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Optical Engineering

Demonstration of an uncooled LiTaO3-detector-based differential absorption radiometer for remote sensing of chemical effluents
Author(s): Stephen Keith Holland; Roland H. Krauss; Gabriel Laufer
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Paper Abstract

Differential absorption radiometers (DARs) using uncooled detectors are introduced as a simple method for low-cost remote sensing of chemical vapors for domestic security. A DAR consisting of a pair of uncooled LiTaO3 pyroelectric detectors integrated with bandpass filters selected to detect methanol, a simulant of many hazardous vapors, was demonstrated. At a signal-to-noise ratio (SNR) 5, the measured detection limit for methanol was 0.014 atm cm. This corresponds to a detection limit of 5.70×10–4 atm cm (31.5 mg m–2) for dimethyl methylphosphonate (DMMP). For comparison, a DAR consisting of a pair of cryogenically cooled HgCdTe (MCT) detectors was also tested. The detector-limited noise equivalent temperature differential (NETD) of the MCT detectors was measured to be 0.38 mK, whereas for the pyroelectric detector it was 115 mK. Despite the much lower detector noise, the MCT-based DAR provided a detection limit of only 0.005 atm cm for methanol, corresponding to 2.04×10–4 atm cm (11.25 mg m–2) for DMMP. The relatively poor sensitivity of the MCT-based DAR was shown to be limited by small temperature gradients of 15 mK across the noncoincident fields of view of the detectors in the DAR and by environmental fluctuations, which contributed a total NETD = 37 mK.

Paper Details

Date Published: 1 October 2004
PDF: 9 pages
Opt. Eng. 43(10) doi: 10.1117/1.1782612
Published in: Optical Engineering Volume 43, Issue 10
Show Author Affiliations
Stephen Keith Holland, Univ. of Virginia (United States)
Roland H. Krauss, Rammatek, LLC (United States)
Gabriel Laufer, Univ. of Virginia (United States)

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