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:
Nov. 09, 1999
Filed:
May. 20, 1997
Kazumasa Takata, Moriguchi, JP;
Kanji Nishii, Osaka, JP;
Kenji Takamoto, Suita, JP;
Masami Ito, Moriguchi, JP;
Atsushi Fukui, Osaka, JP;
Tomohisa Kishi, Moriguchi, JP;
Abstract
The present invention provides an optical encoder capable of using the recesses and convexes of a movable plate and a fixed plate to accurately generate a Z phase signal in synchronism with an A/B phase signal. Phase type diffraction gratings on the moving and fixed plates including a plurality of tracks with different grating pitches cause parallel coherent beams to interfere with one another, and a light receiving part detects the intensity of light to obtain a plurality of synchronous signals with different periods. On the other hand, the light receiving part detects light spots formed by condensing elements on the movable plate to generates a single pulse per rotation as a reference position. One of the plurality of synchronous signals that has the shortest period is selected as an A/B phase signal that depends on the movement of the movable plate. The conjunction of the reference position signal and the plurality of synchronous signals is determined as a Z phase signal indicating the origin of the movable plate, thereby obtaining a Z phase signal in synchronism with one pulse of the A/B phase signal.