为了克服双随机相位编码系统的局限性, 提出基于光学衍射成像原理的图像加密方法.该方法在光学衍射加密系统中加入可变光阑, 形成透光面积不同的振幅板, 对明文进行加密, 得出多个密文.解密时, 通过相位恢复算法, 从多幅衍射强度图像中恢复原始明文.仿真表明, 由于只需要记录光波的衍射强度, 在密文记录过程无需使用干涉装置, 通过可变光阑可以方便地调节振幅板的透光面积, 无需改变光学结构或者移动光学器件, 因此, 大大降低了加密过程实施的难度.

In order to overcome the disadvantages of the double random phase encoding, a novel method for image encryption by employing the diffraction imaging technique was proposed. In this method, irisdiaphragm was used in optical diffraction encryption system, and to form amplitude plate of the different transmittance. Using this encryption system to encrypt the plaintext, multiple ciphertexts were obtained. During image decryption, by iterative phase retrieval algorithm the original plaintext is completely extracted from multiple diffraction intensity patterns. Computer simulations indicate that, since only needing to record the diffraction intensity of optical wave, the ciphertexts can be recorded without using interference methods. In addition, by means of iris-diaphragm, the transmittance of amplitude plate is easily adjusted, without changing optical structure or moving optical device, so that is greatly reducing the difficulty of implementation in the encryption process. Simulation results are presented to verify the validity of the proposed approach.