Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-04-16
2004-06-29
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S078040
Reexamination Certificate
active
06757126
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic recording medium which is capable of recording/reproducing information magnetically and a magnetic head apparatus for recording/reproduction and, more specifically, relates to a magnetic recording medium on which track information as one kind of auxiliary information is recorded and a magnetic head apparatus.
On a magnetic disk, at first auxiliary information is written. The auxiliary information is information, which is necessary for recording/reproducing information on/from a magnetic disk, such as track information for locating on a track of a magnetic head, address information for managing a recording position of information, PLL clock information for reading out an address, and the like. A servo writer is known as an apparatus for writing such auxiliary information on a magnetic disk.
In the servo writer, a guide pin which received an instruction from a locating control circuit pushes out a magnetic head so as to determine a position on the disk, and the magnetic head so as to determine a position on the disk, and the magnetic head records auxiliary information given from an auxiliary data preparation circuit. Such servo writer has problems such that a long time is required for writing track information on a magnetic disk, the servo writer is expensive, and the whole of a servo writer apparatus must be installed in a clean room environment.
In order to solve these problems, there is suggested a magnetic disk to which a technique of an optical disk is applied (NIKKEI ELECTRONICS Jul. 19, 1993 (No. 586) p. p. 169-181). The magnetic disk magnetically reproduces a pit formed on the disk surface so as to obtain auxiliary information. The magnetic disk is formed so that a substrate having spiral or coaxially circular grooves is coated with a magnetic film, and pits corresponding to auxiliary information are previously formed on tracks of the substrate. When the auxiliary information is recorded, the magnetic head is moved in a radial direction in an area where the pits are formed, and applies a strong magnetic field so that convex portions and concave portions are magnetized in an identical direction. Next, while the magnetic head is being moved in the same direction in the same area, the magnetic head applies a weak magnetic field having a direction opposite to that of the strong magnetic field so that only the magnetization of the convex portions is inverted. Since the concave and convex areas on the tracks are magnetized respectively in opposite directions, the auxiliary information which was recorded by the pits can be read out by magnetically reproducing it from the tracks. The grooves are formed in order to prevent fracturing of the reproducing signal due to a leakage of magnetic field between tracks.
When the pits are formed on the magnetic disk according to the track information and the magnetization is executed as mentioned above, the auxiliary information can be easily recorded on the magnetic disk, and thus the servo writer is not required. However, since the pit groups formed according to the auxiliary information are formed with intervals on the tracks, an error in reading a tracking error signal becomes great when a disk rotational number is increased or a track pitch is short.
BRIEF SUMMARY OF THE INVENTION
The present invention is achieved with such points in view, and its one object is to provide a magnetic recording medium, in which magnetization changes areas where magnetic flux is changed along the length of tracks are provided so that track information can be recorded easily, and even if a track pitch is narrow, an error in reading the track information does not occur. Moreover, its object is to provide a magnetic recording medium in which groove sections with a non-uniform width along the length of tracks are provided respectively on both sides of the track so that track information can be recorded easily, and an error in reading track information does not occur.
In addition it is another object of the invention to provide a magnetic head apparatus for controlling tracking of a magnetic recording medium using magnetization change areas whose magnetic flux changes, and further to provide a magnetic head apparatus for controlling tracking of a magnetic recording medium having grooves with identical widths.
A magnetic recording medium of the invention is characterized by including: tracks formed on the magnetic layer, along which information is recorded magnetically; and magnetization change areas for tracking control formed on the magnetic layer, from which a change in magnetic flux along the length of the tracks can be read out.
Since the magnetization change areas where the magnetic flux changes along the length of the tracks are provided, the change in magnetic flux is obtained from the magnetization change areas on both sides of the tracks, and these outputs are differentially detected so that the tracking control can be executed. Therefore, track information can be recorded easily on a magnetic disk and can be reproduced accurately.
In addition, a magnetic recording medium of the invention is characterized by including: tracks formed on the magnetic layer, along which information is recorded magnetically; and groove sections for tracking control formed on the magnetic layer, each of said groove sections having a width non-uniform along the length of the tracks and being magnetization change area which is magnetized in a direction opposite to a magnetization direction of the tracks.
Since each of the groove sections has a width non-uniform in the direction along the tracks, when the groove sections are provided on both sides of the tracks, the magnetic flux changes on both sides of the tracks. The changes in magnetic flux on both groove sections are obtained as track information and the changes are subtracted so that the tracking control can be executed. As a result, the track information can be recorded on the magnetic disk easily and reproduced accurately.
Further, the magnetic recording medium of the invention is characterized in that the magnetization change areas are non-magnetic areas whose width is non-uniform along the length of the tracks.
Therefore, the changes in magnetic flux on both the sides of the magnetic areas (tracks) between the non-magnetic areas are obtained as the track information, and the changes are subtracted so that the tracking control can be executed. Accordingly, the track information can be recorded on the magnetic disk easily and reproduced accurately.
Furthermore, the magnetic recording medium of the invention is characterized in that the magnetization change areas which are adjacent to each other have respective widths where change rates are different from each other.
Therefore, since the change rates of the widths of the groove sections formed on both sides of the track are different from each other, even when the track information of both the groove sections are read out by one magnetic head, for example, the track information of the respective groove sections can be obtained through filters according to frequencies of the change rates. As a result, the tracking control can be executed by differentially detecting the track information. In such a manner, the track information can be recorded easily and reproduced accurately.
A magnetic head apparatus of the present invention is characterized by including: a reproduction head section for detecting the change in magnetic flux; and a differential circuit for obtaining a differential signal between outputs detected by the reproduction head section from the magnetization change areas on both sides of the track.
Therefore, the magnetic flux which changes along the length of the tracks is detected by the reproduction head section, and outputs are obtained from the magnetization change areas on both sides of the tracks, and the tracking control is executed so that the output on one side has a value identical to a value of the output on the other side.
In addition, the magnetic head apparatus of the inventi
Iida Koichi
Kuroda Sumio
Fujitsu Limited
Greer Burns & Crain Ltd.
Hudspeth David
Wong K.
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