METHOD AND APPARATUS FOR ANALYZING A BODY HAVING A MARKER LOCATED THEREON

A video motion analysis system wherein a camera converts an image of a body having illuminated markers placed thereon into a plurality of image frames. Each image frame comprises a plurality of image lines, and each image line comprises a plurality of pixels. An image preprocessor receives the plurality of image lines and detects the occurrence of each marker in each image line. This is done by comparing each pixel amplitude value to a threshold value and indicating when the pixel amplitude value exceeds the threshold value. When a pixel amplitude value exceeds the threshold value, an offset value representing the difference between the pixel amplitude value and the threshold value is added to a running total of amplitude values for the detected marker. Similarly, the offset value is used to calculate the moment value for each pixel in each marker based on the position of the pixel in the scan line. The calculated moment value is added to a running total of moment values for the detected marker. The amplitude and moment sums for each series of pixels for each marker in each image line are passed to a signal processor which groups the amplitude and moment sums for each marker together. The grouped values are used to calculate a centroid value for each marker. Centroid calculation is performed in real time and the resulting values are provided to a master CPU for further processing.