Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-05-19
2001-12-11
Hindi, Nabil (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077120, C360S078020, C360S316000, C360S322000
Reexamination Certificate
active
06330123
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to tape servo tracking. More particularly, the present invention relates to tape servo systems and methods, servo track configurations, and read/write heads utilized therewith.
BACKGROUND OF THE INVENTION
It is common to provide magnetic tape write/read head assemblies having one or more write/read transducer heads positioned transverse to the intended path of a magnetic recording medium, i.e., tape, for writing data on and reading data from parallel tracks on the tape. It is also known to include servo information on at least some of the tracks and provide servo transducer heads for reading such information to enable control of the lateral position of the head assembly, thereby dynamically maintaining the respective transducer heads of the head assembly relative to tape tracks. With the use of servo control, data track widths can be made significantly narrower and the capacity of the recording medium can therefore be increased.
Various techniques for providing the servo information contained in tracks, i.e., servo tracks, have been previously employed. For example, it is known to provide dedicated servo tracks on the medium at the time of manufacture. However, it is desirable to enable an end-user to write a servo pattern on the medium in the field as opposed to factory writing of servo information. This allows the end-user to add the servo information to either a blank medium or utilize a medium which was either intentionally or unintentionally erased.
There are a substantial number of different servo track configurations for providing servo control. For example, some of the different configurations are generally characterized by the utilization of either alternating information containing tracks embedded on an erased band and a single head or a center tapped head, as shown in
FIG. 1
, or alternating tracks with different distinguishable characteristics such as one or more discrete monofrequencies and a single head or a center tapped head, such as shown in FIG.
2
. As shown in
FIG. 1
, a single servo transducer
14
is utilized for sensing servo information on the alternating servo tracks
12
in servo band
10
on an erased background for use in positioning data heads
19
within the data bands
18
. Alternatively, a center tapped head
16
may be utilized for providing position error signals as a function of the position of the head
16
over the tracks
12
within the servo band
10
.
As shown in
FIG. 2
, a single servo head
24
may be utilized for providing servo information from alternating servo tracks
22
within servo band
20
having different distinguishable characteristics. The information is then used to position the data heads
29
correctly within the data bands
28
for performing read and/or write functions. Alternatively, a center tapped head (or two servo transducer elements)
26
may be utilized to generate a position error signal from the servo information recorded within the servo band
20
.
However, these different servo configurations have ambiguity associated with identifying which servo track is being used for deriving the position error signal to provide for servo control of the system. Although the servo track provides adequate positioning information, it does not provide any information as to which servo track the servo head is currently utilizing to generate the position error signal for servo control. Therefore, if the servo transducer is unintentionally repositioned, a misidentification of the servo track being used for servo positioning of the data read/write heads occurs.
Various configurations attaining some improvement with respect to the above configurations are shown in
FIGS. 3
,
4
, and
5
, wherein multiple heads are utilized for generating positioning information from the servo information written in the servo band. As shown in
FIG. 3
, multiple heads
32
are utilized for reading servo information from a servo track
34
recorded in servo band
30
for positioning data heads
36
within the data bands
38
. Further, as shown in
FIG. 4
, multiple servo heads
42
are utilized for reading servo information from a pair of distinguishable servo tracks
44
within servo band
40
to position data heads
46
within data bands
48
.
The above configurations either rely on a single servo track utilizing multiple servo heads (wherein the number of heads is at least N−2 and N is the number of data tracks in a data band), rely on a pair of distinguishable servo tracks which also requires the use of at least N−2 servo heads, or rely on a set of alternating distinguishable tracks which fill the servo bands. With the use of multiple heads and a single servo track or a pair of distinguishable servo tracks (FIGS.
3
and
4
), an undesirable large number of servo heads is necessary. With regard to the latter multiple alternating distinguishable tracks, such tracks are very difficult to write in situ in a tape drive.
For example, in writing multiple distinguishable tracks, servo write heads may not be placed adjacent to one another. Therefore, when servo tracks are written contiguous with one another as in the pair of alternating distinguishable servo tracks (
FIG. 4
) and set of multiple alternating distinguishable servo track (
FIG. 2
) configurations, it is required that they be written on multiple passes or with heads along multiple gap lines. For precision writing, this typically requires that the pattern be written in the factory. In many cases it is desirable to write servo information in the field. Further, although with the use of multiple alternating distinguishable tracks written across the servo band, the number of servo heads necessary is reduced to one or two heads, the problem of ambiguity in servo track identification is still applicable.
In another servo configuration which utilizes multiple spaced heads as shown in
FIG. 5
(extracted from U.S. Pat. No. 5,262,908, to Iwamatsu et al., issued Nov. 16, 1993), multiple heads
52
are utilized for reading information from a plurality of spaced servo tracks
54
within servo band
50
for positioning data read/write heads
56
within data bands
58
. However, with respect to such a configuration and the other configurations as described above which use multiple servo heads, it is difficult to produce head assemblies that include such multiple servo heads. Particularly, in thin film heads, limited space is allotted between adjacent data bands and therefore, space is limited for the leads from each of the multiple servo heads. In high track density heads, such leads are much larger than the width of the track pitch. As such, production of such multiple heads in the head assembly in such thin film heads is difficult.
For the above reasons and other reasons that will be apparent from the description below, alternatives to the configurations such as those described above are needed to overcome difficulties associated therewith. For example, the unambiguous identification of individual servo tracks is desired. Further, it is desired to reduce the number of servo heads necessary for providing servo control and also it is desirable to write servo tracks in the field in a single pass.
SUMMARY OF THE INVENTION
A tape servo system in accordance with the present invention includes tape having a plurality of bands of tracks. The plurality of bands of tracks include at least one data band having a plurality of data tracks of track pitch P and a servo band dedicated for servo information. The servo band includes two or more noncontiguous servo tracks with each pair of adjacent servo tracks of the two or more noncontiguous servo tracks having a center to center separation equal to M*P, wherein M for each pair of adjacent servo tracks may be any integer≧2. The system further includes a head assembly having a single magnetoresistive read element tapped to provide at least (K+1) tapped servo read elements for use in reading servo information written to the servo band; wherein K is equal to the integer M for the pair of adjacen
Schwarz Theodore A.
Tran Hung T.
Youngquist Robert J.
Hindi Nabil
Imation Corp.
Levinson Eric D.
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