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 defo-