Camera Calibration Technique Improvement for 3D Optical Gait Analyzer System

In the present work, improvement in camera calibration technique to increase the accuracy of 3D optical gait analyzer system is presented. The improvement was based on correction and modification of the work that has been reported by Zhengyou Zhang. Lens distortions: radial, decentering, and thin-prism distortion were also considered into camera calibration process to minimize the systems error. In the calibration, the projection matrix of Zhangs model was corrected. In addition to that, non-linear constraint in lens distortion calculation was also avoided in order to make the calculation process more efficient. To evaluate the accuracy and efficiency of the proposed method, comparison between present calibration techniques with other camera calibration techniques is conducted. The results show that the proposed technique gives the most accurate result and most efficient calculation process compared to the Direct Linear Transformation (DLT) and Modified Direct Linear Transformation (MDLT) techniques. By using the proposed technique, the root mean square error of the results, if all the lens distortions are considered in calculation, is 0.627 cm with the processing time of 0.1152 s.