Lateral positioning of a monocular head-worn display

Abstract

Head-worn displays (HWDs) such as Google Glass are becoming more common. However, the optimal location for the display of such devices is an open question. Existing devices have displays located above, below, and in line with the primary position of gaze. In addition to vertical displacement, an HWD can be displaced laterally. In fact, several studies point to potential advantages of lateral displacement. Yet, little research has examined the effects of laterally displacing a HWD.

We evaluate lateral displacement of a monocular HWD across a representative set of activities for which a monocular HWD may be used. The selected activities include situations where interacting with the HWD is the primary or sole task and situations where focus is shifted back and forth between the HWD and the real world. Specifically, we conduct three studies. The first two examine effects of lateral displacement on a long duration reading task. The third considers effects of lateral displacement on a modification of a common industrial task, order picking.

The general thesis proposed is that displacing a monocular head-worn display more than 10 degrees laterally negatively affects subjective perception of visual comfort. Across multiple studies, we found that a display offset at 0 degrees, 10 degrees or 20 degrees was rated more comfortable than a display offset at 30 degrees. Post hoc analysis of other measures such as preference, eye strain, and workload result in similar findings. Although there are also differences between measurements made at 0 degrees and 10 degrees compared to 20 degrees, they are less pronounced. Interestingly, there was no significant difference between conditions for most task performance measures such as speed or accuracy.

Given the relative consistency of results across multiple studies and participant comments, we suggest that small field of view (FOV) displays should be mounted at lateral displacement angles of 20 degrees and less for sustained use. However, users may prefer offsets between 0 degrees and 10 degrees, with 10 degrees sometimes being more preferred because it keeps the display out of the way.