Headlights began very simply as lanterns mounted on the earliest horseless carriages. As the versatility of automobiles widened, improved lighting systems were needed and the incandescent, sealed beam headlight was devised and used almost universally for decades.

The incandescent headlight consisted of a housing or assembly, a light bulb as the light source, a reflector that bounced the light forward, a protective lens or cover that focused the light beam and protected the bulb, and connections to the car's electrical system. Double filaments in the bulb allowed for a high and a low beam. The bulbs produced a yellowish beam that caused eyestrain; they also darkened and dimmed with age. This type of headlight produced a sufficient amount of directed light for the driver to see without blinding oncoming drivers, but it was inefficient because more than 70 percent of the light produced by the bulb was either lost...