Two-dimensional digital image correlation (2D-DIC) is a widely used optical technique to measure displacement and strain during asphalt concrete (AC) testing. An accurate 2-D DIC measurement can only be achieved when the camera's principal axis is perpendicular to the planar specimen surface. However, this requirement may not be met during testing due to device constraints. This paper proposes a simple and reliable method to correct errors induced by non-perpendicularity. The method is based on image feature matching and rectification. No additional equipment is needed. A theoretical error analysis was conducted to quantify the effect of a non-perpendicular camera alignment on measurement accuracy. The proposed method was validated numerically using synthetic images and experimentally in an AC fracture test. It achieved relatively high accuracy, even under considerable camera rotation angle and large deformation. As a pre-processing technique, the proposed method showed promising performance in assisting the recently developed CrackPropNet for automated crack propagation measurement under a non-perpendicular camera alignment.

翻译：二维数字图像相关法（2D-DIC）是一种广泛应用于沥青混凝土（AC）试验中位移与应变测量的光学技术。仅当相机主光轴垂直于平面试样表面时，才能实现精确的2D-DIC测量。然而，受设备条件限制，试验过程中可能无法满足该要求。本文提出一种简单可靠的校正方法，用于修正由非垂直性引起的误差。该方法基于图像特征匹配与校正技术，无需额外设备。通过理论误差分析，定量研究了相机非垂直对准对测量精度的影响。利用合成图像进行数值验证，并在沥青混凝土断裂试验中完成实验验证。实验结果表明，即使在较大相机旋转角度和大变形条件下，该方法仍具有较高精度。作为预处理技术，该方法在辅助最新开发的CrackPropNet实现非垂直相机对准下的裂缝扩展自动测量时，展现出良好的应用前景。