Amplitude and phase recovering from a micro-digital hologram using angular spectrum

Abstract

In this paper we present a method to get the complex amplitude of a digital hologram obtained through phase shifting transmission digital holographic microscopy. This is based on the angular spectrum method as a reconstruction algorithm employing an in-line experimental setup. The reconstruction technique automatically eliminates the zero order and the twin images from the digital hologram. By means of a reference hologram reconstruction method, a temporal averaging procedure and a focus distance averaging of the reconstructed complex amplitude, we extend an already efficient methodology to obtain high precision phase images with a reduced amount of aberrations caused by the microscope objective, and at the same time, we reduce the optical noise of the reconstructed complex amplitude. Using a homemade micro-thin film step surface, our system was calibrated and made traceable to an atomic force microscope (AFM). It is shown that our experimental results, compared to those given by the AFM, reach an axial accuracy of 9.7 nm from a typical phase sample.