Binocular Focusing on a Repeating Pattern

Abstract

SOME correspondence appeared in NATURE in 1938 about the phenomenon described by Brewster¹, which is obtained by focusing on a surface covered by a repeating pattern while converging on a point nearer than, or beyond it, so that the images of different units of the pattern fall on corresponding points of the two retinæ. Paget² found that when he converged, the patterned surface seemed to approach to the position of the point of convergence, the units appearing correspondingly smaller. This experiment has now been tried on eight subjects, and Paget's result only obtained with four of them. They were asked to estimate, and then indicate with a ruler the distance and size of the pattern. Two saw the images at the distance for which they were focusing, however much they squinted, and two saw them in a rather indeterminate intermediate position.