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Proceedings Paper

Development of twin-illumination and subtraction technique for detection of concave and convex defects on steel surfaces
Author(s): Hiroaki Ono; Akihiro Ogawa; Takahiro Yamasaki; Takahiro Koshihara; Toshifumi Kodama; Yukinori Iizuka; Takahiko Oshige
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Paper Abstract

Optical surface inspection of steel mill products such as pipes, plates and slabs usually has the problem of overdetection, which is caused by signals from harmless parts such as scale and surface texture. The authors propose a new inspection technique based on the experience that most harmful defects on these products have a concave or convex shape, whereas most harmless parts that might be overdetected have flat shapes. The proposed technique is called the ‘twin-illumination and subtraction technique’. In this technique, firstly, two images of the target area on a steel surface illuminated from the two sides are captured, respectively. A subtraction image is then calculated from these images. Comparing the images illuminated from the different sides, the images from concave or convex defects look different due to their different shadows, while images from harmless flat parts look the same because illumination does not cause any shadow. As a result, two images with the same appearances from a harmless part are canceled by subtraction, and two images with different appearances from a concave or convex defect remain even after subtraction. Finally, it is possible to detect only concave or convex defects without overdetecting flat patterns. In this manuscript, first, we explain the proposed technique and confirmation experiments in the laboratory. We also explain a new optical inspection system based on the concept described above and its application to moving hot pipes in a steel manufacturing plant to prove the effectiveness of the technique. We concluded that the inspection system has sufficient performance for use as a practical system.

Paper Details

Date Published: 26 September 2016
PDF: 9 pages
Proc. SPIE 9961, Reflection, Scattering, and Diffraction from Surfaces V, 99610I (26 September 2016); doi: 10.1117/12.2236437
Show Author Affiliations
Hiroaki Ono, JFE Steel Corp. (Japan)
Akihiro Ogawa, JFE Steel Corp. (Japan)
Takahiro Yamasaki, JFE Steel Corp. (Japan)
Takahiro Koshihara, JFE Steel Corp. (Japan)
Toshifumi Kodama, JFE Steel Corp. (Japan)
Yukinori Iizuka, JFE Steel Corp. (Japan)
Takahiko Oshige, JFE Steel Corp. (Japan)

Published in SPIE Proceedings Vol. 9961:
Reflection, Scattering, and Diffraction from Surfaces V
Leonard M. Hanssen, Editor(s)

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