• Journal of Korean Ophthalmic Optics Society
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• v.3 no.1
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• pp.189-199
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• 1998

The system for optical tolerances of completion spectacles was made to sum of the accumulated error - the circumstances on composing prescription, the visual-distance, the tilting angle, the losing of a temple, the vertex distance, the axis of toric lens and the sloping of lens etc. It was given by the relation of allowed values size(T) and power(D), $T=T_0e^{-aD}$. Here, $T_0$ is the size of allowed values of plane-lens with power is 0 and ${\alpha}$ is the factor of allowed values. In case of being adopted to new form s tolerance corresponding to RAL 915, for the tolerance is large direction, the factor of allowed values ${\alpha}$ is $0.166(T_0=5.90)$ and for the tolerance is small direction, the factor of allowed values ${\alpha}$ is $0.166(T_0=2.95)$.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.967-970
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• 2000

본 논문에서는 기동하는 표적을 추적하기 위한 표적의 운동 모델링 방법에 대해서 다룬다. 실제 표적의 운동은 진행방향으로의 가속과 이와는 독립적인 방향 전환으로 이루어진다는 점에 착안하여 표적의 진행방향에 따라 동작 잡음의 분산 행렬이 변화하는 표적 중심 모델을 제안하고, 이를 IMMPDAF(Interacting Multiple Model Probabilistic Data Association Filter)에 적용하였다. 모의실험을 통해 기존의 모델을 사용한 IMMPDAF와 비교하였으며, 그 결과 기동 구간의 오차가 30% 정도 줄어들며 추적 실패율도 낮아짐을 볼 수 있었다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.124-125
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• 2003

레이저 광선이 발명이 된 이래로 레이저 빔을 360도 전 방향으로 발사시키는 광학적 장치의 필요성이 매우 컸으며, 이를 이용한 응용장치가 많이 있다. 그러나, 불행히도 이제까지 레이저 빔을 360도 전 방향으로 발사시키는 광학적인 단일 요소가 개발된 적이 없었다. 이 레이저 빔을 360도 전 방향으로 발사시키는 광학적 장치는 회전거울 혹은 회전 홀로그램을 이용한 것이 고작이었다. 하지만, 이러한 회전식장치는 장치의 복잡성, 회전 모터의 회전축의 오차 등 여러 가지 불편한 점이나, 유지보수의 어려움 등을 가지고 있었다. (중략)

• Progress in Medical Physics
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• v.22 no.2
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• pp.67-71
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• 2011

We evaluated the overall setup accuracy for the On-Board Imager (OBI, Varian Medical Systems Inc., Palo Alto, CA, USA), with attention to the laser, the gantry, and operator performance. We let experienced technicians place the marker block on the couch using a lock bar system, with alignment to the isocenter of the laser, every morning. A pair of radiographic images of the marker block was acquired at $0^{\circ}$ and $270^{\circ}$ angles to the kV arm to correct the position using a 2D/2D matching technique. Once the desired match was achieved, the couch was moved remotely to correct the setup error and the parameters were saved. The average for the vertical and the longitudinal displacements were 0.65 mm and 0.66 mm, and 0.01 mm for the lateral displacement. The average for the vertical and longitudinal displacements were statistically significant at the 0.05 level (p value=0.000 for both), while the p value for the lateral direction was 0.829. These results show that the tendencies to displacement in vertical and longitudinal directions occur through systematic error, while systematic error was not found in the lateral displacement. This daily overall evaluation is practical and easy to find the systematic and random errors in the setup system; however, a daily QA for laser and OBI alignment is still needed to minimize the systematic error in aligning patients.

• Journal of Broadcast Engineering
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• v.1 no.2
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• pp.176-187
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• 1996

This paper deals with the accurate estimation of 3- D pose (position and orientation) of a moving object with reference to the world frame (or robot base frame), based on a sequence of stereo images taken by cameras mounted on the end - effector of a robot manipulator. This work is an extension of the previous work[1]. Emphasis is given to the 3-D pose estimation relative to the world (or robot base) frame under the presence of not only the measurement noise in 2 - D images[ 1] but also the camera position errors due to the random noise involved in joint angles of a robot manipulator. To this end, a new set of discrete linear Kalman filter equations is derived, based on the following: 1) the orientation error of the object frame due to measurement noise in 2 - D images is modeled with reference to the camera frame by analyzing the noise propagation through 3- D reconstruction; 2) an extended Jacobian matrix is formulated by combining the result of 1) and the orientation error of the end-effector frame due to joint angle errors through robot differential kinematics; and 3) the rotational motion of an object, which is nonlinear in nature, is linearized based on quaternions. Motion parameters are computed from the estimated quaternions based on the iterated least-squares method. Simulation results show the significant reduction of estimation errors and also demonstrate an accurate convergence of the actual motion parameters to the true values.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.32-45
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• 2000

This paper presents the analytic derivation of the SINR, when a linear array antenna is accommodated into the cellular CDMA basestation receiver, in relation to the two major performance effecting factors in beamforming(BF) applications, i. e., the direction selectivity, which refers to the narrowness of the mainbeam width, and the direction-of-arrival(DOA) estimation accuracy. The analytically derived results are compared with the operation simulation of the receiver realized with the several BF algorithms and their agreements are confirmed, consequently verifying the correctness of the analysis and the operation simulation. In order to investigate separately the effects of the errors occurring in the direction estimation and in the interference suppression, which are the two major functional components of general BF algorithms, both the algorithms of steering BF and the minimum- variance- distortionless-response(MVDR) BF are applied to the analysis. A signal model to reflect the spatially scattering phenomenon of the RF waves entering into the .:nay antenna, which directly affects on the accuracy of the BF algorithm's direction estimation, is also suggested in this paper and applied to the analysis and the operation simulation. It is confirmed from the results that the enhancement of the direction selectivity of the away antenna is not desirable in view of both the implementation economy and the BF algorithm's robustness to the erroneous factors. Such a trade-off characteristics is significant in the sense that it can be capitalized to obtain an economic means of BF implementation that does not severely deteriorate its performance while ensuring the robustness to the erroneous effects, consequently manifesting the significance of the analysis results of this paper that can be used as a design reference in developing BF algorithms to the cellular CDMA system.

• Journal of radiological science and technology
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• v.36 no.2
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• pp.123-129
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• 2013

This study investigated the rate of setup variance by the rotating unbalance of gantry in image-guided radiation therapy. The equipments used linear accelerator(Elekta Synergy TM, UK) and a three-dimensional volume imaging mode(3D Volume View) in cone beam computed tomography(CBCT) system. 2D images obtained by rotating $360^{\circ}$and $180^{\circ}$ were reconstructed to 3D image. Catpan503 phantom and homogeneous phantom were used to measure the setup errors. Ball-bearing phantom was used to check the rotation axis of the CBCT. The volume image from CBCT using Catphan503 phantom and homogeneous phantom were analyzed and compared to images from conventional CT in the six dimensional view(X, Y, Z, Roll, Pitch, and Yaw). The variance ratio of setup error were difference in X 0.6 mm, Y 0.5 mm Z 0.5 mm when the gantry rotated $360^{\circ}$ in orthogonal coordinate. whereas rotated $180^{\circ}$, the error measured 0.9 mm, 0.2 mm, 0.3 mm in X, Y, Z respectively. In the rotating coordinates, the more increased the rotating unbalance, the more raised average ratio of setup errors. The resolution of CBCT images showed 2 level of difference in the table recommended. CBCT had a good agreement compared to each recommended values which is the mechanical safety, geometry accuracy and image quality. The rotating unbalance of gentry vary hardly in orthogonal coordinate. However, in rotating coordinate of gantry exceeded the ${\pm}1^{\circ}$ of recommended value. Therefore, when we do sophisticated radiation therapy six dimensional correction is needed.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2004.03a
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• pp.141-146
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• 2004

본 연구에서는 Canada Southern Alberta Network의 6곳의 GPS(Global Positioning System) 상시관측소 데이터를 바탕으로 관측소와 각 GPS 위성간의 시선방향 습윤지연량을 결정하였다. 고정밀 GPS 데이터를 이용하여 천정방향 습윤지연량을 결정하고 이를 WVR(Water Vapor Radiometer)에서 측정한 천정방향 습윤지연량과 비교하였다. 그 결과 WVR의 천정방향 습윤지연량과 비교할 때 GPS로 관측한 천정방향 습윤지연량은 최대 1.39cm, 최소 0.99cm의 RMS 오차를 보였다. 또한 GPS로 관측한 시선방향 습윤지연량은 WVR과 비교할 때, PRN 25번 위성의 경우최대 17cm, 최소 0.05cm의 차이가 났다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.3 no.1
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• pp.15-25
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• 1985

This paper improves the accuracy of horizontal positioning by means of the analytical Intersection and Resection. For this purpose, by increasing the number of Known points, the magnitude of errors occurred in unknown points is represented by error ellipse, and the variation of error ellipse is examined. Also, by applying weights according to each measured angles and distances, the variation of error ellipse is analysized.

• Journal of the Korean Solar Energy Society
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• v.29 no.6
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• pp.22-31
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• 2009

Canting is the optical alignment of mirror facets of heliostat such that the heliostat could focus the energy as a unit concentrator. Canting could improve the optical performance of heliostat and thus improves the efficiency of heliostat and ultimately improves the efficiency of the solar thermal power plant. This study discusses the effect of mirror canting, especially off-axis canting, used to compensate the sun tracking error caused by the heliostat geometrical errors. We first show that the canting could compensate the sun tracking error caused by the heliostat geometrical errors. Then we show that the proper canting time could exist, depending on the heliostat location. Finally we show how much the sun tracking performance could be improved by canting, by providing RMS sun tracking error. The limitation and caution of using canting to improve the sun tracking performance are also discussed.