• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.111-117
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• 2011

Full-range spectral domain optical coherence tomography (SD-OCT) with a 1-${\mu}m$ band light source is shown here. The phase of the reference beam is continuously stepped while the probing beam scans the sample laterally (B-scan). The two dimensional spectral interferogram obtained is processed by a Fourier transform method to obtain a complex spectrum leading to a full-range OCT image. A detailed mathematical explanation of the complex conjugate resolving method utilized is provided. The system's measurement speed was 7.96 kHz, the measured axial resolution was $9.6{\mu}m$ in air and the maximum sensitivity 99.4 dB. To demonstrate the effect of mirror image elimination, In vivo human eye pathology was measured.

• 대한치과의사협회지
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• 제56권12호
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• pp.686-694
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• 2018

Purpose: The aim of this study was to evaluate the validity of swept-source optical coherence tomography (SS-OCT) for detecting sealant microleakage. Materials and Methods: A total of 31 extracted sound human molar, assigned as suitable for sealant application, were chosen and divided into two groups: (1) no microleakage group and (2) microleakage group by applying sealant using the different methods. All specimens were immersed in 1% methylene blue for 24 h and sectioned to confirm the absence or presence of sealant microleakage as a gold standard method. Subsequently, all the sectioned specimens were digitally photographed using a microscope with a magnification of ${\times}50$. Presence of microleakage was evaluated on a 2-point rating scale. The association of histological method with conventional methods (visual and tactile assessment) and SS-OCT was assessed using a chi-squared test. The intra- and inter-examiner reliability was calculated using Cohen's Kappa. Results: The SS-OCT showed a sensitivity of 0.73 and a specificity of 1.00, while visual and tactile assessment showed a sensitivity of 0.67 and a specificity of 0.86. The inter-examiner reliability of SS-OCT was 0.79, whereas that of the visual and tactile assessment was 0.53. Conclusions: SS-OCT can be used to non-invasively detect sealant microleakage and to monitor pit and fissure sealant in the clinics.

• 센서학회지
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• 제22권4호
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• pp.262-267
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• 2013

We developed a real-time screening system using optical coherence tomography (OCT) to distinguish the fruitful melon seeds efficiently. Cross-section images of melon seeds infected with Cucumber green mottle mosaic virus (CGMMV) showed an additional layer that did not appear in normal seeds. Additional layer appeared under $100{\sim}300{\mu}m$ from the surface of the seed. OCT can visualize the micro-structural and morphological changes of the internal seed structure. Real-time OCT seed screening system provided the real-time, non-destructive, cross-section image and quantitative information such as A-scan analysis of selected region in the cross-section image. We can distinguish the viral infection seeds while monitoring the averaged A-scan analysis graph in real-time by considering the second peak value of the graph which refers to the layer that occurred owing to the virus. Real-time OCT seed screening system could assist to distinguish the disease caused by CGMMV.

• 산업기술연구
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• 제28권A호
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• pp.163-166
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• 2008

In this paper, the swept source optical coherence tomography system has realized using a free-space interferometer based on a beam splitter. Personal computer has completed the control for tunable wavelength laser digitally and the B-scan motor as well. From each experiment for an onion and a salmon egg, we confirmed that the in vivo epidermal cross-sectional images for them can be obtained appropriately.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.380-385
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• 2011

Common-path interferometers are widely used for endoscopic optical coherence tomography (OCT) because an arbitrary arm length can be chosen for the endoscopic imaging probe. However, the scheme suffers from the limited range of the sample position distance from the end of the imaging probe because the position between the reference reflector and the sample is limited by the optical path-length difference (OPD) to induce an interference signal. In this study, we developed a novel method for compensating the arbitrary sample position in common-path swept-source OCT by adding an extra Mach-Zehnder interferometer in the post-path of the interfered optical signal. Theoretical analysis and an experimental demonstration of imaging depth tuning for the flexible sample position of an endoscopic OCT image are discussed. After post-tuning of sample position distance, the positioning limitation between the reference reflector and the sample can be solved for various sample positions over a range of 26 mm for the cross-sectional images of a fish eye sample.

• Journal of Veterinary Science
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• 제24권2호
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• pp.30.1-30.6
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• 2023

A 4-year-old Chihuahua dog was referred for bilateral corneal ulcers. Slightly raised white fluorescein-positive plaque-like corneal lesions in both eyes appeared as intense hyperreflective areas with posterior shadowing on optical coherence tomography (OCT). Based on corneal cytology and culture, Candida albicans-induced fungal keratitis was diagnosed. Despite treatment, on OCT, endothelial plaques, increased stromal infiltration thickness, vertical shapes of the ulcer edge, and necrotic stromal space were judged to be aggravation of the disease, and surgery was performed. Conjunctival grafting surgery with topical 1% voriconazole effectively resolved fungal keratitis. OCT can provide detailed and objective information related to the disease prognosis.

• 조명전기설비학회논문지
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• 제18권5호
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• pp.126-131
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• 2004

본 논문은 인체에 무해하며 고분해능의 단층영상과 저가격 및 소형으로 제작이 가능하여 전세계적으로 많은 연구가 진행되고 있는 광영상 단층촬영기(Optical coherence tomography system : OCT)에 관한 것이다. 이러한 OCT시스템은 검출되는 신호가 매우 미약하여 신호처리 및 영상화에 많은 어려움을 가지고 있다. 이러한 문제점을 해결하기 위하여 간섭계의 개선을 통해 신호대 잡음비(Signal to noise ration : SNR)가 향상되도록 하였다. OCT 시스템의 SNR 향상을 위하여 광원의 입력단에 광서큘레이터를 첨가하여 광원부에서 손실되는 단층영상신호를 검출할 수 있도록 간섭계를 개선하였다. SNR 특성평가로는 시뮬레이션을 통한 비교 분석과 기준 샘플의 측정값을 통해 확인하였다. 또한 측정된 데이터의 실시간 영상화를 위한 영상처리 프로그램을 구성하였다. 시뮬레이션 결과로는 개선된 마이켈슨 간섭계가 약 10[dB] 개선됨을 확인하였으며, 기준시편을 이용하여 측정한 결과로는 약 5[dB]가 개선됨을 확인하였다. 개선된 마이켈슨 간섭계를 이용한 OCT 시스템이 보다 높은 대비도로 인해 선명도가 뛰어난 단층을 영상을 얻을 수 있음을 확인 하였다.

• Journal of the Optical Society of Korea
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• 제13권3호
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• pp.316-320
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• 2009

A novel broadband wavelength-swept Raman laser was used to implement Fourier-domain mode locked (FDML) swept-source optical coherence tomography (SS-OCT). Instead of a conventional semiconductor optical amplifier, this study used broadband optical fiber Raman amplification, over 50 nm centered around 1545 nm, using a multi-wavelength optical pumping scheme, which was implemented with the four laser diodes at the center wavelengths of 1425, 1435, 1455 and 1465 nm, respectively, and the maximum operating power of 150 mW each. The operating swept frequency of the laser was determined to 16.7 kHz from the FDML condition of 12 km optical fiber in the ring cavity. The OCT images were obtained using the novel broadband wavelengthswept Raman laser source.

• 센서학회지
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• 제21권3호
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• pp.217-222
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• 2012

Optical coherence tomography(OCT) is a noninvasive optical imaging tool for biomedical applications. OCT can provide depth resolved two/three dimensional morphological images on biological samples. In this paper, we integrated an OCT system that was composed of an SLED(Superluminescent Light Emitting Diode, ${\lambda}_0$=1305 nm bandwith= 141 nm), a reference arm adopting a rapid scanning optical delay line(RSOD) to get high speed imaging, and a sample arm that used a micro electro mechanical systems(MEMS) scanning mirror. The sample arm contained a compact probe for imaging dental structures. The performance of the system was evaluated by imaging in-vivo human teeth with dental calculus, and the results indicated distinct appearance of dental calculus from enamel, gum or decayed teeth. The developed probe and system could successfully confirm the presence of dental calculus with a very high spatial resolution($6{\mu}m$).

• 산업기술연구
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• 제27권B호
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• pp.121-123
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• 2007

As a reflector of reference arm in OCT systems, a coated fiber reflector has mostly used. Instead, this paper has realized the swaept source optical coherence tomography system using a loop mirror within a reference arm. Through the experiments for a tilted thin glass plate, we found that the loop mirror is better than the coated fiber typed mirror for obtaining the clear image.