Method and apparatus for controlling the focusing and tracking of a light beam using a main and secondary light beam in association with multiple detectors
US4453239A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 14, 1981 |
| Grant date | Jun 5, 1984 |
| Priority date | — |
| Expiry date | Aug 14, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0919
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An apparatus and method for recording optically an information signal on a disk-like record medium as a spiral track or concentrical tracks by modulating a main beam by the information signal to be recorded and projecting the modulated main beam onto the record medium. In order to obtain a tracking error signal, a sub beam is also projected on the record medium at an edge of an adjacent track which has been previously recorded and the sub beam reflected by the record medium is detected by a light detector to produce the tracking error signal which is then supplied to a high pass filter to remove a low frequency component from the tracking error signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.