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A method of evaluating the uniformity of an illumination pattern of an automotive head lamp on a road surface is presented. The most critical area where the beam pattern uniformity can be identified is the high intensity region. In this area three parameters are used to evaluate beam pattern uniformity, correlation set, contrast level and relative intensity factor gradient. In a low intensity region of the illumination pattern, the same principle can be applied.

A design strategy for implementing High Intensity Discharge (HID) light sources in low beam head lamps with Free-Form Reflectors (FFRs) is presented. A theoretical analysis of a light source image formed by each portion of a reflector is presented as well as a strategy for using those images to create a head lamp beam pattern. Simulation results are shown for a head lamp design using this strategy.

This paper discusses the optical design of motor vehicle head lamps using the new federal visual optical aim requirements. Methodology for using filament images from a head lamp reflector to create the required sharp gradient for visual aimable lamps is presented. The paper discusses hardware tolerance factors which would degrade a sharp cut-off, and methods are reviewed for accounting for and designing robustness against the tolerance factors. Hardware results are shown for designs using the techniques described in the paper.

A method to obtain a quantitative value for similarity between automotive beam patterns is presented. The use of the quantitative value for similarity is discussed in two contexts. First, similarity calculations are used to judge the correlation between computer predicted photometric performance and hardware photometric performance of Free-Form Reflector (FFR) low beam head lamps. A method for improving the similarity between hardware result and software prediction is discussed. In a second application, the similarity calculations are used to judge the resemblance of a benchmark beam pattern vs. three other beam patterns. In this application, we attempt to quantitatively judge whether a new “candidate” beam pattern exhibits similar behavior on the road as a benchmark or “goal” beam pattern. Finally, conclusions about the usage of beam pattern similarity are presented.

This paper discusses methodologies for the optical design of a High Intensity Discharge (HID) light source reflector optic low beam head lamp which meets visual optical aim (VOA) requirements. Methods of optimizing the gradient of the sharp cut-off required for visual aiming are presented. A merit function with conditional equations is introduced to optimize the design to maximize the gradient, maximize the hot spot, and control glare light. Design results are shown both before and after the design has been optimized.