• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.4
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• pp.1-9
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• 2012

A method to estimate the 3-D shape of surface with specular reflection is proposed, where the difference between the images reflected from a flat surface and a curved surface is used. First, we analyzed the geometry of the spatial reflection at specular surface and the variation of reflected light due to curved surface, whose results are used to estimate 3-D shape. The proposed method is shown to be effective via experiments using the illumination with spatially distributed light source and the CCD camera to capture the light reflected from a surface. In experiments, the captured images from curved surface with specular reflection are processed to approximately estimate 3-D shape.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.6
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• pp.1303-1311
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• 1988

Described is method for development of an optical roughness measurement sensor for in-subequality assurance in the precision grinding. Main approach is made based upon the Brckmann's light scattering theory, in which general solutions of the optical scattering behaviour are given under many simplifying assumptions on the model of the surfaces illuminated. For the ground surface, the assumptions are verified through computer simulation and experimental work in order to examine the validity of Beckmann's theory on predicting the optical responses according to the roughness variation. As a result, an optical monitoring strategy is derived which can evaluate the roughness value of the ground surface by statistically detecting the pattern of intensity distribution of the scattered light. Finally, the strategy is proven by comparing with the results using the stylus method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2113-2120
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• 2013

In this study, an efficient machine vision based inspection system is developed for the in-line measurement of phosphor resin dispensing shapes on LED chip package. Since the phosphor resin (target material) has semitransparent characteristics, illuminated light beam is reflected from the bottom of the chip as well as from the surface. Since such phenomenon can deteriorate inspection reliability, a white LED and a 635nm laser slit beams are experimentally tested to decide suitable illumination optics. Also, specular and diffuse reflection methods are tested to decide suitable optical triangulation. As a result, it can be known that the combination of a white slit beam source and specular reflection method show the best inspection results. The Catmull-Rom spline interpolation is applied to the obtained data to form smoother surface. From the results, it can be conclude that the developed system can be sucessfully applied to the in-line inspection of LED chip packaging process.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.168-178
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• 1994

This paper presents an optical surface roughness sensor developed for intermediate- process measurement on the machine. The light scattering method is adopted for the sensor, which is designed conpact and flexible enough to apply to 'on the machine' measurement of surface roughness. The developed sensor has special features such that it makes use, as the measurement parameter, of the ratio between fluxes of the incident light, and the specularly and partly diffusely reflected light, and that it can adjust the incident light angle. The experimental investigation reveals not only the sensor has good performance as a surface roughness sensor but the sensor is very robust so as to be useful in in-process measurement.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.564-569
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• 2021

In this paper, for the typical LED and the tilted LED, when there is no electrode, when 20% absorption (80% reflection) occurs at the electrode, and when 60% absorption (40% reflection) occurs at the electrode, the effect of the absorption at the electrode and the height of the active region on the photon extraction efficiency and the mean photon path length was investigated, and an appropriate height of the active region was proposed. In a typical LED, as the absorption of the electrode increases, the photon extraction efficiency decreases from 18% to 15% and 13%, and the photon extraction efficiency is highest when the height of the active area is located in the center between the two electrodes. In the tilted LED, as the absorption of the electrode increases, the photon extraction efficiency decreases from 38% to 33% and 25%, and the photon extraction efficiency is highest when the height of the active area is located in the center between the two electrodes. The tilted LED can increase the photon extraction efficiency more than twice than that of a typical LED, where photons are trapped inside the chip due to total reflection.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.2 s.95
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• pp.145-152
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• 1999

This paper presents the principle and experimental results of a non-contact surface roughness measurement by means of screen projected pattern of lase beam reflected from a polished surface. In the reflected laser beam pattern especially from a fine surface like ground or polished one, light intensity varies from the center fo the image to its boundary as the Gaussian distribution. The standard deviation of a light intensity distribution is assumed to be a good non-contact estimator for measuring the surface roughnes, because the light reflectivity is known to be well related with the surface roughness. This method doesn't need to discriminate between the specularly reflected light and the diffusely reflected one, whereas the scattered laser intensity method must do. Nor it needs to adjust the change of light intensity caused by environmental lights or specimen materials. Reflected laser beam pattern narrowly spreads out in the vertical direction to tiny scratches on the polished surface due to abrasives. The deeper the scratch the more the dispersion, which means the rougher surface. The standard deviation of the pattern is nearly in proportion to the surface roughness. Measurement errors by this method are shown to be below 10 percent compared with those obtained by a common contact method. The inclination of measuring unit from the normal axis causes the measurement errors up to 10 percent for an angle of 4 degree. Therefore the proposed method can be used as an on-the-machine quick roughness estimator within 10 percent measurement error.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.05a
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• pp.30-37
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• 2005

태양광 채광시스템은 자연광의 유입이 어려운 공간에 주광을 유입하기 위하여 개발된 장치로써 에너지를 절약하고 인간의 쾌적성을 향상시키는 등 지속가능한 건축을 위해 도입 및 확대가 크게 기대 되는 장치이다. 이에 본 연구는 기존에 본 연구실에서 개발된 시스템의 문제점을 보완하고 개선하여 건축물 적용시의 채광성능을 평가하는데 연구목적이 있다. 본 시스템의 설치는 2004년 10월 25일 (주) 동아산전과의 공동작업으로 설치되었으며, 수원에 있는 K대학 공과대학 5층 옥상 파라펫에 설치하였다. 평가실험은 2005년 4월 5일 9시30분부터 15시30분까지 청천공 상태에서 실시하였고, 총32개의 측정점을 선정하여 주광조도비로 채광성능을 평가하였다. 실험결과, 반사거울을 설치 시 창이 있을 경우 실내의 주광조도비는 평균 20.3[%] 상승하였고 창을 제거할 경우 실내의 주광조도비는 평균 38.2[%]정도 상승하여 채광학적으로 유효한 것으로 분석되었다. 따라서 본 시스템은 건축물의 실내 및 옥외의 음영진 곳에서 유용하게 사용될 수 있음이 입증되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.283-283
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• 2010

17~18% 대역의 고효율 결정질실리콘 태양전지를 양산하기 위하여 국내외에서 다양한 연구개발이 수행되고 있으며 국내 다결정실리콘 태양전지 양산에서도 새로운 구조와 개념에 입각한 공정기술과 관련 장비의 국산화에 집중적인 투자를 진행하고 있다. 주지하는 바와 같이, 태양전지의 광전효율은 표면에 입사되는 태양광의 반사를 제외하면 흡수된 광자에 의해 생성되는 전자-정공쌍의 상대적인 비율인 내부양자효율에 의존하게 된다. 실제 생성된 전자-정공쌍은 기판재료의 결정상태와 전기광학적 물성 등에 의해 일부가 재결합되어 2차적인 광자의 생성이나 열로서 작용하고 최종적으로 전자와 정공이 완전히 분리되고 전극에 포집되어 실질적인 유효전류로 작용한다. 16% 이상의 고효율 결정질 실리콘 태양전지 양산이 요구되고 있는 현실에서 광전효율 개선 위해 가장 우선적으로 고려되어야 할 변수는 입력 태양광스펙트럼에 대한 결정질 실리콘 표면반사율을 최소화하여 광흡수를 극대화하는 것이라 할 수 있다. 현재까지 다결정 실리콘 표면을 화학적으로 혹은 플라즈마이온으로 50-100nm 직경의 바늘형 피라미드형상으로 texturing 함으로 단파장대역에서 광반사율의 감소를 기대할 수 있기 때문에 결정질실리콘 태양전지효율 개선에 긍정적인 영향을 미치는 것으로 알려져 있다. 고효율 다결정실리콘 태양전지 양산공정에 적용하기 위해 마스크를 사용하지 않는, RIE기반 건식 저반사율 결정질실리콘 표면 texturing 패턴연구를 수행하였다. 마스크없이 표면 texturing이 완료된 시료들에 대하여 A1.5G 표준태양광스펙트럼의 300-1100nm 파장대역에서 반사율과 minority carrier들의 life time 분포를 측정하고 검토하여 공정조건을 최적화 하였다. 저반사율의 건식 결정질실리콘 표면 texturing에 가장 적합한 플라즈마파워는 100W 내외로 낮았고 $SF_6/O_2$ 혼합비율은 0.8~0.9 범위엿다. 본 연구에서 확인된 최적의 texturing을 위한 플라즈마공정 조건은 이온에 의한 Si표면원자들의 스퍼터링과 화학반응에 의한 증착이 교차하는 상태로서 확인된 최저 평균반사율은 ~14% 내외였고 p-형 결정질실리콘 표면 texturing 패턴과 minority carrier의 life time 상관는 단결정이 16uS대역에서 14uS대역으로 감소하는 반면에서 다결정은 1.6uS대역에서 1.7uS대역으로 오히려 미세한 증가를 보여 다결정 웨이퍼생산과정에서 발생하는 saw-damage 제거의 긍정적 효과와 texturing공정의 표면 결함발생에 의한 부정적 효과가 상쇄되어 큰 변화를 보이지 않는 것으로 해석된다.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.51-54
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• 2016

This paper present a method which resolves an optical discontinuity in bezel of digital signage using light guide film. On a polycarbonate film, a light guide film is bonded to produce refraction, reflection, diffraction of light. Arc shaped light guide film is assembled on the top LED light sources (red and green) to see light propagation through the film. When the two light sources (red and green) are mechanically attached at the end of the film, optical convergence brings new colors which have light wavelength between red and green. This result indicates that the light waveguide method could solve the light discontinuity on bezel of the digital signage system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.605-606
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• 2012