{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,1]],"date-time":"2025-11-01T12:58:23Z","timestamp":1762001903800,"version":"build-2065373602"},"reference-count":26,"publisher":"MDPI AG","issue":"24","license":[{"start":{"date-parts":[[2020,12,18]],"date-time":"2020-12-18T00:00:00Z","timestamp":1608249600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000003","name":"Boeing","doi-asserted-by":"publisher","award":["C15-2A38-Boeing"],"award-info":[{"award-number":["C15-2A38-Boeing"]}],"id":[{"id":"10.13039\/100000003","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Non-contact optical detection of ultrasound critically depends on the amount of light collected from the detection surface. Although it can be optimized in multiple ways for an ideal flat polished surface, industrial non-destructive testing and evaluation (NDT&amp;E) usually requires optical detectors to be robust for unpolished material surfaces that are usually rough and curved. Confocal detectors provide the best light collection but must trade off sensitivity with depth of field. Specifically, detection efficiency increases with the numerical aperture (NA) of the detector, but the depth of field drops. Therefore, fast realignment of the detector focal point is critical for in-field applications. Here, we propose an optical distance and angle correction system (DACS) and demonstrate it in a kHz-rate laser-ultrasound inspection system. It incorporates a Sagnac interferometer on receive for the fast scanning of aircraft composites, which minimizes the required initial alignment. We show that DACS performs stably for different composite surfaces while providing \u00b12\u00b0 angular and \u00b12 mm axial automatic correction with a maximum 100 ms realignment time.<\/jats:p>","DOI":"10.3390\/s20247266","type":"journal-article","created":{"date-parts":[[2020,12,21]],"date-time":"2020-12-21T01:01:08Z","timestamp":1608512468000},"page":"7266","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Distance and Angle Correction System (DACS) for a kHz A-Scan Rate Pump-Probe Laser-Ultrasound Inspection"],"prefix":"10.3390","volume":"20","author":[{"given":"Ryan A.","family":"Canfield","sequence":"first","affiliation":[{"name":"Department of Bioengineering, University of Washington, Box 355061, Seattle, WA 98195, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jan","family":"Ahrens","sequence":"additional","affiliation":[{"name":"TEM Messtechnik GmbH, Gro\u00dfer Hillen 38, D-30559 Hannover, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jill","family":"Bingham","sequence":"additional","affiliation":[{"name":"Boeing Research and Technology, 9725 E Marginal Way S, Tukwila, WA 98108, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Barry","family":"Fetzer","sequence":"additional","affiliation":[{"name":"Boeing Research and Technology, 9725 E Marginal Way S, Tukwila, WA 98108, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Thomas","family":"M\u00fcller-Wirts","sequence":"additional","affiliation":[{"name":"TEM Messtechnik GmbH, Gro\u00dfer Hillen 38, D-30559 Hannover, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8780-7613","authenticated-orcid":false,"given":"Matthew","family":"O\u2019Donnell","sequence":"additional","affiliation":[{"name":"Department of Bioengineering, University of Washington, Box 355061, Seattle, WA 98195, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gary","family":"Georgeson","sequence":"additional","affiliation":[{"name":"Boeing Research and Technology, 9725 E Marginal Way S, Tukwila, WA 98108, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ivan","family":"Pelivanov","sequence":"additional","affiliation":[{"name":"Department of Bioengineering, University of Washington, Box 355061, Seattle, WA 98195, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,12,18]]},"reference":[{"key":"ref_1","first-page":"485","article-title":"Optical detection of ultrasound","volume":"UFFC-33","author":"Monchalin","year":"1985","journal-title":"IEEE Trans. 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