基于不对称非标准傅里叶变换的光学图像加密

针对以往光学图像加密系统中输入面和频谱面对称性的缺点，在不增加系统元件的基础上，利用球面波照射不对称非标准傅里叶变换系统进行图像加密。通过把相位掩模置于该系统的傅里叶变换平面，利用不对称非标准傅里叶变换系统的输入面和频谱面的不对称性以及频谱面对于点光源相关参数的依赖性，克服了以前光学加密系统中输入面和频谱面的对称性所带来的安全隐患，并且获得了除相位掩模以外的另外四重密匙。理论分析和模拟实验表明：该方法不仅可行，而且多增加了几重密匙，增强了系统的安全性能。

Optical image encryption based on asymmetric abnormal Fourier transform

To overcome the disadvantage of the symmetry of input and frequency planes in the previous optical image encoding systems, an improved encryption method is proposed. Instead of adding optical elements, the optical image encryption is realized by spherical wave illumination on asymmetric non-normal Fourier transform system and by placing the phase mask on the Fourier transform plane of the system. Due to the asymmetry of this system and the dependence of the Fourier spectrum plane on relevant parameters of the spotlight, it overcomes the hidden trouble resulting from the symmetry of the previous optical image encoding system and increases four fold security keys. Theoretic analysis and computer simulation indicate that this method is feasible and enhances the security greatly.