	US 7,538,888 B2
	Method for estimating absolute distance of tracking laser interferometer and tracking laser interferometer
Shinichi Hara, Tsukuba (Japan); Naoyuki Taketomi, Tsukuba (Japan); and Makoto Abbe, Tsukuba (Japan)
Assigned to Mitutoyo Corporation, Kawasaki-shi (Japan)
Filed on May 08, 2007, as Appl. No. 11/745,749.
Claims priority of application No. 2006-136487 (JP), filed on May 16, 2006.
Prior Publication US 2007/0268494 A1, Nov. 22, 2007
Int. Cl. G01B 11/02 (2006.01)

U.S. Cl. 356—498

5 Claims

1. A method for estimating an absolute distance of a tracking laser interferometer comprising the steps of:

providing a retroreflector and a two-axis rotating mechanism;

reflecting and returning an incident measurement light in an incident direction;

rotating the two-axis rotating mechanism in an exit direction of the measurement light such that optical axes of the measurement light and the returned light are collimated;

outputting a measurement value according to an increase or a decrease in distance between the interferometer and the retroreflector;

setting a deviation amount of the return light from the retroreflector relative to a predetermined position to a predetermined value;

and

performing an arithmetic operation based on an angular position variation of the two-axis rotating mechanism to estimate an absolute distance between the interferometer and the retroreflector.