• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제12권1호
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• pp.41-46
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• 2023

CT의 반복재구성법은 투영과 역투영을 번갈아 가며 최적의 단면 영상을 얻을 때까지 반복 수행하기 때문에 계산 시간이 오래 걸리는 단점이 있다. 영상재구성 시간을 단축하기 위하여 계산 시간이 많이 소요되는 투영을 빠르게 수행할 수 있는 알고리즘이 필요하다. 본 논문은 Siddon 알고리즘을 개선한 Jacobs 버전보다 대략 10% 빠른 알고리즘을 제안하였다. 제안한 알고리즘은 기존의 Jacobs 버전의 루프 횟수를 줄임으로써 계산 시간을 줄이도록 하였다. 제안한 방법은 계산속도뿐만 아니라 영상 품질 측면에서도 우수한 성능을 보였다. 평행빔의 경우에 대해 조사되었지만 향후 부채살빔 및 콘빔의 경우로 확장이 가능하다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1991년도 춘계학술대회
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• pp.5-7
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• 1991

We have developed an efficient and robust image reconstruction algorithm for static impedance imaging. This improved Newton-Raphson method produced more accurate images by reducing the undesirable effects of the ill-conditioned Hessian matrix. We found that our electrical impedance tomography (EIT) system could produce two-dimensional static images from a physical phantom with 7% spatial resolution at the center and 5% at the periphery. Static EIT image reconstruction requires a large amount of computation. In order to overcome the limitations on reducing the computation time by algorithmic approaches, we implemented the improved Newton-Raphson algorithm on a parallel computer system and showed that the parallel computation could reduce the computation time from hours to minutes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.232-235
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• 1988

Recently, an iterative reconstruction-reprojection (IRR) algorithm has been suggested for application to incomplete data computed tomography (CT). In the IRR, the interpolation operation is performed in the image space during reconstruction-reprojection. The errors associated with the interpolation degrade the reconstructed image and may cause divergence unless a large number of rays is used. In this paper, we propose an improved IRR algorithm which eliminates the need for interpolation. The proposed algorithm adopts a new sampling scheme in which samples (projection data) is taken in phase with the samples of the Cartesian grid.

• 전자공학회논문지B
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• 제33B권2호
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• pp.111-117
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• 1996

In tis paper, a new morphological algorihtm for binary image reconstruction from graayscale skeleton is proposed. In the proposed algorithm, grayscale morphological dilation is utilizedm instead of binary morphological operatons for the conventional methods. The algorithm is proven mathematically and verified by computer simulation results.

• 대한방사성의약품학회지
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• 제3권2호
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• pp.65-71
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• 2017

To assess the effects of filter and reconstruction of Cu-64 PET data on Siemens scanner, the various reconstruction algorithm with various filters were assessed in terms of spatial resolution, non-uniformity (NU), recovery coefficient (RC), and spillover ratio (SOR). Image reconstruction was performed using filtered backprojection (FBP), 2D ordered subset expectation maximization (OSEM), 3D reprojection algorithm (3DRP), and maximum a posteriori algorithms (MAP). For the FBP reconstruction, ramp, butterworth, hamming, hanning, or parzen filters were used. Attenuation or scatter correction were performed to assess the effect of attenuation and scatter correction. Regarding spatial resolution, highest achievable volumetric resolution was $3.08mm^3$ at the center of FOV when MAP (${\beta}=0.1$) reconstruction method was used. SOR was below 4% for FBP when ramp, Hamming, Hanning, or Shepp-logan filter were used. The lowest NU (highest uniform) after attenuation & scatter correction was 5.39% when FBP (parzen filter) was used. Regarding RC, 0.9 < RC < 1.1 was obtained when OSEM (iteration: 10) was used when attenuation and scatter correction were applied. In this study, image quality of Cu-64 on Siemens Inveon PET was investigated. This data will helpful for the quantification of Cu-64 PET data.

• 로봇학회논문지
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• 제10권3호
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• pp.146-153
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• 2015

In order to contain as much information as possible in a single image, a wide FOV(Field-Of-View) imaging system is required. The catadioptric imaging system with hyperbolic cylinder mirror can acquire over 180 degree horizontal FOV realtime panorama image by using a conventional camera. Because the hyperbolic cylinder mirror has a curved surface in horizontal axis, the original image acquired from the imaging system has the geometrical distortion, which requires the image processing algorithm for reconstruction. In this paper, the image reconstruction algorithms for two cases are studied: (1) to obtain an image with uniform angular resolution and (2) to obtain horizontally rectilinear image. The image acquisition model of the hyperbolic cylinder mirror imaging system is analyzed by the geometrical optics and the image reconstruction algorithms are proposed based on the image acquisition model. To show the validity of the proposed algorithms, experiments are carried out and presented in this paper. The experimental results show that the reconstructed images have a uniform angular resolution and a rectilinear form in horizontal axis, which are natural to human.

• 방송공학회논문지
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• 제8권1호
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• pp.19-29
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• 2003

기존의 영상 획득 시스템들이 어느 정도의 엘리어싱을 허용하도록 제작되어왔음에도 불구하고, 고해상도 영상에 대한 요구는 점점 더 증가하고 있다. 본 논문에서는 부정확한 부화소 단위의 위치 추정 오류를 고려한 고해상도 재구성 알고리즘을 제안한다. 부정확한 부화소 위치 추정 오류로 인해 생기는 불량위치문제(ill-posedness)를 해결하기 위해 정규화 반복 연산법을 적용하였다, 특히 여러 장의 저해강도 영상들을 개별적으로 고려하기에 적합한 다중채널 영상 재구성 방법을 도입하였다. 각 저해상도 영상에서 발생하는 움직임 추정오류는 서로 다른 경향성을 나타내므로, 정규화 파라미터들은 각 채널에 맞게 결정되어야 한다. 이를 위해 정규화 파라미터들을 자동으로 결정하는 방법을 제안한다. 제안한 알고리즘은 움직임 추정 오류에 매우 안정하며, 원 영상과 잡음에 대한 사전정보를 필요로 하지 않는다. 또한 주관적인 측면과 객관적인 측면에서 모두 우수한 결과를 실험적으로 보인다.

• 로봇학회논문지
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• 제4권4호
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• pp.298-304
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• 2009

This paper describes an algorithm that improves 3D reconstruction result using a multi-sensor fusion disparity map. We can project LRF (Laser Range Finder) 3D points onto image pixel coordinatesusing extrinsic calibration matrixes of a camera-LRF (${\Phi}$, ${\Delta}$) and a camera calibration matrix (K). The LRF disparity map can be generated by interpolating projected LRF points. In the stereo reconstruction, we can compensate invalid points caused by repeated pattern and textureless region using the LRF disparity map. The result disparity map of compensation process is the multi-sensor fusion disparity map. We can refine the multi-sensor 3D reconstruction based on stereo vision and LRF using the multi-sensor fusion disparity map. The refinement algorithm of multi-sensor based 3D reconstruction is specified in four subsections dealing with virtual LRF stereo image generation, LRF disparity map generation, multi-sensor fusion disparity map generation, and 3D reconstruction process. It has been tested by synchronized stereo image pair and LRF 3D scan data.

• Journal of the Korean Wood Science and Technology
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• 제33권5호통권133호
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• pp.29-37
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• 2005

A previous study verified that the SIRT (simultaneous iterative reconstruction technique) method is more efficient than the back-projection method as a CT algorithm for wood. However, it was expected that the determination of the initial model function of the SIRT method would influence the quality of CT image. Therefore, in this study, we intended to develop a technique that could be used to determine an adequate initial model function. For this purpose, we proposed several techniques, and for each technique we examined the effects of the initial model function on the average errors and the CT image at each iteration. Through this study, it was shown that the average error was decreased and the image quality was improved using the proposed techniques. This tendency was most pronounced when the back-projection method was used to determine the initial model function. From the results of this study, we drew the following conclusions: 1) The initial model function of the SIRT method should be determined with careful attention, and 2) the back-projection method efficiently determines the initial model function of the SIRT method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.804-809
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• 2004

It is essential to calibrate a camera in order to recover 3-dimensional reconstruction from uncalibrated images. This paper proposes a new technique of the camera calibration using a homography between the planar patterns image taken by the camera, which is located at the three planar patterns image. Since the proposed method should be computed from the homography among the three planar patterns from a single image, it is implemented more easily and simply to recover 3D object than the conventional. Experimental results show the performances of the proposed method are the better than the conventional. We demonstrate the examples of 3D reconstruction using the proposed algorithm from image sequence.