Iterative partial phase encoding based on joint fractional Fourier transform correlator adopting phase-shifting digital holography

In this paper, digital holography based on two-step phase shifting interference (PSI) was applied to realize the iterative partial phase encoding with joint fractional transform correlator (JFTC). By this security system, the primitive image is encoded in two joint fractional power spectra (JFPS) corresponding to different phase-shifting values. The encrypted image can be deduced directly from the JFPSs by digital means, thus eliminating the noise interference of dc and conjugate terms. JFTC not only relaxes the alignment requirement but also avoids the beam splitting required by traditional holography. In the iterative partial phase encoding, the random phase masks (RPMs) are generated by chaotic mapping, and encoding areas are confined by a sequence of random binary masks. To recover the primitive image, decipher must regenerate the partial RPMs with correct chaotic conditions and perform inverse fractional Fourier transforms with correct orders. The decryption process can be realized by JFTC or by totally digital means. Simulation and experimental results have been presented to test security level and feasibility of the scheme.