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. 25, 1991
Filed:
Sep. 20, 1989
Koh Ishizuka, Urawa, JP;
Tetsuharu Nishimura, Kawasaki, JP;
Masaaki Tsukiji, Tokyo, JP;
Satoshi Ishii, Tokyo, JP;
Canon Kabushiki Kaisha, Tokyo, JP;
Abstract
In the reference-position detection method and apparatus for detecting a reference position of a scale, first and second patterns are disposed on the scale so that respective detection timings shift inversely to each other in response to a deviation in attitude of the scale. The first and second patterns are detected with timings different from each other by corresponding first and second sensors, and the reference position of the scale is determined according to outputs of respective sensors. Hence, even if the attitude of the scale changes from a predetermined attitude due to an inclination of the scale or a deviation in position of the scale, it is possible to exactly detect the reference position of the scale. Accordingly, it becomes also possible to increase the performance of a displacement measuring apparatus.