Preliminary Investigations On Information Compression Of Holograms

The development of holography brings hope to the three-dimensional hologram display. The realization of hologram storage and communication is of great significance to the true sense dynamic 3-D display. However, as a kind of communication used for the three-dimensional display technology, the three-dimensional information is huge recorded by hologram. The information compression, storage, reproduction and the reconstructed image quality evaluation must be first considered to enable the hologram the large amount of information used for the real-time transmission. Hologram compression technology becomes an important issue on effective storage, transmission because of its information content larger than 2D dynamic image information.At first, this paper made a summary to the development of holography and the research conditions of digital hologram information compression, and then, the point source Fresnel hologram recording and reproducible process are discussed on the basis of the Fresnel diffraction theory. The point light Fresnel hologram generation and reconstruction are simulated by computer using MATLAB program. The convolution and Fresnel Transform algorithm are discussed. Meantime, the methods removing the zero-level and conjugated images of digital hologram are discussed. Digital Fresnel holograms generation and reconstruction of objects are achieved by MATLAB program using computer simulation.The mathematical expressions of the amount of hologram information are derived theoretically, and the relevant factors impacting the amount of digital hologram information are analyzed simultaneity. The feasibility of using the dynamic video coding method to achieve hologram compression is discussed. Then the application of the wavelet analysis in hologram compression is investigated as the resolution of hologram is sacrificed. The information compression of the point light source hologram and Fresnel number hologram is discussed. Utilizing the wavelet analysis method, the low frequency sub-image information of hologram is retained, and high frequency component is replaced by zero at horizontal, vertical and diagonal direction. At the same principle, the same operation is performed to the low frequency sub-image after one time wavelet decomposition until the Shannon sampling law isn't met for the next grade low frequency sub-image. The threshold compression method after the pyramid wavelet decomposition is adopted to further enhancing the compression rate. In the case of guarantying the quality of the reconstructed images, a good compression ratio could be obtained by compressing hologram using the above method.