Optical security system using multiple-reference joint transform correlation

Abstract

A new security system is proposed using optical joint transform correlation technique which employs multiple phase-shifted reference images. In the proposed technique, the address code is used as the reference image and fed into four channels after performing phase shifting on them by different amount. The output signals from each channel are added with the input image to be encrypted for security purpose. Joint power spectra (JPS) signals can then be derived by applying Fourier transformation, and the resultant signals are phase-shifted and combined to form a modified JPS signal. Inverse Fourier transformation of the modified JPS signal yields the encrypted image which is now secure from any unauthorized access and/or loss of information. For decryption purpose, the received encrypted signal is first Fourier transformed and multiplied by the address code used in encryption, which is then inverse Fourier transformed to generate the output signal. The proposed technique does not involve any complex mathematical operation on the address code otherwise required in other security techniques. The proposed technique requires a simple architecture and operates fast, automatic and is invariant to noise and distortions. Performance of the proposed scheme is investigated using computer simulation using binary as well as gray images in both noise-free and noisy conditions.