Microstructure-Based Optical Film for Wide-Angle HUD Applications

Head-up display (HUD) can significantly enhance driving safety. However, when drivers turn their heads to observe road conditions, the brightness of existing HUD may reduce sharply. What is more, for a driver, the head movements in horizontal direction are usually much larger than movements in vertical direction. Therefore, the viewing angle of a HUD should be regulated to have larger horizontal angle. This paper designs an optical film with microstructures to regulate viewing angle of HUD based on digital light processing (DLP) projection. A simulation model is established in the optical design software LightTools. The simulation results show that the horizontal viewing angle of 50% maximum luminance increases from 14° without the optical film to 40° with the optical film. The optical film with the designed microstructures is prepared and measured. The practical measurement results indicate that the horizontal viewing angle of 50% maximum luminance increases from 14° without the optical film to 36° with the optical film, which proves the optical film can significantly expand the horizontal viewing angle. The proposed microstructure design method enables independent control of horizontal and vertical viewing angles, thereby accommodating a variety of application scenarios.