Objective lens for optical pick-up
US7239598B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 16, 2004 |
| Grant date | Jul 3, 2007 |
| Priority date | — |
| Expiry date | Dec 29, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
There is provided an objective lens for an optical pick-up which is used to record/reproduce data to/from at least three types of optical discs. Thicknesses t1, t2 and t3 of cover layers of first, second third optical discs are t1≅0.6 mm, t2≅0.6 mm, and t3≅1.2 mm. Numerical apertures NA1, NA2 and NA3 for the first, second and third optical discs satisfy a relationship NA1≧NA2>NA3. When the first optical disc is used, a substantially collimated light beam is incident on the objective lens. When the second or third optical disc is used, a diverging beam is incident on the objective lens. With regard to magnifications M1, M2 and M3 and focal lengths f1, f2 and f3 of the objective lens for the first, second and third optical discs, the following conditions (1), (2) and (3) are satisfied:−0.02<f1×M1<0.02 (1)−0.10<f2×M2<−0.04 (2)−0.29<f3×M3<−0.19. (3)
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.