• 한국자기학회:학술대회 개요집
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• 한국자기학회 1999년도 춘계연구발표회 논문개요집
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• pp.114-115
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• 1999

• 한국자기학회:학술대회 개요집
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• 한국자기학회 1998년도 추계연구발표회 논문개요집
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• pp.26-27
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• 1998

• 정보저장시스템학회논문집
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• 제4권1호
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• pp.1-5
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• 2008

Super-resolution near-field structure (super-RENS) technology and solid immersion lens (SIL) based near-field (NF) technology have been expected as promising approaches to increase data capacity or areal density of optical disc. Super-RENS technology has been studied until now using mainly numerical aperture (NA) of 0.85 far-field optical system and possibility of tangential data density increment have been presented. NF technology has been studied with NA over 1 and presented demonstration of removable performance. To achieve much higher density, approach to increase NA of super-RENS by NF technology (Near-Field Super-Resolution, NFSR) can be a candidate and we think this technology would be advantageous compared to wavelength reduction or much higher NA increment of NF technology or much smaller effective optical spot size reduction of far-field super-resolution technology. In this paper we present readout result of ROM media having monotone pits using NF optical system with wavelength of 405nm and NA of 1.84 surface type SIL. GeSbTe material was used for super resolution active layer and pit length is 37.5nm which is shorter than resolution limit 55nm. We present the feasibility of NFSR technology by confirming the CNR threshold according to readout power (Pr) and CNR 33dB over threshold Pr.

• 대한전자공학회논문지SD
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• 제41권9호
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• pp.49-56
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• 2004

HgCdTe 64×2 중원적외선 이중대역 동시검출기를 위한 포화전류차단 회로를 갖는 BDI입력방식의 신호취득회로(ROIC)를 설계하였다. 제안된 포화차단 회로를 통해서 중적외선 신호가 포화되면 원적외선 신호도 왜곡이 일어나던 기존의 문제점을 해결함으로써 120k정도 더 넓은 온도 영역의 물체까지 측정할 수 있는 범위를 확보하고 중적외선 검출기에서 발생하는 dead pixel에 의해 원적외선 검출기의 성능은 영향받지 않는 특성을 보였다. 회로 제작에 사용한 공정은 0.Sum 2-poly 3-metal Hynix CMOS 공정이었다. 측정결과 중적외선 신호와 원적외선 신호가 동시에 처리되는 것을 확인할 수 있었다. 또한, 측정된 잡음의 크기는 상온에서 53uV로서 동작온도 77K의 값으로 환산시켜 보았을 때 27uV로 ROIC의 특성이95% BLIP 조건을 만족함을 알 수 있었다.

• 전자공학회논문지SC
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• 제46권1호
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• pp.43-48
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• 2009

광섬유 격자 센서어레이용 파장가변 광섬유 레이저의 출력파장변화를 복조할 수 있는 시스템을 제안하였다. 광섬유 레이저는 반도체 광증폭기와 Fabry-Perot 필터를 이용하여 제작하였고, 더블패스 마하젠더 간섭계 구조를 적용하여, $90^{\circ}$위상차를 가지는 내부 트리거를 생성하였다. 내부 트리거를 이용하여 얻은 Lissajous 그래프에 원형 피팅을 적용하여 2.51 mrad의 평균위상오차를 얻었다. 실험을 통하여 파장가변필터의 비선형 동작 특성에 의한 광섬유 레이저의 비선형 출력을 확인하였다. 제안한 파장검출 방법을 적용하면 파장가변광원의 비선형성을 보상하여 광섬유격자 센서시스템을 위한 효율적인 광원으로 적용이 가능할 것으로 예상된다.

• 천문학논총
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• 제23권1호
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• pp.1-12
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• 2008

Understanding of the basic characteristics of an astronomical instrument is a prerequisite to obtaining reliable data from the instrument. We have analyzed more than 1,000 calibration images from the Fairchild 486 CCD (hereafter the Maidanak 4k CCD system) attached to the AZT-22 1.5m telescope at Maidanak Astronomical Observatory in Uzbekistan. The Maidanak 4k CCD system supports three readout modes through 1, 2, or 4 amplifiers. In most cases observers use 4-amplifier readout mode to save time. We have tested the stability and seasonal variation of zero levels and confirm that two quadrants of the images (Amp 1 & 2) show no appreciable seasonal variation. but the other two quadrants (Amp 3 & Amp 4) show an evident seasonal variation in the bias level. The Cryo Tiger, the cooling system used at the Maidanak 4k CCD system, maintains the CCD temperature at -108'E, and effectively suppresses the dark electrons. The mean value versus the variance plot of the flat images does not show the expected relation for an ideal Poisson noise distribution and this is attributed to the large variation in quantum efficiency between different pixels. In addition, we confirm that there is no appreciable difference in gain between readout amplifiers, but there is a large variation in quantum efficiency across CCD chip especially in U. Due to the finite length of shutter opening and closing time, the effective exposure time varies across the science images. We introduce two parameters to quantify the effect of this uneven illumination and present a method to remove these effects. We also present a method to remove the interference patterns appearing in the images obtained with longer wavelength filters and investigate the spatial variation of the point spread function.

• Progress in Superconductivity
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• 제7권1호
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• pp.46-51
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• 2005

We have developed control electronics to operate flux-locked loop (FLL), and analog signal filters to process FLL outputs for 64-channel Double Relaxation Oscillation SQUID (DROS) magnetocardiography (MCG) system. Control electronics consisting of a preamplifier, an integrator, and a feedback, is compact and low-cost due to larger swing voltage and flux-to-voltage transfer coefficients of DROS than those of dc SQUIDs. Analog signal filter (ASF) serially chained with a high-pass filter having a cut-off frequency of 0.1 Hz, an amplifier having a gain of 100, a low-pass filter of 100 Hz, and a notch filter of 60 Hz makes FLL output suitable for MCG. The noise of a preamplifier in FLL control electronics is $7\;nV/{\surd}\;Hz$ at 1 Hz, $1.5\;nV/{\surd}\;Hz$ at 100 Hz that contributes $6\;fT/{\surd}\;Hz$ at 1 Hz, $1.3\;fT/{\surd}\;Hz$ at 100 Hz in readout electronics, and the noise of ASF electronics is $150\;{\mu}V/{\surd}\;Hz$ equivalent to $0.13\;fT/{\surd}\;Hz$ within the range of $1{\sim}100\;Hz$. When DROSs are connected to readout electronics inside a magnetically shielded room, the noise of 64-channel DROS system is $10\;fT/{\surd}\;Hz$ at 1 Hz, $5\;fT/{\surd}\;Hz$ at 100 Hz on the average, low enough to measure human MCG.

• Imaging Science in Dentistry
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• 제51권1호
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• pp.63-71
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• 2021

Purpose: The aim of this study was to assess the artefacts of 12 fixed orthodontic appliances in magnetic resonance images obtained using 1.5-T and 3-T scanners, and to evaluate different imaging sequences designed to suppress metal artefacts. Materials and Methods: In vitro, study casts of 1 adult with normal occlusion were used. Twelve orthodontic appliances were attached to the study casts and scanned. Turbo spin echo (TSE), TSE with high readout bandwidth, and TSE with view angle tilting and slice encoding for metal artefact correction were used to suppress metal artefacts. Artefacts were measured. In vivo, 6 appliances were scanned: 1) conventional stainless-steel brackets; 2) nickelfree brackets; 3) titanium brackets; 4) a Herbst appliance; 5) a fixed retainer; and 6) a rapid maxillary expander. The maxilla, mandible, nasopharynx, tongue, temporomandibular joints, and cranial base/eye globes were assessed. Scores of 0, 1, 2, and 3 indicated no artefacts and minor, moderate, and major artefacts, respectively. Results: In vitro, titanium brackets and the fixed retainer created minor artefacts. In vivo, titanium brackets caused minor artefacts. Conventional stainless-steel and nickel free brackets, the fixed retainer, and the rapid maxillary expander caused major artefacts in the maxilla and mandible. Conventional stainless-steel and nickel-free brackets caused major artefacts in the eye globe (3-T). TSE with high readout bandwidth reduced image artefacts in both scanners. Conclusion: Titanium brackets, the Herbst appliance, and the fixed retainer caused minor artefacts in images of neurocranial structures(1.5-T and 3-T) when using TSE with high readout bandwidth.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3133-3139
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• 2023

Neutron imaging technology as a means of non-destructive detection of materials is complementary to X-ray imaging. Silicon photomultiplier (SiPM), a new type of optical readout device, has overcome some shortcomings of traditional photomultiplier tube (PMT), such as high-power consumption, large volume, high price, uneven gain response, and inability to work in strong magnetic fields. Its application in the field of neutron detection will be an irresistible general trend. In this paper, a thermal neutron imaging detector based on ⁶LiF/ZnS scintillation screen and SiPM array readout was developed. The design of the detector geometry was optimized by geant4 Monte Carlo simulation software. The optimized detector was evaluated with a step wedge sample. The results show that the detector prototype with a 48 mm × 48 mm sensitive area can achieve about 38% detection efficiency and 0.26 mm position resolution when using a 300 ㎛ thick ⁶LiF/ZnS scintillation screen and a 2 mm thick Bk7 optical guide coupled with SiPM array, and has good neutron imaging capability. It provides effective data support for developing high-performance imaging detectors applied to the China Spallation Neutron Source (CSNS).

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 1997년도 한국우주과학회보 제6권2호
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• pp.22.1-22
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• 1997