Improved Algorithm for Diffraction Calculation

An improved algorithm for diffraction calculation is proposed, which is suitable for near-field and far-field diffraction simulation simultaneously. Angular spectrum method ( AS) used frequently in diffraction calculation is based on Rayleigh-Sommerfeld integral formula. It is adaptable to a long range of diffracting distance, because there is not approximation with respect to propagation distance in this formula. However, in numerical calculation the sampling problem of transfer function makes it not adapt to near-field and far-field diffraction simulation simultaneously. In this study, this method is improved by limiting the spatial frequency range of diffracting wave. By using the improved method, the problem existed in far-field diffraction simulation with AS is resolved. Simulating examples are presented to validate the proposed method with band-width limit in the paper.