Objective lens for optical pick-up
US6594222B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 27, 2000 |
| Grant date | Jul 15, 2003 |
| Priority date | — |
| Expiry date | Jan 24, 2021 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Disclosed is an objective lens of an optical pick-up that includes a refractive lens and a diffractive lens structure that is formed as a large number of concentric ring areas having minute steps in an optical axis direction at the boundaries therebetween. The lens surface of the objective lens is divided into a high NA exclusive area for a DVD only, and a common area that is surrouned by the high NA exclusive area. The diffractive lens structure in the common area changes the spherical aberration in the undercorrected direction as the wavelength of the incident laser beam increases. The diffractive lens structure formed in the high NA exclusive area has a smaller wavelength dependence of a spherical aberration than that formed in the common area, and is designed such that a spherical aberration at the short wavelength is adequately corrected for the thin cover type optical disc.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.