Incorrect focus cues in stereo displays: effects on visual performance and viewer fatigue

Stereoscopic displays have become important for many applications including vision research, operation of remote devices, medical imaging, surgical training, scientific visualization, virtual prototyping, and more. In many of these applications, it is important for the graphic image to create a faithful impression of the 3d structure of the portrayed object or scene. Unfortunately, 3d displays often yield distortions in perceived 3d structure compared with the percepts of the real scenes the displays depict. A likely cause of such distortions is the fact that computer displays present images on one surface. Thus, focus cues---accommodation and blur in the retinal image---specify the depth of the display rather than the depths in the depicted scene. Additionally, such displays require the viewer to override the normal coupling of vergence and accommodation. I will discuss the development of displays that present focus cues that are correct or nearly correct for the depicted scene. Such displays can create retinal images that are a reasonable approximation to the images formed in natural viewing of depth-varying scenes. Research with these displays has shown that presenting correct or nearly correct focus cues allows a much larger percentage of viewers to fuse binocular images, reduces the time required to identify a stereoscopic stimulus, reduces distortions in perceived depth, and decreases viewer fatigue and discomfort. I will discuss the implications of this work for basic vision research and applications of stereoscopic presentation.