NONLINEAR PHASE CORRECTION OF INTERFEROGRAMS OBTAINED IN FOURIER SPECTROSCOPY

摘要

A review of the theory and techniques of Fourier Spectroscopy is given, and the present state-of-the-art of reducing data obtained by this means is discussed. Certain inherent problems are present in today's methods of reducing the data obtained by Fourier Spectroscopy techniques, the so-called interferogram. They are:n(1) In the case of a symmetric interferogram where digital recording is used, the point corresponding to zero path difference may not be recorded. A simple cosine transform of this data leads to incorrect results,n(2) In the case of improper compensation of an interferometer, asymmetric interferograms result. The method of reducing these is to pick an approximate center, take a sine and cosine transform about it, and compute the spectrum as the square root of the sum of the squares of the sine and cosine transform respectively. There are two disadvantages to this type of reduc¬tion, namely that one requires twice as many points to obtain the same resolution ás in the symmetric case, and that the process is non linear with respect to signal-to-noise ratio in the spectrum.