Track following servo system

Claim 2

A servo system for positioning a transducer relative to a storage medium to read information stored on the medium, said system comprising: positioning means energizeable for moving the transducer laterally to preselected recording positions relative to the storage medium, means to effect relative movement between the storage medium and the transducer thereby to enable the transfer of information between the medium and transducer, a plurality of side-by-side closely-spaced first and second servo waveforms recorded on the medium such that a pair of first and second servo waveforms identifies a preselected position on the medium and wherein the first and second waveforms are at different but similar cyclic frequencies whereby movement of the transducer to a position near said preselected position will enable the transducer to generate a position signal resulting from reading both servo waveform signals with the magnitude of such position signal being indicative of the lateral position of the transducer relative to that servo waveform, first and second channels receiving the position signal from the transducer and each including modulators capable of mixing cyclic signals, means to supply to the first and second channel modulators, first and second modulating signals respectively having frequencies similar to the frequencies of the first and second servo waveforms respectively to generate a difference signal resulting by the subtraction of the position signal and the modulating signal in each channel with each difference signal having a magnitude indicative to the relative position of the transducer to one servo waveform, means to detect the difference signal in each channel, and means to energize the positioning means responsive to the magnitudes of the difference signals thereby to move the transducer towards the preselected position between the servo waveforms.

Claim 3

A servo system for positioning a transducer relative to a storage medium to read information stores in the medium, said system comprising: positioning means energizeable for moving the transducer laterally to preselected positions relative to the storage medium, means to effect relative movement between the storage medium and the transducer thereby to enable the transfer of information between the medium and transducer, a plurality of side-by-side closely-spaced servo waveforms recorded on the medium such that a pair of waveforms identifies a preselected position in the medium and wherein each pair of waveforms are at different cyclic frequencies whereby movement of the transducer to a position near said preselected position will enable the transducer to generate a position signal including both servo waveform signals with the magnitude of the signals resulting from detection of the different servo waveforms being indicative of the lateral position of the transducer relative to the respective waveform, first and second channels adapted to receive the position signal from the transducer and each including modulators capable of mixing cyclic signals, means to supply to the first channel a modulating signal similar in frequency to that of one cyclic waveform and to the second channel a second modulating signal similar in frequency to that of the other cyclic waveform of the preselected recording position, whereby the modulator of each channel will generate a plurality of resultant frequency signals to include a difference signal equal in frequency to the difference between the modulating signal supplied to the modulator and the cyclic waveform signal of different frequency than the modulating signal with each difference signal having an amplitude responsive to the relative position of the transducer and that servo waveform, means in each channel to filter the difference signal from the other resultant frequency signals thereby leaving in each channel a difference signal having a magnitude indicative of the magnitude Of one of the cyclic waveform signals of the preselected position near which the transducer is positioned, and means to energize the positioning means responsive to the magnitude of the two difference signals thereby to center the transducer relative to the preselected recording position.

Claim 4

A servo system for positioning a transducer relative to a storage medium to read information stores in the medium, said system comprising: positioning means energizeable for moving the transducer laterally to preselected positions relative to the storage medium, means to effect relative movement between the storage medium and the transducer thereby to enable the transfer of information between the medium and transducer, a plurality of side-by-side closely-spaced servo waveforms recorded on the medium such that a pair of waveforms identifies a preselected position in the medium and wherein each pair of waveforms are at different cyclic frequencies whereby movement of the transducer to a position near said preselected position will enable the transducer to generate a position signal including both servo waveform signals with the magnitude of the signals resulting from detection of the different servo waveforms being indicative of the lateral position of the transducer relative to the respective waveform, first and second channels adapted to receive the position signal from the transducer and each including modulators capable of mixing cyclic signals, means to supply to the first channel a modulating signal similar in frequency to that of one cyclic waveform and to the second channel a second modulating signal similar in frequency to that of the other cyclic waveform of the preselected recording position, whereby the modulator of each channel will generate a plurality of resultant frequency signals to include a difference signal equal in frequency to the difference between the modulating signal supplied to the modulator and the cyclic waveform signal of different frequency than the modulating signal with each difference signal having an amplitude responsive to the relative position of the transducer and that servo waveform, means in each channel to filter the difference signal from the other resultant frequency signals thereby leaving in each channel a difference signal having a magnitude indicative of the magnitude Of one of the cyclic waveform signals of the preselected position near which the transducer is positioned, and means to energize the positioning means responsive to the magnitude of the two difference signals thereby to center the transducer relative to the preselected recording position.

Claim 5

A servo system as defined in claim 2 including means to vary the frequency of the modulating signal responsive to changes in the speed of the relative movement between the transducer and the medium.

Claim 6

A servo system as defined in claim 2 wherein the modulating signal is supplied by a phase-locked oscillator operable to generate the modulating signal in response to the speed of relative movement between the transducer and the storage medium.

Claim 7

A servo system for positioning a transducer on a storage medium to read information from the medium comprising: means to effect relative lateral movement between the medium and the transducer thereby to enable the reading of data from the medium, positioning means energizeable for moving the transducer to preselected positions on the medium, said medium including a plurality of servo tracks recorded thereon, said tracks comprising a first and second recorded cyclic waveform signal positioned to each side thereof with the cyclic waveform signal on one side being of a similar but different frequency than the cyclic waveform signal on the other side of the data track, a transducer capable of generating a signal responsive to the reading simultaneously of the cyclic signals of two juxtaposed cyclic waveforms of a preselected position near which the transducer is positioned, first and second circuit means for modulating said transducer signal, means to supply to the first circuit a modulating signal equal to said first cyclic waveform signal and to supply to the second circuit a modulating signal equal to said second cyclic waveform signal for modulating said transducer signal, means to detect the difference signal between the transducer signal and the first and second cyclic signal in said first and second circuit means respectively, means to compare the magnitude of the difference signals from said first and second signals for generating a servo signal, and means for energizing the positioning means with the servo signal for moving the transducer laterally toward the preselected position.

Claim 8

A servo system for positioning a transducer on a storage medium to read information from the medium comprising: means to effect relative lateral movement between the medium and the transducer thereby to enable the reading of data from the medium, positioning means energizeable for moving the transducer to preselected positions on the medium, said medium including a plurality of servo tracks recorded thereon, said tracks comprising a first and second recorded cyclic waveform signal positioned to each side thereof with the cyclic waveform signal on one side being of a similar but different frequency than the cyclic waveform signal on the other side of the data track, a transducer capable of generating a signal responsive to the reading simultaneously of the cyclic signals of two juxtaposed cyclic waveforms of a preselected position near which the transducer is positioned, first and second circuit means for modulating said transducer signal, means to supply to the first circuit a modulating signal equal to said first cyclic waveform signal and to supply to the second circuit a modulating signal equal to said second cyclic waveform signal for modulating said transducer signal, means to detect the difference signal between the transducer signal and the first and second cyclic signal in said first and second circuit means respectively, means to compare the magnitude of the difference signals from said first and second signals for generating a servo signal, and means for energizing the positioning means with the servo signal for moving the transducer laterally toward the preselected position.