HUD projection correction method based on equal optical path difference

With the continuous development of the automotive industry, head-up display (HUD) technology has become widely implemented in modern vehicles. However, in the HUD off-axis three-mirror system, the curved shape of the windshield causes image distortion, negatively affecting the driver’s visual experience. To address this issue, this paper proposes a correction method for HUD projection based on optical path difference. Using the equal optical path difference criterion, the optical path difference from the eye box to the main reflector is calculated to determine the deflection value of the main reflector (M2). Subsequently, Zemax simulation software is used to correct the deflection of M2 and the subsequent overall structure. The subsequent surface positions are determined using the main ray tracing method. The simulation results demonstrate that this approach effectively corrects the projection tilt, yielding high-quality HUD projection images. Moreover, it simplifies the optimization process of system components, improving the overall performance and visual experience. This method offers a practical solution for enhancing HUD image quality in real-world driving conditions.