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 Köhler 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.
Highlights
Vehicle headlamps have been undergoing rapid development by researchers and car manufacturers in recent years to improve traffic safety and comfort
The new generation of vehicle headlamp system comes to the high-resolution headlamp, which can provide functionalities, such as precise glare-free high beam and on-road lighting symbol projection [1,2]
A glare-free high beam optimizes the illumination condition for drivers by allowing full-time use of the high beam when driving in the night
Summary
Vehicle headlamps have been undergoing rapid development by researchers and car manufacturers in recent years to improve traffic safety and comfort. On-road projection enables lighting information to be displayed on the road, with which drivers can perceive information directly from the road, and communicate with other road users [2,4,5] These lighting functionalities require a high-resolution distribution from the headlamp. Because of this reason, area-based light modulator technologies, for example, LCD (liquid crystal display), DMD (digital micromirror device), and LCoS (liquid crystal on silicon) are considered to be integrated into headlamp systems [6,7,8,9,10]. Sci. 2020, 10, 4569 to have a reliable light shaping method to fulfill the relevant requirements for headlamp systems and achieve a good projection performance simultaneously
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