Research On The Key Technical Problems Of Computer-generated Holography Display

The technology of three-dimensional(3D)display has been widely used in the field of entertainment,military,medical treatment and so on.With the development of society,people gradually want to obtain a more realistic visual experience,which promotes the progress of research in the domain of 3D display technique.Existing 3D display technologies,such as stereoscopic and volumetric 3D display,lack sufficient depth information required by the human eye to perceive 3D objects.The holographic display can provide all the depth information required by the human eye to perceive the 3D object,giving a comfortable and realistic 3D stereoscopic sense,which is called true 3D display technique.And the computer-generated holography display has become a research hotspot in the field of holographic 3D display because of its characteristics of high efficiency,large storage capacity and low cost.However,up to now,the technique of computer-generated holography display still has key technical problems such as poor quality of display,slow speed of calculation and complicated evaluation method of display quality.In view of the above key technical issues,the research works and innovations carried out in this paper are as follows:1.The basic principle of computer-generated holographic display are studied,including discrete Fresnel diffraction,convolution calculation and angular spectrum calculation in numerical calculation of diffraction problems,including point-oriented method,panel method and tomography method in 3D computer holographic algorithm,including the amplitude encoding and phase encoding in the computer holographic encoding method,and analyzes their respective advantages and disadvantages.It is finally determined that the computer holographic algorithm based on the angular-spectrum diffraction of the tomographic method is used to calculate the hologram.The principle and algorithm flow of the algorithm are elaborated in detail.2.In order to improve the display quality and speed of calculation at the same time,an error diffusion method based on layered angular-spectrum is proposed for the problem of speckle noise in the phase-only holographic reconstructed image.This algorithm calculates the complex amplitude hologram of the 3D object by the layered angular-spectrum algorithm.Then the phase-only hologram is calculated by the error diffusion method,and a clear reconstructed image is reconstructed,which realizes the suppression of the speckle noise of the phase-only holographic reconstructed image.The simulation results show that the running time of this algorithm is 0.887s under the same conditions,and the running time of the GS algorithm based on the angular-spectrum diffraction theory is 2.648s.It means that this algorithm greatly accelerates the running speed.Numerical simulation experiments on three-dimensional objects show that the speckle index of phase-only holographic reconstructed images after direct removal of magnitude with three different reconstruction distance are greater than 1;the speckle index of phase-only holographic reconstructed images of this algorithm are reduced,which are less than 1.It can be proved that this algorithm is effective for suppressing the speckle noise in the phase-only holographic display of 3D object,and the quality of reconstructed image is obviously improved.3.In order to find a convenient and intuitive method for evaluating the quality of computer-generated holography display,the defects and limitations of the commonly used evaluation methods for display quality are analyzed.Considering that in optics,point spread function can be used as a basic imaging function to check the features and quality of the reconstructed image.Therefore,the point spread function is introduced,and the point spread function is proposed as an evaluation method for display quality of computer holographic.The reconstructed image can be regarded as the image obtained by convolving the point spread function with the original image.Therefore,the quality of the point spread function model reflects the quality of the reconstructed image.The point source is taken as the experimental object,and the variation of the point spread function model corresponding to the change of different experimental parameters is analyzed.According to the quality of the point spread function model,the experimental parameters corresponding to the best display quality are obtained.