The Research Of Viewing-angle Enlargement And Encoding Efficiency

With the development of computer technology ,high resolving digital image sensor (CCD or CMOS) and high resolving digital spatial light modulator (SLM), Computer-generated holography (CGH) which is used in dynamic real-time three-dimensional (3D) display and optical micromanipulation is a powerful technology. However, the CGH used in the 3D dynamic real-time reconstruction has its disadvantage. In the generation and reconstruction process of computer-generated holograms pattern, the encoding is very important .Usually the 3D real objects can be approximated as a collection of self-luminous points of light, the fringe patterns for all object points are directly calculated respectively. Finally all the fringe patterns are added up to obtain the whole interference pattern of the object image. This approach shows a computation complexity, since it requires one by one calculation of the fringe pattern per image point per hologram sample. Thus, real-time generation of the CGH pattern for a 3-D image can not be achievable easily. In this paper we mainly research the problems and the solutions of CGH for 3D real object in the common method:[1] In order to enlarge reconstraction viewing-angle, wo suggest a viewing-angle enlargement method. Because the pixel pitches of the SLM are not fine, its diffracted trait decide the reconstruction of 3D object exceed the viewing-zone .we can achieve viewing-angle enlargement by viewing-angle transforming, In this method, the pretreatment is done for object information whose angle exceeding sampling frequency of SLM. After this pretreatment the angle of this object's wave satisfies the sampling theorem. Then the recorded object is encoded . This hologram can be reconstructed by SLM . The reconstructed image of the object can be reproduced in the high-order of the SLM , so we can reconstruct the object by large view angle . The encoding method and some expressions according to the analysis of theory are given . Finally the example of encoding in this way and the simulation result of prove that this method is right.[2] In order to alleviate computation of the digital holograms of 3-D objects, this paper suggests a new LUT method. A 3-D object can be treated a set of image planes discretely sliced in the z-direction, in which each image plane having a fixed depth is approximated as some collection of self-luminous object points of light. In this method, only the fringe patterns of the center points on each image plane are pre-calculated, called principal fringe patterns and those be stored . Then, the fringe patterns for other object points on each image plane can be obtained by simply shifting this pre-calculated principal fringe patterns according to the displaced values from the center to those points and adding them together.