Optical encryption method of multiple-image based on θ modulation and computer generated hologram

An optical multiple images encryption method based on theta modulation and computer generated hologram is proposed. After modulated by double random phases in Fresnel transform and theta modulation system, the images are superimposed together and encoded into a binary real value CGH. The decryption is achieved in optical spatial filtering and Fresnel transform system with spatial light modulator. Multiple images can be encrypted at once in the proposed method which has high efficiency. Except the random phase, the diffraction distance and wavelength can be used as keys to improve the security. The numerical simulation and experimental results verify the validity of proposed method in this paper.