Patent ID: 6509971
Filing Date: 2003-01-21
Classification: G03F

Abstract:
An interferometric measuring system comprising:a movable member having a measurement reflector attached thereto; a stationary member having a reference reflector attached thereto; a light source for providing a light beam; and an optical support block having first and second beam splitters mounted thereon; the first beam splitter being operable to convert said light beam into a first pair of beams, and arranged to direct one of said first pair of beams along a reference path to the reference reflector and the other of said first pair of beams along a measurement path to the measurement reflector to create a measurement interference pattern between said first pair of beams for measuring a position of the movable member; the second beam splitter being operable to form a second pair of beams and arranged to direct said second pair of beams along support block measurement paths to the reference reflector, the second beam splitter being configured to form a correction interference pattern between said second pair of beams for determining error in the measured position of the movable member due to movement of the optical support block.