CN113341427A - Distance measuring method, distance measuring device, electronic equipment and storage medium - Google Patents

Distance measuring method, distance measuring device, electronic equipment and storage medium Download PDF

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CN113341427A
CN113341427A CN202110788115.1A CN202110788115A CN113341427A CN 113341427 A CN113341427 A CN 113341427A CN 202110788115 A CN202110788115 A CN 202110788115A CN 113341427 A CN113341427 A CN 113341427A
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pulse repetition
target
ranging
repetition frequencies
distance
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CN113341427B (en
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徐飞虎
叶俊天
黎正平
余超
曹原
潘建伟
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University of Science and Technology of China USTC
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/4802—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section

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  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Optical Radar Systems And Details Thereof (AREA)

Abstract

The disclosure provides a distance measuring method, a distance measuring device, an electronic device and a storage medium. The distance measurement method comprises the following steps: determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies; measuring a first target by adopting at least two pulse repetition frequencies in turn to obtain measurement data under different pulse repetition frequencies; based on the maximum a posteriori probability estimates, the distance of the first target is calculated from the measurement data at different pulse repetition frequencies.

Description

Distance measuring method, distance measuring device, electronic equipment and storage medium
Technical Field
The disclosure relates to the field of laser radars, in particular to a ranging method, a ranging device, electronic equipment and a storage medium.
Background
The traditional distance measurement method generally adopts a single pulse repetition frequency to carry out distance measurement, and the distance measurement range is limited within the round-trip flight length corresponding to one period. When the target distance exceeds this length, there is a problem of distance confusion, i.e., it is not possible to determine in which period the photon returns.
In addition, for long-distance ranging, the signal-to-noise ratio is also a major limiting factor. When the measurement distance is long, even if the echo light signal can be detected, the weak signal is submerged in a large amount of noise. Therefore, how to extract signals from data with extremely low signal-to-noise ratio and realize ranging is an urgent problem to be solved.
Disclosure of Invention
In view of the above, the present disclosure provides a ranging method, a ranging apparatus, an electronic device, and a storage medium.
According to an aspect of the present disclosure, a ranging method is provided, including:
determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies;
measuring a first target by adopting at least two pulse repetition frequencies in turn to obtain measurement data under different pulse repetition frequencies;
based on the maximum a posteriori probability estimates, the distance of the first target is calculated from the measurement data at different pulse repetition frequencies.
Preferably, calculating the distance of the first target from the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimate comprises:
acquiring the width of a signal peak according to measurement data under different pulse repetition frequencies;
convolving the measurement data under different pulse repetition frequencies according to the widths of the signal peaks to obtain probability vectors under different pulse repetition frequencies after convolution;
for each pulse repetition frequency, traversing all possible ranging values by taking a first preset ranging precision as a step length to obtain a first probability corresponding to each ranging value; under different pulse repetition frequencies, a plurality of range values traversed by taking first preset range accuracy as a step length are correspondingly the same;
adding the first probabilities under different pulse repetition frequencies aiming at each ranging value to obtain a first total probability corresponding to each ranging value;
and selecting the ranging value corresponding to the maximum first total probability as the distance of the first target.
Preferably, calculating the distance of the first target from the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimate comprises:
compressing the measurement data under different pulse repetition frequencies to obtain low-precision measurement data vectors under different pulse repetition frequencies;
acquiring the width of a signal peak according to the measurement data vectors with low precision under different pulse repetition frequencies;
convolving the measurement data under different pulse repetition frequencies with low precision according to the width of the signal peak to obtain probability vectors under different pulse repetition frequencies after low-precision convolution;
traversing all possible ranging values by taking second preset ranging precision as a step length according to each pulse repetition frequency to obtain a second probability corresponding to each ranging value; under different pulse repetition frequencies, a plurality of range values traversed by taking second preset range accuracy as a step length are correspondingly the same; the value of the second preset distance measurement precision is greater than the value of the first preset distance measurement precision;
adding the second probabilities under different pulse repetition frequencies aiming at each ranging value to obtain a second total probability corresponding to each ranging value, and selecting the ranging value corresponding to the largest second total probability as the estimated distance of the first target;
performing convolution on the measurement data under different pulse repetition frequencies to obtain probability vectors under different pulse repetition frequencies after convolution;
traversing all possible ranging values by taking the estimated distance of the first target as a central value and the first preset ranging precision as a step length within a second preset ranging precision range to obtain a third probability corresponding to each ranging value;
and adding the third probabilities under different pulse repetition frequencies aiming at each ranging value to obtain a third total probability corresponding to each ranging value, and selecting the ranging value corresponding to the maximum third total probability as the distance of the first target.
Preferably, the preset conditions include: the values of the periods of all the pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relations:
Figure BDA0003156574080000031
wherein, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, N denotes the number of pulse repetition frequencies in the pulse repetition frequency combination, [ T ═ T [ ]1，T2，…，TN]Representing the least common multiple, D, of the period of all pulse repetition frequencies in a pulse repetition frequency combinationmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
Preferably, the distance of the first target satisfies the following relationship:
Figure BDA0003156574080000032
wherein, i is less than N,
Figure BDA0003156574080000033
wherein the content of the first and second substances,
Figure BDA0003156574080000034
representing the maximum a posteriori probability estimate, D representing an estimate of the distance to the first target, N representing the number of pulse repetition frequencies in the pulse repetition frequency combination, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, NiDenotes the number of periods, t, corresponding to the i (i ═ 1, 2, …, N) th pulse repetition frequencyi，qDenotes the time of flight of the qth photon at the ith pulse repetition frequency, σ denotes the width of the signal peak, b denotes the intensity of the noise floor, DmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
Preferably, the measuring of the first target by using at least two pulse repetition frequencies in turn to obtain the measurement data under different pulse repetition frequencies includes:
measuring a first target in a preset measurement period aiming at each pulse repetition frequency, wherein the preset measurement period comprises a plurality of transceiving periods;
in each transceiving period, the first target is measured in a manner of separating emission from detection in a time sequence.
Preferably, the method further comprises:
according to the distance of the first target, signal peaks corresponding to the first target in the measurement data under different pulse repetition frequencies are erased;
acquiring the distance of a second target according to a distance measurement method aiming at the first target;
according to the distance of the second target, signal peaks corresponding to the second target in the measurement data under different pulse repetition frequencies are erased;
by analogy, the distances of the multiple targets are obtained according to the distance measuring method aiming at the first target.
According to another aspect of the present disclosure, there is provided a ranging apparatus including:
the determining module is used for determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies;
the measuring module is used for measuring the first target by adopting at least two pulse repetition frequencies in turn to obtain measuring data under different pulse repetition frequencies;
and the calculation module is used for calculating the distance of the first target according to the measurement data under different pulse repetition frequencies based on the maximum posterior probability estimation.
According to another aspect of the present disclosure, there is provided an electronic device including: a processor and a memory, the memory having stored therein at least one instruction, which when executed by the processor, implements the method as above.
According to another aspect of the present disclosure, there is provided a computer-readable storage medium having stored therein at least one instruction which, when executed by a processor, implements a method as above.
It should be understood that the statements in this section do not necessarily identify key or critical features of the embodiments of the present disclosure, nor do they limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.
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The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:
fig. 1 schematically illustrates a flow chart of a ranging method according to an embodiment of the present disclosure;
fig. 2A schematically shows a block diagram of a ranging system to which the ranging method of the embodiments of the present disclosure may be applied;
FIG. 2B schematically shows a signal timing diagram of the operation of the ranging system of FIG. 2A;
fig. 3 schematically illustrates a flow chart of a ranging method according to an embodiment of the present disclosure;
FIG. 4 schematically illustrates a flow chart of a ranging method according to an embodiment of the present disclosure;
FIG. 5A illustrates the position of a ranging target in a first embodiment of the disclosure;
FIG. 5B is a diagram illustrating ranging signals obtained by measuring the ranging target of FIG. 5A according to the ranging method of the embodiment of the disclosure;
FIG. 6A illustrates the location of a ranging target in a second embodiment of the disclosure;
FIG. 6B is a diagram illustrating ranging signals obtained by measuring the ranging target of FIG. 6A according to the ranging method of the embodiment of the disclosure;
FIG. 7 schematically illustrates a block diagram of a ranging device according to an embodiment of the disclosure;
FIG. 8 schematically shows a block diagram of an electronic device according to an embodiment of the disclosure.
Detailed Description
Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is illustrative only and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It is noted that the terms used herein should be interpreted as having a meaning that is consistent with the context of this specification and should not be interpreted in an idealized or overly formal sense.
Where a convention analogous to "at least one of A, B and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B and C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.). Where a convention analogous to "A, B or at least one of C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B or C" would include but not be limited to systems that have a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).
Some block diagrams and/or flow diagrams are shown in the figures. It will be understood that some blocks of the block diagrams and/or flowchart illustrations, or combinations thereof, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the instructions, which execute via the processor, create means for implementing the functions/acts specified in the block diagrams and/or flowchart block or blocks. The techniques of this disclosure may be implemented in hardware and/or software (including firmware, microcode, etc.). In addition, the techniques of this disclosure may take the form of a computer program product on a computer-readable storage medium having instructions stored thereon for use by or in connection with an instruction execution system.
As described in the background, the conventional ranging method usually uses a single pulse repetition frequency for ranging, and for long-distance ranging, the problem of target distance measurement error is often caused by mutual interference of multiple signal peaks. In addition, for long-distance ranging, the signal-to-noise ratio is also a major limiting factor. When the measurement distance is long, even if the echo light signal can be detected, the weak signal is submerged in a large amount of noise. In view of the above, the present disclosure provides a ranging method, a ranging apparatus, an electronic device and a medium, which are intended to at least partially solve the above technical problems.
Fig. 1 schematically shows a flow chart of a ranging method according to an embodiment of the present disclosure.
As shown in fig. 1, an embodiment of the present disclosure provides a ranging method including operations S110 to S130.
In operation S110, determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies.
In operation S120, the first target is measured by using at least two pulse repetition frequencies in turn, so as to obtain measurement data at different pulse repetition frequencies.
In operation S130, a distance of the first target is calculated from the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation.
According to the technical scheme, the multi-pulse repetition frequency combination meeting the preset condition is selected, and the targets are measured in turn based on the multiple pulse repetition frequencies in the pulse repetition frequency combination, so that the problem of mutual interference among multiple signal peaks in the traditional method is solved, the method is suitable for long-distance measurement of a single target, and multi-target or multi-depth target distance measurement can be realized. On the other hand, the distance measurement method in the embodiment of the disclosure processes the measurement result by adopting the maximum posterior probability estimation method, can realize high-precision distance measurement under the condition of extremely low signal-to-noise ratio, and is more suitable for long-distance high-precision distance measurement.
In some embodiments of the present disclosure, in the step S110, the preset conditions include: the values of the periods of all the pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relations:
Figure BDA0003156574080000071
wherein, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, N denotes the number of pulse repetition frequencies in the pulse repetition frequency combination, [ T ═ T [ ]1，T2，…，TN]Representing the least common multiple, D, of the period of all pulse repetition frequencies in a pulse repetition frequency combinationmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
When a traditional distance measurement mode is adopted to measure a long-distance target, the area of a light spot covering an object is large, the light spot often has multiple depths, and the time distribution width of a measured signal can generally reach dozens of nanoseconds. In addition, for the ranging of multiple targets, interference may occur between multiple signal peaks due to improper frequency selection, and both of the above cases may result in erroneous ranging results for a high repetition frequency laser ranging system. The ranging method according to the embodiment of the present disclosure avoids the above problem to the greatest extent by selecting a pulse repetition frequency combination (where the pulse repetition frequency combination includes at least two pulse repetition frequencies) that satisfies the above predetermined condition.
The pulse repetition frequency combination (T) satisfying the predetermined condition can be obtained according to the above formula (1)1，T2，…，TN) So that subsequently a pulse repetition frequency combination (T) can be used1，T2，…，TN) The multiple pulse repetition frequencies are used for measuring the first target in turn, so that the problem of mutual interference among multiple signal peaks in the traditional method is solved, the method is not only suitable for long-distance ranging of a single target, but also capable of realizing multi-target or multi-depth target ranging.
In the embodiment of the present disclosure, the farthest distance D that the first target is likely to appear may be set according to actual needsmaxAnd the number N of pulse repetition frequencies in the pulse repetition frequency combination, which is not limited herein. The first targets are measured in turn by adopting a larger number of pulse repetition frequencies, so that the method is applicable to a larger distance measurement range, and the distance measurement requirements of more distant and more targets are met.
In some embodiments of the present disclosure, in step S120, at least two pulse repetition frequencies are used to measure the first target in turn, so as to obtain measurement data at different pulse repetition frequencies, which specifically includes the following operations:
and measuring the first target in a preset measuring period aiming at each pulse repetition frequency, wherein the preset measuring period comprises a plurality of transceiving periods. In each transceiving period, the first target is measured in a manner of separating emission from detection in a time sequence. In the process of measuring the first target by each pulse repetition frequency, a mode of separating emission and detection is adopted in a time sequence, so that the detected atmospheric scattering noise can be greatly reduced, and further, the high signal-to-noise ratio is realized.
Fig. 2A schematically shows a block diagram of a ranging system to which the ranging method of the embodiments of the present disclosure may be applied; fig. 2B schematically shows a signal timing diagram of the operation of the ranging system of fig. 2A. The process of measuring the first target by using a plurality of pulse repetition frequencies in turn in the embodiment of the present disclosure will be described in detail below with reference to fig. 2A and 2B. It should be understood that the ranging system structure and signal timing diagram shown in fig. 2A and 2B are only exemplary to help those skilled in the art understand the technical content of the present disclosure, and are not intended to limit the present disclosure.
As shown in fig. 2A, the ranging system includes a signal source 201, a laser 202, an optical path/turret system 203, a detector 204, a time measurement module 205, and a controller 206. The distance measuring system is based on a transmitting and receiving non-coaxial optical path, and the optical path/rotary table system comprises a transmitting and receiving optical path and a rotary table system. In embodiments of the present disclosure, a distance measurement may be made of the target 207 (e.g., the first target) using the ranging system described above.
The working process of the distance measuring system is simply described as follows:
when each pulse repetition frequency is used for measuring the target 207, the signal source 201 generates a pulse signal to trigger the laser 202 to emit a laser pulse (the laser pulse signal corresponds to one pulse repetition frequency), and the signal source 201 also generates the same pulse signal to the time measurement module 205 and the detector 204 as a synchronization signal. After the laser pulse is emitted through the optical path and illuminates the target 207, the laser pulse is reflected by the target and received by the receiving optical path, and enters the detector 204, and the reflected signal photon is detected by the detector 204. The detector 204 converts the single photon signal into an electrical pulse signal to the time measurement module 205, and the time measurement module 205 measures the time of flight of the photons. According to the distance measuring method, at least two pulse repetition frequencies in the pulse repetition frequency combination are adopted to measure the target 207 in turn, and measurement data under different pulse repetition frequencies are obtained. Wherein the measurement data characterizes the distribution of the number of photons over time.
In the process of ranging the target 207 by the ranging system, the controller 206 is configured to control signal transceiving of each structure (as shown in fig. 2B) and receive measurement data at different pulse repetition frequencies output by the time measurement module 205 and the detector 204, and output a distance of the target according to the measurement data at different pulse repetition frequencies.
Compared with the traditional single-repetition-frequency ranging method, the method has the advantages that the multiple pulse repetition frequencies are transmitted in turn, the measurement result is the photon flight time statistics in one corresponding measurement period under different pulse repetition frequencies, so that the data volume is small, the data transmission speed is high, the occupied memory is small, the data processing speed is high, the hardware requirement is low, and the ranging method in the embodiment of the invention can meet the requirement of long-distance real-time fast ranging.
In order to improve the accuracy of ranging, the noise of a ranging system is effectively reduced, and a high signal-to-noise ratio is realized. In the disclosed embodiment, the above-mentioned objective is achieved by separating the laser pulse emission and the photon detection in time sequence when the target 207 is measured at each pulse repetition frequency. The use of multiple pulse repetition frequencies for performing the round-robin measurement over time in the disclosed embodiment will be briefly described below in conjunction with fig. 2B.
The signal timing is as shown in fig. 2B, and it is assumed that the pulse repetition frequency combination determined in step S110 includes N (N is a positive integer greater than 1) pulse repetition frequencies. For each pulse repetition frequency (the period of the pulse repetition frequency represents the corresponding pulse repetition frequency, denoted as T, as shown in fig. 2B), the target 207 is measured in a preset measurement period P, and the measurement result is the flight time of the signal photon in the corresponding pulse repetition frequency period, that is, for each pulse repetition frequency, statistical distribution measurement data of a photon time count is obtained. After each measurement period is over, the signal source 201 changes the generated pulse repetition frequency and maintains the measurement time P. In the embodiment of the present disclosure, the N pulse repetition frequencies are alternately measured on the target 207 within the measurement period P, for example, the measurement sequence of the pulse repetition frequencies is frequency 1 → frequency 2 → … … → frequency N → frequency 1 → … … → frequency i → … …. In the embodiment of the present disclosure, the number of times of measuring the target by using the N pulse repetition frequencies may be set according to actual situations, for example, the target may be tested for 1 round, 2 rounds, 10 rounds, and the like by using the N pulse repetition frequencies, which is not limited herein.
During each measurement period P (i.e. for each pulse repetition frequency), a plurality of transceiving periods with a period S (S ═ G + M) can be set according to the maximum range of the ranging system, where G is the time during which the laser emits a laser pulse during each transceiving period S and M is the time during which the detector detects a signal photon during each transceiving period S. In each receiving and transmitting period S, the working time sequence of the laser and the detector is controlled to separate the laser pulse emission from the photon detection in time, so that the noise of the ranging system is effectively reduced, and the high signal-to-noise ratio is realized. Specifically, at the beginning of the transmit-receive cycle S, the laser 202 emits a laser pulse for a duration G, at which time the detector 204 does not detect. After the laser stops pulsing, detector 204 turns on detection for a time M.
In some embodiments of the present disclosure, the laser pulse emitted by the laser 202 may be, for example, a near-infrared laser with high repetition frequency and low pulse energy, which can ensure the safety of human eyes, and has strong concealment, and can be used in combination with a fiber laser, which is flexible and convenient. It is to be understood that the above description of laser pulses is only an example for the convenience of understanding the present solution, and the present application does not limit the type of laser and the type of laser pulses emitted.
Fig. 3 schematically shows a flow chart of a ranging method according to another embodiment of the present disclosure.
As shown in fig. 3, in the above operation S130, the distance of the first target is calculated from the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation, including operations S310 to S350.
In operation S310, the width of a signal peak is acquired according to measurement data at different pulse repetition frequencies.
The measured data under different pulse repetition frequencies is a one-dimensional vector, the subscript of the vector corresponds to the flight time, and the value of the vector corresponds to the photon count. Generally, different pulse repetition frequencies are adopted to carry out ranging on the same target in turn, and the widths of signal peaks in the obtained measurement data under different pulse repetition frequencies are the same. In the present operation S310, the peak searching is performed on the measurement data at different pulse repetition frequencies, and the width of the signal peak can be obtained.
In operation S320, the measurement data at different pulse repetition frequencies are convolved according to the widths of the signal peaks, so as to obtain probability vectors at different pulse repetition frequencies after convolution.
The width of the convolution function is determined by the width of the measured signal peak, so that the convolution function can be determined according to the width of the signal peak, and the measurement data under different pulse repetition frequencies are convolved to obtain probability vectors under different pulse repetition frequencies after convolution. Wherein the subscript of the probability vector corresponds to the time of flight and the value of the vector corresponds to a probability.
In operation S330, for each pulse repetition frequency, all possible ranging values are traversed by using the first preset ranging precision as a step size to obtain a first probability corresponding to each ranging value. Under different pulse repetition frequencies, a plurality of range values traversed by taking the first preset range accuracy as a step length are correspondingly the same.
Assume that for the first pulse repetition frequency after convolution (denoted as T)1) The probability vector of the next step, with the first preset distance measurement precision as the step length, traverses all possible distance measurement values and is respectively D1、D2、D3、…、Dm(where m is a positive integer greater than 1), then for the probability vectors at other pulse repetition frequencies after convolution, e.g., the second through Nth pulse repetition frequencies (denoted as T)2～TN) The lower probability vector is also used for traversing D by taking the first preset distance measurement precision as a step length1、D2、D3、…、DmAnd waiting for the ranging values, and then obtaining first probabilities corresponding to each ranging value under different pulse repetition frequencies. For example, for the ranging value D1First probabilities P at first to Nth pulse repetition frequencies can be obtained11、P12、……、P1N(ii) a For the distance measurement value D2First probabilities P at first to Nth pulse repetition frequencies can be obtained21、P22、……、P2N(ii) a By analogy, for the distance measurement value DmFirst probabilities P at first to Nth pulse repetition frequencies can be obtainedml、Pm2、……、PmN。
Obtaining a first probability for each ranging value at each pulse repetition frequency comprises the operations of:
suppose that at the ith (i ═ 1, 2, …, N) pulse repetition frequency, forAt the distance measurement value Dj(j ═ 1, 2, …, m) based on the distance measurement value DjAnd the formula (2) obtains the distance measurement value DjCorresponding time of flight tiAccording to the time of flight tiThe corresponding first probability P can be obtained according to the probability vector in operation S320ji。
Figure BDA0003156574080000111
Wherein, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, NiDenotes the number of periods, t, corresponding to the i (i ═ 1, 2, …, N) th pulse repetition frequencyiIndicating the range value D at the ith pulse repetition frequencyjThe corresponding time of flight, c, represents the speed of light.
Specifically, the period T of the ith pulse repetition frequency in equation (2)iCan be obtained according to the formula (1) and has a distance measurement value DjCan be set according to actual needs, and both sides of the equation of the formula (2) are divided by TiThen, the number of cycles n corresponding to the ith pulse repetition frequency can be obtainediAnd a distance measurement value DjCorresponding time of flight tiAnd can then be based on this time of flight tiObtaining a corresponding first probability P according to the probability vector in operation S320ji。。
In the embodiment of the present disclosure, the value of the first preset ranging accuracy may be set according to actual needs, which is not limited herein.
In operation S340, for each ranging value, the first probabilities at different pulse repetition frequencies are added to obtain a first total probability corresponding to each ranging value.
Follow the example of the ranging value in operation S330, e.g., with the ranging value D1The step of the present operation S340 will be explained for an example. For the distance measurement value D1Adding the first probabilities at different pulse repetition frequencies, i.e. P11、P12、……、P1NAdding to obtain the sum distance value D1Corresponding first total probability P1(ii) a By analogy, the distance measurement can be obtainedValue D2～DmCorresponding first total probability P2～Pm。
In operation S350, the ranging value corresponding to the maximum first total probability is selected as the distance of the first target.
In the embodiment of the present disclosure, it is assumed that in single photon ranging, the flight time of a photon corresponds to the distance of a target, and if the number of returned photons in a certain time period is larger, it indicates that the probability that the target exists at the corresponding distance is larger. Based on the above assumptions, a first total probability P is selected1～PmThe distance value corresponding to the maximum value in the range is used as the distance of the first target. For example, assume a first total probability P3The maximum of the m total probabilities will be the first total probability P3Corresponding distance measurement value D3As the distance of the first target.
In the embodiment of the present disclosure, the maximum a posteriori probability estimation is implemented based on the above method, so as to obtain the distance of the first target. The method makes full use of each detected signal photon in algorithm, and can realize high-precision ranging even under the condition of extremely low signal-to-noise ratio.
When the time measurement resolution is set to a high resolution, the measured data amount may be large, which may result in a slow data processing speed. Another embodiment of the present disclosure provides a ranging method, which can improve the above-mentioned slow data processing speed problem, and will be described in detail with reference to fig. 4.
Fig. 4 schematically shows a flow chart of a ranging method according to another embodiment of the present disclosure.
As shown in fig. 4, in the above operation S130, the distance of the first target is calculated from the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation, including operations S410 to S480.
In operation S410, the measurement data at different pulse repetition frequencies are compressed to obtain low-precision measurement data vectors at different pulse repetition frequencies, where the measurement data represents the distribution of photon numbers over time.
Specifically, for example, vector elements may be reduced by combining vector elements and performing count accumulation on the measurement data at different pulse repetition frequencies, so as to achieve the effect of data compression, thereby obtaining a measurement data vector with low precision.
In operation S420, the width of a signal peak is obtained according to the measurement data vector at different pulse repetition frequencies with low precision.
Specifically, peak searching is performed on the measurement data vectors under different pulse repetition frequencies with low precision, and the width of a signal peak is obtained.
In operation S430, the measurement data at different pulse repetition frequencies with low precision is convolved according to the widths of the signal peaks, so as to obtain probability vectors at different pulse repetition frequencies after low-precision convolution.
The width of the convolution function is determined by the width of the measured signal peak, so that the convolution function can be determined according to the width of the signal peak, and the measurement data under different pulse repetition frequencies with low precision are convolved to obtain probability vectors under different pulse repetition frequencies after low-precision convolution. Wherein the subscript of the probability vector corresponds to the time of flight and the value of the vector corresponds to a probability.
In operation S440, for each pulse repetition frequency, all possible ranging values are traversed by using the second preset ranging precision as a step length to obtain a second probability corresponding to each ranging value. Under different pulse repetition frequencies, a plurality of distance measurement values traversed by taking the second preset distance measurement precision as the step length are correspondingly the same, and the value of the second preset distance measurement precision is greater than that of the first preset distance measurement precision.
In the present operation S440, the value of the second preset ranging accuracy is greater than the value of the first preset ranging accuracy (i.e. a larger step size is used), which means that all possible ranging values are traversed with a low ranging accuracy, in this way, the amount of data to be calculated can be reduced, thereby increasing the calculation speed.
The step of traversing all possible ranging values by using the second preset ranging precision as the step length to obtain the second probability corresponding to each ranging value is the same as or similar to operation S330, and is not repeated herein.
In the embodiment of the present disclosure, the values of the first preset ranging accuracy and the second preset ranging accuracy may be set according to actual needs, which is not limited herein.
In operation S450, for each ranging value, the second probabilities at different pulse repetition frequencies are added to obtain a second total probability corresponding to each ranging value, and the ranging value corresponding to the largest second total probability is selected as the estimated distance of the first target.
In operation S450, the process of obtaining the second total probability corresponding to each ranging value is the same as that of operation S340, and details are not repeated here.
Based on the compressed measured data under different pulse repetition frequencies, the estimated distance of the first target can be obtained, and then the accurate distance of the first target is confirmed on the basis of the estimated distance of the first target.
In operation S460, the measurement data at different pulse repetition frequencies are convolved to obtain probability vectors at different pulse repetition frequencies after convolution. In operation S470, all possible ranging values are traversed by taking the estimated distance of the first target as a center value and the first preset ranging precision as a step size within a second preset ranging precision range, so as to obtain a third probability corresponding to each ranging value.
In the present operation, it is assumed that the estimated distance of the first target is DEstimation ofThe second predetermined distance measurement accuracy is W2Then is at (D)Estimation of-W2)～(DEstimation of+W2) And in the range, traversing all possible ranging values by taking the first preset ranging precision as a step length to obtain a third probability corresponding to each ranging value. The manner of obtaining the third probability is similar to that in operation S330, and is not described herein again.
In operation S480, for each ranging value, the third probabilities at different pulse repetition frequencies are added to obtain a third total probability corresponding to each ranging value, and the ranging value corresponding to the largest third total probability is selected as the distance of the first target.
In the embodiment of the disclosure, rough ranging is firstly completed by compressing original measurement data, that is, the estimated distance of the first target is confirmed, and then high-precision ranging is realized according to the result of the rough ranging.
In some embodiments of the present disclosure, the distance of the first target satisfies the following relationship:
Figure BDA0003156574080000141
wherein, i is less than N,
Figure BDA0003156574080000142
wherein the content of the first and second substances,
Figure BDA0003156574080000143
representing the maximum a posteriori probability estimate, D representing an estimate of the distance to the first target, N representing the number of pulse repetition frequencies in the pulse repetition frequency combination, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, NiDenotes the number of periods, t, corresponding to the i (i ═ 1, 2, …, N) th pulse repetition frequencyi，qDenotes the time of flight of the qth photon at the ith pulse repetition frequency, σ denotes the width of the signal peak, b denotes the intensity of the noise floor, DmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
When the traditional distance measurement method is used for measuring multiple targets or multiple depth targets, the measurement result is wrong due to interference among multiple signal peaks. The distance measurement method disclosed by the embodiment of the disclosure can realize distance measurement of one target and can also realize distance measurement of a plurality of targets or a plurality of depth targets.
Specifically, when a first target is measured, a plurality of targets may be actually observed within the range of sight, that is, a plurality of targets may exist within the measurement range from the measurement point to the position of the first target. In the process of ranging the first target, the ranging method in the present disclosure may also be used to simultaneously range a plurality of targets (here, ranging data at different pulse repetition frequencies) within the range of the distance range except the first target. The ranging method in the embodiment of the present disclosure will be briefly described below as applied to ranging of a plurality of targets.
The present disclosure also provides a ranging method applicable to a multi-target or multi-depth target, the method including operations S510 to S530.
In operation S510, signal peaks corresponding to the first target in the measurement data at different pulse repetition frequencies are erased according to the distance of the first target.
Specifically, according to the distance of the first target, a signal peak corresponding to the first target can be found in the measurement data and erased, so that the interference of the signal peak of the first target on the subsequent target ranging is eliminated, and the accuracy of the multi-target or multi-depth target ranging is improved.
In operation S520, a distance of a second target is acquired according to a ranging method for the first target.
Specifically, the distance measurement method for the second target is the same as or similar to the above-described process, and is not repeated herein.
In operation S530, signal peaks corresponding to the second target in the measurement data at different pulse repetition frequencies are erased according to the distance of the second target; by analogy, the distances of the multiple targets are obtained according to the distance measuring method aiming at the first target.
In the embodiment of the disclosure, the signal peak of the previous target is erased to eliminate the interference of the signal peak of the target on the subsequent target ranging, so that the defect of wrong measurement results caused by the traditional multi-target ranging method is overcome, and the accuracy of multi-target or multi-depth target ranging is improved.
In order that those skilled in the art will be able to more clearly understand the technical solutions of the present disclosure, the advantages of the present disclosure will be described below with reference to specific embodiments.
Example one
In this embodiment, a ranging system as shown in fig. 2A is adopted, and a technical solution of the present disclosure is described by taking the implementation of ranging of 12.18km as an example.
In the disclosed embodiment, a pulse repetition frequency combination comprising 5 pulse repetition frequencies is calculated, with corresponding periods of 1 μ s, 1.01 μ s, 1.02 μ s, 1.03 μ s and 1.04 μ s, respectively.
The signal source 201 alternately generates the trigger signals with the above-mentioned 5 pulse repetition frequencies to the laser 202 and the time measuring module 205, respectively. The measurement period duration P of each pulse repetition frequency is 160 mus. In a transceiving period, S is 160 μ S, the signal source 201 outputs a continuous pulse signal to the time measurement module 205, and the pulse duration G to the laser 202 is 79 μ S. The pulse start is synchronized with the start of the transceiving period. The signal source 201 also outputs a transmit-receive periodic signal to the detector 204 as a gate control signal, the pulse duration M of the detector 204 is 81 μ s, and the laser 202 and the detector 204 are isolated in time sequence.
Ranging for 12.18km (the position of the ranging target is shown in fig. 5A) is accomplished by the above scheme.
Fig. 5B illustrates a ranging signal diagram obtained by measuring the ranging target in fig. 5A according to the ranging method of the embodiment of the disclosure. Where the X-axis represents the photon flight time and the Y-axis represents the photon count.
As shown in fig. 5B, there is a distinct echo signal peak from the target building on the photon count-time plot. The distance to the target was 12.184515km, which could be obtained from the measurement data of fig. 5B. For the ranging of a 12.18km target, the ranging speed is 20Hz, the selected time resolution is 100ps, the ranging precision is 1.5cm, and the algorithm processing time is 10 ms.
Therefore, the distance measuring method can accurately measure the distance of the target, has small distance measuring error and high calculation speed, and can meet the requirement of long-distance real-time quick distance measurement.
Example two
In order to show the application of the ranging method in the disclosure in multi-target ranging, in the second embodiment, the boundary positions of 3 targets with different distances are selected for ranging, a visible light camera photograph of the target is shown in fig. 6A, a white cross in the drawing is a ranging position, the target distance on the left half of the ranging point is 2.6km, the target distance on the lower right is 4.7km, and the target distance on the upper right is 13.3 km. In the second embodiment, for the ranging of three targets, the parameter setting of the ranging system is the same as that in the first embodiment, and is not described herein again.
Fig. 6B shows a signal diagram for ranging the three targets in the present embodiment. The signal diagram shows the measured signal at a repetition frequency of 1MHz, and the three peaks in the diagram correspond to the signal peaks of three targets respectively.
In the ranging of the three targets, the measured target distances are 2.57598km, 4.67844km and 13.34820km respectively, the ranging speed is 5Hz, the ranging precision is 1.5cm, and the algorithm processing time is 30 ms. Therefore, the application of the distance measuring method in the disclosure to multi-target distance measurement can also obtain accurate and quick effects.
In addition, in the second embodiment, the measurement data obtained by the ranging method disclosed by the present disclosure contains more information, can directly reflect information such as the number of targets, the shape of target echo signals, and the depth level of the target, is convenient for extracting and analyzing signals from ranging results, and is suitable for applications such as ranging and identification of multiple targets.
Based on the distance measuring method, the disclosure also provides a distance measuring device. The apparatus will be described in detail below with reference to fig. 7.
Fig. 7 schematically shows a block diagram of a ranging apparatus according to an embodiment of the present disclosure.
As shown in fig. 7, ranging apparatus 700 includes a determination module 710, a measurement module 720, and a calculation module 730.
A determining module 710, configured to determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies.
The measuring module 720 is configured to measure the first target by using at least two pulse repetition frequencies in turn, so as to obtain measurement data at different pulse repetition frequencies.
A calculating module 730, configured to calculate a distance of the first target according to the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation.
It should be noted that the implementation, solved technical problems, implemented functions, and achieved technical effects of each module/unit/subunit and the like in the apparatus part embodiment are respectively the same as or similar to the implementation, solved technical problems, implemented functions, and achieved technical effects of each corresponding step in the method part embodiment, and are not described herein again.
Any number of modules, sub-modules, units, sub-units, or at least part of the functionality of any number thereof according to embodiments of the present disclosure may be implemented in one module. Any one or more of the modules, sub-modules, units, and sub-units according to the embodiments of the present disclosure may be implemented by being split into a plurality of modules. Any one or more of the modules, sub-modules, units, sub-units according to embodiments of the present disclosure may be implemented at least in part as a hardware circuit, such as a Field Programmable Gate Array (FPGA), a Programmable Logic Array (PLA), a system on a chip, a system on a substrate, a system on a package, an Application Specific Integrated Circuit (ASIC), or may be implemented in any other reasonable manner of hardware or firmware by integrating or packaging a circuit, or in any one of or a suitable combination of software, hardware, and firmware implementations. Alternatively, one or more of the modules, sub-modules, units, sub-units according to embodiments of the disclosure may be at least partially implemented as a computer program module, which when executed may perform the corresponding functions.
For example, any of the determination module 710, the measurement module 720, and the calculation module 730 may be combined in one module to be implemented, or any one of them may be split into a plurality of modules. Alternatively, at least part of the functionality of one or more of these modules may be combined with at least part of the functionality of the other modules and implemented in one module. According to an embodiment of the present disclosure, at least one of the determining module 710, the measuring module 720 and the calculating module 730 may be implemented at least partially as a hardware circuit, such as a Field Programmable Gate Array (FPGA), a Programmable Logic Array (PLA), a system on a chip, a system on a substrate, a system on a package, an Application Specific Integrated Circuit (ASIC), or may be implemented in hardware or firmware by any other reasonable manner of integrating or packaging a circuit, or in any one of three implementations of software, hardware and firmware, or in a suitable combination of any of them. Alternatively, at least one of the determining module 710, the measuring module 720 and the calculating module 730 may be at least partly implemented as a computer program module, which when executed may perform a corresponding function.
Fig. 8 schematically shows a block diagram of an electronic device adapted to implement the above described method according to an embodiment of the present disclosure. The electronic device shown in fig. 8 is only an example, and should not bring any limitation to the functions and the scope of use of the embodiments of the present disclosure.
As shown in fig. 8, electronic device 800 includes a processor 810, a computer-readable storage medium 820. The electronic device 800 may perform a method according to an embodiment of the disclosure.
In particular, processor 810 may include, for example, a general purpose microprocessor, an instruction set processor and/or related chip set and/or a special purpose microprocessor (e.g., an Application Specific Integrated Circuit (ASIC)), and/or the like. The processor 810 may also include on-board memory for caching purposes. Processor 810 may be a single processing unit or a plurality of processing units for performing different actions of a method flow according to embodiments of the disclosure.
Computer-readable storage medium 820, for example, may be a non-volatile computer-readable storage medium, specific examples including, but not limited to: magnetic storage devices, such as magnetic tape or Hard Disk Drives (HDDs); optical storage devices, such as compact disks (CD-ROMs); a memory, such as a Random Access Memory (RAM) or a flash memory; and so on.
The computer-readable storage medium 820 may include a computer program 821, which computer program 821 may include code/computer-executable instructions that, when executed by the processor 810, cause the processor 810 to perform a method according to an embodiment of the present disclosure, or any variation thereof.
The computer program 821 may be configured with, for example, computer program code comprising computer program modules. For example, in an example embodiment, code in computer program 821 may include one or more program modules, including, for example, module 821A, module 821B, … …. It should be noted that the division and number of modules are not fixed, and those skilled in the art may use suitable program modules or program module combinations according to actual situations, and when the program modules are executed by the processor 810, the processor 810 may execute the method according to the embodiment of the present disclosure or any variation thereof.
According to an embodiment of the present invention, at least one of the determining module 710, the measuring module 720 and the calculating module 730 may be implemented as a computer program module described with reference to fig. 8, which, when executed by the processor 810, may implement the respective operations described above.
The present disclosure also provides a computer-readable storage medium, which may be contained in the apparatus/device/system described in the above embodiments; or may exist separately and not be assembled into the device/apparatus/system. The computer-readable storage medium carries one or more programs which, when executed, implement the method according to an embodiment of the disclosure.
According to embodiments of the present disclosure, the computer-readable storage medium may be a non-volatile computer-readable storage medium, which may include, for example but is not limited to: a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the present disclosure, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams or flowchart illustration, and combinations of blocks in the block diagrams or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Those skilled in the art will appreciate that various combinations and/or combinations of features recited in the various embodiments and/or claims of the present disclosure can be made, even if such combinations or combinations are not expressly recited in the present disclosure. In particular, various combinations and/or combinations of the features recited in the various embodiments and/or claims of the present disclosure may be made without departing from the spirit or teaching of the present disclosure. All such combinations and/or associations are within the scope of the present disclosure.
While the disclosure has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents. Accordingly, the scope of the present disclosure should not be limited to the above-described embodiments, but should be defined not only by the appended claims, but also by equivalents thereof.

Claims (10)

1. A method of ranging, comprising:
determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies;
measuring the first target by adopting the at least two pulse repetition frequencies in turn to obtain measurement data under different pulse repetition frequencies;
calculating the distance of the first target from the measurement data at the different pulse repetition frequencies based on a maximum a posteriori probability estimation.
2. The method of claim 1, wherein calculating the distance to the first target from the measurement data at the different pulse repetition frequencies based on the maximum a posteriori probability estimation comprises:
acquiring the width of a signal peak according to the measurement data under different pulse repetition frequencies;
convolving the measurement data under different pulse repetition frequencies according to the widths of the signal peaks to obtain probability vectors under different pulse repetition frequencies after convolution;
for each pulse repetition frequency, traversing all possible ranging values by taking a first preset ranging precision as a step length to obtain a first probability corresponding to each ranging value; under different pulse repetition frequencies, a plurality of range values traversed by taking the first preset range accuracy as a step length are correspondingly the same;
adding the first probability under different pulse repetition frequencies aiming at each ranging value to obtain a first total probability corresponding to each ranging value;
and selecting the ranging value corresponding to the maximum first total probability as the distance of the first target.
3. The method of claim 1, wherein calculating the distance to the first target from the measurement data at the different pulse repetition frequencies based on the maximum a posteriori probability estimation comprises:
compressing the measurement data under different pulse repetition frequencies to obtain low-precision measurement data vectors under different pulse repetition frequencies;
acquiring the width of a signal peak according to the measurement data vector under different pulse repetition frequencies with low precision;
convolving the measurement data under different pulse repetition frequencies with low precision according to the width of the signal peak to obtain probability vectors under different pulse repetition frequencies after low-precision convolution;
traversing all possible ranging values by taking second preset ranging precision as a step length according to each pulse repetition frequency to obtain a second probability corresponding to each ranging value; under different pulse repetition frequencies, a plurality of range values traversed by taking the second preset range accuracy as a step length are correspondingly the same; the value of the second preset distance measurement precision is greater than the value of the first preset distance measurement precision;
adding the second probabilities under different pulse repetition frequencies aiming at each ranging value to obtain a second total probability corresponding to each ranging value, and selecting the ranging value corresponding to the largest second total probability as the estimated distance of the first target;
convolving the measurement data under different pulse repetition frequencies to obtain probability vectors under different pulse repetition frequencies after convolution;
traversing all possible ranging values by taking the estimated distance of the first target as a central value and the first preset ranging precision as a step length within a second preset ranging precision range to obtain a third probability corresponding to each ranging value;
and adding the third probabilities under different pulse repetition frequencies aiming at each ranging value to obtain a third total probability corresponding to each ranging value, and selecting the ranging value corresponding to the maximum third total probability as the distance of the first target.
4. The ranging method according to claim 1, wherein the preset condition comprises: the values of the periods of all the pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relations:
Figure FDA0003156574070000021
wherein, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, N denotes the number of pulse repetition frequencies in the pulse repetition frequency combination, [ T ═ T1，T2，...，TN]Representing the least common multiple, D, of the periods of all pulse repetition frequencies in said combination of pulse repetition frequenciesmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
5. A ranging method according to any of claims 1 to 3, characterized in that the distance of the first target satisfies the following relation:
Figure FDA0003156574070000022
wherein, i is less than N,
Figure FDA0003156574070000031
wherein the content of the first and second substances,
Figure FDA0003156574070000032
representing the maximum a posteriori probability estimate, D representing an estimate of the distance to said first target, N representing the number of pulse repetition frequencies in said combination of pulse repetition frequencies, TiDenotes the period of the i (i-1, 2, …, N) th pulse repetition frequency, NiDenotes the number of periods, t, corresponding to the i (i ═ 1, 2, …, N) th pulse repetition frequencyi，qDenotes the time of flight of the qth photon at the ith pulse repetition frequency, σ denotes the width of the signal peak, b denotes the intensity of the noise floor, DmaxRepresenting the farthest distance at which the first target is likely to appear and c the speed of light.
6. The method of claim 1, wherein the measuring the first target by using the at least two pulse repetition frequencies in turn to obtain the measurement data at different pulse repetition frequencies comprises:
measuring the first target in a preset measurement period aiming at each pulse repetition frequency, wherein the preset measurement period comprises a plurality of transceiving periods;
and in each transceiving period, measuring the first target in a manner of separating emission from detection in a time sequence.
7. The ranging method of claim 2, further comprising:
according to the distance of the first target, signal peaks corresponding to the first target in the measurement data under different pulse repetition frequencies are erased;
acquiring the distance of a second target according to the distance measuring method aiming at the first target;
according to the distance of the second target, signal peaks corresponding to the second target in the measurement data under different pulse repetition frequencies are erased;
and in the same way, the distances of the multiple targets are obtained according to the distance measuring method aiming at the first target.
8. A ranging apparatus, comprising:
the determining module is used for determining a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies;
the measuring module is used for measuring the first target by adopting the at least two pulse repetition frequencies in turn to obtain measuring data under different pulse repetition frequencies;
and the calculation module is used for calculating the distance of the first target according to the measurement data under different pulse repetition frequencies based on the maximum posterior probability estimation.
9. An electronic device, comprising:
a processor;
a memory having stored therein at least one instruction that is loaded and executed by the processor to implement the method of any of claims 1-7.
10. A computer-readable storage medium having stored therein at least one instruction, which is loaded and executed by a processor to implement the method of any one of claims 1 to 7.
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