At one time, professor at New York University Alan Lewis (Lewis) studied in detail the so-called Troxler effect that occurs when blinding with bright light. As it turned out, in addition to short-term loss of vision, the driver’s reaction time also increases, up to 1.4 s. During this time, at a speed of 100 km / h, the car travels about 40 m! It is worth the effort and money to solve the problem.
This is how the automatically darkening mirrors NVS (Night Vision Safety) appeared. The transparency of the glass is controlled by a controller comparing signals from two photosensors. The first, directed forward, measures the general illumination, the second, looking back, catches the rays of the headlights of the cars traveling behind you. Too much difference between the readings of the sensors (dark front, bright back) indicates the danger of blinding! A command is issued immediately to darken the glass of the mirrors.
Want to see how automatic mirror dimming works? A colleague once tried to shine a lighter with the flame of it, but only “dimmed” the ceiling. Everything is much simpler. Feel the window on the back of the case and close it with your finger. The same difference in lighting will appear, and you will be able to observe how the picture is “tinted” in the mirror …
The early versions were arranged similarly to the liquid crystal displays of calculators: a thin layer of liquid was enclosed between two glass plates, which changes the coefficient of light absorption under the influence of an applied electric voltage. The disadvantage is that performance is reduced at low temperatures (however, such mirrors are usually heated).