Modern Streamline Car Shapes - Challenges for the Optical Design of Signal Functions in Headlamps

Doris Boebel, Norbert Möller; Automotive Lighting, Germany

Keywords:       Headlamp styling, signal functions, photometry, visibility requirements

Introduction

The actual trend in the styling of cars shows a growing lengths and inclination of the outer lens of headlamps. Especially the inclination is contradictory to the requirements of signal lamps regarding several photometrical aspects. On one side the efficiency of the function is reduced by Fresnel losses in the outer lens and in additional inner lenses, if used. Also the requirements on the homogeneity of the day and night appearance are difficult to fulfill, if the dimension of the light emitting area parallel to the driving direction is getting longer in comparison to the “useful” dimension normal to driving direction. The main aspect discussed in this paper is the visibility of the signal functions. Especially the visibility requirements 45 degrees inboards are hard to fulfill if the inclination of the outer lens converges to this critical angle. In this paper principal limitations and optical solutions to direct the light 45 degrees inboard are shown as well as practical solutions to apply in headlamps.