Abstract

An imaging Fourier transform spectrometer developed at TUHH was used for short-range remote detection and identification of liquids on surfaces. The method is based on the measurement of infrared radiation emitted and reflected by the surface and the liquid. A radiative transfer model that takes both the real and imaginary parts of the refractive index of the materials into account has been developed. The model is applied for the detection and identification of potentially hazardous liquids. Measurements of various liquids on diverse surfaces were performed. The measured spectra depend on the optical properties of the background surface. However, using the radiative transfer model, automatic remote detection and identification of the liquids is possible. The agreement between measured spectra and spectra calculated using the radiative transfer model is excellent.

© 2008 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
  6. R. Harig, J. Gerhard, R. Braun, C. Dyer, B. Truscott, R. Moseley: "Remote Detection of Gases and Liquids by Imaging Fourier Transform Spectrometry using a Focal Plane Array Detector: First Results," Proc. SPIE 6378, 637816, 1-12 (2006).
  7. ASTER spectral library, http://speclib.jpl.nasa.gov/

2006

R. Harig, J. Gerhard, R. Braun, C. Dyer, B. Truscott, R. Moseley: "Remote Detection of Gases and Liquids by Imaging Fourier Transform Spectrometry using a Focal Plane Array Detector: First Results," Proc. SPIE 6378, 637816, 1-12 (2006).

2004

2001

R. Harig and G. Matz, "Toxic Cloud Imaging by Infrared Spectrometry: A Scanning FTIR System for Identification and Visualization," Field Analytical Chemistry and Technology 5, 75-90 (2001).
[CrossRef]

1993

Appl. Opt.

Appl. Spectrosc.

Field Analytical Chemistry and Technology

R. Harig and G. Matz, "Toxic Cloud Imaging by Infrared Spectrometry: A Scanning FTIR System for Identification and Visualization," Field Analytical Chemistry and Technology 5, 75-90 (2001).
[CrossRef]

Proc. SPIE

R. Harig, J. Gerhard, R. Braun, C. Dyer, B. Truscott, R. Moseley: "Remote Detection of Gases and Liquids by Imaging Fourier Transform Spectrometry using a Focal Plane Array Detector: First Results," Proc. SPIE 6378, 637816, 1-12 (2006).

A. Bell, C. Dyer, A. Jones, and K. Kinnear, "Stand-off liquid CW detection," Proc. SPIE 5268, 302-309 (2004).
[CrossRef]

Other

ASTER spectral library, http://speclib.jpl.nasa.gov/

O. Stenzel, The Physics of Thin Film Optical Spectra, (Springer, 2005).

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Figures (7)

Fig. 1.
Fig. 1.

Experimental set-up.

Fig. 2.
Fig. 2.

Reflection by a thin film on a surface.

Fig. 3.
Fig. 3.

Right: Clay tile with methyl salicylate applied to the surface. Left: Brightness temperature spectra of an area covered with methyl salicylate (a, solid line) and an area not covered by methyl salicylate (b, dotted line).

Fig. 4.
Fig. 4.

Left: Measured spectrum of methyl salicylate on pressboard (red solid line) and a reference spectrum calculated using the radiative transfer model (blue dashed line) fitted to the measurement. Right: Identification of methyl salicylate.

Fig. 5.
Fig. 5.

Left: Measured spectrum of methyl salicylate on wood (red solid line) and fitted reference spectrum (blue dashed line). Right: Identification of methyl salicylate.

Fig. 6.
Fig. 6.

Left: Measured spectrum of methyl salicylate on steel (red solid line) and the calculated spectrum for methyl salicylate on a highly reflective background fitted to the measurement. Right: Identification of methyl salicylate.

Fig. 7.
Fig. 7.

Above: Steel plate covered with triethyl phosphate. Below: Triethyl phosphate on a clay tile. Left: Brightness temperature spectrum of a contaminated area (red solid line) and simulated reference spectrum fitted to measured data (blue dashed line). Right: Identification of triethyl phosphate on steel and on clay.

Equations (6)

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L m = ( 1 τ air ) B air + τ air ( L e + L r ) .
L e = ( 1 R ) B S .
L r = R L in .
r 123 = r 12 + t 12 r 23 t 21 e 2 i δ 1 r 21 r 23 e 2 i δ ,
δ = 2 π σ d ( n + i κ ) 2 sin ( φ in ) 2 .
R = r 12 + r 23 e 2 i δ 1 + r 12 r 23 e 2 i δ 2 .

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