C.-K. LiaoM.-L. LiPAI-CHI LI2018-09-102018-09-102004-1101469592http://scholars.lib.ntu.edu.tw/handle/123456789/310857https://www.scopus.com/inward/record.uri?eid=2-s2.0-9144245647&doi=10.1364%2fOL.29.002506&partnerID=40&md5=acac40fdff4edae7715eeceb871adeb7Optoacoustic imaging takes advantage of high optical contrast and low acoustic scattering and has found several biomedical applications. In the common backward mode a laser beam illuminates the image object, and an acoustic transducer located on the same side as the laser beam detects the optoacoustic signal produced by thermoelastic effects. A cross-sectional image is formed by laterally scanning the laser beam and the transducer. Although the laser beam width is generally narrow to provide good lateral resolution, strong optical scattering in tissue broadens the optical illumination pattern and thus degrades the lateral resolution. To solve this problem, a combination of the synthetic aperture focusing technique with coherence weighting is proposed. This method synthesizes a large aperture by summing properly delayed signals received at different positions. The focusing quality is further improved by using the signal coherence as an image quality index. A phantom comprising hair threads in a 1% milk solution was imaged with an optoacoustic imaging system. The results show that the proposed technique improved lateral resolution by 400-800% and the signal-to-noise ratio by 7-23 dB over conventional techniques. © 2004 Optical Society of America.journal article10.1364/ol.29.002506155842762-s2.0-9144245647WOS:000224600000016Acoustic transducer; Optical illumination; Optoacoustic (OA) imaging; Quality index; Imaging techniques; Laser beams; Lighting; Photoacoustic effect; Signal processing; Signal to noise ratio; Transducers; Synthetic apertures; diagnostic agent; acoustics; article; comparative study; cytology; evaluation; hair; human; image enhancement; image quality; instrumentation; laser; methodology; optical coherence tomography; reproducibility; sensitivity and specificity; validation study; vibration; Acoustics; Hair; Humans; Image Enhancement; Lasers; Phantoms, Imaging; Reproducibility of Results; Sensitivity and Specificity; Tomography, Optical Coherence; Vibration