| 摘要 |
PURPOSE:To determine visibility accurately when an actual object is viewed, by calculating the visibility of the object from the difference between the brightness of the object and that of its background and from a brightness difference threshold. CONSTITUTION:A brightness distribution measuring section 1 measures a brightness distribution object-wise in a field of view containing an object and outputs a signal corresponding to brightness to a brightness difference calculating section 3, which calculates the difference between the brightness of objects and that of its background adjoining thereon. A brightness difference threshold calculating section 6 receives outputs from an equivalent photoscreen brightness measuring section 4 and a center cavity adaptive brightness measuring section 5 to calculate a brightness difference threshold when objects are observed. A visibility calculating section 7 calculates visibility of individual objects from a signal inputted from the brightness difference calculating section 3 and a signal inputted from the brightness difference threshold calculating section 6. Thus, a signal is outputted to a visibility distribution chart display section 8 according to the visibility of the objects.
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