Dirt deposits influence on luminous flux distribution of passing lights

In each discipline of lighting technology where light has influence on the users' health and safety, for the use of lighting devices, the so called, maintenance systems was established. Based on the accepted algorithms, among the others, intervals of light sources replacement and cleaning of luminaries are determined. The subject of the influence of headlamps dust deposits' on their photometric parameters is very rarely tackled in the vehicle lighting technology. Probably the reason for this is the assumption that a driver will control visually lighting condition of his vehicle. Unfortunately, in practice this assumption is not met usually. Only a few vehicle models are equipped with headlamp washers or wipers. During normal service life of the vehicle the lenses of headlamps are cleaned occasionally, mostly during the vehicle washing, or sometimes after noticing heavy dirt deposits. However, internal surfaces of headlamp are not cleaned at all. Paradoxically, in the winter, when it gets dark earlier and headlamps' light is used for a longer periods, the vehicle cleaning is more rare, because of very low temperatures. The article present examples of measurement results of dirt deposits' influence on illuminance distribution changes on the road surface (on measuring screen) of headlamp equipped with halogen bulb and discharge light source. The concept of solving headlamp lens maintenance problem by using lens soiling detector, is also illustrated.