Abstract

Inspection of a spatial triangular luminance profile gives rise to the perception of an illusory square wave grating.¹ Since the illusory square wave could be seen in the afterimage of an objective triangle wave, Leguire et al.¹ suggested that the illusion was not due to eye movements. We have investigated the role of eye movements by comparing the illusion in unstabilized viewing conditions and in stabilized retinal image conditions using an SRI double Purkinje-image eyetracker.² Compared with unstabilized viewing, stabilized viewing facilitated the appearance of the illusion in two ways. First the latency of the illusion (measured from triangle wave onset to the first appearance of the illusory square wave) was reduced. Second, the illusory square wave percept was evident for a greater proportion of viewing time in stabilized rather than in unstabilized viewing conditions. However, while retinal image stabilization tended to stabilize the perception of the illusory square wave, it did not eliminate the apparent contrast reversal of the illusory pattern.

© 1986 Optical Society of America