Spatial amplification: an image-processing technique using the selective amplification of spatial frequencies.

A novel technique of processing optical images that we call spatial amplification is proposed and demonstrated. The basic idea is to amplify coherently a set of selected spatial frequency components of an image. Unlike in the usual spatial filtering techniques, in which the components are selectively blocked out at the Fourier plane of a coherent processor, spatial amplification does not discard any of the incident image information. The advantages of the proposed technique over spatial filtering include high energy efficiency and the possibility for cascading several stages. In the demonstrated experiments, the required amplification is provided by two-beam energy coupling in a photorefractive BaTiO(3) crystal with a nonuniform pump beam.