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The invisibility cloak

It’s not magical, it’s a simple combination of lenses that add up to the ability to conceal objects across a certain range of angles, developed at Rochester’s Institute of Optics.

January 2015

The invisibility cloak It’s not magical, it’s a simple combination of lenses that add up to the ability to conceal objects across a certain range of angles, developed at Rochester’s Institute of Optics IMA Lab

Everybody fantasizes about being able to make themselves invisible in certain situations.
That’s why Harry Potter’s Invisibility Cloak is so popular.

The best scientists have preserved something of the curiosity and imagination of children: two of them of recently developed several ways of concealing physical objects from view.
The basic idea common to all attempts at achieving this is to take light and have it pass around something as though it wasn’t there. Up until now, most experiments have involved
exotic or high-tech materials, but the latest effort, developed at the University of Rochester, is significant not only because it overcomes some of the limitations of previous devices,
it also uses inexpensive, readily available materials… but arranged in a novel configuration.

John Howell, a professor of physics at the University of Rochester, together with PhD student Joseph Choi, developed a combination of four standard lenses which keeps an object hidden, but the striking thing here is that this perception persists even when the viewer moves up to several degrees away from the optimal viewing position.
The things is, many cloaking designs work perfectly well when you look at an object from a  precise position and at a precise angle, but if you move your viewpoint even a little,
the object becomes visible.

“This is the first device that we know of that can do three-dimensional, continuously multidirectional cloaking, which works for transmitting rays in the visible spectrum,” said Choi.

In order to both cloak an object and leave the background undisturbed, the researchers determined the lens type and power needed, as well as the precise distances necessary between each of the four lenses. In this set-up, if you change the viewing angle by moving from side to side while looking through the lenses, the grid shifts accordingly, maintaining the illusion of invisibility as if the cloaking device was not there. 

The Rochester Cloak can be scaled upwards to as large as the size of the lenses, allowing fairly large objects to be cloaked. And, unlike some other devices, it’s broadband, which means it works for the whole visible spectrum of light, rather than only for specific frequencies.

Howell and Choi’s system has a long way to go before it can perform like Harry Potter’s invisibility cloak, but it does represent a notable "private" achievement, having created simple cloaking devices with off-the-shelf materials while working on a holiday project with their children.
Now this initial achievement is being carried over into research into potential applications.
Howell cites the possibility of using cloaking to effectively let a surgeon “look through his hands to see what he is actually operating on” and the same principles could be applied to allow truck drivers to see through blind spots on their vehicles.


The next challenge for their research, in other words, is to achieve… maximum visibility!

 

References:

http://www.rochester.edu/newscenter/watch-rochester-cloak-uses-ordinary-lenses-to-hide-objects-across-continuous-range-of-angles-70592/

http://www.smh.com.au/technology/sci-tech/scientists-unveil-invisibility-cloak-to-rival-harry-potters-20140927-10n1dp.html