Читать книгу Optical Cryptosystems - Naveen K. Nishchal - Страница 19

During the last few decades, many signal processing operations have been brought into the realm of Fourier optics. Some of them belong to the class of the linear canonical transforms (LCTs). LCT is a four parameter class of linear integral transforms, which is a flexible transform and possesses extra degrees of freedom without increasing the computational complexity [10]. It has received considerable attention over the period in optical information processing in general and information security applications in particular. Fractional Fourier transform (FRT), Fresnel transform (FrT), and gyrator transform (GT) belong to such a class while wavelet transformation, fractional convolution, and Wigner distribution belong to the category of linear combinations of LCTs or as cascades of such transformations. After the implementation of basic DRPE, subsequent optical encryption methods based on such transformations have been focused on encoding information. There are clear benefits (additional keys without extra computational cost) of these optical transforms in image encryption, watermarking, and steganography applications. The brief introduction of such systems has been discussed in the following subsections.