Metal sheet thickness profile measurement method based on two-side line triangulation and continuous vibration compensation

Petri Lehtonen, Jari Miettinen, Heimo Keränen, Tapio Vaarala

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

2 Citations (Scopus)

Abstract

Dimension measurements in metal production are getting increasingly important to improve quality and yield. One important measurement is thickness profile, in this case of copper strip. Knowing the strip profile in entrance and exit side of milling line helps optimizing the milling depth and give information about tool wearing. In this study a comparative measurement method was traversing point measurement system. It gives profile as a series of points which take a relatively long time to measure. Now presented method is based on two-side optical triangulation formed by line illuminators and CMOS-cameras and enables instantaneous thickness profile measurement. Results from both sides are fixed together using reference plates on both ends of the measurement area. From 1.3 m stand-off distance, 1.4 m wide measurement area is achieved. This paper presents the measurement method and results of laboratory and on-line tests. Using laser line illumination the accuracy of thickness was 150 µm when measuring 9 mm thick test plate. Accuracy was limited by laser speckle during static calibration. Other illumination method based on white light was therefore tested and the accuracy was 12 µm correspondingly. Measurement time for one profile was 1 second and resolution in cross machine direction 50 mm after averaging. Now presented method enables thickness profile measurement of copper and other metal sheets. Using white light the accuracy is at same level as the present traversing point measurement. Method has also continuous reference measurement to compensate errors caused by vibration; therefore the system can be realized at reasonable cost. (9 refs.)
Original languageEnglish
Title of host publicationProceedings of the SPIE
Subtitle of host publicationOptical Sensors 2008
EditorsFrancis Berghmans
PublisherInternational Society for Optics and Photonics SPIE
ISBN (Print)978-0-8194-7201-4
DOIs
Publication statusPublished - 2008
MoE publication typeA4 Article in a conference publication
EventPhotonics Europe 2008 - Strasbourg, France
Duration: 7 Apr 200810 Apr 2008

Publication series

SeriesProceedings of SPIE
Volume7003
ISSN0277-786X

Conference

ConferencePhotonics Europe 2008
CountryFrance
CityStrasbourg
Period7/04/0810/04/08

Keywords

  • thickness measurement
  • optical triangulation
  • laser speckle
  • thickness profile
  • metal sheet measurement

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    Lehtonen, P., Miettinen, J., Keränen, H., & Vaarala, T. (2008). Metal sheet thickness profile measurement method based on two-side line triangulation and continuous vibration compensation. In F. Berghmans (Ed.), Proceedings of the SPIE : Optical Sensors 2008 [70030P] International Society for Optics and Photonics SPIE. Proceedings of SPIE, Vol.. 7003 https://doi.org/10.1117/12.780800