Optical pickup apparatus capable of suppressing offset of a tracking error signal
US6181667A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1998 |
| Grant date | Jan 30, 2001 |
| Priority date | — |
| Expiry date | Mar 12, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/094
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A grating surface of a diffraction grating diffracts a laser beam emitted from a semiconductor laser device in .+-.1st order directions. The grating surface is formed in a rectangular or elliptic shape in such dimensions that a light spot formed on an objective lens by .+-.1st order diffracted beams is located in an aperture of the objective lens and not displaced from the aperture even if the objective lens is horizontally moved in a tracking operation. A grating surface of another diffraction grating has a width smaller than the width of an overlap region of a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the +1st direction, entering an objective lens and a light spot on the diffraction grating corresponding to a part of a beam, diffracted in the -1st direction, entering the objective lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.