CN113341427B - Distance measurement method, device, electronic device and storage medium - Google Patents

Abstract

The disclosure provides a ranging method, a ranging device, electronic equipment and a storage medium. The ranging method comprises the following steps: determining pulse repetition frequency combinations according to preset conditions; wherein the pulse repetition frequency combination comprises at least two pulse repetition frequencies; measuring the 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 posterior probability estimate, a distance of the first target is calculated from the measurement data at the different pulse repetition frequencies.

Description

Distance measurement method, device, electronic device and storage medium

Technical Field

The present disclosure relates to the field of laser radar, and in particular to a ranging method, device, electronic equipment and storage medium.

Background technique

Traditional distance measurement methods usually use a single pulse repetition frequency for distance measurement, and the distance measurement range is limited to the round-trip flight length corresponding to one cycle. When the target distance exceeds this length, there will be a distance confusion problem, that is, it is impossible to determine in which cycle 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 far, even if the echo light signal can be detected, the weak signal will be submerged in a large amount of noise. Therefore, how to extract the signal from the data with extremely low signal-to-noise ratio and realize ranging is a difficult problem that needs to be solved urgently.

Summary of the invention

In view of this, the present disclosure provides a ranging method, device, electronic device and storage medium.

According to one aspect of the present disclosure, a ranging method is proposed, comprising:

Determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies;

Using at least two pulse repetition frequencies to measure the first target in turn, and obtaining measurement data at different pulse repetition frequencies;

Based on the maximum a posteriori probability estimation, the distance of the first target is calculated according to the measurement data at different pulse repetition frequencies.

Preferably, based on the maximum a posteriori probability estimation, calculating the distance of the first target according to the measurement data at different pulse repetition frequencies includes:

According to the measurement data at different pulse repetition frequencies, the width of the signal peak is obtained;

Convolve the measured data at different pulse repetition frequencies according to the width of the signal peak to obtain the probability vectors at different pulse repetition frequencies after convolution;

For each pulse repetition frequency, with a first preset ranging precision as a step length, traverse all possible ranging values to obtain a first probability corresponding to each ranging value; wherein, under different pulse repetition frequencies, the multiple ranging values traversed with the first preset ranging precision as a step length correspond to the same;

For each ranging value, first probabilities at different pulse repetition frequencies are added to obtain a first total probability corresponding to each ranging value;

The distance measurement value corresponding to the largest first total probability is selected as the distance of the first target.

Preferably, based on the maximum a posteriori probability estimation, calculating the distance of the first target according to the measurement data at different pulse repetition frequencies includes:

Compressing the measurement data at different pulse repetition frequencies to obtain low-precision measurement data vectors at different pulse repetition frequencies;

Obtain the width of the signal peak according to the low-precision measurement data vectors at different pulse repetition frequencies;

Convolving the low-precision measurement data at different pulse repetition frequencies according to the width of the signal peak, and obtaining the probability vectors at different pulse repetition frequencies after the low-precision convolution;

For each pulse repetition frequency, all possible ranging values are traversed with the second preset ranging precision as a step length to obtain a second probability corresponding to each ranging value; wherein, under different pulse repetition frequencies, the multiple ranging values traversed with the second preset ranging precision as a step length correspond to the same; and the value of the second preset ranging precision is greater than the value of the first preset ranging precision;

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;

Convolve the measured data at different pulse repetition frequencies to obtain probability vectors at different pulse repetition frequencies after convolution;

Taking the estimated distance of the first target as the center value, within a second preset ranging accuracy range, taking the first preset ranging accuracy as the step length, traversing all possible ranging values, and obtaining a third probability corresponding to each ranging value;

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.

Preferably, the preset condition includes: the values of the periods of all pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relationship:

Wherein, _Ti represents the period of the i-th (i=1, 2, ..., N) pulse repetition frequency, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, [ _T1 , _T2 , ..., _TN ] represents the least common multiple of the periods of all pulse repetition frequencies in the pulse repetition frequency combination, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light.

Preferably, the distance of the first target satisfies the following relationship:

Among them, i＜N,

in, represents the maximum a posteriori probability estimation result, D represents an estimate of the distance to the first target, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, _Ti represents the period of the i-th (i=1, 2, …, N) pulse repetition frequency, _ni represents the number of periods corresponding to the i-th (i=1, 2, …, N) pulse repetition frequency, _ti,q represents the flight time of the q-th photon at the i-th pulse repetition frequency, σ represents the width of the signal peak, b represents the intensity of the background noise, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light.

Preferably, at least two pulse repetition frequencies are used to measure the first target in turn to obtain measurement data at different pulse repetition frequencies, including:

For each pulse repetition frequency, measuring the first target within a preset measurement period, the preset measurement period including a plurality of transmission and reception periods;

In each transmission and reception cycle, the first target is measured in a timing-sequential manner by separating transmission and detection.

Preferably, the method further comprises:

According to the distance of the first target, the signal peak corresponding to the first target in the measurement data under different pulse repetition frequencies is erased;

Obtaining the distance of the second target according to the distance measurement method for the first target;

According to the distance of the second target, the signal peak corresponding to the second target in the measurement data under different pulse repetition frequencies is erased;

By analogy, the distances of multiple targets are obtained according to the distance measurement method for the first target.

According to another aspect of the present disclosure, a distance measuring device is provided, comprising:

A determination module, used to determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies;

A measuring module, used to measure the first target in turn using at least two pulse repetition frequencies to obtain measurement data at different pulse repetition frequencies;

The calculation module is used to calculate the distance of the first target according to the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation.

According to another aspect of the present disclosure, an electronic device is provided, including: a processor and a memory, wherein at least one instruction is stored in the memory, and when the instruction is executed by the processor, the above method is implemented.

According to another aspect of the present disclosure, a computer-readable storage medium is provided, in which at least one instruction is stored, and when the instruction is executed by a processor, the above method is implemented.

It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG1 schematically shows a flow chart of a distance measurement method according to an embodiment of the present disclosure;

FIG2A schematically shows a block diagram of a distance measurement system to which the distance measurement method according to an embodiment of the present disclosure can be applied;

FIG2B schematically shows a signal timing diagram of the working process of the ranging system in FIG2A;

FIG3 schematically shows a flow chart of a distance measurement method according to an embodiment of the present disclosure;

FIG4 schematically shows a flow chart of a distance measurement method according to an embodiment of the present disclosure;

FIG5A shows the position of the ranging target in the first embodiment of the present disclosure;

FIG5B shows a ranging signal diagram obtained by measuring the ranging target in FIG5A according to the ranging method of an embodiment of the present disclosure;

FIG6A shows the position of the ranging target in the second embodiment of the present disclosure;

FIG6B shows a ranging signal diagram obtained by measuring the ranging target in FIG6A according to the ranging method of an embodiment of the present disclosure;

FIG7 schematically shows a block diagram of a distance measuring device according to an embodiment of the present disclosure;

FIG8 schematically shows a block diagram of an electronic device according to an embodiment of the present disclosure.

Detailed ways

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and/or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

In the case of using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc.). In the case of using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted in accordance with the meaning of the expression generally understood by those skilled in the art (for example, "a system having at least one of A, B, or C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc.).

Some block diagrams and/or flow charts are shown in the accompanying drawings. It should be understood that some boxes or combinations thereof in the block diagrams and/or flow charts can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that these instructions can create a device for implementing the functions/operations described in these block diagrams and/or flow charts when executed by the processor. The technology of the present disclosure can be implemented in the form of hardware and/or software (including firmware, microcode, etc.). In addition, the technology of the present disclosure can take the form of a computer program product on a computer-readable storage medium storing instructions, which can be used by an instruction execution system or used in conjunction with an instruction execution system.

As described in the background technology, the traditional distance measurement method usually uses a single pulse repetition frequency for distance measurement. For long-distance distance measurement, the mutual interference of multiple signal peaks often causes the problem of target distance measurement error. In addition, for long-distance distance measurement, the signal-to-noise ratio is also a major limiting factor. When the measurement distance is far, even if the echo light signal can be detected, the weak signal will be submerged in a large amount of noise. In view of this, the present disclosure provides a distance measurement method, a distance measurement device, an electronic device and a medium, in order to at least partially solve the above technical problems.

FIG1 schematically shows a flow chart of a distance measurement method according to an embodiment of the present disclosure.

As shown in FIG. 1 , an embodiment of the present disclosure provides a distance measurement method, which includes operations S110 to S130 .

In operation S110, a pulse repetition frequency combination is determined according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies.

In operation S120, at least two pulse repetition frequencies are used to measure the first target in turn to obtain measurement data at different pulse repetition frequencies.

In operation S130 , the distance of the first target is calculated based on the maximum a posteriori probability estimation according to the measurement data at different pulse repetition frequencies.

In the technical solution of the present disclosure, by selecting a multi-pulse repetition frequency combination that meets the preset conditions, and measuring the target in turn based on the multiple pulse repetition frequencies in the pulse repetition frequency combination, the problem of mutual interference between multiple signal peaks in the traditional method is solved, which is not only suitable for long-distance ranging of a single target, but also can achieve ranging of multiple targets or multi-depth targets. On the other hand, the ranging method in the embodiment of the present disclosure processes the measurement results by adopting the maximum a posteriori probability estimation method, which can achieve high-precision ranging in the case of extremely low signal-to-noise ratio, and is more suitable for high-precision ranging over long distances.

In some embodiments of the present disclosure, in the above step S110, the preset condition includes: the values of the periods of all pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relationship:

Wherein, _Ti represents the period of the i-th (i=1, 2, ..., N) pulse repetition frequency, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, [ _T1 , _T2 , ..., _TN ] represents the least common multiple of the periods of all pulse repetition frequencies in the pulse repetition frequency combination, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light.

When using the traditional ranging method to measure a distant target, the light spot covers a large area of the object, often with multiple depths, and the time distribution width of the measured signal can generally reach tens of nanoseconds. In addition, for the ranging of multiple targets, due to improper frequency selection, interference will occur between the multiple signal peaks formed. For a high-repetition-rate laser ranging system, both of the above situations may lead to erroneous ranging results. The ranging method of the disclosed embodiment avoids the above problems to the greatest extent by selecting a pulse repetition frequency combination that meets the above preset conditions (wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies).

According to the above formula (1), a pulse repetition frequency combination (T ₁ , T ₂ , ..., T _N ) that meets the preset conditions can be obtained. In this way, multiple pulse repetition frequencies in the pulse repetition frequency combination (T ₁ , T ₂ , ..., T _N ) can be used to measure the first target in turn, thereby solving the problem of mutual interference between multiple signal peaks in the traditional method. This method is not only suitable for long-distance ranging of a single target, but also can realize ranging of multiple targets or multiple depth targets.

In the disclosed embodiment, the maximum distance D _max at which the first target may appear and the number N of pulse repetition frequencies in the pulse repetition frequency combination can be set according to actual needs, and are not limited here. Among them, using a larger number of pulse repetition frequencies to measure the first target in turn can be applicable to a larger ranging range, thereby meeting the ranging requirements of farther and more targets.

In some embodiments of the present disclosure, in the above step S120, at least two pulse repetition frequencies are used to measure the first target in turn to obtain measurement data at different pulse repetition frequencies, which specifically includes the following operations:

For each pulse repetition frequency, the first target is measured in a preset measurement cycle, and the preset measurement cycle includes multiple transceiver cycles. In each transceiver cycle, the first target is measured in a timing separation mode of transmission and detection. In the process of measuring the first target at each pulse repetition frequency, the timing separation mode of transmission and detection is adopted, which can greatly reduce the detected atmospheric scattering noise, thereby achieving a high signal-to-noise ratio.

FIG2A schematically shows a block diagram of a ranging system to which the ranging method of the embodiment of the present disclosure can be applied; FIG2B schematically shows a signal timing diagram of the ranging system working process in FIG2A. The following will be combined with FIG2A and FIG2B to describe in detail the process of measuring the first target in turn using multiple pulse repetition frequencies in the embodiment of the present disclosure. It should be understood that the ranging system structure and signal timing diagram shown in FIG2A and FIG2B 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/turntable system 203, a detector 204, a time measurement module 205, and a controller 206. The ranging system is based on a non-coaxial optical path for transmitting and receiving, and the optical path/turntable system includes an optical path for transmitting and receiving and a turntable system. In the embodiment of the present disclosure, the above-mentioned ranging system can be used to measure the distance of a target 207 (e.g., a first target).

The working process of the above ranging system is briefly described as follows:

When measuring the target 207 with each pulse repetition frequency, the signal source 201 generates a pulse signal to trigger the laser 202 to emit a laser pulse (the laser pulse signal corresponds to a 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, it is reflected back by the target and received by the receiving optical path, 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 photon flight time. According to the above-mentioned ranging method, at least two pulse repetition frequencies in the pulse repetition frequency combination are used to measure the target 207 in turn, and measurement data under different pulse repetition frequencies are obtained. Among them, the measurement data characterizes the distribution of the number of photons over time.

In the process of the ranging system measuring the distance of the target 207, the controller 206 is used to control the signal reception and transmission of each structure (as shown in Figure 2B) and the measurement data at different pulse repetition frequencies output by the receiving time measurement module 205 and the detector 204, and output the distance of the target according to the measurement data at different pulse repetition frequencies.

Compared with the traditional single-frequency ranging method, the present invention adopts multiple pulse repetition frequencies to transmit in turn, and the measurement result is the statistics of photon flight time within a measurement cycle corresponding to different pulse repetition frequencies. Therefore, the data volume is small, the data transmission speed is fast, and the memory usage is small. At the same time, the data processing speed is faster and the hardware requirements are lower. The ranging method in the embodiment of the present invention can meet the needs of long-distance real-time and fast ranging.

In order to improve the accuracy of ranging, effectively reduce the noise of the ranging system, and achieve a high signal-to-noise ratio. In the embodiment of the present disclosure, when measuring the target 207 at each pulse repetition frequency, the laser pulse emission and photon detection are separated in timing to achieve the above purpose. The following will be combined with Figure 2B to briefly explain the use of multiple pulse repetition frequencies in time to perform measurements in turn in the embodiment of the present disclosure.

The signal timing is shown in FIG2B , assuming 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 corresponding pulse repetition frequency is represented by the period of the pulse repetition frequency, denoted as T, as shown in FIG2B ), the target 207 is measured within a preset measurement period P, and the measurement result is the flight time of the signal photon within the corresponding pulse repetition frequency period, that is, for each pulse repetition frequency, a statistical distribution measurement data of a photon time count is obtained. After each measurement period, the signal source 201 replaces the generated pulse repetition frequency and maintains the measurement time P. In the embodiment of the present disclosure, N pulse repetition frequencies take turns to measure the target 207 within the measurement period P, for example, the measurement order of multiple pulse repetition frequencies is frequency 1→frequency 2→…→frequency N→frequency 1→…→frequency i→…. In the embodiment of the present disclosure, the rounds of target measurement by N pulse repetition frequencies can be set according to actual conditions, for example, N pulse repetition frequencies can be used to test the target for 1 round, 2 rounds, 10 rounds, etc., without limitation here.

In each measurement cycle P (i.e., for each pulse repetition frequency), multiple transceiver cycles (S=G+M) with a period of S can be set according to the maximum range of the ranging system, where G is the time for the laser to emit laser pulses in each transceiver cycle S, and M is the time for the detector to detect signal photons in each transceiver cycle S. In each transceiver cycle S, the laser pulse emission and photon detection are separated in time by controlling the working timing of the laser and the detector, thereby effectively reducing the noise of the ranging system and achieving a high signal-to-noise ratio. Specifically, at the beginning of the transceiver cycle S, the laser 202 emits a laser pulse for a period of time G, and the detector 204 does not detect at this time. After the laser stops emitting pulses, the detector 204 starts detection for a period of time M.

In some embodiments of the present disclosure, the laser pulse emitted by the laser 202 can be, for example, a near-infrared laser with a high repetition frequency and low pulse energy, which can ensure the safety of human eyes and has strong concealment, and can be used in conjunction with a fiber laser, which is flexible and convenient. It can be understood that the above description of the laser pulse is only an example made to facilitate understanding of the present solution, and the present application does not limit the type of laser and the type of laser pulse emitted.

FIG3 schematically shows a flow chart of a distance measurement method according to another embodiment of the present disclosure.

As shown in FIG. 3 , in the above operation S130 , based on the maximum a posteriori probability estimation, the distance of the first target is calculated according to the measurement data at different pulse repetition frequencies, including operations S310 to S350 .

In operation S310, the width of a signal peak is obtained according to measurement data at different pulse repetition frequencies.

The measurement 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 speaking, when different pulse repetition frequencies are used to measure the distance of the same target in turn, the width of the signal peak in the measurement data under different pulse repetition frequencies is the same. In this operation S310, the measurement data under different pulse repetition frequencies are peak-searched to obtain the width of the signal peak.

In operation S320, the measurement data at different pulse repetition frequencies are convolved according to the width of the signal peak to obtain probability vectors at different pulse repetition frequencies after the convolution.

The width of the convolution function is determined by the width of the measured signal peak. Therefore, the convolution function can be determined according to the width of the signal peak, and the measured data at different pulse repetition frequencies are convolved to obtain the probability vector at different pulse repetition frequencies after convolution. Among them, the subscript of the probability vector corresponds to the flight time, and the value of the vector corresponds to a probability.

In operation S330, for each pulse repetition frequency, all possible ranging values are traversed with the first preset ranging precision as the step length to obtain a first probability corresponding to each ranging value. In which, at different pulse repetition frequencies, the multiple ranging values traversed with the first preset ranging precision as the step length correspond to the same.

Assume that for the probability vector at the first pulse repetition frequency after convolution (denoted as T ₁ ), the first preset ranging accuracy is used as the step length, and all possible ranging values traversed are D ₁ , D ₂ , D ₃ , … , D _m (where m is a positive integer greater than 1). Then, for the probability vectors at other multiple pulse repetition frequencies after convolution, for example, the probability vectors at the second to Nth pulse repetition frequencies (denoted as T ₂ to T _N ), the first preset ranging accuracy is also used as the step length, and ranging values such as D ₁ , D ₂ , D ₃ , … , D _m are traversed, and then the first probability corresponding to each ranging value at different pulse repetition frequencies is obtained. For example, for the ranging value D ₁ , the first probabilities at the first to N-th pulse repetition frequencies can be obtained as P ₁₁ , P ₁₂ , ... , P _1N , respectively; for the ranging value D ₂ , the first probabilities at the first to N-th pulse repetition frequencies can be obtained as P ₂₁ , P ₂₂ , ... , P _2N , respectively; and so on, for the ranging value D _m , the first probabilities at the first to N-th pulse repetition frequencies can be obtained as P _ml , P _m2 , ... , P _mN , respectively.

At each pulse repetition frequency, obtaining the first probability corresponding to each ranging value includes the following operations:

Assuming that at the i-th (i=1, 2, ..., N) pulse repetition frequency, for the ranging value D _j (j=1, 2, ..., m), the flight time _ti corresponding to the ranging value D _j is obtained according to the ranging value D _j and formula (2), and the corresponding first probability P _ji can be obtained according to the flight time _ti according to the probability vector in operation S320.

Wherein, _Ti represents the period of the i-th (i=1, 2, ..., N) pulse repetition frequency, _ni represents the number of periods corresponding to the i-th (i=1, 2, ..., N) pulse repetition frequency, _ti represents the flight time corresponding to the ranging value _Dj at the i-th pulse repetition frequency, and c represents the speed of light.

Specifically, the period _Ti of the i-th pulse repetition frequency in formula (2) can be obtained according to formula (1), and the ranging value _Dj can be set according to actual needs. By dividing _Ti on both sides of formula (2), the period number n _i corresponding to the i-th pulse repetition frequency and the flight time _ti corresponding to the ranging value _Dj can be obtained. Then, according to the flight time _ti , the corresponding first probability _Pji can be obtained according to the probability vector in operation S320.

In the embodiment of the present disclosure, the value of the first preset ranging accuracy can be set according to actual needs and is not limited here.

In operation S340, for each ranging value, first probabilities at different pulse repetition frequencies are added to obtain a first total probability corresponding to each ranging value.

The example of the ranging value in operation S330 is used to illustrate the steps of operation S340, for example, taking the ranging value _D1 as an example. For the ranging value _D1 , the first probabilities under different pulse repetition frequencies are added, that is, _P11 , _P12 , ..., _P1N are added, and the first total probability _P1 corresponding to the ranging value _D1 can be obtained; and by analogy, the first total probabilities _P2 to _Pm corresponding to the ranging values _D2 to _Dm can be obtained.

In operation S350, the distance measurement value corresponding to the largest first total probability is selected as the distance of the first target.

In the disclosed embodiment, it is assumed that in single-photon ranging, the flight time of the photon corresponds to the distance of the target. If the number of photons returned within a certain time period is greater, it indicates that the probability of the existence of the target at the corresponding distance is greater. Based on the above assumption, the ranging value corresponding to the largest value among the first total probabilities P ₁ to P _m is selected as the distance of the first target. For example, assuming that the first total probability P ₃ is the largest among the m total probabilities, the ranging value D ₃ corresponding to the first total probability P ₃ is used as the distance of the first target.

In the disclosed embodiment, the maximum a posteriori probability estimation is implemented based on the above method, so as to obtain the distance of the first target. The above method makes full use of each detected signal photon in the algorithm, and can achieve high-precision distance measurement even in the case of extremely low signal-to-noise ratio.

When the time measurement resolution is set to high resolution, the amount of data measured will be large, which will result in slow data processing. Another embodiment of the present disclosure provides a distance measurement method that can improve the above-mentioned problem of slow data processing speed, which will be described in detail below in conjunction with FIG.

FIG4 schematically shows a flow chart of a distance measurement method according to another embodiment of the present disclosure.

As shown in FIG. 4 , in the above operation S130 , based on the maximum a posteriori probability estimation, the distance of the first target is calculated according to the measurement data at different pulse repetition frequencies, including operations S410 to S480 .

In operation S410, measurement data at different pulse repetition frequencies are compressed to obtain low-precision measurement data vectors at different pulse repetition frequencies, wherein the measurement data represents a distribution of the number of photons over time.

Specifically, for example, the measurement data at different pulse repetition frequencies may be combined into vector elements, counted and accumulated, etc. to reduce the vector elements, thereby achieving a data compression effect, thereby obtaining a low-precision measurement data vector.

In operation S420, the width of the signal peak is obtained according to the low-precision measurement data vectors at different pulse repetition frequencies.

Specifically, peak searching is performed on low-precision measurement data vectors at different pulse repetition frequencies to obtain the width of the signal peak.

In operation S430, low-precision measurement data at different pulse repetition frequencies are convolved according to the width of the signal peak to obtain low-precision probability vectors at different pulse repetition frequencies after the convolution.

The width of the convolution function is determined by the width of the measured signal peak, so the convolution function can be determined according to the width of the signal peak, and the low-precision measurement data at different pulse repetition frequencies are convolved to obtain the probability vector at different pulse repetition frequencies after low-precision convolution. Among them, the subscript of the probability vector corresponds to the flight time, and the value of the vector corresponds to a probability.

In operation S440, for each pulse repetition frequency, all possible ranging values are traversed with the second preset ranging precision as a step length to obtain a second probability corresponding to each ranging value. Wherein, under different pulse repetition frequencies, the multiple ranging values traversed with the second preset ranging precision as a step length correspond to the same, and the value of the second preset ranging precision is greater than the value of the first preset ranging precision.

In this operation S440, if 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), it means that all possible ranging values are traversed with low ranging accuracy. This method can reduce the amount of calculated data, thereby speeding up the calculation speed.

The step of traversing all possible ranging values with the second preset ranging accuracy as the step length to obtain the second probability corresponding to each ranging value is the same as or similar to operation S330, and will not be repeated herein.

In the embodiment of the present disclosure, the values of the first preset ranging accuracy and the second preset ranging accuracy can be set according to actual needs, which are not limited here.

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 this operation S450, the process of obtaining the second total probability corresponding to each ranging value is the same as the process of operation S340, which will not be repeated here.

Based on the compressed measurement data at different pulse repetition frequencies, the estimated distance of the first target can be obtained, and then the precise distance of the first target can be confirmed based on 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 within a second preset ranging accuracy range and with the first preset ranging accuracy as a step size, to obtain a third probability corresponding to each ranging value.

In this operation, assuming that the estimated distance of the first target is _Destination and the second preset distance measurement accuracy is _W2 , then within the range of ( _Destination - _W2 ) to ( _Destination + _W2 ), with the first preset distance measurement accuracy as the step length, all possible distance measurement values are traversed to obtain the third probability corresponding to each distance measurement value. The method of obtaining the third probability is similar to that in operation S330, which will not be repeated here.

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 present disclosure, rough ranging is first completed by compressing the original measurement data, that is, the estimated distance of the first target is confirmed, and then high-precision ranging is achieved based on the rough ranging result. Compared with the ranging method in Figure 3, the ranging method in the embodiment of the present disclosure greatly reduces the amount of data processed, thereby speeding up the calculation speed and improving the ranging efficiency, thereby meeting the needs of real-time and fast ranging.

In some embodiments of the present disclosure, the distance of the first target satisfies the following relationship:

Among them, i＜N,

in, represents the maximum a posteriori probability estimation result, D represents an estimate of the distance to the first target, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, _Ti represents the period of the i-th (i=1, 2, …, N) pulse repetition frequency, _ni represents the number of periods corresponding to the i-th (i=1, 2, …, N) pulse repetition frequency, _ti,q represents the flight time of the q-th photon at the i-th pulse repetition frequency, σ represents the width of the signal peak, b represents the intensity of the background noise, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light.

When traditional distance measurement methods measure multiple targets or targets at multiple depths, interference between multiple signal peaks may lead to measurement errors. The distance measurement method of the disclosed embodiment can not only measure the distance of one target, but also measure the distance of multiple targets or targets at multiple depths.

Specifically, when measuring the distance of a first target, multiple targets can actually be observed within the line of sight, that is, multiple targets may exist within the measurement range from the ranging point to the first target position. In the process of measuring the distance of the first target using the ranging method in the present disclosure, multiple targets other than the first target within the line of sight can also be measured at the same time (here, it refers to obtaining ranging data at different pulse repetition frequencies). The following is a brief description of the ranging method in the embodiment of the present disclosure applied to the ranging of multiple targets.

The present disclosure also provides a ranging method applicable to multiple targets or multiple depth targets, and the method includes operations S510 to S530.

In operation S510, signal peaks corresponding to the first target in 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, the signal peak corresponding to the first target can be found in the measurement data and erased, thereby eliminating the interference of the first target signal peak on subsequent target ranging, thereby improving the accuracy of multi-target or multi-depth target ranging.

In operation S520, a distance to the second target is acquired according to a distance measurement method for the first target.

Specifically, the distance measurement method for the second target is the same as or similar to the process described above, and will not be repeated here.

In operation S530, according to the distance of the second target, the signal peak corresponding to the second target in the measurement data under different pulse repetition frequencies is erased; and so on, according to the distance measurement method for the first target, the distances of multiple targets are obtained.

In the disclosed embodiment, the signal peak of the previous target is erased to eliminate the interference of the signal peak of the target on the ranging of subsequent targets, thereby overcoming the defect of erroneous measurement results caused by the traditional multi-target ranging method and improving the accuracy of multi-target or multi-depth target ranging.

In order to enable those skilled in the art to more clearly understand the technical solution of the present disclosure, the advantages of the present disclosure will be explained below in conjunction with specific embodiments.

Embodiment 1

In this embodiment, a distance measurement system as shown in FIG. 2A is adopted, and the technical solution of the present disclosure is introduced by taking the distance measurement of 12.18 km as an example.

In the embodiment of the present disclosure, a pulse repetition frequency combination including five pulse repetition frequencies is calculated, and the corresponding periods thereof are 1 μs, 1.01 μs, 1.02 μs, 1.03 μs and 1.04 μs respectively.

The signal source 201 generates the trigger signals of the above five pulse repetition frequencies in turn, and gives them to the laser 202 and the time measurement module 205 respectively. The measurement period of each pulse repetition frequency lasts P = 160 μs. In a transceiver cycle S = 160 μs, the signal source 201 outputs a continuous pulse signal to the time measurement module 205, and the pulse duration to the laser 202 lasts G = 79 μs. The pulse start is synchronized with the start of the transceiver cycle. The signal source 201 also outputs the transceiver cycle signal to the detector 204 as a gating signal. The pulse duration of the detector 204 lasts M = 81 μs, and the laser 202 and the detector 204 are isolated in timing.

The above scheme completes the ranging of 12.18 km (the position of the ranging target is shown in FIG5A ).

FIG5B shows a ranging signal diagram obtained by measuring the ranging target in FIG5A using the ranging method according to an embodiment of the present disclosure, wherein the abscissa X represents the photon flight time, and the ordinate Y represents the photon count.

As shown in Figure 5B, there is an obvious echo signal peak from the target building on the photon count-time graph. According to the measurement data in Figure 5B, the distance of the target can be obtained as 12.184515km. Among them, for the ranging of the 12.18km target, the ranging speed is 20Hz, the selected time resolution is 100ps, the ranging accuracy is 1.5cm, and the algorithm processing time is 10ms.

It can be seen that the distance measurement method in the present disclosure can accurately measure the distance of the target, and the distance measurement error is very small, and the calculation speed is fast, which can meet the needs of long-distance real-time fast distance measurement.

Embodiment 2

In order to demonstrate the application of the ranging method disclosed in the present disclosure in multi-target ranging, in the second embodiment, the boundary position of three targets at different distances is selected for ranging, and the visible light camera photo of the target is shown in Figure 6A, in which the white cross is the ranging position, the target distance of the left half of the ranging point is 2.6km, the target distance of the lower right is 4.7km, and the target distance of the upper right is 13.3km. In the second embodiment, for the ranging of the three targets, the parameter setting of the ranging system is the same as that of the first embodiment, and will not be repeated here.

Fig. 6B shows a signal diagram of the distance measurement of the above three targets in this embodiment. The signal diagram shows the measurement signal at a repetition frequency of 1 MHz, and the three peaks in the diagram correspond to the signal peaks of the three targets respectively.

In the distance measurement of three targets, the measured target distances are 2.57598km, 4.67844km and 13.34820km respectively, the ranging speed is 5Hz, the ranging accuracy is 1.5cm, and the algorithm processing time is 30ms. It can be seen that the application of the ranging method in the present disclosure to multi-target ranging can also achieve accurate and fast results.

In addition, in the second embodiment, the measurement data obtained by the ranging method disclosed in the present invention contains more information, which can directly reflect the number of targets, the shape of the target echo signal, the target depth level and other information, which is convenient for signal extraction and analysis of the ranging results, and is suitable for applications such as ranging and identification of multiple targets.

Based on the above distance measurement method, the present disclosure further provides a distance measurement device, which will be described in detail below in conjunction with FIG.

FIG. 7 schematically shows a structural block diagram of a distance measuring device according to an embodiment of the present disclosure.

As shown in FIG. 7 , the distance measuring device 700 includes a determination module 710 , a measurement module 720 and a calculation module 730 .

The determination module 710 is used to determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies.

The measurement module 720 is used to measure the first target in turn using at least two pulse repetition frequencies to obtain measurement data at different pulse repetition frequencies.

The calculation module 730 is used to calculate the distance of the first target based on the maximum a posteriori probability estimation and the measurement data at different pulse repetition frequencies.

It should be noted that the implementation methods, technical problems solved, functions realized, and technical effects achieved of each module/unit/sub-unit in the device part embodiment are the same or similar to the implementation methods, technical problems solved, functions realized, and technical effects achieved of each corresponding step in the method part embodiment, and will not be repeated here.

According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits, or at least part of the functions of any one of them can be implemented in one module. According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits can be split into multiple modules for implementation. According to the embodiments of the present invention, any one or more of the modules, submodules, units, and subunits can be at least partially implemented as hardware circuits, such as field programmable gate arrays (FPGAs), programmable logic arrays (PLAs), systems on chips, systems on substrates, systems on packages, application specific integrated circuits (ASICs), or can be implemented by hardware or firmware in any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation methods of software, hardware, and firmware, or in any appropriate combination of any of them. Alternatively, according to the embodiments of the present invention, one or more of the modules, submodules, units, and subunits can be at least partially implemented as computer program modules, and when the computer program modules are run, the corresponding functions can be performed.

For example, any multiple of the determination module 710, the measurement module 720 and the calculation module 730 can be combined in one module for implementation, or any one of the modules can be split into multiple modules. Alternatively, at least part of the functions of one or more of these modules can be combined with at least part of the functions of other modules and implemented in one module. According to an embodiment of the present disclosure, at least one of the determination module 710, the measurement module 720 and the calculation module 730 can be at least partially implemented 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 can be implemented by hardware or firmware such as any other reasonable way of integrating or packaging the circuit, or implemented in any one of the three implementation modes of software, hardware and firmware or in any appropriate combination of any of them. Alternatively, at least one of the determination module 710, the measurement module 720 and the calculation module 730 can be at least partially implemented as a computer program module, and when the computer program module is run, the corresponding function can be performed.

Fig. 8 schematically shows a block diagram of an electronic device suitable for implementing the method described above 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 scope of use of the embodiment of the present disclosure.

As shown in Fig. 8, the electronic device 800 includes a processor 810 and a computer-readable storage medium 820. The electronic device 800 can execute the method according to the embodiment of the present disclosure.

Specifically, the processor 810 may include, for example, a general-purpose microprocessor, an instruction set processor and/or a related chipset and/or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 810 may also include an onboard memory for cache purposes. The processor 810 may be a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

The computer-readable storage medium 820 may be, for example, a non-volatile computer-readable storage medium, specific examples of which include but are not limited to: magnetic storage devices, such as magnetic tapes or hard disks (HDDs); optical storage devices, such as compact disks (CD-ROMs); memories, such as random access memories (RAMs) or flash memories; and the like.

The computer-readable storage medium 820 may include a computer program 821 , which 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 to have, for example, a computer program code including a computer program module. For example, in an example embodiment, the code in the computer program 821 may include one or more program modules, for example, including module 821A, module 821B, ... It should be noted that the division method and number of modules are not fixed, and those skilled in the art may use appropriate program modules or program module combinations according to actual conditions, and when these program module combinations 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 determination module 710, the measurement module 720 and the calculation 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 corresponding operations described above.

The present disclosure also provides a computer-readable storage medium, which may be included in the device/apparatus/system described in the above embodiments; or may exist independently without being assembled into the device/apparatus/system. The above computer-readable storage medium carries one or more programs, and when the above one or more programs are executed, the method according to the embodiment of the present disclosure is implemented.

According to an embodiment of the present disclosure, a computer-readable storage medium may be a non-volatile computer-readable storage medium, for example, may include but is not limited to: a portable computer disk, 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 disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present disclosure. In this regard, each box in the flow chart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some implementations as replacements, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of the boxes in the block diagram or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

It will be appreciated by those skilled in the art that the features described in the various embodiments and/or claims of the present disclosure may be combined and/or combined in a variety of ways, even if such combinations and/or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and/or claims of the present disclosure may be combined and/or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and/or combinations fall within the scope of the present disclosure.

Although the present disclosure has been shown and described with reference to specific exemplary embodiments of the present disclosure, it should be understood by those skilled in the art that various changes in form and details may be made to the present disclosure without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents. Therefore, the scope of the present disclosure should not be limited to the above-mentioned embodiments, but should be determined not only by the appended claims, but also by the equivalents of the appended claims.

Claims (9)

1. A distance measurement method, comprising: Determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies; Using the at least two pulse repetition frequencies to measure the first target in turn, to obtain measurement data at different pulse repetition frequencies; Based on maximum a posteriori probability estimation, calculating the distance of the first target according to the measurement data at the different pulse repetition frequencies; The preset condition includes: the values of the periods of all pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relationship: Wherein, _Ti represents the period of the i-th pulse repetition frequency, the value of i is 1, 2, ..., N, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, [ _T1 , _T2 , ..., _TN ] represents the least common multiple of the periods of all pulse repetition frequencies in the pulse repetition frequency combination, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light. 2. The distance measurement method according to claim 1, characterized in that the calculation of the distance of the first target based on the maximum a posteriori probability estimation according to the measurement data under the different pulse repetition frequencies comprises: Acquiring the width of the signal peak according to the measurement data at the different pulse repetition frequencies; Convolving the measurement data at different pulse repetition frequencies according to the width of the signal peak to obtain probability vectors at different pulse repetition frequencies after convolution; For each pulse repetition frequency, taking a first preset ranging precision as a step length, traversing all possible ranging values, and obtaining a first probability corresponding to each ranging value; wherein, under different pulse repetition frequencies, the multiple ranging values traversed by taking the first preset ranging precision as a step length correspond to the same; For each of the ranging values, add the first probabilities at different pulse repetition frequencies to obtain a first total probability corresponding to each of the ranging values; The distance measurement value corresponding to the largest first total probability is selected as the distance of the first target. 3. The distance measurement method according to claim 1, characterized in that the calculating the distance of the first target based on the measurement data at different pulse repetition frequencies based on the maximum a posteriori probability estimation comprises: Compressing the measurement data at different pulse repetition frequencies to obtain low-precision measurement data vectors at different pulse repetition frequencies; Acquiring the width of the signal peak according to the measured data vectors at different pulse repetition frequencies of the low precision; Convolving the low-precision measurement data at different pulse repetition frequencies according to the width of the signal peak to obtain probability vectors at different pulse repetition frequencies after low-precision convolution; For each pulse repetition frequency, taking the second preset ranging precision as a step length, traversing all possible ranging values, and obtaining a second probability corresponding to each ranging value; wherein, under different pulse repetition frequencies, the multiple ranging values traversed by taking the second preset ranging precision as a step length correspond to the same; and the value of the second preset ranging precision is greater than the value of the first preset ranging precision; For each ranging value, add the second probabilities at different pulse repetition frequencies to obtain a second total probability corresponding to each ranging value, and select the ranging value corresponding to the largest second total probability as the estimated distance of the first target; Convolving the measurement data at different pulse repetition frequencies to obtain probability vectors at different pulse repetition frequencies after convolution; Taking the estimated distance of the first target as the center value, within a range of the second preset ranging accuracy and taking the first preset ranging accuracy as the step length, traversing all possible ranging values to obtain a third probability corresponding to each ranging value; 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. 4. The distance measurement method according to any one of claims 1 to 3, characterized in that the distance of the first target satisfies the following relationship: Among them, i<N, in, represents the maximum a posteriori probability estimation result, D represents an estimate of the distance to the first target, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, _Ti represents the period of the i-th pulse repetition frequency, _ni represents the number of periods corresponding to the i-th pulse repetition frequency, the value of i is 1, 2, …, N, _ti,q represents the flight time of the q-th photon at the i-th pulse repetition frequency, σ represents the width of the signal peak, b represents the intensity of the background noise, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light. 5. The distance measurement method according to claim 1, characterized in that the step of using the at least two pulse repetition frequencies to measure the first target in turn to obtain measurement data at different pulse repetition frequencies comprises: For each pulse repetition frequency, measuring the first target within a preset measurement period, wherein the preset measurement period includes a plurality of transceiver periods; Wherein, in each of the transmitting and receiving cycles, the first target is measured in a timing manner by separating transmission and detection. 6. The distance measurement method according to claim 2, characterized in that the method further comprises: According to the distance of the first target, erasing the signal peak corresponding to the first target in the measurement data at the different pulse repetition frequencies; Acquire the distance of the second target according to the distance measurement method for the first target; According to the distance of the second target, erasing the signal peak corresponding to the second target in the measurement data at the different pulse repetition frequencies; By analogy, the distances of multiple targets are obtained according to the distance measurement method for the first target. 7. A distance measuring device, comprising: A determination module, used to determine a pulse repetition frequency combination according to a preset condition; wherein the pulse repetition frequency combination includes at least two pulse repetition frequencies; A measuring module, configured to measure the first target in turn using the at least two pulse repetition frequencies to obtain measurement data at different pulse repetition frequencies; A calculation module, configured to calculate the distance of the first target according to the measurement data at the different pulse repetition frequencies based on maximum a posteriori probability estimation; The preset condition includes: the values of the periods of all pulse repetition frequencies in the pulse repetition frequency combination satisfy the following relationship: Wherein, _Ti represents the period of the i-th pulse repetition frequency, the value of i is 1, 2, ..., N, N represents the number of pulse repetition frequencies in the pulse repetition frequency combination, [ _T1 , _T2 , ..., _TN ] represents the least common multiple of the periods of all pulse repetition frequencies in the pulse repetition frequency combination, _Dmax represents the farthest distance at which the first target may appear, and c represents the speed of light. 8. An electronic device, comprising: processor; A memory, wherein at least one instruction is stored in the memory, and the instruction is loaded and executed by the processor to implement the method according to any one of claims 1 to 6. 9. A computer-readable storage medium, characterized in that at least one instruction is stored in the computer-readable storage medium, and the instruction is loaded and executed by a processor to implement the method according to any one of claims 1 to 6.