SURFACE DEFECT DETECTING METHOD, SURFACE DEFECT DETECTING DEVICE, METHOD FOR MANUFACTURING STEEL MATERIAL, STEEL MATERIAL QUALITY CONTROL METHOD, STEEL MATERIAL MANUFACTURING EQUIPMENT, METHOD FOR CREATING SURFACE DEFECT DETERMINATION MODEL, AND SURFACE DEFECT DETERMINATION MODEL

摘要

A surface-defect detecting method according to the present invention is a surface-defect detecting method of optically detecting a surface defect of a steel material and includes an irradiation step of irradiating a same examination target part with illumination light beams from different directions by using two or more distinguishable light sources; and a detection step of detecting a surface defect in the examination target part based on the degree of overlapping of bright portions extracted from two or more images formed by reflected light beams of the illumination light beams.