High-precision and full-field measurement of 3D deformation based on multi-camera network joint constraint optimization

To realize full-field measurements of the deformation of slender and large specimens, a novel stereo measurement method based on digital image correlation is proposed. By establishing a joint constraint relationship for the multi-camera network, any two CCD cameras can be bound as a whole to complete partial measurements of the specimen for subsequent mapping onto a unified reference coordinate system. Consequently, the influence of large nonlinear imaging distortions caused by rough full-field measurements is diminished, while the effective spatial resolution of the acquired images is maintained. In addition, an optimized joint constraint relationship accurately restricts the search for stereo matching points between image pairs to the epipolar line instead of the entire image, thereby reducing the search space and improving the search speed. Moreover, by optimizing the position and altitude parameters between the specimen and the multi-camera network, the accuracy of the reconstructed three-dimensional coordinates of the speckle space is further improved. Finally, the displacement and deformation measurement experiments illustrate the effectiveness of the proposed strategy. Within the spatial range of [0.8 m, 0.5 m, 0.6 m], the translation measurement error of the target is less than 0.044 mm and the out-of-plane displacement measurement accuracy is high (±0.06 mm), which meets the application requirements of aircraft ground physical simulation tests. © 2021, Science Press. All right reserved.