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Proceedings Paper

New structured light measurement and calibration method for 3D documenting of engineering structures
Author(s): Robert Sitnik; Małgorzata Kujawińska; Paweł M. Błaszczyk
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Paper Abstract

In the paper a new approach for two step calibration process allowing 3D measurement in large volumes is presented. The maximum assumed volume is equal to 20m x 15m x 6m and the developed system is portable and easy to operate by one person. To set-up a traditional 3D structured light system a long enough base distance between projector and detector is required to ensure sufficient measurement sensitivity. In this setup to achieve measurement uncertainty in the range of 20mm the minimum 10m base distance is required. For this base distance it is nearly impossible to set-up a rigid frame for fixing projector-detector configuration and allow to anyone for easy manipulation of such system. Taking into consideration the above mentioned requirements a new calibration method has been proposed. Its main assumption is that there is no requirement for fixing projector and detector during a calibration phase. The relation between projector and detector is established just before measurement where they are finally positioned to capture 3D shape of investigated surface. It works in two steps: the first one is based on independent calibration of projector and detector devices to establish relation between their the pixel (i, j) co-ordinates and lines in free space; the second one is based on a set of measurements of a known calibration model and their analysis allowing calculation of a relative transformation between detector and projector co-ordinate spaces. The first step is always done in laboratory and the second one is performed just after any change in a relative position between projector and detector. In the paper the initial assessment of measurement uncertainty is discussed in relation to the calibration model versus a measurement volume size. Also some exemplary measurements of real engineering structures will be presented and functionality of the system are discussed.

Paper Details

Date Published: 26 May 2011
PDF: 11 pages
Proc. SPIE 8082, Optical Measurement Systems for Industrial Inspection VII, 808218 (26 May 2011); doi: 10.1117/12.889403
Show Author Affiliations
Robert Sitnik, Warsaw Univ. of Technology (Poland)
Małgorzata Kujawińska, Warsaw Univ. of Technology (Poland)
Paweł M. Błaszczyk, Warsaw Univ. of Technology (Poland)

Published in SPIE Proceedings Vol. 8082:
Optical Measurement Systems for Industrial Inspection VII
Peter H. Lehmann; Wolfgang Osten; Kay Gastinger, Editor(s)

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