Stereo digital image correlation (stereo-DIC) technique shows a powerful capacity on full-field three-dimensional (3D) deformation measurement of rotary machine structures. However, it remains a challenge for underwater applications due to difficulties in imaging, stereo calibration, light refraction, and so on. In this paper, its potential in characterizing 3D dynamic deformation of the underwater rotor blades is shown by solving these problems. A stroboscopic stereo-DIC system is established to capture clear speckle images of a blade that rotates in the windowed cavitation tunnel under different flow speeds. To calibrate the stereo camera for underwater object measurement, an improved planar pattern-based calibration method and a globally optimal relative pose estimation algorithm are proposed to calibrate the intrinsic and extrinsic parameters of the stereo-DIC system separately. In particular, a novel refractive 3D reconstruction method for underwater objects is presented to recover the true 3D shape according to flat refraction geometry, ensuring the correctness and reliability of the measured 3D displacement fields. Several experiments demonstrated that the proposed stereo-DIC system and methods are feasible and accurate. Based on this, the measured dynamic displacement fields of a propeller blade are presented and discussed. Results herald a possibility for monitoring the full-field 3D dynamic response and structural health of underwater rotating structures by the proposed technique.

立体数字图像相关（stereo-DIC）技术在旋转机械结构的全场三维（3D）变形测量方面显示出强大的能力。然而，由于成像、立体校准、光折射等方面的困难，它仍然是水下应用的挑战。在本文中，通过解决这些问题，展示了它在表征水下转子叶片的 3D 动态变形方面的潜力。建立了频闪立体DIC系统来捕捉叶片在不同流速下在窗口空化隧道中旋转的清晰散斑图像。为了校准用于水下物体测量的立体相机，提出了一种改进的基于平面模式的校准方法和全局最优的相对姿态估计算法，分别校准立体DIC系统的内在和外在参数。特别是，提出了一种新的水下物体折射 3D 重建方法，根据平面折射几何恢复真实的 3D 形状，确保测量的 3D 位移场的正确性和可靠性。几个实验表明，所提出的立体 DIC 系统和方法是可行和准确的。在此基础上，提出并讨论了螺旋桨叶片的实测动态位移场。结果预示着通过所提出的技术监测水下旋转结构的全场 3D 动态响应和结构健康状况的可能性。