We developed a novel system, for tracking a freely moving object (animal) in a limited 3D space, based on a closed loop TV and PC. Instead of using a pair of TV cameras to capture the 3D scene through the pair of its orthogonal projections, the system captures these projections by using a single TV camera. The direct view of the scene (e.g, its ground plan, i.e. projection onto the x-y plane) is captured together with its side projection, (i.e, projection onto the z-x plane) observed in a slanted mirror. The system uses a simple detection algorithm and hardware that were originally developed for 2D tracking of a single, contrast object on a stable and homogeneous background. All three coordinates of the tracked object are evaluated, displayed and stored in real-time, at 25 interlaced frames (samples) per second. The system was implemented on an IBM PC enhanced by an universal I/O board (Kaminsky, Yu, Krekule, I. Universal multifunctional IBM PC I/O board for clinical examinations and experimental research in neuroscience. Physiol Res 1994;43:193-199) and tested by tracking a LED marker, a small living fish in a water tank and a pair of LED markers which were activated one at the time in alternating TV frames thereby demonstrating the ability to simultaneously track two or more objects in 3D. (C) 1999 Elsevier Science B.V. All rights reserved.
