Patent ID: 11022553

Abstract:
A surface inspection system (10) for inspecting the surface of sheet elements (4) present in an inspection area (20). The system includes an image evaluation unit (18), a camera (12), a dark-field illuminator (14) and a bright-field illuminator (16). The image evaluation unit (18) subtracts a line image captured under bright-field illumination conditions from a line image captured under dark-field illumination conditions. A method of identifying highly reflective surface areas on a sheet element (4) being moved through a sheet element processing machine, wherein first a line image (I16) of the surface of the sheet element (4) in the viewing area (20) is captured under bright-field illumination conditions and a line image (I14) of the same surface of the sheet element (4) in the viewing area (20) is captured under dark-field illumination conditions, and then the two line images (I14, I16) are compared, in particular subtracted from each other, wherein the surface is identified as being reflective if the difference (Sn) between the two line images (I14, I16) is above a predefined threshold.