• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.28-29
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• 2002

하트만 센서를 이용한 파면 왜곡 측정에서 측정 정밀도와 측정 속도는 왜곡을 실시간으로 보정하고자 하는 적응광학 기술에서 중요한 요소이다. 파면왜곡을 측정하고 보정하는 실제 환경에서 적응광학장치는 전기적으로 안정된 시스템의 구성이 요구된다. 본 논문에서는 하트만 센서를 이용한 파면 측정과정에서 넓은 측정 범위를 가지면서도 고속 정밀한 파면 정보를 추출할 수 있는 알고리즘을 연구하였고 적응광학 부품들을 제어함에 있어 전기적으로 안정된 하드웨어 장치들을 구성하였다. (중략)

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.122-124
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• 2014

보간 기법은 영상의 해상도를 변경하는 것이다. 멀티미디어 기기의 해상도가 다양하기 때문에 원 영상은 각각에 맞는 해상도로 변경되어야 한다. 해상도 변경은 존재하지 않는 값을 임의로 만들어 채우는 것이기 때문에 왜곡이 발생한다. 대부분의 scaler에서는 수평과 수직 방향으로 해상도 변경을 하는데, 이 때문에 edge 영역에서는 왜곡이 더 많이 발생하며 쉽게 눈에 띈다. 본 논문에서는 edge 방향에서 발생하는 왜곡을 극복하기 위해 영상의 edge 정보와 Cubic Convolution을 이용해 임의의 배율로 해상도를 변경하는 방법을 제안한다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.460-464
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• 1998

일반적으로 파형 부호화법에서는 발성자의 개성과 메시지 정보를 보존하여 음질의 명료성이 우수하다. 하지만 파형 부호화법이 규칙에 의한 합성에 적응되도록 하기 위해서는 운유 조절에서 피치 변경법이 요구되어 진다. 본 논문에서는 스펙트럼의 왜곡율을 최소화하면서도 위상을 그대로 보존할 수 있는 시간영역에서의 피치변경법을 적용하였다. 이러한 방법들은 시간영역에서만 처리됨으로써 계산량을 줄여 실시간 운율조절에 적합하다. 결과적으로 피치주기를 100%에서 50%로 압축한 경우 평균 스펙트럼 왜곡율은 5.62%이고, 피치주기를 100%에서 200%로 신장한 경우 평균 스펙트럼 왜곡율은 4.20%정도로 비교적 우수한 결과가 얻어졌다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2002.10a
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• pp.195-199
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• 2002

SAR(Synthetic Aperture Radar) 영상은 경사촬영을 수행하므로 지형의 기복에 따른 영향을 많이 받는다. 따라서 SAR영상을 이용하여 여러 가지 정보들을 추출하여 이용하기 위해서는 전처리 과정으로서 지형의 기복에 따른 여러 가지 왜곡들을 보정해야 한다. 이에 본 연구에서는 RADARSAT SAR 영상을 이용하여 궤도모델링, 정사보정을 수행하고 역산란계수, 국부입사각 계산 등을 통해 지형기복에 따른 방사왜곡보정을 수행하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.6
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• pp.577-582
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• 2011

In remote sensing, spatial/spectral distortions are recognized as two of the main problems in the pansharpening algorithm. Most pansharpening methodologies show a tendency to distort spatial information from objects such as buildings and vehicles because there are local spatial dissimilarities among multispectral bands in Worldview-2 satellite imagery. In this paper, we propose a new pansharpening algorithm in order to minimize the effects of the local displacement of spatial information in the pansharpening process. In experiments using Worldview-2 images, our method provided better spectral and spatial quality than pre-existing pansharpening methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1103-1109
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• 2014

The motion recognition system has been broadly studied in digital image and video processing fields. Recently, method using th depth image is used very useful. However, recognition accuracy of depth image based method will be loss caused by size and shape of object distorted for angle of the depth sensor. Therefore, distortion correction of depth sensor is positively necessary for distinguished performance of the recognition system. In this paper, we propose a pre-processing algorithm to improve the motion recognition system. Depth data from depth sensor converted to real world, performed the corrected angle, and then inverse converted to projective world. The proposed system make progress using the OpenCV and the window program, and we test a system using the Kinect in real time. In addition, designed using Verilog-HDL and verified through the Zynq-7000 FPGA Board of Xilinx.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.143-150
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• 2005

Camera image is very sensitive to illumination that result in difficulties for recognizing character. Also Camera captured document images have not only skew but also vignetting effect and geometric distortion. Vignetting effect make it difficult to separate characters from the document images. Geometric distortion, occurred by the mismatch of angle and center position between the document image and the camera, make the shape of characters to be distorted, so that the character recognition is more difficult than the case of using scanner. In this paper, we propose a method that can increase the performance of character recognition by correcting the geometric distortion of document images using a linear approximation which changes the quadrilateral region to the rectangle one. The proposed method also determine the quadrilateral transform region automatically, using the alignment of character lines and the skewed angles of characters located in the edges of each character line. Proposed method, therefore, can correct the geometric distortion without getting positional information from camera.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.5
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• pp.458-464
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• 2016

This paper proposes the compensation method which decreases the radiation pattern distortion caused by the mutual coupling in an array antenna. If the element distance of an array antenna decreases, the radiation pattern could be distorted by the strong mutual coupling, which changes the magnitude and phase of input signals and causes an unwanted radiation pattern. To remove the pattern distortion, compensated input signals are inserted in an array antenna. The magnitude and phase of input signals are determined by Particle Swarm Optimization (PSO) algorithm. A $4{\times}1$ dipole array antenna with omnidirectional elements is used to confirm the validity of the algorithm, where each element is placed in 0.2 wavelength to evoke the strong coupling. After input signals are optimized by PSO, it is found that the compensated radiation results in the same as the ideal case.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.499-508
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• 2017

A new digital pre-distortion technique to linearize power amplifier (PA) is proposed for concurrent dual-band transmitters. In the conventional dual-band DPD techniques, two independent dual-feedback paths are required to compensate nonlinear cross-products between different bands as well as the nonlinear self-products of each band's own signal. However, it increases hardware complexity and expense. In this paper, we propose a new DPD method requiring only a single feedback path. In this new structure, the proposed technique first estimates the dual-band PA characteristics using the single feedback path. The DPD parameters are then extracted from the estimated PA characteristics. The DPD performance of the proposed method is validated through computer simulation. According to the results, the proposed technique can achieve comparable performance to the conventional two feedback DPD with significantly reduced hardware complexity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2645-2652
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• 2013

For a variety of vision systems such as car omni-directional surveillance systems and robot vision systems, many cameras have been equipped and used. In order to detect corners of grid pattern in AVM(Around View Monitoring) systems, after the non-linear radial distortion image obtained from wide-angle camera is corrected, corners of grids of the distortion corrected image must be detected. Though there are transformations such as Sub-Pixel and Hough transformation as corner detection methods for AVM systems, it is difficult to achieve automatic detection by Sub-Pixel and accuracy by Hough transformation. Therefore, we showed that the automatic detection proposed in this paper, which detects corners accurately from the distortion corrected image could be applied for AVM systems, by designing and implementing it, and evaluating its performance.