• 한국방사선학회논문지
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• 제12권1호
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• pp.85-91
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• 2018

전산화단층촬영기법은 투영 영상을 재구성하여 단면 영상을 획득하는 기법으로 다양한 분야에 적용되고 있다. 재구성된 영상의 공간분해능은 장치, 대상, 재구성 과정에 의존한다. 본 논문은 평행빔 구조에서 투영 영상의 개수 및 검출기의 픽셀 크기가 재구성된 영상의 공간분해능에 미치는 영향을 조사하였다. 재구성 프로그램은 Visual C++로 작성하였으며 단면 영상은 $512{\times}512$ 크기로 하였다. 공간분해능의 특성을 평가하기 위해 수학적 막대 팬텀을 구성하였고, Min-Max 방법을 도입하였다. 재구성에 사용되는 투영의 개수가 작은 경우 허상이 나타났으며 Min-Max도 낮았다. 투영의 개수를 지속적으로 증가시키면 재구성된 영상의 공간분해능을 나타내는 Min-Max는 상향 포화되었다. 검출기의 픽셀 크기를 재구성되는 단면 영상의 픽셀 크기의 50%로 줄이면 영상은 거의 완벽하게 복원되고, 검출기픽셀 크기가 증가할수록 Min-Max는 감소하였다. 본 연구는 CT장치 설계 시 요구되는 공간분해능을 달성하기 위해 필요한 검출기 및 회전 스테이지의 정밀도를 결정하는데 도움이 될 것이다.

• 한국컴퓨터정보학회논문지
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• 제16권6호
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• pp.71-77
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• 2011

본 논문에서는 번호판 인식 시스템에서 번호판 영상의 화질 개선을 위하여 국부 블록(Local block : LB) 학습기반의 초해상도 알고리즘을 제안한다. 본 논문에서 국부 블록은 영상 내에서 정보를 담고 있는 최소 단위로 정의하였으며, 학습의 기본 단위가 된다. 제안된 방법은 먼저 다양한 환경에 적합한 훈련 국부 블록 set을 생성하였다. 훈련 국부 블록 set은 고해상도 국부 블록과 저해상도 국부 블록의 순서쌍으로 구성되며 다양한 크기의 번호판과 열화 영상에 대응하기 위하여 다양한 크기와 열화를 갖는 저해상도 국부 블록 훈련 set을 구성하였다. 그 다음으로는 저해상도 입력 영상에서 복원해야할 정보를 훈련 국부 블록 set에서 추출/융합하는 과정을 제안하였다. 모의 실험결과, 열화된 저해상도 번호판 영상에 대해 제안한 방법이 효과적인 복원 성능을 나타내는 것을 확인할 수 있었다.

• 천문학회보
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• 제44권2호
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• pp.70.4-70.4
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• 2019

Image super-resolution (SR) is a technique that enhances the resolution of a low resolution image. In this study, we use three SR models (RCAN, ProSRGAN and Bicubic) for enhancing solar SDO/HMI magnetograms using deep learning. Each model generates a high resolution HMI image from a low resolution HMI image (4 by 4 binning). The pixel resolution of HMI is about 0.504 arcsec. Deep learning networks try to find the hidden equation between low resolution image and high resolution image from given input and the corresponding output image. In this study, we trained three models with HMI images in 2014 and test them with HMI images in 2015. We find that the RCAN model achieves higher quality results than the other two methods in view of both visual aspects and metrics: 31.40 peak signal-to-noise ratio(PSNR), Correlation Coefficient (0.96), Root mean square error (RMSE) is 0.004. This result is also much better than the conventional bi-cubic interpolation. We apply this model to a full-resolution SDO/HMI image and compare the generated image with the corresponding Hinode NFI magnetogram. As a result, we get a very high correlation (0.92) between the generated SR magnetogram and the Hinode one.

• Journal of Yeungnam Medical Science
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• 제31권2호
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• pp.152-156
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• 2014

We report on a patient who showed visual recovery following bilateral occipital lobe infarct, as evaluated by follow up functional magnetic resonance imaging (fMRI) and diffusion tensor tractography (DTT). A 56-year-old female patient exhibited severe visual impairment since onset of the cerebral infarct in the bilateral occipital lobes. The patient complained that she could not see anything, although the central part of the visual field remained dimly at 1 week after onset. However, her visual function has shown improvement with time. As a result, at 5 weeks after onset, she notified that her visual field and visual acuity had improved. fMRI and DTT were acquired at 1 week and 4 weeks after onset, using a 1.5-T Philips Gyroscan Intera. The fiber number of left optic radiation (OR) increased from 257 (1-week) to 353 (4-week), although the fiber numbers for right OR were similar. No activation in the occipital lobe was observed on 1-week fMRI. By contrast, activation of the visual cortex, including the bilateral primary visual cortex, was observed on 4-week fMRI. We demonstrated visual recovery in this patient in terms of the changes observed on DTT and fMRI. It appears that the recovery of the left OR was attributed more to resolution of local factors, such as peri-infarct edema, than brain plasticity.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.18-21
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• 2008

Lee (2008) proposed the pansharpening method to reconstruct at the higher resolution the multispectral images which agree with the spectral values observed from the sensor of the lower resolution values. It outperformed over several current techniques for the statistical analysis with quantitative measures, and generated the imagery of good quality for visual interpretation. However, if a small object stretches over two adjacent pixels with different spectral characteristics at the lower resolution, the pixels of the object at the higher resolution may have different multispectral values according to their location even though they have a same intensity in the panchromatic image of higher resolution. To correct this problem, this study employed an iterative technique similar to the image restoration scheme of Point-Jacobian iterative MAP estimation. The effect of pansharpening on image segmentation/classification was assessed for various techniques. The method was applied to the IKONOS image acquired over the area around Anyang City of Korea.

• ETRI Journal
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• 제32권3호
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• pp.390-394
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• 2010

In this paper, we propose a new super-resolution technique based on interpolation of the high-frequency subband images obtained by discrete wavelet transform (DWT) and the input image. The proposed technique uses DWT to decompose an image into different subband images. Then the high-frequency subband images and the input low-resolution image have been interpolated, followed by combining all these images to generate a new super-resolved image by using inverse DWT. The proposed technique has been tested on Lena, Elaine, Pepper, and Baboon. The quantitative peak signal-to-noise ratio (PSNR) and visual results show the superiority of the proposed technique over the conventional and state-of-art image resolution enhancement techniques. For Lena's image, the PSNR is 7.93 dB higher than the bicubic interpolation.

• 대한원격탐사학회지
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• 제16권1호
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• pp.87-98
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• 2000

상업위성에서 공급되는 고해상도영상의 활용을 증대하기 위한 영상합성에 대한 관심이 증가하고 있다. 합성에 사용된 고해상도 흑백영상과 저해상도 다중분광영상은 항공기탑재 다중분광 주사기에 의해 촬영된 네 밴드의 영상을 이용하여 모의 제작하였다. 모의 합성된 2rl 해상도의 흑백 영상과 Bnl 해상도의 네 밴드 영상에 대하여 다섯 가지 합성방법(MWD, ItIS, PCA, HPF, CN, PCA) 을 적용하였다. 합성된 영상에 대해서 원래 영상들이 가지고 있던 공간해상도와 분광정보 측면의 특성을 분석하고자, 육안판독, 통계치비교, semivariogram, 분광반사특성 등을 비교하였다. MWD 변환방법에 의하여 합성된 영상이 공간해상도 및 분광정보 측면에서 모두 합성에 사용된 원래 영상과 근접한 결과를 보였다.

• 대한원격탐사학회지
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• 제39권4호
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• pp.459-466
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• 2023

In the last decade, artificial intelligence's dramatic advancement with the development of various deep learning techniques has significantly contributed to remote sensing fields and satellite image applications. Among many prominent areas, super-resolution research has seen substantial growth with the release of several benchmark datasets and the rise of generative adversarial network-based studies. However, most previously published remote sensing benchmark datasets represent spatial resolution within approximately 10 meters, imposing limitations when directly applying for super-resolution of small objects with cm unit spatial resolution. Furthermore, if the dataset lacks a global spatial distribution and is specialized in particular land covers, the consequent lack of feature diversity can directly impact the quantitative performance and prevent the formation of robust foundation models. To overcome these issues, this paper proposes a method to generate benchmark datasets by simulating the modulation transfer functions of the sensor. The proposed approach leverages the simulation method with a solid theoretical foundation, notably recognized in image fusion. Additionally, the generated benchmark dataset is applied to state-of-the-art super-resolution base models for quantitative and visual analysis and discusses the shortcomings of the existing datasets. Through these efforts, we anticipate that the proposed benchmark dataset will facilitate various super-resolution research shortly in Korea.

• Journal of Mechanical Science and Technology
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• 제17권10호
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• pp.1411-1422
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• 2003

The detection of free spaces between obstacles in a scene is a prerequisite for navigation of a mobile robot. Especially for stereo vision-based navigation, the problem of correspondence between two images is well known to be of crucial importance. This paper describes multi-range approach of area-based stereo matching for grid mapping and visual navigation in uncertain environment. Camera calibration parameters are optimized by evolutionary algorithm for successful stereo matching. To obtain reliable disparity information from both images, stereo images are to be decomposed into three pairs of images with different resolution based on measurement of disparities. The advantage of multi-range approach is that we can get more reliable disparity in each defined range because disparities from high resolution image are used for farther object a while disparities from low resolution images are used for close objects. The reliable disparity map is combined through post-processing for rejecting incorrect disparity information from each disparity map. The real distance from a disparity image is converted into an occupancy grid representation of a mobile robot. We have investigated the possibility of multi-range approach for the detection of obstacles and visual mapping through various experiments.

• 인지과학
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• 제26권4호
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• pp.453-481
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• 2015

본 연구는 시각작업기억의 표상 특성에 대해 상반되는 주장을 펼치고 있는 고정해상도 슬롯 모형과 탄력적 자원 모형을 개관하고, 두 모형 간 상충을 해소하기 위한 노력이 필요함을 강조하였다. 이를 위해 고정해상도 슬롯과 탄력적 자원 모형을 태동시킨 객체 및 병렬 저장 가설을 살펴보고 두 모형의 상반되는 주장에 대한 이론적 근거를 소개하였다. 다음으로 두 모형을 지지한 구체적인 연구 사례를 통해 경험적 지지 증거의 객관성을 평가하고 관련 신경생리학적 모형에 대한 이해를 시도하였다. 마지막으로 두 모형 간의 상충을 해소하기 위한 이론적 그리고 방법론적 재고와 이를 달성하기 위한 수렴적 증거 확보의 필요성을 강조하였다.