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Applied Optics

Applied Optics


  • Editor: Joseph N. Mait
  • Vol. 48, Iss. 6 — Feb. 20, 2009
  • pp: 1091–1097

All-sky imaging: a simple, versatile system for atmospheric research

Axel Kreuter, Matthias Zangerl, Michael Schwarzmann, and Mario Blumthaler  »View Author Affiliations

Applied Optics, Vol. 48, Issue 6, pp. 1091-1097 (2009)

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A simple and inexpensive fully automated all-sky imaging system based on a commercial digital camera with a fish-eye lens and a rotating polarizer is presented. The system is characterized and two examples of applications in atmospheric physics are given: polarization maps and cloud detection. All-sky polarization maps are obtained by acquiring images at different polarizer angles and computing Stokes vectors. The polarization in the principal plane, a vertical cut through the sky containing the Sun, is compared to measurements of a well-characterized spectroradiometer with polarized radiance optics to validate the method. The images are further used for automated cloud detection using a simple color- ratio algorithm. The resulting cloud cover is validated against synoptic cloud observations. A Sun coverage parameter is introduced that shows, in combination with the total cloud cover, useful correlation with UV irradiance.

© 2009 Optical Society of America

OCIS Codes
(100.2960) Image processing : Image analysis
(120.5410) Instrumentation, measurement, and metrology : Polarimetry
(010.1615) Atmospheric and oceanic optics : Clouds
(110.5405) Imaging systems : Polarimetric imaging

ToC Category:
Imaging Systems

Original Manuscript: November 17, 2008
Revised Manuscript: January 16, 2009
Manuscript Accepted: January 17, 2009
Published: February 13, 2009

Axel Kreuter, Matthias Zangerl, Michael Schwarzmann, and Mario Blumthaler, "All-sky imaging: a simple, versatile system for atmospheric research," Appl. Opt. 48, 1091-1097 (2009)

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