The rearview mirror is divided by the mounting position and is divided into an exterior rear view mirror, a lower rear view mirror and an inner rear view mirror. Divided by purpose, the exterior rearview mirror reflects the rear side of the car, the lower rearview mirror reflects the front and rear of the car, and the rear view mirror reflects the rear of the car and the inside of the car. The use is different and the mirror structure will be different. Generally, there are two types of mirrors in the rear view. One is a flat mirror. As the name suggests, the mirror surface is flat. The terminology is “the radius of curvature R is infinite”. This is the same as the general household mirror. This type of mirror is often used as an interior rearview mirror. The other is a convex mirror with a spherical surface and a radius of curvature of different sizes. Its image is smaller than the visual field, but the field of view is large. It is like the role of a camera "wide-angle lens". This convex mirror is often used as an exterior mirror. And the rear view mirror. Cars and other light passenger cars are typically equipped with exterior and interior mirrors, while large commercial vehicles (buses and large trucks) are typically equipped with exterior rearview mirrors, lower rearview mirrors and interior rearview mirrors.