A Geometric Method for Calibration of Internal Camera Parameters of Fish-Eye Lenses

摘要

Fish-eye cameras (cameras with a fish-eye lens) have a very wide view angle of about 180° and a great depth of field. Therefore, it is possible to take pictures of broad scenes with a fixed posture, and it is suitable for uses like 3D modeling and surveillance cameras for indoor and outdoor environments. Geometrical and optical calibration of the internal parameters are necessary for improvement of the measuring accuracy in the real world. In this paper, we address the geometrical calibration problem. Some geometrical methods for calibration of the internal camera parameters of fish-eye cameras force the eye camera into a perspective model that is not applicable in wide views of 180° or more. We propose a calibration method using spherical projection and projection models, which combine the projection function of the fish-eye lens and geometrical distortion models. Our method can perform calibration quickly and with high accuracy by using patterns of horizontal and vertical parallel lines shown on a liquid crystal display (LCD), which can display such patterns with high accuracy. We show the effectiveness of our method by an experimental evaluation with a fish-eye camera of orthographic projection type, which obtains high resolution near the edges of the imaging area.