Randomisation of undersampled pixels for image duplicate suppression in holographic projection

Abstract

Computer-generated holography is a technology valuable for efficient projection and three-dimensional displays, with a growing number of calculation algorithms and relatively simple optical setups for image reconstruction. Among available technologies, liquid crystal on silicon spatial light modulators can provide uncomplicated phase modulation of incident wavefronts. However, these devices face challenges to overcome, such as the presence of multiple image duplicates in hologram reconstructions. Here, we propose a method for reducing visibility of those duplicates in which the volume and complexity of the setup remain the same. It is based on randomisation of positions of light-modulating pixels and distorting the otherwise regular pixel array of the modulator, without modifying the device. We present a theoretical analysis and results obtained in both simulations and experiment. Signal-to-noise ratio in the areas surrounding the desired image is shown to decrease, suppressing the presence of image duplicates. Various levels of randomisation are considered and can be selected with specific applications in mind.