Pupil-centric imaging model for zoom camera calibration.

Zoom camera calibration has always been challenging, as arbitrary zoom/focus settings change the camera parameters. Current calibration methods are based on the pinhole imaging model, which results in coupled calibration parameters due to the lack of geometric/physical constraints. In this Letter, we present a novel, to the best of our knowledge, pupil-centric imaging model that accounts for the camera's radial, decentering, and mustache distortions at various zoom settings using exit pupil offsets and a non-frontal lens-sensor model. Therefore, we provide a reasonable physical explanation for the different distortion effects. Global optimization is performed based on the proposed initial camera calibration and bundle adjustment under several zoom and autofocus setting combinations. Experiments using three representative zoom cameras demonstrate the effectiveness of the proposed method. Its relative measurement accuracy is better than that of current state-of-the-art methods.