NDTnet 1998 Aug, Vol.3 No.8

Abstract

Holographic interferometry
Optical methods are widely used in the non-destructive study of cultural heritage, for identification and during restoration. During the last decade coherent-optical methods have also been applied in museum practice. Two main directions are now recognized as very useful and promising. The first is display holography, which allows three-dimensional (3D) optical copies of unique museum objects to be made and the second is interferometry, which in fact visualises the difference in optical path between the wavefronts diffracted by an object before and after a change. It is a non-contacting, full-field technique that is very sensitive, as displacements of about 0,25 µm can be visualised.One of the cases studied is the deformation of a precolumbian statuette due to a heat change of about 2°C. (see Figure)

Fig.: Crack in terracotta statuette visualised by holographic interferometry.



Conclusion
Holographic interferometry and its electronic variant are very promising techniques for the nondestructive evaluation of defects and stress analysis in works of art made of various materials including oil paintings on canvas or wood, terracotta and metallic objects. Advantages of this system are that it is a relatively rapid, sensitive, full-field method that requires only a very small amount of loading (normally less than the usual variations in the environment, even under museum conditions). Quantitative measurements can also be made, so that the evolution of important deterioration can be followed as a function of time.

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:

Publication Contact:
7th ECNDT, Park Alle 345, DK-2605 Broendby, Denmark, Fax: +45 46 26 70 11, Email: 101373.3414@compuserve.com