Geometric waveguide optimization for ghost reduction in near-eye light field display

Most near-eye displays with one fixed focal plane suffer from the vergence-accommodation conflict (VAC) and cause visual discomfort to users. In contrast, a light field display with continuous focal planes offers the most natural and comfortable AR/VR visual experiences without VAC and holds the promise to be the ultimate near-eye 3-D display. It projects light rays onto human retina as if the light rays were emanated from a real object. This paper considers a near-eye light field display comprising a light field generator, a collimator, and a geometric waveguide as the three main components. It takes 4-D light field data in the form of an array of 2-D subview images as input and generates a light field as output. The light field generator is the device responsible for converting the light emitted from the display panel to the light representing the light field of a virtual scene. The geometric waveguide along with a collimator ensures that the light rays propagating in the waveguide are collimated. The partially reflective mirrors of the waveguide replicate the optical path to achieve exit pupil expansion (EPE) and a large eyebox. However, existing waveguide eyepieces for near-eye AR/VR displays are not designed for, and hence may not fit light field displays. In this work, we look into a geometric waveguide for light field display and find that the light fields replicated by the partially reflective mirrors cannot perfectly overlap on the user's retina, resulting in the appearance of multiple repetitive images—a phenomenon we call "ghost artifact". This paper delves into the cause of this artifact and develops a solution for applications that require short-range interaction with virtual objects, such as surgical procedures. We define a working range devoid of noticeable ghost artifact based on the angular resolution characteristics of human eye and optimize the orientation of an array of partially reflective mirrors of the waveguide to meet the image quality requirement for short-range interaction. With the optimized waveguide, the ghost artifact is significantly reduced. More results of the optimized waveguide will be shown at the conference.