Comparative effects of vergence/accommodation conflicts with different interocular separation and viewing distances

摘要

As pointed out by Kotulak, vergence/accommodation mismatch in Night Vision Systems, usually due tornmisadjustments of eyepiece focus, is sometimes a source of visual performance decrement. The increased separationrnbetween sensors existing in some modern binocular Helmet Mounted Display systems, creating "hyperstereopsis",rnwas also identified to be potentially responsible for decreased performance at distances less than 5 meters.rnBased upon basic knowledge pertaining to vergence and accommodation mechanisms, a study was performed usingrna sensory approach, with the goal of better understanding the problem of dissociation between accommodation andrnconvergence. In this study, different conditions of interocular separation (nominal IPD, X3, X4) and viewingrndistances (6m, 4m, 2m) were used. Six subjects participated in the experiment and were asked to view Landolt Crncharts using NVGs and specially developed optical tools allowing changes to sensor separation.rnThe results show that, with a fixed eyepiece focus at 10m, the decrease in resolution performance is roughlyrnproportional to the interocular separation when looking at short distances. A fixed focus at a distance of 4mrnconsiderably reduces the conflict and results in improved resolution for increased separation conditions.rnAn additional experiment was conducted to investigate the setting of objectives lenses focus at infinity (nominalrnlanding condition). With this setting, for visual acuity test, the decrease in resolution at short distance was such thatrneffects of the mismatch between accommodation and convergence are no longer apparent regardless of interocularrnseparation.