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The PRIMAS system derives from a long line of development at Delft University of Technology , originating from [1] with subsequent innovations such as strobed illumination (1974) of reflective markers, to obtain the simultaneous, equidistant, periodic sampling of all marker positions; real-time estimation of the marker centroids from the full, digitized, contours (1984) to retain the on-line data reduction, while enhancing the resolution; interfacing to industry-standard AT type personal computers, with modest disk requirements and no buffering, even for long data runs; 100 Hz, 0.1 ms integration time, electronically-shuttered TV cameras, to get an optimum marker contrast in high ambient or outdoor light conditions (1986). System specifications include a precision of typ. 1:18000 (X) for 2-D coordinate noise or repeatability. With the 100 Hz sample rate this implies an unprecedented spatio-temporal resolution [2]. This favors 3-D reconstruction, as well as a low noise propagation in the estimation of first and higher order derivatives, as are routinely required in biomechanics analysis. The latest feature is real-time marker identification by a software module within the data acquisition program. This option, for the not too complex situations, is feasible only by the data reduction inherent in on-line marker centroid processing. The 3-D calibration, reconstruction and further analytical and display programs are available in the ASYST 3.2 Scientific Language System. A source code option caters for customer extensions. The internal VME/VSB system bus allows the basic dual or quad camera 3-D systems to be readily expanded to larger configurations.
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