Axial asymmetry in holographic and incoherent correlation imaging

Abstract

In optical lens imaging, the main attention has traditionally been paid to the lateral resolution roughly estimated by a two-dimensional point spread function (PSF) describing sharp image of a point object. In three-dimensional (3D) imaging and methods based on depth information, an axial profile of the PSF becomes of particular importance. In studies on the 3D PSF, the axial image asymmetry and shift of the intensity maximum out of the focal plane were revealed for optical systems characterized by low Fresnel numbers. In this paper, the 3D PSF is examined in terms of digital imaging, where a point object is recorded optically and its image reconstructed numerically. The analysis includes methods of digital holography, in which the axial image asymmetry is examined in relation to different geometries of coherent recording waves. Attention is also devoted to the Fresnel incoherent correlation imaging that enables recording of 3D objects in spatially incoherent light.