Objective optical system for optical recording media and optical pickup device using it
US7443779B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 23, 2004 |
| Grant date | Oct 28, 2008 |
| Priority date | — |
| Expiry date | Jul 14, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/13727
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An objective optical system includes a diffractive optical element on the light source side of an objective lens for focusing incident light of three different wavelengths with two different numerical apertures onto three different optical recording media. The diffractive optical element is formed of two lens elements made of different materials that are cemented together at a diffractive surface. Three conditions are satisfied so as to achieve optimum imaging. The diffractive surface may be shaped so that the order of the diffracted light of the shortest wavelength λ2 having the largest diffracted intensity is 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.