Good vision without blinding

You may have noticed if you have driven in a dark environment without street lighting or oncoming traffic. The image your normal headlights give is very different from that of a strong flashlight. The latter is a round light cone. If you have a Maglite where you can adjust the cone, you will see that you can choose between a concentrated or a fanned light shape. But your headlights give an angular image. It seems as if they shine to the right. That is also true.

Shine with your headlights on a wall and you can clearly see what's going on. It seems as if the light is cut in half from left to right. The upper half is not there and the right-hand side of the reflection slopes upwards. If you now switch to high beam instead of low beam you will see the picture change. If you now drive away from that wall and shine into the street, you will see that your lamps can shine farther to the right than forward. How is that possible? We look at a headlight with a double lamp. The double lamp in your headlight unit contains two filaments. One wire is the low beam and the other wire is for the high beam. With the low beam, there is also a cap for the filament, so that the light is bent downwards and through the bottom of the mirror in the lamp houses is radiated forward. That cap also ensures the sharp separation between light and dark and the asymmetrical light image. At the MOT inspection it is therefore also checked whether the position of the headlights is correctly adjusted. And whether the light image is still good. This to avoid dazzling. (There are, by the way lamp units with extra dividers. That differs per brand). However, xenon lighting is now fitted in a number of modern cars. Which sometimes also turns around in the bends. A great system that provides a lot more light than the old-fashioned light bulbs. Owners of youngtimers would like to build such lamps in their cars. But these lamps can also blind the oncoming traffic very easily and therefore they have to be perfectly adjusted. If you go to England with a car with this modern lighting you will have to take the left-hand traffic into account. The lamps should shine to the left instead of to the right. With 'normal' lighting you can cover the lamps with special stickers. However, that is not possible with the xenon lighting. The position of the headlight must be changed there. You can imagine that this is not very useful when you have to do this manually with your car by dismantling the complete headlight unit when you just get off the boat and it is dark and there is also an English rain shower . You will be 'not amused' to say the least.

Photo and text: Jacques van den Bergh