• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1516-1519
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• 2004

A tele-operated robot should be used to maintain and inspect nuclear power plants to reduce the radiation exposure to the human operators. During an overhaul of the nuclear power plants in Korea, a ROV(Remotely Operated Vehicle) may enter a cold-leg connected to the reactor to examine the state of the thermal sleeve and it's position in the safety injection nozzle. To measure the positions of the thermal sleeve or scratches from the video images captured during the examination, the camera parameters should be identified. However, the focal length of the CCD camera could be increased to a close up of the target and the aspect ratio and the center of the image could also be varied with capturing devices. So, it is desired to self-calibrated the intrinsic parameters of the camera and capturing device with the video images captured during the examination. In the video image of the safety injection nozzle, two or more circular grooves around the nozzle are shown as ellipse contours. In this paper, we propose a camera self-calibration method using a single image containing two circular grooves which are the greatest circles of the cylindrical nozzle whose radius and distance are known.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.2
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• pp.261-269
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• 2018

This paper presents a convenient method to estimate the internal parameters of plenoptic camera using CCD(charge-coupled device) camera model. The images used for plenoptic camera calibration generally use the checkerboard pattern used in CCD camera calibration. Based on the CCD camera model, the determinant of the plenoptic camera model can be derived through the relationship with the plenoptic camera model. We formulate four equations that express the focal length, the principal point, the baseline, and distance between the virtual camera and the object. By performing a nonlinear optimization technique, we solve the equations to estimate the parameters. We compare the estimation results with the actual parameters and evaluate the reprojection error. Experimental results show that the MSE(mean square error) is 0.309 and estimation values are very close to actual values.

• Korean Journal of Optics and Photonics
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• v.10 no.1
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• pp.10-14
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• 1999

One dimensional inhomogeneous phase modulation effects on the MTF of optical system was investigated. The lens under test was a doublet made in Korea. It was 36 mm effective diameter, 128.04 mm effective focal length. The ray-fans and spot diagrams were calculated and presented on the picture for on-axis and off-axis (field of view, $1^{\circ}$ and $2^{\circ}$). Phase modulation was carried out by positioning a phase modulator close contacted with the lens under test. One was linear type that had linearly increasing phase retardation and the other was stepped type which had phase difference $\pi$ for each step. The MTFs were measured on the Gaussian image plane and were compared with one another. The MTFs of linear type phase modulated apertures had a little lower values than the MTF of unmodulated aperture for on-axis but most of all the MTFs of one dimensional phase modulated aperture are improved than the MTF of unmodulated aperture.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.12
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• pp.1923-1932
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• 2013

In order to solve the problem of severely distorted images from a wide-angle camera, we propose a calibration method which corrects a radial distortion in wide-angle images by estimation and validation of camera model. First, we estimate a camera model consisting of intrinsic and extrinsic parameters from calibration patterns, where intrinsic parameters are the focal length, the principal point and so on, and extrinsic parameters are the relative position and orientation of calibration pattern from a camera. Next we validate the estimated camera model by re-extracting corner points by inversing the model to images. Finally we correct the distortion of the image using the validated camera model. We confirm that the proposed method can correct the distortion more than 80% by the calibration experiments using the lattice shaped pattern images captured from a general web camera and a wide-angle camera.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.131-137
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• 2013

The barrel distortion makes serious problems in a wide-angle camera employing a lens of a short focal length. This paper presents a low-complexity hardware architecture for a real-time barrel distortion corrector and its implementation. In the proposed barrel distortion corrector, the conventional algorithm is modified so that the correction is performed incrementally, which results in the reduction of the number of required hardware modules for the distortion correction. The proposed barrel distortion corrector has a pipelined architecture so as to achieve a high-throughput correction. The correction rate is 74.86 frames per sec at the operating frequency of 314MHz in a $0.11{\mu}m$ CMOS process, where the frame size is $2048{\times}2048$. The proposed barrel distortion corrector is implemented with 14.3K logic gates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.4
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• pp.447-459
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• 2013

Many problems need to be solved before vision systems can actually be applied in industry, such as the precision of the kinematics model of the robot control algorithm based on visual information, active compensation of the camera's focal length and orientation during the movement of the robot, and understanding the mapping of the physical 3-D space into 2-D camera coordinates. An algorithm is proposed to enable robot to move actively even if the relative positions between the camera and the robot is unknown. To solve the correction problem, this study proposes vision system model with six camera parameters. To develop the robot vision control algorithm, the N-R and EKF methods are applied to the vision system model. Finally, the position accuracy and processing time of the two algorithms developed based based on the EKF and the N-R methods are compared experimentally by making the robot perform slender bar placement task.

• The Journal of the Korea Contents Association
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• v.17 no.6
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• pp.287-295
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• 2017

This study is aimed at observing effects of fingerprint image quality on various photographing conditions in the aspect of resolution. Discrimination between two friction ridges plays an important role in the value of fingerprint image, and it can be confirmed with quantification of pixels of boundary region which is existing between two friction ridges. In this study, several factors were estimated with same fingerprint image using Adobe photoshop CS 6 for analysis: changes of image quality by ISO, movement when photographing, and photographers' experience and skill. Consequently, there was no significant change of image quality by ISO. Furthermore, there was no significant difference in the hand-held images between crime scene investigators and laymen, yet there was significant difference between hand-held images and images using tripod in the aspect of resolution. This study shows that using tripod is very important in forensic fingerprint photography through empirical methods.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.2
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• pp.81-89
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• 2006

The purpose of this study was to evaluate the applicability of small RC(radio controlled) helicopter and single lens reflect camera as SFAP(Small Format Aerial Photography) aquisition system to monitor the vegetation coverage of wetland. The system used to take pictures of small artificial wetland were a common optical camera(Nikon F80 with manual lens whose focal length was 28mm) attached to the bottom of a RC helicopter with a 50 cubic inch size glow engine. Three hundreds pictures were taken at the altitude of 50m above the ground, from 23rd June to 7th September 2005. Four from the images were selected and scanned to digital images whose dimension were 2048${\times}$1357 pixels. Those images were processed and rectified with GCP(Ground Control Poins) and digital map, and then classified by the supervised- classification module of image processing program PG-steamer Version 2.2. The major findings were as follows ; 1. The final images processed had very high spatial resolution so that the objects bigger than 30mm like lotus(Nelumbo nucifera), rock and deck were easily identified. 2. The dominant plants of the monitoring site were Monochoria ragianlis, Typha latifolia, Beckmannia syzigachne etc. Because those species have narrow and long leaves and form irregular biomass, the individuals were hardly identifiable, but the distribution of population were easily identifiable depending on the color difference. 3. The area covered by vegetation was rapidly increased during the first month of monitoring. At the beginning of the monitoring 23th June 2005, The rate of area covered by vegetation were only 34%, but after 27 and 60 days it increased to 74%, and the 86% respectively.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.1
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• pp.11-17
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• 2004

We tried to design and manufacture a night scope which is used in the leisure sports field. The whole system consists of an IR light source part, an objective lens part, an intensifier tube part and an eye_piece lens part. We designed an objective lens part to the infinite object imaging optical-system with 80mm focal-length, 40mm effective-aperture and 14mm image-field-size of which the chromatic aberration is reduced by using materials of BK7 and FD4. The resolution of this system is about 25lines/mm at the 40% MTF value criterion. The eye_piece lens is adopted goods to be used commercially to save cost of production. The design technique which gets in this development will be utilized greatly in good developments of the dot, the sight and the day/night riflescope system at the hereafter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.6
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• pp.2457-2462
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• 2011

The need for rapid and accurate measurement of 3-dimensional objects is increasing due to the paradigmatic shift in manufacturing from mass production to small batch production. A three dimensional measurement technique which can provide the dimensional information of the object manufactured or to be manufactured has been developed. This method is based on phase shifting moire topology. Digital-Micromirror-Device (DMD) has been used in generating phase shifting moire fringes. And the mechanically moving optical components used for phase shifting, which might result in measurement errors, have been replaced by the DMD. Inherent $2\pi$-ambiguity problem, occurring in the calculation of phase from the light intensity distribution due to the nature of arctangent function, has been overcome by adapting the phase unwrapping method. The advantage of this technique is the easy change of the range and the resolution of the measurement by simply changing the computer generated grid pattern with the appropriate combination of projection lens of various focal length.