Space-variant optical correlator based on the fractional Fourier transform: implementation by the use of a photorefractive Bi(12)GeO(2(a)) (BGO) holographic filter.

A space-variant optical correlator is proposed on the basis of the fractional Fourier transform. The optical device uses as a recording medium for the holographic filter a photorefractive Bi(12)GeO(2) (BGO) crystal. The experimental results confirm the shift-variance properties. Some limitations that arise from the volume diffraction are also considered.