Computer simulation of light wave diffraction by screens of different shape

The Fresnel diffraction integral is carried out with numerical methods using fast Fourier transform(FFT),and the diffraction of light wave by different screens are simulated.The light field distribution of Fraunhofer diffraction and Fresnel diffraction can be calculated directly when an observer plane is placed at different distances from the screen.Simulation of diffraction of common slit/hole on computer is of advantage for us to understand the difference of diffraction in near and far fields and the pattern distribution.