Kotaro Oikawa¹, Ruggero Micheletto¹; ¹Yokohama City University

Nowadays, video communication technology is widely used. Although many technological developments have improved video communication, the mechanism of perceptual effects such as flicker has not yet been clarified, and this remains a challenge for achieving better video quality. We focused on the curve of critical fusion frequency and duty ratio (C.F.F. - DR curve), which is the threshold of flicker generation by repeated flashing stimuli. In our previous work, we reported that the symmetry of the curve changed between single LED and multiple LED (3x3 grid) stimuli. In this study, we measured the C.F.F. - DR curve by decomposing the multiple-LED stimuli into vertical and horizontal stimuli. Specifically, an analog square wave generator was used to present flashing stimuli with different duty ratios. The vertical and horizontal stimuli were masked from each other using covers to align the light intensity. Subjects then adjusted the frequency of each flashing stimulus and recorded the C.F.F. value. The distance between stimulus and subject was 1.5 m and was done in a dark room. Asymmetric values were calculated by adding up the normalized vertical and horizontal C.F.F. - DR curves of the differences with a duty ratio of 50% as the boundary. The resulting asymmetry value for the vertical stimulus was approximately 15% higher than that for the horizontal stimulus on average for the subjects (these asymmetry values were increased in all subjects). It is suggested that this reflects the orientation between vertical and horizontal in the visual system. Furthermore, the experimental results are consistent with the parameters of the spatial filtering process in our previously reported model.