Research On Coherent Laser Phase Detection Technology Based On Interferometric Images

Laser coherent synthesis is the main research field for obtaining high power and high beam quality laser output,which refers to the superposition of laser beams with the same frequency,linear polarization,and phase synchronization.In order to achieve the laser coherent synthesis,it needs to realize the phase synchronization between each laser beams.This thesis focuses on the phase synchronization between laser beams for the high-power laser coherent synthesis and studies the extraction technology of coherent laser phase information by means of interference images formed by two coherent lasers.The main research is as follows:(1)Based on the phase control technology of interferometric images,a phase information extraction system for two coherent laser beams using interferometric image method was constructed based on the active coherent synthesis system model.The implementation principle of the system was analyzed in detail,and the functional form of the coherence between the two laser beams was derived.(2)Considering different background light intensities and modulation systems,the phase extraction accuracy and computational speed of the random phase shift algorithm based on least squares iterative fitting(AIA)and the random phase shift algorithm based on principal component analysis(PCA)was analyzed and compared with Matlab.The results show that the AIA algorithm has high accuracy in phase extraction and is sensitive to background light intensity and modulation of the interferogram.Without the iterative extraction,the calculation process of principal component analysis is fast and insensitive to background light intensity.However,its extraction accuracy is relatively lower compared with the AIA algorithm.Besides,the number of fringes in the interferogram is necessary.In order to improve the convergence of the AIA algorithm due to inconsistent contrast between interference images,two compensation factors background light intensity fluctuation coefficient and modulation fluctuation coefficient were introduced into the AIA algorithm.The Simulation results show that the AIA algorithm with these two compensation factors presents improved demodulated phase when the interference varies with the background.(3)A coherent laser phase extraction system platform is built and the corresponding phase extraction software system is developed based on Qt.In this way,the visual operation of laser coherence performance,image acquisition and control performance,and real-time phase information extraction performance of the fusion contrast compensation AIA algorithm are realized.(4)Finally,the experiments are conducted.The phase extraction with the contrast compensation AIA algorithm and the comparison between the AIA algorithm and principal component analysis algorithm are verified.The results show that the contrast compensation AIA algorithm has a good ability of higher accuracy phase extraction.The error between the detected phase difference and the theoretical phase difference introduced by the displacement platform is within 0.0639 rad.Furthermore,the solution time is 0.4931 s which can meet the real-time requirements of following phase feedback control.