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Proceedings Paper

On-machine characterization of moving paper using a photo-emf laser ultrasonics method
Author(s): Bruno F. Pouet; Emmanuel F. Lafond; Brian Pufahl; Gerald David Bacher; Pierre H. Brodeur; Marvin B. Klein
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Paper Abstract

Stiffness properties of paper materials can readily be characterized in the laboratory using conventional ultrasonic techniques. For on-line inspection on a paper machine, due to the high translation velocity and the somewhat fragile nature of the moving paper web, contact ultrasonic techniques using piezoelectric transducers are of limited use. To overcome this limitation, non-contact laser- based ultrasonic techniques can be used. Due to the rough surface of the paper, the reflected light is composed of many speckles. For efficient detection, the receiver must be able to process as many speckles as possible. Adaptive receivers using the photorefractive or photo-emf effects are characterized by a large etendue, and thus, are well suited for detection on paper and paperboard. Moreover, the translation velocity of the moving web implies that the detection system must adapt extremely quickly to the changing speckle pattern. In this work, a photo-emf receiver was used to detect Lamb waves excited using a pulsed Nd:YAG laser in moving paper. Experiments were performed using a variable-speed web simulator at speeds much higher than 1 m.s-1. Results corresponding to various translation speeds are shown, demonstrating the feasibility of laser- based ultrasound for on-machine inspection of paper and paperboard during production.

Paper Details

Date Published: 4 February 1999
PDF: 10 pages
Proc. SPIE 3589, Process Control and Sensors for Manufacturing II, (4 February 1999); doi: 10.1117/12.339961
Show Author Affiliations
Bruno F. Pouet, Lasson Technologies, Inc. (United States)
Emmanuel F. Lafond, Institute of Paper Science and Technology (United States)
Brian Pufahl, Institute of Paper Science and Technology (United States)
Gerald David Bacher, Lasson Technologies, Inc. (United States)
Pierre H. Brodeur, Institute of Paper Science and Technology (United States)
Marvin B. Klein, Lasson Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 3589:
Process Control and Sensors for Manufacturing II
David M. Pepper, Editor(s)

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