Abstract
While digital image correlation method (DIC) implemented for displacement measurement of large scale object, the pointing knowledge is an important parameter of the measurement. The 2D DIC system always uses a single camera for imaging, the pointing knowledge is known as the point where camera line-of-sight intersects object surface. Knowing from the previous study, DIC determined displacement field has an additional error if the camera line-of-sight is not perpendicular to the object surface because in-plan measurement sensitivity of 2D-DIC is higher than out-of-plan one. In-plan displacement along object surface can be decomposed into normal and parallel to line-of-sight respectively. 2D-DIC can evaluate the displacement vector normal to the camera line-of-sight well. 3D-DIC has a similar problem, the in-plan and out-of-plan displacement resolutions are different. Comparing with 2D-DIC, 3D-DIC system has more complex parameters. For a typical camera pair of 3D-DIC imaging system always consists of two cameras. The cameras can be considered as two sub-apertures of an imaging device. The line-of-sight of assembled imaging system defines the pointing knowledge of an imaging system with respect to the subject. In this paper, the errors introduced by pointing knowledge of a camera pair used for 3D-DIC is investigated and discussed.