JPS643547A - Surface defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To enable exact, objective and automatic inspection by projecting prescribed bright and dark patterns on a surface to be inspected by means of a linear light source and plural bar-shaped lenses, picking up the image of said surface and detecting the defect of the surface in accordance with the various intensity level signals of light. CONSTITUTION:S tripe pattern projecting device 1 projects the stripe patterns of prescribed pitches on the surface of the object OB to be inspected via the bar-shaped lens 12 and slits 13a from the linear light source 11. The images thereof are picked up by a television camera 21. A synchronizing signal SS is separated by a distributor 31 and an offset voltage component is removed therefrom by an HPF 32 to lower an intermediate lightness part bad and the boundary between the bright part and dark part to nearly a zero level. The signal is then inputted together with the floating threshold signal SL past an LPF 34 to a comparator 35 via an absolute value circuit 33 and is binarized. This signal is passed through a decision circuit 37 by which the dark part of the stripe patterns is erased and only the bad is displayed; in addition, an NG signal is outputted as a defect part when the area of the bad is above the prescribed value in a defect part extracting circuit 52. The inspection is thereby exactly and automatically executed.