• 대한원격탐사학회지
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• 제38권6_2호
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• pp.1589-1605
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• 2022

위상 언래핑은 위성레이더 간섭기법의 필수적인 자료처리 절차다. 이에 따라 비 딥러닝 기반 언래핑 기법이 다수 개발되었으며 최근에는 딥러닝 기반 언래핑 기법이 제안되고 있다. 본 논문에서는 딥러닝 기반 위성레이더 언래핑 기법을 1) 언래핑된 위상의 예측 방법, 2) 위상 언래핑을 위한 딥러닝 모델의 구조 그리고 3) 학습데이터 제작 방법의 측면에서 최근 연구 동향을 소개하였다. 언래핑된 위상을 예측하는 방법은 모호 정수 분류방법, 위상 단절 구간 탐지 방법, 위상 예측 방법, 딥러닝과 전통적인 언래핑 기법의 연계 방법에 따라 다시 세분화하여 연구 동향을 나타냈다. 일반적으로 활용되는 딥러닝 모델 구조의 특징과 전체 위상 정보를 파악하기 위한 모델 최적화 방법에 대한 연구 사례를 소개하였다. 또한 학습데이터 제작 방법은 주로 위상 변이 제작과 노이즈 시뮬레이션 방법으로 구분하여 연구 동향을 정리하였으며 추후 발전 방향을 제시하였다. 본 논문이 추후 국내의 딥러닝 기반 위상 언래핑 연구의 발전 방향을 모색하는 데에 필요한 기반 자료로 활용되기를 기대한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.715-716
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• 2010

• 대한기계학회논문집A
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• 제22권3호
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• pp.684-687
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• 1998

The biggest problem common on to all forms of Phase Shift Interferometer is unwrapping the phase. Simple phase unwrapping algorithms assume that every pixel is within radians of its neighbors. If this is true, any reasonable algorithm will return the correct unwrapped phase. If not, correct unwrapped phase will not be obtained. In rough surface, frequently, neighboring pixels have phase steps greater than. This paper proposes the new method which makes phase steps smaller than by sub-pixel movement.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.330-333
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• 2002

This study Presents improvement of Precision in the non-contacted laser application measuring techniques. The phase map of deformation obtained by phase shifting method in Electronic Speckle Pattern Interferometry displays the wrapped image by the arctangent function, which is a characteristic of 4-step phase shifting method. To obtain deformation distribution from the results, the wrapped phase map is processed by an unwrapping method. But a previous method cannot apply discontinuous object as like plate with a circular hole to obtain precious deformation distribution To solve this problem, new algorithm is developed and the result is compared with previous method.

• Journal of electromagnetic engineering and science
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• 제14권4호
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• pp.332-335
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• 2014

This paper investigates the phase singularity problem in microwave image reconstruction utilizing unwrapped phase data. The measured phases of the electric fields in most microwave measurement systems are wrapped. Thus, a certain phase unwrapping process is necessary for reconstruction of the image of a high contrast object. This unwrapping, however, is difficult in the presence of scattering nulls on/near the unwrapping path. At the null point, the phase value will be rendered, resulting in a poor image reconstruction. In this paper, we investigate the phase singularity arising from electromagnetic scattering nulls in microwave breast tomographic imaging. We then propose a transformation technique for the measured electric fields that avoids phase singularity.

• Journal of Internet Technology
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• 제21권3호
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• pp.841-847
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• 2020

In this paper, a novel technique that improves the performance of generalized mixture decomposition algorithm (GMDA) based on pre-training phase unwrapping. From the investigation of the GMDA scheme, it was discovered that the conventional GMDA technique cannot fully consider phase unwrapping, because the estimated inter-channel phase difference (IPD) slope is initialized randomly. To avoid this phenomenon, the proposed GMDA approach initialized the IPD slope from the data of low-frequency bins. Experimental results show that comparing to the conventional GMDA technique, the proposed GMDA technique based on pre-training phase unwrapping obtains a lower estimation error. When integrated into a source localization system, the result of source localization is improved.

• Journal of the Optical Society of Korea
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• 제18권1호
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• pp.37-44
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• 2014

The use of a laser interferometer as a metrological tool in micro-optics measurement is demonstrated. A transmissive interferometer is effective in measuring an optical specimen having a high angle slope. A configuration that consists of an optical resolution of 0.62 micron is adapted to measure a specimen, which is a micro-Fresnel lens-shaped lenticular lens. The measurement result shows a good repeatability at each fraction of facets, however, a reconstruction of the lens shape profile is disturbed by a known problem of $2{\pi}$-ambiguity. To solve this $2{\pi}$-ambiguity problem, we propose a two-step phase unwrapping method. In the first step, an unwrapped phase map is obtained by using a conventional unwrapping method. Then, a proposed unwrapping method based on the shape modeling is applied to correct the wrongly unwrapped phase. A measured height of each facet is compared with a profile result measured by AFM.

• 한국정밀공학회지
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• 제29권1호
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• pp.48-55
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• 2012

Pressure vessels in vehicle industries, power plants, and chemical industries are often affected by flaw and defect generated inside the pressure vessels due to production processes or being used. It is very important to detect such internal defects of pressure vessel because they sometimes bring out serious problems. In this paper, an optical defect detection method using digital shearography is used. This method has advantages that the inspection can be performed at a real time measurement and is less sensitive to environmental noise. Shearography is a laser-based technique for full-field, non-contacting measurement of surface deformation (displacement or strain). The ultimate goal of this paper is to detect flaws in pressure vessels and to measure the lengths of the flaws by using unwrapping, phase images which are only obtained by Phase map. Through this method, we could decrease post-processing (next processing). Real length of a pixel can be calculated by comparing minimum and maximum unwrapping images with shearing angle. Through measuring several specimen defects which have different lengths and depths of defect, it can be possible to interpret quantitatively by calculating gray level.

• 한국방사선학회논문지
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• 제3권2호
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• pp.23-26
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• 2009

본 연구는 향상된 중심배열 정렬 위상 펼침 방법(ICASPL)을 제안하고 자기공명 위상 영상을 재구성하여 성능을 평가하였다. 제안된 방법을 수행하기 위해 2% 한천젤에 0.6mM/l를 첨가한 팬텀을 제작하여 임상용젠작하5T 자기공명영상와젠상용화된 무릎코일을 이용하여 MR위상영상을 얻었다. 획득된 k 공간 자료는 PC로 옮긴 뒤 매트랩 프로그램을 이용하여 영상을 재구성하였다. 제안된 ICASPU의 오차를 2차 회귀분석읕 이용하여 기존의 중심배열 정렬 위상 펼침과 비교 평가하였다. 그 결과 기존의 ICASPU방법에 비해 제안된 ICASPU방법이 5배 정도 오차가 향상된 것을 확인할 수 있었다. 본 연구는 향상된 중심배열 정렬 위상 펼침 방법을 이용한 위상영상 펼침의 유용성을 확인하였으며, 향후 위상 정보를 포함한 영상 적용에 매우 유용할 것이라 기대된다.

• 한국정밀공학회지
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• 제18권7호
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• pp.149-154
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• 2001

This study discusses a non-contact optical technique, electronic speckle pattern interferometry(ESPI), that is well suited for a deformation measurement of structure. Phase shifting method and unwrapping method have used to make deformation quantitative widely. In this paper, a previous numerical formula for phase shifting method is reconstructed in addition to least square fitting method to improve sensitivity and phase unwrapping based on vertical-horizontal scanning method is applied to analyze in-plane and out-of-plane deformation quantitatively.