During the manufacturing process of heavy forgings, simple contact measuring techniques are still used to check thedimensions, therefore an optical measuring system is in demand. In this paper, a camera calibration method for the passivemeasuring system, which is being developed in collaboration with an industrial partner, is proposed. Our approach is basedon space resection and works with robust coded targets, which are distributed in the field of view. The coordinates oftargets are measured using TRITOP (GOM) measuring system. This solution allows to build a large calibration field,without a need of large calibration objects. The camera calibration works in 2 steps - at first, the intrinsic parameters ofthe camera, including lens distortion, are calibrated. These parameters are considered as stable, due to the use of specialcamera covers. Multi-image version of the calibration method and dense field of calibration targets are used. The secondstep is performed from every image and employs a single-image extrinsic camera parameters calibration method. Only afew coded calibration targets, mounted on stable objects in the scene, are required. The calibration method was tested inindustrial conditions. The method showed great results, the average reprojection error was under 0.1 px. The effect ofthermally affected zone on the calibration process is discussed.
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