Camera calibration method for close range large field of view camera based on compound target

A compound target for camera calibration in wind tunnels is developed, solving problems of low precision and high costs caused by a large field of view, small object distance and severe distortions of optical images. Moreover, a camera calibration method for close range photogrammetry system based on different constraints in different regions was presented in this paper. The 1-D calibration frame and 2-D planar in the compound target were utilized to divide the field-of-view into two regions. Based on distinguished constraints offered by the two calibration references, camera intrinsic, extrinsic and distortion parameters for the two regions were calculated respectively. Then the 3-D coordinates of targets can be reestablished with high precision according to the image region where interesting features lie in. In the end, accuracy contrast test and verification test with respect to the proposed calibration method had been conducted. The results show that the root mean square calibration error of inner region is 0.165 and the root mean square calibration error of exterior region is 0.276, verifying that this method is simple, effective and of high accuracy, meeting the precision requirements.