This paper deals with the generation of different light distributions for LED headlamps, especially with an adequate cut-off. Based on diverse optical systems the efficiency of shutter-less solutions for improved light output will be discussed. Relevant surfaces, responsible for generating the cut-off (CPC, CHC, parabolas) have been pre-analysed regarding optical and mathematical aspects. Such surfaces have been integrated in different optical systems to provide the desired light distributions and than enhanced via a software-based optimisation progress. Thereby it is irrelevant whether the light distribution is including a z-shape, a slope of 15 or only with a horizontal cut-off. Due to these different options a higher flexibility in design, an excellent and efficient illumination on the road is provided. All these systems have been implemented in different combinations in prototype headlamps, which have been tested and evaluated in road trials. Their variability allows to create compact headlamp modules generating the complete low beam distribution. The system's high efficiency is able to compensate the insufficient luminous flux of today's LEDs compared to state-of-the-art HID-systems. The regulation ECE R 98 specifies an cut-off contrast level of 19 Ix per 1,15 deg of angle This is resulting from the 1 Ix limit in the HV and the required minimum of 20 Ix in 75 R In the low beam distribution showed below an increase of 40 Ix per 1,15 deg of angle is obtained It is possible to change the value of the increase from the upper to the lower legal limit by only a small modification of the primary lens. Equipped with an additional small reflector as well as two additional primary lenses and the associated LED's a high beam can be realized The saved space in this compact construction gives us the opportunity of implementing other functions like static bending light, fog lamp or IR-night view function.
Cut-off generation for LED - headlamps
Herstellung des Begrenzungsbereichs von LED-Scheinwerfern
2007
9 Seiten, 17 Bilder, 4 Quellen
Aufsatz (Konferenz)
Englisch
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