Abstract
Several past studies have examined temporal properties of stereopsis, and have proposed that there are at least two systems mediating human stereopsis. However, these arguments are based on the results using stimuli of limited spatio-temporal frequency ranges, although more general spatio-temporal characteristics of stereopsis are indispensable for such arguments.
In this study, thus, we measured contrast threshold of binocular depth detection with stimuli extending a wide range of spatio-temporal frequencies. We used spatially band-pass filtered random dot stereograms. Stimuli were generated by Gaussian filters that have one-octave half-height. There were 9 center spatial frequencies between 0.5 c/deg and 8 c/deg in half octave steps. Stimuli were static or temporally modulated (counter-phase) at 2, 4, 5, 10 and 20 Hz. It was found that, although contrast threshold at higher spatial frequencies increased as temporal frequency increased, threshold at lower spatial frequencies decreased for higher temporal frequencies. In the second experiment, we measured the reaction time for depth detection for contrasts near the detection threshold. Reaction times for lower spatial frequencies were shorter than those for higher spatial frequencies. These results are consistent with temporal property for detection of luminance modulations, and suggest a similarity between the detections of spatial modulations in disparity and luminance domain.