Method and apparatus for focusing a recording light beam on a recording medium
US5561645A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 21, 1995 |
| Grant date | Oct 1, 1996 |
| Priority date | — |
| Expiry date | Aug 21, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0916
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for, in an optical data recorder, focusing a recording light beam on a recording medium. In the apparatus, an optical head has focusing means movable in a direction perpendicular to the recording medium for changing the focus position of the recording light beam on the recording medium. The method comprises the steps of: i) detecting light reflected from the optical recording medium and for producing a corresponding focus error signal; ii) generating a mark formation effectiveness signal for each of a plurality of trial focus positions, each mark formation effectiveness signal being associated with a given value of the focus error signal; iii) determining the mark formation effectiveness signal corresponding to an in-focus position and determining an offset value of the associated focus error signal; and iv) during data recording periods, in response to the focus error signal, adjusting the position of the movable focusing means so that the value of the focus error signal is maintained at the offset value.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.