Optical encryption of unlimited-size images based on ptychographic scanning digital holography

The ptychographic scanning operation is introduced into digital holography to expand the field-of-view (FOV). An optical image encryption method based on this technique is further proposed and analyzed. The plaintext is moved sequentially in the way of ptychographic scanning and corresponding pairs of phase-shifted interferograms are recorded as ciphertexts. Then the holographic processing and the ptychographic iterative reconstruction are both employed to retrieve the plaintext. Numerical experiments demonstrate that the proposed system possesses high security level and wide FOV. The proposed method might also be used for other potential applications, such as three-dimensional information encryption and image hiding.