Speckle reduction in holographic projection using temporal-multiplexing of spatial frequencies

We present a method that significantly reduces the speckle effect in holographic projection. It is based on zero-padding the predefined projected intensity and calculating an extended phase distribution using an optimized iterative approach based on the generalized projection method. The extended phase distribution is divided into several finite ones with the size of the spatial light modulator (SLM). The SLM manipulates an incident plane wave to generate the projected intensity at a remote plane. Utilizing the temporal-multiplexing property of a phase-only SLMand incoherent superposition of the redundant intensities projected across the observation plane reduce the speckle effect. In contrast to the state of the art, no mechanical moving parts and no additional information are required during the projection process. The basic principle of this technique and its experimental verification are described.