On Controlling Light Transport in Poor Visibility Environments Improving Image Contrast using Polarization + Light Stripe Scanning Mohit Gupta Srinivasa G. Narasimhan Yoav Y. Schechner Polarized flood lighting Unpolarize d light striping Polarized light striping Strong scattering Increasing image contrast Where to Place the Camera and the Source for the Best Image Quality? Small camera- source separation Large camera- source separation OR ? High contrast High noise Low contrast Low noise Optimal separation The optimal separation for flood- lighting z S e 1 1 Image contrast SNR ) 1 ( p B S S Large separation High noise Image quality versus separation Flood lighting Polarized light striping Comparison No post-processing Increasing image contrast How to Illuminate the Scene in Poor Visibility Environments? Light Transport in Scattering Media 1. Flood Lighting Floodlit (Low contrast) Object 2. High-frequency Illumination [Nayar et al] Global (Low contrast) Direct (High noise) 3. Confocal Imaging [Levoy et al] Synthetic aperture Scanning Coded aperture 4. Light Stripe Scanning [Narasimhan et al] Light striping input Less backscatter Increased contrast Signal S(x,y) Backscat ter ) , ( ) , ( ) , ( ) , ( y x B y x A y x D y x E Treibitz et al, CVPR06 edsphotoblog.com Backscat ter degrades visibili ty Unpolarized vs. Polarized Light Striping The optimal light stripe scan Image from the optimal scan Delineation of light- plane stripe ) 1 ( ) 1 ( p B A D p B D Image quality versus separation Rotating Transla ting Combinati on Unpolarized light stripe Polarized light stripe Difference Removed backscatter