A diffraction model of direction multiplexing method for hiding multiple images

Spherical surface (or cylinder) is considered to be regarded as the observing plane in an optical system. Several original images are placed at different directions on a sphere (or cylinder). The diffraction model between two slant planes is proposed to construct the propagation relation equation of the light field expressed by two images. The interference of two optical beams is used for hiding a secret pattern into two phase-only masks. The geometric parameters of the system (orientation and distance) can serve as an additional key for enhancing security. The numerical simulation results are made in order to validate the performance of the multiple encryption schemes.