Photoacoustic spectroscopy for remote detection of liquid contamination

Abstract

The remote detection and identification of liquid chemical contamination is a difficult problem for which no satisfactory solution has yet been found. We have investigated a new technique, pulsed indirect photoacoustic spectroscopy (PIPAS), and made an assessment of its potential for operation at stand-off ranges of order 10m. The method involves optical excitation of the liquid surface with a pulsed laser operating in the 9-11μm region. Pulse lengths are of order 3μs, with energy ∼300μJ and repetition rates ∼200Hz. Rapid heating of the liquid by the laser pulse produces acoustic emission at the surface, and this is detected by a sensitive directional microphone to increase the signal-to-noise ratio and reduce background clutter. The acoustic pulse strength is related to the liquid's absorption coefficient at the laser wavelength; tuning allows spectroscopic investigation and a means of chemical identification. Maximum coverage rates have been examined, and further experiments have examined the specificity of the technique, allowing a preliminary assessment of false-alarm and missed-signal rates. The practical aspects of applying the technique in a field environment have been assessed.

Publication DOI: https://doi.org/10.1117/12.577513
Divisions: Engineering & Applied Sciences > Aston Institute of Photonics Technology
Additional Information: Copyright 2004 SPIE. One print or electronic copy may be made for personal use only. Systematic reproduction, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Uncontrolled Keywords: Chemical,Liquid,Photoacoustic,Remote-sensing,Spectroscopy,Stand-off,Electronic, Optical and Magnetic Materials,Condensed Matter Physics,Computer Science Applications,Applied Mathematics,Electrical and Electronic Engineering
Full Text Link:
Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
https://www.spi ... /12.577513.full (Publisher URL)
PURE Output Type: Conference article
Published Date: 2004-12-01
Authors: Harris, Michael
Perrett, Brian
Benton, David M. ( 0000-0003-0663-1404)
Willetts, David V.

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