• 한국세라믹학회지
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• 제40권11호
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• pp.1047-1057
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• 2003

A sub-nanometer resolution Scanning Nonlinear Dielectric Microscope (SNDM) was developed for observing ferroelectric polarization. We also demonstrate that the resolution of SNDM is higher than that of a conventional piezo-response imaging. Secondly, we report new SNDM technique detecting higher nonlinear dielectric constants $\varepsilon$$\_$3333/ and $\varepsilon$$\_$33333/. Higher order nonlinear dielectric imaging provides higher lateral and depth resolution. Finally, the formation of artificial small inverted domain is reported to demonstrate that SNDM system is very useful as a nano-domain engineering tool. The nano-size domain dots were successfully formed in LiTaO$_3$ single crystal. This means that we can obtain a very high density ferroelectric data storage with the density above 1T-bits/inch$^2$.

• 천문학회보
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• 제39권1호
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• pp.62.2-62.2
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• 2014

We compiled near-infrared photometric and polarimetric catalog of sources in ~3 $9^{\prime}{\times}69^{\prime}$ size field in the eastern side of the Large Magellanic Cloud (LMC). This catalog lists all 1969 sources which are brighter than 14 mag and which signal to noise ratio of degree of polarization is greater than 3 in the J, H, and Ks bands. The photometric and polarimetric data were simultaneously obtained in J, H, and Ks bands using SIRPOL, an imaging polarimeter of the InfraRed Survey Facility (IRSF), in 2008 December and 2011 December. We classified the objects into several groups based on their locations on the color-magnitude diagram and compared their general properties of polarization. We measured wavelength dependence of this field to verify interstellar polarization of the LMC which occurred from the dichroic extinction. We also discuss the polarization structure in this field with the results from molecular cloud studies.

• Medical Lasers
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• 제9권1호
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• pp.25-33
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• 2020

Optical-based imaging technology has high resolution and can assess images in real time. Numerous studies have been conducted for its application in the dental field. The current research introduces an oral camera that includes fluorescent imaging, a second study examining a 3D intraoral scanner applying a confocal method and a polarization structure that identifies the 3D image of a tooth, and finally, an optical coherence tomography technique. Using this technique, we introduce a new concept 3D oral scanner that simultaneously implements 3D structural imaging as well as images that diagnose the inside of teeth. With the development of light source technology and detector technology, various optical-based imaging technologies are expected to be applied in dentistry.

• Current Optics and Photonics
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• 제8권2호
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• pp.192-200
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• 2024

Wheat stripe rust, caused by Puccinia striiformis, has reduced winter wheat yield globally for ages. In this work, multi-spectral Mueller matrix imaging with 37 measurements using the method of double rotatable quarter-wave plates was used to investigate wheat stripe rust. Individual Mueller matrix measurements were performed on incident monochromatic light with nine bands in the range of 430 to 690 nm. As a result, it was found that the infected area absorbed linearly polarized light and was sensitive to circularly polarized light in the spectral domain. Both linear depolarization and linear diattenuation images distinguished between wheat stripe rust and healthy tissue. The responsiveness of stripe rust to polarized light reveals the potential of using polarization imaging to detect plant diseases. This further suggests that the multi-spectral Mueller matrix imaging system provides us with an alternative approach to agricultural disease detection.

• IUGG한국위원회:학술대회논문집
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• IUGG한국위원회 2003년도 정기총회 및 학술발표회
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• pp.14-14
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• 2003

SAR (Synthetic Aperture Radar) is an imaging radar which can scan and image Earth System targets without solar illumination. Most Earth observation Shh systems operate in X-, C-, S-, L-, and P-band frequencies, where the shortest wavelength is approximately 1.5 cm. This means that most opaque objects in the SAR signal path become transparent and SAR systems can image the planetary surface targets without sunlight and through rain, snow and/or even volcanic ash clouds. Most conventional SAR systems in operation, including the Canada's RADARSAT-1, operate in one frequency and in one polarization. This has resulted in black and with images, with which we are familiar now. However, with the launching of ENVTSAT on March 1 2002, the ASAR system onboard the ENVISAT can image Earth's surface targets with selected polarimetric signals, HH+VV, HH+VH, and VV+HV. In 2004, Canadian Space Agency will launch RADARSAT-II, which is C-band, fully polarimetric HH+VV+VH+HV. Almost same time, the NASDA of Japan will launch ALOS (Advanced land Observation Satellite) which will carry L-band PALSAR system, which is again fully polarimetric. This means that we will have at least three fully polarimetric space-borne SAR system fur civilian operation in less than one year. Are we then ready for this new all weather Earth Observation technology\ulcorner Actual imaging process of a fully polarimetric SAR system is not easy to explain. But, most Earth system scientists, including geologists, are familiar with polarization microscopes and other polarization effects in nature. The spatial resolution of the new generation of SAR systems have also been steadily increased, almost to the limit of highest optical resolution. In this talk some new applications how they are used for Earth system observation purpose.

• 비파괴검사학회지
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• 제33권3호
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• pp.283-288
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• 2013

This paper describes development of a high speed Doppler OFDI system for non-invasive vascular imaging. Doppler OFDI (optical frequency domain imaging) is one of the phase-resolved second generation OCT (optical coherence tomography) techniques for high resolution imaging of moving elements in biological tissues. To achieve a phase-resolved imaging, two temporally separated measurements are required. In a conventional Doppler OCT, a pair of massively oversampled successive A-lines is used to minimize de-correlation noise at the expense of significant imaging speed reduction. To minimize a de-correlation noise between targeted two measurements without suffering from significant imaging speed reduction, several methods have been developed such as an optimized scanning pattern and polarization multiplexed dual beam scanning. This research represent novel imaging technique using frequency multiplexed dual beam illumination to measure exactly same position with aimed time interval. Developed system has been verified using a tissue phantom and mouse vessel imaging.

• Medical Lasers
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• 제10권3호
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• pp.123-131
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• 2021

Optical imaging modalities with properties of real-time, non-invasive, in vivo, and high resolution for image-guided surgery have been widely studied. In this review, we introduce two optical imaging systems, that could be the core of image-guided surgery and introduce the system configuration, implementation, and operation methods. First, we introduce the optical coherence tomography (OCT) system implemented by our research group. This system is implemented based on a swept-source, and the system has an axial resolution of 11 ㎛ and a lateral resolution of 22 ㎛. Second, we introduce a fluorescence imaging system. The fluorescence imaging system was implemented based on the absorption and fluorescence wavelength of indocyanine green (ICG), with a light-emitting diode (LED) light source. To confirm the performance of the two imaging systems, human malignant melanoma cells were injected into BALB/c nude mice to create a xenograft model and using this, OCT images of cancer and pathological slide images were compared. In addition, in a mouse model, an intravenous injection of indocyanine green was used with a fluorescence imaging system to detect real-time images moving along blood vessels and to detect sentinel lymph nodes, which could be very important for cancer staging. Finally, polarization-sensitive OCT to find the boundaries of cancer in real-time and real-time image-guided surgery using a developed contrast agent and fluorescence imaging system were introduced.

• 천문학회보
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• 제40권2호
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• pp.28.3-29
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• 2015

$Ly{\alpha}$ nebulae, or "$Ly{\alpha}$ blobs", are extended (~100 kpc), bright (L[$Ly{\alpha}$] ~ 1044 erg/s) clouds of $Ly{\alpha}$-emitting gas. The origin of the $Ly{\alpha}$ emission remains unknown, but recent theoretical work suggests that measuring the polarization could discriminate among powering mechanisms. we will discuss current status of $Ly{\alpha}$ polarization observations at high-redshift and our on-going survey program. We will present the first narrow-band, imaging polarimetry of a $Ly{\alpha}$ blob, B3 J2330+3927 at z=3.09, with an embedded, radio-loud AGN (C. You et al. in prep.). The AGN lies near the blob's $Ly{\alpha}$ emission peak and its radio lobes align roughly with the blob's semi-major axis. With the SPOL polarimeter on the MMT telescope, we map the polarization in a grid of circular apertures of radius 0.6" (4.4 kpc), detecting a significant (>$2{\sigma}$) polarization fraction P% in 10 apertures and achieving strong upper-limits (as low as 2%) elsewhere. The degree of the polarization map increases from P% ~ 5% at ~5 kpc from the blob center to ~20% at the outer part (~30 kpc). The detections are distributed asymmetrically, roughly along the blob's major axis. The polarization angles (${\Theta}$) are mostly perpendicular to this axis. These results are consistent with the picture that $Ly{\alpha}$ photons produced at the AGN (or the host galaxy) are resonantly scattered away from the center. Higher polarization fraction on the radio jet suggests that the gas is more optically thin along the jet than the off-axis region.

• 천문학회보
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• 제43권1호
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• pp.35.4-36
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• 2018

$Ly{\alpha}$ blobs are mysterious, giant (~100 kpc), glowing gas clouds in the distant universe. They occupy the dark matter halos that will evolve into the richest groups and clusters today. The blob's gas may be the proto-intracluster medium and their embedded galaxies are considered as the progenitors of massive cluster galaxies. Yet we do not know why $Ly{\alpha}$ blobs glow. There are evidences of kinematic measurements to exclude shocks and winds from AGN or starbursts as a power source, suggesting that photoionizing radiation or scattering of $Ly{\alpha}$ photons might be responsible. Polarization mapping can discriminate between these photo-ionization and scattering. Previous results of imaging polarimetry for $Ly{\alpha}$ nebulae are roughly consistent with scattering models. However the polarization morphologies in those of previous results are all different, motivating our polarimetric survey of $Ly{\alpha}$ nebulae for the statisticallymeaningful sample. As initial results of our survey, we present the total polarization map of the LABd05 which has the spatial offset between the peak of $Ly{\alpha}$ surface brightness and an obscured AGN. We detect the significant polarization in this target with the radially increasing polarization gradient, suggesting that scattering plays major role within this nebula. The polarization pattern is more aligned with the $Ly{\alpha}$ peak rather than the AGN (the potential energy source), indicating that the $Ly{\alpha}$ photons are originated from the region near the peak of $Ly{\alpha}$ intensity.

• 대한원격탐사학회지
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• 제36권4호
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• pp.535-544
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• 2020

In synthetic aperture radar (SAR) based ship detection application, false alarms frequently occur due to various noises caused by the radar imaging process. Among them, radio frequency interference (RFI) and azimuth smearing produce substantial false alarms; the latter also yields longer length estimation of ships than the true length. These two noises are prominent at cross-polarization and relatively weak at co-polarization. However, in general, the cross-polarization data are suitable for ship detection, because the radar backscatter from background sea surface is much less in comparison with the co-polarization backscatter, i.e., higher ship-sea image contrast. In order to improve the ship detection accuracy further, the RFI and azimuth smearing need to be mitigated. In the present letter, Sentinel-1 VV- and VH-polarization intensity data are used to show a novel technique of removing these noises. In this method, median image intensities of noises and background sea surface are calculated to yield arithmetic tendency. A band-math formula is then designed to replace the intensities of noise pixels in VH-polarization with adjusted VV-polarization intensity pixels that are less affected by the noises. To verify the proposed method, the adaptive threshold method (ATM) with a sliding window was used for ship detection, and the results showed that the 74.39% of RFI false alarms are removed and 92.27% false alarms of azimuth smearing are removed.