Correction techniques for Fourier transform spectrometer measurements of short infrared pulses

Abstract

The acquisition of an interferogram by a Fourier transform spectrometer takes a finite time and the source being measured must not vary during the acquisition. Even with a fast scanning spectrometer it can happen that the source of interest vary during the acquisition. We were faced with this problem when we wanted to measure the spectrum of gun flashes. In this paper we present interferogram correction techniques that we developed to handle this problem. Using the fact that smallarms flashes are reproducible, we acquired a small set of interferograms with zero path difference (ZPD) points occurring at different times during the flash. We either measured or estimated these times of occurrence. Then, after properly filtering the original interferograms, we constructed a new set of interferograms, by piecing together parts of different filtered interferograms, to obtain instantaneous interferograms for various times during the flash. We show the utility of having a good estimate of the flash total intensity as a function of time, as estimated from the interferograms ZPD values or by measurements with a radiometer, to correct for amplitude variations. Even with such a small set of interferograms, the application of these correction techniques allows good measurements of the temporal evolution of the spectral emission of short pulses, such as gun flashes in the infrared region between 2 and 5microns.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.