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Proceedings Paper

Laser radar and laser photoacoustics in paper pulp measurements
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Paper Abstract

The size distribution and total amount of the particles in paper pulp is vital information for the paper manufacturer in optimising process control and maintaining a high product quality. There is a further need for improving the on-line measurement methods to measure these parameters. It is known that fibre and fines fractions in the pulp have different optical and acoustic properties. In this study, we simultaneously use laser radar and laser generation of acoustic waves to further study optical and acoustic parameters, such as optical time delay, acoustic speed and attenuation. A near infrared pulse laser is used to illuminate the pulp suspensions and the time-of-flight of scattering photons is recorded; and at the same time, a high energy pulsed laser is applied to produce an acoustic wave. The acoustic wave propagates through the pulp suspensions and an acoustic transducer is used to detect the signals from which the attenuation and acoustic speed are determined. The results show that these combined optical techniques can potentially determine the content of fibres and fine particles simultaneously.

Paper Details

Date Published: 29 September 2005
PDF: 8 pages
Proc. SPIE 5953, Acousto-optics and Photoacoustics, 595305 (29 September 2005); doi: 10.1117/12.623537
Show Author Affiliations
Matti Törmänen, Meri Lappi Institute, Univ. of Oulu (Finland)
Univ.of Oulu (Finland)
Zuomin Zhao, Univ. of Oulu (Finland)
Risto Myllylä, Univ. of Oulu (Finland)

Published in SPIE Proceedings Vol. 5953:
Acousto-optics and Photoacoustics
Antoni Sliwinski; Rainer Reibold; Vitaly B. Voloshinov, Editor(s)

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