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
Unpolarized light striping
Polarized light striping
Stro
ng sc
atter
ing
Increasing image contrast
Where to Place the Camera and the Source for the Best Image Quality?Small camera-source
separationLarge 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( pBSS
Large separationHigh noise
Image quality versus separation
Flood lighting Polarized light striping ComparisonNo post-processing
Increasing image contrast
How to Illuminate the Scene in Poor Visibility Environments?Light Transport in Scattering Media1. 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 inputLess backscatter Increased contrastSignal S(x,y) Backscatter
),(),(),(),( yxByxAyxDyxE
Treibitz et al, CVPR06 edsphotoblog.com
Backscatter degrades visibility
Unpolarized vs. Polarized Light Striping
The optimal light stripe scan
Image from the optimal scan
Delineation of light-plane stripe
)1()1(pBAD
pBD
Image quality versus separation
Rotating Translating Combination
Unpolarized light stripe
Polarized light stripe
Difference Removed backscatter
