ABSTRACT
The Vander Lugt correlator is a coherent optical correlator, utilizing the Fourier transform property of a lens. The Vander Lugt correlation filter is a complex matched spatial filter, which is essentially an off-axis Fourier hologram. A correlator is naturally unable to recognize the searched objects when they are rotated or scaled. This entry discusses the basic methods for rotation-invariant and scale-invariant correlations.
