| Holographic three-dimensional(3D)display is usually regrard as one of the most promising 3D display techniques for its capability to provide all depth cues of human visual system.It has become one of the international advanced research hot points.For the flexibility of controlling optical wavefronts,optoelectronic holographic 3D display(OEHD)based on spatial light modulator(SLM)has aroused increasing interest.To realize high-quality full-color enlarged-viewing-angle OEHD,this dissertation has paid more attention to research the relative key techniques.They are described in detail as follows:After analyzing two typical algorithms for calculating the CGHs of 3D object,a novel algorithm is proposed and named as point-based Fresnel diffraction algorithm(PB-FDA).This algorithm can remove the zero-order image of SLM,eliminate the distortion of reconstructions and suppress the magnification chromatic aberration of color reconstructions.The shortest recording distance and optimal recording distance of the PB-FDA are analyzed to improve the quality of reconstructed images.Numerical reconstructions and optical reconstructions are illustrated to verify the feasibility of the algorithm and compare with other algorithms.To realize the full-color holographic display,the CGHs calculation and numerical reconstructions of color 3D object are implemented using the proposed PB-FDA.The speckle noise will seriously influence the quality of reconstructions in holographic displays.The mechanism of sepeckle noise existing in holographic image is analyzed.In order to suppress the speckle noise quickly,a novel method which combines temporal averaging method and a rotating symmetric diffuser is proposed.The speckle index(SI)is introduced to evaluate the effect of speckle noise suppression in the reconstructions.The OEHD systems with suppressing speckle noise by temporal averaging method and the novel method are built,respectively.The optical reconstructions depicted that the speckle noises can be quickly suppressed by using the novel speckle noise suppressing method.In the process of OEHD,viewing-angle of the reconstructions is limited by the SLM act as diffractive optical element.This dissertation analyzed the principles of different SLMs' tiling configurations to enlarge the viewing-angle of holographic reconstructions.According to the different singinal readout ways of transmissive and reflective liquid crystal SLM(LC-SLM),the enlarged viewing-angle OEHD systems based on LC-SLMs are designed.To further increase the viewing-angle,a 4F optical system consisting of two concave mirrors,whose focal length ratio is 2:1,is applied.The changes of the intrinsic viewing-angle,the tiled angle,the reconstruction distance and the image size of the holographic images after the 4f concave mirrors system are analyzed.The experimental results indicate that the proposed display system is feasible to reconstruct a holographic 3D image with viewing-angle of 14.8°,which is by about 3.9 times wider than the viewing-angle formed by a single SLM.A dynamic holographic 3D projection system based on a phase-only LC-SLM is introduced.A special designed cylindrical fog 3D screen is proposed to use as the scattered carrying medium to project the dynamic 3D images.Though this system,a large-size dynamic holographic 3D reconstruction can be observed by some observers at the same time.To realize wide viewing-angle and full-color holographic display,an increased-viewing-angle full-color OEHD system using a 4f concave mirrors system and a temporal-spatial multiplexing method is proposed.A temporal-spatial multiplexing synchronization control(TSMSC)method is developed to achieve a full-color image.The lateral chromatic aberration,axial chromatic aberration and the color crosstalk of the RGB images in the process of color holographic display are analyzed and compensated.The experimental results indicate that the proposed system is feasible to reconstruct a color holographic 3D image with viewing-angle of 12.8°. |
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