We studied the degree of visual fatigue in subjects watching HDTV stereoscopic images. The images used as visual stimuli contained only absolute, with no relative, parallax. The examination of visual fatigue was carried out with a five-grade subjective evaluation test and measurements of the accommodation response after watching the images for one hour. We found that when they were displayed within the corresponding range of depth of focus and remained static in the depth direction, the degree of visual fatigue was almost the same as that induced by watching the images displayed on the screen. However, visual fatigue was clearly induced, when they were displayed outside the corresponding range. Moreover, even if they were displayed within the corresponding range, visual fatigue was induced if they were moved in depth according to a step pulse function.
