Multiple-stage optical information processing system

Claim 1

An optical pattern identification system comprising: an input transparency containing patterns to be recognized, first means for projecting a beam of light through said input transparency, second means composed of a plurality of stationary light reflective units for causing any portion of said light beam passing through said input device to follow a zigzag optical path, at least some of said reflective units being concave mirrors, a first complex matched optical spatial filter having a Fourier transform characteristic matched to one of the patterns to be identified disposed along said zigzag optical path intermediate a first pair of said concave mirrors at the location of an optical Fourier transform of said input transparency, a second complex matched optical spatial filter having a Fourier transform characteristic matched to another of said patterns to be identified disposed along said zigzag optical path intermediate another pair of said concave mirrors at the location of an optical Fourier transform of said input transparency, a first apertured observation screen means disposed along said zigzag optical path intermediate said first and second pairs of concave mirrors at a location where said transparency is imaged, said screen having a central aperture of a size sufficiently large to pass said image of said transparency and sufficiently small to permit convolution spots to form on said screen, and a second apertured observation screen disposed along said zigzag path beyond said second pair of concave mirrors at a location where said transparencY is again imaged, said screen having a central aperture of a size sufficiently large to pass said latter image of said transparency and sufficiently small to permit other convolution spots to form on said second screen.