• 정보처리학회논문지B
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• 제13B권4호
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• pp.369-376
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• 2006

디지탈 변환과 기기간의 전송 영향으로 화질이 떨어진 디지탈 영상의 복구는 잡음 발생 및 그 역 과정의 모형화를 통해 이루어낼 수 있다. 스캐너로 읽혀진 서류 영상이나 위성 사진에서 잡음 및 반점을 제거하는 과정이 좋은 예이다. 그러나 잡음 발생의 비선형성은 그 역 과정의 이론적 이해를 어렵게한다. 본 논문에서는 충격 잡음에의해 화질이 떨어진 이진 서류 영상의 복구 방법들을 심층 분석하는 것에 촛점을 맞추었다. 본 연구 결과에 의하면 이진 서류 영상의 잡음 제거 방식으로 '가중 중앙값' 여과기와 '리' 여과기가 다른 여과기에 비해 효과적임을 보여준다. 반면 '웨이브렛' 여과 방식은 타 방식보다 100여배의 시간이 소요되어 비효율적이다. 본 논문에서는 가중 중앙값 여과기에 쓰이는 가중치에 대한 연구 결과를 제시하였다.

• 한국통신학회논문지
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• 제28권11C호
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• pp.1098-1110
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• 2003

본 논문에서는 스펙클 잡음으로 열화 된 영상을 복원하기 위하여 에지 영역을 고려한 호모모르픽 웨이브렛 기반 MMSE 필터를 제안한다. 제안된 방법에서는 스펙클 잡음이 섞인 영상을 로그 영역으로 변환한 다음 호모모르픽 방향성 MMSE 필터로 복원된 영상에 DIP 연산자를 적용하여 각 화소를 평탄 영역과 에지 영역으로 분류한다. 평탄 영역에서는 호모모르픽 웨이브렛 기반 MMSE 필터링을 수행하고 에지 영역에서는 호모모르픽 웨이브렛 기반 MMSE 필터링의 결과와 호모모르픽 방향성 MMSE 필터링의 결과를 가중하여 합하는 가중 평균 필터링을 수행한다. 그런 다음 지수 함수를 이용하여 공간 영역으로 역 변환하여 복원된 영상을 얻는다. 실험 결과 제안된 방법으로 복원된 영상은 기존의 호모모르픽 평균 필터와 메디안 필터에 의하여 복원된 영상에 비하여 3.3-4.0 ㏈의 ISNR 성능 향상을 보였다. 또한 0.0103-0.0126의 에지 보존도 측정 파라미터 $\beta$ 성능 향상을 보이고, 에지가 잘 보존되면서 잡음이 잘 제거된 우수한 주관적 화질을 보였다.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.126-130
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• 2008

We propose and experimentally demonstrate an effective method to reduce near-field speckle noise at the output of a 50 ${\mu}m$ graded index multimode fiber using a short cylindrical piezoelectric transducer(PZT) vibrating in the radial direction. The fiber was coiled as tightly as possible around the mandrel of the PZT and a periodic stretching effect was caused by the radial oscillations of the actuator. The output of the optical fiber using the He-Ne laser source was intensively observed by a CCD camera. By counting all the pixels corresponding to relative intensity graded into 256 levels in the selected area and by calculating standard deviation and mean value of the intensity, we could measure the speckle contrast and vibration effect quantitatively with reduction ratio of pixels and line profile of the illuminated region. It was clearly observed that the characteristics of the speckle pattern in the vibration-on state were significantly improved over that of the vibration-off state due to time-averaged smoothing.

• 한국정밀공학회지
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• 제21권10호
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• pp.154-161
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• 2004

An experimental method for measuring side-necking deformation near a crack-tip is described. It is based on Stereoscopic Digital Speckle Photography and Digital Image Correlation, and it is simple and robust to mechanical vibration inherent to a hydraulic material test system. The validity and accuracy are evaluated through a calibration fur rigid body translation. A case study has been performed for a CT specimen made of a ductile steel and the three dimensional profiles of the side-necked region are presented as the load increases. Also, the details of the procedure and the surface treatment are discussed.

• Transactions on Electrical and Electronic Materials
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• 제10권6호
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• pp.189-192
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• 2009

The leakage current in a CMOS image sensor (CIS) can have various origins. Leakage current investigations have focused on such things as cobalt-salicide, source and drain scheme, and shallow trench isolation (STI) profile. However, there have been few papers examining the effects on leakage current of nitride stringers that are formed by gate sidewall etching. So this study reports the results of a series of experiments on the effects of a nitride stringer on real display images. Different step heights were fabricated during a STI chemical mechanical polishing process to form different nitride stringer sizes, arsenic and boron were implanted in each fabricated photodiode, and the doping density profiles were analyzed. Electrons that moved onto the silicon surface caused the dark leakage current, which in turn brought up the speckle defect on the display image in the CIS.

• 한국산학기술학회논문지
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• 제8권2호
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• pp.245-249
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• 2007

본 논문은 핵발전소의 초음파 비파괴 평가를 수행하기 위하여 핵발전소 설비의 초음파 비파괴 평가시 발생될 수 있는 스펙클 잡음을 억제하고 디컨벌루션 기법을 이용하여 결함의 정확한 위치 및 크기를 추정할 수 있는 영상 처리 기법을 제안하였다. 제안된 방법은 실제 핵발전소의 증기발생기 파이프라인으로 만들어진 시편을 이용하여 영상의 선명도를 확인 할 수 있었다.

• 천문학회지
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• 제47권2호
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• pp.43-47
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• 2014

Many advanced ground-based solar telescopes improve the spatial resolution of observation images using an adaptive optics (AO) system. As any AO correction remains only partial, it is necessary to use post-processing image reconstruction techniques such as speckle masking or shift-and-add (SAA) to reconstruct a high-spatial-resolution image from atmospherically degraded solar images. In the New Vacuum Solar Telescope (NVST), the spatial resolution in solar images is improved by frame selection and SAA. In order to overcome the burden of massive speckle data processing, we investigate the possibility of using the speckle reconstruction program in a real-time application at the telescope site. The code has been written in the C programming language and optimized for parallel processing in a multi-processor environment. We analyze the scalability of the code to identify possible bottlenecks, and we conclude that the presented code is capable of being run in real-time reconstruction applications at NVST and future large aperture solar telescopes if care is taken that the multi-processor environment has low latencies between the computation nodes.

• 대한기계학회논문집A
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• 제20권2호
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• pp.564-574
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• 1996

This paper describes as Electronic Speckle Pattern Interferometry system which has been designed for measuring vibration patterns and quantitative measurement of vibration amplitude fields by using the time average method on a object. Visbility of fringe patterns is more improved by using the phase stepping and frame average method to reduce speckle and electric noise. And a bias vibration is introduced into the reference beam to shift the $\frac{2}{0}$ fringes so that fringe shift algorithms can be used to determine vibration amplitude. The experimental results are compared to those of the FFT analyzer and the FEM model analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.91-95
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• 1997

ESPI(Electronic Speckle Pattern Interferometry) is new optical measuring method to be able to measure the surface deformations of engineering components and materials in industrial areas. Conventional measuring method of surface deformation such as the strain gauge have many demerits because it is contact and point-to-point measuring one. But ESPI that is non-contact, whole field measuring method can overcome previous disadvantages. The speckle pattern to be formed with interference phenomena of scattering light from rough surfaces illuminated by laser light have phase information of surface In this study we used this interference phenomena and the phase shifting method to measure the in- plane deformation, together with the use of digital equipment to process the information contained in the speckle pattern and to display consequent inter ferograms. Finally we obtained good agreement between the experimenta results and those of FEM..

• 대한전자공학회논문지
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• 제26권8호
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• pp.1282-1289
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• 1989

Dual field speckle interferometry that is sensitive to the surface displacement of the object is constructed, and fringe patterns that have the displacement-informations are analysed using digital image processing. From 10\ulcorner to 80\ulcorner with respect to each specklegrams are obtained by double-exposure techniques, which are analysed by the proposed system and algorithm. Up to 10\ulcorner displacement, near measurable lower bound of Speckle Interferometry, fringe visibility is decreased due to decreasing fringe density, therefore relative errors are produced over 10% but over that displacement, relative errors are produced below 5%. Particularly, it is observed that spatial frequencies of each displacement are comparatively linear.