DETECTION FOR SURFACE DEFECT OF HOT METALLIC MATERIAL

摘要

PURPOSE:To improve the detection precision of surface defects by reducing effectively bad influences of an iron oxide generated on the surface of hot metallic materials. CONSTITUTION:A light projector 1 consisting of a superhigh pressure mercury- arc lamp is provided with an infrared cut filter so that it can irradiate the light having a wavelength which does not interfere in the natural light radiated from a part 2a to be detected of hot metallic materials 2. A photographic camera 3 for reflected light and a photographic camera 5 for spontaneous light receive a reflected light 4 from the part 2a to be detected and a radiated natural light 6 and convert them photoelectrically. Photoelectrically converted electric signals of cameras 3 and 5 are sent to binarizing circuits 8 and 9 of a signal processing circuit 7 and are binarized with a preliminarily set threshold to obtain defect signals. AND between both defect signals is operated by a circuit 12, and defects are discriminated on a basis of the result, thereby suppressing bad influences of noise to reduce generation of erroneous detection.