Measurements of vergence and accommodation while viewing a real 3D scene and its 2D image on a display

It is widely thought that conflict between vergence and accommodation may be a major factor of visual fatigue and discomfort caused by viewing stereoscopic images on 3D displays. However, few studies measured vergence and accommodation simultaneously while viewing a real 3D scene and its 2D image on a traditional display. In this study we measured vergence and accommodation responses simultaneously while viewing a 3D real object located at various distances from the participant and its 2D image (photograph) including background scene presented on a display located at fixed distance. The result shows that vergence and accommodation varied with changing target distance while viewing the 3D real object, as expected. On the other hand changing target distance depicted in the photographic image while viewing the 2D display evoked no systematic change of vergence and accommodation. Some participants showed that noticeable accommodation lag and fixation disparity. In addition to that we observed considerable conflicts between vergence and accommodation in both 3D and 2D conditions, but no one reported perceived defocus and/or double vision. There were varieties of individual differences in the pattern of the conflicts.