title: Remote photoacoustic detection of liquid contamination of a surface.
abstract: A method for the remote detection and identification of liquid chemicals at ranges of tens of meters is presented. The technique uses pulsed indirect photoacoustic spectroscopy in the 10-microm wavelength region. Enhanced sensitivity is brought about by three main system developments: (1) increased laser-pulse energy (150 microJ/pulse), leading to increased strength of the generated photoacoustic signal; (2) increased microphone sensitivity and improved directionality by the use of a 60-cm-diameter parabolic dish; and (3) signal processing that allows improved discrimination of the signal from noise levels through prior knowledge of the pulse shape and pulse-repetition frequency. The practical aspects of applying the technique in a field environment are briefly examined, and possible applications of this technique are discussed.
authors.affiliation: Sensors and Electronics Division, Qinetiq Malvern, Worcestershire, WR14 3PS, UK. bjperrett@qinetiq.com
authors.forename: Brian
authors.initials: B
authors.lastname: Perrett
authors.forename: Michael
authors.initials: M
authors.lastname: Harris
authors.forename: Guy N
authors.initials: GN
authors.lastname: Pearson
authors.forename: David V
authors.initials: DV
authors.lastname: Willetts
authors.forename: Mark C
authors.initials: MC
authors.lastname: Pitter