Control And Image Processing Of X-ray Wavefront Inspection System

In synchrotron radiation experiment,grazing incidence mirror is often used to realize optical path transformation.The grazing incidence mirror is a large-scale and high-precision optical surface used to focus X-ray beams.The surface error of the mirror directly affects the focal spot size.The goal of this project is to detect the error of non-destructive surface.The basic principle of the experiment is X-ray grating phase contrast imaging.The research group designed and built the X-ray wavefront detection device based on phase contrast imaging.The feasibility of X-ray wavefront detection device is confirmed by theoretical analysis and experimental research.Mainly completed the circuit system construction,motion control system design,image software algorithm system design,and completed the research and Simulation of phase step information extraction method.The main research contents and contributions are as follows:(1)In this paper,the characteristics of X-ray and matter interaction are analyzed from the point of X-ray and matter interaction,and then X-ray phase contrast imaging is introduced.Contrast analysis of phase contrast and absorption contrast imaging and analyze the advantages and disadvantages of different phase contrast imaging,then the theoretical basis and experimental principle of the X-ray wavefront testing device are determined.The X ray wave surface detection device is designed and built and the feasibility of the experimental device is verified by experiments.I am responsible for the circuit system,motion control system,which runs well in experiment process.The system can accurately control the movement of the experimental platform and realize the multi degree of freedom movement of the experimental platform.The monitoring device realized the remote control experiment platform.(2)According to the parameters of X-ray detector and MATLAB,this paper designs the image processing software system based on MATLAB.In this paper,the original image is recorded on MATLAB,and the image processing is realized directly by the upper computer software based on MATLAB.The main image processing algorithms include:illumination nonuniformity correction algorithm,combined filter denoising algorithm,image enhancement algorithm,threshold segmentation algorithm,moire fringe thinning algorithm,moire fringe spacing measurement algorithm.I encapsulate these image processing algorithms in the upper computer software of image processing based on MATLAB.In this way,image acquisition and processing can be carried out conveniently and quickly.(3)In the algorithm of Moire fringe image processing,I analyzed different correction algorithms of illumination nonuniformity,and finally determined to use two-dimensional gamma correction algorithm for illumination nonuniformity correction.In filtering and denoising algorithm,I compared the spatial filtering algorithm with the frequency filtering algorithm and considered the fringe characteristics of Moire fringe.I designed a combined filter for Moire fringe characteristics.Complete moire fringe information can be obtained by filtering and denoising with combined filter.In the image enhancement algorithm,I compared the histogram equalization algorithm with the high hat and low hat algorithm,and used the high hat and low hat algorithm to realize image enhancement.In the threshold segmentation algorithm,I compared and analyzed the iterative threshold segmentation algorithm and the Ostu threshold segmentation algorithm,and adopted the Ostu threshold segmentation algorithm.Finally,combining with the characteristics of moire fringes,the fringes are refined and the spacing is calculated,the calculation result meets the expected goal.(4)Based on the characteristics of X-ray phase contrast imaging,this paper analyzes the moire fringe information extraction method,and designs the phase step information extraction method.Combined with the phase unwrapping algorithm,the least square phase unwrapping algorithm is applied.I simulated and analyzed the extraction of grating phase step information,and got the grating phase step expansion curve and phase step expansion diagram.Then I get the three-dimensional phase diagram of grating phase stepping.So I verified that the information extraction of Moire fringe image of X-ray wavefront detection device can be realized by the least square phase unwrapping algorithm.This laid a foundation for the further study of related experiments.