• 한국광학회지
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• 제4권2호
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• pp.140-144
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• 1993

Optical Transfer Function(OTE)으로부터 Edge Response Function(ERF)을 계산하는 computer program을 작성하였다. 이 program을 사용하여 무수차 광학계와 몇가지 형태의 수차를 포함하는 광학계의 ERF를 계산하였다. 왜곡수차, 촛점이동, 비점수차, 코마 또는 구면수차 등의 단일수차 및 이들이 조합된 몇가지 형태의 복합수차 등을 포함하는 광학계를 고려하였다. 계산의 결과로부터 sagital case의 경우, 촛점이동이나 구면수차가 코마에 비하여 ERF에 나쁜 영향을 미치며, tangential case의 경우, 코마가 촛점이동과 구면수차보다 나쁜 영향을 미침을 알았다. 한편 코마는 tangential case의 ERF의 형태와 위치를 변화시키지만 왜곡수차는 상의 위치만을 변화시킨다는 것도 확인 할 수 있었다. 또한 코마와 왜곡수차를 포함하는 광할계의 tangential case의 ERF는 이들중 하나의 수차만 포함하는 경우보다 오히려 좋은 형태를 나타내어 두 수차가 상호 보완적인 영향을 미침을 알았다.

• 한국광학회지
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• 제13권3호
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• pp.182-188
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• 2002

위상이동 간섭무늬 투영 방법을 이용한 3차원 형상측정 시스템의 위상계산오차를 분석하였다. 본 연구에서 다룬 오차의 요소에는 물체 표면의 특성에 따라 검출기에 나타나는 양자화 크기의 변이 효과, 물체 표면에 맺히는 간섭무늬 패턴의 초점 어긋남 효과, 간섭무늬의 위상이동 오차에 의한 효과, 위상 이동된 간섭무늬 패턴이 투영된 여러 개의 물체 상을 받아들이는 도중에 시스템 및 주위 환경 변화에 의한 오차, 그리고 투영되는 격자 패턴의 왜곡에 의한 효과들을 계산하고 논의하였다.

• 전자공학회논문지B
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• 제32B권6호
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• pp.886-898
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• 1995

One of the ways to measure the distance in the computer vision is to use the focus and defocus. There are two methods in this way. The first method is caculating the distance from the focused images in a point (MMDFP: the method measuring the distance to the focal plane). The second method is to measure the distance from the difference of the camera parameters, in other words, the apertures of the focal planes, of two images with having the different parameters (MMDCI: the method to measure the distance by comparing two images). The problem of the existing methods in MMDFP is to decide the thresholding vaue on detecting the most optimally focused object in the defocused image. In this case, it could be solved by comparing only the error energy in 3x3 window between two images. In MMDCI, the difficulty is the influence of the deflection effect. Therefor, to minimize its influence, we utilize two differently focused images instead of different aperture images in this paper. At the first, the amount of defocusing between two images is measured through the introduction of regularization and then the distance from the camera to the objects is caculated by the new equation measuring the distance. In the results of simulation, we see the fact to be able to measure the distance from two differently defocused images, and for our approach to be robuster than the method using the different aperture in the noisy image.

• 마이크로전자및패키징학회지
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• 제21권4호
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• pp.63-68
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• 2014

For a nanoscale Cu/low-k wafer, inter-layer dielectric (ILD) and metal layers peelings, cracks, chipping, and delamination are the most common dicing defects by traditional diamond blade saw process. Sidewall void in sawing street is one of the key factors to bring about cracks and chipping. The aim of this research is to evaluate laser grooving & mechanical sawing parameters to eliminate sidewall void and avoid top-side chipping as well as peeling. An ultra-fast pico-second (ps) laser is applied to groove/singulate the 28-nanometer node wafer with Cu/low-k dielectric. A series of comprehensive parametric study on the recipes of input laser power, repetition rate, grooving speed, defocus amount and street index has been conducted to improve the quality of dicing process. The effects of the laser kerf geometry, grooving edge quality and defects are evaluated by using scanning electron microscopy (SEM) and focused ion beam (FIB). Experimental results have shown that the laser grooving technique is capable to improve the quality and yield issues on Cu/low-k wafer dicing process.

• 한국광학회지
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• 제15권1호
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• pp.56-62
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• 2004

거친 표면의 형상을 측정하기 위해서 큰 등가파장 회절격자간섭계를 구성하였다. 제안된 시스템은 두 개의 투과회적격자를 사용해서 두 광을 측정물체에 각각 다른 각으로 경사지게 입사시켜서, 그 입사각에 따른 큰 등가파장의 간섭무늬를 얻는다. 이런 등가파장 간섭계는 기존의 광학 간섭계보다 넓은 영역에 걸쳐서 거친 표면을 빠른 시간에 측정할 수 있다. 제안된 시스템은 편광광속분할기와, 광속분할기, 프리즘을 사용해서, 불필요한 광을 제거하는 부분을 설계하여, 회절격자의 불필요한 회절광을 최소화하고, 회절격자의 형상으로 인한 시스템 오차를 줄였다. 뿐만 아니라, 큰 작동거리를 가지며 정렬이 쉽다. 측정정밀도를 향상시키기 위하여 위상편이법을 도입하였고, 등가파장보정법을 제안하였다. 실험을 통해서 측정시스템을 평가해보았다.

• 한국레이저가공학회지
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• 제5권1호
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• pp.33-42
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• 2002

In order to investigate the characteristics of the plasma induced by lap-joint CO$_2$ laser welding of automotive steel sheets, the effects of welding speed, shield gas flow rate, gap size, and laser beam defocus to plasma intensity emitted from keyhole have been investigated. The plasma light is measured by fiber and photodiode. Also, the plasma images were captured by the high speed digital camera in 1000frames/sec in order to correlate the plasma light signal with plasma pattern. From the results, it is observed that the difference of the plasma intensity for between the deep penetration and partial penetration exists from 1.2 to 2 times. The plasma light intensity decreased in case of the deep penetration Is observed due to the exhausting of the plasma gas under the sheet. On the other hand, under the conditions of the deep penetration, the plasma intensity is significantly increased by controling the conditions decreasing the penetration depth. It was specially founded that the effect of 0.3mm gap size at partial penetration condition is approximately similar to deep penetration in 0mm gap. It is concluded that the plasma intensity is able to evaluate the penetration depth in lap-joint welding and appears to offer the most straightforward correlation to the welding process.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.101-106
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• 2016

A pupil filter is a useful technique for modifying the light intensity distribution near the focus of an optical system to realize depth of field (DOF) extension and superresolution. In this paper, we proposed a new design of the phase only pupil filter by using Zernike polynomials. The effect of design parameters of the new filters on DOF extension and superresolution are discussed, such as defocus Strehl ratio (S.R.), superresolution factor (G) and relative first side lobe intensity (M). In comparison with the other two types of pupil filters, the proposed filter presents its advantages on controlling both the axial and radial light intensity distribution. Finally, defocused imaging simulations are carried out to further demonstrate the effectiveness and superiority of the proposed pupil filter on DOF extension and superresolution in an optical imaging system.

• Journal of Advanced Marine Engineering and Technology
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• 제30권5호
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• pp.629-635
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• 2006

Manufacture of motor by laser has been studying realization that was demands on market for lightening and miniaturization. Moreover. early in the 1980s. manufacture of parts for automobiles by laser welding was already successfully introduced. The purpose of this study was to develop production technology of the high quality laminated stator core for motor by pulsed Nd:YAG laser heat source. In the event of adjusting defocus and voltage to control humping in laser welding of the laminated core. sound bead could be obtained. but deep penetration was not. Therefore. explosive evaporating plasma was controlled by adjustment of peak power on pulse width. Particularly, because explosive evaporating plasma induced high peak power, made molten metal in keyhole scatter. a suitable adjustment of peak power was required to obtain sound bead. As a results of experiment. sound bead and deep penetration could be obtained.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2012년도 하계학술대회
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• pp.275-278
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• 2012

본 논문에서 2D-3D 자동 영상 변환을 위하여 2D 상으로부터 깊이 지도(depth map)을 생성하는 방법을 제안한다. 제안하는 방법은 보다 정확한 깊이 지도 생성을 위해 영상의 전경 깊이 지도(foreground depth map)와 배경 깊이 지도(background depth map)를 각각 생성 한 후 결합함으로써 보다 정확한 깊이 지도를 생성한다. 먼저, 전경 깊이 지도를 생성하기 위해서 라플라시안 피라미드(laplacian pyramid)를 이용하여 포커스/디포커스 깊이 지도(focus/defocus depth map)를 생성한다. 그리고 블록정합(block matching)을 통해 획득한 움직임 시차(motion parallax)를 이용하여 움직임 시차 깊이 지도를 생성한다. 포커스/디포커스 깊이 지도는 평탄영역(homogeneous region)에서 깊이 정보를 추출하지 못하고, 움직임 시차 깊이 지도는 움직임 시차가 발생하지 않는 영상에서 깊이 정보를 추출하지 못한다. 이들 깊이 지도를 결합함으로써 각 깊이 지도가 가지는 문제점을 해결하였다. 선형 원근감(linear perspective)와 선 추적(line tracing) 방법을 적용하여 배경깊이 지도를 생성한다. 이렇게 생성된 전경 깊이 지도와 배경 깊이 지도를 결합하여 보다 정확한 깊이 지도를 생성한다. 실험 결과, 제안하는 방법은 기존의 방법들에 비해 더 정확한 깊이 지도를 생성하는 것을 확인할 수 있었다.

• 반도체디스플레이기술학회지
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• 제19권3호
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• pp.7-11
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• 2020

Enormous methods have been proposed for the detection and segmentation of blur and non-blur regions of the images. Due to the limited available information about the blur type, scenario and the level of blurriness, detection and segmentation is a challenging task. Hence, the performance of the blur measure operators is an essential factor and needs improvement to attain perfection. In this paper, we propose an effective blur measure based on the local binary pattern (LBP) with the adaptive threshold for blur detection. The sharpness metric developed based on LBP uses a fixed threshold irrespective of the blur type and level which may not be suitable for images with large variations in imaging conditions and blur type and level. Contradictory, the proposed measure uses an adaptive threshold for each image based on the image and the blur properties to generate an improved sharpness metric. The adaptive threshold is computed based on the model learned through the support vector machine (SVM). The performance of the proposed method is evaluated using a well-known dataset and compared with five state-of-the-art methods. The comparative analysis reveals that the proposed method performs significantly better qualitatively and quantitatively against all the methods.