What is the purpose of the black line on the left rearview mirror of an Audi?

[VonJoy]

The function of the black line on the left rearview mirror of an Audi is to identify distance and position. Significance of the black line: The inner side of the black line provides a normal field of view for observing nearby conditions. Due to its larger curvature, it allows for a clear view of nearby situations, such as seeing the position of the rear wheels and adjacent vehicles when reversing. The outer side of the black line expands the driver's field of vision. During normal use, the Audi's rearview mirror combines two different curvatures to cover both near and far fields of view, effectively reducing blind spots and enhancing safety. Design principle of the Audi left rearview mirror: The black dotted line serves as a dividing line, with the right side being a flat mirror and the left side a convex mirror. This design can double the field of vision while maintaining minimal distortion and almost eliminating blind spots during turns, allowing the driver to see a panoramic view behind the vehicle.