Computer Generated Hologram Encoding Technique

Computer-generated Hologram is based on the combination of modern optics and digital computing. Since the advent of laser, holographic technology has become vigorous again, "Holographic Tide" was very popular in the optical field.With the rapid and wide development of digital computer and digital signal processing technology CGH technology is improved dramatically in optical data processing, storage and encryption, interferometry and three-dimensional objects, etc.which can not only record completely the object wave amplitude and phase information as optical holography, but also has high flexibility, repeatability, and so on.Holographic technology is a rapidly developing imaging technology, which attracts much attention on option fields and others, and great achievements have been made in theory and application. Recording of the wave surface and reproduction of the wavefront is the two main steps of the holography imaging process, original object wave applying monochromatic light or white light. It is represented by hologram which is recorded in the Recording ware surface medium. According to the frequency difference of waves used in holography, such as visible light waves, microwaves, sound waves and radio waves, hologram can be classificed as optical, radio and acoustic hologram. Holography and computer technology can be combined so as to generate hologram using computer. The procedure of the method is to input the mathematical description of the input object wave into computer, and to map the hologram after processing, finally to reproduce the object by optical methods, which reveals that the images of objects are not necessary for compter-generated hologram. Hence, the holograms can be made by photographic plates after the information is displayed by a micrometer or plotted by a graphic plotter controlled by a computer. In the process of producting hologram, all wavefronts of recording and reconstruction are complex space signals which must be encoded for computer-generated hologram. In order to ensure that the complete optically complex function could be reproduced by optical methods via a micrometer or a graphic potter, the discrete spatial complex form was converted to real values of the non-complex holographic function, and the complex-valued signal CGH encoding process was focused on. The basic principle was firstly to be studied and the comparison of its advantages and disadvantages were carried out, Based on the basic principle of CGH, combination of calculation hologram coding algorithm and the cipher algorithm was tested. Besides, by contrast, algorithms coincided with the principle of CGH encoding were selected form various algorithms in cryptography. Finally, hologram was reproduced by computer simulation, and the results were analyzed by the simulation.