Abstract

The atmosphere attenuates IR radiation in certain frequency bands even at distances as short as 1 m. Within the 3–5-μm range used by many IR thermographic systems, H2O and CO2 absorb a finite fraction of the source radiation. To achieve reliable quantitative IR thermography, it is necessary to correct the received signal for this attenuation. This paper develops a simple model and presents numerical calculations of the attenuation expected at a few meters distance for one typical thermographic imaging system. (The extension to other equipment could easily be done by substituting different numerical data for the detector response.) The attenuation factors due to CO2 and H2O are 6 and 8%, respectively, at a 10-m range. A wide variety of target temperature and ambient humidity conditions were examined; representative curves selected from this output are presented. Because of the importance of precise IR measurements for industrial applications, the effect of varying CO2 concentrations was also studied.

© 1983 Optical Society of America

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References

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  1. Energy, suppl. to Natl. Geogr. 159, No. 2 (Feb.1981).
  2. D. M. Burch, “Use of Aerial Infrared Thermography to Compare the Thermal Resistances of Roofs,” Natl. Bur. Stand. U.S. Tech. Note 1107 (Aug.1979); available from U.S. Superintendent of Documents, Washington, D.C.
  3. C. W. Hurley, K. G. Kreider, “Application of Thermography for Energy Conservation in Industry,” Natl. Bur. Stand. U.S. Tech. Note 923 (Oct.1976).
  4. Visions in Infrared (film) (AGA Corp., Lidingo, Sweden, 1975).
  5. K. G. Kreider, T. P. Sheahen, “Use of Infrared Thermography for Industrial Heat Balance Calculations,” Natl. Bur. Stand. U.S. Tech. Note 1129 (July1980).
  6. D. E. Gray, Ed., American Institute of Physics Handbook, (McGraw-Hill, New York, 1963).
  7. W. L. Wolfe, G. J. Zissis, Eds., The Infrared Handbook, (Environmental Research Institute of Michigan, Ann Arbor, 1978).
  8. R. Stair, R. G. Johnston, J. Res. Natl. Bur. Stand. 53, 211 (1954).
    [CrossRef]
  9. AGA 680, manufactured by AGA Corp., Lidingo, Sweden. The reader should be aware that the National Bureau of Standards does not endorse one instrument manufacturer over another, and the choice of AGA for this study should not be construed as such.
  10. Electro-Optical Industries model SS143 with Temperature Controller model 205.
  11. AGA Thermovision 680/102B Operating Manual (AGA Corp., Lidingo, Sweden); supplemented by private communications.
  12. H. Levinstein, J. Mudar, Proc. IEEE 63, 6 (1975).
    [CrossRef]
  13. The chopper is a reflecting aluminum disk <3 cm from the detector. The remainder of the detector’s field of view is at 77 K. Although the chopper radiates at ambient temperatures (say 293 K) with an emittance between 0.05 and 0.1, the tail of the Planck function in the 4–5-μm wavelength range makes it act like a blackbody radiator near 240 K.
  14. R. M. Goody, Atmospheric Radiation (Oxford U.P., London, 1964).
  15. R. C. Jones, Infrared Phys. 5, 11 (1965); also F. Nicodemus, “Self-Study Manual on Optical Radiation Measurements,” Natl. Bur. Stand. U.S. Tech. Note 910-2 (Feb.1978), Chap. 4.
    [CrossRef]
  16. F. X. Kneizys et al., “Atmospheric Transmittance/Radiance: Computer Code lowtran 5,” AFGL-TR-80-0067, Air Force Geophysics Laboratory (1980); available from National Technical Information Service, Washington, D.C.
  17. A. J. LaRocca, R. E. Turner, “Atmospheric Transmittance and Radiance: Methods of Calculation,” Report 107600-10-T, Environmental Research Institute of Michigan. J. N. Hamilton, J. A. Rowe, D. Anding, “Atmospheric Transmission and Emission Program,” Report TOR-0073 (3050-02)-3 (Aerospace Corp., El Segundo, Calif., 1973).
  18. L. M. McMillin, H. E. Fleming, M. L. Hill, Appl. Opt. 18, 1600 (1979).
    [CrossRef] [PubMed]
  19. For example, see A. T. Mecherikunnel, J. C. Richmond, “Spectral Distribution of Solar Radiation,” NASA Tech. Memo. 82021 (Sept.1980). Available from U.S. Superintendent of Documents, Washington, D.C.
  20. J. H. Pierluissi, K. Tomiyama, R. B. Gomez, Appl. Opt. 18, 1607 (1979).
    [CrossRef] [PubMed]
  21. lowtran 5 was modified to allow the concentration of the “uniformly mixed gases” to increase in the ratio of ×/330, with × an input parameter. This minor fix was sufficient because CO2 was the only one of those gases with an absorption band within the instrument bandpass.
  22. J. Hansen et al., Science 213, 957 (1981).
    [CrossRef] [PubMed]
  23. J. C. Richmond, in Proc. Soc. Photo-Opt. Instrum. Eng. 226, 110 (1980).
  24. W. L. Wolfe, Proc. Soc. Photo-Opt. Instrum. Eng. 226, 133 (1980).
  25. C. E. Scarborough, T. P. Sheahen, measurements in NBS photometric range (unpublished data).

1981 (2)

Energy, suppl. to Natl. Geogr. 159, No. 2 (Feb.1981).

J. Hansen et al., Science 213, 957 (1981).
[CrossRef] [PubMed]

1980 (3)

J. C. Richmond, in Proc. Soc. Photo-Opt. Instrum. Eng. 226, 110 (1980).

W. L. Wolfe, Proc. Soc. Photo-Opt. Instrum. Eng. 226, 133 (1980).

K. G. Kreider, T. P. Sheahen, “Use of Infrared Thermography for Industrial Heat Balance Calculations,” Natl. Bur. Stand. U.S. Tech. Note 1129 (July1980).

1979 (2)

1976 (1)

C. W. Hurley, K. G. Kreider, “Application of Thermography for Energy Conservation in Industry,” Natl. Bur. Stand. U.S. Tech. Note 923 (Oct.1976).

1975 (1)

H. Levinstein, J. Mudar, Proc. IEEE 63, 6 (1975).
[CrossRef]

1965 (1)

R. C. Jones, Infrared Phys. 5, 11 (1965); also F. Nicodemus, “Self-Study Manual on Optical Radiation Measurements,” Natl. Bur. Stand. U.S. Tech. Note 910-2 (Feb.1978), Chap. 4.
[CrossRef]

1954 (1)

R. Stair, R. G. Johnston, J. Res. Natl. Bur. Stand. 53, 211 (1954).
[CrossRef]

Burch, D. M.

D. M. Burch, “Use of Aerial Infrared Thermography to Compare the Thermal Resistances of Roofs,” Natl. Bur. Stand. U.S. Tech. Note 1107 (Aug.1979); available from U.S. Superintendent of Documents, Washington, D.C.

Fleming, H. E.

Gomez, R. B.

Goody, R. M.

R. M. Goody, Atmospheric Radiation (Oxford U.P., London, 1964).

Hansen, J.

J. Hansen et al., Science 213, 957 (1981).
[CrossRef] [PubMed]

Hill, M. L.

Hurley, C. W.

C. W. Hurley, K. G. Kreider, “Application of Thermography for Energy Conservation in Industry,” Natl. Bur. Stand. U.S. Tech. Note 923 (Oct.1976).

Johnston, R. G.

R. Stair, R. G. Johnston, J. Res. Natl. Bur. Stand. 53, 211 (1954).
[CrossRef]

Jones, R. C.

R. C. Jones, Infrared Phys. 5, 11 (1965); also F. Nicodemus, “Self-Study Manual on Optical Radiation Measurements,” Natl. Bur. Stand. U.S. Tech. Note 910-2 (Feb.1978), Chap. 4.
[CrossRef]

Kneizys, F. X.

F. X. Kneizys et al., “Atmospheric Transmittance/Radiance: Computer Code lowtran 5,” AFGL-TR-80-0067, Air Force Geophysics Laboratory (1980); available from National Technical Information Service, Washington, D.C.

Kreider, K. G.

K. G. Kreider, T. P. Sheahen, “Use of Infrared Thermography for Industrial Heat Balance Calculations,” Natl. Bur. Stand. U.S. Tech. Note 1129 (July1980).

C. W. Hurley, K. G. Kreider, “Application of Thermography for Energy Conservation in Industry,” Natl. Bur. Stand. U.S. Tech. Note 923 (Oct.1976).

LaRocca, A. J.

A. J. LaRocca, R. E. Turner, “Atmospheric Transmittance and Radiance: Methods of Calculation,” Report 107600-10-T, Environmental Research Institute of Michigan. J. N. Hamilton, J. A. Rowe, D. Anding, “Atmospheric Transmission and Emission Program,” Report TOR-0073 (3050-02)-3 (Aerospace Corp., El Segundo, Calif., 1973).

Levinstein, H.

H. Levinstein, J. Mudar, Proc. IEEE 63, 6 (1975).
[CrossRef]

McMillin, L. M.

Mecherikunnel, A. T.

For example, see A. T. Mecherikunnel, J. C. Richmond, “Spectral Distribution of Solar Radiation,” NASA Tech. Memo. 82021 (Sept.1980). Available from U.S. Superintendent of Documents, Washington, D.C.

Mudar, J.

H. Levinstein, J. Mudar, Proc. IEEE 63, 6 (1975).
[CrossRef]

Pierluissi, J. H.

Richmond, J. C.

J. C. Richmond, in Proc. Soc. Photo-Opt. Instrum. Eng. 226, 110 (1980).

For example, see A. T. Mecherikunnel, J. C. Richmond, “Spectral Distribution of Solar Radiation,” NASA Tech. Memo. 82021 (Sept.1980). Available from U.S. Superintendent of Documents, Washington, D.C.

Scarborough, C. E.

C. E. Scarborough, T. P. Sheahen, measurements in NBS photometric range (unpublished data).

Sheahen, T. P.

K. G. Kreider, T. P. Sheahen, “Use of Infrared Thermography for Industrial Heat Balance Calculations,” Natl. Bur. Stand. U.S. Tech. Note 1129 (July1980).

C. E. Scarborough, T. P. Sheahen, measurements in NBS photometric range (unpublished data).

Stair, R.

R. Stair, R. G. Johnston, J. Res. Natl. Bur. Stand. 53, 211 (1954).
[CrossRef]

Tomiyama, K.

Turner, R. E.

A. J. LaRocca, R. E. Turner, “Atmospheric Transmittance and Radiance: Methods of Calculation,” Report 107600-10-T, Environmental Research Institute of Michigan. J. N. Hamilton, J. A. Rowe, D. Anding, “Atmospheric Transmission and Emission Program,” Report TOR-0073 (3050-02)-3 (Aerospace Corp., El Segundo, Calif., 1973).

Wolfe, W. L.

W. L. Wolfe, Proc. Soc. Photo-Opt. Instrum. Eng. 226, 133 (1980).

Appl. Opt. (2)

Energy, suppl. to Natl. Geogr. (1)

Energy, suppl. to Natl. Geogr. 159, No. 2 (Feb.1981).

Infrared Phys. (1)

R. C. Jones, Infrared Phys. 5, 11 (1965); also F. Nicodemus, “Self-Study Manual on Optical Radiation Measurements,” Natl. Bur. Stand. U.S. Tech. Note 910-2 (Feb.1978), Chap. 4.
[CrossRef]

J. Res. Natl. Bur. Stand. (1)

R. Stair, R. G. Johnston, J. Res. Natl. Bur. Stand. 53, 211 (1954).
[CrossRef]

Natl. Bur. Stand. U.S. Tech. Note 1129 (1)

K. G. Kreider, T. P. Sheahen, “Use of Infrared Thermography for Industrial Heat Balance Calculations,” Natl. Bur. Stand. U.S. Tech. Note 1129 (July1980).

Natl. Bur. Stand. U.S. Tech. Note 923 (1)

C. W. Hurley, K. G. Kreider, “Application of Thermography for Energy Conservation in Industry,” Natl. Bur. Stand. U.S. Tech. Note 923 (Oct.1976).

Proc. IEEE (1)

H. Levinstein, J. Mudar, Proc. IEEE 63, 6 (1975).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (2)

J. C. Richmond, in Proc. Soc. Photo-Opt. Instrum. Eng. 226, 110 (1980).

W. L. Wolfe, Proc. Soc. Photo-Opt. Instrum. Eng. 226, 133 (1980).

Science (1)

J. Hansen et al., Science 213, 957 (1981).
[CrossRef] [PubMed]

Other (14)

C. E. Scarborough, T. P. Sheahen, measurements in NBS photometric range (unpublished data).

lowtran 5 was modified to allow the concentration of the “uniformly mixed gases” to increase in the ratio of ×/330, with × an input parameter. This minor fix was sufficient because CO2 was the only one of those gases with an absorption band within the instrument bandpass.

The chopper is a reflecting aluminum disk <3 cm from the detector. The remainder of the detector’s field of view is at 77 K. Although the chopper radiates at ambient temperatures (say 293 K) with an emittance between 0.05 and 0.1, the tail of the Planck function in the 4–5-μm wavelength range makes it act like a blackbody radiator near 240 K.

R. M. Goody, Atmospheric Radiation (Oxford U.P., London, 1964).

D. E. Gray, Ed., American Institute of Physics Handbook, (McGraw-Hill, New York, 1963).

W. L. Wolfe, G. J. Zissis, Eds., The Infrared Handbook, (Environmental Research Institute of Michigan, Ann Arbor, 1978).

F. X. Kneizys et al., “Atmospheric Transmittance/Radiance: Computer Code lowtran 5,” AFGL-TR-80-0067, Air Force Geophysics Laboratory (1980); available from National Technical Information Service, Washington, D.C.

A. J. LaRocca, R. E. Turner, “Atmospheric Transmittance and Radiance: Methods of Calculation,” Report 107600-10-T, Environmental Research Institute of Michigan. J. N. Hamilton, J. A. Rowe, D. Anding, “Atmospheric Transmission and Emission Program,” Report TOR-0073 (3050-02)-3 (Aerospace Corp., El Segundo, Calif., 1973).

For example, see A. T. Mecherikunnel, J. C. Richmond, “Spectral Distribution of Solar Radiation,” NASA Tech. Memo. 82021 (Sept.1980). Available from U.S. Superintendent of Documents, Washington, D.C.

Visions in Infrared (film) (AGA Corp., Lidingo, Sweden, 1975).

D. M. Burch, “Use of Aerial Infrared Thermography to Compare the Thermal Resistances of Roofs,” Natl. Bur. Stand. U.S. Tech. Note 1107 (Aug.1979); available from U.S. Superintendent of Documents, Washington, D.C.

AGA 680, manufactured by AGA Corp., Lidingo, Sweden. The reader should be aware that the National Bureau of Standards does not endorse one instrument manufacturer over another, and the choice of AGA for this study should not be construed as such.

Electro-Optical Industries model SS143 with Temperature Controller model 205.

AGA Thermovision 680/102B Operating Manual (AGA Corp., Lidingo, Sweden); supplemented by private communications.

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Figures (11)

Fig. 1
Fig. 1

Through-the-lens spectral response of detector system for the particular IR thermographic scanner used here.

Fig. 2
Fig. 2

Planck radiation function on a linear scale. The overlap integral of the detector response G(ν) (Fig. 1) with this temperature-dependent function produces the fiducial calibration curve prior to attenuation corrections.

Fig. 3
Fig. 3

Calibration curve in moderate temperature range. Solid curve = manufacturer’s typical calibration in agreement with our measurements. Dashed curve = theoretical curve of Eq. (1). The vertical scale is in arbitrary units, so the two curves were matched at the upper end of this chart.

Fig. 4
Fig. 4

Calibration curves in low temperature range. Solid curve, manufacturer’s typical calibration; dashed curve, theoretical curve with radiation level from the chopper subtracted off (chopper correction). Arbitrary unit curves were matched near 150°C. Enlargement of low temperature range shows discrepancy of two isotherm units out of full scale of 1000 due to imperfect chopper correction.

Fig. 5
Fig. 5

Atmospheric absorption over frequency range of interest for this detector at a distance of 10 m through ambient air at 20°C and 66% RH.

Fig. 6
Fig. 6

Atmospheric absorption at a distance of 5 m through ambient air at 20°C and 66% RH but with CO2 concentration doubled above normal air. Comparing Fig. 6 with Fig. 5 shows that the CO2 absorption is the same, but H2O absorption is less at the shorter distance.

Fig. 7
Fig. 7

Transmittance (as a function of distance) of the radiation from three different blackbody radiators passing through 20°C air with 66% RH. Radiation by the intervening column of air is deliberately omitted here.

Fig. 8
Fig. 8

Apparent transmittance from several different temperature radiators including radiation from the intervening air column at 20°C and 66% RH. The vertical axis is the ratio of radiation received with and without the air column. At high temperatures changes due to sterisent are negligible, but at low temperatures the effect is important.

Fig. 9
Fig. 9

Variation of apparent transmittance (received radiation) at 10-m distances as a function of target temperature with an intervening air column of 20°C. Two different humidity levels are compared. Solid curve, with sterisent correction; dashed curve, no correction for air radiation. Clearly the air radiation contributes a very small percentage above 300°C.

Fig. 10
Fig. 10

Apparent transmittance at two distances as a function of humidity in the intervening air column at 20°C. Solid curves, 100°C blackbody target; dashed curves, 800°C target.

Fig. 11
Fig. 11

Effect of CO2 variation on apparent transmittance. With a target temperature of 100°C and intervening air at 20°C and 66% RH, the CO2 concentration of the atmosphere was varied for two fixed distances, 5 and 10 m.

Equations (10)

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L ( T ) = 0 G ( ν ) B ( ν , T ) d ν ,
L ( S ) = L ( 0 ) exp [ τ ( S , 0 ) ] + o S J ( S ) exp [ τ ( S , S ) ] k ρ d S ,
τ ( S , S ) = S S k ρ d s .
L ( S ) = L ( 0 ) exp ( k ρ S ) + B ( ν , T a ) [ 1 exp ( k ρ S ) ] .
L ( S , T H , A ) = 0 G ( ν ) { B ( ν , T H ) exp ( k ρ S ) + B ( ν , T a ) [ 1 exp ( k ρ S ) ] } d ν ,
L ( S , T , A ) = L ( T ) f 1 ( R S ) f 2 ( C S ) ,
f 1 ( R S ) = exp [ 0.0326 ( R S ) 1 / 2 ] .
f 2 ( C S ) = 1.014 exp [ 0.0283 ( C S ) 1 / 3 ]
f 2 ( C S ) = 1.0033 exp [ 0.0164 ( C S ) 1 / 2 ] .
T = 100 ° C Δ T = 6 ° C , T = 400 ° C Δ T = 17 ° C , T = 700 ° C Δ T = 34 ° C .

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