The lights should provide good illumination and should minimize glare. For the headlights, in order to balance the above two requirements, the two conditions of high beam and low beam are adopted. The high beam is a long-distance illumination beam that is used when there is no car in the front or does not follow other cars. It is generated by a main filament located at the focal point of the reflector and has a relatively high power. The beam direction is approximately horizontal. It is usually stipulated that the maximum luminous intensity of a single lamp should not be less than 20,000 candelas. In order to ensure driving safety, the illumination distance of the high beam (the distance between the obstacles found and identified) should be greater than the braking distance for timely parking. In view of the fact that the required high beam luminous intensity is approximately proportional to the fourth power of the speed, most countries implement speed limits. In addition, in order to change the far and near-light conditions, the driver will not be able to lose recognition ability for a short time because of the disparity between light and dark. Therefore, it is stipulated that the sum of the maximum luminous intensity of all the headlights of the headlights shall not exceed 225,000 candelas. The low beam is a close-range illumination beam used in a rendezvous or trailing other car, produced by a lower power sub-filament, which is projected downward due to deviation from the reflector focus and optical axis. In order to limit the beam above the horizontal direction, a metal light shield is usually placed under the sub-filament, so that a light and dark shape is formed on the vertical screen. When the vehicle is relocated, the driver's eyes are located in the low-light dark area. Inside, thereby maximizing glare suppression.