Patent ID: 6367931
Filing Date: 2002-04-09
Classification: A61B,A61F

Abstract:
A method for optically tracking movement of an object, comprising:selecting a reference mark on an object where first and second surface areas on opposite sides of the reference mark on the object are different in an optical property; repetitively scanning an optical probe beam from the first surface area to the second surface area across the reference mark at a selected scanning speed along a selected direction so that a property of a scattered probe beam that is scattered from the object changes due to the change in the optical property in the first and second surface areas when the probe beam passes through the reference mark; detecting a time at which the change in the property of the scattered probe beam occurs when the probe beam scans across the reference mark; determining a time difference between the time and a reference time; and using the time difference to determine an amount of movement of the object along the selected direction.