Dynamic ablation morphology measurement of thermal protection materials using structured light vision

Measuring the dynamic ablation process of thermal protection materials is critical for designing and predicting the performance of thermal protection systems. However, acquiring data on this process in arc-jet wind tunnels is challenging due to the extremely high temperature and intense brightness. In this paper, a novel optical measurement method leveraging structured light and binocular stereo-vision was proposed to capture the dynamic ablation morphology of thermal protection materials in aerodynamic thermal tests. This method utilized the active projection of short-wave multi-line structured light, combined with bandpass filtering, to obtain clear images. Binocular image matching was accomplished using depth-of-field and epipolar constraints. A measurement platform incorporating this methodology was constructed in an arc-jet wind tunnel. Room-temperature accuracy tests demonstrate the following results: An approximate interval of 1.1 mm between adjacent points in the shape point cloud, a standard deviation of plane point cloud fitting not exceeding 0.12 mm, a plane angle measurement error within 0.3°, a standard deviation of spherical point cloud fitting below 0.14 mm, and a relative deviation of diameter measurement less than 1%. High-temperature measurements were conducted on a spherical convex model made of fiberglass. Three-dimensional point cloud data of the model were acquired at interval of 8 seconds under maximum surface temperature of 1430 ℃, with the measurement time for a single point cloud being less than 1 second. The measurement accuracy at room temperature, point cloud density, dynamic velocity, and applicable temperature range demonstrate the effectiveness and potential of the proposed method in measuring the high-temperature dynamic ablation characteristics of thermal protection materials.