• 한국음향학회지
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• 제32권1호
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• pp.22-31
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• 2013

본 논문에서는 전송된 수중통신신호로부터 MMSE(Minimun Mean Squared Error) 기법으로 채널 응답을 추정하고, CFAR(Constant False Alarm Rate) 기법을 이용하여 응답성분의 전력을 기준으로 채널의 지배적인 응답을 자동적으로 구하는 방법을 제안한다. 그리고 표류상태의 송수신단을 이용한 해상실험 데이터로부터 얻은 지배적인 응답에서 응답세기 분포와 위상 변화 그리고 시간 상관도를 산출하여 통계적 특성을 분석한다. 제안된 방법을 이용하여 구해진 통계적 특성을 실제 측정 데이터에 적용했을 때 모든 데이터 구간에서의 채널을 추정하지 않더라도 모든 데이터 구간에서의 채널을 추정하는 경우보다 비트 오류율이 약 1.2배로 차이가 크지 않음을 보였다.

• Journal of the Optical Society of Korea
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• 제19권1호
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• pp.55-62
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• 2015

In this study we demonstrate ultrahigh-resolution spectral domain optical coherence tomography (UHR SD-OCT) with a linear-wavenumber (k) spectrometer, to accelerate signal processing and to display two-dimensional (2-D) images in real time. First, we performed a numerical simulation to find the optimal parameters for the linear-k spectrometer to achieve ultrahigh axial resolution, such as the number of grooves in a grating, the material for a dispersive prism, and the rotational angle between the grating and the dispersive prism. We found that a grating with 1200 grooves and an F2 equilateral prism at a rotational angle of $26.07^{\circ}$, in combination with a lens of focal length 85.1 mm, are suitable for UHR SD-OCT with the imaging depth range (limited by spectrometer resolution) set at 2.0 mm. As guided by the simulation results, we constructed the linear-k spectrometer needed to implement a UHR SD-OCT. The actual imaging depth range was measured to be approximately 2.1 mm, and axial resolution of $3.8{\mu}m$ in air was achieved, corresponding to $2.8{\mu}m$ in tissue (n = 1.35). The sensitivity was -91 dB with -10 dB roll-off at 1.5 mm depth. We demonstrated a 128.2 fps acquisition rate for OCT images with 800 lines/frame, by taking advantage of NVIDIA's compute unified device architecture (CUDA) technology, which allowed for real-time signal processing compatible with the speed of the spectrometer's data acquisition.

• 한국통신학회논문지
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• 제22권10호
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• pp.2317-2328
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• 1997

본 논문은 융선의 방향정보를 사용하여 지문을 실시간 자동 인식하는 알고리즘을 제안한다. 융선의 방향정보는 웨이블렛 변환(WT) 그리고 경사 가우시안(gradient of Gaussian)과 코히리언스(coherence)로부터 얻어진 주된 국부 방향(dominant local orientation)을 사용하여 추출한다. 웨이블렛 변환의 적용은 기존에 제안된 알고리즘들에 포함되어 있는 평활화(smoothing), 이진화(binarization), 세션화(thinning) 및 보정(restoration)등 여러 전처리 과정의 생략을 의미하며, 따라서 제안하는 알고리즘의 실시간 처리를 가능하게 한다. 지문 인식은 웨이블렛 변환상에서 3개의 영역-크기가 1/4로 작아진 영역(LL), 수직 성분이 강조된 영역(LH), 그리고 수평 영역이 강조된 영역(HL)-에 나타나는 주된 국부 방향을 사용하여 빠르고 효율적으로 수행된다. 제안한 알고리즘은 SunSparc-2 워크 스테이션 환경의 X-window에서 구현되었으며, $256{\times}256$ 화소 크기의 지문 영상에 적용하여 성능을 평가하였다. 그 결과, 상이한 지문을 동일 지문으로 오인식하는 Type II 에러율을 0%로 했을때, 동일 지문을 상이한 지문으로 오인식 하는 Type I 에러율은 2.5%로서 매우 좋은 성능을 보였다.

• 한국시뮬레이션학회논문지
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• 제10권3호
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• pp.95-103
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• 2001

Rendering of 3D terrain data in real-time is difficult because of its large scale. So, it is necessary to use level-of-detail(LOD) that uses fewer data, but makes almost similar image to the original. We present an algorithm for real-time LOD generation and rendering of 3D terrain data. The algorithm applies wavelet transform to the terrain data, and then generates quadtree based view-dependent LOD using wavelet coefficients that are the output of wavelet transform. It also uses frame-to-frame coherence and view culling for high frame rates.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.42-47
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• 2006

M-mode imaging of the in vivo murine myocardium using optical coherence tomography (OCT) is described. Application of conventional techniques (e.g. MRI, Ultrasound imaging) for imaging the murine myocardium is problematic because the wall thickness is less than 1.5 mm (20 g mouse), and the heart rate can be as high as six hundred beats per minute. To acquire a real-time image of the murine myocardium, OCT can provide sufficient spatial resolution ($10{\mu}m$) and imaging speed (1000 A-scans/s). Strong light scattering by blood in the heart causes significant light attenuation, which makes delineation of the endocardium-chamber boundary problematic. To measure the thickness change of the myocardium during one heart beat cycle, a myocardium edge detection algorithm is developed and demonstrated.

• 한국멀티미디어학회논문지
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• 제11권6호
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• pp.755-763
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• 2008

Silhouette is useful in computer graphics for a number of techniques such as non-photorealistic rendering, silhouette clipping, and blueprint generating. Methods for generating silhouette are classified into three categories: image-based, object-based, and hybrid-based. Hybrid-based method is effective in terms of time complexity but spatial coherence problem still remains. In this paper, we proposed a new hybrid-based method which produces 3D data for silhouette and also guarantees no spatial coherence problem. To verify the efficiency of the proposed algorithm, several experiments are conducted for various 3D models from simple to quite complex. Results show that our algorithm generates no gap between any two consecutive silhouette lines when the silhouette model is magnified significantly.

• Current Optics and Photonics
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• 제5권3호
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• pp.278-288
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• 2021

We propose a characterization method for the scattering property of microspheres using spectroscopic optical coherence tomography (OCT). To prove the effectiveness of the proposed method, we prepare solutions of different concentrations using microspheres ranging from 28 to 2300 nm in diameter. Time-frequency analysis is performed on the measured interference spectrum of each solution, and the resulting spectroscopic information is converted into histograms for centroid wavelengths. The histograms present a very sensitive response to changes in the concentration and size of microspheres. We classify them into three categories according to their characteristics. When the histogram of each category is replaced with the corresponding calculated value of the scattering coefficient, each category is mapped to a different scattering-coefficient region. It is expected that the proposed method could be used to investigate the optical characteristics of a biological sample from OCT images, which would be helpful for optical diagnostic and therapeutic applications.

• Medical Lasers
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• 제9권1호
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• pp.25-33
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• 2020

Optical-based imaging technology has high resolution and can assess images in real time. Numerous studies have been conducted for its application in the dental field. The current research introduces an oral camera that includes fluorescent imaging, a second study examining a 3D intraoral scanner applying a confocal method and a polarization structure that identifies the 3D image of a tooth, and finally, an optical coherence tomography technique. Using this technique, we introduce a new concept 3D oral scanner that simultaneously implements 3D structural imaging as well as images that diagnose the inside of teeth. With the development of light source technology and detector technology, various optical-based imaging technologies are expected to be applied in dentistry.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.281-282
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• 2008

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 하계학술발표회 논문집
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• pp.163-164
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• 2008