Method and apparatus for recording optically an information signal on a record medium along tracks
US4423495A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 10, 1981 |
| Grant date | Dec 27, 1983 |
| Priority date | — |
| Expiry date | Sep 10, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2007/0919
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In a method and apparatus of recording optically an information signal on a disc along tracks by projecting a main beam modulated with the information signal onto the rotating disc by means of an objective lens, in order to obtain focussing and tracking error signals, a sub beam inclined with respect to the main beam is also projected onto the disc by means of the objective lens. The main and sub beams reflected by the video disc are made incident as parallel light fluxes upon a detection prism surface which is set substantially at a critical angle with respect to the main beam, but at an angle smaller or larger than the critical angle with respect to the sub beam, and two light fluxes of the reflected main beam which situate on respective sides of a boundary plane including the central light ray and perpendicular to a plane of incidence, and are reflected by the reflection surface are separately received by two light receiving regions which are divided along a boundary plane including the main beam reflected by the reflection surface and perpendicular to the plane of incidence. The focussing error signal is derived as a difference between output signals from the two light receivin…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.