Based On Phase-encoded Optical Image Encryption Research

The development of home and abroad and the theory of the optical image encryption are described briefly in this thesis. The characteristics of primary method are analysed, and the deficiencies in practicalities are pointed out.The theory, optical implementation and computer simulation of the optical image encryption based on phase encoding have been studied systematically.The phase encryptlon and decryptlon of optical image using double random phase encoding are studied by computer simulation．The method of image encryption using periodic phase plate is proposed.Two phase mask plate with independent periodicity are used to encode image in the both of the spatial domain and the frequency domain,so as to make the original image a noise.The characteristic of this method is when decoding,the alignment precision for the phase mask plate is allowed tolerance,and moreover,owing to the fact that the phase distribution is periodic,the owner of secure key has only in hand the decisive function and the secure key can be regenerated.It makes the practical use convenient.The optical image encryption with rotating invariance based on joint transform correlator is studied. Two phase mask plate with independent chirp signals are used to encode image in the joint transform correlator,so as to make encrypt the original image.The characteristic of this method is when decoding,the rotation of encrypted image can not affected decoding effect,and moreover,owing to the fact that phase distribution is a decisive function only grasped by owner of secure key and the secure key can be regenerated.It makes the practical use convenient.The results of computer simulation shows the feasibility of this method.Finally, the way of the optical image encryption with chaotic sequence based on joint transform correlator is proposed. The phase mask plate with chaotic sequence is used to encode image in the joint transform correlator,so as to make encrypt the original image.The characteristic of this method is the method is high security,and moreover, the secure key can be regenerated.It makes the practical use convenient.The results of computer simulation shows the feasibility of this method.