Information storage disk transducer position control system using a prerecorded servo pattern requiring no alignment with the storage disk

Information storage disk apparatus of the type wherein a radially positionable transducer reads information from or writes information into any desired one of many individual information storage tracks on a spinning information storage disk, comprising:

• a translationally invariant pattern of detectable marks carried by said information storage disk;
• a mark detector mounted for common movement with said transducer for detecting the rate at which said marks pass said detector;
• means defining a plurality of individual information storage tracks, each individual storage track corresponding to a discrete mark detection rate, each discrete mark detection rate defining an individual mark detector path on said storage disk along which the rate at which said marks are detected by said mark detector substantially equals said discrete detection rate;
• and
• means for controlling the radial position of said mark detector so as to cause said mark detector to follow any desired one of said individual mark detector paths,
• said commonly mounted transducer thereby following the corresponding individual information storage track defined thereby.

In information storage disk apparatus of the type wherein a radially positionable transducer reads information from or writes information into a desired one of many individual information storage tracks on a spinning disk, the improvement comprising:

• a dense array of detectable marks on said disk;
• sensor means mounted for common radial movement with said transducer, said sensor means defining a mark sensing region on said disk, said mark sensing region moving radially with said sensor means and transducer, said sensor means detecting passage of said marks through said mark sensing region as said disk spins;
• means responsive to said sensor means for obtaining a current mark sensing rate corresponding to the rate at which said marks are currently passing through said sensing region;
• means defining a discrete mark sensing rate corresponding with each information storage track on said disk and for producing a desired discrete mark sensing rate corresponding with a desired information storage track;
• servo means responsive to said current mark sensing rate and said desired discrete mark sensing rate for continuously adjusting the radial position of said transducer and sensor means so that the current mark sensing rate becomes substantially equal to and remains substantially equal to said desired discrete mark sensing rate,
• whereby said transducer follows a desired information storage track defined by a discrete mark sensing rate.