The reflector DE headlight has the form of a three-axis ellipsoid (DE). The reflector directs the light onto the focal point of a lens that projects the light, parallel and onto the road. The outline of the screen behind the lens is projected as the light-dark boundary onto the road. The DE Headlight is based on the principle of projection.
The projection system is very well suited for a deeper penetration through fog, since it can produce very sharp light-dark boundaries. However with the headlight low beam, soft and small proportions of scattered light are desired so that road signs (which are placed at a height above the road surface) are visible.
The DE headlight is advantageous when compared to the paraboloid headlight owing to a better lighting performance in the low beam and also requires a smaller mounting space. Long-range headlights however offer no significant advantages.
The variation parameters for adjustment of the lighting characteristics are:
Size and relation of the focal lengths and axes.
Position of the glowing filament in the reflector.
Size and focal length of the lens.
Optics of the headlight glass.