Image reconstruction of long‐wavelength holograms by digital filter technique

Abstract

AbstractA digital filter is used to reconstruct images from Fresnel‐transformed holograms by directly performing an inverse Fresnel transform with respect to a fixed plane which is defined by special parameters of propagation. In sampling holograms at the sampling interval Δx, the sampled propagator becomes a periodic function for sampling number N at distance 3p. An efficient digital filter can be constructed when N is an even squared number. The present method is also applicable to the hologram constructed at the propagation distance other than 3p if a corrected phase function is used. According to the computer simulation for comparison with other methods, the images reconstructed by the present method are as good as that by the one‐time Fourier transform method. This digital filter technique requires more computation than the FFT method, but it allows effective parallel processing and fast hardware realization.