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Open AccessArticle

Surface Topography Measurement of Mirror-Finished Surfaces Using Fringe-Patterned Illumination

1
Advanced Remanufacturing and Technology Centre (Agency for Science, Technology and Research), Singapore 637143, Singapore
2
JM Vistec System Pte Ltd., Singapore 415938, Singapore
3
Department of Mechanical Engineering, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
*
Author to whom correspondence should be addressed.
Metals 2020, 10(1), 69; https://doi.org/10.3390/met10010069
Received: 27 November 2019 / Revised: 18 December 2019 / Accepted: 19 December 2019 / Published: 1 January 2020
(This article belongs to the Special Issue Advanced Surface Enhancement)
Mirror-finished surface products have a wide range of applications in different engineering industries, such as power generation, aerospace, semiconductors and optics. The surface topography of mirror-finished products is typically measured in a metrology laboratory, which is typically time consuming and cannot be integrated into the manufacturing process. To allow for in-situ product quality assurance and automatic tool change for manufacturing processes, a more accurate and responsive surface-measurement method is needed. For highly polished surfaces, a sub-micron surface fluctuation makes it possible to use light-scattering effects and image processing for surface texture analysis. A non-contact surface inspection system using a fringe-patterned illumination method is proposed in this paper. A predesigned pattern was projected onto the target surface, and its reflected image was captured by a camera. It was found that the surface parameters Sa and Sq, which are widely used to evaluate surface quality, are significantly correlated with luminous-intensity distribution. Another parameter, Str, which quantifies the uniformity of surface-texture directions due to polishing or grinding marks, was traditionally quantified after a complete-surface topographic measurement. In this research, a new approach is proposed to determine surface isotropy through a luminance-intensity distribution analysis. By rotating the test coupon, the variation of specular reflection showed correlation with the significance of surface-texture direction. The experimental results demonstrate that mirror-finished surfaces with a large deviation in luminance intensity across the pattern possess low Str values, which indicates low uniformity in surface texture. View Full-Text
Keywords: in-situ inspection; luminance contrast; fringe-patterned illumination; surface topography in-situ inspection; luminance contrast; fringe-patterned illumination; surface topography
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MDPI and ACS Style

Fu, S.; Cheng, F.; Tjahjowidodo, T. Surface Topography Measurement of Mirror-Finished Surfaces Using Fringe-Patterned Illumination. Metals 2020, 10, 69.

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