Abstract: An apparatus for performing the correlation of a real-time signal, and a red signal or signals, and two methods of storing signals as index of refraction variation patterns in piezoelectric crystals. A modulated R.F. signal is stored in a piezoelectric crystal by converting the signal to an acoustic signal which is then propagated across the length of the crystal. A portion of the surface of the crystal is irradiated by a high-frequency, short-duration laser pulse, and the acoustic signal is stored as a variable index of refraction pattern at the irradiated areas. When a real-time signal is propagated across the stored signal, and the surface of the crystal is irradiated with a laser beam, the correlation of the real-time signal and the stored signal is obtained upon demodulation of the laser beam.

Abstract: An acousto-optic correlator device comprised of two parallel piezoelectric rystals having different acoustic velocities. Acoustic transducers are located at one end of the respective crystals, and high frequency acoustic waves, the pulse envelopes of which correspond to the signals to be correlated are simultaneously launched from the transducers on the respective crystals. One of the acoustic waves "slides" past the other, and a laser beam, which is directed approximately perpendicular to the direction of acoustic propagation is modulated by the acoustic waves. The laser beam is demodulated and the desired correlation is obtained.