• 한국정밀공학회지
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• 제23권10호
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• pp.22-29
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• 2006

This paper considers the lens distortions such as a fisheye distortion and a perspective distortion. While a fisheye lens has a wide field-of-view, it causes a large distortion to the images. Regardless of a fisheye lens or a rectilinear lens, a lens generates perspective distortion in a vertical direction when the lens views in an upward direction or downward direction. These distortions deform images differently from human visual functions. Therefore, this paper presents a method to correct the distortions, and whereby, the research in this paper enlarges choices of images to image processing algorithm that may select the distorted images and the corrected images depending on applications. An infinite polynomial model is employed in the fisheye radial distortion correction, and the vertical perspective distortion correction is done by using a vanishing point. The methods introduced in this paper are implemented on the images captured by a rear-view camera installed on a vehicle and showed their robustness of the correction.

• Journal of the Optical Society of Korea
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• 제14권3호
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• pp.245-259
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• 2010

We have developed mathematically precise image-processing algorithms for extracting panoramic images from fisheye images. Furthermore, we have successfully built a DSP-based panoramic camera employing single fisheye lens.

• IEIE Transactions on Smart Processing and Computing
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• 제2권6호
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• pp.339-344
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• 2013

This paper presents an automatic focal length estimation method to correct the fisheye lens distortion in a spatially adaptive manner. The proposed method estimates the focal length of the fisheye lens by generating two reference focal lengths. The distorted fisheye lens image is finally corrected using the orthographic projection model. The experimental results showed that the proposed focal length estimation method is more accurate than existing methods in terms of the loss rate.

• 대한전자공학회논문지SP
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• 제49권4호
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• pp.16-22
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• 2012

본 논문에서는 어안렌즈의 교정(calibration)과 기하학적 왜곡을 보정하기 위해서 광학 시뮬레이터에 적합한 나선형 패턴을 제안하고, 이를 이용하여 별도의 수학적 모델링이 필요 없는 교정 알고리듬을 제안한다. 나선형 패턴을 광학 시뮬레이터의 입력 영상으로 이용하여 어안렌즈로 왜곡 시킨 영상에서 기하학적으로 이동된 점들의 정합을 통하여 교정을 수행한다. 이러한 과정에서 나선형 패턴 영상에서 중심으로부터 멀어지는 점들이 어안렌즈의 기하학적 왜곡을 거쳐 이동되는 정보를 왜곡되기 전의 위치와 정합하기 때문에 정확한 교정이 가능한 동시에, 별도의 모델링이 필요 없기 때문에 효율적인 처리가 가능하다. 제안된 기술은 어안렌즈를 이용한 패턴인식 시스템에서 손실 없는 디지털 영상 확대를 통하여 정확한 정보를 추출하는 데에 이용할 수 있다. 또한 넓은 시야각을 필요로 하는 다양한 영상처리 분야에 적용하여 어안렌즈의 교정과 왜곡 보정을 가능하게 한다.

• Journal of the Optical Society of Korea
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• 제12권2호
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• pp.79-87
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• 2008

We have developed a miniature fisheye lens with $190^{\circ}$ field of view operating simultaneously in the visible and the near infrared wavelengths. The modulation transfer function characteristic for the visible wavelength is sufficient for a mega-pixel-grade image sensor. The lens also has a fair resolution in the infrared wavelength region. The calibrated $f-{\theta}$ distortion is less than 5%, and the relative illumination is over 90%. In consequence, a sharp wide-angle image can be obtained which is uniform in brightness over the entire range of field angles. The real image heights for the visible and the near infrared wavelengths have been fitted to polynomial functions of incidence angle with sub-pixel accuracies. Combined with the near equidistance projection scheme of the lens, this lens can be advantageously employed in various image-processing applications requiring a wide-angle lens.

• 센서학회지
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• 제22권6호
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• pp.393-399
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• 2013

We propose a method of sensing the rotation and distance of a camera by using a fisheye lens system as a vision sensor. We estimate the rotation angle of a camera with a modified correlation method by clipping similar regions to avoid symmetry problems and suppressing highlight areas. In order to eliminate the rectification process of the distorted points of a fisheye lens image, we introduce an offline process using the normalized focal length, which does not require the image sensor size. We also formulate an equation for calculating the distance of a camera movement by matching the feature points of the test image with those of the reference image.

• 대한공간정보학회지
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• 제19권4호
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• pp.55-63
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• 2011

어안렌즈는 사각이 넓어서 터널 내부 벽면의 영상을 취득하는 데 유용하다. 원통투영의 원리를 이용하여 어안렌즈터널 영상을 우리의 눈에 익숙한 일반 영상으로 변환시킬 수 있는데, 이 과정에서 여러 종류의 왜곡이 발생하게 된다. 본 논문은 투영영상의 터널 바닥면과 벽면 사이 경계선에서 발생하는 왜곡을 다루고 있다. 경계선 왜곡의 발생 원인을 분석하고 모형을 제작하여 보정량 계산식을 유도하였다. Visual C++로 제작한 소프트웨어를 이용하여 계산된 보정량을 투영영상에 적용한 결과 경계선이 보정된 영상을 얻을 수 있었다. 투영영상에 나타난 다른 왜곡에 대한 연구가 추가된다면 어안렌즈 영상을 통해 실제 터널 벽면과 유사한 영상을 얻을 수 있을 것으로 기대된다.

• 보존과학회지
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• 제37권4호
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• pp.312-321
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• 2021

Underwater archaeology relies heavily on photography and video image recording during surveillances and excavations like ordinary archaeological studies on land. All underwater images suffer poor image quality and distortions due to poor visibility, low contrast and blur, caused by differences in refractive indices of water and air, properties of selected lenses and shapes of viewports. In the Yellow Sea (between mainland China and the Korean peninsula), the visibility underwater is far less than 1 m, typically in the range of 30 cm to 50 cm, on even a clear day, due to very high turbidity. For photographing 1 m x 1 m grids underwater, a very wide view angle (180°) fisheye lens with an 8 mm focal length is intentionally used despite unwanted severe barrel-shaped image distortion, even with a dome port camera housing. It is very difficult to map wide underwater archaeological excavation sites by combining severely distorted images. Development of practical compensation methods for distorted underwater images acquired through the fisheye lens is strongly desired. In this study, the source of image distortion in underwater photography is investigated. We have identified the source of image distortion as the mismatching, in optical axis and focal points, between dome port housing and fisheye lens. A practical image distortion compensation method, using customized image processing software, was explored and verified using archived underwater excavation images for effectiveness in underwater archaeological applications. To minimize unusable area due to severe distortion after distortion compensation, practical underwater photography guidelines are suggested.

• 제어로봇시스템학회논문지
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• 제15권10호
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• pp.1021-1028
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• 2009

In this paper, a location identification for a cleaning robot using a camera shooting forward a room ceiling which kas three point landmarks is introduced. These three points are made from a laser source which is placed on an auto charger. A fisheye lens covering almost 150 degrees is utilized and the image is transformed to a camera image grabber. The widly shot image has an inevitable distortion even if wide range is coverd. This distortion is flatten using an image warping scheme. Several vision processing techniques such as an intersection extraction erosion, and curve fitting are employed. Next, three point marks are identified and their correspondence is investigated. Through this image processing and image distortion adjustment, a robot location in a wide geometrical coverage is identified.

• 한국멀티미디어학회논문지
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• 제22권2호
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• pp.128-135
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• 2019

This paper presents a deep learning-based object detection method for recognizing vehicles in images acquired through cameras installed on ceiling of underground parking lot. First, we present an image enhancement method, which improves vehicle detection performance under dark lighting environment. Second, we present a new CNN-based multiscale classifiers for detecting vehicles in images acquired through cameras with fisheye lens. Experiments show that the presented vehicle detector has better performance than the conventional ones.