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Proceedings Paper

Data extraction system for underwater particle holography
Author(s): J. J. Nebrensky; Gary Craig; Peter R. Hobson; R. S. Lampitt; Helge Nareid; A. Pescetto; Andrea Trucco; John Watson
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Paper Abstract

Pulsed laser holography in an extremely powerful technique for the study of particle fields as it allows instantaneous, non-invasive high- resolution recording of substantial volumes. By relaying the real image one can obtain the size, shape, position and - if multiple exposures are made - velocity of every object in the recorded field. Manual analysis of large volumes containing thousands of particles is, however, an enormous and time-consuming task, with operator fatigue an unpredictable source of errors. Clearly the value of holographic measurements also depends crucially on the quality of the reconstructed image: not only will poor resolution degrade the size and shape measurements, but aberrations such as coma and astigmatism can change the perceived centroid of a particle, affecting position and velocity measurements. For large-scale applications of particle field holography, specifically the in situ recording of marine plankton with Holocam, we have developed an automated data extraction system that can be readily switched between the in-line and off-axis geometries and provides optimised reconstruction from holograms recorded underwater. As a videocamera is automatically stepped through the 200 by 200 by 1000mm sample volume, image processing and object tracking routines locate and extract particle images for further classification by a separate software module.

Paper Details

Date Published: 31 August 2000
PDF: 10 pages
Proc. SPIE 4076, Optical Diagnostics for Industrial Applications, (31 August 2000); doi: 10.1117/12.397940
Show Author Affiliations
J. J. Nebrensky, Brunel Univ. (United Kingdom)
Gary Craig, Aberdeen Univ. (United Kingdom)
Peter R. Hobson, Brunel Univ. (United Kingdom)
R. S. Lampitt, Southampton Univ. (United Kingdom)
Helge Nareid, Aberdeen Univ. (United Kingdom)
A. Pescetto, Univ. of Genoa (Italy)
Andrea Trucco, Univ. of Genoa (Italy)
John Watson, Aberdeen Univ. (United Kingdom)

Published in SPIE Proceedings Vol. 4076:
Optical Diagnostics for Industrial Applications
Neil A. Halliwell, Editor(s)

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