Method and apparatus for detecting focussing and tracking error signals
US4525825A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 7, 1981 |
| Grant date | Jun 25, 1985 |
| Priority date | — |
| Expiry date | Oct 7, 2001 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/09
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and an apparatus for detecting a focussing error signal and a tracking error signal of an objective lens with respect to an information track of a video disc on which a reading light spot is focussed by the objective lens includes a detection prism having a reflection surface which is set substantially at a critical angle and a light detector for receiving the light flux reflected by the reflection surface. The light detector is arranged in a far field of the track and having four light receiving regions divided along two orthogonal directions. The focussing error signal is derived as a difference between output signals from the regions aligned in a track direction and the tracking error signal is derived as a difference between output signals from the regions aligned in a direction perpendicular to the track direction. An information signal is obtained as a sum of the output signals from the four regions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.