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:
Feb. 25, 1992
Filed:
Jul. 31, 1990
Norio Okutani, Neyagawa, JP;
Yutaka Masuda, Hirakata, JP;
Matsushita Electric Industrial Co., Ltd., Osaka, JP;
Abstract
A method and apparatus for simultaneously detecting and comparing a plurality of upper patterns indicative of Gray code patterns and having greater pattern pitches and a plurality of lower patterns indicative of pure binary code patterns and having smaller pattern pitches to correct the upper pattern detection data and thereby detect an absolute position. An absolute position detecting apparatus includes a code plate formed with a plurality of upper patterns and a plurality of lower patterns which are arranged radially along the periphery of a rotating body; a mask arranged at a position opposite to the code disc and having a plurality of upper slits and a plurality of first slits and a plurality of second slits which are formed to correspond to the lower patterns and having a 90-degree phase difference therebetween; a laser light source arranged at a position on the opposite side of the code plate to the mask to illuminate the code plate to form pattern projection images on the mask; a light detector for detecting the pattern projection images to detect positional alignment between the patterns and the slits; and data processing circuit for correcting detected data of the upper patterns by referring to those of the lower patterns.