when it comes to car projector headlights (BMW used the system with normal Halogens be4 HID became "common"), anyone can very easy touch the system:
Get some of these cheap "projecting beam" additional fog lights and dismantle them.
Inside there is the bulb, housed very deep inside a very deep reflector that focuses into a very short focal point. At this distance there is some kind of "light blocker", usually a metal sheet with a small hole (located at focal point), that blocks ANY light not at the FC. After that there is again some space to have the beam widen and finally a large aspheric lense to align the light.
There are also some flashlights that use this system (Docter Aspherilux) (I have one)
Beam of all of these is only a light tunnel, absolutely no spill (because that is wasted away thanks to the light blocking "sheet").
This is by far my most hated and worst light, its totally useless in my opinion not to use about 50 % of the light emitted from the source.
As a pro, one could mention, that the system can be made with less diameter than traditional headlights. Very good for the designers of modern cars, and the spill from the bulb is also not used very good in normal lights (reflectored back)
By changing the hole You can make different outcomes. f.e. widening the hole and also direct spill comes to the lense and thus leaves the light as spill
PS: back on topic: an optic wont work with any bulb source