• Journal of Korea Multimedia Society
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• v.3 no.2
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• pp.112-120
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• 2000

In this paper, we implement a real-time textile dimension inspection system. It can detect various types of real defects which determine the quality of fabric product, defect positions of textile, classify the distortion angel of moving textile and the density. In the implemented system, we measure the density of textile using zone-crossing method with optical lens to solve the noise and real-time problems. And we compensate distortion angel of textile with the classification of distortion types using gaussian gradient and mean gradient features. And also, it detecs real defects of textile and its positions using gray level co-occurrence matrix features. The implemented texile demension inspection systemcan inspect textile dimensions such as density, distortion angle, defect of textile and defect position at real-time. In the implemented proposed texitile dimension inspection system, It is possible to calculate density and detect default of textile at real-time dimension inspection system, it is possible to calculate density and detect default of textile at textile states throughout at all the significant working process such as dyeing, manufacturing, and other texitle processing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.129-134
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• 2009

This study is on the development of photogrammetric methode for measuring the size of object without control points. The model is composed of interior orientation parameters, which are consist of specifications of CCD camera and lens distortion parameters, and exterior orientation parameters, which are calculated through relative orientation and scale adjustment. We evaluated the accuracy of the model to find that it is possible to measure the size of object using the model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.9
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• pp.1270-1275
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• 2013

A lot of research about camera calibration and lens distortion for wide-angle lens has been made. Especially, calibration for fish-eye lens which has 180 degree FOV(field of view) or above is more tricky, so existing research employed a huge calibration pattern or even 3D pattern. And it is important that calibration parameters (such as distortion coefficients) are suitably initialized to get accurate calibration results. It can be achieved by using manufacturer information or lease-square method for relatively narrow FOV(135, 150 degree) lens. In this paper, without any previous manufacturer information, camera calibration and barrel undistortion for fish-eye lens with over 180 degree FOV are achieved by only using one calibration pattern image. We applied QR decomposition for initialization and Regularization for optimization. With the result of experiment, we verified that our algorithm can achieve camera calibration and image undistortion successfully.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.2
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• pp.56-68
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• 1994

The objective of camera calibration is to determine the internal optical characteristics of camera and the three-dimensional position and orientation of camera with respect to the real world. Calibration procedure for computer vision should be automatical, accurate and applicable to general purpose cameras and lenses. In this paper, we present camera calibration method which meets the above requirements. The algorithm is based on the two-stage method which takes into account lens distortion in the second stage. In this paper, the overdetermined nonlinear system is established in terms of the constraints to all directions and our calibration algorithm is proposed which is constructed by using Marquardt iterations and our calibration algorithm is proposed which is constructed by using Marquardt iteration method in solving nonlinear equations. Experimental results indicate that lens distortion should be taken into consideration for the calibration of the general-purpose lens. With 24 calibration points acquired out of 512$\times$512 image, the proposed algorithm came up with average error of less than 1 pixel and showed a higher accuracy over the conventional two-stage method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.11a
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• pp.46-49
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• 2012

본 논문에서는 3차원 입체 비디오처리 기술의 최종목표인 디지털 홀로그램을 생성하는데 필요한 객체의 좌표와 색상정보가 들어있는 같은 시점과 해상도인 RGB 영상과 깊이 영상을 획득하여 가상 시점의 디지털 홀로그램을 생성하는 시스템을 제안한다. 먼저, 가시광선과 적외선의 파장을 이용하여 파장에 따라 투과율이 달라지는 콜드 미러를 사용하여 각각의 시점이 같은 다시점 RGB와 깊이 영상을 얻는다. 카메라 시스템이 갖는 다양한 렌즈 왜곡을 없애기 위한 보정 과정을 거친 후에 해상도가 서로 틀린 RGB 영상과 깊이 영상의 해상도를 같게 조절한다. 그 다음, DIBR(Depth Image Based Rendering) 알고리즘을 이용하여 원하는 가상 시점의 깊이 정보와 RGB 영상을 생성한다. 그리고 깊이 정보를 이용하여 디지털 홀로그램으로 구현할 객체만을 추출한다. 마지막으로 컴퓨터 생성 홀로그램 (computer-generated hologram, CGH) 알고리즘을 이용하여 추출한 가상 시점의 객체를 디지털 홀로그램으로 변환한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.3 no.2
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• pp.32-38
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• 1985

The purpose of this paper is to develope the analytical calibration model and to present its efficiency and problems for elimination of systematic errors. For this purpose, lens distortion in close-range photogrammetry is analized. From the obtained accuracy of object space coordinates, it is found that the calibration model included only $K_1$ term is effective for metric camera, and film deformation has to be considered not only in non-metric camera but also in metric camera.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2561-2563
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• 2003

본 논문은 비-스플라인(B-spline) 보간법을 이용한 영상의 변환에 대하여 논한다. 국소적인 영상의 정보나 세분화된 영상의 정보를 얻기 위해 영상의 확대 변환이 필요하다. 본 논문에서는 영상의 확대 변환을 위해 선형 (linear), 큐빅 (cubic), 인근치 (nearest neighbour)등의 보간법 [2]과 비-스플라인(B-Spline) 보간법[1][3][4]을 적용하였다. 실험을 통하여 비-스플라인 보간법이 현재 많이 사용되고있는 인근치 보간법, 선형 보간법, 큐빅 보간법들 보다 상대적으로 우월한 영상의 질을 가져옴을 보였다. 결론적으로, 영상의 기하학적 변환에 있어 기존의 세 가지 보간법들 보다 비-스플라인 보간법을 사용한 경우에 더 좋은 결과를 가지며, 비-스플라인 함수의 차수가 고차로 갈수록 영상의 질이 향상됨을 알 수 있다. 렌즈 등에 의한 왜곡현상을 가지고 있는 위성 사진이나 의료 영상을 기하학적 변환을 통하여 보정하는데 비-스플라인 보간법을 적용할 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.239-242
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• 2006

골다공증은 해면골의 골소주 두께 감소 및 파단에 기인한 전체적인 골질이 저하되는 질병이다. 골다공증을 예방과 조기진단을 하기 위해서는 골밀도를 측정하여야 한다. 보다 나은 이미지를 얻기 위해 Digital X-Ray로 골밀도를 측정하여 영상 처리하기 위한 방법을 제시한다. 먼저 디지털 센서에서 증감지와 렌즈간 거리가 가까워서 증감지의 중심과 주변부의 광 경로차이가 발생하므로 왜곡이 발생하는데 이를 균일화하여야 한다. 그리고 X-Ray장비의 조건에 따라 영상에 많은 차이를 보이므로 영상의 밝기를 보정하는 과정이 필수적이다.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.4
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• pp.503-507
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• 2013

Purpose: This study was to design wide angle mobile camera corrected optical distortion for peripheral area, which were reduced optical distortion and TV distortion by using 4 aspherical lenses. Methods: The optical design was satisfied with ${\pm}1%$ optical distortion in viewing angle of $95^{\circ}$ and total length of optical system was less than 4.5 mm which was considering a thickness of mobile camera. 1/3.2 inch (5M) CCD sensor was used in the optical system and set design condition to satisfy MTF which was over than 20% in 140 lp/mm. Results: Optimized wide angle mobile camera showed ${\pm}1%$ optical distortion in full field of $95^{\circ}$ viewing angle and TV distortion was 0.46% so that distortion of peripheral area was reduce. MTF showed over than 20% in every field. Ray aberration and astigmatism were small amount so that it showed stable performance. Conclusions: Obtain wider and clearer view which is reduced image distortion of surrounding area via optical method in wide angle mobile camera which has wider view angle than current mobile camera. And it was able to fix a demerit when it occurred via software correction. It is able to apply to study of camera which is related to spectacles.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.41-49
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• 2009

In this paper, the multi-camera calibration algorithm for optical motion capture system is proposed. This algorithm performs 1st camera calibration using DLT(Direct linear transformation} method and 3-axis calibration frame with 7 optical markers. And 2nd calibration is performed by waving with a wand of known length(so called wand dance} throughout desired calibration volume. In the 1st camera calibration, it is obtained not only camera parameter but also radial lens distortion parameters. These parameters are used initial solution for optimization in the 2nd camera calibration. In the 2nd camera calibration, the optimization is performed. The objective function is to minimize the difference of distance between real markers and reconstructed markers. For verification of the proposed algorithm, re-projection errors are calculated and the distance among markers in the 3-axis frame and in the wand calculated. And then it compares the proposed algorithm with commercial motion capture system. In the 3D reconstruction error of 3-axis frame, average error presents 1.7042mm(commercial system) and 0.8765mm(proposed algorithm). Average error reduces to 51.4 percent in commercial system. In the distance between markers in the wand, the average error shows 1.8897mm in the commercial system and 2.0183mm in the proposed algorithm.