Abstract
Stereoscopic augmented reality (AR) displays have a fixed focus plane and they suffer from visual discomfort due to vergence-accommodation conflict (VAC). In this study, we demonstrated a biocular (i.e. common optics for two eyes and same images are shown to both eyes) two focal-plane based AR system with real-time gaze tracker, which provides a novel interactive experience. To mitigate VAC, we propose a see-through near-eye display mechanism that generates two separate virtual image planes at arm’s length depth levels (i.e. 25 cm and 50 cm). Our optical system generates virtual images by relaying two liquid crystal displays (LCDs) through a beam splitter and a Fresnel lens. While the system is limited to two depths and discontinuity occurs in the virtual scene, it provides correct focus cues and natural blur effect at the corresponding depths. This allows the user to distinguish virtual information through the accommodative response of the eye, even when the virtual objects overlap and partially occlude in the axial direction. The system also provides correct motion parallax cues within the movement range of the user without any need for sophisticated head trackers. A road scene simulation is realized as a convenient use-case of the proposed display so that a large monitor is used to create a background scene and the rendered content in the LCDs is augmented into the background. Field-of-view (FOV) is 60 × 36 degrees and the eye-box is larger than 100 mm, which is comfortable enough for two-eye viewing. The system includes a single camera-based pupil and gaze tracker, which is able to select the correct depth plane based on the shift in the interpupillary distance with user’s convergence angle. The rendered content can be distributed to both depth planes and the background scene simultaneously. Thus, the user can select and interact with the content at the correct depth in a natural and comfortable way. The prototype system can be used in tasks that demand wide FOV and multiple focal planes and as an AR and vision research tool.
Highlights
There is a rapid growth in the development of three-dimensional (3D) virtual and augmented reality (AR) displays in recent years
In conventional see-through near-eye displays, a pair of parallax images for two eyes are rendered in flat displays so that a virtual image is created at different depths according to the amount of binocular disparity using separate optics for the two eyes
Many recent studies show that vergence-accommodation conflict (VAC) is one of the most significant causes of visual discomfort [3] and it might even lead to error in the perception of the scene geometry [4]
Summary
There is a rapid growth in the development of three-dimensional (3D) virtual and augmented reality (AR) displays in recent years. Despite sophisticated depth sensors and pupil trackers, the system cannot render information at different depth simultaneously and cannot render objects at arm’s length since the depths of focal planes are 1 m and 3 m [14] Even this sophisticated system cannot provide comfortable interaction with objects at arm’s length due to severe VAC and visual discomfort. The biocular implementation provides full motion parallax within the movement range of the user (about 5 cm in both horizontal and vertical directions), which significantly enhances the 3D feeling and removes the complexity and inaccuracies related to head trackers needed in binocular displays This second point is especially worthwhile to emphasize, because during interaction with arm’s length objects, even minor inaccuracies of head trackers lead to noticeable vibrations and jumps in object positions, creating disturbing effects.
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