Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data verification
Reexamination Certificate
2001-07-16
2004-05-18
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data verification
C360S075000, C360S077120
Reexamination Certificate
active
06738210
ABSTRACT:
TECHNICAL FIELD
The invention relates to magnetic storage media and, in particular, to magnetic storage media having pre-written servo patterns.
BACKGROUND
Magnetic storage media having pre-written servo patterns are often used for storage and retrieval of data. For example, magnetic tape media often have pre-recorded servo patterns to enable higher data storage density on the tape. Magnetic tape media remains an economical medium for storing large amounts of data. For example, magnetic tape cartridges, or large spools of magnetic tape, are often used to back up large amounts of data for large computing centers. Magnetic tape cartridges also find application in the backup of data stored on smaller computers such as desktop or laptop computers. Other magnetic storage media, such as magnetic disks, may also utilize pre-recorded servo patterns to increase storage densities.
Servo patterns are referred to as pre-recorded when they are recorded during the fabrication of the media. In other words, pre-recorded servo patterns are servo patterns recorded in the media prior to the media being used for storage of data. These pre-recorded servo patterns allow the media to achieve higher storage densities because the servo patterns enable positions on the media to be located with greater precision. In other words, servo patterns facilitate the ability to pinpoint locations on media surfaces with greater accuracy. Thus, smaller amounts of media surface can be used to store units of data.
SUMMARY
In general, the invention is directed to techniques for verifying that servo patterns have been properly recorded. For example, the amplitude of a signal corresponding to magnetic servo patterns can be detected and then compared to a threshold to determine whether the servo patterns were properly recorded. The signal strength may be determined for a full servo band that includes multiple servo tracks. To enable this determination, a read head can be designed to have sufficient width to enable the head to detect magnetic signal strength corresponding to more than one servo track.
In some embodiments, the invention may involve a method for verifying that a servo pattern has been properly recorded. The method may include recording magnetic servo patterns on a magnetic medium and detecting an amplitude of a signal corresponding to the magnetic servo patterns. For example, the invention may be used to verify servo patterns on magnetic tape. In that case, the method may include un-spooling magnetic tape, recording magnetic servo patterns on the magnetic tape, verifying the magnetic servo pattern prior to re-spooling the magnetic tape, and re-spooling the magnetic tape.
In other embodiments, the invention provides a magnetic head having sufficient width to enable the head to simultaneously detect magnetic signal strength corresponding to more than one servo track. For example, the magnetic head may form part of a servo writing system. The system may include at least one first magnetic head that writes servo patterns. The system may also include a second magnetic head having sufficient width to enable the second head to simultaneously detect magnetic signal strength corresponding to more than one servo track.
Performing servo verification provides several advantages. For example, if dust or debris collect in one or more components that perform the servo writing, the servo patterns may not be properly written. Performing servo verification, however, can ensure that these problems are detected relatively early in the manufacturing process. If problems are detected, the servo writing process can be fixed, thereby avoiding the creation of defective or inferior quality magnetic storage media. In addition, time and energy can be saved as servo writing problems are identified more quickly by a verification process.
Additional details of these and other embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 5689384 (1997-11-01), Albrecht et al.
patent: 6031673 (2000-02-01), Fasen et al.
patent: WO 00/51109 (2000-08-01), None
Langlois Denis J.
Olson Alan R.
Davidson Dan I.
Hudspeth David
Imation Corp.
Levinson Eric D.
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