Patent ID: 8456642
Filing Date: 2013-06-04
Classification: G01B

Abstract:
1. A laser gauge interferometer for measuring a displacement amount of a moving member relative to a base member, comprising: a measurement laser light source for emitting a measurement laser beam; a measurement laser beam dividing unit for dividing the measurement laser beam into a first measurement laser beam and a second measurement laser beam; a correction laser light source for emitting a correction laser beam; a correction laser beam dividing unit for dividing the correction laser beam into a first correction laser beam and a second correction laser beam; a first reflection unit and a second reflection unit provided to cause the first measurement laser beam to pass through a first optical path, to cause the second measurement laser beam to pass through a second optical path and to cause the first correction laser beam to pass through a third optical path, wherein the first optical path and the second optical path have an optical path length changed based on a displacement of the moving member, and at least a part of the first optical path and/or at least a part of the second optical path passes through air; wherein the third optical path has an optical path common to the first optical path and the second optical path; wherein the second reflection unit is provided adjacent to the correction laser beam dividing unit such that a fourth optical path which the second correction laser beam passes through does not pass through air; a measurement interferometer for causing the first measurement laser beam and the second measurement laser beam to interfere with each other, to generate a measurement interference beam; and a correction interferometer for causing the first correction laser beam and the second correction laser beam as a reference light beam to interfere with each other, to generate a correction interference beam.