Among solid-state light sources, LEDs are used as representatives. Previously, LEDs were only used in signal lights, but with the development of technology, LEDs will also be used in headlights. The use of white LEDs can increase the freedom of vehicle design and reduce the thickness of the headlights, and is especially suitable for compact cars and side lighting systems (the lighting system can turn according to the direction of the steering wheel when turning). At present, the factors restricting the use of LEDs in headlamps are: a) The standards for the shape and voltage of white LEDs have not yet been determined. b) The luminous efficiency of white LEDs is low, only 20lm/W ~ 30lm/W; on the contrary, the heat generation is extremely high, and heat dissipation measures must be taken. C) There are only a few manufacturers that can provide high-power white LEDs, and there is no mass production. However, the thinness of LED headlamps and the unique multi-point lighting function will make it a trend for compact car headlamps. At present, Nissan, Honda, Toyota and other Japanese car manufacturers and Daimler- Some compact car concept cars designed by Chrysler are also equipped with LED headlights.