Study On Absolute Ranging By Frequency Scanning And Optical Sampling Using Optical Frequency Comb

With the development of industrial manufacturing and national defense technology,the way to realize high-precision distance measurement of sub-micron level in a large scale of kilometers has become a research hotspot.As a high-precision measurement tool,the optical frequency comb has the characteristics superior to the traditional laser technology,and brings the human ranging technology to a new height.In this paper,the principle of repetitive frequency scanning of laser is introduced into the traditional optical sampling method,and an absolute distance measurement method by frequency scanning and optical sampling using optical frequency comb is proposed.The main research works are as the following:The principle of absolute ranging based on frequency scanning and optical sampling method is studied.The method of eliminating the"blind area"is proposed.The cross-correlation function model of interference fringes is established.The influence of dispersion effect on pulse envelope and cross-correlation fringe is explored and the importance of dispersion compensation is proved;The principle of femtosecond fiber laser and its repetition frequency scanning method are explained,the dispersion of fiber delay line was compensated,the absolute distance measurement system of frequency sweeping and optical sampling was built,and the distance measurement experiment was carried out on the standard long guide rail.The experimental results show an agreement well within 11?m in a range up to 60 m,corresponding to a relative precision of 1.8×10^-7;Based on the principle of frequency and distance difference,an optimization algorithm for calculating cross-correlation fringes is proposed.The experimental results show that the measurement accuracy is improved from 11?m to 4?m and the repeatability error is improved from 10?m to 2?m in the range of 60 m,which indicate that the accuracy and stability of the ranging are significantly improved.In addition,the refractive index of the air group was modified according to the experimental environment and the uncertainty of the measurement was analyzed in detail;A system optimization scheme is proposed.By improving the structure of the femtosecond laser and combining the principles of large-scale frequency sweeping and small-range sweeping,arbitrary distance measurement can be realized.From the perspective of instrument reliability,a preliminary design scheme for the modularization of the measurement system is proposed.The ranging technology based on frequency scanning and optical sampling method has the ability to provide a balance among long range,high resolution,and rapid measurement.And the whole system adopts all-optical fiber path,which has the potential to become a portable instrument in the field of precision measurement in the future.