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Proceedings Paper

Advanced particular digital signal processing in a real-time laser-speckle-correlation-based strain sensor with optical preprocessing
Author(s): Christian M. Kargel; Bernhard G. Zagar
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Paper Abstract

Some material testing procedures do require the determination of surface element displacements and displacement gradients through non-contacting preferably optical techniques able to operate at relatively high measuring rates. They are essential in particular load-dynamic testing of mechanical properties of so called new materials such as ceramics matrix compounds (CMC) which show creep-effects at their usual operating temperature beyond 1000 degrees Celsius but also testing of thin films down to thicknesses in the range of microns where contacting methods are clearly prohibitive. In this paper we present a displacement sensor system and the signal processing necessary to determine engineering strain within specimen which employs both optical and digital signal processing to form -- in a hybrid way -- a two-dimensional cross-correlation function used to estimate feature displacements on speckled images drawn from surface inspection. It is further shown, that optimal Lloyd-Max quantizers implemented in the analog- to-digital converter (ADC) used in combination with a particular digital correlation algorithm are able to yield a further increase of the measuring rates compared with standard digital correlation techniques.

Paper Details

Date Published: 9 September 1999
PDF: 9 pages
Proc. SPIE 3823, Laser Metrology and Inspection, (9 September 1999); doi: 10.1117/12.360971
Show Author Affiliations
Christian M. Kargel, Technische Univ. Graz (Austria)
Bernhard G. Zagar, Technische Univ. Graz (Austria)

Published in SPIE Proceedings Vol. 3823:
Laser Metrology and Inspection
Hans J. Tiziani; Pramod Kumar Rastogi, Editor(s)

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