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"Virtual periscope" could let submarines see up through the water's surface

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May 2, 2014

An image shot from beneath the water's surface, before and after processing by Stella Mari...

An image shot from beneath the water's surface, before and after processing by Stella Maris

It's a classic scene from many a war movie – a submarine's presence is given away by its periscope protruding through the surface of the water. If submariners want to see what's up there, however, they really have no choice ... although that may be about to change. Scientists at the Technion-Israel Institute of Technology have devised a system that allows an underwater camera to look up through the surface from below, with a minimum of distortion.

The system is called Stella Maris, which is short for Stellar Marine Refractive Imaging Sensor. It works by digitally altering the images from the camera, in order to compensate for the visual distortions caused by waves moving through the water's surface. Given that waves move in a random pattern, however, how can it know what sort of alterations are required?

Well, although the waves are random, the position of the sun in the sky at a given time and location is a constant. In Stella Maris, the sun's rays shine through an underwater pinhole array (a thin metal sheet perforated with a grid of laser-cut holes) and down onto a glass image plane.

When the surface of the water is completely flat, the result will be a grid of evenly-spaced points of light on that plane. As waves cause the rays to be refracted in a chaotic manner, however, the points of light on the plane will likewise move around relative to one another.

The system's computer uses a sensor camera (as distinct from the primary imaging camera) to monitor those movements. Since it knows what the grid of light points is supposed to look like, it can tell exactly how the wave-altered pattern is deviating from that model. It applies that information to the picture from the primary camera, altering it in the same way that the jumbled pattern of light points would need to be altered in order to make it uniform again.

It's the same principle used by the Shack-Hartmann astronomical sensor, which compensates for turbulence in the Earth's atmosphere when viewing celestial bodies through a telescope.

Needless to say, its usefulness on submarines looks like it would be limited to situations in which crews were trying to view ships or other objects that were quite close to the vessel. The scientists believe that it could have other applications, however, such as on marine biology research platforms in which cameras need to see both above and below the surface.

More information on how it works is available in the video below.

Source: Technion-Israel Institute of Technology

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.   All articles by Ben Coxworth
4 Comments

Stupid... launch a drone

b@man
2nd May, 2014 @ 07:19 pm PDT

Are we assuming that the water is clear and the periscope is within a foot of the surface? What about the fact that the ocean waves are usually 1-3 feet on a calm day. Are we always looking nearly straight up? Anyone on the surface would surely see a submarine in clear water if they were that close. How about just floating a a tethered good camera to the surface disguised as floating seaweed? That way the sub could be 300 feet deep while making observations. I could even imagine a dolphin shaped water drone with a camera for something more mobile. While I applaud the distortion correcting computer solution, sometimes a simpler way would likely be superior. Maybe there is a good place for this but it looks like using a sledge hammer on a thumbtack.

Bob
3rd May, 2014 @ 04:58 pm PDT

Extraordinarily clever. Easy to dismiss it as unusable, but there might be some interesting use cases, perhaps not involving a submarine hanging around. For example: a field of semi-autonomous sensors floating just below the water level (moving with the waves)...

Oh look - there's a Gizmag article "Special solar cells produce electricity from underwater sunlight" from 11th June, 2012 (http://www.gizmag.com/underwater-solar-cells/22896/). So the sensors could have almost unlimited loiter time, and pop up to communicate only when they have something to say.

Graham Conroy Harris
5th May, 2014 @ 01:27 am PDT

Thought all of our New nuke subs had this feature?

the VA class types IF not FBM types.

USS Seaview used similar since periscope stand in control room is Fwd of Main sail from TV show & movie., thus had to use similar system then in 1961 movie.

Must for all NATO subs to acess.

Ideal for Under Ice navigation ( see Ice Station Zebra, 1968 or DVD)

Stephen N Russell
5th May, 2014 @ 03:14 pm PDT
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