基于单相机四视角成像的双轴三维视频引伸计

Biaxial Three-Dimensional Video Extensometer Based on Single-Camera Four-View Imaging

为解决双视角三维视频引伸计在两个方向测量精度不一致的问题,同时避免使用多相机带来的相机同步和成本高问题的出现,提出了基于单相机四视角成像的三维双轴视频引伸计。在单相机前安装四棱镜,使用一个相机即可从4个视角观察待测区域,通过多视角强约束方程对变形前后的测点进行三维重构,并计算测点之间的线应变。为避免棱镜折射对成像的影响,使用窄带单色光进行照明。通过不锈钢拉伸实验验证了所提双轴视频引伸计的测量精度。实验结果表明,使用基于单相机四视角成像的三维双轴视频引伸计可以高精度地测量X方向和Y方向的线应变。对两个方向的线应变多幅图测量结果取平均去噪后得到的应变绝对误差均在30με以内。将测量的力学参数与应变片的测量结果对比,弹性模量的相对误差为0.56%,泊松比的相对误差为1.8%。

In order to solve the problem that the accuracies of dual-view three-dimensional(3D) video extensometer are different in two directions, and to avoid the problems of camera synchronization and high cost caused by using multiple cameras, a biaxial three-dimensional video extensometer based on single-camera four-view imaging is proposed. A rectangular pyramid prism is installed in front of a single camera, and the area to be measured can be observed from four views by a single camera. The 3D reconstruction of the measured points before and after deformation is carried out by using the strong constraint equation of multiple views, and the linear strain between the measured points is calculated. In order to avoid the influence of prism refraction on imaging, narrow-band monochromatic light is used for illumination. The measuring accuracy of the proposed biaxial video extensometer is verified by stainless steel tensile experiment. The experimental results show that the 3D biaxial video extensometer can accurately measure the linear strains in X and Y directions with high precision. The absolute error of strain is within 30 με after the average de-noising of linear strains in two directions. Comparing the measured mechanical parameters with the measured results of strain gauge, the relative error of elastic modulus and Poisson ratio is 0. 56% and 1. 8%, respectively.