• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.30-34
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• 2005

This paper describes the design and manufacturing of a focused-ion-beam machining system which can make small features of nano size. We use a SIMION simulator in order to obtain the design data of an ion column. The simulation result shows that the focal length of ion beam decreases as the applied voltage of object lens increases. Finally, we obtained the good images of a mesh of 50 micrometers by using the adjustment of applied voltage, acceleration power, and dimension of each elements.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.361-364
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• 2002

의료용 초음파 진단기는 음축 방향 초점거리의 제어를 위해서 각 진동요소의 전기단자에 전기회로를 이용한 가중치를 부가하는 방식을 사용하고 있다. 그러나 본 연구에서는 단일 PVDF로 구성된 트랜스듀서에 바이몰프 타입의 엑츄에이터를 부가하여 진동요소의 배열이나 전기적 가중치의 부가없이 기계적으로 곡률 반경(R.O.C. : Radius Of Curvature)을 제어하는 방법을 제안하였고, 바이몰프 타입 엑츄에이터에 인가한 전압 변화에 따른 트랜스듀서의 곡률 반경 변화를 측정하여 이에 따른 수중에서의 음장 분포 변화를 시뮬레이션 결과와 비교하였다.

• Nuclear Engineering and Technology
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• v.40 no.5
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• pp.419-428
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• 2008

During the overhaul period of nuclear power plants in Korea, an ROV(Remotely Operated Vehicle) enters the cold-leg pipes connected with the reactor to examine the state of the thermal sleeves and their positions in the safety injection nozzles. To measure the positions of the thermal sleeves or scratches with video images recorded during the examination, time-varying camera parameters should be known, such as the focal length and principal points used for the capturing each video image. In this paper, we propose a camera calibration and measurement scheme by using a single image containing two circular grooves of a cylindrical nozzle whose radius and distance are known.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.4
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• pp.161-167
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• 2001

Camera calibration is very important problem in 3D measurement using vision system. In this paper is proposed the simple method for camera calibration. It is designed that uses the principle of vanishing points and the concept of corresponding points extracted from the parallel line pairs. Conventional methods are necessary for 4 reference points in one frame. But we proposed has need for only 2 reference points to estimate vanishing points. It has to calculate camera parameters, focal length, camera attitude and position. Our experiment shows the validity and the usability from the result that absolute error of attitude and position is in $10^{-2}$.

• Journal of Sensor Science and Technology
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• v.22 no.6
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• pp.393-399
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• 2013

We propose a method of sensing the rotation and distance of a camera by using a fisheye lens system as a vision sensor. We estimate the rotation angle of a camera with a modified correlation method by clipping similar regions to avoid symmetry problems and suppressing highlight areas. In order to eliminate the rectification process of the distorted points of a fisheye lens image, we introduce an offline process using the normalized focal length, which does not require the image sensor size. We also formulate an equation for calculating the distance of a camera movement by matching the feature points of the test image with those of the reference image.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.06a
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• pp.125-131
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• 1999

In this paper, we address practical methods for calculating camera lens distortion for real time applications. Although the lens distortion problem can be easily ignored for constant-parameter lenses, in the field of real-time camera calibrations, for zoom lenses a large number of calculations are needed to calculate the distortion. However, if the distortion can be calculated independently of the other camera parameter, we can easily calibrate a camera without the need for a large number of calculations. Based on Tsai's camera model, we propose two different methods for calculating lens distortion. These methods are so simple and require so few calculations that the lens distortion can be rapidly calculated even in real-time applications. The first method is to refer to the focal length - lens distortion Look Up Table(LUT), which is constructed in the initialization process. The second method is to use the relationship between the feature points found in the image. Experiments were carried out for both methods, results of which show that the proposed methods are favorably comparable in performance with non-real full optimization method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.572-575
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• 2005

A microlens connected to microfluidic channel is fabricated. The microlens is sealed with an elastomeric membrane which deforms by pressure of fluid driven by a syringe pump resulting in the shape change of the microlens. The optical properties of the microlens could be controlled by changing the microlens shape. The microlens system were made of an elastomer, PDMS, using molding from a photoplastic master patterned by UV photolithography. The test results show the optical property of the lens could be made into convex and concave type by applying the fluidic pressure positive and negative.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.98-103
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• 1998

Recently, DVD/CD compatible driver is needed for DVD and CD is widely used as a new optical data restoring device. The optical systems of DVD and CD driver are different because they have different optical feature. If only one objective lens is used, the change of an aperture or a dual focal length of the lens is required. This method, however, increases the number of parts and results in loss of the power of laser light. Hence, we propose a dual lens actuator design that can read DVD and CD respectively. Albeit magnetic spring is important mechanism in the dual lens actuator design, there has not been the systematic approach to design the mechanism in the preceding researches. In this article. the guideway to design magnetic spring is presented by using the qualitative theoretical approach and the finite element analysis.

• Korean Journal of Geomatics
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• v.4 no.1
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• pp.9-16
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• 2004

An object-oriented design was carried out for the digital photogrammetric processes. Classes were identified and implemented to develop an integrated digital photogrammetry system using a 3 dimensional self-calibration model for CCD cameras. This integrated system is deemed to be a significant progress from the conventional photogrammetric system which is a series of discrete processes. Object oriented methodology was selected for the implementation of the integrated photogrammetric system because it would be a very complex task to get the same result using a procedural programming language. Besides the simplification of development effort, object oriented methodology has further benefits of better management of program in case when updates to parts of the program are necessary. Using the classes designed in this study, a 3 dimensional self-calibration model was developed for a CCD camera. Classes for data input and image handling as well as classes for bundle adjustment were implemented. The bundle adjustment system was further enhanced with member functions to handle additional parameters for principal point coordinates and focal length, thereby, enabling the application to non-metric CCD cameras.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.742-744
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• 2004

본 논문에서는 두 개의 직교하는 소실점(Orthogonal Vanishing Points)을 이용하여 카메라의 내부 파라미터를 추정하기 위한 방법을 제안한다. 카메라 보정(camera calibration)은 2차원 영상으로부터 3차원 정보를 얻기 위한 중요한 단계이다. 기존의 소실점을 이용한 대부분의 방법들은 세 개의 직교하는 소실점을 사용하여 파라미터론 추정하지만, 실제 영상에서는 세 개의 직교 소실점을 포함하는 영상을 획득하는 것은 어려운 문제이다 따라서 본 논문에서는 2개의 직교 소실점을 사용하여 카메라 U부 보정을 위한 기하적이고 직관적인 새로운 방법을 제안한다. 주점(principal point)과 초점거리(focal length)는 Thales의 이론을 기초한 기하학적 제약사항으로부터 다중 반구(multiple hemispheres)들의 관계로부터 유도된다.