Most stereo displays in everyday use employ temporal interlacinga??temporally alternating presentationa??to deliver different images to the eyes. This yields a temporal disparity between the left and right eyes. The brain interprets this as a spatial disparity thereby yielding a distortion in perceived depth (Mach-Dvorak effect). We asked whether this effect can be minimized by using color interlacing to present images to the eyes. In the first half of a frame, the green channel is presented to the left eye and the red and blue channels to the right eye. In the second half, the channels are reversed: green to right eye, red and blue to left. With a desaturated stimulus, both eyes are stimulated in both half frames, so luminance variation is greatly reduced. If the visual system computes disparity from luminance, color interlacing should significantly reduce depth distortions. If it computes disparity in part from chromatic information, two objects at different depths should be perceived, one caused by temporal disparity in green and the other caused by the opposite disparity in red and blue. We performed psychophysical experiments to determine how color interlacing affects the Mach-Dvorak effect. The stimulus consisted of disks rotating on a circular path. The plane of rotation was nominally frontoparallel, but when depth distortion occurred, it appeared slanted. We added a disparity gradient to eliminate the perceived slant and that gradient quantified the distortion. We presented different colors, varying in hue and saturation. When the exchanges were isoluminant, no depth distortion was observed. When they were non-isoluminant, distortion was observed and its magnitude was proportional to the luminance change. The results show that disparity is measured from luminance variation and that display protocols that minimize the luminance variation at each eye yield reduced distortions in perceived depth.
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