Apparatus and method for head-positioning on a rotatable recording medium
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsRyosuke Shimizu, Noriaki Wakabayashi
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Abstract
In a rotatable recording medium, three servo-patterns are discretely formed in the circular direction. A first servo-pattern is made of at least three-phase dibit patterns each having a period of 3 tracks; a second servo-pattern is made of two-phase dibit patterns having a period of 12 tracks and a shift of 3 tracks from each other; and a third servo-pattern is made of a dibit pattern having a period of 6 tracks and a shift of at least 1.5 tracks from the second servo-pattern. Based on reproduction signals derived from the three servo-patterns on the recording medium, relative position of a head against the recording medium is recognized with a precision up to (1/2.sup.N) of a track width using only a binary-valued process.
Claims9
Method for recognizing head position information comprising the steps of:
- discretely forming servo-patterns in a circular direction of a rotatable recording medium, each servo-pattern comprising at least two sub servo-patterns,
- determining values of said at least two sub servo patterns, and comparing peak values of reproduced signal amplitudes representing values of said sub servo-patterns respectively thereby to form a first binary-valued information,
- subsequently adding a first offset onto at least one of those peak values of said reproduced signal amplitudes in compliance with a value of said first binary-valued information,
- then comparing respective peak values to each other again thereby to form a second binary-valued information,
- further adding a second offset onto a peak value on which said first offset was added in compliance with a value of the second binary-valued information,
- or further adding a different offset from the first offset onto a peak value on which no offset was added at the time when second binary-valued information was produced, then comparing respective peak values to each other again, thereby to form a third binary-valued information, and
- then repeating the above-mentioned steps at least N times (N is an integer), thereby to recognize the head position in the radial direction of a recording medium up to a precision of 1/(2.sup.N) of the information track width based on said servo signal,
- wherein said sub-servo-patterns include a three-phase sub-servo-pattern which has a three-track period and includes two tracks with a pattern thereon and one track without a pattern thereon, said three-phase sub-servo-patterns shifted from each other by a one-track period.
Apparatus for recognizing head position information from servo-patterns placed discretely in a circular direction over a rotatable recording medium and each servo-pattern including at least two sub servo patterns, said apparatus comprising:
- at least two peak holders for holding peak values of reproduced signal amplitudes of said respective sub servo-patterns which are to be compared respectively thereby to form a first binary-valued information,
- at least one comparator for comparing said at least two peak values,
- a first latch for memorizing the output of said comparator, thereby to hold the first binary-valued information,
- an offset decoder for determining to which peak holder an offset is to be added in compliance with the contents of said first latch,
- an offset-adder for adding an offset to a specified peak holder in compliance with the instruction of the offset decoder,
- a second latch for holding a second binary-valued information by memorizing momentarily a result obtained by a comparison between a peak value held by the peak holder to which the offset was already added and a peak value held by the peak holder to which offset was not added using said comparator again,
- N latches for latching N binary-valued information from 1st to N-th binary-valued information, and
- a head position information discrimination element for detecting the relative position relation of a head with respect to tracks with a precision up to 1/(2.sup.N) of the information track width by using contents of said from the 1st latch to the N-th latch.
Method for head positioning comprising:
- discretely forming servo-patterns in a circular direction of a rotatable recording medium, wherein said servo-pattern comprises 3 different servo-patterns;
- a first servo-pattern of at least 3 phases having a period of 3 tracks, and a second servo-pattern of at least 2 phases having a period of 12 tracks with a mutual lag therebetween of 3 tracks, and a third servo-pattern having a period of 6 tracks with a lag of at least 1.5 tracks with respect to the second servo-pattern, and
- positioning-controlling a head in the radial direction of a recording medium in compliance with reproduced signal obtained respectively from said 3 different servo-patterns.
Method for recognizing head position information comprising the steps of:
- discretely forming servo-patterns in a circular direction of a rotatable recording medium, each servo-pattern comprising at least two sub servo-patterns,
- determining values of said at least two sub servo patterns, and comparing peak values of reproduced signal amplitudes representing values of said sub servo-patterns respectively thereby to form a first binary-valued information,
- subsequently adding a first offset onto at least one of those peak values of said reproduced signal amplitudes in compliance with a value of said first binary-valued information,
- then comparing respective peak values to each other again thereby to form a second binary-valued information,
- further adding a second offset onto a peak value on which said first offset was added in compliance with a value of the second binary-valued information,
- or further adding a different offset from the first offset onto a peak value on which no offset was added at the time when second binary-valued information was produced, then comparing respective peak values to each other again, thereby to form a third binary-valued information,
- then repeating the above-mentioned steps at least N times (N is an integer), thereby to recognize the head position in the radial direction of a recording medium up to a precision of 1/(.sup.2) of the information track width based on said servo signal,
- obtaining a desired head position, and
- using said recognized head position to position the head at the desired head position.
Dependencies are inferred from the claim text.