Digital holographic reconstruction image fusion based on mathematical morphology

In digital holography, multi-focus holographic images can be reconstructed by applying values for the reconstruction distance during the reconstruction process. And then the hologram can be fused to extend the depth-of-field by images fusion method. Since the speckle noise in the digital holography images, an efficient fusion algorithm based on mathematical morphology is proposed. First, the decomposed high-frequency and low-frequency sub-band coefficients are obtained by the Wavelet-Controulet transform. Then, it fused coefficients with different rules. To suppress the speckle noise, the local energy combined with mathematical morphology is presented for high-frequency coefficients and the contrast method is used to fuse the low-frequency coefficients. Finally, the invers transform is employed to get the fused image. The effectiveness analysis of the algorithm and the experiment results show that for the digital holography images with speckle noise, the fusion method with mathematical morphology can reduce the speckle noise and keep more detail information. At last, the depth-field of the image can be extended up to 11.5 cm. As compared with the conventional method without mathematical morphology, for dices, the proposed method enhances its Tenengrad and Entropy by 11.8% and 2.7%. For coins, the proposed method enhances its Tenengrad and Entropy by 13.6% and 2.8%.