Horizontal Diplopia Thresholds for Head-Up Displays
AIR FORCE AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OH
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Horizontal diplopia thresholds were determined using a Head-Up Display HUD emulator which superimposed a small vertical line at various degrees of binocular disparity on a rich outdoor scene. The main findings are that observers are more intolerant of negative disparity than positive disparity. In negative disparity, a non-fixated object is optically further than a fixated object. For 32 observers, the overall median negative disparity threshold was 1.2 mrad and the overall median positive disparity threshold was 2.6 mrad. Assuming that pilots fixate on external targets, these results suggest that HUD imagery should be placed at a slightly nearer optical distance than background targets. The results also indicate that 1 longer viewing is more likely to lead to a diplopia effect than short glances, 2 resistance to diplopia appears to be an individual trait, and 3 a large proportion of responses involve suppression of the image in one eye. The report also includes a table of the percentage of observers reporting diplopia as a function of disparity magnitude. This table may be used to predict the incidence rate of diplopia among pilots for any allowed degree of disparity.
- Personnel Management and Labor Relations
- Anatomy and Physiology