| 摘要 |
PURPOSE:To make it possible to ensure the detection of defects at the inner surface of a cylindrical work in a short time by comparing the luminance of each picture element with two threshold values which are set in response to the illumination irregularities. CONSTITUTION:Lighting is applied on the inner surface of a cylindrical work at a low angle. The image of the inner surface is picked up with a two-dimensional camera, and the image is outputted to an image processing device. Since the object to be photographed has the curved surface, illumination irregularities are formed in the obtained image. The luminance value itself at a place without irregularities becomes the curved state. With a curved base line C as a reference, the luminance value at a protruding part 1 on a position line B is increased. The luminance value at a recess part 2 is decreased. Then, the luminance of each picture element is compared with preset two threshold values D and E. A picture element F whose luminance value is larger than one threshold level D having the smaller value is obtained. A picture element E whose luminance value is smaller than smaller threshold value is obtained. The picture elements F and E and the other picture element are binary-coded. The picture element F whose luminance value is larger than one threshold value D whose value is large and the picture element G whose luminance value is smaller than the other smaller threshold value E are detected as the inner defects of the work. |
