On zoom-dependent calibration of consumer grade cameras

Abstract

The objective of geometric camera calibration is to determine a parametric model of the projective features of an imaging device. These features describe the mapping of the image coordinates to the viewing rays in space and are of importance for various applications in computer vision. In this work especially the problem of calibrating consumer grade cameras with zoom optics is addressed. The high dependency of various camera model parameters on zoom level, requires their determination throughout a continuous range of zoom settings. Methods were developed, that enables estimation of the zoom-dependent calibration parameters on the basis of pre-calibrated model and a series of intermediate zoom levels of a planar calibration grid. The camera model incorporates focal length, principal point position, radial distortion, camera center's position and sensor tilt and is parametrized for a given zoom range by the focal nominal length obtained from EXIF metadata. The novelty of the work lies in the parameterziation of the sensor tilt and the camcer centerss relative movement in all 3 spatial directions. In general as empiric results and simulation show the method presented is capable of providing dynamic zoom-dependent parameterized models, that perform, in terms of accuracy, comparably well to those presented in related work.