Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1997-04-18
2001-05-01
Neyzari, Ali (Department: 2752)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
C369S044220
Reexamination Certificate
active
06226233
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to data storage and more particularly to maximum data storage in a magneto-optical data storage system.
2. Background Art
Hard disk technology has historically been limited by conventional magnetic head designs. A typical prior art Winchester magnetic storage system includes a magnetic head that has a slider element and a magnetic read/write element and is coupled to a rotary actuator magnet and coil assembly by a suspension and actuator arm so as to be positioned over a surface of a spinning magnetic disk. In operation, lift forces are generated by aerodynamic interactions between the magnetic head and the spinning magnetic disk. The lift forces are opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk.
Flying head designs have been proposed for use with magneto-optical (MO) storage technology. One motivation for using magneto-optical technology stems from the higher areal density capabilities of magneto-optical storage disks. However, despite the historically higher areal storage density available with MO storage technology, the prior art MO disk drive volumetric storage capacity has generally not kept pace with the volumetric storage capacity of magnetic disk drives.
One factor that continues to limit MO disk drives is the physical size of the head necessary to hold the various components required for accessing magneto-optical information. Conventional magneto-optical heads, while providing access to magneto-optical disks with areal densities on the order of 1 Gigabit/in
2
, have been based on relatively large optical assemblies, which have made the physical size and mass of the heads rather bulky (typically 3-5 mm in a dimension).
A number of flying MO head designs incorporating magnetic and optical elements are described in U.S. Pat. No. 5,295,122 by Murakami, including: use of free-space alignment of a laser beam with a dynamically moving target, and a number of different configurations of the magnetic and optical elements that are required for reading and writing using the magneto-optical Kerr effect. The large size, mass, and number of elements limits the minimum head size and, therefore: the speed at which information from the MO disk may be accessed, the tracking bandwidth, and the data density that may be read or written. In the prior art, the large physical size of MO flying heads also limits the spacing between magneto-optical disks to a finite minimum value. Consequently, because the volume available in standard height disk drives is limited, magneto-optical disk drives for use with magneto-optical flying heads have generally not been available as high capacity multi-platter commercial products.
During conventional writing of information in MO disk drives, an incident laser beam heats a selected spot of interest on the MO disk to approximately the Curie point. A time varying vertical bias magnetic field is used to define a pattern of “up” or “down” magnetic domains in a recording layer. Subsequently, as the selected spot of interest cools, information is recorded on the MO disk. The size of the magnetic field that is generated provides a lower limit on a maximum data density that may be recorded on the MO disk. One prior art approach for generating the necessary magnetic field for writing of information has relied on second surface recording techniques. With the second surface recording method, the magnetic field is applied to the spot of interest on the MO disk from a direction opposite that of the incident laser beam. With this approach, only one side of a MO disk may be used.
In addition to the aforementioned limitations, information access in prior art magneto-optical storage systems is limited by the size of the optical spot to which an incident laser beam may be focused on the disk surface. Magneto-optical information access requires the use of polarized laser light for reading and writing information on an MO disk. In the case of reading information, MO technology makes use of a magneto-optical effect (“Kerr” effect) to detect a modulation of polarization rotation imposed on the linearly polarized incident laser beam by the recorded domain marks in the recording layer. The polarization rotation (representing the information stored at recorded marks or in the edges of the recorded marks) is embodied in a reflection of the linearly polarized laser beam and is converted by optics and electronics for readout.
To date, only conventional quadrilayer MO disk structures have been used in commercial MO drives. With conventional MO disks it has not been possible to access information in magnetic domains when the incident laser beam laser beam covers more than one magnetic domain at a time. This limit is substantially proportional to the ratio of the wavelength of the laser beam to the numerical aperture (NA) of the optical elements used. In conventional prior art quadrilayer MO disk structures, therefore, recordation of magnetic domain marks smaller than the minimum incident optical spot size does not provide any benefit.
What is needed, therefore, is an apparatus and method that improves upon prior art access to, and storage of magneto-optical information.
SUMMARY OF THE INVENTION
The present invention improves access to and storage of magneto-optical information. The present invention includes at least one first surface double-sided storage disk in a data storage and retrieval system. In the present invention, each surface of the at least one storage disk includes at least one layer. In the present invention, the at least one layer includes a storage layer. In the present invention, the storage layer includes a magnetically-induced super resolution structure. The present invention selectively directs an impinging optical beam to form an optical spot on the storage layer and to record data marks in the storage layer. In the present invention, a small size and low profile magnetic coil and yoke improves the ability to record a plurality of small data marks at a high rate and at a short distance from the surface of the storage disk. In the present invention, the plurality of data marks may be recorded within a size of the optical spot. Using the magnetically-induced super resolution structure, the present invention may selectively access within the size of the optical spot a desired one of the plurality of data marks. In the present invention, low-profile and low mass optical and magnetic elements may be offset on an optical head to improve access to data stored at an outer periphery and within the magnetically-induced super resolution structure of the at least one magneto-optical storage disk. In the present invention, the optical head includes a low profile and low mass flying magneto-optical head that permits increased volumetric storage capacity of the magneto-optical data storage and retrieval system. In the present invention, the flying head includes means for moving an optical element so as to maintain and improve access to information stored on at least one storage disk. The present invention may further include means for independent yet simultaneous access of information stored on a plurality of storage disks.
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Davis Joseph E.
Drake Joseph
Drazan Jeff
Heanue John F.
Hurst, Jr. Jerry E.
Flehr Hohbach Test Albritton & Herbert L.L.P.
Neyzari Ali
Seagate Technology Inc.
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