A method for tracking lateral movement of an object is disclosed employing a retro-reflective disk as a positioning reference and a simplified positioning detection to determine the position of the reference disk. The reference disk having a retro-reflective surface is affixed onto the object to be tracked. An illumination beam illuminates the reference disk from one direction and imaging optics forms a bright image spot of the reference disk with the backward scattering from the reference disk. A two-dimensional positioning detector detects the position of the bright image spot and an electronic circuit then generates positioning signals of the object for tracking applications. The bright image spot of the reference disk enables the use of single element two-dimensional positioning detector and thus enable fast detection (>1 kHz) of the object's position. An embodiment of the method on an eye-tracking system is described.
REFERENCES
U.S. Patent Documents 5,620,436 Lang and Clouts April 1997 Method and apparatus for providing precise location of points on the eye 5,632,742 Frey, et al May 1997 Eye movement sensing method and system 5,410,376 Cornsweet, et al April 1995 Eye tracking method and apparatus 5,430,505 Katz July 1995 High speed eye tracking device and method 5,345,281 Taboada, et al September 1994 Eye tracking system and method
This application claims the benefit of U.S. provisional application No. 60/093,618, filed on Jul. 21, 1998.
An eye-tracking method includes the step of removably affixing a ring member to an eye in surrounding relation to a cornea of the eye. A plurality of incident light spots are transmitted onto the ring member, and reflections are detected from the ring member of the incident light spots. By analyzing the reflections, eye movement can be determined. A system for tracking eye movement includes a ring member and a device for removably affixing the ring member to an eye in surrounding relation to a cornea of the eye, such as, for example, by applying a vacuum to the ring. A light transmitter transmits a plurality of incident light spots onto the ring member, and a detector for detecting reflections from the ring member of the incident light spots. A processor and software installed thereon are adapted to perform calculations to determine eye movement from an analysis of the reflections.
