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Sensors 2014, 14(8), 14916-14931; doi:10.3390/s140814916

Design of a Device for Sky Light Polarization Measurements

* ,
College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, Hunan, China
* Author to whom correspondence should be addressed.
Received: 10 June 2014 / Revised: 20 July 2014 / Accepted: 6 August 2014 / Published: 14 August 2014
(This article belongs to the Section Physical Sensors)
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ky polarization patterns can be used both as indicators of atmospheric turbidity and as a sun compass for navigation. The objective of this study is to improve the precision of sky light polarization measurements by optimal design of the device used. The central part of the system is composed of a Charge Coupled Device (CCD) camera; a fish-eye lens and a linear polarizer. Algorithms for estimating parameters of the polarized light based on three images are derived and the optimal alignments of the polarizer are analyzed. The least-squares estimation is introduced for sky light polarization pattern measurement. The polarization patterns of sky light are obtained using the designed system and they follow almost the same patterns of the single-scattering Rayleigh model. Deviations of polarization angles between observation and the theory are analyzed. The largest deviations occur near the sun and anti-sun directions. Ninety percent of the deviations are less than 5° and 40% percent of them are less than 1°. The deviations decrease evidently as the degree of polarization increases. It also shows that the polarization pattern of the cloudy sky is almost identical as in the blue sky.
Keywords: sky light polarization; least-squares estimation; optimal design; Rayleigh scattering; camera calibration; sun compass sky light polarization; least-squares estimation; optimal design; Rayleigh scattering; camera calibration; sun compass
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Wang, Y.; Hu, X.; Lian, J.; Zhang, L.; Xian, Z.; Ma, T. Design of a Device for Sky Light Polarization Measurements. Sensors 2014, 14, 14916-14931.

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