Phase retrieval by amplifying the prism term of the Transport of Intensity Equation with a sliding step function

Abstract

Objectives:We present a novel quantitative phase retrieval method suitable for pure or weakly absorbing phase objects using the Transport of Intensity Equation. Our goal is to improve imaging methods available for analyzing pure phase and weakly absorbent objects. The method is exemplified with an economic and robust setup including no moving parts. Method:Our method is based on the amplification of the prism term in the Transport of Intensity Equation. We project an amplitude mask consisting of a blurred edge with a steep gradient to scan a 2D phase object and repeat the process with its complement. This allows us, by means of the cancellation of the lens term, to acquire the enhanced gradient which we then integrate to retrieve the phase of the sample. Results:We provide an analytic demonstration of our method together with the study of a practical case. The results obtained are in good agreement with the properties of the sample being studied using a partially coherent light and an LCD to display the mask. Conclusions:Our method offers a new option to study pure phase or weakly absorbing objects. It is simple and robust, allowing the design of a system without moving parts.