Abstract
Conventional digital displays present stimuli at only one focal distance because the light comes from a single surface. When the display is meant to create a 3d percept, two significant problems occur. First, depth information from accommodation and the blur gradient is uncontrolled, which can lead to distortions in perceived 3d structure. Second, observers often experience discomfort and have difficulty fusing the two eyes' images because of the decoupling of vergence and accommodation. We devised and implemented a display technique that uses multiple image planes to present stereoscopic stimuli at near-correct focal distances. Each eye's view is the sum of several images, each presented at a different focal distance. Parts of the scene at “intermediate distances” (i.e., between the image planes) are displayed by distributing the image intensity, along lines of sight, across two or more image planes. Experiments showed that the display was effective in reducing problems caused by the accommodation-vergence mismatch. Compared to a fixed display distance, observers required less time to fuse a random-dot stereogram presented at different distances, including distances between the image planes. Stereoscopic depth constancy was also improved. Observers reported, however, that a slanted textured plane viewed monocularly did not look planar. This finding is understandable because focus cues should be given more weight in the absence of disparity signals, and at distances between the image planes, the blur gradient in our display differs significantly from that created by a real slanted plane. Our experiments provide further evidence that depth percepts are affected by focus cues. We conclude that the multiple-planes approach provides a practical solution to some of the problems created by conventional displays.