IR led + collimator = what?

i am trying to make a IR LED focus its light to a dot, instead of shinning in all directions. im working on a simple project that uses an IR light source and a sensor to create a beam of light, and if its broken something will happen. will putting the LED in a laser 'case' do the trick? thanks. if so what 'case' should i use? any links to tutorials or examples would be great.

also. what are the right terminology for the stuff i just mentioned, if anyone understands me. thanks.