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Switching from forward-looking infrared to night vision goggles: transitory effects on visual resolution
1U.S. Army Aeromedical Research Laboratory, Aircrew Health and Performance Division, Fort Rucker, AL 36362-0577.
Aviation, Space, and Environmental Medicine
|April 1, 1994
Summary
Switching between bright forward-looking infrared (FLIR) and lower-luminance night vision goggle (NVG) displays can impair pilot vision. Luminance differences greater than 10 fL cause significant visual loss, impacting aviation safety.
Area of Science:
- Aviation Human Factors
- Visual Perception
- Display Technology
Background:
- Helmet-mounted displays integrate forward-looking infrared (FLIR) and night vision goggle (NVG) sensors for pilots.
- Transitions between FLIR and NVG can involve significant luminance changes, potentially impairing visual performance.
Purpose of the Study:
- To determine critical display luminances causing transient visual impairment when switching from FLIR to NVG.
- To quantify the impact of luminance adaptation on visual resolution during sensor transitions.
Main Methods:
- A letter recognition task assessed visual resolution in five subjects under simulated FLIR-to-NVG luminance shifts.
- Varied letter size, contrast, and exposure time to measure visual loss magnitude and duration.
Main Results:
- A significant reduction in letter recognition occurred within one second when FLIR luminance exceeded 10 fL.
- Visual loss persisted up to 4 seconds, with a 2x decrease in visual acuity and a 3x decrease in contrast sensitivity from a 49.2 fL FLIR display.
Conclusions:
- Large luminance differences between FLIR and NVG displays negatively impact pilot visual performance and aviation safety.
- Optimizing FLIR and NVG luminance balance through design or training is crucial for maintaining visual performance and safety.