The properties of headlamps with regard to good visible range and illumination at minimum glare levels - with a distinction being made between glare to oncoming traffic and driver self-glare due to reflected stray light - are influenced to a major extent by soiling on the cover lens. To be able to visualise and analyse the correlations between degree of soiling and the above-mentioned effects, identical standard headlamps with halogen and xenon equipment and different degrees of soiling were examined in Hella's light testing facility in terms of visible range and glare properties. The results of the light testing facility examinations were evaluated objectively on the basis of Isolux measurements with clean reference headlamps as well as headlamps with exchangeable cover lenses with different degrees of soiling. The effects are basically independent of the light system used. On account of the high power and correspondingly high luminance of xenon headlamps, the effect of glare is much more pronounced with these systems. In terms of visible range, on the other hand, it is much more important for less powerful headlamps not to have their performance reduced even further due to soiling. Whereas the performance of xenon systems - even when heavily soiled - is still better than that of clean halogen systems in terms of visible range, the effect of quite normal soiling leads to such a decline in performance with halogen systems that it has to be regarded as a critical safety factor in terms of a sufficient visible range in road traffic.
Effects of soiling on the photometric properties of headlamps
Auswirkungen der Verschmutzung auf die photometrischen Eigenschaften der Scheinwerfer
2005
10 Seiten, 10 Bilder
Aufsatz (Konferenz)
Englisch
Compact low-cost unit for photometric testing of automotive headlamps
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