Signal Image Enhancement of Projection Type Headlamps by Additional Optics

The percentage of cars using a projection type headlamp is growing quickly. Lens diameters of 40mm, 60mm, and 70mm are being used in combination with halogen bulbs and gas discharge lamps.

The signal image of such projection systems can be improved by increasing the light emitting area with additional optics around the lens. This results in a more comfortable appearance of the headlamps from the viewpoint of oncoming cars. Different optical elements, e.g. Fresnel lenses, prisms, segmented reflectors, are used.

A large set of existing projection systems with additional optics around the projection lens is examined and rated by test persons regarding glare, size of the signal image and homogeneity. Also luminance measurements are presented. The correlation between these results are discussed and recommendations for the deign of signal enhancements are given.