• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.342-348
• /
• 2002

This paper presents a computer image processing system, which measures the thickness of the ALC block and inspects the defect on a real-time basis. The Image processing system was established with a CCD camera, an image grabber, and a personal computer without using assembled measurement equipment. The image obtained by the system was analyzed by a devised algorithm, specially designed for the enhanced measurement accuracy. For the realization of proposed algorithm, the pre-processing method that can be applied to overcome uneven lighting environment, and threshold decision method, and subpixel method are developed. from the experimental results, we could find that the required measurement accuracy specification is sufficiently satisfied using our proposed method.

• 제어로봇시스템학회논문지
• /
• 제22권12호
• /
• pp.1002-1010
• /
• 2016

This paper describes the design of a cellphone curved glass measuring device using by camera. The measuring device was composed of two camera, two backlight system, a body and so on, and the program was made for a camera calibration and noise removal, and also the program was made for height measurement of a cellphone curved glass using by subpixel algorism. And then a new technique for measuring the height of the cell phone curved glass was proposed. The characteristics test of height measurement of gage blocks and cell phone curved glasses was carried out, the error of the height measurement of gage block is less than ${\pm}0.005$ and the error of the height measurement of the cell phone curved glasses is less than ${\pm}0.005$. Thus it thought that the designed cellphone curved glass measuring device and the new technique for measuring the height was used to measure the height of the cellphone curved glass.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
• /
• pp.171-182
• /
• 1998

An automated surface-strain measuring system using the image processing technique is developed in the present study, which consists of the hardware to capture and to display digital images, and the software to calculate the 3D informations of grid points from two views. New or improved algorithms the mapping and establishing correspondence of grid points and elements, the camera calibration, and the subpixel measurement of grid points, are implemented. As an application of the present system the surface-strains of deformed blanks in the limitting dome height test, the square cup deep-drawing and punch stretching to obtain the forming limit diagram are measured. The results are compared with those obtained by conventional manual methods.

• Journal of Welding and Joining
• /
• 제19권2호
• /
• pp.200-207
• /
• 2001

Three-diemnsional bead profile was measured using the biprism stereo vision sensor in GMAW, which consists of an optical filter, biprism and CCD camera. Since single CCD camera is used, this system has various advantages over the conventional stereo vision system using two cameras such as finding the corresponding points along the horizontal scanline. In this wort, the biprism stereo vision sensor was designed for the GMAW, and the linear calibration method was proposed to determine the prism and camera parameters. Image processing techniques were employed to find the corresponding point along the pool boundary. The ism-intensity contour corresponding to the pool boundary was found in the pixel order and the filter-based matching algorithm was used to refine the corresponding points in the subpixel order. Predicted bead dimensions were in broad agreements with the measured results under the conditions of spray mode and humping bead.

• 공학논문집
• /
• 제2권1호
• /
• pp.5-11
• /
• 1997

입자 물질의 흐름(granular flow)은 일반 산업체의 거의 모든 공정에서 발생한다. 본 논문은 중력 하에서 경사진 슈트 (chute)를 통하여 흐르는 입자들의 속도를 측정하기 위하여 고속 디지털 영상을 이용한 방법을 논한다. 유리 입자 들이 이 실험에서 사용되었다. 유리 입자 들의 평균 속도를 측정하기 위하여 블록 매칭 (block matching)이 사용되었으며 유리입자 들의 평균속도는 변동 정규 상관 함수에 보간법을 적용함으로서 화소 간격보다 적은 단위로 측정하였다.

• 대한토목학회논문집
• /
• 제32권1A호
• /
• pp.1-10
• /
• 2012

최근 해안, 도서, 산간지방 등의 개발로 장대교량의 수요가 증가되고 재료 및 설계 시공기술의 지속적 발전으로 인하여 현수교나 사장교 등 장지간을 가지는 교량의 건설이 증가하고 있다. 장대교량은 사장재 또는 주 케이블 및 행어로 주형을 지지하는 고차 부정정구조물로 다양한 형태의 설계가 가능하고 구조물의 외관이 뛰어나기 때문에 현재 많은 교량에 적용되고 있다. 케이블지지교량은 시공 중 그리고 공용상태에서 케이블의 장력을 지속적으로 측정함으로써 교량의 건전성을 파악할 수 있다. 케이블의 장력을 추정하는 기법으로 로드셀 및 유압잭 등을 이용하여 케이블의 응력을 직접 측정하는 방법과 케이블의 형상조건과 계측된 동적 특성을 활용하여 장력을 구하는 진동법이 많이 활용되고 있다. 본 연구에서는 디지털 영상처리를 이용한 행어케이블의 동특성 추정 방법을 제시하였으며 사용의 편의성과 경제성을 고려하여 원거리에 있는 행어케이블을 측정하기 위한 센서로 휴대용 디지털 캠코더를 사용하였다. 디지털 영상처리를 이용하는 방법은 digital image correlation(DIC) 기법을 사용하였으며 변형이 없는 이미지와 변형이 있는 이미지 사이의 기하학적인 왜곡을 보정하는 이미지 변환함수(ITF)를 사용하여 단위픽셀이하를 계산하였다. 또한 영상계측시스템의 흔들림을 추가적인 센서의 설치 없이 한 영상내의 고정된 물체를 이용하여 보정함으로써 행어케이블의 동적응답 및 모드별 고유진동수의 해상도를 향상시켰다.

• Smart Structures and Systems
• /
• 제20권4호
• /
• pp.397-413
• /
• 2017

Precast concrete (PC) members are currently being employed for general construction or partial replacement to reduce construction period. As assembly work in PC construction requires connecting PC members accurately, measuring the 6-DOF (degree of freedom) relative displacement is essential. Multiple planar markers and camera-based displacement measurement systems can monitor the 6-DOF relative displacement of PC members. Conventional methods, such as direct linear transformation (DLT) for homography estimation, which are applied to calculate the 6-DOF relative displacement between the camera and marker, have several major problems. One of the problems is that when the marker is partially hidden, the DLT method cannot be applied to calculate the 6-DOF relative displacement. In addition, when the images of markers are blurred, error increases with the DLT method which is employed for its estimation. To solve these problems, a hybrid method, which combines the advantages of the DLT and MCL (Monte Carlo localization) methods, is proposed. The method evaluates the 6-DOF relative displacement more accurately compared to when either the DLT or MCL is used alone. Each subsystem captures an image of a marker and extracts its subpixel coordinates, and then the data are transferred to a main system via a wireless communication network. In the main system, the data from each subsystem are used for 3D visualization. Thereafter, the real-time movements of the PC members are displayed on a tablet PC. To prove the feasibility, the hybrid method is compared with the DLT method and MCL in real experiments.

• Journal of the Optical Society of Korea
• /
• 제18권4호
• /
• pp.317-329
• /
• 2014

In vision measurement systems based on structured light, the key point of detection precision is to determine accurately the central position of the projected laser line in the image. The purpose of this research is to extract laser line centers based on a decision function generated to distinguish the real centers from candidate points with a high recognition rate. First, preprocessing of an image adopting a difference image method is conducted to realize image segmentation of the laser line. Second, the feature points in an integral pixel level are selected as the initiating light line centers by the eigenvalues of the Hessian matrix. Third, according to the light intensity distribution of a laser line obeying a Gaussian distribution in transverse section and a constant distribution in longitudinal section, a normalized model of Hessian matrix eigenvalues for the candidate centers of the laser line is presented to balance reasonably the two eigenvalues that indicate the variation tendencies of the second-order partial derivatives of the Gaussian function and constant function, respectively. The proposed model integrates a Gaussian recognition function and a sinusoidal recognition function. The Gaussian recognition function estimates the characteristic that one eigenvalue approaches zero, and enhances the sensitivity of the decision function to that characteristic, which corresponds to the longitudinal direction of the laser line. The sinusoidal recognition function evaluates the feature that the other eigenvalue is negative with a large absolute value, making the decision function more sensitive to that feature, which is related to the transverse direction of the laser line. In the proposed model the decision function is weighted for higher values to the real centers synthetically, considering the properties in the longitudinal and transverse directions of the laser line. Moreover, this method provides a decision value from 0 to 1 for arbitrary candidate centers, which yields a normalized measure for different laser lines in different images. The normalized results of pixels close to 1 are determined to be the real centers by progressive scanning of the image columns. Finally, the zero point of a second-order Taylor expansion in the eigenvector's direction is employed to refine further the extraction results of the central points at the subpixel level. The experimental results show that the method based on this normalization model accurately extracts the coordinates of laser line centers and obtains a higher recognition rate in two group experiments.