Camera calibration is an essential and important part of an augmented reality (AR) system. The use of a plane-based calibration technique can give a good accuracy, which can be important for AR applications. The calibration technique used in the current ARToolKit requires user intervention, which is prone to error and involves a lengthy calibration time. The camera has to be recalibrated every time the focal length changes which is cumbersome and less suitable for applications where a more automated and easier approach is needed. This paper investigates the use of camera self-calibration for the ARToolKit, which has the advantage of simplicity of implementation. In order to improve its accuracy, a distortion model is also investigated. In this context several interesting results are presented.