Objective lens having diffractive structure for optical pick-up
US6807019B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 2002 |
| Grant date | Oct 19, 2004 |
| Priority date | — |
| Expiry date | Mar 28, 2022 |
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 converges light beams of two different wavelengths onto recording layers of optical discs of two different standards, respectively. The objective lens includes a refractive lens having a positive power and a diffractive lens structure formed on one surface of the refractive lens. The diffractive lens structure has a plurality of concentric ring areas with minute steps at the boundaries therebetween. The diffractive lens structure maximizes the diffraction efficiency of the third order diffracted light at the shorter wavelength and maximizes the diffraction efficiency of the second order diffracted light at the longer wavelength. This enables the diffractive lens structure to correct the chromatic aberration at the respective wavelengths with keeping high diffraction efficiency.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.