An accurate calibration method for a camera with telecentric lenses

It is very important to achieve an accurate calibration to obtain high measurement accuracy for a telecentric imaging system. However, the conventional camera calibration methods typically based on a pinhole model are not suitable for telecentric lenses due to the unique behavior of orthographic projection of telecentric lenses. In this paper, we propose a new method to accurately calibrate the telecentric imaging system. An analytical camera model for telecentric lenses is presented with considering the major sources of lens distortions. Based on this model, a two-step calibration procedure is described for the telecentric imaging system. We use a camera with a telecentric lens to verify our model and study the impacts of different distortion models for properly characterizing the distortion of telecentric lens. The experimental results show the maximum distortion of the system reduces 26 times by the presented calibration technology. (c) 2012 Elsevier Ltd. All rights reserved.