Apparatus for recording/reproducing signal on/from optical disk
US6891787B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | Aug 22, 2000 |
| Grant date | May 10, 2005 |
| Priority date | — |
| Expiry date | Dec 14, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2220/2525
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A defect detecting circuit generates a defect detection signal when the level of a sum signal obtained from an optical sensor in an optical pickup is lower than a predetermined level, and a gate circuit responds to the defect detection signal to set the level of a fine clock mark signal to zero, that is a difference signal obtained from the optical sensor in the optical pickup. A fine clock mark is thus distinguished from any defect such as scratch and a correct fine clock mark signal is accordingly generated. Alternatively, the value of a sum signal, which indicates the total amount of reflected light output from the optical pickup, is compared with a predetermined threshold. When the period in which the value of the sum signal is smaller than the threshold lasts for a predetermined threshold time period, it is determined that focus of an objective lens deviates from an optical disk and accordingly focus servo control is stopped. The threshold is defined by gradually reducing a drive signal while detecting peak and bottom values of the sum signal which is generated as the objective lens is moved in the direction of its optical axis, and then setting the threshold between the detec…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.