Move over Harry Potter and your invisible cloak; the “Rochester Cloak” is here!
Cloaking occurs when objects wearing the cloak become hidden from view, while everything around the cloaked objects are visible and appear normal. University of Rochester natives, Professor of physics John Howell and graduate student Joseph Choi, have developed new technologies to create a cloaking configuration that makes objects appear invisible when passing across their device.
“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,” said Choi. Many cloaking devices show faults and reveal the “invisible” objects when looking from different viewpoints, but the Rochester Cloak has found a way around that. Using four lenses, the Rochester inventors have determined the correct lens type, power, and spacing of the lenses needed to cloak objects properly and leave the background undisturbed. To test their device, they placed a cloaked object in front of a gridded background. They looked through the lenses and changed their views from side to side, to ensure the perception of the cloaked object would not falter. The grid behind the object shifted accordingly. There was no discontinuity or distortion in the grid lines, and this confirmed their design.
Besides being as close to magical as one can get with science, the cloaking device has been designed to be extremely useful. The lenses can be swapped out to cloak larger items, and because it is broadband and therefore has the ability to simultaneously transport multiple signals and traffic types, the Rochester Cloak works for not just specific frequencies but for the whole visible spectrum of light. Additionally, it was designed with greater purposes in mind. With a Rochester Cloak, doctors can perform operations with more ease. “I imagine this could be used to cloak a trailer on the back of a semi-truck so the driver can see directly behind him,” Choi said. “It can be used for surgery, in the military, in interior design, art.” The materials used to make their device are also inexpensive and readily available to anyone. The possibilities are endless.
If you don’t want to wait for the Rochester Cloak to go on sale, follow these steps to make your own (DIY credit to rochester.edu):
- Purchase 2 sets of 2 lenses with different focal lengths f1 and f2 (4 lenses total, 2 with f1 focal length, and 2 with f2 focal length)
- Separate the first 2 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).
- Do the same in Step 2 for the other two lenses.
- Separate the two sets by t2=2 f2 (f1+ f2) / (f1— f2) apart, so that the two f2 lenses are t2 apart.
Note that:
- 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.
To learn more about the Rochester Cloak, watch this video:
For a funny demonstration, watch this: