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. 08, 1993
Filed:
Oct. 01, 1990
Henry E Aviles, Tucson, AZ (US);
Edwin R Childers, Tucson, AZ (US);
Tetsuya Kokubo, Kanagawa, JP;
Hiroshi Matsushita, Atsugi, JP;
David P McReynolds, Tucson, AZ (US);
Koichiro Nanke, Fujisawa, JP;
International Business Machines Corporation, Armonk, NY (US);
Abstract
The invention is an optical disk drive which controls mechanical feedback to a focus servo actuator by shifting the phase of the feedback along its path back to the servo an additional 180 degrees to eliminate the degradation of the phase margin and prevent servo instability. The phase shift may be induced at any practical location along the feedback path. The phase shift is preferably induced by creating a slit or opening in the base of the optical disk drive. The opening must be positioned properly, shaped appropriately, and large enough to create a new base resonant frequency which prevents the opposite sides thereof from vibrating in phase. Alternatively, the phase shift may be induced by altering other components in the feedback path. For example, the phase shift can be induced by modifying the spindle motor assembly to create a new spindle resonant frequency.