Researchers at the University of Rochester (UR) have developed an optical illusion that gives the appearance of making objects disappear in the academic quest to create an invisibility cloak.
John Howell, professor of physics at UR said: There’ve been many high tech approaches to cloaking and the basic idea behind these is to take light and have it pass around something as if it isn’t there, often using high-tech or exotic materials.”
Howell collaborated with Joseph Choi, graduate student of the RU Institute of Optics (IO) to develop a combination of four standard lenses that keeps the object hidden as the viewer moves up to several degrees away from the optimal viewing position.
Choi explained: “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.”
Earlier this year, Debashis Chanda at the University of Central Florida (UCF) has created a way to bend light with artificial nanostructures to develop an invisibility cloak.
Chanda and other nanotech experts have developed a large swath of a “multilayer 3-D metamaterial” that operates “in the visible spectral range”.
This was accomplished by “using nanotransfer printing, which can potentially be engineered to modify surrounding refractive index needed for controlling propagation of light.”
In 2012, Hyperstealth announced they have developed SmartCamo, a material that can conceal the wearer by matching their surroundings.
By bending light, the SmartCamo uses nanotechnology “so the object might be invisible to microwaves or infrared” – yet not simultaneously.
Back in November, the Department of Electrical and Computer Engineering (DECE) at the University of Toronto (UoT) revealed researchers created a cloak that is thin, scalable and adaptive to various objects and sizes to hide an object to radar detection.
So far, the object is still visible to the human eye; however this “practical” approach is being hailed as a step toward an actual invisibility cloak.
Researchers said: “We’ve demonstrated a different way of doing it. It’s very simple: instead of surrounding what you’re trying to cloak with a thick metamaterial shell, we surround it with one layer of tiny antennas, and this layer radiates back a field that cancels the reflections from the object.”
Indeed, the array of small antennas that expel the electromagnetic field surrounding the cloak cause the “invisibility” that renders the object un-seeable to radar systems.
Called an active electromagnetic cloak (AEMC), this device “uses an array of elementary sources to cancel the scattered fields created by an object. An active interior cloak does this by placing the sources along the boundary of the object.”
This technology “can be thought of as introducing a discontinuity in the field to cancel out the scattered field by the object.”
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