Pixel Apodization for the Suppression of Higher Diffractive Orders in Computer Holography

Abstract

Demand for a next generation of head-up displays have increased the demand for the applicable holographic displays. From the available spatial light modulators (SLM), Liquid Crystal on Silicon (LCoS) SLMs are the most popular for the simplicity of addressing and their relatively low costs. However, improving its efficiency demands reduction of higher diffraction orders. In this work we propose a new solution, that is the pixel apodization as the means to redirect the light intensity from the undesirable images to the main image. The higher diffraction orders are the result of the rectangular shape of the pixels of the SLM, as it can be concluded from the Fourier Transform (FT) analysis. Hence we exploit the known property that a Gaussian function is, up to a constant multiple, its own FT. The presented simulations support the theoretical conclusions, as the apodization allows for a significant lowering of the intensity of the third and higher diffraction orders, in the same time increasing the intensity directed to the main image.