Comparative Analysis of Visual Function Variations Under Pulse Width Modulation (PWM) and Direct Current (DC) Dimming in Mobile Display

Under low-to-moderate ambient lighting, screen flicker from display devices can lead to considerable visual discomfort. The industry typically addresses this issue through the implementation of Pulse Width Modulation (PWM) and Direct Current (DC) dimming technologies. Current assessments of flicker risks primarily focus on the quantitative analysis of hardware physical parameters. These measurements indirectly characterize flicker intensity based on the fluctuation properties of light sources. However, this methodology does not take into account the physiological variations in human visual responses and overlooks the persistent deviations from optimal optical conditions during standard device usage. As a result, existing methods are insufficient for adequately evaluating the visual function abnormalities that may arise. Research indicates that screen flicker influences brain function by modulating oscillations in the visual cortex. These neurological effects are expected to result in measurable changes in visual performance. However, existing studies predominantly concentrate on detecting brain function, with a notable absence of direct physiological evidence that establishes a link between flicker and visual impairment.To address these limitations, we conducted human-factor experiments assessing PWM and DC dimming effects on ocular function through three physiological markers: Accommodation Microfluctuations (ACC), Higher-Order Aberrations (HOAs), and Modulation Transfer Function (MTF). Participants engaged in 45-minute visual tasks on PWM and DC-dimmed displays, with ocular measurements taken before and after each session.At a brightness level of 45-55 nits, PWM dimming exhibited a significantly greater impact on ocular imaging quality compared to DC dimming during continuous visual tasks.However, $ riangle \mathrm{ACC}$ testing indicated no statistically significant difference in visual fatigue indices between the two technologies. While PWM’s high-frequency brightness oscillations increased wavefront aberrations (spherical and coma aberrations), both technologies demonstrated comparable cumulative effects on retinal neural adaptation fatigue. This study provides empirical guidance for optimizing dimming technology selection in display devices.