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:
Dec. 11, 2007
Filed:
Jun. 30, 2004
Shinji Fujita, Yokohama, JP;
Fumio Isshiki, Yokohama, JP;
Nobuyuki Maeda, Yokohama, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A method and an optical disk apparatus that can accurately and stably correct the spherical aberration even for a blank write-once optical disk and can detect a spherical aberration error signal with a simple construction of parts in real time. In a blank write-once disk, the tracking servo is switched to an inoperative state, push-pull signals from outputs of the photodetectorare detected in a state of 'in focus' and in a state of 'out focus,' respectively, by a push-pull signal generation circuit, and.the amplitudes of these push-pull signals are subjected to difference calculation in a spherical aberration error detectorto obtain a spherical aberration error signal A. Then, the spherical aberration is corrected with this spherical aberration error signal A, and subsequently a specific pattern signal is recorded in a trial writing area, this signal is reproduced in the state of “in focus” and in the state of “out focus,” respectively, the amplitude of each reproduced signal is acquired by a reproduced signal generation circuit, these amplitudes are subjected to difference calculation in the spherical aberration error detectorto obtain a spherical aberration error signal B. The spherical aberration is corrected with this.