17 December 1980 Evaluation Of The Fabry-Perot Etalon For Spectral Discrimination In IR Surveillance
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Abstract
Infrared surveillance systems are often required to discriminate targets powered by combustion devices, such as rocket or jet engines, from the highly cluttered backgrounds of the earth-atmosphere scene against which the target must be viewed. The use of a Fabry-Perot etalon to perform this discrimination function based on the spectral differences between the source and background has been studied both experimentally and analytically. The quantitative results of this study are the subject of this paper. The discrimination factor for hot water sources, based on high resolution spectra in the 2.7μm region is found analytically to be less than 5 and accompanied by a large attenuation of the source signal. Measurements in our laboratory shows that the experimentally observed discrimination factors are even smaller. On the other hand an HF spectrum studied analytically shows discrimination factors as high as 50 may be achieved with as much as 50% of the source energy transmitted by the etalon. These different results are a consequence of the fundamentally different nature of the H2O and HF spectra. Based on these results further studies of selected other plume species, such as CO and CO2 near the head of the 4.3 μm band are suggested. Spectral discrimination of plumes containing hot water should be based on techniques other than an etalon.
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C. M. Randall, P. F. Zittel, L. A. Darnton, F. S. Simmons, "Evaluation Of The Fabry-Perot Etalon For Spectral Discrimination In IR Surveillance", Proc. SPIE 0253, Modern Utilization of Infrared Technology VI, (17 December 1980); doi: 10.1117/12.959515; https://doi.org/10.1117/12.959515
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