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Vision in Bad Weather

Vision in Bad Weather . Shree Nayar and Srinivasa Narasimhan Computer Science Columbia University ICCV Conference Korfu, Greece, September 1999 Sponsors: NSF. Dense Fog. Rain. Noon Haze. Vision and Bad Weather. Clear Day.

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Vision in Bad Weather

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  1. Vision in Bad Weather Shree Nayar and Srinivasa Narasimhan Computer Science Columbia University ICCV Conference Korfu, Greece, September 1999 Sponsors: NSF

  2. Dense Fog Rain Noon Haze Vision and Bad Weather Clear Day

  3. CONDITION PARTICLE TYPE RADIUS (m) CONCENTRATION (cm ) -3 Molecule Aerosol Water Droplet Water Droplet Water Drop AIR HAZE FOG CLOUD RAIN Weather Conditions and Particle Sizes ( McCartney, 1975 )

  4. Incident Beam Size: 0.01 Size: 0.1 Size: 1 • Multiple Scattering : First Order Third Order Incident Beam Second Order 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

  6. Scattering Medium Attenuated Exiting Beam X = d Collimated Incident Beam Unit Cross Section dx X = 0 Total Flux Scattered by Lamina (dx) : Total Scattering Coefficient Attenuation Model ( McCartney, 1975 )

  7. Direct Transmission Beam Irradiance at Distance d : (Bouguer’s Law, 1729) Attenuation of Diverging Beams : ( Allard’s Law, 1876 ) Optical Thickness :

  8. Sunlight Diffuse Skylight Diffuse Ground Light Radiant Intensity of Volume (dV) : Airlight Model ( Koschmieder, 1924 ) Object dV Observer dw dx x d

  9. Horizon Radiance Airlight Image Irradiance due to Volume dV : Image Irradiance due a Path of Length d :

  10. Street Lamp Window Camera Attenuation Model : Image Irradiance for Camera Response s() : Light Sources in Night Fog No Environmental Illumination

  11. , ( Unknown ) Two Weather Conditions : Ratio of Image Irradiances : Difference in Optical Thickness (DOT) : Relative Depths from Two Sources (i, j): Depth of Sources from Two Night Images

  12. Computed Source Locations Clear Night Foggy Night Depth of Sources from Attenuation Clear Day

  13. Weather Condition : ( Dense Haze or Fog) Airlight Model for Camera Response s() : Image Irradiance Relative to the Horizon : Optical Thickness : Structure from Airlight Using a Single Image

  14. Mountain Range Urban Scene Foggy Day Image Foggy Day Image Computed Depth Map Computed Depth Map 3D Structure Stereo ? Motion ? 3D Structure Structure from Airlight

  15. Illumination Occlusion Problem Observer Scene Point

  16. Airlight Direct Transmission Surface Radiance Horizon Radiance Rayleigh’s Law : For Fog : ( Middleton 1952 ) Dichromatic Atmospheric Scattering Model Image Irradiance and Wavelength :

  17. Finite-Dimensional Color Space : E dt (surface + volume) E a (volume) Final Model : 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. Recovered True Color Computed Depth Map 3D Structure 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

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