A new approach for the reconstruction of axisymmetric refractive index fields from background-oriented schlieren measurements

Background-oriented schlieren (BOS) is an optical visualization technique that reconstructs a whole-field flow based on its density gradient. Thanks to the cost-effectiveness of its optical setup and its unlimited field of view, BOS has become an attractive technique for laboratory and large-scale experiments. In BOS, the reconstruction of the refractive index field involves various mathematical calculations, which depend on the flow geometry. In this context, the present study presents a new method for the reconstruction of three-dimensional axisymmetric refractive index fields. The proposed method takes advantage of the bi-sensitivity quality of BOS to gain more accuracy in the reconstructed fields. We demonstrate the method’s precision and robustness against experimental noise throughout a synthetic axisymmetric refraction index field. The application of this new approach is not restricted to the BOS technique but can be extended to several other measurement techniques such as moiré deflectometry, laser speckle photography, and rainbow schlieren.