PURPOSE: To enhance luminance of emitted light while preventing lowering of CCD output by setting the distance between the view of a two-dimensional image input unit and an illuminator while matching with the emission pattern of the illuminator.
CONSTITUTION: In the view of an area type CCD camera 7 in a two-dimensional image input unit, the ratio of distances from the opposite ends of a surface to be inspected and the emission end 11 of an illuminator is set equal to or close to the ratio of intensities of light projected from the illuminator to the opposite ends of the surface to be inspected. When light is projected from the illuminator through an optical fiber light guide 4 onto an inspection surface 1 from the side thereof, a point on the inspection surface 1 remote from (close to) the emission end 11 of the illuminator is irradiated with light having high (low) intensity but the light arriving at the inspection surface 1 has intensity which is lower (higher) as the point is remote (close). Such illumination light provides a shade caused by a defect on the inspection surface 1 clearly regardless of the distance. Image of the inspection surface 1 is picked up by means of the camera 7 and a shade contained in the image signal is detected as a defect by an image processor 8.
FUSE MASAKI
KAGAMI MANABU
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