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:
Apr. 24, 2001
Filed:
Oct. 05, 1998
Takashi Yoshizawa, Yokohama, JP;
Kabushiki Kaisha Toshiba, Kawasaki, JP;
Abstract
This invention provides an optical head apparatus that is not influenced by the offset component contained in a track deviation signal and the track offset caused by lens shift control. According to an optical head apparatus of this invention, portions of light-receiving regions of a photodetector for detecting a track deviation signal are used as offset component detection light-receiving regions for removing any offset component from a track deviation signal. With this arrangement, the offset component contained in a track deviation signal, i.e., the influence of a lens shift on a tracking error signal, is removed by using light from the region where all the 0th-order diffracted light, 1st-order diffracted light, and −1st-order diffracted light of the light reflected by the optical disk overlap each other. In addition, a header signal can be accurately read by using outputs from the two outer detection regions of the photodetector, and the invention can also be applied to an optical disk based on the land/groove recording method. Since a track deviation signal is generated by using outputs from four detection regions obtained by dividing each of the two outer detection regions into two regions, superimposition of an offset component on the track deviation signal can be prevented, thereby realizing stable tracking control.