Objective lens optical system, optical head and optical information reproduction apparatus
US6791934B2 · kind B2 · utility
Assignees
Inventors
Key dates
| Filing date | Feb 19, 2002 |
| Grant date | Sep 14, 2004 |
| Priority date | — |
| Expiry date | Aug 21, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0943
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
When it is intended to realize a lens having a large NA with one lens, an adjustment precision between both surfaces of the lens is very strict. Accordingly an objective lens having an NA of 0.8 or more was usually realized by two lenses. However, a working distance is small, and collision of the objective lens with a disc is apt to occur. A coma corrector for compensating coma caused by decentering of both surfaces in realizing the high NA lens with one lens is added. However, in this case, astigmatism occurs when the objective lens decenters from the coma corrector relatively accompanied with a tracking operation. The objective lens and the coma corrector are fixed to a mirror barrel so as to be unified with each other, and driven by a two-dimensional lens actuator. With such a constitution, decentering of the objective lens and the coma corrector does not occur, and hence astigmatism does not occur.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.