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Accurate characterisation of hole size and location by projected fringe profilometry

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journal contribution
posted on 19.03.2018, 16:59 by Yuxiang Wu, Harshana Dantanarayana, Huimin Yue, Jonathan Huntley
The ability to accurately estimate the location and geometry of holes is often required in the field of quality control and automated assembly. Projected fringe profilometry is a potentially attractive technique on account of being non-contacting, of lower cost, and orders of magnitude faster than the traditional coordinate measuring machine (CMM). However, we demonstrate in this paper that fringe projection is susceptible to significant (hundreds of µm) measurement artefacts in the neighbourhood of hole edges, which give rise to errors of a similar magnitude in the estimated hole geometry. A mechanism for the phenomenon is identified based on the finite size of the imaging system’s point spread function and the resulting bias produced near to sample discontinuities in geometry and reflectivity. A mathematical model is proposed, from which a post-processing compensation algorithm is developed to suppress such errors around the holes. The algorithm includes a robust and accurate sub-pixel edge detection method based on a Fourier descriptor of the hole contour. The proposed algorithm was found to reduce significantly the measurement artefacts near the hole edges. As a result, the errors in estimated hole radius were reduced by up to one order of magnitude, to a few tens of µm for hole radii in the range 2-15 mm, compared to those from the uncompensated measurements.

Funding

The authors acknowledge financial support from the Engineering and Physical Sciences Research Council under the Light Controlled Factory project EP/K018124/1. This work was also supported by National Nature Science Foundation of China (Grant No. 61421002), and the Fundamental Research Funds for the Central Universities.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

Measurement Science and Technology

Volume

29

Issue

6

Citation

WU, Y. ... et al, 2018. Accurate characterisation of hole size and location by projected fringe profilometry. Measurement Science and Technology, 29(6): 065010.

Publisher

© IOP Publishing

Version

AM (Accepted Manuscript)

Acceptance date

14/03/2018

Publication date

2018-05-03

Notes

This is an author-created, un-copyedited version of an article published in Measurement Science and Technology. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-6501/aab67e.

ISSN

0957-0233

eISSN

1361-6501

Language

en

Article number

065010