| 摘要 |
<p>PURPOSE: To obtain a detecting method of a foreign substance on the surface of metal which enables reliable detection of the presence or absence of the foreign substance in a groove of a metal object, at edge parts of the metal object demarcating the groove thereof and on the surface of the metal object. CONSTITUTION: An illuminating light is cast obliquely on a metal object OB so that edge parts 1O of the metal object OB demarcating a groove 50 of the metal object OB be made brighter than the surface of the metal object OB and the inner bottom surface of the groove thereof, and the brightness of the edge parts of the metal object OB demarcating the groove 50, the brightness of a foreign substance, the brightness of the surface of the metal object and that of the inner bottom surface of the groove thereof are compared with one another. Thereby the presence or absence of the foreign substance in the groove 50 of the metal object OB, at the edge parts 70 of the metal object OB demarcating the groove 50 thereof and on the surface of the metal object OB is detected.</p> |
