Moving Visual Images produced by Regular Stationary Patterns

Abstract

THE phenomenon mentioned by Dr. Pirenne is one of several side-effects of our patterns which are being separately investigated because they seem to be distinct from the complementary response. Helmholtz's “rotating sectors” are, of course, well known and may be considered as moiré fringes due to the superposition of displaced replicas of the pattern either in the optical image or at a neural level or both. In the ‘ray’ figure described in my previous communication¹ similarly fleeting ‘figure of 8’ moiré patterns can be seen as accommodation varies. The simplest way of demonstrating their origin is to cover the stimulus figure with a transparency of itself, when similar fringes appear (Fig. 1), and one can in fact measure the amplitude and direction of the effective retinal image-displacement by observing the displacement required in the transparency to produce the same moiré pattern.