A Real-Time Optical 3D Tracker for Head-Mounted Display Systems

In this paper, a new optical system for real-time, three-dimensional position tracking is described. This system adopts and inside-out tracking paradigm. The working environment is a room where the ceiling is lined with a regular pattern of infrared LEDs flashing under the systemss control. Three cameras are mounted on a helmet which the user wears. Each camera uses a lateral effect photodiode as the recording surface. The 2D positions of the LED images inside the field of view of the cameras are detected and reported in real time. The measured 2D image positions and the known 3D positions of the LEDs are used to compute the position and orientation of the camera assembly in space. We have designed an iterative algorithm to estimate the 3D position of the camera assembly in space. The algorithms is a generalized version of the Churchs method, and allows for multiple cameras with nonconvergent nodal points. Several equations are formulated to predict the systems error analytically. The requirements of accuracy, speed, adequate working volume, light weight and small size of the tracker are also addressed. rh