• 한국전기전자재료학회논문지
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• 제19권2호
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• pp.185-188
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• 2006

We studied on the reverse twist near the pixel edge depending on the rubbing direction for the fringe field switching (FFS) mode. Liquid crystal (LC) dynamic and the transmittance near the pixel edge, where the various field directions are generated, depend on the initial rubbing direction because the position of reverse twist is decided by the angle between the electric direction and the LC director at a bias voltage. For example, when the rubbing angle is $7^{\circ}$, the reverse twist appears on the bottom position of the right sharp comer of the pixel edge so that the reverse region exists far away from main active region. But, when the rubbing angle is $-7^{\circ}$, the reverse twist appears on the top position of the right sharp comer of the pixel edge, resulting that the region becomes more close to the main active area and the unstable disclination lines (DLs) easily intrude into the active region. Therefore, it is necessary to keep the reverse twist region far from the active region and it is possible by controlling the rubbing direction in the design of a pixel electrode.

• 한국전기전자재료학회논문지
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• 제18권7호
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• pp.647-651
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• 2005

We studied the external pressure-stable advanced frnge field switching (FFS) pixel design with 3 slit sructue. In this mode, a patterned pixel slit is partitioned into 3 areas, namely, two edges and a center, where the edge slit angle is larger than the center slit angle. Thus the reverse twist region in the pixel edge is reduced comparing to the conventional FFS mode so that the LC dynamics in this region becomes very stable. And also, when the external pressure is applied to the panel at the high voltage, the disclination lines (DLs) were barely intruded into active area. Therefore, the structure is use for the pen based system such as the tablet personal computer (PC), personal digital asistant (PDA).

• 비파괴검사학회지
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• 제21권2호
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• pp.189-196
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• 2001

광탄성법은 전체적인 응력장 해석을 위하여 가장 많이 사용되는 방법중의 하나이다. 광탄성법에서 주응력의 차이와 방향은 등색선과 등경선으로 나타난다. 재래식 방법으로는 주응력 방향은 평면 편광기의 편광자와 검광자를 동시에 회전시켜 수작업으로 측정하며, 이를 타디보간법이라 한다. 이러한 방법은 전체적인 응력장 해석시 매우 번거로우며 많은 시간이 걸린다. 재래식 광탄성법에서는 광탄성 프린지로부터 등경선을 분리시킬 수 없다. 본 연구에서는 광탄성이론을 Jones행렬로 나타내고 4단계와 8단계의 위상이동법에 대해서 기술하였다. 컴퓨터시뮬레이션을 통하여 압축하중을 받는 원형디스크의 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 시험을 하였다. 디스크의 프린지는 응력-광 법칙에 의하여 생성하였다. 8단계 위상이동법으로 얻은 등경선과 등색선의 크기를 이론으로 계산한 값과 비교하였다. 컴퓨터 시뮬레이션으로부터 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 가능성을 예시하였다.

• 대한기계학회논문집A
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• 제23권6호
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• pp.988-1000
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• 1999

An experimental study is presented for the effect of number of terms of a pewee series type stress function on stress analysis around a hole in tensile loaded plate. The hybrid method coupling photoelastsic data inputs and complex variable formulations involving conformal mappings and analytical continuity is used to calculate tangential stress on the boundary of the hole in uniaxially loaded, finite width tensile plate. In order to measure isochromatic data accurately, actual photoelastic fringe patterns are two times multiplied and sharpened by digital image processing. For qualitative comparison, actual fringes are compared with calculated ones. For quantitative comparison, percentage errors and standard deviations with respect to percentage errors are caculated for all measured points by changing the number of terms of stress function. The experimental results indicate that stress concentration factors analyzed by the hybrid method are accurate within three percent compared with ones obtained by theoretical and finite element analysis.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.37-43
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• 2002

Electronic speckle contouring(ESC) based on electronic speckle pattern interferometry is the optical method for measuring object shape by using fringe-projection techniques. This method has the advantages of being non-contact, non-destructive and a whole-field measurement of the surface under investigation. Fringes in ESC represent the difference in depth along the view direction between the master wavefront and the test component. The contour maps of three-dimensional diffuse objects can be obtained by small shifts of optical fiber carrying the dual-object-beams and 4-frame phase shifting. In this study we proposed the contouring method by shifting the collimated illumination beams through optical fiber in order to obtain the contour fringe patterns. And also, we performed the addition of incremental images through the geometrical analysis to obtain the contour fringe interval when we performed the incremental addition of images and experiments based on this method. We obtained both quantitative increment without decorrelation effect and qualitative improvement by reducing the noise of contour fringes.

• 대한기계학회논문집A
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• 제32권2호
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• pp.186-193
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• 2008

[ $Moir{\acute{e}}$ ] interferometry is an optical method, providing whole field contour maps of in-plane displacements with high resolution. The demand for enhanced sensitivity in displacement measurements leads to the technique of microscopic $moir{\acute{e}}$ interferometry. The method is an extension of the $moir{\acute{e}}$ interferometry, and employs an optical microscope for the required spatial resolution. In this paper, the sensitivity of $moir{\acute{e}}$ interferometry is enhanced by an order of magnitude using an immersion interferometry and the optical/digital fringe multiplication(O/DFM) method. In fringe patterns, the contour interval represents the displacement of 52 nm per fringe order. In order to estimate the reliability and the applicability of the optical system implemented, the measurements of rigid body displacements of grating mold and the coefficient of thermal expansion(CTE) for an aluminium block are performed. The system developed is applied to the measurement of thermal deformation in a flip chip plastic ball grid array package.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 기술교육전문연구회
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• pp.136-139
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• 2003

Thermal imaging system is electro-optical imaging device which can make visible the difference of infrared energy naturally emitted by objects. It is acquire the same images at any time of the day or night. There it has been readily available to the night observation such as fire control systems. In this study, we are manufacturing thermal image Al flat mirror. The surface roughness 3.539nm Ra and power 0.382 fringe(at 632.8nm), irregularity 0.835 fringe(at 632.8nm) for form waviness of thermal image Al flat mirror are very satisfied. The results will be reflected for development of the ultra precision application. And a brief review of Ultra-precision system in the field of Ultra-precision at Korea photonics technology institute (KOPTI) is present in this paper.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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• pp.53-54
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• 2008

We have studied electro-optic characteristics as a function of passivation thickness$(t_p)$ in the fringe-field swiching (FFS) mode using the LC with positive dielectric anisotropy. When $t_p$ is increased from $0.29{\mu}m$ to $3.0{\mu}m$, a maximum transmittance is slightly increased to $2{\mu}m$. However, operating voltage is continuously increased up to above 11v. We found that the tilt angle is decreased between the edge of pixel electrode and the center of each pixel electrode. In the FFS mode using the liquid crystal with positive dielectric anisotropy, transmittance is affected by the tilt angle. When tilt angle is increased, transmittance become decrease. Therefore, in the FFS device, a low tilt angle is favored for high transmittance. It is demonstrated that the suitable passivation thickness make a tilt angle decreased.

• 대한기계학회논문집A
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• 제34권9호
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• pp.1287-1292
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• 2010

본 연구에서는 균열선단 주위의 응력장을 균열선단으로부터 떨어진 일직선상에서 유한요소법에 의해 계산된 광탄성 등색프린지 차수와 급수형 등각사상 맵핑함수를 이용하여 해석하였다. 해석된 광탄성 응력장을 실제의 광탄성프린지와 비교하였다. 정성적인 비교가 용이하도록 디지털 영상처리에 의해 등색프린지 패턴을 2 배로 증식시키고, 증식된 프린지를 다시 세선처리하여 서로 비교하였다. 유한요소법으로 계산된 프린지 차수를 이용한 하이브리드 응력장 해석에 의해 계산된 프린지와 광탄성 실험에 의한 실제의 프린지를 정성적이고 정량적인 비교를 하였다. 입력된 변위와 계산된 변위의 퍼센트 오차는 18 개의 데이터 모두 6.0% 이하로 서로 일치하였다. 또한 하이브리드 기법에 의한 정규화시킨 응력확대계수 $K_I$ 및 $K_{II}$는 유한요소법과 경험식으로 계산된 값에 근접하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.469-470
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• 2008

We have studied electro-optic characteristics as a function of splay elastic constants ($K_{11}$) in the fringe-field switching (FFS) mode using the LC with positive dielectric anisotropy. When $K_{11}$ is increased from 7.7pN to 11.7pN, a maximum transmittance is slightly increased and rising time become a little bit fast. However, operating voltage and threshold voltage is independent. In opposition to rising time, decay time is not affected by $K_{11}$. We already know that $K_{11}$ affects tilt angle of liquid crystals. Therefore, on the occasion of high $K_{11}$, liquid crystals are mainly affected by twist deformation because the higher $K_{11}$, the less tilt angle. In the FFS device, high $K_{11}$ is favorable to reduce tilt angle in on state and thus improve rising response time.