The instrumental resolution of a moire extensometer in light of its recent automatisation.

This paper assesses the instrumental resolution of a mechanical extensometer in light of its recent automatisation. The instrument takes advantage of the moire phenomenon of optical interference to measure angular rotation in two perpendicular planes and displacement in three dimensions. Our assessment systematically defines an analytical solution for the complete interpretation of a generic moire pattern and a set of mathematical approximations for the moire patterns used to measure rotation and displacement.