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Automatically dimming

Admittedly, the Americans have been driving around with them for along time now. They place a lot of value on having comforts that they don't have to pay any attention to. In addition of course, an automatically dimming rear-view mirror is also a useful safety feature, because one doesn't have to switch it back and forth all the time. After all, we're constantly being reminded, “keep your hands on the wheel!”

Indeed, how does this wonder-work function, it's hardly any bigger than a rear-view mirror? It is in fact, a complete system with sensors and actuators in the smallest possible space. It does of course, need a power supply, through which the sensors can be called up, as a rule, one to the front and one to the rear. The one shown in our picture, has two to the rear. The brightness is compared, and if more light is coming from the rear than from the front, it is continually dimmed.

This mirror has not only one pane of glass but two, and a sort of liquid, which is made up of uniformly shaped crystals. Normally, they are to be found, well distributed between the two sealed glass panes. In older luxury class vehicles, sometimes a part of the liquid is missing or wrongly distributed. The mirror then has to be replaced, which is pretty expensive.

If the distribution between the glass panes is ok, an AC-current of around only one volt is sufficient to change the position of the crystals, and with the current, to also absorb (or 'swallow') more and more light. Thus the blinding effect on the driver is reduced. Of course, one must realise that, through the dimming effect, the vision to the rear is also restricted. 10/13