Coherent optical multichannel correlator

Abstract

Abstract A coherent optical multichannel correlator for identifying an object by permeating an object with a beam of coherent light which is projected through a Fourier transformation lens onto a filter hologram which reconstructs a reference beam projected on a photo detector when the object to be identified corresponds to the filter hologram characterized by providing a plurality of filter holograms arranged on the focal plane of the lens, and a diffraction grating modulator to modulate the light beam to control the selection of the filter hologram on which the light is projected. Modulation can be either by changing the grating constant to vary the angle phi between the diffracted beam and original beam axis or by rotating the orientation of the diffracted beams through an angle theta. Preferably, the diffraction modulating varies both the angle phi and the angle theta either continuously to have the diffracted beam follow a spiral path along the filter holograms or in a step-like manner to have the diffracted beam follow a path of concentric circles along the filter holograms. The modulator can be a pair of rotatable diffraction gratings, a pair of rotatable diffraction gratings which are thin phase holograms, or a pair of diffraction gratings, one being a volume-phase hologram and the other a thin (phase) hologram. The modulator can also be a fixed grating of electro-optical material which has a grating pattern with a grating constant and orientation which are controlled by the application of an electrical or a magnetic field, or some other means that shifts the illuminating beam on an angle phi.

Inventors

• 👤 N Douklias
• 👤 G Winzer
• 👤 U Wolff

Bibliographic Details