Office of Aerospace Medicine Technical Reports
FAA Office of Aerospace Medicine
Civil Aerospace Medical Institute
Report No: DOT/FAA/AM-71/42
Title and Subtitle: Discrimination of short-duration (two-pulse) flashes as a function of signal luminance and method of measurement
Report Date: November 1971
Authors: Mertens HW, Lewis MF
Abstract: 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.
Key Words: Vision, Visual Signals, Perception
No. of Pages: 5
Civil Aerospace Medical Institute
Report No: DOT/FAA/AM-71/42
Title and Subtitle: Discrimination of short-duration (two-pulse) flashes as a function of signal luminance and method of measurement
Report Date: November 1971
Authors: Mertens HW, Lewis MF
Abstract: 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.
Key Words: Vision, Visual Signals, Perception
No. of Pages: 5
Last updated: Friday, June 1, 2012