High-speed correlation employing chirp-encoded binary phase-only patterns

We describe the principles and performance of a novel form of hybrid electronic/photonic correlator which exploits recent developments in both electronics and photonics to provide a fast, compact and rugged processor. In the earlier Vander Lugt correlator the input image is Fourier Transformed optically and multiplied optically with the conjugate Fourier Transform of a reference pattern; the required correlation function is completed by taking the inverse Fourier Transform of the product optically. The correlator described here is similar, but performs the initial Fourier Transforms and multiplication electronically. In this scheme the Fourier Transforms of both the input scene and reference pattern are reduced to a binary phase-only format, when the multiplication process simplifies to a simple Boolean logic XOR function. The output of this XOR gate is displayed on a state-of-the-art Fast Bit Plane Spatial Light Modulator (FBPSLM). This device is electrically addressed, and employs a ferroelectric liquid crystal so its operation is inherently binary and fast. A consequence of the use of binary phase-only data is the appearance of a second (unwanted) peak in the output plane, but we demonstrate its elimination through the introduction of a chirp function. The complete correlator is demonstrated operating at 10,500 correlations/sec.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.