Optical Image Encryption

In recent years, there have been steadily growing interests in the study of image encryption technique. Various progresses have been made in many areas. Among them, several successful image encryption techniques have been proposed. Because of the parallel and high speed processing of optical information processing system, it has been a new focus of research to study the image encryption by using optical methods. among them, double random phase encoding techniques have received increasing attention at home and abroad for its high security.At first, double random phase encoding techniques are looked back and its improved methods are introduced in detail. In connection with characteristics of spherical wave gene and function of phase mask, one random phase encoding techniques are proposed with spherical wave based on 4f system. Theoretical analysis and results of computer simulation show that the proposed method is not only feasible but also simple comparing with classic method.Secondly, in connection of hidden danger in security due to symmetric system, a novel encoding techniques is proposed with spherical wave illumination based on asymmetric system. The proposed method overcomes flaws in the 4f system. The position of phase mask also can be used as a key of the system besides the phase codes .the key space is significantly enlarged, and high security is consequently achieved.Finally, a method of binary image encryption with optical subtraction based on Mach-Zehnder interferometer architecture is proposed. The proposed method realized binary image encryption with optical subtraction rather then multiplying, and the encrypted date are recorded as the magnitude squared of the amplitude and phase information.