Abstract

Short-wave infrared (SWIR) imaging sensors are increasingly being used in surveillance and reconnaissance systems due to the reduced scatter in haze and the spectral response of materials over this wavelength range. Typically SWIR images have been provided either as full motion video from framing panchromatic systems or as spectral data cubes from line-scanning hyperspectral or multispectral systems. Here, we describe and characterize a system that bridges this divide, providing nine-band spectral images at 30 Hz. The system integrates a custom array of filters onto a commercial SWIR InGaAs array. We measure the filter placement and spectral response. We demonstrate a simple simulation technique to facilitate optimization of band selection for future sensors.

© 2014 Optical Society of America

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References

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  1. M. P. Hansen and D. S. Malchow, “Overview of SWIR detectors, cameras, and applications,” Proc. SPIE 6939, 69390I (2008).
    [CrossRef]
  2. A. A. Richards, “Emerging applications for high-performance near-infrared imagers,” Proc. SPIE 4710, 450–455 (2002).
    [CrossRef]
  3. R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
    [CrossRef]
  4. T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
    [CrossRef]
  5. T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
    [CrossRef]
  6. S. Maimon and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Appl. Phys. Lett. 89, 151109 (2006).
    [CrossRef]
  7. C. O. Davis, J. Bowles, R. A. Leathers, D. Korwan, T. V. Downes, W. A. Snyder, W. J. Rhea, W. Chen, J. Fisher, W. P. Bissett, and R. A. Reisse, “Ocean PHILLS hyperspectral imager: design, characterization, and calibration,” Opt. Express 10, 210–221 (2002).
    [CrossRef]
  8. W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).
  9. B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
    [CrossRef]
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    [CrossRef]
  13. X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
    [CrossRef]
  14. J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
    [CrossRef]
  15. H. Du and K. J. Voss, “Effects of point-spread function on calibration and radiometric accuracy of CCD camera,” Appl. Opt. 43, 665–670 (2004).
    [CrossRef]
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  17. A. V. Kanaev and C. W. Miller, “Multi-frame super-resolution algorithm for complex motion patterns,” Opt. Express 21, 19850–19866 (2013).
    [CrossRef]

2013 (2)

R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
[CrossRef]

A. V. Kanaev and C. W. Miller, “Multi-frame super-resolution algorithm for complex motion patterns,” Opt. Express 21, 19850–19866 (2013).
[CrossRef]

2009 (2)

J. M. Eichenholz and J. Dougherty, “Ultracompact fully integrated megapixel multispectral imager,” Proc. SPIE 7218, 721814 (2009).
[CrossRef]

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

2008 (2)

T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
[CrossRef]

M. P. Hansen and D. S. Malchow, “Overview of SWIR detectors, cameras, and applications,” Proc. SPIE 6939, 69390I (2008).
[CrossRef]

2006 (2)

S. Maimon and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Appl. Phys. Lett. 89, 151109 (2006).
[CrossRef]

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

2005 (1)

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

2004 (1)

2003 (1)

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

2002 (2)

1997 (1)

Baillard, X.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Bakker, T.

T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
[CrossRef]

Battaglia, J.

T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
[CrossRef]

Bissett, W. P.

Bize, S.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Bowles, J.

Bray, J. D.

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

Brubaker, R.

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

Catanzaro, B.

M. Dombrowski and B. Catanzaro, “Spatially corrected full-cubed hyperspectral imager,” U.S. patent7,242,478 (10July2007).

Chen, W.

Clairon, A.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Davis, C. O.

Dereniak, E. L.

Descour, M. R.

Dixon, P.

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

Dombrowski, M.

M. Dombrowski and B. Catanzaro, “Spatially corrected full-cubed hyperspectral imager,” U.S. patent7,242,478 (10July2007).

Dougherty, J.

J. M. Eichenholz and J. Dougherty, “Ultracompact fully integrated megapixel multispectral imager,” Proc. SPIE 7218, 721814 (2009).
[CrossRef]

Downes, T. V.

Driggers, R. G.

R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
[CrossRef]

Du, H.

Eichenholz, J. M.

J. M. Eichenholz and J. Dougherty, “Ultracompact fully integrated megapixel multispectral imager,” Proc. SPIE 7218, 721814 (2009).
[CrossRef]

Eng, B. T.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Fisher, J.

Gaab, K. M.

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

Gagliardi, M.

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

Gauguet, A.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Gu, J.

J. Gu, P. J. Wolfe, and K. Hirakawa, “Filterbank-based universal demosaicking,” in Proceedings of IEEE International Conference on Image Processing, 1981, Hong Kong (2010).

Gunapala, S. D.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Hansen, M. P.

M. P. Hansen and D. S. Malchow, “Overview of SWIR detectors, cameras, and applications,” Proc. SPIE 6939, 69390I (2008).
[CrossRef]

Hirakawa, K.

J. Gu, P. J. Wolfe, and K. Hirakawa, “Filterbank-based universal demosaicking,” in Proceedings of IEEE International Conference on Image Processing, 1981, Hong Kong (2010).

Hodgkin, V.

R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
[CrossRef]

Hook, S. J.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Johnson, W. R.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Kanaev, A. V.

Kendalla, W. B.

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

Korwan, D.

Lambert, B. M.

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

Lamborn, A.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Laurent, P.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Leathers, R. A.

Lemonde, P.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Lomheim, T. S.

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

Maimon, S.

S. Maimon and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Appl. Phys. Lett. 89, 151109 (2006).
[CrossRef]

Malchow, D. S.

M. P. Hansen and D. S. Malchow, “Overview of SWIR detectors, cameras, and applications,” Proc. SPIE 6939, 69390I (2008).
[CrossRef]

Martin, T.

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

Miller, C. W.

Mouroulis, P.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Mumolo, J. M.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Olchowski, F. M.

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

Paine, C.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Realmuto, V.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Reisse, R. A.

Rhea, W. J.

Richards, A. A.

A. A. Richards, “Emerging applications for high-performance near-infrared imagers,” Proc. SPIE 4710, 450–455 (2002).
[CrossRef]

Rosenbusch, P.

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Snyder, W. A.

Stellmanb, C. M.

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

Stevenson, B. P.

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

Sudol, T.

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

Thome, K. J.

Turner, D.

T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
[CrossRef]

Volin, C. E.

Vollmerhausen, R.

R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
[CrossRef]

Voss, K. J.

Wicks, G. W.

S. Maimon and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Appl. Phys. Lett. 89, 151109 (2006).
[CrossRef]

Wilson, D. W.

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

Wolfe, P. J.

J. Gu, P. J. Wolfe, and K. Hirakawa, “Filterbank-based universal demosaicking,” in Proceedings of IEEE International Conference on Image Processing, 1981, Hong Kong (2010).

Appl. Opt. (1)

Appl. Phys. Lett. (1)

S. Maimon and G. W. Wicks, “nBn detector, an infrared detector with reduced dark current and higher operating temperature,” Appl. Phys. Lett. 89, 151109 (2006).
[CrossRef]

Opt. Commun. (1)

X. Baillard, A. Gauguet, S. Bize, P. Lemonde, P. Laurent, A. Clairon, and P. Rosenbusch, “Interference-filter-stabilized external-cavity diode lasers,” Opt. Commun. 266, 609–613 (2006).
[CrossRef]

Opt. Express (2)

Opt. Lett. (1)

Proc. SPIE (8)

M. P. Hansen and D. S. Malchow, “Overview of SWIR detectors, cameras, and applications,” Proc. SPIE 6939, 69390I (2008).
[CrossRef]

A. A. Richards, “Emerging applications for high-performance near-infrared imagers,” Proc. SPIE 4710, 450–455 (2002).
[CrossRef]

R. G. Driggers, V. Hodgkin, and R. Vollmerhausen, “What good is SWIR? Passive day comparison of VIS, NIR, and SWIR,” Proc. SPIE 8706, 87060L (2013).
[CrossRef]

T. Bakker, D. Turner, and J. Battaglia, “Development of a miniature InGaAs camera for wide operating temperature range using a temperature-parameterized uniformity correction,” Proc. SPIE 6940, 69400K (2008).
[CrossRef]

T. Martin, R. Brubaker, P. Dixon, M. Gagliardi, and T. Sudol, “640 × 512 InGaAs focal plane array camera for visible and SWIR imaging,” Proc. SPIE 5783, 12–20 (2005).
[CrossRef]

J. D. Bray, K. M. Gaab, B. M. Lambert, and T. S. Lomheim, “Improvements to spectral spot-scanning technique for accurate and efficient data acquisition,” Proc. SPIE 7405, 74050L (2009).
[CrossRef]

B. P. Stevenson, W. B. Kendalla, C. M. Stellmanb, and F. M. Olchowski, “PHIRST light: a liquid crystal tunable filter hyperspectral sensor,” Proc. SPIE 5093, 104–113 (2003).
[CrossRef]

J. M. Eichenholz and J. Dougherty, “Ultracompact fully integrated megapixel multispectral imager,” Proc. SPIE 7218, 721814 (2009).
[CrossRef]

Other (3)

J. Gu, P. J. Wolfe, and K. Hirakawa, “Filterbank-based universal demosaicking,” in Proceedings of IEEE International Conference on Image Processing, 1981, Hong Kong (2010).

M. Dombrowski and B. Catanzaro, “Spatially corrected full-cubed hyperspectral imager,” U.S. patent7,242,478 (10July2007).

W. R. Johnson, S. J. Hook, P. Mouroulis, D. W. Wilson, S. D. Gunapala, V. Realmuto, A. Lamborn, C. Paine, J. M. Mumolo, and B. T. Eng, “HyTES: thermal imaging spectrometer development,” in Proceedings of 2011 IEEE Aerospace Conference, 1 (Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2011).

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Figures (9)

Fig. 1.
Fig. 1.

Diagram of the nine-band multispectral video rate sensor. A 640×512 array of circular filters with 13 μm diameter clear apertures is bonded to a COTS 2D staring 640×512 FPA with 25 μm pitch. The filter array is composed of a repeating pattern of 3×3 unit cells arranged in the pattern shown in Table 1.

Fig. 2.
Fig. 2.

Diagram of experimental setup used to measure the sensor’s spectral response. A monochromator is illuminated with white light from a tungsten–halogen bulb. Light from the monochromator’s 1.5 mm wide output slit passes through a long-pass filter with transition wavelength of 950 nm into a 6 in. integrating sphere 5 in. away. The uniform field from the sphere’s 0.75 in. diameter exit port illuminates the sensor from a distance of 2.5 in.

Fig. 3.
Fig. 3.

Mean spectral response of eight components of the multispectral sensor (in color). The bands are arranged to span the three SWIR atmospheric transmission windows between 950 and 1700 nm. The spectrum of ambient solar radiance for a typical mid-latitude day is also shown in gray. The nine-band and solar radiance spectral data have been normalized to unity maximum after correction for dark current, spectrometer efficiency, and sensing array efficiency. Wavelengths for the central wavelength of each spectral component are given in Table 1. Equipment limitations prevented determination of the spectral response for the wavelength region over which band 1 is sensitive. The solar radiance is averaged over a diverse array of targets.

Fig. 4.
Fig. 4.

Diagram of the spot-scan experimental setup used to assess the filter placement. A 20×, NA=0.40 SWIR microscope objective focuses 4 ns pulses (at 160 kHz) from a 1541 nm laser into an 5μm diameter spot on the sensor, which is mounted on a piezo-actuated 3D translation stage. The stage is stepped in an xy grid covering 100μm in 38 equal voltage steps in both the x and y directions. The xy grid scan is repeated at five different z positions to ensure that data are collected at optimum focus. The laser intensity is controlled by adjusting the angle between two linear polarizers prior to the microscope objective.

Fig. 5.
Fig. 5.

Plots for the spatial response of two pixels during a scan of a laser spot over a nine-pixel unit cell. (a) Surface plot of the response of band 8 pixel (25,15) as the array is translated in the xy plane near the 5μm focus of a 1541 nm laser. The scan covers the 3×3 unit cell centered on pixel (25,15), an area of 75×75μm in a 38×38 grid of equal steps in piezo-actuator voltage. Response has been corrected for dark current and interpolated onto a spatially square grid to correct of nonlinearity in the piezo-actuator. (b) Intensity response or top-down view of the pixel response shown in (a), where red is the maximum response and the minimum is blue. (c) Surface plot of the response of band 5 pixel (26,14) as the array is translated in the xy plane near the laser focus. (d) Intensity response or top-down view of the pixel response shown in (b). Since the laser wavelength is within band 8’s passband, the signal is much greater on pixel (25,15) than on the band 5 pixel (26,14).

Fig. 6.
Fig. 6.

(a) Mosaic of intensity response images of all the pixels in a unit cell centered on pixel (25,15) as the array is translated in the xy plane near the focus of a 1541 nm laser. The response for each pixel is normalized so that each pixel’s maximum (red) and minimum (blue) values cover the full color scale. The axes on the bottom and left denote the x and y position of the laser spot on the array, while the top and right axes denote the pixel number. The black boxes on each tile of the mosaic show the pixel’s approximate physical boundaries on the scan point array. The strong on-pixel response for pixels (25,15) and (26,16) is due to greater spectral overlap between the passband of the pixel’s filter and the laser line. Signal outside of the black box on any mosaic tile indicates crosstalk from light incident on the filters of nearby pixels. The lack of significant signal outside of the black boxes indicates well-aligned filter and sensing arrays at this location. (b)–(d) Surface plots of the dark-subtracted response of pixels (b) (24,14), (c) (25,15), and (d) (26,16). The surface plots show the significant difference in scales for the different pixels in (a). The signal on pixel (25,15) is two orders of magnitude larger than the signal on all other pixels except pixel (26,16).

Fig. 7.
Fig. 7.

(a) Mosaic of intensity response images of the pixels in a unit cell centered on pixel (625,498) as the array is translated in the xy plane near the focus of a 1541 nm laser. The response for each pixel is normalized so that each pixel’s maximum (red) and minimum (blue) values cover the full color scale. The axes on the bottom and left denote the x and y positions of the laser spot on the array, while the top and right axes denote the pixel number. The black boxes on each tile of the mosaic show the pixel’s approximate physical boundaries on the scan point array. The strong on-pixel response for pixels (625,498) and (626,499) is due to greater spectral overlap between the passband of the pixel’s filter and the laser line. Signal outside of the black box on any mosaic tile indicates crosstalk from light incident on the filters of nearby pixels. The presence of significant signal outside of the black boxes may indicate misalignment of the filter and sensor arrays at this location. (b)–(d) Surface plot of the dark-subtracted response of pixels (b) (624,497), (c) (625,498), and (d) (626,499). The surface plots show the significant difference in scales for the different pixels in (a). The signal on pixel (625,498) is an order of magnitude larger than the signal on all other pixels except pixel (626,499).

Fig. 8.
Fig. 8.

(a) Mosaiced image of part of target array collected with the nine-band, multispectral sensor. (b) Image of the same region under similar lighting conditions generated by averaging over the spectral dimension of a hyperspectral cube. Boxes A, B, and C are the regions of interest used to generate the sensor responses shown in Fig. 9.

Fig. 9.
Fig. 9.

Comparison of measured multispectral data from the nine-band camera with data simulated from the hyperspectral measurement. The measured nine-band multispectral sensor’s spectra for targets A, B, and C averaged over the regions of interest (ROIs) shown in Fig. 8(a) are marked with circles in (a), (b), and (c), respectively. Simulated nine-band spectra calculated from hyperspectral data averaged over the ROIs shown in Fig. 8(b) are marked with xs. For all points the error bars correspond to the standard deviation in the spectra across the ROI.

Tables (4)

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Table 1. Arrangement of Filters in a 3×3 Unit Cell Pattern Listing Band Number and Central Wavelengtha

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Table 2. Percent of Total Signal on each Pixel when the Laser is Illuminating the Expected Area of Pixel (25,15)a

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Table 3. Percent of Total Signal on Each Pixel when the Laser is Illuminating the Expected Area of Pixel (625,498)a

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Table 4. Percent of Total Signal on each Pixel when the Laser is Illuminating the Expected Area of Pixel (337,144)a

Metrics