CN-121978700-A - Absolute distance measurement method and device for double-optical-comb differential time domain signals

CN121978700ACN 121978700 ACN121978700 ACN 121978700ACN-121978700-A

Abstract

The invention relates to an absolute distance measurement method of a double-optical-comb differential time domain signal, which comprises the steps of forming mixed signal light and mixed local light by an inter-frequency optical-frequency comb through an optical fiber beam combiner and a one-to-two optical fiber beam splitter, generating mixed reference signal light and mixed measurement signal light by a half-reflection half lens and a target pyramid, combining the mixed reference signal light and the mixed local light through a polarization beam splitting prism, generating a second harmonic signal with fixed time delay by the combined beam light through twice frequency multiplication, respectively inputting the second harmonic signal into a double port of a balanced differential detector, generating interference signals with opposite slopes by differential operation of the detector, and obtaining the absolute distance by slope separation, fuzzy number judgment and simultaneous formula calculation. The invention has the advantages of no need of rough measurement device and optical comb modulation, single measurement breaking through the non-fuzzy range limit, realization of attosecond time interval extraction by means of differential detection, high ranging precision, modularized design of the optical path, simple and convenient assembly and adjustment, strong anti-interference performance, no step error judgment in dynamic measurement and adaptation to the multi-scene precise ranging requirement.

Inventors

GAO HAORAN
ZHONG WEIMIN
YAN SHUTONG
Ge Pengxiang
ZHAO RUHAI

Assignees

安徽建筑大学

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. The absolute distance measurement method of the double optical comb differential time domain signal is characterized by comprising the following steps of: s1, mixing two femtosecond optical frequency combs emitted by two groups of femtosecond laser sources through an optical fiber combiner to form a mixed optical frequency comb; S2, utilizing a one-to-two optical fiber beam splitter to split the mixed optical frequency comb, and marking the mixed optical frequency comb as mixed signal light and mixed local light; S3, the mixed signal light is split by a half-reflecting and half-transmitting mirror, the original path reflection part is marked as mixed reference signal light, and the rest part which is shot to a measured object and reflected is marked as mixed measurement signal light; S4, after the mixed reference signal light, the mixed measurement signal light and the mixed local light are combined, the combined light passes through a first second-class frequency doubling crystal to generate second harmonic signal light and part of the combined light without frequency doubling effect, and the second harmonic signal light is input to an a port of the balanced differential detector; S5, passing the rest beam combination light without frequency multiplication effect through a second class frequency multiplication crystal, generating second harmonic signal light again, and inputting the second harmonic signal light to a port b of the balanced differential detector; s6, carrying out difference operation on the signals of the port a and the port b by a balance difference detector, generating two groups of mixed double optical comb differential time domain interference signals with positive and negative opposite central zero slopes, and separating, identifying and judging the fuzzy number multiple relation and the simultaneous formula resolving distance through slope characteristics of the two groups of interference signals.
2. The method for measuring absolute distance of differential time domain signals of two optical combs according to claim 1, wherein the two sets of femtosecond optical frequency combs in step S1 are different in frequency, respectively And And (2) and In the middle of Representing the first femtosecond laser source output repetition frequency, Representing the second femtosecond laser source output repetition frequency, Representing the output repetition frequency difference between the first and second femtosecond laser sources.
3. The method for measuring absolute distance of differential time domain signals of double optical combs according to claim 1, wherein in the step S4, before the combined beam enters the first second-class frequency doubling crystal, focusing is performed by a first convex lens, and after the combined beam passes through the first second-class frequency doubling crystal, collimating is performed by a second convex lens.
4. The method according to claim 3, wherein in the step S4, the outgoing light passing through the second convex lens includes second harmonic signal light and part of the combined light without frequency multiplication effect, the second harmonic signal light and part of the combined light without frequency multiplication effect pass through a high-pass dichroic mirror, the second harmonic signal light is reflected by the high-pass dichroic mirror to enter the balanced differential detector, and the combined light without frequency multiplication effect passes through the high-pass dichroic mirror.
5. The method of claim 1, wherein in the step S5, before the combined beam light without frequency multiplication effect enters the second type frequency multiplication crystal, focusing is performed by a third convex lens, and after the combined beam light without frequency multiplication effect passes through the second type frequency multiplication crystal, collimating is performed by a fourth convex lens.
6. The method for measuring absolute distance of differential time domain signals of double optical combs according to claim 5, wherein in the step S5, a fixed time delay τ 0 is introduced into the second type of frequency doubling crystal.
7. The method for measuring absolute distance of double optical comb differential time domain signals according to claim 1, wherein in said step S6, the distance result calculated from the double optical comb signals formed by the local light is The distance result calculated from the double optical comb signal formed by the measurement signal light and the local light is: And obtaining that the slopes of the signal center zero points are opposite when the overlapping directions of the two groups of optical frequency comb signals are different by utilizing a differential time domain interference signal formula, wherein the expression is as follows: Wherein c is the light speed, m 1 ,m 2 represents the integer multiple of the respective non-fuzzy range, n g is the refractive index of air, deltat 1 、Δt 2 is the time interval between the reference signal light and the measurement signal light measured by the respective double optical comb signals, In order to measure the distance to the object to be measured, For the first femtosecond laser source repetition frequency, For the second femtosecond laser source repetition frequency, Representing the non-ambiguous range of the first set of dual optical comb signals, Representing the non-ambiguous range of the second set of dual optical comb signals, Representing the fractional distance in the ambiguity range measured by the first set of dual optical comb signals, Representing the decimal distance in the fuzzy range measured by the second group of double optical comb signals; And Is the peak intensity of the two light pulses, And The pulse widths of the light pulses of the single reference signal light or the measurement signal light and the single local light respectively, For the relative time offset of the two pulses, A fixed time delay is generated for the second type of frequency doubling crystal.
8. The device for the absolute distance measurement method of the double-optical-comb differential time domain signals is characterized by comprising a light source and beam splitting system, a signal transmission and beam combining system, a differential time domain interference system and a signal processing and resolving system, wherein the light source and beam splitting system comprises a rubidium atomic clock, a first femtosecond laser light source, a second femtosecond laser light source, an optical fiber beam combiner and a two-fiber beam splitter, the rubidium atomic clock is respectively connected with the first femtosecond laser light source and the second femtosecond laser light source, the first femtosecond laser light source and the second femtosecond laser light source are respectively communicated with different inlet optical fibers of the optical fiber beam combiner, the optical fiber beam combiner is communicated with a two-fiber optical fiber, the signal processing and resolving system is used for receiving the differential time domain interference signals output by the balanced differential detector, separating and identifying two groups of double-optical-comb distance measurement signals, and extracting a time interval parallel vertical distance measurement formula to resolve the absolute distance of a measured object.
9. The device for measuring absolute distance of double optical comb differential time domain signals according to claim 8, wherein the signal transmission and beam combination system comprises an optical fiber circulator, an optical fiber collimator, a half-reflecting half-lens, a target pyramid, a quarter wave plate and a polarization beam splitter prism; the optical fiber collimator comprises a first optical fiber collimator, a second optical fiber collimator and a third optical fiber collimator, wherein the quarter wave plate comprises a first quarter wave plate and a second quarter wave plate, the one-to-two optical fiber beam splitters are in optical fiber communication with the optical fiber circulator and the third optical fiber collimator, the optical fiber circulator is in optical fiber communication with the first optical fiber collimator and the second optical fiber collimator, one end of the semi-reflective semi-transparent mirror is in optical path communication with the first optical fiber collimator, the other end of the semi-reflective semi-transparent mirror is in optical path communication with a target pyramid optical path, one end of the first quarter wave plate is in optical path communication with the second optical fiber collimator, the other end of the first quarter wave plate is in optical path communication with the third optical fiber collimator, one end of the second quarter wave plate is in optical path communication with the polarization beam splitter prism, the mixed signal light is emitted to the semi-reflective semi-lens after passing through the optical fiber circulator and the optical fiber collimator, the mixed signal light is formed into mixed reference signal light and mixed measurement signal light emitted to a target after passing through the optical fiber circulator, and the mixed signal light is completed at the polarization beam splitting prism position of the polarization pyramid.
10. The device for measuring the absolute distance of the double optical comb differential time domain signal according to claim 8, wherein the differential time domain interference system comprises a convex lens, a second-class frequency doubling crystal, a high-pass dichroic mirror, a reflecting mirror and a balanced differential detector; the convex lenses comprise a first convex lens, a second convex lens, a third convex lens and a fourth convex lens; the second-class frequency doubling crystal comprises a first second-class frequency doubling crystal and a second-class frequency doubling crystal, the reflecting mirror comprises a first reflecting mirror, a second reflecting mirror and a third reflecting mirror, one end of the first convex lens is connected with the polarization beam splitting prism, one end of the second convex lens is connected with the first second-class frequency doubling crystal, one end of the third convex lens is connected with the high-pass double-color mirror, the other end of the third convex lens is connected with the second-class frequency doubling crystal, one end of the fourth convex lens is connected with the second-class frequency doubling crystal, one end of the second reflecting mirror is connected with the first reflecting mirror, one end of the second reflecting mirror is connected with the third reflecting mirror, one end of the third reflecting mirror is connected with one inlet of the balance differential detector, the other inlet of the balance differential detector is connected with the high-pass double-color mirror, the combined beam light is generated through the first group convex lens and the first second-class frequency doubling crystal, the second harmonic wave is generated through the first group convex lens and the high-pass double-color differential detector, the second harmonic wave is generated through the second harmonic wave balancing differential detector, the second harmonic wave is input through the second harmonic wave balancing lens and the second harmonic wave balancing lens is fixed after the second harmonic wave balancing lens is generated through the second harmonic wave balancing lens, and the light is guided by a plurality of reflectors and then is input into the other inlet of the balance differential detector.

Description

Absolute distance measurement method and device for double-optical-comb differential time domain signals Technical Field The invention belongs to the technical field of precision measurement, and particularly relates to an absolute distance measurement method and device for a double-optical-comb differential time domain signal. Background The optical frequency comb establishes accurate connection between optical frequency and microwave frequency by virtue of the equally-spaced frequency comb tooth structure, provides a high-precision and real-time technical means for absolute distance measurement, and has important application prospects in various fields such as industrial precision machining, aerospace assembly, geodetic measurement and measurement standards. By utilizing the advantages of high time resolution and high frequency stabilization, high-precision large-size absolute distance measurement can be realized. However, there are still some technical challenges in large-size spatial multi-target coordinate measurement based on femtosecond optical frequency combs. The measurement result of the femtosecond optical frequency comb absolute distance measurement method is closely related to a non-fuzzy range, and the non-fuzzy range only depends on the repetition frequency of the measurement optical frequency comb. In actual measurement, the integer multiple and the distance measurement within the range of the non-ambiguous length together determine the final measurement. To solve this problem, the prior art generally employs an additional rough measurement device to estimate an integer multiple, or makes a secondary measurement of the measured distance by changing the repetition frequency of the optical frequency comb to determine the multiple. However, the introduction of additional rough measurement devices or the change of frequency for secondary measurement increases the complexity of the measurement system structure and reduces the efficiency of distance measurement. Particularly, in a dynamic measurement scene, multiple measurements are easy to cause measurement errors of integer multiples, so that accuracy of measurement results is affected. The patent number CN117130005A discloses a non-blind area large non-fuzzy range double-optical-comb ranging device and a ranging method, which are characterized in that a double-channel double-optical-comb ranging light path is arranged, double-optical-comb light beams emitted by the double-optical-comb light source are received and used for testing targets to obtain reference interference signals and measurement interference signals, a coarse ranging module is used for testing the targets to obtain coarse ranging results by emitting test light and photosynthetic light of signals emitted by the double-channel double-optical-comb ranging light path, and a signal processing module is used for calculating and obtaining double-optical-comb ranging results based on the reference interference signals and the measurement interference signals and fusing the double-optical-comb ranging results and the coarse ranging results to obtain final ranging results, so that the problem that measurement cannot be carried out due to overlapping of the reference interference signals and the measurement interference signals in a time domain is well solved, and the ranging blind area of a large dynamic range is eliminated. However, in the practical application process, a coarse ranging module is required to be additionally arranged, so that the system structure is complex, the hardware cost is high, the fuzzy number is calculated by means of fusion of the accurate measurement and the coarse measurement result, the measurement flow is complex, the efficiency is low, and the problem of integer multiple judgment errors and poor dynamic adaptability are easily caused by the problem of synchronism of the coarse measurement and the accurate measurement in the dynamic measurement. The patent number CN119064946A discloses an absolute distance measuring system and method based on an on-chip cross double optical comb, the invention generates two sets of microcavity soliton optical frequency combs with slightly different repetition frequencies and staggered comb teeth by arranging an on-chip double optical frequency comb generating module, a distance measuring module, a detecting module and a data processing module, performs dispersion interferometry ranging on the two sets of optical frequency combs, then detects and obtains a spectrum containing distance information and the repetition frequencies of the two sets of optical frequency combs, performs data processing by a data processor to obtain an absolute distance, and combines the two sets of optical frequency combs to realize large-scale expansion of a non-fuzzy range and precise calculation of the distance. However, the method still has the problems that spectrum detection and complex data calculation depending on a dispersion interferometry