AFRL-HE-AZ-TP-2007-08 Visual suppression of monocularly presented symbology against a fused background in a simulation and training environment

When wearing a monocular head-mounted display (HMD), one eye views the HMD symbology while both eyes view an out-the-window scene. This may create interocular differences in image characteristics that could disrupt binocular vision by provoking visual suppression, thus reducing visibility of the background scene, monocular symbology, or both. However, binocular fusion of the background scene may mitigate against the occurrence of visual suppression, a hypothesis that was investigated in the present study. Observers simultaneously viewed a static background scene and HMD symbology while performing a target recognition task under several viewing conditions. In a simulated HMD condition observers binocularly viewed a background scene with monocular symbology superimposed. In another condition, viewing was dichoptic (i.e. completely different images were presented to the left and right eyes). Additionally, one control condition was implemented for comparison. The results indicate that for continuously presented targets binocular rivalry did not have significant effects on target visibility. However, for briefly presented targets, binocular rivalry was shown to increase thresholds for target recognition time in HMD and dichoptic viewing conditions relative to the control. Impairment was less in the HMD condition. Thus, binocular fusion of a background scene can partially mitigate against the occurrence of visual suppression. However, some suppression still exists which occurs between monocular pathways. Implications for the integration of monocular HMDs into Air Force training environments will be discussed.