We tested the effect of direction of retinal disparity and stimulus orientation on stereoscopic depth perception to answer three questions. First, are some directions of disparity more efficient than others in providing stereoscopic depth information? Second, does the orientation of an object affect perceived stereoscopic depth? Third, are there any interactions between these parameters? Subjects were tested using a psychophysical, method of constant stimuli procedure with a modified Wheatstone stereoscopic display. Disparity threshold measurements show a significant effect of direction of retinal disparity. Contrary to expectations however, no significant effect of orientation was found if vertical retinal disparities were excluded from the analyses. Stereoacuity thresholds were measurable with obliquely-oriented stimuli and vertical disparity, however, suggesting that vertical disparities can provide useful information. The implications of these results for the graphics, calibration, and design of stereoscopic displays (e.g., HMDs) are discussed.
A physiological theory of depth perception from vertical disparity
