• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.353-356
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• 2000

최근 복잡한 실제 사물을 가상 공간상에 표현하기 위해 삼차원 모델을 많이 이용하고 있다. 기존의 삼차원 데이터 처리는 주로 정지 모델에 대해 기하학 정보와 위상학 정보를 표현하거나 다중 해상도(Level of Details, LOD)로 나타내는데 역점을 두었다. 그러나 네트웍을 통한 가상 공간에서 삼차원 애니메이션에 대한 응용이 점차 늘어남에 따라 이러한 데이터를 효율적으로 압축하여 전송하거나 저장할 필요가 생겼다 본 논문에서는 삼차원 애니메이션 모델의 공간적 또는 시간적 상관 관계를 이용하여 삼차원 모델 정보를 부호화하는 방법을 제안한다. 먼저 주어진 모델의 움직임을 분석하고 이를 (r,θ,ø)의 구 좌표계로 변환한 후 (θ,ø)의 분포에 따라 모델을 분할(Segmentation)한다. 그리고 움직임 벡터는 Affine 변환을 이용하여 삼차원 공간에서의 움직임을 정의한다. Key프레임에 해당하는 정지 모델의 기하학 정보와 위상학 정보를 압축하고, LOD 기술을 적용하여 손실 혹은 무손실로 부호화하여 전송한다. 또한 Key프레임 사이의 화면에서는 선형 또는 비선형 보간법으로 각 분할 부분을 복원하고, 이를 조합하여 전체적인 삼차원 모델을 복원한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.331-332
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• 2011

디저털 홀로그래피는 CCD를 이용하여 간섭 패턴을 기록하고 기록된 간섭무늬에 담겨진 물체의 정보로 입체영상을 복원하는 기술을 말하며, 현미경을 이용한 디지털 홀로그래피 기술은 3D 형상 복원이나 바이오포토닉스 등 다양한 분야에서 사용되고 있다. 하지만, 디지털 홀로그래피 기술은 촬영된 간섭패턴에서 픽셀의 위상차가 레이저 파장의 1/2 이상일 경우, 기존의 phase unwrapping 알고리즘으로는 해당 픽셀의 위상차이를 계산할 수 없는 문제가 있다. 이와 같은 문제를 해결하기 위해 본 논문에서는 다수의 홀로그램 영상과 깊이맵을 사용하여 완전한 형태의 깊이맵을 구하는 방법을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.978-985
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• 2000

Blind equalizers recover the transmitted data using statistical characteristics of the signal alone. Among many alternatives, steepest gradient descent type algorithms such as the CMA and Sato algorithm are most widely utilized in practice. In this paper we propose a dual-mode NCMA algorithm, which combines the advantages of the dual mode CMA and Normalized CMA (NCMA) with the dual mode phase recovery algorithm. In addition, we perform computer simulations to demonstrate the performance improvement of the proposed algorithm with a QAM system. Simulation results show that the presented algorithm has a faster convergence speed and smaller steady-state residual error than the CMA and dual-mode CMA.

• Broadcasting and Media Magazine
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• v.18 no.3
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• pp.95-108
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• 2013

디지털 홀로그래픽 현미경이나 정량적 위상 현미경(quantitative phase microscopy)과 같은 기존의 간섭현미경은 3차원 이미징 기술로 분류되는데, 이는 획득한 이미지의 복소장(complex field)을 계산을 통해 다른 깊이로 전파시킬 수 있기 때문이다. 그러나 엄밀한 의미에서는 하나의 복소장 이미지는 단지 2차원 맵이기 때문에 근본적으로는 샘플의 2차원 정보만을 가지고, 물체의 3차원 구조의 일부분을 측정하는 것에 지나지 않는다. 본 논문에서는 1969년에 Wolf가 제안한[1,2] 홀로그래픽 회절 토모그래피(Optical Diffraction Tomography: ODT)를 실험적으로 구현한 3차원 위상 현미경(Tomographic Phase Microscopy: TPM)을 소개하고자 한다. TPM은 샘플을 다양한 각도로 조명하여 서로 다른 입사각에 대해 복소장 이미지를 얻고, ODT를 통해서 샘플의 3차원 구조를 복원해내는 기술이다. 보다 구체적으로는 다양하고 독립적인 2차원 이미지들을 샘플의 3차원 푸리에 공간에 맵핑함으로써 샘플 단면의 흡수율과 굴절률을 복원할 수 있다. 굴절률은 분자 농도와 비례하기 때문에, 살아있는 세포에 대한 굴절률의 3차원 맵을 얻을 수 있으면 세포 내부의 분자 구성을 연구할 수 있고, 이를 통해 다양한 생의학적 응용을 연구할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.5
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• pp.1078-1084
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• 2010

This paper presents a speech enhancement system which restores the amplitude components and phase components by discrete Fourier transform (DFT), using neural network training by back-propagation algorithm. First, a neural network is trained using DFT amplitude components and phase components of noisy speech signal, then the proposed system enhances speech signals that are degraded by white noise using a neural network. Experimental results demonstrate that speech signals degraded by white noise are enhanced by the proposed system using the neural network, whose inputs are DFT amplitude components and phase components. Based on measuring spectral distortion measurement, experiments confirm that the proposed system is effective for white noise.

• The Journal of the Acoustical Society of Korea
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• v.11 no.2
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• pp.5-14
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• 1992

In the fields of astronomy, communication, X-ray crystallography, and engineering, it is a very important and useful fact that the original signal can be reconstructed from a partial information, only spectral magnitude or phase, of the signal. In this paper, we proposed a modified iterative algorithm to solve the Magnitude Retrieval Problem (MRP) for 1-D, 2-D signals. In oder to accelerate the convergence rate, the unit constant initial function which is used in the references is replaced by the exponential initial function for the modified adaptive iterative method. As a result, MRP with 1-D signal and low-pass detail image is significantly enhanced from an iterative convergence rate and a computer storage memory points of view.

• The Journal of the Acoustical Society of Korea
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• v.19 no.7
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• pp.28-33
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• 2000

For efficient quantization of speech representation, it is common to incorporate Perceptual characteristics of human hearing. However, the focus has been confined only to the magnitude information of speech, and little attention has been paid to phase information. This paper presents a novel approach, termed perceptually irrelevant phase elimination (PIPE), to find out irrelevant phase information of acoustic signals in terms of perception. The proposed method, which is based on the observation that the relative phase relationship within a critical band is perceptually important, is derived not only for stationary Fourier signal but also for harmonic signal. The proposed method is incorporated into the analysis/synthesis system based on harmonic representation of speech, and subjective test results demonstrate the effectiveness of proposed method.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.1
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• pp.29-35
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• 2003

In this paper, we propose an improved image decryption system using a phase-encoded image and the principle of interference. An original image and a random image consist of only binary values. The phase-encoded original image is encrypted into a binary phase-only image by multiplying with a phase-encoded random key. Therefore the phase-encoded images have two phase values 0 or $\pi$. The proposed decryption technique is simply performed by interfering between a reference wave and a direct pixel-to-pixel mapping of the encrypted image with a decrypting key. Optical experiments confirmed that the proposed technique is a simple and robust architecture for optical encryption.

• The Journal of the Acoustical Society of Korea
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• v.32 no.1
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• pp.71-78
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• 2013

This paper describes a multiple audio watermarking using Quantization Index Modulation (QIM) on frequency phase and magnitude response. Proposed embedding procedure is composed of two stage. At the first stage, the watermark is embedded on the frequency phase response using QIM. In the second stage, the watermark is embedded using adaptive QIM with the step-size that is adaptively determined using the maximum value of the frequency magnitude response of every frame. The watermark is extracted by calculating the Euclidean distance as the blind detection. The proposed method is robust against most of attacks of audio watermark benchmarking. For the Fourier attacks, the proposed method shows over 95% recovery rate.

• Journal of Korea Multimedia Society
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• v.5 no.4
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• pp.426-433
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• 2002

In this paper, we have studied the images which have been reconstructed by using combination of images acquired by the variation of operating frequency. When inner images have been reconstructed, they have been superposed by the surface state effect. In this case, the images of the phase object can be enhanced by the contrast of inner images. In this experiment, there are two kinds of specimens, one is a reference block haying 1/4T, 1/2T, 3/4T side drilled holes as main run piping material 111 the steam generator in NPP(Neuclear Power Plant)s and the another is a part of a hemisphere type specimen having about 1-2㎜ distance gap. It has been shown that the two results of defect shapes have better than before in this processing and phase contrast grow about twice. And we have constructed the acoustic microscope by using a quadrature detector that enables to acquire the amplitude and phase of the reflected signal simultaneously Further more ore have studied the reconstruction method of the amplitude and phase images and the enhancement method of the defect images contrast.