eBay 100W LED Collimator and reflector, unboxing review.
A collimator is a device that narrows a beam of particles or waves. To "narrow" can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., collimated or parallel) or to cause the spatial cross section of the beam to become smaller.
http://en.wikipedia.org/wiki/Collimator
