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Published in:
2022 | OriginalPaper | Chapter
4. Coherent Moiré and Moiré Interferometry
Author : Emmanuel E. Gdoutos
Published in: Experimental Mechanics
Publisher: Springer International Publishing
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Abstract
Geometric moiré is a well-established full-field method for measuring displacements. A serious drawback of the method is its low sensitivity. The density of the gratings cannot exceed 40 lines/mm or the pitch cannot be smaller than 2.5 × 10–2 mm. The displacement difference between two successive fringes is equal to the pitch of the grating and this limits the sensitivity of the method. For higher density gratings diffraction effects enter which alter the nature of the geometric moiré effect. For measuring small displacements moiré methods with much higher sensitivity than geometric moiré have been developed. They use coherent illumination as opposed to geometric moiré which uses ordinary light.