{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T00:43:41Z","timestamp":1777596221850,"version":"3.51.4"},"reference-count":19,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2021,9,2]],"date-time":"2021-09-02T00:00:00Z","timestamp":1630540800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003725","name":"National Research Foundation of Korea","doi-asserted-by":"publisher","award":["NRF-2019R1A2C4070681"],"award-info":[{"award-number":["NRF-2019R1A2C4070681"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["10073159"],"award-info":[{"award-number":["10073159"]}],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Photoplethysmography (PPG) is an optical measurement technique that detects changes in blood volume in the microvascular layer caused by the pressure generated by the heartbeat. To solve the inconvenience of contact PPG measurement, a remote PPG technology that can measure PPG in a non-contact way using a camera was developed. However, the remote PPG signal has a smaller pulsation component than the contact PPG signal, and its shape is blurred, so only heart rate information can be obtained. In this study, we intend to restore the remote PPG to the level of the contact PPG, to not only measure heart rate, but to also obtain morphological information. Three models were used for training: support vector regression (SVR), a simple three-layer deep learning model, and SVR + deep learning model. Cosine similarity and Pearson correlation coefficients were used to evaluate the similarity of signals before and after restoration. The cosine similarity before restoration was 0.921, and after restoration, the SVR, deep learning model, and SVR + deep learning model were 0.975, 0.975, and 0.977, respectively. The Pearson correlation coefficient was 0.778 before restoration and 0.936, 0.933, and 0.939, respectively, after restoration.<\/jats:p>","DOI":"10.3390\/s21175910","type":"journal-article","created":{"date-parts":[[2021,9,6]],"date-time":"2021-09-06T13:18:26Z","timestamp":1630934306000},"page":"5910","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Restoration of Remote PPG Signal through Correspondence with Contact Sensor Signal"],"prefix":"10.3390","volume":"21","author":[{"given":"So-Eui","family":"Kim","sequence":"first","affiliation":[{"name":"Department of AI & Informatics, Graduate School, Sangmyung University, Seoul 03016, Korea"}]},{"given":"Su-Gyeong","family":"Yu","sequence":"additional","affiliation":[{"name":"Department of AI & Informatics, Graduate School, Sangmyung University, Seoul 03016, Korea"}]},{"given":"Na Hye","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of AI & Informatics, Graduate School, Sangmyung University, Seoul 03016, Korea"}]},{"given":"Kun Ha","family":"Suh","sequence":"additional","affiliation":[{"name":"R&D Team, Zena Inc., Seoul 04782, Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6504-3333","authenticated-orcid":false,"given":"Eui Chul","family":"Lee","sequence":"additional","affiliation":[{"name":"Department of Human-Centered Artificial Intelligence, Sangmyung University, Seoul 03016, Korea"}]}],"member":"1968","published-online":{"date-parts":[[2021,9,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"R1","DOI":"10.1088\/0967-3334\/28\/3\/R01","article-title":"Photoplethysmography and Its Application in Clinical Physiological Measurement","volume":"28","author":"Allen","year":"2007","journal-title":"Physiol. 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