A Dual-Threshold Strategy for Maximizing Power Efficiency in Head-Mounted Displays

This study proposes and validates a dual-threshold strategy for foveated brightness control (FBC), which maximizes power efficiency in virtual reality (VR) displays. FBC preserves the brightness based on the user’s point of gaze while dimming the peripheral visual region. We quantified two distinct thresholds of FBC: just noticeable difference threshold (JNDT), which is the objective threshold at which peripheral dimming is just noticeably distinguished from the original, and acceptable dimming level (ADL), which is the subjective limit of dimming users accept without impairing their visual experience. Psychophysical experiments revealed a strong correlation (R2=0.96) between JNDT and the average lightness of image. Conversely, ADL shows minimal content dependency but higher inter-individual variability, indicating diverse personal tolerances to FBC. Power consumption decreased by up to 60.7% under ADLs, compared to up to 37.5% under JNDTs. Correlation analyses further indicate a weak relationship between JNDTs and ADLs, suggesting distinct underlying perceptual mechanisms. Based on these findings, we propose a context-adaptive dual-mode framework: a JNDT-based mode for visually sensitive applications and an ADL-based mode for aggressive power saving. This work establishes a foundation for future personalized systems that can integrate gaze-tracking to optimize both user experience and power efficiency.