The working principle of car headlights varies by type, which are mainly divided into four categories: halogen, xenon (HID), LED, and laser. The halogen gas (such as iodine or bromine) filled in the lamp can form a cyclic reaction with the volatilized tungsten, extending the filament's lifespan to approximately 1000 hours. Their colour temperature is around 3200K, with low cost but high energy consumption. Xenon headlights use high-voltage pulses (about 20000V) to activate xenon gas and generate arc light, with a colour temperature of 6000K-10000K. They are 3 times brighter than halogen headlights and have lower energy consumption, but require a ballast. LED headlights emit light through the recombination of electrons and holes in semiconductor materials, featuring instant response, long lifespan (over 50000 hours), and high energy efficiency (energy consumption is only 1/5 of that of halogen headlights). Their colour temperature is usually 5000K-6000K, and they are widely used in modern vehicle models. Laser headlights produce white light by using blue lasers to excite phosphors, with an irradiation distance of up to 600 meters, small size, and extremely low energy consumption, but have a high technical threshold. In addition, the automatic headlight system monitors ambient brightness through a photoresistor and automatically turns on when the illuminance is below 75 lux. Some vehicle models also integrate matrix technology, which can shield the light of oncoming vehicles in zones. The irradiation distance of low-beam headlights is about 40-60 meters, while that of high-beam headlights reaches 100-150 meters. It is best to regularly check the light transmittance of the lamp cover (cleaning is required if it is below 70%) and the status of the bulbs. When replacing bulbs, the beam angle needs to be adjusted (the horizontal deviation should not exceed 1%).
