Application Research Of Computational Ghost Imaging In Optical Encryption

Ghost Imaging(GI), also known as correlated imaging, is a new imaging method to obtain object information based on the quantum entanglement or optical intensity correlation. With the advent of computational ghost imaging(CGI) with simplified configuration, GI has extensive usage. The application of GI in optical encryption can not only realize multi-dimensional information hiding, but also utilize the non-locality property of GI. We discuss the application of CGI in optical encryption in this thesis.Firstly, based on the principle of CGI and the geometric characteristics of Toeplitz matrix, we propose an optical encryption scheme with Toeplitz matrix. In the proposed scheme, N ?m ?n random phases with the same size of object are generated by Alice as secret key and then shared with Bob. These random phases are cyclically shifted to generate M sets phases with Toeplitz characteristics. Each of them is reshaped to a phase screen with size of m ?n to generate a random speckle pattern with spatial light modulator(SLM). An object is encrypted by means of CGI with these speckle patterns. The measurement results from bucket detector are transmitted to Bob as cipher text. With the same operations on the received random matrix, Bob get M random speckle patterns firstly. Then he reconstructs the imaging of the object with the aid of Orthogonal Matching Pursuit algorithms of compressive sensing. The axial distance between SLM and the object is further also introduced used as another secret key to improve the security of the proposed optical encryption scheme Simulation and experimental results show that the eavesdroppers cannot acquire any information about the object even the eavesdropping ratio is up to 0.9.Secondly, an optical encryption based on wavelength-multiplexing CGI is proposed. In the scheme, three different wavelength of light is used at the same time. The wavelength in the scheme is treated as a secret key. The Encryption time is shorten greatly, and the efficiency is improved substantially.Finally, based on matrix decomposition theorem, CGI with orthogonal speckle is derived. The CGI scheme with orthogonal speckle patterns is discussed in its corresponding optical encryption scheme. Numerical simulations show that the encryption process can be completed even the sampling rate is 0.0061. And the eavesdroppers can acquire information about the object when the eavesdropping ratio is up to 0.6.