A remarkable property of lenses and parabolic mirrors is their ability of performing, in
parallel and at the speed of light, Fourier transform of input wave fronts and to act as “chirp”- spatial
light modulator. This basic property enables creating optical information processing systems for
implementation of optical Fourier analysis, image convolution and correlation. In this chapter, basic
properties of lenses and parabolic mirrors relevant to optical information processing are briefly
explained, elements of the theory of optical correlators for reliable target location in images are an
introduced and their different implementations of optical correlators are described.
