System for rotating an information storage disc at a variable angular velocity to recover information therefrom at a prescribed constant rate
US4223349A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 16, 1978 |
| Grant date | Sep 16, 1980 |
| Priority date | — |
| Expiry date | Nov 16, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B19/24
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Method and apparatus for recovering information at a substantially constant rate from a rotatable information storage disc. The information is stored on the disc in a plurality of substantially circular and concentrically arranged information tracks, with a substantially uniform recording density, and it is recovered by controllably rotating the disc, relative to a transducer, at an angular velocity substantially inversely proportional to the radius of the corresponding track. The apparatus includes a coarse speed control potentiometer for producing a measure of the radius of the particular information track from which information is being recovered, and fine speed control means for comparing the relative phase angles of a periodic signal in the recovered information and a periodic reference signal and for producing a fine speed control signal proportional to the phase difference. The measure of radius and the fine speed control signal are summed together and coupled to a voltage-controlled oscillator to produce a composite speed control signal, which is coupled to a servo to rotate the disc at a corresponding angular velocity.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.