Abstract

We describe a new design for a haploscope. A plug-in board for a pc computer drives a pair of liquid-crystal shutter glasses in synchrony with the vertical retrace interrupt of an EGA monitor. In this manner, alternate frames are displayed independently to each eye. This format allows any stimulus that can be generated with EGA graphics to be displayed stereoscopically at 60 Hz (30 Hz for each eye). This equipment permitted us to quickly and easily perform the following experiment. Four "objects", all squares, were tested for their ability to fuse stereoscopically: (1) subjective contours that were generated with different inducing figures for each eye, (2) squares of fine texture surrounded by coarser texture with different random patterns for each eye, (3) random forms defined solely by motion, and (4) forms defined by vertical lines for one eye and horizontal lines for the other, all surrounded by random patterns of the same mean luminance. All conditions have in common the property of allowing no point-by-point luminance correlation. While there was much inter-subject variability, both overall and between conditions, the results showed that stereopsis for such objects is possible, but difficult (Ramachandran et al., Nature. 1973). Condition 4 was best, but it may have allowed some effective luminance correlation resulting from the well-known neon effect. Condition 1 was the worst, presumably because it had no physical forms to be fused.

© 1989 Optical Society of America