EP0084709A1 — Embedded servo track following system and method …

Claim 1

Independent Claim 162 words

A servo system for positioning a read/write transducer relative to a magnetic storage disc to read and write data stored on the disc, the servo system comprising positioning means energizable for moving the read/write transducer to preselected radial recording positions on the disc, drive means for providing relative movement between the disc and the read/write transducer thereby enabling the transfer of data between the disc and the read/write transducer, characterized in the disc having a plurality of side-by-side, closely-spaced servo tracks recorded thereon, the servo tracks identifying said preselected radial recording positions on the disc; the servo tracks being provided with a nonuniform radial track density, the track density of the servo tracks varying from more dense at the periphery of the disc to less dense at the interior of the disc; servo control means for sensing the output of the read/write transducer and selectively energizing the positioning means for positioning the read/write transducer at preselected radial recording positions on the disc.

Claim 2

Dependent Claim 162 words

A servo system for positioning a read/write transducer relative to a magnetic storage disc to read and write data stored on the disc, the servo system comprising positioning means energizable for moving the read/write transducer to preselected radial recording positions on the disc, drive means for providing relative movement between the disc and the read/write transducer thereby enabling the transfer of data between the disc and the read/write transducer, characterized in the disc having a plurality of side-by-side, closely-spaced servo tracks recorded thereon, the servo tracks identifying said preselected radial recording positions on the disc; the servo tracks being provided with a nonuniform radial track density, the track density of the servo tracks varying from more dense at the periphery of the disc to less dense at the interior of the disc; servo control means for sensing the output of the read/write transducer and selectively energizing the positioning means for positioning the read/write transducer at preselected radial recording positions on the disc.

Claim 3

Dependent Claim 44 words

The servo system of claim 1 characterized in that the servo tracks comprise a plurality of alternately arranged odd and even servo tracks recorded on the disc such that adjacent pairs of the servo tracks identify the preselected radial recording positions on the disc.

Claim 4

Dependent Claim 27 words

The servo system of claim 2 characterized in that the servo control means comprises means for centering the read/write transducer between adjacent pairs of the servo tracks.

Claim 5

Dependent Claim 81 words

The servo system of claim 3 characterized in that both of the odd and even servo tracks comprise a serial array of magnetic transitions recorded on the disc, each of the series of transitions generating a waveform having a net DC component, the DC components of the odd and even servo tracks being equal in magnitude but opposite in polarity whereby the DC components of adjacent odd and even servo tracks cancel each other when the read/write transducer is disposed therebetween.

Claim 6

Dependent Claim 30 words

The servo system of claim 4 characterized in that the servo control means comprises means for nulling the output of the read/write transducer between the odd and even servo tracks.

Claim 7

Dependent Claim 84 words

The servo system of claim 3 characterized in that both of the odd and even servo tracks comprise arrays of equally spaced transition pairs, each of the transition pairs comprisino first and second equally spaced oppositely directed magnetic transitions, each of the transition pairs disposed in the even servo track having an identical order and each of the transition pairs disposed in the odd servo track having an order identically opposite of the order of the transition pairs disposed in the even servo track.

Claim 8

Dependent Claim 76 words

The servo system of claim 6 wherein each of the transition pairs of the odd and even servo tracks is equally spaced, characterized in that the spacing between the transitions of the transition pairs is λ 1 and the spacing between the transition pairs is a 2 , X 2 being greater in magnitude than λ 1 , and in that the odd and even servo tracks are provided with a phase difference of approximately 180°.

Claim 9

Dependent Claim 38 words

The servo system of claim 1 characterized in that the odd and even servo tracks are both provided with more than one frequency, the same frequencies being used to write both of the odd and even servo tracks.

Claim 10

Dependent Claim 35 words

The servo system of claim 8 characterized in that the odd and even servo tracks are both provided with first and second frequencies having differing wavelengths, the second frequency being impressed upon the first frequency.

Claim 11

Dependent Claim 65 words

The servo system of claim 9 characterized in that the even servo tracks each comprise a series of magnetic transitions written on the disc, the order of the transitions in the odd servo track being identically opposite from the order of the transitions in the even servo tracks, the odd servo track being approximately 180° out of phase with respect to the even servo track.

Claim 12

Dependent Claim 65 words

The servo system of claim 1 wherein the storage medium includes a plurality of informational data sectors and a plurality of servo data sectors, the informational data sectors and the servo data sectors being alternately spaced in side-by-side relationship, characterized in that the informational data sectors include cylinder identification data which is read on the fly when the read/write head is traversing the recording media.

Claim 13

Dependent Claim 32 words

The servo system of claim 11 further characterized in having means for generating gating signals defining the positions of the plurality of informational data sectors and the plurality of servo data sectors.

Claim 14

Dependent Claim 30 words

The servo system of claim 12 ' characterized in that the means for generating gating signals comprises a dedicated track and a fixed dedicated servo transducer for following the same.

Claim 15

Dependent Claim 147 words

The servo system of claim 1 wherein the servo control means comprises a position signal demodulator means connected to the read/write transducer for generating a position signal and a velocity transducer for providing a velocity signal representative of the velocity of the read/write transducer as the read/write transducer is radially moved to preselected recording positions on the disc by the positioning means, characterized in that the servo control means further includes a summing means for receiving the position signal, the velocity signal and a velocity profile signal from a controller, the least significant bit of the velocity profile signal being greater than the maximum value of the position signal whereby whenever the velocity profile signal is present the velocity profile signal dominates the position signal causing the summing means to energize the positioning means to move the read/write transducer to a predetermined radial position on the disc.

Claim 16

Dependent Claim 106 words

A magnetic recording disc for use in an embedded servo track system that positions a read/write transducer to read data stored on the disc, the disc comprising a plurality of informational data sectors and a plurality of servo data sectors, the plurality of servo data sectors comprising a plurality of side-by-side, closely-spaced servo tracks recorded on the disc for identifying preselected radial positions on the disc, characterized in that the servo tracks are provided with a nonuniform radial track density, the track density of the servo tracks varying from more dense at the periphery of the disc to less dense at the interior of the disc.

Claim 17

Dependent Claim 106 words

A magnetic recording disc for use in an embedded servo track system that positions a read/write transducer to read data stored on the disc, the disc comprising a plurality of informational data sectors and a plurality of servo data sectors, the plurality of servo data sectors comprising a plurality of side-by-side, closely-spaced servo tracks recorded on the disc for identifying preselected radial positions on the disc, characterized in that the servo tracks are provided with a nonuniform radial track density, the track density of the servo tracks varying from more dense at the periphery of the disc to less dense at the interior of the disc.

Claim 18

Independent Claim 211 words

A method for positioning a read/write transducer relative to a magnetic storage disc to read data stored on the disc, the method comprising the step of driving the disc to provide relative movement between the disc and the read/write transducer thereby enabling the transfer of data between the disc and the transducer; characterized in providing a plurality of side-by-side, closely spaced alternately arranged odd and even servo tracks recorded on the disc such that an adjacent pair of the odd and even servo tracks identifies a preselected radial position on the disc therebetween, each of the odd and even servo tracks generating a waveform having a net DC component, the DC components of the odd and even servo tracks being equal in magnitude but opposite in polarity whereby said DC components of the odd and even servo tracks cancel each other when the read/write transducer is disposed therebetween, the servo tracks being provided with a nonuniform, radial density, the servo tracks being more densely packed on the periphery of the disc and less densely packed on the interior of the disc; and sensing the output of the read/write transducer, and positioning the read/write transducer to null the output of the transducer thus centering the same between odd and even servo tracks.

Claim 19

Independent Claim 211 words

A method for positioning a read/write transducer relative to a magnetic storage disc to read data stored on the disc, the method comprising the step of driving the disc to provide relative movement between the disc and the read/write transducer thereby enabling the transfer of data between the disc and the transducer; characterized in providing a plurality of side-by-side, closely spaced alternately arranged odd and even servo tracks recorded on the disc such that an adjacent pair of the odd and even servo tracks identifies a preselected radial position on the disc therebetween, each of the odd and even servo tracks generating a waveform having a net DC component, the DC components of the odd and even servo tracks being equal in magnitude but opposite in polarity whereby said DC components of the odd and even servo tracks cancel each other when the read/write transducer is disposed therebetween, the servo tracks being provided with a nonuniform, radial density, the servo tracks being more densely packed on the periphery of the disc and less densely packed on the interior of the disc; and sensing the output of the read/write transducer, and positioning the read/write transducer to null the output of the transducer thus centering the same between odd and even servo tracks.

Claim 20

Dependent Claim 46 words

The method of claim 16 characterized in that both of the odd and even servo tracks comprise a serial array of transitions in the recording medium, the DC components of the odd and even servo tracks being coded in the timing and order of the transitions.

Claim 21

Dependent Claim 21 words

The method of claim 17 characterized in that both of the odd and even servo tracks comprise a 110110110... MFM code.

Claim 22

Dependent Claim 50 words

The method of claim 17 further characterized by the steps of: providing alternately spaced informational data and servo data sectors on the recording medium; providing a cylinder identification in the informational data sectors; and reading the cylinder identification on the fly when the read/write transducer is traversing the recording medium.

Claim 23

Independent Claim 207 words

A method for writing a clock track on a magnetic storage medium of a disc system comprising a fixed read/write head, at least one moving read/write head, and means for translating the magnetic storage medium relative to the fixed and the moving heads, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the fixed and the moving heads; characterized by the steps of: writing a single pair of transitions with the fixed head; selecting a predetermined number N of transition pairs for a clock track; reading the single pair of transitions to create a single initial electrical pulse; phase-lock looping the initial electrical pulse to a number of electrical pulses approximately equal to the square root of N; writing an intermediate clock track with the moving head, the intermediate clock track having a number of transition pairs equal to the square root of N; reading the intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N; phase-lock looping the intermediate clock electrical pulses to a number of electrical pulses equal to N; and writing a clock track with the fixed head having N transition pairs.

Claim 24

Independent Claim 207 words

A method for writing a clock track on a magnetic storage medium of a disc system comprising a fixed read/write head, at least one moving read/write head, and means for translating the magnetic storage medium relative to the fixed and the moving heads, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the fixed and the moving heads; characterized by the steps of: writing a single pair of transitions with the fixed head; selecting a predetermined number N of transition pairs for a clock track; reading the single pair of transitions to create a single initial electrical pulse; phase-lock looping the initial electrical pulse to a number of electrical pulses approximately equal to the square root of N; writing an intermediate clock track with the moving head, the intermediate clock track having a number of transition pairs equal to the square root of N; reading the intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N; phase-lock looping the intermediate clock electrical pulses to a number of electrical pulses equal to N; and writing a clock track with the fixed head having N transition pairs.

Claim 25

Dependent Claim 30 words

The method of claim 20 further characterized by the steps of: checking for the correct number of transitions on the clock track; and checking the closure for the clock track.

Claim 26

Dependent Claim 81 words

The method of claim 21 still further characterized by the steps of: providing the fixed head with a plurality of read/write gaps; selecting a second gap on the fixed head; reading the intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N; phase-lock looping the intermediate clock electrical pulses to a number of electrical pulses equal to N; and writing a redundant clock track with the second gap of the fixed head.

Claim 27

Independent Claim 341 words

A method for establishing a desired track density on a magnetic storage medium of a disc system which comprises at least one moving read/write head, means for translating trhe magnetic storage medium relative to the read/write head, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the read/write head, and means for positioning the read/write head at different positions on the storage medium; characterized by the steps of: positioning the read/write head at a first limit stop in the range of travel of the means for positioning; writing a first reference track with the read/write head; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the read/write head; displacing the read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the read/write head; displacing the read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; continuing to write successive reference tracks and displacing the read/write head across the storage medium by writing a reference track and moving.the read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% of its original amplitude; counting the number of reference tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; checking the track density to ensure that it is within a predetermined range of the desired track density; if the track density is high, erasing the storage medium, lowering the X% value and repeating the programming method steps; if the track density is low, erasing the storage medium, increasing the X% value and repeating the aforementioned method steps; and stopping if the track density is within a predetermined range of the desired track density.

Claim 28

Independent Claim 341 words

A method for establishing a desired track density on a magnetic storage medium of a disc system which comprises at least one moving read/write head, means for translating trhe magnetic storage medium relative to the read/write head, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the read/write head, and means for positioning the read/write head at different positions on the storage medium; characterized by the steps of: positioning the read/write head at a first limit stop in the range of travel of the means for positioning; writing a first reference track with the read/write head; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the read/write head; displacing the read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the read/write head; displacing the read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; continuing to write successive reference tracks and displacing the read/write head across the storage medium by writing a reference track and moving.the read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% of its original amplitude; counting the number of reference tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; checking the track density to ensure that it is within a predetermined range of the desired track density; if the track density is high, erasing the storage medium, lowering the X% value and repeating the programming method steps; if the track density is low, erasing the storage medium, increasing the X% value and repeating the aforementioned method steps; and stopping if the track density is within a predetermined range of the desired track density.

Claim 29

Dependent Claim 35 words

The method of claim 23 characterized in that the distance traversed between each reference track written is approximately half of a data track and the X% value is in the range of 25% to 50%.

Claim 30

Dependent Claim 64 words

The method of claim 24 further characterized by the step of varying the X% value as reference tracks are written across the disc, the X% value being larger at the periphery of the disc and lower at the interior of the disc, whereby the track density is more dense at the periphery of the disc and less dense at the interior of the disc.

Claim 31

Independent Claim 384 words

A method for writing embedded servo data on a magnetic storage medium of a disc system comprising a first moving read/write head, means for translating the magnetic storage medium relative to the read/write head, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the read/write head, and means for positioning the read/write head at different positions on the storage medium, characterized by the steps of: positioning the first read/write head at a first limit stop in the range of travel of the means for positioning; dividing the magnetic storage medium into servo data sectors and reference data sectors; writing a first servo data track with the read/write head in the servo data sectors on the storage medium; writing a first reference track with the read/write head in the reference data sectors on the storage medium; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the read/write head; displacing the read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the read/write head in the reference data sectors; displacing the read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; writing a second servo track with the read/write head in the reference data sectors; continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth; keeping a measure of the number of servo data tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; checking the servo track density to ensure that it is within a predetermined range of the desired track density; if the servo track density is high, erasing the storage medium, lowering the X% value and repeating the aforementioned method steps; if the servo track density is low, erasing the storage medium, raising the X% value and repeating the aforementioned method steps; stopping if the servo track density is within a predetermined range of the desired servo track density; and erasing the reference data sectors.

Claim 32

Independent Claim 384 words

A method for writing embedded servo data on a magnetic storage medium of a disc system comprising a first moving read/write head, means for translating the magnetic storage medium relative to the read/write head, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the read/write head, and means for positioning the read/write head at different positions on the storage medium, characterized by the steps of: positioning the first read/write head at a first limit stop in the range of travel of the means for positioning; dividing the magnetic storage medium into servo data sectors and reference data sectors; writing a first servo data track with the read/write head in the servo data sectors on the storage medium; writing a first reference track with the read/write head in the reference data sectors on the storage medium; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the read/write head; displacing the read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the read/write head in the reference data sectors; displacing the read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; writing a second servo track with the read/write head in the reference data sectors; continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth; keeping a measure of the number of servo data tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; checking the servo track density to ensure that it is within a predetermined range of the desired track density; if the servo track density is high, erasing the storage medium, lowering the X% value and repeating the aforementioned method steps; if the servo track density is low, erasing the storage medium, raising the X% value and repeating the aforementioned method steps; stopping if the servo track density is within a predetermined range of the desired servo track density; and erasing the reference data sectors.

Claim 33

Dependent Claim 63 words

The method of claim 26 further characterized by the steps of: providing at least one additional moving read/write head which is displaced relative to a translating storage medium along with the first read/write head by the positioning means; and writing servo data with the additional moving read/write head at the same positions that servo data is written with the first moving read/write head.

Claim 34

Dependent Claim 48 words

The method of claim 26 including the step of alternately writing odd and even servo data tracks and characterized in that the distance traversed between each reference track written is approximately half of a data track and the X% value is in the range of 25% to 50%.

Claim 35

Dependent Claim 64 words

The method of claim 26 further characterized by the step of varying the X% value as reference tracks are written across the disc, the X% value being larger at the periphery of the disc and lower at the interior of the disc whereby the track density is more dense at the periphery of the disc and less dense at the interior of the disc.

Claim 36

Dependent Claim 98 words

The method of claim 28 characterized in that the odd and even servo tracks are both provided with more than one frequency, the same frequencies being used to write both of the odd and even servo tracks, each of the odd and even servo tracks comprising a series of magnetic transitions written on the storage medium, the order of the transitions in the odd servo track being identically opposite from the order of the transitions in the even servo track whereby the odd servo track is approximately 180° out of phase with respect to the even servo track.

Claim 37

Independent Claim 804 words

A method for writing embedded servo data on a magnetic storage medium of a disc system comprising a fixed read/write head, a first moving read/write head, and means for tanslating the magnetic storage medium relative to the fixed and the moving heads, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the fixed and the moving heads; characterized by the steps of: writing a single pair of transitions with the fixed head; selecting a predetermined number N of transition pairs for a clock track; reading the single pair of transitions to create a single initial electrical pulse; phase-lock looping the initial electrical pulse to a number of electrical pulses approximately equal to the square root of N; holding the moving head stationary and writing an intermediate clock track with the moving head, the intermediate clock track having a number of transition pairs equal to the square root of N; reading the intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N; phase-lock looping the intermediate clock electrical pulses to a number of electrical pulses equal to N; writing a clock track with the fixed head having N transition pairs; providing means for positioning the first moving read/write head at different positions on the storage medium; ' positioning the first moving read/write head at a first limit stop in the range of travel of the means-for positioning; writing a first reference track with the first moving read/write head; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the first moving read/write head; displacing the first moving read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude. writing a second reference track with the first moving read/write head; displacing the first moving read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of the original amplitude; continuing to write successive reference tracks and displacing the first moving read/write head across the storage medium by writing a reference track and moving the first moving read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% of its original amplitude; counting the number of reference tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; erasing the storage medium; checking the track density to ensure that it is within a predetermined range of the desired track density; if the track density is high, lowering the X% value and repeating the programming method steps; if the track density is low, increasing the X% value and repeating the aforementioned method steps; if the track density is within a predetermined range of the desired track density: positioning the first moving read/write head at a first limit stop in the range of travel of the means for positioning; dividing the magnetic storage medium into servo data sectors and reference data sectors; writing a first servo data track with the first moving read/write head in the servo data sectors on the storage medium; , writing a first reference track with the first moving read/write head in the reference data sectors on the storage medium; reading the first reference track with the moving read/write head; displacing the first moving read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the first moving read/write head in the reference data sectors; displacing the first moving read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; writing a second servo track with the first moving read/write head in the reference data sectors; continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth; keeping a measure of the number of servo data tracks written; stopping when a second limit step in the range of travel of the means for positioning is encountered; checking the servo track density to ensure that it is within a predetermined range of the desired track density; if the servo track density is high, erasing the storage medium, lowering the X% value and repeating the aforementioned method steps; if the servo track density is low, erasing the storage medium, raising the X% value and repeating the aforementioned method steps; stopping if the servo track density is within a predetermined range of the desired servo track density; and erasing only the reference data sectors.

Claim 38

Independent Claim 804 words

A method for writing embedded servo data on a magnetic storage medium of a disc system comprising a fixed read/write head, a first moving read/write head, and means for tanslating the magnetic storage medium relative to the fixed and the moving heads, whereby information may be written on the medium in the form of magnetic transitions and the magnetic transitions may be read with the fixed and the moving heads; characterized by the steps of: writing a single pair of transitions with the fixed head; selecting a predetermined number N of transition pairs for a clock track; reading the single pair of transitions to create a single initial electrical pulse; phase-lock looping the initial electrical pulse to a number of electrical pulses approximately equal to the square root of N; holding the moving head stationary and writing an intermediate clock track with the moving head, the intermediate clock track having a number of transition pairs equal to the square root of N; reading the intermediate clock track to create a number of intermediate clock electrical pulses equal to the square root of N; phase-lock looping the intermediate clock electrical pulses to a number of electrical pulses equal to N; writing a clock track with the fixed head having N transition pairs; providing means for positioning the first moving read/write head at different positions on the storage medium; ' positioning the first moving read/write head at a first limit stop in the range of travel of the means-for positioning; writing a first reference track with the first moving read/write head; choosing a predetermined percentage of amplitude reduction, X%, that is related to a desired track density; reading the first reference track with the first moving read/write head; displacing the first moving read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude. writing a second reference track with the first moving read/write head; displacing the first moving read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of the original amplitude; continuing to write successive reference tracks and displacing the first moving read/write head across the storage medium by writing a reference track and moving the first moving read/write head away from the last reference track written until the amplitude of the last reference track written is equal to X% of its original amplitude; counting the number of reference tracks written; stopping when a second limit stop in the range of travel of the means for positioning is encountered; erasing the storage medium; checking the track density to ensure that it is within a predetermined range of the desired track density; if the track density is high, lowering the X% value and repeating the programming method steps; if the track density is low, increasing the X% value and repeating the aforementioned method steps; if the track density is within a predetermined range of the desired track density: positioning the first moving read/write head at a first limit stop in the range of travel of the means for positioning; dividing the magnetic storage medium into servo data sectors and reference data sectors; writing a first servo data track with the first moving read/write head in the servo data sectors on the storage medium; , writing a first reference track with the first moving read/write head in the reference data sectors on the storage medium; reading the first reference track with the moving read/write head; displacing the first moving read/write head away from the first limit stop until the amplitude of the first reference track is reduced to X% of its original amplitude; writing a second reference track with the first moving read/write head in the reference data sectors; displacing the first moving read/write head again in the same direction until the amplitude of the second reference track is reduced to X% of its original amplitude; writing a second servo track with the first moving read/write head in the reference data sectors; continuing to alternately write two reference tracks and one servo track according to the method steps previously set forth; keeping a measure of the number of servo data tracks written; stopping when a second limit step in the range of travel of the means for positioning is encountered; checking the servo track density to ensure that it is within a predetermined range of the desired track density; if the servo track density is high, erasing the storage medium, lowering the X% value and repeating the aforementioned method steps; if the servo track density is low, erasing the storage medium, raising the X% value and repeating the aforementioned method steps; stopping if the servo track density is within a predetermined range of the desired servo track density; and erasing only the reference data sectors.

Claim 39

Dependent Claim 64 words

The method of claim 31 further characterized by the steps of: providing at least one additional moving read/write head which is displaced relative to a translating storage medium along with the first moving read/write head by the positioning means; and writing servo data with the additional moving read/write head at the same positions that servo data is written with the first moving read/write head.

Embedded servo track following system and method for writing servo tracks

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