This paper addresses the challenges of low optical efficiency and poor image uniformity in waveguide-based augmented reality (AR) displays, which are critical for long-term usage and user experience. The authors identify an anomalous polarization conversion phenomenon in polarization volume gratings (PVGs) when the incident light direction does not satisfy the Bragg condition. This phenomenon is leveraged to improve in-coupling efficiency and uniformity without compromising eyebox continuity. Through experiments and simulations, the authors demonstrate that using PVGs with first-order polarization conversion can enhance in-coupling efficiency by 2 times and uniformity by 2.3 times compared to conventional couplers in a 50° field of view (FoV) waveguide display. The study also explores the potential of multi-layer PVGs to further improve efficiency and uniformity, especially for full-color displays. The findings suggest that PVGs could revolutionize next-generation waveguide-based AR displays by achieving higher efficiency and superior image uniformity.This paper addresses the challenges of low optical efficiency and poor image uniformity in waveguide-based augmented reality (AR) displays, which are critical for long-term usage and user experience. The authors identify an anomalous polarization conversion phenomenon in polarization volume gratings (PVGs) when the incident light direction does not satisfy the Bragg condition. This phenomenon is leveraged to improve in-coupling efficiency and uniformity without compromising eyebox continuity. Through experiments and simulations, the authors demonstrate that using PVGs with first-order polarization conversion can enhance in-coupling efficiency by 2 times and uniformity by 2.3 times compared to conventional couplers in a 50° field of view (FoV) waveguide display. The study also explores the potential of multi-layer PVGs to further improve efficiency and uniformity, especially for full-color displays. The findings suggest that PVGs could revolutionize next-generation waveguide-based AR displays by achieving higher efficiency and superior image uniformity.