Beam pre-shaping methods using lenslet arrays for area-based high-resolution vehicle headlamp systems

Abstract

High-resolution light distributions are lately in demand for vehicle headlamp systems as an innovative lighting approach. This lighting approach can realize functionalities, such as precise glare avoidance and on-road projection, which are useful for improving traffic comfort and safety. For achieving the required high-resolution light distribution, area-based projection technologies, such as DMD, LCD, and LCoS, are considered to be integrated into such headlamps. These projection devices demand rectangular illumination areas with specific light distributions to fulfill the requirements for illumination efficiency and performance in headlamp systems. Lenslet arrays, based on the principle of Kohler illumination, can effectively homogenize the light and shape it into rectangular shapes simultaneously. Such components are widely used in projection applications. However, they also show functional potentialities to be applied in high-resolution headlamps. This paper explains the design principles and methods of lenslet arrays for beam pre-shaping in headlamp systems. It validates the homogenization using a self-designed and manufactured lenslet array in a demonstrator in the first place. Afterward, this paper introduces two new methods for the centralized beam shaping required by some headlamps. These methods are validated by optical simulations.