Technology Research Of Laser Wavefront Radial Shearing Interferogram Processing

Some characteristics of Radial Shearing Interferometry:no need to set up special reference surface, simple structure, as well as changing measurement precision through shearing ratio regulation, which only needs one interferogram that can gain measured information. In addition, it is widely applied to the measurement of optical element, optical quality of the system and the wavefront detection. The key of optical path radial-shearing interferometry fringe information process is using the collected interferogram from the CCD, to calculate the phase information which is related to the measured directly.In this dissertation, analysed the basic measurement principle of Mach-Zehnder type radial shearing interferometry technique. Based on the characteristics of the interferogram, interferogram phase is be extracted by two-dimensional fast Fourier transform (2DFFT) method. The thesis from both spatial and frequency domain study of fringes de-noising, respectively, emphasis reconstruction algorithm based on a sample block extension interference pattern, and given specific algorithm flowchart, used two kinds of unwrapping algorithm for wrapped phase, respectively, and Zernike polynomial fitted wavefront.Compiled a set of algorithm program with MATLAB software, and the results with the ZYGO interferometer were compared on the same lens test results. The results show that the algorithms in optical element surface measuring for radial shearing interferometry are quite feasible, and the test results of ZYGO interferometer deviation and less than 1% in relative deviation. Moreover, this method can be applied to radial shearing interferometry tests and other surface shape testing.