<title>Fourier optoelectronic signal pre-processor</title>

Abstract

This paper describes an attempt to provide a practical application of a fourier optical signal processing as a preprocessor to a digital signal system. The input illumination is a coherent light source from a HeNe laser and computation of the Fourier Transform (FT) is carried out via an FT lens. An object with its symmetry is placed in the front focal plane of the FT lens and at the back focal plane of the lens, the Joint Fourier transform image results. Limitation and boundary condition of the optical system were studied and experimented. Problem encountered during transformation due to differing light source and intensity to various degree of coherency were also considered both at the optical processing and the digital system processor/compensator. Phase measurement and the digital processor/compensator uses the sum-of-product carry save add-subtract unit with reconfigurability so as to allow optimum cost-performance relationship. The sum-of-product consists of 24-bit floating point units capable of performing efficient multiplication, addition and subtraction. Many of such floating-point units are used in parallel in a pipelined architecture to perform Discrete Fourier Transform or other complex function for Digital Signal Processing computations. This also helps to understand the limitation and accuracy of the transformation and the practical behavior of the optical lens-camera system.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.