Optical headlamp alignment refers to a method of ensuring that headlights on the front of a motor vehicle are configured to properly emit light at the correct angle. The method involves using an optical headlamp aligner to read the strength and focus of the light to determine any necessary adjustments.
Prior to 1990, all motor vehicle headlamps were created with special protrusions called aiming nibs that allowed a manual device to be affixed to the lamp to measure its angle of projection. Optical alignment tools do not use nibs, but instead read the light through sensors.
All motor vehicles are required to have front-mounted lighting systems that allow the driver to see the road ahead of her, as well as allow oncoming traffic to see the car during darkened conditions. In order to ensure the safety of all drivers on the road, these lighting systems, called headlamps or headlights, must be aligned to direct the light within a specific angled range. If the light is angled too high, it does not properly illuminate the road ahead of the driver and runs the risk of causing visual impairment for any oncoming motorists. If the lights are angled too low, it again limits the amount of road the driver can see ahead of her.