Multiplication and Interpolation of Moiré Fringe Orders by Purely Optical Techniques

Abstract

Two new, purely optical techniques are introduced to increase the sensitivity of the moiré method. One of the techniques makes it possible to observe moiré fringes of fractional orders. Observation of moiré fringes of the p/5-order are reported, which means that, with the 300-lines-per-in. grid utilized in the examples presented in the paper, it is possible to observe the same pattern that could be observed with a 1500-lines-per-in. grid. The other technique makes it possible to read fractional orders by a compensation technique similar to Tardy’s compensation process utilized in photoelasticity.