| 摘要 |
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. |
