Objective optical system and optical information recording/reproducing device having the same
US8068401B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 22, 2009 |
| Grant date | Nov 29, 2011 |
| Priority date | — |
| Expiry date | Jan 23, 2030 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is provided an objective optical system used for information recording/reproducing for three types of optical discs. The objective optical system includes an objective lens, and a diffraction structure formed on an optical surface. The diffraction structure includes a first area for contributing to converging the third light beam. The first area includes first and second steps defined by first and second optical path difference functions, respectively. The first step is configured such that diffraction orders at which diffraction efficiencies for the first, second and third light beams are maximized are 1st order, 0-th order and 0-th order, respectively. The first step satisfies a condition:−0.36×102<P12×f1+5.0×103×(n1−n3)<1.80×102 (1)The second step is configured such that diffraction orders at which diffraction efficiencies for the first, second and third light beams are maximized are 2nd order, 1st order and 1st order, respectively.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.