Geometric calibration of a PTZ camera

Camera surveillance systems have become increasingly important. PTZ (Pan/Tilt/Zoom) camera is a promising surveillance system because it has large virtual field-of-view (FOV) (obtained by panning and tilting) and can view a scene over a greater range of scale by zooming action. Moreover, PTZ camera possesses the feasibility to perform the transformation between the 2D camera image space and 3D object space. In order to increase the accuracy of the transformation, this study proposes an operational procedure for the calibration of PTZ camera. The calibration procedures need to consider: (1) the variation of interior orientation parameters with the different scales of the zoom action; (2) the influence on the exterior orientation parameters due to the discrepancy between the rotation center and the projective center of the camera. The results indicate that the calibration is a necessary procedure for improving the geometric accuracy of PTZ camera.