Research On Voxel-based Algorithm Of Computer Generated Hologram Based On LCOS Spatial Light Modulator

Among the various three-dimensional(3D)display technologies,holographic display is the most promising one since it can record and reproduce the whole optical wave field of the 3D scene.For the flexibiity of controlling optical wavefronts,the holographic 3D display based on spatial light modulator(SLM)has been widely studied.Occlusion is one of the most important characteristics in 3D scene.However,there is still a lack of a holographic 3D display algorithm model that can express the occlusion effect of reconstructed 3D images accurately.To solve the occlusion problem in holographic 3D reconstruction images,the dissertation has paid more attention to reseach the relative key techniques.The main contents are described in detail as follows:Firstly,the background of 3D display and the reseach status of holographic 3D display based on SLM are introduced,then the structure parameters and phase modulation principle of LCOS spatial light modulator,the scalar diffration theory and the algorithm for calculating computer generated hologram of 3D object are elaborated and analyzed in detail.Second,a voxel-based algorithm using LCOS spatial light modulator for calculating 3D computer generated hologram with occlusion effect is proposed,and the algorithm is acceletated by the look-up table method.To verify the feasibility of the proposed algorithm,optical experiments are performed by using a single phase-only SLM.The experimental results show that voxel-based algorithm can correctly express the occlusion effect of 3D objects.Thirdly,in view of the limited number of voxels reconstructed by a single LCOS spatial light modulator,a method of increasing the number of reconstructed voxels is proposed,and a holographic 3D display system based on planar splicing of LCOS spatial light modulators is constructed.Combined with the proposed voxel-based algorithm,the feasibility of this method is verified.The experimental results show that the holographic 3D display system based on seamless planar splicing of LCOS spatial light modulators can effectively increase the number of reconstrusted voxels in 3D scene with occlusion effect.Fourthly,in view of the small viewing angle of a single LCOS spatial light modulator,a method of expanding the viewing angle of holographic 3D display is proposed,and a holographic 3D display system based on curved splicing of LCOS spatial light modulators is constructed.Combined with the proposed voxel-based algorithm,the feasibility of this method is verified.The experimental results show that the holographic 3D display system based on curved splicing of LCOS spatial light modulators expands the viewing angle from 3.8° to 7.3°,which is more beneficial to the observation of 3D scene with occlusion effect.Last,in order to improve the computational efficiency for calculating computer generated hologram,a voxel-based optimized algorithm is proposed.The 3D scene can be classified into occluded part and unoccluded part,and the occluded part is decomposed into point unit while the unoccluded part is decomposed into plane unit.Finally,the 3D scene with occlusion effect consisting of different voxel units can be reconstructed by the holographic reconstruction system.By comparing the calculation time of the same hologram calculated by the unoptimized algorithm and the optimized algorithm,the results show that the optimized algorithm significantly improves the computational efficiency.