Optical image encryption by using diffractive imaging with special constraint in the input plane

In order to simplify the optical setup and the encryption process, a diffractive-imaging-based optical encryption system using a single diffraction pattern is proposed. A predesigned binary mask is placed before the plaintext in the encryption process, and three randomly distributed phase only masks are placed in the optical path. Only one diffraction pattern needs to be recorded as ciphertext by CCD. In the decryption process, an iterative phase retrieval algorithm is applied, in which the predesigned binary mask acts as a support constraint in the input plane. After the iterative process, an interpolation operation for the zero-valued pixels is also implemented. The effectiveness and robustness of the proposal are demonstrated by numerical simulation results.