Simultaneous Multiframe Analytical Calibrations (S.M.A.C.) By Recourse To Oblique Observations Of Planar Control Distributions

The use of a flat calibration object with a known 2-D control point distribution for simultaneous estimation of internal and external camera parameters in whole-body movement studies allows coverage of the full observation area as required to avoid extrapolation errors in subsequent 3-D trajectory reconstruction, without the cumbersomeness of more conventional 3-D calibration objects designed to cover the whole observation area. In this adaptation of Simultaneous Multiframe Analytical Calibration (S.M.A.C.), the use of certain oblique (convergent) observations or frames on a planar control distribution allows full recovery of all internal camera parameters, by simultaneous estimation of the various frame positions and attitudes with respect to the camera. Calibration of a second camera whether real or virtual as in mirror photography may be conducted by observing at least one frame through both cameras. The procedure is initialized by means of the fractional linear transformation describing central projection between two planes; the only a priori information required in this approach is an approximate value for the camera principal point; no initial values are generally required for camera principal distance or for the various frame positions and attitudes. In the present paper, the theory and implementation of planar S.M.A.C. are discussed, followed by results from simulation studies. Experimental work is currently in progress.