Three-dimensional varifocal meta-device for augmented reality display

Abstract

Augmented reality (AR) displays have gained significant attention for their ability to blend the real and virtual worlds seamlessly. However, they face challenges like the vergence-accommodation conflict and a limited eyebox. The AR community is actively seeking lightweight, integrative optical elements to overcome these limitations. In this study, we demonstrate a three-dimensional varifocal meta-device for AR display. The meta-device is composed of three cascaded metasurfaces with Moiré and off-center Fresnel lens phase profiles designed to dynamically manipulate the focus point in three-dimensional space. The cascaded metasurfaces are designed and fabricated by the TiO2 nanopillars with varying diameters, which are polarization-insensitive for light field manipulation. The focal point position is precisely controlled by the relative rotation between the metasurfaces. The meta-device achieves an effective focal length ranging from 3.7 mm to 33.2 mm and can adjust the lateral focal point within the same range. The dynamic eyebox size varies from 4.2 mm to 5.8 mm. This lightweight, integrated meta-device is well-suited for various imaging applications, including AR displays, as it simultaneously addresses the vergence-accommodation conflict and expands the eyebox.