Optical disc drive and objective lens for the same
US7839752B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 28, 2006 |
| Grant date | Nov 23, 2010 |
| Priority date | — |
| Expiry date | Jun 9, 2029 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is provided an optical disc drive for recordation/reproduction for three types of optical discs by selectively using one of three types of light beams. The optical disc drive comprises an objective lens. The objective lens has a step structure which gives an optical path length difference to an incident beam at each step. When the third laser beam passes through the objective lens, the objective lens produces normal diffraction order light converging to a recording surface of the third optical disc and undesired diffraction order light converging to a point deviating from the recording surface of the third optical disc. A distance from a point to which the normal diffraction order light converges to a point to which the undesired diffraction order light converges is larger than or equal to twice a pull-in range of a focus error signal obtained when the third optical disc is used.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.