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. 29, 2010
Filed:
Nov. 30, 2007
Toshimitsu Kaku, Sagamihara, JP;
Kazuhide Hamada, Tokyo, JP;
Toshimitsu Kaku, Sagamihara, JP;
Kazuhide Hamada, Tokyo, JP;
Hitachi-LG Data Storage, Inc., Tokyo, JP;
Abstract
Due to the axial runout of an optical disc, a frequency of a high-frequency current to be superimposed onto a DC current could not be maintained. In order to solve the problem described above, a drive signal is generated by superimposing a high-frequency signal onto a DC current, the drive signal is applied to a laser beam light source, thereby the light source is driven; and a servo signal at a signal level corresponding to a defocus amount of the laser beam relative to the surface of the optical disc is generated based on a reflected light of the laser beam from the recording surface of the optical disc, and a low-frequency component of the servo signal is extracted, and thereby the frequency of the high-frequency signal to be superimposed onto the DC current in the light source driver is controlled based on the low-frequency component of the servo signal.