Objective lens for optical pick-up
US6982838B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 3, 2004 |
| Grant date | Jan 3, 2006 |
| Priority date | — |
| Expiry date | Jun 3, 2024 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1374
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is provided an objective lens used for at least three types of optical discs when thicknesses are respectively represented by t1, t2 and t3, t1 as 0.6 mm, t2 is 0.6 mm and t3 is 1.2 mm. When numerical apertures for the first, second and third optical discs are respectively represented by NA1, NA2 and NA3, a relationship NA1>NA2>NA3 is satisfied. When the first and second optical discs are used, collimated light beams are incident on the objective lens. When the third optical disc is used, a diverging beam is incident on the objective lens. The following conditions are satisfied: −0.02<f1×M1<0.02 * * * (1), −0.02<f2×M2<0.02 * * * (2), and −0.29<f3×M3<−0.19 * * * (3). The objective lens includes a diffracting structure having the first region configured such that a diffraction order at which diffraction efficiency of a first light beam is maximized is a second order and the diffraction orders at which diffraction efficiency of second and third light beams are maximized are first orders.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.