Real-time Incoherent Optical Pattern Recognition with Photorefractive Crystals

Incoherent optical pattern recognition has been demonstrated with a simple setup using photorefractive BaTiO 3 crystals. The input patterns to be identified can be transmitted into the system with completely incoherent (both temporal and spatial) light. The setup does not require prefabricated filters for its operation and is thus a real-time system. The working principles of the system involve the photorefractive beam fanning effect and degenerate four-wave mixing.