Faceted simulator displays are widely used because they are relatively compact and economical. One drawback, however, is that viewing distance changes depending on where users are looking. This variation creates a challenge for the integration of binocular head mounted displays (HMDs), because confusing imagery and visual fatigue can result when the user views symbology presented by the HMD at one distance and simulator imagery at different distances. Understanding the best approach to presenting symbology with a binocular HMD in a faceted simulator has become an important issue, with the deployment of the F-35 Joint Strike Fighter and its binocular HMD. Successful integration of a binocular HMD would not only allow current faceted simulators to be retrofit with the F-35 simulator HMD, but would also allow future simulators to have either a dome or faceted design, thus affording acquisition agencies greater flexibility. Binocular HMDs are becoming more prevalent, so solving this integration issue will likely become important for multiple platforms.

We performed an experiment to quantify the best method of presenting symbology on a binocular HMD when used with a faceted simulator display. Five viewing conditions were tested: 1) HMD converged to 36", 2) HMD converged to 42", 3) dynamic HMD vergence, 4) monocular presentation on the HMD, and 5) on-screen presentation. Screen distances ranging from 36" to 54" were tested.

Our results suggest that adaptive vergence is the preferred solution. Both static vergence conditions and the monocular condition resulted in lower comfort scores and poorer performance. The on-screen condition, although rated comfortable, does not represent the real-world flight condition where symbology is displayed using an HMD. Although additional evaluations under more operational conditions remain to be completed, these results indicate that adaptive vergence is a viable solution for the integration of binocular HMDs into faceted flight simulator displays.