Cgh And Optical Images Of The Random Phase Encryption Technology Research

With the social development, the information increasing and the entrance of Internet to the people's life have already become the time sign. In this thesis, the research aims to combine the flexibleness of electrical equipment with the fast parallel optical computing, so that it can realize optical image encryption and recognition and high efficiency of information security protection.Some research works in the execution methods of hologram have been done firstly based on the randomicity of phase function used for encryption. It includes Fourier transform hologram and kinoform mostly. The research indicates that kinoform is more suitable for random phase encryption than the other hologram either the diffraction efficiency or the equality of reconstruction image.The thesis categorizes the encryption methods as two sorts. The first is based on the joint transform system .The expected advantage from this security system is the shift invariance, but the disadvantage is that the amplitude characteristic of filter restricts system's diffractive efficiency. The second is based Vander lugt correlator. This method improves the diffractive efficiency of system because of optical phase-only elements, which produce from project onto constraints algorithm, but at the same time it has the problem of misalignment sensitivity of the filter mask in the VLC system. To obtain high diffractive efficiency and the convenient manipulation in practice simultaneously, the phase-only decryption in the JTC has been adopted based on the above methods' compare. The validity and feasibility of this method is proved though computer simulation and optical experiment result.Finally, the way of information hiding is used in order to transmit the protected image though Internet. Using encrypted and key functions, the original information can be reconstructed very well. But the encryption result may arouse the attackers' notice, so it can be hided in a common image. The simulation illustrates the system ability to recover the hidden image under distortions and the robustness of the hidden image against removal trails. The information capacity which system can be hided is also enormous.