A direct formulation for camera calibration

Conventional camera calibration techniques rely on discrete reference points extracted from a set of input images. While these approaches have been applied successfully for a long time, omitting all image information apart from reference point positions at the initial stage of the calibration pipeline renders correct treatment of uncertainties difficult and gives rise to complications in timestamping measurements in applications where exposure time cannot be neglected. Drawing inspiration from visual state estimation, we employ a direct formulation of the camera measurement model. To this end, we render a view of the target given all calibration parameters, enabling a maximum likelihood estimator formulated on image intensities as measurements. We demonstrate the advantages of avoiding abstraction from image measurements for determining the line delay of a rolling shutter camera and by estimating camera exposure time from motion blur.