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:
May. 28, 1991
Filed:
Jan. 23, 1989
Shigeru Shimonou, Tokyo, JP;
NEC Corporation, , JP;
Abstract
An optical disk system comprising a head positioning system for positioning a head at a desired one of the tracks of an optical disk, and a tracking servo system for maintaining the head at the track by detecting a tracking error signal indicating deflection of the head from the track. In order to accurately position the head to the desired track, a track crossing signal deriving circuit derives an alternating signal component having a frequency corresponding to track crossing of the head from the tracking error signal as a track crossing signal. The track crossing signal is converted to a pulse signal which is counted to produce a counted number as a track crossing number. The track crossing number is compared with a desired track number previously set and a position error signal is produced. A head driving motor is driven until the position error signal becomes zero so that the head is correctly positioned at the desired track. The track crossing signal is converted into a voltage signal as a velocity signal. A slew rate of the track crossing signal deriving circuit is controlled by the velocity signal so that the track crossing signal is reliably derived even if the track crossing velocity increases.