On the Utility of Stereoscopic Displays for Simulation Training

In 1990 Tidwell declared “Stereopsis Takes Off in Flight Simulation” and he and his contemporaries asserted stereoscopic displays were “required” for a range of training tasks including air refueling, formation flight, and low level missions. But, some 22 years later, we find stereoscopic displays in a very small fraction of simulation trainers in current use. A survey of suppliers revealed experienced display systems engineers do not believe the stereopsis cue provides benefit for working distances required in the air refueling task. This belief is consistent with the conclusions published in several papers in the “virtual reality” and “head mounted display” literatures. While developing requirements for air refueling trainers, we noticed an apparent correlation between the recommended working distance of stereopsis and the use of electronic displays. The results of many “vision science” evaluations set the threshold for depth discrimination at about 5 arcsec, corresponding with +/6 inches at the working distance of the KC-10 boom operator. In none of these evaluations were spatially sampled electronic displays used. Our literature review revealed those authors who concluded stereopsis is not useful at longer distances used low resolution, spatially sampled displays and made no mention of antialiasing. This paper describes an evaluation of the effects of spatial resolution and antialiasing on stereoscopic disparity thresholds and ratings of visual comfort. The evaluation revealed eye limited stereoscopic disparity thresholds (5 to 10 arcsec) are attainable on electronic displays with a pixel pitch as coarse as 2 arcmin, but only if sufficient antialiasing is applied. This paper provides a quantitative model of the design trade space for these practical design variables. Our results imply the utility of the stereopsis cue in simulation training applications has been substantially undervalued due to inattention to the antialiasing function.