• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.123-130
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• 1999

The objective of the current study is to understand steady 3-dimensional flow phenomena in a bifurcated duct experimentally. A bifurcation model is fabricated with transparent acrylic resin to visualize the whole flow field with the PIV system. The gray level cross-correlation method is applied to the image processing algorithm. The subpixel and the area interpolation methods are used to obtain the final velocity vectors. The finite volume predictions are used to analyze the flow patterns in the bifurcation model. The results of the computer simulation and the PIV experiment for three-dimensional flow show the recirculation zone and the formation of the paired secondary flow distal to the apex of the bifurcation model. The results obtained with the two methods also show that the branch flow strongly strikes the inner wall due to the inertial effect and accompanied helical motion as it flows toward the outer wall.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.2
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• pp.103-113
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• 1991

The accuracy of input coordinates of ground control points and check points affects great influences to the results of ground coordinate computation in using SPOT digital image data. The original SPOT images displayed on CRT are not usually adequate for identifying the object features and determining the point positioning. Hence, appropriate image processing techniques such as contrast enhancement, subpixel interpolation, edge enhancement, and spatial filtering are needed. In this study, the principles of digital image processing needed for accurate three dimensional positioning and spectral characteristic analysis are investigated. The algorithms for the actual applications are developed and programmed. And using the developed image processing software, some SPOT P-mode and XS-mode images are merged into the SPOT P＋XS, the high-resolution color composite image.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.165-168
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• 2001

본 논문에서는 카메라 또는 카메라 플랫폼의 흔들림 등 외부 영향과 비디오 시퀀스내의 모션이 함께 존재할 경우 출렁이는 비디오를 전자적으로 안정화하는 방법을 제안한다. 일반적인 영상 안정 시스템은 모션 측정과 모션 보상의 두 과정으로 구성되는데 모션 측정에서는 프레임간 모션 모델을 가정하고 파라메타를 측정하며 모션 보상에서는 측정된 파라메타를 이용하여 모션을 보상한다. 영상 내에 카메라 모션 이외의 움직임이 있을 경우 파라메타의 측정을 일관성 없게 만들 수 있으므로 이를 해결하기 위해 MVSD(Motion Vector Scatter Diagram)에 기반한 영상 안정 방법이 제안되었다. 그러나 이 방법은 최적화 파라메타를 정량화 하는데 한계가 있고 또한 계산 시간이 오래 걸리는 단점이 있어 이의 해결을 위해 본 논문에서는 선 기반(Line-based) 영상 안정 방법을 제안한다. 이 방법은 먼저 기준 영상에서 median filter를 이용해 영상 내의 코너를 검출하고 특징적인 두 점을 선택하여 이를 선으로 연결한다. 현재 영상에서 correlation을 이용하여 상응하는 두 특징점을 찾고 subpixel 방법으로 정확한 위치를 계산하여 선을 구한다. 이 두 선을 일치시키는 과정에서 모션 파라메타를 구하는데 먼저 평행 이동을 통해 한쪽 글을 일치시키고 이 과정에서 translation x, y 파라메타를 구한다. 다음 단계에서 한 쪽 끝이 일치된 두 선이 이루는 각을 계산하여 rotation 파라메타를 구한다. 이 방법으로 구해진 파라메타를 이용하여 모션 보상을 함으로서 영상 안정을 이를 수 있었다.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.12
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• pp.1002-1010
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• 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.

• Korean Journal of Remote Sensing
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• v.31 no.1
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• pp.39-46
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• 2015

Outgoing Longwave Radiation (OLR) is emitted energy from the Earth that is an important indicator of cooling effect in global scale and meteorological events in regional scale. Satellite-driven OLR products have its advantages overcoming spatially limited representation. The Korean geostationary satellite, Communication, Ocean and Meteorological Satellite (COMS), has been producing OLR product in accordance with its own algorithm since Apr. 2011. This study introduces Spatio-Temporally Equalized Match-up (STEM) approach to evaluate the COMS OLR products. We have tested a number of cases of thresholds set by standard deviations of a subpixel $10.8{\mu}m$ to find optimal representation of OLR in the selective match-up. Each case was then validated with broadband reference data, Clouds and the Earth's Radiant Energy System (CERES). We found that selective STEM approach was useful to validate OLR product especially its distribution in homogeneous grids.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.2
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• pp.372-379
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• 2015

The latest video compression standard (such as H.264/AVC and HEVC) utilizes quarter-pel accuracy motion estimation in order to retain detailed motion information. Many sub-pixel motion estimation algorithms used in the spatial domain usually encounters increment of computational complexity due to embedded interpolation algorithm. In this paper, an approach to measure sub-pixel accuracy motion estimation in frequency domain using shifting matrix is proposed. Complexity can be reduced utilizing shifting matrix algorithm in frequency domain and simulation results demonstrate not only higher PSNR but lower bit rates than spatial domain algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.5
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• pp.1744-1760
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• 2021

Since correlation filter appeared in the field of object tracking, it plays an increasingly vital role due to its excellent performance. Although many sophisticated trackers have been successfully applied to track the object accurately, very few of them attaches importance to the scale and rotation estimation. In order to address the above limitation, we propose a novel method combined with Fourier-Mellin transform and confidence evaluation strategy for robust object tracking. In the first place, we construct a correlation filter to locate the target object precisely. Then, a log-polar technique is used in the Fourier-Mellin transform to cope with the rotation and scale changes. In order to achieve subpixel accuracy, we come up with an efficient surface fitting mechanism to obtain the optimal calculation result. In addition, we introduce a confidence evaluation strategy modeled on the output response, which can decrease the impact of image noise and perform as a criterion to evaluate the target model stability. Experimental experiments on OTB100 demonstrate that the proposed algorithm achieves superior capability in success plots and precision plots of OPE, which is 10.8% points and 8.6% points than those of KCF. Besides, our method performs favorably against the others in terms of SRE and TRE validation schemes, which shows the superiority of our proposed algorithm in scale and rotation evaluation.

• Smart Structures and Systems
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• v.20 no.4
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• pp.397-413
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• 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 Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.70-78
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• 2001

We have developed a novel driving system of 5' true color FED using voltage controlled PWM method which has current control effect. The proposed method has the advantage of voltage controlled pulse width modulation method and current control method. Also, we propose a new circuit model of FED subpixel for circuit simulation of FED driving circuits, considering some parasitic effects, i.e., cross talk, line coupling effect and leakage current to the adjacent cathode lines. Output stage of the data driving circuit is optimized using the proposed circuit model. In video data processing, FED controller uses the parallel processing of R.G.B input data, so duty ratio is maximized and brightness of FED increases. With this results, no noise and high quality performance is achieved in display of 5' true color FED.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8B
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• pp.1558-1566
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• 1999

While high resolution images are required for various applications, aliased low-resolution images are only available due to the physical limitations of sensors. In this paper, we propose an algorithm to reconstruct a high resolution image from multiple aliased low-resolution images, which is based on the generalized multichannel deconvolution technique. The conventional approaches are based on the discrete Fourier transform (DFT) since the aliasing effect is easily analyzed in the frequency domain. However, the useful solution may not be available in many cases, i.e., the underdetermined cases or the insufficient subpixel information cases. In order to compensate for such ill-posedness, the generalized multichannel regularization was adopted in the spatial domain. Furthermore, the usage of the discrete cosine transform instead of the DFT leads to the computationally efficient reconstruction algorithm. The validity of the proposed algorithm is both theoretically and experimentally demonstrated in this paper. It is also shown that the effect of inaccurate motion information is reduced by regularization.