Image processing in numerical reconstruction for lensless Fourier transform hologram

Based on the characteristics of numerical reconstruction for lensless Fourier transform hologram, a set of digital image processing algorithm is presented to eliminate zero diffraction component and twin image. This method is different from the former one and consists of three steps: hologram contrast enhancement, bandpass filtering and V-filtering, and reconstructed image smoothing. The hologram contrast enhancement pretreatment, which can be achieved by highpass filtering, is adopted to improve the diffraction efficiency of the recorded digital hologram and suppress zero diffraction component of the reconstructed image. Using bandpass filtering and V-filtering to the reconstructed image with background noise, the noise can be eliminated and the viewfield is made homogeneous. Furthermore, smooth processing such as wavelet filtering and median filtering can also enhance the signal-noise ratio of the reconstructed image. It is shown that the method need record hologram only once and these three simple processing steps are effective for improving the reconstructed image quality and obtaining the satisfying results. It is especially applicable for the numerical reconstruction of lensless Fourier transform hologram, and more practical.