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The first DE headlamps were produced by Hella as driving lamps as early as 1905. Our engineers were the first to develop DE dipped beam headlamps to mass production maturity in the 80s.
DE stands for "triaxial ellipsoidal" describing the shape of the reflector surfaces. It allows for particularly small headlamps with high light output. Their operation is similar to that of a slide projector, which also explains the designation "projection system".

The ellipsoidal reflector reflects the light from the bulb concentrating it at the "second focal point"

A shield, acting in the same manner as a slide, limits the light distribution producing the cut off.

A lens projects the light onto the road.

The projection system is exceptionally well suited for penetrating fog because of its extremely sharp cut off. However slight "fuzziness" and a small percentage of stray light is desirable for dipped beams so that traffic signs hanging above the roadway will also be visible.

Today DE systems are used primarily for fog lamps.
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Effective reflector area and shape of shield, front view.
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Creation of cut off and shading with shield, side view.
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Beam path and light concentration at focal point, top view.
Useable light approx. 36%

1. Reflector 2. Light source 3. Shield 4. Cover lens
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Typical dipped beam distribution from DE headlamp as Isolux diagram.
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Typical dipped beam distribution from DE headlamp at cover lens.

 

 
* 1 lx (unit of illuminance) proves just enough light to read a newspaper.

Next: Super DE (combined with FF)

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