Robust optical design for high-contrast cut-off line in vehicle forward lighting

In this paper, we proposed and demonstrated a new optical design scheme for vehicle forward lighting with a high-contrast cut-off line. We first presented a design of a reflector to meet that meets one regulation (e.g., K-mark) but fails in the other regulation (e.g. ECE R113 class A). The design starts from a general approach in forming the cut-off line but with a narrower light pattern to fit the first regulation. Then an optimized cylindrical lens array (CLA) is used to laterally spread the light pattern. The introduction of the CLA can increase the linearity of the cut-off line, and most importantly, suppress the illuminance in the dark zone so that contrast across the cut-off line can be effectively increased. As a result, the headlamp can pass the severer regulation without redesigning the reflector. Additionally, the CLA can compensate for the optical effect by lens/reflector deformation in the manufacture process so that the manufacturing tolerance can be enlarged and the design scheme of forward lighting becomes easier and more robust in practical manufacturing.