ABSTRACT
Head movement towards and away from a display consisting of a stationary grating with a superimposed inclined line leads to the apparent rotation of the line. This phenomenon has been investigated using a television system with a motorized zoom lens to effect such transformations. The direction and magnitude of the apparent rotation depend upon the orientation of the line to the grating, reaching a maximum at a relative orientation of 45°. The shape of the angle function can be described by a simple formulation based on a vectorial analysis of the changes in the display. It is suggested that the apparent rotation is a consequence of a discrepancy between the perceived transformations of the line and the grating. The magnitude of apparent line rotation is influenced by the gravitational orientation of the background grating and by the phase and duration of zooming. The spatial characteristics of the line and grating have relatively little effect on the amount of rotation observed.
