METHOD AND APPARATUS FOR VISUAL INSPECTION

A visual inspection apparatus includes an image-data acquisition unit for acquiring plural pieces of image data A to C on an inspection target, image comparison units for comparing the image data A to C with each other thereby to create plural pieces of sign-affixed difference-image data D and E, the image data A to C being acquired by the image-data acquisition unit, difference-image comparison units for determining the difference between the sign-affixed difference-image data D and E created by the image comparison units, and a judgment unit for subjecting, to a threshold-value processing, difference data F between the difference-image data D and E, the difference data F being acquired by the difference-image comparison units, obtaining a detection sensitivity by enlarging the difference between an abnormal signal level of an image of an area where an abnormality exists from the visual inspection.