Night Vision Current Research and Future Directions, Symposium Proceedings (1987) / Chapter Skim
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Summary: Findings and Recommendations
Summary: Findings and Recommendations
Pages 1-14
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SUGARY: FINDINGS AND ~CO~NDATIONS em?
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recommended equipment for a night vision laboratory. SPECIFICATION OF AMBIENT ILLU}lINANCE LEVELS In order to predict performance under low-illumination conditions, it is necessary to match information describing ambient illuminance levels, task requirements, and psychophysical data relating the capabilities and limitations of human performance to luminance levels.
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A quantitative description of the work environment should include the measurement of ambient lighting conditions, contrast levels, the spatial and temporal frequency properties of the environment, and the range of stimulus conditions under which certain tasks are performed. Task analyses of various jobs should include a comprehensive survey of the most frequent tasks performed, the most critical task components, the types of visual skills necessary for properly conducting the task, an evaluation of the frequency and consequences of errors in task performance, and other related factors.
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.., Validation Studies Regardless of the specific visual functions and test procedures that are examined by a night vision laboratory, we believe that it is critical to correlate vision test results with task performance measures f ram studies with simulators, "field" studies, performance ratings of instructors, or other information sources. This information will be useful in determining which test procedures are the best predictors of task performance and will thereby establish a basis for designing appropriate night vision screening tests.
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Both psychophysical tests under low-luminance conditions (e.g., contrast sensitivity, glare disability, peripheral visual function, dynamic visual acuity, oculomotor function) and task performance measures should be obtained at periodic intervals.
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, induced motion, spatial or ientation, and postural stability can signif icantly Papa fir pert ormance . The Spatial Contrast Sensitivity Function The spatial contrast sensitivity function has received increasing attention in the past 15 years ~ see, for example, Harvey)
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First, optimum performance of visual functions under low-luminance conditions occurs at different visual field eccentricities, depending on the specific task (detection, identification, spatial localization, etc.~. Observers are able to select and maintain a specific nonfoveal locus for performing tasks under free-viewing conditions at low luminances, although it is not clear how this process is accomplished, or what factors are involved.
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At the present time, we have little information pertaining to the functional properties of night vision under static versus dynamic conditions, individual differences in dynamic visual function, and the relationship between dynamic visual properties and task performance capabilities. We recommend that dynamic visual acuity and related tests be considered for evaluation by a night vision laboratory.
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In view of the current rudimentary understanding of the critical factors underlying the performance of night vision tasks, we recommend that computer modeling be considered as one of the activities of a night vision laboratory.
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Presently, there are no standardized night vision screening tests that have been shown to be related to task performance. The design of night vision screening tests should ideally come from thorough laboratory studies that are correlated with actual performance measures of night vision tasks.
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In addition, there are some glare devices that use a high background luminance level that would not be appropriate for investigations of night vision. Although a device to measure glare disability is highly recommended for a night vision laboratory, several issues must be carefully considered prior to purchasing a specific glare tester.
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For more comprehensive evaluations of eye movements, an infrared eye-tracker that monitors the relative positions of the Purkinje images would be a most useful tool in a night vision laboratory. Ideally, one would like to have night vision laboratory personnel with expertise in the following areas: (1)
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