WO2021155567A1 - Frequency modulation nonlinear correction-based ranging method and related device - Google Patents

Abstract

A frequency modulation nonlinear correction-based ranging method, comprising: acquiring a reference path beat frequency signal and a measurement path beat frequency signal (S501); calculating frequency modulation nonlinearity according to the reference path beat frequency signal, and calculating an initial flight time τ according to the measurement path beat frequency signal (S502); when the frequency modulation nonlinearity is not less than a first preset threshold, calculating a frequency modulation nonlinearity term ε(t) of a laser emission signal according to the reference path beat frequency signal, and performing nonlinear iterative correction on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal so as to obtain target flight time (S503); and calculating a target distance according to the target flight time (S504). The ranging accuracy and range of lidars may be improved.

Description

Ranging method and related device based on frequency modulation nonlinear correction Technical field

This application relates to the field of lidar, and in particular to a ranging method and related devices based on frequency modulation nonlinear correction.

Background technique

Frequency Modulated Continuous Wave (Frequency Modulated Continuous, FMCW) Lidar (Light Detection and Ranging, LiDAR) is an optical remote sensing technology that can complete functions such as ranging, speed measurement, target detection, tracking and imaging recognition, and can be applied to intelligent transportation , Autonomous driving, atmospheric environment monitoring, geographic surveying and mapping, unmanned aerial vehicles and other fields.

FMCW LiDAR obtains the position information of the measured target by measuring the coherence of the emitted light signal and the echo signal to obtain the frequency domain response of the beat signal. The basic process is shown in Figure 1. Through frequency domain analysis of the beat signal, the frequency difference f _b between the transmitted signal and the echo signal is estimated, and the flight time τ is calculated according to the frequency difference f _b , and finally the distance of the measured target is calculated according to the flight time.

Figure 2 is a block diagram of a typical FMCW LiDAR system architecture. By injecting appropriate driving current into the tunable laser, the laser is driven to emit a laser signal. After the beam passes through the isolator, it is divided into two laser beams by the coupler. The measured target is called the measuring light. The measuring light is reflected by the target surface and collected by the lens and passed through the circulator. The reference light passes through the coupler. Coherence occurs on the photosensitive surface of the balanced detector to generate a beat signal whose frequency is proportional to the flight time τ; through the beat signal Perform frequency domain analysis to obtain the beat signal frequency f _b , that is, the frequency difference between the transmitted signal and the echo signal; then according to known parameters such as the frequency modulation period and the frequency modulation bandwidth, the flight time τ can be calculated, and then the target distance can be estimated .

In an ideal chirp condition, the frequency modulation curves of the transmitted signal and the echo signal should be consistent and the frequency changes linearly with time. There is only a flight delay between the two, so the frequency modulation linearity of the transmitted signal will greatly affect the FMCWLiDAR The accuracy of ranging. In actual situations, the output frequency of the laser is controlled by changing the drive current of the laser. Due to the inherent frequency modulation effect of the semiconductor laser, the output frequency of the laser exhibits obvious nonlinearity to the modulation current, as shown in Figure 3. Compared with linear frequency modulation, when there is FM nonlinearity, the beat signal is no longer a single-frequency signal, its beat frequency will change with time, and the frequency spectrum will be broadened, resulting in a decrease in the signal-to-noise ratio of the beat signal, which will seriously affect To the ranging accuracy and ranging range.

Summary of the invention

The embodiments of the present application provide a ranging method and related devices based on frequency modulation nonlinear correction, so as to improve the ranging accuracy and ranging range of the lidar.

In the first aspect, an embodiment of the present application provides a ranging method based on frequency modulation nonlinear correction, including:

Obtain the reference road beat signal and the measurement road beat signal. The reference road beat signal and the measurement road beat signal are respectively obtained based on the laser emission signal; the frequency modulation nonlinearity is calculated according to the reference road beat signal; and according to the measurement road The beat frequency signal is calculated to obtain the initial flight time τ; it is determined that the frequency modulation nonlinearity is not less than the first preset threshold, and the frequency modulation nonlinearity term ε(t) of the laser emission signal is calculated according to the reference path beat frequency signal. According to the initial flight time τ and The frequency modulation nonlinear term ε(t) of the laser emission signal performs nonlinear iterative correction on the measurement road beat signal to obtain the target flight time; the target distance is calculated according to the target flight time.

The non-linear iterative correction of the beat signal of the measurement circuit is performed based on the flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal, which eliminates the influence of the non-linear frequency modulation on the beat signal of the measurement circuit and makes the final estimation The deviation between the target flight time and the actual flight time of the target is the smallest, and the target distance can be determined according to the target flight time, which improves the ranging accuracy of the lidar.

In a feasible embodiment, the non-linear iterative correction of the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time includes:

S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-) corresponding to the echo signal of the measurement path. 1} ), the delayed flight time τ'i _-1 is obtained based on the flight time τ _i-1 ;

S2: Perform FM nonlinear correction on the beat frequency signal of the measurement path according to the FM nonlinear term ε(t-τ＇i _{-1) corresponding to the echo signal of the measurement path to obtain a corrected beat frequency signal;}

S3. Determine the target flight time according to the corrected beat frequency signal.

According to the frequency modulation nonlinear term of the laser emission signal, the frequency modulation nonlinearity correction is performed on the measurement road beat signal, which eliminates the influence of the frequency modulation nonlinearity on the measurement road beat signal, and improves the flight time based on the corrected beat signal. Accuracy, thereby improving the accuracy of ranging.

In a feasible embodiment, determining the target flight time according to the corrected beat signal includes:

_{Obtain the flight time τ i} according to the corrected beat signal; when the peak frequency peak _i meets the preset condition, the flight time τ _{i is} determined as the target flight time; when the peak frequency peak _i does not meet the preset condition, let i=i+ 1. Repeat the above steps S1-S3; the peak value of the spectrum peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

When i=1, peak _i-1 is the initial frequency spectrum peak, and the flight time τ _i-1 is the initial flight time τ.

By iteratively correcting the beat signal of the measurement road, the influence of FM nonlinearity on the beat signal of the measurement road can be eliminated to a large extent, and the accuracy of the flight time obtained based on the corrected beat signal is improved, thereby improving Ranging accuracy.

In one possible embodiment, the predetermined condition _{(peak i -peak i-1)} / peak i-1 <Thr rate, Thr _rate as the third predetermined threshold value.

In a feasible embodiment, the non-linear iterative correction of the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time includes:

According to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement path beat frequency signal to obtain the target flight time, M is an integer greater than 1,

Among them, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ'i-1 to obtain the frequency modulation corresponding to the echo signal of the measurement path} The non-linear term ε(t-τ＇i _-1 ); the delayed flight time τ＇i _-1 is obtained based on the flight time τi _-1 ;

Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ＇ _i-1 ) corresponding to the echo signal of the measurement path to obtain the corrected beat signal; obtain the flight time τ according to the corrected beat signal _i ;

Among them, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .

By performing multiple FM nonlinear corrections on the measurement road beat signal, the influence of FM nonlinearity on the measurement road beat signal can be eliminated to a large extent, and the accuracy of the flight time obtained based on the corrected beat signal is improved. , Thereby improving the accuracy of ranging.

In a feasible embodiment, obtaining the flight time τ _i according to the corrected beat signal includes:

Perform FFT on the corrected beat frequency signal to obtain the frequency domain signal corresponding to the corrected beat frequency signal; obtain the flight time τ _i according to the frequency domain signal corresponding to the corrected beat frequency signal.

In one possible embodiment, the correction signal comprises a beat frequency signal a first correction or the second correction beat beat signal; an echo signal corresponding to the measured channel FM nonlinear term _{ε (t-τ 'i-} 1) of Measure the beat signal of the road and perform FM nonlinear correction to obtain the corrected beat signal, including:

When the signal-to-noise ratio of the beat frequency signal of the measurement path is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity term ε(t-τ) corresponding to the echo signal of the measurement path ＇ _I-1 ) Perform FM nonlinear term correction on the beat signal of the measurement road to obtain the first corrected beat signal; when the signal-to-noise ratio of the beat signal of the measurement road is lower than the second preset threshold, according to the measurement road The FM nonlinear term ε(t-τ′i _-1 ) corresponding to the wave signal performs receiving end FM nonlinear term correction on the compensated beat signal to obtain a second corrected beat signal;

Among them, the compensated beat signal is obtained based on the FM nonlinear term ε(t) of the laser emitting signal to compensate the FM nonlinear term of the transmitter of the measurement path beat signal.

When the signal-to-noise ratio of the measured road beat signal is very low, since the initial flight time calculated based on the measured road beat signal will have a large estimation error, in order to reduce the calculation error of the initial flight time and reduce the number of iterations, According to the frequency modulation nonlinear term ε(t) of the laser emission signal, the beat signal of the measurement path is compensated, and the compensated beat signal is obtained. Therefore, when correcting the beat signal of the measurement path, it is only necessary to calibrate the beat signal of the measurement path. The FM nonlinear term of the echo signal performs FM nonlinear correction on the compensated beat signal, and also eliminates the influence of FM nonlinearity on the beat signal of the measurement path.

In a feasible embodiment, calculating the initial flight time τ according to the measured road beat frequency signal includes:

When the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, perform FFT on the measured road beat signal to obtain the frequency domain signal corresponding to the measured road beat signal; The frequency domain signal determines the frequency of the measured road beat signal, and calculates the initial flight time τ according to the frequency of the measured road beat signal;

Wherein, the frequency of the measurement road beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the measurement road beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

In a feasible embodiment, calculating the initial flight time τ according to the measured road beat frequency signal includes:

When the signal-to-noise ratio of the measurement road beat signal is lower than the second preset threshold; according to the FM nonlinear term ε(t) of the laser emitting signal, the measurement road beat signal is compensated by the FM nonlinear term at the transmitting end. After the beat frequency signal; the frequency modulation nonlinear term of the laser emission signal is calculated based on the beat frequency signal of the reference path;

Perform FFT on the compensated beat signal to obtain the frequency domain signal corresponding to the compensated beat signal; determine the frequency of the compensated beat signal according to the frequency domain signal corresponding to the compensated beat signal, and according to the compensated beat signal Calculate the frequency of the beat signal to get the initial flight time τ;

The frequency of the compensated beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the compensated beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

When the signal-to-noise ratio of the measured road beat signal is very low, the initial flight time calculated based on the measured road beat signal will have a larger estimation error. Therefore, in order to reduce the calculation error of the initial flight time and reduce the number of iterations, Use the FM nonlinear term ε(t) of the laser emission signal to compensate the FM nonlinear term of the transmitter on the measuring path beat signal to obtain the beat signal after FM nonlinear term compensation at the transmitter. Only the beat signal remains The frequency modulation nonlinear term corresponding to the echo signal is calculated based on the beat signal to obtain the initial flight time τ with a smaller estimation error.

In a feasible embodiment, the frequency modulation nonlinear term ε(t) of the laser emission signal is calculated according to the reference path beat signal, including:

Perform Hilbert transform on the beat signal of the reference path to obtain the transformed beat signal; calculate the FM frequency of the laser emission signal according to the transformed beat signal; Calculate the FM frequency of the laser emission signal according to the FM frequency and ideal chirp frequency of the laser emission signal The frequency modulation nonlinear term ε(t) of the laser emission signal is calculated.

In a second aspect, an embodiment of the present application provides a ranging device based on frequency modulation nonlinear correction, including:

The acquisition unit is used to acquire the reference road beat signal and the measurement road beat signal, the reference road beat signal and the measurement road beat signal are respectively obtained based on the laser emission signal;

The calculation unit is used to calculate the frequency modulation nonlinearity according to the reference road beat frequency signal; and calculate the initial flight time τ according to the measured road beat frequency signal;

The calculation unit is further configured to calculate the frequency modulation nonlinearity term ε(t) of the laser emission signal according to the reference path beat signal when the determining unit determines that the frequency modulation nonlinearity is not less than the first preset threshold,

The correction unit is used to perform nonlinear iterative correction of the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time;

The calculation unit is used to calculate the target distance according to the target flight time.

By performing nonlinear iterative correction on the beat signal of the measurement circuit based on the flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal, the influence of the frequency modulation nonlinearity on the beat signal of the measurement circuit can be eliminated to a large extent. The influence minimizes the deviation between the last estimated target flight time and the target actual flight time, and the target distance can be determined according to the target flight time, which improves the ranging accuracy of the lidar.

In a feasible embodiment, the correction unit is specifically used for:

S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-) corresponding to the echo signal of the measurement path. 1} ), the delayed flight time τ'i _-1 is obtained based on the flight time τ _i-1 ;

S2: Perform FM nonlinear correction on the beat frequency signal of the measurement path according to the FM nonlinear term ε(t-τ＇i _{-1) corresponding to the echo signal of the measurement path to obtain a corrected beat frequency signal;}

S3. Determine the target flight time according to the corrected beat frequency signal.

In a feasible embodiment, in terms of determining the target flight time according to the corrected beat signal, the correction unit is specifically configured to:

_{Obtain the flight time τ i} according to the corrected beat signal; when the peak frequency peak _i meets the preset condition, the flight time τ _{i is} determined as the target flight time; when the peak frequency peak _i does not meet the preset condition, let i=i+ 1. Repeat the above steps S1-S3; the peak value of the spectrum peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

When i=1, peak _i-1 is the initial frequency spectrum peak, and the flight time τ _i-1 is the initial flight time τ.

In one possible embodiment, the predetermined condition _{(peak i -peak i-1)} / peak i-1 <Thr rate, Thr _rate as the third predetermined threshold value.

In a feasible embodiment, the correction unit is specifically configured to include:

According to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement road beat frequency signal to obtain the target flight time, M is an integer greater than 1,

Among them, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ'i-1 to obtain the frequency modulation corresponding to the echo signal of the measurement path} The non-linear term ε(t-τ＇i _-1 ); the delayed flight time τ＇i _-1 is obtained based on the flight time τi _-1 ;

Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ＇ _i-1 ) corresponding to the echo signal of the measurement path to obtain the corrected beat signal; obtain the flight time τ according to the corrected beat signal _i ;

Among them, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .

In a feasible embodiment, in terms of obtaining the flight time τ _i according to the corrected beat signal, the calculation unit is specifically configured to:

Perform FFT on the corrected beat frequency signal to obtain the frequency domain signal corresponding to the corrected beat frequency signal; obtain the flight time τ _i according to the frequency domain signal corresponding to the corrected beat frequency signal.

In a feasible embodiment, the corrected beat frequency signal includes the first corrected beat frequency signal or the second corrected beat frequency signal; according to the frequency modulation nonlinearity term ε(t-τ' _i-1 ) corresponding to the echo signal of the measurement path Perform FM nonlinear correction on the beat frequency signal of the measurement path to obtain the aspect of correcting the beat frequency signal. The correction unit is specifically used for:

When the signal-to-noise ratio of the beat frequency signal of the measurement path is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity term ε(t-τ) corresponding to the echo signal of the measurement path ＇ _I-1 ) Perform FM nonlinear term correction on the beat signal of the measurement road to obtain the first corrected beat signal; when the signal-to-noise ratio of the beat signal of the measurement road is lower than the second preset threshold, according to the measurement road The FM nonlinear term ε(t-τ′i _-1 ) corresponding to the wave signal performs receiving end FM nonlinear term correction on the compensated beat signal to obtain a second corrected beat signal;

Among them, the compensated beat signal is obtained based on the FM nonlinear term ε(t) of the laser emitting signal to compensate the FM nonlinear term of the transmitter of the measurement path beat signal.

In a feasible embodiment, in terms of calculating the initial flight time τ according to the measured road beat signal, the calculation unit is specifically configured to:

When the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, perform FFT on the measured road beat signal to obtain the frequency domain signal corresponding to the measured road beat signal; The frequency domain signal determines the frequency of the measured road beat signal, and calculates the initial flight time τ according to the frequency of the measured road beat signal;

Wherein, the frequency of the measurement road beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the measurement road beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

In a feasible embodiment, in terms of calculating the initial flight time τ according to the measured road beat signal, the calculation unit is specifically configured to:

When the signal-to-noise ratio of the measurement road beat signal is lower than the second preset threshold; according to the FM nonlinear term ε(t) of the laser emitting signal, the measurement road beat signal is compensated by the FM nonlinear term at the transmitting end. After the beat frequency signal; the frequency modulation nonlinear term of the laser emission signal is calculated based on the beat frequency signal of the reference path;

Perform FFT on the compensated beat signal to obtain the frequency domain signal corresponding to the compensated beat signal; determine the frequency of the compensated beat signal according to the frequency domain signal corresponding to the compensated beat signal, and according to the compensated beat signal Calculate the frequency of the beat signal to get the initial flight time τ;

The frequency of the compensated beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the compensated beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

In a feasible embodiment, in terms of calculating the frequency modulation nonlinear term ε(t) of the laser emission signal according to the reference path beat signal, the calculation unit is specifically configured to:

Perform Hilbert transform on the beat signal of the reference path to obtain the transformed beat signal; calculate the FM frequency of the laser emission signal according to the transformed beat signal; According to the FM frequency and ideal chirp of the laser emission signal Frequency calculation obtains the frequency modulation nonlinear term ε(t) of the laser emission signal.

In a third aspect, an embodiment of the present application provides a ranging device based on frequency modulation nonlinear correction, including:

Memory for storing instructions; and

At least one processor coupled with the memory;

Wherein, when the at least one processor executes the instruction, the instruction causes the processor to execute all or part of the method shown in the first aspect.

In a fourth aspect, an embodiment of the present application provides a computer storage medium that stores a computer program. The computer program includes program instructions that, when executed by a processor, cause the processor to execute All or part of the method shown on the one hand.

In a fifth aspect, an embodiment of the present application provides a laser radar, including a laser and a processor coupled with the laser, and the processor executes all or part of the method shown in the first aspect.

Description of the drawings

In order to more clearly describe the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art.

Figure 1 is a schematic diagram of the FMCW lidar ranging principle;

Figure 2 is a block diagram of the system architecture of FMCW lidar;

Figure 3 shows the beat signal under non-linear frequency modulation;

4 is a schematic diagram of a processing method based on modulated laser drive current predistortion in the prior art;

FIG. 5 is a schematic flowchart of a ranging method based on frequency modulation nonlinear correction according to an embodiment of the application;

FIG. 6 is a schematic flowchart of a non-linear iterative correction of a measurement road beat frequency signal provided by an embodiment of the application;

FIG. 7 is a schematic diagram of another flow chart for performing nonlinear iterative correction on measurement road beat frequency signals according to an embodiment of the application;

FIG. 8 is a schematic flowchart of another ranging method based on frequency modulation nonlinear correction provided by an embodiment of the application;

Figure 9a is a comparison diagram of ranging errors before and after nonlinear correction;

Figure 9b is the frequency spectrum of the beat signal after iterative correction of the nonlinear term;

10 is a schematic structural diagram of a ranging device based on frequency modulation nonlinear correction provided by an embodiment of the application;

FIG. 11 is a schematic structural diagram of another ranging device based on frequency modulation nonlinear correction provided by an embodiment of the application.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application.

In order to improve the accuracy of the ranging and increase the range of the ranging, a method of correcting the non-linearity of the frequency modulation has been proposed. Among the existing methods for correcting frequency modulation nonlinearity, a more common one is a processing method based on the predistortion of the modulated laser drive current. As shown in Figure 4, by estimating _{the frequency difference e k (t) between the actual output frequency v k} (t) of the current measurement laser and the ideal linear frequency v _d (t), the next measurement laser driving current u _{k+ is adjusted 1} (t) to change the output frequency of the laser in the next measurement. After multiple rounds of such iterative corrections, the laser output frequency tends to be linear in the end.

The main problem of this scheme is that by adjusting the drive current to control the output frequency of the laser, the nonlinearity can only be reduced to a relatively small range, but it cannot be completely eliminated in principle. In addition, the results of the current nonlinear correction can only be used for the next measurement. If due to the interference of external factors such as temperature and vibration, the output frequency of the laser in the next measurement is controlled by the drive current estimated by the predistortion in the last measurement, and the frequency value does not match the expected value, which leads to the previous predistortion The estimation result is invalid, and it fails to achieve the purpose of iterative correction.

The resampling algorithm is a method of FM nonlinear correction at the receiving end. The core idea is to resample the beat frequency signal through the estimated sampling time sequence, so that the signal becomes a single frequency signal again. The specific principle is as follows:

(1) Transmission signal:

(2) Echo signal: s _r (t) = s _t (t-τ)

(3) Beat signal:

(Ignore the higher-order terms of τ)

(4) Order

Then s′ _b (t)=exp{j2π[f ₀ +αt′]τ}

The t 'treated as new sample time series of the beat signal s' _b (t) for resampling, so that the beat frequency signal is resampled back single frequency signal.

Is the FM nonlinear term.

The premise of the re-sampling algorithm is that the delay τ of the beat signal is a small value, and the higher-order term of τ can be ignored. For a far target, the delay τ corresponding to the beat signal does not meet the premise assumptions. , Resulting in the corresponding ranging error after resampling is still very large. Therefore, the performance of resampling is related to the distance to be measured, which has great practical limitations.

Based on the foregoing reasons, this application proposes a schematic flow chart of a ranging method based on frequency modulation nonlinear correction. As shown in Figure 5, the method includes:

S501: Obtain a reference road beat signal and a measurement road beat signal.

Specifically, the laser signal emitted by the laser is divided into two paths, one path is the optical signal of the reference path, and the other path is the optical signal of the measurement path. Among them, the frequency and phase of the optical signal of the reference path and the optical signal of the measurement path are the same.

The optical signal of the reference path is divided into two paths, and the _{reference path beat signal s ref} (t) can be obtained by a Mach-Zehnder interferometer (MZI) _{with a preset fixed arm length difference of τ D.} Specifically, one optical signal passes through the short arm of the MZI, and the other optical signal passes through the long arm of the MZI. Because the two optical signals pass through different optical paths, the two optical signals are coherent on the photosensitive surface of the balanced detector to obtain a reference Road beat signal s _ref (t).

The optical signal of the measurement path is divided into two paths, one of which is a local oscillator signal, and the other is emitted to the measured target, and the echo signal is obtained by reflection on the surface of the target. The echo signal and the local oscillator signal are coherent on the photosensitive surface of the balanced detector to obtain the measurement road beat signal s _b (t).

S502: Calculate the frequency modulation nonlinearity according to the reference road beat frequency signal; and calculate the initial flight time τ according to the measured road beat frequency signal.

Specifically, calculating the frequency modulation nonlinearity according to the reference road beat signal includes:

Perform Hilbert transform on the reference road beat signal s _ref (t) to obtain the transformed signal H _b (t), and obtain the instantaneous phase of the reference road beat signal according to the transformed signal

in,

H _{b, real} = real(H _b (t)), H _{b, imag} = imag(H _b (t)), H _b (t)=hilbert(s _ref (t)), real(H _b (t) ) Is the real part of the transformed signal H _b (t), and imag(H _b (t)) is _{the imaginary part of the transformed signal H b} (t).

According to the instantaneous phase of the frequency modulation frequency f(t) of the laser emission signal and the beat frequency signal of the reference path

Calculate the frequency modulation frequency f(t) of the laser emission signal, where,

Calculate the non-linearity of the frequency modulation according to the frequency of the frequency modulation, the non-linearity of the frequency modulation

f _ideal (t) is the ideal chirp frequency, f _ideal (t)=f ₀ t+0.5αt ² , f ₀ is the carrier frequency, α is the corresponding FM slope when ideal chirp, and B is the FM bandwidth.

Optionally, the frequency modulation nonlinearity can also be based on the root mean square sum of the frequency modulation nonlinearity term of the laser emission signal (that is, the difference between the frequency modulation frequency f(t) of the laser emission signal and the ideal chirp frequency f _{ideal (t)).} The frequency modulation bandwidth (B) is calculated, and the frequency modulation nonlinearity can be expressed as:

Optionally, the degree of frequency modulation nonlinearity of the laser can be measured according to the degree of deviation between the frequency modulation frequency f(t) of the laser emission signal and the ideal chirp frequency f _{ideal (t), that is, f(t) and f ideal} (t) Root Mean Squard Error (RMSE) between

It should be noted here that both the FM frequency f(t) and the ideal chirp frequency f _ideal (t) can be regarded as discrete signals, so f _k is the frequency corresponding to the k-th discrete point on the FM frequency f(t), f _{ideal, k} is the frequency corresponding to the k-th discrete point on the ideal chirp frequency f _{ideal (t).}

S503. When the frequency modulation nonlinearity is not less than the first preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal is calculated according to the reference path beat frequency signal, and the frequency modulation nonlinearity term ε(t) of the laser emission signal is calculated according to the initial flight time τ and the frequency modulation nonlinearity of the laser emission signal The term ε(t) performs nonlinear iterative correction on the measured road beat signal to obtain the target flight time.

Wherein, the first preset threshold Thr _nonRate is the maximum non-linearity of the laser that can be received by the FMCW ranging system.

Specifically, the frequency modulation nonlinear term ε(t) of the laser emission signal is obtained based on the following formula:

In a feasible embodiment, calculating the initial flight time τ according to the measured road beat signal s _{b (t) includes:}

When the signal-to-noise ratio of the measured road beat signal s _b (t) is not less than the second preset threshold, _{fast FFT is performed on the measured road beat signal s b} (t) to obtain the measured road beat signal s _b (t ) corresponding to frequency domain signal based on the frequency-domain channel measurement signal to determine the beat signal s _b (t) of frequency f _b; when measured channel beat signal s _b (t) is less than a second predetermined threshold SNR , According to the frequency modulation non-linear term ε(t) of the laser emission signal, perform the frequency modulation non-linear term compensation at the transmitting end of the _{beat frequency signal s b (t) of the measuring path to obtain the compensated beat frequency signal s b} (t); beat signal s compensated _'b (t) for FFT, to obtain a frequency-domain signal of the beat signal corresponding to the compensated; according shot compensated pilot signal corresponding to a frequency domain signal to determine the beat signal s compensated' _b (t) of frequency f _'b; the beat signal s of frequency f _b or compensation of the beat signal' _b (t) of frequency f _'b calculated from the initial flight time [tau]; an initial flight time [tau] is f _b when the corresponding ideal chirp / α or f _'b / α, α chirp rate;

Wherein the measuring channel beat signal s _b (t) of frequency f _b for the measurement channel beat signal s _b (t) corresponding to the peak position frequency corresponding to the frequency domain signal, or a signal half-width of the center position of the frequency domain corresponding to a frequency; beat signal s compensated _'b (t) of frequency f' _b is a beat signal s compensated 'peak point _b (t) corresponding to the frequency domain signal corresponding to the position of the frequency or the frequency The frequency corresponding to the center of the half-height width of the domain signal.

In a feasible embodiment, the non-linear iterative correction is performed according to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal to obtain the target flight time, including:

S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-1) of the echo signal of the measurement path} ), wherein the delayed flight time τ'i _-1 is obtained based on the flight time τ _i-1 ;

S2, according to the FM nonlinear term corresponding to the echo signal of the measurement path, perform FM nonlinear term correction on the beat frequency signal of the measurement path to obtain a corrected beat frequency signal;

S3. Determine the target flight time according to the corrected beat frequency signal.

Further, determining the target flight time according to the corrected beat frequency signal includes:

_{Obtain the flight time τ i} according to the corrected beat signal; when the peak frequency peak _i meets the preset condition, the flight time τ _{i is} determined as the target flight time; when the peak frequency peak _i does not meet the preset condition, let i=i+ 1. Repeat steps S1-S3; the peak value of the spectrum peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

When i=1, peak _i-1 is the initial spectral peak, and the flight time τ _i-1 is the initial flight time τ.

The preset condition is (peak _{i -peak i-1} )/peak _i-1 <Thr _rate , and Thr _rate is the third preset threshold.

In a feasible embodiment, performing nonlinear iterative correction on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time includes:

According to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement path beat frequency signal to obtain the target flight time, M is an integer greater than 1,

Wherein, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ′ i-1 to obtain the measurement path echo} The non-linear term ε(t-τ＇i _-1 ) corresponding to the frequency modulation of the signal; the delayed flight time τ＇i _-1 is obtained based on the flight time τi _-1 ;

Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ＇ _i-1 ) corresponding to the echo signal of the measurement path to obtain the corrected beat signal; obtain the flight time τ according to the corrected beat signal _i ;

Among them, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .

In a feasible embodiment, obtaining the flight time τ _i according to the corrected beat signal includes:

Perform FFT on the corrected beat frequency signal to obtain a frequency domain signal corresponding to the corrected beat frequency signal, and obtain the flight time τ _i according to the frequency domain signal corresponding to the corrected beat frequency signal.

In one possible embodiment, the correction signal comprises a beat frequency signal a first correction or the second correction beat beat signal; an echo signal corresponding to the measured channel FM nonlinear term _{ε (t-τ 'i-} 1) of Measure the beat signal of the road and perform FM nonlinear correction to obtain the corrected beat signal, including:

When the signal-to-noise ratio of the beat frequency signal of the measurement path is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity term ε(t-τ) corresponding to the echo signal of the measurement path ＇ _I-1 ) Perform frequency modulation nonlinear term correction on the beat frequency signal of the measurement path to obtain the first corrected beat frequency signal;

When the signal-to-noise ratio of the beat frequency signal of the measurement path is lower than the second preset threshold, the compensated beat frequency signal _{ε(t-τ＇i-1) corresponding to the frequency modulation nonlinearity of the echo signal of the measurement path} Performing correction of the non-linear term of the FM at the receiving end to obtain the second corrected beat signal;

Among them, the compensated beat signal is based on the FM nonlinear term ε(t) of the laser emission signal to compensate for the FM nonlinear term at the transmitting end of the beat signal of the measuring path, so the compensated beat signal can also be called It is a beat signal that has been compensated for FM nonlinearity at the transmitter.

Specifically, when the signal-to-noise ratio of the measured road beat signal s _b (t) is not lower than the second preset threshold, according to the frequency modulation nonlinear term ε(t) of the laser emission signal and the frequency modulation nonlinear term of the echo signal ε(t-τ _i ) Perform frequency modulation nonlinear term correction on the measurement path beat signal s _b (t) to obtain the first corrected beat signal

When the signal-to-noise ratio of the measured road beat signal s _b (t) is lower than the second preset threshold, the FM nonlinearity term ε(t-τ _i ) of the measured road echo signal is performed on the transmitter. beat signal s' _b (t) FM reception terminal nonlinear term compensation corrected to obtain a second corrected beat signal

Specifically, as shown in Figure 6:

S10A. Obtain the delayed flight time _τ'i-1 according to the flight time τ _i-1 .

Optionally, the delayed flight time τ′ _i-1 =τ _i-1 +p, where p is the preset step length. Of course, the delayed flight time τ′ _i-1 can also be obtained based on other methods.

S20A. Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-1) of the echo signal of the measurement path} ).

In other words, the FM nonlinear term ε(t) of the laser emission signal is _{delayed by τ′ i-1} to obtain the FM nonlinear term ε(t-τ′ _i-1 ) of the echo signal of the measurement path.

S30A. When the signal-to-noise ratio of the measured road beat signal s _b (t) is not lower than the second preset threshold, according to the frequency modulation non-linear term ε(t) of the laser emission signal and the frequency modulation non-linearity of the echo signal of the measurement road The term ε(t-τ＇i _-1 ) performs FM nonlinear term correction on the measurement path beat signal s _b (t) to obtain the first corrected beat signal

Among them, the first corrected beat signal is:

s _b (t) is the initial beat signal of the measurement path, in other words, s _b (t) is the corresponding beat signal before the iterative correction of the nonlinear term of the measurement path. When the signal-to-noise ratio of the measured road beat signal s _b (t) is lower than the second preset threshold, the transmitted frequency modulation is performed according to the frequency modulation non-linear term ε(t-τ＇ _i-1 ) of the measured road echo signal the beat signal s nonlinearity compensation _'b (t) FM reception terminal nonlinear term correction, the second correction to obtain a beat signal

Among them, the second corrected beat signal is:

The first corrected beat signal

Or the second corrected beat signal

Perform FFT to obtain the first corrected beat signal

Or the second corrected beat signal

The corresponding frequency domain signal is used to obtain the flight time τ _i and the spectral peak value peak _i based on the frequency domain signal.

Specifically, the frequency of the first corrected beat signal is determined according to the frequency domain signal corresponding to the first corrected beat signal, and the flight time τ _i is determined according to the frequency of the first corrected beat signal; or corresponding to the second corrected beat signal Determine the frequency of the second corrected beat signal from the frequency domain signal, and determine the flight time τ _i according to the frequency of the second corrected beat signal.

The frequency of the first corrected beat signal is the frequency corresponding to the peak _i position of the frequency domain signal corresponding to the first corrected beat signal, or the frequency corresponding to the center position of the half-height width of the frequency domain signal; the second corrected beat frequency _{The frequency of the signal is the frequency corresponding to the peak i} position of the frequency domain signal corresponding to the second corrected beat frequency signal, or the frequency corresponding to the center position of the half-height width of the frequency domain signal.

S40A. When (peak _i -peak _i-1 )/peak _i-1 ＞= Thr _rate , set i=1+1, and repeat steps S10A-S40A; when (peak _i -peak _i-1 )/peak _{When i-1} &lt; Thr _rate , step S50A is executed. Wherein, Thr _rate is a third preset threshold, and the third preset threshold is a peak growth rate threshold.

Among them, when i=1, peak _i-1 is the initial peak of the spectrum, and the flight time τ _i-1 is the initial flight time τ. When _{the signal-to-noise ratio of the measured road beat signal s b} (t) is not lower than the second predetermined When the threshold is set, the initial spectral peak value is the peak value of the frequency domain signal corresponding _{to the measured road beat signal s b (t); when the signal-to-noise ratio of the measured road beat signal s b} (t) is lower than the second preset threshold, Sign initial spectrum peak frequency compensated signal s peak _'b (t) corresponding to a frequency domain signal.

S50A. Determine the target flight time as the flight time τ _i .

More specifically, as shown in Figure 7:

S10B. Obtain the delayed flight time _τ'i-1 according to the flight time τ _i-1 . Optionally, the delayed flight time τ′ _i-1 =τ _i-1 +p, where p is the preset step length. Of course, the delayed flight time τ′ _i-1 can also be obtained based on other methods.

S20B. Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-1) of the echo signal of the measurement path} ). In other words, the FM nonlinear term ε(t) of the laser emission signal is _{delayed by τ′ i-1} to obtain the FM nonlinear term ε(t-τ′ _i-1 ) of the echo signal of the measurement path.

S30B. When the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, according to the frequency modulation nonlinear term ε(t) of the laser emission signal and the frequency modulation nonlinear term ε(t- τ＇ _i-1 ) Perform FM nonlinear term correction on the measurement path beat signal s _b (t) to obtain the first corrected beat signal

And according to the first corrected beat signal

Obtain the flight time τ _i and the spectral peak peak _i . Among them, the first corrected beat signal is:

s _b (t) is the measurement road beat frequency signal. When the signal-to-noise ratio of the beat frequency signal of the measurement path is lower than the second preset threshold, according to the FM nonlinearity term ε(t-τ＇ _i-1 ) of the echo signal of the measurement path, after the non-linear term of the transmitter FM is compensated beat signal s' _b (t) FM reception terminal nonlinear term correction, the second correction to obtain a beat signal

And according to the second correction beat signal

Obtain the flight time τ _i and the spectral peak peak _i . Among them, the second corrected beat signal is:

Specifically, the frequency of the first corrected beat signal is determined according to the frequency domain signal corresponding to the first corrected beat signal, and the flight time τ _i is determined according to the frequency of the first corrected beat signal; or corresponding to the second corrected beat signal Determine the frequency of the second corrected beat signal from the frequency domain signal, and determine the flight time τ _i according to the frequency of the second corrected beat signal.

The frequency of the first corrected beat signal is the frequency corresponding to the peak _i position of the frequency domain signal corresponding to the first corrected beat signal, or the frequency corresponding to the center position of the half-height width of the frequency domain signal; the second corrected beat frequency _{The frequency of the signal is the frequency corresponding to the peak i} position of the frequency domain signal corresponding to the second corrected beat frequency signal, or the frequency corresponding to the center position of the half-height width of the frequency domain signal.

S40B. When i<M, set i=1+1, and repeat steps S10B-S40B; when i=M, perform step S50B.

S50B. Target flight time = flight time τ _i .

Among them, when i=1, the flight time τ _i-1 is the initial flight time; when i=M, the target flight time is the flight time τ _i .

It should be noted here that before the method shown in FIG. 7 is executed, i is initialized so that i=1.

S504: Calculate the target distance according to the target flight time.

Among them, the target distance R=cT/2, c is the speed of light, and T is the target flight time.

In a specific embodiment, as shown in FIG. 8, the beat signal of the reference path is obtained, and the optical signal of the reference path is specifically divided into two paths. The reference path can be obtained by presetting the MZI with the _{fixed arm length difference τ D.} The beat signal s _ref (t). One of the optical signals passes through the short arm of the MZI, and the other optical signal passes through the long arm of the MZI. Because the two optical signals pass through different optical paths, the two optical signals are coherent on the photosensitive surface of the balanced detector to obtain the reference path beat frequency The signal s _ref (t).

After obtaining the reference path beat frequency signal s _ref (t), the frequency modulation frequency f(t) of the laser emission signal is calculated according to the reference path beat frequency signal s _{ref (t).} Specifically, the Hilbert transform is performed on the reference road beat frequency signal s _ref (t) to obtain the transformed beat frequency signal H _b (t), which can be expressed as H _b (t)=hilbert( s _ref (t)), and then obtain the instantaneous phase of the beat frequency signal of the reference path according to the transformed beat frequency signal

The instantaneous phase

Can be expressed as:

Among them, H _{b, imag} is the imaginary part of H _b (t), and H _{b, real} is the real part of H _b (t).

According to the frequency modulation frequency f(t) of the laser emission signal, the frequency modulation nonlinearity term ε(t) and the frequency modulation nonlinearity non _{rate of the} laser emission signal are calculated. Specifically, according to the instantaneous phase of the frequency modulation frequency f(t) of the laser emission signal and the beat frequency signal of the reference path

Calculate the FM frequency f(t) from the relationship, where,

Then calculate the frequency modulation nonlinearity term ε(t) and the frequency modulation nonlinearity non _{rate of the} laser emission signal according to the frequency modulation frequency f(t). Frequency modulation nonlinear term of laser emission signal

FM nonlinearity

Among them, f _ideal (t) is the ideal chirp frequency, f _ideal (t)=f ₀ t+0.5αt ² , f ₀ is the carrier frequency, α is the corresponding FM slope when ideal chirp, and B is the FM bandwidth.

Optionally, the frequency modulation nonlinearity can also be based on the root mean square sum of the frequency modulation nonlinearity term of the laser emission signal (that is, the difference between the frequency modulation frequency f(t) of the laser emission signal and the ideal chirp frequency f _{ideal (t)).} The frequency modulation bandwidth (B) is calculated, and the frequency modulation nonlinearity can be expressed as:

Optionally, the degree of frequency modulation nonlinearity of the laser can be measured according to the degree of deviation between the frequency modulation frequency f(t) of the laser emission signal and the ideal chirp frequency f _{ideal (t), that is, f(t) and f ideal} (t) Root Mean Squard Error (RMSE) between

It should be noted here that both the FM frequency f(t) and the ideal chirp frequency f _ideal (t) can be regarded as discrete signals, so f _k is the frequency corresponding to the k-th discrete point on the FM frequency f(t), f _{ideal, k} is the frequency corresponding to the k-th discrete point on the ideal chirp frequency f _{ideal (t).}

Obtain the beat signal of the measurement path, specifically, divide the optical signal of the measurement path into two paths, where one signal is used as a local oscillator signal, and the other signal is transmitted to the measured target, and the echo signal is obtained by reflection on the target surface. The echo signal and the local oscillator signal are coherent on the photosensitive surface of the balanced detector to obtain the measurement road beat signal s _b (t).

Perform FFT on the beat frequency signal of the measurement path, and calculate the frequency f _b and the spectral peak peak _{last of the} beat frequency signal. Specifically, when the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, _{perform FFT on the measured road beat signal s b} (t) to obtain the frequency domain signal corresponding to the measured road beat signal, based on The frequency domain signal is calculated to obtain the frequency f _{b of the} measured road beat signal and the peak value of the spectrum peak _last , and the flight time τ is calculated according to the frequency f _{b of the} measured road beat signal; when the signal to noise ratio of the measured road beat signal is lower than when a second preset threshold, compensating for the nonlinear term FM transmitter according to the FM nonlinear term ε (t) of the signal emitted by the laser measurement channel beat signal, a beat signal s to obtain the compensated _'b (t); of the beat signal s compensated _'b (t) for an FFT, a beat signal corresponding to the frequency-domain signal is compensated for, based on the beat signal s from the frequency domain signal calculated measurement path compensating' _b (t) of frequency f _'b and peak _last spectral peaks, the spectrum peak at this time is compensated peak _last beat frequency peak frequency domain signal corresponding to the signal, and the frequency f in accordance with the beat frequency signal after the measurement path compensating' _b is calculated flight time τ .

When the frequency modulation nonlinearity non _{rate is} greater than the first preset threshold Thr _nonRate , the flight time τ is updated according to the step length p, and the updated flight time is τ=τ+p, and the frequency modulation nonlinearity term ε(t ) Perform an updated flight time τ delay to obtain the FM nonlinear term ε(t-τ) of the echo signal corresponding to the measurement path; when the signal-to-noise ratio of the beat frequency signal of the measurement path is not lower than the second preset When the threshold is used, the FM nonlinear term is corrected according to the FM nonlinear term ε(t) and the FM nonlinear term ε(t-τ) on the measurement path beat signal s _b (t) to obtain the first corrected beat signal

When the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, the beat frequency that has been compensated for the originating FM nonlinearity term ε(t-τ) corresponding to the measured road echo signal pilot signal s' _b (t) for correcting the nonlinear term FM receiving end, the beat signal to obtain a second corrected

The first corrected beat signal

Or the second corrected beat signal

Perform FFT to get the first corrected beat signal

Or the second corrected beat signal

Corresponding frequency domain signal, calculate the first corrected beat frequency signal based on the frequency domain signal

Or the second corrected beat signal

The frequency and spectral peak peakcurr, according to the first corrected beat signal

Or the second corrected beat signal

The frequency is calculated to get the flight time τ.

When (peak _curr -peak _last )/peak _last ＞= Thr _rate , to correct the beat signal according to the first correction

Or the second corrected beat signal

Update the flight time τ calculated by the frequency of, to obtain the updated flight time, and repeat the above steps until (peak _curr -peak _last )/peak _last ＜Thr _rate ;

When (peak _curr -peak _last )/peak _last <Thr _rate , the target distance R=cτ/2 is calculated based on the flight time τ calculated according to the frequency of the corrected beat signal, and c is the speed of light, that is, the measured target The distance from the radar.

Figure 9a shows that the FM nonlinearity correction method of the present application effectively improves the accuracy of distance estimation in the case of FM nonlinearity. It can be seen from Fig. 9b that after the iterative correction of the nonlinear term of this application, the spectral peak of the beat signal gradually increases and is close to the ideal value. Therefore, the nonlinear correction method of this application can effectively increase the beat frequency in the case of frequency modulation nonlinearity. The signal-to-noise ratio in the frequency domain of the signal can effectively increase the farthest ranging range.

It can be seen that, in the embodiment of the present application, the frequency modulation nonlinearity of the measurement path signal can be corrected according to the frequency modulation nonlinearity term of the laser emission signal and the frequency modulation nonlinearity term of the measurement path echo signal. Eliminate the influence of non-linear frequency modulation on the measured road beat signal, improve the accuracy of the flight time based on the corrected beat signal, and further improve the ranging accuracy.

Refer to FIG. 10, which is a schematic structural diagram of a distance measurement device based on frequency modulation nonlinear correction provided by an embodiment of the application. As shown in FIG. 10, the distance measuring device 1000 includes:

The acquiring unit 1001 is used to acquire the reference road beat signal and the measurement road beat signal, the reference road beat signal and the measurement road beat signal are obtained based on the laser emission signal respectively;

The calculation unit 1002 is configured to calculate the frequency modulation nonlinearity according to the reference road beat signal; and calculate the initial flight time τ according to the measured road beat signal;

The calculation unit 1002 is further configured to calculate the frequency modulation nonlinearity term ε(t) of the laser emission signal according to the reference path beat signal when the determining unit 1004 determines that the frequency modulation nonlinearity is not less than the first preset threshold,

The correction unit 1003 is configured to perform nonlinear iterative correction on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time;

The calculation unit 1002 is configured to calculate the target distance according to the target flight time.

In a feasible embodiment, the correction unit 1003 is specifically configured to:

S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′ _{i-1 to obtain the FM nonlinear term ε(t-τ′ i-) corresponding to the echo signal of the measurement path. 1} ), the delayed flight time τ'i _-1 is obtained based on the flight time τ _i-1 ;

S2: Perform FM nonlinear correction on the beat frequency signal of the measurement path according to the FM nonlinear term ε(t-τ＇i _{-1) corresponding to the echo signal of the measurement path to obtain a corrected beat frequency signal;}

S3. Determine the target flight time according to the corrected beat frequency signal.

In a feasible embodiment, in terms of determining the target flight time according to the corrected beat signal, the correction unit 1003 is specifically configured to:

_{Obtain the flight time τ i} according to the corrected beat signal; when the peak frequency peak _i meets the preset condition, the flight time τ _{i is} determined as the target flight time; when the peak frequency peak _i does not meet the preset condition, let i=i+ 1. Repeat the above steps S1-S3; the peak value of the spectrum peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

When i=1, peak _i-1 is the initial frequency spectrum peak, and the flight time τ _i-1 is the initial flight time τ.

In one possible embodiment, the predetermined condition _{(peak i -peak i-1)} / peak i-1 <Thr rate, Thr _rate as the third predetermined threshold value.

In a feasible embodiment, the correction unit 1003 is specifically configured to include:

According to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement path beat frequency signal to obtain the target flight time, M is an integer greater than 1,

Among them, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ'i-1 to obtain the frequency modulation corresponding to the echo signal of the measurement path} The non-linear term ε(t-τ＇i _-1 ); the delayed flight time τ＇i _-1 is obtained based on the flight time τi _-1 ;

Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ＇ _i-1 ) corresponding to the echo signal of the measurement path to obtain the corrected beat signal; obtain the flight time τ according to the corrected beat signal _i ;

Among them, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .

In a feasible embodiment, in terms of obtaining the flight time τ _i according to the corrected beat signal, the calculation unit 1002 is specifically configured to:

Perform FFT on the corrected beat frequency signal to obtain the frequency domain signal corresponding to the corrected beat frequency signal; obtain the flight time τ _i according to the frequency domain signal corresponding to the corrected beat frequency signal.

In a feasible embodiment, the corrected beat frequency signal includes the first corrected beat frequency signal or the second corrected beat frequency signal; according to the frequency modulation nonlinearity term ε(t-τ' _i-1 ) corresponding to the echo signal of the measurement path Performing FM nonlinear correction on the beat signal of the measurement path to obtain the aspect of correcting the beat signal, the correction unit 1003 is specifically used for:

When the signal-to-noise ratio of the beat frequency signal of the measurement path is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity term ε(t-τ) corresponding to the echo signal of the measurement path ＇ _I-1 ) Perform FM nonlinear term correction on the beat signal of the measurement road to obtain the first corrected beat signal; when the signal-to-noise ratio of the beat signal of the measurement road is lower than the second preset threshold, according to the measurement road The FM nonlinear term ε(t-τ′i _-1 ) corresponding to the wave signal performs receiving end FM nonlinear term correction on the compensated beat signal to obtain a second corrected beat signal;

Among them, the compensated beat signal is obtained based on the FM nonlinear term ε(t) of the laser emitting signal to compensate the FM nonlinear term of the transmitter of the measurement path beat signal.

In a feasible embodiment, in terms of calculating the initial flight time τ according to the measured road beat signal, the calculation unit 1002 is specifically configured to:

When the signal-to-noise ratio of the measured road beat signal is not lower than the second preset threshold, perform FFT on the measured road beat signal to obtain the frequency domain signal corresponding to the measured road beat signal; The frequency domain signal determines the frequency of the measured road beat signal, and calculates the initial flight time τ according to the frequency of the measured road beat signal;

Wherein, the frequency of the measurement road beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the measurement road beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

In a feasible embodiment, in terms of calculating the initial flight time τ according to the measured road beat signal, the calculation unit 1002 is specifically configured to:

When the signal-to-noise ratio of the measurement road beat signal is lower than the second preset threshold; according to the FM nonlinear term ε(t) of the laser emitting signal, the measurement road beat signal is compensated by the FM nonlinear term at the transmitting end. After the beat frequency signal; the frequency modulation nonlinear term of the laser emission signal is calculated based on the beat frequency signal of the reference path;

Perform FFT on the compensated beat signal to obtain the frequency domain signal corresponding to the compensated beat signal; determine the frequency of the compensated beat signal according to the frequency domain signal corresponding to the compensated beat signal, and according to the compensated beat signal Calculate the frequency of the beat signal to get the initial flight time τ;

The frequency of the compensated beat signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the compensated beat signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal.

In a feasible embodiment, the calculation unit 1002 is specifically configured to:

Perform Hilbert transform on the beat signal of the reference path to obtain the transformed beat signal; calculate the FM frequency of the laser emission signal according to the transformed beat signal; According to the FM frequency and ideal chirp of the laser emission signal Frequency calculation obtains the frequency modulation nonlinear term ε(t) of the laser emission signal.

It should be noted that the aforementioned units (the acquisition unit 1001, the calculation unit 1002, the correction unit 1003, and the determination unit 1004) are used to execute the relevant steps of the aforementioned method. For example, the acquiring unit 1001 is used to execute the related content of step S501, the calculating unit 1002 is used to execute the related content of steps S502 and S504, and the correction unit 1003 and the determining unit 1004 are used to execute the related content of step S503.

In this embodiment, the ranging device 1000 based on frequency modulation nonlinear correction is presented in the form of a unit. The "unit" here can refer to an application-specific integrated circuit (ASIC), a processor and memory that executes one or more software or firmware programs, an integrated logic circuit, and/or other devices that can provide the above-mentioned functions . In addition, the above acquisition unit 1001, calculation unit 1002, correction unit 1003, and determination unit 1004 may be implemented by the processor 1101 of the distance measurement device based on frequency modulation nonlinear correction shown in FIG. 11.

The distance measuring device 1100 shown in FIG. 11 can be implemented with the structure in FIG. 11, and the distance measuring device 1100 includes at least one processor 1101, at least one memory 1102 and at least one communication interface 1103. The processor 1101, the memory 1102, and the communication interface 1103 are connected through the communication bus and complete mutual communication.

The processor 1101 may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of the above program programs.

The communication interface 1103 is used to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area network (Wireless Local Area Networks, WLAN), etc.

The memory 1102 may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, random access memory (RAM), or other types that can store information and instructions The dynamic storage device can also be electrically erasable programmable read-only memory (Electrically Erasable Programmable Read-Only Memory, EEPROM), CD-ROM (Compact Disc Read-Only Memory, CD-ROM) or other optical disc storage, optical disc storage (Including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or can be used to carry or store desired program codes in the form of instructions or data structures and can be used by a computer Any other media accessed, but not limited to this. The memory can exist independently and is connected to the processor through a bus. The memory can also be integrated with the processor.

Wherein, the memory 1102 is used to store application program codes for executing the above solutions, and the processor 1101 controls the execution. The processor 1101 is configured to execute application program codes stored in the memory 1102.

The code stored in the memory 1102 can execute the above-provided ranging method based on FM nonlinear correction, such as obtaining the reference road beat signal and measuring road beat signal; calculating the FM nonlinearity based on the reference road beat signal; and according to the measurement The initial flight time τ is calculated from the road beat frequency signal; when the frequency modulation nonlinearity is not less than the first preset threshold, the frequency modulation nonlinear term ε(t) of the laser emission signal is calculated according to the reference road beat frequency signal, according to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal perform non-linear iterative correction on the measurement road beat signal to obtain the target flight time; the target distance is calculated according to the target flight time.

An embodiment of the present application further provides a computer storage medium, wherein the computer storage medium may store a program, and when the program is executed, it includes any part or All steps.

It should be noted that for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that this application is not limited by the described sequence of actions. Because according to this application, some steps can be performed in other order or at the same time. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by this application.

In the above-mentioned embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in an embodiment, reference may be made to related descriptions of other embodiments.

In the several embodiments provided in this application, it should be understood that the disclosed device may be implemented in other ways. For example, the device embodiments described above are merely illustrative, for example, the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components may be combined or may be Integrate into another system, or some features can be ignored or not implemented. In addition, the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical or other forms.

The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, the functional units in the various embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or software functional unit.

If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable memory. Based on this understanding, the technical solution of the present application essentially or the part that contributes to the existing technology or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a memory. A number of instructions are included to enable a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned memory includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

Those of ordinary skill in the art can understand that all or part of the steps in the various methods of the above-mentioned embodiments can be completed by a program instructing relevant hardware. The program can be stored in a computer-readable memory, and the memory can include: a flash disk , Read-only memory (English: Read-Only Memory, abbreviation: ROM), random access device (English: Random Access Memory, abbreviation: RAM), magnetic disk or optical disc, etc.

The embodiments of the application are described in detail above, and specific examples are used in this article to illustrate the principles and implementation of the application. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the application; at the same time, for Those of ordinary skill in the art, based on the ideas of the application, will have changes in the specific implementation and the scope of application. In summary, the content of this specification should not be construed as limiting the application.

Claims (23)

1. A ranging method based on frequency modulation nonlinear correction, which is characterized in that it comprises:

   Acquiring a reference road beat signal and a measurement road beat signal; the reference road beat signal and the measurement road beat signal are respectively obtained based on the laser emission signal;

   Calculate the frequency modulation nonlinearity according to the reference road beat signal; and calculate the initial flight time τ according to the measured road beat signal;

   It is determined that the frequency modulation nonlinearity is not less than a first preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal is calculated according to the reference path beat frequency signal, and the frequency modulation nonlinearity term ε(t) is calculated according to the initial flight time τ and the The frequency modulation nonlinear term ε(t) of the laser emission signal performs nonlinear iterative correction on the measurement path beat frequency signal to obtain the target flight time;

   The target distance is calculated according to the target flight time.
2. The method according to claim 1, characterized in that the non-linear iterative correction is performed on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal to Get the target flight time, including:

   S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′i _-1 to obtain the FM nonlinear term ε(t) corresponding to the echo signal of the measurement path t-τ′ _i-1 ), the delayed flight time τ′ _i-1 is obtained based on the flight time τ _i-1 ;

   S2: Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ′ _{i-1) corresponding to the measurement path echo signal to obtain a corrected beat signal;}

   S3. Determine the target flight time according to the corrected beat frequency signal.
3. The method according to claim 2, wherein the determining the target flight time according to the corrected beat frequency signal comprises:

   _{Obtain the flight time τ i} according to the corrected beat frequency signal;

   When the spectral peak _i meets a preset condition, the flight time τ _{i is} determined as the target flight time; when the spectral peak _i does not meet the preset condition, let i=i+1 , And repeat steps S1-S3; the spectrum peak peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

   When i=1, the peak _i-1 is the initial frequency spectrum peak, and the flight time τ _i-1 is the initial flight time τ.
4. The method according to claim 3, wherein said predetermined condition is a _{(peak i -peak i-1)} / peak i-1 <Thr rate, the Thr _rate is a third predetermined threshold value.
5. The method according to claim 1, characterized in that the non-linear iterative correction is performed on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation non-linear term ε(t) of the laser emission signal to Get the target flight time, including:

   According to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement path beat frequency signal to obtain the target flight time, where M is An integer greater than 1,

   Wherein, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ′ i-1 to obtain the measurement path echo} The FM nonlinear term ε(t-τ′ _i-1 ) corresponding to the signal; the delayed flight time τ′ _i-1 is obtained based on the flight time τ _i-1 ;

   Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ′ _i-1 ) corresponding to the echo signal of the measurement path to obtain a corrected beat signal; Frequency signal to obtain flight time τ _i ;

   Wherein, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .
6. The method according to any one of claims 3 to 5, characterized in that the obtaining the flight time τ _i according to the corrected beat frequency signal comprises:

   Performing fast Fourier transform FFT on the corrected beat frequency signal to obtain a frequency domain signal corresponding to the corrected beat frequency signal;

   _{Obtain the flight time τ i} according to the frequency domain signal corresponding to the corrected beat frequency signal.
7. The method according to any one of claims 2-6, wherein the corrected beat frequency signal comprises a first corrected beat frequency signal or a second corrected beat frequency signal; the echo signal corresponding to the measurement path corresponds to The FM nonlinear term ε(t-τ′ _i-1 ) performs FM nonlinear correction on the beat frequency signal of the measurement path to obtain a corrected beat frequency signal, including:

   When the signal-to-noise ratio of the measurement path beat signal is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity corresponding to the measurement path echo signal The term ε(t-τ′ _i-1 ) performs frequency modulation nonlinear term correction on the measurement path beat signal to obtain the first corrected beat signal;

   When the signal-to-noise ratio of the measurement path beat frequency signal is lower than the second preset threshold value, the frequency modulation nonlinearity term ε(t-τ′ _i-1 ) corresponding to the measurement path echo signal is compared to the The compensated beat frequency signal is corrected by a frequency modulation nonlinear term at the receiving end to obtain the second corrected beat frequency signal;

   Wherein, the compensated beat frequency signal is obtained based on the frequency modulation nonlinearity term ε(t) of the measurement path beat frequency signal at the transmitting end according to the frequency modulation nonlinearity term ε(t) of the laser transmitting signal.
8. The method according to claim 7, wherein the calculating the initial flight time τ according to the measured road beat frequency signal comprises:

   When the signal-to-noise ratio of the measurement road beat signal is not lower than a second preset threshold, perform an FFT on the measurement road beat signal to obtain a frequency domain signal corresponding to the measurement road beat signal;

   Determine the frequency of the measurement road beat signal according to the frequency domain signal corresponding to the measurement road beat signal, and calculate the initial flight time τ according to the frequency of the measurement road beat signal;

   Wherein, the frequency of the measurement path beat signal is a frequency corresponding to a peak point position of a frequency domain signal corresponding to the measurement path beat signal, or a frequency corresponding to a midpoint position of a half-height width of the frequency domain signal.
9. The method according to claim 7, wherein the calculating the initial flight time τ according to the measured road beat frequency signal comprises:

   When the signal-to-noise ratio of the measurement path beat frequency signal is lower than the second preset threshold; perform the frequency modulation nonlinearity at the transmitting end of the measurement path beat frequency signal according to the frequency modulation nonlinearity term ε(t) of the laser emission signal Term compensation to obtain the compensated beat frequency signal; the frequency modulation nonlinear term of the laser emission signal is calculated based on the reference path beat frequency signal;

   Performing FFT on the compensated beat signal to obtain a frequency domain signal corresponding to the compensated beat signal;

   Determine the frequency of the compensated beat signal according to the frequency domain signal corresponding to the compensated beat signal, and calculate the initial flight time τ according to the frequency of the compensated beat signal;

   Wherein, the frequency of the compensated beat frequency signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the compensated beat frequency signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal .
10. The method according to any one of claims 1-9, wherein the calculation of the frequency modulation nonlinear term ε(t) of the laser emission signal according to the reference path beat frequency signal comprises:

    Performing Hilbert transform on the reference road beat signal to obtain a transformed beat signal;

    Calculating the frequency modulation frequency of the laser emission signal according to the converted beat frequency signal;

    According to the frequency modulation frequency of the laser emission signal and the ideal chirp frequency, the frequency modulation nonlinear term ε(t) of the laser emission signal is calculated.
11. A distance measuring device based on frequency modulation nonlinear correction, which is characterized in that it comprises:

    The acquisition unit is used to acquire the reference road beat frequency signal and the measurement road beat frequency signal;

    The calculation unit is configured to calculate the frequency modulation nonlinearity according to the reference road beat signal; and calculate the initial flight time τ according to the measured road beat signal;

    The determining unit is configured to determine that the frequency modulation nonlinearity is not less than a first preset threshold, and the calculation unit is further configured to calculate the frequency modulation nonlinearity term ε(t ),

    A correction unit, configured to perform nonlinear iterative correction on the measurement path beat frequency signal according to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal to obtain the target flight time;

    The calculation unit is further configured to calculate the target distance according to the target flight time.
12. The device according to claim 11, wherein the correction unit is specifically configured to:

    S1: Delay the FM nonlinear term ε(t) of the laser emission signal according to the delay flight time τ′i _-1 to obtain the FM nonlinear term ε(t) corresponding to the echo signal of the measurement path t-τ′ _i-1 ), the delayed flight time τ′ _i-1 is obtained based on the flight time τ _i-1 ;

    S2: Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ′ _{i-1) corresponding to the measurement path echo signal to obtain a corrected beat signal;}

    S3. Determine the target flight time according to the corrected beat frequency signal.
13. The device according to claim 12, wherein, in the aspect of determining the target flight time according to the corrected beat signal, the correction unit is specifically configured to:

    _{Obtain the flight time τ i} according to the corrected beat frequency signal;

    When the spectral peak _i meets a preset condition, the flight time τ _{i is} determined as the target flight time; when the spectral peak _i does not meet the preset condition, let i=i+1 , And repeat steps S1-S3; the spectrum peak peak _i is the peak value of the frequency domain signal corresponding to the corrected beat signal;

    When i=1, the peak _i-1 is the initial frequency spectrum peak, and the flight time τ _i-1 is the initial flight time τ.
14. The apparatus according to claim 13, wherein said predetermined condition is a _{(peak i -peak i-1)} / peak i-1 <Thr rate, the Thr _rate is a third predetermined threshold value.
15. The device according to claim 11, wherein the correction unit is specifically configured to:

    According to the initial flight time τ and the frequency modulation nonlinear term ε(t) of the laser emission signal, perform M non-linear iterative calculations on the measurement path beat frequency signal to obtain the target flight time, where M is An integer greater than 1,

    Wherein, when the i-th nonlinear iterative calculation is performed, the frequency modulation nonlinear term ε(t) of the laser emission signal is _{delayed according to the delay flight time τ′ i-1 to obtain the measurement path echo} The FM nonlinear term ε(t-τ′ _i-1 ) corresponding to the signal; the delayed flight time τ′ _i-1 is obtained based on the flight time τ _i-1 ;

    Perform FM nonlinear correction on the measurement path beat signal according to the FM nonlinear term ε(t-τ′ _i-1 ) corresponding to the echo signal of the measurement path to obtain a corrected beat signal; Frequency signal to obtain flight time τ _i ;

    Wherein, when i=1, the flight time τ _i-1 is the initial flight time τ; when i=M, the target flight time is the flight time τ _i .
16. The device according to any one of claims 13-15, wherein, in the _{aspect of acquiring the flight time τ i} according to the corrected beat frequency signal, the correction unit is specifically configured to:

    Performing fast Fourier transform FFT on the corrected beat frequency signal to obtain a frequency domain signal corresponding to the corrected beat frequency signal;

    _{Obtain the flight time τ i} according to the frequency domain signal corresponding to the corrected beat frequency signal.
17. The device according to any one of claims 12-16, wherein the corrected beat frequency signal comprises a first corrected beat frequency signal or a second corrected beat frequency signal; the echo signal according to the measurement path The corresponding FM nonlinear term ε(t-τ′ _i-1 ) performs FM nonlinear correction on the measurement path beat signal to obtain the aspect of correcting the beat signal, and the correction unit is specifically configured to:

    When the signal-to-noise ratio of the measurement path beat signal is not lower than the second preset threshold, the frequency modulation nonlinearity term ε(t) of the laser emission signal and the frequency modulation nonlinearity corresponding to the measurement path echo signal The term ε(t-τ′ _i-1 ) performs frequency modulation nonlinear term correction on the measurement path beat signal to obtain the first corrected beat signal;

    When the signal-to-noise ratio of the measurement path beat frequency signal is lower than the second preset threshold value, the frequency modulation nonlinearity term ε(t-τ′ _i-1 ) corresponding to the measurement path echo signal is compared to the The compensated beat frequency signal is corrected by a frequency modulation nonlinear term at the receiving end to obtain the second corrected beat frequency signal;

    Wherein, the compensated beat frequency signal is obtained based on the frequency modulation nonlinearity term ε(t) of the measurement path beat frequency signal at the transmitting end according to the frequency modulation nonlinearity term ε(t) of the laser transmitting signal.
18. The device according to claim 17, wherein, in terms of calculating the initial flight time τ according to the measured road beat frequency signal, the calculating unit is specifically configured to:

    When the signal-to-noise ratio of the measurement road beat signal is not lower than a second preset threshold, perform an FFT on the measurement road beat signal to obtain a frequency domain signal corresponding to the measurement road beat signal;

    Determine the frequency of the measurement road beat signal according to the frequency domain signal corresponding to the measurement road beat signal, and calculate the initial flight time τ according to the frequency of the measurement road beat signal;

    Wherein, the frequency of the measurement path beat signal is a frequency corresponding to a peak point position of a frequency domain signal corresponding to the measurement path beat signal, or a frequency corresponding to a midpoint position of a half-height width of the frequency domain signal.
19. The device according to claim 17, wherein in the aspect of calculating the initial flight time τ according to the measured road beat frequency signal, the calculating unit is specifically configured to:

    When the signal-to-noise ratio of the measurement path beat frequency signal is lower than the second preset threshold; perform the frequency modulation nonlinearity at the transmitting end of the measurement path beat frequency signal according to the frequency modulation nonlinearity term ε(t) of the laser emission signal Term compensation to obtain the compensated beat frequency signal; the frequency modulation nonlinear term of the laser emission signal is calculated based on the reference path beat frequency signal;

    Performing FFT on the compensated beat signal to obtain a frequency domain signal corresponding to the compensated beat signal;

    Determine the frequency of the compensated beat signal according to the frequency domain signal corresponding to the compensated beat signal, and calculate the initial flight time τ according to the frequency of the compensated beat signal;

    Wherein, the frequency of the compensated beat frequency signal is the frequency corresponding to the peak point position of the frequency domain signal corresponding to the compensated beat frequency signal, or the frequency corresponding to the midpoint position of the half-height width of the frequency domain signal .
20. The device according to any one of claims 11-19, wherein, in terms of calculating the frequency modulation nonlinear term ε(t) of the laser emission signal according to the reference path beat frequency signal, the calculation unit specifically uses At:

    Performing Hilbert transform on the reference road beat signal to obtain a transformed beat signal;

    Calculating the frequency modulation frequency of the laser emission signal according to the converted beat frequency signal;

    According to the frequency modulation frequency of the laser emission signal and the ideal chirp frequency, the frequency modulation nonlinear term ε(t) of the laser emission signal is calculated.
21. A distance measuring device based on frequency modulation nonlinear correction, which is characterized in that it comprises:

    Memory for storing instructions; and

    At least one processor coupled with the memory;

    Wherein, when at least one processor executes the instruction, the instruction causes the processor to execute the method according to any one of claims 1-10.
22. A computer storage medium, wherein the computer storage medium stores a computer program, the computer program includes program instructions, and when executed by a processor, the program instructions cause the processor to execute as claimed in claims 1-10. Any of the methods.
23. A radar, characterized in that it includes:

    A laser, and a processor coupled with the laser;

    The processor is configured to execute the method according to any one of claims 1 to 10.

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