Invisibility Cloak Generates Virtual Images

Photo via flickr by pfv

In a new twist from the liquid invisibility cloaks Sptnk reported here, researchers have designed a material that not only makes an object invisible, but also generates one or more virtual images in its place. Because it doesn’t simply display the background environment to a viewer, this kind of optical device could have applications that go beyond a normal invisibility cloak. Plus, unlike previously proposed illusion devices, the design proposed here could be realized with artificial metamaterials.

The team of engineers, Wei Xiang Jiang, Hui Feng Ma, Qiang Cheng, and Tie Jun Cui from Southeast University in Nanjing, China, describes the recently developed class of optical transformation media as “illusion media.” As they explain in a new study, any object enclosed by such an illusion medium layer appears to be one or more other objects. The researchers’ proposed device is designed to operate at microwave frequencies.

“The illusion media make an enclosed object appear like another object or multiple virtual objects,” Cui told  “Hence it can be applied to confuse the detectors or the viewers, and the detectors or the viewers can’t perceive the real object. As a result, the enclosed object will be protected.”

But as the researchers explain, illusion media is similar to an invisibility cloak, except for one main difference. In a perfect invisibility cloak, there are almost no scattering electric fields, so that the illusion space is only free space. In illusion media, on the other hand, the material creates scattered electric field patterns that generate virtual images. Any detector located outside the illusion medium layer will perceive the electromagnetic waves as if they were scattered from a virtual object.

“Generally speaking, different objects will generate different scattering patterns under the illumination of electromagnetic/optical waves,” Ciu explained. “Hence a detector can perceive an object according to its scattering pattern. Our illusion media will change the scattering patterns of the enclosed object to make it appear like another object or multiple virtual objects.”


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