A single-channel encryption method for color images is proposed using chessboard grating and a phase-retrieval algorithm in the Fresnel domain. The pixel sampling operation is introduced to convert the color image to be encrypted into a Bayer image. Thereafter, with a single channel, the Bayer image is encoded by the chessboard grating before being sent into a diffractive-imaging-based encryption scheme. The cryptosystem is simple owing to only one single intensity pattern being required during encryption. In the decryption procedure, the phase-retrieval algorithm and the chessboard grating are combined to extract the plaintext from the intensity pattern. This proposal not only can successfully encrypt a color image into a single diffractive intensity pattern but also can recover the primary color image with high quality from the one single diffraction pattern with a compact optical setup. Numerical simulations are carried out to prove the feasibility and validity of the proposal.
In this paper, we proposed a novel optical encryption and decryption method of gray image based on the computer-generated hologram (CGH), the chaos theory and the logical modulation. In the encryption process, the hologram, which is gotten by Fresnel diffraction from the gray image, is modulated with the chaotic sequence, and the output is encryption image. The decryption is an inverse process of encryption. Experiment results verified the security and robustness of the proposed approach. Moreover, the proposed encryption method could be applied in where requires more security and more flexibility as the field of national defense science and technology.