• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.227.1-227.1
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• 2012

원격탐사 광학탑재체는 촬영 방식에 따라 대상물을 응시하여 촬영하는 응시(staring)방식과 스캔하여 촬영하는 스캐닝(scanning)방식으로 나뉠 수 있다. 인공위성을 이용한 원격탐사에서는 위성의 궤도에 따라 촬영방식에 제한이 생기는데, 저궤도에서 지구관측을 하는 전자 광학 카메라의 경우 위성의 공전속도에 의해서 지표면을 스캔하는 방식으로 촬영을 수행하는 푸시브룸 스캔(push broom scan)방식이 많이 사용된다. 스캔방식으로 영상을 촬영하면 스캔에 평행한 방향과 수직인 방향의 광학적 영상품질이 달라질 수 있다. 스캔에 평행한 방향은 스캔에 의한 영상 번짐 효과가 나타나기 때문이다. 본 연구에서는 스캔에 의한 영상 번짐 효과로 발생하는 MTF 성능에 대하여 분석하였다. 검출기레벨에서의 영상 번짐 효과 및 다단계(multi-phase) 검출기를 사용했을 때의 영향에 대하여 분석하였다.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.4
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• pp.135-140
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• 2014

As the digital image devices are widely used, interests in the software- and the hardware-related image processing become higher and the image processing techniques are applied in various fields such as object recognition, object detection, fingerprint recognition, and etc. For the edge detections Sobel, Prewitt, Laplacian, Roberts and Canny detectors are used and these existing methods can excellently detect the edges of the images without noise. However, in the images corrupted by the impulse noise, these methods are insufficent in noise elimination characteristics, showing unsatisfactory edge detection. Therefore in this paper, in order to obtain excellent edge detection characteristics in the corrupted image by the impulse noise, an detection algorithm is porposed, which uses the central pixel of mask divided by four regions along the axis, calculates the estimated mask according to the representing pixel values in each regions, and detects the final edges by applying the estimates mask and the new directional one.

• Progress in Medical Physics
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• v.24 no.3
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• pp.162-170
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• 2013

Dedicated single-photon emission computed tomography (SPECT) systems based on pixelated semiconductors are being developed for studying small animal models of human disease. To clarify the possibility of using a SPECT system with CdTe for a high resolution low-dose small animal imaging, we compared the quality of reconstructed images from pixelated CdTe detector to those from a small SPECT system with NaI(Tl). The CdTe detector was $44.8{\times}44.8$ mm and the pixels were $0.35{\times}0.35{\times}5$ mm. The intrinsic resolution of the detector was 0.35 mm, which is equal to the pixel size. GATE simulations were performed to assess the image quality of both SPECT systems. The spatial resolutions and sensitivities for both systems were evaluated using a 10 MBq $^{99m}Tc$ point source. The quantitative comparison with different injected dose was performed using a voxelized MOBY phantom, and the absorbed doses for each organ were evaluated. The spatial resolution of the SPECT with NaI(Tl) was about 1.54 mm FWHM, while that of the SPECT with a CdTe detector was about 1.32 mm FWHM at 30 mm. The sensitivity of NaI(Tl) based SPECT was 83 cps/MBq, while that of the CdTe detector based SPECT was 116 cps/MBq at 30 mm. The image statistics were evaluated by calculating the CNR of the image from both systems. When the injected activity for the striatum in the mouse brain was 160 Bq/voxel, the CNR of CdTe based SPECT was 2.30 while that of NaI(Tl) based SPECT was 1.85. The CNR of SPECT with CdTe was overall higher than that of the NaI(Tl) based SPECT. In addition, the absorbed dose was higher from SPECT with CdTe than those from NaI(Tl) based SPECT to acquire the same quantitative values. Our simulation results indicated that the SPECT with CdTe detector showed overall high performance compared to the SPECT with NaI(Tl). Even though the validation study is needed, the SPECT system with CdTe detector appeared to be feasible for high resolution low-dose small animal imaging.

• Proceedings of the KAIS Fall Conference
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• 2002.11a
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• pp.225-228
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• 2002

현대 산업이 점차 세분화되고 산업용 반응조, 수조, 송수관 등 시설물이 증가하고 시설물의 관리가 증가함에 따라 본 논문에서는 감마선을 이용한 결합 검출기를 개발하였다. 물질의 투과성이 좋은 감마선의 특성을 이용하여 물체의 결합을 측정을 한다. 감마선이 물체를 투과하여 수집된 데이터를 영상 신호처리를 하여 이미지로 나타냄으로서 측정을 하는 사용자가 물체의 결합의 위치를 쉽게 알 수 있도록 하였으며 측정기기를 소형화하여 이동을 편리하게 하는데 본 논문은 목적을 두고 하드웨어를 제작하였으며, 물체내부의 결함은 영상 신호처리의 시뮬레이션을 통해서 확인하였다.

• Journal of radiological science and technology
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• v.40 no.4
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• pp.533-542
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• 2017

In diagnostic radiology, the imaging system has been changed from film/screen to digital system. However, the method for removing scatter radiation such as anti-scatter grid has not kept pace with this change. Therefore, authors have devised the indirect flat panel detector (FPD) system with net-like lead in substrate layer which can remove the scattered radiation. In clinical context, there are many radiographic examinations with angulated incident X-ray. However, our proposed FPD has net-like lead foil so the vertical lead foil to the angulate incident X-ray would have bad effect on its performance. In this study, we identified the effect of vertical/horizontal lead foil component on the novel system's performance and improved the structure of novel system for clinical usage with angulated incident X-ray. Grid exposure factor and image contrast were calculated to investigate various structure of novel system using Monte Carlo simulation software when the incident X-ray was tilted ($0^{\circ}$, $15^{\circ}$, and $30^{\circ}$ from the detector plane). More photons were needed to obtain same image quality in the novel system with vertical lead foil only then the system with horizontal lead foil only. An optimal structure of novel system having different heights of its vertical and horizontal lead foil component showed improved performance compared with the novel system in a previous study. Therefore, the novel system will be useful in a clinical context with the angulated incident X-ray if the height and direction of lead foil in the substrate layer are optimized as the condition of conventional radiography.

• Korean Journal of Remote Sensing
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• v.18 no.2
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• pp.91-96
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• 2002

The performance characteristics of a satellite imager using a Time Delay and Integration(TDI) Charge Coupled Device (CCD) with fixed integration time is investigated for the variation of satellite altitude and tilt angle. In consequence of the investigation TDI synchronization using tilt imaging is proposed as a solution to compensate geometric performance degradation due to altitude decrease. The tilt angle optimized for the TDI synchronization at decreased altitude is presented. This result can be used for a TDI CCD imager with variable integration time in a certain range as well.

• Journal of radiological science and technology
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• v.34 no.1
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• pp.9-15
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• 2011

In this paper, an image quality evaluation of amorphous selenium based x-ray system was performed using modulation transfer function (MTF) measurement. MTF as a main factor of imaging quality evaluation was investigated by contrast method from acquired test pattern image. The MTF value was measured to 36.1% at 3.0 lp/mm which is twice as high as that in the film image. Compared with other studies, the results demonstrate that amorphous selenium based x-ray detector is clinically meaningful.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.109-116
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• 2003

In this paper. we Propose an UXGA class LCD controller for controlling the LCD panel. The proposed controller supports the full screen display using GCD between input and output resolutions. The proposed LCD controller includes the motion detector based on median filter which can detect the motion of input image for the enhancement of a image quality. Also, it divides the motion into 3 stages such as still, semi-moving and moving, and uses the different interpolation algorithms according to the degree of motion. In order to evaluate the performance of the proposed interpolation algorithm, we use PSNR method and compare the conventional algorithm by using computer simulation. For the proposed motion detection algorithm, we use a visual verification and the estimation of pixel changes. The proposed LCD controller has been designed and verified by VHDL. It has been synthesized using Xilinx VirtexE FPGA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.95-101
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• 2007

Recently, two phase scheme for removing impulse noise in images is proposed. This algorithms first detect the noise candidates based on the adaptive median filter, and then apply optimizing techniques recursively only to those noise candidates to restore image. Thus the noise detector with high accuracy is important role on this algorithm, In this paper, novel noise detector is proposed, which can detect impose noise with high accuracy while reducing the probability of false detecting image details as impulses. And the method for reducing computational cost of regularization phase is presented also.

• Electronics and Telecommunications Trends
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• v.22 no.5
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• pp.95-107
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• 2007

X-선 측정 및 영상장치를 포함한 다양한 응용분야에서 방사선에 대한 고해상도의 영상을 얻기 위한 목적으로 반도체 검출기에 대한 개발이 활발히 진행되고 있다. 본 고에서는 방사선 검출을 위해 요구되는 반도체 물질의 주요 특성에 대해서 조사하였다. 또한 반도체를 이용한 플랫 패널(flat panel) 시스템, 픽셀 디텍터(pixel detector)와 스트립 디텍터(strip detector) 등의 혼성형 디텍터(hybrid detector), MAPS와 DEPFET 등의 단일형 픽셀 디텍터(monolithic pixel detector)의 디바이스 동작 원리 및 특성과 국내외 기술 동향에 대하여 살펴보았다.