The Physiology of 3D Perception
1.1 Binocular Viewing or Human Stereopsis
As one eye is capable only of perceiving a planar image, 3D viewing is commonly achieved by the cooperation of both eyes in providing each eye with a view of the object. The images that the eyes receive from the same object are different according to the different locations of the eyes. This binocular viewing provides the perception of depth, the third dimension, as further explained by the horopter circle in Figure 1.1. This circle serves as a reference from which the depth is determined [1, 2]. If the eyes are focusing, for which the synonyms fixating, accommodating, or converging are also used, on point M on the horopter circle, the ciliary muscles of the eyes rotate the eyeballs into such a position that the light from M passes the pupils parallel to the axes of the lenses in the eyes. The axes intersect at M. Then the light hits the retina in Figure 1.1 at the foveas ml for the left eye and mr for the right eye. The foveas are in the center of the retina and exhibit the highest density of light receptors. The rotation of the eyes is called the vergence. Obviously the axes of the eyes are no longer parallel, which will provide the depth information required by the brain [1, 3]. In this situation light from point P hits the retinas at the points pl for the left eye and pr for the right eye. The angles α at the periphery of the circle are, as is known from geometry, the same for all points P ...