The detection of phase shifts in two-dimensional images

Abstract

The ability of observers to register the spatial luminance gradients of images in specific locations can be loosely defined by their sensitivity to spatial phase. Here we have investigated the detectability of phase shifts in two-dimensional images as a function of their center frequencies and bandwidths. In three separate experiments, involving the discrimination of such signals in terms of the addition of constant phase offsets to each target frequency component, we have established that: (1) sensitivity to phase shifts is largely independent of a signal's center frequency; (2) sensitivity increases with increases in the phase-shift bandwidth and is extremely weak below l-octave-wide signals; and (3) sensitivity markedly improves with the addition of a reference frequency band to the two signals but decreases with the spectral distance between the reference and phase-shifted regions. © 1985 Psychonomic Society, Inc.