Accession Number : AD0624086

Title :   NONLINEAR PHASE CORRECTION OF INTERFEROGRAMS OBTAINED IN FOURIER SPECTROSCOPY.

Descriptive Note : Scientific rept.,

Corporate Author : UTAH STATE UNIV LOGAN ELECTRO-DYNAMICS LABS

Personal Author(s) : Forman,Michael L. ; Steele,W. H. ; Vanasse,George A.

Report Date : 01 JUL 1965

Pagination or Media Count : 92

Abstract : 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: (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. (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 reduction, namely that one requires twice as many points to obtain the same resolution as in the symmetric case, and that the process is non linear with respect to signal-to-noise ratio in the spectrum. A method is proposed which eliminates the above problems, and yields spectral values that are accurate to within one to three percent. It is based on the fact that there is a fixed function of the interferometer, the so-called phase error, and by making suitable use of it, one can obtain a secondary interferogram from the original interferogram which is symmetric about an effective zero path difference, hence only a cosine transform is required. (Author)

Descriptors :   (*INTERFEROMETERS, SPECTROSCOPY), (*SPECTROSCOPY, FOURIER ANALYSIS), (*FOURIER ANALYSIS, SPECTROSCOPY), INTEGRAL TRANSFORMS, CORRECTIONS, PHASE STUDIES

Subject Categories : Numerical Mathematics
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE