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USGS Patent Pending for a New Underwater Microscope System

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image of sand grains taken with the underwater microscope
Sand grains: Sample image of sand grains on the bed of the Colorado River. Image was taken in highly turbid water and is approximately 1 cm across. The ring of light spots near the outside of the image is a reflection from LED (light-emitting diode) lights built into the video camera assembly.
The U.S. Geological Survey has a patent pending for a new underwater microscope system. Developed by Hank Chezar and David Rubin, the new system digitally collects and analyzes electronic images of sediment grains on a riverbed or seabed. Using the new system, scientists can collect hundreds of electronic samples and later analyze them for grain size in a matter of hours to days, a process that typically takes months using traditional methods of sampling and grain-size analysis. The new system not only saves time but also spares scientists from sampling activities that can be dangerous in areas with strong currents.

the 'Flying Eyeball'
The 'Eyeball:' Video camera assembly (a.k.a. "Flying Eyeball"), including stabilizer fin, camera pressure case, and bridle.
The heart of the system is a close-up microscope lens installed on a modified version of a commercially available camera. The camera is at the bottom of a cylinder encased in a steel ball. To "sample" the bottom, the ball is lowered to the seabed or riverbed while the camera shoots continuous video footage. Operators monitor video images sent in real time to the surface vessel. The ball is settled on the bottom until sand grains are pushed right up against the window in the bottom of the ball, and the scene on the video monitor is still.

topside video console for the underwater microscope
Topside: Video console, including video monitor and digital recorder.
The system acquires a video image of the bottom at 1/4-inch distance from the focal plane of the lens, and sends the video signal through a cable to a digital video-recording console on the surface vessel. The special housing that encases the underwater microscope camera--together with ballasting, winching and operational procedures--permits topside operators to work from a small vessel even in swift-moving river environments. Digital video sequences recorded on the surface vessel are later viewed on a computer, and the most sharply focused frames of each bottom-contact sample are saved. These images are then analyzed electronically for grain size using software developed by David Rubin.

The system is designed to assist sedimentologists, marine geologists, and other scientists interested in studying surficial sediments in lakes, rivers, and oceans. First deployed on the Colorado River in Grand Canyon, the system has also been used off Oahu, Hawaii, and Santa Cruz, California.

Improvements to the system's lens design are in development. These improvements will permit gravel characterizations, which have aquaculture and fish wildlife applications.

Eric Grossman annotates video footage
Eric Grossman annotates video footage from the underwater microscope.
In the photo at right, University of Hawai`i graduate student Eric Grossman annotates video footage from the underwater microscope during fieldwork directed by Bruce Richmond. Here the system is being used to videotape bioclastic grains off Waikiki on the south shore of Oahu, Hawai`i. Physical samples of the sediment were also taken and will be sieved to determine grain size. Grain-size data derived from sieving will be compared to grain-size data derived from digital analysis of the video images to assess the system's usefulness for analyzing angular, bioclastic grains such as those found off Oahu.

Related Sound Waves Stories
Sedimentologic Engineering in Grand Canyon
November, 1999

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Research New Underwater Microscope System

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