Originally Posted by
PatrickGSR94
I don't think it'll be as easy as you think.
Halogen and xenon HID capsules throw out light in all directions except for the bulb base. LED's have a much tighter angle of light output. Since the halogen/HID light is coming out all around, the projector housing uses a parabolic reflector to focus the light forward, and a shield in front of the lower half to prevent the light from bouncing off the bottom of the reflector and up into the air above the horizon. With an LED there won't be any light (or not much light) going down onto a reflector, so a shield is not going to give a sharp cutoff line.
Correct, the parabolic reflector is needed for a bulb, but you're forgetting the projector lens in there (these are the headlights with the glass ball look to the headlights where you can't actually see the bulb). The parabolic reflectors only purpose is to make a roughly collumated light beam that the projection lens then sends out to the road. Replace the parabolic reflector and bulb with a LED and LED-type reflector and place it the desired distance behind the lens and you're good to go. Honestly, you can take a magnifying glass or one of the full sheet magnifier lenses and a LED flashlight in your hands and find the right distance to project an image of the flashlights business end on the wall. Move the flashlight somewhat away from the focal length and you can make a more even beam distribution. At this point, a piece of paper can be used as a cutoff shield. Moving the paper around will vary the sharpness of the cutoff (do you like a razor-sharp cutoff or slightly softer?). Now, the beam will be quite narrow because of the lens being used but the same thing can be done with an automotive projector lens, just replace the light source and reflector.
I tried looking for a projector beam bike light and am not seeing any or have not found the right search terms. All I'm seeing are basically glorified flashlights strapped to the bars... I wonder what it would take to make one with a projector and sell the idea to one of the mass-marketers of bike lights?