1. Articles from Tae Joong Eom

    1-24 of 27 1 2 »
    1. Angiographic Imaging of an In Vivo Mouse Brain as a Guiding Star for Automatic Digital Refocusing in OCT

      Angiographic Imaging of an In Vivo Mouse Brain as a Guiding Star for Automatic Digital Refocusing in OCT

      A method allows the extraction of the recovery factor that maximizes the image contrast of OCT (optical coherence tomography) and/or OCTA (OCT angiography) of a living subject is proposed in this study. Due to the finite depth of focus in imaging optics, the volume OCT imaging suffers from blurriness in the lateral resolution. By utilizing the digital hologram method or angular spectrum method, the blurred image can be refocused. However, for in vivo OCT imaging, evaluation of the image focus is not easy, owing to the cloudy structure of the brain. In the proposed method, the blood flow signals ...

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    2. 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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    3. 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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    4. 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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    5. Microscope-mounted intraoperative optical coherence tomography with actively tunable focus and optical path length

      Microscope-mounted intraoperative optical coherence tomography with actively tunable focus and optical path length

      We present a method for an intraoperative microscope-mounted Fourier-domain optical coherence tomography (FD-OCT) system to maintain high image contrast while dynamic adjusting focal planes. Because two imaging system with different imaging depth are integrated into one system, active control of OCT imaging conditions is indispensible for functioning high quality imaging modality. For the purpose of active adjustment of the focal plane, an electrically focus tunable lens (FTL) was used in the sample arm of the OCT system. Because the OCT image contrast at a depth is given by roll-off characteristics of the FD-OCT that is a function of difference in ...

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    6. 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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    7. 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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    8. Optical coherence tomography application by using optical phase shift based on fiber optic sensor

      Optical coherence tomography application by using optical phase shift based on fiber optic sensor

      We demonstrate fiber-optic sensor applications to full-range complex optical coherence tomography (OCT). To extend imaging range in OCT, real value or interferogram measured from an interferometer is needed to convert into complex value. For the purpose, various treatments such as mechanical, electro-optical, optical and programming based methods have been exploited in the interferometer. To make complex signal in fiber-optic interferometer, we propose vibrationbased optical phase shifting method. The proposed method utilizes optical fiber sensors that are for the detection of vibration using optical fiber. When coiled fiber was exposed to vibration, interferogram presents fringe shift without periodicity variations, which means ...

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    9. Efficient trigger signal generation from wasted backward amplified stimulated emission at optical amplifiers for optical coherence tomography

      Efficient trigger signal generation from wasted backward amplified stimulated emission at optical amplifiers for optical coherence tomography

      This paper propose an optical structure to generate trigger signals for optical coherence tomography (OCT) using backward light which is usually disposed. The backward light is called backward amplified stimulated emission generated from semiconductor optical amplifier (SOA) when using swept wavelength tunable laser (SWTL). A circulator is applied to block undesirable lights in the SWTL instead of an isolator in common SWTL. The circulator also diverts backward amplified spontaneous lights, which finally bring out trigger signals for a high speed digitizer. The spectra of the forward lights at SOA and the waveform of the backward lights were measured to check ...

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    10. Spectral domain optical coherence tomography with balanced detection using single line-scan camera and optical delay line

      Spectral domain optical coherence tomography with balanced detection using single line-scan camera and optical delay line

      We propose a spectral domain optical coherence tomography (SD-OCT) system that uses a single line-scan detection scheme for balanced detection. Two phase-opposed spectra, generated by two optical fiber couplers, were detected by using a spectrometer with fast optical switching. A 2.69 km optical fiber was introduced to provide a proper time delay to prevent phase errors caused by the difference in measurement time between the two opposing spectra and unstable output voltages for controlling the galvano-scanner. Hence, a phase difference of π was obtained between the spectra over the sample depth without a phase error, which improved sensitivity by approximately ...

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    11. 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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    12. 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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    13. 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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    14. Single-camera polarization-sensitive full-field optical coherence tomography with polarization switch

      Single-camera polarization-sensitive full-field optical coherence tomography with polarization switch

      We present a single-channel detection-based polarization-sensitive full-field optical coherence tomography (PS-FF-OCT) for simultaneous acquisition of high-resolution OCT and linear retardance images. A linearly polarized sub-10-fs laser was used as a broadband light source for the OCT system. A bi-stable polarization switching device, composed of a ferroelectric liquid crystal cell and an analyzer, was employed to get the horizontal and the vertical polarization components of a full-field interference signal. The time-switched two perpendicular interference signals were sequentially recorded by a single charge-coupled device camera, then processed to extract en-face functional images of a biological sample. The rat tail tendon was imaged ...

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    15. Speckle reduction using an artificial neural network algorithm

      Speckle reduction using an artificial neural network algorithm

      This paper presents an algorithm for reducing speckle noise from optical coherence tomography (OCT) images using an artificial neural network (ANN) algorithm. The noise is modeled using Rayleigh distribution with a noise parameter, sigma, estimated by the ANN. The input to the ANN is a set of intensity and wavelet features computed from the image to be processed, and the output is an estimated sigma value. This is then used along with a numerical method to solve the inverse Rayleigh function to reduce the noise in the image. The algorithm is tested successfully on OCT images of Drosophila larvae. It ...

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    16. 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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    17. Polarization sensitive full-field optical coherence tomography based on bi-stable polarizaton switch

      Polarization sensitive full-field optical coherence tomography based on bi-stable polarizaton switch

      We present polarization-sensitive full-field optical coherence tomography (PS-FF-OCT), which is based on a bi-stable polarization switch (BSPS) device. The proposed PS-FF-OCT is a Linnik type interferometer, and allows getting both the birefringence-induced phase retardation and the intensity images of specimens with high resolutions using a pair of micro objectives and a BSPS device. Two orthogonal polarization states are formed with a regular time interval by the BSPS device that changes the polarization direction of light in a short time by switching its optic axes. Therefore, both the horizontally polarized light signal and the vertically polarized light signal from the sample ...

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    18. Feature Of The Week 8/26/12: Gwangju Institute of Science and Technology Investigate Tomography Imaging of Single Living Cell Using Optical Tweezers and FF-OCT

      Feature Of The Week 8/26/12: Gwangju Institute of Science and Technology Investigate Tomography Imaging of Single Living Cell Using Optical Tweezers and FF-OCT

      Gwangju Institute of Science and recently proposed a label-free depth-resolved tomographic scheme for imaging a single live cell in fluid. This approach utilizes a modified time-domain full-field optical coherence tomography (FF-OCT) system combined with an optical tweezer technique. The optical trap for holding a moving specimen is made by tightly focusing a 1064 nm Q -switching pulsed laser beam with a 1.0 NA microscope objective in the sample arm of the FF-OCT part. By cosharing the probe for both systems, the optical actions of trapping and cellular resolution tomographic imaging could be achieved simultaneously. Feasibility of the combined system ...

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    19. Tomographic imaging of a suspending single live cell using optical tweezer-combined full-field optical coherence tomography

      Tomographic imaging of a suspending single live cell using optical tweezer-combined full-field optical coherence tomography

      We propose a label-free depth-resolved tomographic scheme for imaging a single live cell in fluid. This approach utilizes a modified time-domain full-field optical coherence tomography (FF-OCT) system combined with an optical tweezer technique. The optical trap for holding a moving specimen is made by tightly focusing a 1064 nm Q -switching pulsed laser beam with a 1.0 NA microscope objective in the sample arm of the FF-OCT part. By cosharing the probe for both systems, the optical actions of trapping and cellular resolution tomographic imaging could be achieved simultaneously. Feasibility of the combined system is demonstrated by imaging micron-sized ...

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    20. Calibration and characterization protocol for spectral-domain optical coherence tomography using fiber Bragg gratings

      Calibration and characterization protocol for spectral-domain optical coherence tomography using fiber Bragg gratings
      We present a calibration protocol to obtain the alignment factors of a custom-made spectrometer and the nonlinear fitting function between the measured CCD pixel domain and the wavelength domain to apply to the spectral-domain optical coherence tomography (SD-OCT) using fiber Bragg gratings. We have used five gratings with different center wavelengths covering the broadband source spectral range. All have a narrow spectral bandwidth (0.05 nm) and the same reflectivity (92%) to calibrate and align the custom-made spectrometer. The implemented SD-OCT system following the proposed protocol showed the alignment factors as 44.37 deg incident angle, 53.11 deg diffraction ...
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    21. K-Domain Linearization Of Wavelength-Swept Laser For Optical Coherence Tomography

      K-Domain Linearization Of Wavelength-Swept Laser For Optical Coherence Tomography

      We propose a new method for k-domain linearization using fiber Bragg gratings (FBGs) in a wavelength-swept source for optical coherence tomography (OCT). A wavelength-swept source with a scanning fiber Fabry-Perot tunable filter is constructed using a conventional ring laser cavity. Five FBGs are used to recalibrate the nonlinear response from the wavelength-swept source. We achieved good quality sample imaging using the k-domain linearization algorithm based on FBGs. The sensitivity at 2 mm is improved by more than 10 dB after k-domain linearization.

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    22. Real time display Fourier-domain OCT using multi-thread parallel computing with data vectorization

      Real time display Fourier-domain OCT using multi-thread parallel computing with data vectorization

      We demonstrate a real-time display of processed OCT images using multi-thread parallel computing with a quad-core CPU of a personal computer. The data of each A-line are treated as one vector to maximize the data translation rate between the cores of the CPU and RAM stored image data. A display rate of 29.9 frames/sec for processed OCT data (4096 FFT-size x 500 A-scans) is achieved in our system using a wavelength swept source with 52-kHz swept frequency. The data processing times of the OCT image and a Doppler OCT image with a 4-time average are 23.8 msec ...

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    23. Calibration protocol for Fourier-domain OCT using optical fiber gratings

      Calibration protocol for Fourier-domain OCT using optical fiber gratings
      We present a calibration protocol to get the alignment factors of a custom-made spectrometer and the nonlinear fitting function between the measured CCD pixel domain and the wavelength domain to apply the Fourier-domain optical coherence tomography (FD-OCT) using optical fiber gratings. We have used 5 different center wavelength gratings covered the broadband source spectral range with a narrow spectral bandwidth (<0.05 nm) and the same reflectivity (>92 %) to calibrate and align the custom-made spectrometer. The implemented SD-OCT system following the proposed protocol showed the alignment factors as 44.37o incident angle, 53.11o diffraction angle, and 70.0 mm focal length. The spectral resolution of 0 ...
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    24. Laser Processing Apparatus For Monitoring Processing State By Using Optical Coherence Tomography Technology (Wo 2009/096750)

      Laser Processing Apparatus For Monitoring Processing State By Using Optical Coherence Tomography Technology (Wo 2009/096750)

      Disclosed is a laser processing apparatus for monitoring a processing state by using optical coherence tomography technology. The disclosed laser processing apparatus comprises: a processing unit that disrupts the molecular binding of a workpiece by using a femtosecond laser beam; a tomographic monitoring unit that monitors a three-dimensional state of the workpiece; and a controller that controls the output of femtosecond laser beam by using a three-dimensional tomographic image. The laser processing apparatus may further include a surface monitoring unit which monitors a surface state of the workpiece. The laser processing apparatus enables active control over its whole processes since ...

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    1-24 of 27 1 2 »
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    1. (27 articles) Tae Joong Eom
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    3. (11 articles) Byeong Ha Lee
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    Spectrally-sampled OCT for sensitivity improvement from limited optical power Laser Processing Apparatus For Monitoring Processing State By Using Optical Coherence Tomography Technology (Wo 2009/096750) Calibration protocol for Fourier-domain OCT using optical fiber gratings Calibration and characterization protocol for spectral-domain optical coherence tomography using fiber Bragg gratings K-Domain Linearization Of Wavelength-Swept Laser For Optical Coherence Tomography Real time display Fourier-domain OCT using multi-thread parallel computing with data vectorization Tomographic imaging of a suspending single live cell using optical tweezer-combined full-field optical coherence tomography Feature Of The Week 8/26/12: Gwangju Institute of Science and Technology Investigate Tomography Imaging of Single Living Cell Using Optical Tweezers and FF-OCT Full-range space-division multiplexing optical coherence tomography angiography Measuring 3D Optic Nerve Head Deformations using Digital Volume Correlation of in vivo Optical Coherence Tomography Data (Thesis) Optical coherence tomography for characterization of nanocomposite materials (Thesis) In Vivo Corneal Microstructural Changes in Herpetic Stromal Keratitis: A Spectral-Domain Optical Coherence Tomography Analysis