Method and apparatus for composite wobbled and push-pull tracking servo system
US4707816A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 8, 1986 |
| Grant date | Nov 17, 1987 |
| Priority date | — |
| Expiry date | Dec 8, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0901
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A composite wobbled tracking servo system uses a rotary optical disc which has a header field and a data field alternately arranged along the direction of rotation, and which includes pregrooves formed in at least the data field and at least one pair of wobbled track marks disposed in each of the header fields in a relation wobbled relative to the center of a track. A light spot is directed toward and onto the optical disc to detect a push-pull tracking error signal from the reflection of the light spot diffracted from the pregroove, and a wobbled tracking error signal is detected from the reflection of the light spot passing the wobbled track marks. After attenuating the gain of the wobbled tracking error signal by a low-pass filter so that the gain of the wobbled tracking error signal becomes equal to that of the push-pull tracking error signal at a frequency fe satisfying the relation EQU 1/50.multidot.N.multidot.fd<fe<1/5.multidot.N.multidot.fd where N is the number of the header fields included in one complete revolution of the disc, and fd is the frequency of rotation of the disc, the attenuated wobbled tracking error signal is combined with the push-pull tracking error signa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.