• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.355-356
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• 2009

• 한국광학회:학술대회논문집
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• 한국광학회 2004년도 하계학술발표회
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• pp.142-143
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• 2004

• 한국통신학회논문지
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• 제28권3A호
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• pp.151-156
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• 2003

Millimeter waves are potentially useful for high resolution ranging and imaging in low optical visibility conditions such as fog and smoke. Also, They can be used for wide band communications since the currently used spectrum bands are already crowded. However, it is necessary to develop a theoretical and experimental understanding of millimeter wave propagation to assess the performance of millimeter wave systems. The intensity fluctuations and mutual coherence function (MCF) describe atmospheric effects on the millimeter wave propagation. Using the quasi-optical method (QOM), a practical and efficient method is suggested to obtain MCF from the flux measurement in the antenna focal plane.

• 전자공학회논문지B
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• 제33B권2호
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• pp.47-55
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• 1996

A microwave incoherent imaging method for a conducting cyliner by using multi-frequency tiem-harmonic field is presented in this study. In this paper, an incoherent intensity pattern of th econducting cylinder is obtained by averagin gout the multi-frequency intensities of the coherent field such as the time-harmonic field scattered from this cylinder. This phenomenon is hsown numerically in scattering by a conducting circular cylinder illuminated by the time-harmonic plane wave, and is interpreted analytically by the mutual coherence functon defined as a frequency-averaged intensity of the time-harmonic fields in th frequency domain.

• 전자통신동향분석
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• 제36권5호
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• pp.1-8
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• 2021

Over the last three decades, the development of Ti:sapphire femtosecond lasers has led to advancements in scientific and industrial fields. In particular, these advanced lasers show great potential for applications with bio-imaging and medical surgery, such as two-photon microscopy, nonlinear Raman microscopy, optical coherence tomography, and ophthalmic surgery. Herein, we present a detailed description of the theoretical and experimental physics of Kerr-lens mode-locked femtosecond Ti:sapphire lasers and its two-photon microscopy.

• 한국광학회지
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• 제20권6호
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• pp.334-338
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• 2009

최근 디스플레이 기기의 수요가 증대되면서 대면적 노광에 대한 요구가 증대되고 있는데, 내부전반사(total internal reflection: TIR)홀로그래픽 리소그라피는 대면적 노광을 위한 효과적인 방법으로 연구가 진행되고 있다. TIR 홀로그래피에서는 일반적으로 레이저를 이용하여 영상을 기록하고 재생한다. 그러나 자외선 램프와 같은 비가간섭광을 이용하여 재생한다면, 가간섭성에 의해 나타나는 영상잡음을 줄일 수 있고, 대면적 노광에도 보다 용이할 것이다. TIR 홀로그램의 재생을 위하여 자외선 램프를 이용할 때, 램프의 유한한 선폭과 확산각이 재생 영상에 미치는 영향을 분석하고, 재생패턴에 나타나는 선폭 확대 결과를 실험을 통하여 검증하였다. ${\mu}m$ 규모의 선폭을 갖는 대면적 패턴을 TIR 홀로그램으로부터 얻기 위한 재생 광원으로, 가간섭성 광원인 레이저 대신 저잡음성과 경제성을 갖춘 일반적인 자외선 램프의 사용이 가능할 것으로 기대된다.

• Korean Journal of Ophthalmology
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• 제32권6호
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• pp.470-477
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• 2018

Purpose: To investigate the relationship between the progression of visual field (VF) loss and changes in lamina cribrosa depth (LCD) as determined by spectral-domain optical coherence tomography (SD-OCT) enhanced depth imaging in patients with primary open angle glaucoma (POAG). Methods: Data from 60 POAG patients (mean follow-up, $3.5{\pm}0.7$ years) were included in this retrospective study. The LCD was measured in the optic disc image using SD-OCT enhanced depth imaging scanning at each visit. Change in the LCD was considered to either 'increase' or 'decrease' when the differences between baseline and the latest two consecutive follow-up visits were greater than the corresponding reproducibility coefficient value ($23.08{\mu}m$, as determined in a preliminary reproducibility study). All participants were divided into three groups: increased LCD (ILCD), decreased LCD (DLCD), and no LCD change (NLCD). The Early Manifest Glaucoma Trial criteria were used to define VF deterioration. Kaplan-Meier survival analysis and Cox's proportional hazard models were performed to explore the relationship between VF progression and LCD change. Results: Of the 60 eyes examined, 35.0% (21 eyes), 28.3% (17 eyes), and 36.7% (22 eyes) were classified as the ILCD, DLCD, and NLCD groups, respectively. Kaplan-Meier survival analysis showed a greater cumulative probability of VF progression in the ILCD group than in the NLCD (p < 0.001) or DLCD groups (p = 0.018). Increased LCD was identified as the only risk factor for VF progression in the Cox proportional hazard models (hazard ratio, 1.008; 95% confidence interval, 1.000 to 1.015; p = 0.047). Conclusions: Increased LCD was associated with a greater possibility of VF progression. The quantitative measurement of LCD changes, determined by SD-OCT, is a potential biomarker for the prediction of VF deterioration in patients with POAG.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.101-106
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• 2004

In this paper, a blood vessel in an angiographic image, which plays an importance role in the diagnose diseases including in the eyes, brain and heart, is enhanced by using a directed diffusion technique. A fundamental component of the angiographic analysis is vessel segmentation that the proposed method provides a preprocessing of the image into a form suitable for human analysis, or more importantly, for machine analysis such the segmentation. Vessel enhancement is a challenging problem due to the complex nature of vascular trees and to imaging imperfections. Some parts of the inherent imperfections in angiography are the intensity inhomogeneity between the larger and smaller vessels, and another imperfection is the leakage of contrast agent into the background tissue that provides to low contrast between vessels and tissue. In the proposed scheme, the directed diffusion solves the problem by formulating a local geometric structure, which consists of direction and scale of the blood vessels. The diffusion process uses the local structure to enhance by a diffusivity tensor. The proposed algorithm can be applied to maintain sharpness and coherence-smooth the intra-regions into homogeneity better than traditional diffusion methods, which are Gaussian regulation and coherence enhancing diffusion.

• 한국멀티미디어학회논문지
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• 제20권8호
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• pp.1291-1298
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• 2017

Optical coherence tomography (OCT) is the most common medical imaging device with the ability to image the retina in eyes at micrometer resolution and to visualize the pathological indicators of many retinal diseases such as Age-Related Macular Degeneration (AMD) and diabetic retinopathy. Accordingly, there have been research activities to analyze and process OCT images to identify those indicators and make medical decisions based on the findings. In this paper, we use a deep convolutional neural network for analysis of OCT volume data to distinguish AMD from normal patients. We propose a novel approach where images in each OCT volume are grouped together into sub-volumes and the network is trained by those sub-volumes instead of individual images. We conducted an experiment using public data set to evaluate the performance of the proposed approach. The experiment confirmed performance improvement of our approach over the traditional image-by-image training approach.

• 대한의용생체공학회:의공학회지
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• 제34권3호
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• pp.135-140
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• 2013

We have developed an ultra wide-field of view Optical Coherence Tomography(OCT) which has capability to 2D and 3D views of cross-sectional structure of in vivo human retina. Conventional OCT has a limitation in visualizing the entire retina due to a reduced field of view. We designed an optical setup to significantly improve the lateral scanning range to be more than 20 mm. The entire human retinal structure in 2D and 3D was reported in this paper with the developed OCT system. Also, we empirically searched an optimized image size for real time visualization by analyzing variation of the frame rate with different lateral scan points. The size was concluded to be $1024{\times}2000{\times}300$ pixels which took 9 seconds for visualization.