Abstract In recent years ,as the rapid development of computer network and communication technology ,the net-information is more widely used .But the information security has attracted much attention. Because of the higher processing speed of the optical information processing system, and it can also quickly achieve correlated operation .All these characteristics are favored by research scholars. Optical system based image encryption technique has important applications in defense security .
The history and current situation of the development of optical encryption technology research is summarized in this paper ,then the traditional Fourier transform method ,characters and its optical realization are also introduced. Besides, the traditional Fourier transform pair are proved by Matlab simulation. The fractional Fourier theory and characters ,such as its additivity, periodicity and continuity are discussed ,then its optical realization is described. Finally a double image encryption algorithm based on fractional Fourier transform is proposed by the mean of analyzing and discussing the fractional Fourier encryption, the random phase encoding encryption,then summarizing their relevant principles. The corresponding optical system encryption devices is also designed. In the end of the paper , four experiments have been designed based on the aboratory facility condition, they include : the analysis of two-dimensional linear systems Fourier , the optical correlator based on Fourier transform, optical image encryption in Fourier Optics and the extraction of an optical correlator information experiments . The feasibility of the theory of double image encryption is proved by the experiments above, besides the result of double image encryption is also analyzed .Finally the conclusion that the double image encryption has higher security, especially the parts of the phase coded image security.
Keywords: optical encryption fractional Fourier transform double image encryption