As we all already know light (as any other EM) can be easly polarized. By seting different polarization angles of emited ray it is posible to have much more then one light beam of same frequency (color) in the same propagation path.

In next video you can se how it is posible to do more then just masking of light source with 3 polarized filters. I also demonstrate some posible logical operations with light so watch carefuly ;)