A new expression of partially coherent light is derived. The formula of the partially coherent optical field is consisted of two terms: spatially coherent part propagated by angular spectrum and incoherent part based on the optical transfer function. Both parts are related to coherent function (degree of coherence). Then a design method for computer generated hologram based on the theory of partially coherent light is proposed. The formation process of CGH is divided into angular spectrum and optical transfer function. Both numerical simulations and optical experiments are done to verify that speckle contrast of holographic reconstructed images is improved without sacrificing in PSNR compared to traditional method. The experimental results show that the speckle contrasts are improved more than 46%, and the image quality is obviously improved. This method can be applied on three-dimensional holographic display, beam shaping and other wave-front modulation techniques.
The liquid crystal spatial light modulator is able to provide flexible wavefront modulation, whereas its nonlinear and spatial varying phase response will influence the modulation accuracy. In this paper, a software based C++ algorithm are designed to calibrate these distortions regionally. Twyman-Green interference method is utilized for gray versus phase shift measurement. The curvature of cover glass is measured by phase shift algorithm. Finally the entire panel is divided into several local regions to overcome the spatial varying phase response. For each sub-region, the nonlinear phase response is calibrated by remapping table. For a Jasper 4K SLM panel, when three local regions are built, the root mean error of linear phase shift is reduced to approximate 0.1 rad. The calibrated SLM is applied for holographic display and the improvement ratios of structural similarity index reach 30.6%, 62.5%, and 43.6% for R, G, and B reconstructed components respectively.
The liquid crystal spatial light modulator (LC-SLM) is able to provide flexible wave front control, whereas its phase response distortions will influence the modulation accuracy. In this paper, we will provide a novel sub-regional phase response calibration method for minimizing these distortions. In our calibration method, the entire panel is divided into several local regions based on the similarity of phase response characteristic. Liquid crystal cells in one sub-region show the same phase response. The calibration method is theoretical analyzed and experimentally verified. For the entire Jasper 4K SLM panel, when three local regions are built, the root mean error of linear phase shifts is reduced to approximate 0.1 rad. The calibrated SLM is applied for holographic display and the structural similarity index of the assessment shows the improvement ratios reach 30.6%, 62.5%, and 43.6% for R, G, and B reconstructed components respectively. It also could be used for the calibration of various SLMs in the future.
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