| 摘要 |
<p>Method and apparatus for recovering information at a substantially constant rate from a rotable information storage disc (110). The information is stored on the disc (110) 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 (128) at an angular velocity substantially inversely proportional to the radius of the corresponding track. The apparatus includes a coarse speed control potentiometer (130) for producing a measure of the radius of the particular information track from which information is being recovered, and fine speed control means (136) 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 (132) to produce a composite speed control signal, which is coupled to a servo (134) to rotate the disc (110) at a corresponding angular velocity.</p> |
