Abstract
A novel and practical self-calibration method for misaligned non-central catadioptric cameras is proposed in this paper. Without the aid of any special calibration patterns in the scene, the developed method is able to automatically estimate the pose parameters of the mirror with respect to the perspective camera. First it uses the ellipse corresponding to the mirror boundary in the image to compute the possible solutions for mirror postures. With two pose candidates, thereafter we propose a novel selection method to find the correct solution by using the image of the lens boundary. The whole calibration process is automatic and convenient to carry out since nothing more than a single image acquired from the catadioptric camera is needed. Experimental results both on synthesized and real images prove our success.
Highlights
A catadioptric camera system usually consists of a revolutionary symmetric reflective mirror and a conventional perspective camera observing a scene reflected by the mirror
We propose a novel self-calibration method for non-central catadioptric systems by using the camera itself as calibration pattern
In order to remove the ambiguity of mirror posture, we present a novel selection method making use of the imaged lens boundary to find the correct solution
Summary
A catadioptric camera system usually consists of a revolutionary symmetric reflective mirror and a conventional perspective camera observing a scene reflected by the mirror. In [3] and [11] the forward projection model to calculate the reflective point on the mirror by non-iterative algorithms was proposed and used in motion estimation and 3D reconstruction They all assume the coaxial mounting of the mirror and the perspective camera. Strelow et al [14] and Goncalves and Araujo [15] proposed methods for calibrating part and full parameters of the entire non-central camera systems by using bundle adjustment They use preset calibration patterns in the scene and calculate the unknown parameters by minimizing the re-projection error. Caglioti [16] proposed a calibration algorithm for large off-axis non-central cameras by using line patterns They need the profile of the mirror to be seen in the image, which is not very practical in lots of cases.
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