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Albert Ahumada, Bettina Beard; Multi-pole estimates of contrast sensitivity functions predict crack detection. Journal of Vision 2005;5(12):46. doi: https://doi.org/10.1167/5.12.46.
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© ARVO (1962-2015); The Authors (2016-present)
For a vision project involving airframe inspectors, we wanted to measure the contrast sensitivity functions (CSFs) of the inspectors. Although we could have used windowed gratings to measure contrast sensitivity as a function of spatial frequency, we wanted to use stimuli that did not require special techniques to present the threshold stimuli. Klein (1989 SPIE) had proposed using multi-pole stimuli to estimate CSFs. Line segments (monopoles) are similar to the cracks that the inspectors were being asked to detect in actual airframe images. For our CRT gamma function, it was possible to choose a line width, duration, and viewing distance such that below threshold lines were easily presented. Dipoles and quadapoles require matching positive and negative levels, a condition not met exactly, but the unwanted line components were well below threshold. Thresholds were estimated for 9 observers. Two parameters were estimated for each observer, the overall sensitivity factor and the difference-of-Gaussian CSF center spread. These same two parameters were estimated for each observer using contrast thresholds from crack detection in actual airframe images. There was good agreement among the two sets of parameters except that the actual crack data could not distinguish among the observers with the smaller center spreads.
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