Evan Ackerman from IEET Spectrum explains more:

The secret to this intelligence is no secret: the door has a fancy custom sensor (a 3D time-of-flight laser scanner) coupled with algorithms that can detect people, track their motion, and make educated guesses about whether or not they're aiming for the door. Somewhat unusually for a research paper like this, there is some serious consideration of practicalities, too. The sensor is designed to function in places with ambient light ranging from direct sunlight to total darkness (between 0 and 200,000 lx), and software can compensate for snow, rain, water on the sensor itself, and interference from other nearby sensors.


Of course, fancy doors like these come at a cost. They're about $1,000 more than a conventional automatic door sensor. But the developers are hoping to bring the price down over the next year or so.

More at IEEE Spectrum.