| 摘要 |
<p>The calibration of a pan/tilt/zoom camera uses a template image that is known to correspond to the optical center of a larger image. A first image is captured, at the camera's maximum zoom setting, that contains a scene containing distinguishing details. After capturing this image, the camera is maintained at the same orientation, set to its minimum zoom setting, and a second image is captured. The first image is scaled down to form a template image, using the known ratio of a camera's minimum and maximum zoom capabilities. The location of this template image within the second image defines the optical center, or principal point, of the camera's image plane. Having determined the optical center of the camera's image plane, the focal length of the camera at various zoom settings can be determined by measuring the displacement of a template image at the optical center corresponding to a slight adjustment of the camera through a known angle at each of the various zoom settings. Conventional curve fitting techniques are used for determining an algorithmic mapping between zoom settings and corresponding lens powers. The use of a lens power measure facilitates a linear determination of the coefficients of the mapping equation, and provides an objective function that is less sensitive to inaccurate focal length determinations at low zoom settings.</p> |
