The Study Of Three-Dimensional Computer-Generated Hologram

As an important branch of modern optics, the Computer-generated hologram (CGH) has its unique merits such as it has smaller noise compares with the tradition optical holography, can be easy to duplicate, has flexible functions, and can be applied to wide range of optical fields. Computer-generated hologram is a new holographic imaging technique that use computer to make the hologram. An important application of CGH is three-dimensional (3-D) displaying. In some branches of the information processing, the three-dimensional object expressed as the form of math are often hoped to display in 3-D. Therefore, the three-dimensional displaying occupied an important position in the application of computer-generated hologram. This paper introduces a new method of three-dimensional displaying by computer-generated hologram. The whole paper includes the following parts:In chapter 1 the history and the main developments of the computer-generated holography are reviewed. The present states of three-dimensional displaying by computer-generated hologram are also reviewed.In chapter 2 the basic theory of the computer-generated holography is described and some conventional encoding methods of the computer-generated hologram are also described.In chapter 3 the encoding algorithms of the CGH are made with the help of Matlab software. The reconstructed images of the CGH are given by computer simulation.In chapter 4 a new method of displaying 3-D object by computer-generated hologram is proposed. A few experiments are done to validate it. In the experiment a three-dimensional object is created by the software of 3Dmax. The 3D object includs three cuboids. The center coordinates of these cuboids are not in the same plane and there is a different letter in each cuboid's front face. A series of projections of the 3-D object from different points of view at two orthogonal directions are recorded by an ordinary digital camera. These recorded data loaded in a computer and done Fast Fourier Transform (FFT) in Matlab. We sample these FFT data and constitute the complex wavefronts of the 3-D object in the later focal plane of a lens. Then a Fresnel CGH can be made with the complex wavefront. When this hologram is illuminated by a plane wave, a 3-D real image of the object is reconstructed. This method is superior to other similar methods in terms of efficiency of projection data, quality of reconstructed images. The experimental results have been presented to verify the principle and validity of this method.