| 摘要 |
PROBLEM TO BE SOLVED: To suppress hunting in exposure control even in such a situation that a dark part and a bright part repeatedly appear on a road surface. SOLUTION: When a road surface brightness equivalent value B<SB>IMG</SB>(weighted average brightness V<SB>IMG</SB>) is different from the brightness equivalent value B<SB>TGT</SB>of a target pixel value M<SB>TH</SB>, a target exposure control amount for bringing the road surface brightness equivalent value B<SB>IMG</SB>close to the brightness equivalent value B<SB>TGT</SB>of the target pixel value M<SB>TH</SB>is calculated. Further, it is judged whether the variation C of the target exposure control amount exceeds an increase threshold value T<SB>HI</SB>or a reduction threshold value T<SB>LO</SB>on the basis of the present exposure control amount. When the variation C is beyond the threshold values, the variation C of the target exposure control amount is restricted to the threshold value. Then, even in such the situation that a sunny place and the shade repeatedly appear on the road surface, the degree of hunting is suppressed. COPYRIGHT: (C)2005,JPO&NCIPI
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