Research on Automatic Design Method of Double Freeform Surface Ar-Hud Imaging System

An automotive augmented reality head-up display (AR-HUD) system is affected by many complex phenomena, such as the influence of moving eyeballs, drivers’ heights, additional aberration correction required due to windshields, and variable structural constraints of vehicle model and other factors. Consequently, it is difficult to optimize the design of such a system. To mitigate this problem, we propose an automatic design method for the automotive AR-HUD imaging system, which is suitable for two freeform surfaces and any type of windshield structure. Based on Malus Law, all the characteristic data points of the freeform surface in the full field of view and full aperture are calculated. Subsequently, the points are fitted to the free-form surface represented by polynomials. The initial structure of the free-form off-axis system with a good imaging quality is directly obtained. Finally, the optical path feedback iterative method is used to further optimize the data point cloud of each field of view to determine the best fitting coefficients, generate the required freeform mirror, and obtain the final structure of the AR-HUD optical system. The proposed AR-HUD designs for an eye-box of and a field of view of exhibit excellent optical performance, demonstrating the feasibility and superiority of the proposed design framework.