Optical head and optical disc apparatus for focusing a collimated laser beam
US7151737B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 15, 2004 |
| Grant date | Dec 19, 2006 |
| Priority date | — |
| Expiry date | Jan 17, 2025 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/1398
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical head includes a laser source (11) irradiating the laser beam having a wavelength not longer than 500 nm, a collimator lens (13) for collimating the laser beam to the parallel rays, an optical beam shaping system (14, 15) that adjusts the cross sectional shape of the beam from the collimator lens, and an objective lens (16) that converges the beam on an optical information medium. The optical head has a relationship between a focal length fCL of the collimator lens and a magnification M of beam shaping satisfies the following equation:in which C is a constant in (λ·mm)1/2, Aso is a maximum astigmatism per displacement of the collimator lens from the focal position, and n is a refractive index of a member of optical beam shaping system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.