Yoav Y. Schechner: Research

Instant Dehazing

We present an approach for easily removing the effects of haze from passively acquired images. Our approach is based on the fact that usually the natural illuminating light scattered by atmospheric particles (airlight, path-radiance) is partially polarized. Optical filtering alone cannot remove the haze effects, except in restricted situations. Our method, however, stems from physics-based analysis that works under a wide range of atmospheric and viewing conditions, even if the polarization is low.

The approach does not rely on specific scattering models such as Rayleigh scattering and does not rely on the knowledge of illumination directions. It can be used with as few as two images taken through a polarizer at different orientations. As a byproduct, the method yields a range map of the scene, which enables scene rendering as if imaged from different viewpoints. It also yields information about the atmospheric particles. We present experimental results of complete dehazing of outdoor scenes, in far-from-ideal conditions for polarization filtering. We obtain a great improvement of scene contrast and correction of color.

Furthermore, in our more recent paper (Blind Haze Separation), we derive a method for blindly recovering the parameter needed for separating the airlight from the measurements, thus recovering contrast, with neither user interaction nor existence of the sky in the frame. In another recent paper, we have derived a distance-dependent regularization method. It denoises the background scene, while avoiding blur of the clear foreground objects.

Publications

1. Yoav Y. Schechner, Srinivas G. Narasimhan, and Shree K. Nayar, “Polarization-based vision through haze,” Applied Optics 42, No. 3, pp. 511-525 (2003), Special issue about Light and Color in the Open Air.
2. Yoav Y. Schechner and Yuval Averbuch, “Regularized image recovery in scattering media,” to be published in IEEE Trans. Pattern Analysis & Machine Intelligence (2007).
3. Yoav Y. Schechner, Srinivas G. Narasimhan and Shree K. Nayar, “Instant dehazing of images using polarization,” Proc. IEEE CVPR, Vol. I, pp. 325-332 (2001).
4. Sarit Shwartz, Einav Namer and Yoav Y. Schechner, “Blind haze separation,” Proc. IEEE CVPR, Vol. 2, pp. 1984-1991 (2006).
5. Einav Namer and Yoav Y. Schechner, “Advanced visibility improvement based on polarization filtered images,” Proc. SPIE 5888: Polarization Science and Remote Sensing II, pp. 36-45 (2005).