Abstract

A differential absorption radiometer sensor that was optimized for near-perfect (∼2%) correction of the absorption by ambient atmospheric species (e.g., water) is described. A target gas is detected remotely by its IR signature viewed through a bandpass filter centered at one of its strongest lines. A second radiometric measurement obtained through a bandpass filter centered at a frequency optimized to match the absorption by an atmospheric trace species (e.g., water vapor) at the sample filter frequency provides near-perfect correction for dominant background absorption effects. The net absorption (emission) by the target gas was obtained through subtraction of the reference signal of the second measurement from that of the target gas measurement. For multiple species detection, additional sample and reference filter pairs can be configured. Predictions show that detection of strong absorbers such as dimethyl methylphosphonate at an optical density below 100 mg/m2 is possible from distances of <6 km.

© 2002 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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1997 (1)

1996 (1)

1995 (1)

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

1993 (1)

F. Lopez, J. de Frutos, “Multispectral interference filters and their application to the design of compact non-dispersive infrared gas analyzers for pollution control,” Sens. Actuators A 37–38, 502–506 (1993).

1991 (1)

M. L. G. Althouse, C. I. Chang, “Chemical vapor detection with a multispectral thermal imager,” Opt. Eng. 30, 1725–1733 (1991).
[CrossRef]

1985 (1)

L. D. Hoffland, R. J. Piffath, J. B. Bouck, “Spectral signatures of chemical agents and simulants,” Opt. Eng. 24, 982–984 (1985).
[CrossRef]

1983 (1)

W. B. Grant, R. T. Menzies, “A survey of laser and selected optical systems for remote measurements of pollutant gas concentrations,” J. Air Pollut. Control Assoc. 33, 187–194 (1983).
[CrossRef]

1975 (1)

Althouse, M. L. G.

M. L. G. Althouse, C. I. Chang, “Chemical vapor detection with a multispectral thermal imager,” Opt. Eng. 30, 1725–1733 (1991).
[CrossRef]

Best, F. A.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Borgnakke, C.

R. E. Sonntag, C. Borgnakke, G. J. Van Wylen, Fundamentals of Thermodynamics, 5th ed. (Wiley, New York, 1998), p. 664.

Bouck, J. B.

L. D. Hoffland, R. J. Piffath, J. B. Bouck, “Spectral signatures of chemical agents and simulants,” Opt. Eng. 24, 982–984 (1985).
[CrossRef]

Chang, C. I.

M. L. G. Althouse, C. I. Chang, “Chemical vapor detection with a multispectral thermal imager,” Opt. Eng. 30, 1725–1733 (1991).
[CrossRef]

de Haseth, J. A.

P. R. Griffiths, J. A. de Haseth, Fourier Transform Spectroscopy (Wiley, New York, 1986), p. 656.

Dedecker, R.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Flanigan, D. F.

Frutos, J. de

F. Lopez, J. de Frutos, “Multispectral interference filters and their application to the design of compact non-dispersive infrared gas analyzers for pollution control,” Sens. Actuators A 37–38, 502–506 (1993).

Grant, W. B.

W. B. Grant, R. T. Menzies, “A survey of laser and selected optical systems for remote measurements of pollutant gas concentrations,” J. Air Pollut. Control Assoc. 33, 187–194 (1983).
[CrossRef]

Griffiths, P. R.

P. R. Griffiths, J. A. de Haseth, Fourier Transform Spectroscopy (Wiley, New York, 1986), p. 656.

Hobbs, P. C. D.

Hoffland, L. D.

L. D. Hoffland, R. J. Piffath, J. B. Bouck, “Spectral signatures of chemical agents and simulants,” Opt. Eng. 24, 982–984 (1985).
[CrossRef]

Howell, H. B.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Knuteson, R. O.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Kruse, P. W.

P. W. Kruse, ed., Uncooled Thermal Imaging, Arrays, Systems, and Applications, Vol. TT51 of the Tutorial Texts (SPIE Press, Bellingham, Wash., 2001), p. 8.

Laufer, G.

G. Laufer, Introduction to Optics and Lasers in Engineering (Cambridge U. Press, Cambridge, UK, 1996), p. 326.

Lopez, F.

F. Lopez, J. de Frutos, “Multispectral interference filters and their application to the design of compact non-dispersive infrared gas analyzers for pollution control,” Sens. Actuators A 37–38, 502–506 (1993).

Menzies, R. T.

W. B. Grant, R. T. Menzies, “A survey of laser and selected optical systems for remote measurements of pollutant gas concentrations,” J. Air Pollut. Control Assoc. 33, 187–194 (1983).
[CrossRef]

Penner, S. S.

S. S. Penner, Quantitative Molecular Spectroscopy and Gas Emissivities (Addison-Wesley, Reading, Mass., 1959).

Piffath, R. J.

L. D. Hoffland, R. J. Piffath, J. B. Bouck, “Spectral signatures of chemical agents and simulants,” Opt. Eng. 24, 982–984 (1985).
[CrossRef]

Revercomb, H. E.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Sachse, G. W.

G. W. Sachse, L.-G. Wang, “Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry,” U.S. patent5,128,797 (7July1992).

G. W. Sachse, “Optical path switching based differential absorption radiometry for substance detection,” U.S. patent6,057,923 (2May2000).

Smith, W. L.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Sonntag, R. E.

R. E. Sonntag, C. Borgnakke, G. J. Van Wylen, Fundamentals of Thermodynamics, 5th ed. (Wiley, New York, 1998), p. 664.

Van Wylen, G. J.

R. E. Sonntag, C. Borgnakke, G. J. Van Wylen, Fundamentals of Thermodynamics, 5th ed. (Wiley, New York, 1998), p. 664.

Wang, L.-G.

G. W. Sachse, L.-G. Wang, “Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry,” U.S. patent5,128,797 (7July1992).

Ward, T. V.

Woolf, H. M.

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Zwick, H. H.

Appl. Opt. (3)

J. Air Pollut. Control Assoc. (1)

W. B. Grant, R. T. Menzies, “A survey of laser and selected optical systems for remote measurements of pollutant gas concentrations,” J. Air Pollut. Control Assoc. 33, 187–194 (1983).
[CrossRef]

J. Atmos. Sci. (1)

W. L. Smith, H. E. Revercomb, R. O. Knuteson, F. A. Best, R. Dedecker, H. B. Howell, H. M. Woolf, “Cirrus cloud properties derived from high spectral resolution infrared spectrometry during FIRE II. Part I: The High Resolution Interferometer Sounder (HIS) system,” J. Atmos. Sci. 52, 4238–4245 (1995).
[CrossRef]

Opt. Eng. (2)

M. L. G. Althouse, C. I. Chang, “Chemical vapor detection with a multispectral thermal imager,” Opt. Eng. 30, 1725–1733 (1991).
[CrossRef]

L. D. Hoffland, R. J. Piffath, J. B. Bouck, “Spectral signatures of chemical agents and simulants,” Opt. Eng. 24, 982–984 (1985).
[CrossRef]

Sens. Actuators A (1)

F. Lopez, J. de Frutos, “Multispectral interference filters and their application to the design of compact non-dispersive infrared gas analyzers for pollution control,” Sens. Actuators A 37–38, 502–506 (1993).

Other (7)

G. W. Sachse, L.-G. Wang, “Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry,” U.S. patent5,128,797 (7July1992).

G. W. Sachse, “Optical path switching based differential absorption radiometry for substance detection,” U.S. patent6,057,923 (2May2000).

P. R. Griffiths, J. A. de Haseth, Fourier Transform Spectroscopy (Wiley, New York, 1986), p. 656.

G. Laufer, Introduction to Optics and Lasers in Engineering (Cambridge U. Press, Cambridge, UK, 1996), p. 326.

S. S. Penner, Quantitative Molecular Spectroscopy and Gas Emissivities (Addison-Wesley, Reading, Mass., 1959).

R. E. Sonntag, C. Borgnakke, G. J. Van Wylen, Fundamentals of Thermodynamics, 5th ed. (Wiley, New York, 1998), p. 664.

P. W. Kruse, ed., Uncooled Thermal Imaging, Arrays, Systems, and Applications, Vol. TT51 of the Tutorial Texts (SPIE Press, Bellingham, Wash., 2001), p. 8.

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Figures (6)

Fig. 1
Fig. 1

Configuration of the DAR for chemical vapor detection. Blackbody radiation I b from the background medium at temperature T b is passing through the vapor cloud that is at temperature T v and transmission τ v and through two sections of the atmosphere at temperatures T 1 and T 2 having transmission coefficients τ1 and τ2, respectively.

Fig. 2
Fig. 2

Variation of the absorption coefficients of DMMP and DIMP. The line centers of the sample and reference filters for two DMMP DARs are also shown. The primary DAR is aligned with the strongest absorption line whereas the secondary DAR is aligned with a weaker DMMP line.

Fig. 3
Fig. 3

Variation of the atmospheric radiance with frequency for a 0–1-km layer as measured from the detector and for the 1-km to ∞ layer. All parameters are for the 1976 U.S. Standard Atmosphere.

Fig. 4
Fig. 4

Variation of the DMMP DAR signal with the centerline frequency of the reference filter, assuming that atmospheric absorption of radiation by a hot source (>1000 K) is induced only by water vapor at 296 K and 0.02325 atm and through a distance of 5 km. The upper curve is with 100-mg/m2 DMMP in the near field (τ2≈1) whereas the lower curve is without DMMP. The sample filter frequency is held constant at 1050 cm-1, a selected reference filter is marked at 955 cm-1.

Fig. 5
Fig. 5

Variation of the net normalized DMMP DAR signal with distance from a hot source (>1000 K). The sample filter is at 1050 cm-1 and the reference filter is at 955 cm-1. The partial pressure of water vapor is 0.02325 atm corresponding to 83% humidity at 23°C.

Fig. 6
Fig. 6

Quadrant detector designed as a dual-DAR sensor for positive identification of DMMP by simultaneous detection of two of its strongest lines while providing for each line near-perfect correction for interference by atmospheric water vapor. The center frequencies of the sample and reference filters are indicated. All filters were assumed to have a bandwidth of 12.9 cm-1 and a peak transmission of 64%.

Tables (2)

Tables Icon

Table 1 Sample and Matched Reference Filter Frequencies of DARs That Were Optimized to Provide Sensitive Detection of the Listed Species While Minimizing Interference by Water-Vapor Absorption

Tables Icon

Table 2 Change in Net Normalized Signal of a Two-Line DMMP DAR Sensor Induced by either DMMP or DIMP in the FOV (Absorption from 1 km and T > 1000 K)

Equations (11)

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τs=ν τsfνexp-αννCLν+DaνLadν,
Da=iαiCi.
Inet=Ir-IsIr,
Is=Ibτ1τvτ2+I1-τ1τ2τv+Iv1-τvτ2+I1-τ2,
Ir=Ibτ1τ2+I1-τ1τ2+I1-τ2=Ibτ1τ2+I1-τ1τ2,
Inet=Ir-IsIrτr-τsτr=1-τv,
Inet=Ib-Iv1-τvτ2Ibτ2+I1-τ2.
Inet=1-τvη,
η=Ib-IvIb+I1/τ2-1.
η=Ib-IvIb τ2.
exp-αwCL955=exp-αwCL1050.

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