Length meter and measuring tracking type laser interferometer

摘要

PROBLEM TO BE SOLVED: To reduce the influence of dust on an incident plane, to be robust against a scratch on the surface of a reference sphere, and to reduce the influence of a local spheric error of a reference sphere.;SOLUTION: The tracking laser gauge interferometer is provided with: a transparent reference sphere 614 placed in a fixed position; a retroreflector (620) placed on a mobile body; a carriage 630 designed to rotate with the center of the reference sphere as the center; a length measuring means (640) which is fixedly arranged on the carriage and includes an optical system for allowing a laser beam (642) to travel between the retroreflector and the reference sphere and measures the distance between the retroreflector and the reference sphere on the basis of interference length measurement; a tracking position detection means 660 which is fixed to the carriage and outputs a signal responsive to an optical axis deviation between the incident light and reflected light of the retroreflector; and a control unit 670 for controlling the rotation of the carriage so that the optical axis deviation may become zero. A laser beam which is made incident on the reference sphere focuses on the center O of the reference sphere and is reflected off the internal spheric surface opposite to the incident side.;COPYRIGHT: (C)2011,JPO&INPIT