I've been taking a look at these swarm robots and am very impressed. There is, however, one aspect of the robots I'm confused about, which is the infrared ranging they use.
The robots have a wide angle infrared transceiver on their undersides, and bounce the beam off the table they stand on to communicate with other robots. This I can understand, but what I can't is the ranging part as stated above. Could someone shed some light on how these robots calculate their range from one another using this infrared method? A general explanation or links to an article would be most appreciated.