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Publication numberUS20100284105 A1
Publication typeApplication
Application numberUS 12/773,544
Publication date11 Nov 2010
Filing date4 May 2010
Priority date30 Jan 2004
Also published asUS7283317, US7576949, US7710675, US20050168869, US20080037166, US20090067087
Publication number12773544, 773544, US 2010/0284105 A1, US 2010/284105 A1, US 20100284105 A1, US 20100284105A1, US 2010284105 A1, US 2010284105A1, US-A1-20100284105, US-A1-2010284105, US2010/0284105A1, US2010/284105A1, US20100284105 A1, US20100284105A1, US2010284105 A1, US2010284105A1
InventorsMatthew P. Dugas, Theodore A. Schwarz
Original AssigneeDugas Matthew P, Schwarz Theodore A
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Apparatuses and methods for pre-erasing during manufacture of magnetic tape
US 20100284105 A1
Abstract
The present invention relates to direct current (“DC”) pre-erasing servo channels of a magnetic tape prior to writing servo data in a servo channel. The present invention particularly relates to those servo recordings which were written with a uni-polar current waveform. The DC pre-erase is performed using a uni-polar direct current of a polarity that is opposite to the polarity of the direct current used to write the servo data. This pre-erase may be done with one or more heads. Also, as will be described, the pre-erase of a servo channel and writing to a servo channel may be done by making two passes over a single head or by using two or more heads to perform both steps. Also, it is within the scope of the present invention to have the heads mounted on a single mount or have the heads on separate mounts and on separate tape decks.
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Claims(22)
1. A method for making a magnetic media, the method comprising:
pre-erasing at least one servo channel of the magnetic media, without direct current pre-erasing the data channels of the magnetic media, by applying a direct current of a first polarity; and
writing a servo pattern by applying a direct current of substantially opposite polarity of the first polarity.
2. The method of claim 1, wherein the pre-erasing and the writing is performed using a compound magnetic recording head.
3. The method of claim 2, wherein the compound magnetic recording head comprises:
a first head comprising a magnetically permeable thin film layer comprising an erase gap pattern for pre-erasing a servo track of a magnetic media; and
a second head comprising a magnetically permeable thin film layer comprising a servo write gap pattern for writing a servo pattern in the servo track.
4. The method of claim 3, wherein the erase gap pattern of the first head and the servo write gap pattern of the second head are lithographically printed using a single mask.
5. The method of claim 4, wherein pre-erasing at least one servo channel is performed by passing a portion of the magnetic media over the erase gap pattern of the first head and writing a servo pattern is performed by then passing a portion of the magnetic media over the servo write gap pattern of the second head.
6. The method of claim 5, wherein the servo write gap pattern of the second head is a timing-based servo pattern.
7. The method of claim 5, wherein the servo write gap pattern of the second head is an amplitude-based servo pattern.
8. The method of claim 1, wherein prior to pre-erasing at least one servo channel of the magnetic media, the magnetic media is alternating current erased.
9. A magnetic tape having at least one servo channel that is direct current pre-erased and has servo data written in the at least one servo channel and at least one alternating current pre-erased data channel for receiving data subsequently written thereon, the magnetic tape made by a method comprising: writing a servo pattern using a direct current of a first polarity; prior to the act of writing a servo pattern, erasing at least one servo channel of the magnetic tape by applying a direct current of a substantially opposite polarity of the first polarity.
10. The magnetic tape of claim 9, wherein the act of writing and erasing is performed using a first head.
11. The magnetic tape of claim 10, wherein the first head comprises a time-based servo pattern.
12. The magnetic tape of claim 10, wherein the first head comprises an amplitude-based servo pattern.
13. The magnetic tape of claim 10, wherein the act of erasing at least one servo channel of the magnetic tape is performed by first passing a portion of the magnetic tape that includes the at least one servo channel to be erased over the first head.
14. The magnetic tape of claim 13, wherein the act of writing a servo pattern in the at least one servo channel of the magnetic tape is performed by then passing a portion of the magnetic tape that includes the at least one servo channel to be written over the first head.
15. The magnetic tape of claim 9, wherein the act of erasing is performed by a first head and the act of writing a servo pattern is performed by a second head.
16. The magnetic tape of claim 15, wherein the second head includes a time based servo pattern.
17. The magnetic tape of claim 15, wherein the second head includes an amplitude-based servo pattern.
18. The magnetic tape of claim 15, wherein the first head includes an erase pattern having an erase gap track width that is substantially the same as the servo gap track width.
19. The magnetic tape of claim 15, wherein the second head is one of a thin film head, ferrite based head, and surface thin film head.
20. The magnetic tape of claim 15, wherein the two heads are located on a single mount.
21. The magnetic tape of claim 15, wherein the two heads are located on separate mounts.
22. The magnetic tape of claim 15, wherein the head used to erase is located on a separate tape deck from the head used to write a servo pattern.
Description
    CROSS-REFERENCE TO RELATED APPLICATIONS
  • [0001]
    This application is a divisional of U.S. patent application Ser. No. 11/838,006, filed on Aug. 13, 2007, which is a continuation of U.S. patent application Ser. No. 10/768,719, filed on Jan. 30, 2004, issued as U.S. Pat. No. 7,283,317, the contents of each of which are incorporated herein by reference.
  • TECHNICAL FIELD
  • [0002]
    The present invention relates to apparatuses and methods for use in the manufacture of magnetic tape. In particular, the present invention relates to apparatuses and methods for pre-erasing a servo channel of a magnetic tape.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Magnetic tape as a data storage medium requires the ability to effectively write and read data to data tracks of the magnetic tape; many such data tracks typically extend linearly along the length of tape and, in part, define tape data storage density. In addition, for providing a controlled movement of tape reading and/or writing heads with respect to the data track, servo tracks, which also extend linearly along the length of tape are commonly used. Servo tracks are typically written in such a way as to span the tape in an efficient manner that maximizes the number of data tracks and minimizes the number of servo tracks for a given tape system.
  • [0004]
    A servo track contains servo data and is read by a servo read head. This information is used to determine the relative position of the servo read head with respect to the magnetic media in a translating direction (i.e., movement across the width of the tape). This is also called the cross track direction. To improve positioning of the tape reading and/or writing heads on a magnetic tape, apparatuses and methods of manufacture to create a servo channel that enables the servo data to be read more effectively would be helpful. The present invention addresses apparatuses and methods to improve a servo control system.
  • BRIEF SUMMARY OF THE INVENTION
  • [0005]
    The present invention relates to direct current (“DC”) pre-erasing servo channels of a magnetic tape prior to writing servo data in a servo channel. The present invention particularly relates to those servo recordings which were written with a uni-polar current waveform. The DC pre-erase is performed using a uni-polar direct current of a polarity that is opposite to the polarity of the direct current used to write the servo data. This pre-erase may be done with one or more heads. Also, as will be described, the pre-erase of a servo channel and writing to a servo channel may be done by making two passes over a single head or by using two or more heads to perform both steps. Also, it is within the scope of the present invention to have the heads mounted on a single mount or have the heads on separate mounts and on separate tape decks.
  • [0006]
    In one embodiment, the present invention relates to a magnetic tape comprising a substrate and a magnetic layer, the magnetic tape having at least one direct current pre-erased servo channel that includes servo data.
  • [0007]
    In another embodiment, the present invention relates to a magnetic tape having at least one servo channel that is direct current pre-erased and has servo data written in the at least one servo channel.
  • [0008]
    The magnetic tape is made by a method comprising writing a servo pattern using a uni-polar direct current of a particular pulse train. Prior to writing a servo pattern, erasing the servo channel of the magnetic tape by applying a direct current of a substantially opposite polarity to that of the servo write current pulse sequence.
  • [0009]
    The present invention also relates to an apparatus for use in pre-erasing magnetic tape, comprising a housing supporting at least two heads, wherein at least one of the two heads includes a gap pattern to direct current pre-erase the servo channels on the magnetic tape, wherein the other of the two heads includes a gap pattern for recording the servo channel that is written after the pre-erase has been first recorded.
  • [0010]
    The present invention further relates to an apparatus for use in pre-erasing magnetic tape, comprising a compound substrate having at least a first substrate and a second substrate, wherein the first substrate includes at least one servo pattern and the second substrate includes at least one direct current pre-erase pattern.
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0011]
    FIG. 1 shows a typical servo track and data track organization on the tape.
  • [0012]
    FIG. 2 is a schematic drawing of one embodiment of the present invention showing a housing supporting two heads with magnetic tape extending over the heads, where one of the heads is used to pre-erase with direct current the servo channels of a magnetic tape and the other is used to record the servo pattern onto the pre-erase servo channels.
  • [0013]
    FIG. 3 is a schematic drawing of one embodiment of the present invention showing a housing supporting one head with the magnetic tape extending over the head, where the head is used to pre-erase with direct current the servo channels of a magnetic tape.
  • [0014]
    FIG. 4 shows an exemplary servo erase gap pattern on the surface of a surface film head.
  • [0015]
    FIG. 5 shows an exemplary servo gap pattern on the surface of a surface film head that may be used to write a servo pattern in the servo channel on a magnetic tape.
  • [0016]
    FIG. 6 shows a two head configuration in which one head has a gap pattern that would be used to DC pre-erase the servo channel and the other head has a timing based servo gap pattern that would write a timing based pattern onto the servo channel on a magnetic tape.
  • [0017]
    FIG. 7 shows a close-up of the patterns shown in FIG. 6. Note that the patterns are matched so that the erase track width is substantially the same as the servo track width.
  • [0018]
    FIGS. 8A-8B show a portion of a magnetic layer and substrate of a magnetic tape and a theoretical output signal from a servo pattern on a magnetic tape in which the tape and servo channel have been AC erased.
  • [0019]
    FIGS. 8C-8D show a portion of a magnetic layer and substrate of a magnetic tape and a theoretical output signal from a servo pattern on a magnetic tape in which the servo channel has been DC erased prior to recording the servo signal.
  • [0020]
    FIGS. 9A and 9B show theoretical waveforms for relating the magnetoresistive (MR) response curve of the head, an input field from the magnetic tape, and an output voltage signal from the MR head element.
  • [0021]
    FIG. 10 shows a two head configuration in which one head is a ferrite MIG head having a gap pattern that would be used to DC pre-erase the servo channel and the other head is a surface thin film head using the low inductance, ferrite sub-gap substrate having a timing based servo gap pattern that would write a timing based pattern onto the servo channel on a magnetic tape.
  • [0022]
    FIG. 11 shows an embodiment of the present invention using a compound substrate.
  • [0023]
    FIG. 12 is a schematic drawing of one embodiment of the present invention showing a first housing supporting one head with the magnetic tape extending over the head, where the head is used to pre-erase with direct current the servo channels of a magnetic tape and a second housing supporting one head with magnetic tape extending over the head, where the head is used to write servo data in the servo channel of the magnetic tape.
  • DETAILED DESCRIPTION
  • [0024]
    The present invention relates to apparatuses and methods used in manufacturing magnetic tape. In particular, the present invention relates to manufacture of magnetic tape that includes servo data in one or more servo channels, where one or more servo channels has been pre-erased with a uni-polar signal prior to the servo data being written in a servo channel. Pre-erasing a servo channel with direct current enables the servo read signal representing the uni-polar written servo pattern to be stronger than a servo read signal in a similar servo channel that is not pre-erased. As such, pre-erasing the servo channel during the manufacture and formatting of the magnetic tape will provide benefits by increasing the signal to noise ration of the servo read signal. This in turn can lead to higher areal data storage densities for the magnetic tape. However, it is important to note that the response of a magnetoresistive (“MR”) head to this technique may be too strong and result in distortion and non-linear servo read signals. Hence this technique is to be used when the media thickness and M.sub.rt ratio has become smaller in more aggressive higher density products and when using such a technique will not overdrive the MR servo read head. Since the result of this technique is to increase the servo read signal, it is important to not use it if it will send the read head into a non-linear response region. On the other hand, as areal densities are ever increasing and typically accompanying this the M.sub.rt ratio is decreasing, the use of this technique may prove beneficial in certain servo systems as tape thicknesses continue to decrease.
  • [0025]
    FIG. 1 shows a magnetic tape 10 having data bands or data tracks 12 (also, may be referred to as data channels) and servo bands or servo tracks 14 (also may be referred to servo channels). The data tracks 12 would be the portion of tape 10 to which data elements 16 would be written and from which data elements 16 would be read. Similarly, servo tracks 14 would include servo data 18 which are written into the servo track during manufacture of the magnetic tape 10. This servo data 18 is used by the servo control system to help properly position the read and write heads with respect to the data tracks 12. The present invention relates to pre-erasing servo tracks 14 with a direct current or uni-polar pre-erase signal prior to writing a uni-polar servo pattern of the opposite polarity in the servo track 14.
  • [0026]
    In the preferred embodiment, only the servo channels 14 of a magnetic tape 10 are pre-erased by applying a uni-polar, direct current erase signal through a precise gap pattern in the head. A uni-polar servo pattern is then written upon the pre-erased servo channel but in the opposite polarity. The servo pattern may be timing based or amplitude based or a combination of both. However, the present invention will typically be used with a time based pattern as timing patterns are typically uni-polar and amplitude patterns are typically bi-polar. On bi-polar current written or recorded servo channels 14, the technique is less effective in increasing the signal-to-noise (“SNR”) of the servo read system.
  • [0027]
    In manufacturing magnetic tape 10, the DC pre-erase and the writing of a servo pattern may be accomplished using two or more heads or using one head. For instance, in one embodiment, a portion of the magnetic tape 10 is first passed over a head to perform a DC erase of servo channels 14 of the magnetic tape 10 and then another head is used to write a servo pattern into the servo channels 14 of the magnetic tape 10. Alternatively, the same head may be used to perform a DC erase of the servo channels 14 on a magnetic tape 10 and then to write a servo pattern in the servo channels 14 of the magnetic tape 10. That is, in this embodiment, the magnetic tape 10 is passed over the head to perform a DC erase of the servo channels 14. A pulse is applied through the pattern in the head to DC erase the servo channels 14 of the magnetic tape 10. Then, the tape 10 is passed over the head a second time to write a servo pattern into the servo channels 14 of the magnetic tape 10.
  • [0028]
    In one embodiment, two heads are used and are mounted into a housing so that an efficient one pass servo formatting system may be used. This embodiment is shown in FIG. 2. However, each head may be separately supported by a separate housing or even a separate tape deck (as shown in FIG. 12).
  • [0029]
    With reference to FIGS. 2 and 3, embodiments of an apparatus for use in DC pre-erasing a servo channel 14 of a magnetic tape 10 will be described. FIG. 2 shows a housing 20 with magnetic tape 10 extending across the two heads 22, 22′. As shown in FIG. 2, the embodiment includes a housing 20 that supports a first head 22 and a second head 22′. The heads have a first surface 24, 24′, a second surface 26, 26′, a first side surface 28, 28′, and a second side surface 30, 30′. The first surface 24, 24′ is in contact with the magnetic tape 10. The second surface 26, 26′ of the heads is attached to and supported by the housing 20. In one embodiment, the heads 22, 22′ are mounted to the housing an epoxy. However, the heads may be mounted using any suitable means.
  • [0030]
    The heads 22 and 22′ are disposed side-by-side separated by a predetermined distance L. As shown in FIG. 2, in one embodiment, the heads 22 and 22′ are spaced apart approximately 1.0 millimeters (“mm”) around the top edge 29, 29′ (i.e., toward the first surface 24) and spaced apart approximately 0.80 mm at the bottom edge 31, 31′ (i.e., toward the second surface 26). It will be appreciated that while the distance between the heads is specified, other distances may be used. Similarly, the angle A formed between the two heads may be varied and even flat contours may be used. While FIG. 2 shows the heads 22 and 22′ not spaced such that the sides 30, 28′ are parallel to each other, the heads may be spaced in such a manner that the sides 30, 28′ of the first and second heads 22 and 22′ are substantially parallel to each other in the vertical direction as shown.
  • [0031]
    Any type of head may be used in the dual head configuration including, but not limited to thin film heads, ferrite based heads, and surface thin film heads. For instance, the first and second heads 22 and 22′ may be heads with low inductance, ferrite sub-gap substrate surface film head structures of the type described in U.S. Pat. No. 6,496,328, which is hereby incorporated by reference in its entirety, a surface thin-film head of the type disclosed in U.S. Pat. No. 6,269,533, which is hereby incorporated by reference in its entirety, or a ferrite metal-in-gap (“MIG”) head. Any combination of these types of heads may be used when using two or more head in implementing an embodiment of the present invention. It will be noted that one head will be optimized as an erase head and the other head will be optimized as a servo write head.
  • [0032]
    In one embodiment of the dual configuration (as shown in FIG. 10), a ferrite MIG head or a surface thin film head with a pattern would be used to perform the DC erase and a surface thin film head using the low inductance, ferrite sub-gap substrate surface film head with a time base servo pattern would be used to write a servo pattern on the servo channel of the magnetic tape. FIG. 10 shows a ferrite MIG head with a pre-erase gap 46 to perform a DC erase with a surface thin film head having gap for an amplitude or a time based servo pattern for writing to a servo channel 14. As shown in FIG. 10, the width of the pre-erase gap is substantially the same as the width of the servo pattern.
  • [0033]
    The housing 20 may be formed from any appropriate material including metal. The housing 20 is milled to position the heads 22, 22′ to the housing. Furthermore, it will be appreciated that while FIG. 2 shows a housing that includes two heads, a housing having more than two heads is within the scope of the present invention.
  • [0034]
    FIG. 3 shows a housing mount 20 that has a first head 22. This embodiment may be used when the heads for performing the DC pre-erase on the servo channels 14 and writing the servo patterns on the servo channels 14 are located on different tape decks or this embodiment may be used when the same head is used to perform both the DC erase on one pass and write the servo data 18 on the servo track 14 on a second pass. FIG. 12 shows a first housing 20 supporting a first head 22 with the magnetic tape 10 extending over the head 22, where the head is used to pre-erase with direct current the servo channels 14 of a magnetic tape 10 and a second housing 20′ supporting a second head 22′ with magnetic tape 10 extending over the second head 22′, where the second head 22′ is used to write servo data in the servo channel 14 of the magnetic tape 10.
  • [0035]
    FIG. 11 shows an alternative embodiment that may be used for more precise pattern combinations than a mechanically assembled dual module head pair. FIG. 11 shows a compound substrate 80. As shown in FIG. 11, the compound substrate 80 has a first substrate 81 and a second substrate 83. The first and second substrates 81 and 83 are spaced apart a predetermined distance L by use of a first block 85 to separate the substrates. The first substrate includes a pre-erase gap 46 to DC erase a servo channel and the second substrate includes a servo pattern that is written in the DC pre-erased servo channel. As shown in FIG. 11, the pre-erase gap is ideally substantially the same width at the servo pattern. The pre-erase gap may have a slightly larger width than the width of the servo pattern. The first block 85 separating the compound substrate may be formed with ceramic. However, other materials may be used to separate the substrates. The substrates may be joined together using epoxy.
  • [0036]
    FIG. 11 shows a compound substrate 80 having a combination of a surface thin film head (of the type described in U.S. Pat. No. 6,269,533) and a low inductance surface thin film head (of the type described in U.S. Pat. No. 6,496,328). Also, while two substrates are joined together in FIG. 11, a compound substrate having more than two substrates is within the scope of the present invention.
  • [0037]
    The compound substrate in FIG. 11 may have all the gaps lithographically printed by a single mask and hence all patterns printed on those sub-gaps will have lithographic precision to the order of 0.1 microns or better. Hence, the compound substrate module may be used for more precise pattern combinations than a mechanically assembled dual module head pair.
  • [0038]
    The apparatuses discussed with respect to FIGS. 2 and 3 may contain various servo patterns where one of the patterns is for performing a DC pre-erase of a servo track 14. FIG. 4 shows an exemplary servo erase gap pattern on the surface of a surface film head. While the servo head itself of FIG. 5 may be used to pre-erase the tape 10 this would require a two pass operation which would be time inefficient. However that would be within the scope of the present invention.
  • [0039]
    FIG. 4 shows an exemplary servo erase gap pattern on the surface of a surface film head. The servo erase gap pattern 32 includes a first termination 34 and a second termination 36. The terminations 34, 36 may have curved portions. As shown in FIG. 4, the terminations 34 and 36 are circular. FIG. 5 shows an exemplary servo gap pattern on the surface of a surface film head that may be used to write a servo pattern in the servo channel 14 on a magnetic tape 10. FIG. 5 shows a servo gap pattern 38 that is time based. The servo gap pattern 38 has a first portion 40 and a second portion 40′, with each portion 40, 40′ having a first termination 42, 42′ and a second termination 44, 44′. As with the pattern in FIG. 4, the terminations 42, 42′, 44, 44′ have curved portions, and as shown, have circular terminations. It will be appreciated that other types servo patterns may be used without departing from the scope of the present invention.
  • [0040]
    FIG. 6 shows a two head configuration in which one head has a gap pattern 32 that would be used to DC pre-erase the servo channel and the other head has a timing based servo gap pattern 38 that would write a timing based pattern onto the servo channel on a magnetic tape 10. FIG. 7 shows a close-up of the patterns shown in FIG. 6. Note that the patterns are matched so that the erase gap track width is substantially the same as the servo gap track width. Such a configuration would allow the entire servo track 14 to be DC erased
  • [0041]
    FIGS. 4-6 show each head having five patterns that may be used to perform a DC pre-erase. Such heads may have the same number of patterns to perform a pre-erase as the number of servo channels or servo tracks 14 contained on the magnetic tape 10.
  • [0042]
    A pre-erase process may be performed during the production of magnetic tape in order to provide a stronger signal for reading the servo pattern. FIG. 8A shows magnetic tape 10 with servo track 14, wherein the servo track 14 has been AC erased but not DC erased. As shown in FIG. 8A, the magnetic tape 10 has a magnetic layer 11 and a substrate 13. The “M” stands for magnetization and shows that a portion 19 of the servo channel 14 is magnetized (e.g., by the writing of servo data). FIG. 8B shows the input signal 50 from a tape 10 as read by a read head of the servo pattern 14 in such a condition. The amplitude B indicates, at least in part, the strength of the signal 50.
  • [0043]
    FIG. 8C shows magnetic tape 10 with servo track 14, wherein the servo track has been DC erased in accordance with the present invention. As in FIG. 8A, the servo channel 14 has be magnetized by the written servo data. However, unlike FIG. 8A, the portion of the servo channel adjacent the servo data has been DC pre-erased. FIG. 8D shows the input signal 52 from the tape 10 as read by the servo read head in such a condition. The amplitude C indicates the strength of the input signal 52 from the DC pre-erased servo channel is theoretically greater than the input signal 50 from the servo channel that was not DC pre-erased. A comparison of FIGS. 8B and 8D shows that, in theory, the input signal 52 from a DC pre-erased servo channel is greater than the input signal 50 from a servo channel that has not been DC pre-erased. In one embodiment, a DC pre-erased channel, in theory, would provide a servo read voltage signal twice as strong as an input signal from a servo channel that has not been DC pre-erased but which had been randomly erased.
  • [0044]
    FIGS. 9A and 9B show a theoretical response curve 70 of the MR stripe, a theoretical input signal from a tape 71 and a theoretical output voltage 72. The response curve 70 includes a peak 73 and a portion that approximates a linear region 74. This response curve is sometime referred to the cosine squared response as the curve can be modeled as .DELTA.R=(.delta..rho./.rho.)R cos.sup.2.phi.). The angel .phi. being the angle between the resultant magnetization vector of the MR stripe and the applied current direction in the stripe. (.delta..rho./.rho.) is called the magnetoresistive coefficient of the material that makes up the stripe.
  • [0045]
    This response curve in turn leads to a voltage .DELTA.V=I.DELTA.R, where I is the bias current of the stripe. This discussion could equally apply to giant magnetoresistive (“GMR”) materials where the response is similar but modeled as a cosine curve.
  • [0046]
    In general, the output voltage should correspond to a waveform shown in FIG. 9A in which the input signal is within the linear region of the response curve. However, as shown in FIG. 9B, when the output voltage has a “rabbit ears” 75, that the input signal extends outside the linear region and, as shown, to the negative slope of there response curve.
  • [0047]
    This condition is not desired. As such, the DC pre-erase must be such that the signal output remains within the liner region of the response curve. As such, the present invention when used appropriately allows for greater voltages of the input signal while still remaining in the linear region of the response curve.
  • [0048]
    Also, in general, the MR read sensor output voltage is a function of the thickness of the magnetic tape. To achieve higher linear recording densities the tape thickness is generally decreased to maintain magnetic bit cell stability. Hence the servo read signals may need to be increased as tape thickness decreases. As such, under proper conditions, and assuming certain system parameters of higher density recordings, performing a DC pre-erase of a servo channel enables a stronger signal to be read without going into the non-linear region of the MR read elements response curve.
  • [0049]
    In practical operation, a dual head system consisting of a servo write head and servo DC erase head would be used in making magnetic tape. The servo DC erase will erase only that part of the medium upon which will be recorded the servo format signal. For all practical purposes, the DC erase head track widths and the servo format head track widths would be the same and they would be matched up within certain engineering tolerances. That is, the magnetic tape would only be DC erased in the servo track region and not in the data track regions. This is because data zones should remain ideally AC erased so that the subsequent data written thereupon will have the highest possible signal-to-noise ration and the data will not be biased by the underlying DC erasure.
  • [0050]
    In principle one could wipe the entire tape width with a DC erase and achieve the same result on the servo track, however that may compromise the subsequently recorded data in the data track areas. Hence, while one could use a full tape width DC erase head this would not be preferred method for reasons that go beyond the scope of this document.
  • [0051]
    During manufacture, the magnetic tape would move in a transducing direction over the heads. The servo channel of the magnetic tape is first pre-erased, and then a servo pattern is written in the servo channel 14 (see FIG. 1). The resulting magnetic tape 10 would have a pre-aligned magnetization of the opposite polarity to that of the servo signal.
  • [0052]
    The dual module head system on one mount, the dual heads on separate individual mountsor the compound substrate head may be used to enable this concept. This concept can apply to timing based servo systems, amplitude based systems or a combination of both in some more advanced servo system. The concept will be most effective when the servo write system is uni-polar in nature and when the DC pre-erase is made using the opposite polarity.
  • [0053]
    In that the foregoing description of the present invention discloses only exemplary embodiments thereof, it is to be understood that other variations are contemplated as being within the scope of the present invention. Accordingly, the present invention is not limited in the particular embodiments which have been described in detail therein. Rather, reference should be made to the appended claims as indicative of the scope and content of the present invention.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2938962 *12 Jul 195531 May 1960KoninsAzimuth seeking reproducing head
US4007493 *6 May 19758 Feb 1977Burroughs CorporationTrack positioning system for magnetic transducer head
US4088490 *14 Jun 19769 May 1978International Business Machines CorporationSingle level masking process with two positive photoresist layers
US4268881 *14 Jun 197919 May 1981Olympus Optical Co., Ltd.Azimuth adjusting device for magnetic head
US4314290 *14 Apr 19802 Feb 1982Burroughs CorporationDi-bit recording technique and associated servo indicia
US4318146 *28 Dec 19792 Mar 1982Sony CorporationRotary head assembly
US4586094 *13 Mar 198429 Apr 1986Irwin Magnetic Systems, Inc.Method and apparatus for pre-recording tracking information on magnetic media
US4642709 *16 Oct 198510 Feb 1987International Business Machines CorporationTwin track vertical magnetic recording servo control method
US4897748 *30 Mar 198830 Jan 1990Matsushita Electric Industrial Co., Ltd.Magnetic head for azimuth recording in a high density magnetic recording system
US4901178 *13 Feb 198713 Feb 1990Sony CorporationThin film magnetic head
US4906552 *22 Feb 19886 Mar 1990Hughes Aircraft CompanyTwo layer dye photoresist process for sub-half micrometer resolution photolithography
US4914805 *12 Jun 198910 Apr 1990Masahiro KawaseMethod of manufacturing a magnetic head having a plurality of magnetic gaps
US4927804 *12 Jul 198822 May 1990U.S. Philips Corp.Thin-film transformer and magnetic head provided with such a transformer
US4992897 *13 Apr 198912 Feb 1991Commissariat A L'energie AtomiqueDevice for reading and writing on a magnetic medium
US5016342 *30 Jun 198921 May 1991Ampex CorporationMethod of manufacturing ultra small track width thin film transducers
US5017326 *5 Oct 198921 May 1991Eastman Kodak CompanyFilm mid roll interrupt protection for a camera using magnetic azimuth recording on film
US5079663 *29 Jan 19907 Jan 1992International Business Machines CorporationMagnetoresistive sensor with track following capability
US5086015 *15 Aug 19894 Feb 1992Hitachi, Ltd.Method of etching a semiconductor device by an ion beam
US5090111 *21 Sep 199025 Feb 1992Commissariat A L'energie AtomiqueProcess for producing a magnetic recording head
US5093980 *15 Jun 199010 Mar 1992Thomson-CsfMethod for making a multitrack head
US5189580 *18 Jan 199123 Feb 1993Ampex CorporationUltra small track width thin film magnetic transducer
US5195006 *6 Jun 199116 Mar 1993Mitsubishi Denki Kabushiki KaishaThin-film magnetic head element having high recording/reproducing characteristics
US5196969 *26 Mar 199023 Mar 1993Sharp Kabushiki KaishaHead positioning system for serpentine magnetic recording/reproducing system
US5211734 *7 Aug 199118 May 1993Tdk CorporationMethod for making a magnetic head having surface-reinforced glass
US5280402 *17 Jul 199218 Jan 1994Minnesota Mining And Manufacturing CompanyCombined stepper motor and voice coil head positioning apparatus
US5293281 *8 Apr 19928 Mar 1994Behr Michael IMethod of reading and writing data transitions on side-by-side tracks on magnetic media
US5301418 *1 Apr 199212 Apr 1994U.S. Philips CorporationMethod of manufacturing a magnetic head
US5307217 *24 Jun 199226 Apr 1994Digital Equipment CorporationMagnetic head for very high track density magnetic recording
US5309299 *7 Oct 19923 May 1994International Business Machines CorporationMethod and system for position error signal generation using auto correlation
US5379170 *31 Jan 19943 Jan 1995Minnesota Mining And Manufacturing CompanyDynamically adjustable head positioning mechanism for tape drives
US5394285 *21 Jul 199328 Feb 1995Storage Technology CorporationMulti-track longitudinal, metal-in-gap head
US5398145 *5 May 199414 Mar 1995Eastman Kodak CompanyTracking control apparatus including a servo head having a tapered transducing gap
US5402295 *3 Jun 199228 Mar 1995Hitachi, Ltd.Magnetic recording head capable of defining narrow track width and magnetic recording apparatus using the same
US5405734 *24 Mar 199311 Apr 1995Seiko Instruments Inc.Method for correcting a patterned film using an ion beam
US5488525 *18 Aug 199430 Jan 1996International Business Machines CorporationDecoupled magnetic head assembly for quarter-inch tape
US5504339 *27 Oct 19942 Apr 1996Kabushiki Kaisha ToshibaMethod of repairing a pattern using a photomask pattern repair device
US5506737 *5 Jul 19949 Apr 1996Industrial Technology Research InstituteHigh-density electronic head
US5593065 *10 Apr 199514 Jan 1997Pakmax, Inc.Metered dual dispenser cap for squeeze containers
US5602703 *27 Dec 199411 Feb 1997Seagate Technology, Inc.Recording head for recording track-centering servo signals on a multi-track recording medium
US5606478 *8 Dec 199425 Feb 1997International Business Machines CorporationNi45 Fe55 metal-in-gap thin film magnetic head
US5616921 *30 Jun 19941 Apr 1997Schlumberger Technologies Inc.Self-masking FIB milling
US5621188 *6 May 199415 Apr 1997Lee; Sang C.Air permeable electromagnetic shielding medium
US5629813 *16 Mar 199513 May 1997International Business Machines CorporationInitialization and calibration of magnetic tape having multiple servo areas
US5710673 *7 Jun 199620 Jan 1998Ampex CorporationAzimuth record head for minimizing and equalizing crosstalk between tracks of opposite azimuths
US5715597 *14 Aug 199510 Feb 1998Applied Magnetics CorporationMethod for manufacturing thin film magnetic head
US5719730 *17 Jul 199617 Feb 1998Headway Technologies, Inc.Low fringe-field and narrow write-track magneto-resistive (MR) magnetic read-write head
US5723234 *28 Feb 19963 Mar 1998Dai Nippon Printing Co., Ltd.Phase shift photomask and phase shift photomask dry etching method
US5726841 *11 Jun 199610 Mar 1998Read-Rite CorporationThin film magnetic head with trimmed pole tips etched by focused ion beam for undershoot reduction
US5737826 *20 Jun 199614 Apr 1998Seagate Technology, Inc.Method of making a thin-film transducer design for undershoot reduction
US5742452 *10 Jan 199621 Apr 1998International Business Machines CorporationLow mass magnetic recording head and suspension
US5751526 *24 Feb 199712 May 1998Mke-Quantum Components Colorado LlcFlux enhanced write transducer and process for producing the same in conjunction with shared shields on magnetoresistive read heads
US5752309 *14 Jun 199619 May 1998Quantum CorporationMethod and apparatus for precisely dimensioning pole tips of a magnetic transducing head structure
US5757575 *31 Oct 199626 May 1998Ampex CorporationTrack-curvature detection using clock phase shift in azimuth recording
US5863450 *4 Nov 199626 Jan 1999Commissariat A L'energie AtomiqueProcess for making a plane magnetic head and magnetic head obtained by this process
US5867339 *4 Dec 19962 Feb 1999Quantum CorporationTwo channel azimuth and two channel non-azimuth read-after-write longitudinal magnetic head
US5890278 *30 Oct 19976 Apr 1999U.S. Philips CorporationMethod of manufacturing a magnetic head having a structure of layers
US6018444 *28 Oct 199725 Jan 2000Hewlett-Packard CompanyBatch fabricated servo write head having low write-gap linewidth variation
US6021013 *29 May 19971 Feb 2000International Business Machines CorporationTiming based servo system for magnetic tape systems
US6025970 *7 Aug 199715 Feb 2000International Business Machines CorporationDigital demodulation of a complementary two-frequency servo PES pattern
US6031673 *4 Mar 199829 Feb 2000Hewlett-Packard CompanyServo band verification in linear tape systems having timing-based servo formats
US6034835 *7 Aug 19977 Mar 2000International Business Machines CorporationMultiple servo track types using multiple frequency servo patterns
US6169640 *4 Mar 19982 Jan 2001Hewlett-Packard Co.Servo band identification in linear tape systems having timing based servo formats
US6190836 *28 Apr 200020 Feb 2001International Business Machines CorporationMethods for repair of photomasks
US6222698 *22 May 199824 Apr 2001Hewlett-Packard CompanyMagnetic tape dimensional instability compensation by varying recording head azimuth angle
US6229669 *24 Nov 19998 May 2001Hewlett-Packard CoServo head design and method of using the same
US6236525 *14 Aug 199822 May 2001Storage Technology CorporationTape head with pattern timing for servo writing application
US6236538 *14 Oct 199322 May 2001Mitsubishi Denki Kabushiki KaishaMagnetic structure and magnetic head using the same
US6542325 *10 Mar 19991 Apr 2003Imation Corp.Time-based servo for magnetic storage media
US6545837 *21 Dec 19998 Apr 2003Imation Corp.Method and apparatus for servo controlled azimuth data recording
US6700729 *17 Oct 20002 Mar 2004Hewlett-Packard Development CompanyAlignment marks for tape head positioning
US6721126 *16 Aug 200013 Apr 2004International Business Machines CorporationPosition identification for a coarse actuator portion of a compound actuator
US6842305 *17 Feb 200311 Jan 2005Imation Corp.Time-based servo for magnetic storage media
US6865050 *7 Jun 20028 Mar 2005Fuji Photo Film Co., Ltd.Servo signal recording device and servo signal verifying device using edge detection
US6873487 *26 Nov 200129 Mar 2005Imation Corp.Hybrid servopositioning systems
US6879457 *13 Feb 200212 Apr 2005International Business Machines CorporationTiming based servo with fixed distances between transitions
US6987648 *23 Jul 200317 Jan 2006Advanced Research CorporationMagnetic media and process of making thereof
US6989950 *6 May 200424 Jan 2006Fuji Photo Film Co., Ltd.Magnetic tape and manufacturing method thereof, and servo writer and servo write method
US6989960 *22 Oct 200224 Jan 2006Advanced Research CorporationWear pads for timing-based surface film servo heads
US7009810 *10 Nov 20037 Mar 2006Advanced Research CorporationThin-film magnetic recording head having a timing-based gap pattern for writing a servo track on magnetic media
US7170702 *25 Jun 200430 Jan 2007Fuji Photo Film Co., Ltd.Servo band recorded magnetic tape, manufacturing method of the same, servo band writer and servo band writing method
US7190551 *5 Nov 200413 Mar 2007Fuji Photo Film Co., Ltd.Composite magnetic head and process for producing the same
US7196870 *10 Oct 200327 Mar 2007Advanced Research CorporationPatterned magnetic recording head with termination pattern having a curved portion
US7206170 *19 May 200417 Apr 2007Imetion Corp.Thin film servo head apparatus with canted servo gaps
US7511908 *18 Nov 200531 Mar 2009International Business Machines CorporationMagnetic-polarity encoded servo position information for magnetic-based storage media
US7515374 *20 Mar 20067 Apr 2009Fujifilm CorporationMagnetic tape and manufacturing method thereof, and servo writer
US7525761 *21 Aug 200728 Apr 2009Advanced Research CorporationMethod of making a multi-channel time based servo tape media
US7679858 *18 Nov 200516 Mar 2010International Business Machines CorporationMethod for differential timing based servo pattern for magnetic-based storage media
US20020034042 *29 Nov 200121 Mar 2002Storage Technology CorporationHighly aligned thin film tape head
US20020058204 *21 Dec 200116 May 2002International Business Machines CorporationUnderlayer compositions for multilayer lithographic processes
US20030016446 *16 Jul 200223 Jan 2003Nitto Denko CorporationOptical film, polarizer and display device
US20030039063 *22 Oct 200227 Feb 2003Advanced Research Corporation, A Minnesota CorporationWear pads for timing-based surface film servo heads
US20030048563 *25 Apr 200213 Mar 2003Magnusson Steven L.Alternating-azimuth angle helical track format using grouped same-azimuth angle heads
US20040001275 *27 Jun 20021 Jan 2004International Business Machines CorporationApparatus and method to read and/or write information to a magnetic tape medium
US20050007323 *8 Jul 200313 Jan 2005Appelbaum Ian RobertMagneto-luminescent transducer
US20050052779 *27 Jul 200410 Mar 2005Fuji Photo Film Co., Ltd.Servo writer and servo writing method
US20050052783 *22 Apr 200410 Mar 2005Fuji Photo Film Co., Ltd.Combined magnetic head and manufacturing method thereof
US20060061906 *10 Nov 200523 Mar 2006Advanced Research CorporationWear pads for timing-based surface film servo heads
US20090097155 *15 Sep 200816 Apr 2009Advanced Research CorporationMagnetic media having a servo track written with a patterned magnetic recording head
US20100002335 *27 Apr 20097 Jan 2010Dugas Matthew PMethod of making a multi-channel time based servo tape media
Classifications
U.S. Classification360/57, G9B/5.026, G9B/5.291, 360/134
International ClassificationG11B5/02, G11B5/008, G11B5/78, G11B5/127
Cooperative ClassificationG11B5/00813
European ClassificationG11B5/008T