Displaytech, for instance, has done much to promote its products for optical correlators. These are devices that compare the Fourier or other transforms of images by creating them optically. The images are displayed on a minidisplay, picked up by a laser beam, and then transformed using lenses or other optical elements. Though they are being used, none of the fast-binary devices are ideal for the job. The time-division multiplexing approach that works perfectly well in displays is not quite so ideal in a correlator.
Speed is good, but the ideal input device has grey levels, too.
Until now, optical correlators have been developed, almost exclusively, by the military and its contractors. If the display industry can produce lots of very cheap light modulators of the right kind, the revolution in displays could be followed by an explosion in machine-vision systems and image processors that literally work at the speed of light.