What is a car headlight?
2 Answers
Headlights refer to the lighting devices installed on both sides of the front of a car, used for illuminating the road during nighttime driving. They can be categorized into two-lamp and four-lamp systems. The illumination effect of headlights directly impacts nighttime driving operations and traffic safety. Therefore, traffic management authorities worldwide generally stipulate headlight illumination standards by law to ensure nighttime driving safety. The headlight optical system is a combination of a bulb, reflector, and lens. Based on the structure of the headlight optical system, headlights can be divided into three types: semi-sealed, sealed, and projection headlights. The details are as follows: 1. Semi-sealed headlights: In semi-sealed headlights, the lens and reflector are glued together and cannot be separated. The bulb can be inserted from the rear of the reflector. The advantage of semi-sealed headlights is that only the bulb needs to be replaced when the filament burns out, while the disadvantage is poor sealing. Composite headlights integrate the front turn signal, front position light, high beam, and low beam into a single unit, with the reflector and lens made from organic materials as a whole. The bulb can be conveniently inserted from the rear. Using composite headlights allows car manufacturers to produce headlight lenses in any style as needed to improve the car's aerodynamic characteristics, fuel economy, and styling. 2. Sealed headlights: Sealed headlights are further divided into standard sealed headlights and halogen-tungsten sealed headlights. The optical system of standard sealed headlights involves welding the reflector and lens into a single unit to form the bulb housing, with the filament welded to the reflector base. The reflector surface is vacuum-aluminized, and the bulb is filled with inert gas and halogen. The advantages of this structure are excellent sealing, no atmospheric contamination of the reflector, high reflection efficiency, and long service life. However, if the filament burns out, the entire light unit must be replaced, which is costly. 3. Projection headlights: The optical system of projection headlights mainly consists of a bulb, reflector, shade, and convex lens. They use a thick, untextured convex lens, and the reflector is elliptical, resulting in a very small outer diameter. Projection headlights have two focal points: the first is the bulb, and the second is formed within the light beam.
When I first bought a car, I also thought the headlights were just ordinary lights. In fact, they are what we commonly call the main headlights, mainly divided into low beam and high beam. The low beam illuminates about 30 meters ahead without dazzling oncoming drivers, while the high beam can reach over 100 meters but should not be used indiscriminately in urban areas. Based on the light source, they are commonly categorized into halogen, xenon, and LED types. Halogen lights are affordable and perform well in foggy conditions, xenon lights are very bright but less effective in rain or snow, and LED lights are now the mainstream trend with ultra-long lifespan and energy efficiency. When modifying lights, remember to choose compliant models, otherwise, you might fail the annual inspection.
