Optical disc recording/reproducing apparatus recording/reproducing information to/from optical discs according to different standards
US6137764A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 29, 1999 |
| Grant date | Oct 24, 2000 |
| Priority date | — |
| Expiry date | Dec 29, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical disc reproducing apparatus includes a semiconductor laser, an objective lens converging a laser beam from the semiconductor laser on a recording surface of an optical disc, a polarization plane rotating unit selectively rotating the plane of polarization of the laser beam according to the thickness of a substrate of the optical disc, and a polarizing filter selectively shading a peripheral portion of the laser beam having the rotated plane of polarization. In one embodiment, a numerical aperture changing unit includes a non-patterned twisted nematic liquid crystal, and the polarizing filter includes a polarizing film having a polarization characteristics at its peripheral portion.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.