WO1994024669A1 - Magnetic recording head with continuously monitored track following servo - Google Patents

Magnetic recording head with continuously monitored track following servo Download PDF

Info

Publication number
WO1994024669A1
WO1994024669A1 PCT/US1994/003721 US9403721W WO9424669A1 WO 1994024669 A1 WO1994024669 A1 WO 1994024669A1 US 9403721 W US9403721 W US 9403721W WO 9424669 A1 WO9424669 A1 WO 9424669A1
Authority
WO
WIPO (PCT)
Prior art keywords
head
track
power frequency
differential power
edges
Prior art date
Application number
PCT/US1994/003721
Other languages
French (fr)
Inventor
Ronald Scott Indeck
Marcel Wettstein Muller
Guo Mian
Original Assignee
Washington University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/046,040 external-priority patent/US5365586A/en
Application filed by Washington University filed Critical Washington University
Priority to AU66262/94A priority Critical patent/AU6626294A/en
Publication of WO1994024669A1 publication Critical patent/WO1994024669A1/en

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B21/00—Head arrangements not specific to the method of recording or reproducing
    • G11B21/02—Driving or moving of heads
    • G11B21/10—Track finding or aligning by moving the head ; Provisions for maintaining alignment of the head relative to the track during transducing operation, i.e. track following
    • G11B21/106—Track finding or aligning by moving the head ; Provisions for maintaining alignment of the head relative to the track during transducing operation, i.e. track following on disks
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
    • G06F21/10—Protecting distributed programs or content, e.g. vending or licensing of copyrighted material ; Digital rights management [DRM]
    • G06F21/101—Protecting distributed programs or content, e.g. vending or licensing of copyrighted material ; Digital rights management [DRM] by binding digital rights to specific entities
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F21/00—Security arrangements for protecting computers, components thereof, programs or data against unauthorised activity
    • G06F21/70—Protecting specific internal or peripheral components, in which the protection of a component leads to protection of the entire computer
    • G06F21/78—Protecting specific internal or peripheral components, in which the protection of a component leads to protection of the entire computer to assure secure storage of data
    • G06F21/79—Protecting specific internal or peripheral components, in which the protection of a component leads to protection of the entire computer to assure secure storage of data in semiconductor storage media, e.g. directly-addressable memories
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K1/00—Methods or arrangements for marking the record carrier in digital fashion
    • G06K1/12—Methods or arrangements for marking the record carrier in digital fashion otherwise than by punching
    • G06K1/125—Methods or arrangements for marking the record carrier in digital fashion otherwise than by punching by magnetic means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/08—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code using markings of different kinds or more than one marking of the same kind in the same record carrier, e.g. one marking being sensed by optical and the other by magnetic means
    • G06K19/10—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code using markings of different kinds or more than one marking of the same kind in the same record carrier, e.g. one marking being sensed by optical and the other by magnetic means at least one kind of marking being used for authentication, e.g. of credit or identity cards
    • G06K19/12—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code using markings of different kinds or more than one marking of the same kind in the same record carrier, e.g. one marking being sensed by optical and the other by magnetic means at least one kind of marking being used for authentication, e.g. of credit or identity cards the marking being sensed by magnetic means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/01—Details
    • G06K7/015—Aligning or centering of the sensing device with respect to the record carrier
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07F—COIN-FREED OR LIKE APPARATUS
    • G07F7/00—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus
    • G07F7/08—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus by coded identity card or credit card or other personal identification means
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07F—COIN-FREED OR LIKE APPARATUS
    • G07F7/00—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus
    • G07F7/08—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus by coded identity card or credit card or other personal identification means
    • G07F7/086—Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus by coded identity card or credit card or other personal identification means by passive credit-cards adapted therefor, e.g. constructive particularities to avoid counterfeiting, e.g. by inclusion of a physical or chemical security-layer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/00094—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/00094—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers
    • G11B20/00123—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers the record carrier being identified by recognising some of its unique characteristics, e.g. a unique defect pattern serving as a physical signature of the record carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59605—Circuits
    • G11B5/59611—Detection or processing of peak/envelop signals
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59633—Servo formatting
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2211/00—Indexing scheme relating to details of data-processing equipment not covered by groups G06F3/00 - G06F13/00
    • G06F2211/007—Encryption, En-/decode, En-/decipher, En-/decypher, Scramble, (De-)compress
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
    • G11B23/28—Indicating or preventing prior or unauthorised use, e.g. cassettes with sealing or locking means, write-protect devices for discs

Definitions

  • a large portion (as high as 30%) of the recorded medium is used to servo a head on track. Most of this servoing is performed in bursts in which the head is aligned with the track (typically at the beginning of the sector) and then the head travels unservoed for a portion of the disc rotation (e.g. for the rest of the sector).
  • the track width is typically 10-20 microns, guard bands of 2-5 microns each are placed between adjacent tracks, and a servo burst of up to 15-20% of the sector is utilized to align the head prior to data recording or retrieval.
  • the inventors herein have succeeded in designing and developing a continuously monitored track following servo for maintaining alignment of a magnetic recording head over a track in a magnetic recording medi ⁇ um by measuring the differential power spectrum between a main recording head and a pair of secondary heads as the heads traverse a data encoded track.
  • the primary head is aligned in the approximate center of the track, and each of the secondary heads is aligned substantially adjacent one of the track edges.
  • the power frequency distribution remains closely correlated for the main head and the right side secondary head, but varies signifi ⁇ cantly, in the range of 200 milliwatts, between the pri- mary head and the left edge secondary head.
  • this difference in power levels is several magnitudes greater than with the technique previously developed which relied on sensing track edge noise.
  • a head assembly may be manufactured which would provide .continuous track head alignment in the submicron range. This is because once the track width is known, the head assembly may be manu ⁇ factured to extremely close tolerances using known manu ⁇ facturing techniques and methods. Once manufactured, the head assembly would be self-centering and adjustments and the like during operation would be anticipated to be minimally required.
  • the present invention has been demonstrated for use with pseudo-random data, with differential power fre- quency measurements made over an appropriate data length, with the window of sampled data moving as the head assem ⁇ bly moves through the track.
  • the frequency spectra would look similar with respect to the various heads so care must be taken to use an appropriate data length in order to ensure the sensing of head alignment.
  • the in ⁇ ventors have not fully investigated to determine the limits of an appropriate data length, it is believed that data lengths between about 10 microns and 100 microns would be appropriate as the window of data to be used for calculating and comparing power frequency spectra.
  • a run- length-limited code might be used to prevent long runs of contiguous DC tracks and data might be encoded different ⁇ ly in alternate tracks so that adjacent tracks containing identical data would still possess track edges readily sensed by this differential frequency power spectra tech- nique.
  • Figure 1 is a schematic diagram of a multiple head assembly with micro positioner and controller for imple ⁇ menting the track following servo of the present inven- tion;
  • Figure 2 is a top view of a head assembly of the present invention aligned over a track between two adja ⁇ cent tracks.
  • the present invention 20 includes a primary head 22 for reading data encoded on the track of a magnetic medium 24.
  • Micro positioner 28 both mechanically fixes the relative positions of heads 22, 26 and also reposi ⁇ tions heads 22, 26 in response to the controller 30 which receives and processes the power spectrum measured by heads 22, 26, as is explained in greater detail below.
  • the primary head 22 is ideally centered over a track 32 which is defined by a left edge 34 and a right edge 36.
  • Track 32 is surrounded by a track 38 to its left and a track 40 to its right, it being specifically noted that in the present invention there is no need for guard bands or dead spaces between adjacent tracks 32, 38, 40.
  • the secondary head assembly 26 is comprised of a left track edge head 42 and a right track edge head 42.
  • Each of track edge heads 42, 44 sense their respective associated edges 34, 36 and main ⁇ tain the alignment of primary head 22 as the head assem ⁇ bly traverses track 32 to read the magnetically encoded data 46.
  • both secondary heads 42, 44 produce similar spectral power differences with respect to the primary head 22.
  • their differential power spectrum is well correlated for appropriate data lengths and the controller does not adjust the position of the head assembly.
  • the head assembly strays off track to the left by a distance such that left edge head 42 senses magnetically encoded data not only on track 32 but also on track 38, the power spectrum difference read by head 42 with respect to head 22 will change sharply while the power spectrum difference read by head 44 with re ⁇ spect to head 22 will change only slightly (due to the head sensitivity functions).
  • controller 30 will then cause micro positioner 28 to reposition the head back to the right and centered on track 32.
  • controller 30 will readjust through micro positioner 38 the position of the head assembly back onto track 32.

Abstract

A head assembly and method for maintaining the head assembly on a data encoded track of a magnetic medium is disclosed. The head assembly includes a main head (22) for reading the encoded data, a left track edge auxiliary head (26/42) and a right track edge auxiliary head (26/44). The outputs of each of the three heads are used to create a differential power frequency spectrum which, in excess of a threshold value, indicates misalignment of the head assembly with respect to the track. The disclosed head assembly and method eliminates the requirement for guard bands between adjacent tracks of a magnetic medium, eliminates the encoded burst at the beginning of a track used in the prior art to align a head prior to its sweeping through a track sector, and thereby reduces the overhead or wasted space in a magnetic recording medium.

Description

MAGNETIC RECORDING HEAD WITH CONTINUOUSLY MONITORED TRACK FOLLOWING SERVO
Background and Summary of the Invention
In current magnetic recording systems, such as hard disc drives, a large portion (as high as 30%) of the recorded medium is used to servo a head on track. Most of this servoing is performed in bursts in which the head is aligned with the track (typically at the beginning of the sector) and then the head travels unservoed for a portion of the disc rotation (e.g. for the rest of the sector). In a typical hard disc drive, the track width is typically 10-20 microns, guard bands of 2-5 microns each are placed between adjacent tracks, and a servo burst of up to 15-20% of the sector is utilized to align the head prior to data recording or retrieval. In floppy discs or diskettes, because of the anisotropic expansion and contraction of the medium, the actual portion of the floppy diskette which stores data or is available for storing recorded data is much less. As can be appre¬ ciated, present prior art servoing techniques require a significant portion of the magnetic recording medium to be used for purposes other than data storage. This pro¬ vides obvious drawbacks but has been accepted by the prior art as necessary for ensuring the reliable reading and writing of data to and from the magnetic medium. The inventors herein have previously investigated this phenomenon and identified a technique which sought to maintain head alignment by sensing the track edge noise and, with a micro positioner, maintain the position of the head as it moved along a track and through a sec- tor. This technique was disclosed and described in the inventors' prior article entitled Noise Correlation of Magnetic Thin Film Media published in August of 1991 in the Japanese Journal of Applied Physics. Vol. 30, No. 8B, pages L1483-L1485. This investigation was conducted for a thin film medium, as explained more thoroughly in that article. Although strong correlative data were found, and a block diagram for a high performance track follow¬ ing servo was proposed, the technique and method de¬ scribed therein must be extremely sensitive in order to perform as power levels relating to head displacement with respect to track edges is in the micro watt range. At these levels, differences in power readings which must be sensed in order to determine if the head is on or off the track are difficult to discern and, consequently, difficult to implement in the laboratory, much less in commercial application.
To solve these and other problems in the prior art, and as an improvement and change in approach from their prior work, the inventors herein have succeeded in designing and developing a continuously monitored track following servo for maintaining alignment of a magnetic recording head over a track in a magnetic recording medi¬ um by measuring the differential power spectrum between a main recording head and a pair of secondary heads as the heads traverse a data encoded track. The primary head is aligned in the approximate center of the track, and each of the secondary heads is aligned substantially adjacent one of the track edges. As the head assembly remains on track, there is a close correlation between the power- frequency distribution between the primary head and each of the secondary heads. However, as the head assembly drifts to the left, for example, the power frequency distribution remains closely correlated for the main head and the right side secondary head, but varies signifi¬ cantly, in the range of 200 milliwatts, between the pri- mary head and the left edge secondary head. As can be appreciated, this difference in power levels is several magnitudes greater than with the technique previously developed which relied on sensing track edge noise.
It is anticipated that a head assembly may be manufactured which would provide .continuous track head alignment in the submicron range. This is because once the track width is known, the head assembly may be manu¬ factured to extremely close tolerances using known manu¬ facturing techniques and methods. Once manufactured, the head assembly would be self-centering and adjustments and the like during operation would be anticipated to be minimally required.
The present invention has been demonstrated for use with pseudo-random data, with differential power fre- quency measurements made over an appropriate data length, with the window of sampled data moving as the head assem¬ bly moves through the track. For long sections of track, the inventors expect that the frequency spectra would look similar with respect to the various heads so care must be taken to use an appropriate data length in order to ensure the sensing of head alignment. While the in¬ ventors have not fully investigated to determine the limits of an appropriate data length, it is believed that data lengths between about 10 microns and 100 microns would be appropriate as the window of data to be used for calculating and comparing power frequency spectra. While this range has been found to be effective, the inventors believe that the range of appropriate data lengths is dependent upon several factors including the magnetically recorded linear bit density and head speed. A run- length-limited code might be used to prevent long runs of contiguous DC tracks and data might be encoded different¬ ly in alternate tracks so that adjacent tracks containing identical data would still possess track edges readily sensed by this differential frequency power spectra tech- nique.
While the principal advantages and features of the present invention have been described above, a more com¬ plete and thorough understanding of the invention may be attained by referring to the drawings and description of the preferred embodiment which follow. Brief Description of the Drawings
Figure 1 is a schematic diagram of a multiple head assembly with micro positioner and controller for imple¬ menting the track following servo of the present inven- tion; and
Figure 2 is a top view of a head assembly of the present invention aligned over a track between two adja¬ cent tracks. Detailed Description of the Preferred Embodiment As shown in Figure 1, the present invention 20 includes a primary head 22 for reading data encoded on the track of a magnetic medium 24. A secondary head assembly 26, which may be two separate heads (as shown in Figure 2) or two separate portions of a split head as- sembly for sensing the edges of a track on recording medium 24. Micro positioner 28 both mechanically fixes the relative positions of heads 22, 26 and also reposi¬ tions heads 22, 26 in response to the controller 30 which receives and processes the power spectrum measured by heads 22, 26, as is explained in greater detail below. As shown in Figure 2, the primary head 22 is ideally centered over a track 32 which is defined by a left edge 34 and a right edge 36. Track 32 is surrounded by a track 38 to its left and a track 40 to its right, it being specifically noted that in the present invention there is no need for guard bands or dead spaces between adjacent tracks 32, 38, 40. The secondary head assembly 26 is comprised of a left track edge head 42 and a right track edge head 42. Each of track edge heads 42, 44 sense their respective associated edges 34, 36 and main¬ tain the alignment of primary head 22 as the head assem¬ bly traverses track 32 to read the magnetically encoded data 46.
The operation of the present invention may be readily understood by referring to Figure 2. When the head assembly is on track, both secondary heads 42, 44 produce similar spectral power differences with respect to the primary head 22. Thus, their differential power spectrum is well correlated for appropriate data lengths and the controller does not adjust the position of the head assembly. When the head assembly strays off track to the left by a distance such that left edge head 42 senses magnetically encoded data not only on track 32 but also on track 38, the power spectrum difference read by head 42 with respect to head 22 will change sharply while the power spectrum difference read by head 44 with re¬ spect to head 22 will change only slightly (due to the head sensitivity functions). This difference in power spectrum will be sensed by controller 30 and it will then cause micro positioner 28 to reposition the head back to the right and centered on track 32. Similarly, when the head assembly moves off track to the right, the power difference read by heads 22, 42 will be virtually un¬ changed while the power spectrum differences between heads 22, 44 will change sharply such that controller 30 will readjust through micro positioner 38 the position of the head assembly back onto track 32.
There are various changes and modifications which may be made to the invention as would be apparent to those skilled in the art. However, these changes or modifications are included in the teaching of the disclo¬ sure, and it is intended that the invention be limited only by the scope of the claims appended hereto.

Claims

What Is Claimed Is:
1. In a magnetic medium data storage and retrieval device, said device having a head for reading or writing data as it moves along a track on a multi-track magnetic medium, said track having a pre-determined width between two edges thereof and data recorded on said track at least after said head traverses said track, the improve¬ ment comprising means for continuously monitoring the lateral position of said head with respect to said track and means responsive thereto for maintaining said head in alignment laterally with respect to and between said track edges as said head traverses said track.
2. The device of Claim 1 wherein said monitoring means comprises a first auxiliary head positioned closer to one of said track edges and a second auxiliary head positioned closer to the other of said track edges.
3. The device of Claim 2 further comprising means for creating a differential power frequency spectrum from an output from the head and the first auxiliary head, means for creating a differential power frequency spec- trum from an output from the head and the second auxilia¬ ry head, said monitoring means being responsive to said differential power frequency spectrums.
4. The device of Claim 1 wherein said monitoring means comprises a split head having a portion thereof positioned closer to one of said track edges and a second portion thereof positioned closer to the other of said track edges.
5. A method for continuously monitoring and main¬ taining the position of a head as it traverses a track in a magnetic medium, said method comprising the steps of measuring a differential power frequency spectrum between a primary head and a first auxiliary head, said first auxiliary head being positioned closer to one of said track edges, measuring a differential power frequency spectrum between said main head and a second auxiliary head positioned closer to the other of said track edges, and determining when either of said differential power frequency spectrums exceeds a threshold thereby indicat¬ ing drifting of the main head off track to the left or right.
6. The method of Claim 5 further comprising the step of repositioning the main head in response to the differential power frequency spectrum exceeding a thresh¬ old.
PCT/US1994/003721 1993-04-09 1994-04-05 Magnetic recording head with continuously monitored track following servo WO1994024669A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU66262/94A AU6626294A (en) 1993-04-09 1994-04-05 Magnetic recording head with continuously monitored track following servo

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US08/046,040 US5365586A (en) 1993-04-09 1993-04-09 Method and apparatus for fingerprinting magnetic media
US08/046,040 1993-04-09
US10056793A 1993-07-30 1993-07-30
US08/100,567 1993-07-30

Publications (1)

Publication Number Publication Date
WO1994024669A1 true WO1994024669A1 (en) 1994-10-27

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1994/003721 WO1994024669A1 (en) 1993-04-09 1994-04-05 Magnetic recording head with continuously monitored track following servo

Country Status (2)

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AU (1) AU6626294A (en)
WO (1) WO1994024669A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0693202A1 (en) * 1993-04-09 1996-01-24 Washington University Method and apparatus for noise reduction in magnetic media
US5959794A (en) * 1993-04-09 1999-09-28 Washington University Method for precompensating signals for magnetic media noise

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Publication number Priority date Publication date Assignee Title
US3769469A (en) * 1972-06-28 1973-10-30 Ibm Trim erase mead assembly for providing a uniform erase field
US4513333A (en) * 1982-02-24 1985-04-23 Dymek Corporation Diagnostic recording
US4802030A (en) * 1986-06-25 1989-01-31 Hewlett-Packard Company Head-tape alignment apparatus with a tape edge find operation
US4970616A (en) * 1988-08-17 1990-11-13 Digital Equipment Corporation Recording head to minimize undershoots in readback pulses
US4972336A (en) * 1983-10-14 1990-11-20 Applied Magnetics Corporation Read while write magnetic head assembly
US5137750A (en) * 1990-11-06 1992-08-11 Seagate Technology, Inc. Method of making a thin film head with contoured pole face edges for undershoot reduction
US5233487A (en) * 1991-06-27 1993-08-03 International Business Machines Corporation Functional measurement of data head misregistration

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3769469A (en) * 1972-06-28 1973-10-30 Ibm Trim erase mead assembly for providing a uniform erase field
US4513333A (en) * 1982-02-24 1985-04-23 Dymek Corporation Diagnostic recording
US4972336A (en) * 1983-10-14 1990-11-20 Applied Magnetics Corporation Read while write magnetic head assembly
US4802030A (en) * 1986-06-25 1989-01-31 Hewlett-Packard Company Head-tape alignment apparatus with a tape edge find operation
US4970616A (en) * 1988-08-17 1990-11-13 Digital Equipment Corporation Recording head to minimize undershoots in readback pulses
US5137750A (en) * 1990-11-06 1992-08-11 Seagate Technology, Inc. Method of making a thin film head with contoured pole face edges for undershoot reduction
US5233487A (en) * 1991-06-27 1993-08-03 International Business Machines Corporation Functional measurement of data head misregistration

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0693202A1 (en) * 1993-04-09 1996-01-24 Washington University Method and apparatus for noise reduction in magnetic media
EP0693202A4 (en) * 1993-04-09 1996-02-07
US5959794A (en) * 1993-04-09 1999-09-28 Washington University Method for precompensating signals for magnetic media noise

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Publication number Publication date
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