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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Results after the cylindrical back-projection: (a,c,e) Results after the cylindrical back-projection on the best observation regions of cameras of the three samples; (b,d,f) Results after the cylindrical back-projection on the image of the full side of the caps of the three samples.