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Proceedings Paper

Imaging FTIR emissivity measurement method
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Paper Abstract

Though many materials behave approximately as greybodies across the long-wave infrared (LWIR) waveband, certain important infrared (IR) scene modeling materials such as brick and galvanized steel exhibit more complex optical properties1. Accurately describing how non-greybody materials interact relies critically on the accurate incorporation of the emissive and reflective properties of the in-scene materials. Typically, measured values are obtained and used. When measured using a non-imaging spectrometer, a given material’s spectral emissivity requires more than one collection episode, as both the sample under test and a standard must be measured separately. In the interval between episodes changes in environment degrade emissivity measurement accuracy. While repeating and averaging measurements of the standard and sample helps mitigate such effects, a simultaneous measurement of both can ensure identical environmental conditions during the measurement process, thus reducing inaccuracies and delivering a temporally accurate determination of background or ‘down-welling’ radiation. We report on a method for minimizing temporal inaccuracies in sample emissivity measurements. Using a LWIR hyperspectral imager, a Telops Hyper-Cam2, an approach permitting hundreds of simultaneous, calibrated spectral radiance measurements of the sample under test as well as a diffuse gold standard is described. In addition, we describe the data reduction technique to exploit these measurements. Following development of the reported method, spectral reflectance data from 10 samples of various materials of interest were collected. These data are presented along with comments on how such data will enhance the fidelity of computer models of IR scenes.

Paper Details

Date Published: 23 September 2013
PDF: 7 pages
Proc. SPIE 8870, Imaging Spectrometry XVIII, 88700B (23 September 2013); doi: 10.1117/12.2023415
Show Author Affiliations
Edward M. Burdette, Georgia Tech Research Institute (United States)
C. Spencer Nichols, Georgia Tech Research Institute (United States)
Sarah E. Lane, Georgia Tech Research Institute (United States)
Keith F. Prussing, Georgia Tech Research Institute (United States)
J. Michael Cathcart, Georgia Tech Research Institute (United States)


Published in SPIE Proceedings Vol. 8870:
Imaging Spectrometry XVIII
Pantazis Mouroulis; Thomas S. Pagano, Editor(s)

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