Abstract

Vertical square-wave gratings were binocularly presented to subjects on a video monitor. The stereo illusion of several discontinuous levels of depth was seen as previously reported.¹ We examined the parameters of this illusion. (1) The number of levels seen varied as a function of spatial frequency at a constant viewing distance of 63 cm and a constant visual field size of 18.5 × 23.3°. Spatial frequencies were varied from 0.8 to 8.8 cycles/deg in 1-cycle/deg steps. (2) If the vertical gratings were reversed there was no significant change in the number of levels seen within the examined range from 0 to 15 Hz at a spatial frequency of 4 cycles/deg. (3) The contrast of 3-cycle/deg gratings affected the probability of seeing the stereo illusion. When the contrast is 10%, ~50% of the time two or more levels of depth were seen. When contrast reached 30%, 100% of the time two or more levels of depth were seen. The monitors had mean luminance of 106 cd/m²for above-mentioned studies (1) and (2) and 164 cd/m² for study (3).

© 1988 Optical Society of America