将光学中的干涉与衍射原理相结合，提出了一种新的光学加密系统。该光学加密系统将图像信息隐藏于两个相位板(POM)及一个振幅板(AOM)中，其中振幅板使用计算机随机生成，两个相位板则通过解析方法得到。解密时，使用相干光照射两个相位板，并通过分束镜使二者的衍射光场进行相干叠加，此干涉场被振幅板调制，再经衍射一段距离后所得衍射场强度即为原始图像，此图像可以采用CCD等图像传感器件直接记录。本方法不但消除了先前提出的基于干涉原理加密方法存在的“轮廓像”问题，也对部分密钥泄露攻击具有很强的稳健性，具有较高的安全性。此外，本方法原理简单，加密过程无需迭代，解密系统易于物理实现。计算机模拟结果证实了本方法的有效性。

A novel optical encryption system is proposed by combining the optical principle of interference and diffraction. In this system, the original image is hidden into three masks, including two phase only masks (POMs) and one amplitude only mask (AOM). The AOM is randomly generated by computer while the POMs are obtained analytically. For decryption, the diffraction field of the two POMs is first superposed by utilizing the beam splitters and then modulated by the amplitude mask. After that the wavefront propagates for a certain distance and the intensity of the complex field, which is exactly the original image, can be recorded by CCD camera. Compared with the existing interference-based method, the approach is simple and easy to be realized by optical elements. Moreover, the silhouette problem that exists in the method with two POMs can be solved in our method. At the same time, the proposal is also proved to be robust to partial key exposure attack. Simulation results are presented to verify the validity of the proposed approach.