Design of a head-up display based on freeform reflective systems for automotive applications

Automotive head-up display (HUD), a typical application in augmented reality (AR), has gained popularity in recent years. In this paper, we propose a novel design configuration of freeform off-axis three-mirror systems for automotive head-up display (HUD) application. In the configuration, the image source, the flat mirror, and the freeform mirror are allocated on the same horizontal level to guarantee a compact structure as well as to make the optical elements easy to be assembled. The whole design philosophy and procedure, including the analytic method to determine initial structure, structure constraints, and optimization strategy, are demonstrated in detail. Superior optical performance is achieved regardless of the pupil being located at any position inside a rectangular eye box.