Headlamp innovations: optical concepts for fully adaptive light distributions

Glare avoidance and marking lights are two of the many functionalities offered by advanced automotive headlamps such as Matrix-LED systems. DMD-based headlamps offer resolution enhancements to these two adaptive lighting functionalities. This is achieved via a precise optical system that exhibits high marking and glare avoidance efficiencies. This work evaluates two concepts for an optical system that enables fully adaptive light distributions. Light distributions from automotive headlamps are characterized by a wide aspect ratio and a centrally located hotspot marked by a high luminous intensity. Due to the popular use of DMDs in video projectors, DMD properties counter-productive to automotive applications are regularly encountered. For example, DMDs for projectors require to be illuminated homogeneously in order to obtain a homogeneous projection whereas headlamps require a hotspot centric distribution. It is possible to digitally create a hotspot with conventional projection optics but the results come with a significant loss in optical efficiency. The two concepts for an optical system compared in this paper are: anamorphic optics and optics with pincushion distortion. This comparison is conducted using optical simulations. Photometric measurements are then taken from a vehicle headlamp based DMD and distorting optics and compared with the simulation as a validation step. Due to the strong distortion of the lens system the relation between the DMD image and the final light distribution is highly non-linear. The paper is concluded with key observations with regards to this non-linearity.