Objective lens for optical recording media and optical pickup device using it
US7457223B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Aug 23, 2004 |
| Grant date | Nov 25, 2008 |
| Priority date | — |
| Expiry date | Jan 19, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/13727
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An objective lens consists of two lens elements of different materials that are cemented. The lens surfaces that are cemented includes a phase function so that the cemented surface forms a optical diffractive surface that enables the objective lens to focus incident light of three different wavelengths with different numerical apertures onto different optical recording media. Three conditions are satisfied so as to achieve optimum imaging. The optical diffractive surface is shaped so that the order of the diffracted light of the shortest wavelength λ1 having the largest diffracted intensity is zero and different from the order of the diffracted light of the second wavelength λ2 having the largest diffracted intensity, and the order of the diffracted light of the first wavelength λ1 having the largest diffracted intensity is also different from the order of the diffracted light of the third wavelength λ3 having the largest diffracted intensity.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.