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:
Oct. 15, 1991
Filed:
Nov. 30, 1989
Norihito Hikawa, Yokohama, JP;
Wataru Ishibashi, Kawasaki, JP;
Mitutoyo Corporation, Tokyo, JP;
Abstract
A reference light transmission window is provided in the vicinity of a sub grating disposed on a usual index scale, and a light transmitted by the reference light transmission window is photoelectrically converted to a reference signal. When a main scale is of an optical transmission type, a light transmitted through a reference light transmission window of a second index scale, which is provided on the opposite side to the usual index scale so as to put the main scale between the second index scale and the usual index scale, or a light among those modulated by the main grating and by the sub grating, which light is not used for displacement detection, is photoelectrically converted to a DC level detection signal. The reference signal or DC level detection signal is used to correct DC level variations of the displacement detection signal.