• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.415-416
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• 2008

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.256-259
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• 2010

본 논문에서는 적응적 평활화 필터를 이용한 스캔된 하프톤 문서의 하프톤 잡음 제거 방법을 제안한다. 하프톤 잡음은 잡음의 편차가 커서 에지 영역과 유사한 특성을 나타내므로 일반적인 에지 보존 평활화 필터를 적용할 경우에는 잡음 제거 효과가 떨어진다. 또한 인쇄물에 주로 사용되는 집중형 도트 방식의 하프톤은 컬러 영상에서 채널간의 간섭 현상으로 인해 모아레 패턴을 생성한다. 따라서 본 논문에서는 스캔된 하프톤 문서의 하프톤 잡음과 모아레 패턴을 효과적으로 제거하기 위해 하프톤 잡음의 방향성에 기반한 적응적 평활화 필터 방법을 제안한다. 하프톤 잡음의 경우 영상의 에지와 달리 등방성을 가지므로 영상을 블록 단위로 나누어 지배적인 에지의 크기와 방향성을 살핌으로써 적응적 평활화 필터를 구성할 수 있다. 실험 결과, 제안하는 방법은 다양한 인쇄 매체를 통해 생성된 하프톤 문서에 대하여 효과적으로 하프톤 잡음을 제거하면서도 영상의 에지를 보존하는 것을 확인할 수 있었다.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.90-95
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• 2001

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) are characterized by high sensitive $moir{\acute{e}}$ interferometry. $Moir{\acute{e}}$ fringe patterns are recorded and analyzed at several various bending loads and temperature steps. At the temperature higher that $100^{\circ}C$, the inelastic deformation in solder balls became more dominant. As a result the bending of the molding compound decreased while temperature increased. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder. The results also show that $moir{\acute{e}}$ interferometry is a powerful and effective tool in experimental studies of electronic packaging.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1079-1086
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• 1990

Recently, demand for the experimental analysis of crack, such as arbitrary or distributed ones which has been considered quite difficult to investigate by the theoretical and numerical method, is increasing. Among existent experimental methods applied to the analysis of stress intensity factors, the slab analogy method have the following merits; cracks can be replaced by similarity-shaped rigid body, and the distribution of stress is represented by slab curvature of duly bent specimen. For the accuracy improvement of this method, multi-point selection method was introduced and its accuracy proved by applying this method to the analysis of centrally linear and inclined cracks in a finite plate which are theoretically known. In this paper, moreover, the stress intensity factors of eccentric and skew-symmetric bent cracks were determined by multi-point selection method and newly developed moire tilted master grating method. The results obtained by this method showed good agreement with the reliably theoretical solutions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3442-3447
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• 2014

A simple method to evaluate the hygroscopic characteristics of polymer of microelectronic plastic package is suggested. To evaluate the characteristics, specimens were prepared, and the internally absorbed moisture masses were measured as a function of the absorbing time and calculated numerically. The hygroscopic pressure ratio was calculated by heat transfer analysis supported by commercial FEM code because the hygroscopic diffusion equation has the same form as the heat transfer equation. The moisture masses were then summed by the self developed code. The nonconductive polymers had quite different characteristics for the different lots, even though they were the same products. The absorbed moisture mass variations were calculated for several different characteristics, and the optimal curve of the mass variation close to experimental data was selected, whose solubility and diffusivity were affected by the hygroscopic characteristics of the material. The method can be useful in the industrial fields to quickly characterize the polymer material of the semiconductor package because the fast correspondence is normally required in industry. The weight changes in the aluminum-nonconductive-polymer joint due to moisture absorption were measured. The deformed system was also measured using the Moire Interferometry system and compared with the results of finite element analysis.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.81-87
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• 2012

This paper focuses on three-dimensional measurement system of micro balls on micro Ball-Grid-Array(BGA) packages in-line. Most of visual inspection system still suffers from sophisticate reflection characteristics of micro balls. For accurate shape measurement of them, a specially designed visual sensor system is proposed under the sensing principle of phase shifting moire interferometry. The system consists of a pattern projection system with four projection subsystems and an imaging system. In the projection system, four subsystems have spatially different projection directions to make target objects experience the pattern illuminations with different incident directions. For the phase shifting, each grating pattern of subsystem is regularly moved by PZT actuator. To remove specular noise and shadow area of BGA balls efficiently, a compact multiple-pattern projection and imaging system is implemented and tested. Especially, a sensor fusion algorithm to integrate four information sets, acquired from multiple projections, into one is proposed with the basis of Bayesian sensor fusion theory. To see how the proposed system works, a series of experiments is performed and the results are analyzed in detail.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.684-692
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• 2016

In the manufacturing process of the LQFP/TQFP (Low-profile Quad Flat Package/Thin Quad Flat Package), the requirement of a 3 dimensional inspection is increasing rapidly and a 3D inspection of the shape of a chip has become an important report of quality control. This study developed a 3 dimensional measurement system based on PMP (Phase Measuring Profilometry) for an inspection of the LQFP/TQFP chip and image processing algorithms. The defects of the LQFP/TQFP chip were classified according to the dimensions. The 2 dimensional optical system was designed by the dorm illumination to achieve constant light distribution, In the 3 dimensional optical system, PZT was used for moving 90 degree in phase. The problem of 2 ambiguity was solved from the measured moir? pattern using the ambiguity elimination algorithm that finds the point of ambiguity and refines the phase value. The proposed 3D measurement system was evaluated experimentally.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.204-205
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• 2002

근래 활발히 연구되고 있는 광통신 분야에서 광섬유는 중요한 위치를 차지하고 있으며 현재까지 여러 가지 연구가 되어져 왔다. 광섬유 중 플라스틱 광섬유는 근거리 광통신 분야에 사용을 위해서 활발한 연구와 개발이 이루어지고 있다. 이러한 광섬유의 특성을 결정짓는 중요한 요소 중 하나가 광섬유의 굴절률 분포이다. 광섬유의 굴절률 분포는 광 전송특성을 결정짓는 요소로서 이러한 이유 때문에 좋은 전송특성을 위해 GRIN 광섬유의 개발과 연구가 이루어져 왔다. (중략)

• 프린팅코리아
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• s.23
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• pp.98-110
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• 2004

인쇄의 품질을 높이는 방법은 여러 가지가 있다. 그 중에서 어떤 스크리닝 기술을 선택하느냐에 따라서도 인쇄의 품질이 달라질 수 있다. 그래서 프리프레스 솔루션 공급업체들은 고품위 인쇄를 위해 300선 이상의 고정세 인쇄, 미세 도트 밀도에 의해 화상의 농담을 표현하는 FM 스크린 그리고 AM과 FM 스크린의 장점을 이용해 사용하고 있는 혼합 망점 등을 활용할 수 있는 기술들을 소개하고 있다. 이것은 인쇄업계에서 일반적으로 사용하고 있는 175선의 AM 스크린이 모아레(얼룩무늬)가 생긴다는 단점이 있었기 때문에 이를 보완하기 위해 나온 기술들이다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.412-419
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• 2003

The most product is manufactured by mould in usual life. From drawing to manufacturing is to be automatically. But inspection is handwork usually. An alternative idea of this problem is reverse engineering. In this study, press forming is measured by 3D non-contact coordinate measuring machine and problem will be analyzed by comparing with 3D data Through the study, it will achieve improvement of press mould process.