• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.231-236
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• 2003

This paper presents a simple approach on the rotational motion estimation and correction for the roll stabilization of the sight system. The algorithm first computes the rotational center from the selected local velocity vectors of related pixels by least square methods. And then, rotational angle is found from the special subset of the motion vector. Finally, motion correction is performed by the nearest neighbor interpolation technique. In order to show the performance of the algorithm, the evaluation for the synthetic and real image was performed. The test results show good performance compared with previous approach.

• 대한의용생체공학회:의공학회지
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• 제41권1호
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• pp.28-34
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• 2020

In this paper, we introduce motion artifact reduction algorithm for interleaved MRI using an advanced 3D approximation algorithm. The motion artifact framework of this paper is data corrected by post-processing with a new 3-D approximation algorithm which uses data structure for each voxel. In this study, we simulate and evaluate our algorithm using Shepp-Logan phantom and T1-MRI template for both scattered dataset and uniform dataset. We generated motion artifact using random generated motion parameters for the interleaved MRI. In simulation, we use image coregistration by SPM12 (https://www.fil.ion.ucl.ac.uk/spm/) to estimate the motion parameters. The motion artifact correction is done with using full dataset with estimated motion parameters, as well as use only one half of the full data which is the case when the half volume is corrupted by severe movement. We evaluate using numerical metrics and visualize error images.

• Korean Journal of Radiology
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• 제20권1호
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• pp.94-101
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• 2019

Objective: To investigate the efficacy of motion-correction algorithm (MCA) in improving coronary artery image quality and measurement accuracy using an anthropomorphic dynamic heart phantom and 256-detector row computed tomography (CT) scanner. Materials and Methods: An anthropomorphic dynamic heart phantom was scanned under a static condition and under heart rate (HR) simulation of 50-120 beats per minute (bpm), and the obtained images were reconstructed using conventional algorithm (CA) and MCA. We compared the subjective image quality of coronary arteries using a four-point scale (1, excellent; 2, good; 3, fair; 4, poor) and measurement accuracy using measurement errors of the minimal luminal diameter (MLD) and minimal luminal area (MLA). Results: Compared with CA, MCA significantly improved the subjective image quality at HRs of 110 bpm (1.3 ± 0.3 vs. 1.9 ± 0.8, p = 0.003) and 120 bpm (1.7 ± 0.7 vs. 2.3 ± 0.6, p = 0.006). The measurement error of MLD significantly decreased on using MCA at 110 bpm (11.7 ± 5.9% vs. 18.4 ± 9.4%, p = 0.013) and 120 bpm (10.0 ± 7.3% vs. 25.0 ± 16.5%, p = 0.013). The measurement error of the MLA was also reduced using MCA at 110 bpm (19.2 ± 28.1% vs. 26.4 ± 21.6%, p = 0.028) and 120 bpm (17.9 ± 17.7% vs. 34.8 ± 19.6%, p = 0.018). Conclusion: Motion-correction algorithm can improve the coronary artery image quality and measurement accuracy at a high HR using an anthropomorphic dynamic heart phantom and 256-detector row CT scanner.

• 핵의학기술
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• 제18권2호
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• pp.28-32
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• 2014

심근 관류 SPECT 검사 중 환자의 움직임은 관류 결손과 인공물을 발생시켜 정확한 진단에 영향을 줄 수 있는 인자이다. 움직임으로 왜곡된 데이터를 보정하는 방법으로 움직임 보정방법이 개발되었고 각 방법마다 사용된 알고리즘이 다르기에 상황에 비교하고자 한다. 실험에 사용된 장비는 GE Ventri Gamma Camera와 Anthropomorphic Torso Phantom을 이용하였다. 팬텀을 환자 조건과 동일하게 하기 위하여 심근에 74 kBq/mL, 연부조직 1.1 kBq/mL, 폐 2.6 kBq/mL, 간 9.6 kBq/mL의 Tl-201을 주입하여 제작하고, 움직이는 상황에서 결손의 변화 관찰 목적으로 심근의 Anterior wall에 임의로 결손을 삽입하였다. 움직이지 않는 정상군과 일정간격(2 cm, 3 pixel) 상하 1회 이동, 상하 반복 이동, 좌우 1회 이동, 좌우 반복 이동한 데이터에 나누어 영상 획득하고 MDC, Hopkins, Stasis 방법을 적용하여 Polar map과 정량분석 Score로 비교 하였다. 환자와 동일한 조건으로 회전각 $6^{\circ}$, 50sec/frame으로 영상 획득하고, OSEM (2 iterations, 10 subsets), Butterworth filter (order 10; cutoff frequency; 0.32 cycle per pixel)를 적용, scatter correction, 감쇠보정은 적용하지 않았다. 팬텀 실험에서 세 가지 방법들에서 MDC 방법이 Visual 인공물 없이 잘 보정하였으나, 환자의 데이터에 이를 적용 하였을 때, 환자마다 움직임 보정방법 적용 결과들이 일정하지 않았다. 이는, 환자의 움직임이 일정하지 않고, 장기내의 동위원소의 비율도 다르기에 발생한다고 생각되며 추가적인 연구와 상황에 맞는 움직임 보정방법의 유동적인 사용이 필요하다고 사료된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.259-260
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• 2007

In this paper, a frame rate up-conversion algorithm using the motion vector frequency of neighboring blocks to reduce the block artifacts caused by failure of conventional motion estimation based on block matching algorithm is proposed. Experimental results show good performance of the proposed scheme with significant reduction of the erroneous motion vectors and block artifacts.

• 한국멀티미디어학회논문지
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• 제23권3호
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• pp.395-401
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• 2020

In this paper, a motion-based ROI extraction algorithm from a high resolution fisheye image is proposed for multi-view monitoring systems. Lately fisheye cameras are widely used because of the wide angle-of-view and they basically provide a lens correction functionality as well as various viewing modes. However, since the distortion-free angle of conventional algorithms is quite narrow due to the severe distortion ratio, there are lots of unintentional dead areas and they require much computation time in finding undistorted coordinates. Thus, the proposed algorithm adopts an image decimation and a motion detection methods, that can extract the undistorted ROI image with a standard angle-of-view for the fast and intelligent surveillance system. In addition, a mesh-type ROI is presented to reduce the lens correction time, so that this independent ROI scheme can parallelize and maximize the processor's utilization.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.153-155
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• 2004

This paper proposes a real-time approach on the rotational motion estimation and correction for the roll stabilization of the sight system. This method first estimates a rotation center by the least-mean square algorithm based on the motion vectors of some feature points. And, then, a rotation angle is searched for a best matching block between a reference block image and seccessive input images using MPC(maximum pixel count) matching criterion. Finally, motion correction is performed by the bilinear interpolation technique. Various computer simulations show that the estimation performance is good and the proposed algorithm is a real-time implementable one to the TMS320C6415(500MHz) DSP.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권10호
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• pp.4971-4987
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• 2019

Node localization is the basic task of underwater wireless sensor networks (UWSNs). Most of the existing underwater localization methods rely on ranging accuracy. Due to the special environment conditions in the ocean, beacon nodes are difficult to deploy accurately. The narrow bandwidth and high delay of the underwater acoustic communication channel lead to large errors. In order to reduce the ranging error and improve the positioning accuracy, we propose a localization algorithm based on ranging correction and inertial coordination. The algorithm can be divided into two parts, Range Correction based Localization algorithm (RCL) and Inertial Coordination based Localization algorithm (ICL). RCL uses the geometric relationship between the node positions to correct the ranging error and obtain the exact node position. However, when the unknown node deviates from the deployment area with the movement of the water flow, it cannot communicate with enough beacon nodes in a certain period of time. In this case, the node uses ICL algorithm to combine position data with motion information of neighbor nodes to update its position. The simulation results show that the proposed algorithm greatly improves the positioning accuracy of unknown nodes compared with the existing localization methods.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.397-400
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• 2010

동영상은 촬영 당시의 주변의 조명변화에 의해 원치 않는 밝기 변화가 발생한다. 이러한 훼손을 플리커라 하고 시각적으로 불안정한 영상의 흔들림으로 인지된다. 플리커는 동영상 시퀸스로부터 유용한 정보를 추출하기 힘들게 하므로 미리 제거하여 안정된 형태로 만들어야 한다. 본 논문은 플리커의 발생을 감마보정요소를 포함하는 선형모델로 모델링하고 이를 분석하여 제거하는 새로운 알고리즘을 제안한다. 제안하는 알고리즘은 플리커를 유발하는 게인과 오프셋 파라미터를 분리하고 게인 요소를 감마 보정으로 추정한다. 이 과정을 통하여 추정된 게인과 오프셋 플리커 영상 시퀸스에 역으로 적용하여 플리커를 제거한다. 제안하는 방법의 객관적인 성능을 보이기 위해 움직임이 없는 인위적인 테스트 영상 시퀸스에 대해 실험한 결과와 움직임이 있는 실제 영상 시퀸스에 적용한 결과를 제시하였다.

• 제어로봇시스템학회논문지
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• 제12권8호
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• pp.810-817
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• 2006

This paper presents a rotational motion estimation and correction technique for digital image stabilization. An equivalent rotation model is derived so as to accommodate a combined rotational and the translational motion. Thanks to this simplification, the suggested estimation algorithm can directly find the rotational center using geometric characteristic of local motion vectors instead of using searching method. And we also present recursive version of frame to reference algorithm(FRA) for the real time implementation. The proposed DIS system does not require time consuming parameter searching process, while showing comparatively good performance compared with the previous ones. To show the effectiveness of the DIS scheme, the algorithm has been implemented on the DSP based hardware system and experimental results are also discussed.