Camera-projector installation and reducing projector feedback I'm working on a top-down projection game where i detect objects from the real world and project contours on them. My problem is with the output of the projector, I would like to know how to eliminate the feedback/not pick up the projector's output. Will using an infrared camera guarantee that or should i use other things? 
I tried placing a solar filter (from a floppy disk) in front of the camera which helped but i had to have a bigger light source in order to see the real objects.
This is my first time working on such a project so i would appreciate your help.
If you place an IR-blocking filter in front of the projector and a IR-pass filter in front of an IR-sensitive camera and illuminate your objects with IR light, then the camera will see nothing from the projector, and you can color your contours with any visible light colors.