NDTnet 1998 Aug, Vol.3 No.8

Abstract

The on-line dimensional control of the structural profiles at the end of the laminating process in a steel-making rolling mill is a very important and difficult task. The standard measures of an H-shaped profile need to be recovered without contact, as the profile has a temperature above 600 °C. A CEC financed Brite-Euram project, OMEGA, uses a new technology called Conoscopic Holography in order to obtain these measures. The overall aspects of the project have already been presented in (1) and (2).

Conoscopic Holography is an incoherent and colinear interferometric technique. It uses a birefringent crystal to separate an object wavefront into ordinary and extraordinary waves and make them interfere to form a Gabor Zone Lens pattern. The absolute distance of the point source is retrieved by counting fringes in the interferogram. The company CDO (Paris-France) owns the exclusive rights of this technique protected by several patents. Placing the appropriate optics before and after the crystal, it's possible to record an hologram of the intersection of an illuminating plane with the object to be measured, where each line of a CCD detector contains the interference figure of one point of this intersection (see figure).

Fig.

A first prototype using twoconoscopic rangefinders has been installed at Aceralia in Gijon (Spain), covering an area of 600 x 300 mm. Novel calibration procedures are presented in this paper, together with the first plant results.

The precision obtained in a very first prototype is about ±0.4 mm. The achievable precision is estimated below ±0.1 mm with further improvements in the system.

1. E. Laso, E Obeso, Y. Malet, C. Nerriec, V. Patera, I Alvarez. "OMEGA: Novel Optical Sensor 3D MEasuring system for complex Geometry in Adverse environment". In SPIE/IS&T's Symposium on Electronic Imaging, Science & Technology. Practical Holography IXSession. San Diego, CA-USA, 5-10/Feb/1995.

2. E. Laso, F. Obeso, Y. Malet, C. Nerriec, V. Patera, I. Alvarez. "OMEGA: Novel Optical Sensor 3D MEasuring system for complex Geometry in Adverse environment". In Forum on European SteelMaking Developments & Perspectives in Rolling & ReheaCEC/DBXII-C4 "Steel". Luxembourg, 1-2/Feb/1995.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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