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

• 한국광학회지
• /
• 제23권5호
• /
• pp.179-188
• /
• 2012

어안렌즈(fisheye lens)란 통상 초 광각의 시야각을 가지는 렌즈를 일컫는다. 초 광각의 시야각을 가지는 렌즈에서는 주변부시야각으로 갈수록 상의 조도가 급격히 저하하게 되는데, 본 논문에서는 이의 원인과 개선방안에 관해 논의한다. 왜냐하면 어안렌즈와 같은 초 광각의 렌즈에서는 기하광학적인 수차특성보다 오히려 시야각의 안정적인 확보가 광학적인 성능을 훨씬 더 좌우할 수 있기 때문이다. 그러므로 이를 위해, 먼저, 방향코사인벡터의 부호규약과 곡면 상에서의 법선벡터의 방향을 해석기하학적으로 다룬다. 이어서 해석기하학적인 논의를 바탕으로 조도저하의 다양한 원인들에 대해 수치 및 원리적인 분석을 실시하고, 개선에 대한 방안들을 제시한다.

• 한국멀티미디어학회논문지
• /
• 제23권3호
• /
• pp.395-401
• /
• 2020

In this paper, a motion-based ROI extraction algorithm from a high resolution fisheye image is proposed for multi-view monitoring systems. Lately fisheye cameras are widely used because of the wide angle-of-view and they basically provide a lens correction functionality as well as various viewing modes. However, since the distortion-free angle of conventional algorithms is quite narrow due to the severe distortion ratio, there are lots of unintentional dead areas and they require much computation time in finding undistorted coordinates. Thus, the proposed algorithm adopts an image decimation and a motion detection methods, that can extract the undistorted ROI image with a standard angle-of-view for the fast and intelligent surveillance system. In addition, a mesh-type ROI is presented to reduce the lens correction time, so that this independent ROI scheme can parallelize and maximize the processor's utilization.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2022년도 춘계학술대회
• /
• pp.672-673
• /
• 2022

본 논문에서는 TOF 센서와 동일한 View로 고정되고 차량의 진행 방향으로 수평 설치 가능한 카메라에 대하여 논한다. 이 카메라는 객체 인식 정확도 향상을 위해 1,280×720 해상도 적용하고 30fps로 영상을 출력하며 180°이상의 광각 어안렌즈를 적용 가능하다.

• 보존과학회지
• /
• 제37권4호
• /
• pp.312-321
• /
• 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.

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

• Journal of the Optical Society of Korea
• /
• 제18권6호
• /
• pp.720-731
• /
• 2014

There are many kinds of optical systems to widen a field of view. Fisheye lenses with view angles of 180 degrees and omni-directional systems with the view angles of 360 degrees are recognized as proper systems to widen a field of view. In this study, we proposed a new optical system to overcome drawbacks of conventional omni-directional systems such as a limited field of view in the central area and difficulties in manufacturing. Thus we can eliminate the undesirable reflection components of the omni-directional system and solve the primary drawback of the conventional system. Finally, tolerance analysis using Zernike polynomial coefficients was performed to confirm the productivity of the new optical system. Furthermore, we established a method of optical axis alignment and compensation schemes for the proposed optical system as a result of tolerance analysis. In a sensitivity calculation, we investigated performance degradation due to manufacturing error using Code V(R) macro function. Consequently, we suggested compensation schemes using a lens group decentering. This paper gives a good guidance for the optical design and tolerance analysis including the compensation method in the extremely wide angle system.

• 한국정보통신학회논문지
• /
• 제11권11호
• /
• pp.2116-2120
• /
• 2007

본 논문은 어안 렌즈 카메라의 영상 왜곡 보정 처리 시스템 구현에 관한 것이다. 영상 보정 처리 알고리즘은 역맵핑기법을 적용하고 실시간 처리를 위해 DSP 프로세서를 사용하여 시스템을 구현하였다. 알고리즘 적용시 카메라의 왜곡 계수는 실시간 처리를 위해 룩업 테이블화하여 처리한다. 실험 결과, 원영상과 각도변화에 대한 PSNR 변화는 8.3%정도로 안정적 자연스러우며, 화질보다는 실시간 처리에 중점을 두어 한 프레임 $720{\times}480$ 왜곡영상 처리 시간이 약 31.3ms 소요되었다.

• 전기학회논문지
• /
• 제62권9호
• /
• pp.1270-1275
• /
• 2013

A lot of research about camera calibration and lens distortion for wide-angle lens has been made. Especially, calibration for fish-eye lens which has 180 degree FOV(field of view) or above is more tricky, so existing research employed a huge calibration pattern or even 3D pattern. And it is important that calibration parameters (such as distortion coefficients) are suitably initialized to get accurate calibration results. It can be achieved by using manufacturer information or lease-square method for relatively narrow FOV(135, 150 degree) lens. In this paper, without any previous manufacturer information, camera calibration and barrel undistortion for fish-eye lens with over 180 degree FOV are achieved by only using one calibration pattern image. We applied QR decomposition for initialization and Regularization for optimization. With the result of experiment, we verified that our algorithm can achieve camera calibration and image undistortion successfully.

• 한국멀티미디어학회논문지
• /
• 제19권2호
• /
• pp.418-427
• /
• 2016

A smart parking management requires to track a vehicle in a indoor parking lot and to detect the place where the vehicle is parked. An advanced parking system watches all space of the parking lot with CCTV cameras. We can use these cameras for vehicles tracking and detection. In order to cover a wide area with a camera, a fisheye lens is used. In this case the shape and size of an moving vehicle vary much with distance and angle to the camera. This makes vehicle detection and tracking difficult. In addition to the fisheye lens, the vehicle headlights also makes vehicle detection and tracking difficult. This paper describes a method of realtime vehicle detection and tracking robust to the harsh situation described above. In each image frame, we update the region of a vehicle and estimate the vehicle movement. First we approximate the shape of a car with a quadrangle and estimate the four sides of the car using multiple histograms of oriented gradient. Second we create a template by applying a distance transform to the car region and estimate the motion of the car with a template matching method.