Filter method used to eliminate the zero-order image

Abstract

The existence of zero-order image has certain effect on the quality of reconstructed images in off-axis digital holography. For eliminating the zero-order image in off-axis digital holography, a method of zero-order image elimination in off-axis digital holography by using of FIR (Finite Impulse Response) filter is proposed in this paper. This method is based on digital image processing. First, by analyzing the spatial spectrum characteristic of off-axis digital hologram and the principle of using FIR filter to eliminate zero-order image, the paper theoretically proved that the zero-order image can be effectively eliminated by the FIR filter method before reconstruction. Then, the digital simulation and experiment recorded holograms were processed in the program with the FIR filter method and reconstruction. Both the theoretical analysis and digital reconstruct results show that it can effectively eliminate the large bright spot in the center of the reconstructed image which caused by zero-order image, and improve the image quality significantly, give better contrast of the reconstructed image. This method is very simple and convenient for free of phase modulator or any extra optical element and needing only one time record.