Storage method, data processing method, lidar, and computer-readable storage medium

Abstract

The present invention provides a method for storing detection data of a radar, including: S101: receiving detection data, where the detection data includes time information and intensity information corresponding to the time information; and S102: storing the intensity information at a first time accuracy according to the weight of the time information; where the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the radar, where n > 1; the weight is associated with the time interval between the time information and at least one first time scale. Through the storage method of the present invention, the ranging accuracy can be maintained while reducing the storage space.

Description

Technical Field

[0001] The present disclosure generally relates to the technical field of optoelectronic detection, and particularly relates to a storage method for detection data of a radar, a data processing method, a lidar, and a computer-readable storage medium. Background Art

[0002] A lidar is a radar system that emits laser beams to detect characteristics such as the position and speed of a target, and is an advanced detection method that combines laser technology with optoelectronic detection technology. Due to its advantages such as high resolution, good concealment, strong anti-active interference ability, good low-altitude detection performance, small size, and light weight, lidar is widely used in fields such as autonomous driving, traffic communication, unmanned aerial vehicles, intelligent robots, and resource exploration.

[0003] In a lidar, a time-to-digital converter is usually used to obtain time information, including the arrival time of an echo and / or the flight time of the echo. In a measurement system using a high-precision time-to-digital converter (TDC), the time information obtained from each measurement is accumulated into a histogram, consuming a large amount of storage space. Some lidars use a single-photon avalanche diode (SPAD) as a detector. The SPAD can be triggered by a single photon to cause an avalanche, and the TDC can give a measurement with picosecond-level accuracy of the trigger moment timestamp for each trigger. In certain applications, the output terminals of multiple SPADs are connected to the same TDC, serving as a macro-pixel. While providing the trigger moment timestamp, the TDC gives the number cnt of SPADs that are triggered simultaneously within the macro-pixel.

[0004] With the existing storage and ranging methods, since the precision unit of the trigger moment timestamp is in the order of picoseconds, when a long tof detection is required, storing a complete histogram requires consuming a large amount of memory and a large amount of storage space. Especially to improve the ranging ability, it is necessary to increase the measurement duration and the number of repeated measurements, and the requirements for storage space are also continuously increasing.

[0005] The content in the background art section is only the technology known to the applicant and does not of course represent the prior art in this field. Summary of the Invention

[0006] In view of at least one defect of the prior art, the present invention provides a method for storing detection data of a radar, including:

[0007] S101: Receiving detection data, where the detection data includes time information and intensity information corresponding to the time information; and

[0008] S102: Store the intensity information according to the weight of the time information with a first time accuracy.

[0009] Wherein, the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the radar, where n > 1.

[0010] The weight is associated with the time interval between the time information and at least one first time scale.

[0011] According to one aspect of the present invention, the weight includes a first weight and a second weight. The first weight is associated with the time interval between the time information and one of the adjacent first time scales, and the second weight is associated with the time interval between the time information and the other adjacent first time scale. The step S102 includes: storing the intensity information according to the first weight and the second weight respectively with a first time accuracy.

[0012] According to one aspect of the present invention, the first weight is n - x, and the second weight is x, where x represents that the time interval between the time information and the adjacent first time scale is x times the time resolution of the radar detection data.

[0013] According to one aspect of the present invention, the first weight is the weight of the time information corresponding to the first time scale adjacent to its left, and the second weight is the weight of the time information corresponding to the first time scale adjacent to its right, where x represents that the time interval between the time information and the first time scale adjacent to its left is x times the time resolution of the radar detection data.

[0014] According to one aspect of the present invention, the first weight is 1 - (x / n), and the second preset weight is x / n, where x represents that the time interval between the time information and the first time scale adjacent to its left is x times the time resolution of the radar detection data.

[0015] According to one aspect of the present invention, n = 2 m , m is a positive integer.

[0016] According to one aspect of the present invention, the intensity information includes the trigger count of the detection unit.

[0017] According to one aspect of the present invention, the memory has storage units corresponding to each first time scale. The step S102 includes: storing the intensity information in two storage units corresponding to two first time scales adjacent to the time information according to the first weight and the second weight.

[0018] According to one aspect of the present invention, the step S102 further includes: when storing the intensity information into one of the storage units according to the weight,

[0019] reading the value stored in the storage unit;

[0020] accumulating the value calculated from the intensity information according to the weight and the read value; and

[0021] writing the accumulated result into the storage unit.

[0022] According to one aspect of the present invention, the storage method further includes: when it is determined that one of the storage units overflows or is about to overflow, allocating another storage address for the storage unit from a reserved register.

[0023] According to one aspect of the present invention, the reserved register includes N groups of registers, where N is a preset value, and each group of registers is used for a storage unit that overflows or is about to overflow.

[0024] The present invention also provides a data processing method applicable to a lidar, including:

[0025] S201: Obtaining the reception time of the optical signal and the intensity information;

[0026] S202: Determining time information based on the emission time of the detection pulse and the reception time;

[0027] S203: Storing the intensity information at a first time accuracy according to the weight of the time information;

[0028] wherein, the first time accuracy is the time interval between any two adjacent first time scales, and is n times the time resolution of the detection data of the lidar, where n>1;

[0029] The weight is associated with the time interval between the time information and at least one first time scale.

[0030] According to one aspect of the present invention, the lidar performs multiple scans on a field of view, and the step S203 includes: storing the intensity information obtained from the multiple scans superimposed at a first time accuracy.

[0031] According to one aspect of the present invention, the data processing method further includes:

[0032] After completing the multiple scans, reading the values stored in the storage units corresponding to each first time scale;

[0033] Calculating the centroid of the values on the time axis;

[0034] Take the center of gravity as the time of flight.

[0035] According to one aspect of the present invention, the data processing method further includes:

[0036] After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale to obtain the leading edge time of the echo pulse;

[0037] Wherein, the leading edge time is:

[0038] Compare the value corresponding to the leading edge of the echo pulse with a preset threshold, and take the time information corresponding to the value whose intensity is equal to the preset threshold as the leading edge time.

[0039] The present invention also provides a lidar, including:

[0040] A transmitting module, including a plurality of transmitting units, for transmitting laser detection pulses;

[0041] A detection module, including a plurality of detection units, for receiving the echo after the laser detection pulse is reflected on the target and converting the echo into an electrical signal;

[0042] A sampling device; converting the electrical signal into a digital signal;

[0043] A processing device, coupled to the sampling device, configured to determine detection data according to the digital signal, the detection data including time information and intensity information corresponding to the time information, and store the intensity information with a first time accuracy according to the weight of the time information;

[0044] Wherein, the first time accuracy is the time interval between any two adjacent first time scales, and is n times the time resolution of the detection data of the lidar, where n>1; the weight is associated with the time interval between the time information and at least one first time scale.

[0045] According to one aspect of the present invention, the lidar is configured to perform multiple scans on a field of view range, wherein the processing device is configured to superimpose and store the intensity information obtained from the multiple scans with a first time accuracy.

[0046] According to one aspect of the present invention, the processing device is further configured to:

[0047] After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale;

[0048] Calculate the center of gravity of the values on the time axis;

[0049] Take the center of gravity as the time of flight.

[0050] According to one aspect of the present invention, the processing device is further configured to:

[0051] After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale, and obtain the leading edge time of the echo pulse;

[0052] Wherein, the leading edge time is:

[0053] Compare the value corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the value whose intensity is equal to the preset threshold as the leading edge time.

[0054] According to one aspect of the present invention, the multiple transmitting units emit detection beams to different field of view ranges, and the multiple field of view ranges constitute the detection range of the lidar.

[0055] According to one aspect of the present invention, the detection unit includes a detection unit based on Geiger mode, and the sampling device includes a time-to-digital converter.

[0056] According to one aspect of the present invention, each of the transmitting units sequentially emits a detection beam to a corresponding field of view range. When one of the transmitting units emits a detection beam, at least one detection unit corresponding to the field of view range of the transmitting unit is activated to start detection.

[0057] The present invention also provides a computer-readable storage medium, including computer-executable instructions stored thereon, and the executable instructions, when executed by a processor, implement the storage method as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The drawings constituting a part of this disclosure are used to provide a further understanding of this disclosure. The schematic embodiments and descriptions thereof of this disclosure are used to explain this disclosure and do not constitute an improper limitation of this disclosure. In the drawings:

[0059] Figure 1 Illustrates the triggering of a single-photon avalanche diode during multiple detection scans of a lidar;

[0060] Figure 2 Illustrates the histogram formed after superimposing multiple scans;

[0061] Figure 3 Illustrates the data storage method according to the prior art;

[0062] Figure 4 Illustrates the storage method of detection data of a radar according to an embodiment of the present invention;

[0063] Figure 5 Illustrates the detection unit of a lidar according to an embodiment of the present invention;

[0064] Figure 6 and Figure 7 shows a specific schematic diagram of a storage method according to a preferred embodiment of the present invention;

[0065] Figure 8 shows a schematic diagram of a storage effect according to an embodiment of the present invention;

[0066] Figure 9 shows a schematic diagram of a memory allocation method according to a preferred embodiment of the present invention;

[0067] Figure 10 shows a data processing method applicable to lidar according to an embodiment of the present invention; and

[0068] Figure 11 shows a block diagram of a lidar according to an embodiment of the present invention. Detailed Description of the Invention

[0069] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are regarded as being exemplary in nature rather than restrictive.

[0070] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0071] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection: it can be a mechanical connection, an electrical connection, or a connection that allows mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over", and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature. The first feature being "below", "beneath", and "underneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the first feature has a lower horizontal height than the second feature.

[0073] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0074] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0075] In some time-to-digital converters of lidar, a corresponding storage location is required for each time scale of its time resolution. All the information cnt of the triggered SPAD numbers obtained from multiple measurements is stored in the storage location corresponding to the time. The time resolution of the time-to-digital converter TDC can reach the order of picoseconds (ps), so a register with a very large space is required. The specific explanation is as follows.

[0076] The SPAD can be triggered by a single photon to cause an avalanche effect, so it is vulnerable to ambient light noise. On the other hand, the photon detection efficiency (PDE) of the SPAD for the photon detection wavelength band commonly used in lidar is low, and the signal intensity obtained from a single detection is very weak. As Figure 1 shown, in a single detection scan, only a few triggers may occur within the detection time window ( Figure 1 two triggers in Figure 1 ), and it is impossible to distinguish whether it is an echo signal or ambient light noise. To improve the ranging performance of the lidar and reduce the influence of noise, as

[0077] shown, during a single detection process of the lidar for the same field of view, multiple repeated measurements can be performed (one measurement is called one sweep, and the number of repetitions can reach 400 - 500 times, or more or fewer times). The results of multiple measurements or sweeps are accumulated to obtain a histogram, and the distance is measured based on this, and then a point on the lidar point cloud is obtained. a (a represents the a-th sweep). For one sweep, the controller of the lidar gates some (a row or a column or any shape of interest) macro-pixels by supplying high voltage to the SPAD, and then sends a synchronization signal to notify the laser at the transmitting end to emit light. The laser at the transmitting end emits a light pulse for detection at time t 1a This light pulse encounters an external obstacle, is reflected by the obstacle and returns to the lidar, and can be received by the photodetector at the receiving end. When the photodetector is an SPAD(s) array, once the SPAD receives a photon, an avalanche electrical signal is generated and transmitted to the time-to-digital converter, and the time-to-digital converter outputs the time signal t 1a of the SPAD trigger 1a and the number signal cnt a of the SPADs triggered at the same time 1a (here 1a represents the first trigger of the a-th sweep). After passing through a subtraction program to calculate the time stamp 1a of t 1a -t 1a 2a and stores the tp 2a and the trigger number cnt

[0078] ​In the next scan b, the controller of the lidar sends a signal again according to a preset program to control the emission end to emit a detection optical pulse at time t b Once the SPAD receives a photon, the avalanche electrical signal is transmitted to the time-to-digital converter TDC, and the time signal t 1b triggered by the SPAD output by the time-to-digital converter TDC and the number signal cnt 1b (the first trigger of the bth detection), and the subsequent memory stores the SPAD trigger time t 1b -t b timestamp of 1b (hereinafter referred to as tp 1b ) and the trigger number cnt of this timestamp 1b signal. A macro-pixel includes multiple SPADs, and the SPAD can detect again after the dead time. Therefore, in one scan, SPAD triggering may occur at another time, and the memory stores the tp 2b and cnt 2b of this trigger.

[0079] In hundreds of measurements, the trigger number cnt obtained each time is stored in the corresponding memory location according to the timestamp. When a new trigger number cnt arrives at the position corresponding to the same timestamp, the original stored value is added to the new trigger number cnt and then updated to this position. After multiple scans are superimposed, a histogram is saved in the memory. As Figure 2 shown, the histogram reflects the total trigger number cnt corresponding to different timestamps on the time axis. In this way, operations such as calculating the centroid or leading edge time using the histogram are used to obtain the time information corresponding to the echo, which is used as the flight time for distance calculation to generate a point on the point cloud.

[0080] A data storage method is as Figure 3 shown. The abscissa is time t, and the scale interval of the abscissa is the resolution of the TDC. Each time scale corresponds to a storage location R (register). For example, in a certain detection scan a, SPAD triggering occurs at time scale 0. The timestamp tp1 (trigger time - this emission time) and trigger number information cnt are calculated based on the emission time and the trigger time transmitted by the TDC 1a , and cnt 1a is stored in the storage location R1 corresponding to the tp1 moment; if SPAD triggering occurs at time scale 4, the time information tp5 and cnt 5a are obtained, and cn 5aStored at the storage location R5 corresponding to tp5. In another detection scan b, an SPAD trigger also occurred at time scale 4, obtaining the time information tp5 and cnt 5b , cnt 5b also corresponds to the storage location R5. At this time, cnt 5a is read out, and then cnt 5b is added to the value of cnt 5a and updated to R5. (Combined with Figure 3 , a represents the a-th detection, b represents the b-th detection, the numbers represent the corresponding time scales and the corresponding storage locations; the storage location R corresponds one-to-one with the time scale, and the memory only stores the trigger count cnt. When the data processing circuit reads the data, it can know the time corresponding to the trigger count cnt according to the storage location).

[0081] Reference Figure 3 shows that a histogram is obtained by accumulating data from many detection scans (400 - 500 times). During the process of superimposing the detection results of hundreds of scans into a histogram and obtaining a point in the point cloud, the storage location corresponding to a certain time scale stores the sum of all trigger counts cnt triggered at that moment. Although SPAD triggers do not occur at every time scale during a single scan, as Figure 3 shown, a histogram data is superimposed by many detection results, and SPAD triggers may occur at each time scale during a certain scan, causing the memory to receive the corresponding data. Therefore, for a TDC, each time scale needs to have a corresponding storage location, and all trigger counts cnt obtained from multiple measurements are stored in the storage location corresponding to the moment. The time interval of tp, that is, the resolution of the TDC, reaches the ps level, and a register with a very large space is required.

[0082] Using such a storage and ranging method, since the precision unit of the timestamp is at the ps level, when a long tof detection is required, storing a complete histogram requires consuming a huge amount of memory and a large amount of storage space. Especially in order to improve the ranging ability, it is necessary to increase the measurement duration and the number of repeated measurements, and the requirement for the storage space also increases continuously.

[0083] The inventor of the present application conceived that it is not necessary to set a corresponding storage location for each time scale of the TDC time resolution. When storing detection data, instead of storing according to the time resolution, it is stored with a lower time precision according to the weight of the time information. The present invention adopts a weighted accumulation data storage method to compress the original signal while retaining the ranging accuracy, greatly reducing the storage space required for storing the histogram. Specifically, the weighted accumulation data storage method can reduce the total storage space to within 1 / 10 of the original range.

[0084] Specifically, the time precision for storing the intensity information in the present invention is the first time precision, and the first time precision can be n times the time resolution of the time-to-digital converter (TDC). The intensity information refers to the optical signal intensity information corresponding to the time information. For different photodetectors, different parameters can be used to characterize the optical signal intensity. For example, if the detector is a SPAD array, the number of simultaneously triggered SPADs corresponding to the time information can be used as the intensity information. If the detector is a SiPM, the output level / current intensity corresponding to the time information can be used to represent the optical signal intensity information.

[0085] The following will be described in detail with reference to the accompanying drawings.

[0086] Figure 4 A method 100 for storing detection data of a radar according to an embodiment of the present invention is shown. Figure 5 A schematic diagram of a detection module according to a preferred embodiment of the present invention is shown, wherein the detection module 22 of the lidar includes a plurality of detection units, and a single-photon avalanche diode (SPAD) is used as the photodetector, and each detection unit includes a plurality of SPADs.

[0087] As Figure 4 shown, in step S101, detection data is received, and the detection data includes time information and intensity information corresponding to the time information.

[0088] As Figure 5 shown, the detection module 22 includes a plurality of detection units, which are shown as detection units 221-1, 221-2, and 221-n in Figure 5 . In Figure 5In an embodiment, each detection unit includes a plurality of (for example, 9 as shown in the figure, or 3, 4, ……, specifically, it may include p, where p is a positive integer ≥ 1) single-photon avalanche diodes (SPADs). The output terminals of the single-photon avalanche diodes of each detection unit are connected to a time-to-digital converter (TDC). The range of the detection window of each detection unit (i.e., the time period during which the SPAD can sense incident photons) is independently adjustable, that is, each detection unit can be independently controlled to be in an active state (the SPAD is in Geiger mode, that is, a reverse bias greater than the breakdown voltage is applied to the SPAD so that the SPAD can trigger an avalanche effect when receiving photons) or a deactivated state (a state where the avalanche cannot be triggered by photons). After photons are incident on the detection units 221-1, 221-2, and 221-n, the single-photon avalanche diodes (SPADs) are triggered and electrical signals are generated. Each detection unit is coupled to the time-to-digital converter (TDC), and the time-to-digital converter (TDC) can determine the arrival time of the photons. The data processing device (not shown in the figure) connected to the TDC can obtain the emission time of the detection light, determine the time difference between the arrival time of the photons and the emission time of the detection light, and store the result in the memory.

[0089] Take Figure 5 the detection unit shown as an example, Figure 4 the time information therein is the time when one or more single-photon avalanche diodes (SPADs) in the macro-pixel are triggered, and the intensity information is the number of single-photon avalanche diodes (SPADs) triggered at this trigger time, that is, the intensity of the optical signal is characterized by the number of single-photon avalanche diodes (SPADs) triggered. According to a preferred embodiment of the present invention, the time information is the timestamp of the single-photon avalanche diode (SPAD) trigger, that is, the time difference t a between the time t 1a when the laser is emitted and the time t 1a when the single-photon avalanche diode (SPAD) is triggered, t a .

[0090] Figure 5 In the embodiment, the single-photon avalanche diode (SPAD) is taken as an example for illustration. It is easy for those skilled in the art to understand that the present invention is not limited thereto, and other types of photodetectors can also be used, including but not limited to avalanche photodiodes (APDs), silicon photomultipliers (SiPMs), etc.

[0091] In step S102: Store the intensity information with a first time accuracy according to the weight of the time information; the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the radar, where n > 1; the weight is associated with the time information and the time interval of at least one first time scale.

[0092] Figure 6 and Figure 7 shows a specific schematic diagram of the storage method according to a preferred embodiment of the present invention. The implementation of step S102 will be described in detail below with reference to Figure 6 and Figure 7 the details.

[0093] Figure 6 In, the abscissa is the time of flight, and the interval of the time scale on the abscissa is, for example, the time resolution of the lidar, such as the time resolution of the time-to-digital converter TDC, which can reach the order of picoseconds ps. As Figure 6 shown, a first time scale is set on the basis of the time resolution of the lidar. As shown by A and A + 1 in Figure 6 , the interval between two adjacent first time scales spans 16 intervals of the time resolution of the lidar. When photons are detected at time x (for example, one or more single-photon avalanche diodes SPADs in a macro-pixel of the receiving unit 22 shown in 5 are triggered), the detected intensity value is stored according to the weight of time x. Time x represents that the time interval between this time and the adjacent first time scale A on its left is x times the time resolution of the radar detection data.

[0094] Those skilled in the art can easily understand that since the time resolution of the lidar is small and the interval of the first time scale is large, the time scale corresponding to the time resolution of the lidar can also be called a "fine scale", and the first time scale can also be called a "coarse scale".

[0095] As Figure 6 shown, the weight of time x includes a first weight and a second weight. The first weight is associated with the time interval between time x and one of the adjacent first time scales, and the second weight is associated with the time interval between time x and the other adjacent first time scale. After determining the first weight and the second weight, store the intensity information with a first time accuracy according to the first weight and the second weight respectively.

[0096] According to a preferred embodiment of the present invention, the first weight is associated with the time interval between the moment x and the first time scale A adjacent to its left side. The first weight is, for example, (16 - x). The second weight is associated with the time interval between the moment x and the first time scale A + 1 adjacent to its right side. The second weight is, for example, x. Therefore, the moment x is represented by substituting it with its weights at two adjacent coarse scales (A, A + 1), where the weight of x at the coarse scale A is (16 - x), and the weight at the coarse scale A + 1 is x (x represents the distance of this moment from A), so as to equivalently represent the fine scale of the moment x. In other words, by using x as the weight, the data at the fine scale is stored at the corresponding addresses of two adjacent coarse scales to represent the value of the scale x, rather than storing the scale x itself. This process is represented by the following equation:

[0097] A*(16 - x)+(A + 1)*x = A*16 + x

[0098] In the formula, the left side of the equal sign is the sum of the weights applied to the storage according to the coarse scale, the starting value and the ending value of the coarse scale, and the right side of the equal sign is the specific value of the time stamp. The storage method of coarse scale + weight can represent the specific value of the time stamp.

[0099] Similarly, when the triggered signal includes, in addition to the time stamp, information such as the number or intensity of the trigger, i.e., the trigger quantity cnt, the additional intensity information on the coarse scale A is cnt*(16 - x), and the additional intensity information on the coarse scale A + 1 is cnt*x, and they can be accumulated separately in multiple scans. Refer to Figure 7 for a detailed description. The fine scale represents the time resolution of the time-to-digital converter TDC. For a certain time stamp timestamp, the starting value of its coarse scale is A, and its fine scale is at the 0 - 15 fine scale x position corresponding to its coarse scale.

[0100] Refer to Figure 7 , a register is allocated for each coarse scale. The coarse scale interval on the abscissa is 16 times the TDC resolution, and each coarse scale corresponds to a register. During a certain scan a, an SPAD trigger occurs at the time scale 0, and the time information tp1 (corresponding x 1a = 0) and the trigger quantity information cnt 1a are obtained. Respectively, store cnt 1a *(16 - x 1a ) in the register A corresponding to the coarse scale A, and store cnt 1a *x 1a in the register A + 1 corresponding to the coarse scale A + 1; at another time scale 5, the time information tp6 (corresponding x6 a = 5) and the trigger quantity information cnt 6a, read out the data stored in register A corresponding to coarse scale A, add cnt 6a *(16 - x 6a ) and then store it in register A; read out the data in register A+1 corresponding to coarse scale A+1, add cnt 6a *x 6a and then re-store it in register A+1. Within one coarse scale time (fine scale 0 to 15), weights are applied to all trigger count information cnt, and after summing with the original data, it is stored in the registers corresponding to storage locations A and A+1. For the trigger count information cnt in the next coarse scale time, after applying weights, it is stored in the registers corresponding to coarse scales A+1 and A+2. For example, at time 2’, an SPAD trigger occurs, obtaining time information tp3’ and cnt 3a ’, then add cnt 3a ’*(16 - x 3a ’) to the data stored in register A+1 corresponding to coarse scale A+1, and store cnt 3a ’*x 3a ’ in register A+2 corresponding to coarse scale A+2.

[0101] During the next scan of b, the received signals tp2 and cnt 2b , respectively assign weights cnt 2b *(16 - x 2b ) and cnt 2b *x 2b at coarse scales A and A+1, and sum them with the original stored data and then store them in the registers corresponding to coarse scales A and A+1. A histogram is obtained by accumulating data from many scans. During several scans, all trigger counts cnt corresponding to triggers occurring at times 0 to 15 are stored in the registers corresponding to coarse scales A and A+1.

[0102] The comparison relationship between the coarse scale and the fine scale is as Figure 8 shown. Compared with the scheme that requires a register for data storage at each fine scale, the present invention adopts a weighted accumulation storage method, only needs to set registers corresponding to the coarse scales from 0 to n +
1 in Figure 8 , and the required number of registers is reduced to 1 / 16 of the original. Although the bit width stored in each register increases and the occupied space becomes larger, because the number of storage locations to be allocated is greatly reduced, the weighted accumulation data storage method can reduce the total storage space to within 1 / 10 of the original.

[0103] Figures 6 - 8In the embodiment, the time interval between adjacent first time scales (coarse scales) is 16 times the time resolution of radar detection data (fine scales), that is, data compression is performed using 16 as the weight. It is easy for those skilled in the art to understand that the present invention is not limited thereto, and the weight here can be any large positive integer, preferably 2 m , where m is a positive integer, thus facilitating implementation in FPGA or ASIC.

[0104] In the above embodiment, the first weight is (16 - x), and the second weight is x. The present invention is not limited thereto. The first weight can be x, the second weight can be (16 - x), or the first weight can be 1 - (x / n), and the second preset weight can be x / n, as long as the first weight is associated with the time interval between the moment x and one of the adjacent first time scales, and the second weight is associated with the time interval between the moment x and the other adjacent first time scale.

[0105] Through the data storage method of the present invention, the ranging accuracy can be maintained while reducing the storage space. The following is a detailed description.

[0106] Taking Figure 6 and Figure 8 as an example, storing with a 4-bit width (that is, 16 fine scales form a coarse scale), and using the centroid method to calculate the echo arrival time. Accumulate 16 time fine scales into a coarse scale, and then record the number of photons arriving on the kth fine scale of the coarse scale from n to n + 1 as In this way, the centroid formula of the number of photons on all fine scales within 0 - n + 1 coarse scales on the fine coordinate scale can be obtained:

[0107]

[0108] G0 represents the echo arrival time calculated by the centroid method when stored in binary.

[0109] After compressing and storing the time information and intensity information of photons using weighted accumulation by using the above storage method 100, the weight value Bi assigned to the ith coarse scale is as follows:

[0110] When i > 0 and i < n + 1,

[0111]

[0112]

[0113]

[0114] The centroid formula after weighted accumulation is

[0115]

[0116] G1 represents the echo arrival time calculated by the centroid method when the weighted accumulation method of the present invention is used for data storage. The numerator of the above formula is arranged according to Mismatch items are combined to obtain

[0117]

[0118] It can be confirmed that the results of G1 and G0 are consistent. Similarly, the accuracy of the ranging result using the leading edge method will not be lost due to this compression.

[0119] Reference Figure 7 , the data stored in the register corresponding to the coarse scale of the present invention is the sum of the weighted values of the trigger counts cnt in the two intervals on the left and right of the coarse scale. Its value will be relatively large at a strong signal, but the value of the noise outside the echo signal will not be very large. The bit width for storing the noise does not need to be the same as the bit width for storing the signal. According to the actual detection situation of the system, the register bits may require a memory bit width of 16 bits, but only 8 bits of memory bit width may be required for storing the noise.

[0120] Therefore, according to a preferred embodiment of the present invention, a more register space-saving scheme is proposed. Because during the entire detection time period, the time span occupied by the echo pulse is very small, and most other positions are noise. Allocating 16-bit registers to each coarse scale will cause some waste of space. 8-bit registers can be used, as Figure 9 shown, 8-bit registers are sufficient to store the trigger count cnt at the noise location. However, for the echo pulse, because the trigger count cnt is large and exceeds 8 bits, it may cause bit overflow. Therefore, according to an embodiment of the present invention, the storage method further includes: when it is determined that one of the storage units overflows or is about to overflow, an additional storage address is allocated for the storage unit from the reserved registers. A number of 8-bit registers are reserved according to the number of echoes to be detected, divided into N groups, with M in each group (a total of M*N registers). Once bit overflow is found during the process of accumulating the histogram, the register address is assigned to a group of reserved registers as its high bit, and the storage is performed in the M reserved registers. The next time bit overflow occurs, another group of reserved registers is allocated to store the overflow data, thus avoiding the loss of echo signals.

[0121] According to a preferred embodiment of the present invention, the reserved register includes N groups of registers, where N is a preset value, and each group of registers is used for a storage unit that has overflowed or is about to overflow. The number of N is determined according to the maximum number of echo pulses allowed by the system. For example, if the system can statistically calculate at most 3 echo pulse information, let N = 3. M is determined according to the maximum value of the stored data. For example, if originally a 16-bit register is required at most, 32 8-bit registers can be set as a group of reserved registers.

[0122] Through the above method, for the detection data obtained by multiple scans, the intensity information in the detected data will be stored with the first time accuracy according to the weight of the time information. According to the stored data, a histogram can be formed. By using this histogram to calculate the center on the time axis, a more accurate echo pulse position and flight time can be obtained.

[0123] Therefore, the present invention also provides a data processing method, wherein the data is stored in the storage unit of the memory by the above storage method 100, and the processing method includes:

[0124] Read the value stored in the storage unit corresponding to each first time scale;

[0125] Calculate the centroid of the value on the time axis.

[0126] After calculating the centroid of the value on the time axis, the coordinate of the time axis corresponding to the centroid (such as the coordinate of the fine scale) can be used as the flight time of the echo pulse for calculating the distance of the target object.

[0127] As another preferred embodiment, the processing method includes:

[0128] After completing the multiple scans, read the value stored in the storage unit corresponding to each first time scale; obtain the leading edge time of the echo pulse. Specifically, compare the value corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the value whose intensity is equal to the above preset threshold as the leading edge time for calculating the distance of the target object.

[0129] As a specific implementation, the preset threshold is the noise threshold.

[0130] As a specific implementation, the preset threshold is the average value of the noise threshold and the pulse peak value.

[0131] The present invention also provides a data processing method 200 applicable to lidar, as Figure 10 shown, including:

[0132] In step S201: Receive the reception time and intensity information of the echo. For example, use Figure 5The receiving unit 22 as shown receives the echo of the lidar. The receiving moment is the moment when the single-photon avalanche diode (SPAD) in each macro-pixel is triggered. The intensity information can be characterized by the number of single-photon avalanche diodes triggered at this moment.

[0133] In step S202: Determine the time information based on the emission moment of the detection pulse and the receiving moment.

[0134] Based on the emission moment of the detection pulse and the receiving moment of the echo, the time difference, that is, the flight time of this echo, can be obtained and used as the time information.

[0135] In step S203: Store the intensity information with the first time accuracy according to the weight of the time information; where the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the lidar, where n > 1; the weight is associated with the time information and the time interval of at least one first time scale.

[0136] As described above with reference to Figures 6 - 8 described, store the intensity information with the first time accuracy (relatively coarser accuracy, rather than the accuracy of the time resolution of the lidar or the accuracy that the lidar system can achieve), according to the weight of the time information, which will not be elaborated here.

[0137] According to a preferred embodiment of the present invention, when the lidar detects a field of view (for example, a part in a three-dimensional environment), it scans the field of view multiple times, and obtains the distance information of this part according to the detection information of the multiple scans. Step S203 includes: storing the intensity information obtained from the multiple scans by superimposing with the first time accuracy.

[0138] After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale, and then for example, a histogram can be generated, calculate the centroid of the values on the time axis, use the time information corresponding to the centroid as the flight time, and calculate the distance corresponding to this flight time.

[0139] As another preferred embodiment, after completing the multiple scans, read the values stored in the storage units corresponding to each first time scale; obtain the leading edge time of the echo pulse. Specifically, compare the value corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the value whose intensity is equal to the preset threshold as the leading edge time.

[0140] As a specific implementation, the preset threshold is the noise threshold.

[0141] As a specific embodiment, the preset threshold is the average of the noise threshold and the pulse peak value.

[0142] The present invention also provides a lidar 20, as Figure 11 shown. The lidar 20 includes a transmitting module 21, a detecting module 22, a sampling device 23, and a processing device 24. The transmitting module 21 includes a plurality of transmitting units (such as a plurality of lasers) for emitting laser detection pulses L into a three-dimensional environment to detect a target object. The detecting module 22 includes a plurality of detecting units for receiving the echo L' after the laser detection pulse L is reflected by the target object and converting the echo into an electrical signal. The detecting module 22 may adopt, for example, Figure 5 the detecting module 22 shown, which includes a plurality of detecting units composed of single-photon avalanche diodes SPAD. The sampling device converts the electrical signal into a digital signal and / or can obtain the arrival time of the echo. According to a preferred embodiment of the present invention, the sampling device may include an analog-to-digital converter ADC and a time-to-digital converter TDC. The processing device 24 is coupled to the sampling device 23 and may also be coupled to the transmitting unit 21 at the same time, and is configured to determine detection data according to the digital signal. The detection data includes time information and intensity information corresponding to the time information, and stores the intensity information with a first time accuracy according to the weight of the time information; wherein, the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the lidar, where n>1; the weight is associated with the time information and the time interval of at least one first time scale.

[0143] According to an embodiment of the present invention, the lidar is configured to perform multiple scans on a field of view range, and the processing device is configured to store the intensity information obtained from the multiple scans by superimposing with a first time accuracy.

[0144] According to an embodiment of the present invention, the processing device is further configured to: after completing the multiple scans, read the values stored in the storage units corresponding to each first time scale; calculate the centroid of the values on the time axis; and use the time information corresponding to the centroid as the flight time.

[0145] As another embodiment of the present invention, the processing device is further configured to: after completing the multiple scans, read the values stored in the storage units corresponding to each first time scale; and obtain the leading edge time of the echo pulse. Specifically, compare the value corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the value whose intensity is equal to the preset threshold as the leading edge time.

[0146] As a specific embodiment, the preset threshold is the noise threshold.

[0147] As a specific embodiment, the preset threshold is the average of the noise threshold and the pulse peak value.

[0148] According to an embodiment of the present invention, the multiple transmitting units correspond to different field-of-view ranges, that is, the detection beams are transmitted to different field-of-view ranges, and the multiple field-of-view ranges constitute the detection range of the lidar.

[0149] According to an embodiment of the present invention, each of the transmitting units sequentially emits a detection beam to the corresponding field-of-view range. When one of the transmitting units emits a detection beam, at least one detection unit corresponding to the field-of-view range of the transmitting unit is activated to start detection.

[0150] The present invention also relates to a computer-readable storage medium, including computer-executable instructions stored thereon, and the executable instructions, when executed by a processor, implement the storage method 100 as described above.

[0151] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for storing detection data of a radar, comprising: S101: Receiving detection data, where the detection data includes time information and intensity information corresponding to the time information; and S102: Storing the intensity information with a first time accuracy according to the weight of the time information; wherein, the first time accuracy is the time interval between any two adjacent first time scales, and is n times the time resolution of the detection data of the radar, where n>1; The weight is associated with the time interval between the time information and at least one first time scale.

2. The storage method according to claim 1, wherein the weights include a first weight and a second weight, the first weight is associated with the time interval between the time information and one of the adjacent first time scales, the second weight is associated with the time interval between the time information and the other adjacent first time scale, and the step S102 includes: Store the intensity information with a first time accuracy according to the first weight and the second weight respectively.

3. The storage method according to claim 2, wherein, The first weight is n-x, and the second weight is x, where x represents that the time interval between the time information and the adjacent first time scale is x times the time resolution of the radar detection data.

4. The storage method according to claim 3, wherein the first weight is the weight corresponding to the first time scale adjacent to the left of the time information, and the second weight is the weight corresponding to the first time scale adjacent to the right of the time information, where x represents that the time interval between the time information and the first time scale adjacent to the left of it is x times the time resolution of the radar detection data.

5. The storage method according to claim 2, the first weight is 1-(x / n), and the second weight is x / n, where x represents that the time interval between the time information and the first time scale adjacent to the left of it is x times the time resolution of the radar detection data.

6. The storage method according to claim 1, wherein n = 2 m , and m is a positive integer.

7. The storage method according to any one of claims 1-6, wherein the intensity information includes the trigger count of the detection unit.

8. The storage method according to any one of claims 1-6, wherein the memory has storage units corresponding to each first time scale, and the step S102 includes: Store the intensity information in two storage units corresponding to two first time scales adjacent to the time information according to the first weight and the second weight.

9. The storage method according to claim 8, wherein the step S102 further includes: When storing the intensity information into one of the storage units according to the weight, Read the value stored in the storage unit; Accumulate the value calculated from the intensity information according to the weight and the read value; and Write the accumulated result into the storage unit.

10. The storage method according to claim 8 further includes: When it is determined that one of the storage units overflows or is about to overflow, allocate another storage address for the storage unit from the reserved register.

11. The storage method according to claim 10, wherein the reserved register includes N groups of registers, where N is a preset value, and each group of registers is used for a storage unit that overflows or is about to overflow.

12. A data processing method applicable to a lidar, comprising: S201: Obtaining the reception time and intensity information of the optical signal; S202: Determining time information based on the emission time of the detection pulse and the reception time; S203: Storing the intensity information with a first time accuracy according to the weight of the time information; wherein, the first time accuracy is the time interval between any two adjacent first time scales, and is n times the time resolution of the detection data of the radar, where n>1; The weight is associated with the time interval between the time information and at least one first time scale.

13. The data processing method according to claim 12, wherein the lidar performs multiple scans on a field of view range, and the step S203 includes: Store the intensity information obtained from the multiple scans by superimposing at a first time accuracy.

14. The data processing method according to claim 13, further comprising: After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale; Calculate the centroid of the values on the time axis; Use the centroid as the time of flight.

15. The data processing method according to claim 13, further comprising: After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale to obtain the leading edge time of the echo pulse; Wherein, the leading edge time is: Compare the values corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the values with an intensity equal to the preset threshold as the leading edge time.

16. A lidar, comprising: A transmitting module, including a plurality of transmitting units, for transmitting laser detection pulses; A detection module, including a plurality of detection units, for receiving the echo after the laser detection pulse is reflected by the target and converting the echo into an electrical signal; A sampling device; Convert the electrical signal into a digital signal; A processing device, coupled to the sampling device, configured to determine detection data according to the digital signal, the detection data including time information and intensity information corresponding to the time information, and store the intensity information at a first time accuracy according to the weight of the time information; Wherein, the first time accuracy is the time interval between any two adjacent first time scales and is n times the time resolution of the detection data of the lidar, where n>1; the weight is associated with the time interval between the time information and at least one first time scale.

17. The lidar according to claim 16, wherein the lidar is configured to perform multiple scans on a field of view range, and the processing device is configured to store the intensity information obtained from the multiple scans by superimposing at a first time accuracy.

18. The lidar according to claim 17, wherein the processing device is further configured to: After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale; Calculate the centroid of the values on the time axis; Use the centroid as the time of flight.

19. The lidar according to claim 17, wherein the processing device is further configured to: After completing the multiple scans, read the values stored in the storage units corresponding to each first time scale to obtain the leading edge time of the echo pulse; Among them, The leading edge time is: Compare the values corresponding to the leading edge of the echo pulse with a preset threshold, and use the time information corresponding to the values with an intensity equal to the preset threshold as the leading edge time.

20. The lidar according to any one of claims 16-19, wherein the plurality of transmitting units emit detection beams to different field of view ranges, and the plurality of field of view ranges constitute the detection range of the lidar.

21. The lidar according to any one of claims 16-19, wherein the detection unit includes a Geiger-mode based detection unit, and the sampling device includes a time-to-digital converter.

22. The lidar according to any one of claims 16-19, wherein each of the transmitting units sequentially emits a detection beam to a corresponding field of view range, and when one of the transmitting units emits a detection beam, at least one detection unit corresponding to the field of view range of the transmitting unit is activated to start detection.

23. A computer-readable storage medium, including computer-executable instructions stored thereon, and the executable instructions, when executed by a processor, implement the storage method according to any one of claims 1-11.

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