It is an electric light source lamp, an improved type of incandescent lamp, was developed in 1960. Because its luminous efficiency can reach 22lm/W ~ 25lm/W, nearly double that of incandescent lamps, and its service life is greatly improved, it is widely used in headlamps soon, and the performance of the headlamp system has also been significantly improved. At present, the halogen bulbs used are mainly H1, H3, H4, H7, HB3, HB4, etc., among which H1, H4 and H7 are mainly used in headlamps, H1, H3 are mainly used in front fog lamps, HB3, HB4 are American standard headlight bulbs. The halogen bulbs under development are H8, H9, H11 and H13, etc. They are characterized by shortened filament diameter and filament length, improved luminous efficiency and less heat radiation, which is beneficial to improve the brightness of halogen headlamps and reduce lamps size.