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Tali Treibitz, Yoav Y. Schechner Technion, Israel

Polarization- Beneficial for Visibility Enhancement?. Tali Treibitz, Yoav Y. Schechner Technion, Israel. Visibility in Haze. Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?. L. object. total intensity. object radiance. airlight. I. A. D.

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Tali Treibitz, Yoav Y. Schechner Technion, Israel

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  1. Polarization- Beneficial for Visibility Enhancement? Tali Treibitz, Yoav Y. Schechner Technion, Israel

  2. Visibility in Haze Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  3. L object total intensity object radiance airlight I A D direct transmission scattering 0 z 1 0 z

  4. Visibility in Haze Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  5. best polarized image Haze Through a Polarizer Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  6. best polarized image Haze Through a Polarizer increased exposure time single frame- used by photographers Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  7. best polarized image worst polarized image Haze Through a Polarizer post-processing 2 frames two frames- Schechner et al. Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  8. Is it worth using a polarizer? best polarized image unpolarized image post-processing 2 frames • goal: object detection • local contrast stretch- OK Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  9. 9 Method-Independent Visibility Limits • Noise induces a resolution cutoff, without imaging blur • Independent of post processing detection no detection system input SNR frequency “Recovery Limits in Pointwise Degradations”, Treibitz & Schechner, ICCP ’09

  10. Method-Dependent Performance increase acquisition time? gain SNR? constraint: equal acquisition time related works:

  11. Noise Model photon noise dominates courtesy of Brian Curless Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  12. Degradations in Haze deterministic random reduce SNR even if known SNRhaze=

  13. Using a Single Polarized Image I best Best polarized image degree of polarization

  14. acquisition time = exposure time X number of frames technical details in the paper SNR Comparison   equal acquisition time

  15. a single saturated image SNRpolarized SNRunpolarized maximal value in nature Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  16. same total acquisition time SNRpolarized SNRunpolarized p<0.4 in our experiments maximal value in nature Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  17. Experiment larger FOV - average of 2 images same total acquisition time Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  18. Polarization-Based Dehazing I best Best polarized image degree of polarization

  19. Polarization-Based Dehazing I worst Worst polarized image degree of polarization

  20. technical details in the paper SNR Comparison dehazing  equal acquisition time optimal exposures

  21. “In defense of contrast stretch” Our analysis: higher noise in dehazed image dehazing Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  22. Advantages of Polarization-Based Dehazing recover distance map • contrast stretch in non-uniform distances • color • compensate for attenuation • Goal is object detection • Local contrast stretch on areas with similar distances Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  23. Single Image Dehazing • Tan, CVPR ‘08 • Fattal, SIGGRAPH ‘08 • Kopf et al., SIGGRAPH Asia ’08 • He et al., CVPR ‘09 (tomorrow- best paper session) • our context: • Polarization does not give SNR advantage • Puts these methods in a more favorable position Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

  24. Summary • Case study of method comparison • Performance trade-offs • Unpolarized images are best(equal acquisition time) Treibitz & Schechner, Polarization- Beneficial for Visibility Enhancement?

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