GRACE contribution at OPTIMESS 2012!

Antwerp (Belgium) 4th – 5th April 2012

An innovative measurement technique developed within the WP 3 activities has been presented and accepted for presentation at OPTIMESS 2012, the 5th International Conference on Optical Measurement Techniques for Structures and Systems 2012.

OPTIMESS 2012 focuses on optical measurement techniques and their applications in research, testing and production. The conference is a forum for researchers developing or working with optical measurement techniques such as interferometry, vibrometry, profilometry, etc. in application fields such as dimensional metrology, structural mechanics, materials testing, biomedical applications.

Title of Contribution
Vision system based on a conic mirror for dimensional measurements inside near-cylindrical cavities
L. Stroppa | A. Bastari | N. Paone

Abstract
This paper presents an omnidirectional vision system to perform dimensional measurements for quality control applications on the internal surfaces of cylindrical objects; the system is based on a standard camera and a catadioptric optics with a conic mirror mounted in axis with the lens.
Such a vision system performs a geometric transformation that maps a cylindrical surface, whose axis coincides with the camera objective optical axis, into a circular annulus in the image plane domain. From the image analysis, through calibration, it is possible to perform dimensional measurements in real world units.
In this paper results of system calibration are shown and discussed.
Two approaches are presented. In the first approach system uncertainty is assessed according to ISO-Guideline to the Expression of Uncertainty in measurement, using a grid pattern calibration target and it is proven that the system can be effectively used as a measurement instrument in the field of quality control inspections. In the second approach a brief overview of the possibility of implementing an auto-calibration algorithm is given if a known pattern can be found on the image and only measurements on the axial direction are needed.
This system has been integrated in an automatic test bench for in-line quality control of axial dimensions and the achieved results show that the vision system with conic mirror and auto-calibration algorithm can be effectively applied to dimensional measurements, being faster than alternative techniques, such as scanning profilometry for full field measurements.

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