STRAIN MEASURING METHOD AND STRAIN MEASURING SYSTEM

PROBLEM TO BE SOLVED: To provide a strain measuring method and strain measuring system capable of improving the measuring accuracy of strain of a measuring object by certainly image-recognizing a mark put on a surface of the measuring object.SOLUTION: The strain measuring method includes: an imaging process S13 of irregularly arranging a plurality of marks on a surface, imaging the surface of a measuring object in chronological order from the time before deformation to the time after the deformation, and acquiring an initial image before the deformation, an intermediate image during the deformation, and a final image after the deformation; an image selecting process S14 of selecting N images including the initial image, intermediate image, and final image; and a strain calculation process S16 of identifying, from the image X, by image recognition, the position indicating the highest correlation with each of a plurality of areas into which the image X(where, i is 1 or more and N-1 or less) is divided, calculating the moving amount of each area in the image Xand image X, and adding the plurality of moving amounts of the initial image to the final image to each other to calculate the strain of the measuring object.