Projected Augmented Reality to Guide Manual Precision Tasks: An Alternative to Head Mounted Displays

Augmented reality (AR) devices are gaining popularity in industrial development and healthcare as they provide information that would not be accessible in a rapid and intuitive way. Head-mounted displays dominate in this field and are currently being comprehensively tested. Alongside its informative function, AR can be used to steer the user's actions to aid complex or high precision tasks. This is the case in surgery, which is recently seeing the development of ad-hoc head-mounted displays to meet the requirements of safety, ergonomics, and reliability. However, head-mounted displays are subject to perceptual problems that can affect their use in delicate and demanding tasks. This article aims to evaluate projected AR as an alternative to head mounted displays (HMDs) when accurate guidance on the surface is needed. We directly compare them in a user study and evaluate both user accuracy and user perception to assess whether projected AR can be a practical and useful paradigm for precision manual tasks. Ten users performed tracing trajectory tasks under the guidance of an HMD and a projected AR device. Three accuracy levels were quantitatively tested: 0.5, 1, and 2 mm. Statistical analysis showed no significant difference in the accuracy of the two AR visualization modes, whereas the user perception assessment revealed statistical differences in virtual-to-real perception and visual discomfort. The quantitative results of this article proved that both technologies can guide manual precision tasks with the same accuracy, but projected AR features some perceptual advantages.