Vision in Bad Weather

1
Vision in Bad Weather
Shree Nayar and Srinivasa Narasimhan Computer
Science Columbia University ICCV
Conference Korfu, Greece, September
1999 Sponsors NSF
2
Vision and Bad Weather
Clear Day
3
Weather Conditions and Particle Sizes
( McCartney, 1975 )
4
Particle Scattering Mechanisms
( Mie 1908 )

• Single Scattering

5
Atmospheric Optics

• Overviews Middleton 1952 , McCartney 1976
  
• Haze Hulburt 1946 , Hidy 1972
• Fog Koshmeider 1924 , George 1951 , Myers
  1968
• Clouds and Rain Laws 1943 , Houghton
  1951 , Mason 1975
• Snow Ohtake 1970
• Vision Koenderink Richards 1992 ,
  Cozman Krotkov 1997

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Attenuation Model
( McCartney, 1975 )
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Direct Transmission
Beam Irradiance at Distance d
(Bouguers Law, 1729)
Attenuation of Diverging Beams
( Allards Law, 1876 )
Optical Thickness
8
Airlight Model
( Koschmieder, 1924 )
Object
dV
Observer
dw
dx
x
d
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Airlight
Image Irradiance due to Volume dV
Image Irradiance due a Path of Length d
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Light Sources in Night Fog
No Environmental Illumination
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Depth of Sources from Two Night Images
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Depth of Sources from Attenuation
Clear Day
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Structure from Airlight Using a Single Image
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Structure from Airlight
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Illumination Occlusion Problem
Observer
Scene Point
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Dichromatic Atmospheric Scattering Model
Image Irradiance and Wavelength
17
Dichromatic Atmospheric Scattering Model
B
E
G
R
18
True Color from Two Images
Clear Day Image
Defogged and Enhanced Windows
Foggy Day Image
19
Chromatic Decomposition Using Two Images
Clear Day Image
Foggy Day Image
20
Summary

• No Escape from Bad Weather

• Image Processing will Not Suffice

• Bad Weather can be Good for Vision