• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.104-108
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• 2006

There are range and azimuth direction resolution of synthetic aperture radar on the aircraft or satellite. Wide bandwidth chirp pulse generation technology is prerequisite for SAR image with fine resolution. There are two kinds of digital chirp pulse generation technology as arbitrary waveform generator(AWG) and direct digital synthesizer(DDS). In this paper, we design and implement a digital chirp pulse generator to generate 300MHz wide bandwidth linear FM chirp pulse for the fine resolution image with direct digital synthesizer. Implemented chirp pulse generator can be useful for the SAR sensors to make 50cm range resolution image.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.287-290
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• 2011

분산 동영상 부호화 시스템에서는 복호기에서 움직임 보상 보간 기법을 이용하여 부가정보를 생성한다. 생성된 부가정보와 원 Wyner-Ziv 프레임간의 차이를 채널 부호로 오류 정정하게 되는데 이때 부호기에서는 복호기에서의 오류 정정을 위하여 패리티 비트인 Wyner-Ziv 비트를 복호기로 보내게 되고 복호기에서는 이 Wyner-Ziv 비트를 이용하여 Wyner-Ziv 프레임을 복원하는데 더 많은 Wyner-Ziv 비트가 필요할 경우 피드백 채널을 통해 Wyner-Ziv 비트를 요청하게 된다. 이때 부호기에서 조건부 엔트로피를 구할 수 있다면 이를 이용하여 Wyner-Ziv 비트 전송량을 제어함으로써 피드백 채널을 제거 할 수 있다. 이를 위해 부호기에서도 부가정보를 알아야하는데 복호기에서 사용하는 부가정보 생성 기법은 복잡도가 높기 때문에 사용할 수 없다. 본 논문에서는 부호기에서 간단한 부가정보를 생성하는 방법을 제안하고 분산 동영상 부호화 시스템에 적용하여 피드백 채널을 제거하였을 때의 성능을 분석하였다.

• Journal of Korea Multimedia Society
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• v.3 no.3
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• pp.241-252
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• 2000

In this paper, a translation, rotation and scale invariant system for the recognition of closed 2-D images using the bispectrum of a contour sequence and a weighted fuzzy classifier is derived and compared with the recognition process using one of the competitive neural algorithm, called a LVQ( Loaming Vector Quantization). The bispectrum based on third order cumulants is applied to the contour sequences of an image to extract fifteen feature vectors for each planar image. These bispectral feature vectors, which are invariant to shape translation, rotation and scale transformation, can be used to the represent two-dimensional planar images and are fed into a weighted fuzzy classifier. The experimental processes with eight different shapes of aircraft images are presented to illustrate a relatively high performance of the proposed recognition system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.7
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• pp.1696-1705
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• 1996

The theory of stack filtering, which is a generalization of median filtering, is used to the detection of intensity edges in noisey images. The proposed approach, called the Difference of Estimates(DoE) approach, is a new formulation of a morphological scheme which has been very sensitive to impulse noise. In this approach, stack filters are applied to a noisy image to obtain local estimates of the dilated and eroded versions of the noise-free image. Thresholding the difference between these two estimates yields the binary edge map. We find that this approach yields results comparable to those obtained with the Canny operator for images with additive Gaussian noise, burt works much better when the noise is impulsive.

• 한국ITS학회:학술대회논문집
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• 2003.11a
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• pp.230-233
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• 2003

• Proceedings of the Acoustical Society of Korea Conference
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• 1991.06a
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• pp.136-141
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• 1991

초음파 영상 진단기에서 영상의 질을 높이기 위해서는 넓은 범우에서 높은 측 방향 해상도가 요구된다. 측 방향 해상도는 변환기에 의해 발생되는 초음파 빔폭에 의해 좌우되는데 기존의 변환기는 초점 부근에서는 빔폭이 매우 좁으나 집속 범위가 제한되는 단점이 있다. 본 논문에서는 넓은 범위에서 균일한 빔폭을 얻을 수 있는 새로운 형태의 변환기를 제안하고 변환기에 의한 음장 분포를 전산기 모의 실험을 통해 구하였으며 그 결과 초점 부근에서는 빔 폭이 기존의 변환기에 비해 다소 넓어지나 집속 범위가 기존의 변화기에 비해 넓어지는 것을 확인할 수 있었다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.212.1-212.1
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• 2012

2010년 6월 성공적으로 발사된 천리안위성(COMS; Communication, Ocean, and Meteorological Satellite)의 기상영상기(MI; Meteorological Imager)를 통해 관측된 원시 기상영상은 지상국인 국가기상위성센터에서 지표기준과 위성궤도 및 자세 정보를 이용하여 영상위치보정 과정이 수행된다. 본 연구에서는 정규운영 초기 1년 동안의 운영 자료를 분석하여 계절 및 일변화를 나타내는 천리안위성 기상영상의 영상위치보정 성능 및 특성을 기술하였다. 이를 통하여 천리안위성 기상영상 가시 및 적외 채널의 영상위치결정 정확도 및 영상 위치유지 정확도는 기준값인 $56{\mu}rad$(약 2km) 이내로 유지되는 것을 확인하였다. 이는 천리안위성 기상영상이 우수한 품질의 위치정확도를 가지며 기상현상 분석 및 응용 연구에 높은 효용성을 가지는 것을 보여준다. 또한 본 연구의 결과는 후속 기상위성 영상위치보정 시스템 설계에도 유용하게 활용될 것이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.1
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• pp.190-196
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• 2013

Curved integral imaging is a simple method to display 3D images in space using lens array and provides wide viewing angle. In this paper, we propose a nonlinear 3D correlator based on the direct pixel-mapping (DPM) method in order to improve the recognition performance of 3D target object in curving-effective integral imaging. With this scheme, the elemental image array (EIA) originally picked up from a partially occluded 3-D target object can be converted into a resolution enhanced new EIA by using DPM method. Then, through nonlinear cross-correlations between the reconstructed reference and the target plane images, the improved pattern recognition can be performed from the correlation outputs. To show the feasibility of the proposed method, some preliminary experiments are carried out and results are presented by comparing the conventional method.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.4
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• pp.273-280
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• 2013

This paper presents novel OCS-LBP (Oriented Center Symmetric Local Binary Patterns) based on orientation of pixel gradient and image retrieval system based on BoF (Bag-of-Feature) and random forest classifier. Feature vectors extracted from training data are clustered into code book and each feature is transformed new BoF feature using code book. BoF features are applied to random forest for training and random forest having N classes is constructed by combining several decision trees. For testing, the same OCS-LBP feature is extracted from a query image and BoF is applied to trained random forest classifier. In contrast to conventional retrieval system, query image selects similar K-nearest neighbor (K-NN) classes after random forest is performed. Then, Top K similar images are retrieved from database images that are only labeled K-NN classes. Compared with other retrieval algorithms, the proposed method shows both fast processing time and improved retrieval performance.

• Journal of the Korean Society of Radiology
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• v.16 no.5
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• pp.585-594
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• 2022

The detector for digital radiography testing, which is currently mainly used, consists of a detector with a flat structure, making it impossible to fully adhere to the digital radiography testing of the test object with curvature. In this study, a curved panel detector capable of adhering to curvature was fabricated to improve the quality of the digital image during the digital radiography testing of piping welds at industrial sites, and digital radiography images using flat and curved panel detectors were obtained for 6in pipes with different nominal thickness. As a result of the experiment, it was confirmed that the flat panel detector does not fully adhere to the pipe, resulting in a gap between the outer part of the pipe and the detector, resulting in a difference in the unsharpness and diffusion of the digital image. On the other hand, it was confirmed that the curved panel detector minimizes the gap between the pipe outer part and the detector, so that digital image diffusion is less than that of the flat panel detector. The higher the confidence of the image, the lower the quality and error in reading, so it is believed that higher quality images can be obtained than conventional flat panel detectors when using detectors that can be closely attached to the inspection object.