• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.205-211
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• 1998

The MTF(modulation transfer function) measuring system with a linear CCD(charge coupled-device) was constructed to cvaluate a color CRT(catode ray tube). The measured MTF values were corrected by considering the spectral response and the pixel sizes of CCD. The effects of a spot size, video bandwidth, pitch of shadow mask holes, display luminance, and ambient illumination on image quality were studied. The uniformity of resolution and the contrast Ioss by ambient light of the color CRT monitor were measured, and the results were analyzed by MTFA(modulation threshold area).

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.47-47
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• 2001

본 논문에서는 균일한 색 분포를 위한 밝기 사상과 최대 색도 재현을 위한 색역 사상 방법을 제안한다. 기존의 밝기 사상시 발생하는 두 색역에서의 평균 밝기의 차이의 증가 및 어두운 영역과 밝은 영역에서의 색 변화의 차이가 증가하는 문제를 해결하기 위하여 각 색상의 정점에서의 밝기 차이를 최소화하고 밝은 영역과 어두운 영역에서의 균일한 색 분포를 가지는 밝기 사상 방법을 제안하였다. 또한, 최대 채도 유지 및 균일 색 분포를 위한 가변 닻점과 고정 닻점을 혼합으로 사용하는 색역 사상 방법을 제안하였다. 따라서 저가의 칼라 출력장치에서 고화질의 칼라를 재현할 수 있게 한다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.6
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• pp.124-131
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• 2003

In this paper, we propose a Progressive scalable video coding algorithm using frequency weighting in the DCT domain. Since the human visual system (HVS) can be modeled as a nonlinear point transformation, called the modulation transfer function (MTF), we tan use the frequency weighting matrix to enhance the video image quality. We change this frequency weighting matrix into the frequency shift matrix to apply to the bit-plane coding method for the fine granular scalable (FGS) video coding We also define a new error metric JNDE (just noticeable difference) to measure the perceptual image quality in terms of human vision.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.73-81
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• 2018

The quality of side scan sonar images is determined by the frequency of a sonar. A side scan sonar with a low frequency creates low-quality images. One of the factors that lead to low quality is a high-level noise. The noise is occurred by the underwater environment such as equipment noise, signal interference and so on. In addition, in order to compensate for the transmission loss of sonar signals, the received signal is recovered by TVG (Time-Varied Gain), and consequently the side scan sonar images contain non-homogeneous noise which is opposite to optic images whose noise is assumed as homogeneous noise. In this paper, the SSCS (Structural Sparsity based Compressive Sensing) is proposed for removing non-homogeneous noise. The algorithm incorporates both local and non-local models in a structural feature domain so that it guarantees the sparsity and enhances the property of non-local self-similarity. Moreover, the non-local model is corrected in consideration of non-homogeneity of noises. Various experimental results show that the proposed algorithm is superior to existing method.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.819-825
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• 2020

The purpose of this study was to evaluate the usefulness of the developed air mattress for reducing the deterioration of image quality due to the scattered radiation generated on the computed tomography equipment table. 5 cm and 10 cm thick air mattresses were developed and the image quality was measured by scanning the AAPM phantom according to thickness and thickness. Statistical significance was confirmed by One Way Analysis of Variance(ANOVA) Compared with the AAPM phantom scanned in the standard method, the image with the air mattress did not show any difference, but when the air mattress was not applied, the CT number and uniformity were low and the noise was high, and the spatial resolution Respectively. The developed air mattress has no harmful effect on the diagnostic image, it is very effective in improving the image quality and can increase the CT image quality by simply applying Air Mattress to existing equipment without using the technology applied to the latest and high-cost equipment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.2
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• pp.27-31
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• 2000

Thermal imaging system is implemented for the measurement and the analysis of the thermal distribution of the target objects. The main Part of the system is thermal camera in which a focal plane array typed sensor is introduced The sensor detects mid-range infrared spectrum or target objects and then it output generic video signal which should be processed to form a thermal image frame. A digital signal processor(DSP) in the system inputs analog to digital converted data. performs algorithms to improve the thermal images and then outputs the corrected frame data to frame buffers for NTSC encoding and for digital outputs.. To enhance the quality of the thermal images, two point correction method is applied. Figures indicate that the corrected thermal images are much improved.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.371-380
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• 2001

In this paper, lightness mapping for uniform color distribution and gamut mapping for maximum chroma reproduction are proposed. In the conventional lightness mapping, the average lightness difference between the two gamut is increased and different color changes in bright and dark regions are also increased. To solve these problems, a lightness mapping is proposed that minimizes the lightness difference of the cusps at each hue angle and produces same color changes in bright and dark regions. Also, gamut mapping that utilize variable anchor point and an anchor point are proposed for maximum chroma reproduction and uniform color change. Accordingly, the proposed algorithm can reproduce high quality images with low-cost color devices.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.303-307
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• 2002

디지털 영상압축 방법인 ITU-T H.263++ 부호화기법 중에는 계층 모드(scalability mode)를 지원한다. 계층 모드는 한 개의 송신 영상에 대해서도 복호기와 전송로에 따라서 여러 가지 화질의 재생 영상을 얻을 수 있게 한다. 계층 모드는 시간적, 공간적, SNR(signal-to-noise ratio)로 나누어진다. 그 중에서 SNR 계층 모드는 고급계층에 따라서 다양한 해상도를 가질 수 있다. 계층부호화에는 크게 기본계층과 고급계층으로 나누어지는데, 기본계층은 QoS를 보장하여, 화질은 떨어지나 에러 없이 영상을 전송하고, 고급계층에서는 기본계층에 해상도 에러에 대한 나머지 정보를 전송한다. 고급계층으로 전송되는 정보는QoS가 보장되지 않으므로 비트에러나, 팻킷 에러가 발생 할 수 있다. 따라서 고급계층에 에러가 발생하게 되고, 에러 전파 현상이 일어난다. 본 논문에서는 단일계층부호화와 2 Layer 계층부호화에서 발생되는 에러의 차이점을 알아보고, 데이터 손실 없는 기본계층과 에러가 발생하는 고급계층에 상관관계를 분석하여, SNR계층부호화에서 맞는 고급계층 에러은닉 기법을 제안한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.11a
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• pp.46-48
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• 2020

HEVC (High Efficiency Video Coding)의 In-Loop 필터 중 하나인 디블로킹 필터는 예측과 변환 블록 주변의 균일하지 않은 잡음을 제거하기 위해 사용된다. 영상을 복원할 때 텍스쳐 정보의 경우, 디블로킹 필터로 눈에 보이는 잡음을 제거하는 데 유리하지만 깊이 정보는 깊이를 예측하여 합성하는 데 사용되므로 디블로킹 필터를 적용하면 합성에 방해가 될 수 있다. 이에 본 논문은 TMIV (Test Model 6 for MPEG Immersive Video) 인코더를 거쳐 나온 기본 시점과 추가 시점의 텍스쳐와 깊이 영상에 디블로킹 필터를 적용하여 BD-Rate의 향상 정도와 인지 화질적 관점에서의 화질 개선 여부를 실험을 통해 검증한다.

• Journal of Korea Multimedia Society
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• v.8 no.10
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• pp.1360-1368
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• 2005

PDP is the flat panel display, suitable for high definition television because of large-sire and high-brightness. It has many advantages such as fast response, wide viewing angle, low weight, and simple manufacturing process for fabrication. However, there are some disadvantages and one of them is the image quality degradation, which is dependent on the digital signal processing. Although image quality of PDP is improving by many researches and experimentations, it still isn't as good as that of CRT because of various factors. One of them is worm-like pattern generated by an error diffusion process. And the worm-like pattern is severely increased after an APL process. An increased worm-like pattern occur a drop of resolution in image and a change of CCT according to each grayscale. In this paper, a method for improvement of image quality using the error diffusion which considers the APL process is proposed. In the proposed method, the APL process is performed before the error diffusion process. Simulation results showed that the proposed method has better performances for resolution in images and CCT uniformity according to each grayscale than the conventional method.