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○宮崎大輔(東大,10月から広島市立大) Mahdi Ammar (ESPCI, 4~7月に東大でインターン ) 川上玲(東大) 池内克史(東大). Theory Experimental setup Experimental results Clear sky Overcast sky Camera rotation Conclusion. Motivation. Skylight polarization patterns : Metrology : atmospheric turbidity
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○宮崎大輔(東大,10月から広島市立大) Mahdi Ammar (ESPCI, 4~7月に東大でインターン) 川上玲(東大) 池内克史(東大)
Theory Experimental setup Experimental results Clear sky Overcast sky Camera rotation Conclusion
Motivation Skylight polarization patterns : • Metrology : atmospheric turbidity • Biology : compass (bee, ant, horseshoe crab, water flea) Objective: • Understand • Double-check • Find applications
Rayleigh Scattering: How about the degree of polarization? Maximally polarized light : 90°
Neutral points: Babinet & Arago • Rayleigh’ s theory (single scattering) • 2 unpolarized points: Sun & anti-Sun • Observation (multiple scattering) • Babinet point: above Sun • Brewster point : below Sun • Arago point : above anti-Sun
3 inputs Brightness Angle of polarization Degree of polarization
Experimental results • Clear Sky • Overcast Sky • Camera rotation
Results: Clear sky d(DOP) Maximum at 90
Clear sky :angle of polarization Eight shaped
Results: overcast sky: d(DOP) Low DOP (d~10%)
Overcast sky: angle of polarization • Qualitatively same as clear sky (eight shaped) • Sun direction: foggy, smoky, cloudy days
Rotation of fisheye camera • Rotate 35° around x-axis • 10 measurements around z-axis (15° interval)
Angle of polarization through rotation Non-rotated Rotation (qi =-35 °,jcamera=0°) (qi =-35 °,jcamera=30°) (qi =-35 °,jcamera=60°) (qi =-35 °,jcamera=90°)
Method accuracy We need only 2 equations to solve
Conclusion (1/3): Degree of polarization d • Double-checked experiment • Atmosphere condition: clear, cloudy, overcast sky d
Conclusion (2/3): Angle of polarization a • Double-checked experiment • Robust position of sun: clear, foggy, cloudy, smoky • Compass orientation a
Conclusion (3/3): General configuration • Result: Camera in general orientation • Next step: Normal lens • Next step: Liquid crystal or PLZT camera • Next step: Application d a
All images are compressed. http://www.cvl.iis.u-tokyo.ac.jp/ 宮崎大輔, Mahdi Ammar, 川上玲, 池内克史, "レイリー散乱による天空光の偏光解析および魚眼カメラによる太陽方向推定," 電子情報通信学会パターン認識・メディア理解研究会, Vol.108, No.198, pp.25-32, 慶應義塾大学, 神奈川, 2008.9