{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:22:10Z","timestamp":1785435730786,"version":"3.56.0"},"reference-count":51,"publisher":"Optica Publishing Group","issue":"7","license":[{"start":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T00:00:00Z","timestamp":1780876800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/doi.org\/10.1364\/OA_License_v2#VOR-OA"},{"start":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T00:00:00Z","timestamp":1780876800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/opg.optica.org\/policies\/opg-tdm-policy.json"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"crossref","award":["NO 416\/4-1 675252"],"award-info":[{"award-number":["NO 416\/4-1 675252"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/018mejw64","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002347","name":"Bundesministerium f\u00fcr Forschung, Technologie und Raumfahrt","doi-asserted-by":"crossref","award":["03RU1U153C"],"award-info":[{"award-number":["03RU1U153C"]}],"id":[{"id":"10.13039\/501100002347","id-type":"DOI","asserted-by":"crossref"},{"id":"https:\/\/ror.org\/04pz7b180","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":["opg.optica.org"],"crossmark-restriction":false},"short-container-title":["Biomed. Opt. Express"],"published-print":{"date-parts":[[2026,7,1]]},"abstract":"<jats:p>Camera-based contactless oxygen saturation estimation enables comfort and hygienic long-term monitoring. Deep learning methods have shown promise in extracting rich spatiotemporal features from facial videos, yet they often struggle to generalize across domain shifts, such as inter-subject variability, skin tone differences, spectral discrepancies, sensor system changes, and lab-to-clinic transitions. To address this, we propose a multi-level target unsupervised domain adaptation framework for contactless oximetry from multispectral facial video. Building upon a previously established spatiotemporal 3D CNN baseline, the proposed method aligns source and target feature distributions across multiple network hierarchies together with a dynamically weighted training scheduler and adaptive batch normalization. The framework is systematically evaluated on three custom datasets acquired with two different sensor systems, covering controlled laboratory experiments and real-world clinical recordings. In leave-one-participant-out validation on a breath-holding dataset of 23 healthy subjects, the proposed method reduces the mean absolute error (MAE) from 2.31 % to 1.98 %, desaturation-specific MAE from 3.26 % to 2.60 %, and improves Pearson\u2019s correlation coefficient from 0.64 to 0.71. Consistent performance gains are observed under cross-skin-type, cross-spectral, and cross-sensor-system domain shifts. In a clinical validation involving real sleep apnea patients with 796 oxygen desaturation events, the error between our estimations and polysomnography ground truth stays within 2 % for 90 % of the recorded time. These results demonstrate that the proposed deep domain adaptation framework substantially enhances the robustness and generalization of camera-based contactless oximetry, demonstrating its potential for practical deployment in clinical and real-world monitoring.<\/jats:p>","DOI":"10.1364\/boe.595711","type":"journal-article","created":{"date-parts":[[2026,4,23]],"date-time":"2026-04-23T02:00:06Z","timestamp":1776909606000},"page":"3474","update-policy":"https:\/\/doi.org\/10.1364\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Towards generalizable contactless oximetry from multispectral video via deep domain-adaptive learning strategy"],"prefix":"10.1364","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1165-5171","authenticated-orcid":true,"given":"Wang","family":"Liao","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01weqhp73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fengyuan","family":"Liang","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01weqhp73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8942-4624","authenticated-orcid":true,"given":"Chen","family":"Zhang","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01weqhp73","id-type":"ROR","asserted-by":"publisher"}]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gunther","family":"Notni","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01weqhp73","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Fraunhofer Institute for Applied Optics and Precision Engineering"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"285","published-online":{"date-parts":[[2026,6,8]]},"reference":[{"key":"boe-17-7-3474-R1","doi-asserted-by":"publisher","first-page":"643","DOI":"10.1016\/S0020-7489(00)00119-X","type":"journal-article","volume":"38","author":"Evans","year":"2001","journal-title":"Int. J. Nursing Studies"},{"key":"boe-17-7-3474-R2","doi-asserted-by":"publisher","first-page":"e0210875","DOI":"10.1371\/journal.pone.0210875","type":"journal-article","volume":"14","author":"Brekke","year":"2019","journal-title":"PLoS One"},{"key":"boe-17-7-3474-R3","doi-asserted-by":"publisher","first-page":"1551","DOI":"10.1016\/j.rmed.2012.06.016","type":"journal-article","volume":"106","author":"Vold","year":"2012","journal-title":"Respiratory Medicine"},{"key":"boe-17-7-3474-R4","doi-asserted-by":"publisher","first-page":"958","DOI":"10.1164\/arrd.1984.130.6.958","type":"journal-article","volume":"130","author":"Smith","year":"1984","journal-title":"Am. Rev. Respir. Dis."},{"key":"boe-17-7-3474-R5","doi-asserted-by":"publisher","first-page":"i3","DOI":"10.1093\/bja\/aep299","type":"journal-article","volume":"103","author":"Murkin","year":"2009","journal-title":"Br. J. Anaesth."},{"key":"boe-17-7-3474-R6","doi-asserted-by":"publisher","first-page":"475","DOI":"10.1111\/resp.13635","type":"journal-article","volume":"25","author":"Terrill","year":"2020","journal-title":"Respirology"},{"key":"boe-17-7-3474-R7","doi-asserted-by":"publisher","first-page":"57","DOI":"10.4103\/0972-5229.68215","type":"journal-article","volume":"14","author":"Sood","year":"2010","journal-title":"Indian J. Crit. Care Med."},{"key":"boe-17-7-3474-R8","doi-asserted-by":"publisher","first-page":"272","DOI":"10.1186\/s13054-015-0984-8","type":"journal-article","volume":"19","author":"Jubran","year":"2015","journal-title":"Critical care"},{"key":"boe-17-7-3474-R9","doi-asserted-by":"publisher","first-page":"59","DOI":"10.1016\/S0735-6757(99)90019-0","type":"journal-article","volume":"17","author":"Sinex","year":"1999","journal-title":"The American journal of emergency medicine"},{"key":"boe-17-7-3474-R10","doi-asserted-by":"publisher","first-page":"6791","DOI":"10.1364\/BOE.471332","type":"journal-article","volume":"13","author":"Van Gastel","year":"2022","journal-title":"Biomed. Opt. Express"},{"key":"boe-17-7-3474-R11","doi-asserted-by":"publisher","first-page":"26551","DOI":"10.1109\/JSEN.2023.3284196","type":"journal-article","volume":"23","author":"Wu","year":"2023","journal-title":"IEEE Sens. J."},{"key":"boe-17-7-3474-R12","doi-asserted-by":"publisher","first-page":"3320","DOI":"10.1364\/BOE.6.003320","type":"journal-article","volume":"6","author":"Guazzi","year":"2015","journal-title":"Biomed. Opt. Express"},{"key":"boe-17-7-3474-R13","doi-asserted-by":"publisher","first-page":"86","DOI":"10.1364\/BOE.6.000086","type":"journal-article","volume":"6","author":"Bal","year":"2015","journal-title":"Biomed. Opt. Express"},{"key":"boe-17-7-3474-R14","doi-asserted-by":"publisher","first-page":"5227","DOI":"10.1364\/BOE.423508","type":"journal-article","volume":"12","author":"Wei","year":"2021","journal-title":"Biomed. Opt. Express"},{"key":"boe-17-7-3474-R15","doi-asserted-by":"publisher","first-page":"1091","DOI":"10.1109\/TBME.2015.2481896","type":"journal-article","volume":"63","author":"Shao","year":"2015","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"boe-17-7-3474-R16","doi-asserted-by":"publisher","first-page":"1409","DOI":"10.1109\/JBHI.2020.3045859","type":"journal-article","volume":"25","author":"Van Gastel","year":"2020","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"boe-17-7-3474-R19","doi-asserted-by":"publisher","first-page":"1034","DOI":"10.1007\/s10439-005-5763-2","type":"journal-article","volume":"33","author":"Wieringa","year":"2005","journal-title":"Ann. Biomed. Eng."},{"key":"boe-17-7-3474-R20","first-page":"177","article-title":"Oxygen saturation estimation from near-infrared multispectral video data using 3d convolutional residual networks","author":"Liao","year":"2023"},{"key":"boe-17-7-3474-R21","doi-asserted-by":"publisher","first-page":"e70001","DOI":"10.1002\/jbio.70001","type":"journal-article","volume":"18","author":"Yizhuo","year":"2025","journal-title":"J. Biophotonics"},{"key":"boe-17-7-3474-R23","doi-asserted-by":"publisher","first-page":"104421","DOI":"10.1016\/j.infrared.2022.104421","type":"journal-article","volume":"127","author":"Lan","year":"2022","journal-title":"Infrared Phys. Technol."},{"key":"boe-17-7-3474-R24","doi-asserted-by":"publisher","first-page":"2603","DOI":"10.1109\/JBHI.2018.2887209","type":"journal-article","volume":"23","author":"Ding","year":"2018","journal-title":"IEEE J. Biomed. Health Inform."},{"key":"boe-17-7-3474-R25","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1109\/JTEHM.2022.3217428","type":"journal-article","volume":"10","author":"Mahmud","year":"2022","journal-title":"IEEE J. Transl. Eng. Health Med."},{"key":"boe-17-7-3474-R26","doi-asserted-by":"publisher","first-page":"107105","DOI":"10.1016\/j.bspc.2024.107105","type":"journal-article","volume":"100","author":"Chowdhury","year":"2025","journal-title":"Biomed. Signal Process. Control"},{"key":"boe-17-7-3474-R27","doi-asserted-by":"publisher","first-page":"104487","DOI":"10.1016\/j.bspc.2022.104487","type":"journal-article","volume":"81","author":"Hu","year":"2023","journal-title":"Biomed. Signal Process. Control"},{"key":"boe-17-7-3474-R28","doi-asserted-by":"publisher","first-page":"251","DOI":"10.3390\/bioengineering11030251","type":"journal-article","volume":"11","author":"Cheng","year":"2024","journal-title":"Bioengineering"},{"key":"boe-17-7-3474-R29","doi-asserted-by":"publisher","first-page":"S33309","DOI":"10.1117\/1.JBO.29.S3.S33309","type":"journal-article","volume":"29","author":"Liao","year":"2024","journal-title":"J. Biomed. Opt."},{"key":"boe-17-7-3474-R30","doi-asserted-by":"publisher","first-page":"4097","DOI":"10.3390\/s22114097","type":"journal-article","volume":"22","author":"Selvaraju","year":"2022","journal-title":"Sensors"},{"key":"boe-17-7-3474-R31","doi-asserted-by":"publisher","first-page":"108069","DOI":"10.1016\/j.bspc.2025.108069","type":"journal-article","volume":"110","author":"Wuyart","year":"2025","journal-title":"Biomed. Signal Process. Control"},{"key":"boe-17-7-3474-R32","doi-asserted-by":"publisher","first-page":"151","DOI":"10.1007\/s10994-009-5152-4","type":"journal-article","volume":"79","author":"Ben-David","year":"2010","journal-title":"Machine Learn."},{"key":"boe-17-7-3474-R33","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1145\/3400066","type":"journal-article","volume":"11","author":"Wilson","year":"2020","journal-title":"ACM Trans. Intell. Syst. Technol."},{"key":"boe-17-7-3474-R35","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1109\/TIM.2025.3635333","type":"journal-article","volume":"74","author":"Xie","year":"2025","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"boe-17-7-3474-R37","doi-asserted-by":"publisher","first-page":"19144","DOI":"10.1038\/s41598-024-70192-1","type":"journal-article","volume":"14","author":"Zhu","year":"2024","journal-title":"Sci. Rep."},{"key":"boe-17-7-3474-R38","doi-asserted-by":"publisher","first-page":"2477","DOI":"10.1056\/NEJMc2029240","type":"journal-article","volume":"383","author":"Sjoding","year":"2020","journal-title":"N. Engl. J. Med."},{"key":"boe-17-7-3474-R41","doi-asserted-by":"publisher","author":"Li","year":"2016","DOI":"10.48550\/arXiv.1603.04779","type":"preprint"},{"key":"boe-17-7-3474-R42","doi-asserted-by":"publisher","first-page":"123","DOI":"10.3390\/jimaging6110123","type":"journal-article","volume":"6","author":"Zhang","year":"2020","journal-title":"J. Imaging"},{"key":"boe-17-7-3474-R43","doi-asserted-by":"publisher","first-page":"90","DOI":"10.1016\/j.optlaseng.2016.02.017","type":"journal-article","volume":"87","author":"Heist","year":"2016","journal-title":"Opt. Lasers Eng."},{"key":"boe-17-7-3474-R44","doi-asserted-by":"publisher","first-page":"101647","DOI":"10.1016\/j.measen.2024.101647","type":"journal-article","volume":"38","author":"Liao","year":"2025","journal-title":"Measurement: Sensors"},{"key":"boe-17-7-3474-R46","doi-asserted-by":"publisher","first-page":"7361","DOI":"10.1364\/OE.412655","type":"journal-article","volume":"29","author":"Hubold","year":"2021","journal-title":"Opt. Express"},{"key":"boe-17-7-3474-R47","first-page":"012031","article-title":"Exact correction of image distortion in a filter wheel multispectral camera with focus adjustment","author":"Zhang","year":"2018"},{"key":"boe-17-7-3474-R48","doi-asserted-by":"publisher","first-page":"421","DOI":"10.3390\/electronics7120421","type":"journal-article","volume":"7","author":"An","year":"2018","journal-title":"Electronics"},{"key":"boe-17-7-3474-R49","doi-asserted-by":"publisher","first-page":"869","DOI":"10.1001\/archderm.1988.01670060015008","type":"journal-article","volume":"124","author":"Fitzpatrick","year":"1988","journal-title":"Arch. Dermatol."},{"key":"boe-17-7-3474-R52","doi-asserted-by":"publisher","first-page":"82","DOI":"10.1016\/j.patrec.2017.10.017","type":"journal-article","volume":"124","author":"Bobbia","year":"2019","journal-title":"Pattern Recognition Letters"},{"key":"boe-17-7-3474-R53","doi-asserted-by":"publisher","first-page":"2123","DOI":"10.2147\/NSS.S388238","type":"journal-article","volume":"14","author":"Wang","year":"2022","journal-title":"Nat. Sci. Sleep"},{"key":"boe-17-7-3474-R54","doi-asserted-by":"publisher","first-page":"4205","DOI":"10.3390\/jcm12134205","type":"journal-article","volume":"12","author":"Bikov","year":"2023","journal-title":"J. Clin. Med."},{"key":"boe-17-7-3474-R55","doi-asserted-by":"publisher","first-page":"132","DOI":"10.3399\/bjgp22X718769","type":"journal-article","volume":"72","author":"Silverston","year":"2022","journal-title":"Br. J. Gen. Pract."},{"key":"boe-17-7-3474-R56","doi-asserted-by":"publisher","first-page":"540","DOI":"10.1007\/BF00273571","type":"journal-article","volume":"15","author":"Fanconi","year":"1989","journal-title":"Intensive Care Med."},{"key":"boe-17-7-3474-R57","doi-asserted-by":"publisher","first-page":"136","DOI":"10.1213\/ANE.0000000000001381","type":"journal-article","volume":"124","author":"Verkruysse","year":"2017","journal-title":"Anesthesia Analgesia"},{"key":"boe-17-7-3474-R58","doi-asserted-by":"publisher","first-page":"2813","DOI":"10.1364\/BOE.419199","type":"journal-article","volume":"12","author":"van Gastel","year":"2021","journal-title":"Biomed. Opt. Express"},{"key":"boe-17-7-3474-R59","doi-asserted-by":"publisher","first-page":"3857","DOI":"10.3390\/app9183857","type":"journal-article","volume":"9","author":"van Gastel","year":"2019","journal-title":"Appl. Sci."},{"key":"boe-17-7-3474-R60","doi-asserted-by":"publisher","first-page":"197","DOI":"10.1109\/JSTSP.2022.3152352","type":"journal-article","volume":"16","author":"Tian","year":"2022","journal-title":"IEEE J. Sel. Top. Signal Process."},{"key":"boe-17-7-3474-R61","first-page":"2579","type":"journal-article","volume":"9","author":"Van der Maaten","year":"2008","journal-title":"Journal of Machine Learning Research"}],"container-title":["Biomedical Optics Express"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/opg.optica.org\/viewmedia.cfm?URI=boe-17-7-3474&seq=0","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T14:18:54Z","timestamp":1780928334000},"score":1,"resource":{"primary":{"URL":"https:\/\/opg.optica.org\/abstract.cfm?URI=boe-17-7-3474"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,8]]},"references-count":51,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026]]},"published-print":{"date-parts":[[2026]]}},"URL":"https:\/\/doi.org\/10.1364\/boe.595711","relation":{},"ISSN":["2156-7085","2156-7085"],"issn-type":[{"value":"2156-7085","type":"print"},{"value":"2156-7085","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,8]]},"assertion":[{"value":"Optica Publishing Group","name":"publisher","label":"This article is maintained by"},{"value":"https:\/\/doi.org\/10.1364\/BOE.595711","name":"articlelink","label":"Crossref DOI link to publisher maintained version"},{"value":"research-article","name":"content_type","label":"Article type"},{"value":"Screened by Similarity Check","name":"cross_check","label":"Similarity check"},{"value":"Yes","order":0,"name":"peer_reviewed","label":"Peer reviewed","group":{"name":"peer_review","label":"Peer review"}},{"value":"Single blind","order":1,"name":"review_process","label":"Review process","group":{"name":"peer_review","label":"Peer review"}},{"value":"13 February 2026","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"16 April 2026","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"8 June 2026","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}},{"value":"\u00a9 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement","name":"copyright","label":"Copyright"}]}}