• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2005년도 춘계학술발표대회
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• pp.813-816
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• 2005

최근 휴대폰의 활용 범위는 단순히 사용자간의 통신이라는 기본적인 목적을 넘어서 다양한 기능을 제공하고 있다. 그중 휴대폰에 카메라를 탑재하여 디지털 카메라의 기능을 혼합한 휴대폰은 최근 각광을 받고 있으며 휴대폰에 탑재된 카메라의 기능은 디지털 카메라의 메가 픽셀 급 화질을 제공하는 정도의 수준으로 발전하였으며 이미 그 수요는 대중화되어 가고 있다. 이런 카메라 폰을 응용한 연구 분야로 생체 인식 기술을 적용할 수 있으며, 본 논문에서는 휴대폰 환경에서의 홍채 인식을 위한 홍채 영역에서의 홍채 코드 추출에 관한 방법을 제안한다. 휴대폰에서의 홍채 인식에 사용되는 홍채 코드 추출 과정은 다음과 같다. 먼저 휴대폰 카메라를 통해 얻은 메가 픽셀 급 영상($2048{\times}1536$ pixel 8bit gray Image)에서 동공위치 추적 & 홍채 영역 추출 알고리즘[1]을 이용하여 눈 영상($640{\times}480$ pixel 8bit gray Image))을 추출한다. 이렇게 추출된 눈 영상 중에 홍채 코드 인식 에러율을 좀더 낮추기 위해 눈썹영역, 안경에 의해 반사되는 반사광(Specular Reflection), 눈꺼풀 영역을 눈 영역에서 제거 하는 과정을 거친다. 이 논문에서는 위와 같은 과정을 거쳐 얻어진 홍채 영상에 그대로 극좌표 가버 필터[2]를 씌워 홍채 코드를 추출해내기 때문에 기존 보간법을 이용한 스트레칭 된 홍채 영상에서의 홍채 코드 추출보다 잘못된 홍채 코드 정보를 줄일 수 있으며 휴대폰이라는 특수한 환경에서의 홍채 코드 추출이란 점을 고려하여 가버 필터를 고주파와 저주파로 나누어 미리 설계해두어 좀더 빠르고 정확한 홍채 코드를 추출해 내는 방법을 제안한다. 실험 결과, 기존 방식보다 극좌표 가버 필터를 사용한 홍채 코드 추출 실험에서 보다 높은 인식률을 보였다.

• 제어로봇시스템학회논문지
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• 제8권1호
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• pp.21-27
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• 2002

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. A number of visual or optical technologies have been successfully applied to measure three-dimensional surfaces. However, those conventional visual or optical methods have inherent shortcomings such as occlusion and variant surface reflection. X-ray vision system can be a good solution to these conventional problems, since we can extract the volume information including both the surface geometry and the inner structure of any objects. In the x-ray system, the surface condition of an object, whether it is lambertian or specular, does not affect the inherent characteristics of its x-ray images. In this paper, we propose a three-dimensional x-ray imaging method to reconstruct a three dimensional structure of an object out of two dimensional x-ray image sets. To achieve this by the proposed method, two or more x-ray images projected from different views are needed. Once these images are acquired, the simultaneous algebraic reconstruction technique(SART) is usually utilized. Since the existing SART algorithms have several shortcomings such as low performance in convergence and different convergence within the reconstruction volume of interest, an advanced SART algorithm named as USART(uniform SART) is proposed to avoid such shortcomings and improve the reconstruction performance. Because, each voxel within the volume is equally weighted to update instantaneous value of its internal density, it can achieve uniform convergence property of the reconstructed volume. The algorithm is simulated on various shapes of objects such as a pyramid, a hemisphere and a BGA model. Based on simulation results the performance of the proposed method is compared with that of the conventional SART method.

• 한국콘텐츠학회논문지
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• 제10권1호
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• pp.1-9
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• 2010

물체 표면의 재질을 실물에 가깝게 렌더링 하는 것은 그래픽 콘텐츠의 사실감을 위한 중요한 요소이다. 본 논문은 속성이 다른 여러 구성 물질에 의해 복잡한 무늬가 형성된 표면을 한 장의 스틸 사진만을 이용하여 셰이딩하는 기법을 제안한다. 기존 방법들은 이와 같은 이종물질에 의한 불규칙한 텍스처의 렌더링을 위해 많은 이미지를 필요로 하거나 특수 촬영 장비를 사용했으며, 수작업에 의해 물질별 표면 영역을 나누어 주어야 했다. 본 연구에서는 영상의 히스토그램 분포 특성에 따른 물질별 텍스처 영역 분할법의 자동 선택 방식을 제시하였고, 그 결과로 구분된 물질별 레이어에 대해 근사화(approximate)된 양방향 반사도 분포함수(BRDF) 값을 구함으로써 주어진 사진과 다른 조명 조건이나 시야(view)에 대해서도 대응되는 렌더링 및 셰이딩 결과를 생성할 수 있음을 보였다.

• 농업과학연구
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• 제47권4호
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• pp.995-1010
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• 2020

In this study, a multivariate analysis model of partial least square regression (PLSR) was developed to predict the moisture content of green peppers using hyperspectral imaging (HSI). In HSI, illumination is essential for high-quality image acquisition and directly affects the analytical performance of the visible near-infrared hyperspectral imaging (VIS/NIR-HSI) system. When green pepper images were acquired using a direct lighting system, the specular reflection from the surface of the objects and their intensities fluctuated with time. The images include artifacts on the surface of the materials, thereby increasing the variability of data and affecting the obtained accuracy by generating false-positive results. Therefore, images without glare on the surface of the green peppers were created using a polarization filter at the front of the camera lens and by exposing the polarizer sheet at the front of the lighting systems simultaneously. The results obtained from the PLSR analysis yielded a high determination coefficient of 0.89 value. The regression coefficients yielded by the best PLSR model were further developed for moisture content mapping in green peppers based on the selected wavelengths. Accordingly, the polarization filter helped achieve an uniform illumination and the removal of gloss and artifact glare from the green pepper images. These results demonstrate that the HSI technique with a polarized lighting system combined with chemometrics can be effectively used for high-throughput prediction of moisture content and image-based visualization.

• 영어영문학
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• 제58권2호
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• pp.189-215
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• 2012

This paper reads Mary Shelley's Frankenstein (1818) in light of the 18th-century understanding of 'sympathy' including those of Hume and Smith and also in light of what Michael Hardt in our century has called "affective labor." I argue that the imaginative capacity and "seeing" are crucial in understanding Smith's idea of 'sympathy.' By showing how the monster's ugliness precludes any human character from sympathizing with him, Mary Shelley exposes that Smith's idea of sympathy fails to maintain social harmony. Mary Shelley revises Smith's 'sympathy' and makes it more radical by suggesting that the active affective labor could bridge the epistemological distance lying between the agent concerned and the impartial spectator. I first read Smith's idea of sympathy as an imaginative capacity which is inevitably influenced by 'seeing' and visual perception. Then I analyze the scenes in which the creature in Frankenstein fails to acquire any human sympathy due to his ugliness, and show how the specular nature of 'sympathy' is disrupted when one party is visually ugly and deformed. I conclude that affective labor and active moral reflection on the part of the spectator need to be provided when the agent concerned is 'ugly' and thus challenges our habitual epistemological boundary. Shelley's re-evaluation of Smith's sympathy, thus, suggests that affective labor may not be something that women alone have to perform, but an ethical practice that concerns all human beings and that can transform the otherwise flawed human capacity for sympathy.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2592-2598
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• 2022

Research groups in the field of PET instrumentation are studying time-of-flight(TOF) technology to improve the signal-to-noise ratio of PET images. Scintillation light transport and collection plays an important role in improving the coincidence resolving time(CRT) of PET detector based on a pixelated crystal array. Four crystal arrays were designed by the different optical reflection configuration such as external reflectors and surface treatment on the CRT and compared with the light output, energy resolution and CRT. The design proposed in the study was composed of 8 × 8 LYSO crystal array consisted of 3 × 3 × 15 mm³ pixels. The entrance side was roughened while the other five surfaces were polished. Four sides of all crystal pixels were wrapped with ESR-film, and the entrance surface was covered by Teflon-tape. The design provided an excellent timing resolution of 210 ps and improved the CRT by 16% compared to the conventional method using a polishing treatment and ESR-film. This study provided a method for improving the light output and CRT of a pixelated scintillation crystal-based brain TOF PET detector. The proposed configuration might be an attractive detector design for TOF brain PET requiring fast timing performance with high cost-effectiveness.

• 한국재료학회지
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• 제22권4호
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• pp.185-189
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• 2012

We report plasma-assisted molecular beam epitaxy of $In_XGa_{1-X}N$ films on c-plane sapphire substrates. Prior to the growth of $In_XGa_{1-X}N$ films, GaN film was grown on the nitride c-plane sapphire substrate by two-dimensional (2D) growth mode. For the growth of GaN, Ga flux of $3.7{\times}10^{-8}$ torr as a beam equivalent pressure (BEP) and a plasma power of 150 W with a nitrogen flow rate of 0.76 sccm were fixed. The growth of 2D GaN growth was confirmed by $in-situ$ reflection high-energy electron diffraction (RHEED) by observing a streaky RHEED pattern with a strong specular spot. InN films showed lower growth rates even with the same growth conditions (same growth temperature, same plasma condition, and same BEP value of III element) than those of GaN films. It was observed that the growth rate of GaN is 1.7 times higher than that of InN, which is probably caused by the higher vapor pressure of In. For the growth of $In_xGa_{1-x}N$ films with different In compositions, total III-element flux (Ga plus In BEPs) was set to $3.7{\times}10^{-8}$ torr, which was the BEP value for the 2D growth of GaN. The In compositions of the $In_xGa_{1-x}N$ films were determined to be 28, 41, 45, and 53% based on the peak position of (0002) reflection in x-ray ${\theta}-2{\theta}$ measurements. The growth of $In_xGa_{1-x}N$ films did not show a streaky RHEED pattern but showed spotty patterns with weak streaky lines. This means that the net sticking coefficients of In and Ga, considered based on the growth rates of GaN and InN, are not the only factor governing the growth mode; another factor such as migration velocity should be considered. The sample with an In composition of 41% showed the lowest full width at half maximum value of 0.20 degree from the x-ray (0002) omega rocking curve measurements and the lowest root mean square roughness value of 0.71 nm.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.454-454
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• 2014

Silicon microwire array is one of the promising platforms as a means for developing highly efficient solar cells thanks to the enhanced light trapping efficiency. Among the various fabrication methods of microstructures, deep reactive ion etching (DRIE) process has been extensively used in fabrication of high aspect ratio microwire arrays. In this presentation, we show precisely controlled Si microwire arrays by tuning the DRIE process conditions. A periodic microdisk arrays were patterned on 4-inch Si wafer (p-type, $1{\sim}10{\Omega}cm$) using photolithography. After developing the pattern, 150-nm-thick Al was deposited and lifted-off to leave Al microdisk arrays on the starting Si wafer. Periodic Al microdisk arrays (diameter of $2{\mu}m$ and periodic distance of $2{\mu}m$) were used as an etch mask. A DRIE process (Tegal 200) is used for anisotropic deep silicon etching at room temperature. During the process, $SF_6$ and $C_4F_8$ gases were used for the etching and surface passivation, respectively. The length and shape of microwire arrays were controlled by etching time and $SF_6/C_4F_8$ ratio. By adjusting $SF_6/C_4F_8$ gas ratio, the shape of Si microwire can be controlled, resulting in the formation of tapered or vertical microwires. After DRIE process, the residual polymer and etching damage on the surface of the microwires were removed using piranha solution ($H_2SO_4:H_2O_2=4:1$) followed by thermal oxidation ($900^{\circ}C$, 40 min). The oxide layer formed through the thermal oxidation was etched by diluted hydrofluoric acid (1 wt% HF). The surface morphology of a Si microwire arrays was characterized by field-emission scanning electron microscopy (FE-SEM, Hitachi S-4800). Optical reflection measurements were performed over 300~1100 nm wavelengths using a UV-Vis/NIR spectrophotometer (Cary 5000, Agilent) in which a 60 mm integrating sphere (Labsphere) is equipped to account for total light (diffuse and specular) reflected from the samples. The total reflection by the microwire arrays sample was reduced from 20 % to 10 % of the incident light over the visible region when the length of the microwire was increased from $10{\mu}m$ to $30{\mu}m$.

• 마이크로전자및패키징학회지
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• 제19권1호
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• pp.81-87
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• 2012

본 논문에서는 마이크로 BGA 패키지 내외부의 마이크로 볼의 3차원 형상을 측정하는 광학 측정 시스템을 제안하고 이를 구현한다. 대부분의 시각 검사 시스템은 마이크로 볼의 복잡한 반사 특성 때문에 검사에 어려움을 겪고 있다. 정확한 형상의 측정을 위해서, 특별히 설계된 시각 센서 시스템을 제안하고, 위상이송 모아레 간섭계의 측정원리에 기반한 형상측정 알고리즘을 제안한다. 센서 시스템은 4개의 서브시스템을 보유한 패턴 투사 시스템과 영상획득 시스템으로 구성된다. 패턴 투사용 서브시스템은 공간상으로 서로 상이한 투사 방향을 가지며, 이는 측정 물체에 각기 다른 입사 방향을 가지는 패턴 조명이 투사될 수 있도록 하는 것을 목적으로 한다. 위상이송 모아레 간섭계의 구현을 위한 정밀 위상이송을 위해서, 각 서브시스템의 패턴 격자는 PZT 구동기를 이용하여 일정 간격으로 이송한다. 최종적으로 측정되는 마이크로 볼의 경면반사와 그림자 영역을 효과적으로 제거하기 위해서, 다중 패턴 투사 시스템과 영상획득 시스템을 구현하고, 이를 테스트한다. 특히, 다중 프로젝션을 이용하여 획득되는 다중 높이 정보를 효과적으로 융합하기 위하여, 베이지안 센서 융합 이론을 기반으로한 센서 융합 알고리즘이 제안된다. 제안되는 시스템의 원리검증과 성능확인을 위해, 마이크로 BGA볼과 기판 범프의 측정대상물에 대해서, 측정 반복성을 중심으로 실험이 수행되었으며, 획득된 실험 결과를 분석하고 논의한다.

• 한국측량학회지
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• 제25권3호
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• pp.231-238
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• 2007

본 연구에서는 가까운 장래에 실현될 GNSS(Global Navigation Positioning System) 결합측위의 가용성을 평가하기 위하여, GPS(Global Positioning System), Galileo 및 QZSS(Quasi-Zenith Satellites System)의 직달파(direct signal), 반사파(reflected signal), 회절파(diffracted signal) 식별을 위한 신호 전달 모형을 수립하고 이를 3차원 지리정보시스템과 결합함으로써, 위성 가시도와 측위 오차 요소를 모사 측정하였다. 중고층 빌딩이 밀집한 일본 동경도청 부근의 $1km{\times}1km$ 구역을 40,000개의 $5m{\times}5m$ 격자로 구획하여 실시한 시뮬레이션을 통해, GPS 측위와 GNSS 결합측위에 있어서 가시위성의 개수, 위성 고도, 정밀도 저하율(dilution of position : DOP), 의사거리 다중 경로 오차(pseudorange multipath error : PME)를 비교 평가하였다. GNSS 결합측위에서는 가시위성 및 직달파 위성의 개수가 현격히 증가함을 확인할 수 있었으며, 위성고도의 평균은 GPS 측위에서보다 약간 낮게 나타나지만, 위성들의 기하학적 배치가 양호하게 이루어져 정밀도 저하율이 매우 감소함을 알 수 있다. 고밀도 도시공간에서는 빌딩 등의 전파 반사로 인해 발생하는 의사거리 다중경로 오차를 완화하는 것이 사용자 위치 정확도를 향상시키기 위한 핵심적인 요소이므로, 수신기 안테나의 설계 및 배치, 신호처리 및 공간통계 기법 등을 GNSS 결합측위에 적합하도록 개선하는 것이 필요할 것이다.