结合计算全息和频移的JTC系统多图像光学加密方法

为了提高JTC光学图像加密系统的实用性，解决其噪声问题，提高其加密效率和安全性，提出了一种基于计算全息和傅里叶变换频移特性的JTC系统多图像光学加密方法。首先多幅不同尺寸和类型的图像经过随机相位调制和傅里叶变换，然后傅里叶频谱经过频移相位调制后叠加并编码为二元实值计算全息图，最后经过JTC光学图像加密系统完成加密。解密时，加密图像经过4F系统解密获得计算全息图，二元实值计算全息图具有很强的抗噪性，可消除噪声，然后经过傅里叶变换获得多幅解密图像。仿真实验结果表明，该方法可实现多幅不同尺寸和类型图像的并行加密和解密，具有高加密效率，同时多幅图像互为密钥和双重光学密钥使得该方法具有很高的安全性。

Multi-image optical encryption method of JTC system combining CGH and frequency shift

In order to improve the practicability of JTC optical image encryption system, solve its noise problem, improve its encryption efficiency and security, a multi-image optical encryption method based on computer generated hologram (CGH) and the frequency shift of Fourier transform was proposed. Firstly, each image with different size and type was modulated by random phase and Fourier transform, then the frequency spectrum of multiple images was modulated by frequency-shift phase and superimposed to be encoded into binary real-value CGH, finally the CGH was encrypted into joint power spectrum by JTC optical image encryption system. In the decryption process, the encrypted image was decrypted by 4F system to obtain the CGH. The binary real-value CGH has strong noise resistance to eliminate the effects of noise. Then, multiple decrypted images can be obtained after Fourier transform. Simulation results show that the proposed method can encrypt and decrypt multiple images of different sizes and types in parallel, and has high encryption efficiency. Meanwhile, multiple images with mutual keys and double optical keys ensure the security of the encryption system.