Track following servo system

Claim 2

In combination: a movable member having a plurality of side-by-side tracks, each track having a signal impressed thereon at a given frequency, no two adjacent tracks having the same frequency; means movable in a direction substantially normal to the direction in which said tracks extend, including first and second transducer means, an equal portion of each ideally positioned opposite a selected one of said tracks, the remaining portion of each extending into one and the other opposed adjacent tracks respectively, but which transducer means may be offset from said ideal position in said normal direction, said first and second transducer means producing signals at the frequency of said selected track proportional to the portion of said transducer means opposite said selected track; and means responsive to a difference in said signal level produced by said first transducer means relative to that produced by said second transducer means at the frequency of said selected track for moving said movable means to restore said transducer means to said ideal position.

Claim 3

The combination as set forth in claim 1 wherein said movable member comprises a plurality of stacked, spaced apart discs having magnetizable material on the surface thereof, one surface of which has said plurality of tracks, the other surfaces of which have data in tracks corresponding to said plurality of tracks.

Claim 4

In combination: a rotatable disc assembly comprising a plurality of stacked spaced apart discs having magnetic recording surfaces thereon, one such surface having a plurality of cIrcumferential tracks recorded thereon, every other track having a signal recorded at a first frequency an the remaining tracks being recorded at a second different frequency; a transducer assembly and means for moving said transducer assembly in a direction radial of the disc surface to a position opposite any selected one of said tracks, said transducer assembly comprising two transducer means, each including a high reluctance gap extending in the radial direction and offset from one another in the radial direction so that when said transducer assembly is centered over a track, equal portions of said gaps are opposite said track while the remaining portions extend opposite one and the other adjacent tracks respectively, said transducer means producing signals at any given frequency proportional to the portion of gap opposite a track having that frequency; means responsive to signals from the transducer means and to an indication of the frequency of a track to be selected for providing signals from each transducer means only at the selected track frequency; and means responsive to said signals at the selected track frequency from each transducer means for producing an error signal indicative of unbalance between the two signals, said error signal being applied to said means for moving said transducer assembly for moving the transducer assembly until it is centered over the selected track and the signal unbalance is eliminated.

Claim 5

In combination: a rotatable disc assembly comprising a plurality of stacked spaced apart discs having magnetic recording surfaces thereon, one such surface having a plurality of cIrcumferential tracks recorded thereon, every other track having a signal recorded at a first frequency an the remaining tracks being recorded at a second different frequency; a transducer assembly and means for moving said transducer assembly in a direction radial of the disc surface to a position opposite any selected one of said tracks, said transducer assembly comprising two transducer means, each including a high reluctance gap extending in the radial direction and offset from one another in the radial direction so that when said transducer assembly is centered over a track, equal portions of said gaps are opposite said track while the remaining portions extend opposite one and the other adjacent tracks respectively, said transducer means producing signals at any given frequency proportional to the portion of gap opposite a track having that frequency; means responsive to signals from the transducer means and to an indication of the frequency of a track to be selected for providing signals from each transducer means only at the selected track frequency; and means responsive to said signals at the selected track frequency from each transducer means for producing an error signal indicative of unbalance between the two signals, said error signal being applied to said means for moving said transducer assembly for moving the transducer assembly until it is centered over the selected track and the signal unbalance is eliminated.

Claim 6

In combination: a movable member having a plurality of side-by-side tracks, each track having a signal impressed thereon at a given frequency, no two adjacent tracks having the same frequency; means movable in a direction substantially normal to the direction in which said tracks extend, including first and second transducer means, an equal portion of each ideally positioned opposite a selected one of said tracks, the remaining portion of each extending into one and the other opposed adjacent tracks respectively, but which transducer means may be offset from said ideal position in said normal direction, said first and second transducer means producing signals at the frequency of said selected track proportional to the portion of said transducer means opposite said selected track; means responsive to a difference in said signal level produced by said first transducer means relative to that produced by said second transducer means at the frequency of said selected track for moving said movable means to restore said transducer means to said ideal position; and means producing a signal indicating the frequency of the track being selected, wherein said means responsive to a difference in said signal level includes means coupled to said first transducer means responsive to signals therefrom of at least two frequencies and to said signal from said means producing a signal indicating the frequency of the track being selected for producing a signal at only the selected track frequency and includes a similar means coupled to said second transducer means.

Claim 7

In combination: a movable member having a plurality of side-by-side tracks, each track having a signal impressed thereon at a given frequency, no two adjacent tracks having the same frequency; means movable in a direction substantially normal to the direction in which said tracks extend, including first and second transducer means, an equal portion of each ideally positioned opposite a selected one of said tracks, the remaining portion of each extending into one and the other opposed adjacent tracks respectively, but which transducer means may be offset from said ideal position in said normal direction, said first and second transducer means producing signals at the frequency of said selected track proportional to the portion of said transducer means opposite said selected track; means responsive to a difference in said signal level produced by said first transducer means relative to that produced by said second transducer means at the frequency of said selected track for moving said movable means to restore said transducer means to said ideal position; and means producing a signal indicating the frequency of the track being selected, wherein said means responsive to a difference in said signal level includes means coupled to said first transducer means responsive to signals therefrom of at least two frequencies and to said signal from said means producing a signal indicating the frequency of the track being selected for producing a signal at only the selected track frequency and includes a similar means coupled to said second transducer means.