Dynamic magnetic information storage or retrieval – General recording or reproducing
Reexamination Certificate
1998-05-11
2002-02-26
Kim, W. Chris (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
C360S121000, C360S135000, C428S065100, C428S690000
Reexamination Certificate
active
06351339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to information storage systems, and more particularly, to magnetic information storage systems.
2. Description of Related Art
Conventional magnetic storage devices are generally of the continuous magnetization type, wherein units of information, representing information bits, take on the form of successive discrete magnetic fields each having an orientation which is either in alignment or in opposition to the next field in the succession. A read head passing over these fields detects a voltage peak when encountering a pair of successive bits having opposite orientations due to the repulsive forces between the fields. By contrast, absence of a peak at an expected boundary between fields indicates identical orientation of the successive fields. More specifically when successive bits both have either a North-South orientation on the one hand, or a South-North orientation on the other, then no voltage peak is sensed by the reading head, indicating a first logic state. Conversely, when successive bits respectively have South-North followed by North-South orientations on the one hand, or North-South followed by South-North orientations on the other, the read head detects a voltage peak and registers this as a second logic state. In this manner, two bit states can be identified and a binary information storage system implemented.
Directionally, the alignment of the bits in conventional continuous magnetization storage devices is in parallelism with the bitstream direction. That is, the magnetic fields of the bits are aligned in the direction of relative travel between the reading (or writing) head and the storage medium, with each field being either in the North-South direction or in the South-North direction. In this sense, information storage in conventional devices is one-dimensional, with the single dimension extending in the bitstream direction.
The one-dimensional limitation of the prior art is in part imposed by the continuous nature of the storage medium. By disposing the magnetic fields contiguously with each other, interactions between the fields preclude practical implementations of field alignment in directions other than along the bitstream direction. Hence, only two bit states, as described above, are possible.
In any magnetic recording medium, there must be some minimal spacing between adjacent magnetic domains or else it will be impossible to separately write and read the magnetic state of an individual magnetic domain because of interference from adjacent, abutting, or overlapping domains. Crosstalk and mutual magnetization occurs in which information is lost, rendering a magnetized domain useless. The magnetized domain becomes machine unreadable. Ordered data in the form of a series of sequential, magnetized holes is impossible.
U.S. Pat. No. 4,393,110 discloses that holes are formed in a non-magnetic substrate by electron beams or by laser beams. The holes are subsequently filled with magnetic material. The holes have diameters between 200 A and 5000 A. Holes that are larger or smaller than this range of diameters are not suitable for the disclosed magnetic recording medium. There are between 1.6×10
7
and 1.6×10
11
holes/cm
2
. Greater or lesser densities are not suitable for the disclosed magnetic recording medium. The magnetic recording medium has a (linear) recording density of 100 KBPI (kilobits per inch).
Electron beam systems involve the movement of an electron gun or the movement of a mechanical stage. Variations that arise in the fabrication of holes using an electron beam system include: 1) variation of the stage movement and placement of the substrate and system mechanical components; 2) variations in the nature of the beam; and 3) variations in the process of hole creation in the sense of limits imposed by physics and chemistry.
Known reading/writing heads for magnetic recording media are only capable of reading/writing information when the information is in specific locations on the magnetic recording medium. In a typical reading/writing arrangement, a head is held in position over a rotating magnetic recording medium and magnetizes or detects the magnetic state of particular magnetic domains (i.e., areas of magnetized material corresponding to a single bit of information) of the magnetic medium moving relative to the head. The head is also often movable, such as by being movable radially outwardly and inwardly over the disk. Successive magnetic domains represent ordered data. If, when a disk is moved relative to a head, no magnetizable material, or insufficient magnetizable material, is disposed beneath the head, or if magnetizable material is not disposed sufficiently close to the head, the head cannot read or write on the disk. Information storage is impossible with the non-symmetrical domains because the distance of the head from the non-symmetrical domains permits only some of the domains to be written on so that information stored in the domains is machine readable. Unless all of the successive magnetic domains are capable of being written on and read, information storage is impossible.
Because of the particular physical arrangement of the Fukuda system, that system essentially discloses a magnetic recording medium of the type having a substantially continuous layer of magnetic material in the form of numerous holes filled with magnetic material, and wherein bits of information are stored by magnetizing successive, spaced groups of the filled holes. For this type of magnetic recording medium, typically, a head detects a magnetic state within an area on the surface of a disk medium because, within the area, there is likely to be a group of the small, filled holes that can be magnetized and detected. Given the limits of electron beam technology and the disclosure of Fukuda, Fukuda does not disclose a magnetic recording medium where each hole filled with magnetic material corresponds to one bit of information because such a magnetic recording medium would have overlapping or interfering magnetic domains.
In disk media having numerous randomly located holes filled with magnetic material, the holes are sufficiently numerous and close together such that, although the filled holes are discontinuous, the overall effect of the holes is to simulate continuous magnetic material. A head vertically or horizontally magnetizes (i.e., writes) and/or detects the magnetic state of transitions (i.e., reads) between radially and/or concentric groups of the filled holes. In vertical recording media, a magnetic head device magnetizes successive, contiguous magnetic regions of recording medium at right angles to the surface of the medium, i.e., an axis between N-S poles of a magnetized region extend perpendicularly to the surface of the medium. In horizontal recording media, transitions in a magnetically recorded waveform follow each other on a tape or disk with N-S and S-N transitions recorded end to end. In both vertical and horizontal recording media, a transition in polarity between successive regions of the recording medium represents a bit of information. For example, a N-N or S-S transition might correspond to a “1” and a N-S transition might correspond to a “0”, or vice versa. Known writing and/or reading technology requires that at least one of the head and the disk be moved such that the head passes over the specific radial and concentric areas of the disk to read successive bits of previously written information.
Existing writing and/or reading technology is incapable of detecting the magnetic state of individual ones of randomly located filled holes, since there is no ordered succession in radial or concentric directions of the filled holes. No known reading and/or writing head is configured to identify the location of each successive filled hole or to magnetize or detect the magnetic state of the magnetizable material filled in the holes for such disks. Moreover, the individual filled holes are ordinarily so small and densely packed relative to one another that existi
Burns Doane Swecker and Mathis LLP
Kim W. Chris
Neal Regina Y.
Ronni Corporation
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