The design principle of automobile headlamp is to determine the refractive index of astigmatic mirror glass, the required diffusion angle and the width of the folding surface of small astigmatic mirror, and then calculate the surface size of the inner surface of the astigmatic mirror. As for the enclosed lamp, it has reached more than 90% popularity. The enclosed lamp is made of glass, which is a self-contained bulb. One end of the glass bulb has a joint, which can be electrified. It is the overall structure used as the headlamp body. The glass it uses is hard glass with very small coefficient of thermal expansion, the brightness is almost not reduced in use; it has a longer life, high quality and even quality than the previous bulb; because it has been standardized, it is easy to replace new products, and the maintenance is simple. The trend of using headlights in automobiles is increasing in Japan due to the influence of the wide popularity of corner type in the United States. The high efficiency halogen sealed light bulb with the advantages of closed type has also attracted people's attention at present, and the halogen sealed light bulb for automobile has been developed.