Optical encryption scheme for multiple-image based on spatially angular multiplexing and computer generated hologram

We propose an optical encryption scheme for multiple images based on angle multiplexing and computer generated hologram(CGH) in this paper. In the encryption process, the original images are firstly modulated by two random phase keys in Fresnel transform with different diffraction distances. Secondly, the modulated images are coherent superposition with solid angle multiplexed reference beams to generate interference fringes and form a compound image. Finally, the compound image is encoded to a CGH by Roman coding method. In the decrypted process, the corresponding experimental system using SLM is built, in which multiple images can be encrypted synchronously with high efficiency. Except random phase key, the proposed encryption system has multiple kind of keys including diffraction distance and wavelength to improve the security. Due to the characteristics of high storage efficiency and simple calculation, this optical multiple-image encryption scheme has important application prospect in improving the efficiency of information transmission and multi-user authentication.