İkili uzamsal ışık modülatörleri kullanan holografik ekranlar için sinyal işleme tabanlı çözümler

Holography is a promising method to realize satisfactory quality threedimensional(3D) video displays. Spatial light modulators (SLM) are used inholographic video displays. Usually SLMs with higher dynamic ranges are preferred.But currently existing multilevel SLMs have important drawbacks. Someof the associated problems can be avoided by using binary SLMs, if their lowdynamic range is compensated for by using appropriate signal processing techniques.In the first solution, the complex-valued gray level SLM patterns thatsynthesize light fields specified in the non-far-field range are halftoned into binarySLM patterns by solving two decoupled real-valued constrained halftoningproblems. As the synthesis region, a sufficiently small sub-region of the centraldiffraction order region of the SLM is chosen such that the halftoning error isacceptable. The light fields are synthesized merely after free space propagationfrom the SLM plane and no other complicated optical setups are needed. In thisrespect, the theory of halftoning for ordinary real-valued gray scale images is extendedto complex-valued holograms. Simulation results indicate that light fieldsthat are given either on a plane or within a volume can be successfully synthesizedby our approach. In the second solution, a new full complex-valued combinedSLM is effectively created by forming a properly weighted superposition of anumber of binary SLMs where the superposition weights can be complex-valued.The method is a generalization of the well known concepts of bit plane decompositionand representation for ordinary images and actually involves a trade-offbetween dynamic range and pixel count. The coverage of the complex plane bythe complex values that can be generated is much more satisfactory than that isachieved by those methods available in the literature. The design is also easy tocustomize for any operation wavelength. As a result, we show that binary SLMs,with their robust nature, can be used for holographic video display designs.