Sensitivity-enhanced complex amplitude retrieval using multi-plane intensity detection and a lens

Phase retrieval methods like the classical Gerchberg-Saxton algorithm have an advantage compared to interferometric and holographic methods, because they require no reference wave. Thus the set-up can be very simple and stable. Recently, Pedrini has proposed a method for complex amplitude retrieval from a sequence of diffraction intensities [1]. The method is very reliable for high contrast phase distributions. For weak phase distributions, however, the intensity change along the propagation direction z is very small, thus phase retrieval is only possible by increasing the z-sampling. Here we propose an extension of this method by including a lens or a microlens array. The lens enhances the intensity variation in the recorded patterns and it is numerically easy to eliminate from the recovered phase distribution. The improved performance of the algorithm is demonstrated by numerical simulations. [1] G. Pedrini, W. Osten and Y. Zhang Opt. Lett. 30, 833-835 (2005)