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Coarse stereopsis is important for orientation in space while moving, for example when descending a flight of stairs. Fine stereopsis is mainly based on static differences. It allows the individual to determine the depth of objects in the central visual area (Panum's fusional area) and is therefore also called quantitative stereopsis.
A random-dot stereogram (RDS) is stereo pair of images of random dots that, when viewed with the aid of a stereoscope, or with the eyes focused on a point in front of or behind the images, produces a sensation of depth due to stereopsis, with objects appearing to be in front of or behind the display level.
Stereopsis is merely relative because a greater or lesser disparity for nearby objects could either mean that those objects differ more or less substantially in relative depth or that the foveated object is nearer or further away (the further away a scene is, the smaller is the retinal disparity indicating the same depth difference).
Stereoscopy creates the impression of three-dimensional depth from a pair of two-dimensional images. [5] Human vision, including the perception of depth, is a complex process, which only begins with the acquisition of visual information taken in through the eyes; much processing ensues within the brain, as it strives to make sense of the raw information.
For example, for a disparity of 1, the patch in the left image would be compared to a similar-sized patch in the right, shifted to the left by one pixel. The comparison between these two patches can be made by attaining a computational measure from one of the following equations that compares each of the pixels in the patches.
A good procedure is a chart, analogous to the familiar Snellen visual acuity chart, in which one letter in each row differs in depth (front or behind) sequentially increasing in difficulty. For children the fly test is ideal: the image of a fly is transilluminated by polarized light; wearing polarizing glasses the wing appears at a different ...
In 1833, an English scientist Charles Wheatstone discovered stereopsis, the component of depth perception that arises due to binocular disparity.Binocular disparity comes from the human eyes having a distance between them: A 3D scene viewed through the left eye creates a slightly different image than the same scene viewed with the right eye, with the head kept in the same position.
Yet another evolutionary example of chromostereopsis comes from cuttlefish. It has been suggested that cuttlefish estimate the distance of prey via stereopsis. Additional evidence suggests that their choice of camouflage is also sensitive to visual depth based on color-induced depth effects. [15]