Fundamentals of stereopsis

The human brain is able to register slight differences in the position of the images of an object on the two retinas and uses this shift to compute precise estimates of relative depth. This binocular cue to depth, called stereopsis, is a fundamental source of information about the volume and separation of objects in our world, and the world’s three dimensional layout. It is used to make very fine depth judgments, as when threading a needle, and helps us navigate rough terrain. This entry summarizes the basic 3D viewing geometry underpinning stereopsis, its upper and lower limits and knowledge of its neural mechanisms.