Objective lens and optical information recording/reproducing device having the same
US8279738B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 9, 2008 |
| Grant date | Oct 2, 2012 |
| Priority date | — |
| Expiry date | Jan 10, 2031 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0908
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is provided an objective lens for information recording/reproducing for three types of optical discs, which includes a first area contributing to converging a third light beam onto a record surface of a third optical disc. The first area includes a phase shift structure having refractive surface zones concentrically formed about a predetermined axis. The phase shift structure includes first and second step groups. The first step group is configured such that an optical path length difference ΔOPD1 (nm) given by each step of the first step group to a first light beam satisfies a condition: 2N1+1.10<|ΔOPD1/λ1|<2N1+1.40, where N1 is an integer or zero, and the second step group is configured such that an optical path length difference ΔOPD2 (nm) given by each step of the second step group to the first light beam satisfies a condition: 2N2−0.10<|ΔOPD2/λ1|<2N2+0.10, where N2 is an integer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.