Eye-tracking systems certainly would add a lot to augmented reality glasses, as they could adjust visual content based on what users are looking at, or be used for hands-free control of games. Their integration into such eyewear has been limited, though, because they require so much power. That said, scientists have now developed eye-tracking glasses powered by nothing but onboard solar cells.

Ordinarily, mobile eye-tracking systems utilize miniature cameras that are pointed at the eyes, plus they require a lot of image-processing power – this means that they can be costly, plus they require a fairly large battery, or a smaller one that has to be charged quite often. The inexpensive new prototype system, however, reportedly gets around that limitation.

Created by a Dartmouth College team led by associate professor Xia Zhou, it consists of off-the-shelf eyeglass frames equipped with commercially-available hardware including a microprocessor, near-infrared LEDs, photodiodes, and thin solar cells located on the frames' arms.

Powered by those cells, the LEDs illuminate the user's left eye from multiple directions. The photodiodes detect the reflected light patterns, with the processor then analyzing those patterns in order to ascertain the position of the pupil in real time. More specifically, it utilizes custom algorithms to track the pupil's trajectory, velocity, and acceleration at a sub-millimeter level.

The glasses apparently get all the power they need from regular indoor lighting. In fact, they so far only work indoors – this is because the infrared spectrum of sunlight saturates the photodiodes, keeping them from detecting the reflected near-infrared of the LEDs. It is hoped that future versions of the technology will address that problem, along with featuring further-miniaturized electronics that can be integrated into various styles of glasses.

"This is an exciting advancement for gamers, developers and other users of smart glasses," says Zhou. "It's the first-ever eye tracker that can fit into your everyday glasses and run without batteries."