ACCURATE MEASUREMENT OF 3-DIMENSIONAL DEFORMATIONS IN DEFORMABLE AND RIGID BODIES USING COMPUTER VISION
ACCURATE MEASUREMENT OF 3-DIMENSIONAL DEFORMATIONS IN DEFORMABLE AND RIGID BODIES USING COMPUTER VISION
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DOI：
10.1007/bf02322488
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发表时间：
1993-06-01
影响因子：
2.4
通讯作者：
PETERS, WH
中科院分区：
文献类型：
--
作者：
LUO, PF;CHAO, YJ;PETERS, WH
近年来，数字图像相关技术已被用于精确确定二维平面内位移和应变。本文提出了一种将二维方法扩展到从一对立体CCD相机获取精确的三维表面位移数据的方法。采用针孔相机模型，利用相机的外在参数和内在参数来表示三维世界坐标到二维计算机图像坐标的转换。通过(a)使用具有三维世界坐标的几个点，其精度在0.001 mm以内；(b)使用精度在0.05像素以内的二维图像相关方法，获得各个物体位置的计算机图像坐标，独立获得每个相机的准确相机模型参数。采用非线性最小二乘法选择最优相机参数，使测量图像位置与估计图像位置之间的偏差最小。使用相机的多个方向，通过执行平移测试来测试方法的准确性。利用理论误差估计，给出了误差分析。为了验证该方法在实际试验中的正确性，采用立体视觉技术对304L不锈钢压紧拉伸试样进行了表面、悬臂梁位移场和三维位移场的实验研究。结果表明，三维测量方法与亚像素精度的二维数字相关相结合，是一种精确测量表面位移和应变的可行工具。
Recently, digital-image-correlation techniques have been used to accurately determine two-dimensional in-plane displacements and strains. An extension of the two-dimensional method to the acquisition of accurate, three-dimensional surface-displacement data from a stereo pair of CCD cameras is presented in this paper.A pin-hole camera model is used to express the transformation relating three-dimensional world coordinates to two-dimensional computer-image coordinates by the use of camera extrinsic and intrinsic parameters. Accurate camera model parameters are obtained for each camera independently by (a) using several points which have three-dimensional world coordinates that are accurate within 0.001 mm and (b) using two-dimensional image-correlation methods that are accurate to within 0.05 pixels to obtain the computer-image coordinates of various object positions. A nonlinear, least-squares method is used to select the optimal camera parameters such that the deviations between the measured and estimated image positions are minimized.Using multiple orientations of the cameras, the accuracy of the methodology is tested by performing translation tests. Using theoretical error estimates, error analyses are presented. To verity the methodology for actual tests both the displacement field for a cantilever beam and also the surface, three-dimensional displacement and strain fields for a 304L stainless-steel compact-tension specimen were experimentally obtained using stereo vision. Results indicate that the three-dimensional measurement methodology, when combined with two-dimensional digital correlation for subpixel accuracy, is a viable tool for the accurate measurement of surface displacements and strains.