High dynamic range head-up displays.

TLDR: A full-color high dynamic range head-up display (HUD) based on a polarization selective optical combiner, which is a three-layer cholesteric liquid crystal (CLC) film, which indicates that the dynamic range can be improved by ∼50x (17 dB).

Abstract: We demonstrate a full-color high dynamic range head-up display (HUD) based on a polarization selective optical combiner, which is a three-layer cholesteric liquid crystal (CLC) film. Such a CLC film has three reflection bands corresponding to the three primary colors. A key component in our HUD system is a polarization modulation layer (PML) consisting of a twisted-nematic LC polarization rotator sandwiched by two quarter-wave plates. This spatially switchable PML generates opposite polarization states for the displayed image and its background area. Thus, this optical combiner reflects the displayed image to the observer and transmits the background noise, making the black state darker. Furthermore, by matching the reflection spectra of the optical combiner with the colors of the display panel, the bright state gets brighter. Therefore, both bright state and dark state are improved simultaneously. Our experimental results show that the dark state of the new HUD is lowered by 3x and bright state is boosted by 2.5x. By applying antireflection coating to the optical components and optimizing the degree of polarization, our simulation results indicate that the dynamic range can be improved by ∼50x (17 dB). Potential applications of the proposed HUDs for improving the driver’s safety are foreseeable.