• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.3 no.1
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• pp.47-49
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• 1973

The author have observed mucoid retention cyst in the right maxillary sinus of the patient, 41 years old woman, complained discharging of purulent exudate on the right maxillary molar teeth area, and obtained the following conclusions; 1. The mucoid retention cyst in maxillary sinus casts a faint dome shaped shadow into the radiolucent image of maxillary sinus. 2. The mucoid retention cyst in maxillary sinus may be occured without a history of trauma. 3. Intraoral standard films are also valuable for the interpretation of the lesions in maxillary sinus but only extraoral roentgenograms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.92-96
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• 1993

Modern NC machine tools require a more and more exact monitoring and control of cutting process. A very important parameter is tool wear used to optimize cutting data and to change tools at the right time. In this study, a real-time multi-tool fracture method is proposed for measuring crater from fringe patterns generated by uni-shadow-moire. An optical technique using laser for non-contact measurement of tool fracture is presented. The technology in which the tool is illuminated by a beam of He-Ne laser and then the image of tool fracture CCD camera.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.327-328
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• 2007

에너지 흉부 단순 X선 영상으로부터 폐 종류 음영을 검출하기 위한 필터를 예측해서 성능좋게 평가하기 위한 방법을 제안한다. 더욱이 그 평가방법을 이용해서 기존에 제안된 다중 해상도 ${\nabla}^{2}G$ 필터의 평가를 행한다. 전문의의 진단보조 혹은 총합자동진단시스템의 구성요소로서 필터가 수행한 역할을 고려한 후, 필터가 만족해야만 하는 조건 및 그 조건을 만족한 경우에 있어서 몇가지 성능평가 척도를 명확히 한다. 제안한 평가방법을 통해서 다중해상도 필터가 단일해상도 필터에 비해 좋은 성능을 나타내고 있음을 명확히 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.748-750
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• 2004

주행 중인 차량 뒷 번호판을 획득하여 이진화하는 과정에서 번호판 주변의 움푹 들어간 차량구조 영향으로 인하여 번호판에 그림자가 드리워지게 된다. 그림자가 진 상황에서 영상을 이진화를 하게 되면 번호판 문자가 확실하게 나오지 않게 된다. 따라서 그림자가 드리워진 번호판에 대해서 그림자 영역의 경계를 구하여 처리를 하고, 그림자가 진 부분과 그림자가 지지 않은 부분을 각각 이진화한 후 두 부분을 합하여 번호판 문자를 얻어낸다. 그림자 처리 방법을 사용할 경우 일반적인 이진화를 했을 때 보다 훨씬 좋은 번호판 문자를 얻을 수 있었다.

• Journal of Korea Multimedia Society
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• v.18 no.11
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• pp.1332-1341
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• 2015

This paper proposes a novel reversible secret sharing scheme using AES algorithm in encrypted images. In the proposed scheme, a role of the dealer is divided into an image provider and a data hider. The image provider encrypts the cover image with a shared secret key and sends it to the dealer. The dealer embeds the secret data into the encrypted image and transmits encrypted shadow images to the corresponding participants. We utilize Galois polynomial arithmetic operation over 2⁸ and the coefficient of the higher-order term is fixed to one in order to prevent the overflow. In experimental results, we demonstrate that the PSNR is sustained close to 44dB and the embedding capacity is 524,288 bits.

• Korean Journal of Remote Sensing
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• v.36 no.5_2
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• pp.989-1006
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• 2020

Building change monitoring based on building detection is one of the most important fields in terms of monitoring artificial structures using high-resolution multi-temporal images such as CAS500-1 and 2, which are scheduled to be launched. However, not only the various shapes and sizes of buildings located on the surface of the Earth, but also the shadows or trees around them make it difficult to detect the buildings accurately. Also, a large number of misdetection are caused by relief displacement according to the azimuth and elevation angles of the platform. In this study, object-based building detection was performed using the azimuth angle of the Sun and the corresponding main direction of shadows to improve the results of building change detection. After that, the platform's azimuth and elevation angles were used to detect changed buildings. The object-based segmentation was performed on a high-resolution imagery, and then shadow objects were classified through the shadow intensity, and feature information such as rectangular fit, Gray-Level Co-occurrence Matrix (GLCM) homogeneity and area of each object were calculated for building candidate detection. Then, the final buildings were detected using the direction and distance relationship between the center of building candidate object and its shadow according to the azimuth angle of the Sun. A total of three methods were proposed for the building change detection between building objects detected in each image: simple overlay between objects, comparison of the object sizes according to the elevation angle of the platform, and consideration of direction between objects according to the azimuth angle of the platform. In this study, residential area was selected as study area using high-resolution imagery acquired from KOMPSAT-3 and Unmanned Aerial Vehicle (UAV). Experimental results have shown that F1-scores of building detection results detected using feature information were 0.488 and 0.696 respectively in KOMPSAT-3 image and UAV image, whereas F1-scores of building detection results considering shadows were 0.876 and 0.867, respectively, indicating that the accuracy of building detection method considering shadows is higher. Also among the three proposed building change detection methods, the F1-score of the consideration of direction between objects according to the azimuth angles was the highest at 0.891.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.6 no.2
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• pp.42-52
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• 1988

The main object of this study is to prove the effectiveness of Landsat data in detecting the stressed areas in forest by extracting these areas. And also to choose the effective bands for this type of survey and to reduce the effect of shadow in forest to improve the accuracy of classification are the other objects. In this study Landsat-5 TM data is used and image processing techniques such as spatial filtering and ratio are taken to reduce the effect of shadow and to improve the classification accuracy. As a result following conclusions are obtained. First, Landsat TM data is useful to detect the stressed areas in forest. Second, when detecting the stressed area, band 4 and 5 are the most effective. Third, spatial filtering and ratio are useful to reudce the effect of shadow and improve the classification accuracy. Especially, ratio has great effect on improving the classification accuracy between forest and other areas.

• Journal of Multimedia Information System
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• v.4 no.1
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• pp.9-18
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• 2017

Ubiquitous computing is a novel paradigm that is rapidly gaining in the scenario of wireless communications and telecommunications for realizing smart world. As rapid development of sensor technology, smart sensor system becomes more popular in automobile or vehicle. In this study, a new vehicle detection mechanism in real-time for blind spot area is proposed based on imaging sensors. To determine the position of other vehicles on the road is important for operation of driver assistance systems (DASs) to increase driving safety. As the result, blind spot detection of vehicles is addressed using an automobile detection algorithm for blind spots. The proposed vehicle verification utilizes the height and angle of a rear-looking vehicle mounted camera. Candidate vehicle information is extracted using adaptive shadow detection based on brightness values of an image of a vehicle area. The vehicle is verified using a training set with Haar-like features of candidate vehicles. Using these processes, moving vehicles can be detected in blind spots. The detection ratio of true vehicles was 91.1% in blind spots based on various experimental results.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.475-477
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• 2010

본 논문에서는 객체 위주의 3D 파노라마를 생성하기 위하여 객체를 중심으로 영상을 촬영할 시, 조명의 위치나 방향에 의해 나타나는 영상 내 음영과 같은 휘도의 차이를 보정하는 방법을 제안한다. 제안하는 방법에서는 먼저 촬영한 영상을 그레이스케일 영상으로 변환한 후, 임계값(threshold)을 기반으로 객체 내 어두운 영역과 밝은 영역을 분류하고, 그레이스케일 영상의 히스토그램을 분석하여 분류한 영역의 차이를 완화시킬 수 있는 최적의 휘도 경계 값을 도출한다. 다음으로는 어두운 영역(shadow)과 밝은 영역(non-shadow)에 해당하는 히스토그램의 요소들을 추출하고, 추출한 요소들을 휘도 경계 값으로 이동하여 조명에 의해 발생된 영사의 휘도 차이를 보정한다. 제안한 방법을 건조물 문화재를 중심으로 촬영한 영상에 적용하였을 시, 조명에 의해 발생된 영상 내 급격한 휘도의 차이를 보정할 수 있었으며, 보정된 결과에서는 보정 전 어두운 영역에서는 관찰하기 어려웠던 건조물 문화재의 내부문양과 같은 정보들을 보다 명확히 확인할 수 있었다.

• Journal of Korean Society for Geospatial Information Science
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• v.22 no.1
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• pp.71-79
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• 2014

Most researches have created the impervious surface map by using low-spatial-resolution satellite imagery and are inefficient to generate the object-based impervious map with a broad area. In this study, segment-based impervious surface mapping algorithm is proposed using the RapidEye satellite imagery in order to map impervious area. At first, additional bands are generated by using TOA reflectance conversion RapidEye data. And then, shadow and water class are extracted using training data of converted reflectance image. Object-based impervious surface can be generated by spectral mixture analysis based on land cover map of Ministry of Environment with medium scale, in the case of other classes except shadow and water classes. The experiment shows that result by our method represents high classification accuracy compared to reference data, quantitatively.