A simulated Plan Position Indicator (PPI) scope was used to evaluate the effects of a number of visual variables upon the minimum signal luminance increment (ΔI) required for the detection of a separation between two identical signals. The signal luminance increment is the difference between the signal luminance and the scope face luminance. All of the variables, viz., background luminance, distance between signals, scan rate, and simulated phosphorescence decay were of importance in determining threshold logΔI values. Moreover, most of the interactions among the variables were statistically significant.
As the background luminance increases, an increase in logΔI is required for detection of a given separation. The background luminance is the most important determinant of the threshold logΔI. In general, for a given background luminance, the threshold logΔI must increase as the separation between signals decreases. The influence of simulated phosphorescence decay and scan rate upon logΔI thresholds is relatively small.
© 1956 Optical Society of AmericaFull Article | PDF Article
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