基于联合功率谱分区复用的光学多图像加密方法与实验

Experimental Research and Encryption Method of Optical Multi-Images Based on Joint Power Spectral Partition Multiplexing

针对光学多图像加密出现的串扰噪声大和复用容量小的问题,提出了一种基于联合功率谱(JPS)分区复用的光学多图像加密方法。该方法首先利用相位恢复算法开展相位模板优化设计,压缩了单通道JPS面积,然后在优化后的相位模板上叠加线性相位,使各通道JPS在频谱面上产生不同的位置平移,再经过窗口滤波,实现无串扰叠加。此外,以"密钥相位核+偏转角数据包"形式进行密钥内容规划,在确保加密方法安全性以及密钥空间足够大的同时,压缩了需传递的密钥数据量。数值仿真结果表明,对9幅灰度图像进行加密,其解密图像与原始图像的相关系数值均达到0.94以上,解密效果显著。当解密质量评判阈值设定在0.95时,灰度图像和二值图像的最大压缩效率因子分别达到12和32,密文压缩能力显著。最后,搭建光学实验系统,进一步验证了该方法的可行性。

Aiming at the problems of large cross-talk noise and small multiplexing capacity in the optical multi-image encryption system, an optical multi-image encryption method based on joint power spectral (JPS) partition multiplexing is proposed. First, the phase retrieval algorithm is utilized for the optimal design of phase masks and the single-channel JPS area is thus compressed. Then, the corresponding linear phases are superimposed on the optimized phase masks and so that the each-channel JPS is shifted differently in its spectral plane. After the window filtering operation, the superposition without crosstalk is realized. In addition, the key content planning is carried out in the form of “key phase kernel plus deflection angle packet”. While the security of encryption method and the large enough key space are ensured, the key data needed to be transferred is compressed. The numerical simulation results show that, when nine gray-scale images are encrypted, the correlation coefficients between the decrypted images and the original images are over 0.94 and the decryption effect is obvious. When the evaluation threshold of decryption quality is set as 0.95, the maximum compression efficiency factors of gray-scale and binary images reach 12 and 32, respectively. The cipher-text compression ability is remarkable. Finally, an optical experiment system is built and the feasibility of this method is further verified.