8 March 2002 Detection of surface defects on raw milled steel blocks using range imaging
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This paper shows an efficient and reliable method for the detection of surface defects with a three dimensional characteristic whereby the surface reflection properties are altering strongly. Due to this fact traditional intensity imaging techniques yield inferior performance. Therefore, light sectioning in conjunction with fast imaging sensors is applied to gather the range image of the steel block. Two different approaches for defect detection are treated, whereby the first algorithm is based on a line-wise examination of the acquired profiles by unwrapping the surface using spline interpolation. The noise in the unwrapped orthogonal distance may be reduced by applying statistical measures. The second method refers to surface segments and is based on the mean square error between the segment and its approximation gained from singular value decomposition. Due to vibrations the acquired profiles are arbitrary located within a range of a few millimeters which requires a geometric transformation to reconstruct the three dimensional surface of the steel block.
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Franz Pernkopf, Friedrich Pernkopf, Paul O'Leary, "Detection of surface defects on raw milled steel blocks using range imaging", Proc. SPIE 4664, Machine Vision Applications in Industrial Inspection X, (8 March 2002); doi: 10.1117/12.460195; https://doi.org/10.1117/12.460195

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