Multiplexing onto a spatial light modulator using random binary patterns

We introduce an approach for encoding a variety of independent outputs from a computer-generated diffractive optical element displayed on a spatial light modulator (SLM). In this approach, random binary 0-1 orthogonal patterns are multiplied to the different phase functions, effectively multiplexing the corresponding different outputs. We show experimental results with different examples of multiplexed phase functions. Additional functions can be multiplexed simply by adding more random binary patterns. We demonstrate the generation of up to eight different independent outputs. Although the technique was demonstrated years ago, nowadays it can be applied with high-resolution SLMs with a very large number of pixels, thus allowing for a larger number of multiplexed functions without significant degradation. Nevertheless, high-resolution SLMs are affected by pixel crosstalk caused by the fringing field effect. We show that the random patterns are quite sensitive to this effect, leading to a significant undesired DC order. Two alternative strategies to avoid this degradation and make the random multiplexing technique efficient are discussed.