title: High-accuracy thickness measurement of a transparent plate with the heterodyne central fringe identification technique.
abstract: In a modified Twyman-Green interferometer, the optical path variation is measured with the heterodyne central fringe identification technique, as the light beam is focused by a displaced microscopic objective on the front/rear surface of the test transparent plate. The optical path length variation is then measured similarly after the test plate is removed. The geometrical thickness of the test plate can be calculated under the consideration of dispersion effect. This method has a wide measurable range and a high accuracy in the measurable range.
authors.affiliation: Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, 1001 University Road, Hsinchu 30010, Taiwan.
authors.forename: Wang-Tsung
authors.initials: WT
authors.lastname: Wu
authors.forename: Hung-Chih
authors.initials: HC
authors.lastname: Hsieh
authors.forename: Wei-Yao
authors.initials: WY
authors.lastname: Chang
authors.forename: Yen-Liang
authors.initials: YL
authors.lastname: Chen
authors.forename: Der-Chin
authors.initials: DC
authors.lastname: Su