including a plurality of light sources, the light sources are configured to emit a plurality of detection light signals into a detection space within a detection frame, the detection frame includes corresponding multiple detection time periods, each light source emits one of the detection light signals within each detection time period, and the moment when each light source emits the detection light signal within each detection time period has a preset delay time compared with the start moment of the detection time period; wherein, for two light sources within a preset spacing range, the repetition rate of the delay times of the detection light signals emitted by each of them within the same detection time period does not exceed a preset threshold;

[0007] A light receiver, comprising a plurality of pixels configured to receive a detection optical signal from a detection space and output a corresponding photo-induced signal;

[0008] A processing circuit, electrically connected to the light emitter and the light receiver, configured to analyze and process the time information of the detection optical signal emitted by the light source and the photo-induced signal output by the pixel that work synchronously, so as to determine the flight time of the detection optical signal reflected by an object to be measured in the detection space.

[0009] In a second aspect, an embodiment of the present application further provides a distance measurement method based on flight time, including:

[0010] Controlling a light source of a light emitter to emit a plurality of detection optical signals into a detection space within a detection frame, the detection frame including corresponding multiple detection time periods, the light source emitting one detection optical signal corresponding to each detection time period, and the time when the light source emits the detection optical signal within each detection time period having a preset delay time compared to the start time of the detection time period; wherein, the repetition rate of the delay times of the detection optical signals emitted by two light sources within the same detection time period within a preset distance range does not exceed a preset threshold;

[0011] Controlling pixels of a light receiver to receive a detection optical signal from the detection space and output a corresponding photo-induced signal;

[0012] Analyzing and processing the time information of the detection optical signal emitted by the light source and the photo-induced signal output by the pixel that work synchronously, so as to determine the flight time of the detection optical signal reflected by an object to be measured in the detection space.

[0013] In a third aspect, an embodiment of the present application further provides a computer-readable storage medium storing a computer program, characterized in that when the computer program is executed by a processor, the steps of the distance measurement method based on flight time as described in the second aspect are implemented.

[0014] The embodiments of the present application at least have the following technical effects:

[0015] Based on the time-of-flight distance measurement system or method provided by the embodiments of the present application, by configuring the detection optical signal emitted by the light source of the light emitter, the repetition rate of the delay time of the detection optical signals emitted by two light sources within a preset distance range in the same detection period does not exceed a preset threshold, so as to ensure that the delay times of the multiple detection optical signals emitted by two light sources within a preset distance range in a detection frame are not exactly the same, making the false counts formed by the crosstalk between pixels during histogram counting also randomly distributed and not forming a crosstalk peak at a fixed time bin, thereby converting the photon counts received due to the crosstalk between pixels into background noise, avoiding the influence of optical crosstalk between pixels, and further improving the accuracy of distance measurement. Description of the Drawings

[0016] Figure 1a Shown is the time-of-flight count histogram of one pixel without crosstalk between two pixels (far apart) in the prior art;

[0017] Figure 1b Shown is the time-of-flight count histogram of another pixel without crosstalk between two pixels (far apart) in the prior art;

[0018] Figure 1c is Figure 1b the schematic diagram of the crosstalk peak formed at the time bin position corresponding to the highest-intensity signal peak in Figure 1a the corresponding histogram;

[0019] Figure 1d is Figure 1a the schematic diagram of the crosstalk peak formed at the time bin position corresponding to the highest-intensity signal peak in Figure 1b the corresponding histogram;

[0020] Figure 2a Shown is the time-of-flight count histogram of one pixel without crosstalk between two pixels (close together) in the prior art;

[0021] Figure 2b Shown is the time-of-flight count histogram of another pixel without crosstalk between two pixels (close together) in the prior art;

[0022] Figure 2c is Figure 2a the schematic diagram of the crosstalk peak formed at the time bin position corresponding to the highest-intensity signal peak in Figure 2b the corresponding histogram;

[0023] Figure 3 Shown is the schematic diagram of the working principle of a time-of-flight distance measurement system provided by the embodiments of the present application;

[0024] Figure 4Schematic diagram of the distribution of light sources and pixels in one embodiment provided by the embodiments of the present application;

[0025] Figure 5 Schematic diagram of the crosstalk peak formed by the time bin position corresponding to the signal peak of the histogram corresponding to one pixel provided by the embodiments of the present application in the histogram corresponding to another pixel;

[0026] Figure 6 Schematic diagram of the distribution of light sources and pixels in another embodiment provided by the embodiments of the present application;

[0027] Figure 7 Schematic diagram of the distribution of light sources and pixels in yet another embodiment provided by the embodiments of the present application;

[0028] Figure 8 Schematic diagram of detection optical signals emitted by different light sources of a time-of-flight based distance measurement system provided by the embodiments of the present application at different detection time periods;

[0029] Figure 9 Schematic diagram of the working principle of another time-of-flight based distance measurement system provided by the embodiments of the present application;

[0030] Figure 10 Schematic diagram of the detection optical signals of the same light source at different detection time periods provided by the embodiments of the present application;

[0031] Figure 11 Schematic diagram of yet another time-of-flight based distance measurement system provided by the embodiments of the present application;

[0032] Figure 12 Schematic flow chart corresponding to the time-of-flight based distance measurement method provided by the embodiments of the present application. Detailed implementation manners

[0033] Next, the time-of-flight based distance measurement principle will be described. The Time of Flight (TOF) technology calculates the distance of an object by measuring the flight time of light in space. Due to its advantages such as high precision and large measurement range, it is widely used in fields such as consumer electronics, driverless, laser autofocus, presence recognition, AR / VR, 3D modeling, and real-scene navigation.

[0034] First, the time-of-flight based distance measurement principle will be explained. The Time of Flight (TOF) technology calculates the distance of an object by measuring the flight time of light in space. Since it has advantages such as high precision and large measurement range, it is widely used in fields such as consumer electronics, driverless, laser autofocus, presence recognition, AR / VR, 3D modeling, and real-scene navigation.

[0035] TOF may include direct time-of-flight (dToF). The measurement principle of dToF is that the emitter periodically emits pulses of detection optical signals, which are reflected by the object and received by the photosensitive device. Then, by calculating the time of flight between the emission and reception of the detection optical signals, the distance of the object can be determined.

[0036] The distance of the object can be calculated by the following formula:

[0037] D = c * t / 2

[0038] where c is the speed of light and t is the time of flight.

[0039] LiDAR (Light Detection and Ranging) is a sensor that uses the dToF principle for ranging. Depending on the scanning method, it corresponds to different emission and reception working modes. At the same moment, LiDAR may perform emission and reception for single-pixel, multi-pixel, or full-pixel ranging, and then scan through all pixels to cover the entire field of view. When only single-pixel ranging is performed at the same moment, since the other pixels are not turned on, there is no optical crosstalk problem between pixels. When multi-pixel ranging is performed at the same moment, because LiDAR systems usually design these multiple pixels to be adjacent in space, there is an optical crosstalk problem between pixels. The optical crosstalk between pixels may span one pixel or multiple pixels (such as 2 - 5 pixels) depending on the actual situation, such as pixel pitch or optical path design. The larger the span between pixels, the smaller the crosstalk.

[0040] In actual measurement, multiple pixels or all pixels in the optical receiver are synchronized with the emission of the detection optical signals from the optical emitter, each receiving the echo of the detection optical signals reflected by the object within the corresponding field of view angle, and recording the corresponding time-of-flight timestamps. By repeatedly emitting the detection optical signals multiple times, a histogram is formed by statistically analyzing the timestamps of the received detection optical signal echoes, and the histogram is processed and analyzed to obtain distance data. The whole process is a detection frame. Usually, for multiple pixels working in any detection frame, their emission and reception are unified, that is, multiple pixels and the light sources corresponding to the pixels are synchronized to turn on, and there is no time difference between them. This makes the miscount due to optical crosstalk between pixels during histogram counting also have no time difference and is always distributed in fixed time bins. After multiple accumulations, a crosstalk peak is formed, thus affecting the ranging accuracy.

[0041] Figure 1a and Figure 1b are respectively the time-of-flight count histograms of two pixels without crosstalk. When crosstalk exists, since the two pixels and the corresponding light sources work synchronously, the signal peaks with the highest intensity of each other may form crosstalk peaks at the positions of the corresponding time bins in the histograms of the other party (see Figure 1c and Figure 1d) This may cause misjudgment during ranging analysis of the sensing chip, believing that the crosstalk peak is also the signal peak generated by the object existing in the detection space, or the output object distance value is inaccurate, resulting in unclear lidar imaging.

[0042] It should be noted that although Figure 1c and 1d only show the problem that the signal peaks in two pixels interfere with each other to form an interference peak in the histogram, Figure 1a and 1b the background noise in also crosstalks with each other in the histograms of each other, increasing the miscount. However, since the count value of the background noise is usually low and the crosstalk probability is not large, the miscount caused by the crosstalk of the background noise is correspondingly not high and can be ignored, so it is not shown in the figure.

[0043] The pixels at the receiving end of the existing lidar generally use single photon avalanche diodes (Single Photon Avalanche Diode, SPAD) as photosensitive devices. When the SPAD receives photons and triggers the avalanche effect, after generating an avalanche current, it needs to be quenched and reset to receive the next photon. During this period, it is the dead time when the SPAD cannot sense external optical signals, forming a certain detection time blind area. In this case, as Figure 2a and Figure 2b shown, if the time bins corresponding to the signal peaks measured by two pixels are relatively close (less than or close to the dead time), the crosstalk between pixels causes the SPAD in the pixel that should originally be used to receive the echo of the detection optical signal returning later to be triggered in advance and enter the dead time, resulting in that when the echo of the detection optical signal returning later arrives at the pixel, there are not enough SPADs to receive it. Therefore, as Figure 2c shown, not only will there be crosstalk peaks, but also the counting amplitude of the real signal peak will be significantly reduced and may be less than the crosstalk peak. Such a phenomenon makes the object distance value output by the pixel incorrect, and there is no difference in the outputs of the two pixels, thus affecting the accuracy of distance measurement.

[0044] Therefore, in order to solve the above deficiencies existing in the prior art, the embodiments of the present application provide a time-of-flight based distance measurement system and method.

[0045] In the first aspect, the time-of-flight based distance measurement system provided by the embodiments of the present application includes:

[0046] A light emitter, comprising a plurality of light sources configured to emit a plurality of detection optical signals into a detection space within a detection frame. The detection frame includes corresponding multiple detection time periods, and each light source emits one detection optical signal corresponding to each detection time period. The time when the light source emits the detection optical signal within each detection time period has a preset delay time compared to the start time of the detection time period. Among them, the repetition rate of the delay times of the detection optical signals emitted by two light sources within the preset spacing range in the same detection time period does not exceed a preset threshold.

[0047] A light receiver, comprising a plurality of pixels configured to receive the detection optical signals from the detection space and output corresponding light sensing signals.

[0048] A processing circuit, electrically connected to the light emitter and the light receiver, is configured to analyze and process the time information of the detection optical signals emitted by the light sources and the light sensing signals output by the pixels that work synchronously, so as to determine the flight time of the detection optical signals reflected by the object to be measured in the detection space.

[0049] Optionally, in some embodiments, within the preset spacing range, the repetition rate of the delay times of the detection optical signals emitted by every two adjacent light sources in the same detection time period does not exceed a preset threshold.

[0050] Optionally, in some embodiments, the distance between two light sources within the preset spacing range is less than or equal to 3 times the light source spacing, and the light source spacing is the center distance between two adjacent light sources. The preset threshold is greater than 0 and less than or equal to 20%.

[0051] Optionally, in some embodiments, among the multiple light sources of the light emitter, the delay times of the detection optical signals emitted by two light sources outside the preset spacing range in the corresponding same detection time period can be the same.

[0052] Optionally, among the multiple light sources of the light emitter, the distance between two light sources with exactly the same delay time of emitting the detection optical signal in each detection time period of a detection frame is at least M times the light source spacing. The light source spacing is the distance between two adjacent light sources, and the multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system can withstand, and satisfies the condition: the Mth power of P is less than Q.

[0053] Optionally, in some embodiments, the repetition rate of the delay times of the detection optical signals emitted by the same light source of the light emitter in different detection time periods of a detection frame is 0; or, the delay times of the detection optical signals emitted by the same light source of the light emitter are repeated in some detection time periods within a detection frame.

[0054] Optionally, in some embodiments, the detection time periods during which the same light source of the light emitter emits detection light signals within a detection frame are not connected to each other with repeated delay times.

[0055] In a second aspect, a time-of-flight based distance measurement method provided by an embodiment of the present application includes:

[0056] Controlling a light source of a light emitter to emit a plurality of detection light signals into a detection space within a detection frame, where the detection frame includes corresponding multiple detection time periods, the light source emits one detection light signal corresponding to each detection time period, and the time when the light source emits the detection light signal within each detection time period has a preset delay time compared to the start time of the detection time period; wherein, the repetition rate of the delay times of the detection light signals emitted by two light sources within a preset spacing range in the same detection time period does not exceed a preset threshold;

[0057] Controlling pixels of a light receiver to receive detection light signals from the detection space and output corresponding light sensing signals;

[0058] Analyzing and processing the time information of the detection light signals emitted by the light sources and the light sensing signals output by the pixels that work synchronously to determine the flight time of the detection light signals reflected by the object to be measured in the detection space.

[0059] Optionally, in some embodiments, the repetition rate of the delay times of the detection light signals emitted by two light sources within a preset spacing range in the same detection time period does not exceed a preset threshold, including:

[0060] Within the preset spacing range, the repetition rate of the delay times of the detection light signals emitted by every two adjacent light sources in the same detection time period does not exceed the preset threshold;

[0061] Or, within the preset spacing range, the repetition rate of the delay times of the detection light signals emitted by two light sources with a spacing greater than 1 times the light source spacing in the same detection time period does not exceed the preset threshold;

[0062] Wherein, the distance between two light sources within the preset spacing range is less than or equal to 3 times the light source spacing, and the light source spacing is the distance between two adjacent light sources.

[0063] Optionally, in some embodiments, the time-of-flight based distance measurement method further includes:

[0064] Among the multiple light sources of the light emitter, the delay times of the detection light signals emitted by two light sources outside the preset spacing range in the corresponding same detection time period can be the same;

[0065] Alternatively, the distance between two light sources that emit the detection optical signal with exactly the same delay time in each detection period of a detection frame is at least M times the light source spacing, where the light source spacing is the distance between two adjacent light sources, and the multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the system can tolerate, and satisfies the condition: the Mth power of P is less than Q.

[0066] Optionally, in some embodiments, controlling a light source of a light emitter to emit a plurality of detection optical signals into a detection space in a detection frame further includes:

[0067] Controlling the repetition rate of the delay time of the detection optical signal emitted by the same light source of the light emitter in different detection periods within a detection frame to be 0; or, controlling the delay time of the detection optical signal emitted by the same light source of the light emitter to repeat in some detection periods within a detection frame.

[0068] In the embodiments of the present application, by asynchronously processing the emission times of the detection optical signals emitted by two light sources within a preset spacing range, crosstalk peaks formed at the corresponding time bin positions of the histograms of other pixels by the detection optical signals received by the pixels are avoided, which is beneficial to improving the detection accuracy. The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0069] As Figure 3 shown, the embodiments of the present application provide a time-of-flight based distance measurement system. Figure 3 The distance measurement system shown includes: a light emitter 100, a light receiver 200, and a processing circuit 300. Among them, the light emitter 100 is configured to emit a detection optical signal into a detection space to detect distance information of an object in the detection space, and a part of the detection optical signal will be reflected back by the object to form a detection optical signal echo carrying the distance information of the object. The light receiver 200 is configured to sense the detection optical signal from the detection space and output a corresponding light sensing signal. The processing circuit 300 is configured to analyze and process the light sensing signal to obtain the moment when the detection optical signal echo is sensed by the light receiver 200, and obtain the distance information of the object according to the time difference between the emission moment of the detection optical signal and the sensed moment of the corresponding detection optical signal echo, that is, the flight time of the detection optical signal. It should be understood that the detection space can be defined as the three-dimensional space range in which the distance measurement system can effectively perform distance detection, and can also be called the field of view angle of the distance measurement system.

[0070] Optionally, the distance measurement system may be, for example, a lidar sensor. An embodiment of the present application further provides an electronic device, which includes a distance measurement system or a lidar sensor. The electronic device can implement corresponding functions according to the distance information measured by the distance measurement system or the lidar sensor. The electronic device is, for example: a mobile phone, a car, a robot, an access control / monitoring system, a smart door lock, a drone, etc. The three-dimensional information is, for example: the proximity information, depth information, distance information, coordinate information, etc. of an object in the detection space. Among them, the three-dimensional information can be used, for example, in fields such as 3D modeling, face recognition, autonomous driving, machine vision, monitoring, drone control, augmented reality (AR) / virtual reality (VR), simultaneous localization and mapping (SLAM), object proximity determination, etc. The embodiments of the present application do not limit this.

[0071] Optionally, the processing circuit 300 may be disposed on the distance measurement system or the lidar sensor; or, all or part of the functional units of the processing circuit 300 may also be disposed on the electronic device.

[0072] Optionally, the processing circuit 300 may be an independent dedicated circuit, such as a system-on-a-chip (SOC) chip, a field programmable gate array (FPGA) chip, an application specific integrated circuit (ASIC) chip, etc. Or, the processing circuit 300 may also be a general-purpose processor. For example, when the distance measurement system is integrated into a smart terminal such as a mobile phone, a TV, or a computer, the processor in the terminal can be at least a part of the processing circuit 300.

[0073] In this embodiment, the processing circuit 300 is electrically connected to the light emitter 100 and the light receiver 200, so as to drive the light emitter 100 and the light receiver 200 to work according to the corresponding configuration. The processing circuit 300 acquires the time information of the detection light signal emitted by the light source 110 and the pixel 210 that work synchronously and the output optical induction signal, and processes the time information to determine the flight time of the detection light signal reflected by the object 400 to be detected in the detection space.

[0074] Optionally, in some embodiments, the detection light signal is, for example, visible light, infrared light or near-infrared light, and the selection range of the wavelength is, for example, 390 nm (nanometers)-780 nm, 700 nm-1400 nm, 800 nm-1000 nm, 900 nm-1600 nm.

[0075] Optionally, in some embodiments, the optical transmitter 100 is configured to periodically emit laser pulses as detection optical signals at a preset frequency within a detection frame. Wherein, the time period for each emission of a laser pulse can correspond to a detection period within the current detection frame, that is, the time interval between the emission time of one laser pulse and the emission time of the next laser pulse. It should be understood that, in the embodiments of the present application, the optical transmitter 100 may include multiple light sources 110, and the emission times of the detection optical signals by different light sources 110 can be different. The detection period at least includes the time period between the earliest emission time and the latest emission time of the detection optical signals by different light sources 110 during each emission process of the detection optical signals. For the multiple light sources 110 of the optical transmitter 100, some of the light sources 110 may also miss the emission of one or more detection optical signals, and the embodiments of the present application do not make specific limitations on this.

[0076] Optionally, in some embodiments, each light source 110 includes one or a plurality of light-emitting units. The light-emitting units belonging to the same light source emit light beams simultaneously, and the emitted light beams serve as the detection optical signals emitted by the light source. Optionally, the light-emitting unit can be a light-emitting structure in the form of a light-emitting diode, an edge-emitting laser, a vertical cavity surface emitting laser (VCSEL), a fiber laser, etc.

[0077] Optionally, the light-emitting units can be formed in an array on the same semiconductor substrate. For example, a VCSEL array light source chip formed by a plurality of VCSEL light-emitting units arranged in an array. The optical transmitter 100 may further include a driver, and the light source 110 can emit detection optical signals under the drive of the driver.

[0078] Optionally, in some embodiments, the detection range of the distance measurement system includes a plurality of detection regions located at different orientations within the detection space. The multiple light sources 110 of the optical transmitter 100 are configured to respectively emit multiple detection optical signals in different directions into the detection space to correspondingly irradiate the detection regions located at different orientations within the detection space. It can be understood that the multiple light sources 110 of the optical transmitter 100 can simultaneously emit multiple detection optical signals in different directions respectively, or can respectively emit multiple detection optical signals with different directions in different time periods. The number of detection optical signals emitted in each different time period can be the same or different. Among them, the light beam emitted by the light source 110 is modulated by the emission optical device to form a detection optical signal that irradiates the corresponding detection region along a preset specific emission direction.

[0079] Further, the optical receiver 200 includes a plurality of pixels 210, and each pixel 210 may include one or a plurality of photosensitive devices. The pixels 210 are configured to receive an optical signal from the detection space and output a corresponding photoinductive signal. Among them, there may be a corresponding setting relationship between the pixels 210 and the light source 110, that is, after the detection optical signal emitted by the light source 110 irradiates the corresponding detection area in the detection space through a pre-set optical path, the returned detection optical signal echo is received by the corresponding pixel 210.

[0080] Optionally, the photosensitive device in the embodiments of the present application may be, for example, an avalanche photodiode (APD), a single-photon avalanche diode (SPAD), or a silicon photomultiplier (SiPM) formed by a plurality of SPADs connected in parallel. Among them, there is a certain probability that the incident single photon will trigger an avalanche effect in the SPAD, and then an avalanche current is output to the processing circuit 300 as a photoinductive signal. It should be noted that the SPAD is taken as an example for exemplary description in each embodiment of the present application.

[0081] Optionally, in some embodiments, the pixels 210 and the light source 110 with the above corresponding relationship are synchronously turned on, so that the other pixels 210 that do not correspond to the light source 110 do not need to be synchronously turned on, further avoiding crosstalk between pixels and also being beneficial to reducing the power consumption of the device.

[0082] Optionally, in some embodiments, the pixels 210 may be kept always on. When the pixels 210 are kept always on, the counting of the detection optical signal echo corresponding to the pixels 210 can be started while the light source 110 emits the detection optical signal, and the relevant counting is stopped when the light source 110 does not emit the detection optical signal. Thus, even if the pixels 210 are always on, it will not affect the accuracy of photon counting, and keeping the pixels 210 always on can reduce the switching frequency of the pixels 210, which is beneficial to extending the service life of the pixels 210.

[0083] Optionally, in some embodiments, the light source 110 may emit multiple laser pulses within a detection frame, and the time difference between the emission times of two adjacent laser pulses may be defined as an emission period of the laser pulse. The pixel 210 has a periodic sensing period for the detection region within the detection space to be sensed, and the pixel 210 has corresponding sensing periods for the detection optical signals returned from the detection regions at different positions within the detection space. Among them, the pixel 210 periodically performs sensing at the same preset frequency as the emission period, and the sensing period has the same start time and end time as the emission period. Each time a laser pulse is emitted, the corresponding pixel 210 starts to sense the photons returned from the detection range, and the processing circuit 300 counts the photoinduction signals generated by the sensed photons. The processing circuit 300 statistically processes the counts accumulated in the corresponding time bins due to the sensed photoinduction signals during multiple sensing periods of a detection frame by the optical receiver 200 to generate a corresponding statistical histogram.

[0084] In the embodiments of the present application, in order to avoid optical crosstalk between different pixels, the emission periods of different light sources 110 within a preset spacing range and the sensing periods of the corresponding pixels 210 are set to have a certain delay time relative to the start time of the corresponding detection period. For example, the time when the light source 110 emits a detection optical signal within the detection period and the time when the pixel 210 starts to sense the echo of the detection optical signal within the detection period can be quantitatively described by a preset delay time relative to the start time of the detection period, so as to facilitate the differential setting of the time when different light sources 110 emit detection optical signals within the detection period and the time when the corresponding pixels 210 start to sense the echo of the detection optical signal within the detection period.

[0085] In some embodiments, for multiple light sources 110 of the optical transmitter 100, the repetition rate of the times when two light sources 110 within a preset spacing range emit detection optical signals respectively within the same detection period (i.e., the repetition rate of the delay time of the time when the detection optical signal is emitted relative to the start time of the detection period) does not exceed a preset threshold, so that the times when these two different light sources 110 emit detection optical signals respectively within multiple detection periods corresponding to a detection frame are staggered from each other. Among them, the preset spacing range is used to define the range where crosstalk effects exist between different light sources, and this preset spacing range can be determined according to factors such as the spacing between light sources, the pixel crosstalk probability, and the anti-interference ability between pixels.

[0086] Optionally, the size of the preset spacing range can be represented by the number of light sources included. Exemplarily, assuming that the light emitter 100 includes 10 (rows) × 10 (columns) light sources 110, the corresponding preset spacing range can be a range including a 4×4 light source array, or a range including a 4×2 light source array, or can also be a range including a 3×3 light source array. Specifically, it needs to be set according to the actual detection accuracy requirements, and this embodiment does not make specific limitations.

[0087] Optionally, the size of the preset spacing range can also be represented by the length of the distance between two light sources 110. For example, the preset spacing range can be a multiple of the light source spacing. If the distance between two light sources 110 is less than or equal to a preset multiple of the light source spacing, it is considered to be within the preset spacing range, and it is necessary to meet the condition that the repetition rate of the delay time of the detection optical signal emitted by each of them within the same detection period does not exceed a preset threshold. It should be understood that the distance between the light sources 110 here can be measured by the distance between the centers of the two light sources 110. The light source spacing refers to the minimum value of the distance between one light source 110 and another adjacent light source 110 in each direction. For a regularly equally spaced matrix arrangement of light source arrays, the light source spacing is a preset fixed value.

[0088] Optionally, in order to improve the anti-crosstalk ability between pixels, for example, the distance between two light sources 110 within the preset spacing range is less than or equal to 3 times the light source spacing and greater than or equal to 1 times the light source spacing, which is equivalent to the maximum distance between two light sources 110 within the preset spacing being 3 times the light source spacing and the minimum distance being 1 times the light source spacing.

[0089] Optionally, in order to further improve the anti-crosstalk ability between pixels, the center distance between two light sources 110 within the preset spacing range is less than or equal to 2 times the light source spacing and greater than or equal to 1 times the light source spacing.

[0090] It should be understood that the pixels 210 on the optical receiver 200 can be set in the above manner corresponding to the light sources 110. That is, the repetition rate of the start time of the two pixels 210 within the preset spacing range on the optical receiver 200 to sense the detection optical signal echo within the same detection period (that is, the repetition rate of the delay time of the start time of sensing the detection optical signal echo compared to the start time of this detection period) does not exceed the preset threshold, and details are not elaborated here.

[0091] It should be noted that if the delay times of the two light sources 110 emitting detection optical signals in the same detection period relative to the start time of the detection period are the same, it is considered that the delay times of the two light sources 110 emitting detection optical signals are repeated in this detection period. The repetition rate of the delay times of the two light sources 110 emitting detection optical signals in this detection frame refers to the ratio of the number of detection periods in which the delay times of the two light sources 110 emitting detection optical signals are the same in this detection frame to the total number of detection periods in this detection frame. Similarly, if the delay times of the two pixels 210 starting to sense the echo of the detection optical signal in the same detection period relative to the start time of the detection period are the same, it is considered that the delay times of the two pixels 210 starting to sense in this detection period are repeated. The repetition rate of the delay times of the two pixels 210 starting to sense in this detection frame refers to the ratio of the number of detection periods in which the delay times of the two pixels 210 starting to sense are the same in this detection frame to the total number of detection periods in this detection frame.

[0092] In this embodiment, by limiting the above ratio within a preset threshold range, the emission times of different light sources 110 emitting detection optical signals in multiple detection periods corresponding to one detection frame are staggered as much as possible, and at the same time, the start times of different corresponding pixels 210 sensing the detection optical signals in multiple detection periods corresponding to one detection frame are also staggered as much as possible. In this way, when performing histogram counting on detection periods with different delay times, the miscounts caused by optical crosstalk also have different time differences, so they will not be distributed in fixed time bins. The preset threshold in this embodiment is used to limit the repetition rate of the delay time. In order to reduce or avoid optical crosstalk between pixels, the value of the preset threshold should not be too large, so as to limit the repetition rate to a relatively low level as much as possible to reduce the control difficulty for different light sources 110 and pixels 210.

[0093] Optionally, in some embodiments, as Figure 4 shown, Figure 4 The dashed box of the optical transmitter 100 in Figure 4The specific reference numerals of these 16 light sources 110 within the dashed box are shown in the figure, which facilitates the description of the crosstalk relationship between the light sources 110. The repetition rate of the delay times of the detection optical signals emitted by two light sources 110 within this preset spacing range during the same detection period does not exceed a preset threshold. For example: The 11th light source (the light source 110 labeled 11) in the optical transmitter 100 is located in the upper left corner within the preset spacing range, and the 44th light source (the light source 110 labeled 44) is located in the lower right corner within the preset spacing range. These two are the two light sources 110 with the largest mutual distance within the preset spacing range. The 11th light source and the 44th light source respectively emit detection optical signals, and the 11th pixel (the pixel 210 labeled 11) and the 44th pixel (the pixel 210 labeled 44) in the corresponding optical receiver 200 respectively receive the echoes of the detection optical signals emitted by the corresponding light sources 110. It should be noted that the reference numerals of the light sources 110 do not represent the quantity and order of the light sources, but are only used to distinguish different light sources 110.

[0094] Specifically, the emission periods of the 11th light source and the 44th light source respectively have corresponding preset delay times relative to the start moment of the detection period, and the repetition rate of the delay times in different detection periods is less than or equal to a preset threshold, for example: 30%. That is, the ratio of the number of detection periods with the same delay time of the detection optical signals emitted by the 11th light source and the 44th light source in different detection periods of a detection frame to the total number of detection periods of this detection frame is at most 30%. Correspondingly, the repetition rate of the delay times of the sensing periods when the 11th pixel corresponding to the 11th light source 110 and the 44th pixel corresponding to the 44th light source start to receive optical signals in different detection periods of a detection frame is less than or equal to the preset threshold of 30%. In this way, the receptions of the two pixels 210 are asynchronous in multiple detection periods, and there are random time differences in the degree of asynchrony in different detection periods, so that even if optical crosstalk occurs between the 11th pixel and the 44th pixel, the resulting miscounts will be randomly distributed into their respective corresponding multiple time bins (as Figure 5 shown), and thus no crosstalk peaks will be formed in their respective corresponding histograms. It should be noted that this preset spacing range is determined by factors such as the spacing between the light sources, the pixel crosstalk probability, and the anti-interference ability between the pixels. There is a high probability that two light sources 110 within this preset spacing range will cause optical crosstalk between the corresponding pixels 210. Therefore, it is necessary to minimize the adverse impact of optical crosstalk on the ranging accuracy by satisfying the condition that the repetition rate of the delay times of the detection optical signals emitted by each during the same detection period does not exceed the preset threshold.

[0095] Optionally, in some embodiments, as Figure 6 shown, Figure 6The dashed box of the medium light emitter 100 represents the corresponding preset spacing range. For every two adjacent light sources 110 within the preset spacing range in the light emitter 100, the repetition rate of the moments when they emit detection optical signals respectively within the same detection period does not exceed the preset threshold. Hereinafter, the light sources 11 and 21 will be taken as examples for specific illustration.

[0096] Specifically, since the emission periods of the 11th light source and the 21st light source have a certain delay time relative to the start time of the detection period, and the repetition rate of the delay times of different detection periods is less than or equal to the preset threshold, for example: 10%. That is, the ratio of the number of detection periods with the same delay time when the 11th light source and the 21st light source emit detection optical signals within different detection periods of a detection frame to the total number of detection periods of this detection frame is at most 10%. Correspondingly, the repetition rate of the delay times of the sensing periods when the 11th pixel and the 21st pixel corresponding to the 11th light source and the 21st light source start to receive optical signals within different detection periods of a detection frame is less than or equal to 10%. In this way, the receptions of the two pixels 210 are asynchronous within multiple detection periods.

[0097] It should be noted that since the preset spacing range roughly defines the crosstalk range between light sources and between corresponding pixels, the delay times of the emission periods of the respective light sources 110 within the preset spacing range relative to the start moment of the detection period are set asynchronously (the number and distribution mode of the asynchronously set light sources may not be specifically limited in this embodiment), so that the sensing periods of the corresponding pixels 210 also have the same asynchronous delay time relative to the start moment of the detection period.

[0098] Optionally, the preset thresholds corresponding to different pixel spacings may be different. For example: as Figure 6 shown, the spacing between the 11th pixel and the 21st pixel is relatively small, and the value of the preset threshold can be set relatively small (for example: 10%). In this way, the repetition rate of the delay time can be reduced and the ranging accuracy can be improved; as Figure 4 shown, the spacing between the 11th pixel and the 44th pixel is relatively large, and the value of the preset threshold can be set relatively large (for example: 30%). In this way, appropriately increasing the repetition rate of the delay time will not affect the ranging accuracy.

[0099] Optionally, in some embodiments, as Figure 7 shown, Figure 7 the dashed box of the medium light emitter 100 is meant to represent the preset spacing range corresponding to this light emitter 100. This preset spacing range is centered on a certain light source 110 with a preset distance ( Figure 7It is indicated in the figure that the range enclosed by a radius (which is 3 times the light source spacing) has a repetition rate of the delay times of the detection optical signals emitted by two light sources 110 within the preset spacing range during the same detection period not exceeding a preset threshold. Specifically, centered on the 33rd light source, the distances between the 3rd light source, 11th light source, 30th light source, 51st light source, 63rd light source, 55th light source, 36th light source, and 15th light source located within the preset spacing range and the 33rd light source are basically the same. Among them, the 3rd light source, 11th light source, 11th light source, 30th light source, 51st light source, 63rd light source, 55th light source, 36th light source, and 15th light source respectively have corresponding preset delay times relative to the start time of the detection period during their respective emission periods with respect to the 33rd light source, and the repetition rate of the delay times in different detection periods is less than or equal to the preset threshold, for example: 20%. That is, the ratio of the number of detection periods with the same delay time of the detection optical signals emitted by the 3rd light source, 11th light source, 30th light source, 51st light source, 63rd light source, 55th light source, 36th light source, and 15th light source respectively and the 33rd light source in different detection periods of a detection frame to the total number of detection periods of this detection frame is at most 20%. Correspondingly, the repetition rate of the delay times of the sensing periods when the 3rd pixel, 11th pixel, 30th pixel, 51st pixel, 63rd pixel, 55th pixel, 36th pixel, and 15th pixel respectively start to receive optical signals and the 33rd pixel in different detection periods of a detection frame is less than or equal to 20%, so that the reception with different pixels 210 is asynchronous in multiple detection periods.

[0100] It can be understood that in some embodiments, the repetition rate of the delay times of the sensing periods when the 13th pixel, 31st pixel, 53rd pixel, and 35th pixel, which are relatively close to the 33rd pixel, respectively start to receive optical signals and the 33rd pixel in different detection periods of a detection frame is less than or equal to 15%. The repetition rate of the delay times of the sensing periods when the 23rd pixel, 32nd pixel, 43rd pixel, and 34th pixel adjacent to the 33rd pixel respectively start to receive optical signals and the 33rd pixel in different detection periods of a detection frame is less than or equal to 10%.

[0101] The distance measurement system based on time of flight provided by the embodiments of the present application configures the time when the light source 110 of the light emitter 100 emits a detection optical signal, so that the repetition rate of the delay time of the detection optical signals emitted by two light sources 110 within a preset distance range during the same detection period does not exceed a preset threshold, thereby ensuring that the delay times of the multiple detection optical signals emitted by the two light sources 110 within the preset distance range in a detection frame are not completely the same, so that the false counts formed by the crosstalk between pixels 210 during histogram counting will also be randomly distributed in multiple time bins within a certain range and will not form a crosstalk peak in a fixed time bin, thereby converting the photon counts received due to the crosstalk between pixels 210 into background noise, avoiding the influence of optical crosstalk between pixels, and further improving the accuracy of distance measurement.

[0102] Optionally, in some embodiments, continue to refer to Figure 6 , within the preset distance range, the repetition rate of the delay time of the detection optical signals emitted by every two adjacent light sources 110 (for example: the 11th light source and the 21st light source, or the 21st light source and the 31st light source, or the 31st light source and the 41st light source) during the same detection period does not exceed the preset threshold, that is, the emission of every two adjacent light sources 110 and the reception of the corresponding pixels 210 are asynchronous during multiple detection periods, so as to further reduce the crosstalk between pixels. For the repetition rate of the delay time of the detection optical signals emitted by the 11th light source and the 41st light source which are far apart, it is not required to be within the same preset threshold range. For example: it can be greater than the repetition rate of the delay time of the detection optical signals emitted by the 11th light source and the 21st light source. Therefore, the size of the preset threshold can be adjusted according to the distance between different light sources and the corresponding pixels. For example: the preset threshold is set in positive correlation with the distance.

[0103] Of course, the emission of different light sources 110 with a relatively large interval distance (for example: exceeding the preset distance range) and the reception of the corresponding pixels 210 can be synchronized, so that to a certain extent, it can not only avoid pixel crosstalk, but also reduce the processing difficulty of the processing circuit.

[0104] In this embodiment, by limiting the repetition rate of the delay time of the detection optical signals emitted by two adjacent light sources within the preset distance range during the same detection period to within the preset threshold range, it is ensured that the delay times of the multiple detection optical signals emitted by two adjacent light sources within the preset distance range in a detection frame are not completely the same, and the optical crosstalk between adjacent pixels is avoided as much as possible, further improving the accuracy of distance measurement.

[0105] In some alternative embodiments, to ensure the distance detection accuracy, it is necessary to limit the repetition rate of the delay time of the detection optical signals emitted by two light sources 110 within a preset spacing range during the same detection period in a detection frame within a certain range (that is, the repetition rate of the time when the detection optical signals are emitted or the emission time of the detection optical signals does not exceed a preset threshold). In this way, the times when adjacent light sources 110 emit detection optical signals during different detection periods are staggered as much as possible, which is more conducive to converting the photon counts received by adjacent pixels 210 into background noise, and further improving the distance measurement accuracy.

[0106] Optionally, the preset threshold is greater than 0 and less than or equal to 20%. When the preset threshold exceeds 20%, the repetition rate of the delay time of the detection optical signals emitted by two light sources 110 within a preset spacing range during the same detection period in a detection frame is relatively large. In this way, the probability of miscounting due to crosstalk when the corresponding two pixels 210 receive optical signals and count according to their reception times increases, thus reducing the accuracy of distance detection.

[0107] Exemplarily, assume that the detection frame includes 100 detection periods, and the repetition rate of the delay time of the detection optical signals emitted by two adjacent light sources 110 is set to 10%. This indicates that there are 10 detection periods in these 100 detection periods where the delay times of the emitted detection optical signals are repeated. Among them, the delay times of the detection optical signals emitted in these 10 detection periods can all be the same, or the delay times are the same every 5 detection periods, or the delay times of these 10 detection periods are the same in pairs; of course, other arbitrary combinations of repetition methods can also be adopted, and the present embodiment does not specifically limit the repetition arrangement method.

[0108] Optionally, the preset threshold is greater than 0 and less than or equal to 1%.

[0109] It can be understood that the repetition rate of the delay time of the detection optical signals emitted by at least two adjacent light sources 110 during the same detection period can be set to 0, that is, the delay times of the multiple detection optical signals emitted by at least two adjacent light sources 110 during the corresponding detection periods in a detection frame are not repeated, which is more conducive to improving the detection accuracy.

[0110] In this embodiment, through reasonable setting of the preset threshold, on the one hand, it allows a small part of the repetition of the delay times of the detection optical signals emitted during different detection periods, which is conducive to the encoding setting of the delay time by the processing circuit 300 and reduces the difficulty of data processing; on the other hand, it makes the repetition rate of the delay time of the detection optical signals emitted by adjacent light sources 110 during the same detection period at a lower level, which is more conducive to converting the miscounting caused by crosstalk between pixels 210 into background noise, thereby avoiding the miscounting caused by crosstalk between pixels and further improving the detection accuracy.

[0111] In some embodiments, among the multiple light sources 110 of the light emitter 100, the delay times of two light sources 110 outside the preset spacing range for emitting detection optical signals respectively within corresponding identical detection time periods may be the same, that is, the repetition rate of the delay times of two light sources 110 outside the preset spacing range for emitting detection optical signals respectively within corresponding identical detection time periods may be 100%.

[0112] Specifically, due to the fact that the optical crosstalk of the pixel 210 has a certain distance limitation, the larger the span between pixels, the lighter the crosstalk. Therefore, after a certain number of light sources 110 are separated, the random code used to represent the delay time can be repeated, which can reduce the number of types of random codes generated by the system, thereby reducing the design difficulty of the system.

[0113] Assume that the maximum spacing between light sources 110 within the preset spacing range is 3 times the light source spacing. Then, the multiple light sources 110 are arranged in a linear array (that is, including multiple rows and multiple columns), and the delay times of the detection optical signals emitted by two light sources 110 with a spacing of 4 times the light source spacing (that is, each interval of 1 time the light source spacing is equivalent to 1 Pitch) or more in each row or each column within the corresponding identical detection time period are exactly the same. Since the span of the pixels 210 corresponding to these two light sources 110 is large, even if a random code with repeated delay times is used, no miscounting problem caused by pixel crosstalk will occur. Therefore, the miscounting caused by crosstalk of pixels outside the preset spacing range is less, and the influence on the final ranging result can be basically ignored.

[0114] It can be understood that the maximum spacing between light sources 110 within the preset spacing range being 3 times the light source spacing is equivalent to at most 2 other light sources 110 being spaced between two light sources 110 within the preset spacing range. Therefore, the delay times of two light sources 110 separated by 3 or more other light sources 110 for emitting detection optical signals respectively within the corresponding identical detection time period may be the same.

[0115] In some embodiments, among the multiple light sources of the light emitter, the distance between two light sources that emit detection optical signals with exactly the same delay time during each detection period of a detection frame is at least M times the light source pitch, where the light source pitch is the distance between two adjacent light sources. The multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system can tolerate, and satisfies the condition: P^M < Q, that is, the Mth power of P needs to be less than Q. Among them, the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system expects pixel crosstalk to occur are determined by the structure and performance of the distance measurement system. It should be noted that the crosstalk probability P between adjacent pixels refers to the probability of optical crosstalk when two adjacent pixels sense the echo of the detection optical signal without delay or with exactly the same delay time (the repetition rate is 100%) during the same detection period.

[0116] Exemplarily, as Figure 8 shown, assuming P = 1 / 10 and Q = 1 / 1000, then M needs to satisfy being greater than 3, that is, at least 4 times the light source pitch is spaced apart (equivalent to spacing 3 light sources). For example, the distance between the 1st light source and the 5th light source is 4 times the light source pitch (equivalent to spacing 3 light sources) or the distance between the 1st light source and the 6th light source is 5 times the light source pitch (equivalent to spacing 4 light sources), both of which can meet the requirements. Among them, the 1st light source represents Figure 8 the light source 110 with label 1 in Figure 8 and the 5th light source is Figure 8 the light source 110 with label 5 in

[0117] In a specific embodiment, as Figure 9 shown, the asynchronous transceiver between multiple different pixels 210 is achieved by setting different delay times for each pixel 210 and the corresponding light source 110 relative to the start time of the detection period. As Figure 9 shown, for the emission timings of the four light sources 110 (the 1st light source to the 4th light source) corresponding to the four pixels 210 respectively, a total of N detection optical signals (laser pulses) will be emitted during the N detection periods of a single detection frame, that is, one detection optical signal is emitted corresponding to each detection period, and the period (detection period) of each emission and reception is T, and the pulse width of the emitted laser pulse is W.

[0118] Specifically, the emission and reception of each light source 110 and the corresponding pixel 210 are synchronous, that is, the emitting light source 110 and the corresponding receiving pixel 210 are turned on simultaneously, but the emission and reception between different light sources 110 and the corresponding pixels 210 are asynchronous, that is, Figure 9The light source 110 shown increases the delay time Φ before emitting the detection optical signal. The delay times Φ of different light sources 110 are not exactly the same in different detection cycles (the repetition rate is less than a preset threshold), and the Φ of the same pixel 210 in different detection cycles is also not exactly the same. This is to ensure that the asynchrony of the transceiver of different pixels 210 is not a fixed time deviation. Therefore, for the light source 110 corresponding to the 1st pixel, the delay times of its randomly encoded emissions are Φ1.1, Φ1.2 to Φ1.N. It can be understood that for the Xth light source corresponding to the Xth pixel, the delay times of the corresponding randomly encoded emissions are ΦX.1, ΦX.2 to ΦX.N.

[0119] In a specific embodiment, continue to refer to Figure 8 , assuming that the 1st light source to the 6th light source and the 1st pixel to the 6th pixel are correspondingly arranged and are all linearly arranged. Since the 5th pixel is far from the 1st pixel, the probability of being crosstalked by the 1st pixel is very small. Then the delay time of the detection optical signal emitted by the 5th light source corresponding to the 5th pixel can be exactly the same as that of the 1st light source corresponding to the 1st pixel, both being Φ1.1, Φ1.2 to Φ1.N. Similarly, the 6th light source repeats the random encoding of the delay time of the 2nd light source.

[0120] It should be noted that the number of types of randomly encoded delay times required for specific light sources and the distribution of the random encoding need to be determined according to the arrangement of the light sources and corresponding pixels in the lidar sensor and the severity of crosstalk. If the optical crosstalk between different pixels in the distance measurement system is severe, a larger distance between light sources is required to use repeated random encoding for transceiver.

[0121] In some embodiments, on the premise that the repetition rate of the delay times of the detection optical signals emitted by two light sources 110 within a preset detection range in each detection period of a detection frame does not exceed the preset threshold, the delay times of the detection optical signals emitted by the same light source 110 in different detection periods of a detection frame may not be specifically limited in this embodiment.

[0122] Optionally, the repetition rate of the delay times of the detection optical signals emitted by the same light source 110 of the optical transmitter 100 in different detection periods of a detection frame is 0, that is, the delay times of the detection optical signals emitted by the same light source 110 in different detection periods of a detection frame are all different, and the delay time can be defined in the manner of random time encoding.

[0123] Optionally, the delay times of the detection optical signals emitted by the same light source 110 of the optical transmitter 100 in some detection periods of the same detection frame can be repeated, that is, the delay times of the detection optical signals emitted by the same light source 110 in different detection frames are the same.

[0124] Exemplarily, taking the detection frame including 100 detection periods as an example for illustration, among the detection optical signals emitted by the same light source 110 within 100 detection periods, the delay times of 10 detection periods can be the same. Among them, the delay times of the detection optical signals emitted in these 10 detection periods can all be the same, or the delay times of every 5 detection periods are the same, or the delay times of these 10 detection periods are pairwise the same; of course, other arbitrary combinations of repetition methods can also be adopted, and this embodiment does not specifically limit the repetition method.

[0125] In some embodiments, as Figure 10 shown, the detection periods in which the delay times of the detection optical signals emitted by the same light source 110 of the optical transmitter 100 within a detection frame are repeated are not connected (or not continuous), for example: repeating at an interval of 1 detection period or multiple detection periods, so as to avoid the same light source 110 emitting detection optical signals with the same delay time in adjacent detection periods.

[0126] Specifically, for multiple detection periods within the detection frame, it is ensured that the delay times of the detection optical signals emitted by the same light source 110 in two adjacent detection periods are not the same, or the number of detection periods between two adjacent detection periods with the same delay time is increased as much as possible, so as to separate the detection periods with repeated delay times as much as possible.

[0127] Exemplarily, continue to refer to Figure 10 , for the light source 110, assuming that the random time code Φ1.1 of the delay time of the detection optical signal emitted by the light source 110 within the detection period 1 (1T) is 20 ns, and the random time code Φ1.4 of the delay time of the detection optical signal emitted by the light source 110 within the detection period 4 (4T) is 20 ns; assuming that the random time code Φ1.2 of the delay time of the detection optical signal emitted by the light source 110 within the detection period 2 (2T) is 30 ns, and the random time code Φ1.5 of the delay time of the detection optical signal emitted by the light source 110 within the detection period 5 (5T) is 30 ns, so as to asynchronously set the delay times of the detection optical signals emitted in two adjacent detection periods and ensure that the detection periods with the same delay time are separated by as many detection periods as possible.

[0128] In some embodiments, as Figure 11As shown, the processing circuit 300 includes a time determination unit and a histogram construction unit. The time determination unit may include a plurality of time determination subunits distributed in an array. The plurality of time determination subunits have a corresponding relationship with a plurality of pixels 210. For example, one time determination subunit corresponds to one pixel 210, or one time determination subunit corresponds to a plurality of pixels 210. The time determination unit may be, for example, a time interval method (TIM), a time digitizer, a time counter (TC), a time to digital convert (TDC), etc.

[0129] In the embodiments of the present application, taking the TDC and the SPAD as examples, the TDC may be connected to the SPAD. To more accurately determine the reception time of the light induction signal, the TDC may start timing when the SPAD is activated to determine the reception time of the SPAD receiving the light induction signal. In a measurement system using the SPAD, when a single photon enters the SPAD, an avalanche will be caused, and the SPAD will output an avalanche signal to the TDC. The TDC may detect the reception time of the SPAD receiving the light induction signal. When the TDC, the SPAD, and the transmitter are synchronized, the reception time of the SPAD receiving the light induction signal determined by the TDC can represent the time interval between the photon being emitted from the transmitter and being received by the SPAD.

[0130] After multiple measurements, the histogram construction unit may construct a histogram according to the reception time of the pixels 210 receiving the light induction signal. The histogram is collected in a memory, and the memory includes a plurality of memory units, where each memory unit stores the photon count of a time bin. A time bin may represent a time period or a time interval. The time determination unit may convert the reception time into a time code (such as binary code, temperature code, etc.) and send the time code to the histogram construction unit. The histogram construction unit may perform counting (such as adding 1) on the corresponding memory unit based on the time code. After multiple measurements, the histogram construction unit may count the photon counts in all memory units and construct a histogram. The photon count may be implemented by time-correlated single-photon counting (TCSPC) in the histogram construction unit.

[0131] Based on the same inventive concept, as Figure 12 shown, the embodiments of the present application provide a time-of-flight based distance measurement method. The distance measurement method may be applied to the distance measurement system of the foregoing embodiments (refer to Figure 3) It should be understood that the description of the embodiments of the distance measurement method corresponds basically to the description of the embodiments of the distance measurement system. Therefore, for the parts not described in detail, reference can be made to the embodiments of the distance measurement system above.

[0132] The time-of-flight based distance measurement method provided in this embodiment specifically includes the following steps S100 to S300:

[0133] S100, controlling the light source 110 of the light emitter 100 to emit a plurality of detection light signals into the detection space within one detection frame. The detection frame includes corresponding multiple detection time periods. The light source 110 emits one detection light signal corresponding to each detection time period. The time when the light source 110 emits the detection light signal within each detection time period has a preset delay time compared to the start time of this detection time period; wherein, for two light sources 110 within a preset distance range, the repetition rate of the delay times of the detection light signals emitted by them within the same detection time period does not exceed a preset threshold.

[0134] S200, controlling the pixels 210 of the light receiver 200 to receive the light signals from the detection space and output corresponding light induction signals.

[0135] S300, analyzing and processing the time information of the detection light signals emitted by the light source 110 and the light induction signals output by the pixels 210 that work synchronously to determine the flight time of the detection light signal reflected by the object 400 to be measured within the detected space.

[0136] It should be noted that steps S100 to S300 only represent the numbers of the corresponding method execution steps and do not represent the execution order of the method steps. In addition, for the detailed description of the above steps, reference can be made to the content of each embodiment of the distance measurement system, and details will not be repeated here.

[0137] The time-of-flight based distance measurement method provided in this embodiment controls the light source 110 of the light emitter 100, so that the repetition rate of the delay times of the detection light signals emitted by two light sources 110 within a preset detection range within the same detection time period does not exceed a preset threshold, thereby ensuring that the delay times of the multiple detection light signals emitted by the two light sources 110 within a preset detection distance range within one detection frame are not exactly the same, making the false counts formed by the crosstalk between the pixels 210 also randomly distributed during histogram counting and not forming a crosstalk peak at a fixed time binning, thereby converting the photon counts received due to the crosstalk between the pixels 210 into background noise, avoiding the influence of optical crosstalk between adjacent pixels, and further improving the accuracy of distance measurement.

[0138] In some alternative embodiments, for step S100 of the above embodiments, the repetition rate of the delay times of the detection optical signals respectively emitted by two light sources within a preset detection range within the same detection period not exceeding a preset threshold may include various different situations, specifically as follows:

[0139] Optionally, within a preset spacing range, the repetition rate of the delay times of the detection optical signals respectively emitted by every two adjacent light sources within the same detection period does not exceed a preset threshold. Among them, the preset threshold does not exceed 20%, so as to control the repetition rate within a relatively low range, which is beneficial to improving the accuracy of distance measurement.

[0140] Optionally, the repetition rate of the delay times of the detection optical signals respectively emitted by three adjacent light sources within the same detection period does not exceed a preset threshold.

[0141] Exemplarily, the three adjacent light sources may be arranged linearly (for example: light source 1, light source 2, and light source 3 are arranged linearly in sequence, and the distance between light source 1 and light source 3 is relatively far), or may be arranged at a right angle (light source 1, light source 2, and light source 3 are arranged at a right angle in sequence, and the distance between light source 1 and light source 3 is relatively close). Of course, regardless of the arrangement mode of the light sources, the repetition rate of the delay times of the detection optical signals respectively emitted by any two of these three light sources within the same detection period does not exceed a preset threshold.

[0142] Optionally, the repetition rate of the delay times of the detection optical signals respectively emitted by four adjacent light sources within the same detection period does not exceed a preset threshold.

[0143] Exemplarily, the four adjacent light sources may be arranged linearly (for example: light source 1, light source 2, light source 3, and light source 4 are arranged linearly in sequence, and the distance between light source 1 and light source 4 is relatively far), or may be arranged at a right angle (light source 1, light source 2, light source 3, and light source 4 are arranged at a right angle in sequence, and the distance between light source 1 and light source 4 is medium), or may be arranged in a cross shape (light source 1, light source 2, light source 3, and light source 4 are arranged in a cross shape in sequence, and light source 1 and light source 4 are adjacent). Of course, regardless of the arrangement mode of the light sources, the repetition rate of the delay times of the detection optical signals respectively emitted by any two of these four light sources within the same detection period does not exceed a preset threshold.

[0144] It should be noted that when counting the repetition rate of the delay times of the detection optical signals emitted by adjacent light sources, the more the number of light sources, the fewer the number of detection periods with repeated delay times, and the lower the repetition rate of the delay times of the detection optical signals emitted by two adjacent light sources, so the higher the detection accuracy.

[0145] In some embodiments, within a preset spacing range, the repetition rate of the delay times of the detection optical signals emitted by two light sources spaced more than 1 times the light source spacing within the same detection period does not exceed a preset threshold; wherein, the distance between the two light sources within the preset spacing range is less than or equal to 3 times the light source spacing, and the light source spacing is the distance between the centers of two adjacent light sources.

[0146] Optionally, the distance between the two light sources within the preset spacing range is less than or equal to 2 times the light source spacing, which can further reduce the influence of optical crosstalk between pixels.

[0147] It can be understood that the number of the above light sources and the repetition rate of the delay times of the corresponding emitted detection optical signals in this embodiment are only for illustrative purposes and do not represent an exhaustive list of all situations. As long as the repetition rate of the delay times of the detection optical signals emitted by two light sources within the preset spacing range within the same detection period does not exceed the preset threshold, these two light sources can be arranged adjacent to each other, or spaced 2 times the light source spacing, or 3 times the light source spacing. Among them, there is one light source between the two light sources. As long as the repetition rate of the delay times of the detection optical signals emitted by these two light sources within the same detection period does not exceed the preset threshold, and compared with these two light sources, the repetition rate of the delay times of the detection optical signals emitted by the middle light source within the same detection period exceeds the preset threshold, it is also within the protection scope of the embodiments of the present application.

[0148] In some alternative embodiments, in order to ensure the distance detection accuracy, it is necessary to limit the repetition rate of the delay times of the detection optical signals emitted by adjacent light sources within a certain range, so that the moments when adjacent light sources emit detection optical signals within different detection periods are staggered as much as possible, which is more conducive to converting the photon counts received by adjacent pixels into background noise and further improving the distance measurement accuracy.

[0149] Optionally, the preset threshold is greater than 0 and less than or equal to 20%.

[0150] Exemplarily, assuming that a detection frame includes 100 detection periods, and the repetition rate of the delay times of the detection optical signals emitted by two adjacent light sources is set to 10%, it means that there are 10 detection periods in these 100 detection periods where the delay times of the emitted detection optical signals are repeated. Among them, the delay times of the detection optical signals emitted in these 10 detection periods can be all the same, or the delay times of every 5 detection periods are the same, or the delay times of these 10 detection periods are the same in pairs; of course, other arbitrary combinations of repetition methods can also be adopted, and the present embodiment does not specifically limit the repetition arrangement method.

[0151] Optionally, the preset threshold is greater than 0 and less than or equal to 1%.

[0152] It can be understood that the repetition rate of the delay times of the detection optical signals emitted by at least two adjacent light sources within the same detection period can be 0. That is to say, the delay times of the multiple photometric signals emitted by at least two adjacent light sources during the corresponding detection periods within a detection frame are not repeated. This is more conducive to improving the detection accuracy.

[0153] In this embodiment, through reasonable setting of the preset threshold, on the one hand, a small part of the repetition of the delay times of the detection optical signals emitted in different detection periods is allowed, which is conducive to the encoding setting of the delay times by the processing circuit and reduces the difficulty of data processing; on the other hand, the repetition rate of the delay times of the detection optical signals emitted by adjacent light sources within the same detection period is at a lower level, which is more conducive to converting the false counting caused by the crosstalk between pixels into background noise, thereby avoiding the false counting caused by the crosstalk between pixels and further improving the detection accuracy.

[0154] In some embodiments, in addition to the above steps, the distance measurement method further includes: for two light sources outside the preset spacing range among the multiple light sources of the light emitter, the delay times of the detection optical signals emitted by them during the corresponding same detection period are the same.

[0155] Specifically, since there is a certain distance limit for the optical crosstalk of pixels, the greater the span between pixels, the lighter the crosstalk. Therefore, the random coding used to represent the delay time can be repeated after a certain number of light sources are separated, which can reduce the number of types of random coding generated by the system, thereby reducing the design difficulty of the system.

[0156] It should be noted that the number of types of random coding required for specific light sources and the distribution of random coding need to be determined according to the arrangement of light sources and corresponding pixels in the lidar sensor and the severity of crosstalk. If the optical crosstalk between pixels is serious, a greater number of light sources need to be separated before repeating the random coding for transmission and reception. Therefore, the false counting caused by crosstalk for pixels outside the preset spacing range is less, and the impact on the final ranging result can be basically ignored.

[0157] In some embodiments, among the multiple light sources of the light emitter, the distance between two light sources that emit detection optical signals with exactly the same delay time during each detection period of a detection frame is at least M times the light source pitch, where the light source pitch is the distance between two adjacent light sources. The multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system can tolerate, and satisfies the condition: P^M < Q, that is, the Mth power of P is less than Q. Among them, the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system expects pixel crosstalk to occur are determined by the structure and performance of the lidar sensor. It should be noted that the crosstalk probability P between adjacent pixels refers to the probability of optical crosstalk when two adjacent pixels sense the echo of the detection optical signal without delay or with exactly the same delay time (the repetition rate is 100%) during the same detection period.

[0158] Exemplarily, as Figure 8 shown, assuming P = 1 / 10 and Q = 1 / 1000, then M needs to satisfy being greater than 3, that is, at least 4 times the light source pitch is spaced apart (equivalent to spacing 3 light sources). For example, the distance between the 1st light source and the 5th light source is 4 times the light source pitch (equivalent to spacing 3 light sources) or the distance between the 1st light source and the 6th light source is 5 times the light source pitch (equivalent to spacing 4 light sources) can both meet the requirements. Among them, the 1st light source represents Figure 8 the light source 110 with label 1 in Figure 8 the light source 110 with label 5 in Figure 8 and other light sources 110 and the corresponding pixels 210 in

[0159] In some embodiments, for step S100 of the above embodiment, controlling the light sources of the light emitter to emit multiple detection optical signals into the detection space within a detection frame further includes:

[0160] Controlling the repetition rate of the delay time of the detection optical signals emitted by the same light source of the light emitter within different detection periods of a detection frame to be 0; or, controlling the delay time of the detection optical signals emitted by the same light source of the light emitter within some detection periods of a detection frame to repeat.

[0161] Optionally, the repetition rate of the delay time of the detection optical signals emitted by the same light source of the light emitter within different detection periods of a detection frame is 0, that is, the delay times of the detection optical signals emitted by the same light source within different detection periods of a detection frame are all different, and the delay time can be set in the way of random time coding.

[0162] Optionally, the delay time of the detection optical signal emitted by the same light source of the optical transmitter within a partial detection period in a detection frame is repeated, that is, the delay time of the detection optical signal emitted by the same light source in different detection frames is the same.

[0163] Exemplarily, taking a detection frame including 100 detection periods as an example for illustration, among the detection optical signals emitted by the same light source within 100 detection periods, there are 10 detection periods in which the delay time is repeated. Among them, the delay times of the detection optical signals emitted in these 10 detection periods may all be the same, or the delay times of every 5 detection periods among them are the same, or the delay times of these 20 detection periods are the same in pairs; of course, other arbitrary combinations of repetition methods can also be adopted, and the present embodiment does not specifically limit the repetition method.

[0164] In some embodiments, the delay time of the detection optical signal emitted by the same light source of the optical transmitter within a partial detection period in a detection frame in the above embodiment is repeated, including: the detection periods in which the delay time of the detection optical signal emitted by the same light source of the optical transmitter within a detection frame is repeated are not adjacent.

[0165] Specifically, for multiple detection periods within a detection frame, it is ensured that the delay times of the detection optical signals emitted by the same light source in two adjacent detection periods are not the same, or the time interval (i.e., the number of intervals of detection periods) between two adjacent detection periods with the same delay time is increased as much as possible, so as to separate the detection periods with repeated delay times as much as possible.

[0166] In some embodiments, after step S300, it includes: determining the distance of the object to be detected according to the flight time of the detection optical signal.

[0167] Specifically, according to the dTOF principle, the processing circuit can calculate the distance between the object to be detected and the optical transmitter and optical detector of the distance measurement system through the flight time of the detection optical signal (specifically, the distance calculation formula of the object can be referred to above). It can be understood that the optical transmitter and optical detector provided in the present embodiment basically process the same reference plane inside the distance detection system, which is beneficial to the design of the hardware system.

[0168] Based on the same inventive concept, the embodiment of the present application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the steps of the time-of-flight-based distance measurement method as described in the foregoing embodiments. The computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device, or a combination thereof.

[0169] In the description of this specification, the descriptions referring to terms such as "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0170] Although the embodiments of this application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on this application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A time-of-flight based distance measurement system, characterized in that, Comprising: An optical transmitter including a plurality of light sources configured to emit a plurality of detection optical signals into a detection space within a detection frame. The detection frame includes corresponding multiple detection time periods, and each light source emits one of the detection optical signals within each detection time period. The time when the light source emits the detection optical signal within each detection time period has a preset delay time compared to the start time of the detection time period. Among them, the repetition rate of the delay times of the detection optical signals emitted by two light sources within the preset spacing range in the same detection time period does not exceed a preset threshold; An optical receiver including a plurality of pixels configured to receive the detection optical signals from the detection space and output corresponding optical induction signals; A processing circuit electrically connected to the optical transmitter and the optical receiver, configured to analyze and process the time information of the detection optical signals emitted by the light sources and the optical induction signals output by the pixels that work synchronously, so as to determine the flight time of the detection optical signals reflected back by the object to be measured in the detection space.

2. The time-of-flight based distance measurement system according to claim 1, wherein Within the preset spacing range, the repetition rate of the delay times of the detection optical signals emitted by every two adjacent light sources in the same detection time period does not exceed the preset threshold.

3. The time-of-flight based distance measurement system according to claim 1 or 2, characterized in that, The distance between two light sources within the preset spacing range is less than or equal to 3 times the light source spacing, and the light source spacing is the distance between two adjacent light sources; the preset threshold is greater than 0 and less than or equal to 20%.

4. The time-of-flight based distance measurement system according to claim 1 or 2, characterized in that, Among the multiple light sources of the optical transmitter, the delay times of the detection optical signals emitted by two light sources outside the preset spacing range in the corresponding same detection time period are the same.

5. The time-of-flight based distance measurement system according to claim 1 or 2, characterized in that, Among the multiple light sources of the optical transmitter, the distance between two light sources with exactly the same delay time of emitting the detection optical signal in each detection time period of a detection frame is at least M times the light source spacing, where the light source spacing is the distance between two adjacent light sources, and the multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the distance measurement system can tolerate, and satisfies the condition: the Mth power of P is less than Q.

6. The time-of-flight based distance measurement system according to claim 1 or 2, characterized in that, The repetition rate of the delay times of the detection optical signals emitted by the same light source of the optical transmitter in different detection time periods of a detection frame is 0; or, the delay times of the detection optical signals emitted by the same light source of the optical transmitter are repeated in some detection time periods within a detection frame.

7. The time-of-flight based distance measurement system according to claim 6, wherein, The detection time periods in which the delay times of the detection optical signals emitted by the same light source of the optical transmitter are repeated within a detection frame are not connected.

8. A time-of-flight based distance measurement method, characterized in that, Comprising: Controlling the light sources of the optical transmitter to emit a plurality of detection optical signals into the detection space within a detection frame. The detection frame includes corresponding multiple detection time periods, and each light source emits one of the detection optical signals within each detection time period. The time when the light source emits the detection optical signal within each detection time period has a preset delay time compared to the start time of the detection time period. Among them, the repetition rate of the delay times of the detection optical signals emitted by two light sources within the preset spacing range in the same detection time period does not exceed a preset threshold; The pixels of the light receiver control receive the detection optical signal from the detection space and output corresponding photo-induced signals; Analyze and process the time information of the detection optical signal emitted by the light source corresponding to the pixel and the output photo-induced signal that work synchronously to determine the flight time of the detection optical signal reflected by the object to be measured in the detection space.

9. The time-of-flight based distance measurement method according to claim 8, wherein The repetition rate of the delay time of the detection optical signal emitted by two of the light sources within the preset spacing range in the same detection period does not exceed a preset threshold, including: Within the preset spacing range, the repetition rate of the delay time of the detection optical signal emitted by every two adjacent light sources in the same detection period does not exceed a preset threshold; Or, within the preset spacing range, the repetition rate of the delay time of the detection optical signal emitted by two light sources with a spacing greater than 1 times the light source spacing in the same detection period does not exceed a preset threshold; Wherein, the distance between two of the light sources within the preset spacing range is less than or equal to 3 times the light source spacing, and the light source spacing is the distance between two adjacent light sources.

10. The time-of-flight based distance measurement method according to claim 8, characterized in that, It further includes: Among the multiple light sources of the light emitter, the delay times of the detection optical signals emitted by two light sources outside the preset spacing range in the corresponding same detection period are the same; or, the distance between two light sources with the same delay time of the detection optical signal emitted in each detection period of a detection frame is at least M times the light source spacing, the light source spacing is the distance between two adjacent light sources, and the multiple M is determined by the crosstalk probability P between adjacent pixels and the maximum crosstalk probability Q that the system can withstand, and satisfies the condition: the Mth power of P is less than Q.

11. The time-of-flight based distance measurement method according to claim 8, characterized in that, The light source of the light emitter controls to emit multiple detection optical signals to the detection space in a detection frame, and further includes: Controlling the repetition rate of the delay time of the detection optical signal emitted by the same light source of the light emitter in different detection periods within a detection frame to be 0; or, controlling the delay time of the detection optical signal emitted by the same light source of the light emitter in some detection periods within a detection frame to repeat.

12. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the time-of-flight based distance measurement method according to any one of claims 8 to 11.

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