A real-time optical 3D tracker for head-mounted display systems

Abstract

Introductio nIn this paper, a new optical system for real-time , three-dimensional position tracking is described . This system adopts an "inside-out" tracking paradigm . The working environment is a room where the ceiling is lined wit h a regular pattern of infrared LEDs flashing under the system's control . Three cameras are mounted on a helme t which the user wears . Each camera uses a lateral effec t photodiode as the recording surface . The 2D positions o f the LED images inside the field of view of the cameras ar e detected and reported in real time . The measured 2D image positions and the known 3D positions of the LEDs ar e used to compute the position and orientation of the camer a assembly in space .We have designed an iterative algorithm to estimat e the 3D position of the camera assembly in space . The algorithm is a generalized version of the Church's method , and allows for multiple cameras with nonconvergent nodal points . Several equations are formulated to predict th e system's error analytically . The requirements of accuracy , speed, adequate working volume, light weight and small siz e of the tracker are also addressed .A prototype was designed and built to demonstrat e the integration and coordination of all essential component s of the new tracker . This prototype uses off-the-shelf components and can be easily duplicated . Our results indicat e that the new system significantly out-performs other existing systems . The new tracker provides more than 200 updates per second, registers 0 .1-degree rotational movement s and 2-millimeter translational movements, and processes a working volume about 1,000 ft 3 (10 ft on each side) .

Ranging Fusion for Accurating State of the Art Robot Localization

“…However, they are most useful in well-constrained environments, and tend to be expensive and mechanically complex. Example of this class of positioning devices are head tracker system (Wang et. al, 1990).…”

The HiBall Tracker

“…In particular we want to acknowledge the many contributions of past members Philip Winston, Scott Williams, and Pawan Kumar. We also want to acknowledge the many early contributions of previous members Ronald Azuma, Stefan Gottschalk, and Jih-Fang Wang [25], and the contributions of Al Barr (California Institute of Technology) and John "Spike" Hughes (Brown University) to the original off-line LED calibration work [13] that led to the simpler Ceiling panels shown in Figure 3. Finally we want to acknowledge our many collaborators in the NSF Science and Technology Center for Computer Graphics and Scientific Visualization, specifically our collaborators in mechanical design and fabrication at the University of Utah: Rich Riesenfeld, Sam Drake, and Russ Fish.…”

“…In 1991 the University of North Carolina demonstrated a working scalable optoelectronic head-tracking system in the Tomorrow's Realities gallery at that year's ACM SIGGRAPH conference [24,25,261. The system used four head-mounted lateral effect photo diode (LEPD) sensors that looked upward at a regular array of infrared light-emitting diodes (LEDs) installed in preciseIy machined ceiling panels as shown in Figure 1.…”

Virtual Reality in Medicine

“…Head-tracking systems are used to define the spatial position of the user and to supply the computer with this information [23,36,41,42]. While several devices are based on electromagnetic technology (e. g., the Polhemus system), recent tracking systems are also based on optical technology (e. g., the optical 3D tracker) [42]. The advantages of using optical tracking include a faster update-rate with low latency, better accuracy and better resolution.…”