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. 17, 1995
Filed:
Oct. 19, 1993
Naoyuki Kagami, Fujisawa, JP;
Makoto Takekoshi, Yokohama, JP;
International Business Machines Corporation, Armonk, NY (US);
Abstract
The present invention ensures successful focus acquisition in an optical disk drive independent of a travelling speed of an objective lens at the time when a focus servo circuit loop is closed. The present invention provides sending a signal to a focus actuator for bringing an objective lens close to an in-focus position while a focus servo circuit loop is opened; closing the loop by shutting off the signal sent to the focus actuator; adding an offset of a predetermined level to the focus error signal; detecting that the focus error signal to which the offset is added reaches a predetermined level; and closing the loop when it is detected that the predetermined level is reached, and gradually decreasing the value of the offset to be added to the focus error signal.