Use of the Fast Fourier Transform in evaluation of laser Raman and fluorescence decay times

Two methods have been proposed for remote identification of oil slicks on water using an airborne lidar system. Both techniques require estimating the time decay of physical quantities from the measured return signal pulse. The purpose of this paper is to suggest the use of a Fast Fourier Transform technique to deconvolve the oil-fluorescence-on-water Raman decay time from the return pulse. This is a convolution of the required time varying signal with pulse shape, pulse broadening due to surface scattering, and instrument response. It is shown that the method yields results in agreement with those of Measures, Houston and Stephenson. The FFT method is faster and requires little storage and could be implemented in real time on airborne minicomputers or microcomputers.