Photorefractive acoustoelectrooptic correlator

Abstract

Optical correlators have been widely used for pattern recognition and information processing. The proposed photorefractive acoustoelectrooptic correlator can be implemented with a single crystal and thus has advantages over conventional optical correlator systems. It is also possible to operate the correlator in real time. In this device, a 2-D light intensity pattern is stored as an electric field pattern induced through the photorefractive effect and serves as a 2-D reference image of the correlator. An acoustic signal generated by a transducer represents a 1-D object signal of the correlator. The interaction of optical waves with acoustic waves and electric field patterns gives intermodulations of the two signals. The analysis of the photorefractive acoustoelectrooptic effect shows that the amplitude of this intermodulation is a product of the amplitudes of the acoustic and electric fields for small diffraction efficiencies. The proposed correlator is based on this intermodulation. To obtain a coherent correlation we then use a lens to make a Fourier transformation of the product amplitude and detect the light intensity of the intermodulation on the focal plane with a pinhole detector.