Light Adaptation: Night Vision Goggle Effect On Cockpit Instrument Reading Time
C. M. Howard, M.A., Ph.D., J. T. Riegler, B.A., M.A., and J. J. Martin, B.A., M.B.A.
Aviat Space Environ Med 2001; 72:529-33
Abstract
Background: Light adaptation to the intensified image provided by a night vision device may handicap pilots who have set cockpit instrument luminance too low.
Methods: Under conditions simulating night flying, subjects adapted to an NVG image at 3 or 10 footlamberts (fL), then used a joystick to indicate the position of the horizon in an ADI illuminated by NVIS-compatible light at luminances 2 to 3.5 log units lower than the NVG image.
Results: Response times increased no more than a few tenths of a second when the decrease in luminance was only 2 log units. Greater decreases produced correspondingly longer delays in response, reaching as much as 5.5 s for subjects in their twenties and 8-15 s for older subjects.
Conclusions: While a decrease of more than 2 log units is not likely to occur under most operational conditions, it is certainly possible, and pilots should be aware that significant risk can be incurred by setting cockpit instruments to luminance levels below 0.03 fL.
Keywords: light adaptation, night vision devices, mesopic sensitivity, visual acuity, contrast sensitivity.
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