CN105259548A - Dispersion mismatch correction method used in FMCW absolute distance measurement technology - Google Patents

Abstract

The present invention relates to a dispersion mismatch correction method, and puts forward a dispersion mismatch correction method used in an FMCW (Frequency Modulated Continuous Wave) absolute distance measurement technology by aiming at solving the problem that improvement effect of measurement accuracy of traditional dispersion software is not obvious. The dispersion mismatch correction method is achieved through the following steps: 1, acquiring an auxiliary interferometer signal I(f) with dispersion of an auxiliary interferometer; 2, forming a measurement interferometer signal Im; 3, calculating an Iend(m) through adoption of an Im(f); 4, calculating a numerical signal Im(m) obtained by sampling for an interference signal of an object reflected light and an interference signal of a reference light by the auxiliary interferometer; 5, using coefficients P(k) of various chirp signal components in the sum of chirp signals as a distance spectrum of the signals; 6, judging the distance range of a measured object to range from R1 to R2; and 7, decomposing the Im(m), and simultaneously optimizing the resolution ratio of the distance spectrum of the signals in the step 4. The dispersion mismatch correction method is applied to the field of dispersion mismatch correction.

Description

A kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology

Technical field

The present invention relates to dispersion mismatch repair method, particularly one is used for dispersion mismatch repair method in FMCW absolute distance measurement technology.

Background technology

Traditional dispersion software correction method has phase correction and Fourier Transform of Fractional Order.The method of phase correction needs first to carry out matching to the phase slope of signal, and Fourier Transform of Fractional Order needs first to determine to convert exponent number, and both is as broad as long in essence.But the precision of phase slope matching is by effect of signals, in twice repeated experiment all can there is difference in fitting result, the error of fitting of this phase slope will introduce a stochastic error to last measurement result, therefore existing method can improve Measurement Resolution, but improves less effective to measuring accuracy.

Summary of the invention

The object of the invention is to improve the problem of DeGrain and the one that proposes for dispersion mismatch repair method in FMCW absolute distance measurement technology to solve traditional dispersion software measurement precision.

Above-mentioned goal of the invention is achieved through the following technical solutions:

Auxiliary interferometer built by step one, employing optical fiber, obtains auxiliary interferometer signal I (f) that auxiliary interferometer exists dispersion;

If there is auxiliary interferometer signal I (f) of dispersion as data collecting card sampling clock in step 2, data collecting card sampling clock often in coordinate axis 0 time, obtain a sampled point, sampled point composition stellar interferometer signal I _always;

Wherein, the laser frequency variable quantity that each sampled point is corresponding is f (m); Stellar interferometer signal I _alwaysbe divided into two parts, the fiber end face reflected light of a part of interferometer measurement light and reference light interference signal I _end(f), another part interferometer measurement light by end face outgoing, through target reflection after get back in light path with reference light interference signal I _m(f);

The fiber end face reflected light of step 3, laser frequency variable quantity f (m) obtained according to step 2 and step 2 and reference light interference signal I _endf () calculates fiber end face reflected light and the numerical signal I of reference light interference signal after auxiliary interferometer is sampled _end(m);

Step 4, laser frequency variable quantity f (m) and the interference signal I that obtain according to step 2 _mf () calculates the interference signal of target reflecting light and the numerical signal I of the interference signal of reference light after auxiliary interferometer is sampled _m(m), namely

$I_m\left(m\right)=A_{m}cos\[2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{R_m}{c}\]---\left(11\right)$

Wherein, A _mfor measuring-signal amplitude, R _endfor the optical path difference between the fiber end face reflected light of interferometer measurement light and reference arm; R ₀for auxiliary interferometer two-way length difference; M is sampled point sequence; C represents the light velocity; n _g0for the optical fiber group index that original frequency is corresponding; R _mthe laser light path of passing by free space and testing distance; d _ffor optical fiber coefficient;

Step 5, by signal I _m(m) be decomposed into chirp signal and in the FACTOR P (k) of each chirp signal component, with chirp signal and in the signal distance spectrum of FACTOR P (k) of each chirp signal component;

Wherein, j is the imaginary part of symbol; K=1,2 ... N;

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{n_{g0}{R}_0}{cN}k\]---\left(15\right)$

Step 6, by signal I _mm () carries out a Fourier transform, judge that measured target distance range is R ₁~ R ₂; Wherein, R ₁for the lower limit of the distance of measured target; R ₂for the upper limit of the distance of measured target;

Step 7, at measured target distance range R ₁~ R ₂interior to signal I _mm () decomposes; The resolution of the distance spectrum of signal in step 4 is optimized simultaneously and obtains tested distance R _m, be changed to by formula (15):

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})(\frac{R_2-R_1}{M}k+R_1)\]---\left(16\right)$

Wherein, k=1,2 ... M, M are that conversion is counted, (R ₂-R ₁)/M is the resolution of distance spectrum.

Can obtain in conjunction with formula (11) and formula (16), when P (k) gets maximal value, corresponding tested distance R _m, namely

$R_m=\frac{R_2-R_1}{M}{k}_{max}+R_1$

Wherein, k _maxfor the sequence number that P (k) maximal value is corresponding.

Invention effect

The present invention proposes a kind of algorithm new for dispersion mismatch repair in frequency modulation continuous wave FMCW (FrequencyModulatedContinuousWave) absolute distance measurement technology.Because dispersion causes measurement result to become a chirp signal, and chirp value changes with target range change.In order to overcome this impact, the present invention proposes signal decomposition be a series of chirp signal and, with the signal distance spectrum of the coefficient of component of respectively warbling, the impact of dispersion can be eliminated, obtain target range value.Namely

$\begin{array}{c}P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{n_{g0}{R}_0}{cN}k\]\\ k=1,2...N\end{array}---\left(15\right)$

In order to reduce operand, first can carry out a Fourier transform to signal, roughly judging target range scope R ₁~ R ₂, then within the scope of this, signal is decomposed.The resolution of spectrum of simultaneously can adjusting the distance is optimized, and the signal to noise ratio (S/N ratio) of effective resolution and signal has relation usually.Now above formula can be changed to

$\begin{array}{c}P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})(\frac{R_2-R_1}{M}k+R_1)\]\\ k=1,2...M\end{array}---\left(16\right)$

Wherein, (R ₂-R ₁)/M is the resolution of distance spectrum.Ratio between this resolution with system intrinsic accuracy is relevant with Signal-to-Noise.The impact that the method effectively can be eliminated dispersion and brings is found in experiment, distance spectrum after not carrying out dispersion correction when Fig. 2 is different swept frequency range and utilizing the method to carry out dispersion correction, the distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain.The method all can obtain good effect at different swept frequency range as found from the results.

Dispersion mismatch can bring impact to measuring accuracy, in order to verify the raising of the method to absolute distance measurement precision, when different swept frequency range, respectively not carrying out dispersion correction, utilize traditional approach to carry out carrying out precision analysis when dispersion correction and new method carry out dispersion correction.As shown in Table 1, result shows the method can effectively improve absolute distance measurement precision to the uncertainty (k=2) wherein obtained.

Accompanying drawing explanation

Fig. 1 is the FMCW absolute distance measurement technology light channel structure sketch that embodiment one proposes;

Fig. 2 (a) for embodiment one propose for not carrying out dispersion correction and utilize the method to carry out the distance spectrum after dispersion correction when swept frequency range is 1.07THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

Fig. 2 (b) is not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction when swept frequency range that embodiment one proposes is 1.6THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

Fig. 2 (c) is not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction when swept frequency range that embodiment one proposes is 2.13THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

Fig. 2 (d) is not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction when swept frequency range that embodiment one proposes is 2.66THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

Fig. 2 (e) is not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction when swept frequency range that embodiment one proposes is 3.19THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

Fig. 2 (f) is not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction when swept frequency range that embodiment one proposes is 3.72THz; The distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain.

Embodiment

Embodiment one: the one of composition graphs 1 present embodiment is used for dispersion mismatch repair method in FMCW absolute distance measurement technology, specifically prepares according to following steps:

Laser linear frequency modulation continuous wave technology by tunable laser on a large scale continuously adjustable feature measure; Usual laser instrument cannot accomplish absolute linear frequency modulation, and in order to overcome the impact that nonlinear frequency modulation brings, means conventional are at present Frequency Sampling Methods; FMCW absolute distance measurement technology light channel structure sketch obtains interference signal I as utilized the linear modulation laser assisted interferometer of tunable laser output frequency in Fig. 1, Fig. 1 ₀be expressed as:

I ₀(f)＝A ₀cos(2πfτ ₀)(1)

Wherein, τ ₀for the group delay of auxiliary interferometer two-way is poor, A ₀for interference signal amplitude; Interferometer is a Mach Zehnder interferometer;

Utilize tunable laser output frequency linear modulation laser, calculate sampling pre-test interferometer signal I according to frequency chirp laser _always; Stellar interferometer signal I _alwaysbe expressed as:

I _always=A _mcos (2 π f τ _m) (2)

Wherein, τ _mfor the group delay of stellar interferometer two-way is poor;

According to interference signal I ₀with stellar interferometer signal I _alwaysdetermine interference signal phase place and stellar interferometer signal phase direct proportionality, thus eliminate the non-linear impact brought of tunable laser modulation, according to proportional relationship determination interference signal I ₀as the optical path signal of data collecting card sampling clock;

Step one, dispersion mismatch analysis; Owing to adopting optical fiber to build auxiliary interferometer, obtain auxiliary interferometer signal I (f) that auxiliary interferometer exists dispersion;

If there is auxiliary interferometer signal I (f) of dispersion as data collecting card sampling clock in step 2, data collecting card sampling clock often in coordinate axis 0 time, obtain a sampled point, sampled point composition stellar interferometer signal I _always;

Wherein, the laser frequency variable quantity that each sampled point is corresponding is f (m); The stellar interferometer signal I that FMCW absolute distance measurement systematic survey interferometer measurement light and step 2 obtain _alwaysbe divided into two parts, the fiber end face reflected light of a part of interferometer measurement light and reference light interference signal I _end(f), another part interferometer measurement light by end face outgoing, through target reflection after get back in light path with reference light interference signal I _m(f); I _mf () light path is divided into two sections, one section of flashlight at inside of optical fibre, one section of flashlight in free space; In free space, the dispersion of flashlight is very little, can ignore;

The fiber end face reflected light of step 3, laser frequency variable quantity f (m) obtained according to step 2 and step 2 and reference light interference signal I _endf () calculates fiber end face reflected light and the numerical signal I of reference light interference signal after auxiliary interferometer is sampled _end(m);

Step 4, laser frequency variable quantity f (m) and the interference signal I that obtain according to step 2 _mf () calculates the interference signal of target reflecting light and the numerical signal I of the interference signal of reference light after auxiliary interferometer is sampled _m(m), namely

$I_m\left(m\right)=A_{m}cos\[2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{R_m}{c}\]---\left(11\right)$

Wherein, A _mfor measuring-signal amplitude, R _endfor the optical path difference between the fiber end face reflected light of interferometer measurement light and reference arm; To I _endm () carries out Fourier transform can try to achieve light path R between the fiber end face reflected light of interferometer measurement light and reference arm _end; R ₀for auxiliary interferometer two-way length difference; M is sampled point sequence; C represents the light velocity; n _g0for the optical fiber group index that original frequency is corresponding; R _mthe laser light path of passing by free space and testing distance; d _ffor optical fiber coefficient;

Step 5, dispersion mismatch compensation scheme; Because dispersion causes numerical signal I in measurement result and step 3 _mm () becomes a chirp signal, and chirp value changes with target range change; In order to overcome this impact, by signal I _m(m) be decomposed into chirp signal and in the FACTOR P (k) of each chirp signal component, with chirp signal and in the signal distance spectrum of FACTOR P (k) of each chirp signal component, the impact of dispersion can be eliminated;

Wherein, j is the imaginary part of symbol; K=1,2 ... N;

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{n_{g0}{R}_0}{cN}k\]---\left(15\right)$

Step 6, in order to reduce operand, by signal I _mm () carries out a Fourier transform, judge that measured target distance range is R ₁~ R ₂; Wherein, R ₁for the lower limit of the distance of measured target; R ₂for the upper limit of the distance of measured target;

Step 7, at measured target distance range R ₁~ R ₂interior to signal I _mm () decomposes; The resolution of the distance spectrum of signal in step 4 is optimized simultaneously and obtains tested distance R _m, the signal to noise ratio (S/N ratio) of effective resolution and signal has relation usually; Be changed to by formula (15):

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})(\frac{R_2-R_1}{M}k+R_1)\]---\left(16\right)$

Wherein, k=1,2 ... M, M are that conversion is counted, (R ₂-R ₁)/M is the resolution of distance spectrum; Ratio between this resolution with system intrinsic accuracy is relevant with Signal-to-Noise; Can obtain in conjunction with formula (11) and formula (16), when P (k) gets maximal value, corresponding tested distance R _m, namely

$R_m=\frac{R_2-R_1}{M}{k}_{max}+R_1.$

Wherein k _maxfor the sequence number that formula (16) maximal value is corresponding;

The impact that the method effectively can be eliminated dispersion and brings is found in experiment, Fig. 2 (a) ~ (f) be not for carrying out dispersion correction and utilizing the method to carry out the distance spectrum after dispersion correction during different swept frequency range, the distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain;

From table result, find that present embodiment all can obtain good effect at different swept frequency range; Dispersion mismatch can bring impact to measuring accuracy, in order to verify the raising of the method to absolute distance measurement precision, when different swept frequency range, respectively not carrying out dispersion correction, utilize traditional approach to carry out carrying out precision analysis when dispersion correction and new method carry out dispersion correction; As shown in Table 1, result shows the method can effectively improve absolute distance measurement precision to the uncertainty (k=2) wherein obtained;

Present embodiment effect:

Present embodiment proposes a kind of algorithm new for dispersion mismatch repair in frequency modulation continuous wave FMCW (FrequencyModulatedContinuousWave) absolute distance measurement technology.Because dispersion causes measurement result to become a chirp signal, and chirp value changes with target range change.In order to overcome this impact, present embodiment propose signal decomposition be a series of chirp signal and, with the signal distance spectrum of the coefficient of component of respectively warbling, the impact of dispersion can be eliminated, obtain target range value.Namely

$\begin{array}{c}P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{n_{g0}{R}_0}{cN}k\]\\ k=1,2...N\end{array}---\left(15\right)$

In order to reduce operand, first can carry out a Fourier transform to signal, roughly judging target range scope R ₁~ R ₂, then within the scope of this, signal is decomposed.The resolution of spectrum of simultaneously can adjusting the distance is optimized, and the signal to noise ratio (S/N ratio) of effective resolution and signal has relation usually.Now above formula can be changed to

$\begin{array}{c}P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})(\frac{R_2-R_1}{M}k+R_1)\]\\ k=1,2...N\end{array}---\left(16\right)$

Wherein, (R ₂-R ₁)/M is the resolution of distance spectrum.Ratio between this resolution with system intrinsic accuracy is relevant with Signal-to-Noise.The impact that the method effectively can be eliminated dispersion and brings is found in experiment, distance spectrum after not carrying out dispersion correction when Fig. 2 is different swept frequency range and utilizing the method to carry out dispersion correction, the distance spectrum obtained when wherein solid line is and does not carry out dispersion correction, dotted line is the distance spectrum utilizing the method to carry out dispersion correction to obtain.The method all can obtain good effect at different swept frequency range as found from the results.

Dispersion mismatch can bring impact to measuring accuracy, in order to verify the raising of the method to absolute distance measurement precision, when different swept frequency range, respectively not carrying out dispersion correction, utilize traditional approach to carry out carrying out precision analysis when dispersion correction and new method carry out dispersion correction.As shown in Table 1, result shows the method can effectively improve absolute distance measurement precision to the uncertainty (k=2) wherein obtained.

Embodiment two: present embodiment and embodiment one unlike: auxiliary interferometer signal I (f) that in step one, auxiliary interferometer exists dispersion is expressed as:

$\begin{array}{c}I\left(f\right)\≈A_0\cos \left(2\mathrm{\π}{\∫}_0^f\frac{n_g{R}_0}{c}{\mathrm{df}}^{\′}\right)=A_0\cos \left(2\mathrm{\π}\frac{R_0}{c}{\∫}_0^f\right(d_f{f}^{\′}+n_{g0}){\mathrm{df}}^{\′})\\ =A_0\cos \[2\mathrm{\π}\left(\frac{0.5d_f{R}_0{f}^2+n_{g0}{R}_{0}f}{c}\right)\]\end{array}---\left(3\right)$

Wherein, f ₀time auxiliary interferometer optical fiber group index; A ₀for interference signal amplitude; F is laser instrument Instantaneous frequency variations amount; n _gfor auxiliary interferometer optical fiber group index.Other step and parameter identical with embodiment one.

Embodiment three: present embodiment and embodiment one or two unlike: in step 2, sampled point is obtained by formula (4):

$2\mathrm{\π}\left(\frac{0.5d_f{R}_0{f}^2+n_{g0}{R}_{0}f}{c}\right)=2\mathrm{\π}m,m=0,2...N-1---\left(4\right)$

Wherein, N is sampling number.Other step and parameter identical with embodiment one or two.

Embodiment four: present embodiment and one of embodiment one to three unlike: laser frequency variable quantity f (m) that in step 2, each sampled point is corresponding is specially:

$f\left(m\right)=\frac{-n_{g0}{R}_0\±\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}}{d_f{R}_0}---\left(5\right)$

Wherein, addition represents frequency to be increased, and subtraction represents frequency and reduces.Other step and parameter identical with one of embodiment one to three.

Embodiment five: one of present embodiment and embodiment one to four unlike: utilize the fiber end face reflecting interference signal of FMCW absolute distance measurement systematic survey interferometer measurement light and reference light interference signal to there is dispersion I in step 2 _endf () is expressed as:

$I_{end}\left(f\right)=A_{end}cos\[2\mathrm{\π}\left(\frac{0.5d_f{R}_{end}{f}^2+n_{g0}{R}_{end}f}{c}\right)\]---\left(6\right)$

Wherein, A _endfor fiber end face reflected light and the reference light interference signal amplitude of interferometer measurement light.Other step and parameter identical with one of embodiment one to four.

Embodiment six: one of present embodiment and embodiment one to five unlike: utilize fiber end face reflected light and reference light interference signal I in step 3 _endf () calculates I _endm the detailed process of () is:

Bring formula (5) into formula (6), then there is dispersion I in fiber end face reflecting interference signal and reference light interference signal _endf () becomes I after auxiliary interferometer sampling _end(m):

other step and parameter identical with one of embodiment one to five.

Embodiment seven: one of present embodiment and embodiment one to six are unlike I in step 4 _mm the concrete derivation of () is:

Step 4 one, interferometer measurement light by end face outgoing, through target reflection after get back in light path with I in reference light interference signal light _mthe interference signal I of the flashlight in the free space of (m) _mf () is expressed as:

$\begin{array}{c}{I}_m\left(f\right)=A_{m}cos\[2\mathrm{\π}{\∫}_0^f\left(\frac{n_g{R}_{end}+R_m}{c}\right){\mathrm{df}}^{\′}\]\\ =A_{m}cos\[2\mathrm{\π}\left(\frac{0.5d_f{R}_{end}{f}^2+n_{g0}{R}_{end}f}{c}\right)+2\mathrm{\π}f\frac{R_m}{c}\]\end{array}---\left(8\right)$

Step 4 two, formula (5) brought into formula (8) the numerical signal of interference signal after auxiliary interferometer adopts of target reflecting light and reference light:

$I_m\left(m\right)=A_{m}cos(2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}\frac{-n_{g0}{R}_0+\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}}{d_f{R}_0}\frac{R_m}{c})---\left(9\right)$

Step 4 three, in order to simplify formula (9), right carry out Taylor expansion and omit higher order term obtaining:

$\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}\≈n_{g0}{R}_0+\frac{d_{f}cm}{n_{g0}}-\frac{d_f^2{c}^2{m}^2}{2n_{g0}^3{R}_0}---\left(10\right)$

Step 4 four, formula (10) brought into formula (9):

$I_m\left(m\right)=A_{m}cos\[2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{R_m}{c}\]---\left(11\right).$ Other step and parameter identical with one of embodiment one to six.

Claims (7)

1., for a dispersion mismatch repair method in FMCW absolute distance measurement technology, it is characterized in that, specifically carry out according to following steps:

Auxiliary interferometer built by step one, employing optical fiber, obtains auxiliary interferometer signal I (f) that auxiliary interferometer exists dispersion;

If there is auxiliary interferometer signal I (f) of dispersion as data collecting card sampling clock in step 2, data collecting card sampling clock often in coordinate axis 0 time, obtain a sampled point, sampled point composition stellar interferometer signal I _always;

Wherein, the laser frequency variable quantity that each sampled point is corresponding is f (m); Stellar interferometer signal I _alwaysbe divided into two parts, the fiber end face reflected light of a part of interferometer measurement light and reference light interference signal I _end(f), another part interferometer measurement light by end face outgoing, through target reflection after get back in light path with reference light interference signal I _m(f);

The fiber end face reflected light of step 3, laser frequency variable quantity f (m) obtained according to step 2 and step 2 and reference light interference signal I _endf () calculates fiber end face reflected light and the numerical signal I of reference light interference signal after auxiliary interferometer is sampled _end(m);

Step 4, laser frequency variable quantity f (m) and the interference signal I that obtain according to step 2 _mf () calculates the interference signal of target reflecting light and the numerical signal I of the interference signal of reference light after auxiliary interferometer is sampled _m(m), namely

$I_m\left(m\right)=A_{m}cos\[2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{R_m}{c}\]---\left(11\right)$

Wherein, A _mfor measuring-signal amplitude, R _endfor the optical path difference between the fiber end face reflected light of interferometer measurement light and reference arm; R ₀for auxiliary interferometer two-way length difference; M is sampled point sequence; C represents the light velocity; n _g0for the optical fiber group index that original frequency is corresponding; R _mthe laser light path of passing by free space and testing distance; d _ffor optical fiber coefficient;

Step 5, by numerical signal I _m(m) be decomposed into chirp signal and in the FACTOR P (k) of each chirp signal component, with chirp signal and in the signal distance spectrum of FACTOR P (k) of each chirp signal component;

Wherein, j is the imaginary part of symbol; K=1,2 ... N;

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\mathrm{\Σ}}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g_0}^3{R}_0^2})\frac{n_{g0}{R}_0}{cN}k\]---\left(15\right)$

Step 6, by signal I _mm () carries out a Fourier transform, judge that measured target distance range is R ₁~ R ₂; Wherein, R ₁for the lower limit of the distance of measured target; R ₂for the upper limit of the distance of measured target;

Step 7, at measured target distance range R ₁~ R ₂interior to signal I _mm () decomposes; The resolution of the distance spectrum of signal in step 4 is optimized simultaneously and obtains tested distance R _m, be changed to by formula (15):

$P\left(k\right)=\underset{m=0}{\overset{N-1}{\Σ}}{I}_m\left(m\right)\exp \[-j2\mathrm{\π}\frac{R_{end}m}{R_0}-j2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g_0}^3{R}_0^2})(\frac{R_2-R_1}{M}k+R_1)\]---\left(16\right)$

Wherein, k=1 _,2 ... M, M are that conversion is counted, (R ₂-R ₁)/M is the resolution of distance spectrum.

Can obtain in conjunction with formula (11) and formula (16), when P (k) gets maximal value, corresponding tested distance R _m, namely

$R_m=\frac{R_2-R_1}{M}{k}_{max}+R_1$

Wherein, k _maxfor the sequence number that P (k) maximal value is corresponding.

2. be a kind ofly according to claim 1 used for dispersion mismatch repair method in FMCW absolute distance measurement technology, it is characterized in that: auxiliary interferometer signal I (f) that in step one, auxiliary interferometer exists dispersion is expressed as:

$\begin{array}{c}I\left(f\right)\≈A_{0}cos\left(2\mathrm{\π}{\∫}_0^f\frac{n_g{R}_0}{c}{\mathrm{df}}^{\′}\right)=A_{0}cos\left(2\mathrm{\π}\frac{R_0}{c}{\∫}_0^f\right(d_f{f}^{\′}+n_{g0}){\mathrm{df}}^{\′})\\ =A_{0}cos\[2\mathrm{\π}\left(\frac{0.5d_f{R}_0{f}^2+n_{g0}{R}_{0}f}{c}\right)\]\end{array}---\left(3\right)$

Wherein, f ₀time auxiliary interferometer optical fiber group index; A ₀for interference signal amplitude; F is laser instrument Instantaneous frequency variations amount; n _gfor auxiliary interferometer optical fiber group index.

3. a kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology according to claim 2, it is characterized in that: in step 2, sampled point is obtained by formula (4):

$2\mathrm{\π}\left(\frac{0.5d_f{R}_0{f}^2+n_{g0}{R}_{0}f}{c}\right)=2\mathrm{\π}m,m=0,2...N1---\left(4\right)$

Wherein, N is sampling number.

4. a kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology according to claim 3, it is characterized in that: laser frequency variable quantity f (m) that in step 2, each sampled point is corresponding is specially:

$f\left(m\right)=\frac{-n_{g0}{R}_0\±\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}}{d_f{R}_0}---\left(5\right).$

5. a kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology according to claim 4, it is characterized in that: I in step 2 _endf () is expressed as:

$I_{end}\left(f\right)=A_{end}cos\[2\mathrm{\π}\left(\frac{0.5d_f{R}_{end}{f}^2+n_{g0}{R}_{end}f}{c}\right)\]---\left(6\right)$

Wherein, A _endfor fiber end face reflected light and the reference light interference signal amplitude of interferometer measurement light.

6. a kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology according to claim 5, it is characterized in that: in step 3, utilize fiber end face reflected light and reference light interference signal I _endf () calculates I _endm the detailed process of () is:

Bring formula (5) into formula (6), then there is dispersion I in fiber end face reflecting interference signal and reference light interference signal _endf () becomes I after auxiliary interferometer sampling _end(m):

$I_{end}\left(m\right)=A_{end}cos\left(2\mathrm{\π}\frac{R_{end}m}{R_0}\right)---\left(7\right).$

7. a kind of for dispersion mismatch repair method in FMCW absolute distance measurement technology according to claim 6, it is characterized in that: I in step 4 _mm the concrete derivation of () is:

Step 4 one, interferometer measurement light by end face outgoing, through target reflection after get back in light path with I in reference light interference signal light _mthe interference signal I of the flashlight in the free space of (m) _mf () is expressed as:

$\begin{array}{c}{I}_m\left(f\right)=A_{m}cos\[2\mathrm{\π}{\∫}_0^f\left(\frac{n_g{R}_{end}+R_m}{c}\right){\mathrm{df}}^{\′}\]\\ =A_{0}cos\[2\mathrm{\π}\left(\frac{0.5d_f{R}_{end}{f}^2+n_{g0}{R}_{end}f}{c}\right)+2\mathrm{\π}f\frac{R_m}{c}\]\end{array}---\left(8\right)$

Step 4 two, formula (5) brought into formula (8) the numerical signal of interference signal after auxiliary interferometer adopts of target reflecting light and reference light:

$I_m\left(m\right)=A_{m}cos(2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}\frac{-n_{g0}{R}_0+\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}}{d_f{R}_0}\frac{R_m}{c})---\left(9\right)$

Step 4 three, in order to simplify formula (9), right carry out Taylor expansion and omit higher order term obtaining:

$\sqrt{n_{g0}^2{R}_0^2+2d_f{R}_{0}cm}\≈n_{g0}{R}_0+\frac{d_{f}cm}{n_{g0}}-\frac{d_f^2{c}^2{m}^2}{2n_{g0}^3{R}_0}---\left(10\right)$

Step 4 four, formula (10) brought into formula (9):

$I_m\left(m\right)=A_{m}cos\[2\mathrm{\π}\frac{R_{end}m}{R_0}+2\mathrm{\π}(\frac{cm}{n_{g0}{R}_0}-\frac{d_f{c}^2{m}^2}{2n_{g0}^3{R}_0^2})\frac{R_m}{c}\]---\left(11\right).$