1. Articles from Jun Geun Shin

    1-18 of 18
    1. Buffered polarization diverse detection for single-camera polarization-sensitive optical coherence tomography

      Buffered polarization diverse detection for single-camera polarization-sensitive optical coherence tomography

      Herein we propose a method to mitigate a position mismatch problem for a spectral-domain polarization-sensitive optical coherence tomography (SD-PS-OCT) system that uses a single line-scan detection scheme. A single detector-based PS-OCT detects two orthogonal polarization components as two adjacent A-scan signals in turns. Thus, two adjacent A-scan signals are not scattered at a fixed point in time (position mismatch problem), resulting in uncorrelated signals between them. To achieve sequential detection of simultaneously scattered light, a buffering single-mode fiber was connected to one of the two ports coming out of the optical switch, provided a proper time delay. A single-mode optical ...

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    2. Akinetic swept-source optical coherence tomography based on a pulse-modulated active mode locking fiber laser for human retinal imaging

      Akinetic swept-source optical coherence tomography based on a pulse-modulated active mode locking fiber laser for human retinal imaging

      Optical coherence tomography (OCT) is a noninvasive imaging modality that can provide high-resolution, cross-sectional images of tissues. Especially in retinal imaging, OCT has become one of the most valuable imaging tools for diagnosing eye diseases. Considering the scattering and absorption properties of the eye, the 1000-nm OCT system is preferred for retinal imaging. In this study, we describe the use of an akinetic swept-source OCT system based on a pulse-modulated active mode locking (AML) fiber laser at a 1080-nm wavelength for in-vivo human retinal imaging. The akinetic AML wavelength-swept fiber laser was constructed with polarization-maintaining fiber that has an average ...

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    3. Deep brain optical coherence tomography angiography in mice: in vivo, noninvasive imaging of hippocampal formation

      Deep brain optical coherence tomography angiography in mice: in vivo, noninvasive imaging of hippocampal formation

      The hippocampus is associated with memory and navigation, and the rodent hippocampus provides a useful model system for studying neurophysiology such as neural plasticity. Vascular changes at this site are closely related to brain diseases, such as Alzheimer’s disease, dementia, and epilepsy. Vascular imaging around the hippocampus in mice may help to further elucidate the mechanisms underlying these diseases. Optical coherence tomography angiography (OCTA) is an emerging technology that can provide label-free blood flow information. As the hippocampus is a deep structure in the mouse brain, direct in vivo visualisation of the vascular network using OCTA and other microscopic ...

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    4. Quantitative discrimination of pearls using polarization-sensitive optical coherence tomography

      Quantitative discrimination of pearls using polarization-sensitive optical coherence tomography

      We propose a robust method that can quantitatively discriminate genuine pearls from imitation ones by introducing the concept of entropy in the polarization-sensitive optical coherence tomography (PS-OCT). Qualitatively, by examining the birefringence properties of the nacre region of pearls with PS-OCT, the genuine pearls can be easily discriminated. To quantify the amount of birefringence formation, however, the concept of phase retardation entropy is introduced, which is expected to have a higher value when a PS-OCT tomogram has more diverse phase retardation values in its histogram. Experimental confirmation demonstrated that the phase retardation entropy of a genuine pearl was always higher ...

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    5. In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      In vivo three-dimensional imaging of human corneal nerves using Fourier-domain optical coherence tomography

      We have employed Fourier-domain optical coherence tomography (FD-OCT) to achieve corneal nerve imaging, which could be useful in surgical planning and refractive surgery. Because the three-dimensional (3-D) images of the corneal nerves were acquired in vivo, unintentional movement of the subject during the measurement led to imaging artifacts. These artifacts were compensated for with a series of signal processing techniques, namely realigning A-scan images to flatten the boundary and cross-correlating adjacent B-scan images. To overcome the undesirably large signal from scattering at the corneal surface and iris, volume rendering and maximum intensity projections were performed with only the data taken ...

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    6. Examination of Gland Dropout Detected on Infrared Meibography by Using Optical Coherence Tomography Meibography

      Examination of Gland Dropout Detected on Infrared Meibography by Using Optical Coherence Tomography Meibography

      Purpose To elucidate the anatomic details of gland dropout detected on two-dimensional infrared (IR) meibography in cases of dry eye associated with meibomian gland dysfunction (MGD) by using three-dimensional optical coherence tomography (OCT) meibography. Methods In this cross-sectional, observational case series, we enrolled gland dropout detected on IR meibography; the condition was then examined using a real-time swept-source OCT system. Accordingly, a series of 500 raster B-scan OCT images, with the gland dropout site (observed on IR imaging) at the center, were obtained and rendered as three-dimensional volume images. The OCT images were classified based on the anatomic details, including ...

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    7. An All-Fiber-Optic Combined System of Noncontact Photoacoustic Tomography and Optical Coherence Tomography

      An All-Fiber-Optic Combined System of Noncontact Photoacoustic Tomography and Optical Coherence Tomography

      We propose an all-fiber-based dual-modal imaging system that combines noncontact photoacoustic tomography (PAT) and optical coherence tomography (OCT). The PAT remotely measures photoacoustic (PA) signals with a 1550-nm laser on the surface of a sample by utilizing a fiber interferometer as an ultrasound detector. The fiber-based OCT, employing a swept-source laser centered at 1310 nm, shares the sample arm of the PAT system. The fiber-optic probe for the combined system was homemade with a lensed single-mode fiber (SMF) and a large-core multimode fiber (MMF). The compact and robust common probe is capable of obtaining both the PA and the OCT ...

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    8. All optical fiber combined-imaging system of photoacoustic and optical coherence tomography

      All optical fiber combined-imaging system of photoacoustic and optical coherence tomography

      We present an all optical fiber combined-imaging system that integrates non-contact photoacoustic tomography (NPAT) and optical coherence tomography (OCT) to simultaneously provide PA and OCT images. The fiber-based PAT system utilizing a Mach-Zehnder interferometer with a fiber laser of 1550 nm measures the photoacoustic signal at the sample surface. For the generation of a PA signal, a pulse train from a bulk type Nd:YAG laser illuminates the sample via a large core multimode optical fiber. The fiber-based OCT operating at a center wavelength of 1310 nm allowed is combined with the fiber-based PAT system by sharing the same optical ...

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    9. Short cavity active mode locking fiber laser for optical sensing and imaging

      Short cavity active mode locking fiber laser for optical sensing and imaging

      We demonstrate a highly linear wavenumber- swept active mode locking (AML) fiber laser for optical sensing and imaging without any wavenumber-space resampling process. In this all-electric AML wavenumber-swept mechanism, a conventional wavelength selection filter is eliminated and, instead, the suitable programmed electric modulation signal is directly applied to the gain medium. Various types of wavenumber (or wavelength) tunings can be implemented because of the filter-less cavity configuration. Therefore, we successfully demonstrate a linearly wavenumber-swept AML fiber laser with 26.5 mW of output power to obtain an in-vivo OCT image at the 100 kHz swept rate.

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    10. Three-dimensional volumetric human meibomian gland investigation using polarization-sensitive optical coherence tomography

      Three-dimensional volumetric human meibomian gland investigation using polarization-sensitive optical coherence tomography

      In this study, polarization-sensitive optical coherence tomography (PS-OCT) capable of providing polarization contrasts such as phase retardation and degree of polarization uniformity (DOPU) was used for visualizing human meibomian glands (MGs) and investigating morphological characteristics of them. Especially, with the help of the DOPU contrast, MGs were exclusively extracted from the volumetric OCT image. In vivo PS-OCT measurements were performed on the upper eyelids of different age groups. From these measurements, different age-dependent aspects of the MG structure were also observed. Based on these observations, it can be inferred that the PS-OCT system has the potential for clinical diagnosis and ...

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    11. Segmentation method for in vivo meibomian gland OCT image

      Segmentation method for in vivo meibomian gland OCT image

      We demonstrate segmentation of human MGs based on several image processing technic. 3D volumetric data of upper eyelid was acquired from real-time FD-OCT, and its acini area of MGs was segmented. Three dimensional volume informations of meibomian glands should be helpful to diagnose meibomian gland related disease. In order to reveal boundary between tarsal plate and acini, each B-scan images were obtained before averaged three times. Imaging area was 10x10mm and 700x1000x500 voxels. The acquisition time was 60ms for B-scan and 30sec for C-scan. The 3D data was flattened to remove curvature and axial vibration, and resized to reduce computational ...

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    12. Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography

      Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography

      We propose a single-step method appropriated for a fiber-optic probe-based full-range spectral domain optical coherence tomography (OCT). The fiber-optic probe was scanned over a sample with a magnetically driven actuator. In the reference arm, a phase shift of π / 2 was applied during two neighbor axial scanning, from which the complex spectral interferogram was directly reconstructed. Since the complex-conjugate-free OCT image is obtained by doing just one Fourier transform on the complex interferogram, obtaining the full-range image is simple in algorithm and effective in computation time. Some full-range images of biological samples created with the proposed method are presented and the ...

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    13. In Vivo 3D Meibography of the Human Eyelid Using Real Time Imaging Fourier-Domain OCT

      In Vivo 3D Meibography of the Human Eyelid Using Real Time Imaging Fourier-Domain OCT

      Recently, we reported obtaining tomograms of meibomian glands from healthy volunteers using commercial anterior segment optical coherence tomography (AS-OCT), which is widely employed in clinics for examination of the anterior segment. However, we could not create 3D images of the meibomian glands, because the commercial OCT does not have a 3D reconstruction function. In this study we report the creation of 3D images of the meibomian glands by reconstructing the tomograms of these glands using high speed Fourier-Domain OCT (FD-OCT) developed in our laboratory. This research was jointly undertaken at the Department of Ophthalmology, Seoul St. Mary's Hospital (Seoul ...

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    14. Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter

      Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter

      We present a full range handheld probe type spectral domain optical coherence tomography (SD-OCT) method. Here, the sample arm is composed of a tilted fiber-optic cantilever scanner; thus, the phase shift concurrently occurs while sample scanning. With the phase shift, we could achieve a full range complex-conjugate-free OCT image with no additional phase shifters in the reference arm. To realize this technique, a magnetically actuated probe was adopted. Full range SD-OCT images of a pearl, human fingernail, and human tooth were subsequently obtained using this suggested probe. The scanning range and acquisition speed were 3 mm and 20  frames/s ...

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    15. Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter

      Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter

      We propose full-range spectral domain optical coherence tomography equipped with a fiber-based sample scanner, which is used for sample scanning and phase shifting for full-range image at the same time. For a fiber-based sample scanner, since the fiber tip oscillates as a free standing cantilever in general, unintentional phase shift occurs inevitably. The unintentional phase shift was used for eliminating the bothersome complex conjugate ghost image of OCT. In addition, fiber was tilted a few degree to give proper phase shift. In this scheme, moreover, image can be obtained without any physical modification of the scanner. To realize this technique ...

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    16. Characterization of wet pad surface in chemical mechanical polishing (CMP) process with full-field optical coherence tomography (FF-OCT)

      Characterization of wet pad surface in chemical mechanical polishing (CMP) process with full-field optical coherence tomography (FF-OCT)
      Chemical mechanical polishing (CMP) is a key process for global planarization of silicon wafers for semiconductors and AlTiC wafers for magnetic heads. Removal rate of wafer material is directly dependent on the surface roughness of a CMP pad, thus the structure of the pad surface has been evaluated with variable techniques. However, under in situ CMP process, the measurements have been severely limited due to the existence of polishing fluids including the slurry on the pad surface. In here, we newly introduce ultra-high resolution full-field optical coherence tomography (FF-OCT) to investigate the surface of wet pads. With FF-OCT, the wet ...
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    17. Two-dimensional scanning probe driven by a solenoid-based single actuator for optical coherence tomography

      Two-dimensional scanning probe driven by a solenoid-based single actuator for optical coherence tomography
      We propose the two-dimensional scanning probe operating with a single actuator, which is thought useful as a sample probe for optical coherence tomography (OCT). The probe was designed to use a single-body lensed fiber cantilever loaded with an iron-bead and driven by a single-solenoid actuator. Elliptic spiral trace patterns were achieved using off-axis magnetic fields of the solenoid. A three-dimensional OCT image was obtained for a scanning area of 3.8 mm×3.4 mm at an acquisition speed of 16.7 s/V. Up to 27 Hz B-scan rate, the proposed probe worked well, and 1000 A-scans were made ...
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    18. Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy

      Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy
      , , , , , , , We present an integrated optical system that consists of optical coherence tomography (OCT) and laser-induced fluorescence (LIF) spectroscopy for multimodal analysis of pearls and pearl treatments. The OCT source and the LIF excitation beams were aligned together to illuminate the same spot of a ... [Opt. Express 19, 6420-6432 (2011)]
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    1-18 of 18
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  2. Topics in the News

    1. (18 articles) Jun Geun Shin
    2. (16 articles) Gwangju Institute of Science and Technology
    3. (15 articles) Byeong Ha Lee
    4. (9 articles) Tae Joong Eom
    5. (4 articles) University of Tsukuba
    6. (4 articles) Jae Hwi Lee
    7. (4 articles) Yoshiaki Yasuno
    8. (4 articles) Eun Jung Min
    9. (3 articles) Pusan National University
    10. (3 articles) National Institutes of Health
    11. (2 articles) Chang-Seok Kim
    12. (1 articles) Medical University of Vienna
    13. (1 articles) Columbia University
    14. (1 articles) University of Iowa
    15. (1 articles) University of Rochester
    16. (1 articles) National Eye Institute
    17. (1 articles) Peter E. Andersen
    18. (1 articles) Mona K. Garvin
    19. (1 articles) Santec
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    Multimodal analysis of pearls and pearl treatments by using optical coherence tomography and fluorescence spectroscopy Two-dimensional scanning probe driven by a solenoid-based single actuator for optical coherence tomography Characterization of wet pad surface in chemical mechanical polishing (CMP) process with full-field optical coherence tomography (FF-OCT) Full-range spectral domain optical coherence tomography using fiber-based sample scanner as self-phase shifter Full range spectral domain optical coherence tomography using a fiber-optic probe as a self-phase shifter In Vivo 3D Meibography of the Human Eyelid Using Real Time Imaging Fourier-Domain OCT Single-step method for fiber-optic probe-based full-range spectral domain optical coherence tomography Segmentation method for in vivo meibomian gland OCT image Three-dimensional volumetric human meibomian gland investigation using polarization-sensitive optical coherence tomography Short cavity active mode locking fiber laser for optical sensing and imaging Vitreous Seeding in Retinocytoma: Importance of Optical Coherence Tomography Utility of Spectral-Domain Optical Coherence Tomography in Differentiating Papilledema From Pseudopapilledema: A Prospective Longitudinal Study