Pickup device
US6353582B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Dec 10, 1999 |
| Grant date | Mar 5, 2002 |
| Priority date | — |
| Expiry date | Dec 10, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0006
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A pickup device for writing or reading information onto or from an optical disk having a recording surface that is covered with a transmission substrate. The pickup device detects first reflected light corresponding to first illuminated light which is illuminated via a portion with a numerical aperture that is less than or equal to a second predetermined numerical aperture which is smaller than the first predetermined numerical aperture, of a reflected light from the recording surface, generates a first error signal which indicates a focus error of the first illuminated light on the recording surface, detects second reflected light corresponding to second illuminated light which is illuminated via a portion with a numerical aperture that is less than or equal to a predetermined numerical aperture which is greater than the second predetermined numerical aperture, of the reflected light, generates a second error signal which indicates a focus error of the second illuminated light on the recording surface and obtains a signal corresponding to spherical aberration by using at least one of the first or second error signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.