Eye tracking employing a retro-reflective disk

A system, comprising:

• a surgical laser configured to produce a surgical laser beam for removing a tissue of an eye located at a selected position;
• a surgical beam scanner positioned in an optical path of said surgical laser beam to control and direct said surgical laser beam to a surgical area on the eye;
• a reflector configured to attach to the eye outside the surgical area to move with the eye and having a retro-reflective surface producing backward scattering many orders of magnitude stronger than that from the tissue of said eye;
• an illumination source configured to produce a single infrared illumination beam projected near the visual axis onto the eye with a beam size greater than said reflector to illuminate at least an area within which said reflector moves with the eye;
• an optical collector configured and positioned to collect backward scattered infrared light from said reflector to form a bright image spot of said reflector at a selected image location, wherein said bright image spot appears at said selected image location over a substantially dark background;
• a single-element positioning detector positioned at said selected image location to receive said bright image spot and configured to measure a two-dimensional position of said bright image spot of said reflector on said positioning detector;
• and
• an electronic circuit coupled to said positioning detector to produce positioning signals indicative of a position of said reflector according to a centroid of said bright image spot based on said measured two-dimensional position of said bright image spot on said positioning detector, said electronic circuit operable to control said surgical beam scanner to track movement of the eye according to said position of said reflector.

A method for tracking eye movement comprising the steps of:

• affixing onto an eye a reference having an artificial retro-reflective surface producing backward scattering many orders of magnitude stronger than that from the tissue of said eye;
• projecting near the visual axis of said eye an infrared illumination beam onto said reference;
• controlling said infrared illumination beam to have a beam size at said eye to cover an area in which said reference moves with said eye;
• collecting backward scattered illumination light from said reference to form a bright image spot of said reference over a substantially dark background;
• using a single-element positioning detector to receive said bright image spot and to detect a two-dimensional position of said bright image spot of said reference on said positioning detector;
• causing a centroid of said bright image spot to be obtained to represent a position of said reference and hence said eye based on said two-dimensional position on said positioning detector;
• and
• using said position to control a surgical laser beam directed onto said eye so as to follow movement of said eye.

A method for tracking lateral movement of an object comprising the steps of:

• affixing onto the object an artificial reference having a retro-reflective surface producing backward scattering many orders of magnitude stronger than that from said object;
• projecting an illumination beam from a predetermined direction onto said reference;
• controlling said infrared illumination beam to have a beam size at said object to cover said reference and an area within which said reference moves with said object;
• providing an optical means to collect backward scattered light from said reference to form a bright image spot of said reference over a substantially dark background;
• providing a single-element, two-dimensional positioning detector to detect the position of said bright image spot of said reference;
• providing an electronic circuit coupled to said two-dimensional positioning detector to produce positioning signals of said object according to a centroid of said bright image spot;
• and
• using said positioning signals to track movement of said object.