计算机模拟研究了光学图像频域相位加密和解密过程，用混沌序列构造相位值并采用环形相位分布，不仅可以压缩密匙的数据量方便保存和传输，而且使加密图像具有中心旋转不变性从而避免解密中对加密图像方向自由度的要求，同时能使解密过程具有一定高低通滤波作用实现滤除噪声或边缘增强。在此加密方法中，解密的关键是加密图像频域中低频分量的解调，高频分量对解密质量和解密图像信噪比虽有影响但比低频分量的影响作用小。

The phase encryption and decryption of optical image in Fourier domain are studied by computer simulation. The chaotic sequence is used to construct the phase array to compress the data of decryption key to make it saving and transferring conveniently. A novel phase-ring distribution is used to make encrypted image with a rotative invariance so that the orientation of encrypted image is unconsidered during decryption. The noise can be reduced and the edges can be enhanced because this type of phase array has some functions as same as high-pass or low-pass filters. In this encryption method the ultra-low-frequency components of encrypted image in Fourier domain is more important and has a greater influence on the quality and signal-to-noise ratio of decrypted image than the high-frequency components do.