26 September 2016 Development of twin-illumination and subtraction technique for detection of concave and convex defects on steel surfaces
Author Affiliations +
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.
Conference Presentation
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hiroaki Ono, Hiroaki Ono, Akihiro Ogawa, Akihiro Ogawa, Takahiro Yamasaki, Takahiro Yamasaki, Takahiro Koshihara, Takahiro Koshihara, Toshifumi Kodama, Toshifumi Kodama, Yukinori Iizuka, Yukinori Iizuka, Takahiko Oshige, Takahiko Oshige, "Development of twin-illumination and subtraction technique for detection of concave and convex defects on steel surfaces", Proc. SPIE 9961, Reflection, Scattering, and Diffraction from Surfaces V, 99610I (26 September 2016); doi: 10.1117/12.2236437; https://doi.org/10.1117/12.2236437


Stain defect detection for mobile phone camera modules
Proceedings of SPIE (March 06 2014)
Novel methods for inspection of damage on airframes
Proceedings of SPIE (November 05 2018)
Multispectral inspection station detects defects on apples
Proceedings of SPIE (December 28 2000)
Automation Of Surface Defect Detection And Evaluation
Proceedings of SPIE (March 21 1988)
Intelligent Visual Inspection Machines
Proceedings of SPIE (December 18 1985)

Back to Top