• 한국방사선학회논문지
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• 제15권5호
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• pp.731-739
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• 2021

이 연구는 산업현장에서 구조물의 용접부 검사를 디지털 방사선을 이용한 비파괴검사를 효과적으로 수행할 수 있도록 디지털 방사선의 밝기 교정과 중첩 영상에 따른 신호 대 잡음 비와 기본 공간 분해능을 비교분석 하였다. 평판형 용접 시험편을 대상으로 ⁷⁵Se 방사선원을 사용하였고 촬영 전 밝기 교정과 영상 중첩을 세분화하여 총 130장의 영상을 획득하였다. 연구 결과, 밝기 교정의 수와 영상 중첩의 수가 증가할수록 신호 대 잡음 비가 향상됨을 확인하였다. 기본 공간 분해능은 촬영된 영상 모두 기준치를 만족하였다. 산란 방사선을 대비한 납 차폐를 설치 후 촬영한 영상을 비교하여 신호 대 잡음 비가 비슷함을 확인하였다. 영상 중첩이 증가할수록 신호 대 잡음 비가 증가하지만, 방사선의 노출시간이 증가하면서 작업자의 피폭 및 작업 효율에 영향을 미치기 때문에 적절한 촬영기법을 강구 한다면 좋은 상질의 디지털 방사선 영상을 획득 할 수 있을 것으로 사료된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.510-514
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• 1994

This paper deals with an application of neural network to camera calibration with wide angle lens and 2-D range finding. Wide angle lens has an advantage of having wide view angles for mobile environment recognition ans robot eye in hand system. But, it has severe radial distortion. Multilayer neural network is used for the calibration of the camera considering lens distortion, and is trained it by error back-propagation method. MLP can map between camera image plane and plane the made by structured light. In experiments, Calibration of camers was executed with calibration chart which was printed by using laser printer with 300 d.p.i. resolution. High distortion lens, COSMICAR 4.2mm, was used to see whether the neural network could effectively calibrate camera distortion. 2-D range of several objects well be measured with laser range finding system composed of camera, frame grabber and laser structured light. The performance of 3-D range finding system was evaluated through experiments and analysis of the results.

• 센서학회지
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• 제12권6호
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• pp.258-264
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• 2003

본 연구에서는 영상처리를 통한 부액계의 교정방법을 연구한다. 이 방법은 부액계를 교정하기 위해 선정된 부액계의 측정눈금과 기준액체의 수평면을 교정자의 조작 없이 자동으로 일치시킨다. 이 시스템은 CCD카메라, frame grabber, 스텝모터, 영상처리를 포함한 시스템프로그램으로 구성된다. 영상처리프로그램은 부액계의 측정눈금부위와 기준액체의 수평면사이에서 발생하는 메니스커스를 검색하여 눈금을 일치시키는 부분과 스텝모터를 제어하는 부분으로 구성한다. 본 연구에서 개발한 시스템의 성능을 검증하기 위하여 교정자의 눈으로 직접 메니스커스와 측정눈금을 관측한 수동교정방법의 교정결과와 비교한다 각각의 교정값의 차이가 $0.004\;kg/m^3$ 이하로서 교정값의 측정 불확도 $0.06\;kg/m^3$을 고려하면 두 방법의 교정결과가 거의 같은 연구결과를 얻었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.786-791
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• 1992

When a mobile robot moves from one place to another, position error occurs due to the limit of accuracy of robot and the effect of environmental noise. In this paper. an accurate method of estimating the position and orientation of a mobile robot using the camera calibration is proposed. Kalman filter is used as the estimation algorithm. The uncertainty in the position of camera with repect to robot base frame is considered well as the position error of the robot. Besides developing the mathematical model for mobile robot calibration system, the effect of relative position between camera and calibration points is analyzed and the method to select the most accurate calibration points is also presented.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1278-1284
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• 2008

This study carried out bender element tests in a calibration chamber in order to estimate the characteristics of soil specimen prepared in a calibration chamber. Basically, the purpose of bender element test is to measure the shear wave velocity. Bender element test cannot only confirm the status of soil specimen deposited in a chamber, but also estimate the consolidation process indirectly. In order to carry out bender element test in a calibration chamber, a pair of bender elements was installed inside the chamber, using the 'ㄷ' shaped frame. For the sandy soils having various relative densities in various stress conditions, the maximum shear modulus was estimated. From the comparison with bender element test results in a triaxial testing device, testing device and procedure was validated.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제7권3호
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• pp.216-220
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• 2007

Camera calibration in machine vision is the process of determining the intrinsic camera parameters and the three-dimensional (3D) position and orientation of the camera frame relative to a certain world coordinate system. On the other hand, Takagi-Sugeno-Kang (TSK) fuzzy system is a very popular fuzzy system and approximates any nonlinear function to arbitrary accuracy with only a small number of fuzzy rules. It demonstrates not only nonlinear behavior but also transparent structure. In this paper, we present a novel and simple technique for camera calibration for machine vision using TSK fuzzy model. The proposed method divides the world into some regions according to camera view and uses the clustered 3D geometric knowledge. TSK fuzzy system is employed to estimate the camera parameters by combining partial information into complete 3D information. The experiments are performed to verify the proposed camera calibration.

• 대한원격탐사학회지
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• 제31권4호
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• pp.353-360
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• 2015

Earth's gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite's star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth' gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth's gravity field maps, the new Earth's gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth's gravity field maps.

• 디지털산업정보학회논문지
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• 제9권4호
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• pp.51-57
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• 2013

Research on calibration of array antenna has become a hot spot in the area of signal processing and it is necessary to obtain the phase mismatch of each antenna channel. This paper presents a new calibration method for an array antenna system. In order to calibrate the phase mismatch of each antenna channel, we used primary synchronization signal (PSS) which exists in LTE downlink frame. Primary synchronization signal (PSS) is based on a Zadoff-Chu sequence which has a good correlation characteristic. By using correlation calculation, we can extract primary synchronization signal (PSS). After extracting primary synchronization signal (PSS), we use it to calibrate and reduce the phase errors of each antenna channel. In order to verify the new array antenna calibration algorithm which is proposed in this paper, we have simulated the proposed algorithm by using MATLAB. The array antenna system consists of two antenna elements. The phase mismatch of first antenna and second antenna is calculated accurately by proposed algorithm in the experiment test. Theory analysis and MATLAB simulation results are shown to verify the calibration algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.511-513
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• 2004

Camera Calibration should certain)y be achieved to take an accurate measurement using image system. Calibration is to prove the relation between an measurement object and camera and to estimate twelve internal and external parameters. In this paper, we suggest that an algorithm should estimate the external parameters from the road image and use a vanishing point's character from parallel straight lines in a space. also, we use Hough Transform to estimate an accurate vanishing point. Hough Transform has one of the advantages which is an application for each road environment. we assume a variety of environments to prove the usability of a suggested algorithm and show simulation results with a computer.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권4호
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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 $10^{-2}$.