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A dolphin submarine. Photo by Tomer Appelbaum
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Technion-Israel Institute of Technology
Underwater views: Distorted, left, and corrected, right. Photo by Technion-Israel Institute of Technology

The submarine periscope may become a thing of the past, due to a new technology developed by a team from the Technion, Israel's institute of technology.

The "virtual periscope" technology, which enables accurate rendition of above-surface and airborne objects from underwater, was introduced at an international conference on computational photography, held in Santa Clara, California, last weekend.

Called “Stella Maris” (Stellar Marine Refractive Imaging Sensor,) the underwater imaging system uses technology developed for astronomy to counter blurring and distortion caused by layers of atmosphere when viewing stars. The technology gets around the inevitable distortion caused by water-surface waves when using a submerged camera.

The system consists of a camera, a pinhole array to admit light (a thin metal sheet with precise, laser-cut holes), a glass diffuser, and mirrors. Sunrays are projected through the pinholes to the diffuser, which is imaged by the camera, beside the distorted object of interest. The latter is then corrected for distortion.

“When the water surface is wavy, sun-rays refract according to the waves and project onto the solar image plane,” explains Associate Professor Yoav Schechner, of the Technion Department of Electrical Engineering. “With the pinhole array, we obtain an array of tiny solar images on the diffuser.”

When all of the components work together, the Stella Maris system acts as both a wave sensor to estimate the water surface, and a viewing system to see the above-surface image of interest through a computerized, “reconstructed” surface.

The virtual periscope may have potential uses in addition to submarines, where they could reduce the need for traditional periscopes that have been in use for more than a century, according to the developers.

Submerged on the sea floor, Stella Maris could be useful for marine biology research, where viewing and imaging both beneath and above the waves simultaneously is important. Stella Maris could, for example, monitor the habits of seabirds as they fly, then plunge into water and capture prey.