광신호의 공간 해상도 향상을 위한 초 분해능 알고리즘 연구

이병진,유봉국,김경석,Lee, Byung-Jin,Yu, Bong-Guk,Kim, Kyung-Seok 한국인터넷방송통신학회 2018 한국인터넷방송통신학회 논문지 Vol.18 No.1

현재 설치된 광섬유의 문제를 모니터링 하는데 가장 널리 사용되는 방법은 Optical Time Domain Reflectometer(OTDR)이다. OTDR는 FTTx 네트워크를 테스트하기 위해 설계된 계측기이며, 전송 손실 및 접속 손실과 같은 광섬유의 물리적 특성을 평가한다. OTDR을 이용하여 광로상의 문제점을 정확히 파악하기 위해서는 Spatial resolution을 높이는 것이 중요하다. 펄스폭이 두 반사체 사이의 거리 두 배보다 작을 때는 두 반사체에서 반사되는 신호는 상호간에 겹침 없이 반사되므로 반사되는 신호의 구분이 가능하지만 펄스폭이 두 반사체 사이의 거리 두 배보다 클 때에는 두 반사 펄스가 겹쳐져 반사되는 신호가 구분되지 못한다. 이와 같은 한계를 극복하기 위해서 본 논문에서는 초 분해능 알고리즘을 적용하여 Spatial resolution 향상 방법을 제안하였으며, 시뮬레이션 결과, 초 분해능 알고리즘 적용 시에 분해능이 향상 되어 이벤트 구간을 더 정밀하게 분석할 수 있었다. The optical time domain reflectometer (OTDR) is the most widely used method to monitor problems with currently installed optical fibers. The OTDR is an instrument designed to test the FTTx network and evaluates the physical properties of the fiber, such as transmission loss and connection loss. It is important to improve the spatial resolution in order to accurately grasp the optical path problems by using the OTDR. When the pulse width is less than twice the distance between the two reflectors, the signals reflected from the two reflectors are reflected without overlap, so that the reflected signal can be distinguished. However, when the pulse width is larger than twice the distance between the two reflectors, so that the reflected signal can not be distinguished. In order to overcome these limitations, this paper proposed a method of improving spatial resolution by applying a super resolution algorithm. As a result of the simulation, the resolution is improved when the super resolution algorithm is applied, and the event interval can be analyzed more precisely.

Real Time Optical-electrical Characterization of PbTe Thin Film Material for Super-resolution Optical Memory

( Hyun Seok Lee ),( Taek Sung Lee ),( Jeung Hyun Jeong ),( Su Youn Lee ),( Won Mok Kim ),( Byung Ki Cheong ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 ELECTRONIC MATERIALS LETTERS Vol.3 No.1

An experimental study was conducted in an effort to elucidate the origin of the nonlinear optical Properties of PbTe thin film, which previously had been demonstrated to be potentially usable for super-resolution optical memory. Using PbTe thin film device designed expressly for the experiment, transient optical transmittance and reflectance were measured together with the electrical voltage across the PbTe during pulsed irradiation with a 658nm laser of varying power. From the measured data, the absorption coefficient was derived as well as the carrier concentration as a function of laser power, demonstrating vividly that a decrease in the absorption coefficient with increasing laser power is directly related to the increase in photo-generated carriers. The observed correlation underlying the nonlinear optical properties of PbTe may be understood in light of saturable absorption resulting from band filling by carriers photo-generated under thermal influence and is a major cause of the material`s super-resolution effect.

Super-resolution visible photoactivated atomic force microscopy

Lee, Seunghyun,Kwon, Owoong,Jeon, Mansik,Song, Jaejung,Shin, Seungjun,Kim, HyeMi,Jo, Minguk,Rim, Taiuk,Doh, Junsang,Kim, Sungjee,Son, Junwoo,Kim, Yunseok,Kim, Chulhong Nature Publishing Group 2017 Light, science & applications Vol.6 No.11

<P>Imaging the intrinsic optical absorption properties of nanomaterials with optical microscopy (OM) is hindered by the optical diffraction limit and intrinsically poor sensitivity. Thus, expensive and destructive electron microscopy (EM) has been commonly used to examine the morphologies of nanostructures. Further, while nanoscale fluorescence OM has become crucial for investigating the morphologies and functions of intracellular specimens, this modality is not suitable for imaging optical absorption and requires the use of possibly undesirable exogenous fluorescent molecules for biological samples. Here we demonstrate super-resolution visible photoactivated atomic force microscopy (pAFM), which can sense intrinsic optical absorption with ~8 nm resolution. Thus, the resolution can be improved down to ~8 nm. This system can detect not only the first harmonic response, but also the higher harmonic response using the nonlinear effect. The thermoelastic effects induced by pulsed laser irradiation allow us to obtain visible pAFM images of single gold nanospheres, various nanowires, and biological cells, all with nanoscale resolution. Unlike expensive EM, the visible pAFM system can be simply implemented by adding an optical excitation sub-system to a commercial atomic force microscope.</P>

컴퓨터로 설계한 홀로그램 광 저대역 필터의 특성 분석

김인길,고춘수,임성우,오용호,이재철 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.12

Since the grating optical low-pass fillet degrades the resolution of images, we developed a hologram optical low-pass filter that show low degradation of the image and studied its characteristics. We designed the hologram that divides input beam into circular shaped 21 beams with a Monte-Carlo based hologram generation program and calculated its MTE characteristics to compare it with that of a grating filter. The hologram was manufactured through the optical lithography process and attached to a digital imaging device (Zoran 732212) for measurement. The moirfiltering is compared with zone plate images and the resolution loss is measured with USAF resolution chart. The hologram optical low-pass filter showed better characteristics in both moly filtering and resolution.

Usefulness of a Small-Field Digital Mammographic Imaging System Using Parabolic Polycapillary Optics as a Diagnostic Imaging Tool: a Preliminary Study

천권수,박정곤,박성훈,강성훈,김혜원,손현화,김혜원,김헌수,윤권하 대한영상의학회 2009 Korean Journal of Radiology Vol.10 No.6

Objective: To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. Materials and Methods: We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an Xray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. Results: The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-μm thickness. With a thicker molybdenum filter (100 μm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-μm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. Conclusion: A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue. Objective: To evaluate the efficacy for spatial resolution and radiation dose of a small-field digital mammographic imaging system using parabolic polycapillary optics. Materials and Methods: We developed a small-field digital mammographic imaging system composed of a CCD (charge coupled device) detector and an Xray source coupled with parabolic polycapillary optics. The spatial resolution and radiation dose according to various filters were evaluated for a small-field digital mammographic imaging system. The images of a test standard phantom and breast cancer tissue sample were obtained. Results: The small-field digital mammographic imaging system had spatial resolutions of 12 lp/mm with molybdenum and rhodium filters with a 25-μm thickness. With a thicker molybdenum filter (100 μm thick), the system had a higher spatial resolution of 11 lp/mm and contrast of 0.48. The radiation dose for a rhodium filter with a 25-μm thickness was 0.13 mGy within a 10-mm-diameter local field. A larger field image greater than 10 mm in diameter could be obtained by scanning an object. On the small-field mammographic imaging system, microcalcifications of breast cancer tissue were clearly observed. Conclusion: A small-field digital mammographic imaging system with parabolic polycapillary optics may be a useful diagnostic tool for providing high-resolution imaging with a low radiation dose for examination of local volumes of breast tissue.

차트 프로젝터 광학계 설계

이동희,마기중,이채호 대한시과학회 2000 대한시과학회지 Vol.2 No.2

시시력표 차트 프로젝터의 광학계는 조명광학계, 투사광학계로 구성된다. 프로책터 의 조명광학계는 대부분 콸러방식의 조명광학계를 사용하지만 우리는 object(ch따t reel)의 크기와 투사렌즈의 유효경올 고려하여 콸러방식올 변형하여 셜계하였다. 조명 광학계의 렌즈구성은 3매의 +굴절력의 렌즈로 하였다. 투사광학계는 색수차를 고려하여 doublet으로 셜계하였다. 투사광학계의 분해능은 5m 거 리 의 직 경 361 mm 0비ect에 대 해서 15line pairs/mm에 서 약 45% 이 상의 MTF (modulation transfer function) 특성 올 보 였 다. The optical system for a ch따t projector is composed of an illumination optical system and a projection optical system. Though the illumination optic려 sys따n of the Kóh!er type has been generally used in the illumination optical system for projectors, we designed the illumination optical system by the modified Kóhler structure considering the size of the object(chart reel) and the effective apeπure of a projection lens. The lenses of the illumination optic떠 system consist of three lenses with plus powers. Further, we designed the projection optical system by the doublet style considering minimization of the chromatic aberration. The resolution power of the designed projection optical system showed a feature of approximately 45% MTF in 15 line pairs/mm conceηling the diagonal object size of 361 mm in the projection distance of 5 m.

GOCI 자료를 이용한 고해상도 에어로졸 광학 깊이 산출

이서영,최명제,김준,김미진,임현광 대한원격탐사학회 2017 大韓遠隔探査學會誌 Vol.33 No.6

Despite of large demand for high spatial resolution products of aerosol properties from satellite remote sensing, it has been very difficult due to the weak signal by a single pixel and higher noise from clouds. In this study, aerosol retrieval algorithm with the high spatial resolution (500 m × 500 m) was developed using Geostationary Ocean Color Imager (GOCI) data during the Korea-US Air Quality (KORUS-AQ) period in May-June, 2016. Currently, conventional GOCI Yonsei aerosol retrieval (YAER) algorithm provides 6 km × 6 km spatial resolution product. The algorithm was tested for its best possible resolution of 500 m product based on GOCI YAER version 2 algorithm. With the new additional cloud masking, aerosol optical depth (AOD) is retrieved using the inversion method, aerosol model, and lookup table as in the GOCI YAER algorithm. In some cases, 500 m AOD shows consistent horizontal distribution and magnitude of AOD compared to the 6 km AOD. However, the 500 m AOD has more retrieved pixels than 6 km AOD because of its higher spatial resolution. As a result, the 500 m AOD exists around small clouds and shows finer features of AOD. To validate the accuracy of 500 m AOD, we used dataset from ground-based Aerosol Robotic Network (AERONET) sunphotometer over Korea. Even with the spatial resolution of 500 m, 500 m AOD shows the correlation coefficient of 0.76 against AERONET, and the ratio within Expected Error (EE) of 51.1%, which are comparable to the results of 6 km AOD. 위성을 이용한 에어로졸 원격탐사에서 높은 공간해상도의 정보에 대한 요구가 많았음에도 그동안단일화소가 갖는 물리적인 에어로졸 신호의 약화와 구름 등에 의한 오차 증가로 인해 산출에 어려움을 겪어왔다. 본 연구에서는 GOCI 자료를 이용하여 한-미 협력 국내 대기질 공동조사 캠페인 기간인 2016년 5, 6월에 대해 GOCI의 최대 공간 해상도인 500 m에서 고해상도 에어로졸 광학 깊이를 산출하였다. 기존의 GOCI 알고리즘은 6 km 해상도로 에어로졸 산출물을 제공해왔으며, 이번 연구에서 개발한 고해상도 산출 알고리즘은 기존 알고리즘을 기반으로 한다. 에어로졸 모형, 조견표 구성 및 역추산 과정은 동일하게 이용되었으나, 높은 해상도에서의 구름 제거 방법이 개선되었다. 그 결과, 몇 가지 사례에 대하여 6 km 산출물과 비교하였을 때 500 m 산출물의 분포 및 크기는 유사하게 나타났으나 공간 해상도가 높기 때문에 더 많은 화소에 대하여 산출되었다. 이에 따라 작은 규모의 구름 주위에서도 산출이 되었고, 에어로졸의 공간적인 변화를 세밀하게 살펴볼 수 있었다. 정확도 검증을 위하여 지상 관측 장비와 비교를 하였을 때 공간해상도가 크게 좋아졌음에도 상관 계수가 0.76, 기대 오차 내에 들어오는 비율이 51.1%로 6 km 산출물과 유사한 검증 결과를보였다.

Quantitative Determination of 3D-Printing and Surface-Treatment Conditions for Direct-Printed Microfluidic Devices

남궁현,KABA ABDI MIRGISSA,오현규,전현진,윤정환,Haseul Lee,김도현 한국바이오칩학회 2022 BioChip Journal Vol.16 No.1

We report a quantitative and systematic method for determining 3D-printing and surface-treatment conditions that can help improve the optical quality of direct-printed microfluidic devices. Digital light processing (DLP)-stereolithography (SLA) printing was extensively studied in microfluidics owing to the rapid, one-step, cleanroom-free, maskless, and high-definition microfabrication of 3D-microfluidic devices. However, optical imaging or detection for bioassays in DLP-SLA-printed microfluidic devices are limited by the translucence of photopolymerized resins. Various approaches, including mechanical abrasions, chemical etching, polymer coatings, and printing on transparent glass/plastic slides, were proposed to address this limitation. However, the effects of these methods have not been analyzed quantitatively or systematically. For the first time, we propose quantitative and methodological determination of 3D-printing and surface-treatment conditions, based on optical-resolution analysis using USAF 1951 resolution test targets and a fluorescence microbead slide through 3D-printed coverslip chips. The key printing parameters (resin type, build orientation, layer thickness, and layer offset) and surfacetreatment parameters (grit number for sanding, polishing time with alumina slurry, and type of refractive-index-matching coatings) were determined in a step-wise manner. As a result, we achieved marked improvements in resolution (from 80.6 to 645.1 lp/mm) and contrast (from 3.30 to 27.63% for 645.1 lp/mm resolution). Furthermore, images of the fluorescence microbeads were qualitatively analyzed to evaluate the proposed 3D-printing and surface-treatment approach for fluorescence imaging applications. Finally, the proposed method was validated by fabricating an acoustic micromixer chip and fluorescently visualizing cavitation microstreaming that emanated from an oscillating bubble captured inside the chip. We expect that our approach for enhancing optical quality will be widely used in the rapid manufacturing of 3D-microfluidic chips for optical assays.

광정렬용 초정밀 다축 위치제어 장치 개발에 관한 연구

정상화,차경래,이경형,김광호 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

As optical fiber communication grows, the fiber alignment become the focus of industrial attention. This greatly influence the overall production rates for the opto-electric products. We proposed multi-axis nano positioning stage for optical fiber alignment. This device has 3 DOF translation and sub nanometer resolution. This nano stage consist of 3 PZT-driven flexure stages which are stacked parallel. The displacement of it is measured with capacitance gauge and is controlled by computer-embedded main controller. The design process of flexure stage using FEM is proposed and the performance evaluation of this system is verified with experiments.

광소자 정렬용 극초정밀 다축 위치 제어장치 개발

정상화(S. H. Jeong),이경형(K. H. Lee),차경래(K. R. Cha),김현욱(H. U. Kim),최석봉(S. B. Choi),김광호(G. H. Kim),박준호(J. H. Park) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월

As optical fiber communication grows, the fiber alignment become the focus of industrial attention. This greatly influence the overall production rates for the opto-electric products. We proposed multi-axis nano positioning stage for optical fiber alignment. This device has 3 DOF translation and sub nanometer resolution. This nano stage consist of 3 PZT-driven flexure stages which are stacked parallel. The displacement of it is measured with capacitance gauge and is controlled by computer-embedded main controller. The design process of flexure stage using FEM is proposed and the performance evaluation of this system is verified with experiments.