博士 / 國立臺灣大學 / 電機工程學研究所 / 91 / A new methodology for surveying the computer model of fisheye cameras is developed. Among the obtained parameters, the extraction of a single viewpoint is the key contribution of this paper. The fundamental postulations are the common optical characteristics well-known in the related fields. Accordingly, a measuring system utilizes a planar circular symmetric target, which is adopted to emulate the mechanism of the relatively aged multicollimator method; by further combining the techniques of image processing and measurement, the fisheye camera vision model is attained
Based on the postulation of images presented on the computer screen which are symmetrically deformed and determined by a principal point, a central-symmetric image is attained by maximizing the image region. Consequently five of the six extrinsic parameters are deduced by referring to the prearranged world coordinates of the positioned target, while the principal point and the aspect ratio can be extracted from the geometry of the presented image. As to the remaining parameters, two methods are developed: first, accepting that the projection function complies with a circular function within at least a part of a given field of view, constrained by the obtained object-to-image radial mapping and a constant focal length, the best-fitting point of the optical origin is tested along the optical axis; secondly, referring to the postulation of the exclusively bilateral mapping between an imaged point and its scenic sight ray, a measuring technique is developed to survey the world coordinates which will fabricate a projecting path to the imaged points located on the imageable region of the image plane in order to directly model the projection geometries involved. The methodology developed can be used vis-a-vis cameras of any projection functions, even the ones with strange projection curves, such as the foveated lens which simulates the human visual system. The methods accordingly developed have the capacity to handle lenses of ultrawide view angles; the wider the view angles the higher the operational sensitivity will be.
Proposing the use of cheap and thin components, a fisheye camera associating a fisheye lens of the board type with a regular CCD camera acts as an omnidirectional vision sensor. According to the parameters of its computer vision model, alternative image formats are remapped through the adoption of cartographic techniques. Finally, to prove the validity of the method developed, similar sensors are provided to set up a 3D vision metrological instrument; it can achieve a view angle larger than 100 degrees with suitable metrological accuracy. Consequently, this implies that a smaller studio is adequate while working with such a large view angle. The evaluation reveals the broader potential applications of fisheye images.
| Identifer | oai:union.ndltd.org:TW/091NTU00442086 |
| Date | January 2003 |
| Creators | Chuang-Jan Chang, 張創然 |
| Contributors | Gwo-Jen Jan, 詹國禎 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 0 |
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