Abstract

A solid-state video camera is used as the focal plane detector in an underwater spectrometer system to acquire multiple spectra simultaneously within the water column. Signal-to-noise enhancement of the spectra is accomplished by use of a combination of frame averaging and dark field mapping so that the dynamic range of the individual frame can be increased from ∼7 bits to >13.5 bits. This method also removes the need for shuttering to determine the dark background or device cooling to reduce the dark current noise. The dark mapping algorithm is shown to be valid over a range of device temperatures so that the detector can vary freely with the ambient water temperature without loss in mapping accuracy. Despite observation times that can be up to an order of magnitude greater than cooled devices, the use of frame averaging and dark mapping eliminates the need for additional detector cooldown time and can provide a smaller, simpler, more power efficient, and robust design.

© 2003 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  16. K. D. Moore, K. J. Voss, H. R. Gordon, “Spectral reflectance of whitecaps: instrumentation, calibration, and performance in coastal waters,” J. Atmos. Oceanic Technol. 15, 496–509 (1998).
    [CrossRef]
  17. E. O’Mongain, Spectral Signatures Ltd, Roebuck, Belfield, Dublin 4, Ireland (personal communication, 2003).
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    [CrossRef]
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2000 (1)

1999 (1)

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

1998 (2)

O. H. Y. Zalloum, “Design of a modern optical fibre spectral transmissometer and a 120 degrees scattering meter,” J. Opt. 29, 53–62 (1998).
[CrossRef]

K. D. Moore, K. J. Voss, H. R. Gordon, “Spectral reflectance of whitecaps: instrumentation, calibration, and performance in coastal waters,” J. Atmos. Oceanic Technol. 15, 496–509 (1998).
[CrossRef]

1997 (2)

1992 (1)

M. O’Malley, E. O’Mongain, “Charge-coupled devices: frame adding as an alternative to long integration times and cooling,” Opt. Eng. 31, 522–526 (1992).
[CrossRef]

1987 (1)

1978 (1)

R. C. Smith, K. S. Baker, “The bio-optical state of ocean waters and remote sensing,” Limnol. Oceanogr. 23, 247–259 (1978).
[CrossRef]

1970 (1)

R. W. Holmes, “The Secchi disk in turbid coastal waters,” Limnol. Oceanogr. 15, 688–694 (1970).
[CrossRef]

1939 (1)

A. Gershun, “The light field,” J. Math. Phys. 18, 51–151 (1939).

Aas, E.

Austin, R. W.

J. L. Mueller, R. W. Austin, “Ocean optics protocols for SeaWiFS validation,” in SeaWiFS Project Technical Report Series, , Vol. 5, S. B. Hooker, E. R. Firestone, eds. (NASA Goddard Space Flight Center, Greenbelt, Md., 1992).

Baker, K. S.

R. C. Smith, K. S. Baker, “The bio-optical state of ocean waters and remote sensing,” Limnol. Oceanogr. 23, 247–259 (1978).
[CrossRef]

Beynon, J. D. E.

J. D. E. Beynon, D. R. Lamb, Charge Coupled Devices and Their Applications (McGraw-Hill, London, 1980).

Booth, R. C.

D. A. Neuschuler, R. C. Booth, J. H. Morrow, “Innovative applications of optical fibers in the measurement of in situ spectra,” in Ocean Optics XI, G. D. Gilbert, ed., Proc. SPIE1750, 338–353 (1992).

Bree, M.

E. O’Mongain, D. Buckton, S. Green, M. Bree, K. Moore, R. Doerrfer, S. Danaher, H. Hakvoort, J. Kennedy, J. Fischer, F. Fell, D. Papantoniou, M. McGarrigle, “Spectral absorption coefficient measured in situ in the North Sea with a marine radiometric spectrometer system,” Appl. Opt. 36, 5162–5167 (1997).
[CrossRef] [PubMed]

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

Buckton, D.

Bulmer, M. G.

M. G. Bulmer, Principles of Statistics (Dover, New York, 1979).

Chapin, A.

Danaher, S.

Doerffer, R.

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

Doerrfer, R.

Fell, F.

Fischer, J.

Gershun, A.

A. Gershun, “The light field,” J. Math. Phys. 18, 51–151 (1939).

Gordon, H. R.

K. D. Moore, K. J. Voss, H. R. Gordon, “Spectral reflectance of whitecaps: instrumentation, calibration, and performance in coastal waters,” J. Atmos. Oceanic Technol. 15, 496–509 (1998).
[CrossRef]

Green, S.

Hakvoort, H.

Holmes, R. W.

R. W. Holmes, “The Secchi disk in turbid coastal waters,” Limnol. Oceanogr. 15, 688–694 (1970).
[CrossRef]

Hu, C.

Janesick, J. R.

J. R. Janesick, Scientific Charged-Coupled Devices, Vol. PM 83 of SPIE Press Monograph Series (SPIE Press, Bellingham, Wash., 2000).

Kennedy, J.

Lamb, D. R.

J. D. E. Beynon, D. R. Lamb, Charge Coupled Devices and Their Applications (McGraw-Hill, London, 1980).

McGarrigle, M.

Monti, M.

Moore, K.

Moore, K. D.

K. D. Moore, K. J. Voss, H. R. Gordon, “Spectral reflectance of whitecaps: instrumentation, calibration, and performance in coastal waters,” J. Atmos. Oceanic Technol. 15, 496–509 (1998).
[CrossRef]

K. D. Moore, “In situ spectral radiometer for the characterization of the optical properties of marine waters,” Ph.D. dissertation (National University of Ireland, Dublin, Ireland, 1993).

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

Morrow, J. H.

D. A. Neuschuler, R. C. Booth, J. H. Morrow, “Innovative applications of optical fibers in the measurement of in situ spectra,” in Ocean Optics XI, G. D. Gilbert, ed., Proc. SPIE1750, 338–353 (1992).

Mueller, J. L.

J. L. Mueller, R. W. Austin, “Ocean optics protocols for SeaWiFS validation,” in SeaWiFS Project Technical Report Series, , Vol. 5, S. B. Hooker, E. R. Firestone, eds. (NASA Goddard Space Flight Center, Greenbelt, Md., 1992).

Neuschuler, D. A.

D. A. Neuschuler, R. C. Booth, J. H. Morrow, “Innovative applications of optical fibers in the measurement of in situ spectra,” in Ocean Optics XI, G. D. Gilbert, ed., Proc. SPIE1750, 338–353 (1992).

O’Malley, M.

M. O’Malley, E. O’Mongain, “Charge-coupled devices: frame adding as an alternative to long integration times and cooling,” Opt. Eng. 31, 522–526 (1992).
[CrossRef]

O’Mongain, E.

E. O’Mongain, D. Buckton, S. Green, M. Bree, K. Moore, R. Doerrfer, S. Danaher, H. Hakvoort, J. Kennedy, J. Fischer, F. Fell, D. Papantoniou, M. McGarrigle, “Spectral absorption coefficient measured in situ in the North Sea with a marine radiometric spectrometer system,” Appl. Opt. 36, 5162–5167 (1997).
[CrossRef] [PubMed]

M. O’Malley, E. O’Mongain, “Charge-coupled devices: frame adding as an alternative to long integration times and cooling,” Opt. Eng. 31, 522–526 (1992).
[CrossRef]

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

E. O’Mongain, Spectral Signatures Ltd, Roebuck, Belfield, Dublin 4, Ireland (personal communication, 2003).

Papantoniou, D.

Plunkett, S.

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

Robinson, I. S.

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

Schwarz, J. N.

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

Smith, R. C.

R. C. Smith, K. S. Baker, “The bio-optical state of ocean waters and remote sensing,” Limnol. Oceanogr. 23, 247–259 (1978).
[CrossRef]

Trundle, K. T.

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

Voss, K. J.

Weeks, A. R.

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

Zalloum, O. H. Y.

O. H. Y. Zalloum, “Design of a modern optical fibre spectral transmissometer and a 120 degrees scattering meter,” J. Opt. 29, 53–62 (1998).
[CrossRef]

Zhang, H.

Appl. Opt. (4)

J. Atmos. Oceanic Technol. (1)

K. D. Moore, K. J. Voss, H. R. Gordon, “Spectral reflectance of whitecaps: instrumentation, calibration, and performance in coastal waters,” J. Atmos. Oceanic Technol. 15, 496–509 (1998).
[CrossRef]

J. Math. Phys. (1)

A. Gershun, “The light field,” J. Math. Phys. 18, 51–151 (1939).

J. Opt. (1)

O. H. Y. Zalloum, “Design of a modern optical fibre spectral transmissometer and a 120 degrees scattering meter,” J. Opt. 29, 53–62 (1998).
[CrossRef]

Limnol. Oceanogr. (2)

R. W. Holmes, “The Secchi disk in turbid coastal waters,” Limnol. Oceanogr. 15, 688–694 (1970).
[CrossRef]

R. C. Smith, K. S. Baker, “The bio-optical state of ocean waters and remote sensing,” Limnol. Oceanogr. 23, 247–259 (1978).
[CrossRef]

Meas. Sci. Technol. (1)

A. R. Weeks, I. S. Robinson, J. N. Schwarz, K. T. Trundle, “The Southampton underwater multiparameter optical-fibre spectrometer system (SUMOSS),” Meas. Sci. Technol. 10, 1168–1177 (1999).
[CrossRef]

Opt. Eng. (1)

M. O’Malley, E. O’Mongain, “Charge-coupled devices: frame adding as an alternative to long integration times and cooling,” Opt. Eng. 31, 522–526 (1992).
[CrossRef]

Other (8)

D. A. Neuschuler, R. C. Booth, J. H. Morrow, “Innovative applications of optical fibers in the measurement of in situ spectra,” in Ocean Optics XI, G. D. Gilbert, ed., Proc. SPIE1750, 338–353 (1992).

J. D. E. Beynon, D. R. Lamb, Charge Coupled Devices and Their Applications (McGraw-Hill, London, 1980).

K. D. Moore, “In situ spectral radiometer for the characterization of the optical properties of marine waters,” Ph.D. dissertation (National University of Ireland, Dublin, Ireland, 1993).

K. D. Moore, E. O’Mongain, S. Plunkett, R. Doerffer, M. Bree, “In situ marine spectral radiometer using frame addition techniques and its calibration,” in Underwater Light Measurements, H. Eilertsen, ed., Proc. SPIE2048, 153–165 (1993).

E. O’Mongain, Spectral Signatures Ltd, Roebuck, Belfield, Dublin 4, Ireland (personal communication, 2003).

J. R. Janesick, Scientific Charged-Coupled Devices, Vol. PM 83 of SPIE Press Monograph Series (SPIE Press, Bellingham, Wash., 2000).

J. L. Mueller, R. W. Austin, “Ocean optics protocols for SeaWiFS validation,” in SeaWiFS Project Technical Report Series, , Vol. 5, S. B. Hooker, E. R. Firestone, eds. (NASA Goddard Space Flight Center, Greenbelt, Md., 1992).

M. G. Bulmer, Principles of Statistics (Dover, New York, 1979).

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Figures (9)

Fig. 1
Fig. 1

MARAS collector configuration.

Fig. 2
Fig. 2

Signal and dark window locations on the detector. Note that signal windows 9 and 10 share the same dark window.

Fig. 3
Fig. 3

Digitization noise plotted as a function of the rms input noise for different averaging quantities (number of samples shown at right).

Fig. 4
Fig. 4

Correlation between the analog input and the digital output as a function of the input rms noise expressed in terms of 1 - r.

Fig. 5
Fig. 5

Dark window values plotted against the signal windows for each channel taken under dark conditions as the temperature varied. The linear regression is calculated for the same spectral pixel in each channel. The values at lower left correspond to ∼9 and ∼22 °C at upper right.

Fig. 6
Fig. 6

(a) Mean slope coefficient (ai) and (b) the mean intercept coefficient (bi) calculated for each channel. The error bars denote the standard deviation on the mean.

Fig. 7
Fig. 7

Example of binning, frame averaging, and dark mapping applied to a low intensity signal. The signal and dark values are taken at the single frame level from a row of pixels running across their respective windows. The background-corrected spectrum is shown for 256 frame averaging and 16 pixel binning. The dark row values are offset by 2 DN for display.

Fig. 8
Fig. 8

Frame averaged and background-subtracted collector spectra taken at four depths, i.e., 2, 5, 8, and 12 m. That is, (a) vector downwelling upper [Ed(z1)], (b) vector downwelling lower [Ed(z2)], (c) scalar downwelling [Eod(z1)], (d) scalar upwelling [Eou(z1)], (e) vector upwelling upper [Eu(z1)], (f) vector upwelling lower [Eu(z2)], (g) the radiance collector [Lu(z2)].

Fig. 9
Fig. 9

Downwelling diffuse attenuation coefficient at two depths, i.e., 2 and 5 m. Spectral values greater than ∼720 nm have been truncated because of high absorption properties of the water and low signal strengths at these wavelengths. Features for the 5-m depth in the far blue are due to poor detector sensitivity and low signal strengths. The spectra have been smoothed with a 5-nm bandpass filter.

Equations (19)

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

Ddi=n=1nb=1b=16pdi, b, nbn,
Si+Dsi=n=1nb=1b=16psi, b, nbn,
Si=GSi+Dsi+O,
Ddi=GDdi+O.
GDsi+O=aiDdi+bi
ŜiGSiSi-GDsi+O,
ŜiSi-aiGDdi+O+bi,
Si=G+Si+Dsi+O+,
Ddi=G+Ddi+O+.
G+Dsi+O+=aiDdi+bik+O+1-ai+Okai-1,
ŜiG+SiSi-aiDdi+bik+O+1-ai+Okai-1.
DiT=DiTo+ΔDiT-To,
Dsi+ΔDsi=aiDdi+ΔDdi+bi.
Kdλ=1z2-z1lnEdz1, λEdz2, λ,
Sg=s+gσ.
Sg=fDSg,
Sg=j=1kfDs+gσjk.
Sg=j=1ks+gσjk.
QNg= Sg-Sg25121/2.

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