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Color correction without color patterns for stereoscopic camera systems
Youngbae Hwang,Je Woo Kim,Byeong Ho Choi,Wangheon Lee 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
Color consistency between image pairs from stereo camera systems is crucial for 3D display systems as well as depth estimation by stereo matching. Even though we use the same type of cameras with the same hardware settings, color response can be significantly different due to the variation of lighting conditions and radiometric characteristics. In this paper, we propose a color correction method for stereoscopic camera systems. Previously, color patterns were used to search out color matches between two or multiple images. In spite of accurate estimation of the previous work, using color patterns has the limitation for various applications. Without color patterns, we automatically find correspondences of a stereo pair using feature detection and RANSAC-based stereo matching. Then, by calculating color transform matrix, we reduce color discrepancy between the stereo pair. The accuracy of color correction is dependent on feature detectors, matching procedures and color transform methods. Experimental results show that appropriate types of them should be chosen according to target applications in the view of the processing time and accuracy.
Application of Artificial Intelligence in Capsule Endoscopy: Where Are We Now?
Youngbae Hwang,박준석,Yun Jeong Lim,Hoon Jai Chun 대한소화기내시경학회 2018 Clinical Endoscopy Vol.51 No.6
Unlike wired endoscopy, capsule endoscopy requires additional time for a clinical specialist to review the operation and examine thelesions. To reduce the tedious review time and increase the accuracy of medical examinations, various approaches have been reportedbased on artificial intelligence for computer-aided diagnosis. Recently, deep learning–based approaches have been applied to manypossible areas, showing greatly improved performance, especially for image-based recognition and classification. By reviewing recentdeep learning–based approaches for clinical applications, we present the current status and future direction of artificial intelligence forcapsule endoscopy.
황영배(Youngbae Hwang),김제우(Je Woo Kim),최병호(Byeong Ho Choi) 한국방송·미디어공학회 2011 한국방송공학회 학술발표대회 논문집 Vol.2011 No.7
두 카메라 혹은 다수의 카메라에서의 컬러 보정은 알고리즘의 성능 향상 및 양안식 3D 카메라에서 매우 중요한 기술이다. 최근 컬러 보정 방법들이 다수 제안되었지만 이 방법들의 결과에 대한 정확한 측정 방법이 많지 않으며 기존의 측정 방법은 두 영상이 카메라의 위치에 따른 서로 다른 장면을 가지고 있을 경우에 적합하지 않을 수 있다. 본 논문에서는 컬러 보정을 위한 컬러 간의 유사성 측정 기법을 제안한다. 이 기법은 대상이 되는 두 영상의 장면이 일치하지 않는 경우를 고려하여 대응점 검색을 통해 두 장면 간의 같은 컬러를 가져야 하는 대응점을 찾고 이 대응점 주위의 영역으로부터 통계치를 계산하여 컬러의 유사성을 비교한다. 이 경우 두 영상의 위치 변화에 따른 장면 변화와 대응점의 약간의 어긋남에 대해서 고려할 수 있다. 또한 대응점들이 영상의 모든 영역을 포함하지 않을 수 있기 때문에 전체 영상의 통계치를 계산하여 컬러의 유사성을 비교도 동시에 수행하여 결과적인 컬러의 유사성은 대응점 기반과 전체 영상 기반의 유사성의 가중치의 합으로 결정되며 이 가중치는 대응점 기반의 컬러 비교가 영상 내의 얼마만큼의 영역을 포함하는지에 따라서 결정된다.
Recent Development of Computer Vision Technology to Improve Capsule Endoscopy
박준석,Youngbae Hwang,Ju-Hong Yoon,Min-Gyu Park,Jungho Kim,Yun Jeong Lim,Hoon Jai Chun 대한소화기내시경학회 2019 Clinical Endoscopy Vol.52 No.4
Capsule endoscopy (CE) is a preferred diagnostic method for analyzing small bowel diseases. However, capsule endoscopes capturea sparse number of images because of their mechanical limitations. Post-procedural management using computational methodscan enhance image quality. Additional information, including depth, can be obtained by using recently developed computer visiontechniques. It is possible to measure the size of lesions and track the trajectory of capsule endoscopes using the computer visiontechnology, without requiring additional equipment. Moreover, the computational analysis of CE images can help detect lesions moreaccurately within a shorter time. Newly introduced deep leaning-based methods have shown more remarkable results over traditionalcomputerized approaches. A large-scale standard dataset should be prepared to develop an optimal algorithms for improving thediagnostic yield of CE. The close collaboration between information technology and medical professionals is needed.
Statistical analysis of interfacial gap in a cementless stem FE model.
Park, Youngbae,Choi, Donok,Hwang, Deuk Soo,Yoon, Yong-San American Society of Mechanical Engineers 2009 Journal of biomechanical engineering Vol.131 No.2
<P>In cementless total hip arthroplasty, a fair amount of interfacial gap exists between the femoral stem and the bone. However, the effect of these gaps on the mechanical stability of the stem is poorly understood. In this paper, a finite element model with various interfacial gap definitions is used to quantify the effect of interfacial gaps on the primary stability of a Versys Fiber Metal Taper stem under stair climbing loads. In the first part, 500 random interfacial gap definitions were simulated. The resulting micromotion was approximately inversely proportional to the contact ratio, and the variance of the micromotion was greater with a lower contact ratio. Moreover, when the magnitude of the micromotion was compared between the gap definitions that had contact at a specific site and those that had no contact at that site, it was found that gaps located in the proximal-medial region of the stem surface had the most important effect on the micromotion. In a second trial, 17 gap definitions mimicking a gap pattern that has been observed experimentally were simulated. For a given contact ratio, the micromotion observed in the second trial was lower than the average result of those in the first, where the gaps were placed randomly. In either trial, when the contact ratio was higher than 40%, the micromotion showed no significant difference (first trial) or a gentle slope (-0.24 mum% in the second trial) in relation to the contact ratio. Considering the reported contact ratios for properly implanted stems, variations in the amount of interfacial gap would not likely cause a drastic difference in micromotion, and this effect could be easily overshadowed by other clinical factors. In conclusion, differences in interfacial gaps are not expected to have a noticeable effect on the clinical micromotion of this cementless stem.</P>