CCD-based system for three-dimensional real-time positioning

Based upon the direct position detection approach and pixel analysis technique, a CCD-based system has been developed for three-dimensional real-time positioning. A data sampling interface card has been designed to gather the 2D coordinates of the LED markers. The spatial positions of moving multiple spots can be obtained instantly. A calibration frame has been constructed to acquire the system parameters before detection. A modified DLT (Direct Linear Transformation) algorithm is presented to correct the nonlinear lens distortion using a planar spot-grid. The precision of the system is less than /spl plusmn/1 mm in a 500 mm/spl times/500 mm/spl times/500 mm space. This corresponds to a spatial resolution of about one part in 500 or 0.2% overall accuracy. This system has been applied in evaluating the therapeutic effect of Lumbar Spine Function in manipulative orthopedics. Some discussions about how to acquire more accurate results by modifying the system and the algorithm are also presented.