Abstract
Critical Flicker-Fusion Frequency (CFF) means the frequency at which people see a stable single light when a light is presented with alternating bright and dark. While most displays have been developed with a refresh rate of 60Hz, revealed as the frequency above CFF, state-of-the-art displays that can support the frequency under CFF are emerging. Simulating the images with 30Hz, we observed the effect of waveform and brightness on display flicker perception. Additionally, we compared the result with various index, representing the degree of flickering. In the experiment, using a 240Hz LCD monitor, two types of 30Hz waveform in LCD displays were simulated: Three stimuli had a waveform that reduced the brightness within one frame (Son, Yoo, & Jang, 2004). Two were simulated as the square waves with duty cycles called PWM (Pulse-Width Modulation). The control one had the former type with 60Hz. The second independent variable was brightness of the stimulus. Maintaining the shape of waveform, we adjusted luminances of stimuli using an option in the brightness settings of monitor (three levels: 0, 50, 100 at the Monitor brightness). Participants were asked to rate flicker scores: 0 as the non-flicker stimulus and 5 as same to a reference flicker stimulus on a separate monitor. There was no upper limit on the flicker score. Even though stimulus with duty cycles was 60Hz, participants perceived flicker. Additionally, the brighter the stimulus, the more severe flicker perception. Comparing the result with various index (JEITA(IDMS), Flicker Visibility(IDMS), Flicker Modulation Amplitude(IEC)), the correlations were low (r2 = .427(JEITA); .661(F.V.); -.155 (FMA) (p < .001)) since all index did not reflect the effect of brightness. FMA had a negative correlation with the result: the brighter the stimulus, the lower the FMA. Therefore, it is required to modify the flicker index for displays.