Composite tracking servo system for optical disc apparatus with track offset correction
US4866688A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 17, 1986 |
| Grant date | Sep 12, 1989 |
| Priority date | — |
| Expiry date | Dec 17, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/00745
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A tracking servo system includes in addition to a composite servo system composed of a push-pull track deviation detecting loop operative with pregrooves formed in an optical disc and a wobbling track deviation detecting loop operative with intermittently provided wobbled tracking marks, an offset correcting loop for detecting offset component possibly produced due to tilt, deformation and eccentricity of a recording medium or change in optical and mechanical parameters in the course of time lapse to drive forcibly a light spot by applying an electrical offset to cancel out the offset component. In the offset correcting loop, light reflected by wobbled tracking marks provided intermittently or mirror areas formed by interrupting intermittently the pregroove is utilized for detecting the offset component.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.