Dynamic magnetic information storage or retrieval – Miscellaneous
Reexamination Certificate
1999-03-29
2004-08-10
Chen, Tianjie (Department: 2652)
Dynamic magnetic information storage or retrieval
Miscellaneous
Reexamination Certificate
active
06775100
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to data storage and retrieval systems that utilize optical and magnetic elements.
BACKGROUND
In prior art magneto-optical (MO) disk drives, data is read as a clockwise or counter-clockwise polarization rotation imposed on a polarized laser light by the up or down orientations of magnetic domains within an area of stored data. The minimum area that the data can comprise is a function of the size of an optical spot formed by the polarized light. The information embedded in the polarization rotation requires an optical readout means. The optical readout means in the prior art includes a plurality of bulky and complex optical elements, some of which are located on a magneto-optical head. The optical elements can degrade the signal to noise ratio (SNR) of the information signal obtained from the polarization rotation.
Magnetic based disk drives are also well known in the art. In magnetic drives, magneto-resistive elements on magnetic heads are typically used. Recent advances in magnetic recording technology have provided magnetic heads that use giant magneto-resistive (GMR) technology; see, for example, “Giant Magnetoresistance: A Primer”, by Robert White, IEEE Transactions On Magnetics, Vol. 28, No. 5, September 1992, incorporated herein by reference. GMR heads may be manufactured to be more sensitive to magnetic fields than conventional magneto resistive heads. GMR technology has also been incorporated with Spin-Valve structures that are well known in the art.
Magnetic storage drive technology is subject to the “super paramagnetic limit”, which simply states that when longitudinally oriented (in plane) magnetic domains are written in granular thin film metallic media, these domains will tend to demagnetize each other at some high flux reversal density and at high temperature.
Today the smallest mark written by a 220 KBPI PR-4 recording system, at say a 2 &mgr;m track pitch, is about 0.1 &mgr;m long along the track by 1.8 &mgr;m wide across the track. The north-to-south poles of the longitudinal domains are oriented along the track. Typically, there are at least four limitations encountered in prior art magnetic storage drive technology when trying to make the track pitch more narrow, including:
1) For tracking, a very high servo error rejection needs to be implemented, which requires a coarse and fine tracking actuator, for example, a crossover frequency of greater than 2 Khz is required for a track pitch of 1 &mgr;m.
2) The photolithographic tolerances for making a read/write head is limited to about 10% of the thickness of the head permalloy poles. If the poles are about 4 &mgr;m thick, the head tolerances are about 0.4 &mgr;m.
3) A typical prior art head causes side-erasure of data tracks of about 0.3 &mgr;m. This side erasure is desired for proper operation during the record/playback process so as to eliminate old information. Because, side-erasure scales with the head gap width, the gap width will be a function of a desired magnetic domain density.
4) The writing of the radial and circumferential position sensing patterns (servo writing) is not very accurate because of disk flutter and spindle bearing non-repeatable runout. One can typically expect a servo writing accuracy of about 0.2 &mgr;m with 0.8 mm thick 3.5 inch disks spinning on a ball bearing spindle.
What is needed therefore is an improvement that takes into account the limitations of the prior art magnetic and optical drive technologies.
Summary Of The Invention
The present invention provides for the enhancement of the storage capacity of a data disk drive while reducing optical path optics, electronics and/or the mass and complexity of associated read/write heads. The system utilizes light transmitted by optical elements to servo track a data disk and to heat the data disk during writing and reading of data, and inductive and magnetic elements for actual writing and reading. In doing so, the present invention provides an improved signal-to-noise-ratio (SNR) for a signal that is representative of data recorded as regions of magnetic domain marks on the data disk as well as improved storage capacity of the disk drive.
The data storage disk may include depressions and/or raised features, which may be filled and/or polished with various materials. In this way, a smooth surface is provided for the read/write head that is aerodynamically maintained in a flying condition very close to the data disk surface. By providing a smooth surface, accumulation of contaminants may be reduced or eliminated. The filler material may be made to be reflective such that an optical signal reflected from the depressions and/or raised features can be provided with a larger amplitude. The reflection of the light from the material used for filling the depression and/or raised feature may be used for sector identification and track following. Additionally, the depressions and/or raised features may be made to present a reflective area that is proportional to the radius of the data disk at which they are disposed. Consequently, the frequency content and/or amplitude variations of the reflected optical signal may be minimized over a radius of the data disk.
In the present invention, the data storage disk may further comprise a set of channels and/or mesas disposed in-between data tracks comprising the data storage disk. The channels and/or mesas may be used to thermally channel and direct the thermal effects of the light applied to the data disk such that the shape of data domain marks that are used to store data along the data tracks may be confined in a cross track direction and defined to more accurately match a preferred rectangular or square geometry. The storage density and SNR may consequently be increased. The channels and/or mesas may be also be filled with a filler material.
In addition, the present invention may comprise a recording and playback system in which data track edges are defined thermally and in which a tracking mechanism utilizes a radial motion of a focused laser spot comprising: a flying head, said flying head disposed above a storage disk and the tracking mechanism may comprising: at least one optical element for producing said focused laser spot, said at least one optical element disposed next to at least one magnetic field writing element, said at least one magnetic field writing element disposed next to at least one magnetic field sensing element; and a storage disk; said storage disk comprising: servo sector information, said servo sector information encoding coarse and fine radial and rotational positions on said storage disk; heat directing features disposed between said data tracks, and a thin film that is designed to change magnetic properties when heated during recording and writing of data. The thin film may comprise at least one layer of amorphous magnetic material or a readout layer and a storage layer.
The present invention may include an assembly for selectively directing a light along an optical path between a source of the light and a storage location of a storage media, to comprising: at least one optical element, the optical element directing the light along the optical path and toward the storage location; and at least one magnetic element, wherein the magnetic element operates in timed cooperation with the light so as to access the storage location.
The at least one optical element and the at least one magnetic element may be coupled to a flying head.
The at least one magnetic element may comprise a magneto-resistive element and/or a magnetic field generating element.
The at least one optical element may comprise an optical fiber, a steerable mirror, an objective optics. The steerable mirror may comprise a micro-machined mirror.
The storage location may comprise a region of data comprising magnetic domains (data domain mark), wherein the light heats the storage location, wherein the at least one magnetic element comprises a magnetic field detecting element, and wherein the at least one magnetic element accesses the heated storage location by dete
Belser Karl A.
Durnin James
Gage Edward C.
Hutchinson Christina L.
McDaniel Terry
Chen Tianjie
Pietragallo Bosick & Gordon
Seagate Technology LLC
Towner, Esq. Alan G.
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