Two new, purely optical techniques are introduced to increase the sensitivity of the moire´ method. One of the techniques makes it possible to observe moire´ fringes of fractional orders. Observation of moire´ 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.

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