• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.28-32
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• 2009

In order to obtain high quality images of thin objects, we performed an experiment of proton radiography by using low energy protons generated from the interaction of an ultrashort ultraintense laser with solid targets. The protons were produced from a thin polyimide target irradiated by the laser pulse, and their maximum energy was estimated at up to 1.8 MeV. A CR-39 nuclear track detector was used as a proton radiography screen. The proton images were obtained by using an optical microscope and the spatial resolution was evaluated by a Modulation Transfer Function (MTF). We have achieved about $10\;{\mu}m$ spatial resolution of images. The obtained spatial resolution shows about $4{\sim}5$ times better value than the conventional X-ray radiography for inspection or non-destructive test (NDT) purpose.

• 한국광학회지
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• 제19권5호
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• pp.370-375
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• 2008

본 논문에서 비동시성 광샘플링(asynchronous optical sampling; AOS) 방식을 이용하는 고속 고분해 테라헤르츠 시간영역 분광(terahertz time domain spectroscopy; THz-TDS)을 시연한다. 모터로 구동되는 선형 스테이지를 사용하지 않고, 약간 다른 반복 주파수를 갖는 두 대의 펨토초 레이저를 각각 테라헤르츠파 발생과 검출에 사용하여 고속으로 10 ns의 시간축 상의 신호를 획득하고 fast Fourier transformation(FFT)을 통하여 100 MHz의 주파수 분해능을 갖는 고분해 분광을 구현한다. Cross-correlation 방법에 의해 시간 분해능은 278 fs으로 측정되었다. 또한, 본 분광기를 이용하여 수증기의 투과 스펙트럼을 측정하고 흡수선들을 분석하였다.

• Current Optics and Photonics
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• 제5권6호
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• pp.711-720
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• 2021

A novel optical hybrid device that doubles the multilevel demodulation resolution by adding the optical interferometer with a waveguide crossover is proposed, theoretically analyzed and experimentally verified. We report two types of all-passive phase control schemes that will be referred to as a phase compensation scheme and a phase optimization scheme. We also apply the proposed phase control schemes to a 45° optical hybrid consisting of two parallel 90° optical hybrids together with the proposed phase control scheme for demodulating 8-level differential phase shift keying optical signals. Octagonal phase response with low wavelength sensitive excess loss of <0.8 dB over 31-nm-wide spectral range will be demonstrated in the InP-based material platform.

• Current Optics and Photonics
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• 제8권4호
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• pp.327-344
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• 2024

Optical phantoms are essential in optical imaging and measurement instruments for performance evaluation, calibration, and quality control. They enable precise measurement of image resolution, accuracy, sensitivity, and contrast, which are crucial for both research and clinical diagnostics. This paper reviews the recent advancements and challenges in phantoms for optical coherence tomography, photoacoustic imaging, digital holographic microscopy, optical diffraction tomography, and oximetry tools. We explore the fundamental principles of each technology, the key factors in phantom development, and the evaluation criteria. Additionally, we discuss the application of phantoms used for enhancing optical-image quality. This investigation includes the development of realistic biological and clinical tissue-mimicking phantoms, emphasizing their role in improving the accuracy and reliability of optical imaging and measurement instruments in biomedical and clinical research.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.691-697
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• 2014

Optical measurements of the morphological and biochemical imaging of phytoplankton are presented. Employing quantitative phase imaging techniques, 3-D refractive index maps and high-resolution 2-D quantitative phase images of individual live phytoplankton are simultaneously obtained without exogenous labeling agents. In addition, biochemical information of individual phytoplankton including volume, mass, and density of individual phytoplankton are also quantitatively obtained from the measured refractive index distributions. We expect the present method to become a powerful tool for the study of phytoplankton.

• 대한기계학회논문집A
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• 제32권2호
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• pp.186-193
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• 2008

[ $Moir{\acute{e}}$ ] interferometry is an optical method, providing whole field contour maps of in-plane displacements with high resolution. The demand for enhanced sensitivity in displacement measurements leads to the technique of microscopic $moir{\acute{e}}$ interferometry. The method is an extension of the $moir{\acute{e}}$ interferometry, and employs an optical microscope for the required spatial resolution. In this paper, the sensitivity of $moir{\acute{e}}$ interferometry is enhanced by an order of magnitude using an immersion interferometry and the optical/digital fringe multiplication(O/DFM) method. In fringe patterns, the contour interval represents the displacement of 52 nm per fringe order. In order to estimate the reliability and the applicability of the optical system implemented, the measurements of rigid body displacements of grating mold and the coefficient of thermal expansion(CTE) for an aluminium block are performed. The system developed is applied to the measurement of thermal deformation in a flip chip plastic ball grid array package.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.150-155
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• 2016

To evaluate the autofocusing performance of recent mobile phone cameras, it is necessary to determine the peak position of the center field MTF (Modulation Transfer Function), -known as the through focus MTF- of the module. However, the MTF peak position found by conventional methods deviates from the ideal position due to the focus scanning resolution of mobile phone cameras. This inaccurate peak position results in false judgements of the optical performance, leading to yield losses or customer complaints. An increase in the focus scanning resolution can address this problem, but the manufacturing UPH (Unit per Hour) level will also unfortunately increase as well, resulting in a loss of manufacturing capabilities. In this paper, several fitting models are studied to find an accurate MTF peak position within a short period of time. With an analysis of a large amount of manufacturing data, it is demonstrated that the fitting methods can reduce false judgements and simultaneously increase the capabilities of the manufacturing system.

• 천문학회보
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• 제42권1호
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• pp.54.2-54.2
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• 2017

We present the results of high-resolution optical (R ~ 30,000) and near-infrared (R ~ 45,000) spectroscopic monitoring observations of a new FU Orionis-like young stellar object, 2MASS J06593158-0405277. FU Orionis objects (FUors) are well-studied examples of episodic accretion because of their outburst phenomenon. Recently, 2MASS J06593158-0405277 exhibited an outburst and was identified as an FUor. It provides an important opportunity to investigate the whole FUors phenomenon from its pre-outburst to its post-outburst phase. We observed 2MASS J06593158-0405277 with the Bohyunsan Optical Echelle Spectrograph (BOES) of the Bohyunsan Optical Astronomy Observatory (BOAO) and the Immersion GRating INfrared Spectrograph (IGRINS) of Harlan J. Smith Telescope (HJST) at the McDonald observatory since December 24, 2014. We detected a number of lines and present here our analysis for time variations of those spectral lines.

• 한국IT서비스학회지
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• 제11권sup호
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• pp.103-111
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• 2012

In epigraph field to study ancient scripts, alternative readability improvement technologies have been developed to replace existing rubbing method which has low resolution and causes surface pollution of heritages from the viewpoints of extraction process and used materials. Recently many methods which are based on analysis of pixel data for extracting outlines of the specific image have been developed with advancement of image processing techniques. But these methods are not applicable and the results are not satisfied in the damaged inscriptions which are weathered by wind and rain for a long time and in the narrowed one. In this paper laser scanning techniques which uses optical triangulation measurement principle are developed to minimize scanning error. The proposed techniques are consisted of 3 parts：(1) the understanding of optical triangulation measurement principle to find scanning guideline (2) determinations of points interval, scanning distance and scanning angle to guarantee scanning data quality (3) identification of valid point data area which will be used in registration process. The proposed character identification method contributed in decoding an ancient inscription on SeukBingGo in Kyungju.

• 천문학논총
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• 제30권2호
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• pp.269-270
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• 2015

We carried out near-IR photometric and optical spectroscopic observations of V582 Aur, which is a FU Orionis type object, to investigate any periodic and/or aperiodic variations. We obtained light curves on the scale of a night and a year, in J, H and Ks bands with KASINICS (KASI Near Infrared Camera System) attached to the BOAO (Bohyun-san Optical Astronomy Observatory) 1.8-m reflector in Youngcheon, South Korea and examined photometric variations on the two time scales. So far we have not found any periodic brightness variations on the scale of a night. On the other hand, we have found that there seems to be a periodic brightness variation with a period of approximately 45 days. In addition, high-resolution optical spectroscopic observations of V582 Aur were performed from February 2013 to May 2014 with the high-resolution echelle spectrograph BOES attached to the BOAO 1.8-m reflector. We analyzed several spectral lines to understand the physical state of V582 Aur. The P Cyg profiles are clearly shown in the $H{\alpha}$ line and Na I D line.