SURFACE DEFECT DETECTING METHOD AND DEVICE FOR COATED BAR

摘要

PROBLEM TO BE SOLVED: To provide a coated bar surface defect detecting method and device obtained by incorporating a coated bar surface defect detecting optical technique for detecting the surface defect precisely and automatically by an image and an optical system to perform the technique. SOLUTION: The surface defect detecting method and device is constituted so that whether it is defect or not is discriminated by using an optical system constituted of a belt like light source 1 used for both dark field lighting and bright field lighting and a light receiving element 3 for detecting the defect in the dark field and bright field and comparing the taken image with a prescribed value.