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Applied Optics

Applied Optics


  • Vol. 42, Iss. 24 — Aug. 20, 2003
  • pp: 4887–4900

Detection, identification, and estimation of biological aerosols and vapors with a Fourier-transform infrared spectrometer

Avishai Ben-David and Hsuan Ren  »View Author Affiliations

Applied Optics, Vol. 42, Issue 24, pp. 4887-4900 (2003)

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Two experiments were conducted with a Fourier-transform infrared (FTIR) spectrometer. The purpose of the first experiment was to detect and identify Bacillus subtilis subsp. niger (BG) bioaerosol spores and kaolin dust in an open-air release for which the thermal contrast between the aerosol temperature and background brightness temperature is small. The second experiment estimated the concentration of a small amount of triethyl phosphate (TEP) vapor in a closed chamber in which an external blackbody radiation source was used and where the thermal contrast was large. The deduced BG (TEP) extinction spectrum (identification) showed an excellent match to the library BG (TEP) extinction spectrum. Analysis of the time sequence of the measurements coincided well with the presence (detection) of the BG during the measurements, and the estimated concentration of time-dependent TEP vapor was excellent. The data were analyzed with hyperspectral detection, identification, and estimation algorithms. The algorithms were based on radiative transfer theory and statistical signal-processing methods. A subspace orthogonal projection operator was used to statistically subtract the large thermal background contribution to the measurements, and a robust maximum-likelihood solution was used to deduce the target (aerosol or vapor cloud) spectrum and estimate its mass-column concentration. A Gaussian-mixture probability model for the deduced mass-column concentration was computed with an expectation-maximization algorithm to produce the detection threshold, the probability of detection, and the probability of false alarm. The results of this study are encouraging, as they suggest for the first time to the authors’ knowledge the feasibility of detecting biological aerosols with passive FTIR sensors.

© 2003 Optical Society of America

OCIS Codes
(000.5490) General : Probability theory, stochastic processes, and statistics
(010.1300) Atmospheric and oceanic optics : Atmospheric propagation
(070.4790) Fourier optics and signal processing : Spectrum analysis
(280.1100) Remote sensing and sensors : Aerosol detection
(280.1120) Remote sensing and sensors : Air pollution monitoring
(300.6340) Spectroscopy : Spectroscopy, infrared

Original Manuscript: April 7, 2003
Revised Manuscript: March 19, 2003
Published: August 20, 2003

Avishai Ben-David and Hsuan Ren, "Detection, identification, and estimation of biological aerosols and vapors with a Fourier-transform infrared spectrometer," Appl. Opt. 42, 4887-4900 (2003)

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