Abstract

A series of psychophysical experiments was conducted to investigate the perception of raggedness of edge images whose tangential edge or boundary profiles are not straight. The profiles used were either sinusoidal or determined by the sum of several sine waves. In the first experiments the just-detectable or threshold amplitude of the sine wave was determined as a function of the sine-wave frequency. The observers’ sensitivities were maximum in the region of 1–2 cycles/mm at a viewing distance of 400 mm, at which the peak-to-peak threshold amplitude was approximately 7 μm; the threshold values increased at higher and lower frequencies. Experiments using the sum of two sine waves with a frequency ratio of 3:1 indicated that the detection threshold was not affected by the relative phase of the two components even though the shape and peak-to-peak amplitudes of the profiles changed radically. In a second set of experiments observers were asked to rate the raggedness of suprathreshold profiles relative to two anchor images. For sine-wave profiles raggedness ratings increased linearly with peak-to-peak amplitude. For two-component sine-wave profiles with a frequency ratio of 3:1, the rated raggedness was not affected by the relative phase of the components. The implications for a general model of raggedness perception and for a further understanding of spatial frequency channels in the visual system are discussed.

© 1981 Optical Society of America

Spatiotemporal characteristics of thresholds adjacent to a luminance edge

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