There is a gap between mechanical measurement methods under laboratory conditions and those under real conditions of structural monitoring. This paper proposes a method that applies well-established computer vision developments to photomechanics in difficult conditions. It is therefore a technique that is flexible and versatile while maintaining satisfying accuracy. It consists in marker tracking using ArUco fiducial markers as measurement points. It allows locating markers in non-optimal conditions of camera orientation and position. A homography process was used to analyse pictures taken with a view angle. The accuracy of the method was estimated, especially in case of out-of-plane motions, and the impact of the view angle and of the distance between camera and markers on the location error was studied. The method was applied in creep tests to measure crack parameters as well as the transverse expansion of wooden beams. In the application example presented, it enabled to compute distances between markers with only 0.28% of relative error and hence to measure the crack parameters and the long-term shrinkage-swelling of the wooden beams. However, the impacts of brightness variations and camera parameters have not been estimated. This method is very promising when experimental conditions are variable and when multiple measurements are necessary.

实验室条件下的力学测量方法与实际结构监测条件下的力学测量方法存在差距。本文提出了一种方法，将成熟的计算机视觉开发应用于困难条件下的光机械。因此，它是一种灵活且通用的技术，同时保持令人满意的准确性。它包括使用 ArUco 基准标记作为测量点的标记跟踪。它允许在相机方向和位置的非最佳条件下定位标记。使用单应性过程来分析以视角拍摄的照片。评估了该方法的准确性，尤其是在平面外运动的情况下，并研究了视角和相机与标记之间的距离对定位误差的影响。该方法应用于蠕变试验，以测量裂缝参数以及木梁的横向膨胀。在给出的应用示例中，它能够以仅 0.28% 的相对误差计算标记之间的距离，从而测量木梁的裂缝参数和长期收缩膨胀。然而，尚未估计亮度变化和相机参数的影响。当实验条件可变且需要多次测量时，此方法非常有前途。尚未估计亮度变化和相机参数的影响。当实验条件可变且需要多次测量时，此方法非常有前途。尚未估计亮度变化和相机参数的影响。当实验条件可变且需要多次测量时，此方法非常有前途。