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:
Apr. 26, 1994
Filed:
Sep. 12, 1991
Hitachi, Ltd., Tokyo, JP;
Abstract
An optical information memory apparatus in which after a coarse seeking operation to position an optical head to a position near a seeking target address at a high speed has been executed, only at a time point when a light spot has reached a predetermined region from the center of a track near a seeking target address, the pull-in control of the light spot to the track center is executed. The optical information memory apparatus has: a zero-cross pulse generator for receiving a tracking error signal and for producing tracking error zero-cross pulses; and a window comparator for receiving the tracking error signal and for producing tracking error window pulses which are obtained by slicing the tracking error signal by predetermined binary slice levels of an upper limit and a lower limit. Further, at a time point when a period of time of the low level of the tracking error zero-cross pulse is equal to or larger than a predetermined time interval T.sub.0 and the tracking error window pulse has been set to the low level, the tracking control to pull the light spot into the track near the desired seeking target address is executed.