Estimating object and field phase through in-line intensity measurements using a twinning algorithm

Abstract

A method to estimate the object phase as well as the field phase through in-line multiple transverse plane intensity measurements is demonstrated, with no requirement for a reference field. A twinning mechanism to estimate the object phase while simultaneously estimating the phase of the light field (field phase) at any plane before and after the object is outlined. The twinning mechanism is illustrated through its implementation on a Gerchberg–Saxton (GS) type algorithm. A forward propagating GS-type algorithm is twinned with a backward propagating GS-type algorithm, through an intersection occurring at the object plane. The efficacy of the algorithm is demonstrated through comparison with a standard interferometric method on numerically generated intensities corresponding to random as well as dislocated phase objects. It is seen that for low noise conditions, the fidelity of the retrieved object phase, is comparable to that obtained through the interferometric method. Estimation of the object, as well as the field phase, is experimentally demonstrated through the twinned GS-type algorithm on both random as well as dislocated phase objects.