Research On The CGH Display Method Based On An Improved Burch Coding

Computer-generated hologram（CGH）is the combining product of computer technology and modern optics. Different from traditional optical techniques, the technology of CGH can not only comprehensive record the waves of amplitude and phase, but also can be recorded the hologram of virtual objects. Thus it has unique advantages and great flexibility. CGH have a wide range of applications in displaying the two-dimension and three-dimensional image, spatial filtering, holographic interferometry, data storage, and other fields.This paper research on two types of coding method——Detour phase encoding (LohmannⅠⅡⅢ) and modified off-axis reference beam (Burch encoding, Huang encoding, Lee encoding) encoding method. And the advantages and disadvantages of the two encoding methods were analyzed. Through the MATLAB programming, the Lohmann Ⅲ and Burch encoding, Huang encoding, Lee encoding were used to manufacture, simulate and reconstruct the Fourier transform CGH. The operation time of detour phase encoding and modified off-axis reference beam encoding method (Burch encoding as example) were compared under the conditions of same sampling points. The quality of the three kinds of modified off-axis reference beam encoding method was analyzed qualitatively.The paper focused on the research of an improved Burch coding method to eliminate the aliasing phenomenon, which caused by the original image and conjugate image in the process of reconstruction of Fourier CGH. According to the analysis of the process of CGH reconstruction by Fourier transform, the method which put the original sampling points into a larger null matrix has been used to separate the original image and conjugate image. After the disperse Fourier transform with the new matrix, CGH has been obtained by Burch coding, then a high pass filter is used to eliminate the influences of interference of background light to the visual impression when image reconstructed. The experimental results show that the degree of separation of the original image and conjugate image of CGH produced by this method can be controlled with the size of the null matrix, the larger the null matrix, the greater the degree of separation. The influence of zero-order and conjugate images is eliminated by this method, and can be used in all gray images coding.