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Proceedings Paper

Oblique effect in stereopsis?
Author(s): Elizabeth Thorpe Davis; Robert A. King; Alana M. Anoskey
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Paper Abstract

Contrast thresholds are lower for detection of a vertical pattern than for an obliquely-oriented pattern. Is there an analogous oblique effect for the depth threshold of a stereoscopic luminance pattern? If so, why? Are the causes different from those for an oblique effect with monocular vision? To explore these issues, we used stereoscopic blurry bar (D6) luminance patterns with a peak spatial frequency of 2 or 4 cycles/degree (cpd) and either a vertical or an oblique orientation. We obtained psychometric functions for data obtained from a method of constant stimuli procedure, using 100 forced-choice trials for each datum. For each of three observers we estimated stereoacuity with a maximum-likelihood curve-fitting procedure. Subjects showed better stereoacuity for the vertical spatial patterns than for the oblique patterns. Some possible causes are that for oblique patterns (unlike vertical patterns) (1) the total vertical extent of the pattern is shrunk by a factor of sin((theta) ), where (theta) equals 90 degree(s) for vertical; (2) the pattern is 'stretched out' in the horizontal direction by a factor of csc((theta) ); (3) there are vertical as well as horizontal retinal disparities. Perhaps the resulting sparseness of horizontal disparity information or the potential vertical disparities in the oblique patterns reduce stereoacuity. To disentangle these causes, we used several different experimental conditions (e.g., elongation of oblique patterns) run in randomized blocks of trials. We will discuss these results and implications for stereopsis.

Paper Details

Date Published: 27 August 1992
PDF: 11 pages
Proc. SPIE 1666, Human Vision, Visual Processing, and Digital Display III, (27 August 1992); doi: 10.1117/12.135992
Show Author Affiliations
Elizabeth Thorpe Davis, Georgia Institute of Technology (United States)
Robert A. King, Georgia Institute of Technology (United States)
Alana M. Anoskey, Georgia Institute of Technology (United States)

Published in SPIE Proceedings Vol. 1666:
Human Vision, Visual Processing, and Digital Display III
Bernice E. Rogowitz, Editor(s)

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