Precision Reference Subsystem for Head-Mounted Displays

Using time-synchronized optical sources and a constellation of receivers, Visidyne proposes to design and demonstrate a remote metrology system capable of measuring the six degrees of freedom of a Head-Mounted Display System and do it with minimal latency. The approach closely parallels the Global Positioning System (GPS), but substitutes intensity-modulated optical beams for the L-band microwave amplitude carrier of the GPS. This overlap should make it possible to apply much of the technology base already developed for GPS RF, IF, and digital subsections as well as software routines, thus reducing future costs and improving prospects for commercial entry. The basic measurement unit of the proposed system consists of a light source, such as a laser diode which is intensity-modulated in the gigahertz range, and a PIN diode detector. Changes in range between the source and the detector are determine by accurate measurements of the phase of the source modulation relative to the phase observed by the detector. Changes in range on the order of 30 micromweters should be detectable. By using multiple detectors and/or sources, translational and rotational measurements can be made. The technique is innovative in that it uses optical beams. Relative to microwave beams, optical beams can be more effieiently generated and can utilize inexpensive, standard components. The proposed program consists of laboratory tests of the basic concept, a study of the system design parameters, and preliminary design of an optical metrology system to be constructure and tested in Phase II. ANTICIPATED BENEFITS: The commercial potential of the technology would appear to be vast. Applications include use in flight simulators, heads-up displays, instructional and training systems, virtual reality systems, machine tool/robotic control, and indoor navigation for hospitals, warehouses, etc. Using this technology, it will be possible to construct what are essentially mini-GPS metrology facilities in any laboratory, machine ship, factory, or construction site. However, this technique will utilize inexpensive components and provide considerably more precision than GPS.