| 摘要 |
PURPOSE:To automatically adjust the light quantity of an illuminating device so that the distribution of a luminance histogram is a proper state by inputting an image with high contrast following the change of an objective image. CONSTITUTION:An object illuminated by the illuminating device 1b is image- picked up by a camera 15 and a luminance histogram indicating the number of picture elements for luminance is formed from the image data. A difference l1 (=a-L) between the minimum level L of the image luminance and a minimum luminance level (a) including the picture element and a difference l2 (=H-b) between the maximum level H of the image luminance and the maximum luminance level (b) including the picture element are found out respectively and the light quantity of the illuminating device 1b is automatically adjusted so that the difference between l1 and l2 is reduced. The luminance histogram can be moved to the center of the L and H and optimum illuminating light quantity can be obtained by controlling the illuminating light so that the difference between l1 and l2 is reduced, preferably l1=l2 is formed.
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