{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,31]],"date-time":"2026-07-31T01:35:38Z","timestamp":1785461738679,"version":"3.56.0"},"reference-count":32,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2022,12,14]],"date-time":"2022-12-14T00:00:00Z","timestamp":1670976000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"FWO\u2014research foundation"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In 3D printing, as in other manufacturing processes, there is a push for zero-defect manufacturing, mainly to avoid waste. To evaluate the quality of the printed parts during the printing process, an accurate 3D measurement method is required. By scanning the part during the buildup, potential nonconformities to tolerances can be detected early on and the printing process could be adjusted to avoid scrapping the part. Out of many, shape-from-focus, is an accurate method for recovering 3D shapes from objects. However, the state-of-the-art implementation of the method requires the object to be stationary during a measurement. This does not reconcile with the nature of 3D printing, where continuous motion is required for the manufacturing process. This research presents a novel methodology that allows shape-from-focus to be used in a continuous scanning motion, thus making it possible to apply it to the 3D manufacturing process. By controlling the camera trigger and a tunable lens with synchronous signals, a stack of images can be created while the camera or the object is in motion. These images can be re-aligned and then used to create a 3D depth image. The impact on the quality of the 3D measurement was tested by analytically comparing the quality of a scan using the traditional stationary method and of the proposed method to a known reference. The results demonstrate a 1.22% degradation in the measurement error.<\/jats:p>","DOI":"10.3390\/s22249805","type":"journal-article","created":{"date-parts":[[2022,12,14]],"date-time":"2022-12-14T03:21:52Z","timestamp":1670988112000},"page":"9805","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["A Continuous Motion Shape-from-Focus Method for Geometry Measurement during 3D Printing"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9306-5078","authenticated-orcid":false,"given":"Jona","family":"Gladines","sequence":"first","affiliation":[{"name":"Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0590-2770","authenticated-orcid":false,"given":"Seppe","family":"Sels","sequence":"additional","affiliation":[{"name":"Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5859-8402","authenticated-orcid":false,"given":"Michael","family":"Hillen","sequence":"additional","affiliation":[{"name":"Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7975-1338","authenticated-orcid":false,"given":"Steve","family":"Vanlanduit","sequence":"additional","affiliation":[{"name":"Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium"},{"name":"Department of Mechanical Engineering, Pleinlaan 2, Vrije Universiteit Brussel, 1050 Brussel, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,12,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"May, G., and Kiritsis, D. (2019, January 3\u20136). Zero Defect Manufacturing Strategies and Platform for Smart Factories of Industry 4.0. Proceedings of the 4th International Conference on the Industry 4.0 Model for Advanced Manufacturing, Belgrade, Serbia.","DOI":"10.1007\/978-3-030-18180-2_11"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"055012","DOI":"10.1088\/1361-6552\/ab9957","article-title":"Beat the machine (learning): Metal additive manufacturing and closed loop control","volume":"55","author":"Freeman","year":"2020","journal-title":"Phys. Educ."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1007\/s00170-020-05663-6","article-title":"Additive manufacturing methods: Techniques, materials, and closed-loop control applications","volume":"109","author":"Rivera","year":"2020","journal-title":"Int. J. Adv. Manuf. Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"659","DOI":"10.1016\/j.procir.2018.08.053","article-title":"Model assisted closed-loop control strategy for selective laser melting","volume":"74","author":"Renken","year":"2018","journal-title":"Procedia Cirp"},{"key":"ref_5","first-page":"696","article-title":"Investigating Laser Scanner Accuracy","volume":"34","author":"Boehler","year":"2003","journal-title":"Int. Arch. Photogramm. Remote. Sens. Spat. Inf. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Kienle, P., Batarilo, L., Akg\u00fcl, M., K\u00f6hler, M.H., Wang, K., Jakobi, M., and Koch, A.W. (2020). Optical Setup for Error Compensation in a Laser Triangulation System. Sensors, 20.","DOI":"10.3390\/s20174949"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1016\/j.optlaseng.2016.05.005","article-title":"Calibration procedure for a laser triangulation scanner with uncertainty evaluation","volume":"86","author":"Genta","year":"2016","journal-title":"Opt. Lasers Eng."},{"key":"ref_8","unstructured":"Ribbens, B., Vanlanduit, S., Dirckx, J.J.J., and Cools, P. (2011, January 12\u201313). Fringe projection simulation software for 3D shape measurements. Proceedings of the 10th IMEKO Symposium Laser Metrology for Precision Measurement and Inspection in Industry, Braunschweig, Germany."},{"key":"ref_9","unstructured":"Sels, S. (2019). Linking Real-World Measurements and Sensor Data with 3D CAD Models, University of Antwerp, Faculty of Applied Engineering."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"106192","DOI":"10.1016\/j.optlaseng.2020.106192","article-title":"Microscopic fringe projection profilometry: A review","volume":"135","author":"Hu","year":"2020","journal-title":"Opt. Lasers Eng."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"824","DOI":"10.1109\/34.308479","article-title":"Shape from Focus","volume":"16","author":"Nayar","year":"1994","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1415","DOI":"10.1016\/j.patcog.2012.11.011","article-title":"Analysis of focus measure operators for shape-from-focus","volume":"46","author":"Pertuz","year":"2013","journal-title":"Pattern Recognit."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"245","DOI":"10.5545\/sv-jme.2010.175","article-title":"Focus variation\u2014A robust technology for high resolution optical 3D surface metrology","volume":"57","author":"Danzl","year":"2011","journal-title":"Stroj. Vestnik\/J. Mech. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Onogi, S., Kawase, T., Sugino, T., and Nakajima, Y. (2021). Investigation of shape-from-focus precision by texture frequency analysis. Electronics, 10.","DOI":"10.3390\/electronics10161870"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"110311","DOI":"10.1016\/j.measurement.2021.110311","article-title":"Development of a compact focus variation microscopy sensor for on-machine surface topography measurement","volume":"187","author":"Santoso","year":"2022","journal-title":"Measurement"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2483","DOI":"10.1002\/jemt.23781","article-title":"A new focus measure operator for enhancing image focus in 3D shape recovery","volume":"84","author":"Jang","year":"2021","journal-title":"Microsc. Res. Tech."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Gladines, J., Sels, S., Blom, J., and Vanlanduit, S. (2021). A fast shape-from-focus-based surface topography measurement method. Sensors, 21.","DOI":"10.3390\/s21082574"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"108559","DOI":"10.1016\/j.patcog.2022.108559","article-title":"Energy minimization for image focus volume in shape from focus","volume":"126","author":"Ali","year":"2022","journal-title":"Pattern Recognit."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"656","DOI":"10.1002\/jemt.23623","article-title":"A simplified approach using deep neural network for fast and accurate shape from focus","volume":"84","author":"Mutahira","year":"2021","journal-title":"Microsc. Res. Tech."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Erinosho, M.F., Akinlabi, E.T., and Johnson, O.T. (2019). Effect of scanning speed on the surface roughness of laser metal deposited copper on titanium alloy. Mater. Res., 22.","DOI":"10.1590\/1980-5373-mr-2019-0297"},{"key":"ref_21","unstructured":"Optotune (2019). Fast Electrically Tunable Lens EL-10-30 Series, Optotune."},{"key":"ref_22","unstructured":"Thorlabs (2022, July 04). 12 mm (0.47\") Motorized Translation Stages. Available online: https:\/\/www.thorlabs.com\/newgrouppage9.cfm?objectgroup_id=2163."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"266","DOI":"10.1109\/34.368191","article-title":"Accurate Recovery of Three-Dimensional Shape from Image Focus","volume":"17","author":"Subbarao","year":"1995","journal-title":"IEEE Trans. Pattern Anal. Mach. Intell."},{"key":"ref_24","first-page":"411","article-title":"Three-dimensional shape recovery from image focus using polynomial regression analysis in optical microscopy","volume":"4","author":"Lee","year":"2020","journal-title":"Curr. Opt. Photonics"},{"key":"ref_25","unstructured":"Pertuz, S. (2022, July 04). Shape from Focus. Available online: https:\/\/www.mathworks.com\/matlabcentral\/fileexchange\/55103-shape-from-focus."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"188","DOI":"10.1109\/83.988953","article-title":"Extension of phase correlation to subpixel registration","volume":"11","author":"Foroosh","year":"2002","journal-title":"IEEE Trans. Image Process."},{"key":"ref_27","unstructured":"Kuglin, C.D., and Hines, D.C. (1975, January 23\u201325). The Phase Correlation Image Alignment Method. Proceedings of the 1975 International Conference on Cybernetics and Society, San Francisco, CA, USA."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.mfglet.2013.08.004","article-title":"Performance evaluation of 3D imaging systems based on GD&T","volume":"1","author":"Carrier","year":"2013","journal-title":"Manuf. Lett."},{"key":"ref_29","first-page":"379","article-title":"Image Quality Assessment for Performance Evaluation of Focus Measure Operators","volume":"34","author":"Memon","year":"2015","journal-title":"Mehran Univ. Res. J. Eng. Technol."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Lee, S.A., Jang, H.S., and Lee, B.G. (2019). Jitter elimination in shape recovery by using adaptive neural network filter. Sensors, 19.","DOI":"10.3390\/s19112566"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Mahmood, M.T., Choi, Y.K., and Shim, S.O. (2012, January 14\u201317). Estimating shape from focus by Gaussian process regression. Proceedings of the Conference Proceedings-IEEE International Conference on Systems, Man and Cybernetics, Seoul, Republic of Korea.","DOI":"10.1109\/ICSMC.2012.6377920"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"74393","DOI":"10.1109\/ACCESS.2019.2920421","article-title":"Optimizing Image Focus for Shape from Focus Through Locally Weighted Non-Parametric Regression","volume":"7","author":"Jang","year":"2019","journal-title":"IEEE Access"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/24\/9805\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T01:40:58Z","timestamp":1760146858000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/24\/9805"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,12,14]]},"references-count":32,"journal-issue":{"issue":"24","published-online":{"date-parts":[[2022,12]]}},"alternative-id":["s22249805"],"URL":"https:\/\/doi.org\/10.3390\/s22249805","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,12,14]]}}}