Autore: ExtremeTech

Chinese ghost cloaking illusion device

Chinese physicists have created an illusory, ghosting invisibility cloak — a cloak that changes the appearance of an object so that it looks like something else. In theory, you could cover a soldier with this cloak and make it look like something else — a cactus perhaps, or a dog.

In general, ghost cloaks — which are a type of illusion cloak — have two functions. First they must hide the subject, like an invisibility cloak, and then they must somehow project the image of another object. If you read ExtremeTech, you’ll already know that we’ve made some great strides towards devices that provide some semblance of invisibility — but we’re still a long way from creating the metamaterials required to provide true, three-dimensional, panchromatic invisibility cloaks. Instead, the Chinese physicists decided to skip the invisibility bit, and jump straight to the second step: creating a cloak that projects the image of another object.

Tie Jun Cui and his colleagues at Southeast University in Nanjing, China have created a cloak that scatters incoming light to create two “ghost” images either side of the cloaked object. Depending on the construction of the cloaking device, the shape and other properties of the ghost images can be altered. The cloak itself is fashioned out of thousands of split-ring resonators (pictured above) — a structure commonly used in metamaterials that affects electromagnetic waves in weird and wonderful ways.

Ghosting cloak diagram thing

The end result is that the cloaked object is still visible, but significantly shrunk and distorted. Once you factor in the two ghosts, the overall picture is very different and much more complex than the original. If we imagine a real-world example, this cloak could turn an aircraft — which has a very recognizable radar signal — into a small, indeterminate object, flanked by a couple of birds. Whether the cloaked object is distorted enough for this approach to be effective remains to be seen, though.

Still, it’s easy to see how a ghosting device could be used in concert with other techniques to evade detection — if not from radar and other advanced sensing technologies, then at least from human eyes. It’s also exciting to imagine the possibilities of an illusion cloak, when we finally crack true invisibility. Instead of simply vanishing — which is admittedly rather neat — you could become something or someone else.

Now read: Canadian camouflage company claims to have created perfect invisibility cloak, US military soon to be invisible

Research paper: DOI:arXiv:1301.3710 – “Creation of Ghost Illusions Using Metamaterials in Wave Dynamics”