Optical pickup unit and optical disk drive for accurate and stable information recording and reproduction
US6822771B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 26, 2002 |
| Grant date | Nov 23, 2004 |
| Priority date | — |
| Expiry date | Jan 3, 2023 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical pickup unit includes a light source of semiconductor laser chips of different light-emission wavelengths; a plurality of holograms placed between the light source and an optical recording medium, the holograms including at least one non-polarization hologram having a substantially uniform diffraction efficiency irrespective of the direction of polarization of incident light and at least one polarization hologram having a diffraction efficiency varying depending on the direction of polarization of incident light; and a wave plate provided between the optical recording medium and the polarization hologram. The returning beam of a light beam emitted from a selected one of the semiconductor laser chips is diffracted by the corresponding one of said holograms to be received by a light-receiving element. The wave plate turns the direction of polarization of the returning beam to a different direction from that of the emitted light beam.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.