Invisibility cloak may become reality

Harry Potter fans, rejoice: Researchers from the University of Rochester have discovered an inexpensive way to recreate the fictional wizard’s famous invisibility cloak. 

Joseph Choi, a graduate student at the University of Rochester’s Institute of Optics, led the team that created the Rochester Cloak. The cloak is, to the best of their knowledge, the first device that can perform three-dimensional, continuously multidirectional cloaking.

Choi, working with physics professor John Howell, created a cloak that is able to disguise the object behind it without shifting the background even if the viewer shifts their viewpoint by up to 15 degrees away from the optimal viewing position.

Cloaking, an optical illusion that conceals an object by making it invisible, has fascinated both the popular culture and scientific communities for quite a while. The fundamental physical principle behind the illusion is to try to bend light around an object without distorting the background, rendering the object invisible as a result.

Previous cloaking devices, such as the blanket-like Quantum Stealth, have depended on advanced technology or expensive and exotic materials to make an object disappear. However, most of these devices only work when you are looking through them from a certain angle. If you shift your viewpoint even the slightest bit to the left or right, the object pops back into sight, or the background shifts and the illusion is lost. Other attempts have not been able to completely shield an object.

The Quantum Shield, which is considered one of the best cloaking devices, can render an object or person 95 to 98 percent invisible and was reported to show a few flashes of color when an object moves behind the blind. Environmental conditions such as color of the background and lighting seem to have a pronounced effect on the Quantum Shield’s efficiency in minimizing distortion of the background.

The research team used two sets of two lenses, where the first pair was of one focal length and the second pair was of a different length. They then took one lens from each pair and positioned them on an optical bench such that the distance between the two lenses is the sum of their focal lengths. The remaining two lenses were oriented in the same way.

The second pair of lenses were then positioned to a calculated distance apart, so if an object were placed between the first two lenses, it would be effectively cloaked from view. This simple design is not only inexpensive and practical, it is also able to overcome some of the limitations of previous cloaking device designs.

The beauty of the Rochester researchers’ design is that it scales up — the Rochester Cloak can make anything invisible, as long as the lenses are big enough.

However, the scientists are not suggesting that their device will be made into a cloak similar to the one described in the pages of the Harry Potter series any time soon.

Instead, Choi imagines that their cloak could be used to eliminate blind spots when driving or even conceal nurses’ hands during a surgery so they do not obstruct a doctor’s view.

The idea for a simple cloaking device, which came to Howell while he was working on a project with his children, has now blossomed into a design with potential for real world integration. For now, Howell and Choi have submitted their study to the journal Optics Express and filed for a patent for their device.