Zhengyou Zhang has proposed a Two-Stages camera calibration method by viewing a plane recently. It can calibrate camera easilywith high accuracy and is considered as a presentation of Two-Stages method. But only radial distortion is considered in his camera model

and when the tangential distortion is distinct in some lenses

such as in fish-eye lenses

the camera model will be unsuitable. Therefor his camera model is improved in this paper and an improvedTwo-stages method is proposed. Through the proposed method the initial parameters are solved by using the points near the image plane center. As the distortion is very litter nearthe image plane center

the solved initial parameters can be very close to exact ones

then

a subspace trust regionmethod based on the interior-reflective Newton method is applied to solve all the camera parameters accurately. Both computer simulation and real data have been used to test the proposed technique and very good results have been obtained. Compared with Zhang’s method

the proposed method is more accurate and it works better robustness.