Disk on which servo pattern is recorded and arithmetic...

Details Disk on which servo pattern is recorded and arithmetic... Disk on which servo pattern is recorded and arithmetic...

1999-08-20

2002-10-22

Neal Holder, Regina (Department: 2651)

Dynamic magnetic information storage or retrieval

General processing of a digital signal

Data in specific format

C360S077080, C360S078040

Reexamination Certificate

active

06469852

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk on which a servo pattern to compensate for head tracking is formed at the predetermined location on the track such as a magnetic disk and particularly to a disk on which signals are never switched between track pitches and an arithmetic processing method for servo pattern read from the disk.
2. Description of the Related Art
In a high capacity flexible magnetic disk and a hard disk, a servo pattern to compensate for tracking of a magnetic head is formed on tracks on its recording surface.
FIG. 6
illustrates a recording surface of a disk, while
FIG. 7
illustrates an enlarged example of the servo pattern recorded on the tracks of the recording surface. On the recording surface of the disk, the tracks T are concentrically set and a servo pattern which is continuous on the radius line R of the disk is formed in a plurality of areas.
In
FIG. 7
, the track center of each track 1, 2, 3, . . . is indicated by a chain line Tc. Tp indicates the distance (track pitch) between the neighboring track centers. The scanning direction of the magnetic head H for reproduction is defined in the right direction in the figure and track width Tw of the magnetic head for reproduction is narrower than the track pitch Tp.
In the servo pattern a preamble (Sync) and an address mark (AM) are recorded first. The preamble and address mark are signals continuous without any switching in the radius direction of a disk crossing each track. The preamble is the signal in which single frequency is continuous toward the head scanning direction and when the magnetic head reproduces this signal, an amplifier gain of the reproducing circuit is fixed (AGC lock). Moreover, timing of the signal reproduction is set, for example, by locking of the PLL circuit with the preamble. Moreover, timing until the next address signal can be set by reproduction of the address mark explained above.
In the address signal, an address value such as track number (track No-) is recorded and this address signal is recorded within a constant width Aw in both sides of the track center Tc. This address signal can express an address value with a plurality of bits. The address signal is different for each track 1, 2, 3, . . . and the width Aw has the width interval equal to that of the track pitch Tp and the address signal is switched at the center between the track centers Tc.
Following the address signal, the A burst signal and B burst signal are recorded as the tracking signals. These A burst signal and B burst signal are recorded sandwiching the track center to have a time difference in the head scanning direction. The A burst signal and B burst signal are recorded in the equal amplitude intensity and are repetitive signals of the single frequency.
In the seek operation, whether the magnetic head H for reproduction has reached the target track or not is determined by reading the address signal. Moreover, when the magnetic head H for reproduction is scanning on the track, a servo gain is fixed by reading the preamble, moreover the single frequency signal of preamble is sampled to become the reference clock and thereby the address signal is read and the A burst signal and B burst signal are read. The tracking control is performed so that the center of track width Tw of the magnetic head H for reproduction is matched with the track center Tc by comparison between the reproduced intensity of the A burst signal and B burst signal read through timing difference.
In the servo pattern of the related art as illustrated in
FIG. 7
, the A burst signal and B burst signal are recorded to be switched defining the track center Tc as the boundary. Meanwhile, the address signal is the same signal in the width Aw defining the track center Tc as the center thereof and this address signal is recorded to be switched at the center of the track centers Tc.
Therefore, for the recording of servo pattern illustrated in
FIG. 7
, it is required to continuously write each signal for each half track pitch (Tp/2). Namely, the address signal
1
-
a
and A burst signal A
1
are recorded in the width of Tp/2. Next, the magnetic head for recording is fed for half track pitch (Tp/2) in the radius direction to record the address signal
2
-
a
and A burst signal A
2
. This process is performed sequentially. The address signals
2
-
a
and
2
-
b
are same signals. Moreover,
3
-
a
and
3
-
b
,
4
-
a
and
4
-
b
,
5
-
a
and
5
-
b
are same signals, respectively.
When the track centers Tc are concentric on the recording surface of disk, following operation is necessary. That is, recording is performed for one circumference using the magnetic head for recording, the magnetic head for recording is fed only for half track pitch (Tp/2) in the radius direction during a turn of the disk, recording is performed during the next turn and moreover the magnetic head is fed for half track pitch (Tp/2) during the next turn of disk. As a result, the disk must be rotated for four turns in order to complete the recording of servo pattern in regard to one track center Tc.
Therefore, a certain time is required until recording of all servo patterns is completed on the recording surface of disk. Particularly, in the case of a disk aiming at larger capacity, the track pitch Tp is rather short and many tracks are formed. Therefore, much more time is required in the recording method which requires the time for four turns of disk to record the servo pattern of one track as explained above.
In addition, in the case when it is attempted to record the servo pattern illustrated in
FIG. 7
during formation of spiral track center Tc on the recording surface of disk, signal must be recorded for half track pitch (Tp/2) respectively in both sides of the spiral track. Therefore, it is impossible that the magnetic head is scanned continuously along the spiral locus to record all servo patterns with only one spiral locus. Namely, the operation to write without any gap two kinds of different signals along the spiral locus is required but such recording is substantially impossible.
SUMMARY OF THE INVENTION
The present invention has been proposed to solve the problems of the related art and it is therefore an object of the present invention to provide a disk which can complete the recording of servo pattern with the minimum rotation thereof and allows recording of servo pattern enabling formation of track of spiral locus and also provide an arithmetic processing method for the servo pattern read from the disk.
The present invention is characterized in that the servo patterns are formed without any switching of signal in the track crossing direction between track centers in the disk where servo patterns are continuously formed in the track crossing direction at the predetermined positions of the recording surface of disk and this servo pattern includes an address signal which is switched at the track center defined as the boundary, an address identifying signal which is switched at the track center defined as the boundary, an even number/odd number detecting signal for identifying the even number and odd number of the track number of each track and a tracking signal which is recorded in different conditions in both sides of the track center.
The address signal and address identifying signal are switched, for example, for every two tracks. In this case, both address signal and address identifying signal are switched, defining different track centers as the boundaries.
The tracking signal is composed, as illustrated in FIG.
1
and
FIG. 2
, of the A burst signal and B burst signal recorded in the position which are different in the timing defining the track center as the boundaries. Alternatively, it is also possible that the signals of different frequencies are recorded on the same position in timing in both sides of the track center.
In the present invention explained above, the signal of the same width as the track pitch Tp is recorded, for example, by the over-writing which may be attained by utilizing the mag

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