cloaking – It's Interesting

By Lee Roop

Scientists in England have made an object disappear using a composite material of nano-sized particles to change the way its surface appears.

It’s not the invisibility cloak from J.K. Rowling’s Harry Potter novels, but reports on the research say it moves the world one step closer.

Here’s the way it worked. Researchers coated a curved surface with a nanocomposite medium with seven distinct layers, each with a different electrical property depending on position. The effect was to “cloak” an object allowing it to appear flat to electromagnetic waves.

The picture at left shows the cloak not in use where the presence of the object along the path of the traveling wave drastically changes its electric field configuration. At right, where the cloak is in action and the nanocomposite has been applied, there is a reduction in the amount of shadowing seen immediately after the object, as well as a noticeable improvement in the reconstruction of wave fronts. (Queen Mary University of London)

“The design is based on transformation optics, a concept behind the invisibility cloak,” said professor and study co-author Yang Hao of Queen Mary University of London’s School of Electronic Engineering and Computer Science.

Scientists see an early use of the coating in changing how antennas are tethered to a platform. It could allow antennas of different shapes and sizes to be attached to a platform without being detectable.

The underlying design approach could be applied to control any kind of electromagnetic surface waves, researchers said.

http://www.al.com/news/huntsville/index.ssf/2016/07/scientists_move_one_step_close.html

Doctoral student Joseph Choi demonstrates a multidirectional ‘perfect paraxial’ cloak using 4 lenses.

Choi uses his hand to further demonstrate his device.

A laser shows the paths that light rays travel through the system, showing regions that can be used for cloaking an object.

Scientists at the University of Rochester have discovered a way to hide large objects from sight using inexpensive and readily available lenses.

Cloaking is the process by which an object becomes hidden from view, while everything else around the cloaked object appears undisturbed.

“A lot of people have worked on a lot of different aspects of optical cloaking for years,” John Howell, a professor of physics at the upstate New York school, said on Friday.

The so-called Rochester Cloak is not really a tangible cloak at all. Rather the device looks like equipment used by an optometrist. When an object is placed behind the layered lenses it seems to disappear.

Previous cloaking methods have been complicated, expensive, and not able to hide objects in three dimensions when viewed at varying angles, they say.

“From what, we know this is the first cloaking device that provides three-dimensional, continuously multidirectional cloaking,” said Joseph Choi, a graduate student who helped develop the method at Rochester, which is renowned for its optical research.

In their tests, the researchers have cloaked a hand, a face, and a ruler – making each object appear “invisible” while the image behind the hidden object remains in view. The implications for the discovery are endless, they say.

“I imagine this could be used to cloak a trailer on the back of a semi-truck so the driver can see directly behind him,” Choi said. “It can be used for surgery, in the military, in interior design, art.”

Howell said the Rochester Cloak, like the fictitious cloak described in the pages of the Harry Potter series, causes no distortion of the background object.

Building the device does not break the bank either. It cost Howell and Choi a little over $US1000 ($1140) in materials to create it and they believe it can be done even cheaper.

Although a patent is pending, they have released simple instructions on how to create a Rochester Cloak at home for under $US100 (114).

There is also a one-minute video about the project on YouTube.