NDTnet 1998 Aug, Vol.3 No.8

Abstract

In engineering problems, a fast visual technique for measuring the displacement, deformation, rotation or tilt of different kinds of structures is often required.
We present two simple methods for determining composite movements of a rough surface, made up of displacements and a rotation. Both methods are a digital and an analogical-digital version, and have proved more powerful than the photographical techniques developed in previous works made by our team, which are based on the null displacement ring of the speckle explained in previous papers (1, 2, 3, 4). Furthermore, other techniques available at present (speckle photographic methods, ESPI, etc.) are probably a little more complicated than our methods.

In one of them, a CCD camera is used for recording the two speckle patterns projected on a screen, obtained before and after the movement of the surface. Then, the parameters of the movement are calculated from the null displacement ring using digital image processing.
The second one makes use of a filter obtained as the photographic record of the speckle pattern before the movement. The developed plate is the exactly repositions at its place, lying between the diffusing rough surface and a screen. A CCD camera is focused on the screen to gather information on the movement of the surface, as the initial blacked out image coming trough the speckle filter, begins to get illuminated when the surfaces moves.
We compare the experimental results of both methods with the values obtained with a goniometer and translation stages.

1. Hogert, EN., and. Gaggioli NG, J. Optics (Paris). 1986,17: 203-207.
2. Hogert, EX, Lunazzi, JJ., Gaggioli, NG., Appl. Optics. 1989, 28: 722-725.
3. Landau, MR., Hogert, EX, Rebollo, MA., Gaggioli, NG., J. Mod. Optics. 1992, 39: 2161-2168.
4. Landau, MR., Hogert, EX, Rebollo, MA., Gaggioli, NG., J. Mod Optics. 1994, 41: 2229-2232

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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