Study on the depth of focus of lensless Fourier transform digital holographic imaging system

Abstract

Based on the principle of digital holography and the criterion of the depth of focus of coherent lens imaging system, the depth of focus (DOF) of off-axis lensless Fourier transform digital holographic system is analyzed. The DOF expressions of digital holographic systems with symmetrical and unsymmetrical offset of reference point sources are deduced and presented. By using a minute vertical bar object the corresponding simulations are performed. The recorded holograms are reconstructed digitally at the focal plane and its vicinity. The results verified the correctness of the analysis and show that the DOF of digital holographic imaging system is not only dependent on the optical wavelength and the recording numerical aperture but also strongly on the optical setup, which indicates that the DOF of digital holographic image system isn't the same as that of the coherent lens imaging system.