• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.133-134
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• 2008

• Korean Journal of Optics and Photonics
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• v.23 no.5
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• pp.179-188
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• 2012

Lenses with an ultra wide angle of view are usually called fisheye lenses since a fish can see an ultra wide panoramic view under water. As the angle of view for these kinds of lenses reaches a wide angle, the illumination on an image sensor is reduced by a rapid drop. In this paper, we discuss the causes and the ways to correct for a rapid drop. First, it is treated for the sign convention of directional cosine vectors and normal vectors on the curved surface by means of analytic geometry. And, from the fundamental discussion for these vectors, the rapid illumination drop is numerically analyzed for various kinds of causes by utilizing geometrical optics and radiometry as well as Fresnel equations derived from electromagnetic boundary conditions. As a result, we are able to get the full understanding for the rapid illumination drop and to propose ways to correct effects due to an wide angle of view.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.4
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• pp.256-262
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• 2004

A key component of an autonomous mobile robot is to localize itself and build a map of the environment simultaneously. In this paper, we propose a vision-based localization and mapping algorithm of mobile robot using fisheye lens. To acquire high-level features with scale invariance, a camera with fisheye lens facing toward to ceiling is attached to the robot. These features are used in mP building and localization. As a preprocessing, input image from fisheye lens is calibrated to remove radial distortion and then labeling and convex hull techniques are used to segment ceiling and wall region for the calibrated image. At the initial map building process, features we calculated for each segmented region and stored in map database. Features are continuously calculated for sequential input images and matched to the map. n some features are not matched, those features are added to the map. This map matching and updating process is continued until map building process is finished, Localization is used in map building process and searching the location of the robot on the map. The calculated features at the position of the robot are matched to the existing map to estimate the real position of the robot, and map building database is updated at the same time. By the proposed method, the elapsed time for map building is within 2 minutes for 50㎡ region, the positioning accuracy is ±13cm and the error about the positioning angle of the robot is ±3 degree for localization.

• Journal of the Mineralogical Society of Korea
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• v.28 no.4
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• pp.325-332
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• 2015

Apophyllite (KF)($K_{0.84}Ca_{3.99}Si_{7.70}O_{20}F_{0.72}{\cdot}8H_2O$), one of the sheet silicates, was compressed up to 7.7 GPa at ambient temperature and 15 high pressure data were obtained. Lattice parameters of the starting specimen were as follows: $a_0=8.954(2)\;{\AA}$, $c_0=15.795(2)\;{\AA}$, $V_0=1266.4(4)\;{\AA}^3$. Symmetrical diamond anvil cell was employed with synchrotron radiation in the mode of angular dispersive X-ray diffraction. Bulk modulus was determined to be 59(4) GPa when ${K_0}^{\prime}$ is 4. No clear first order phase transition symptom was observed in the series of XRD pattern. However, second-order phase transition cannot be ruled out from the correlation between normalized pressure and strain.

• The Optical Journal
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• s.129
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• pp.65-69
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• 2010

렌즈들의 고유한 초점거리는 모두 대각선 방향의 화각을 표시한 것으로 화각은 말 그대로 화면을 담을 수 있는 각도를 말한다. 화각이 제일 넓은 렌즈는 물고기가 바라보는 것과 같다고 해서 붙여진 어안렌즈를 비롯하여 광각렌즈, 망원렌즈 등이 있다. 이번호에서는 표준렌즈, 망원렌즈, 광각렌즈 등을 통해 초점 거리별 렌즈의 활용법을 알아보자.

• The Korean Publising Journal, Monthly
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• s.142
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• pp.2-3
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• 1994

책의 두께란 책 안의 현재 속에 책 밖의 과거와 미래가 응축되어 있는 모습이다. 책이 두껍다는 것은 그것이 자신의 현재 속에 끌어안고 있는 과거와 미래가 그만큼 두터운 시간을 형성하고 있다는 것을 말한다. 그 두께는 단지 과거와 미래를 살아있는 현재 속에 보존하는 그릇으로 그치는 것이 아니라 나아가서 문명 전체를 자기 속에 담아내는 부피로 변해버린다. 문명적 사유란 책이 만드는 두께를 터전으로 하는 사유이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4C
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• pp.408-414
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• 2010

When we are collecting traffic information on CCTV images, we have to install the detect zone in the image area during pan-tilt system is on duty. An automation of detect zone with pan-tilt system is not easy because of machine error. So the fisheye lens attached camera or convex mirror camera is needed for getting wide area images. In this situation some troubles are happened, that is a decreased system speed or image distortion. This distortion is caused by occlusion of angled ray as like trembled snapshot in digital camera. In this paper, we propose two methods of de-blurring to overcome distortion, the one is image segmentation by nonlinear diffusion equation and the other is deformation for some segmented area. As the results of doing de-blurring methods, the de-blurring image has 15 decibel increased PSNR and the detection rate of collecting traffic information is more than 5% increasing than in distorted images.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2116-2120
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• 2007

A realization for image distortion correction processing system with DSP processor is presented in this paper. The image distortion correcting algorithm is realized by DSP processor for focusing on more real time processing than image quality. The lens and camera distortion coefficients are processed by the Lookup Tables and the correcting algorithm is applied to reverse mapping method for geometrical transform. The system experimentation results in the processing time about 31.3 msec $720{\times}480$ wide range image, and the image is stable and spontaneous to be about 8.3% average PSNR variation with changing a wide angle.

• Journal of the Speleological Society of Korea
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• no.77
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• pp.43-52
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• 2007

중국 호남성의 장가계시 무릉원(武陵源)에는 위로 천문산(天門山)의 천문동(天門洞)과 땅 아래로 뻗혀 있는 황룡동굴(黃龍洞窟)이 있다. 천문동은 오나라 때의 대지진으로 인하여 생긴 것이며, 황룡동굴은 이 지역에 분포된 석회암 지대로 말미암아 영겁의 세월을 통하여 생성된 지하생성물의 극치이다. 천문산 고봉의 하늘 맞닿은 높은 곳에 형성된 천문동혈(天門同穴)과, 4층 규모로 된 땅속의 산 같은 석회동 구조물과 강물을 무색케 하는 지중뱃길수로를 끌어안고 있는 황룡동굴은 과연 천산용동(天山龍洞)의 바로 그것이 아닌가. [답사보고서 중에서]

• Journal of the Korean Society for information Management
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• v.24 no.2
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• pp.71-87
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• 2007

With the rapid change of the Web and E-transaction application, the search interface is providing more powerful search and visualization methods, while offering smoother integration of technology with task. Especially, visualization techniques for long menu-lists are applied in retrieval system with the goal of improving performance in user's ability to select one item from a long list. In order to review visualization techniques appropriate to the types of users and data set, this study compared the five visualization browsers such as the Tree-structured menu, the Table-of-contents menu, the Roll-over menu, the Click menu, and Fisheye menu. The result of general analyses shows that among the hierarchical methods, the experienced group prefers the Table-of-contents method menu, whereas the novice's group prefers the Tree-structure method menu. Among the linear methods, the two groups prefer the Roll-over menu. The Roll-over menu is most preferred among the five browsers by the two groups.