Digital color encryption using a multi-wavelength approach and a joint transform correlator

Abstract

We propose a digital color image encryption technique by using a joint transform correlator (JTC) architecture and a wavelength multiplexing operation. In our optical arrangement, the color image to be encrypted is separated into three channels: red, green and blue. One of the JTC apertures contains the input image information corresponding to a determined color channel bonded to a random phase mask, while the other JTC aperture contains the reference random phase key code. Since the speckle size generated by the random phase masks is wavelength dependent, the illuminating wavelength variation will produce a corresponding joint power spectrum (JPS) modification. Consequently, wavelength changes can be used to multiplex the encrypted information associated to each color channel. We sequentially store every JPS in the same medium. We present digital results that confirm our approach.