You don't need glasses to know where IR is, it's everywhere, so it's big, very big. Everything with a temperature above 0 degrees K emits IR energy. Now how do you keep IR energy from adversely effecting people?
You're right -- I was envisioning the "spot" that the IRT is reading as a projection of the IRT and therefore standing out from its surroundings, but its actually like the "spot" that ones sees through a telescope, merely a defined area. I guess we're stuck with laser dots and crosshairs for the time being.