Changes in Binocular Color Fusion Limit Caused by Different Disparities

Abstract

When the color asymmetry between the left and right eyes exceeds a threshold value, named binocular color fusion limit, the color rivalry is said to occur. For stereoscopic displays, the horizontal disparity is the most important information to produce depth perception. When the stereo pair stimuli are presented separately to both eyes with disparities and those two stimuli also differ in color but share an iso-luminance polarity, it is possible for stereopsis and color rivalry to coexist. In this paper, we conducted a psychophysical experiment to quantitatively measure the color fusion limit at different disparity levels. In particular, it examined how disparities affect the binocular color fusion limit. A binocular color fusion limit was measured at five relative disparity levels: 0, ±60, and ±120 arc minutes for five sample color points, which were selected from the 1976 CIE u'v' chromaticity diagram. The experimental results show that the color fusion limit for each sample point varies with the disparity magnitude, disparity sign, and color direction. It is new research finding that the color fusion limit increases as the disparity increases from -120 to +120 arc minutes. The average color fusion limit ranges from 0.036 to 0.064 in terms of Euclidean distance in the u'v' chromaticity diagram ( \Delta \text {E}-{\mathrm {u'v'}} ). The new finding shows that the human eye has different information processing mechanisms for crossed disparity (sign -) and uncrossed disparity (sign +), and uncrossed disparity can contribute to color fusion. We suggest that the color fusion limit varies with the color direction, but it has nothing to do with the distribution of cone cells. The color fusion limit was quantified by using ellipses in the chromaticity diagram, and the axis of the ellipses ranges from 0.017 to 0.145~\Delta \text {E}-{\mathrm {u'v'}}. The experiments and data analysis in this paper indicate that the binocular disparity fusion affects binocular color fusion. This research result can strongly support 3D system design and 3D content creation.