Abstract

Piggins¹ reported that dichoptically presented gratings induce an illusion of multiple levels of depth. Tyler² attributed this perception to operation of fusional displacement and the vertical horopter. Three experiments were performed to quantify the Piggins illusion as a function of grating orientation and spatial frequency. In each experiment the grating presented to one eye was varied in orientation relative to the orientation of the grating for the other eye. Subjects were asked to indicate the number of distinct edges they saw and if they sensed rivalry, depth, or fusion. Spatial frequency of the gratings varied from 1.7 to 5.5 cycles/deg in 4 steps. The stereo illusion can be accounted for on the basis of the disparities generated by the differences in orientation.

© 1987 Optical Society of America