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Keywords: simplified three-dimensional digital image correlation, direction calibration, sensor.

Summary

In the simplified three-dimensional digital image correlation (DIC) method [1], the observed object or the image capture device would be moved laterally so that two images can be taken from two different positions. The most important advantage of the simplified three-dimensional DIC method is that only one image capture device is used in this method. Therefore, the optical and mechanical properties of the image capture device will stay unchanged when the images are captured. In addition, this method is carried out with the assumption that the sensor plane of the image capture device and the movement direction are parallel. While the traditional three-dimensional digital image correlation method [2] uses a complicated algorithm to calculate the three-dimensional coordinates, the calculation algorithm for the simplified three-dimensional digital image correlation method is much simpler.

If the sensor plane of the image capture device cannot be adjusted to parallel to the movement direction in an experiment, additional errors could be induced. Therefore, to make sure that the sensor plane of the image capture device is parallel to the movement direction is relatively important. To reach this purpose, two methods are proposed in this research to calibrate the sensor direction so that it can be kept parallel to the movement direction. In these two methods, the projected movement lengths of the central points on both the images before and after movement are analysed first. The following conclusions can be drawn according to the analysis results:

Theoretically, two methods derived in this research can be used to identify the direction where the sensor plane and the lateral movement direction are parallel.
The first method is to find the direction where the addition of both the central point movements has a maximum. However, it is seriously affected by the measurement error of the DIC method. Consequently, this method is relative unreliable.
The second method is to find the direction where the subtraction of both the central point movements is equal to zero. The analysis result shows that the regression curve is certainly a straight line. This is consistent with the result derived in the theory. In addition, the measurement error of the DIC method seems not to affect the result. Hence, this method is much reliable than the first one.

References

1: S.H. Tung, M.H. Shih, "Precision Verification of a Simplified Three-Dimensional DIC Method", Optics and Lasers in Engineering, 49, 937-945, 2011. doi:10.1016/j.optlaseng.2011.02.006
2: P.F. Luo, Y.J. Chao, M.A. Sutton, W.H. Peters, "Accurate measurement of three-dimensional deformations in deformable and rigid bodies using computer vision", Experimental Mechanics, 33(2), 123-32, 1993. doi:10.1007/BF02322488

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 100 PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: B.H.V. Topping Paper 56 Calibration of the Sensor Direction in the Simplified Three-Dimensional Digital Image Correlation Method S.-H. Tung¹, M.-H. Shih² and W.-P. Sung³ ¹Department of Civil and Environmental Engineering, National University of Kaohsiung, Taiwan ²Department of Civil Engineering, National Chi Nan University, Nantou, Taiwan ³Department of Landscape Architecture, National Chin-Yi University of Technology, Taichung, Taiwan doi:10.4203/ccp.100.56 purchase the full-text of this paper Full Bibliographic Reference for this paper S.-H. Tung, M.-H. Shih, W.-P. Sung, "Calibration of the Sensor Direction in the Simplified Three-Dimensional Digital Image Correlation Method", in B.H.V. Topping, (Editor), "Proceedings of the Eighth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 56, 2012. doi:10.4203/ccp.100.56 Keywords: simplified three-dimensional digital image correlation, direction calibration, sensor. Summary In the simplified three-dimensional digital image correlation (DIC) method [1], the observed object or the image capture device would be moved laterally so that two images can be taken from two different positions. The most important advantage of the simplified three-dimensional DIC method is that only one image capture device is used in this method. Therefore, the optical and mechanical properties of the image capture device will stay unchanged when the images are captured. In addition, this method is carried out with the assumption that the sensor plane of the image capture device and the movement direction are parallel. While the traditional three-dimensional digital image correlation method [2] uses a complicated algorithm to calculate the three-dimensional coordinates, the calculation algorithm for the simplified three-dimensional digital image correlation method is much simpler. If the sensor plane of the image capture device cannot be adjusted to parallel to the movement direction in an experiment, additional errors could be induced. Therefore, to make sure that the sensor plane of the image capture device is parallel to the movement direction is relatively important. To reach this purpose, two methods are proposed in this research to calibrate the sensor direction so that it can be kept parallel to the movement direction. In these two methods, the projected movement lengths of the central points on both the images before and after movement are analysed first. The following conclusions can be drawn according to the analysis results: Theoretically, two methods derived in this research can be used to identify the direction where the sensor plane and the lateral movement direction are parallel. The first method is to find the direction where the addition of both the central point movements has a maximum. However, it is seriously affected by the measurement error of the DIC method. Consequently, this method is relative unreliable. The second method is to find the direction where the subtraction of both the central point movements is equal to zero. The analysis result shows that the regression curve is certainly a straight line. This is consistent with the result derived in the theory. In addition, the measurement error of the DIC method seems not to affect the result. Hence, this method is much reliable than the first one. References 1 S.H. Tung, M.H. Shih, "Precision Verification of a Simplified Three-Dimensional DIC Method", Optics and Lasers in Engineering, 49, 937-945, 2011. doi:10.1016/j.optlaseng.2011.02.006 2 P.F. Luo, Y.J. Chao, M.A. Sutton, W.H. Peters, "Accurate measurement of three-dimensional deformations in deformable and rigid bodies using computer vision", Experimental Mechanics, 33(2), 123-32, 1993. doi:10.1007/BF02322488 purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £50 +P&P)
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