在一种改进的光学联合变换相关加密系统中，将附加密钥改为圆形并提出了基于附加密钥旋转复用而实现多幅二值图像加密的方法。加密时，对于不同的待加密的图像，将附加密钥旋转至不同的角度，生成相应的联合功率谱。将这些得到的联合功率谱进行叠加，得到的复合联合功率谱即为最终的密文。解密时，将附加密钥旋转至加密时所处于的对应角度，对复合联合功率谱进行解密，即得到相应的解密结果。理论分析和计算机模拟结果表明，解密结果对附加密钥的旋转角度非常敏感，因而该旋转角度可作为一个有效的参数来实现多图像加密。同时，也分析了加密图像的数量对于解密结果的影响。

A key rotation multiplexing method to the modified joint transform correlator arrangement is introduced. For encryption, the rounding key with a certain rotation angle is assigned to each image to be encrypted to generate a corresponding joint power spectrum. Then the final encryption result, namely multiplexed joint power spectrum, will be obtained by summing the above mentioned joint power spectrum. The decryption of the multiplexed joint power spectrum with the correct rotation angle of the additional key will show the corresponding primary images. Theoretical analysis and computer simulations reveal that rotation angle of the additional key is a valid parameter to perform image multiplexing encoding with the modified joint transform correlator architecture. Also, computer simulations to investigate how the number of encrypted images affects the decryption quality are performed.