[youtube=http://www.youtube.com/watch?v=iKYCob7getU]

In this writeup, you can see how to build a cheap compound eye system for your robot.  Using 4 IR LEDs and 4 phototransistors, [oddbot] gave “Mr General” the ability to follow movement in objects fairly well, assuming that they are within 200 mm. Being IR, it has the typical drawbacks such as sensitivity to light or overly reflective surfaces, but we like the idea. It is perfect for a nocturnal or low light robot.

[via Hacked Gadgets]