| Summary: | The digital image correlation (DIC) method is widely used in deformation measurement due to the advantages of being non-contact, high precision, full field measurement, and requiring simple experimental equipment. Traditionally, the grayscale speckle patterns captured by a monochromatic camera are used in the DIC method. With the growing development of consumer color cameras, there is a great potential for developing color information in the DIC method. This paper proposes a scaling- and rotation-invariant DIC (SRI-DIC) method based on the color speckle patterns. For the integer-pixel matching stage, the scaling- and rotation-invariant color histogram feature is used to estimate the initial value of the deformation parameters. For the sub-pixel matching stage, a new error function using the three-channel information of color camera is proposed to avoid the influence of illumination changes. In addition, this paper proposes a reverse retrieve strategy instead of the forward search to reduce the search time. Experiments show that the proposed SRI-DIC algorithm not only has scaling and rotation invariance, robustness, and high efficiency, but also that the average accuracy of the strain result can reach 0.1%.
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