Abstract
Purpose: To investigate the effect of exposure duration on stereopsis and its spatial frequency dependency, we measured disparity threshold for the depth discrimination varying stimulus exposure duration between 0.05 and 2 sec for various spatial frequencies. Method: The stimulus display consisted with four squares filled with sinusoidal gratings arranged in a 2×2 array with gaps to separate them. The gratings in the upper right and the lower left squares had the same disparity that was opposite of those in the other two squares. The observers responded which pair appeared to be closer in depth. Stimuli were luminance gratings with three spatial frequencies (0.23, 0.94 and 3.75 c/deg) and two stimulus contrasts (1 and 0.05). The gratings were stationary during the exposure. Results: The results showed that disparity threshold decreased with increase in exposure duration up to certain duration beyond which was approximately constant. The critical duration was about 200 ms for gratings with low and middle spatial frequencies (0.23 and 0.94 c/deg) while the duration was about 700 ms for gratings with high spatial frequency (3.75 c/deg). This suggests that temporal integration property varies dependently on stimulus spatial frequency A simulation showed that a model with two channels with different spatial and temporal frequency tunings predicts the results of all spatial frequencies.