为了实现仅用两个密钥对彩色图像进行加密，提出了一种基于光栅调制的彩色图像加密方法.该方法首先把彩色图像分成三基色分量：红，绿，兰.然后，把这三帧灰度图像分别用空间频率不同正弦振幅光栅调制，之后，再把调制结果进行叠加而形成一个实值目标图像，该目标图像包含了原始彩色图像的全部信息.对此目标图像进行双随机相位加密系统的加密，即实现了彩色图像的加密隐藏.由于正弦光栅的调制作用，R、G、B灰度图像的频谱在实值目标图像的频谱中分离开来，通过选取合适的滤波窗口，就可以对他们的频谱分别提取并予以重建，并最终实现重构原始彩色图像.本文给出了理论分析和计算机模拟，实验结果证实了该方法的可行性.

For the purpose of color image encryption using two keys, a method based on grating modulation is proposed. First of all, a color image is separated into three components: red, green, and blue. The three grey images are multiplied by sine gratings with different spatial frequencies, and a superposition of the modulated results is introduced. Thus a real-valued target image that contains the whole information of the color image is obtained. Then the target image is encrypted using double phase encoding system, which means the original color image is encrypted. Due to the introduction of the sine gratings, the R, G, B frames are able to be spatially separated, so the color map can be reconstructed and the original color image can be recovered. Both theoretical analysis and simulations are proposed, and the validity of this method is verified by experimental results.