Optical interference-based multiple-image encryption using spherical wave illumination and gyrator transform.

A new optical interference-based multiple-image encryption using spherical wave illumination and gyrator transform is proposed. In this proposal, each secret color image is divided into normalized red, green, and blue component images and independently encoded into corresponding phase-only component images. Then each phase-only component image of all the images are combined together to produce a single-phase-only component image as an input component image, which is bounded with a random phase mask to form a complex image. The two phase-only masks are analytically obtained from the inverse Fourier transformation of the complex image. The host image is chosen as the first phase-only mask, and the complex image hidden in the host image is regarded as the second phase-only mask. The spherical wave is generated to simultaneously illuminate phase-only masks. Then two modulated masks are gyrator transformed. The corresponding transformed images are phase truncated to obtain encrypted images and amplitude truncated to construct decryption keys. The decryption keys, angles of gyrator transform, wavelength and radius of the spherical wave, and individual decryption keys for authorized users are sensitive keys, which enhance the security layers of the system. The proposed system can be implemented by using optoelectronic architecture. Numerical simulation results demonstrate the flexibility of the system.