The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 28, 1993
Filed:
Dec. 06, 1991
Alan H Field, Essex, CT (US);
Joseph Bakach, Bridgeport, CT (US);
Zygo Corporation, Middlefield, CT (US);
Abstract
A pair of orthogonally polarized optical beams that differ in frequency by a constant oscillator-generated reference frequency are directed through and traverse respective fixed and variable length paths of a heterodyne interferometer, following which the beams are mixed and directed to a detector that generates an electrical measurement signal having a phase that varies with changes in the variable path length. Changes in the measurement signal phase are determined by counting cycle-to-cycle phase changes of the reference frequency signal between sampling instants defined by time-spaced occurrences of a known phase of the measurement signal. The resulting count is simultaneously used to determine both changes in length of the variable length path and the elapsed time interval between the sampling instants. Each of the change in path length and and elapsed time interval determinations are accumulated over an extended plurality of sampling instant pairs to provide the current path length and the time of the final measurement of path length change.