Digital reconstruction of Fourier optical signal using efficient 24-bit floating point multiply-add-subtract module

摘要

This paper describes a practical Fourier optical signal processor (FOSP) as a pre-processor for digital signal processing (DSP). 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 image is placed in the front focal plane of the FT lens and at the back focal plane of the lens, the Fourier transform image results. Using the method reported by Xu (1988) for the measurement of the phase information the real and imaginary information is retrieved and fed electronically into a Fast Fourier Transform (FFT) module, using 24-bit floating point units capable of performing efficient multiplication, addition and subtraction to reconstruct the original image. Many of such floating-point units are used in parallel in a pipelined architecture to perform FFT or other complex function for digital signal processing (DSP) computations.