Study On Key Technologies Of Computer Generated Holography

Holography is a promising three-dimensional(3D)display technology,which can fully reproduce wave-front of a 3D object,and has received more and more attention.With the development of computing technique,it has enabled the simulation of recording process for hologram generation,which is called computer generated holography(CGH).Compared with traditional optical holography,CGH has the characteristics of low cost,simple hologram production,3D display of virtual and real scenes,and convenient data storage and transmission,which has great perspective and research significance.Driven by CGH,dynamic holographic 3D display and large scale high resolution static holographic 3D display have achieved significant progress.Dynamic holographic 3D display mainly uses low-bandwidth spatial light modulators as display devices.Currently,spatial light modulators have low resolution and large pixel size,which is difficult to meet the practical requirements for holographic 3D display.For large-size high-resolution holographic 3D display,the development of holographic output devices has promoted the commercial application such as the use of holographic packaging with computer generated color rainbow holograms.The large-size,high-resolution,computer-generated holograms such as the Fresnel hologram and the color rainbow hologram are known able to produce high definition 3D effect for monochrome or colored 3D display.However,the computation of large-scale high-resolution hologram is time-consuming despite that many algorithms have been proposed.How to rapidly implement large-scale high-resolution hologram calculation with new algorithms and theories as well as display system design are urgent problems to be solved.This article focuses on the large-scale high-resolution hologram calculation and display system design,including the following three aspects:1,Large-size high-resolution computer-generated synthetic holographyUsing the projected images in different views of the 3D object,the spectrum is calculated respectively and spliced in the frequency domain to form the first order object light spectrum of the large-size high-resolution synthetic hologram.According to the sparse characteristics of the object light spectrum of synthetic hologram,the effective spectrum region is first inverse Fourier transformed in one-dimensional row direction,then the transformed data is Fourier transformed in one-dimensional column direction,and the real part is taken and normalized to obtain the composite hologram.Using this algorithm model,synthetic full parallax image holography,synthetic color rainbow holography and synthetic half-circle view-able color rainbow holography are studied.The basic principle and calculation method of each synthetic holograms are analyzed individually.Matlab programming is used for parallel calculation.Three types of holograms are calculated and printed using home-made holographic printer,and optical reproductions are given.Finally,computational error and the size of reproduced image point in the proposed algorithm are theoretically studied and we conclude that the error is sufficiently small for human visual perception given that parallax angle and object depth are within acceptable limits.2,True 3D display of rainbow holograms by combining the wave-front recording plane(WRP)and the frequency domain splicing methodThe WRP is used to record the wave-front information of different color channels at different viewing angles of color 3D model.2D Fourier transform,coordinate transformation and linear interpolation are performed in the frequency domain to obtain the local spectrum of object light in the global frequency domain coordinate system.Frequency domain splicing is applied to form the first order object light spectrum of color rainbow hologram.And then one dimensional inverse Fourier transformation in row direction is firstly performed for the effective spectrum area and one dimensional inverse Fourier transformation is applied and the real part is took and normalized to obtain a color rainbow hologram.Optical experiments and theoretical analysis are given.3,Fresnel holographic color 3D display based on time-space extended LED light sourcesThe information capacity of the hologram is studied.Spatial sampling is used to reduce data redundancy while keeping better quality of reconstructed image to fulfill human eye needs,thereby reducing the calculation burden of the hologram.The characteristics of the reconstructed image of the spatially sampled Fresnel hologram are studied,and four methods for eliminating the fence effect during the reconstruction of spatially sampled Fresnel hologram are introduced.Design of spatially sampled Fresnel hologram design and color matching method are given.A display system using of time-space extended three-color LED light sources is designed for holographic color 3D display with great flexibility.In the imaging plane of this system,a color grating structure is formed.The designed spatially sampled color Fresnel hologram is placed and accurately aligned to realize large-scale high-resolution full-parallax color 3D holographic display.The experimental verification and theoretical analysis of the reconstructed image under different parameter conditions are carried out,and the method of improving the reproduced image quality is given.The research results of this thesis have some application value in the calculation and display of large-size high-resolution holograms.Although the research content of this paper focuses on static holographic display,its basic algorithm,system parameter selection and display scheme still have some potential guiding significance for future large-size high-resolution dynamic holographic display.