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Optical Engineering

In-line digital holographic sensor for monitoring and characterizing marine particulates
Author(s): Robert B. Owen; Alex A. Zozulya
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Paper Abstract

We report an in-line digital holographic sensor (DHs) for monitoring and characterizing marine particulates. This system images individual particles over a deep depth of field (>25 cm) with a resolution of 5 ?m. The DHS projects a collimated beam through the water column and onto a lensless CCD array. Some light is diffracted by particulates and forms an object beam; the undeflected remainder constitutes the reference beam. The two beams combine at the CCD array and create an in-line hologram, which is then numerically reconstructed. The DHS eliminates many problems traditionally associated with holography. The CCD recording material considerably lowers the exposure time and eliminates most vibration problems. The laser power needs are low; the DHS uses a small 10-mW diode laser. Rapid numerical reconstruction eliminates photographic processing and optical reconstruction. We successfully operated the DHS underwater on a remotely operated vehicle; our test results include tracing a single particle from one hologram to the next, thus deriving a velocity vector for marine mass transport. We outline our digital holographic reconstruction procedure, and present our graphical user interface and user software tools. The DHS is particularly useful for providing in situ ground-truth measurements for environmental remote sensing.

Paper Details

Date Published: 1 August 2000
PDF: 11 pages
Opt. Eng. 39(8) doi: 10.1117/1.1305542
Published in: Optical Engineering Volume 39, Issue 8
Show Author Affiliations
Robert B. Owen, Owen Research Inc. (United States)
Alex A. Zozulya, Worcester Polytechnic Institute (United States)

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