Abstract

Night vision systems in vehicles are a new emerging technology. A crucial problem in active (laser-based) systems is distortion of images by saturation and blooming due to strong retroreflections from road signs. We quantify this phenomenon. We measure the Mueller matrices and the polarization state of the reflected light from three different types of road sign commonly used. Measurements of the reflected intensity are also taken with respect to the angle of reflection. We find that different types of sign have different reflection properties. It is concluded that the optimal solution for attenuating the retroreflected intensity is using a linear polarized light source and a linear polarizer with perpendicular orientation (with regard to the source) at the detector. Unfortunately, while this solution performs well for two types of road sign, it is less efficient for the third sign type.

© 2008 Optical Society of America

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References

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  1. L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.
  2. N. S. Martinelli and S. A. Boulanger, “Cadillac DeVille thermal imaging night vision system,” SAE Technical Paper Series 2000-01-0323 (2000).
  3. J. E. Kallhammer, “The road ahead for car night-vision,” Nat. Photon. , 12-13 (2006).
    [CrossRef]
  4. O. David, N. S. Kopeika, and B. Weizer, “Range gated active night vision system for automobiles,” Appl. Opt. 45, 7248-7254 (2006).
    [CrossRef] [PubMed]
  5. M. Holz and E. Weidel, “Night vision enhancement system using diode laser headlights,” SAE Technical Paper Series #982778 (1997).
  6. 3M United States, “Permanent Signing Solutions,” http://solutions.3m.com/wps/portal/3M/en_US/Traffic_Safety/TSS/Offerings/Products/Permanent_Signing/, last accessed 7 October 2008.
  7. D. Goldstein, Polarized Light, 2nd ed. (Marcel Dekker, 2003).
    [CrossRef]
  8. E. Collett, Polarized Light In Fiber Optics, (The PolaWave Group, 2003).
  9. R. A. Chipman, “Polarimetry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, 1995), Vol. 2, Chap. 22.

2006 (2)

2003 (2)

D. Goldstein, Polarized Light, 2nd ed. (Marcel Dekker, 2003).
[CrossRef]

E. Collett, Polarized Light In Fiber Optics, (The PolaWave Group, 2003).

2000 (1)

N. S. Martinelli and S. A. Boulanger, “Cadillac DeVille thermal imaging night vision system,” SAE Technical Paper Series 2000-01-0323 (2000).

1997 (1)

M. Holz and E. Weidel, “Night vision enhancement system using diode laser headlights,” SAE Technical Paper Series #982778 (1997).

1995 (2)

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

R. A. Chipman, “Polarimetry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, 1995), Vol. 2, Chap. 22.

Boulanger, S. A.

N. S. Martinelli and S. A. Boulanger, “Cadillac DeVille thermal imaging night vision system,” SAE Technical Paper Series 2000-01-0323 (2000).

Browning, N.

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

Chipman, R. A.

R. A. Chipman, “Polarimetry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, 1995), Vol. 2, Chap. 22.

Collett, E.

E. Collett, Polarized Light In Fiber Optics, (The PolaWave Group, 2003).

David, O.

Goldstein, D.

D. Goldstein, Polarized Light, 2nd ed. (Marcel Dekker, 2003).
[CrossRef]

Holz, M.

M. Holz and E. Weidel, “Night vision enhancement system using diode laser headlights,” SAE Technical Paper Series #982778 (1997).

Kallhammer, J. E.

J. E. Kallhammer, “The road ahead for car night-vision,” Nat. Photon. , 12-13 (2006).
[CrossRef]

Kopeika, N. S.

Madigan, E. F.

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

Mangold, S. J.

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

Martinelli, N. S.

N. S. Martinelli and S. A. Boulanger, “Cadillac DeVille thermal imaging night vision system,” SAE Technical Paper Series 2000-01-0323 (2000).

Pierowicz, J. A.

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

Tijerina, L.

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

Weidel, E.

M. Holz and E. Weidel, “Night vision enhancement system using diode laser headlights,” SAE Technical Paper Series #982778 (1997).

Weizer, B.

Appl. Opt. (1)

Nat. Photon. (1)

J. E. Kallhammer, “The road ahead for car night-vision,” Nat. Photon. , 12-13 (2006).
[CrossRef]

Other (7)

L. Tijerina, N. Browning, S. J. Mangold, E. F. Madigan, and J. A. Pierowicz, “Examination of reduced visibility crashes and potential IVHS countermeasures,” DOT HS 808 210, U.S. Department of Transportation, 1995.

N. S. Martinelli and S. A. Boulanger, “Cadillac DeVille thermal imaging night vision system,” SAE Technical Paper Series 2000-01-0323 (2000).

M. Holz and E. Weidel, “Night vision enhancement system using diode laser headlights,” SAE Technical Paper Series #982778 (1997).

3M United States, “Permanent Signing Solutions,” http://solutions.3m.com/wps/portal/3M/en_US/Traffic_Safety/TSS/Offerings/Products/Permanent_Signing/, last accessed 7 October 2008.

D. Goldstein, Polarized Light, 2nd ed. (Marcel Dekker, 2003).
[CrossRef]

E. Collett, Polarized Light In Fiber Optics, (The PolaWave Group, 2003).

R. A. Chipman, “Polarimetry,” in Handbook of Optics, M. Bass, ed. (McGraw-Hill, 1995), Vol. 2, Chap. 22.

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Figures (4)

Fig. 1
Fig. 1

Three sign types are: (a) the Diamond Grade Reflective Sheeting (DGRS), (b) the High-Intensity Grade Reflective Sheeting (HIGS), and (c) the Engineer Grade Reflective Sheeting (EGRS).

Fig. 2
Fig. 2

Experimental setups: (a) measurement of the Mueller matrices of the road signs. An unpolarizerd He–Ne laser light passes through the Stokes generator (the rotating QWP and LP) toward the road sign. The reflected light passes through two lenses (L1) and (L2), and the analyzer (a circular polarizer), and the final intensity is measured at the detector. The four Stokes parameters are measured at four different orientations of the circular polarizer. This measurement is repeated for all six polarization states generated by the Stokes generator. (b) Measurement of the intensity of the retroreflected light from the road signs as a function of the reflection angle. A He–Ne LHP laser is retroreflected from the road sign. The reflected light passes through a lens and a removable linear polarizer (LHP or LVP) before it reaches a detector.

Fig. 3
Fig. 3

Left column: the measured reflected light intensity as a function of the angle with an LHP or LVP polarizer and without a polarizer, for (a) the EGRS, (c) the HIGS, and (e) the DGRS signs. Right column: the transmission of the linear polarizer for the light reflected from (b) the EGRS , (d) the HIGS, and (f) the DGRS signs, as a function of the reflection angle. It can be seen that, for the EGRS and the HIGS signs, the intensity of the reflected light that passes through an LVP polarizer is almost entirely attenuated, while for the DGRS sign it is not reduced significantly.

Fig. 4
Fig. 4

(a) Image captured by an active night vision system without a crossed polarizer. The road signs are HIGS and DGRS located from right to left, respectively, at a distance of about 80 m . It can be seen that both signs are saturated and introduce very strong blooming into the image, which makes them appear to be only one sign. (b) The same scene but with a crossed polarizer in the receiver. Here the HIGS sign appears saturated but nearly without blooming around it. The DGRS sign appears saturated with blooming around it, though the blooming is smaller than that seen in (a).

Equations (6)

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S = [ S 0 , S 1 , S 2 , S 3 ] T .
I LHP = M [ 1100 ] T , I LVP = M [ 1 100 ] T , I L + 45 ° = M [ 1010 ] T , I L 45 ° = M [ 10 10 ] T , I RCP = M [ 1001 ] T , I LCP = M [ 100 1 ] T ,
M HIGS M EGRS ( 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 ) .
M DGRS ( 1 0 0 0 0.034 0.628 0.049 0.014 0.032 0.008 0.013 0.427 0.031 0.053 0.414 0.029 ) .
M DGRS ( 1 0 0 0 0.044 0.348 0.017 0.049 0.007 0.031 0.092 0.294 0.031 0.007 0.328 0.027 ) ,
M DGRS ( 1 0 0 0 0.023 0.023 0 0 0 0 0.01 0.028 0.023 0.023 0 0.028 ) .

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