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.