A NOVELTY-FILTERED OPTICAL-INTENSITY CORRELATOR USING PHOTOREFRACTIVEBSO

We present details of an optical processor which carries out the dual operation of character recognition and novelty filtering. Dynamic Fres nel holographic filters are written in photorefractive Bi12SiO20 at 51 4 nm and read out using spatially incoherent illumination at 633 nm. T ransient enhancement of the readout beam is achieved by uniform illumi nation of the crystal, using a white-light source. Digital thresholdin g is then used to completely suppress the static background to provide ideal novelty filter characteristics.