Effects Of Ambient Luminance And AR-display Message Brightness On Character Recognition Threshold During Treadmill Exercise

Optical head-mounted displays (OHMD) with augmented reality (AR) technology have integrated into many different applications. Its technology allows users the ability to perform mobile tasks such as walking or jogging while simultaneously reading messages. PURPOSE: In this study, we investigate if walking speed, AR-display message brightness, and ambient illumination affects users’ recognition threshold of characters shown on OHMDs when performing treadmill exercises. METHODS: Thirty participants were asked to wear an OHMD device and walk on a treadmill to perform the legibility test by reading over a series of messages. Each message was composed of five randomly selected characters shown on the AR-display under various tested settings. The sequence of each test condition was randomly assigned and the character recognition threshold of each participant was recorded. Factors examined in this study include walking speed (Slow: 80%, Normal:100%, Fast: 120% of each users’ preferred walking speed defined prior to the test), message brightness (Low:33%, Medium:66%, High:100% of default setting), and ambient luminance (Low:200, Medium:400, High:600 lux). Statistical analysis was performed to investigate the effects of the factors on character recognition threshold. RESULTS: The ANOVA analysis results indicate that each main factor significantly affect the character recognition threshold (p < 0.05). Slower (0.513a LogMAR) walking speed yielded smaller character recognition threshold in comparison to normal (0.543b LogMAR) and fast (0.556b LogMAR) walking speeds. Lowering message brightness required larger character size in order for participants to identify it (Low: 0.636a LogMAR, Medium: 0.503b LogMAR, High: 0.474c LogMAR), whereas increasing ambient luminance (Low: 0.486a LogMAR, Medium: 0.513b LogMAR, High: 0.613c LogMAR) would lead to needing a larger character size. The influence of interactions among the main factors are also found (P < 0.05). CONCLUSION: The findings of this study conclude that a user’s ability to accurately recognize information shown on AR-display not only depends on the display features of the OHMD device itself but could also be affected by factors such as different dynamic movement conditions as well as various light situations in the surrounding area.