Design, fabrication, and testing of freeform mirror-based head-up display system

Abstract

Head-up displays (HUDs) in aircraft, spacecraft, and automobiles are principally considered a safety assistance system. HUDs are transparent displays that are installed in the vehicle in an order that the observer, driver, or pilot can see pertinent information in their line of sight. Current HUD systems are developed with conventional optics, which requires a large amount of space occupancy in the cabin or cockpit, thus creating accommodation challenges for the other devices. HUD systems containing multiple components have more operational challenges such as precise micron-level angular movement of folding mirror and associated significant amount of power drain of the vehicle’s battery. In this research article, a HUD design containing a single freeform mirror without compromising the optical performance of the system is proposed. The novel design provides the opportunity to make the system more compact and energy efficient as no separate electro-mechanical component is required for beam folding and additional tracking devices. Also, the larger Eyebox dimension obtained with the use of freeform mirror makes the HUD system definitive for extreme operational conditions and flexible observation from various heights. With the utilization of concurrent engineering, a two-phase authentic developmental process chain is presented for the freeform mirror-based HUD system. Ultra-precision single-point diamond turning with on-machine surface measurement is utilized to convert the design of various surfaces to physical functional elements of sub-micron level form accuracy and nano-metric level surface roughness. Finally, the HUD system is validated through optical functional testing.