Abstract
In non-orthostereoscopic video see-through (VST) head-mounted displays (HMDs), the perception of the three-dimensional space is negatively altered by geometrical aberrations, which may lead to perceptual errors, problems of hand-eye coordination, and discomfort for the user. Parallax-free VST HMDs have been proposed, yet their embodiments are generally difficult to create. The present study investigates the guidelines for the development of non-orthostereoscopic VST HMDs capable of providing perceptually coherent augmentations for close-up views, hence specifically devoted to guide high-precision manual tasks. Our underlying rationale is that, under VST view, a perspective-preserving conversion of the camera frames is sufficient to restore the natural perception of the relative depths around a pre-defined working distance in non-orthostereoscopic VST HMDs. This perspective conversion needs to account for the geometry of the visor and the working distance. A simulation platform was designed to compare the on-image displacements between the direct view of the world and the perspective-corrected VST view, considering three different geometrical arrangements of cameras and displays. A user study with a custom-made VST HMD was then conducted to evaluate quantitatively and qualitatively which of the three configurations was the most effective in mitigating the impact of the geometrical aberrations around the reference distance. The results of the simulations and of the user study both proved that, in non-orthostereoscopic VST HMDs, display convergence can be prevented, as the perspective conversion of the camera frames is sufficient to restore the correct stereoscopic perception by the user in the peripersonal space.
Highlights
In ideal visual augmented reality (AR) systems there should not be any perceivable difference between the user’s natural view of the world and his/her augmented view through the display
We identify and mitigate the perceptual problems caused by the optical aberrations inevitably present in non-orthostereoscopic video see-through (VST) headmounted displays (HMDs) that are designed to guide high-precision manual tasks
We aim to provide a conclusive answer as to whether, in order to mitigate the perspective distortions due to the optical aberrations in VST HMDs, the convergence of the cameras should be associated with an equivalent physical rotation of the displays, or a perspective correction using software is sufficient
Summary
In ideal visual augmented reality (AR) systems there should not be any perceivable difference between the user’s natural view of the world and his/her augmented view through the display This is especially true when they are designed to aid complex manual tasks that demand great dexterity (e.g., surgical procedures). Avoiding this difference entails an accurate AR registration and ergonomic interaction with the augmented scene. To ensure a consistent perception of the augmented world and to improve the interaction with it, the real world and the virtual enrichment must be perfectly integrated with each other photometrically, temporally, and spatially
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