UDC 528.7
CSCSTI 36.29
The article presents the results of calibration of digital cameras equipped with a longfocus lens using a series of images with a common projection center. When calibrating cameras with a long-focus lens on standard test objects, the calibration parameters are determined with low accuracy, and in some cases, calibration is impossible. This is due to poor geometric parameters and conditions. Each picture includes a small number of marked points of the test object, the intersection angle is sharp, and the depth of field is insufficient (the difference in the position of the far and near points). Obviously, a special test object must be designed for long-focus calibration. We propose a different approach to the calibration process. The camera is mounted on a tripod with a panoramic head used by photographers to obtain spherical panoramas. The main condition for panoramic shooting is that the center of rotation of the camera and the projection center of the lens optical system must be at the same point. The article also presents a brief theory of central projection from the point of view of optics. The main misconceptions associated with the projection center and nodal points are described. The concepts of entrance and exit pupils of an optical system, as well as their roles in the optical system of a lens, are considered.
calibration, digital camera, long focal length camera, center of projection, entrance pupil, optical system, photogrammetry
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