Rotating stripes and the impulse response of the eye: I. Uniform illumination*

Abstract

A rotating striped pattern produces an unexpected visual effect: a band of relatively high contrast is seen obliquely across the striped pattern, moving steadily around with the pattern and lagging behind the perpendicular to the stripes. Photographs of the moving pattern display similar effects. An analysis of the effect (based on a simple linear model) shows that the perceived contrast observed at any instant across the pattern represents the temporal modulation transfer function of the eye and the asymmetrical shape of the lines is a display of the phase transfer function. The analysis establishes and uses an analogy with the amplitude distribution in a Fraunhofer diffraction pattern. The temporal impulse response of the eye is related to the perceived contrast in the same way that the aperture function is to the amplitude distribution in the diffraction pattern. The binocularly perceived contrast distribution is considered as the interference or phasor addition of the two monocularly perceived effects, and the clinical potential of this approach is illustrated. In addition, since the band itself is not an object with a physical boundary, but a perceptual consequence of blurring and spatial averaging, the effect provides a means for investigating the perceived location of moving objects in general.