Optical See-Through Head-Mounted Display With Mitigated Parallax-Related Registration Errors: A User Study Validation

For an optical see-through (OST) augmented reality (AR) head-mounted display (HMD) to assist in performing high-precision activities in the peripersonal space, a fundamental requirement is the correct spatial registration between the virtual information and the real environment. This registration can be achieved through a calibration procedure involving the parameterization of the virtual rendering camera via an eye-replacement camera that observes a calibration pattern rendered onto the OST display. In a previous feasibility study, we demonstrated and proved, with the same eye-replacement camera used for the calibration, that, in the case of an OST display with a focal plane close to the user's working distance, there is no need for prior-to-use viewpoint-specific calibration refinements obtained through eye-tracking cameras or additional alignment-based calibration steps. The viewpoint parallax-related AR registration error is indeed submillimetric within a reasonable range of depths around the display focal plane. This article confirms, through a user study based on a monocular virtual-to-real alignment task, that this finding is accurate and usable. In addition, we found that by performing the alignment-free calibration procedure via a high-resolution camera, the AR registration accuracy is substantially improved compared with that of other state-of-the-art approaches, with an error lower than 1mm over a notable range of distances. These results demonstrate the safe usability of OST HMDs for high-precision task guidance in the peripersonal space.