• 한국통신학회논문지
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• 제29권3C호
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• pp.419-425
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• 2004

본 논문은 카메라로 찍은 투사 사영(Perspective Projection)의 한 영상으로부터 물체의 크기와 위치를 계산하기 위해서 3 개의 소실 점만을 사용해서 계산하는 새로운 방법을 제안한다. 우리의 접근 방법은 투사 사영의 영상으로부터 초점 거리(Focal Length), 회전 행렬(Rotation Matrix) 등의 정보들 없이 3개의 소실 점만을 가지고 계산하는 방법이다. 물체는 꼭지점(vertices)의 좌표가 크기 벡터 v 의 선형 함수로서 표현할 수 있는 다각형으로써 모델이 된다는 것을 가정한다. 이 재구성의 입력은 영상에서 특징 점과 모델에서 특징 점 사이 대응점의 집합으로 표현할 수 있다. 이 매개 변수 모델의 각각 크기를 최적화하기 위해서, 재구성의 최적화는 동일하게 매개 변수 공간을 샘플링에 의한 최적화기에 대하여 다중 시작점(multiple starting points)을 발생하는 다중 시작(multi-start) 방법을 가지는 표준 비선형 최적화 기법을 효과적으로 해결할 수가 있다.

• 한국정보과학회논문지:시스템및이론
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• 제32권4호
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• pp.168-176
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• 2005

본 논문에서는 모델 기반으로 한 장의 사진으로부터 중점 정보를 포함한 선분을 이용하여 물체를 3차원 재구성하는 방법을 제안한다. 미리 정의된 다면체를 원시기하모델로 사용하며 한 장의 영상으로부터 복원을 시도하였다. 미리 정의된 다면체 모델을 원시기하모델로 사용하며 사용자가 원시기하모델(primitive)의 각 대응점(correspondence point)을 사진에 매핑 시키는 것으로서 3차원 재구성이 수행된다. 기존의 모델기반 3차원 재구성은 카메라 파라미터들을 복원하거나 반복(iteration)을 통한 오차최소화 기법을 사용하였다. 하지만 본 논문은 원시기하모델에 포함되어 있는 선분들과 그 선분들의 중점 정보로부터 선분을 3차원 복원하며 복원된 선분들로부터 원시기하모델을 재구성하는 방법을 제안한다. 이러한 방법은 선분을 복원하는 단계에서 요구되는 최소한의 카메라 파라미터(focal length) 만으로 원시기하모델을 재구성 할 수 있다.

• 한국통신학회논문지
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• 제31권4C호
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• pp.381-390
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• 2006

본 논문에서는 비 교정 영상에서 3장의 평면 패턴 영상들을 위치시켜, 한 장의 영상으로 찍어 얻은 영상으로부터 이들 평면 패턴 영상 간에 호모그래피(homography)로 카메라 교정을 하는 새로운 기법이 제안된다. 비교정 영상에서 3차원 재구성을 하려면 카메라 교정이 필수적이다. 제안된 방법은 대상 영상내에 존재하는 패턴 영상 간에 호모그래피를 계산함으로써, 3차원 재구성 시, 보다 쉽고 간단히 구현한다. 실험 결과는 제안된 방법(한 장내에 3장의 패턴영상 사용에 의한 카메라 교정법이 기존 방법(3장의 패턴영상 사용에 비해 매우 유용함을 확인한다. 또한, 비 교정 입력 영상에서 제안된 알고리즘을 이용한3차원 재구성의 예로 증명한다.

• 대한의용생체공학회:의공학회지
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• 제15권4호
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• pp.377-382
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• 1994

In the conventional Fourier imaging method in MRI (Magnetic Resonance Imaging), intramotion such as pulsatile flow makes zipper-like artifact along the phase encoding direction. On the other hand, line-integral projection reconstruction (LPR) method has advantages such as imaging of short T2, object and reduction of the flow artifact by elimination of the flow-induced phase fluctuation. The LPR, however, necessarily requires time consuming filtering and back-projection processes, so that the reconstruction takes long time. To overcome the long reconstruction time of the LPR and to obtain the flow artifact reduction effect, we adopted phase corrected concentric square raster sampling (CSRS) method and improved its imaging performance. The CSRS is a fast reconstruction method which has the same properties with the LPR. In this paper, we proposed a new method of flow artifact reduction using the CSRS method. Through computer simulations and experiments, we verified that the proposed method can eliminate phase fluctuations, thereby reducing the flow artifact and re- markably shorten the reconstruction time which required long time in the LPR.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.63.3-63
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• 2001

Inspection and shape measurement of three-dimensional objects are widely needed in industries for quality monitoring and control. In this paper, we propose a three dimensional volume reconstruction method, which is an iterative method and as uniform and simulated algebraic reconstruction technique (USART). In this method, two or more x-ray images projected from different views are needed, and also the geometry of the imaging system need to be a priori identified well. That is to say, the relative locations between the x-ray source, imaging plane and the object should be determined exactly by calibration. To achieve this, we propose a series of coordinate calibration methods of the x-ray imaging system using grid pattern images. Some experimental results of these calibrations is presented and discussed in detail ...

• 대한치과의사협회지
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• 제52권10호
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• pp.596-601
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• 2014

Computer-aided surgery is popular and useful in the field of oral and maxillofacial surgery, because of the possibility of simulation with a high accuracy. In all aspects of surgery, proper planning facilitates more predictable operative results, however before the use of virtual planning, much of this relied on 2-dimensional (2-D) imaging for treatment planning on a 3-dimensional (3-D) object and surgical trial and error. With real-time instrument positioning and clear anatomic identification, a computer-assisted navigation system (CANS) is exceptionally helpful in maxillofacial surgery. These techniques enable performing precise bony ablation and reconstruction, and also decrease surgical time and donor site defect.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.513-516
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• 2002

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents two intelligent optimization algorithm techniques such as genetic algorithm and simulated annealing for the solution of the static EIT inverse problem. We summarize the simulation results for the three algorithm forms: modified Newton-Raphson, genetic algorithm, and simulated annealing.

• Journal of the Optical Society of Korea
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• 제4권1호
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• pp.48-53
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• 2000

In Optical Scanning Holography(OSH), 3-D holographic information of an object is generated by 2-D active optical scanning. The optical scanning beam can be a time-dependent Gaussian apodized Fresnel zone plate. In this technique, the holographic information manifests itself as an electric signal which can be sent to an electron-beam-addressed spatial light modulator for coherent image reconstruction. In this paper, we briefly review optical scanning holography and analyze the resolution achievable with the system. We also present mathmatical expressions of real and virtual images which are responsible for holographic image reconstruction. We then show the twin-image noise effect on the reconstruction in conjunction with the size of the Fresnel zone pattern through computer simulation.

• 대한의용생체공학회:의공학회지
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• 제18권2호
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• pp.113-120
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• 1997

This paper presents an optimal design for the SPECT reconstruction filter, based on a physical limit of SPECT lesion detection capability. To increase the performance of the filter on lesion detectability, the filter design was focused on increasing the local SyW ratio of a threshold lesion, that was determined by minimum detectable lesion size (MDU) from SPECT lesion detectabllity contrast-detail curve. The proposed filter showed flexible window characteristics of resolution recovery and noise smoothing for MDLSs in the resolution-limited and photon-limited regions, respectively, compennting for the relative impact of the main limitation factors on threshold detectability. The simulated results showed good adaptability of the proposed filter to the changes in physical parameters of photon counts, object contrast, and detector system resolution.

• 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.