Multi-line scan systems have been introduced as linear light field cameras and subsequently for 3D ranging for industrial inline applications. Up to now there have been no viable calibration methods to determine intrinsic and extrinsic parameters of such a system which would allow (i) metric measurements and (ii) line-scan image geometric rectification. Our work closes the gap by exploiting special properties of a typical multi-line scan setup, which internally uses a fast area-scan sensor that can also be operated in the line-scan mode. This allows the use of standard calibration approaches to determine the intrinsic camera parameters. We introduce a novel method to compute extrinsic camera parameters w.r.t. the transport direction. Consecutively, the images are rectified for all constructed line-scan views. This takes into account estimated camera model parameters in order to generate an EPI-corrected linear light field that is suitable for accurate 3D reconstructions. Furthermore, we introduce a novel calibration target that is characteristic by an asymmetric central element as well as a tailored fast detection algorithm. The proposed method significantly improves the 3D reconstruction quality and allows for absolute 3D measurements in metric units using the multi-line scan setup. The performance of the proposed method is demonstrated on several representative real world examples.
Bernhard Blaschitz, Svorad Štolc, Doris Antensteiner, "Geometric calibration and image rectification of a multi-line scan camera for accurate 3D reconstruction" in Proc. IS&T Int’l. Symp. on Electronic Imaging: Intelligent Robotics and Industrial Applications using Computer Vision, 2018, pp 240-1 - 240-6, https://doi.org/10.2352/ISSN.2470-1173.2018.09.IRIACV-240