Discrimination of Short-Duration (Two Pulse) Flashes as a Function of Signal Luminance and Method of Measurement
FEDERAL AVIATION ADMINISTRATION OKLAHOMA CITY OK CIVIL AEROMEDICAL INST
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The recent introduction of strobe lights for anticollision purposes raises the possibility of using temporal patterns of short duration flashes as information carrying signals. The current experiments are concerned with the detection of the minimum duration dark interval between signal light pulses as a function of signal luminance and the psychophysical method of measurement. Experiment I tested the theory of signal detectability TSD prediction that observer sensitivity is independent of the psychophysical method used in measurement. Discrimination of a constant duration stimulus three msec and a variable duration test stimulus seven to 32 msec was measured with a two- alternative Forced-Choice FC procedure and a Yes-No procedure. Sensitivity was comparable under the two psychophysical procedures, thus supporting the application of TSD to the sensory processes involved in discrimination of two- pulse stimuli. Experiment II measured discrimination with the FC procedure at three luminance levels 31.8, 318, and 3183 candelas per square meter. Discriminability increased with luminance. Thus, pulses separated by a dark interval short enough so that only a single flash is seen over the entire scotopic intensity range may, however, be seen at photopic intensities as two pulses, or appear to flicker, or otherwise appear to be of different character.
- Human Factors Engineering and Man Machine Systems