From this page,
Canesta’s electronic perception technology is a patented, low cost, and practical technology that enables machines and electronic devices to "see" by tracking nearby objects in three dimensions in real time. Using EPT, Canesta CMOS chips emit a field of continuous field of infrared light and measure the time it takes for that light to reflect back to the chip – for every pixel. In real-time, the chip processes those distances to create a three dimensional image of the objects in its field of vision.
and this page,
In a recently-granted U.S. patent, Canesta describes several of its inventions for "timing" the travel time of light to a unique, new class of low-cost sensor chips.
Fundamentally, the chips work in a manner similar to radar, where the distance to remote objects is calculated by measuring the time it takes an electronic burst of radio waves to make the round trip from a transmitting antenna to a reflective object (like a metal airplane) and back. In the case of these chips, however, a burst of unobtrusive light is transmitted instead.