Abstract

We describe the video-rate operation of a compact (30 × 30 × 10 cm) joint transform optical image correlator using two cw diode lasers and a semi-insulating GaAs/AlGaAs multiple-quantum-well photorefractive device as the erasable holographic element. The video images of the objects to be correlated are introduced to the system through a liquid crystal spatial light modulator (SLM) containing 320 × 220 pixels, and the resultant correlation is read out with a CCD camera. With only 1 mW incident write power at 830 nm, the response time of the photorefractive device is sub-microsecond, presenting the possibility of more than 10⁶ correlations per second in a compact system. Furthermore, the small interaction length of the multiple-quantum-well device (2 μm) removes the spatial-bandwidth limitations of correlators based on thick photorefractive materials operating in the Bragg regime. We will discuss the performance of this system for pattern and character recognition.

© 1992 Optical Society of America