Radial Shear The Interference Test Technology Research

The cyclic radial shearing interferometer (CRSI) is a system of a laser beam diagnosis, which can figure out the phase and amplitude of wavefront of the measured laser beam by one single radial shearing interferogram. In the dissertation, various algorithms are used to abstract the phase and amplitude of wavefront from a collected radial shearing interferogram, and a comparative research on the precision and corresponding error of these algorithms is finished. The work is a direct assistance of optimizing the CRSI characteristic. Some usefull results haved summarized as follows:1. According to the CRSI, the three crucial algorithms have been analysed well, which are used on a procress of reconstructing the phase of wavefront. The first one is to extend the fringes, the second one is to recover the surface of wavefront from one single interforfram, and the last one is a sort of iterative algorithm reconstructiong an original wavefront.2. A 2-DFFT algorithm is used to spread the circular region of fringes to square region, which adopts a hamming filter. The extended fringes obtain the same duration construction as the ones of the circular region. Meanwhile, the average value of the data of the circular region is added as the background of the extended fringes, which can keep the contrast consistent between the inner and outer of the circular region.3. A derivation of FFT and Wavelet Transform algorithm is accomplished. By the simulation and experiment, the precision and error of the two algorithms are particularly analysed.4. A derivation of a called "find+1 order spectrum" iterative algorithm is accomplished. By the simulation and experiment, its precision is the same as the "search the maxium" algorithm. When the coordinates of the real number of the+1 order spectrum is needed, the iterative algorithm is superior.5. A derivation of wavefront reconstruction iterative algorithm is submitted.The first 6 Zernike polynomials are used to fit the ideal original wavefront, the reconstruction original wavefront and the shearing wavefront. Each coefficient of the reconstruction original wavefront is really close to the ideal original wavefront, which proves the effectiveness of wavefront reconstruction iterative algorithm.6. On a real wavefront reconstruction process, the entire error of the algorithms is analysed and calculated. Three main error of algorithm are involved:(1) the error of FFT algorithm on the calculating shearing wavefront process, (2) the own error of iterative algorithm, (3) the extra error of iterative algorithm by the offset. Finally, the entire error of PV and RMS of reconstructing the phase of wavefront are obtained.7. According to the wavefront reconstruction iterative algorithm, the amplitude reconstruction iterative algorithm is deducted. The correlative simulation and experiment have been implemented.As above mentioned, we conclude that abstracting the phase or amplitude of wavefront from one single radial shearing interferogram usually needs three steps:(1)the fringes extension,(2)recoving the shearing wavefront or background of the interferogram, (3) using iterative algorithm to reconstruct the phase or amplitude of wavefront. The analysis of the precision and error of the used algorithms is described, the entire error of PV and RMS of reconstructing the phase of wavefront are 10.32% and 4.10%, and the entire error of reconstructing the amplitude of wavefront is 7.29%.