This paper presents a new method for the correction of the lens distortion for full-field measurement using dot centroid method. Displacement and strain can be obtained from full-field digital images, which include centroids represented by many dots on the specimen. The captured images are distorted by an optical system. Several ideas to remove such a distortion are developed, however the image is corrected by an interpolation for brightness intensity level. In short it is hard to achieve high accuracy for strain measurement by the interpolation, because high accuracy needs sub-pixel effect for computing a centroid.

In this paper, the dot centroid method is employed and the centroids are directly corrected by the proposed method, which directly compute the only positions of centroids. Due to the correction, 0.1% strain accuracy is accomplished and total computation time is reduced. Effectiveness of the idea is shown through numerical examples and the result of strain field measurement is presented and discussed.

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