Optical pattern recognition using a unidirectional photorefractive oscillator coupled with an angular multiplexing volume hologram

We propose and demonstrate a unidirectional photorefractive ring oscillator that couples with an external angular multiplexing volume hologram for pat tern recognition. By configuring the hologram externally, a computer-genera ted hologram (CGH) and a spatial light modulator are utilized to generate r eference beams for the hologram. Two-dimensional images are stored in the f orm of resonating beams in the system, whereby the nonlinear interaction be tween the beams allows the image that most resembles an input object to be recognized. Five images were used to illustrate the pattern recognition abi lity of the oscillator. It was found that the input object was successfully recognized within 10s. The fact that CGHs can generate a large number of b eamlets enhances significantly the storage capacity in this system.