A Robust Optical Framework for High-Density Structural Marker Tracking in Fluid-Structure Interaction Experiments

This paper establishes a robust optical measurement framework designed for the high-density tracking of structural markers within fluid-structure interaction wind tunnel environments. The methodology specifically addresses challenges associated with industrial testing including restricted optical access, anisotropic illumination, and high-dynamic-range glare. The processing pipeline introduces a novel multi-stage algorithm for 2D marker localization and 3D reconstruction. A probability-based element classification combined with an iterative deconvolution strategy is employed to precisely localize markers. This approach mitigates the halo effect induced by high-intensity laser reflections which enables the recovery of faint markers obscured by the glare of brighter neighbors. Subsequently, a Symmetric Consensus Triangulation algorithm is introduced to resolve the 3D correspondence problem in dense fields. Unlike traditional asymmetric algorithms, this method utilizes a Hybrid Score defined as the product of reprojection error and topological ambiguity to robustly reject ghost particles without reliance on temporal history. Furthermore, a surface-guided recovery stage retrieves markers visible in only two cameras due to geometric occlusions while a density-based spatial clustering filter ensures topological consistency. The framework is validated on a flat plate calibration target and a flexible DLR-F15 high-lift airfoil model in the NLR Aeroacoustic Wind Tunnel. Results demonstrate a reconstruction completeness of 99\% relative to 2D detections and a sub-pixel root mean square reprojection error of 0.15 pixels which confirms the suitability of the system for high-fidelity aeroelastic characterization.