Patent ID: 6604825
Filing Date: 2003-08-12
Classification: A61B,A61F

Abstract:
A hybrid tracking system for tracking lateral movement of an object, comprising of:a closed-loop position sensing device projecting on said object a first scanning probe beam and a second scanning probe beam, wherein said first scanning probe beam scans linearly and repeatedly across a first position of a curved mark on said object and senses a first relative location of said curved mark along a first scanning direction of said first probe beam, and said second scanning probe beam scans linearly and repeatedly across a second position of said curved mark on said object and senses a second relative location of said curved mark along a second scanning direction of said second probe beam, wherein said first scanning direction and said second scanning direction are approximately perpendicular to each other, and wherein said closed-loop position sensing device employs a first beam steering module to actively maintain said first relative location and said second relative location as constants; a second beam steering module to direct a light beam onto said object; and a control unit coupled to said closed-loop position sensing device and generating a control signal to drive said second beam steering module as is in an open loop configuration, wherein said control signal consists of an offset signal to compensate for position change of said object; wherein said second beam steering module directs said light beam to desired positions on said object regardless of any movement of said object.