19-09-2017, 08:51 AM
Stereopsis is a term most frequently used to refer to the perception of depth and three-dimensional structure obtained from visual information derived from two eyes by individuals with normally developed binocular vision. Because the eyes of humans, and many animals, are in different lateral positions on the head, binocular vision gives rise to two slightly different images projected to the retinas of the eyes. The differences are mainly in the relative horizontal position of the objects in the two images. These differences in position are termed horizontal disparities or, more generally, binocular disparities. Disparities are processed in the visual cortex of the brain to produce depth perception. While binocular disparities are naturally present when viewing a real three-dimensional scene with two eyes, they can also be simulated by artificially presenting two different images separately to each eye using a method called stereoscopy. The depth perception in such cases is also known as "stereoscopic depth".
However, the perception of depth and three-dimensional structure is possible only with information visible from a single eye, such as differences in object size and parallax of movement (differences in the image of an object with the movement of the observer ), although the impression of depth in these cases is usually not as vivid as that obtained from binocular disparities. Therefore, the term stereopsis (or stereoscopic depth) may also refer specifically to the unique depth impression associated with binocular vision; what is known colloquially as seeing "in 3D".
It has been suggested that the impression of a "real" separation in depth is linked to the precision with which depth is derived, and that a conscious awareness of this precision - perceived as an impression of interactivity and reality - can help guide the motor planning action.