Theoretical Modeling And Analysis Of Point Diffraction Based On FDTD Method

This dissertation mainly research on a method for analyzing point-diffraction wavefront error. Based on the method, has writed a MATLAB simulation program which can be used to analyze the point diffraction wavefront error and the energy distribution. The content of this dissertation include:After review of importance of point-diffraction wavefront error analysis, there is also a review over the current point-diffraction wavefront error analysis methods, especailly vector diffraction thoery.The principal of Finite Difference Time Domain (FDTD) method, which can numerical solve Maxwell equation based on the discrete space and time, is detailed. Algorithm stability condition and numerical dispersion phenomenon of FDTD method is analyzed in detail. Then the importance of absorbing boundary for the FDTD simulation and Perfectly Matched Layer (PML) absorbing boundary was introduced.Considering the impact factors of point diffraction wavefront error and efficiency of computer simulation, has established three sets of simulation models. They are the plane-wave incident model, the convergence-wave incident model and three dimensional model, respectively. Based on the Huygens principle and Green function, a new near-field to far-field method is derived, which can use for the wavefront with large numerical aperture in two-dimension or three-dimension.The simulation of relationship between the point-diffraction error and diameter of the pinhole, the thickness of pinhole, the aberration amount of incident light, has been carried out by the MATLAB simulation program. Simulation results show that the pinhole has a very good role in shaping wavefront, and diffraction wavefront error is smaller, when the pinhole has the smaller diameter. And transmission of energy and the intensity uniformity of diffraction wavefront have been analyzed. The analysis of point-diffraction wavefront error and engry distribution with FDTD method provides theoretical basis for choosing dimension of pinhole in the experiments and testing with point-diffraction interferometer.