![]() The planes have focal distances of 1.87, 2.54, and 3.21D ( Figure 4A). The display presents nearly correct focus information by optically summing light from three image planes via mirrors and beam splitters. We achieved this by using a fixed-viewpoint, volumetric display (Akeley, Watt, Girshick, & Banks, 2004). We needed a means of presenting stimuli in which we could show geometrically equivalent stimuli with and without appropriate focus information. The dark blue zone is the region where fixation is possible and there is a perceptible inter-ocular focal difference. The red zone marks the region where objects are closer than 8D, and an observer would typically step back to fixate. The gray region shows the range of positions that an observer would typically make a head movement to fixate. The blue region indicates the locations where the focal difference is greater than the eyes' depth of focus and therefore the focal difference should be perceptible. The black contours depict the locations in space where the inter-ocular focal difference is constant. Inter-ocular focal difference is the difference between the reciprocals of the distances to the two eyes in meters ( Equation 7). The abscissa is object position parallel to the inter-ocular axis and the ordinate is object position perpendicular to that axis. B) Inter-ocular focal difference as a function of object position. The distances from the object to the two eyes are d L and d R. An object is presented at distance D and azimuth γ from the eyes, which are separated by I. ![]() Inter-ocular differences in focal distance. This shows that blur aids the interpretation of scene layout near monocular occlusions. When the occluded and occluding textures were presented with different blurs, rivalry was significantly reduced. When the occluder's texture was sharp along with the occluded texture, binocular rivalry was prominent. In a second experiment, we presented images in which one eye could see texture behind an occluder that the other eye could not see. Depth discrimination performance improved significantly when focus information was correct, which shows that the visual system utilizes the information contained in depth-of-field blur in solving binocular correspondence. In another condition, the planes were presented on two image planes at different focal distances, simulating focus information in natural viewing. In one condition, the two planes were presented with sharp rendering on one image plane, as is done in conventional stereo displays. To do this, they had to solve the correspondence problem. Observers judged the slant of the farther plane, which was seen through the nearer plane. We presented transparent scenes consisting of two planes. We examined the use of focus information in solving the binocular correspondence problem and in interpreting monocular occlusions. Focus information-blur and accommodation-is highly correlated with depth in natural viewing.
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