Vehicle-mounted waveguide head-up display system based on reflective microprism

The traditional vehicle-mounted augmented reality head-up display system is limited by the large size of the optical lens. The space when installed in the car is very limited. This paper proposes an optical waveguide structure based on multiarea reflective microprism for use in a vehicle-mounted augmented reality head-up display system, which can adapt to the narrow installation space of the dashboard area in the vehicle. The input coupling end of the waveguide structure adopts a transflective film with a specific beam splitting ratio placed obliquely instead of a flat mirror, where the transmitted light beam through the transflective film directly enters the exit pupil, which can reduce the use of a microprism structures and reduce the volume of the waveguide. The reflected light beams continue to propagate in the horizontal and vertical waveguides in sequence, and are coupled out through the right-angle triangular prism array microprism structure with different duty ratios to achieve a two-dimensional exit pupil expansion. Through theoretical calculation and simulation optimization, the results show that when the field of view is 10°×5°, the uniformity of illuminance on the exit pupil within the eyebox range of 140mm×60mm reaches more than 70%, the horizontal waveguide size is 324mm×37mm×30mm, and the vertical waveguide size is 324mm×146mm×12mm, and the head-up display system volume is less than 4L, which has great potential for in-vehicle applications.