Spatial Resolution Thresholds During the Course of Dark Adaptation: An Evaluation of the Recovery of Visual Function Following Failure of Optical Image Intensifiers.
Annual rept. Jan-Dec 77,
TEXAS TECH UNIV LUBBOCK DEPT OF OPHTHALMOLOGY AND VISUAL SCIENCES
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Optical Image Intensifiers serve to aid night vision by amplifying the amount of light reaching the retina. A failure of this device leaves the observer visually handicapped for a period of time equal to the time that it takes the visual system to adapt to the darkened conditions. Important information, which is not now available, is a quantitative estimate of the degree and time course of visual performance impairment in the event of a night vision aid failure. Because of the many possible permutations in describing the visual environment, a prediction of the resolution tasks that may confront the user in the field is impractical. However, any complex stimulus can be described in terms of its Fourier components viz. sinusoids. Therefore, by examining the visual resolution of spatial sine-wave gratings the necessary elementary information for generalization to any stimulus configuration can be obtained. In the field, the observer will be adapted to the chromaticity and luminance of the optical image intensifier for an indefinite period of time preceding its unexpected failure. The visual recovery time is independent of the duration of exposure to the adaptation source when it is longer than some critical time.
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