title: Distance meter utilizing the intermode beat of a He-Ne laser.
abstract: A distance meter was built utilizing the intermode beat of a He-Ne laser instead of an optical modulater. Its performance was tested at distances between 10 and 1300 m on a 300-m baseline in a tunnel. The resolution was about 20 microm and the total uncertainty was within 0.1 mm, if the air was stable. The length of the tunnel was measured by a distance meter, and the annual periodic strain of the tunnel was observed with submillimeter precision.
authors.forename: K
authors.initials: K
authors.lastname: Seta
authors.forename: T
authors.initials: T
authors.lastname: O'ishi