The feasibility of automatic focusing in digital holography by using Fresnel transform as numerical holographic reconstruction algorithm

Several automatic focusing approaches have been proposed in the past to compute the refocus distance in digital holography (DH) and digital holographic microscopy (DHM). Most of the automatic focusing approaches are in combination with the convolution or angular spectrum method as numerical reconstruction algorithms for digital hologram. Relatively little work has been done on the combination of detecting the focus distance by automatic focusing approaches with Fresnel transform based method for digital holographic reconstruction. In this letter, the feasibility and application of the Fresnel transform based method to perform a digital holographic reconstruction in automatic focusing in DH are studied. The numerical simulation and experimental results are given. The results validate that the Fresnel transform based reconstruction algorithm can also be effectively applied to automatic focusing in DH and DHM.