Telecentric stereo micro-vision system: Calibration method and experiments

• We calibrate a stereo rig consisting of very small field-of-view telecentric lenses.
• The planar-object-based calibration method is simple, practical, and accurate.
• An inherent problem induced by the planar-object-based calibration method is solved.
• The method can be extended to calibrate any affine cameras.
• The method possesses good generality of application.

When a telecentric stereo micro-vision system is used for 3D measurement, the fundamental and key issue is the calibration of the system. However, a telecentric lens generally possesses a small field of view (FOV), which renders the calibration complicated and difficult. In our case, the FOV is 2.4 mm×3.2 mm. From the existing literature published to date, little attention has been paid to the calibration of visual systems with limited FOVs; therefore, a highly effective calibration method is required. In this paper, a new and accurate calibration method is proposed. First, we present a geometric model of the telecentric camera used in this study, considering lens distortion. Afterward, a method for single-camera calibration is described in detail. With respect to recovering the camera rotation matrix, the problem of sign ambiguity induced by the planar-object-based calibration technique is successfully solved. Based on this technique, a method for calibrating a telecentric stereo micro-vision system is presented. The results of experiments conducted in this study show that the method is quite accurate and reliable.