{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,17]],"date-time":"2026-03-17T10:01:17Z","timestamp":1773741677545,"version":"3.50.1"},"reference-count":44,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2022,1,7]],"date-time":"2022-01-07T00:00:00Z","timestamp":1641513600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The search for dents is a consistent part of the aircraft inspection workload. The engineer is required to find, measure, and report each dent over the aircraft skin. This process is not only hazardous, but also extremely subject to human factors and environmental conditions. This study discusses the feasibility of automated dent scanning via a single-shot triangular stereo Fourier transform algorithm, designed to be compatible with the use of an unmanned aerial vehicle. The original algorithm is modified introducing two main contributions. First, the automatic estimation of the pass-band filter removes the user interaction in the phase filtering process. Secondly, the employment of a virtual reference plane reduces unwrapping errors, leading to improved accuracy independently of the chosen unwrapping algorithm. Static experiments reached a mean absolute error of \u223c0.1\u00a0mm at a distance of 60\u00a0cm, while dynamic experiments showed \u223c0.3\u00a0mm at a distance of 120\u00a0cm. On average, the mean absolute error decreased by \u223c34%, proving the validity of the proposed single-shot 3D reconstruction algorithm and suggesting its applicability for future automated dent inspections.<\/jats:p>","DOI":"10.3390\/s22020433","type":"journal-article","created":{"date-parts":[[2022,1,9]],"date-time":"2022-01-09T23:08:26Z","timestamp":1641769706000},"page":"433","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":11,"title":["Automated Aircraft Dent Inspection via a Modified Fourier Transform Profilometry Algorithm"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3396-5744","authenticated-orcid":false,"given":"Pasquale","family":"Lafiosca","sequence":"first","affiliation":[{"name":"Integrated Vehicle Health Management Centre, Cranfield University, Cranfield MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6691-935X","authenticated-orcid":false,"given":"Ip-Shing","family":"Fan","sequence":"additional","affiliation":[{"name":"Integrated Vehicle Health Management Centre, Cranfield University, Cranfield MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1314-0603","authenticated-orcid":false,"given":"Nicolas P.","family":"Avdelidis","sequence":"additional","affiliation":[{"name":"Integrated Vehicle Health Management Centre, Cranfield University, Cranfield MK43 0AL, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,7]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1016\/S0169-8141(99)00063-3","article-title":"A review of human error in aviation maintenance and inspection","volume":"26","author":"Latorella","year":"2000","journal-title":"Int. J. Ind. Ergon."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Papa, U., and Ponte, S. (2018). Preliminary design of an unmanned aircraft system for aircraft general visual inspection. Electronics, 7.","DOI":"10.3390\/electronics7120435"},{"key":"ref_3","unstructured":"(2021, December 19). Airbus Launches Advanced Indoor Inspection Drone. Available online: https:\/\/www.airbus.com\/en\/newsroom\/press-releases\/2018-04-airbus-launches-advanced-indoor-inspection-drone-to-reduce-aircraft."},{"key":"ref_4","unstructured":"(2021, December 19). Drones Finally Approved For Lightning Checks. Available online: https:\/\/aviationweek.com\/mro\/drones-finally-approved-lightning-checks-dent-measurement-next."},{"key":"ref_5","first-page":"692","article-title":"Review of non-contact methods for automated aircraft inspections","volume":"62","author":"Lafiosca","year":"2020","journal-title":"Insight-Non-Destr. Test. Cond. Monit."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"456","DOI":"10.1016\/j.infrared.2019.02.002","article-title":"Application of NDT thermographic imaging of aerospace structures","volume":"97","author":"Deane","year":"2019","journal-title":"Infrared Phys. Technol."},{"key":"ref_7","unstructured":"The Boeing Company (2015). Structural Repair Manual B737-400, The Boeing Company."},{"key":"ref_8","unstructured":"Civil Aviation Authority (2003). CAP 716\u2014Aviation Maintenance Human Factors."},{"key":"ref_9","unstructured":"Civil Aviation Authority (2013). Paper 2013\/03\u2014Reliability of Damage Detection in Advanced Composite Aircraft Structures."},{"key":"ref_10","first-page":"1","article-title":"3D point cloud analysis for detection and characterization of defects on airplane exterior surface","volume":"36","author":"Pham","year":"2017","journal-title":"J. Nondestruct. Eval."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Do\u011fru, A., Bouarfa, S., Arizar, R., and Aydo\u011fan, R. (2020). Using convolutional neural networks to automate aircraft maintenance visual inspection. Aerospace, 7.","DOI":"10.20944\/preprints202011.0527.v1"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Guehring, J. (2001, January 21\u201324). Dense 3-D surface acquisition by structured light using off-the-shelf components. Proceedings of the SPIE\u2014The International Society for Optical Engineering, San Jose, CA, USA.","DOI":"10.1117\/12.410877"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"827","DOI":"10.1016\/j.patcog.2003.10.002","article-title":"Pattern codification strategies in structure light systems","volume":"37","author":"Salvi","year":"2004","journal-title":"Pattern Recognit."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"70","DOI":"10.1016\/j.optlaseng.2017.10.013","article-title":"Micro Fourier Transform Profilometry (\u03bcFTP): 3D shape measurement at 10,000 frames per second","volume":"102","author":"Zuo","year":"2017","journal-title":"Opt. Lasers Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"18445","DOI":"10.1364\/OE.24.018445","article-title":"Pixel-wise absolute phase unwrapping using geometric constraints of structured light system","volume":"24","author":"An","year":"2016","journal-title":"Opt. Express"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"94104","DOI":"10.1117\/1.OE.60.9.094104","article-title":"Fast two-step phase-shifting method for measuring the three-dimensional contour of objects","volume":"60","author":"Chen","year":"2021","journal-title":"Opt. Eng."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1097","DOI":"10.1016\/j.optlaseng.2012.01.007","article-title":"Review of single-shot 3D shape measurement by phase calculation-based fringe projection techniques","volume":"50","author":"Zhang","year":"2012","journal-title":"Opt. Lasers Eng."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"H\u00fcgli, H., and Ma\u00eetre, G. (1988, January 19\u201323). Generation And Use Of Color Pseudo Random Sequences For Coding Structured Light In Active Ranging. Proceedings of the 1988 International Congress on Optical Science and Engineering, Hamburg, Germany.","DOI":"10.1117\/12.949215"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1109\/34.44402","article-title":"Range image acquisition with a single binary-encoded light pattern","volume":"12","author":"Vuylsteke","year":"1990","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Ulusoy, A., Calakli, F., and Taubin, G. (October, January 27). One-shot scanning using De Bruijn spaced grids. Proceedings of the 2009 IEEE 12th International Conference on Computer Vision Workshops, Kyoto, Japan.","DOI":"10.1109\/ICCVW.2009.5457499"},{"key":"ref_21","unstructured":"Zhang, l., Curless, B., and Seitz, S. (2002, January 19\u201321). Rapid Shape Acquisition Using Color Structured Lightand Multi-pass Dynamic Programming. Proceedings of the First International Symposium on 3D Data Processing Visualization and Transmission, Padova, Italy."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"3977","DOI":"10.1364\/AO.22.003977","article-title":"Fourier transform profilometry for the automatic measurement of 3-D object shapes","volume":"22","author":"Takeda","year":"1983","journal-title":"Appl. Opt."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2666","DOI":"10.1016\/j.patcog.2010.03.004","article-title":"A state of the art in structured light patterns for surface profilometry","volume":"43","author":"Salvi","year":"2010","journal-title":"Pattern Recognit."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"5408","DOI":"10.1364\/AO.47.005408","article-title":"Windowed Fourier transform for fringe pattern analysis: Theoretical analyses","volume":"47","author":"Kemao","year":"2008","journal-title":"Appl. Opt."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"141","DOI":"10.1016\/j.optlaseng.2009.04.003","article-title":"Comparison of Fourier transform, windowed Fourier transform, and wavelet transform methods for phase extraction from a single fringe pattern in fringe projection profilometry","volume":"48","author":"HUANG","year":"2010","journal-title":"Opt. Lasers Eng."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Watkins, L. (2010, January 21\u201323). Phase Recovery Using The Wavelet Transform. Proceedings of the AIP Conference Proceedings, Penang, Malaysia.","DOI":"10.1063\/1.3426093"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2670","DOI":"10.1364\/AO.46.002670","article-title":"Multiscale windowed Fourier transform for phase extraction of fringe patterns","volume":"46","author":"Zhong","year":"2007","journal-title":"Appl. Opt."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2797","DOI":"10.1016\/j.optcom.2011.01.068","article-title":"Automatic window size selection in Windowed Fourier Transform for 3D reconstruction using adapted mother wavelets","volume":"284","author":"Fernandez","year":"2011","journal-title":"Opt. Commun."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"106193","DOI":"10.1016\/j.optlaseng.2020.106193","article-title":"Status, challenges, and future perspectives of fringe projection profilometry","volume":"135","author":"Xu","year":"2020","journal-title":"Opt. Lasers Eng."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"106622","DOI":"10.1016\/j.optlaseng.2021.106622","article-title":"Calibration of fringe projection profilometry: A comparative review","volume":"143","author":"Feng","year":"2021","journal-title":"Opt. Lasers Eng."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"83601","DOI":"10.1117\/1.2336196","article-title":"Novel method for structured light system calibration","volume":"45","author":"Zhang","year":"2006","journal-title":"Opt. Eng."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"7942","DOI":"10.1364\/AO.53.007942","article-title":"Structured light system calibration method with optimal fringe angle","volume":"53","author":"Li","year":"2014","journal-title":"Appl. Opt."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"6563","DOI":"10.1364\/AO.49.006563","article-title":"Universal calculation formula and calibration method in Fourier transform profilometry","volume":"49","author":"Wen","year":"2010","journal-title":"Appl. Opt."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1330","DOI":"10.1109\/34.888718","article-title":"A Flexible New Technique for Camera Calibration","volume":"22","author":"Zhang","year":"2000","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/j.optlaseng.2018.02.017","article-title":"High-speed 3D shape measurement with structured light methods: A review","volume":"106","author":"Zhang","year":"2018","journal-title":"Opt. Lasers Eng."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"53604","DOI":"10.1117\/1.2931517","article-title":"Accurate calibration method for a structured light system","volume":"47","author":"Li","year":"2008","journal-title":"Opt. Eng."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Martynov, I., Kamarainen, J.K., and Lensu, L. (2011, January 1). Projector Calibration by \u201cInverse Camera Calibration\u201d. Proceedings of the Scandinavian Conference on Image Analysis, Ystad, Sweden.","DOI":"10.1007\/978-3-642-21227-7_50"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Moreno, D., and Taubin, G. (2012, January 13\u201315). Simple, Accurate, and Robust Projector-Camera Calibration. Proceedings of the 2012 Second International Conference on 3D Imaging, Modeling, Processing, Visualization & Transmission, Zurich, Switzerland.","DOI":"10.1109\/3DIMPVT.2012.77"},{"key":"ref_39","unstructured":"Gdeisat, M., and Lilley, F. (2021, November 17). One-Dimensional Phase Unwrapping Problem. Available online: https:\/\/www.ljmu.ac.uk\/~\/media\/files\/ljmu\/about-us\/faculties-and-schools\/fet\/geri\/onedimensionalphaseunwrapping_finalpdf.pdf."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"28","DOI":"10.1016\/j.optlaseng.2018.03.003","article-title":"Absolute phase retrieval methods for digital fringe projection profilometry: A review","volume":"107","author":"Zhang","year":"2018","journal-title":"Opt. Lasers Eng."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"2470","DOI":"10.1364\/AO.21.002470","article-title":"Analysis of the phase unwrapping algorithm","volume":"21","author":"Itoh","year":"1982","journal-title":"Appl. Opt."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"543","DOI":"10.1016\/j.precisioneng.2021.06.001","article-title":"Mapping and correcting the distortion of 3D structured light scanners","volume":"72","author":"Dickin","year":"2021","journal-title":"Precis. Eng."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"5126","DOI":"10.1364\/OE.19.005126","article-title":"Noise robust linear dynamic system for phase unwrapping and smoothing","volume":"19","author":"Estrada","year":"2011","journal-title":"Opt. Express"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"219","DOI":"10.4236\/opj.2020.1010023","article-title":"Methods and Devices of Speckle-Noise Suppression","volume":"10","author":"Kompanets","year":"2020","journal-title":"Opt. Photonics J."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/2\/433\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,13]],"date-time":"2025-10-13T14:01:35Z","timestamp":1760364095000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/2\/433"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,1,7]]},"references-count":44,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2022,1]]}},"alternative-id":["s22020433"],"URL":"https:\/\/doi.org\/10.3390\/s22020433","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,1,7]]}}}