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Speckle Generation by Phase-Only Spatial Modulators: Random Phase Properties That Produce Fully Complex Modulation and that Model Optical Processor Performance.

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Final technical rept. Jun 92-Mar 96,

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Optoelectronic processors that use phase only and amplitude phase coupled spatial light modulators SLMs can be profoundly affected by phase errors. These errors arise not only from irregularities in the modulators themselves, but at a number of points along the signal processing chain. Traditional theories of speckle generation by rough surface scattering are adapted to analyzing SLMs. SLMs are modeled as arrays of subaperturespixels that are perturbed by random phase components constant and linear retardations. The effects of not only random, but also systematic. phase errors on the performance of diffractive optical elements DOEs and optical correlators are evaluated. While traditional speckle theory models random surfaces as stationary random processes, SLMs can be programmed to produce nonstationary optical surfaces. This generalization is used to devise a new class of computer generated holographic algorithms, referred to as pseudorandom encoding. The method is notable in that it 1 uses all available space bandwidth of the SLM 2 produces diffraction patterns having large signal to noise ratio and, most notably, 3 can be calculated in real time by serial processors. Simulations and experimental demonstrations using SLMs are presented, and applications to pattern recognition, optical interconnects, multispot beam steering, and acceleration of DOE design algorithms are described.

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  • Electrooptical and Optoelectronic Devices
  • Holography

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