Effects of HMD Backlight Bleed-Through in Low-Light Augmented Reality Applications
SCHOOL OF AEROSPACE MEDICINE WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
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Many liquid crystal displays LCDs operate by acting as a light valve to selectively block or transmit light emitted from a backlight. Due to the imperfect nature of the LCD light valve, when the LCD pixel is in the off state, it is not perfectly opaque, and some small portion of the backlight bleeds through. This imperfect dark state, or black level, is a well-known drawback of LCD displays. In low-light augmented reality helmet mounted display HMD applications, this bleed-through can significantly obscure real-world objects viewed through the display. In this work, we investigate the performance impact of a non-zero dark state in simulated low-light formation flight scenarios using a monochrome green HMD. Observer performance was evaluated at several different dark state luminance levels for tasks that require locating or tracking an aircraft with active navigation lights under starlight illumination. Adaptation time between relatively high and low dark state conditions was also characterized. In this paper we focus on the challenges associated with implementing the operational scenario, including calibration of both the simulation and HMD, with discussion of human performance under varying brightness conditions. These methods can be used to accurately calibrate training simulations in which highly realistic representations of low-light see-through HMD operations are a critical requirement for effective training.