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The perception of stereoscopic surfaces

Lunn, Peter D.; (1995) The perception of stereoscopic surfaces. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Human stereoscopic vision depends upon the slightly different geometrical projections of the world to the two eyes. Horizontal disparities between the eyes produce the sensation of depth. But what is stereopsis for. One theory is that stereopsis extracts the spatial derivatives of horizontal disparity for the perception of shape and surface orientation. Discrimination tasks are devised here which compare sensitivity to the slant and curvature of stereoscopic surfaces with sensitivity to relative depth, both within and across tasks. Contrary to previous studies, where cues other than the second derivative were available, best Weber fractions for disparity curvature disrimination by these methods are no better than 15%. This compares with 6% for disparity gradient and 3.5 % for relative disparity. Discrimination of the orientation, size (or separation) and position of cyclopean corrugated surfaces reveals these stimulus attributes are discriminated as accurately as their counterparts in the luminance domain, provided the spatial scale is quite coarse. Other analogous results include the independence of spatial discriminations on relative disparity, the meridional anisotropy for cyclopean orientation discrimination and a range of relative disparity effects analogous to classical simultaneous contrast effects in luminance vision. It was also found, contrary to a previous study, that cyclopean textures could be segregated pre-attentively. These findings taken together imply that disparity is processed by spatial filters in a similar manner to luminance. This view of stereoscopic vision allows a fresh look at an old phenomenon: the stereoscopic slant anisotropy. An explanation is proposed on the basis of interactions between cyclopean spatial filters and a representation of disparity upon which they act. If sensitivity is a guide to function, stereopsis is for estimating the position, location, size and orientation of nearby objects, but probably not for estimating their shape.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The perception of stereoscopic surfaces
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Health and environmental sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10104356
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