SURFACE FLAW INSPECTION METHOD AND SURFACE FLAW INSPECTION DEVICE FOR STEEL PLATE

摘要

To provide a surface flaw inspection method and a surface flaw inspection device for steel plate capable of minimizing loss from right after the start of surface inspection even when a steel plate which does not have its surface processed by plating etc., is targeted as an object of inspection.SOLUTION: A surface flaw inspection method for steel plate according to the present invention includes irradiating an imaging-object region on a surface of a steel plate (12) with illumination light. Reflected light from the imaging object region is imaged. An image signal obtained by the imaging is binarized based upon a predetermined threshold, and a flaw of the steel plate (12) is determined from the binarized data based upon a predetermined rule. At this time, the image signal is brought under feedback control with respect to at least one of an amplification width thereof and the emission quantity of the illumination light so that a signal level thereof is put in a predetermined gradation region. Then initial values of the amplification width and the emission quantity of light are individually set based upon a manufacture history of the inspection object steel plate (12).SELECTED DRAWING: Figure 2