Apparatus for and method of determining transverse position of a transducer head relative to read data tracks

A method of detecting the transverse position of a transducer head relative to reference positions defining even and odd numbered longitudinal axes between longitudinally extending adjacent tracks, each of said tracks including a plurality of longitudinally extending, equal length cells, like numbered cells of said tracks having aligned boundaries, said tracks being translated longitudinally relative to said transducer, said cells having physical variations and said transducer being responsive to the variations in the cells of both tracks so that the transducer derives a series of sequential waveforms respectively having first and second like amplitudes and shapes for even and odd numbered cells as the tracks are translated relative to the head, the waveforms for each of the odd numbered cells including successive equal first amplitude pulses of first and second different polarities, the waveforms for each of the even numbered cells including successive equal second amplitude pulses of first and second different polarities, the number of pulses and the approximate shapes of the pulses for the even and odd numbered cells being the same, the first and second amplitudes being indicative of the transverse position of the transducer relative to the axis, the method comprising determining whether the transducer is in the neighborhood of an even or odd numbered axis, responding to the even or odd numbered determination and the waveforms so that both pulses of each odd numbered cell have one of the polarities and both pulses of each even numbered cell have the other polarity while substantially retaining the shape and amplitude of the pulses to derive a resulting waveform, and integrating the resulting waveform over an integral number of the cells to derive an indication of the transverse position relative to the axis in the transducer neighborhood.

Apparatus for detecting the transverse position of a transducer head relative to a reference position defining a longitudinal axis between longitudinally extending adjacent tracks, each of said tracks including a plurality of longitudinally extending, equal length cells, like numbered cells of said tracks having aligned boundaries, said tracks being translated longitudinally relative to said transducer, said cells having physical variations in the cells of both tracks so that the transducer derives a series of sequential waveforms respectively having first and second like amplitudes and shapes for even and odd numbered cells as the tracks are translated relative to the head, the waveforms for each of the odd numbered cells including successive equal first amplitude pulses of first and second different polarities, the waveforms for each of the even numbered cells including successive equal second amplitude pulses of first and second different polarities, the number of pulses and the approximate shapes of the pulses for the even and odd numbered cells being the same, the first and second amplitudes being indicative of the transverse position of the transducer relative to the axis, the apparatus comprising means responsive to the waveforms for selectively altering the pulses so that both pulses of each odd numbered cell have one of the polarities and both pulses of each even numbered cell have the other polarity while substantially retaining the shape and amplitude of the pulses to derive a resulting waveform, and means for integrating the resulting waveform over an integral number of the cells to derive an indication of the transverse positions.

Apparatus for detecting the transverse position of a transducer head relative to reference positions defining even and odd numbered longitudinal axes between longitudinally extending adjacent tracks, each of said tracks including a plurality of longitudinally extending, equal length cells, like numbered cells of said tracks having aligned boundaries, said tracks being translated longitudinally relative to said transducer, said cells having physical variations and said transducer being responsive to the variations in the cells of both tracks so that the transducer derives a series of sequential waveforms respectively having first and second like amplitudes and shapes for even and odd numbered cells as the tracks are translated relative to the head, the waveforms for each of the odd numbered cells including successive equal first amplitude pulses of first and second different polarities, the waveforms for each of the even numbered cells including successive equal second amplitude pulses of first and second different polarities, the number of pulses and the approximate shapes of the pulses for the even and odd numbered cells being the same, the first and second amplitudes being indicative of the transverse position of the transducer relative to the axis, the apparatus comprising means for determining whether the transducer is in the neighborhood of an even or odd numbered axis, means responsive to the even or odd numbered determination and the waveforms for selectively altering the pulses so that both pulses of each odd numbered cell have one of the polarities and both pulses of each even numbered cell have the other polarity while substantially retaining the shape and amplitude of the pulses to derive a resulting waveform, and means for integrating the resulting waveform over an integral number of the cells to derive an indication of the transverse position relative to the axis in the transducer neighborhood.

In combination, a transducer head, a record with physical variations to which the transducer is responsive, said record including a reference position defining a longitudinal axis between longitudinally extending adjacent tracks, each of said tracks including a plurality of longitudinally extending, equal length cells, like numbered cells of said tracks having aligned boundaries, means for translating said tracks longitudinally relative to said transducer, said cells having physical variations and said transducer being responsive to the variations in the cells of both tracks so that the transducer derives a series of sequential waveforms respectively having first and second like amplitudes and shapes for even and odd numbered cells as the tracks are translated relative to the head, the waveforms for each of the odd numbered cells including successive equal first amplitude pulses of first and second different polarities, the waveforms for each of the even numbered cells including successive equal second amplitude pulses of first and second different polarities, the number of pulses and the approximate shapes of the pulses for the even and odd numbered cells being the same, the first and second amplitudes being indicative of the transverse position of the transducer relative to the axis, means responsive to the waveforms for selectively altering the pulses so that both pulses of each odd numbered cell have one of the polarities and both pulses of each even numbered cell have the other polarity while substantially retaining the shape and amplitude of the pulses to derive a resulting waveform, and means for integrating the resulting waveform over an integral number of the cells to derive an indication of the transverse position.

In combination, a transducer head, a record with physical variations to which the transducer is responsive, said record including reference positions defining even and odd numbered longitudinal axes between longitudinally extending adjacent tracks, each of said tracks including a plurality of longitudinally extending, equal length cells, like numbered cells of said tracks having aligned boundaries, means for translating said tracks longitudinally relative to said transducer, said cells having physical variations and said transducer being responsive to the variations in the cells of both tracks so that the transducer derives a series of sequential waveforms respectively having first and second like amplitudes and shapes for even and odd numbered cells as the tracks are translated relative to the head, the waveforms for each of the odd numbered cells including successive equal first amplitude pulses of first and second different polarities, the waveforms for each of the even numbered cells including successive equal second amplitude pulses of first and second different polarities, the number of pulses and the approximate shapes of the pulses for the even and odd numbered cells being the same, the first and second amplitudes being indicative of the transverse position of the transducer relative to the axis, means for determining whether the transducer is in the neighborhood of an even or odd numbered axis, means responsive to the even or odd numbered determination and the waveforms for selectively altering the pulses so that both pulses of each odd numbered cell have one of the polarities and both pulses of each even numbered cell have the other polarity while substantially retaining the shape and amplitude of the pulses to derive a resulting waveform, and means for integrating the resulting waveform over an integral number of the cells to derive an indication of the transverse position relative to the axis in the transducer neighborhood.

A method for measuring the position of a read/write head with respect to a reference position of a data carrier including a plurality of tracks, each of said tracks including a sub-unit for positional data recorded within groups of reference zones, each track being associated with at least two reference zones, the reference position being defined by at least one boundary between adjacent even and odd zones, the head being translated relative to the positional data in the neighborhood of the boundary to derive a signal equal to the algebraic sum of an even part S.sub.1 and an odd part S.sub.2, the even and odd parts having the same period and being shifted in time with respect to each other, the even and odd parts corresponding respectively to signals indicative of positional data of the even and odd zones, said method comprising:

• (a) assigning all pulses of even part S.sub.1 the same first predetermined polarity and all pulses of odd part S.sub.2 the same second predetermined polarity which is opposite to the first polarity, thereby to derive a signal SAS having a period P, and
• (b) calculating the integral of signal SAS over an integration interval extending over N consecutive periods where N is an integer, the integration interval being no greater than the time to read the positional data in the zones, the calculated integral having a predetermined value for the reference position of the head, the position occupied by the head with respect to the reference position being defined by the value of the calculated integral.

Apparatus for measuring the position of a read/write head with respect to a reference position of a data carrier including a plurality of tracks, each of said tracks including a sub-unit for positional data recorded within groups of reference zones, each track being associated with at least two reference zones, the reference position being defined by at least one boundary between adjacent even and odd zones, the head being translated relative to the positional data in the neighborhood of the boundary to derive a signal equal to the algebraic sum of an even part S.sub.1 and an odd part S.sub.2, the even and odd parts having the same period P and being shifted in time with respect to each other, the even and odd parts corresponding respectively to signals indicative of positional data of the even and odd zones, said apparatus comprising:

• means responsive to the odd and even parts of the signal derived by the head for causing all pulses of even part S.sub.1 to have the same first predetermined polarity and all pulses of odd part S.sub.2 to have a second predetermined polarity which is opposite to the first polarity, thereby to derive a signal SAS having a period P, and means responsive to the pulses of even and odd parts S.sub.1 and S.sub.2 for integrating the pulses over an integration interval extending over N periods where N is an integer, the integration interval having a maximum duration equal to the time required for the positional data of the zones to be read by the head, the last named means thereby deriving an integrated value indicative of the head position relative to the reference position.