Geometric calibration of a digital camera with a long-focus lens using a series of images with a common center of projection in the ProjNet software package

Abstract. The article is a continuation of the research of the method of calibration of digital cameras equipped with a long-focus 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. To solve the problem of calibrating digital cameras with long-focus lenses, we propose a different approach that allows calibration on standard spatial test objects. The camera is mounted on a tripod with a panoramic head used by photographers to obtain spherical panoramas. The main condition for panoramic photography is that the center of rotation of the camera and the center of projection of the lens's optical system must be at the same point.The article provides detailed information about the specialized software package ProjNet, specially developed for this calibration method and allowing you to calibrate digital cameras using images with a common projection center. The results of practical application of the calibration method are presented.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 the entrance and exit pupils of the optical system, as well as their roles in the optical system of the lens, are considered.