A dispersion interferometric distance measuring method

Abstract

The application provides a dispersion interferometric distance measurement method, two sets of optical frequency combs with a repetition frequency difference are transmitted to a dispersion interferometric distance measurement system to generate corresponding distance interference spectra; two sets of distance interference spectra are processed respectively to obtain current measurement distances L DPI1 and L DPI2 ; for each period in each relationship curve, the measurement distance difference of each position in the period on the two relationship curves is set as a first difference and a second difference, the first difference of the first position in the set period, the second difference of the associated second position in the period increases by ΔL every time the serial number of the period increases by one; the serial number of the period of the current actual distance is determined according to the first difference of the first position in the set period, ΔL, the serial number of the set period, the first position in the period which is the same as the first position in the set period, the second position associated in the period and the difference ΔLa of L DPI1 and L DPI2 . The application can fundamentally solve the problem of period ambiguity in distance measurement.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of distance measurement, and particularly relates to a dispersion interference distance measurement method. BACKGROUND

[0002] For dispersion interference distance measurement, the distance measured in theory can reach thousands of kilometers, and the measurement accuracy can reach the micron level. Dispersion interference distance measurement can use an optical frequency comb as a distance measurement light source. The optical frequency comb is a series of pulses with equal time intervals in the time domain, and has a repetition frequency of several tens of GHz, which makes the interval between different values in the spectral domain sufficient to match the resolution of a general commercial spectrum analyzer, thereby reducing the measurement dead zone. The optical frequency comb is an ideal light source in dispersion interference distance measurement technology. The existing dispersion interference distance measurement system usually uses a Michelson interference structure for distance sensing. When the reference light and the sensing light meet, interference occurs. The measurement distance and the free spectral range (FSR) of the interference spectrum are in a linear relationship. The FSR of the interference spectrum decreases with the increase of the optical path difference of the two interference arms, and increases with the decrease of the optical path difference of the two interference arms. Therefore, the density of the FSR of the interference spectrum is currently used to reflect the measurement distance.

[0003] However, the measured distance is not the actual distance. In fact, there is a certain correspondence between the measured distance and the actual distance. The correspondence is fixed and represented by a waveform curve. After the measured distance is determined, the actual distance corresponding to the measured distance can be found from the waveform curve. The horizontal coordinate of the waveform curve is the actual distance, and the vertical coordinate is the measured distance. With the increase of the actual distance, the waveform of the measured distance and the actual distance will periodically change. The length of one period can be L pp , and there is a turning point L pp / 2. In order to obtain the measured distance, two methods are commonly used to demodulate the interference spectrum at present: the first method is to use two Fourier transforms to extract the measured distance information, wherein after the first Fourier transform, the Fourier transform spectrum (FTS) is filtered out and then inverse Fourier transform, phase unwrapping, phase slope and a series of operations are used to obtain the corresponding measured distance information. Although this method can extract the measured distance information and has high precision, when the distance difference between the two interference arms is very small, the FTS and zero frequency are blurred due to overlap, so that the measured distance cannot be extracted; in addition, when filtering, the type of filter will also affect the precision of the final measured distance. The second method is to use one Fourier transform to solve the measured distance information. Although this method can obtain the measured distance information simply, it is special that at the beginning point, end point and turning point of the triangular wave period, the relationship between the measured distance and the actual distance is relatively fuzzy, that is, even if the measured distance is obtained by demodulation, it is also difficult to accurately find the corresponding actual distance from the waveform curve. In addition, the traditional dispersive interferometric distance measurement system itself cannot determine the period in which the actual distance is located, so that the determination of the actual distance is periodically ambiguous. In order to solve the problem of period ambiguity, other auxiliary measuring devices can be added to determine the period, which undoubtedly increases the complexity of the system. SUMMARY

[0004] The present application provides a dispersive interferometric distance measurement method to solve the problems that the relationship at the beginning point, end point and turning point of the period is relatively fuzzy when determining the current actual distance according to the relationship curve between the measured distance and the actual distance, and that an auxiliary device needs to be added to determine the period in which the current actual distance is located, and the system is relatively complex.

[0005] According to a first aspect of the embodiments of the present application, a dispersive interferometric distance measurement method is provided, comprising:

[0006] In step S110, two sets of optical frequency combs with a repetition frequency difference are transmitted to a dispersive interferometric distance measurement system, and each set of optical frequency combs generates a corresponding distance interference spectrum during transmission in the dispersive interferometric distance measurement system.

[0007] In step S120, Fourier transform is performed on the two sets of distance interference spectra respectively, distance coarse measurement is performed according to the peak values of the Fourier transformed interference spectra, and the current measured distances L DPI1 and L DPI2 are obtained respectively.

[0008] Step S130: In the relationship curves corresponding to each set of optical frequency combs, the relationship between the measured distance and the actual distance changes periodically. For each relationship curve, one period of the relationship curve is selected as its set period. For each period of the relationship curve, each first position in the set period is associated with the corresponding second position in the period. The difference in the measured distance of each position in the set period on the two relationship curves is taken as the first difference. The difference in the measured distance of each position in the period on the two relationship curves is taken as the second difference. Relative to the first difference corresponding to the first position in the set period, for each increment of the sequence number of the period, the second difference corresponding to the associated second position in the period increases by ΔL, where ΔL is any value greater than 0.

[0009] Step S140: For each relationship curve, based on the current measured distance L corresponding to that relationship curve... DPI1 or L DPI2 Find the value of the current measured distance L within the set period of the relationship curve. DPI1 or L DPI2 The corresponding undetermined actual distance is used to determine the first position of the undetermined actual distance within the set period and the first difference corresponding to the first position within the set period.

[0010] Step S150: For each period in the relationship curve, determine the second position associated with the first position within the set period, based on the first difference corresponding to the first position within the set period, ΔL corresponding to the relationship curve, the sequence number of the set period, the first position within the same period as the first position within the set period, the associated second position within the period, and the current measurement distance L. DPI1 With L DPI2 The difference ΔLa is used to determine the cycle number of the current actual distance on the relationship curve;

[0011] Step S160: After determining the period numbers k1 and k2 of the current actual distance in the two relationship curves respectively, determine the current actual distance based on the determined period numbers k1 or k2.

[0012] In one optional implementation, for each optical frequency comb, the relationship curve between the measured distance and the actual distance is an isosceles triangular wave relationship within each period of the relationship curve; the horizontal axis of the relationship curve is the actual distance, and the vertical axis is the measured distance.

[0013] For each relationship curve, each first triangular wave in the relationship curve is associated with a second triangular wave selected from another relationship curve, the actual distance corresponding to the measured distance maximum of the first triangular wave in the pair of associated triangular waves and the actual distance corresponding to the measured distance maximum of the second triangular wave are respectively taken as a first actual distance and a second actual distance, the difference between the first actual distance and the second actual distance is less than a half-period actual distance, the relationship curve and the other relationship curve are respectively based on a first set of optical frequency combs and a second set of optical frequency combs, the first set of optical frequency combs is transmitted to the dispersion interference distance measurement system earlier than the second set of optical frequency combs;

[0014] For each first triangular wave in the relationship curve, the region between the first triangular wave and the actual distance minimum of the associated second triangular wave is taken as a first region, the region between the first region and the first actual distance is taken as a second region, the region between the first actual distance and the second actual distance is taken as a third region, and the region between the second actual distance and the actual distance maximum of the first triangular wave is taken as a fourth region;

[0015] As the period corresponding to the first triangular wave increases, the ranges of the first region and the third region gradually increase, and the increasing proportions of the first region in each period are different from each other compared to the set period, and the increasing proportions of the third region in each period are also different from each other; as the period corresponding to the first triangular wave increases, the ranges of the second region and the fourth region gradually decrease;

[0016] For each relationship curve, each period in the relationship curve corresponds to the same position coordinate range in the position coordinate system, the position coordinate range of the first region and the third region with the smallest range in each period of the relationship curve is respectively taken as a first position range and a third position range of each period, the position coordinate range of the second region and the fourth region with the smallest range in each period is respectively taken as a second position range and a fourth position range of each period, for each period, the region between the first position range and the second position range of the period is taken as a fifth position range of the period, and the region between the third position range and the fourth position range of the period is taken as a sixth position range of the period;

[0017] For each period in the relationship curve, if the to-be-determined actual distance is within the second position range or the fourth position range of the set period, the first position in the set period has the same position coordinate as the second position associated with the period; if the to-be-determined actual distance is within the first position range or the third position range of the set period, the position coordinate of the first position in the set period is multiplied by an increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinate of the second position associated with the period; if the to-be-determined actual distance is within the fifth position range or the sixth position range of the set period, the first position in the set period and the second position associated with the period have one of the following two relationships: the first position in the set period has the same position coordinate as the second position associated with the period; the position coordinate of the first position in the set period is multiplied by an increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinate of the second position associated with the period.

[0018] In another optional implementation, the step S150 specifically includes:

[0019] The step S151 determines in which position range of the first to the sixth position range of the set period the to-be-determined actual distance is located. If the to-be-determined actual distance is within the second position range or the fourth position range of the set period, it indicates that the first position in the set period is the same as the second position associated with each period, and the step S152 is performed. If the to-be-determined actual distance is within the first position range or the third position range of the set period, it indicates that the first position in the set period is not the same as the second position associated with each period, and the step S154 is performed. If the to-be-determined actual distance is within the fifth position range or the sixth position range of the set period, it indicates that the first position in the set period may be the same as or not the same as the second position associated with each period, and the steps S152 to S154 are performed.

[0020] The step S152 determines, according to the difference ΔLa between the current measured distance L DPI1 and L DPI2 , the first difference corresponding to the first position in the set period, ΔL corresponding to the relationship curve, and the sequence number of the set period, a period sequence number in which the current actual distance is located in the relationship curve.

[0021] The step S153 determines whether the period sequence number is an integer. If the period sequence number is an integer, no processing is performed. Otherwise, the step S154 is performed.

[0022] Step S154, for each period in the relationship curve, according to the first difference value corresponding to the first position in the set period, the ΔL corresponding to the relationship curve and the serial number of the period, determining the second difference value corresponding to the second position in the period, according to the first position, the second position in the period and the second difference value corresponding to the second position in the period, determining the second difference value corresponding to the first position in the period, judging whether the difference value ΔLa of the current measured distance L DPI1 and L DPI2 is equal to the second difference value corresponding to the first position in the period, if yes, taking the serial number of the period as the period serial number where the current actual distance is located on the relationship curve, wherein the first position in the period and the set period is the same.

[0023] In another optional implementation, the step S152 specifically comprises: calculating the difference value ΔLa of the current measured distance L DPI1 and L DPI2 , subtracting the first difference value corresponding to the first position in the set period from the difference value ΔLa, dividing by the ΔL corresponding to the relationship curve, and adding the serial number of the set period to obtain the period serial number where the current actual distance is located on the relationship curve.

[0024] In another optional implementation, the step S154 specifically comprises:

[0025] Step S101, setting that each period in the relationship curve corresponds to the same position coordinate range in the position coordinate system, and the position coordinate system takes the minimum value of the actual distance of each period as the zero point;

[0026] Step S102, for each period in the relationship curve, multiplying the position coordinate X1 of the first position in the set period by the increasing proportion corresponding to the period to obtain the position coordinate X2 of the associated second position in the period, the position coordinate X1 of the first position in the set period is the position coordinate of the first position in the period, wherein when the to-be-determined actual distance is in the first position range and the fifth position range of the set period, the position coordinate X1 is multiplied by the increasing proportion corresponding to the first region of the period, and when the to-be-determined actual distance is in the third position range and the sixth position range of the set period, the position coordinate X1 is multiplied by the increasing proportion corresponding to the third region of the period; selecting one of the two intersection points of the two relationship curves in the period which is closest to the position coordinates X1 and X2, and setting the position coordinate of the selected intersection point as X3;

[0027] Step S103, calculating the second difference value ΔL 22 corresponding to the second position in the period according to the following formula:

[0028] ΔL 22= the sequence number of the period * ΔL + the first position corresponding to the first difference value ΔL in the set period 11 ;

[0029] Step S164, the second difference value ΔL corresponding to the first position in the period is calculated according to the following formula 21 :

[0030] ;

[0031] Step S105, it is judged whether the difference ΔLa of the current measurement distance L DPI1 and L DPI2 is equal to the second difference value ΔL corresponding to the first position in the period 21 , if yes, the sequence number of the period is taken as the period sequence number of the current actual distance on the relationship curve.

[0032] In another optional implementation, it is assumed that the measurement distance peak value corresponding to the actual distance L pp1 / 2 in each period of the first relationship curve is L max1 , and the measurement distance peak value corresponding to the actual distance L pp2 / 2 in each period of the second relationship curve is L max2 ;

[0033] The step S160 specifically includes:

[0034] Step S161, it is judged whether the current measurement distance L DPI1 is equal to 0 or L max1 , if yes, step S162 is executed, otherwise, the current actual distance corresponding to the current measurement distance L DPI1 is found from the k1th period of the first relationship curve;

[0035] Step S163, the current actual distance corresponding to the current measurement distance L DPI2 is found from the k2th period of the second relationship curve.

[0036] In another optional implementation, the step S160 specifically includes:

[0037] Step S201, the current actual distance and its period sequence number on the corresponding relationship curve, the period size of the corresponding relationship curve, the selected extreme point wavelength in the distance interference spectrum and the multiplication coefficient of the wavelength exist an equation relationship, according to the period sequence numbers k1 and k2 of the current actual distance on two sets of optical frequency comb corresponding relationship curves respectively, the corresponding period sizes L pp1 and L pp2The wavelengths of k extreme points selected from the first optical frequency comb corresponding to the first distance interference spectrum and the multiplication coefficient of each wavelength, the wavelengths of k extreme points selected from the second optical frequency comb corresponding to the first distance interference spectrum and the multiplication coefficient of each wavelength, are used to establish 2k equations based on the above equation relationship, and the corresponding multiplication coefficients are obtained by solving them, where k is an integer greater than 1.

[0038] Step S202: Substitute the multiplication coefficients obtained from the solution into the equation to calculate the current actual distance.

[0039] In another optional implementation, in step S201, the equation relating the current actual distance to its period index on the corresponding curve, the period of the corresponding curve, the wavelength of the extreme point selected in the corresponding distance interference spectrum, and the multiplication coefficient of that wavelength is: Current actual distance La = Period index on the corresponding curve * Period of the corresponding curve + Wavelength of the extreme point selected in the corresponding distance interference spectrum * Multiplication coefficient of that wavelength; Step S201 specifically includes:

[0040] Two maxima or minima are selected from the first distance interference spectrum corresponding to the first optical frequency comb, and the wavelengths λ of the two maxima or minima are determined. 11 and λ 12 wavelength λ 11 and λ 12 The multiplication coefficients are m 11 and m 12 Two maxima or minima are selected from the second distance interference spectrum corresponding to the second optical frequency comb, and the wavelengths λ of the two maxima or minima are determined. 21 and λ 22 wavelength λ 21 and λ 22 The multiplication coefficients are m 21 and m 22 ,

[0041] Based on the aforementioned equations, the following four equations are established:

[0042] k1*L pp1 +m 11 *λ 11 =k2*L pp2 +m 21 *λ 21

[0043] k1*L pp1 +m 11 *λ 11 =k2*L pp2 +m 22 *λ 22

[0044] k1*L pp1 +m 12 *λ 12 =k2*L pp2 +m 21 *λ 21

[0045] k1*L pp1 +m 12 *λ 12 =k2*L pp2 +m 22 *λ 22 ;

[0046] Solving the four equations simultaneously, the multiplication coefficient m 11 , m 12 , m 21 , m 22 .

[0047] The step S202 specifically comprises:

[0048] According to the formula La=k1*L pp1 +m 11 *λ 11 , the current actual distance La is calculated.

[0049] In another optional implementation, in the step S201, for each set of optical frequency comb corresponding distance interference spectrum, the extreme point in the distance interference spectrum is selected according to the following steps:

[0050] Determine the k maximum or minimum values collected in the distance interference spectrum;

[0051] For each extreme point determined, the extreme point and the corresponding points near it are fitted to obtain a fitted extreme point, and the fitted extreme point is taken as the selected extreme point.

[0052] In another optional implementation, the measurement range is adjusted by adjusting the repetition frequency difference of the two sets of optical frequency combs, wherein the smaller the repetition frequency difference is, the lower the lower limit of the measurement range is, and when the repetition frequency difference of the two sets of optical frequency combs is adjusted, ΔL should be greater than or equal to the preset measurement error.

[0053] The beneficial effects of the present application are:

[0054] 1. The application is aimed at each relationship curve, the first position in the set period in the relationship curve is associated with the corresponding second position in each period in the relationship curve, so that the serial number of the period increases by one, compared with the measurement distance difference value of the first position in the set period on the two relationship curves, the measurement distance difference value of the associated second position on the two relationship curves in the period increases ΔL, when determining the period of the current actual distance, no additional auxiliary device is needed, only the first to be determined actual distance corresponding to the obtained current measurement distance is found out from the set period of the relationship curve, so as to determine the first position of the to-be-determined actual distance in the set period and the first position corresponding to the first position in the set period, then according to the first difference value corresponding to the first position in the set period, the ΔL corresponding to the relationship curve, the serial number of the set period, the first position in the period which is the same as the first position in the set period, the associated second position in the period and the difference value ΔLa of the current measurement distance L DPI1 and L DPI2 , the period serial number of the current actual distance on the relationship curve is determined, the period ambiguity problem is solved, and the structure is simpler; in addition, after the to-be-determined actual distance is found out, the difference value ΔLa of the current measurement distance L DPI1 and L DPI2 is not compared with the measurement distance difference value corresponding to the to-be-determined actual distance in each period to obtain the period of the current actual distance, but only the first position corresponding to the to-be-determined actual distance in the set period and the measurement distance difference value corresponding to the first position are queried and determined, and then the period of the current actual distance is determined according to the designed calculation judgment logic, so the period determination efficiency is higher; since the period of the current actual distance is determined, the current actual distance determination accuracy is high; in addition, since there are two relationship curves in the application, when the current measurement distance on one of the relationship curves is located at the starting point, the ending point and the turning point of the period, the other relationship curve is selected, and the current actual distance is determined according to the current measurement distance on the other relationship curve, so that the current actual distance can be determined by completely avoiding the comparison of the relationship of the starting point, the ending point and the turning point in the period in the relationship curve, thereby the current actual distance determination accuracy can be further improved;

[0055] 2、The present application divides each cycle of the relationship curve into six position ranges, and uses the corresponding calculation and judgment logic (such as steps S152 or S154 or S152 to S154) to determine the cycle in which the actual distance to be determined is located according to the position range of the actual distance to be determined, instead of running the entire set of calculation and judgment logic (such as steps S152 to S154) regardless of the position of the actual distance to be determined, thereby further improving the determination efficiency of the cycle;

[0056] 3、The present application improves the distance measurement resolution to the nanometer level, and determines the current actual distance based on two sets of optical frequency combs with a repetition frequency difference, the cycle number of the current actual distance on the corresponding relationship curve, the cycle size of the corresponding relationship curve, the selected extreme point wavelength in the corresponding distance interference spectrum, and the equation relationship of the multiplication coefficient of the wavelength, wherein the present application only involves extreme point wavelength positioning when determining the current actual distance, and does not need to determine the current actual distance based on the phase change amount, nor does it need to reverse the phase based on the intensity signal, so that the present application can avoid the intensity noise introduced in the phase reverse process, thereby improving the determination accuracy of the current actual distance; in addition, when calculating the current actual distance and positioning the wavelength, the present application performs wavelength positioning on the fitted extreme point, and the wavelength positioning error is in the nanometer level, so that the determination accuracy of the current actual distance is further improved; since the wavelength positioning resolution is in the nanometer level, the determination accuracy of the current actual distance can also reach the nanometer level when the present application calculates the current actual distance based on the extreme point wavelength;

[0057] 4、When solving the multiplication coefficient, if only one extreme point is selected from one distance interference spectrum to establish the equation set, system error caused by frequency jitter may be introduced, therefore the present application selects the same number of extreme points from two distance interference spectra to establish the equation set, so that common mode error can be eliminated, thereby reducing system error and improving the determination accuracy of the multiplication coefficient; when the multiplication coefficient is substituted into the equation relationship to calculate the current actual distance, the determination accuracy of the current actual distance can be improved; the present application calculates the current measurement distance according to the above equation relationship, so that the measurement rate of the dispersion interference distance measurement system of the present application is mainly limited by the refresh frame rate of the spectrometer, and in actual application, if there is a higher requirement for the measurement rate, only a spectrometer acquisition system with a higher refresh rate needs to be replaced;

[0058] 5、When selecting the extreme point, the present application fits the extreme point and the corresponding points near the extreme point, and uses the fitted extreme point as the selected extreme point, so that the determination accuracy of the extreme point is improved, and compared with using only one comb tooth to determine the extreme point, the present application uses the fitted extreme point, thereby reducing the influence of laser thermal noise on the determination of the current actual distance, and improving the determination accuracy of the current actual distance. Attached Figure Description

[0059] Figure 1 This is a flowchart of an embodiment of the dispersive interferometric ranging method of the present invention;

[0060] Figure 2 This is a schematic diagram of the region division of each period in one of the relationship curves of this invention;

[0061] Figure 3 This is a schematic diagram illustrating the division of the position range of each period in one of the relationship curves of this invention;

[0062] Figure 4 When the first position within a given period and the associated second position within the same period are not the same, the first position within that period corresponds to a first difference ΔL. 21 A schematic diagram illustrating the calculation principle;

[0063] Figure 5 This is a schematic diagram of an embodiment of the high-accuracy dispersive interferometric ranging system of the present invention. Detailed Implementation

[0064] To enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention, and to make the above-mentioned objectives, features and advantages of the embodiments of the present invention more apparent and understandable, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0065] In the description of this invention, unless otherwise specified and limited, it should be noted that the term "connection" should be interpreted broadly. For example, it can be a mechanical connection or an electrical connection, or it can be a connection between two internal components. It can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above term according to the specific circumstances.

[0066] See Figure 1 This is a flowchart illustrating an embodiment of the dispersive interferometric ranging method of the present invention. The dispersive interferometric ranging method may include:

[0067] Step S110: Transmit two sets of optical frequency combs with a frequency repetition difference to the dispersive interferometric ranging system. Each set of optical frequency combs generates a corresponding distance interference spectrum during the transmission process in the dispersive interferometric ranging system.

[0068] In this embodiment, the optical frequency comb has a spectral range of hundreds of nanometers and a pulse repetition frequency of tens of GHz. When the laser generates two optical frequency combs with a repetition frequency difference, the magnitude of the repetition frequency difference can be adjusted by adjusting the cavity temperature and other methods.

[0069] Step S120, respectively, on two sets of distance interferometric spectrum Fourier transform, according to the Fourier change after the peak of the interferometric spectrum distance rough measurement, respectively, to obtain the current measurement distance L DPI1 And L DPI2 .

[0070] This step can first be separated according to the wavelength interval of two sets of distance interferometric spectrum, and then respectively on two sets of distance interferometric spectrum Fourier transform. In the distance interferometric spectrum, the more the spectral components, the higher the positioning accuracy of the interferometric spectrum peak.

[0071] Step S130, in the relationship curve corresponding to each set of light frequency comb, the relationship between the measured distance and the actual distance is periodically changed, for each relationship curve, select a period in the relationship curve as its set period, for each period in the relationship curve, each first position in the set period is associated with the corresponding second position in the period, the measured distance difference of each position in the set period on the two relationship curves is taken as the first difference, the measured distance difference of each position in the period on the two relationship curves is taken as the second difference, relative to the first difference corresponding to the first position in the set period, the second difference corresponding to the associated second position in the period increases ΔL with the increase of the serial number of the period by one, ΔL is any value greater than 0.

[0072] In this embodiment, the relationship diagram of the two relationship curves corresponding to the two sets of light frequency comb can be as shown in Figure 2 From the figure, it can be seen that each relationship curve is used to represent the relationship between the measured distance and the actual distance, the horizontal coordinate is the actual distance, and the vertical coordinate is the measured distance, the relationship curve 1 and the relationship curve 2 are obtained based on the first set of light frequency comb and the second set of light frequency comb, respectively, the first set of light frequency comb is transmitted to the dispersion interferometric distance measurement system before the second set of light frequency comb. For the relationship curve corresponding to each set of light frequency comb, the measured distance and the actual distance are isosceles triangle wave relationship in each period of the relationship curve, and each period can be divided into two symmetrical half periods relative to the vertical direction. Figure 2 It can also be seen from the figure that as the period increases synchronously, the difference between the actual distances corresponding to the same measured distance in the two relationship curves increases, for example, in the nth period of the two relationship curves, the actual distance corresponding to the same measured distance in the two relationship curves is D1, and in the n+1 period of the two relationship curves, the actual distance in the two relationship curves is D2 under the same measured distance, D2 is greater than D1, where n is an integer greater than 0. It should be noted that each position in the present application refers to an actual distance.

[0073] Step S140, for each relationship curve, according to the current measured distance LDPI1 or L DPI2 , the current measurement distance L DPI1 or L DPI2 , the first position of the to-be-determined actual distance in the set period and the first difference value corresponding to the first position in the set period.

[0074] Step S150, for each period in the relationship curve, determine the second position in the period associated with the first position in the set period, according to the first difference value corresponding to the first position in the set period, ΔL corresponding to the relationship curve, the serial number of the set period, the first position in the period which is the same as the first position in the set period, the associated second position in the period and the difference value ΔLa between the current measurement distance L DPI1 and L DPI2 , determine the serial number of the period in which the current actual distance is located on the relationship curve.

[0075] In this embodiment, as shown in Figure 2 , for each relationship curve, the set period T2 in the relationship curve can be selected as its set period, each first triangular wave in the relationship curve is associated with a second triangular wave selected from another relationship curve, the actual distance corresponding to the maximum measurement distance of the first triangular wave in the pair of associated triangular waves and the actual distance corresponding to the maximum measurement distance of the second triangular wave are respectively taken as the first actual distance and the second actual distance, the difference value between the first actual distance and the second actual distance is less than half the period actual distance, the relationship curve and the other relationship curve are respectively obtained based on a first set of optical frequency combs and a second set of optical frequency combs, and the first set of optical frequency combs is transmitted to the dispersion interference distance measurement system earlier than the second set of optical frequency combs. For each first triangular wave in the relationship curve, the region between the first triangular wave and the actual distance minimum value of the associated second triangular wave is taken as the first region 1, the region between the first region 1 and the first actual distance is taken as the second region 2, the region between the first actual distance and the second actual distance is taken as the third region 3, and the region between the second actual distance and the actual distance maximum value of the first triangular wave is taken as the fourth region 4.

[0076] As can be seen from Figure 2 , with the increase of the corresponding period of the first triangular wave, the ranges of the first region 1 and the third region 3 gradually increase, and the increase proportions of the first region 1 in each period are different from each other, and the increase proportions of the third region 3 in each period are also different from each other; with the increase of the corresponding period of the first triangular wave, the ranges of the second region 2 and the fourth region 4 gradually decrease.

[0077] As Figure 3As shown, for each relationship curve, assume that each period of the relationship curve corresponds to the same position coordinate range in the position coordinate system. The position coordinate ranges of the first region 1 and the third region 3, which have the smallest ranges in each period of the relationship curve, are respectively taken as the first position range A1 and the third position range A3 of each period. The position coordinate ranges of the second region 2 and the fourth region 4, which have the smallest ranges in each period, are respectively taken as the second position range A2 and the fourth position range A4 of each period. Figure 3 The positions of the smallest regions (first region 1, second region 2, third region 3, and fourth region 4) are all marked with black squares. For each cycle, the area between its first and second position ranges is designated as the fifth position range for that cycle, and the area between its third and fourth position ranges is designated as the sixth position range for that cycle. Figure 2 and Figure 3 As shown, among all periods T1 to T5 of the relationship curve L1, the range of the first region 1 corresponding to the set period T2 is the smallest. Therefore, the position coordinate range of the first region 1 within the set period T2 is taken as the first position range A1 of each period in the relationship curve L1. Among all periods T1 to T5 of the relationship curve L1, the range of the third region 3 corresponding to the first period T1 is the smallest. Therefore, the position coordinate range of the third region 3 within the first period T1 is taken as the third position range A3 of each period in the relationship curve L1. Among all periods T1 to T5 of the relationship curve L1, the range of the second region 2 corresponding to the fifth period T5 is the smallest. Therefore, the position coordinate range of the second region 2 within the fifth period T5 is taken as the second position range A2 of each period in the relationship curve L1. Among all periods T1 to T5 of the relationship curve L1, the range of the fourth region 4 corresponding to the fifth period T5 is the smallest. Therefore, the position coordinate range of the fourth region 4 within the fifth period T5 is taken as the fourth position range A4 of each period in the relationship curve L1.

[0078] For each period in the relationship curve, if the to-be-determined actual distance is within the second position range or the fourth position range of the set period, the first position in the set period has the same position coordinate as the second position associated with the period; if the to-be-determined actual distance is within the first position range or the third position range of the set period, the position coordinate of the first position in the set period is multiplied by an increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinate of the second position associated with the period; if the to-be-determined actual distance is within the fifth position range or the sixth position range of the set period, the first position in the set period and the second position associated with the period have one of the following two relationships: the first position in the set period has the same position coordinate as the second position associated with the period; the position coordinate of the first position in the set period is multiplied by an increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinate of the second position associated with the period.

[0079] The step S150 can specifically include:

[0080] The step S151 determines which position range among the first to sixth position ranges of the set period the to-be-determined actual distance is located in. If the to-be-determined actual distance is within the second position range or the fourth position range of the set period, it indicates that the first position in the set period is the same as the second position associated with each period, and the step S152 is executed. If the to-be-determined actual distance is within the first position range or the third position range of the set period, it indicates that the first position in the set period is not the same as the second position associated with each period, and the step S154 is executed. If the to-be-determined actual distance is within the fifth position range or the sixth position range of the set period, it indicates that the first position in the set period can be the same as the second position associated with each period, or can not be the same, and the steps S152 to S154 are executed.

[0081] The step S152 determines the period sequence number in which the current actual distance is located on the relationship curve according to the difference ΔLa between the current measured distance L DPI1 and L DPI2 , the first difference corresponding to the first position in the set period, ΔL corresponding to the relationship curve, and the sequence number of the set period.

[0082] The step S153 determines whether the period sequence number is an integer. If the period sequence number is an integer, no processing is performed. Otherwise, the step S154 is executed.

[0083] Step S154, for each period in the relationship curve, according to the first difference value corresponding to the first position in the set period, the ΔL corresponding to the relationship curve and the serial number of the period, determine the second difference value corresponding to the second position in the period, according to the first position, the second position in the period and the second difference value corresponding to the second position in the period, determine the second difference value corresponding to the first position in the period, judge whether the difference ΔLa of the current measured distance L DPI1 and L DPI2 is equal to the second difference value corresponding to the first position in the period, if yes, take the serial number of the period as the period serial number where the current actual distance is located on the relationship curve, wherein the first position in the period and the set period is the same.

[0084] Wherein, the step S152 can specifically include: calculate the difference ΔLa of the current measured distance L DPI1 and L DPI2 , subtract the first difference value corresponding to the first position in the set period from the difference ΔLa, divide by the ΔL corresponding to the relationship curve, and add the serial number of the set period to obtain the period serial number where the current actual distance is located on the relationship curve. The calculation formula of the period serial number k can be expressed as: k= (ΔLa-the first difference value corresponding to the first position in the set period) / ΔL+the serial number of the set period.

[0085] The step S154 can specifically include:

[0086] Step S101, set that each period in the relationship curve corresponds to the same position coordinate range in the position coordinate system, and the position coordinate system takes the minimum value of the actual distance of each period as the zero point;

[0087] Step S102, for each period in the relationship curve, multiply the position coordinate X1 of the first position in the set period by the increasing proportion corresponding to the period to obtain the position coordinate X2 of the associated second position in the period, the position coordinate X1 of the first position in the set period is the position coordinate of the first position in the period, wherein when the to-be-determined actual distance is in the first position range and the fifth position range of the set period, the position coordinate X1 is multiplied by the increasing proportion corresponding to the first region of the period, and when the to-be-determined actual distance is in the third position range and the sixth position range of the set period, the position coordinate X1 is multiplied by the increasing proportion corresponding to the third region of the period; select the intersection point closest to the position coordinates X1 and X2 from the two intersection points of the two relationship curves in the period, and set the position coordinate of the selected intersection point as X3;

[0088] Step S103, calculate the second difference value ΔL 22 corresponding to the second position in the period according to the following formula:

[0089] ΔL 22 = the serial number of the period * ΔL + the first position corresponding to the first difference value ΔL in the set period 11 ;

[0090] Step S164, the second difference value ΔL corresponding to the first position in the period is calculated according to the following formula 21 :

[0091] ;

[0092] Step S105, judge whether the difference ΔLa between the current measured distance L DPI1 and L DPI2 is equal to the second difference value ΔL 21 corresponding to the first position in the period, if yes, the serial number of the period is taken as the period serial number of the current actual distance on the relationship curve.

[0093] Step S160, after determining the period serial numbers k1 and k2 of the current actual distance in the two relationship curves respectively, the current actual distance is determined according to the determined period serial number k1 or k2.

[0094] Suppose that the measured distance peak value corresponding to the actual distance L pp1 / 2 in each period of the first relationship curve is L max1 , and the measured distance peak value corresponding to the actual distance L pp2 / 2 in each period of the second relationship curve is L max2 ; the step S160 can specifically include:

[0095] Step S161, judge whether the current measured distance L DPI1 is equal to 0 or L max1 , if yes, execute step S162, otherwise, find out the current actual distance corresponding to the current measured distance L DPI1 from the k1th period of the first relationship curve;

[0096] Step S163, find out the current actual distance corresponding to the current measured distance L DPI2 from the k2th period of the second relationship curve.

[0097] From the above embodiment, the present application is aimed at each relationship curve, associates each first position in the set period in the relationship curve with the corresponding second position in each period in the relationship curve, so that the serial number of the period increases by one, the measured distance difference value of the associated second position in the two relationship curves in the period increases by AL compared with the measured distance difference value of the first position in the set period in the two relationship curves, when determining the period in which the current actual distance is located, no additional auxiliary device is needed, only the first to be determined actual distance corresponding to the obtained current measured distance is found out from the set period of the relationship curve, so as to determine the first position of the to-be-determined actual distance in the set period and the first difference value corresponding to the first position in the set period, then according to the first difference value corresponding to the first position in the set period, the AL corresponding to the relationship curve, the serial number of the set period, the first position in the period which is the same as the first position in the set period, the associated second position in the period and the difference value ALa of the current measured distance L DPI1 and L DPI2 , the serial number of the period in which the current actual distance is located on the relationship curve is determined, the present application solves the period ambiguity problem and has a simpler structure; in addition, after the to-be-determined actual distance is found out, the present application does not compare the difference value ALa of the current measured distance L DPI1 and L DPI2 with the measured distance difference value corresponding to the to-be-determined actual distance in each period one by one to obtain the period in which the current actual distance is located, but only the first position corresponding to the to-be-determined actual distance in the set period and the measured distance difference value corresponding to the first position are queried and determined, then the period in which the current actual distance is located is determined according to the designed calculation and judgment logic, so the period determination efficiency of the present application is higher.

[0098] Since the present application determines the period in which the current actual distance is located, the current actual distance determination accuracy is high, so the current actual distance corresponding to the current measured distance is found out in the period, which can improve the current actual distance determination accuracy; in addition, since the present application has two relationship curves, when the current measured distance on one of the relationship curves is located at the starting point, the ending point and the turning point of the period, the other relationship curve is selected, and the current actual distance is determined according to the current measured distance on the other relationship curve, so that the present application can completely avoid using the ambiguous relationship at the starting point, the ending point and the turning point of the period in the relationship curve to determine the current actual distance when the current actual distance is determined according to the relationship curve, so that the current actual distance determination accuracy can be further improved.

[0099] In addition, the present application divides each cycle of the relationship curve into six position ranges, and uses corresponding calculation and judgment logic (such as steps S152 or S154 or S152 to S154) to determine the cycle in which the current actual distance is located according to the position range in which the to-be-determined actual distance is located, instead of running the entire set of calculation and judgment logic (such as steps S152 to S154) regardless of the position of the to-be-determined actual distance, thereby further improving the determination efficiency of the cycle.

[0100] In the above embodiment, when the corresponding current actual distance is found from the relationship curve according to the current measured distance, the resolution can only reach tens of microns due to the limited spectral range of the light source, for example, a spectral range of hundreds of nanometers. At present, although the measurement accuracy can be improved by fitting and combining zero difference interference, measurement errors caused by intensity jitter and common mode noise are introduced at the same time.

[0101] In order to improve the measurement accuracy while avoiding the introduction of measurement errors caused by intensity jitter and common mode noise, the above step S160 can further include:

[0102] Step S201, the current actual distance and its cycle sequence number on the corresponding relationship curve, the cycle size of the corresponding relationship curve, the selected extreme point wavelength in the corresponding distance interference spectrum, and the multiplication coefficient of the wavelength exist an equation relationship, according to the current actual distance respectively in two sets of optical frequency comb corresponding relationship curve cycle sequence number k1 and k2, two relationship curve corresponding cycle size L pp1 And L pp2 , the wavelength of the k extreme points selected from the first distance interference spectrum corresponding to the first optical frequency comb and the multiplication coefficient of each wavelength, the wavelength of the k extreme points selected from the first distance interference spectrum corresponding to the second optical frequency comb and the multiplication coefficient of each wavelength, based on the equation relationship, 2k equations are established, and the corresponding multiplication coefficient is solved, k is an integer greater than 1.

[0103] In this step, since the optical frequency comb is discrete in frequency, in order to avoid measurement dead zone, an optical frequency comb with large comb spacing is usually used as a measurement light source, so the distance interference spectrum corresponding to the optical frequency comb is also discrete. In the step S201, for the distance interference spectrum corresponding to each set of optical frequency comb, the extreme points in the distance interference spectrum can be selected according to the following steps:

[0104] Determine the k maximum values or minimum values collected in the distance interference spectrum;

[0105] For each determined extreme point, the extreme point and the corresponding points near the extreme point are fitted to obtain a fitted extreme point, and the fitted extreme point is taken as the selected extreme point.

[0106] In selecting extreme points, this invention uses a fitting process to the extreme point and its corresponding nearby points, and uses the fitted extreme point as the selected extreme point. This improves the accuracy of extreme point determination. Compared to using only one comb tooth to determine the extreme point, this invention uses the fitted extreme point, which reduces the impact of laser thermal noise on the determination of the current actual distance and improves the accuracy of the determination of the current actual distance.

[0107] Furthermore, in step S201, the equation relating the current actual distance to its period index on the corresponding curve, the period of the corresponding curve, the wavelength of the extreme point selected in the corresponding distance interference spectrum, and the multiplication coefficient of that wavelength is: Current actual distance La = Period index on the corresponding curve * Period of the corresponding curve + Wavelength of the extreme point selected in the corresponding distance interference spectrum * Multiplication coefficient of that wavelength; Step S201 may specifically include:

[0108] Two maxima or minima are selected from the first distance interference spectrum corresponding to the first optical frequency comb, and the wavelengths λ of the two maxima or minima are determined. 11 and λ 12 wavelength λ 11 and λ 12 The multiplication coefficients are m 11 and m 12 Two maxima or minima are selected from the second distance interference spectrum corresponding to the second optical frequency comb, and the wavelengths λ of the two maxima or minima are determined. 21 and λ 22 wavelength λ 21 and λ 22 The multiplication coefficients are m 21 and m 22 ,

[0109] Based on the aforementioned equations, the following four equations are established:

[0110] k1*L pp1 +m 11 *λ 11 =k2*L pp2 +m 21 *λ 21

[0111] k1*L pp1 +m 11 *λ 11 =k2*L pp2 +m 22 *λ 22

[0112] k1*L pp1 +m 12 *λ 12 =k2*Lpp2 +m 21 *λ 21

[0113] k1*L pp1 +m 12 *λ 12 =k2*L pp2 +m 22 *λ 22 ;

[0114] Solving the four equations simultaneously, the multiplication coefficient m 11 , m 12 , m 21 , m 22 .

[0115] In the application, if only extreme points in one distance interference spectrum are selected to establish equation set when solving the multiplication coefficient, system error caused by frequency jitter may be introduced, therefore, the same number of extreme points in two distance interference spectrums are selected to establish equation set, so that common mode error can be eliminated, system error can be reduced, and the determination accuracy of the multiplication coefficient can be improved; when the multiplication coefficient is substituted into the equation relationship to calculate the current actual distance, the determination accuracy of the current actual distance can be improved.

[0116] In step S202, the multiplication coefficient obtained by solving is substituted into the equation relationship, and the current actual distance is calculated. The step S202 can specifically include:

[0117] According to the formula La=k1*L pp1 +m 11 *λ 11 , the current actual distance La is calculated.

[0118] Zero difference interference needs to improve the distance measurement resolution to nanometer level by judging the phase change amount at a certain wavelength. The present application improves the distance measurement resolution to nanometer level based on two sets of optical frequency comb with frequency difference, determines the current actual distance according to the equation relationship of the current actual distance and the period number on the corresponding optical frequency comb relationship curve, the period size of the corresponding relationship curve, the extreme point wavelength selected in the corresponding distance interference spectrum and the multiplication coefficient of the wavelength. The present application only involves extreme point wavelength positioning when determining the current actual distance, does not need to determine the current actual distance based on the phase change amount, and also does not need to determine the phase based on the intensity signal. Therefore, the present application can avoid the intensity noise introduced in the phase backstepping process, thereby improving the determination accuracy of the current actual distance. In addition, when calculating the current actual distance and positioning the wavelength, the present application performs wavelength positioning on the fitted extreme point, and the wavelength positioning error is in nanometer level, so the wavelength positioning error is greatly reduced, thereby further improving the determination accuracy of the current actual distance. Since the wavelength positioning resolution is in nanometer level, the determination accuracy of the current actual distance can also reach nanometer level when the present application calculates the current actual distance according to the extreme point wavelength. In the embodiment, the resolution of the dispersion interference distance measurement system is mainly determined by the spectral range of the light source. The wider the spectral range, the higher the distance measurement resolution. In theory, for an optical frequency comb with a spectral range of hundreds of nm, its distance measurement resolution can reach several microns. Since the repetition frequency of the optical frequency comb used is very high, the corresponding L pp is small, and the resolution of the oscilloscope is sufficient at this time. The theoretical measurement range of the distance measurement system is only limited by the line width of the optical frequency comb. For an optical frequency comb with a line width of tens of Hz, the measurement distance can reach hundreds of kilometers. The present application calculates the current measurement distance according to the above equation relationship, so the measurement rate of the dispersion interference distance measurement system of the present application is mainly limited by the refresh frame rate of the spectrometer. In actual application, if the measurement rate is required to be higher, only the optical spectrum acquisition system with higher refresh rate needs to be replaced.

[0119] In addition, the present application can adjust the measurement range by adjusting the frequency difference of the two sets of optical frequency comb. The smaller the frequency difference, the lower the lower limit of the measurement range. When adjusting the frequency difference of the two sets of optical frequency comb, ΔL should be greater than or equal to the preset measurement error. For short distance high precision measurement, the frequency difference of the two sets of comb teeth can be adjusted to a small scale according to the measurement requirements, so as to meet the distance measurement requirements in short distance.

[0120] The dispersion interferometric distance measuring system with high accuracy can comprise a laser and a dispersion interferometric distance measuring system connected in sequence, the laser transmits two sets of optical frequency combs with a frequency difference to the dispersion interferometric distance measuring system. The dispersion interferometric distance measuring system can comprise a first collimator, a beam splitter, a reference mirror, a measurement mirror, a second collimator and a spectrometer, wherein for each set of optical frequency combs, the set of optical frequency combs is transmitted to the beam splitter after being collimated by the first collimator, the beam splitter divides the set of optical frequency combs into two paths, which are transmitted to the reference mirror and the measurement mirror as reference light and measurement light respectively, the reference mirror and the measurement mirror return the reflected light to the beam splitter respectively, the reflected light returned by the reference mirror and the measurement mirror interferes at the beam splitter to generate an interference light signal; the beam splitter transmits the interference light signal to the second collimator, which is transmitted to the spectrometer after being collimated by the second collimator, so that the spectrometer obtains a corresponding distance interference spectrum. The second collimator and the spectrometer can be replaced by a first grating and a high-speed linear array CCD, the grating is used to receive the interference signal, the output end of the grating is connected to the input end of the high-speed linear array CCD, and the output end of the high-speed linear array CCD is connected to the spectrometer.

[0121] In one example, the central wavelength is 1560nm, the spectral bandwidth is 100nm, and the double optical frequency combs with a repetition frequency of 50GHz and 50GHz are divided into two paths by the 80:20 beam splitter after passing through the first collimator. The path with low power is used as reference light, and the path with high power is used as measurement light and directly irradiates the measurement mirror. The reflected light of the measurement mirror and the reflected light of the reference mirror return to the beam splitter, thereby generating an interference light signal. The interference light is coupled to the optical fiber by the second collimator, and then the signal is collected and stored by the spectrometer. Due to the optical path difference between the reference arm and the signal arm, the interference spectrum FSR is different in density. Through the above measurement method, nanoscale resolution and long distance distance measurement can be realized.

[0122] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0123] It should be understood that the application is not limited to the precise construction and method described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the application is limited only by the claims that follow.

Claims

1. A dispersion interferometric distance measuring method, characterized by, The method comprises the following steps: Step S110, transmitting two sets of optical frequency combs with a repetition frequency difference to a dispersion interferometric distance measurement system, each set of optical frequency combs generates a corresponding distance interference spectrum during transmission in the dispersion interferometric distance measurement system; Step S120, respectively, on two sets of distance interferometric spectrum Fourier transform, according to the Fourier change after the interference spectrum peak value carries out distance rough measurement, respectively obtains the current measurement distance L DPI1 and L DPI2 ; Step S130, in the relationship curves corresponding to each set of optical frequency combs, the relationship between the measured distance and the actual distance changes periodically, for each relationship curve, a period in the relationship curve is selected as a set period, for each period in the relationship curve, each first position in the set period is associated with a corresponding second position in the period, the measured distance difference of each position in the set period on the two relationship curves is taken as a first difference value, the measured distance difference of each position in the period on the two relationship curves is taken as a second difference value, relative to the first difference value corresponding to the first position in the set period, the second difference value corresponding to the associated second position in the period increases by ΔL with the increase of the period number by one, and ΔL is any value greater than 0; Step S140: For each relationship curve, based on the current measured distance L corresponding to that relationship curve... DPI1 or L DPI2 Find the value of the current measured distance L within the set period of the relationship curve. DPI1 or L DPI2 The corresponding undetermined actual distance is used to determine the first position of the undetermined actual distance within the set period and the first difference corresponding to the first position within the set period. Step S150, for each cycle in the relationship curve, determining a second position in the cycle associated with the first position in the set cycle, according to the first difference value corresponding to the first position in the set cycle, the ΔL corresponding to the relationship curve, the serial number of the set cycle, the first position in the cycle which is the same as the first position in the set cycle, the second position associated in the cycle, and the difference value ΔLa between the current actual distance L and L DPI1 and L DPI2 , determining the serial number of the cycle where the current actual distance is located on the relationship curve; Step S160, after determining the period numbers k1 and k2 of the current actual distance in the two relationship curves respectively, the current actual distance is determined according to the determined period number k1 or k2; For each relationship curve corresponding to each set of optical frequency combs, the relationship between the measured distance and the actual distance in each period of the relationship curve is an isosceles triangular wave relationship; the abscissa of the relationship curve is the actual distance, and the ordinate is the measured distance; For each relationship curve, each first triangular wave in the relationship curve is associated with a second triangular wave selected from another relationship curve, the actual distance corresponding to the maximum measured distance of the first triangular wave in the associated pair of triangular waves and the actual distance corresponding to the maximum measured distance of the second triangular wave are taken as the first actual distance and the second actual distance respectively, the difference between the first actual distance and the second actual distance is less than half the period actual distance, the relationship curve and another relationship curve are obtained based on the first set of optical frequency combs and the second set of optical frequency combs respectively, and the first set of optical frequency combs is transmitted to the dispersion interferometric distance measurement system earlier than the second set of optical frequency combs; For each first triangular wave in the relationship curve, the region between the first triangular wave and the minimum actual distance in the associated second triangular wave is taken as a first region, the region between the first region and the first actual distance is taken as a second region, the region between the first actual distance and the second actual distance is taken as a third region, and the region between the second actual distance and the maximum actual distance of the first triangular wave is taken as a fourth region; With the increase of the corresponding period of the first triangular wave, the ranges of the first region and the third region gradually increase, and the increase proportions of the first region and the third region in each period are different from each other compared with the set period; with the increase of the corresponding period of the first triangular wave, the ranges of the second region and the fourth region gradually decrease. For each relationship curve, the position coordinate range of the first region with the smallest range in all periods of the relationship curve is taken as the first position range of each period, the position coordinate range of the third region with the smallest range in all periods of the relationship curve is taken as the third position range of each period, the position coordinate range of the second region with the smallest range in all periods of the relationship curve is taken as the second position range of each period, and the position coordinate range of the fourth region with the smallest range in all periods of the relationship curve is taken as the fourth position range of each period. For each period, the region between the first position range and the second position range of the period is taken as the fifth position range of the period, and the region between the third position range and the fourth position range of the period is taken as the sixth position range of the period. For each period in the relationship curve, if the to-be-determined actual distance is in the second position range or the fourth position range of the set period, the position coordinates of the first position in the set period and the associated second position in the period are the same; if the to-be-determined actual distance is in the first position range or the third position range of the set period, the position coordinates of the first position in the set period are multiplied by the increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinates of the associated second position in the period; if the to-be-determined actual distance is in the fifth position range or the sixth position range of the set period, the first position in the set period and the associated second position in the period have one of the following two relationships: the position coordinates of the first position in the set period and the associated second position in the period are the same; the position coordinates of the first position in the set period are multiplied by the increase ratio corresponding to the first region or the third region of the period, and the result is the position coordinates of the associated second position in the period.

2. The dispersive interferometric distance measuring method according to claim 1, characterized in that The step S150 specifically includes: Step S151, determining which position range in the first to sixth position ranges of the set period the to-be-determined actual distance is in. If the to-be-determined actual distance is in the second position range or the fourth position range of the set period, it indicates that the first position in the set period and the associated second position in each period are the same, and step S152 is performed. If the to-be-determined actual distance is in the first position range or the third position range of the set period, it indicates that the first position in the set period and the associated second position in each period are not the same, and step S154 is performed. If the to-be-determined actual distance is in the fifth position range or the sixth position range of the set period, it indicates that the first position in the set period and the associated second position in each period can be the same or not the same, and steps S152 to S154 are performed. Step S152, determining the period sequence number of the current actual distance on the relationship curve according to the current measured distance L DPI1 and the difference ΔLa of L DPI2 , the first difference corresponding to the first position in the set period, ΔL corresponding to the relationship curve, and the sequence number of the set period. Step S153, determining whether the period serial number is an integer. If it is an integer, no processing is performed. Otherwise, step S154 is performed. Step S154, for each cycle in the relationship curve, according to the first difference value corresponding to the first position in the set period, the ΔL corresponding to the relationship curve and the serial number of the cycle, determine the second difference value corresponding to the second position in the cycle, according to the first position, the second position and the second difference value corresponding to the second position in the cycle, determine the second difference value corresponding to the first position in the cycle, judge whether the difference value ΔLa of the current measured distance L DPI1 and L DPI2 is equal to the second difference value corresponding to the first position in the cycle, if yes, the serial number of the cycle is taken as the cycle serial number where the current actual distance is located on the relationship curve, wherein the first position in the cycle and the set period is the same.

3. The dispersive interferometric distance measuring method according to claim 2, characterized in that The step S152 specifically includes: calculating the difference ΔLa between the current measured distance L DPI1 and L DPI2 , subtracting the first difference corresponding to the first position in the set period from the difference ΔLa, dividing the result by ΔL corresponding to the relationship curve, and adding the sequence number of the set period to obtain the sequence number of the period in which the current actual distance is located on the relationship curve.

4. The dispersive interferometric ranging method of claim 1, wherein the dispersion is provided by a material having a refractive index that varies with wavelength. The actual distance in each cycle of the first relationship curve is L pp1 / 2, and the corresponding measured distance peak value is L max1 / 2, and the corresponding measured distance peak value is L pp2 / 2, and the corresponding measured distance peak value is L max2 ; wherein L pp1 and L pp2 are the cycle sizes corresponding to the two relationship curves, respectively. The step S160 specifically includes: Step S161, judging whether the current measured distance L DPI1 is equal to 0 or L max1 , if yes, executing step S162, otherwise, finding out the corresponding current actual distance from the k1th period of the first relationship curve. DPI1 ​ Step S162, find out the current measurement distance L DPI2 corresponding current actual distance.

5. The dispersive interferometric ranging method of claim 1, wherein, The step S160 specifically includes: Step S201, the current actual distance and its period number on the corresponding relationship curve, the period size of the corresponding relationship curve, the selected extreme point wavelength in the corresponding distance interference spectrum and the multiplication coefficient of the wavelength exist an equation relationship, according to the current actual distance, the period numbers k1 and k2 of the two sets of optical frequency comb corresponding relationship curves respectively, the corresponding period sizes L pp1 and L pp2 , the wavelengths of the k extreme points selected from the first distance interference spectrum corresponding to the first optical frequency comb and the multiplication coefficient of each wavelength, the wavelengths of the k extreme points selected from the first distance interference spectrum corresponding to the second optical frequency comb and the multiplication coefficient of each wavelength, based on the equation relationship, 2k equations are established, and the corresponding multiplication coefficient is solved, k is an integer greater than 1; Step S202, substituting the multiplication coefficient obtained by solving into the equation relationship, and calculating the current actual distance.

6. The dispersive interferometric distance measuring method according to claim 5, characterized in that In step S201, the equation relating the current actual distance to its period index on the corresponding curve, the period of the corresponding curve, the wavelength of the extreme point selected in the interference spectrum of the corresponding distance, and the multiplication coefficient of that wavelength is: Current actual distance La = Period index on the corresponding curve * Period of the corresponding curve + Wavelength of the extreme point selected in the interference spectrum of the corresponding distance * Multiplication coefficient of that wavelength; Step S201 specifically includes: Selecting two maximum points or minimum points from the first distance interference spectrum corresponding to the first optical frequency comb, and determining the wavelengths λ 11 and λ 12 of the two maximum points or minimum points 11 The multiplication coefficients of the wavelengths λ 12 and λ 11 are m 12 and m 21 respectively Selecting two maximum points or minimum points from the second distance interference spectrum corresponding to the second optical frequency comb, and determining the wavelengths λ 22 and λ 21 of the two maximum points or minimum points 22 The multiplication coefficients of the wavelengths λ 21 and λ 22 are m and m respectively Based on the aforementioned equations, the following four equations are established: k1*L pp1 + m 11 * λ 11 = k2*L pp2 + m 21 * λ 21 k1*L pp1 + m 11 * λ 11 = k2*L pp2 + m 22 * λ 22 k1*L pp1 + m 12 * λ 12 = k2*L pp2 + m 21 * λ 21 k1*L pp1 + m 12 * λ 12 = k2*L pp2 + m 22 * λ 22 ; Solving the four equations simultaneously gives the multiplication factor m 11 , m 12 , m 21 , m 22 ; Step S202 specifically includes: The current actual distance La is calculated according to the formula La = k1*L pp1 + m 11 * λ 11 .

7. The dispersive interferometric distance measuring method according to claim 5 or 6, characterized in that In step S201, for each optical frequency comb, the extreme points in the range interference spectrum are selected according to the following steps: Determine the k maxima or minima collected in the distance interferometric spectrum; For each determined extreme point, the extreme point and its corresponding nearby points are fitted to obtain the fitted extreme point, which is then selected as the extreme point.

8. The dispersive interferometric ranging method of claim 1, wherein, The measurement range is adjusted by adjusting the repetition frequency difference between the two optical frequency combs. The smaller the repetition frequency difference, the lower the lower limit of the measurement range. When adjusting the repetition frequency difference between the two optical frequency combs, ΔL should be greater than or equal to the preset measurement error.

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