HYBRID (REFRACTIVE-DIFFRACTIVE) FOURIER PROCESSOR - A NOVEL OPTICAL ARCHITECTURE FOR ACHROMATIC PROCESSING WITH BROAD-BAND POINT-SOURCE ILLUMINATION

We report on an achromatic Fourier processor constituted basically by a quasi-wavelength-independent imaging forming system whose first half performs an achromatic Fourier transform of the colour input. The nov el optical architecture, only formed by a small number of diffractive and refractive lenses, works under white-light point-source illuminati on and provides an intermediate achromatic real Fraunhofer plane and a final colour image without chromatic distortion. In this way, our opt ical processor performs simultaneously, with a single filter, the same spatial filtering operation for all the spectral components of the br oadband illumination. The practical capabilities of our proposal are c learly shown by means of a colour multiple-imaging experiment. (C) 199 8 Elsevier Science B.V. All rights reserved.