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:
Jun. 23, 1992
Filed:
Jun. 05, 1990
Hitachi Electronics Engineering Co., Ltd., Tokyo, JP;
Abstract
A laser length measuring instrument in which a first and a second sinusoidal wave interference signals differing in phase by .pi./2 are generated from a plurality of interference wave signals received from an interferometer; a plurality of third sinusoidal wave interference signals differing in phase by m.pi./2 n (where n=integer 2 or greater; m=positive integer sequentially selected from among 0<m.pi./2n<.pi.) with respect to the first sinusoidal wave interference signal are generated out of the first and the second sinusoidal wave interference signals in a phase difference signal generating circuit; a signal indicating the polarity inversion of each sinusoidal wave interference signal is generated, out of the plurality of third sinusoidal wave interference signals generated therein, and the first and the second sinusoidal wave interference signals, utilizes a polarity inversion signal generating circuit to render the signal indicating the polarity inversion corresponding to either first or second sinusoidal wave interference signal into a first measuring signal, and the signal indicating a plurality of polarity inversions respectively corresponding to the plurality of third sinusoidal wave interference signals, and the first and the second sinusoidal wave interference signals into a second measuring signal. The two kinds of measuring signals are combined for measuring purposes to suppress the accumulation of errors affecting the results of measurement in order to obtain accurate, high-resolution displacement measuring data which is hardly affected by signal detection errors on the whole.