| Playing an important role of three-dimensional display,holographic display technology has become the future development direction because it can represent all stereo information of three-dimensional scenery,which has been widely studied at home and abroad.Different from common display technology,holographic display controls the amplitude and phase of the wavefront of diffracted light field by loading a computer-generated hologram on the carrier device,so as to control the reconstructed image in space.A relatively perfect holographic image should have a natural lighting and occlusion performance similar to the effect of optical holography from a continuous perspective,which is called "view-window"To date the research of CGH(computer-generated holograph/hologram)algorithm is mainly focused on improving the image quality and computing efficiency,with a lack of comprehensive algorithm and corresponding practical and efficient solution to fully display the three-dimensional object stereoscopic sense with view-window,which is difficult to provide enough stereoscopic psychological implications for viewers.Therefore,this paper proposes a point source CGH algorithm and the corresponding practical solution based on LCOS device and view-window to realize real-time and dynamic control of the expression of the three-dimensional information of the reconstructed image,so as to reproduce the three-dimensional scene with full parallax,accurate occlusion,anisotropic natural lighting effect and dynamic interaction,and give people a more real and vivid three-dimensional visual experience.The main contents of this paper are as follows:1.The development history of holographic technology,the research status of 3D display technology at home and abroad are introduced,the concept of view-window is expounded,the current algorithms of CGH based on LCOS are listed,and their characteristics are analyzed and compared.2.Based on the Fresnel diffraction theory,the imaging mechanism of the point source method and the cause of the interference between the reconstructed image points are deduced,and the influence of the grating-like structure of the phase-only LCOS on the imaging is analyzed.The dynamic random phase,amplitude pre-modulation factor,interpolated term of background noise are proposed to solve the problem,so that the intensity of image points can be modulated precisely and individually.3.In this paper,the computer graphics theory is introduced to adjust the light intensity according to the lighting model,and a more efficient and accurate holographic occlusion algorithm is proposed based on the graphics,which makes the 3D reconstruction image more natural and realistic.Based on the algorithm,the corresponding computer implementation scheme is proposed.In this scheme,C++programming language and OpenGL interface are used to give full play to the highly parallelized architecture of GPU(graphics processing unit)platform.The design program realizes the real-time automatic operation of data extraction,transformation,illumination calculation,occlusion processing and the calculation and generation of phase-only hologram of 3D models,synchronously outputs to LCOS and forms interactive 3D stereo image.4.The experiment of image intensity distribution based on LCOS holographic system is accomplished,and the validity of the algorithm proposed in this paper is verified.The view-windowed real-time generation of 3D holographic reconstruction object is realized which is with natural material performance,accurate occlusion and dynamic interaction. |
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