9/23/2023 0 Comments Mening of motion parallax![]() ![]() Neurophysiological studies in cortical area MT show that these neurons appear to use an extra-retinal signal in order to code unambiguous depth motion parallax ( Nadler et al., 2008), and that the smooth eye movement system is the source of the required signal ( Nadler et al., 2006 Nadler et al., submitted). That extra-retinal signal does not appear to come from other potential sources ( Nawrot & Joyce, 2006). Recent psychophysical studies ( Nawrot, 2003 Naji & Freeman, 2004 Nawrot & Joyce, 2006) have shown that the pursuit eye movement system provides a necessary extra-retinal signal for the unambiguous perception of depth from motion parallax. ![]() This motion/pursuit law finally provides a quantitative and unambiguous measure of depth from motion parallax, a crucial step in understanding the brain mechanisms for depth perception. ![]() Here we use the dynamic geometry of motion parallax to show that the visual system relies on a ratio of retinal image motion and pursuit eye movement to disambiguate near and far depth from motion parallax, and to show that this ratio provides a reliable metric for relative depth of objects in a scene. Another important monocular depth perception cue is motion parallax, the relative movement of objects in a scene created by the translation of an observer ( Gibson, 1950). This retinal disparity is an important cue for the perception of relative depth from binocular stereopsis. Historically, knowledge of the underlying static geometry was central to understanding how the lateral separation of the two eyes creates retinal images with objects in different positions ( Wheatstone, 1838 Wade, 1998). Therefore, geometry provides a crucial starting point for understanding how the visual system produces a neural representation of relative depth. To perceive a three-dimensional world the human visual system must rely on the information falling upon a two-dimensional retina. The theoretical framework provided by the motion/pursuit law provides the quantitative foundation necessary to study this fundamental visual depth perception ability. Results of a psychophysical experiment show that changes in the motion/pursuit ratio have a much better relationship to changes in the perception of depth from motion parallax than do changes in motion or pursuit alone. ![]() We show that this could have been obtained with the approaches of Nakayama and Loomis (1974) or Longuet-Higgins and Prazdny (1980) by adding pursuit to their treatments. Mathematically, the ratio of retinal image motion (motion) and smooth pursuit of the eye (pursuit) provides the necessary information for the computation of relative depth from motion parallax. While the static optical geometry of retinal disparity explains the perception of depth from binocular stereopsis, we propose a new formula to link the pertinent dynamic geometry to the computation of depth from motion parallax. Relative binocular parallax See stereoscopic visual acuity.One of vision’s most important functions is specification of the layout of objects in the 3D world. Example: when viewing the landscape through the window of a moving train near objects appear to move much more quickly than distant objects. Motion parallax Apparent difference in the direction of movement or speed produced when the subject moves relative to his environment (Fig. Monocular parallax The apparent change in the relative position of an object when the eye is moved from one position to another. See chromostereopsis longitudinal chromatic aberration. This phenomenon is attributed to the chromatic aberration of the eye. The relative displacement of the two images becomes reversed when the pinhole is on the other side of that axis. When the pupil is centred on the achromatic axis (in some people the pinhole may have to be placed away from the centre of the pupil), the two images appear superimposed. a blue object and a red object) when observed through a disc with a pinhole placed near the edge of the pupil. Apparent displacement of an object viewed from two different points not on a straight line with the object.īinocular parallax The difference in angle subtended at each eye by an object that is viewed first with one eye and then with the other.Ĭhromatic parallax Apparent lateral displacement of two monochromatic sources (e.g. ![]()
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