Absolute Ranging Of Asynchronous Optical Sampling Based On Mode-locked Laser

With the continuous development of industrial processing and national defense technology,distance measurement technology has changed rapidly.How to combine theoretical research with the actual measurements and achieve high precision results has become current technical research direction.Femtosecond laser is a kind of ultrashort pulse laser with a certain repetition rate realized by mode-locking mechanism.Its spectral width can reach femtosecond magnitude.Compared with general light sources,femtosecond laser has unique advantages in absolute distance measurement.In this thesis,an asynchronous optical sampling ranging scheme based on mode-locked laser is proposed and further applied to rough surface ranging.The main research works are as follows:1.The principle of absolute ranging based on asynchronous optical sampling is studied,and the advantages of asynchronous sampling and the influence of repetition frequency difference on asynchronous sampling were explored by comparing various traditional measurement methods.The importance of stabilizing repetition frequency difference was confirmed.And then,the scanning principle of femtosecond laser was introduced.The influence of polarization state of the mode-locked laser on the quality of the laser source and the distance measurement on the rough surface were introduced.The time jitter factors affecting the experimental results were analyzed theoretically.2.An absolute distance measurement system for asynchronous optical sampling was set up and a high-precision telescope system was independently designed.The scattering characteristics of the focus spot size on the rough surface were investigated,and the absolute distance measurement of the mirror surface is compared with that of the rough surface.The experimental results show that the residual distance measurement of the rough surface can be maintained within 10 ?m in sampling time of2 ms.3.Based on the characteristics of sampled signals,a peak-seeking algorithm based on peak fitting was developed.The efficiency of data processing was greatly improved.In addition,the refractive index of air group was modified according to the experimental environment,and the measurement uncertainty was analyzed in detail.4.A system optimization scheme was proposed.The error caused by air refractive index was further eliminated by adding frequency doubling crystals.From the angle of instrumentation and the premise of instrumentation reliability,the preliminary design scheme of system modularization was put forward.