Research On Phase Extraction Technology Based On Window Fourier Transform

Optical interferometry has become one of the most commonly used methods in the field of precision metrology due to its non-contact,high precision,and high sensitivity.In this measurement technique,the acquisition of interference fringes in the early stage and the processing of interference fringes in the later stage are the key links.This subject is mainly dedicated to the processing of interference fringes in the later period,that is,by extracting the phase information implied in the interference fringes,to obtain a series of physical quantities to be measured such as height,thickness,and refractive index.The phase extraction technique of interference fringes is widely used in 3D profile measurement,laser interferometry and structured smooth surface shape measurement.In this paper,based on the accuracy requirements of the current optical interferometry technology,based on the analysis of the basic principles of the window Fourier transform method,the accuracy analysis and experimental verification are carried out by means of simulation and experiment,and the problems in the research are addressed Improvements have been made,the specific research work is as follows:The basic theory of window Fourier phase extraction technology: first of all,theoretical derivation and simulation analysis of the traditional Fourier transform method to determine the optimal filter window type of FFT algorithm;Basic theory and theoretical derivation of the optimal parameter selection criteria for the derived algorithms—Window Fourier Ridged method and Window Fourier Filtering method.Accuracy analysis of Window Fourier phase extraction technology: Based on the basic theory of WFT and the optimal parameter theory corresponding to the two algorithms,the results of the simulation of interference fringe patterns using Matlab are used to analyze the accuracy of the above theoretical results.The method of error calculation determines the optimal parameter selection criteria of the Window Fourier transform algorithm.Experimental verification of Window Fourier phase extraction technology: use Zygo interferometer to collect experimental interference fringes,perform phase extraction processing of FFT method and WFT method and fit the corresponding surface shape,and compare the results with the results obtained by Zygo interferometer A comparison is made to achieve the accuracy comparison of various phase extraction techniques and to check the accuracy of the optimal parameter selection criteria determined during the simulation.Research on the improvement of window Fourier phase extraction technology: In order to solve the phase distortion phenomenon of window Fourier phase extraction technology during the experiment,a Fourier-window Fourier joint phase extraction technology was proposedSimulations and experiments verify that the technology is more accurate and applicable than traditional window Fourier phase extraction technology,and realize the improvement of window Fourier phase extraction technology.