Optical Near Field Measurements and Ray-Tracing Simulations of Coated and Uncoated Halogen Lamps for Glare Analysis

Automotive lamps for headlights are constantly reevaluated for causes of glare issues. Lead wires, glass, sockets and even filaments reflect and/or scatter the light from the filament into undesired directions, possibly causing glare. The best way to account for scattered light in the design process is to measure the near field radiation pattern. A high-resolution camera on a goniometer is used to characterize the headlamp. The results are further analyzed in an optical ray-tracing package. This paper will look at the new double filament lamp (H13) in respect to glare as well as the effect of “cool blue” absorption coatings. Measurements of the emission patterns of the lamps with and without coating are compared. A ray-tracing model will simulate the effect of the coating and amplify the effect to determine how much increase in scattering is necessary to cause a glare problem. The goal is to show that the measured effect of absorption coatings on lamps is too small to cause glare.