Moiré Patterns: Their Application to Refractive Index and Refractive Index Gradient Measurements

Abstract

The general theory of moiré patterns obtained from parallel rulings and concentric circles is presented. Near superposition of a regular ruling on to parallel rulings of variable spacings results in a curved moiré pattern which is functionally related to the deviation in spacings. When two figures consisting of uniformly spaced concentric circles are overlapped, the resulting moiré patterns are hyperbolas defined by the center-to-center distance of the figures and the inter-ring spacing.