• 한국HCI학회:학술대회논문집
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• 2006.02a
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• pp.988-992
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• 2006

본 논문은 PC카메라 환경에서 명암왜곡에 강인한 얼굴검출을 위한 컴포넌트 기반 얼굴검출 기법을 제시한다. 영상 내의 얼굴검출을 위해 에지(edge) 분석, 색상 분석, 형판정합(template matching), 신경망(Neural Network), PCA(Principal Component Analysis), LDA(Linear Discriminant Analysis) 등의 기법들이 사용되고 있고, 영상의 왜곡을 보정하기 위해 히스토그램 분석(평활화, 명세화), gamma correction, log transform 등의 영상 보정 방법이 사용되고 있다. 그러나 기존의 얼굴검출 방법과 영상보정 방법은 검출대상 객체의 부분적인 잡음 및 조명의 왜곡에 대처하기가 어려운 단점이 있다. 특히 PC카메라 환경에서 획득된 이미지와 같이 전면과 후면, 상하좌우에서 비추어지는 조명에 의해 검출 대상 객체의 일부분이 왜곡되는 상황이 발생될 경우 기존의 방법으로는 높은 얼굴 검출 성능을 기대할 수 없는 상황이 발생된다. 본 논문에서는 기울어진 얼굴 및 부분적으로 명암 왜곡된 얼굴을 효율적으로 검출할 수 있도록 얼굴의 좌우 대칭성을 고려한 가로방향의 대칭평균화로 얼굴검출을 위한 모델을 생성하여 얼굴검출에 사용한다. 이 방법은 부분적으로 명암왜곡된 얼굴이미지를 기존의 영상 보정기법을 적용한 것 보다 잘 표현하며, 얼굴이 아닌 후보는 비얼굴 이미지의 형상을 가지게 하는 특성이 있다.

• The Journal of the Korea Contents Association
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• v.15 no.11
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• pp.18-26
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• 2015

Geometric distortion and shadow effect due to capturing angle could be included in document copy images that are captured by a camera in stead of a scanner. In this paper, a clean black and white document image generation algorithm by distortion correction and shadow elimination based on a camera, is proposed. In order to correct geometric distortion such as straightening un-straight boundary lines occurred by camera lens radial distortion and eliminating outlying area included by camera direction, second derivative filter based document boundary detection method is developed. Black and white images have been generated by adaptive binarization method by eliminating shadow effect. Experimental results of the black and white document image generation algorithm by recovering geometrical distortion and eliminating shadow effect for the document images captured by smart phone camera, shows very good processing results.

• Journal of the Korea Society for Simulation
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• v.19 no.1
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• pp.23-31
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• 2010

Due to the fact that fisheye lens can provide super wide angles with the minimum number of cameras, field-of-view over 180 degrees, many vehicles are attempting to mount the camera system. Not only use the camera as a viewing system, but also as a camera sensor, camera calibration should be preceded, and geometrical correction on the radial distortion is needed to provide the images for the driver's assistance. In this thesis, we introduce a geometric correction technique to minimize the loss of the image data from a vehicle fish-eye lens having a field of view over $180^{\circ}$, and a asymmetric distortion. Geometric correction is a process in which a camera model with a distortion model is established, and then a corrected view is generated after camera parameters are calculated through a calibration process. First, the FOV model to imitate a asymmetric distortion configuration is used as the distortion model. Then, we need to unify the axis ratio because a horizontal view of the vehicle fish-eye lens is asymmetrically wide for the driver, and estimate the parameters by applying a non-linear optimization algorithm. Finally, we create a corrected view by a backward mapping, and provide a function to optimize the ratio for the horizontal and vertical axes. This minimizes image data loss and improves the visual perception when the input image is undistorted through a perspective projection.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2003.04a
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• pp.575-580
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• 2003

KOMPSAT-1 위성의 EOC영상은 위성에서 지구를 촬영하는 동안 발생하는 영상 왜곡을 포함하고 있다. 본 연구는 EOC영상의 영상왜곡을 보정하기 위하여 수치지도를 이용하는 정밀기하보정에 대하여 연구한다. 정밀기하보정 과정은 수치지도와 EOC영상의 좌표계를 통합하는 과정을 거쳐 오버레이를 만들어 수치지도의 삼각점을 기준으로 위성영상에서 GCP를 선택하고, 이 GCP를 이용하여 위성 영상을 딜로니 삼각형들의 Mesh형태로 변환하여 모든 딜로니 삼각형을 리샘플링하는 과정을 거쳐 보정된 EOC영상을 얻는다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.36-45
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• 2006

In this paper, multiview calibration system for an effective 3D display is proposed. This system can be obtain 4-view image from multiview camera system. Also it can be rectify lens and camera distortion, error of bright and color, and it can be calibrate distortion of geometry. In this paper, we proposed the signal processing skill to calibrate the camera distortions which are able to take place from the acquisited multiview images. The discordance of the brightness and the colors are calibrated the color transform by extracting the feature point, correspondence point. And the difference of brightness is calibrated by using the differential map of brightness from each camera image. A spherical lens distortion is corrected by extracting the pattern of the multiview camera images. Finally the camera error and size among the multiview cameras is calibrated by removing the distortion. Accordingly, this proposed rectification & calibration system enable to effective 3D display and acquire natural multiview 3D image.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.18-24
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• 2004

SPECT technology is used for the reconstructed image in the field of industry noncontact measurement system. One of the distortion problems in reconstructed image quality is a collimator characterictic. The image distortion is caused by a geometrical structure of the collimator. This paper indicated a correction method to remove the image distortion by the structure of the collimator, and compared with the existing correction method. The correction. method removed the image distortion to use deconvolution of projection data with the shift-variant blurring function in the frequency domain. In this pater, I simulated with the collimator angle and distance between the detector and the center of object. and verified with expeimental data. The validity and limitation of correction method is studied for actual industrial applications.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10b
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• pp.116-120
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• 2006

최근 유비쿼터스 환경에서 프로젝터를 기반으로 사용자가 원하는 위치에 영상을 제공하는 유비쿼터스 디스플레이 연구가 진행 중이다. 프로젝터는 투사방향에 따라 영상의 왜곡이 발생함으로써, 프로젝터 기반의 유비쿼터스 디스플레이는 왜곡된 영상을 보정하는 것이 매우 중요하다. 영상 보정을 위한 기존 연구는 특정마커를 설치하거나 특정 패턴의 영상을 투사하는 등의 선행 작업을 통해 기하보정을 수행한다. 이 방법들은 투사방향이 변화될 때마다 선행 작업을 요구하므로 실시간 기하보정을 수행할 수 없다는 단점이 있다. 본 논문은 특정마커나 카메라와 같은 별도의 장치 없이도 투사되는 방향에 따라 영상의 왜곡 정도를 예측하여 실시간으로 보정된 영상을 제공하는 기하보정 시스템을 제안한다. 제안된 시스템은 특정 보정장치를 사용하지 않고 보정함으로써, 약 27fps의 빠른 처리속도를 가진다. 또한 상용 리모컨을 사용하여 프로젝터의 투사방향을 쉽게 제어하는 편리한 인터페이스를 제공한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.12
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• pp.1923-1932
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• 2013

In order to solve the problem of severely distorted images from a wide-angle camera, we propose a calibration method which corrects a radial distortion in wide-angle images by estimation and validation of camera model. First, we estimate a camera model consisting of intrinsic and extrinsic parameters from calibration patterns, where intrinsic parameters are the focal length, the principal point and so on, and extrinsic parameters are the relative position and orientation of calibration pattern from a camera. Next we validate the estimated camera model by re-extracting corner points by inversing the model to images. Finally we correct the distortion of the image using the validated camera model. We confirm that the proposed method can correct the distortion more than 80% by the calibration experiments using the lattice shaped pattern images captured from a general web camera and a wide-angle camera.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.271-275
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• 2003

In this paper, we propose a method that corrects the geometric distortion of mouth in an image. the method is composed of two steps - detecting key points and correcting geometric distortion. First, key points of lips in source and destination images are found by using lips detection algorithm. Then, the two images are mapped by using affine transformation and information found in first step. In experiment result for various mouths with different geometric distortion, we found that the proposed method have satisfactory efficiency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.597-602
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• 2013

In this paper, the lens module of mega pixel type was designed for barrel distortion calibration due to the barrel distortion of ultra wide angle. And the performance of this camera module was improved with the images from wide dynamic range 2 megapixel CMOS image sensor.