Enhancement of optical image encryption based on radial shearing interference

We present a security enhanced method for optical image encryption based on a radial shearing interferometer (RSI). In the encryption process, an image (plaintext) is first encoded into a phase-only mask (POM) and then successively modulated by a random phase mask (RPM) and a random amplitude mask (RAM). As the input of the radial shearing interferometer, the modulated plaintext is illuminated by a coherent light and then divided into two beams, which will interference with each other leading to an interferogram (ciphertext) at the output plane. The decryption process could only be analytically accomplished with the help of a recursive algorithm. Numerical simulations are provided to demonstrate the validity of this scheme.