Visual Psychophysical Thresholds for Perceiving Objects and Letters on Monocular Head-Up Displays in Indoor and Outdoor Lighting Conditions

Monocular and binocular head-up displays (HUD) can enhance situational awareness by providing hands-free, real-time information to users on the move. These displays hold the potential for enhancing human experience in many activities, including ambulatory first responders or military personnel. The present study involved a visual psychophysics assessment of three commercially available HUD systems: Vuzix M2000AR, Epson BT-200, and Google Glass. Testing involved 36 participants viewing 112 trials of shape and letter stimuli, presented using the Ascending Methods of Limits psychophysics approach. Half of the trials were completed indoors and half completed outdoors for each HUD. Results demonstrated that participants were able to reliably perceive smaller stimulus sizes with the Epson and Google devices, relative to the Vuzix. This was especially the case in outdoor environments. Results demonstrate the importance of identifying perceptual thresholds for reliably perceiving and interpreting visual stimuli, with large implications for conveying information to the HUD user. Findings of this study demonstrate important practical considerations for selecting commercially-available HUD systems, with particular emphasis on understanding system-specific resolution in tandem with the inherent perceptual capabilities and limitations of human users.