Optical information disc apparatus with autofocusing servo system
US4542491A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 3, 1982 |
| Grant date | Sep 17, 1985 |
| Priority date | — |
| Expiry date | Nov 3, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B7/0909
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An optical information disc apparatus includes a laser source, a recording medium with an information track, an optical system for emitting a laser beam from the laser source onto the information track, a photodetector detecting the focus error of the optical system using the light reflected from the information track, and an auto-focusing servo system operating the optical system to make the focus of the system follow the upward and downward movement of the recording medium, the optical information disc apparatus being further provided with a control circuit to make the auto-focusing servo system effective only when the optical system is in a position equivalent to the linear region of a defocusing signal having an S-curve characteristic.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.