Calibration of an active binocular head

In this paper we show how an active binocular head the IIS head can be easily calibrated with very high accuracy Our calibration method can also be applied to many other binocular heads In addition to the proposal and demonstration of a four stage calibration process there are three major contributions in this paper First we propose a MFL Motorized Focus Lens camera model which assumes constant nominal extrinsic parameters The advantage of having constant extrinsic parameters is to have a simple head eye relation Second a calibration method for the MFL camera model is proposed in this paper which separates the estimation of the image center and e ective focal length from the estimation of the camera orientation and position This separation has been proved to be crucial otherwise the estimates of camera parameters would be very noise sensitive Thirdly we show that once the parameters of the MFL camera model is calibrated a nonlinear recursive least square estimator can be used to re ne all the kinematic parameters Real experiments have shown that the proposed method can achieve accuracy of one pixel prediction error and pixel epipolar error even when all the joints including the left and right focus motors are moved simultaneously This accuracy is good enough for many D vision applications such as D navigation D object tracking and even D reconstruction