Focusing apparatus for use in a system for recovering information from an optically-readable storage medium
US4374323A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 11, 1980 |
| Grant date | Feb 15, 1983 |
| Priority date | — |
| Expiry date | Aug 11, 2000 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B2220/20
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for recovering information from a movable information storage medium by scanning with a beam of radiation, the system including a movable lens for focusing the beam of radiation. The movable information storage medium includes a plurality of substantially parallel information tracks containing a pilot signal having a phase angle aligned with the phase angle of the pilot signal recorded on adjacent tracks. The movement of the lens to acquire focus of the beam is controlled such that the lens is retracted until the pilot signal is no longer detected. When detection of the pilot signal ceases, the retraction of the lens also ceases. The lens is subsequently advanced until focus is achieved. Defining the limits of retraction of the lens based on the limits of detection of the pilot signal minimize the range over which the lens must be moved for initial acquisition of focus.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.