A demonstrated optical tracker with scalable work area for head-mounted display systems

An optoelectronic head-tracking system for head-mounted displays is described. The system features a scalable work area that currently measures 10 x 12, a measurement update rate of 20-100 Hz with 20-60 ms of delay, and a resolution specification of 2 mm and 0.2 degrees. The sensors consist of four head-mounted imaging devices that view infrared lightemitting diodes (LEDs) mounted in a 10 x 12 grid of modular 2 x 2 suspended ceiling panels. Photogrammetric techniques allow the heads location to be expressed as a function of the known LED positions and their projected images on the sensors. The work area is scaled by simply adding panels to the ceilings grid. Discontinuities that occurred when changing working sets of LEDs were reduced by carefully managing all error sources, including LED placement tolerances, and by adopting an overdetermined mathematical model for the computation of head position: space resecfion by collinearity. The working system was demonstrated in the Tomorrows Realities gallery at the ACM SIGGRAPH 91 conference.