Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-06-08
2003-04-29
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06556370
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of writing a tracking servo signal pattern on a magnetic disc of a magnetic disc device for use in recording and reproducing information with a magnetic head along a concentric information track of a predetermined track pitch on the magnetic disc which is driven into a rotation.
BACKGROUND OF THE INVENTION
For magnetic disc devices such as a hard disc device, it has been a usual practice that a tracking servo signal pattern is recorded in advance at a leading portion in each of a plurality of sectors provided by dividing a concentric information track, in order to record and reproduce information as the concentric information track having a predetermined track pitch on a magnetic disc.
FIG. 4
depicts an example of the tracking servo signal pattern. As shown, a magnetic disc rotates in a direction of an arrow
500
, and a magnetic head unit, which includes a reproduction-only magnetic head
12
fixed integrally with a recording magnetic head
14
, moves in a diametric direction
510
of the magnetic disc. First burst signals
81
and
82
, second burst signals
91
and
92
, third burst signals
101
and
102
, and fourth burst signals
110
,
111
and
112
having predetermined frequencies are recorded in advance as tracking servo signals in respective positions, which are separated in opposite directions with respect to each other from centerlines
131
and
132
of the information tracks along the diametric direction
510
of the magnetic disc, and are shifted from one another in a direction of the centerline
131
of the information track.
The device is so constructed that the reproduction-only head
12
reproduces each of at least two signals out of the first, second, third and fourth burst signals, when recording or reproducing information. The device then records or reproduces the information on a predetermined information track by aligning a position of the recording head
14
, while controlling a position of the reproduction-only head
12
in a such manner that a ratio in level between the reproduced signals of the reproduced burst signals becomes equal to a predetermined proportion.
A consideration is given now for an example in that information is recorded on or reproduced from an information track, where the first burst signal
81
and the second burst signal
91
are positioned with respect to the centerline
131
of the information track, as shown in FIG.
4
. The device reproduces the first burst signal
81
and the second burst signal
91
, and controls a position of the magnetic head unit in a manner that a ratio in level of the first burst signal
81
and the second burst signal
91
becomes equal to a predetermined value, so as to obtain a normal tracking. Or, if the device records or reproduces information on another information track, where the third burst signal
102
and the fourth burst signal
111
are positioned with respect to the centerline
132
of the information track, the device obtains a normal tracking by reproducing the third burst signal
102
and the fourth burst signal
111
, and controlling a position of the magnetic head unit in a manner that a ratio in reproduced signal level of the third burst signal
102
and the fourth burst signal
111
becomes equal to a predetermined value.
As a conventional method of writing the tracking servo signal pattern having the afore-noted first, second, third and fourth burst signals on a magnetic disc, a device called “servo track writer” designed exclusively for writing has been used. The servo track writer records the first, second, third and fourth burst signals
81
,
82
,
91
,
92
,
101
,
102
,
110
,
111
,
112
and so on by controlling a position as well as a recording and an erasing timings of a magnetic head unit provided in a magnetic disc device with a control system of the servo track writer, while rotating the magnetic disc of the magnetic disc device.
A conventional method of writing the tracking servo signal pattern using a servo track writer will be described hereinafter by referring to FIG.
5
.
Firstly, the recording head
14
is aligned in a position where a burst signal
81
a
is to be written, and the burst signal
81
a
is written in. A time required for this process is the sum of an aligning time and a time for the disc to rotate for a full turn. Then, the recording head
14
is aligned in another position where a burst signal
101
a
is to be written, and the burst signal
101
a
is written in. A time required for this process is also the sum of the aligning time and the time for the disc to rotate for a full turn.
Next, the recording head
14
is aligned in a position where a burst signal
91
a
is to be written in the diametric direction
510
of the magnetic disc, and the burst signal
91
a
is written immediately after demagnetizing a portion
81
b
of the already written burst signal
81
a
. A time required for this process is also the sum of the aligning time and the time for the disc to rotate for a full turn. The recording head
14
is then aligned in a position where a burst signal
111
a
is to be written in the diametric direction
510
of the magnetic disc, and the burst signal
111
a
is written immediately after demagnetizing a portion
101
b
. A time required for this process is the sum of the aligning time and the time for the disc to rotate for a full turn.
Then, the recording head
14
is aligned in a position where a burst signal
82
a
is to be written, and a portion
91
b
is demagnetized immediately after writing the burst signal
82
a
. A time required for this process is the sum of the aligning time and the time for the disc to rotate for a full turn.
All of the burst signals are written by repeating the process described above. Hence, a time necessary for writing can be given by the following formula:
(aligning time+time for a disc to rotate for a full turn)×number of burst signals
However, a servo track writer for use in the foregoing writing method is very expensive equipment. Therefore, it is desirable for such expensive equipment to be utilized efficiently. However, it has not necessarily been utilized efficiently, since all of the first, second, third, and fourth burst signals are recorded under control of the servo track writer, as has been described.
SUMMARY OF THE INVENTION
A portion of the tracking servo signals or a special signal of the magnetic disc device is written under control of a control system of the servo track writer and writing the rest of the tracking servo signals thereafter under control of the magnetic disc device's own control system based on the already written tracking servo signals without using the servo track writer.
Thus, method of writing a tracking servo signal pattern for a magnetic disc device in accordance with an exemplary embodiment of the present invention includes the steps of: recording a set of tracking servo signals out of a plurality of sets with a magnetic head unit equipped within the magnetic disc device under control of a control system of a writing device of tracking servo signals (“servo track writer”); reproducing the set of tracking servo signals with the magnetic head unit equipped in the magnetic disc device under control of a control system of the magnetic disc device by itself; and recording tracking servo signal pattern not yet recorded among the plurality of sets with the magnetic head unit equipped in the magnetic disc device, while controlling a position of the magnetic head unit under control of a control system of the magnetic disc device by itself based on the reproduced signals.
According to this method, a utilization efficiency of the servo track writer is improved by at least equal to or more than double, since the servo track writer records only one set of the tracking servo signals. Also, the invention does not necessitate any consideration, in particular, for utilization efficiency and so on of a special equipment such as the servo track writer because the tracking servo signal pattern of the other se
Hudspeth David
Tzeng Fred F.
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