The camera films the hand passing in front of the colorful, vertical bars. But the video displayed on the iPad shows only the bars, rendering the hand invisible.
Optics researchers have successfully transformed an iPad into a tiny digital invisibility cloak.
Unlike previous cloaks, this new method works on all viewing angles and colors of light — no magic required.
The method was created by Joseph S. Choi and John C. Howell, researchers in the University of Rochester’s Institute of Optics. You might remember Choi from the invisibility cloak he made two years ago out of standard optical lenses.
This time, rather than guiding light around an object, the researchers collected light rays digitally — for example, via a digital camera — at one position and then displayed them digitally at another — such as on an iPad.
For their demonstration, Choi and Howell used the video function of a digital camera to capture light rays from a background scene. By placing the camera on a mechanical slider, they were able to move the camera horizontally and capture numerous positions. That video got transmitted to a laptop for processing with a sophisticated computer program before being displayed on an Apple iPad mini covered in an array of cylindrical lenses for 3-D effect.
The computer program ran calculations on the light rays in order to transfer the right pixels, colors, and angles to the correct positions onto the output display, according to the researchers.
“We used currently available commercial digital technology, which is only going to improve over time, to make a good approximation to what you would expect from a cloak like Harry Potter’s,” Choi said in a university press release. The researchers just published a paper describing their approach in the journal Optica (abstract).
Such a method wouldn't have been enough to hide Harry Potter from Death Eaters, but the researchers have interesting potential applications in mind. One, which I’ve heard about before, is a way to make a surgeon’s hand see-through during delicate procedures. Another is a cloaking device for car interiors that would eliminate blind spots.
So far the biggest downside is that the scanning and processing Choi and Howell used for their demonstration created a lag time around one minute long. Not ideal. Fortunately, the researchers think a real-time version could be achieved with an array of detectors, improved hardware interfaces, and automated data processing.
They also sound confident about creating a flexible version based on their method. Howell said in the press release that he thinks that’s possible in theory, although such a cloak would require heavy engineering and significant computational power to constantly recognize the position and orientation of the detector and display.
That will be tough, but not impossible. Next the researchers plan to continue developing their cloak with an eye on making it wearable. Not bad for muggles.