Geometric and Timing Calibration for Unsynchronized Cameras Using Trajectories of a Moving Marker

For 3D measurement of moving objects, timing calibration is important to compensate lags in shutter timing between cameras as well as calibrating 3D positions and poses of them. This paper presents a new method for calibrating the geometric relationship and the lags in shutter timing between unsynchronized cameras from trajectories of a moving marker. We call it geometric and timing calibration. Geometric calibration generally requires many point correspondences between images of the calibration objects. It is, however, difficult to obtain stable point correspondences from images. Our method does not require point correspondences. It uses, instead, a pair of trajectories of a freely moving maker. Our method estimates a fundamental matrix and a lag in shutter timing simultaneously by analyzing the gap between the trajectories. In experiments, our method has attained accuracy of mean errors within 0.8 pixels in image coordinates and timing errors within 0.3 milliseconds. Another experiment using a radio-controlled helicopter has shown that it works well for flying objects in the sky