Tilted objects EFI in digital holography by two different numerical approaches

Limited depth of field (DOF) is one of the main shortage for many optical imaging systems. This is a limitation that precludes to get in focus, in a single plane, objects that are located at different distances, but that fall in the same field of view. Furthermore, the depth of field is reduced as much as greater is the requirement for a high magnification and to obtain an extended focus image (EFI) of these objects remains one of the major challenges. In this work we propose and compare two different approaches to build the EFI of holograms recorded on a tilted plane. In the first case, a simplified three-dimensional (3D) formulation of the angular spectrum method (ASM) is proposed. It allows to generate the entire stack of propagated images in a single shot. In the second approach, a numerical cubic phase plate (CPP) is included into the reconstruction process of digital holograms with the aim to enhancing DOF of optical imaging system. Theoretical formulations of the two approaches are supported by experimental evidences. The obtained results show that the proposed strategies allow to reconstruct effectively an EFI from holograms recorded on an inclined plane.