An ‘invisibility’ device you can build at home

(Courtesy of the University of Rochester)

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ROCHESTER, New York — Researchers have developed a new way to “cloak” items, and it’s simple enough it can be recreated outside of a lab.

Cloaking is an optical illusion that makes an object appear as if it isn’t there. Researchers from the University of Rochester said people have always been excited about the idea of being invisible, but that it has gained popularity in recent years with the introduction of Harry Potter’s invisibility cloak.

“There’ve been many high tech approaches to try and achieve cloaking, and the basic idea behind these high-tech or exotic materials is to take light and have it pass around something as if it isn’t there,” said professor John Howell in a video. “We just figured a very simple way of doing that can just be using standard lenses and things we would normally find in the lab.”

The team developed a four-lens system that can hide objects even when the viewer moves. The cloaking device can be seen in action in a video on YouTube.

In the future, researchers said the cloaking device made of lenses could allow surgeons to effectively look at their hands to see what they are operating on, or help drivers see through blind spots.

Researchers filed a patent for the “Rochester Cloak,” but they shared the steps for making it at home. The directions are posted below. Previously, the research team posted a video about how to use mirrors as a simple cloaking device.

How to build a Rochester Cloak (instructions from the University of Rochester):

  1. Purchase two sets of two lenses with different focal lengths f1 and f2 (four lenses total, two with f1 focal length, and two with f2 focal length)
  2. Separate the first two lenses by the sum of their focal lengths (So f1 lens is the first lens, f2 is the 2nd lens, and they are separated byt1= f1+ f2).
  3. Do the same in Step 2 for the other two lenses.
  4. Separate the two sets by t2=2 f2 (f1+ f2) / (f1— f2) apart, so that the two f2 lenses are t2 apart.
Notes for building the cloak (from the University of Rochester):

  • Achromatic lenses provide best image quality.
  • Fresnel lenses can be used to reduce the total length (2t1+t2)
  • Smaller total length should reduce edge effects and increase the range of angles.
  • For an easier, but less ideal, cloak, you can try the 3 lens cloak in the paper.
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Natalie Crofts


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