Marker-referred movement measurement with grey-scale coordinate extraction for high-resolution real-time 3D at 100Hz

A review of early history in photography highlights the origin of cinefilm as a scientific tool for image-based measurement of human and animal motion. The paper is concerned with scanned-area video sensors (CCD) and a computer interface for the real-time, high-resolution extraction of image coordinates of moving markers. Algorithms and implementations an reviewed for the estimation of marker midpoints. Two-valued (above-threshold) representations of the video signal, as well as grey-scale digitizing are discussed. Attainable resolutions and computational effort an presented. Distributed, per-camera processing is a new option, which uses an embedded microcomputer for image reduction to real-time marker midpoint data. Developments are discussed in 3-D camera calibration and in the real-time 3-D matching of marker images, essential in realtime 3-D reconstruction. Applications are in 3-D motion capture for animation and in motion analysis of wind turbine rotors.