There are always riders who say what is the black line in the rearview mirror? To tell you the truth, Xiaobian didn't understand the automobile industry at all when he didn't contact with it. It was also out of curiosity, so I'll give you a popular science today

因為這種后視鏡用的是雙曲率鏡片，也就一個鏡片2種曲率，后視鏡內側的2/3鏡片采用平面鏡，外側的1/3鏡片采用凸面鏡，中間就是這條黑線分隔以讓駕駛員更好的看清后面的情況。

Because this kind of rear-view mirror uses hyperbolic lenses, that is to say, one lens has two kinds of curvature. The two-thirds of the lenses inside the rear-view mirror are flat mirrors, and the one-third of the lenses outside the rear-view mirror are convex mirrors. This black line is used in the middle to separate them, so that the driver can better see the situation behind.

1、平面鏡部分用來觀察車身側面較近位置的情況。

1. The flat mirror part is used to observe the near position of the body side.

2、凸面鏡部分用來觀察車身側面較遠位置的情況，另外可以減少后視鏡的盲區，轉彎時視野擴大了兩倍，幾乎可以完全消除盲點。

2. Convex mirror is used to observe the far position of the side of the car body. In addition, it can reduce the blind area of the rear-view mirror. When turning, the field of vision is doubled, and the blind spot can be almost completely eliminated.

3、雙曲率鏡面技術原理：依據車型、駕駛員眼點位置與后視鏡相對位置、視野要求三個要素，運用光學原理和數據方法，對車輛的前后左右不同視野角度選擇不同的曲率半徑，并平滑過渡。

3. The principle of hyperbolic mirror technology: according to the vehicle type, the driver's eye position and the relative position of the rearview mirror, and the field of vision requirements, using optical principles and data methods, different curvature radii are selected for the front, back, left and right different field of vision angles of the vehicle, and the smooth transition is achieved.

這樣，能夠在滿足基本不失真的條件下進一步擴大視野、減少盲區，既滿足了國家強制性標準，又解決了盲區問題。另外，在鏡面的設計上采用分界線的辦法來警示駕駛員變曲率面僅供觀察車后大致情況。

In this way, we can further expand the field of vision and reduce the blind area under the condition of basically no distortion, which not only meets the national mandatory standards, but also solves the problem of blind area. In addition, in the design of the mirror, the dividing line method is used to warn the driver, and the variable curvature surface is only used to observe the general situation behind the car.