Objective lens for optical disc
US7035193B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 13, 2005 |
| Grant date | Apr 25, 2006 |
| Priority date | — |
| Expiry date | Apr 29, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An objective lens for recording data to and/or reproducing data from first and second optical discs. The objective lens is provided with at least one surface including a plurality of annular zones divided by steps. The steps has functions of phase shifting a wavefront of light passing through the plurality of annular zones so that a beam spot formed at a converging point of an average wavefront of the wavefront phase shifted by the steps is used for the first and second optical discs. The plurality of annular zones of the at least one surface includes at least one annular zone structure which includes first and second annular zone groups, each of which has at least three steps for phase shifting the wavefront in a first direction, and a first return step which is a step formed at a boundary between the first and second annular zone groups. The first return step phase shifts the wavefront in a second direction opposite to the first direction. An absolute value |Δψ1| of a phase shifting amount of the first light beam given by the first return step satisfies a condition: 6π<|Δψ1|<14π . . . (1). The absolute value |Δψ1| of the phase shifting amount of the first light beam given by the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.