{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,14]],"date-time":"2026-04-14T05:11:07Z","timestamp":1776143467784,"version":"3.50.1"},"reference-count":28,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2019,11,14]],"date-time":"2019-11-14T00:00:00Z","timestamp":1573689600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51674031"],"award-info":[{"award-number":["51674031"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["51874022"],"award-info":[{"award-number":["51874022"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Visual inspections of nuclear power plant (NPP) reactors are important for understanding current NPP conditions. Unfortunately, the existing visual inspection methods only provide limited two-dimensional (2D) information due to a loss of depth information, which can lead to errors identifying defects. However, the high cost of developing new equipment can be avoided by using advanced data processing technology with existing equipment. In this study, a three-dimensional (3D) photometric stereo (PS) reconstruction technique is introduced to recover the lost depth information in NPP images. The system uses conventional inspection equipment, equipped with a camera and four light-emitting diodes (LEDs). The 3D data of the object surface are obtained by capturing images under multiple light sources oriented in different directions. The proposed method estimates the light directions and intensities for various image pixels in order to reduce the limitation of light calibration, which results in improved performance. This novel technique is employed to test specimens with various defects under laboratory conditions, revealing promising results. This study provides a new visual inspection method for NPP reactors.<\/jats:p>","DOI":"10.3390\/s19224970","type":"journal-article","created":{"date-parts":[[2019,11,14]],"date-time":"2019-11-14T10:56:34Z","timestamp":1573728994000},"page":"4970","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Improved Visual Inspection through 3D Image Reconstruction of Defects Based on the Photometric Stereo Technique"],"prefix":"10.3390","volume":"19","author":[{"given":"Sanao","family":"Huang","sequence":"first","affiliation":[{"name":"University of Science and Technology Beijing, Collaborative Innovation Center of Steel Technology, Beijing 100083, China"},{"name":"In-Service Testing Center, CGN Inspection Technology Co., Ltd, Suzhou 215000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1809-7413","authenticated-orcid":false,"given":"Ke","family":"Xu","sequence":"additional","affiliation":[{"name":"University of Science and Technology Beijing, Collaborative Innovation Center of Steel Technology, Beijing 100083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ming","family":"Li","sequence":"additional","affiliation":[{"name":"In-Service Testing Center, CGN Inspection Technology Co., Ltd, Suzhou 215000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mingren","family":"Wu","sequence":"additional","affiliation":[{"name":"University of Science and Technology Beijing, Collaborative Innovation Center of Steel Technology, Beijing 100083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Cumblidge, S.E., Doctor, S.R., and Anderson, M.T. (2006, January 23\u201327). The Capabilities and Limitations of Remote Visual Methods to Detect Service-Induced Cracks in Reactor Components. Proceedings of the ASME Pressure Vessels and Piping Conference, Volume 5: High Pressure Technology, Nondestructive Evaluation, Pipeline Systems, Vancoucer, BC, Canada.","DOI":"10.1115\/PVP2006-ICPVT-11-93389"},{"key":"ref_2","unstructured":"U.S. Nuclear Regulatory Commission (2004). Regulatory Guide 1.147: Inservice Inspection Code Acceptability, ASME Section, X.I, Division 1."},{"key":"ref_3","unstructured":"Arias, J., and Hummel, W. (2009, January 6\u201310). Fuel Services Progress in Visual Examination and Measurements on Fuel Assemblies and Associated Core Components Track 1. Proceedings of the Top Fuel 2009, Paris, France."},{"key":"ref_4","unstructured":"Heinsius, J., and Tsvetkov, E. (2016, January 13\u201317). ENIQ-Qualified Visual Examinations by Means of a Remote Controlled Submarine. Proceedings of the 19th World Conference on Non-Destructive Testing, Munich, Germany."},{"key":"ref_5","unstructured":"Spinnler, K., Bergen, T., Sandvoss, J., Wittenberg, T., and Fraunhofer-Institut f\u00fcr Integrierte Schaltungen IIS R\u00f6ntgentechnik (2016, January 13\u201317). Digital Image Processing for the Automation of NDT by Means of Endoscopy. Proceedings of the 19th World Conference on Non-Destructive Testing, Munich, Germany."},{"key":"ref_6","first-page":"28","article-title":"Machine Vision Technology","volume":"30","author":"Hebel","year":"2012","journal-title":"Nucl. Plant J."},{"key":"ref_7","unstructured":"Williams, T., and Hammel, K. (2016, January 13\u201317). Time is Money and Image is Everything. Proceedings of the 19th World Conference on Non-Destructive Testing, Munich, Germany."},{"key":"ref_8","first-page":"1","article-title":"Improved Visual Inspection of Advanced Gas-Cooled Reactor Fuel Channels","volume":"6","author":"West","year":"2015","journal-title":"Int. J. Progn. Health Manag."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"139","DOI":"10.1117\/12.7972479","article-title":"Photometric Method for Determining Surface Orientation from Multiple Images","volume":"19","author":"Woodham","year":"1980","journal-title":"Opt. Eng."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"039701","DOI":"10.1117\/1.OE.52.3.039701","article-title":"Development of an Inspection System for Planar Steel Surface using Multispectral Photometric Stereo","volume":"52","author":"Kang","year":"2013","journal-title":"Opt. Eng."},{"key":"ref_11","unstructured":"Eva, W., Sebastian, Z., Matthias, S., and Eitzinger, C. (2015, January 3\u20135). Photometric Stereo Sensor for Robot-assisted Industrial Quality Inspection of Coated Composite Material Surfaces. Proceedings of the SPIE 12th International Conference on Quality Control by Artificial Vision, Le Creusot, France."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"4888","DOI":"10.1109\/TIP.2015.2471081","article-title":"Photometric Stereo for General BRDFs via Reflection Sparsity Modeling","volume":"24","author":"Han","year":"2015","journal-title":"IEEE Trans. Image Process."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"271","DOI":"10.1109\/TPAMI.2018.2799222","article-title":"A Benchmark Dataset and Evaluation for Non-Lambertian and Uncalibrated Photometric Stereo","volume":"41","author":"Shi","year":"2019","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1561\/0600000065","article-title":"A Survey of Photometric Stereo Techniques","volume":"9","author":"Ackermann","year":"2015","journal-title":"Found. Trends Comput. Graph. Vis."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Mo, Z.P., Shi, B.X., Lu, F., Yeung, S.K., and Matsushita, Y. (2018, January 18\u201322). Uncalibrated Photometric Stereo under Natural Illumination. Proceedings of the CVPR 2018, Salt Lake City, UT, USA.","DOI":"10.1109\/CVPR.2018.00310"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Xie, W.Y., Dai, C.K., and Wang, C. (2015, January 7\u201312). Photometric Stereo with Near Point Lighting: A solution by mesh deformation. Proceedings of the CVPR 2015, Boston, MA, USA.","DOI":"10.1109\/CVPR.2015.7299089"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.optlaseng.2014.07.006","article-title":"A Practical Means for Calibrating an LED-based Photometric Stereo System","volume":"64","author":"Xie","year":"2015","journal-title":"Opt. Lasers Eng."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2732","DOI":"10.1137\/140968100","article-title":"Near Field Photometric Stereo with Point Light Source","volume":"7","author":"Mecca","year":"2014","journal-title":"SIAM J. Imaging Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s10851-017-0761-1","article-title":"LED-based Photometric Stereo: Modeling, Calibration and Numerical Solution","volume":"60","author":"Queau","year":"2018","journal-title":"J. Math. Imaging Vis."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Logothetis, F., Mecca, R., and Cipolla, R. (2017, January 22\u201325). Semi-calibrated Near Field Photometric Stereo. Proceedings of the CVPR 2017, Honolulu, HI, USA.","DOI":"10.1109\/CVPR.2017.481"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Papadhimitri, T., and Favaro, P. (2014, January 1\u20135). Uncalibrated Near-Light Photometric Stereo. Proceedings of the BMVC 2014, Nottingham, UK.","DOI":"10.5244\/C.28.128"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Queau, Y., Wu, T., and Cremers, D. (2017, January 4\u20138). Semi-calibrated Near-Light Photometric Stereo. Proceedings of the SSVM 2017, Kolding, Denmark.","DOI":"10.1007\/978-3-319-58771-4_52"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1016\/j.nucengdes.2015.11.037","article-title":"Automated In-Core Image Generation from Video to Aid Visual Inspection of Nuclear Power Plant Cores","volume":"300","author":"Murray","year":"2016","journal-title":"Nucl. Eng. Des."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Papadhimitri, T., and Favaro, P. (2013, January 23\u201328). A New Perspective Uncalibrated Photometric Stereo. Proceedings of the CVPR 2013, Portland, OR, USA.","DOI":"10.1109\/CVPR.2013.194"},{"key":"ref_25","unstructured":"Horn, B.K. (1986). Robot Vision, The MIT Press."},{"key":"ref_26","unstructured":"Smith, D.J.G., and Bors, A.G. (2002, January 1\u20133). Height Estimation from Vector Fields of Surface Normal. Proceedings of the International Conference on Digital Signal Processing, Hellas, Greece."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1239","DOI":"10.1109\/TPAMI.2003.1233898","article-title":"The 4-Source Photometric Stereo Technique for 3-Dimensional Surfaces in the Presence of Highlights and Shadows","volume":"25","author":"Barsky","year":"2003","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1109\/34.3909","article-title":"A Method for Enforcing Integrability in Shape from Shading Algorithms","volume":"10","author":"Frankot","year":"1988","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/22\/4970\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T13:34:34Z","timestamp":1760189674000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/19\/22\/4970"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2019,11,14]]},"references-count":28,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2019,11]]}},"alternative-id":["s19224970"],"URL":"https:\/\/doi.org\/10.3390\/s19224970","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2019,11,14]]}}}