Line spread function variation near the fovea

Abstract

Line spread functions (LSFs) for thin lines at five eccentricities near the fixation point were measured psychophysically by subthreshold addition of flanking lines. With increasing eccentricity, the LSFs decrease in height and increase in excitatory center and inhibitory trough width. The LSF data are used to define a model consisting of an inhomogeneous linear filter followed by a peak output detector. This model is consistent with the threshold data for any shape bar whenever the filter output for that bar has only one peak. Probability summation between independent events is adequate to account for thresholds for some multipeak patterns.