Computer-aided photorefractive pattern recognition

A hybrid pattern recgnition system which consists of photorefractive crystal, SLM and computer is designed and analyzed. In this system, photorefractive crystals are used as dynamic real-time recording meterials and optical coherent spatial filters. The problems of excessive sensitivity to scale and rotation in general optical matched filters are solved by computer-aided digital pre-processing. And that the limitation of anglular deviation apart from the Bragg condition due to volume hologram leads to no shift invariant is analyzed theoretically and examined experimentally. Due to that the optical properties such as hologram recording speed and diffraction efficiency of FWM in photorefractive crystals are different and strongly depended on the operation condition, we design the most suitable architectures to fit the purpose of the system. Finally, the performance of the whole system is also discussed.