• 대한전자공학회논문지SP
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• 제49권4호
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• pp.58-66
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• 2012

다양한 방법으로 영상을 재현하는 많은 장치들이 있다. 그러나 지원할 수 있는 색의 범위인 색역의 차이 때문에 동일한 칼라 영상이 장치별로 서로 다르게 보이는 현상이 발생한다. 최근 색역 사상은 이미지내의 주변 픽셀에 적응적으로 색역 사상을 수행하는 방법인 공간적인 색역 사상이 많이 사용되고 있다. 그러나 공간적인 색역 사상 방법은 색상 이동, 후광 효과, 상세정보 보존에 대한 문제점을 가지고 있다. 본 논문에서는 기존의 색역 사상 방법에서 색역 밖 영역의 경계영역 보존으로 인해 상세정보 보존이 잘 되지 않는 문제점을 해결하기 위하여 입력 영상의 정보를 활용해서 영상의 상세정보를 보존하는 공간적인 색역 사상 방법을 제안한다. 제안한 방법은 먼저, 입력 영상을 색역 절단 방법을 이용해서 색역 사상을 수행하고 입력 영상과 색역 사상된 영상을 각각 저역 통과 필터링 한 후, 입력 영상의 상세정보과 색역 사상된 영상의 상세정보를 계산한다. 제안한 방법의 상세정보는 입력영상의 상세정보와 색역 사상된 영상의 상세정보의 차로 구할 수 있다. 마지막으로 제안한 방법으로 구한 상세정보를 색역 사상된 영상에 더 해줌으로써 상세정보가 보상된 영상을 얻게 된다. 그리고 상세정보 보상과정에서 색역 밖으로 나간 값을 색역 안으로 넣어주기 위해 다시 색역 절단 방법을 이용한 색역 사상을 수행해서 결과 영상을 얻는다. 제안한 방법을 모니터와 프린터 간에 색재현에 적용하는 실험을 통해 보다 선명하고 대비가 높은 영상 얻을 수 있다.

• 한국의학물리학회지:의학물리
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• 제19권4호
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• pp.269-275
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• 2008

슬관절 퇴행성 질환을 진단하기 위하여 자기공명영상(magnetic resonance imaging: MRI)이 많이 사용되지만 간혹 슬관절 병후 및 예후를 잘못 진단하는 경우가 종종 발생한다. 본 연구에서는 슬관절 질환의 진단에 도움을 주기 위하여 자화전이(magnetization transfer: MT) 영상법을 소개하고자 한다. 슬관절 환자 7명으로부터 스핀 에코(SE) T2 강조 영상(3,400-3,500/90-100 ms)과 슬관절 환자 7명으로부터 FSE T2 강조 영상(4,500-5,000/100-108 ms)과 또한 슬관절 환자 3명으로부터 gradient echo (GRE) T2 강조 영상들(9/4.56 ms, 50 flip angle, NEX 1)을 획득하였다. 6명의 슬관절 환자에서 지방 억제가능 T2 강조 STIR 펄스시퀀스(TR/TE=2894-3215 ms/70 ms, NEX 3, ETL 9)를 사용하였다. 지방 포화도에 있어서 위상감도 방법은 Larmor frequency 차이에 따른 위상 차이를 이용하므로, 각각의 픽셀에 대한 자화전이율(magnetization transfer ratio: MTR)의 측정은 포화된 영상과 포화되지 않은 영상의 비율에 따라 산출하였다. 따라서 각 입력된 영상들은 동차원성을 가지고, 시각적으로 신호강도 정도가 회색의 명암도만으로 평가될 수 있기 때문에 생리학적, 정량적 진단을 위하여 3차원 등방성 체적영상과 자기공명 삼원색을 매핑하였고 정량적 특정은 자화전이율 지도로서 표현하였다. 자화전이율 영상은 병변 부위에서 높은 대조도를 나타내어 환자의 병태를 추적하는데 도움을 주었고 정량화하였다. 자화전이율 영상들과 기존의 MRI 사이에 명암도 차이는 회색상으로 표현되며, 자화전이율 영상화의 효과에 대해 프로파일 그래프는 자화전이 펄스로 인하여 신호강도에 있어서 정량적 측정값이 상대적으로 감소하였다. 슬관절의 정확한 병리상태를 진단하기 위해 프로파일 그래프의 측정값을 영상과 함께 표현하였다. 본 연구에서 수행한 예비적 데이터들을 통하여 슬관절의 자화전이율 영상들이 매우 임상학적으로 유용함을 확인하였다. 자화전이율 영상에 대한 물리적 변화를 관찰함으로써 자화전이율 영상에 대한 물리적, 기술적 기반에 대한 더 많은 통찰력을 제공할 수 있다. 무릎 질환 환자의 자화전이율 영상들을 이용하여 매우 높은 대조도를 확보할 수 있으므로 슬관절 질환의 정밀 진단에 매우 도움을 줄 수 있다.

• 대한치과기공학회지
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• 제37권4호
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• pp.213-218
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• 2015

Purpose: The purpose of this study compared of reproducibility of prepared tooth impression scanning utilized with white and blue light scanners. Methods: To evaluate reproducibility with white and blue light scanners, the impression of premolar were rotated by $10^{\circ}{\sim}20^{\circ}$ and scanned. These data were compared with the first 3-D data (STL file), and the error sizes were measured (n=5). Independent t test was used to evaluation the reproducibility of impression of premolar with white versus blue light scanners through discrepancies of mean, RMS (${\alpha}=0.05$). Results: Discrepancies of mean with regard to reproducibility were $11.2{\mu}m$, $5.8{\mu}m$, respectively, with white and blue light scanners (p<0.047). And discrepancies of RMS with regard to reproducibility were $33.4{\mu}m$, $18.8{\mu}m$, respectively, with white and blue light scanners (p<0.045). Conclusion: Our results indicate a good reproducibility of prepared tooth impression digitized with blue light scanner more than that with white light scanner.

• The Journal of Advanced Prosthodontics
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• 제8권3호
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• pp.214-218
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• 2016

PURPOSE. We assessed the repeatability and reproducibility of abutment teeth dental impressions, digitized with a blue light scanner, by comparing the discrepancies in repeatability and reproducibility values for different types of abutment teeth. MATERIALS AND METHODS. To evaluate repeatability, impressions of the canine, first premolar, and first molar, prepared for ceramic crowns, were repeatedly scanned to acquire 5 sets of 3-dimensional data via stereolithography (STL) files. Point clouds were compared and the error sizes were measured (n=10, per type). To evaluate reproducibility, the impressions were rotated by $10-20^{\circ}$ on the table and scanned. These data were compared to the first STL data and the error sizes were measured (n=5, per type). One-way analysis of variance was used to assess the repeatability and reproducibility of the 3 types of teeth, and Tukey honest significant differences (HSD) multiple comparison test was used for post hoc comparisons (${\alpha}=.05$). RESULTS. The differences with regard to repeatability were 4.5, 2.7, and $3.1{\mu}m$ for the canine, premolar, and molar, indicating the poorest repeatability for the canine (P<.001). For reproducibility, the differences were 6.6, 5.8, and $11.0{\mu}m$ indicating the poorest reproducibility for the molar (P=.007). CONCLUSION. Our results indicated that impressions of individual abutment teeth, digitized with a blue light scanner, had good repeatability and reproducibility.

• 대한치과기공학회지
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• 제41권4호
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• pp.263-269
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• 2019

Purpose: The purpose of this study was to evaluate the internal fitness of prostheses fabricated with non-contact extra-oral scanner and those fabricated with intra-oral video scanner, with a comparative accuracy analyses of their precision and trueness. Methods: A polymethyl methacrylate (PMMA) model was fabricated by replicating a master model. The prostheses in the first group were fabricated based on the PMMA model with an intra-oral video scanner (IVS group). Following the fabrication of work models with Type IV Stone that were based on the PMMA model, the prostheses in the second group were fabricated with a non-contact extra-oral scanner (ENB group). The precision and trueness of the prostheses were calculated from comparisons of the three-dimensional images of the internal surfaces of the prostheses and those of the master model. Kruskal-Wallis tests were used to determine the statistical significance, with the level of type 1 error set at 0.05. Results: Trueness (P < 0.009) and precision (P < 0.001) did not differ significantly between the ENB and IVS groups. The IVS group exhibited lower trueness values and larger precision values than the ENB group. Conclusion: Although no significant differences were found in the internal fitness of the prostheses that were fabricated by the two different scanners, the intraoral video scanner-fabricated prostheses had better trueness, whereas the non-contact extra-oral scanner-fabricated prostheses had better precision.

• 한국정보통신학회논문지
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• 제15권4호
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• pp.851-859
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• 2011

본 논문에서는 인간과 컴퓨터의 상호작용을 위해 연속된 입력영상에서 인체의 실루엣과 조인트를 자동추출하고 조인트를 추적함으로 객체를 추적하는 방법을 제안한다. 또한 추출된 조인트를 이용하여 인체를 매핑하여 사람의 동작을 재현한다. 이를 위해 인체의 치수를 이용하여 인체 움직임을 제어하는 14개의 조인트로 인체를 모델링한다. 제안방법은 단일카메라로 RGB 컬러로 입력되는 영상을 색상, 채도, 명암의 영상으로 변환한 후 차 영상기법을 이용하여 인체의 실루엣을 추출한다. 추출된 실루엣의 코너점과 인체 모델링 정보를 이용하여 조인트를 자동 검출한다. 객체의 움직임 추적은 전체 영상 중 조인트를 중심으로 블록매칭 기법을 이용하며 추출된 조인트의 위치정보를 이용하여 인체의 움직임을 매핑한다. 제안방법을 실험동영상에 적용한 결과 인체의 실루엣과 조인트를 자동 검출하며 추출된 조인트로 인체의 매핑이 효율적으로 이루어졌다. 또한 조인트의 추적이 매핑된 인체에 반영되어 인체의 움직임도 적절히 표현되었다.

• 한국환경복원기술학회지
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• 제9권2호
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• pp.81-89
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• 2006

The purpose of this study was to evaluate the applicability of small RC(radio controlled) helicopter and single lens reflect camera as SFAP(Small Format Aerial Photography) aquisition system to monitor the vegetation coverage of wetland. The system used to take pictures of small artificial wetland were a common optical camera(Nikon F80 with manual lens whose focal length was 28mm) attached to the bottom of a RC helicopter with a 50 cubic inch size glow engine. Three hundreds pictures were taken at the altitude of 50m above the ground, from 23rd June to 7th September 2005. Four from the images were selected and scanned to digital images whose dimension were 2048${\times}$1357 pixels. Those images were processed and rectified with GCP(Ground Control Poins) and digital map, and then classified by the supervised- classification module of image processing program PG-steamer Version 2.2. The major findings were as follows ; 1. The final images processed had very high spatial resolution so that the objects bigger than 30mm like lotus(Nelumbo nucifera), rock and deck were easily identified. 2. The dominant plants of the monitoring site were Monochoria ragianlis, Typha latifolia, Beckmannia syzigachne etc. Because those species have narrow and long leaves and form irregular biomass, the individuals were hardly identifiable, but the distribution of population were easily identifiable depending on the color difference. 3. The area covered by vegetation was rapidly increased during the first month of monitoring. At the beginning of the monitoring 23th June 2005, The rate of area covered by vegetation were only 34%, but after 27 and 60 days it increased to 74%, and the 86% respectively.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.265-270
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• 2018

PURPOSE. The purpose of this in vitro study was to evaluate the accuracy of a new implant impression technique using bite impression coping and a dual arch tray. MATERIALS AND METHODS. Two implant fixtures were placed on maxillary left second premolar and first molar area in dentoform model. The model with two fixtures was used as the reference. The impression was divided into 2 groups, n=10 each. In group 1, heavy/light body silicone impression was made with pick up impression copings and open tray. In group 2, putty/light body silicone impression was made with bite impression copings and dual arch tray. The reference model and the master casts with implant scan bodies were scanned by a laboratory scanner. Surface tessellation language (STL) datasets from test groups was superimposed with STL dataset of reference model using inspection software. The three-dimensional deviation between the reference model and impression models was calculated and illustrated as a color-map. Data was analyzed by independent samples T-test of variance at ${\alpha}=.05$. RESULTS. The mean 3D implant deviations of pick up impression group (group 1) and dual arch impression group (group 2) were 0.029 mm and 0.034 mm, respectively. The difference in 3D deviations between groups 1 and 2 was not statistically significant (P=.075). CONCLUSION. Within limitations of this study, the accuracy of implant impression using a bite impression coping and dual arch tray is comparable to that of conventional pick-up impression.

• 제어로봇시스템학회논문지
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• 제19권11호
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• pp.1029-1035
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• 2013

This paper proposes a real time lane detection algorithm using LRF (Laser Range Finder) for autonomous navigation of a mobile robot. There are many technologies for safety of the vehicles such as airbags, ABS, EPS etc. The real time lane detection is a fundamental requirement for an automobile system that utilizes outside information of automobiles. Representative methods of lane recognition are vision-based and LRF-based systems. By the vision-based system, recognition of environment for three dimensional space becomes excellent only in good conditions for capturing images. However there are so many unexpected barriers such as bad illumination, occlusions, and vibrations that the vision cannot be used for satisfying the fundamental requirement. In this paper, we introduce a three dimensional lane detection algorithm using LRF, which is very robust against the illumination. For the three dimensional lane detections, the laser reflection difference between the asphalt and lane according to the color and distance has been utilized with the extraction of feature points. Also a stable tracking algorithm is introduced empirically in this research. The performance of the proposed algorithm of lane detection and tracking has been verified through the real experiments.

• 대한치과기공학회지
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• 제39권1호
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• pp.1-7
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• 2017

Purpose: The purpose of this in vitro study compared to evaluation of repeatability of scanning abutment tooth stone model and impression applied CAD/CAM ISO standard in dentistry. Methods: To evaluate repeatability of scanning abutment tooth stone model, were repeatedly scanned to obtain 11 data via 3D stereolithography (STL) files. 10 data (STL files) were compared with the first 3D data (STL file), and the error sizes were measured by using 3D superimposing software(n=10). Also, the repeatability of scanning abutment tooth impression was evaluated with the same procedure. Independent t test was performed to evaluate the repeatability of scanning abutment tooth stone model versus impression through root mean square(RMS) and standard deviation(SD)(${\alpha}=0.05$). Results: $RMS{\pm}SD$ with regard to repeatability were $14.7{\pm}2.5{\mu}m$, $17.1{\pm}4.0{\mu}m$, respectively, with scanning abutment tooth stone model and impression(p=0.129). Conclusion: This study results showed a little different repeatability of scanning abutment tooth stone model and impression applied CAD/CAM ISO standard in dentistry, will suggest futures good studies and clinical advantages.