Imaging and non-imaging illumination of a DLP for high resolution headlamps

Matrix-LED systems offer different functionalities to increase road safety, e.g. glare-free high beam and marking light. Shortly after their introduction, efforts have been made to increase the amount of pixels. One of the results is the EVIYOS LED consisting of 1024 individually controllable pixels, which practically set the stage for pixel light systems. Current efforts to implement high-resolution pixel light systems are focused towards the exploration of an efficient light source in combination with the use of spatial light modulators. One approach to implement high-resolution pixel light systems is the use of LED arrays as a light source to illuminate a DLP. Unlike video projectors which require a homogeneous illumination of the DLP in order to obtain a homogeneous projection, headlamps require an inhomogeneous light distribution with high illuminance in the center. In order to receive a high system efficiency preforming the desired illuminance onto the active area of the modulator is advantageous. To further increase the systems efficiency an imaging illumination of the DLP, where the images of the emission surfaces of the LEDs are superposed onto the active area of the DLP, is worthwhile. In this paper, concepts for imaging and non-imaging illumination strategies of a DLP for high resolution headlamps will be introduced. For both illumination strategies the most promising concept will be selected to set up an optical system to illuminate a DLP. The paper concludes with a comparative analysis of the imaging and non-imaging optical system with regards to the system architecture and system efficiency