Image Encryption Based On Phase Encoding And Fractional Fourier Transform

In recent years, there have been steadily growing interests in the study of image encryption. And many image encryption methods 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. Phase encoding techniques and fractional Fourier encoding techniques have received increasing attention at home and abroad for their high security and more keys.At first, two kinds of definition of Fractional Fourier are analyzed and the characteristic of equipollence of them is testified. The nicer nature of mathematics and discretization algorithm are analyzed. The ways of optical realization are introduced.Secondly, they are done that computer simulation and performance analyzing of optical encryption based on double random phase mask. The theory of method of improvement is refered. They are done that computer simulation and performance analyzing of optical encryption based on Fresnel transform.Computer simulation and performance analyzing of three optical encryption methods based on fractional Fourier transform are done. In this paper, the first method is phase encoding based on fractional Fourier transform. And the second is the image encryption based on iterative fractional Fourier transform. The third is the image encryption based on fractional Fourier transform and the three step phase shifting interferometry.Finally, according to the trait of more keys of optical encryption based on fractional Fourier transform and the characteristic of lensless of image encryption based on Fresnel transform, image encryption based on iterative fractional Fourier transform and Fresnel transform is proposed. Computer simulation validates the reliability and the sensitivity to the fractional orders and Fresnel transform distance parameter.