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LEDs Outsmart Smart Phones

LEDs Outsmart Smart Phones

Preventing photography in galleries and museums in the age of the smart phone has become incredibly difficult. Researchers from the University of California San Diego and the University of Wisconsin-Madison have got together and have come up with a solution that involves smart LEDs.


They harnessed the capacity of smart LEDs to flicker in a predictable pattern and created something called LiShield, which interferes with the lens on smart phone cameras. The high frequency flickering can’t be perceived by the human eye, but exploits the way that smart phones capture images. Smart phones expose each row of pixels in sequence. The rapid on/off flickering of the LED overexposes and then underexposes the sequence, creating an unwelcome striped effect in the captured image. As one of the researchers, Shilin Zhu, says: “The basic principle is to illuminate the environment with an eye-transparent light waveform, so that captured images or video are distorted because of the camera’s rolling shutter mechanism.”

Bar code

Even if the ambient light is stronger than the LED and allows the camera to take a picture that is usable, the characteristic striping pattern can still be detected as a sort of bar code online and acts as a digital watermark.
The technology is still in an experimental phase, but already looks promising for straightforward indoor applications such as art galleries.

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