<title>Two-stage multiple cameras calibration</title>

Abstract

The problem of determining spatial position and orientation of several cameras, knowing corresponding coordinates obtained by perspective projections onto the camera planes, is considered. Input data for calibration also include distances between some points in space. The calibration is carried out in two stages. In the first stage, position and orientation for pairs of images (stereo pairs) are determined. Every image is calibrated being included in one calibrated stereo pair. A special tree-like structure is built up as a result of the first stage. This structure contains input data and some information about links between the images. The calibration parameters obtained after each stereo pair calibration are considered as an initial approximation for the second stage. In this stage, the simultaneous calibration of all the images is performed to provide consistency and compatibility of final results. The proposed approach permits to avoid possible conflicts between calibration parameters and alleviates the problem of obtaining a good initial approximation for simultaneous calibration of multiple cameras. The experiments with real images produced promising results.