Optical color image hiding scheme based on chaotic mapping and Hartley transform

We present a color image encryption algorithm by using chaotic mapping and Hartley transform. The three components of color image are scrambled by Baker mapping. The coordinates composed of the scrambled monochrome components are converted from Cartesian coordinates to spherical coordinates. The data of azimuth angle is normalized and regarded as the key. The data of radii and zenith angle are encoded under the help of optical Hartley transform with scrambled key. An electro-optical encryption structure is designed. The final encrypted image is constituted by two selected color components of output in real number domain.