Real-time Close Range Web-cam Photogrammetry Suited to the Coordination of Optical Topography Sensors Located on the Human Head

Optical topography is an emerging neuroimaging technique for the non-invasive monitoring of human cerebral haemodynamics. The technique is capable of localising brain activity if the positions and orientations of its network of optical sensing devices (optodes) are known relative to the anatomy of the human head. This paper describes the application of a photogrammetric network of low cost web-cams in coordinating and subsequently tracking the locations of targets situated on an optode equipped sensing pad to better than 1mm. Reported investigations include camera calibration and accuracy assessment with a network of Logitech C500 web-cam images at a resolution of 1280 by 1024; a comparison between images from a single colour channel selection and RGB multi-channel frames in terms of real time target detection and coordination. The paper also presents a working solution of 3D target coordination from the real time web-cam tracking system.