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Smart Structures and Systems Volume 24, Number 5, November 2019 , pages 659-668 DOI: https://doi.org/10.12989/sss.2019.24.5.659 |
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Assessment of speckle image through particle size and image sharpness |
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Boxing Qian, Jin Liang and Chunyuan Gong
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| Abstract | ||
| In digital image correlation, speckle image is closely related to the measurement accuracy. A practical global evaluation criterion for speckle image is presented. Firstly, based on the essential factors of the texture image, both the average particle size and image sharpness are used for the assessment of speckle image. The former is calculated by a simplified auto-covariance function and Gaussian fitting, and the latter by focusing function. Secondly, the computation of the average particle size and image sharpness is verified by numerical simulation. The influence of these two evaluation parameters on mean deviation and standard deviation is discussed. Then, a physical model from speckle projection to image acquisition is established. The two evaluation parameters can be mapped to the physical devices, which demonstrate that the proposed evaluation method is reasonable. Finally, the engineering application of the evaluation method is pointed out. | ||
| Key Words | ||
| digital image correlation; speckle image; particle size; image sharpness; autocovariance; focusing evaluation function | ||
| Address | ||
| Boxing Qian, Jin Liang and Chunyuan Gong: State Key Laboratory for Manufacturing Systems Engineering, School of Mechanical Engineering, Xi\'an Jiaotong University, Xi\'an 710049, China | ||