Effects of Depth Layer Switching between an Optical See-Through Head-Mounted Display and a Body-Proximate Display (1909.02988v1)

Abstract: Optical see-through head-mounted displays (OST HMDs) typically display virtual content at a fixed focal distance while users need to integrate this information with real-world information at different depth layers. This problem is pronounced in body-proximate multi-display systems, such as when an OST HMD is combined with a smartphone or smartwatch. While such joint systems open up a new design space, they also reduce users' ability to integrate visual information. We quantify this cost by presenting the results of an experiment (n=24) that evaluates human performance in a visual search task across an OST HMD and a body-proximate display at 30 cm. The results reveal that task completion time increases significantly by approximately 50 % and the error rate increases significantly by approximately 100 % compared to visual search on a single depth layer. These results highlight a design trade-off when designing joint OST HMD-body proximate display systems.

• The paper found that splitting visual information between an AR HMD and a body-proximate display significantly increased task completion time (50%) and error rate (100%) compared to using the HMD alone.
• These results indicate that depth layer switching in multi-display AR systems imposes increased cognitive and visual load, requiring careful design to avoid performance degradation in critical applications.
• Future research could explore vari-focal HMDs or strategies to minimize simultaneous processing across different depth layers to mitigate the performance costs identified in this study.

An Examination of Depth Layer Switching in Multi-Display Environments

The paper "Effects of Depth Layer Switching between an Optical See-Through Head-Mounted Display and a Body-Proximate Display" investigates the performance ramifications of using Optical See-Through Head-Mounted Displays (OST HMDs) in conjunction with body-proximate displays, such as smartwatches or smartphones. The primary focus is on understanding the integration performance costs incurred when visual information is distributed across these two different depth layers.

Study Motivation and Context

OST HMDs, like the Microsoft HoloLens, are gaining traction in various industries. They typically display virtual content at a fixed focal distance, which presents a challenge when integrating information from other sources at different focal depths. This paper is vital in an era where body-proximate multi-display systems are being explored for expanding OST HMD functionality—essentially augmenting the display area and providing more reliable input interfaces.

The experiment conducted in the paper evaluates how the performance of a visual search task is affected when information is presented at a single focal depth on an HMD versus when it is distributed across both an HMD and a nearby display. Prior research indicates that OST HMDs introduce increased visual and cognitive load, particularly when integrating virtual and real-world information across different focal distances.

Experimental Design and Results

The experiment, involving 24 participants, used a within-subjects design to assess task performance across two conditions:

1. HMD-only display, where the task was executed solely using the HMD.
2. HMD+PROJECTOR condition, where the task was split across an HMD and a body-proximate screen.

The key findings revealed a significant increase in task completion time (approximately 50%) and error rate (approximately 100%) when the display was split across depth layers. Specifically, the mean reaction time increased from 2171 ms (HMD) to 3233 ms (HMD+PROJECTOR), while the error rate rose from 3.84% to 8.30%. The paper also concluded that perceived workload was greater in the multi-depth condition, though no notable difference in simulator sickness was observed.

Implications and Future Directions

These results underscore a critical trade-off in the design of joint OST HMD and body-proximate display systems. The increased cognitive and visual load presented by depth layer switching necessitates careful consideration in application design, especially in scenarios requiring quick and accurate information integration, such as in industrial settings or interactive AR applications.

The paper suggests several avenues for future research. Exploring vari-focal or multi-focal OST HMDs could potentially alleviate some identified performance costs by better matching vergence and accommodation distances. Further, methods to minimize simultaneous information processing across depth layers in critical contexts could provide practical solutions, potentially utilizing adaptive sharpness techniques or intelligent content distribution strategies.

Finally, replication of such studies with different display technologies, such as those with wider fields of view or improved display characteristics, could offer further insights into mitigating the integration costs of distributed AR systems. Understanding these dynamics will be crucial as OST HMDs are advanced as pivotal tools for immersive, multi-faceted user experiences.