Multiplexed computer-generated holograms with irregular-shaped polygonal apertures and discrete phase levels.

Abstract

We propose a novel type of multiplexed computer-generated hologram (MCGH) with irregular-shaped polygonal apertures and discrete phase levels. Each elementary cell forming the new MCGH is divided into a central aperture and several peripheral apertures. The new MCGH allows us to exploit the huge space-bandwidth product provided by standard lithography technologies. With use of the Abbe transform, the Fraunhofer diffraction patterns from the polygonal apertures and, therefore, the layout coefficients can be computed with simple algebraic expressions. Several symmetries related to the polygonal apertures also facilitate the layout-coefficient computation. In the novel iterative subhologram design algorithm (ISDA), we consider all subholograms equally and apply the image-plane constraint to the total reconstructed image, which is the coherent addition of the subimages from the subholograms. We designed MCGHs with several billions of pixels per period, which cannot be achieved with the classical iterative Fourier transform algorithm, because of the prohibitive computational cost and memory limitation. MCGHs with irregular polygonal apertures and discrete phases, which were designed by the ISDA, reconstruct a desired image of large size with high diffraction efficiencies and low reconstruction errors.