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