What is the Principle of Auto-Dimming Rearview Mirrors?
2 Answers
Anti-glare rearview mirrors can be divided into two types: manual anti-glare and auto-dimming, each with different working principles. Below is an introduction to the principles of anti-glare rearview mirrors: 1. Principle of manual anti-glare rearview mirrors: The mirror of a manual anti-glare rearview mirror is not a flat mirror with uniform thickness but a wedge-shaped mirror with an angle of approximately 10°. When the anti-glare lever is pushed forward, the entire mirror tilts upward by about 10°. At this point, what is observed is only the semi-transparent light-transmitting coating of the rearview mirror, which has a lower refractive index to light, thus providing a certain anti-glare effect. 2. Principle of auto-dimming rearview mirrors: An auto-dimming rearview mirror consists of a special mirror, two photodiodes (front and rear), and an electronic control unit. The electronic control unit receives signals from the front and rear photodiodes. If the rear photodiode detects stronger light than the front one, the electronic control unit outputs a voltage to the conductive layer of the mirror. This conductive layer then changes the color of the mirror's electrochromic layer (the higher the voltage, the darker the color). As a result, strong light reflected by the anti-glare rearview mirror to the driver's eyes appears dim and non-glaring. 3. Usage of anti-glare rearview mirrors: For manual anti-glare mirrors, the method is to toggle the anti-glare lever located below the mirror. Auto-dimming rearview mirrors, except for a few models that can be manually turned on or off via buttons on the mirror, are typically enabled by default.
I guess you might be asking this because you're bothered by the high beams from the car behind you at night, right? Actually, the core of this thing relies on two light sensors. The small dot on the windshield is responsible for monitoring the brightness of the headlights behind you, and there's also a forward-facing sensor checking the cabin light. It's quite smart in calculations—when it detects that the headlights behind are much stronger than those in front, the liquid crystal layer starts to darken, similar to how your LCD TV adjusts brightness. The most considerate part is that it remembers your settings and automatically restores them the next time you get in the car. However, I should remind you that it can't do anything about the headlights from cars behind you shining through the side windows.
