Optical image hiding in the Fresnel domain
Yishi Shi, Guohai Situ, Jingjuan Zhang · Journal of Optics A Pure and Applied Optics · 2006
A technique of optical image hiding in the Fresnel domain is proposed. In our method, a secret image can be hidden in the watermarked image through the phase only masks that are efficiently generated by the phase retrieval algorithm. The corresponding key distribution scheme is also investigated. Since the watermarked image can be the same as the host image and the secret image's available dimension is equal to the host one, the imperceptibility and the capacity requirements of the image hiding are both satisfied excellently in the proposed system. The properties of the phase keys are discussed and their dominating role in the system is revealed, which provides the system with robustness to attacks and distortions to the amplitude of the watermarked image. Due to the particularly employed optical keys, including the wavelength key and the mask position key, in this Fresnel hiding system, the system's security is further improved and the flexibility of the designs for different application purposes is introduced. Further, we also analyse the implementation of this lensless system by the pure digital method and the opt-digital method.