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Effective Five Directional Partial Derivatives-Based Image Smoothing and a Parallel Structure Design
Choongsang Cho,Sangkeun Lee IEEE 2016 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.25 No.4
<P>Image smoothing has been used for image segmentation, image reconstruction, object classification, and 3D content generation. Several smoothing approaches have been used at the pre-processing step to retain the critical edge, while removing noise and small details. However, they have limited performance, especially in removing small details and smoothing discrete regions. Therefore, to provide fast and accurate smoothing, we propose an effective scheme that uses a weighted combination of the gradient, Laplacian, and diagonal derivatives of a smoothed image. In addition, to reduce computational complexity, we designed and implemented a parallel processing structure for the proposed scheme on a graphics processing unit (GPU). For an objective evaluation of the smoothing performance, the images were linearly quantized into several layers to generate experimental images, and the quantized images were smoothed using several methods for reconstructing the smoothly changed shape and intensity of the original image. Experimental results showed that the proposed scheme has higher objective scores and better successful smoothing performance than similar schemes, while preserving and removing critical and trivial details, respectively. For computational complexity, the proposed smoothing scheme running on a GPU provided 18 and 16 times lower complexity than the proposed smoothing scheme running on a CPU and the L0-based smoothing scheme, respectively. In addition, a simple noise reduction test was conducted to show the characteristics of the proposed approach; it reported that the presented algorithm outperforms the state-of-the art algorithms by more than 5.4 dB. Therefore, we believe that the proposed scheme can be a useful tool for efficient image smoothing.</P>
Numerical twin image suppression by nonlinear segmentation mask in digital holography.
Cho, ChoongSang,Choi, ByeongHo,Kang, HoonJong,Lee, SangKeun Optical Society of America 2012 Optics express Vol.20 No.20
<P>The in-line holography has obvious advantages especially in wider spatial bandwidth over the off-axis holography. However, a direct current(DC)-noise and an unwanted twin image should be separated or eliminated in the in-line holography for a high quality reconstruction. An approach for suppressing the twin image is proposed by separating the real and twin image regions in the digital holography. Specifically, the initial region of real and twin images is obtained by a blind separation matrix, and the segmentation mask to suppress the twin image is calculated by nonlinear quantization from the segmented image. For the performance evaluation, the proposed method is compared with the existing approaches including the overlapping block variance and manual-based schemes. Experimental results showed that the proposed method has a better performance at the overlapped region of the real and twin images. Additionally, the proposed method causes less loss of real image than the overlapping block variance-based scheme. Therefore, we believe that the proposed scheme can be a useful tool for high quality reconstruction in the in-line holography.</P>
Laplace Operation-Based DC Noise Reduction in Digital Holography
Choongsang Cho,Byeongho Choi,Hoonjong Kang,Sangkeun Lee IEEE 2013 Photonics Technology Letters Vol.25 No.12
<P>The in-line holography has obvious advantages especially in wider spatial bandwidth over the off-axis holography. However, a direct current (DC)-noise and an unwanted twin image should be separated or eliminated for a high quality reconstruction. Therefore, we introduce an effective Laplace operation-based numerical approach for DC-noise reduction in the in-line holography. The DC-noise in a holographic fringe pattern can be efficiently reduced by applying a second derivative operation while maintaining the two real and twin terms. For the performance evaluation, the proposed method is compared with the existing approaches, including the intensity average subtraction and frequency-domain filtering, which are generally used for the numerical holographic reconstruction. Experimental results show that the proposed method is numerically appropriate, and provides the high quality reconstruction for a digital holography. Therefore, we believe that the proposed scheme can be a useful tool for high quality reconstruction in the in-line holography.</P>
공간오디오 코딩기법을 사용한 UHD 오디오 변환 시스템에 대한 연구
조충상(Choongsang Cho),이영한(Yong Han Lee),김제우(Jewoo Kim) 한국방송·미디어공학회 2015 한국방송공학회 학술발표대회 논문집 Vol.2015 No.7
본 논문에서는 다양한 멀티 채널 오디오 규격들을 설명하고, 스테레오와 5.1 채널과 같이 기존에 많이 사용되고 있는 오디오 시스템 구조와 UHD 오디오 채널 시스템이 호환되기 위한 구조를 제안한다. 제안된 구조는 두 채널을 공간 오디오 코딩 기법으로 한 채널 오디오 신호화 공간 파라미터를 출력하는 구조를 기반으로 셋 채널을 한 채널로 변환하는 모듈과, 넷 채널을 한 채널로 변환하는 시스템을 설계한다. 이렇게 설계된 변환모듈을 이용하여, 22.2 채널을 10.2 채널로 변환하기 위한 구조와 10.2 채널을 5.1 채널로 변환하기 위한 다채널오디오 변환 시스템을 설계한다. 설계된 다채널 오디오 변환 구조를 실험하기 위하여 22.2 채널 오디오를 스테레오와 공간 파라미터로 변환하고, 다시 스테레오와 공간 파라미터를 이용하여 22.2 채널로 복원한 후 해당채널에 대한 비교를 수행한다. 실험에서 보이는 바와 같이 스테레오와 공간 파라미터로부터 본원 된 경우임에도 불구하고 원음에 매우 유사한 파형의 결과를 얻을 수 있다.