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Simulating systematic scene-change artifacts in Fourier-transform spectroscopy
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Paper Abstract

Improved understanding of midwave infrared (1-5μm) spectral emissions from detonation fireballs is needed to develop a battle space optical forensics capability. While Fourier-transform spectrometers (FTS) are an attractive tool, interferometer-based spectroscopic measurements can be corrupted when the observed scene intensity systematically varies during the measurement time. Approximating a detonation fireball as a blackbody radiator with a time-varying temperature T and modified by atmospheric attenuation τ(~ν), double-sided interferograms from an ideal FTS were calculated and converted to measured spectra Lm(~ν) to characterize the nature and magnitude of scene-change artifacts. T(x) decreased exponentially with optical path difference x, -xm ≤ x ≤ xm, at various rates relative to the Michelson mirror speed so that changing scene spectra could be simulated on 1700 ≤ ~ν ≤ 7900cm-1 at δ ~ν = 3.64cm-1 resolution (xm = 0.25cm, Hamming apodization). The real part of Lm(~ν), Re{Lm(~ν)}, is well approximated by the instantaneous spectrum at zero path difference, L(~ν,x = 0). In regions where τ(~ν) is highly structured, both the imaginary component Im{Lm(~ν)} and the differences between Re{Lm(~ν)} and L(~ν,0) exhibit spectral features, and in general |Im{Lm(~ν)}|>>|Re{Lm(~ν)}-L(~ν,0)|. In a region of highly structured absorption, 2800 ≤~ν ≤ 3500cm-1, a 600K decrease in temperature produced RMS values of 62 and 5μW/(cm2 • sr •cm-1) in Im{Lm(~ν)} and Re{Lm( ~ν)-L(~ν,0)}, respectively, compared with an RMS value of 1924μW/ (cm2 • sr • cm-1) in Re{Lm(~ν)}. A method based on theoretical expressions developed by Kick et al. is devised to interpret Lm(~ν) and provide estimates of the temporal evolution T(x) when its functional formis not known a priori.

Paper Details

Date Published: 13 May 2010
PDF: 9 pages
Proc. SPIE 7695, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI, 76951Y (13 May 2010); doi: 10.1117/12.849128
Show Author Affiliations
Kevin C. Gross, Air Force Institute of Technology (United States)
Anthony M. Young, Air Force Institute of Technology (United States)
Christoph Borel, Riverside Research Institute (United States)
Bryan J. Steward, National Air and Space Intelligence Ctr. (United States)
Glen P. Perram, Air Force Institute of Technology (United States)

Published in SPIE Proceedings Vol. 7695:
Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI
Sylvia S. Shen; Paul E. Lewis, Editor(s)

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