Large field-of-view calibration via circular targets and scale constraints

Flexible and high-precision calibration of large field-of-view (FOV) vision systems faces significant challenges due to the manufacturing costs, operational difficulties, and structural deformation associated with traditional large-scale precision targets. To address these limitations, this paper proposes a flexible calibration method that integrates structure from motion (SfM) with geometric scale constraints. Eliminating the need for large calibration boards, the proposed approach utilizes a moving camera to capture stationary circular control points, thereby establishing a multi-view geometric framework. To resolve the inherent scale ambiguity in monocular SfM, we construct a global bundle adjustment optimization model that incorporates the physical radius of the circular targets as a rigorous geometric constraint while accounting for projection eccentricity errors. Experimental results demonstrate that the proposed method achieves high-precision estimation of both intrinsic and extrinsic parameters while ensuring operational flexibility, providing a robust and efficient solution for large-scale industrial vision metrology.