{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,2]],"date-time":"2026-04-02T19:20:42Z","timestamp":1775157642432,"version":"3.50.1"},"reference-count":34,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2023,2,27]],"date-time":"2023-02-27T00:00:00Z","timestamp":1677456000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["20021979"],"award-info":[{"award-number":["20021979"]}],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["RS-2020-KD000065"],"award-info":[{"award-number":["RS-2020-KD000065"]}],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Korea Medical Device Development Fund Grant funded by the Korea government","award":["20021979"],"award-info":[{"award-number":["20021979"]}]},{"name":"Korea Medical Device Development Fund Grant funded by the Korea government","award":["RS-2020-KD000065"],"award-info":[{"award-number":["RS-2020-KD000065"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A method to enhance laser ultrasound (LUS) image reconstruction with the time-domain synthetic aperture focusing technique (T-SAFT) is presented, in which the acoustic velocity is extracted in situ with curve fitting. The operational principle is provided with the help of a numerical simulation, and the confirmation is provided experimentally. In these experiments, an all-optic LUS system was developed by using lasers for both excitation and detection of ultrasound. The acoustic velocity of a specimen was extracted in situ by fitting a hyperbolic curve to its B-scan image. The needle-like objects embedded within a polydimethylsiloxane (PDMS) block and a chicken breast have been successfully reconstructed using the extracted in situ acoustic velocity. Experimental results suggest that knowing the acoustic velocity in the T-SAFT process is important not only in finding the depth location of the target object but also for producing a high resolution image. This study is expected to pave the wave to the development and usage of all-optic LUS for bio-medical imaging.<\/jats:p>","DOI":"10.3390\/s23052635","type":"journal-article","created":{"date-parts":[[2023,2,28]],"date-time":"2023-02-28T02:01:51Z","timestamp":1677549711000},"page":"2635","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Acoustic Velocity Measurement for Enhancing Laser UltraSound Imaging Based on Time Domain Synthetic Aperture Focusing Technique"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-1305-0467","authenticated-orcid":false,"given":"Taeil","family":"Yoon","sequence":"first","affiliation":[{"name":"School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea"}]},{"given":"Younggue","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea"}]},{"given":"Muhammad","family":"Awais","sequence":"additional","affiliation":[{"name":"School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4544-1232","authenticated-orcid":false,"given":"Byeongha","family":"Lee","sequence":"additional","affiliation":[{"name":"School of Electrical Engineering and Computer Science, Gwangju Institute of Science and Technology, 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1016\/j.ultras.2004.01.101","article-title":"Non-Contact Ultrasonic Techniques","volume":"42","author":"Green","year":"2004","journal-title":"Ultrasonics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"701","DOI":"10.1016\/j.ndteint.2005.04.002","article-title":"Post-Processing of the Full Matrix of Ultrasonic Transmit\u2013Receive Array Data for Non-Destructive Evaluation","volume":"38","author":"Holmes","year":"2005","journal-title":"NDT E Int."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/j.pacs.2014.01.001","article-title":"NDT of Fiber-Reinforced Composites with a New Fiber-Optic Pump\u2013Probe Laser-Ultrasound System","volume":"2","author":"Pelivanov","year":"2014","journal-title":"Photoacoustics"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"113105","DOI":"10.1063\/1.4868463","article-title":"A New Fiber-Optic Non-Contact Compact Laser-Ultrasound Scanner for Fast Non-Destructive Testing and Evaluation of Aircraft Composites","volume":"115","author":"Pelivanov","year":"2014","journal-title":"J. Appl. Phys."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Selim, H., Trull, J., Delgado Prieto, M., Pic\u00f3, R., Romeral, L., and Cojocaru, C. (2019). Fully Noncontact Hybrid NDT for 3D Defect Reconstruction Using SAFT Algorithm and 2D Apodization Window. Sensors, 19.","DOI":"10.3390\/s19092138"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1038\/s41377-019-0229-8","article-title":"Full Noncontact Laser Ultrasound: First Human Data","volume":"8","author":"Zhang","year":"2019","journal-title":"Light Sci. Appl."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Park, S., Lee, J., Kim, Y., and Lee, B.H. (2020). Nanometer-Scale Vibration Measurement Using an Optical Quadrature Interferometer Based on 3 \u00d7 3 Fiber-Optic Coupler. Sensors, 20.","DOI":"10.3390\/s20092665"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Kim, M., Cho, B., Lee, H., Yoon, T., and Lee, B. (2022). Implementation of Hemispherical Resonator Gyroscope with 3 \u00d7 3 Optical Interferometers for Analysis of Resonator Asymmetry. Sensors, 22.","DOI":"10.3390\/s22051971"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3099","DOI":"10.1121\/1.423889","article-title":"The Direct Estimation of Sound Speed Using Pulse\u2013Echo Ultrasound","volume":"104","author":"Anderson","year":"1998","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"3540","DOI":"10.1121\/1.429422","article-title":"The Impact of Sound Speed Errors on Medical Ultrasound Imaging","volume":"107","author":"Anderson","year":"2000","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1177\/0161734612455576","article-title":"A Method for Direct Localized Sound Speed Estimates Using Registered Virtual Detectors","volume":"34","author":"Byram","year":"2012","journal-title":"Ultrason. Imaging"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Opretzka, J., Vogt, M., and Ermert, H. (2010, January 11\u201314). A Synthetic Aperture Focusing Technique with Optimized Beamforming for High-Frequency Ultrasound. Proceedings of the 2010 IEEE International Ultrasonics Symposium, San Diego, CA, USA.","DOI":"10.1109\/ULTSYM.2010.5935794"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1016\/j.ultras.2014.09.018","article-title":"A Time-Domain Synthetic Aperture Ultrasound Imaging Method for Material Flaw Quantification with Validations on Small-Scale Artificial and Natural Flaws","volume":"56","author":"Guan","year":"2015","journal-title":"Ultrasonics"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"5872","DOI":"10.1364\/AO.39.005872","article-title":"Image Reconstruction for Photoacoustic Scanning of Tissue Structures","volume":"39","author":"Hoelen","year":"2000","journal-title":"Appl. Opt."},{"key":"ref_15","unstructured":"Zhao, H., Gachagan, A., Dobie, G., Wallace, C., and West, G. (2018, January 10). Synthetic Aperture Focusing Technique for Correction of Poorly- Focused Ultrasonic Pressure Tube Inspection Data. Proceedings of the 9th Euripean Worshop on Structual Health Monitoring Series (EWSHM), Manchester, UK."},{"key":"ref_16","unstructured":"Stepinski, T., and Lingvall, F. (2010, January 10). Synthetic Aperture Focusing Techniques for Ultrasonic Imaging of Solid Objects. Proceedings of the 8th European Conference on Synthetic Aperture Radar, Aachen, Germany."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1784\/insi.46.4.196.55648","article-title":"Synthetic Aperture Focusing Techniques in Time and Frequency Domains for Photoacoustic Imaging","volume":"46","author":"Boonsang","year":"2004","journal-title":"Insight"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e5","DOI":"10.1016\/j.ultras.2006.07.017","article-title":"Synthetic Aperture Ultrasound Imaging","volume":"44","author":"Jensen","year":"2006","journal-title":"Ultrasonics"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Huang, K.-Y., Chang, C.-H., Chang, Y.-F., Liu, J.-W., and Chang, J.-W. (2022). The Feasibility of Shadowed Image Restoration Using the Synthetic Aperture Focusing Technique. Appl. Sci., 12.","DOI":"10.3390\/app12189297"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3648","DOI":"10.4028\/www.scientific.net\/AMM.380-384.3648","article-title":"Time Domain\/Frequency Domain SAFT Imaging in Thin-Diameter Rod","volume":"380\u2013384","author":"Zhao","year":"2013","journal-title":"AMM"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/j.ultrasmedbio.2014.05.019","article-title":"Computed Ultrasound Tomography in Echo Mode for Imaging Speed of Sound Using Pulse-Echo Sonography: Proof of Principle","volume":"41","author":"Jaeger","year":"2015","journal-title":"Ultrasound Med. Biol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"4497","DOI":"10.1088\/0031-9155\/60\/11\/4497","article-title":"Full Correction for Spatially Distributed Speed-of-Sound in Echo Ultrasound Based on Measuring Aberration Delays via Transmit Beam Steering","volume":"60","author":"Jaeger","year":"2015","journal-title":"Phys. Med. Biol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"215016","DOI":"10.1088\/1361-6560\/ac96c6","article-title":"Pulse-Echo Speed-of-Sound Imaging Using Convex Probes","volume":"67","author":"Jaeger","year":"2022","journal-title":"Phys. Med. Biol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"e43","DOI":"10.1016\/j.ultras.2006.06.061","article-title":"Sound Speed Correction in Ultrasound Imaging","volume":"44","author":"Napolitano","year":"2006","journal-title":"Ultrasonics"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"8773","DOI":"10.1109\/TIP.2021.3120053","article-title":"A Deep Learning-Based Model That Reduces Speed of Sound Aberrations for Improved In Vivo Photoacoustic Imaging","volume":"30","author":"Jeon","year":"2021","journal-title":"IEEE Trans. Image Process."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1057","DOI":"10.1016\/S0041-624X(02)00256-1","article-title":"Performance of Laser-Ultrasonic F-SAFT Imaging","volume":"40","author":"Blouin","year":"2002","journal-title":"Ultrasonics"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"531","DOI":"10.1364\/OE.2.000531","article-title":"Improved Resolution and Signal-to-Noise Ratio in Laser-Ultrasonics by SAFT Processing","volume":"2","author":"Blouin","year":"1998","journal-title":"Opt. Express"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"3424","DOI":"10.1121\/1.428196","article-title":"A Pulsed Phase-Sensitive Technique for Acoustical Measurements","volume":"106","author":"Kozhevnikov","year":"1999","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1260","DOI":"10.1016\/j.phpro.2015.08.280","article-title":"Sound Speed Measurement of Chicken Liver from 22 \u00b0C to 60 \u00b0C","volume":"70","author":"Contreras","year":"2015","journal-title":"Phys. Procedia"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2148","DOI":"10.1002\/2016GL071225","article-title":"Sound Velocity and Density of Magnesiow\u00fcstites: Implications for Ultralow-velocity Zone Topography","volume":"44","author":"Wicks","year":"2017","journal-title":"Geophys. Res. Lett."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"152","DOI":"10.1016\/j.ultras.2018.10.002","article-title":"A PDMS-Based Broadband Acoustic Impedance Matched Material for Underwater Applications","volume":"94","author":"Guillermic","year":"2019","journal-title":"Ultrasonics"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"963","DOI":"10.1016\/j.ultrasmedbio.2007.11.010","article-title":"Role of Ultrasonic Shear Rate Estimation Errors in Assessing Inflammatory Response and Vascular Risk","volume":"34","author":"Tsou","year":"2008","journal-title":"Ultrasound Med. Biol."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Shishitani, T., Yoshizawa, S., and Umemura, S. (2010, January 11\u201314). Change in Acoustic Impedance and Sound Speed of HIFU-Exposed Chicken Breast Muscle. Proceedings of the 2010 IEEE International Ultrasonics Symposium, San Diego, CA, USA.","DOI":"10.1109\/ULTSYM.2010.5935709"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"231524","DOI":"10.1016\/j.jpowsour.2022.231524","article-title":"Effects of Patterned Electrode on near Infrared Light-Triggered Cesium Tungsten Bronze\/Poly(Vinylidene)Fluoride Nanocomposite-Based Pyroelectric Nanogenerator for Energy Harvesting","volume":"536","author":"Gokana","year":"2022","journal-title":"J. Power Sources"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/5\/2635\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T18:44:11Z","timestamp":1760121851000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/5\/2635"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,2,27]]},"references-count":34,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2023,3]]}},"alternative-id":["s23052635"],"URL":"https:\/\/doi.org\/10.3390\/s23052635","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,2,27]]}}}