基于相位恢复算法的单强度记录光学加密系统

在传统的双随机相位光学加密系统的基础上，提出一种新的单强度记录光学加密技术。在加密时，将原始图像置于4-f系统的输入平面上进行双随机相位光学加密，利用CCD等感光器件记录输出平面上的光强分布作为密文，该光学加密过程只需一次曝光，在解密时，利用相位恢复算法进行迭代计算就可以由密文恢复原始图像。由于解密过程采用数字方式，因此可以在解密过程中引入各种数字图像处理技术来抑制散斑噪声，进一步改善解密图像质量。通过一系列仿真实验，证明该光学加密系统可以实现对二值图像和灰度图像的光学加密，并且能够很好地抵御已知明文攻击、选择明文攻击等方法的攻击。理论分析和计算机仿真表明，该光学加密技术系统结构简单，实现方便，并且不易受到各种攻击，安全性较高。

Single-intensity-recording optical encryption technology based on phase retrieval algorithm

Based on the traditional double-random phase optical encryption system, a new single-intensity-recording optical encryption technology was proposed. In the encryption process, the original image was placed on the input plane of 4-f system to have a double random phase encryption. Using CCD sensitization devices, only the intensity distribution on the output plane was recorded as ciphertext. The optical encryption process only needed one exposure. In the decryption process, the original image could be retrieved from the ciphertext using phase retrieval algorithm. Since the decryption process used digital method, a variety of digital image processing technology could be introduced in the decryption process to suppress speckle noise, so as to further improve the decrypted image quality. Through a series of simulation experiments, it is proved that the proposed encryption system can be used for binary image and grayscale image encryption. Moreover, it can well resist known plaintext attack and chosen plaintext attack. Theoretical analysis and computer simulations show that this optical encryption system is simple in structure, easy to achieve, invulnerable to various attacks and of high security.