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Proceedings Paper

Standoff photoacoustic detections with high-sensitivity microphones and acoustic arrays
Author(s): Fow-Sen Choa; Chen-Chia Wang; Jacob Khurgin; Alan Samuels; Sudhir Trivedi; Deepa Gupta
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Paper Abstract

Standoff detection of dangerous chemicals like explosives, nerve gases, and harmful aerosols has continuously been an important subject due to the serious concern about terrorist threats to both overseas and homeland lives and facility. Compared with other currently available standoff optical detection techniques, like Raman, photo-thermal, laser induced breakdown spectroscopy,...etc., photoacoustic (PA) sensing has the advantages of background free and very high detection sensitivity, no need of back reflection surfaces, and 1/R instead of 1/R2 signal decay distance dependence. Furthermore, there is still a great room for PA sensitivity improvement by using different PA techniques, including lockin amplifier, employing new microphones, and microphone array techniques. Recently, we have demonstrated standoff PA detection of isopropanol vapor, solid phase TNT and RDX at a standoff distance. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated signal enhancement and noise reduction using an array of 4 microphone/4 reflector system as well as an array of 16-microphone/1 reflector. In this work we will review and compare different standoff techniques and discuss the advantages of using different photoacoustic techniques. We will also discuss new advancement of using new types of microphone and the performance comparison of using different structure of microphone arrays and combining lock-in amplifier with acoustic arrays. Demonstration of out-door real-time operations with high power mid-IR laser and microphone array will be presented.

Paper Details

Date Published: 12 May 2016
PDF: 11 pages
Proc. SPIE 9824, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVII, 98240M (12 May 2016); doi: 10.1117/12.2224270
Show Author Affiliations
Fow-Sen Choa, Univ. of Maryland, Baltimore County (United States)
Chen-Chia Wang, Brimrose Corp. of America (United States)
Jacob Khurgin, Johns Hopkins Univ. (United States)
Alan Samuels, U.S. Army Edgewood Chemical Biological Ctr. (United States)
Sudhir Trivedi, Brimrose Corp. of America (United States)
Deepa Gupta, Univ. of Maryland, Baltimore County (United States)

Published in SPIE Proceedings Vol. 9824:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XVII
Augustus Way Fountain III, Editor(s)

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