Abstract

The design and evaluation of a backscatter-absorption gas-imaging sensor that operates in a pulsed mode is described. It is capable of video visualization of natural gas leaks. Its development was motivated by the need for a methane imaging system to operate at ranges and sensitivities useful to the natural gas industry. The imager employs pulsed laser illumination at a repetition rate of 30 Hz and an average power of ∼150 mW to image gas at standoff ranges of as long as 100 m, using a backscatter target with a reflectivity of 0.016 sr-1. This is a tenfold improvement over an earlier raster-scanned imager. Natural gas leaks as small as 1.6 × 10-4 standard liters/s [equal to 0.02 standard cubic feet per hour (scfh)] were imaged at short ranges; leaks as low as 7.9 × 10-4 standard liters/s (0.1 scfh) were observed at long ranges. Data are compared with model predictions, and potential extensions to a fieldable prototype are discussed. The optimization of a direct-injection focal-plane array for detecting short (nanosecond) laser pulses is described.

© 1998 Optical Society of America

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References

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  1. T. G. McRae, T. J. Kulp, “Backscatter absorption gas imaging: a new technique for gas visualization,” Appl. Opt. 32, 4037–4050 (1993).
    [PubMed]
  2. P. E. Powers, T. J. Kulp, R. Kennedy, “Issues affecting differential absorption laser imaging of gas leaks,” in Conference on Lasers and Electro-Optics, Vol. 9 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 54.
  3. T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.
  4. T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
    [CrossRef]
  5. T. G. McRae, L. L. Altpeter, “Application of backscatter absorption gas imaging to natural gas leak detection,” in Proceedings of the 1992 International Gas Research Conference 2, H. A. Thompson, ed. (Government Institutes, Inc., Rockville, Md., 1993) pp. 1312–1322.
  6. R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley, New York, 1984), Chap. 7.
  7. T. S. McKechnie, “Speckle reduction,” in Laser Speckle and Related Phenomena, J. C. Dainty, ed., Vol. 9 of Topics in Applied Physics (Springer-Verlag, New York, 1975), pp. 123–171.
    [CrossRef]
  8. M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
    [CrossRef]
  9. F. M. Dickey, B. D. O’Neil, “Multifaceted laser beam integrators: general formulation and design concepts,” Opt. Eng. 27, 999–1007 (1988).
    [CrossRef]
  10. J. DiBenedetto, G. Capelle, S. Lutz, “Uniform field laser illumination for remote sensing,” in Earth and Atmospheric Remote Sensing, Proc. SPIE1492, 115–125 (1991).
    [CrossRef]
  11. R. Cannata, Raytheon Amber Engineering, Goleta, Calif. 93117 (personal communication, 1994).
  12. H. Henshall, J. Cruickshank, “Reflectance characteristics of selected materials for reference targets for 10.6-μm laser radars,” Appl. Opt. 27, 2748–2755 (1988).
    [CrossRef] [PubMed]

1993 (1)

1992 (1)

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

1988 (2)

F. M. Dickey, B. D. O’Neil, “Multifaceted laser beam integrators: general formulation and design concepts,” Opt. Eng. 27, 999–1007 (1988).
[CrossRef]

H. Henshall, J. Cruickshank, “Reflectance characteristics of selected materials for reference targets for 10.6-μm laser radars,” Appl. Opt. 27, 2748–2755 (1988).
[CrossRef] [PubMed]

Adomatis, D.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

Altpeter, L. L.

T. G. McRae, L. L. Altpeter, “Application of backscatter absorption gas imaging to natural gas leak detection,” in Proceedings of the 1992 International Gas Research Conference 2, H. A. Thompson, ed. (Government Institutes, Inc., Rockville, Md., 1993) pp. 1312–1322.

Cannata, R.

R. Cannata, Raytheon Amber Engineering, Goleta, Calif. 93117 (personal communication, 1994).

Capelle, G.

J. DiBenedetto, G. Capelle, S. Lutz, “Uniform field laser illumination for remote sensing,” in Earth and Atmospheric Remote Sensing, Proc. SPIE1492, 115–125 (1991).
[CrossRef]

Cruickshank, J.

Delong, M.

T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
[CrossRef]

DiBenedetto, J.

J. DiBenedetto, G. Capelle, S. Lutz, “Uniform field laser illumination for remote sensing,” in Earth and Atmospheric Remote Sensing, Proc. SPIE1492, 115–125 (1991).
[CrossRef]

Dickey, F. M.

F. M. Dickey, B. D. O’Neil, “Multifaceted laser beam integrators: general formulation and design concepts,” Opt. Eng. 27, 999–1007 (1988).
[CrossRef]

Garvis, D.

T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
[CrossRef]

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

Hanna, D. C.

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

Henshall, H.

Kennedy, R.

T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
[CrossRef]

P. E. Powers, T. J. Kulp, R. Kennedy, “Issues affecting differential absorption laser imaging of gas leaks,” in Conference on Lasers and Electro-Optics, Vol. 9 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 54.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

Kulp, T. J.

T. G. McRae, T. J. Kulp, “Backscatter absorption gas imaging: a new technique for gas visualization,” Appl. Opt. 32, 4037–4050 (1993).
[PubMed]

P. E. Powers, T. J. Kulp, R. Kennedy, “Issues affecting differential absorption laser imaging of gas leaks,” in Conference on Lasers and Electro-Optics, Vol. 9 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 54.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
[CrossRef]

Lutz, S.

J. DiBenedetto, G. Capelle, S. Lutz, “Uniform field laser illumination for remote sensing,” in Earth and Atmospheric Remote Sensing, Proc. SPIE1492, 115–125 (1991).
[CrossRef]

McIlveen, T. J.

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

McKechnie, T. S.

T. S. McKechnie, “Speckle reduction,” in Laser Speckle and Related Phenomena, J. C. Dainty, ed., Vol. 9 of Topics in Applied Physics (Springer-Verlag, New York, 1975), pp. 123–171.
[CrossRef]

McRae, T. G.

T. G. McRae, T. J. Kulp, “Backscatter absorption gas imaging: a new technique for gas visualization,” Appl. Opt. 32, 4037–4050 (1993).
[PubMed]

T. G. McRae, L. L. Altpeter, “Application of backscatter absorption gas imaging to natural gas leak detection,” in Proceedings of the 1992 International Gas Research Conference 2, H. A. Thompson, ed. (Government Institutes, Inc., Rockville, Md., 1993) pp. 1312–1322.

Measures, R. M.

R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley, New York, 1984), Chap. 7.

Milton, M. J. T.

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

O’Neil, B. D.

F. M. Dickey, B. D. O’Neil, “Multifaceted laser beam integrators: general formulation and design concepts,” Opt. Eng. 27, 999–1007 (1988).
[CrossRef]

Powers, P. E.

P. E. Powers, T. J. Kulp, R. Kennedy, “Issues affecting differential absorption laser imaging of gas leaks,” in Conference on Lasers and Electro-Optics, Vol. 9 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 54.

Seppala, L.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

Stahovec, J.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

Woods, P. T.

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

Appl. Opt. (2)

Opt. Commun. (1)

M. J. T. Milton, T. J. McIlveen, D. C. Hanna, P. T. Woods, “A high-gain optical parametric amplifier tunable between 3.27 and 3.65 μm,” Opt. Commun. 93, 186–190 (1992).
[CrossRef]

Opt. Eng. (1)

F. M. Dickey, B. D. O’Neil, “Multifaceted laser beam integrators: general formulation and design concepts,” Opt. Eng. 27, 999–1007 (1988).
[CrossRef]

Other (8)

J. DiBenedetto, G. Capelle, S. Lutz, “Uniform field laser illumination for remote sensing,” in Earth and Atmospheric Remote Sensing, Proc. SPIE1492, 115–125 (1991).
[CrossRef]

R. Cannata, Raytheon Amber Engineering, Goleta, Calif. 93117 (personal communication, 1994).

P. E. Powers, T. J. Kulp, R. Kennedy, “Issues affecting differential absorption laser imaging of gas leaks,” in Conference on Lasers and Electro-Optics, Vol. 9 of 1996 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1996), p. 54.

T. J. Kulp, R. Kennedy, D. Garvis, L. Seppala, D. Adomatis, J. Stahovec, “Further advances in gas imaging: field testing of an extended-range gas imager,” in Proceedings of the International Conference on Lasers ’90, D. G. Harris, J. Herbelin, eds. (Society for Optical and Quantum Electronics, McLean, Va., 1991), pp. 407–413.

T. J. Kulp, R. Kennedy, M. Delong, D. Garvis, “The development and testing of a backscatter absorption gas imaging system capable of imaging at a range of 300 m,” in Applied Laser Radar Technology, G. M. Kamerman, W. E. Keicher, eds., Proc. SPIE1936, 204–212 (1993).
[CrossRef]

T. G. McRae, L. L. Altpeter, “Application of backscatter absorption gas imaging to natural gas leak detection,” in Proceedings of the 1992 International Gas Research Conference 2, H. A. Thompson, ed. (Government Institutes, Inc., Rockville, Md., 1993) pp. 1312–1322.

R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley, New York, 1984), Chap. 7.

T. S. McKechnie, “Speckle reduction,” in Laser Speckle and Related Phenomena, J. C. Dainty, ed., Vol. 9 of Topics in Applied Physics (Springer-Verlag, New York, 1975), pp. 123–171.
[CrossRef]

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Figures (10)

Fig. 1
Fig. 1

Schematic of a full-field illuminated pulsed imager.

Fig. 2
Fig. 2

Diagram of the breadboard pulsed imager. The DFG is a difference-frequency crystal, and the OPA is a crystal used as an optical parametric amplifier.

Fig. 3
Fig. 3

General schematic of a DI readout circuit.

Fig. 4
Fig. 4

Response plot of the off-the-shelf DI FPA at several bias voltages. Response is plotted in volts at the analog-to-digital converter and in electrons integrated in the unit cell. Response is plotted as a function of relative energy injected into the integrating sphere.

Fig. 5
Fig. 5

Response plot of the custom DI FPA. Note that the saturation point (in electrons) is higher than that in Fig. 4, and that the volts per electron is higher as well.

Fig. 6
Fig. 6

Image of a 0.1-scfh methane leak taken at a range of 20 m with the pulsed imager.

Fig. 7
Fig. 7

Plot of the measured and calculated backscatter signal as a function of range.

Fig. 8
Fig. 8

Plot of the calculated and measured noise in the backscatter signal versus range.

Fig. 9
Fig. 9

Plot of the measured and calculated total noise and the contributions to the calculated noise. Note that noise squared is actually plotted. The factors of 2 for some noise terms arise because of the bias-sum-subtract process.

Fig. 10
Fig. 10

Plot of the measured and calculated signal-to-noise ratios for the pulsed imager.

Tables (1)

Tables Icon

Table 1 System Parameters Used in the Pulsed Imager Model

Equations (8)

Equations on this page are rendered with MathJax. Learn more.

n a : i , j = E L λ L exp - 2 k a λ L R β i , j η T η R fO π d 2 hc 4 R 2 xy ,
N sp : i , j 2 = n a : i , j 4 λ L π d θ px 2 ,
n p : i , j = π 2 w px 2 λ L 4 hcf # 2   L λ L ,   T i , j f i , j η R Δ t Δ λ ,
e t : i , j = e a : i , j + e p : i , j + e dark : i , j = Qn a : i , j + Qn p : i , j + i d Δ t q e ,
N AD = N bit V fs HC fs ,
SN eo i , j = e a : i , j exp - 2 k g λ L l i , j N sh , a 2 + 2 N sh , p 2 + N sp 2 i , j + 2 N AD 2 + 2 N r 2 1 / 2 = e a : i , j exp - 2 k g λ L l i , j N eo : i , j ,
k g = C g σ g .
SN eo exp - 2 k g λ L l = 12 .

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